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  • 1
    Electronic Resource
    Electronic Resource
    Diethylene glycol (DEG)-associated myocardial changes: A pilot investigation of chronic intoxication in guinea-pigs (1991)
    Springer
    International journal of legal medicine 104 (1991), S. 93-97 
    Details
    ISSN: 1437-1596
    Keywords: Diethylene glycol ; Intoxication ; Myocardium ; Myocytolysis ; Ultrastructure ; Mitochondria ; Guinea pig ; Diethylenglycol ; Intoxikation ; Myokard ; Myozytolyse ; Ultrastruktur ; Mitochondrien ; Meerschweinchen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Law
    Description / Table of Contents: Zusammenfassung Das Myokard von Meerschweinchen, welche mit subletalen Mengen von Diethylenglycol über eine Zeitdauer von 2–11 Tagen gefüttert worden waren, wurde mikroskopisch und elektronenmikroskopisch untersucht. Eine Koagulationsmyozytolyse und Verlust von Myofibrillen war fleckförmig verstreut über das Myokard. Diese Veränderungen waren in den Kontrollen nicht zu beobachten. Die begleitenden ultrastrukturellen Veränderungen bestanden in Schwellung, Pleomorphie, Hyperplasie von Mitochondrien, begleitet von einer Erweiterung der interfibrillären Räume und Verlagerung, Verzerrung und Ruptur angrenzender Fibrillen.
    Notes: Summary The myocardium of guinea pigs fed on sublethal doses of diethylene glycol (DEG) over a period of 2–11 days was examined for microscopical and ultrastructural changes. Coagulative myocytolysis and loss of myofibrils, not observed in the controls, was patchily distributed throughout the myocardium. The accompanying ultrastructural features included swelling, pleomorphism and hyperplasia of mitochondria with an associated distension of the interfibrillary spaces and a displacement, distortion and rupture of adjacent myofibrils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01626038
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of dopamine agonist medication on prolactin producing pituitary adenomas (1991)
    Springer
    Virchows Archiv 418 (1991), S. 439-446 
    Details
    ISSN: 1432-2307
    Keywords: Bromocriptine ; Pituitary neoplasm ; Prolactin ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Conventional light microscopy, immunocyto-chemistry, electron microscopy and in situ hybridization were used to evaluate the effect of dopamine agonists (bromocriptine-LAR and bromocriptine) on the morphology of surgically removed prolactin (PRL)-producing pituitary adenomas. Dopamine agonist therapy resulted in decrease of serum PRL, clinical improvement and tumour shrinkage. Using light and electron microscopy cellular atrophy, interstitial and perivascular fibrosis were noted; in several tumours connective tissue accumulation was pronounced. The cellular response was not uniform. In some adenomas populations of large cells and small cells were distinguished. The large cells contained immunoreactive PRL and expressed the PRL gene indicating resistance to dopamine agonists. It appears that these cells retained the potential to secrete PRL and proliferate despite exposure to dopamine agonists. In the small cells, PRL immunoreactivity and PRL gene expression decreased providing evidence that both PRL release and synthesis were blocked. Small cells can persist in tumours after discontinuation of dopamine agonist medication suggesting these small cells are irreversibly suppressed and are not capable of regaining their endocrine function and proliferative capability. The formation of irreversibly suppressed PRL cells may explain why some PRL-producing adenomas do not recur after withdrawal of dopamine agonists.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01605931
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  • 3
    Electronic Resource
    Electronic Resource
    Immunohistochemical characterization of HLA-DR-antigen positive dendritic cells in phaeochromocytomas and paragangliomas as a prognostic marker (1991)
    Springer
    Virchows Archiv 418 (1991), S. 33-39 
    Details
    ISSN: 1432-2307
    Keywords: HLA-DR ; Phaeochromocytomas ; Paragangliomas ; Immunohistochemistry ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Twelve cases of phaeochromocytoma (PCC) and four cases of paraganglioma (PGG) were studied by immunohistochemistry and immunoelectron microscopy in order to demonstrate HLA-DR (Ia)-antigen-positive dendritic cells (IaDCs). Dense infiltration of IaDCs was detected in the majority of PCCs revealing high urinary or serum catecholamine levels, but in aggressively growing PCCs, a familial PCC and all PGGs, few IaDCs were demonstrated. Interestingly, these IaDCs were negative for S-100 protein. Although S-100-protein-positive sustentacular-like cells (SCs), morphologically similar to IaDCs, were also present, these were clearly distinguished from IaDCs by our double immunostaining method. Ultrastructurally, IaDCs had smooth or slightly indented nuclei and contained a moderate amount of endoplasmic reticulum, small mitochondria and vacuoles, extending elongated cytoplasmic processes. These results suggest that determination of the quantity of IaDCs is a highly effective method of assessing the character of PCCs, in particular, their prognosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01600242
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  • 4
    Electronic Resource
    Electronic Resource
    Cell-mediated cytotoxicity in acute rat cardiac allograft rejection: An immunological and ultrastructural study (1991)
    Springer
    Virchows Archiv 418 (1991), S. 41-50 
    Details
    ISSN: 1432-2307
    Keywords: Cell-mediated cardiocyte injury ; Acute cardiac allograft rejection ; Mononuclear cellular infiltration ; Immunohistochemistry ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To clarify the immune mechanism of cytotoxicity in acute cardiac allograft rejection, we observed interactions between cardiocytes and mononuclear cells using immunohistochemistry and light and electron microscopy. All allografted WKA rat hearts transplanted to F344 recipients stopped beating by the 7th day after the transplantation. The population of helper/inducer T cells (Th) and IL2R+ cells was large for the first 3 days, whereas that of cytotoxic/suppressor T cells (Tc-s) and macrophages increased from the 4th day. TheTh/Tc-s ratios were more than 2.0 until the 3rd day, then decreased to less than 1.0. In circulating T lymphocytes; theTh/Tc-s ratios were under 1.0 on the 1st, 6th and 7th days. Electron microscopically IL2R+ cells, Tc-s and macrophages were often seen in close contact with the plasma membrane of the cardiocytes. The majority of IL2R+ cells are NK cells, Tc-s andTh. Of these, the population of Tc-s was small until the 3rd day. Thus, NK cells play a pivotal role in the early stage of the rejection, and Tc-s and macrophages then aggravate cell-mediated cardiocyte injury.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01600243
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  • 5
    Electronic Resource
    Electronic Resource
    Ultrastructure of oesophageal melanocytosis (1991)
    Springer
    Virchows Archiv 418 (1991), S. 515-522 
    Details
    ISSN: 1432-2307
    Keywords: Oesophagus ; Melanocyte ; Melanoma ; Ultrastructure ; Endoscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Four examples of an endoscopically detected oesophageal melanotic lesion were examined by light microscopy, light microscope histochemistry and transmission electron microscopy, and were compared with 13 control samples of normal oesophageal epithelium. By light microscopy, pigmented melanocytes lacking atypia and mitoses were observed amongst the keratinocytes in the basal layer of the oesophageal mucosa. Junctional activity was absent. The mechanism of pigmentation was studied and found to consist of: an increase in the number of melanocytes in the basal layer of the mucosa, an increase in the quantity of melanin in these melanocytes, transfer of melanin from melanocytes to keratinocytes and to macrophages and fibroblasts in the tunica propria. Since all the lesions demonstrated increased numbers of both melanocytes and melanosomes, the term oesophagealmelanocytosis rather thanmelanosis is suggested, to emphasise the essential character of the lesion as a cellular proliferation. The value of sampling these pigmented lesions during endoscopy is emphasised as a means of obtaining well-preserved material for the evaluation of a lesion which some authorities have viewed as a possible precursor for oesophageal malignant melanoma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01606502
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  • 6
    Electronic Resource
    Electronic Resource
    Ultrastructural abnormalities of mitochondria and deficiency of myocardial cytochromec oxidase in a patient with ventricular tachycardia (1991)
    Springer
    Virchows Archiv 419 (1991), S. 63-68 
    Details
    ISSN: 1432-2307
    Keywords: Mitochondrial cardiomyopathy ; Ultrastructure ; Cytochromec oxidase deficiency ; Ventricular tachycardia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A 30-year-old woman presented with lifethreatening ventricular tachycardia without overt heart disease. Ultrastructural investigation of endomyocardial biopsy disclosed abnormally structured and often enlarged mitochondria. Morphometry revealed the ratio of volume density of mitochondria to myofibrils to be markedly increased to 0.667 as compared with five controls (mean: 0.46; range: 0.445–0.479). Investigation of mitochondrial respiratory chain enzymes revealed a 90% reduction in activity of cytochromec oxidase. Our data suggest that mitochondrial cardiomyopathy may induce malignant ventricular arrhythmias.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01600154
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  • 7
    Electronic Resource
    Electronic Resource
    Varicocele in the rat: a new experimental model (1991)
    Springer
    Urological research 19 (1991), S. 319-322 
    Details
    ISSN: 1434-0879
    Keywords: Varicocele ; Rat, Histology ; Ultrastructure ; Temperature ; Infertility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary With no consistent animal prototype for the study of varicocele, we set out to create a model in the rat by complete ligation of the main branch of left spermatic vein (MBSV) or by partial ligation of the left renal vein. Three months later, the histology, ultrastructure and temperature of the testis and epididymis were studied. Microscopically, spermatogenic arrest was the most frequent anomaly seen. The most frequently noted ultrastructural change of the testis was distension of smooth endoplasmic reticula in Sertoli cells. The microvilli of columnar epithelia in epididymis were sparse and showed local defects. Lesions and increased temperatures in the testis and epididymis induced by the ligation of the left MBSV were similar to those seen in partial ligation of the left renal veins, with no significant differences between left and right. Significant differences were found, however, on comparison with the controls.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00299069
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  • 8
    Electronic Resource
    Electronic Resource
    Morphology of the synovium during its differentiation and development in the mouse knee joint (1991)
    Springer
    Anatomy and embryology 183 (1991), S. 537-544 
    Details
    ISSN: 1432-0568
    Keywords: Synovial membrane ; Development ; Ultrastructure ; Scanning electron microscopy ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The prenatal and postnatal development of the mouse knee joint was investigated by transmission and scanning electron microscopy. In the prenatal stage, following the appearance of a narrow intercellular cleft between two skeletal elements on the 16th fetal day, clefting extended into the lateral synovial mesenchyme. In some regions, the extension of the cleft was very rapid, but in a certain region (future fat pad region), it was somewhat slower. Macrophage-like cells appeared in the synovial mesenchyme on the 16th fetal day, and then increased in number, and were distributed as if they were clustering around the presumptive clefting zone in the future fat pad region on the 17th–18th fetal day. This suggests that macrophage-like cells may participate in joint development, as they phagocytize and remove some kinds of solid extracellular matrix, and facilitate the cleft extension. In the early postnatal stage, scanning electron microscopic observations showed that there were two different types of cell in the synovial lining. One of them exhibited a surface morphology corresponding to that of macrophages: a spherical cell body and numerous pseudopodia. The other type of cell exhibited various cell shapes with many cytoplasmic processes extending along the synovial surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00187902
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  • 9
    Electronic Resource
    Electronic Resource
    Endothelial heterogeneity in the chick wing bud: A morphometric study (1991)
    Springer
    Anatomy and embryology 184 (1991), S. 47-53 
    Details
    ISSN: 1432-0568
    Keywords: Wing bud ; Endothelial cell ; Development ; Ultrastructure ; Morphometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The microvascular endothelium of the chick wing bud at stages 22, 27, and 32 was evaluated by ultrastructural morphometry. The rationale for this study is based on the hypothesis that endothelial cells exhibit variation in structure and function during cytodifferentiation. The microvessels had a luminal diameter range such that they were classified as capillaries. The thin continuous endothelium was devoid of a basal lamina. The endothelium had a very small number of plasmalemmal vesicles; vacuoles were however present for all stages and in some cases were abundant. The temporal findings were that endothelial cell thickness increases, plasmalemmal vesicle densities decrease, and the densities of cytoplasmic vacuoles increase. The spatial results were that endothelial cells in proximal regions of the limb have a greater thickness, contain fewer vesicles and have more vacuoles than those in distal regions. In general, these results indicate that endothelial ultrastructural heterogeneity occurs within a 31/2 day timespan of wing bud development. The discussion considers the results with regard to recent reports on endothelial cell heterogeneity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01744260
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  • 10
    Electronic Resource
    Electronic Resource
    Development of taste organs inRana temporaria (1991)
    Springer
    Anatomy and embryology 184 (1991), S. 363-369 
    Details
    ISSN: 1432-0568
    Keywords: Taste organs ; Amphibia ; Development ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In tadpoles ofRana temporaria two successive generations of taste organs: taste buds (TBs) and taste disks were studied. The TBs are located in the apices of oral premetamorphic papillae. Each TB consists of vertically elongated receptor cells (probably taste) and supporting cells. No basal (Merkel) cells were observed there. Morphologically, two types of receptor cells have been distinguished in a TB. Complete synaptic structures were observed in the TBs between the 30th and 41st of Gosner's (1960) developmental stages, though synaptic vesicles occur already at stage 26. The taste disks consist of taste cells, supporting cells and basal cells. Dense-core synaptic vesicles occur in the gustatory cells at stage 41, but complete synaptic structures were not observed earlier than at stage 45. Synaptic junctions observed at some of the gustatory cells seem to be reciprocal (bidirectional).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00957898
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  • 11
    Electronic Resource
    Electronic Resource
    The anatomy and fine structure of the echidnaTachyglossus aculeatus snout with respect to its different trigeminal sensory receptors including the electroreceptors (1991)
    Springer
    Anatomy and embryology 184 (1991), S. 371-393 
    Details
    ISSN: 1432-0568
    Keywords: Tachyglossus aculeatus (echidna) ; Echidna bill ; Sensory receptors ; Electroreceptor ; Mechanoreceptor ; Trigeminal nerve ; Monotreme ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The gross anatomy and nerve supply of the bill of echidna (Tachyglossus aculeatus) is described in relation to its function as an outstanding sensory organ. The sensory innervation of the skin of the echidna snout was investigated by means of frontal serial sections, after decalcification of the specimens. A comprehensive light and electron microscopic description of the location and fine structure of cutaneous sensory receptors of the trigeminal system was made by this means. The encapsulated and non-encapsulated Ruffini receptors, the types of other free receptors in the connective tissue and the Merkel cell receptor do not differ morphologically from those of higher mammals, whereas the pacinian-like corpuscle shows a unique organization of its outer core. This is composed of large perineural cells containing a unique reticulum of parallel-orientated endoplasmic membranes. Lamellated corpuscles, seen in isolation or in association with push rods, are numerous in the snout and in the tip of the tongue of echidna. Push rod receptor organs occur in the hairless skin of the bill with a very dense array at its rostral end and in the pseudopalatal ridges. Gland duct receptors are restricted to the skin adjacent to the nostrils and the mouth opening, including the pseudopalatal plates. Only about one quarter of the total number of 400 seromucous glands receive a sensory innervation of their intraepidermal duct segment. Within each innervated gland two types of receptor terminals are identified. The distributions of the different receptor types are mapped for different regions of the skin, the mucous membrane of the nasal and oral vestibule and the tip of the tongue. The fine structure of nerve terminals is discussed from a comparative anatomical point of view, and some speculations are made about possible transduction processes that underlie the known electrophysiological properties. The sensory organs such as the “push rod” and “gland duct receptor”, and most of their sensory terminals, are less differentiated in echidna snout than in the platypus (Ornithorhynchus anatinus) bill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00957899
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  • 12
    Electronic Resource
    Electronic Resource
    Immunocytochemical and ultrastructural studies of hyaline inclusions in sporadic motor neuron disease (1991)
    Springer
    Acta neuropathologica 82 (1991), S. 295-301 
    Details
    ISSN: 1432-0533
    Keywords: Hyaline inclusions ; Motor neuron disease ; Amyotrophic lateral sclerosis ; Immunocytochemistry ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We investigated hyaline inclusion bodies (HI) immunocytochemically and ultrastructurally in six cases of sporadic motor neuron disease (MND). All HI contained large amounts of ubiquitin and some HI were stained at the core or the center with anti-neurofilament antibody, with the surrounding halo unstained. No HI were stained with antibodies raised against cytoskeletal proteins such as high-molecular weight microtubule-associated proteins and phosphorylated tau. Ultrastructurally, HI were chiefly composed of filaments measuring about 20 nm in diameter thicker than neurofilaments, and contained fine granules and frequently one or more of four characteristic profiles, i.e., small electron-dense materials resembling Bunina bodies, bundles of tubular filaments measuring approximately 20 nm in diameter, large electron-dense cores, and focal accumulations of randomly arranged neurofilaments. Hyaline inclusions can be regarded as one of the characteristic markers for sporadic MND as well as familial amyotrophic lateral sclerosis. Hyaline inclusions have a markedly heterogeneous ultrastructure and, therefore, differences in immunoreactivity with antineurofilament antibodies are not unexpected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00308815
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  • 13
    Electronic Resource
    Electronic Resource
    Meningiomas differentiating to arachnoid trabecular cells: a proposal for histological subtype “arachnoid trabecular cell meningioma” (1991)
    Springer
    Acta neuropathologica 82 (1991), S. 327-330 
    Details
    ISSN: 1432-0533
    Keywords: Meningioma ; Microcystic meningioma ; Vacuolated meningioma ; Arachnoid trabecular cell ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Three cases of meningiomas which had abundant small vacuoles in the tumor tissue are reported. By electron microscopy, the tumor cells exhibited long and thin processes, the tips of which were united by desmosomes. The tumor tissue was revealed to have wide extracellular spaces which corresponded to the vacuoles observed by light microscopy. In previous literature, various terms have been used when referring to this meningioma, such as microcystic meningioma or vacuolated meningioma. Since the ultrastructure of the tumor showed similarity to that of normal arachnoid trabecular cells, we propose to call the tumor “arachnoid trabecular cell meningioma” denoting its morphological nature clearly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296542
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  • 14
    Electronic Resource
    Electronic Resource
    Galactosialidosis: neuropathological findings in a case of the late-infantile type (1991)
    Springer
    Acta neuropathologica 82 (1991), S. 331-339 
    Details
    ISSN: 1432-0533
    Keywords: Galactosialidosis ; Neuronal storage disease ; Neuropathology ; Ultrastructure ; Neuronal loss
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The neuropathological findings in a 13-year-old Japanese male showing decrease of sialidase and β-galactosidase activities are reported. The patient was the product of normal pregnancy to consanguineous parents. He started to sit at 8 months, stand at 20 months and walk at the age of 2; mental retardation, visual disturbance, cerebellar ataxia, myoclonus and epilepsy developed by the age of 10, and he died at 13. Neuropathological investigation revealed neuronal loss and storage. Severe loss of neurons was observed in the thalamus, globus pallidus, lateral geniculate body, gracile nucleus, Purkinje and retinal ganglion cells. Marked ballooning was seen in the Betz cells and neurons in the basal forebrain, the motor neurons in the cranial nerve nuclei and spinal cord, and in the trigeminal and spinal ganglia. The storage material varied in staining from region to region and from neuron to neuron. Electron microscopic investigation revealed a variety of intracytoplasmic and intranuclear inclusions: membranous cytoplasmic bodies, parallel, wavy-lamellar or tortuous tubular structures, lipofuscin-like irregular-shaped pleomorphic bodies, and cytoplasmic vacuoles with fine granules and lamellar materials. The severity of the neuronal loss did not seem to correlate with the amount of the storage materials, but with the presence of tortuous tubular inclusion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296543
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  • 15
    Electronic Resource
    Electronic Resource
    Intramedullary secretory gangliocytoma (1991)
    Springer
    Acta neuropathologica 82 (1991), S. 402-407 
    Details
    ISSN: 1432-0533
    Keywords: Gangliocytoma ; Ultrastructure ; Catecholamines ; Hypertension ; Spinal cord
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An 8-year-old boy developed severe systemic hypertension during resection of an intramedullary tumor. The histological, ultrastructural and immunocytochemical characteristics of the tumor are those of a gangliocytoma. Based on the demonstration of tyrosine hydroxylase in neuronal tumor cells, it is postulated that catecholamine secretion was responsible for the systemic hypertension.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296552
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  • 16
    Electronic Resource
    Electronic Resource
    Immunocytochemical and ultrastructural studies of Werdnig-Hoffmann disease (1991)
    Springer
    Acta neuropathologica 81 (1991), S. 408-417 
    Details
    ISSN: 1432-0533
    Keywords: Werdnig-Hoffmann disease ; Immunocytochemistry ; Ultrastructure ; Cytoskeleton ; Ubiquitin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neuronal alterations in two cases of Werdnig-Hoffmann disease (WH) were investigated immunocytochemically and ultrastructurally. Ballooned neurons (BNs) were found in anterior horn, Clarke's column, dorsal root ganglion and thalamus. Anti-phosphorylated neurofilament antibodies preferentially stained the peripheral perikarya and proximal neuronal processes of BNs, whereas anti-ubiquitin antibodies preferentially stained the central perikarya of BNs. Ultrastructurally, BNs showed degenerative changes ranging from a diffuse increase of neurofilaments to a centrally accentuated accumulation of mitochondria and vesicular or membranous profiles. Our studies suggest that ubiquitinated degradation products accumulate in the center of the BN's perikaryon and displace aberrantly phosphorylated neurofilaments to the periphery. BNs in WH probably reflect an intrinsic alteration in the metabolism of neurofilaments that is associated with regressive changes in the neuron and eventually neuronal death.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293462
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  • 17
    Electronic Resource
    Electronic Resource
    The effect of denervation on the morphology of regenerating rat soleus muscles (1991)
    Springer
    Acta neuropathologica 82 (1991), S. 21-32 
    Details
    ISSN: 1432-0533
    Keywords: Muscle ; Regeneration ; Denervation ; Ultrastructure ; Snake toxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study examines the level to which muscle regeneration proceeds in the absence of innervation. Regeneration was monitored in rat soleus muscles following localised injection of a snake toxin, notexin. Muscles which had been concomittantly denervated were compared with those that were normally innervated. Until 3–4 days following toxin administration regeneration is identical in both groups. The muscles contain new myotubes in place of the degenerated “parent” fibres. Thereafter, the non-denervated muscles grow rapidly and by 28 days their myofibres attain the size of those from the contralateral controls. Growth of denervated regenerating muscles, however, is retarded and is superseded by a gradual atrophy. In such muscles we further identify ultrastructural abnormalities from 7 days post-injection. These a re loss of individual myosin filaments and the presence of immature and abnormal configurations of the transverse system and triads. We, thus, conclude that innervation is an obligatory requirement for the restoration of normal myofibrillar and sarcotubular morphology, as well as growth, but is not necessary for the neo-formation of myofibres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310919
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  • 18
    Electronic Resource
    Electronic Resource
    Bone marrow transplant in a case of mucopolysaccharidosis I Scheie phenotype: skin ultrastructure before and after transplantation (1991)
    Springer
    Acta neuropathologica 82 (1991), S. 33-38 
    Details
    ISSN: 1432-0533
    Keywords: MPS I-S ; Skin biopsy ; Ultrastructure ; Bone marrow transplant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An 11-year-old girl with mucopolysaccharidosis I Scheie phenotype (MPS I-S) received a bone marrow transplant (BMT) from her heterozygous HLA-identical LMC-non-reactive mother. Multidisciplinary studies were carried out and results evaluated 21 months after transplantation. Herein we report the ultrastructural findings pre-and post-BMT in skin. Multidisciplinary studies are commonly used to evaluate the benefits of metabolic correction following BMT in some MPS and other inherited metabolic disorders, and changes in morphology have been described in liver and few other tissues. In this case, we elected skin, since connective tissue is universally involved in MPS and is safely and easily obtainable. Comparison of skin biopsy specimens taken before and after BMT showed a considerable change in dermal fibroblast morphology, with marked reduction in cell size and the number and size of abnormal lysosomes, thus indicating the clearance of storage. Our results demonstrate that dermal cells respond to enzyme replacement therapy in MPS I-S, with the clearance of glycosaminoglycan lysosomal accumulation in connective tissue fibroblasts, which had near-normal morphology 21 months after BMT. Therefore, the practice of skin biopsy after BMT in MPS and other metabolic disorders in which dermal cells are involved should be encouraged.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310920
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  • 19
    Electronic Resource
    Electronic Resource
    Idiopathic prolactin cell hyperplasia of the pituitary mimicking prolactin cell adenoma: a morphological study including immunocytochemistry, electron microscopy, and in situ hybridization (1991)
    Springer
    Acta neuropathologica 82 (1991), S. 147-151 
    Details
    ISSN: 1432-0533
    Keywords: Hyperplasia ; Pituitary ; Pathology ; Prolactin ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Prolactin cell adenoma is the most frequently found lesion in surgically removed pituitaries of patients with hyperprolactinemia. However, in several instances, instead of prolactin cell adenoma, other lesions are encountered by morphological investigation. We report here the morphological findings in a patient with hyperprolactinemia who underwent transsphenoidal pituitary surgery for suspected prolactin cell adenoma. A morphological diagnosis of tumor could not be confirmed and massive diffuse prolactin cell hyperplasia was identified. The aim of this publication is to describe the lesion by histology, immunocytochemistry, electron microscopy, and in situ hybridization and to call attention to primary prolactin cell hyperplasia which can mimic prolactin cell adenoma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00293958
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  • 20
    Electronic Resource
    Electronic Resource
    Fulminant blastomycosis with blastomycotic infection of a cerebral glioma (1991)
    Springer
    Acta neuropathologica 82 (1991), S. 420-424 
    Details
    ISSN: 1432-0533
    Keywords: Blastomycosis ; North American Blastomy-cosis ; Brain tumor ; Opportunistic infection ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Except for isolated case reports, blastomycosis has not been identified as a significant problem in immunosuppressed patients. We describe an unusual case with blastomycotic infection of a cerebral glioma in a 56-year-old man who underwent radiotherapy for his tumor and died of fulminant blastomycotic pneumonia. This is believed to be the first reported case of Blastomyces dermatitidis infection of a cerebral glioma. The light microscopic and ultrastructural features of B. dermatitidis, the giant forms of which were encountered in our patient, are described, and the role of immuno-suppression due to steroid therapy in the pathogenesis of this fulminant infection are reviewed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296555
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  • 21
    Electronic Resource
    Electronic Resource
    Scrapie inoculation of mice: light and electron microscopy of the superior colliculi (1991)
    Springer
    Acta neuropathologica 81 (1991), S. 562-571 
    Details
    ISSN: 1432-0533
    Keywords: Scrapie ; Ultrastructure ; Vacuolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Ultrastructural examination of the superior colliculi of mice intraocularly inoculated with the ME7 strain of scrapie showed vacuolation early in the course of infection. Brains were examined between 85–260 days after monocular inoculation with scrapie. The mean incubation period for the development of clinical disease was 302 days. Vacuolation was seen initially in the contralateral superior colliculus and subsequently in the ipsilateral colliculus. In coded trails light microscopical vacuolation was seen from 218 days but ultrastructural examination showed that sparse vacuoles were inconsistently present in either or both of the ipsilateral and contralateral colliculi from 85 days; frequent vacuoles were seen from 190 days. Scrapie-induced vacuoles were differentiated from vacuoles present in control tissue by the presence of loculation or by a limiting double membrane which showed protrusion or proliferation of the innermost lamella. Vacuolation was seen in neuronal perikarya, myelinated fibres, dendrites and axonal presynaptic terminals. Vacuoles of myelinated fibres were observed within myelin and possibly also in the inner tongue of oligodendroglial cytoplasm. Whorled membrane configurations were also seen. Tubulovesicular particles, 40 nm in diameter, were recognised in two scrapie-infected mice. It is suggested that some scrapie vacuoles arise as a result of incorporation of abnormal membrane into organelles, possibly mitochondria, in neuronal perikarya and neurites and probably also within oligodendroglial cytoplasm and myelin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310139
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  • 22
    Electronic Resource
    Electronic Resource
    Histopathogenesis of inflammatory linear verrucose epidermal naevus: histochemistry, immunohistochemistry and ultrastructure (1991)
    Springer
    Archives of dermatological research 283 (1991), S. 491-499 
    Details
    ISSN: 1432-069X
    Keywords: Inflammatory linear epidermal naevus ; Keratinization ; DACM ; Involucrin ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Skin lesions of three patients with inflammatory linear verrucose epidermal naevus (ILVEN) were examined. Histologically, orthokeratosis and parakeratosis were alternately seen in the acanthotic epidermis. By N-(7-dimethylamino-4-methyl-3-coumarinyl)maleimide staining, the horny cells in the parakeratotic epidermis showed a cytoplasmic SH pattern and a weak membranous SS pattern. The orthokeratotic epidermis revealed an increased involucrin expression, whereas the parakeratotic epidermis showed almost no involucrin expression. Ultrastructurally, in the parakeratotic epidermis, the living keratinocytes had prominent Golgi apparatuses and vesicles in the cytoplasm. In the intercellular spaces in the upper spinous layer through to the lower horny layer, an electron dense, homogeneous substance was deposited. The cytoplasm of the horny cells was filled with keratin filaments and contained remnants of nucleus and cytoplasmic membrane structures, and some lipid droplets. The marginal band formation was incomplete. Most of these ultrastructural abnormalities were not found in the orthokeratotic epidermis. There are both similarities and differences in histopathogenesis of the parakeratotic epidermis between ILVEN and psoriasis. A unique finding was the lack of involucrin expression in the ILVEN parakeratotic epidermis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371921
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  • 23
    Electronic Resource
    Electronic Resource
    The rhino mouse model: the effects of topically applied all-trans retinoic acid and CD271 on the fine structure of the epidermis and utricle wall of pseudocomedones (1991)
    Springer
    Archives of dermatological research 283 (1991), S. 100-107 
    Details
    ISSN: 1432-069X
    Keywords: Rhino mouse skin ; All-trans retinoic acid ; CD271 ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The histological and ultrastructural effects following 3 weeks' topical treatment with two agents (all-trans retinoic acid and a new synthetic retinoid-like substance, CD271) were evaluated on the epidermis and the epithelial wall of the pseudocomedones in rhino mouse skin. The comedolytic effects of these drugs were similar, and consisted of a reduction of the utricular diameter, with normalization of follicular units. Morphological examinations revealed a hyperplastic response with an increase in the number of cell layers of both epidermis and follicular epithelium, and modifications in keratinocyte differentiation. Ultrastructural changes in the epidermis and epithelial wall were observed mainly in the granular and horny layers, with increased desquamation, and a decrease in the cohesiveness of corneocytes. During the first week of treatment, some cutaneous toxic effects were noticed, but they normalized within two weeks. On the other hand, a fine granular material persisted in the intercellular spaces. It is confirmed that the skin of the rhino mouse is a good model for the evaluation of the comedolytic effects of drugs. Moreover, it reveals the specific effects of retinoids on epidermal differentiation. We have demonstrated that topically applied CD271 induces modifications similar to those obtained with all-trans retinoic acid. It is thus concluded that CD271 is a potentially effective anti-acne agent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371617
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  • 24
    Electronic Resource
    Electronic Resource
    Ultrastructural study of the skin in Sjögren — Larsson syndrome (1991)
    Springer
    Archives of dermatological research 283 (1991), S. 141-148 
    Details
    ISSN: 1432-069X
    Keywords: Sjögren ; Larsson syndrome ; Ichthyosis ; Ultrastructure ; Lamellar body ; Keratinization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The ichthyosiform skin and the uninvolved skin of a 5-year-old Japanese female with Sjögren — Larsson syndrome were examined by light and electron microscopy to elucidate the keratinization disorder. Light microscopically, the epidermis of the ichthyosiform skin showed acanthosis, papillomatosis and hyperkeratosis. The horny cells had a basket-weave appearance. The granular cell layer was slightly thickened. Slight round cell infiltration and vascular dilatation were seen in the upper dermis. The uninvolved skin was histologically normal. Electron microscopically, in both ichthyosiform and uninolved skin, abnormal lamellar or membranous inclusions were present in the cytoplasm of horny cells of the epidermis. These inclusions appeared to be derived from some of the lamellar bodies and/or abnormal membranous structures found in the cytoplasm of spinous and granular cells. Mitochondria in the epidermal basal cells were more numerous in the ichthyosiform skin than in the uninvolved skin. These findings indicate that, whether the skin is involved or not, the epidermis of the patient with this disorder may always have a structural abnormality, which may be genetically determined. Local environmental factors may play a role in inducing the acanthosis and papillomatosis of the epidermis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00372053
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  • 25
    Electronic Resource
    Electronic Resource
    Are accessory nuclei involved in the establishment of developmental gradients in hymenopteran oocytes? (1991)
    Springer
    Development genes and evolution 199 (1991), S. 423-426 
    Details
    ISSN: 1432-041X
    Keywords: Oogenesis ; Accessory nuclei ; Developmental gradients ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In the oocytes ofTenthredo olivacea, accessory nuclei (AN) are formed by budding from the nuclear envelope of the oocyte nucleus. Newly formed AN contain electron-dense material of nuclear origin and are surrounded by a double envelope devoid of pores. Such structures are subsequently transported to the peripheral ooplasm (periplasm), where they grow to reach a final diameter of 5 µm. In the envelopes of advanced AN nuclear pores arise. Through these pores “nuage” material is extruded into the surrounding periplasm. These findings are discussed with respect to a possible involvement of AN in the establishment of developmental gradients in hymenopteran oocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01705853
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  • 26
    Electronic Resource
    Electronic Resource
    The origin of the nascent blastocoele in preimplantation mouse embryos ultrastructural cytochemistry and effect of chloroquine (1991)
    Springer
    Development genes and evolution 200 (1991), S. 77-85 
    Details
    ISSN: 1432-041X
    Keywords: Lysosomes ; Ultrastructure ; Chloroquine ; Blastocyst ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mouse morulae are known to undergo cavitation as soon as some external cells have entered the sixth cell cycle (Garbutt et al. 1987). Since the early cytological features of cavitation are still unclear, we undertook a careful ultrastructural analysis of late morulae-nascent blastocysts. In addition, since maturation of lysosomes might be involved in the first step of cavity formation, we focused our attention on these organelles by means of the cytochemical localization of trimetaphosphatase activity and by the study of the effects of chloroquine on precavitation embryos. Our results suggest that cavitation starts in a few external cells (presumably competent cells entering the sixth cell cycle), by the chloroquine-sensitive formation of degradative autophagic vacuoles engulfing lipid droplets and vacuoles containing osmiophilic material. These complex structures enlarge (as a result of lipid metabolism?) and so transform into intrablastomeric cavities which, by means of a membrane fusion process, very rapidly become extracellular cavities that coalesce. The abembryonic pole of the blastocyst is determined in this way. Moreover, we suggest that the juxtacoelic cytoplasmic processes covering the inner cell mass (ICM) cells, which are known to restrict the expression of their totipotency during early cavitation (Fleming et al. 1984), are the latest remnants of the walls of the growing intrablastomeric cavities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00637187
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  • 27
    Electronic Resource
    Electronic Resource
    Contributions of sodium and chloride to ultrastructural damage after dendrotomy (1991)
    Springer
    Experimental brain research 86 (1991), S. 60-72 
    Details
    ISSN: 1432-1106
    Keywords: Trauma ; Neuron ; Sodium ; Chloride ; Ultrastructure ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary To determine the contributions of sodium and chloride to ultrastructural changes after mechanical injury, we amputated primary dendrites of cultured mouse spinal neurons in low calcium medium in which sodium chloride had been replaced with either choline chloride or sodium isethionate or sodium propionate. Uninjured cultured neurons were also exposed to the sodium ionophore, monensin. A third set of neurons was injured in medium in which all sodium and calcium chloride had been replaced with sucrose. Neurons injured in low-calcium, low-sodium medium exhibited few ultrastructural changes, except very near the lesion, where there was some dilation of mitochondria and cisternae of the smooth endoplasmic reticulum (SER). Mitochondria in other regions of the neurons developed an electron opaque matrix, and those nearer to the lesion converted to the condensed configuration, characterized by expanded intracristal spaces as well as a dense matrix. If sodium but not chloride was present in the medium, there was some dilation of the Golgi cisternae after injury, as well as some increased electron opacity of the mitochondria. Monensin treated neurons also exhibited dilation of the Golgi cisternae. Neurons injured in sucrose-substituted medium showed none of the changes associated with injury in normal culture medium. These results indicate that sodium influx through the lesion is involved in the dilation of the SER, which is seen even in low-calcium medium, and that a permeant anion, such as chloride, is also involved. This dilation of the SER may result from uptake of calcium released from mitochondria in response to elevated cytosolic sodium. Dilation of the Golgi cisternae appears to be a response only to elevated intracellular sodium. Condensation of the mitochondria after injury is thought to be due to increased demands for ATP synthesis and may involve a “futile cycling” of calcium across the mitochondrial membrane, involving sodium-mediated calcium release in response to elevated intracellular calcium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231040
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  • 28
    Electronic Resource
    Electronic Resource
    Secretory tapetum of Brassica oleracea L.: polarity and ultrastructural features (1991)
    Springer
    Sexual plant reproduction 4 (1991), S. 28-35 
    Details
    ISSN: 1432-2145
    Keywords: Tapetal cells ; Brassica oleracea L ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ultrastructure of the secretory, binucleate tapetum of Brassica oleracea in the micro spore mother cell (MMC) stage through to the mature pollen stage is reported. The tapetal cells differentiate as highly specialized cells whose development is involved in lipid accumulation in their final stage. They start breaking down just before anther dehiscence. Nuclei with dispersed chromatin, large nucleoli and many ribosomes in the cytoplasm characterize the tapetal cells. The wall-bearing tapetum phase ends at the tetrade stage. The dissolution of tapetal walls begins from the inner tangential wall oriented towards the loculus and proceeds gradually along the radial walls to the outer tangential one. The plasmodesmata transversing the radial walls between tapetal cells persist until the mature microspore, long after loss of the inner tangential wall. After wall dissolution, the tapetal protoplasts retain their integrity and position within the anther locule. The tapetal cell membrane is in direct contact with the exine of the microspores/pollen grains and forms tubular evaginations that increase its surface area and appear to be involved in the translocation of solutes from the tapetal cells to the microspores/ pollen grains. The tapetal cells exhibit a polarity expressed by spatial differentiation in the radial direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194568
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  • 29
    Electronic Resource
    Electronic Resource
    Brassica napus pollen development during generative cell and sperm cell formation (1991)
    Springer
    Sexual plant reproduction 4 (1991), S. 176-181 
    Details
    ISSN: 1432-2145
    Keywords: Pollen ; Brassica napus ; Mitoses ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Brassica napus pollen development during the formation of the generative cell and sperm cells is analysed with light and electron microscopy. The generative cell is formed as a small lenticular cell attached to the intine, as a result of the unequal first mitosis. After detaching itself from the intine, the generative cell becomes spherical, and its wall morphology changes. Simultaneously, the vegetative nucleus enlarges, becomes euchromatic and forms a large nucleolus. In addition, the cytoplasm of the vegetative cell develops a complex ultrastructure that is characterized by an extensive RER organized in stacks, numerous dictyosomes and Golgi vesicles and a large quantity of lipid bodies. Microbodies, which are present at the mature stage, are not yet formed. The generative cell undergoes an equal division which results in two spindle-shaped sperm cells. This cell division occurs through the concerted action of cell constriction and cell plate formation. The two sperm cells remain enveloped within one continuous vegetative plasma membrane. One sperm cell becomes anchored onto the vegetative nucleus by a long extension enclosed within a deep invagination of the vegetative nucleus. Plastid inheritance appears to be strictly maternal since the sperm cells do not contain plastids; plastids are excluded from the generative cell even in the first mitosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190001
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  • 30
    Electronic Resource
    Electronic Resource
    Ultrastructure of the micropyle and its relationship to pollen tube growth and synergid degeneration in sunflower (1991)
    Springer
    Sexual plant reproduction 4 (1991), S. 166-175 
    Details
    ISSN: 1432-2145
    Keywords: Helianthus annuus ; Ultrastructure ; Micropyle ; Pollen tube ; Synergid degeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Ultrastructural studies made on the micropyle of sunflower before and after pollination resulted in the following observations. (1) The micropyle is closed instead of a hole or canal. The inner epidermis of the integument on both sides of the micropyle is in close contact at the apex of the ovule. The boundary between the two sides consists of two layers of epidermal cuticle. (2) The micropyle contains a transmitting tissue. The micropyle is composed of an intercellular matrix produced by the epidermal cells of the integument. (3) The micropyle is asymmetrical, and is much wider on the side proximal to the funicle. On the funicle side the cells adjacent to the micropyle are similar to those of the transmitting tissue: they have large amounts of intercellular matrix and contain abundant dictyosomes, rough ER, and starch grains, and provide an appropriate environment for growth of the pollen tubes. The cells distal to the funicle are rich in rough ER and lipid bodies; they lack large intercellular spaces. (4) The micropyle is variable in the axial direction, i.e., it is much larger and more asymmetric at the level distal to the embryo sac than at a level close to the embryo sac. After pollination, one to four pollen tubes are seen in a micropyle. During their passage through the micropyle, most pollen tubes are restricted to the side proximal to the funicle. There is a greater tendency (81%) for the degenerate synergid to be located toward the funicle, i.e., at the same side as the pollen tube pathway. The data indicate a close relationship between micropyle organization, orientation of pollen tube growth, and synergid degeneration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190000
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  • 31
    Electronic Resource
    Electronic Resource
    Sperm cells of the pollen tubes of Brassica: Ultrastructure and isolation (1991)
    Springer
    Sexual plant reproduction 4 (1991), S. 226-234 
    Details
    ISSN: 1432-2145
    Keywords: Male germ unit ; Sperm cells ; Isolation ; Pollen tubes ; Brassica napus ; Pollen-tube inner plasma membrane ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Sperm cells of pollen tubes grown both in vivo and in vitro form a male germ unit. Extensions from both sperm cells of each pollen tube are closely associated with the tube nucleus. A high yield (2.7 × 104. 20 mg−1 pollen grains germinated) of intact sperm cells was obtained following release by osmotic shock from pollen tubes grown in vitro. Structural integrity of isolated sperm was maintained by isolation at low temperature in an osmotically balanced medium. At 4° C many isolated sperm pairs were still enclosed within the pollentube inner plasma membrane. Sperm cells not enclosed within this membrane no longer remained connected as a pair. During isolation vesicles formed on the sperm cell surface from disruption of the fibrillar components bridging the periplasmic space. Both in the pollen tube and after isolation the sperm nucleus is in close association with at least one region of the sperm plasma membrane. Sperm isolated at room temperature showed the presence of nucleopores, and nuclei were euchromatic, instead of heterochromatic as in intact sperm in the pollen tube.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190009
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  • 32
    Electronic Resource
    Electronic Resource
    Microsporogenesis and tapetal development in fertile and cytoplasmic male-sterile sugar beet (Beta vulgaris L.) (1991)
    Springer
    Sexual plant reproduction 4 (1991), S. 215-225 
    Details
    ISSN: 1432-2145
    Keywords: Cytoplasmic male sterility ; Beta vulgaris ; Microsporogenesis ; Tapetum ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of sporogenous and tapetal cells in the anthers of male-fertile and cytoplasmic male-sterile sugar beet (Beta vulgaris L.) plants was studied using light and transmission electron microscopy. In general, male-sterile anthers showed a much greater variability in developmental pattern than male-fertile anthers. The earliest deviation from normal anther development was observed to occur in sterile anthers at meiotic early prophase: there was a degeneration or irregular proliferation of the tapetal cells. Other early aberrant events were the occurrence of numerous small vesicles in the microspore mother cells (MMC) and a disorganized chromatin condensation. Deviations that occurred in sterile anthers at later developmental stages included: (1) less distinct inner structures in the mitochondria of both MMC and tapetal cells from middle prophase onwards. (2) dilated ER and nuclear membranes at MMC prophase, in some cases associated with the formation of protein bodies. (3) breakdown of cell walls in MMCs and tapetal cells at late meiotic prophase. (4) no massive increase in tapetal ER at the tetrad stage. (5) a general dissolution of membranes, first in the MMC, then in the tapetum. (6) abortion of microspores and the occurrence of a plasmodial tapetum in anthers reaching the microspore stage. (7) no distinct degeneration of tapetal cells after microspore formation. Thus, it seems that the factors that lead to abortive microsporogenesis are structurally expressed at widely different times during anther development. Aberrant patterns are not restricted to the tetrad stage but occur at early prophase.
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    URL: http://dx.doi.org/10.1007/BF00190008
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  • 33
    Electronic Resource
    Electronic Resource
    Fluoride effects on leaf cell ultrastructure of olive trees growing in the vicinity of the Aluminium Factory of Greece (1991)
    Springer
    Trees 5 (1991), S. 83-89 
    Details
    ISSN: 1432-2285
    Keywords: Air pollutants ; Chloroplasts ; Fluoride ; Olive tree leaves ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Leaves of olive trees growing in the vicinity of the Aluminium Factory of Greece were ultrastructurally investigated in order to determine any malformations caused by environmental air pollutants, especially hydrogen fluoride, in comparison with control samples and normal seasonal senescence. Estimation of some elements accumulated by these leaves showed that they contained high amounts of F and Al attributable to the operation of the nearby factory. The most seriously effected cell components were found to be the mesophyll chloroplasts that show a dilation of the intrathylakoid space, increase of the number of plastoglobuli, discoloration of plastoglobuli, accumulation of large starch grains and an overall disorganized appearance of the organelle. The nuclear crystalloid inclusions have unusual shapes, while the vacuoles contain a fibrillar/granular material that increases their electron density. It is concluded that the ultrastructural malformations are caused by a combination of environmental stresses and air pollutants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227489
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  • 34
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    Electronic Resource
    Different epithelia in the distal human male urethra (1991)
    Springer
    Cell & tissue research 264 (1991), S. 23-32 
    Details
    ISSN: 1432-0878
    Keywords: Male urethra ; Urethral epithelium ; Immunocytochemistry ; Ultrastructure ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The distal segment of the human male urethra, in particular the fossa navicularis, was studied with light- and electron microscopy as well as by means of histochemical and immunocytochemical methods. The fossa navicularis of the urethra contains a circumscribed zone of extremely thick, non-keratinized stratified squamous epithelium composed of cells containing a large amount of glycogen. These cells lack acid phosphatase activity and lysozyme-like immunoreactivity, both of which can be demonstrated to varying extents in the other zones of the distal male urethra. These glycogen-rich cells are considered to be the substrate for an endogenous flora of lactobacteria, whereas the acid-phosphatase activity and the lysozyme-like immunoreactivity indicate the presence of macrophages and the secretion of bactericidal agents at the epithelial surface. These observations suggest that the different zones with heterogeneous properties in the distal male urethra probably represent a defense system against the invasion of pathogenic microorganisms. Moreover, the glycogen-rich zone, which resembles the glycogen-rich epithelium of the vagina, is estrogen-dependent. This is demonstrated in cases of sex reversal in which after long-lasting estrogen treatment the glycogen-rich zone becomes extremely extended by displacement of the neighbouring epithelium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305719
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  • 35
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    Electronic Resource
    Ultrastructure of melatonin-responsive cells in the ovine pars tuberalis (1991)
    Springer
    Cell & tissue research 263 (1991), S. 529-534 
    Details
    ISSN: 1432-0878
    Keywords: Melatonin ; Pituitary gland, pars tuberalis ; Secretory cells ; Cyclic AMP ; Ultrastructure ; Cell culture ; Sheep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Functional receptors for melatonin have been localized and characterized on the pars tuberalis (PT) of a number of mammalian species, but the cell-type responsive to melatonin is unknown. The ultrastructure of the ovine pars tuberalis has been examined and these findings correlated with the functional response of the gland to melatonin. This study revealed that two secretory cell types predominate in the ovine PT, which differ in the abundance of dense-core granules. The most abundant of the cells are either agranular or very sparsely granulated and represent 90% of the total population, with the remaining 10% being composed of cells with abundant dense-core vesicles. Few follicular cells were observed. This ratio of secretory cell-types persisted in primary culture, with the two types non-separable by Percoll gradient centrifugation. Using forskolin, as a non-specific stimulant of adenylate cyclase, melatonin was shown to inhibit the formation of cyclic AMP by 80–90% in cells both before and after Percoll centrifugation. The results demonstrate that the agranular secretory cells of the ovine pars tuberalis are the melatonin responsive cell-type of this gland.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327285
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  • 36
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    Electronic Resource
    Ultrastructure and distribution of somatostatin-like immunoreactive neurons and nerve fibres in the coeliac ganglion of cats (1991)
    Springer
    Cell & tissue research 263 (1991), S. 567-572 
    Details
    ISSN: 1432-0878
    Keywords: Somatostatin ; Coeliac ganglion ; Autonomic innervation ; Ultrastructure ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Somatostatin-like immunoreactivity was localized in nerve cell bodies and nerve terminals in the cat coeliac ganglion. Two types of somatostatin-immunoreactive cell bodies were revealed, the first being large (diameter 35 μm), numerous and weakly labelled, where—as the second was considerably smaller (diameter 10.4 μm), sparsely distributed and heavily stained. The immunoreactive nerve terminals were in synaptic contact with many immunonegative large neurons and dendrites. However, in a few cases, somatostatin-immunoreactive nerve terminals could also be observed on the surface of lightly stained neurons. Transection of vagal or mesenteric nerve failed to affect the distribution or density of somatostatin-like immunoreactive nerve terminals. These results demonstrate the existence of a synaptic input to the principal neurons of the coeliac ganglion of the cat by somatostatin-containing nerve terminals and suggest that this peptide may act as a neuromodulator or neurotransmitter. It is proposed that somatostatin-positive neurons provide intrinsic projections to other somatostatin-positive and to somatostatin-negative neurons throughout the coeliac ganglion, thereby creating a complex interneuronal system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327290
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  • 37
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    Electronic Resource
    Islets of preadipocytes highly committed to differentiation in cultures of adherent rat adipocytes (1991)
    Springer
    Cell & tissue research 264 (1991), S. 243-251 
    Details
    ISSN: 1432-0878
    Keywords: Preadipocytes ; Adipocyte precursor cells ; Adipose tissue ; Differentiation-cell cultures ; Ultrastructure ; Rat (Fischer 344)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Cultures of adherent mature adipocytes, obtained from collagenase-digests of adipose tissue of the rat, invaribly contain rapidly proliferating, fibroblastlike cells despite the washing and centrifugation procedures empolyed during isolation of the fat cells. Such spindle-like cells originate from low-density structures, which we term “islets”, that are present, together with the mature adipocytes, in the floating layer of the digest of adipose tissue. Islets are found in preparations from adult (3–4 months old) as well as aging (17–24 months old) rats. By light-and electron microscopy, the islets appear as clusters of closely associated cells containing a variable amount of lipid-like material. Cells of endothelial or pericytic origin are also present in the islets. Within a few hours of culture, the islets give rise to those spindle-like cells that have been seen to proliferate in the cultures. By 36–48 hours, such cells begin to accumulate lipid droplets and, by 150 hours, assume the morphology of small mature adipocytes (diameter 20–35 μm) with a large central lipid droplet. The pattern of differentiation of these cells recalls that of preadipocytes derived from the stromal-vascular fraction of adipose tissue digests. Nonetheless, the extent and rapidity of their adipose conversion, as well as the culture conditions necessary for differentiation, are different and suggest that these cells are a substantially uniform subpopulation of adipocyte-precursor cells highly committed to differentiation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00313961
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    Postnatal changes in the ultrastructure of the rat olfactory epithelium: the supranuclear region of the supporting cells (1991)
    Springer
    Cell & tissue research 265 (1991), S. 193-196 
    Details
    ISSN: 1432-0878
    Keywords: Postnatal development ; Olfactory epithelium ; Supporting cells ; Receptor cell dendrites ; Ultrastructure ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The present electron-microscopical study reports ultrastructural changes occurring in the supranuclear region of the supporting cells of the rat olfactory epithelium during the first 16 days of postnatal life. These changes are concerned with the enclosure of receptor cell dendrites and an increase in the amount of smooth endoplasmic reticulum, which has a specific distribution in the supporting cell. An increase in microvillous projections at the free cell surface is also observed. Moreover, this report demonstrates that the cytoarchitecture of the apical portion of the olfactory epithelium at the 16th day of postnatal life is similar, with respect to the relationship between supporting cells and receptor cell dendrites, to that of adult animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318154
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  • 39
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    Diversity of ultrastructure in different phenotypes of cultured microvessel endothelial cells isolated from bovine corpus luteum (1991)
    Springer
    Cell & tissue research 266 (1991), S. 37-49 
    Details
    ISSN: 1432-0878
    Keywords: Microvessel endothelial cells ; Cell culture ; Corpus luteum ; Ultrastructure ; Cow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Five different types of cultured microvessel endothelial cells defined by use of light microscopy and scanning electron microscopy in a preceding study were investigated by transmission electron microscopy. Type-1 cells displayed a deep invagination of the cell membrane or a single cilium. Granules of low electron density were abundant. A perinuclear ring of intermediate filaments occurred. Cultures of type-2 cells were subdivided into phenotype A, reminiscent of cell-type 1, and into phenotype B, assumed to be vascular smooth muscle cells. Many highly electron-dense granules appeared in late postconfluent cultures of both phenotypes. Cell-type 3 was conspicuous because of a large intracytoplasmic vacuole. Lysosomes with curvilinear bodies were found in cell-types 3 and 4. Both cell types developed a peripheral regular network of microfilaments. Cell-type 5 showed vesiculation of the rough endoplasmic reticulum, lipid droplets and a peripheral felt-like belt of microfilaments. Tubular forms seen in late postconfluent cultures of cell-types 1 to 3 displayed a core of extracellular matrix. Pseudotubular forms of cell-type 4 contained apoptotic bodies. Thus, as seen at the ultrastructural level, different features are maintained by cultured microvessel endothelial cells, suggesting that they have different inherent properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00678709
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  • 40
    Electronic Resource
    Electronic Resource
    Effect of cytokines on thymic hematopoietic precursors (1991)
    Springer
    Cell & tissue research 264 (1991), S. 369-375 
    Details
    ISSN: 1432-0878
    Keywords: Thymus ; CD4- ; CD8- ; thymocyte ; Thymic hematopoietic precursors ; Cytokines ; Ultrastructure ; Mouse (DBA/2, H-2d)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary We have previously shown that the interaction of thymocytes with thymic accessory cells (macrophages and/or interdigitating cells) is one of the factors required for thymocyte activation. Precursors of both thymic accessory cell and thymocytes are included in the CD4- CD8- Mac-1- Ia- subpopulation, and their respective maturation and/or activation may be modulated by granulocyte-macrophage colony-stimulating factor, interleukin 1 and interleukin 2. When CD4- CD8- thymic cells are activated with granulocyte-macrophage colony-stimulating factor plus interleukin 2, both macrophages and interdigitating-like cells are present, as shown by electron microscopy. When activated with interleukin 1 plus interleukin 2, the interdigitating-like cells is the only accessory cell present. In both culture conditions, large clusters are formed between interdigitating cells and lymphoid cells. These results have led us to propose two-step signals for thymocyte proliferation: first, the maturation of macrophages under granulocyte-macrophage colony-stimulating factor control and the production of interleukin 1, and secondly, the maturation of interdigitating cells under interleukin 1 control, their clustering with thymocytes which are then activated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00313976
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  • 41
    Electronic Resource
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    The fine structure of lamellate cells in the brain of amphioxus (Branchiostoma lanceolatum, Cephalochordata) (1991)
    Springer
    Cell & tissue research 263 (1991), S. 597-600 
    Details
    ISSN: 1432-0878
    Keywords: Lamellate cell ; Ultrastructure ; Ciliary photoreceptors ; Nervous system, prochordates ; Branchiostoma lanceolatum (Acrania)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The lamellate cells of amphioxus have round nuclei, and cytoplasm with many mitochondria and a large amount of glycogen. Each of these cells projects a highly modified, branched cilium into the central canal, where it characteristically forms lamellar structures. Primary branches and secondary lamellae often contain accessory microtubules that are not derived from the axonema. The functional and evolutionary significance of this cell type is discussed in relation to the ciliary photoreceptors found in other chordates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327295
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  • 42
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    Cell types in the fetal pars tuberalis of the human adenohypophysis at mid-gestation (1991)
    Springer
    Cell & tissue research 264 (1991), S. 161-165 
    Details
    ISSN: 1432-0878
    Keywords: Adenohypophysis ; Pars tuberalis ; Ultrastructure ; Immunohistochemistry ; Fetal ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pars tuberalis of the adenohypophysis was investigated in three human fetuses at mid-gestation by electron microscopy or immunohistochemistry. In addition to gonadotrophs and thyrotrophs, identified by immunohistochemistry and ultrastructural morphology, electron microscopy revealed the existence of an additional differentiated cell type closely resembling “pars tuberalis-specific” cells known from other species. The role of this cell type in the human endocrine regulation remains to be elucidated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00305734
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  • 43
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    Effect of 1,10-phenanthroline on ultrastructure of pea leaves (1991)
    Springer
    Protoplasma 161 (1991), S. 23-30 
    Details
    ISSN: 1615-6102
    Keywords: 1,10-Phenanthroline ; Photodynamic herbicides ; Pisum sativum ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have examined ultrastructural changes of mesophyll cells in pea leaves induced by the photodynamic herbicide 1,10-phenanthroline (Phe). Dark incubation of pea plants did not cause any damage in plants or changes in the ultrastructure of mesophyll cells. Two hours of illumination after pretreatment with Phe caused photooxidative damage in plant but was not sufficient to markedly change the ultrastructure, although dilation of endoplasmic reticulum (ER) cisternae occurred. Illumination for 12 h caused inhibition of grana formation in pretreated plants. These ultrastructural changes and the inhibition of chlorophyll (Chl) accumulation may be due to the inhibition of transport of certain proteins to the plastids, diminished accumulation of chlorophyll proteins (e.g., LHCP) and a decrease in activity of the chlorophyll synthetase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01328894
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  • 44
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    Electronic Resource
    Intercellular permeability inAbutilon nectary trichomes (1991)
    Springer
    Protoplasma 161 (1991), S. 150-159 
    Details
    ISSN: 1615-6102
    Keywords: Abutilon ; Lucifer Yellow ; Microinjection ; Nectary ; Transport ; Trichome ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Intercellular transport was examined in nectary hairs ofAbutilon slriatum var.thompsonii using dye-uptake and microinjection followed by fluorescence and electron microscopy. Dye-uptake experiments demonstrated that both Lucifer Yellow CH (LYCH) and diaminobenzidine (DAB) move centrifugally along an apoplastic pathway from the sepellary tissue towards the tip cell. Further, fluorescence of LYCH could also be detected inside the cells of the nectary trichome. When LYCH or LYCH/DAB were microinjected into the tip cell, the dye spread in a centripetal direction towards the stalk cell. Electron microscopical investigations of microinjected nectary hairs revealed numerous electron-opaque globules in the cytoplasm of the nectary hair cells. In addition, multivesicular bodies, nuclei with opaque regions and changes in the rough endoplasmic reticulum (RER) were seen in nectary hair cells even at very low concentrations of injected dye. Ultrastructural investigations provided evidence for cytological changes in microinjected nectary hairs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322727
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  • 45
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    Ultrastructure of the vegetative organisation and initial stages of silica plate deposition in the soil testate amoebaCorythion dubium (1991)
    Springer
    Protoplasma 163 (1991), S. 136-144 
    Details
    ISSN: 1615-6102
    Keywords: Corythion dubium ; Silica deposition ; Testate amoeba ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The siliceous body plates ofCorythion dubium are bound by a band of organic cement which is thickest at the lateral margins. The anterior vacuolar cytoplasm is separated by a pigment zone, which forms a dark band in the mid-body region, from the compact posterior region containing a typical vesicular nucleus surrounded by a region of dense endoplasmic reticulum. A pellicular basket of microtubules surrounds the posterior cytoplasm. The large Golgi complex lies between the nucleus and the fundus. Numerous coated and uncoated vesicles from the Golgi cisternae are seen in the peripheral cytoplasm alongside developing plates. These small siliceous plates are enclosed in silicon deposition vesicles lying in surface ruffles of the plasmalemma, often in association with a pair of microtubules. Observations are made on the formation of these vesicles and the early stages of silica deposition. A comparison is drawn between silica deposition inC. dubium and choanoflagellates where there is a similar association between silicon deposition vesicles and microtubules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01323337
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  • 46
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    Effects of heat shock and thermoadaptation on the ultrastructure of cowpea (Vigna unguiculata) cells (1991)
    Springer
    Protoplasma 163 (1991), S. 125-135 
    Details
    ISSN: 1615-6102
    Keywords: Cowpea ; Heat shock ; Thermoadaptation ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Suspension culture cells of cowpea (Vigna unguiculata) were examined using transmission electron microscopy to characterize morphological changes associated with hyperthermal stress. Cultures maintained at 26°C (unadapted cells) and 38°C (thermoadapted cells) were examined before and after exposure to elevated temperatures of 34°C and 45°C, respectively. Observations indicate that while there were significant ultrastructural differences between unadapted and thermoadapted cells, the following structural modifications in response to heat stress were observed in cells of both cultures: (a) almost a complete loss of polyribosomes, rough ER, and dictyosomes, (b) migration of intracellular waste material (presumably proteinaceous in composition) into the cell vacuole, (c) swelling of the nucleolus with assumed accumulation of preribosomal RNP granules, and (d) retraction of the tonoplast from the cytoplasm into the vacuoles of some cells. Heat shock granules (two size classes) were observed in the cytoplasm of stressed thermoadapted cells along with hollow-cored granules within the leucoplasts. Apart from a few minor differences, the morphological modifications that were made in apparent response to hyperthermal stress were remarkably similar in both cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01323336
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  • 47
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    Ontogeny and ultrastructure of spontaneous nodules in alfalfa (Medicago sativa) (1991)
    Springer
    Protoplasma 162 (1991), S. 1-11 
    Details
    ISSN: 1615-6102
    Keywords: Rhizobium meliloti ; Development ; Symbiosis ; Nitrogen fixation ; Ultrastructure ; Spontaneous nodule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The development of spontaneous nodules, formed in the absence ofRhizobium and combined nitrogen, on alfalfa (Medicago sativa L. cv. Vernal) was investigated at the light and electron microscopic level and compared to that ofRhizobium-induced normal nodules. Spontaneous nodules were initiated from cortical cell divisions in the inner cortex next to the endodermis, i.e., the site of normal nodule development. These nodules, on uninoculated roots, were white multilobed structures, histologically composed of nodule meristems, cortex, endodermis, central zone and vascular strands. Nodules were devoid of intercellular or intracellular bacteria confirming microbiological tests. Early development of spontaneous nodules was initiated by series of anticlinal followed by periclinal divisions of dedifferentiated cells in the inner cortex of the root. These cells formed the nodular meristem from which the nodule developed. The cells in the nodule meristems divided unequally and differentiated into two distinct cell types, one larger type being filled with numerous membrane-bound starch grains, and the other smaller type with very few starch grains. There were no infection threads or bacteria in the spontaneous nodules at any stage of development. This size differentiation is suggestive of the different cell sizes seen inRhizobium-induced nodules, where the larger cell type harbours the invading bacteria and the smaller type is essential in supportive metabolic roles. The ontogenic studies further support the claim that these structures are nodules rather than aberrant lateral roots, and that plant possess all the genetic information needed to develop a nodule with distinct cell types. Our results suggest that bacteria and therefore theirnod genes are not necessarily involved in the ontogeny and morphogenesis of spontaneous and normal nodules in alfalfa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01403895
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  • 48
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    The occurrence and ultrastructure of a mechanoreceptor in the human cricopharyngeus muscle (1991)
    Springer
    European archives of oto-rhino-laryngology and head & neck 248 (1991), S. 144-146 
    Details
    ISSN: 1434-4726
    Keywords: Cricopharyngeus muscle ; Golgi tendon organ ; Ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary An encapsulated nerve structure resembling the Golgi tendon organ was found in a human cricopharyngeus muscle near the cricoid cartilage where muscle fibers terminate. The capsule consisted of lamellated flattened cells with a basal lamina. Capsular cells separated the lumen into small compartments which contained myelinated and/or nonmyelinated nerve fibers. Nonmyelinated nerve fibers were also found in the interlamellar spaces of the capsular cells. Some nonmyelinated nerve fibers were dilated and contained abundant mitochondria, being partly surrounded by a Schwann cell sheath and embedded in collagen bundles. These features indicate that the nerve structure is a mechanoreceptor similar to the Golgi tendon organ. Its location and structure indicate that it is placed to detect the tension of the cricopharyngeus muscle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00178924
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  • 49
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    Properties of a single chain embedded into a polymer matrix of varied thermodynamic quality and densityDedicated to Prof. Dr. D. Braun on the occasion of his 60th birthday (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 185 (1991), S. 189-202 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The properties (squared dimensions, anisotropy, numbers of intra- and intermolecular contacts) of a single five-way cubic lattice chain embedded into an environment (matrix) of chains of the same length n = 50 were evaluated as a function of matrix volume fraction (matrix density) v and intermolecular interaction between the matrix polymer and the minority chain segments, characterized by a parameter φ. No convincing evidence was found for the occurrence of a coil-globule transition in the range of matrix densities (v ≤ 0.7) and repulsive interactions between matrix and minority chain (φ ≤ 0.2) investigated. For moderate attractive interaction (φ ≈ -0.17) a compensation of the chaincompressing action of the matrix and the chain-expanding interaction with the matrix was observed resulting in a zero-dependence of the size and shape of the minority chain on matrix density. It further turned out that there are fixed relations among the various size and shape data irrespective of the specific combination of matrix density and thermodynamic interaction by which a particular polymer dimension is produced. These interrelations are fairly the same as those evaluated for isolated chains the size of which is varied by an intramolecular energy parameter φi.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051850118
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  • 50
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    MATERIAUX TRIPHASIQUES ALVEOLAIRES POLYMERE / CHARGE / LIQUIDE OU GAZ. Préparation de Matériaux triphasiques Polystyrène / billes de Verre / Eau ou AirDédié au Prof. Dr. D. Braun à l'occasion de son 60ème anniversaire (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 185 (1991), S. 227-237 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New three phases composite materials made of glassbeads as filler, water as liquid dispersed phase and polystyrene as matrix were obtained by polymerization of a water in oil emulsion formed by water dispersed in styrene in which glass beads are added. For this purpose glass beads have to be modified by silanization by a coupling agent 3-(Trimethoxysilyl)propylmethacrylate (TPM) or a silane Octadecyltrichlorosilane (ODMS), in order to prevent the wetting of the glass by water. Only low coverage of the glass surface by the coupling agent (0,05% of TPM) are convenient for the preparation cellular materials having good mechanical properties. At higher coverage ratio, strong hydrophobic glass beads are obtained which destabilize the water / styrene emulsion and lead to macroporous products. Study of the rheology of the filled emulsion appears to be the more simple and more sensitive method to determine the level of wettability of the glass bead by the emulsion which is the most significant parameter for the preparation of such three phases composite materials. Composite materials made of glass beads, air and polystyrene are simply obtained by evaporation of water under vacuum.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051850121
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    Gas sorption in poly(butylene terephthalate). A critical test of the influence of molecular gas dataDedicated to Prof. Dr. D. Braun on the occasion of his 60th birthday (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 185 (1991), S. 265-274 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: To test the molecular parameters concerning gas sorption in polymers, the concentration of CO2, N2O, CO, N2, CH4 and the noble gases Ne, He in glassy poly(butylene terephthalate) films (PBTP) has been studied gravimetrically with a recording microbalance at 25°C. The sorption isotherms exhibit downward curvature to the pressure axis. As neither solubility nor adsorption can explain the experimental results, analysis was carried out based on the dual-sorption model: gas dissolution and microvoid filling are considered as independent sorption mechanisms. The parameters of the dual-sorption model for the mentioned penetrants are determined. The results indicate that for parameter correlation the Lennard-Jones potential parameters give a rough idea, but size exclusion of gases in small diameter microvoids is proposed and special chemical interactions must be considered.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051850125
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    RINGÖFFNENDE METATHETISCHE POLYMERISATION (ROMP) VON 5-CYANO-2-NORBORNENHerrn Prof. Dr. D. Braun zum 60. Geburtstag gewidmet (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 185 (1991), S. 283-292 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The ring opening metathesis polymerisation (ROMP) of 5-cyano-2-norbornene with tungsten hexachloride, tungesten oxytetrachloride, bis(dichloralkoxo)tungsten tetrachloride and bis(dichloralkoxo)tungsten oxydichloride as transition metal component was studied. Methylaluminoxan, diethylaluminium ethoxide, tetraisobutyldialuminoxan and tetrabutyltin served as cocatalyst. Toluene, Chlorobenzene and dichloromethane were used as solvents. The concentration of the tungsten components was in the range from 5 × 10-4 to 5 × 10-3 mol/l. Among the catalyst studied, tungsten hexachloride with diethylaluminium ethoxide proved to be the best. The polymerisation was highly selective with this system even at high monomer/tungsten ratios (e.q. 10200:1) and let to high conversions (≥82%).
    Notes: Die ringöffnende metathetische Polymerisation (ROMP) von 5-Cyano-2-norbornen wurde unter Einsatz von Wolframhexachlorid, Wolframoxidterachlorid, Bis(dichloralkoxo)wolframtetrachlorid und Bis(dichloralkoxo)wolframoxiddichlorid als Übergangsmetallkomponente untersucht. Als Cokatalysatoren dienten Methylaluminoxan, Diethylaluminiumethoxid, Tetraisobutyldialuminoxan und Tetrabutylzinn. Als Lösungsmittel wurden Toluol, Chlorbenzol und Dichlormethan verwendet. Die Konzentration der Wolframkomponente lag im Bereich 5 × 10-4 - 5 × 10-3 mol/l. Unter den geprüften Katalysatoren erwies sich Wolframhexachlorid in Verbindung mit Diethylalumiumethoxid als der geeignetste. Mit diesem System verlief die Polymerisation auch bei großen Monomer/Wolfram-Verhältnissen (10200 :1) hochselektiv und führte zu großen Umsätzen (≥82%).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051850127
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    Kinetics of radical polymerization, LIII. The absolute rate constants in the radical polymerization of ethyl acrylateDedicated to Prof. Dr. D. Braun on the occasion on his 60th birthday (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 185 (1991), S. 303-310 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dependence of dilution on the chain propagation and termination rate constants was investigated in the polymerization of ethyl acrylate in benzene solution at 50°C, with the rotating sector method. The errors of the above rate constants were determined and, by our method applied to decrease these errors, the errors of the propagation rate constant was reduced to its half value. By the application of our earlier results in polymerization kinetics, we found that in this system the chain propagation step is exclusively responsible for the solvent effects observed. Our experimental results can be quantitatively described in terms of the hot redical theory.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051850129
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  • 54
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    Organische Gläser mit hohen Glasumwandlungstemperaturen auf Basis niedermolekularer Verbindungen.Herrn Prof. Dr. D. Braun zum 60. Geburtstag Gewidmet (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 185 (1991), S. 329-334 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051850132
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    Soluble maleimide prepolymers containing 1,3,5-triazine groups as composite resin matrices. Synthesis, characterization, and evaluation (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 190 (1991), S. 1-14 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch gemeinsame Reaktion von Benzophenontetracarbonsäuredianhydrid, Maleinsäureanhydrid und Diaminen mit 1,3,5-Triazingruppen wurden niedermolekulare Prepolymere mit Amin-Endgruppen erhalten, die sowohl 1,3,5-Triazingruppen als auch Etherbindungen enthalten. Diese reaktiven Prepolymeren sind in niedrigsiedenden Lösemitteln wie z. B. Chloroform und Tetrahydrofuran löslich. Sie wurden durch Elementaranalyse, IR- und NMR-Spektroskopie, Dampfdruckosmometrie und Viskosimetrie charakterisiert. Beim Erhitzen der Prepolymeren auf Temperaturen zwischen 180 und 190°C tritt Kettenverlängerung durch Michael-Addition auf; gleichzeitig vernetzen sie durch Reaktion der Amin- mit den Maleimid-Endgruppen. Die vernetzten Polymeren sind thermisch stabil; ihr thermisches Verhalten wurde durch TGA, DTA und isotherme Alterung untersucht. Die Biegefestigkeit und interlaminare Scherfestigkeit von aus den Prepolymeren und Carbonfasergeweben hergestellten Laminaten wurden gemessen.
    Notes: Low molecular weight amine-terminated monomaleimide prepolymers containing 1,3,5-triazine groups as well as ether linkages were synthesized by reacting benzophenone tetracarboxylic dianhydride, diamines having 1,3,5-triazine group and maleic anhydride. These reactive prepolymers are soluble in low boiling solvents such as chloroform, tetrahydrofuran etc. They were characterized by elemental analyses, IR and NMR spectroscopy, vapour pressure osmometry, and viscosity. On heating at 180-190°C these prepolymers undergo simultaneous chain extension by Michael addition reaction and crosslinking by mutual reaction between their amine-terminated and maleimide-terminated ends. The cured polymers are thermostable and the thermal behaviour was studied by TGA, DTA, and isothermal aging. Laminates fabricated using these prepolymers and carbon fiber as reinforcing agent were evaluated by their flexural strength and interlaminar shear strength.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1991.051900101
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    Synthesis and properties of cationic resins derived from aniline/benzylamine-modified epoxy resins and diethylamines (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 190 (1991), S. 15-32 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ein Epoxidharz wurde durch Reaktion mit Anilin bzw. Benzylamin in unterschiedlichen molaren Verhältnissen modifiziert. Die modifizierten Harze wurden dann mit Diethylamin und anschließend mit teilblockiertem Toluylendiisocyanat umgesetzt, wobei thermisch vernetzbare Harze mit tertiären Aminen in und am Ende der Polymerkette erhalten wurden. Die partielle Ansäuerung mit Essigsäure lieferte thermisch vernetzbare kationische Harze, aus denen durch Lösen in geeigneten Lösungsmitteln und Zugabe von entionisiertem Wasser Emulsionen hergestellt wurden. Diese wurden hinsichtlich ihrer Eignung zur elektrolytischen Abscheidung untersucht und verglichen. Die Ergebnisse zeigen, daß die Abscheidungsausbeute und das Streuvermögen der Emulsionen aus Benzylamin-modifizierten Epoxidharzen besser sind als die der Anilin-modifizierten Epoxidemulsionen. Ein hohes, vom pH-Wert der Emulsion abhängiges Streuvermögen ist für diese kationischen Harze charakteristisch.
    Notes: Aniline/benzylamine-modified epoxy resins with different molecular weights, which contain tertiary amines in the middle of the polymer chain, were synthesized by the reaction of aniline/benzylamine with epoxy resin at various molar ratios. The resulting aniline/benzylamine-modified epoxy resins were reacted with diethylamine and subsequently reacted with 2-ethylhexanol-blocked toluene diisocyanate to obtain thermally crosslinkable resins which contain tertiary amines at the end and in the middle of the polymer chain. These resins were partially neutralixed with acetic acid to give thermally crosslinkable cationic resins. The resulting cationic resins were dissolved in suitable solvents and mixed with deionized water to form various emulsions. The emulsion and electrodeposition properties of these resins were studied in some detail to compare the properties of these cationic resins. The results show that the deposition yields and throwing power of the emulsions prepared from benzylaminemodified epoxy resins are higher than those of the emulsions prepared from anilinemodified epoxy resins. The emulsion having proper pH values can give a high throwing power. High throwing power is the characteristic property of these modified cationic resins. Factors determining the throwing power and deposition yield of the emulsions were also investigated.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051900102
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    Studies on new non-shrinking, thermally stable araldite-type photopolymers with pendent arylacryloyl-groups. I. Photoreaction of some aryl acrylic-acid methyl esters in solution (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 190 (1991), S. 33-52 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Arylacrylsäuren, wie Furylacrylsäure und Thienylacrylsäure können durch Knoevenagel-Reaktion der Arylcarbaldehyde mit Malonsäure in Pyridin dargestellt werden. Durch einfache Veresterung der Arylacrylsäuren in Methanol/Schwefelsäure werden die entsprechenden Arylacrylsäuremethylester mit guten Ausbeuten erhalten. Diese isomerisieren bei Bestrahlung mit UV-Licht (λ ≥ 280 nm) in methanolischer Lösung. Bei der Photoreaktion in Lösung wurde keine Photodimerisierung beobachtet. Die Reaktionskinetik der Photoreaktionen wurde untersucht.
    Notes: Aryl acrylic acids, e. g. furyl acrylic acid or thienyl acrylic acid are readily formed by the Knoevenagel condensation reaction of arylcarbaldehydes and malonic acid in pyridine. Esterification of these acids with methanol/sulfuric acid gives the corresponding aryl acrylic acid methyl esters in good yields. In methanolic solution these methyl esters isomerize upon irradiation (λ 280 nm). No photodimerization was observed. Kinetic data are given.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051900103
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    Matériaux composites à base de bois rétifié, IIIPartie 2 cf. lit.7.. Etude de l'influence de la granulométrie des charges lignocellulosiques (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 190 (1991), S. 67-80 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Different composite materials, with retified or natural poplar and polyester resin were prepared by molding. The influence of the filler granulometry on certain physicochemical (density, humidity, hardness) or mechanical properties of the materials was studied. The density and the increase of mass in humid atmosphere were always found to be less when the wood was thermally treated. On the other hand, the hardness of the composites made from natural poplar was much higher. The mechanical properties were found to be weak when the wood was retified.When the wood was thermally treated, it was possible to optimise the three parameters, namely, density, water retention capacity and mechanical properties. The optimal granulometry of poplar was determined between 0.75 and 1.5 mm.The results obtained are discussed considering the physico-chemical properties of the different varieties of wood studied and the interactions which exist between the polar resin and the wood.
    Notes: Divers matériaux composites à base de peuplier rétifié ou naturel et de résine polyester insaturée ont été préparés par moulage. L'influence de la granulométrie de la charge a été étudiée sur quelques propriétés physico-chimiques (densité, reprise d'humidité, dureté) ou mécaniques des matériaux obtenus. La densité et la reprise de masse en milieu humide sont toujours plus faibles si la charge est traitée thermiquement sous atmosphère inerte. Par contre, la dureté des composites issus du peuplier naturel est plus importante. Les propriétés mécaniques sont inférieures si la charge est rétifitée.Si la charge lignocellulosique est traitée thermiquement, il est possible d'optimiser les trois paramètres: densité, reprise d'eau et propriétés mécaniques; la granulométrie optimale du peuplier est ainsi comprise entre 0,75 et 1,5 mm.Les résultats obtenus sont expliqués en tenant compte des propriétés physico-chimiques des charges et des interactions existant entre la résine polaire et le bois.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1991.051900105
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    Pervaporation separation of water-ethanol through modified chitosan membranes, IIPart I: cf.1.. Carboxymethyl, carboxyethyl, cyanoethyl, and amidoxime chitosan membranesPresented at The 1990 International Congress on Membranes and Membrane Processes (ICOM ′90), Chicago 20 to 24 August 1990. (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 169-181 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die vorliegende Arbeit untersucht das Wasserdurchlässigkeitsverhalten von vier Arten verschieden modifizierter Chitosanmembranen zur Abtrennung von Wasser aus wäßrigen Ethanolmischungen. Chitosan wurde aus Chitin von Krebstierschalen durch Verseifung (Deacetylierung) gewonnen. Die in dieser Arbeit untersuchten modifizierten Chitosanmembranen enthielten Carboxymethyl-, Carboxyethyl-, Cyanethyl- und Amidoxim-Chitosan. Die Einführung hydrophiler funktioneller Gruppen in der 6-O Position des Chitosans erhöht die Selektivität der modifizierten Membranen im Vergleich zu den mit Essigsäure komplexierten Chitosanmembranen. Die Untersuchungen zeigen, daß Chitosanmembranen, die Carboxygruppen enthalten, die höchste Wasserdampfdurchlässigkeit aufweisen. Carboxymethyl-Chitosanmembranen zeigen eine maximale Quellung und den höchsten Ethanoldurchfluß bei einer Ethanolkonzentration von ca. 15 Gew.-% im Zulauf aufgrund von Bindungs- und Weichmachereffekten.
    Notes: The present study investigates the pervaporation performance of four kinds of modified chitosan membranes to separate water from aqueous ethanol solution. Chitosan was prepared from chitin abstracted from the crab shell and subsequently deacetylated with aqueous NaOH solution. Modified chitosan membranes examined in this study include carboxymethyl chitosan, carboxyethyl chitosan, cyanoethyl chitosan, and amidoxime chitosan. The incorporation of hydrophilic functional groups into the 6-O position of chitosan enhances the selectivity of modified chitosan membrane compared to the previously reported chitosan-acetic acid complex membrane. Among the modified chitosan membranes, membranes containing carboxy groups show the best pervaporation performance. Carboxymethyl chitosan membranes show the maximum swelling and ethanol flux at approx. 15 wt.-% feed ethanol concentration due to the coupling and plasticizing effect.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1991.051920114
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    Zusammenhänge zwischen mechanischem Verhalten und Morphologie von eigenfaserverstärkten Poly(propylen)/Poly(1-buten)-Blends, kristallisiert aus der hochorientierten Schmelze (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 183-197 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The tensile properties of self reinforced poly(propylene)/poly(1-butene) composites, obtained by rapid extension of the melt, have been measured and correlated to morphological parameters derived from x-ray experiments. Critical fiber lengths as a function of sample composition and the elastic modulus and yield stress of the fibers could be determined. It is shown, that, applying a load to the system, the forces are fully taken up by the fibers and the system breaks by fail of the fibers. The longitudinal structure of the fibers is found to be independent of sample composition.
    Notes: Mechanische Parameter wie Elastizitätsmodul, Fliß- und Bruchspannung von aus der hochorientierten Schmelze hergestellten nadelkristallinen Mischungen aus Poly(propylen) und Poly(1-bute) wurden mit morphologischen Parametern, die aus Röntgenmessungen abgeleitet wurden, korreliert. Es wird gezeigt, daß der Elastizitätsmodul des Verbundes aus den E-Moduln der Fasern und der Matrix berechnet werden kann (Mischungsregel). Die an der Probe angreifenden Kräfte werden voll auf die Fasern übertragen; der Verbund kann daher als eigenfaserverstärktes System angesehen werden. Die Abschätzung der kritischen Faserlänge ergibt, daß die Festigkeit der FAsern voll ausgenutzt wird; der Bruch des Systems bei Belastung ist daher auf das Versagen der Fasern zurückzuführen. Das mechanische Verhalten des Verbundes wird stark beeinflußt durch die Komponentenzusammensetzung. Die longitudinale Struktur der Nadeln beider Komponenten bleibt unbeeinflußt von der jeweiligen Co-Komponente.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051920115
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    Cationic polyelectrolytes, XIPart X cf.7.. Polymers with quaternary N-atoms in the main chain obtained by condensation polymerization of epichlorohydrin with amines (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 199-211 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Lösliche kationische Polyelektrolyte mit quartären Stickstoffatomen in der Hauptkette wurden durch Polykondensation von Epichlorhydrin (ECH) mit Dimethylamin (DMA) und N,N-Dialkylaminoakylaminen erhalten. Die Reaktionsparameter, die die Polymereigenschaften hauptsächlich beeinflussen, sind: Molverhältnis DMA/asymmetrische Diamine, Ausgangskonzentration der Aminlösung, Molverhältnis ECH/Amine und die Struktur der asymmetrischen Diamine. Das viskosimetrische Verhalten verdünnter wäßriger Lösungen mit oder ohne Zugabe neutraler Salze veranschaulicht die flexible Natur der Polyelektrolyten.
    Notes: Water soluble cationic polyelectrolytes containing quaternary nitrogen atoms within the main chain were prepared via condensation polymerization of epichlorohydrin (ECH) with dimethylamine (DMA) and N,N-dialkylaminoalkylamines. The main parameters of the reaction that influence the polymer properties are: DMA/asymmetrical diamine molar ratio, the initial concentration of amine solution, NaOH/amine molar ratio, ECH/amine molar ratio, and asymmetrical diamine structure. The feature of flexible polyelectrolyte own to the investigated polymers was emphasized by the viscosimetric behaviour in dilute aqueous solutions with and without salt presence.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051920116
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    MITTEILUNGEN (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 213-213 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051920117
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    Studies on rubber bound antioxidants (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 193 (1991), S. 1-11 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Antioxidantien wurden in einer modifizierten Friedel-Crafts-Reaktion mit wasserfreiem Zinkchlorid als Katalysator an Flüssig-Naturkautschuk mit Hydroxy-Endgruppen gebunden. Die immobilisierten Antioxidantien waren weniger flüchtig und extrahierbar als konventionelle Antioxidantien. Sie wurden sowohl einem Latex als auch trockenem Kautschuk zugesetzt; die daraus hergestellten Vulkanisate zeigten eine bessere Alterungsbeständigkeit als Vulkanisate mit konventionellen Antioxidantien.
    Notes: Antioxidants were attached to hydroxy-terminated liquid natural rubber by modified Friedel-Crafts alkylation reaction using anhydrous zinc chloride as catalyst. The rubber bound antioxidants were found to be less volatile and less extractable compared to conventional antioxidants. The bound antioxidants were tried both in latex compounds and dry rubber compounds. The vulcanizates showed improved ageing resistance compared to vulcanizates based on conventional antioxidants.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051930101
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    Study of the conduction mechanisms in polycarbonate (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 193 (1991), S. 13-20 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Strom-Spannungs-Charakteristik eines Bisphenol-A-Polycarbonats im Span-nungsbereich 50-1000 V und der Einfluß von UV-Bestrahlung (λ = 225 und 300 nm) und Tempern auf die elektrische Leitfähigkeit (σ) des Polycarbonats wurden untersucht. Die Abhängigkeit von σ gegen 1/T deutet auf zwei verschiedene Leitfähigkeits-mechanismen hin. Aus den Ergebnissen wurden die Aktivierungsenergien der Leitfähigkeit und die Sprungdistanzen berechnet.
    Notes: Current-voltage characteristics of polycarbonate samples (PC) have been studied in the voltage range 50-1000 V. The effect of UV-irradiation at λ = 225 and 300 nm, and thermal annealing on the electrical conductivity (σ) of PC was studied. The σ vs. 1/T relationship shows two slopes, i.e. two possible conduction mechanisms. The obtained results made it possible to determine a complete set of conduction parameters including activation energy and jump distance.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051930102
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    Porous terpolymers: Poly(acrylonitrile-co-vinyl acetate-co-divinylbenzene) (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 193 (1991), S. 21-28 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch Suspensionspolymerisation wurden Terpolymere aus Acrylnitril (AN), Vinylacetat (VA) (7,5-30 mol-%, bezogen auf AN) und Divinylbenzol (DVB) (10 Gew.-%) hergestellt. Als Verdünner wurden Mischungen von Toluol oder Cyclohexanol (90 Vo1.-%) mit Hexadecan, Octan, Dodecan, 2-Ethylhexanol oder Benzylalkohol (jeweils 10 Vo1.-%) verwendet.Die Porosität der AN-VA-DVB-Terpolymeren ist mit 0,61-0,68 größer als die der entsprechenden AN-DVB-Copolymeren. Die übermolekulare Struktur der Terpolymeren hängt vom verwendeten Verdünner ab, obwohl sich die Porositäten nicht sehr voneinander unterscheiden. Die beim Erhitzen der Terpolymeren auf Temperaturen über 200°C auftretenden thermischen Effekte sind signifikant größer als die bei der Cyclisierung von AN-Polymeren gemessenen.
    Notes: Terpolymers of acrylonitrile (AN), vinyl acetate (VA) (7.5-30 mol-%, related to AN), and divinylbenzene (DVB) (10 wt.-%) were prepared by suspension polymerization. The diluents used were mixtures of toluene or cyclohexanol (90 vol.-%) with solvents (10 vol.-%) such as hexadecane (HD), octane (O), dodecane (D), 2-ethylhexanol (E) or benzyl alcohol (B).It has been found that AN-VA-DVB terpolymers have a higher porosity, about 0.61-0.68, than corresponding AN-DVB copolymers. The terpolymers obtained with mixtures of various diluents differ in their supermolecular structure although they had similar porosity characteristics.The thermal effects accompanying heating of the terpolymers above 200°C significantly exceed that of nitrile groups cyclization observed of the other AN polymers.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1991.051930103
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    Studies on PE-HD/PE-LLD blends (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 193 (1991), S. 39-49 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die rheologischen und mechanischen Eigenschaften von Blends aus PE-HD und zwei verschiedenen PE-LLD-Typen wurden im gesamten Mischungsbereich gemessen. Die Polymeren sind im festen Zustand und in der Schmelze ausreichend verträglich, so daß ihre vorteilhaften Eigenschaften genutzt werden können.
    Notes: A high density polyethylene grade is blended with two selected grades of linear low density polyethylene and the mechanical and rheological properties of the blends are evaluated over the entire composition range. The blends show sufficient compatibility in the solid phase and in the melt and hence they can be advantageously used to capitalize on their useful properties.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051930105
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    Copolymerization reactivity ratios of N,N-dimethyl acrylamide and isopropyl methacrylate determined by 1H-NMR spectroscopy (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 51-55 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: N,N-Dimethylacrylamid (DMA) und Isopropylmethacrylat (IPM) wurden in Dimethylformamid mit Azoisobutyronitril als Initiator copolymerisiert. Die Copolymerzusammensetzung wurde 1H-NMR-spektroskopisch ermittelt. Die Copolymerisationsparameter (rDMA = 0,58, rIPM = 2,76) wurden nach Kelen-Tüdős berechnet.
    Notes: Copolymers of N,N-dimethyl acrylamide (DMA) and isopropylmethacrylate (IPM) were prepared in dimethyl formamide using azoisobutyronitrile as initiator. The composition of copolymers was determined by 1H-NMR analysis. Reactivity ratios (rDMA = 0.58, rIPM = 2.76) were calculated from these values by using the Kelen-Tüdős differential linear equation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051920104
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    Polymer molecular properties and hydrodynamic lubrication (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 69-79 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wird ein allgemeines numerisches Verfahren vorgestellt, um die Modifikation der Grundgleichung für hydrodynamische Schmierung, die von mit Polymeren versetzten Schmierölen mit scherabhängiger Viskosität erbracht wird, zu berechnen.Das Verfahren basiert auf dem verallgemeinerten Newtonschen Fileßmodell und erlaubt, alle Fileßregionen zwischen dem rein Newtonschen und dem Exponentialgesetzverhalten kontinuierlich zu behandeln. Die Ergebnisse zeigen, daß der Einfluß der scherspannungsabhängigen Viskosität durch eine dimensionslose Zahl vollkommen charakterisiert wird, nämlich U · τ*/h*, wobei U die relative Gleitgeschwindigkeit, h* die charakteristische Filmdicke und τ* die Relaxationszeit des Schmieröles darstellen.Als praktisches Beispiel wird die Anwendung des Verfahrens aufgezeigt, um den Einfluß des Molekulargewichts und der Konzentration der Polymerkomponente des Schmieröls auf die hydrodynamische Schmierung zu bestimmen. Dieser Einfluß ist durch die starke Beziehung zwischen Polymereigenschaften und τ* verursacht.
    Notes: A general numerical procedure is presented to calculate the modification of the basic equation for hydrodynamic lubrication brought about by the use of polymeric fluids with shear depending viscosity. The procedure is based on the generalized Newtonian fluid model and allows to treat continuously all the flow regions between the pure Newtonian and the power law behavior. The results show that the influence of the viscosity depending on shear stress is completely characterized by one dimensionless number, namely U.·τ*/h*, where U is the relative sliding velocity, h* is the characteristic film thickness, and τ* is a characteristic time of the lubricant. The procedure is exemplified by applying it for the determination of the influence of the molecular weight and concentration of the polymeric component of the lubricant on the hydrodynamic lubrication. This influence is brought about by the strong relation between the polymer properties and τ*.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051920106
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    Tensile properties and morphology of injection-molded poly(1-butene) (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 57-67 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Morphologien von spritzgegossenem und formgepreßtem Poly(1-buten) (PB-1) wurden im Polarisationsmikroskop und im Transmissionselektronenmikroskop untersucht. Eine dünne Oberflächenhaut und bis in den Kern der Probekörper reichende abgeplattet-sphärolithische Strukturen werden bei spritzgegossenem PB-1 beobachtet, während in formgepreßtem PB-1 typische Sphärolithe vorliegen. Das Bruchbild des spritzgegossenen PB-1 zeigt unter der Oberflächenhaut viele aufgereihte streifenartige Hohlräume, die senkrecht zur Spritzrichtung zur Mitte des Probekörpers wachsen. Aus diesen Beobachtungen kann geschlossen werden, daß eine beim Spritzgießen durch den Schmelzefluß induzierte Scherspannung nicht nur die Entstehung der Oberflächenhaut verursacht, sondern auch bis in die Mitte des Probekörpers hinein die Bildung abgeplatteter Sphärolithe bewirkt. Diese abgeplattet-sphärolithischen Strukturen sind für die beim Dehnen des spritzgegossenen PB-1 entstehenden, streifenartigen Hohlräume verantwortlich, während die Oberflächenhaut und die abgeplatteten Sphärolithe im Kern die Sprödigkeit und die im Vergleich zu formgepreßtem PB-1 geringere Bruchdehnung bewirken. Diese kann durch Tempern oberhalb des Schmelzpunktes erhöht werden.
    Notes: The injection-molded poly(1-butene) (PB-1) is found to be more brittle than the compression-molded PB-1. The morphologies of these specimens are examined by use of polarized optical microscopy and scanning electron microscopy (SEM). A skin layer and an oblate spherulitic structure extended to the core region are observed in the injection-molded PB-1, while typical spherulites exist in the compression-molded PB-1. Below the skin layer of the injection-molded PB-1, the fracture surface is found to consist of many aligned strip-like voids with ribbon edges propagating to the center of the specimen and perpendicular to the flow direction of injection-molding. Based on these observations, it can be inferred that shear stress induced by the melt flow during the injection-molding does not only cause the formation of skin layer, but also penetrates deeply into the central region of the injection-molded specimen causing the formation of oblate spherulites. The oblate spherulitic structure is responsible for the aligned voids during elongation of PB-1, while the existence of the skin layer and the oblate spherulites in core region is responsible for the brittleness of the injection-molded PB-1. The elongation of the injection-molded PB-1 is found to be lower than that of the compression-molded. This can be attributed not only to the presence of the skin layer but also to the oblate spherulites in the core region. The elongation can be improved by annealing at a temperature above the melting point of PB-1.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051920105
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    Synthesis and biological activity of chlorinated polyketone resins (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 103-111 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch Kondensation von p-Xylol mit Chloracetylchloride, 1,2-Dichlorethan und Dichlormethan mit Aluminiumtrichlorid in Schwefelkohlenstoff wurden Polyketone hergestellt und IR-spektroskopisch sowie bezuglich des Molekulargewichtes charakterisiert. Die thermischen Eigenschaften wurden thermogravimetrisch und mittels DSC untersucht. Die Prüfung der Harze auf ihre biologische Aktivität gegen Pseudomonas fluorescens, Bacillus subtilis and Aspergillus niger ergab, daß deren Wachstum durch die Polyketonharze kontrolliert werden kann.
    Notes: Some polyketones were prepared from p-xylene, chloroacetylchloride, 1,2-dichloroethane and dichloromethane using anhydrous aluminiumtrichloride and carbon disulfide as solvent. The resins thus obtained have been characterized by IR spectra and number average molecular weight. The thermal properties have been studied by thermogravimetry and differential scanning calorimetry. All the resins were tested for their biological activity against Pseudomonas fluorescens, Bacillus subtilis and Aspergillus niger. The results show that the growth of the tested organisms can be controlled by the polyketone resins.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051920109
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    The reaction of pyromellitic dianhydride with 4,4′-diaminodiphenylmethane (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 145-153 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In der Arbeit wurde die homogene Polyaddition von Pyromellitsäuredianhydrid und 4,4′-Diaminodiphenylmethan untersucht. Die Abhängigkeit des zahlenmittleren Molekulargewichts (M̄n) von der Zeit weist ein Maximum auf. Die Ursache der niedrigen Gleichgewichtswerte von M̄n beruht auf einer durch Wasserspuren im Lösungsmittel verursachten Dianhydridhydrolyse und damit einer gestörten Äquimolarität der funktionellen Gruppen. Im Laufe der Stabilisierung des M̄n-Gleichgewichtswertes entsteht auch die wahrscheinlichste Molmassenverteilung.
    Notes: The homogeneous polyaddition reaction of pyromellitic dianhydride with 4,4′-diaminodiphenylmethane was investigated. The dependence of the number average molecular weights on time has a maximum; low equilibrium values of M̄n are caused by a disturbed equimolarity of functional groups due to the hydrolysis of dianhydride with water present in the solvent. In the course of establishment of the equilibrium M̄n value, the molecular weight distribution changes to the most probable value.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051920112
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    Miscibility of polyarylate/phenoxy/poly(butyleneterephthalate) ternary blends (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 133-144 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Das Phasen- und Mischbarkeitsverhalten der binären und ternären Polymermischungen von Polyarylat (PAR), Phenoxid und Poly(butylenterephthalat) (PBT) wurde untersucht. Die Mischungen wurden durch Ausfällen aus gemeinsamen Lösungen hergestellt, und die Mischbarkeit wurde durch DSC-Messungen und Transparenz der Schmelze beurteilt. Im Falle der binären Blends zeigten PAR/PBT und Phenoxid/PBT Mischbarkeit, während sich PAR/Phenoxid nicht mischen ließ. Die Mischbarkeitstendenz der unmischbaren PAR/Phenoxid-Mischungen konnte jedoch durch Zugabe von PBT erhöht werden; eine ausreichende Menge PBT machte die ternären Mischungen mischbar, so daß diese eine einzige Tg in der DSC-Kurve zeigten. Im ternären Phasendiagramm war das Maximum der Mischbarkeitsgrenze in Richtung auf die Phenoxidseite hin verschoben, was auf die bessere Mischbarkeit von PAR/PBT im Vergleich zu Phenoxid/PBT zurückgeführt wird.
    Notes: The phase and miscibility behavior of binary and ternary blends containing polyarylate (PAR), polyhydroxyether of bisphenol AIUPAC: poly[oxy(2-hydroxytrimethylene)oxy-1,4-phenylene-isopropylidene-1,4-phenylene]. (Phenoxy), and poly(butylene terephthalate) (PBT) were studied. The blends were prepared by solution-precipitation method and miscibility was examined by DSC and melt transparency. In binary blends, PAR/PBT and Phenoxy/PBT blends show miscibility, while PAR/Phenoxy appeared to be immiscible. However, the miscibility of incompatible PAR/Phenoxy blend was enhanced by addition of PBT. The addition of sufficient amount of PBT caused the ternary blend to have a single glass transition temperature. The shape of miscibility boundary of ternary blend was skewed to the apex of Phenoxy, which was attributed to the better miscibility of PAR/PBT than that of Phenoxy/PBT.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051920111
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    Solid-state polycondensation of poly(ethylene terephthalate) films (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 155-168 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Festphasen-Polykondensation von amorphen, unorientierten Poly(ethylenterephthalat)-Folien (PET) (Vorstufe der Du Pont Mylar® -Polyesterfilme), die mit einem speziellen Katalysator-und Monomer-System hergestellt wurden, war Gegenstand dieser Arbeit. Der Einfluß verschiedener Reaktionsparameter, wie Reaktionstemperatur und -zeit, auf die inhärente Viskosität (ηinh) und auf die Anzahl der Carboxy-und Hydroxy-Endgruppen wurde untersucht. Aus den Messungen von ηinh wurde eine empirische Gleichung erstellt, die die Berechnung von M̄n der PET-Folien nach der Festphasen-Polykondensation bei gegebener Zeit und Temperatur erlaubt. Das Schmelzverhalten verschiedener Festphasen-Polykondensate wurde ebenfalls untersucht.
    Notes: The solid-state polycondensation of poly(ethylene terephthalate) (PET) amorphous and unoriented films from Du Pont (precursor for their Mylar® Du Pont's registered trade mark for the polyester film. polyester film) prepared from a specified catalyst and monomer system has been studied. The effect of various reaction parameters such as reaction temperature and time on inherent viscosity (ηinh) and number of carboxy and hydroxy end-groups has been investigated. From ηinh measurements an empirical equation was taken which allows the calculation of (M̄n) of PET film after solid-state polycondensation at a certain temperature and time. The melting behaviour of the solid-state polycondensated samples was also studied.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051920113
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    Preparation and properties of porous particles from trimethylolpropane trimethacrylateSystematic UIPAC name: 2,2-bis(methacryloyloxymethyl)butyl methacrylate. (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 113-132 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Sphärische makroporöse Partikel, die als Trägermaterialen für verschiedene Säulen-Operationen eingesetzt werden sollen, wurden mittels Suspensions- und Mikrosuspensionspolymerisation von Trimethylolpropan-trimethacrylat (TRIM) in Gegenwart verschiedener Mengen porogener Reagenzien (Toluol bzw. Mischungen von Toluol und Isooktan) hergestellt. Textur und Eigenschaften der Partikel variierten deutlich mit dem Anteil und der Zusammensetzung des porogenen Reagens und wurden zusätzlich durch die Wahl des Suspensionstabilisators beeinflußt. Die makroporösen Partikel wiesen ein Gesamtporenvolumen von 0,4 bis 3,6 cm3/g und eine spezifische Oberfläche von 7 bis 〉 450 m2/g auf. Alle Partikel enthielten Makroporen und, außer den Teilchen mit sehr niedriger spezifischer Oberfläche, einen gewissen Anteil an Mikroporen (Durchmesser 〈 60 Å). Durch Erniedrigung der Monomerkonzentration und Erhöhung des Isooktan-Gehaltes im porogenen Reagens auf 50 Gew.-% konnte das Auftreten von Mikroporen vollständig unterdrückt werden. Das Erhöhen des Isooktan-Gehaltes führte zu einem vergrößerten Gesamtporenvolumen und zu einem verringerten Quellvermögen der Polymermatrix in Toluol. Der Einfluß einer Hitzebehandlung bei 130°C und eines Aufpfropfens von Polymethylmethacrylat auf die Partikeleigenschaften wurde ebenfalls untersucht.Die Menge an nicht umgesetzten Doppelbindungen in den Partikeln konnte durch Variation der Polymerisationstemperatur verändert werden. Das Vorhandensein leicht zugänglicher Doppelbindungen ist wichtig, da sie zur Funktionalisierung der festen makroporösen Partikel verwendet werden können.
    Notes: Spherical macroporous particles, intended for use as carrier particles in various types of column operations, were prepared by suspension and microsuspension polymerization of trimethylolpropane trimethacrylate (TRIM), in the presence of various amounts of porogenic agents (toluene or mixtures of toluene and isooctane). The texture and properties of the particles varied markedly with the amount and composition of the porogenic agent, and were also affected by the choice of suspension stabilizer. Macroporous particles were prepared, ranging in total pore volume from 0.4 to 3.6 cm3/g, and in specific surface area from 7 to 〉450 m2/g. All of the particles contained macropores, and except for those with very low specific surface area, contained a certain fraction of micropores (diameter 〈60 Å). The presence of micropores could be eliminated completely by decreasing the monomer concentration and increasing the isooctane content of the porogenic agent to 50 wt.-%. Increasing the isooctane content also resulted in an increase in the total pore volume and a decrease in the tendency of the polymer matrix to swell in toluene. The effect on properties of particles by heat treatment at 130°C and by grafting poly(methyl methacrylate) onto the particles was also studied.The amount of unreacted double bonds of the particles could be varied by varying the polymerization temperature. The presence of easily accessible double bonds is important as they can be utilized for functionalization of the rigid macroporous particles.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051920110
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    Interfacial adhesion in short-fibre composites (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 191 (1991), S. 31-38 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Eine einfache Methode für die Bestimmung der Grenzflächenhaftung in kurzfaserverstärkten Polymeren, beruhend auf der Längenverteilung von aus der Bruchfläche herausgezogenen Faserteilen, wurde entwickelt. Die Messungen mit Faserverbundwerkstoffen von isotaktischem Polypropylen mit 32 Gew.-% Kurzglasfasern bestätigen die Brauchbarkeit dieser Methode für eine empfindliche Beurteilung von Unterschieden in der Grenzflächenhaftung. Die Einflüsse von Temperatur, Polymer- und Glasfasermodifizierung sowie Faserorientierung auf die Grenzflächenhaftung wurden untersucht.
    Notes: For the evaluation of the interfacial adhesion in short-fibre composites, a simple method based on fibre pull-out length distribution was proposed. The experiments with three composites of isotactic polypropylene with 32 wt.-% of short-glass fibres confirm the potentials of the method for a sensitive determination of differences in the interfacial adhesion. The effects of temperature, crystallinity and fibre orientation angle on the interfacial adhesion were investigated.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051910103
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    Functionalization of polyethylene and ethylene propylene diene terpolymer in the bulk through dibutyl maleate grafting (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 191 (1991), S. 15-30 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: PE und EPDM-Kautschuk wurden durch Aufpfropfen von Dibutylmaleat (DBM) mit Dicumylperoxid (DCP) als Initiator in Substanz im Temperaturbereich von 140-220°C funktionalisiert. Der Pfropfungsgrad wurde IR-spektroskopisch und durch DSC-Messungen ermittelt. Die für die Pfropfung optimalen DBM- und DCP-Konzentrationen betragen 0,5 bzw. 0,2 Gew.-%. Die Kinetik der Pfropfreaktion ist für PE und EPDM vergleichbar; die Aktivierungsenergien betragen ca. 145 bzw. 130 kJ/mol. Die Pfropfungsgrade sind für PE höher als für EPDM; bei PE/EPDM-Blends steigt der Pfropfungsgrad mit zunehmendem PE-Anteil. Ein Pfropfungsmechanismus, der Nebenreaktionen berucksichtigt, wird vorgeschlagen.
    Notes: Functionalization of polyethylene (PE) and ethylene propylene diene terpolymer (EPDM) in the bulk through dicumyl peroxide (DCP) initiated grafting of dibutyl maleate (DBM) has been studied in the temperature range from 140 to 200°C. The degree of grafting has been determined by infrared spectrophotometry and DSC. The concentration of DBM and DCP has been optimized. 0.5 wt.-% and 0.2 wt.-% DCP for PE and EPDM, respectively, and 10% DBM for both have been found to be the optimum. The kinetics of the grafting reaction is comparable for PE and EPDM. The activation energy of grafting is ca. 145 kJ/mol for PE and ca. 130 kJ/mol for EPDM. The influence of structure of polyolefins on the degree of grafting has also been studied. A higher degree of grafting is obtained for PE than for EPDM. For PE/EPDM blends, the degree of grafting increases with increasing PE content in the blends. A through discussion and proposed mechanism for grafting and other competitive secondary reactions has been provided.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051910102
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    Effect of surface structure of porous silica microballoons on dynamic mechanical properties of amine cured epoxy resin composites (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 191 (1991), S. 71-80 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die dynamisch-mechanischen Eigenschaften von gehärteten Epoxidharzen, gefüllt mit porösen Siliciumdioxid-Mikrokugeln mit unterschiedlichen spezifischen Oberflächen, Porenradien, Porenvolumina und adsorbierter Wassermenge, wurde untersucht. Die Glasubergangstemperaturten (Tg) der Composite sind 12-14°C niedriger als die des ungefullten Harzes, was auf die bevorzugte Adsorption von Härter an den porösen Mikrokugeln zurückgeführt wird. Mit zunehmender adsorbierter Wassermenge steigt die Tg der Composite an. Der Speichermodul ist mit der mit Quecksilber bestimmten spezifischen Oberfläche (Hg-Oberfläche) der Mikrokugeln, die der Summe der Oberfläche von Poren mit einem Durchmesser größer als 4 nm entspricht, korreliert.Das Verbältnis tan δc/tan δm nimmt mit zunehmender Hg-Oberfläche ab.
    Notes: Dynamic mechanical properties were studied for epoxy resin filled with porous silica microballoons with varying surface area, pore radius, pore volume and adsorbed water. The glass transition temperature (Tg) of the composites is 12-14°C lower than the Tg of the unfilled epoxy resin. This Tg depression is attributed to the preferential adsorption of curing agents on the porous silica microballoons. Tg of the composite increases with increase in the adsorbed water on fillers. The storage modulus has a distinct correlation with the Hg-surface area of silica microballoons, which corresponds to the sum of the surface area of pores with radii larger than about 4 nm.Tan δc tan δm decreases with increasing Hg-surface area.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051910105
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    Pervaporation separation of pentane-alcohol mixtures through ionically crosslinked blended membranes. I. Thermal measurements, electron microscopy and tensile studies (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 191 (1991), S. 39-69 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Membranen aus Blends von Nylon 6 mit Poly(acrylsäure) (PAA) mit PAA-Gehalten zwischen 25 und 45 Gew.-% wurden durch Filmgießen hergestellt und anschließend durch Eintauchen in eine Aluminiumsalzlösung ionisch vernetzt. Die Glasübergangstemperaturen (Tg) der Membranen wurden mit der DSC-Methode bestimmt. Alle Proben zeigen eine einzige Tg oberhalb der Tg der Homopolymeren, die sich mit zunehmender Scanzeit verschiebt; dies wird auf die Eliminierung von Wasser und die Bildung von Anhydriden im nicht vernetzten PAA-Anteil zurückgeführt.Die Morphologie wurde rasterelektronenmikroskopisch untersucht; die Membranen zeigen eine dichte, porenfreie Struktur ohne Phasenseparation, was auf eine völlige Mischbarkeit der beiden Homopolymeren im untersuchten Zusammensensetzungsbereich schließen läßt. Die Festigkeit der Membranen liegt je nach PAA-Gehalt zwischen 5 und 26 MPa; Membranen mit hohem PAA-Anteil zeigen trotz höherer Vernetzungsdichte eine geringere Zugfestigkeit, was mit der geringen Festigkeit von PAA und der mit größerem PAA-Anteil zunehmenden Quellung zusammenhängt. Letztere wurde durch Messen der Wasseraufnahme trockener Membranen bestimmt; sie steigt von 23,6 Gew.-% bei einem PAA-Gehalt von 25 auf 76,3 Gew.-% bei einem PAA-Gehalt von 45 Gew.-%.
    Notes: Ionically crosslinked blended membranes were prepared from blends of nylon 6 and poly(acrylic acid) (PAA) with the proportion of PAA ranging from 25 to 45 wt.-%. The technique consists of casting a film of the blend, followed by drying and immersion in an aluminum salt crosslinking solution for a predetermined time. The glass transition temperature (Tg) of the membranes was determined by differential scanning calorimetry (DSC). All the samples exhibited a single Tg, which is higher than that of either polymer. There is also a shift in the Tg with increasing scanning time. This phenomenon is attributed to the elimination of water molecules and the formation of anhydrides in the non-crosslinked PAA portion of the membrane. The membrane morphology was studied using scanning electron microscopy (SEM) and shows a dense structure without any pores. No phase separation is observed by scanning cross-sections of the samples, indicating that nylon 6 and PAA are completely miscible in the ranges studied. The membrane material strength lies in the range of 5 to 26 MPa and varies with the amount of PAA in the membrane. Samples with higher PAA content show lower tensile strength in spite of increased crosslinking density. This is due to the inherent low strength of PAA, coupled with increasing swelling of the membrane with increasing PAA content. The latter is confirmed by the measurement of water uptake into a dry membrane which increases from 23.6% to 76.3% with the membrane PAA content increasing from 25 to 45 wt.%.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051910104
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    Mehrphasensysteme auf basis von fluorpolymeren, 1. Modifizierung von füllstoffoberflächen (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 191 (1991), S. 81-107 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Practically no adhesion is observed at the interface poly(tetrafluoroethylene)/glass fiber. We have investigated methods to improve adhesion between these interfaces. We have also discussed the question of possible reinforcement, i.e. increase of tensile strength and a simultaneous decrease of elongation.In this first part we present some calculations demonstrating the prerequisites for reinforcement using existing theoretical models. We describe the influence of modification of the glass fiber surface by dispersion coating or by plasma polymerization.In a second part the influence of polymer surface modification and of additives will be dealt with.
    Notes: In Mehrphasensystemen aus Poly(tetrafluorethylen) (PTFE) und Glasfasern besteht praktisch keine Haftung zwischen Matrix und Füllstoff. Es wurde der Frage nachgegangen, ob es Wege zur Verbesserung der Grenzflächenhaftfestigkeit gibt und ob diese Verbesserungen ausreichen, eine Verstärkung, d. h. Anhebung der Reißfestigkeit bei gleichzeitigem Rückgang der Dehnung des Gesamtsystems zu erzielen.In diesem ersten Teil wird den theoretischen Voraussetzungen und der Modifizierung der Füllstoffoberflächen mittels Dispersionsbeschichtungen sowie Plasmaätzen und Plasmapolymerisation nachgegangen.In einem zweiten Teil werden Möglichkeiten zur Verbesserung der Grenzflächenhaftung durch Modifizierung der Polymer-Oberfläche und durch Additive untersucht.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051910106
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    Mehrphasensysteme auf basis von fluorpolymeren, 2Teil 1 siehe1.. Modifizierung der polymermatrix (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 191 (1991), S. 109-126 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Practically no adhesion is observed at the interphase of poly(tetrafluoroethylene)/glass fiber. We have investigated methods to improve this adhesion and discuss the influence of this improved adhesion on the mechancial properties of the multiphase system.In this paper the influence of a modified polymer surface and of additives is described.
    Notes: In Mehrphasensystemen aus Poly(tetrafluorethylen) (PTFE) und Glasfasern besteht praktisch keine Haftung zwischen Matrix und Füllstoff.Es wurde die Frage untersucht, ob es Methoden gibt, diese Grenzflächenhaftung zu erhöhen und welchen Einfluß diese Erhöhung auf die Eigenschaften des Verbundsystems hat.In dem hier vorliegenden Teil 2 wird speziell auf den Einfluß der Modifizierung der Polymeroberfläche und des Zusatzes von Additiven eingegangen.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051910107
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    Zur reaktionstechnischen und fluiddynamischen stabilität von multirohrreaktoren für die massepolymerisation (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 191 (1991), S. 127-144 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Due to the very strong variation of the viscosity of the reaction mass with increasing monomer conversion, three stationary states for the tubes of a multitubular system with cooling vessel can be found. As a consequence, a maldistribution of the fluid arises, so that the reactor stability and the polymer quality are negatively influenced. The recycling of the reaction mass is a helpful method to increase the reactor stability. In this paper some fundamental aspects of the use of multitubular reactors for the polymerization of styrene are studied.
    Notes: Infolge der sich mit steigendem Monomerumsatz stark verändernden Viskosität der Reaktionsmasse existieren im Multirohrreaktor mit Kühlung mindestens drei stationaäre Punkte bezüglich des Einzelrohrmassenstromes gleichzeitig. Als Konsequenz ergibt sich eine Ungleichverteilung der Rohrbelastung, die sowohl die Reaktorstabilität als auch die Polymerqualität negativ beeinflußt. Das Betreiben einer Rückführung kann das Reaktorverhalten stabilisieren. In der vorgelegten Arbeit werden einige fundamentale Aspekte der Anwendung von Multirohrreaktoren für die Massepolymerisation von Styrol untersucht.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/apmc.1991.051910108
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    Nucleophilic substitution reaction of ethanolamine onto poly(phenyl acrylate) and substituted poly(phenyl acrylate)s (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 191 (1991), S. 171-176 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die nucleophile Substitution von verschieden substituierten Phenoxygruppen in Polyphenylacrylaten durch Ethanolamin in Dioxan wurde bei 60, 80 und 100°C untersucht. Der Umsatz wurde IR- und 1H-NMR-spektroskopisch und elementaranalytisch bestimmt; er hängt sowohl von der Temperatur als auch von der Art der Substituenten am Phenylring ab.
    Notes: The nucleophilic substitution reaction of differently substituted phenoxy groups with ethanolamine in various poly(phenyl acrylate)s was investigated in dioxane at 60, 80, and 100°C. The conversion, as determined from IR- and 1H-NMR spectroscopy and elemental analysis, depends on the temperature and the kind of substituents at the phenyl ring.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/apmc.1991.051910111
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  • 83
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    Masthead (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310101
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  • 84
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    Heteronuclear two-dimensional 15N- and 13C-nmr studies of DNA oligomers and their netropsin complexes using indirect proton detection (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 45-55 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Heteronuclear multispin coherence proton-detected two-dimensional nmr spectroscopic experiments were used to obtain information on protonated carbons and nitrogens of the self-complementary d (G-G-T-A-T-A-C-C) and d (G-G-A-A-T-T-C-C) duplexes, with and without the drug netropsin dissolved in aqueous solution. Many correlations of protons coupled to 13C nuclei on the base and sugar rings of the octanucleotides were detected, allowing the carbon resonances to be assigned based on previous homonuclear proton two-dimensional nmr studies. Imino nitrogen assignments can also be made using the proton assignments from previous one-dimensional nuclear overhauser effect experiments. Imino nitrogen shifts may be useful indicators of changes in local hydrogen-bonding interactions to base-pair edges.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360310105
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  • 85
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    Polyelectrolyte properties of biopolymers: Conductivity and secondary structure of polyriboadenylic acid and its salts in solutions (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 65-76 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyriboadenylates of alkali metals were obtained from (1) K+-poly(A) (salts I) and (2) H+-poly( A) (salts II) by the ion-exchange method. The conductivity of these salts as well as of H+-poly(A) were studied. Salts I and II of the same counterion were shown to have significantly different conductivity coefficients (f) and polyion conductances (λp0). The charge density parameter (ζ) was 1.3 and 2.5, respectively, with λp0 equal to 44 and 83 ohm-1 cm2 mole-1 for poly(A)-I and poly (A)-II salts, respectively. This is credited to the difference in the conformations of corresponding polyions. The linear dependence of equivalent conductivity on the square root of polymer concentration (Kohlrausch coordinates), earlier obtained for DNA, is also satisfied for the studied polynucleotides. A comparison of the slopes of straight lines in Kohlrausch coordinates for poly(A), simple electrolytes, and for earlier studied polyribouridylic acid salts lends credence to the concepts, developed by a number of authors, that DNA can act as a “buffer” against the ion-ion interaction in concentrated electrolyte solutions. Using the approximation that the polyion conductance is independent of the counterion nature, parameter f (agreeing in this case with Eisenberg parameter φ) has been shown to decrease as the polynucleotide concentration is increased; the decrease is caused by the relaxation effect. The transference numbers of counterions, which have negative values in poly (A)-II solutions, grow with the increase in polymer concentration; the higher the ζ, the more apparent is this increase. This is explained by the increase in the fraction of conductivity along the polyion chains (“surface” conductivity) with the growth of polyelectrolyte concentration.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360310107
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  • 86
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    Study of the “molten globule” intermediate state in protein folding by a hydrophobic fluorescent probe (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 119-128 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Binding of the hydrophobia fluorescent probe, 1-anilino-naphthalene-8-sulfonate (ANS), to synthetic polypeptides and proteins with a different structural organization has been studied. It has been shown that ANS has a much stronger affinity to the protein “molten globule” state, with a pronounced secondary structure and compactness, but without a tightly packed tertiary structure as compared with its affinity to the native and coil-like proteins, or to coil-like, α-helical, or β-structural hydrophilic homopolypeptides.The possibility of using ANS for the study of equilibrium and kinetic molten globule intermediates is demonstrated, with carbonic anhydrase, β-lactamase, and α-lactalbumin as examples.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360310111
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  • 87
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    Premelting thermal fluctuational base pair opening probability of poly(dA) · poly(dT) as predicted by the modified self-consistent phonon theory (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 139-148 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We employ a mean field, modified, self-consistent phonon theory to evaluate the single base-pair opening rate and the probability of a base pair in the amino proton exchangeable state for the homopolymer poly(dA) · poly(dT) at temperatures below the helix-coil transition region. Our calculated premelting single base-pair opening probabilities are in general agreement with several available experimental estimates from imino proton exchange and formaldehyde-induced DNA melting measurements. These calculated opening probabilities, however, are in disagreement with the prediction of the helix-coil transition theory. Possible reasons for the differences are discussed, especially the possible different definition of a meaningful open state in the premelting region. The premelting open state of the modified self-consistent phonon approximation theory seems to be appropriate to describe a solvent-accessible open configuration that is sufficient to facilitate important chemical reactions such as imino proton exchange and formaldehyde reaction with the bases. This can be compared with the completely unstacked open state of the helix-coil transition theory originally defined in the helix-coil transition region. We propose that the amino proton exchangeable state is different from the open state associated with melting and only involves the breaking of the amino interbase H bond. The agreement between the calculated and experimentally estimated probability of a base pair in the amino proton exchangeable state seems to support this hypothesis.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360310202
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  • 88
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    Shielding effects of small ions in gel electrophoresis of DNA (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 169-176 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Results of free electrophoresis and free sedimentation of charged rods are introduced to allow for electrical double-layer effects in the gel electrophoresis of DNA, modeled as a Random flight sequence of rodlike Kuhn chain elements. The kinetics of DNA is shown to depend strongly on the orientation of the chain elements with respect to the external field and with respect to the direction of their velocity. The new theory gives approximate agreement between the DNA charge derived from electrophoresis of free and tethered DNA (close to 1.0e per DNA phosphate in both cases), compared with the earlier discrepancy of a factor 10 or 20 for the theory without shielding by salt. As part of a realistic force field for macromolecular dynamics simulation, the small ion effects are included in an expression for the gel forces restraining the DNA in gel electrophoresis from moving as in free electrophoresis.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360310205
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  • 89
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    A molecular dynamics study of the effect of G · T mispairs on the conformation of DNA in solution (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 211-232 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of G · T mispair incorporation into a double-helical environment was examined by molecular dynamics simulation. The 60-ps simulations performed on the two hexanucleotide duplexes d (G3C3)2 and d (G3TC2)2 included 10 Na+ counterions and first hydration shell waters. The resulting backbone torsional angle trajectories were analyzed to select time spans representative of conformational domains. The average backbone angles and helical parameters of the last time span for both duplexes are reported. During the simulation the hexamers retained B-type DNA structures that differed from typical A- or B-DNA forms. The overall helical structures for the two duplexes are vary similar. The presence of G · T mispairs did not alter the overall helical structure of the oligonucleotide duplex. Large propeller twist and buckle angles were obtained for both duplexes. The purine/pyrimidine crossover step showed a large decrease in propeller twist in the normal duplex but not in the mismatch duplex. Upon the formation of wobble mispairs in the mismatched duplex, the guanines moved into the minor groove and the thymines moved into the major groove. This helped prevent purine/purine clash and created a deformation in the relative orientation of the glycosidic bonds. It also exposed the free O4 of the thymines in the major groove and N2 of the guanines in the minor groove to interactions with solvent and counterions. These factors seemed to contribute to the apparently higher rigidity of the mismatched duplex during the simulation.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360310209
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  • 90
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    Biased sinusoidal field gel electrophoresis for size-dependent DNA separation (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 253-254 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310212
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  • 91
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    Evidential study of correlated events in biochemistry: Physicochemical mechanisms of nucleic acid hydration as revealed by factor analysis (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 255-273 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a factor analysis technique, the experimental physicochemical data on the hydration of mononucleotides, several polynucleotides, their double-helical complexes and natural DNAs were studied. The information about the factors determining the changes in physicochemical parameters vs the hydration was obtained. This work discusses a possible physical sense of the factors obtained and the expedience of using factor analysis to interpret the molecular-biophysical experiments.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310302
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  • 92
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    The Electrostatically Driven Monte Carlo method: Application to conformational analysis of decaglycine (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 319-330 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Electrostatically Driven Monte Carlo (EDMC)method was applied in a study of a decamer of glycine whose conformational behavior is described by the Empirical Conformational Energy Program for Peptides (ECEPP/2) potential energy model. When free neutral end groups were used, it was found that conformations that were not α-helical had significantly lower potential energies than fully α-helical ones. However, when the N- and C-termini were blocked by acetyl and methyl amide groups, respectively, the number of unsatisfied hydrogen-bond donors and acceptors at the helix termini was diminished from 8 to 6; in this case, the possibility of forming two additional α-helical hydrogen bonds was an important enough factor in making the α-helical conformation the one with the lowest energy. The EDMC method was used as a global energy optimizer since it does not often become trapped in high-energy local minima.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360310306
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  • 93
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    1H- and 31P-nmr studies of ditercalinium binding to a d(GCGC)2 and d(CCTATAGG)2 minihelices: A sequence specificity study (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 331-353 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structures of the complexes formed in aqueous solution between ditercalinium, a bisintercalating drug, and both the self-complementary tetranucleotide d(GCGC)2 and octanucleotided(CCTATAGG)2, have been investigated by 400-MHz 1H-nmr and 162-MHz 31P-nmr. All the nonexchangeable protons, as well as the exchangeable imino protons and the phosphorus signals, have been assigned. Both oligonucleotides have been shown to adopt a right-handed B-DNA type structure. The addition of ditercalinium to the oligo-nucleotides lead to the formation of complexes in slow exchange at the nmr time scale with the free helices. At all drug-to-helix ratios studied, the ditercalinium was found in the bound form, whereas free and complexed oligonucleotides were in slow exchange, allowing resonance assignments through two-dimensional chemical exchange experiments.For d(GCGC)2 the strong upfield shifts induced on all aromatic protons of both the bases and the drug by complexation with ditercalinium suggest an interaction by intercalation of the two rings. However, the loss of twofold symmetry upon binding, as well as the chemical shift variation of the drug proton signals of one of the chromophores with temperature and concentration, favor a model in which the drug-nucleotide complexes have one ring of the drug intercalated and the other stacked on top of the external base pair. The intermolecular contacts between drug protons and nucleotide protons give a defined geometry for complexation that is consistent with the proposed model.In contrast, with d(CCTATAGG)2 several drug-nucleotide complexes were formed and a large increase in line broadening was observed at high drug-to-DNA ratios, precluding a detailed analysis of these complexes. However, the large upfield shift in the imino proton resonances together with the shielding of the ditercalinium ring protons favor a model with bis-intercalation of ditercalinium. This model is supported by the downfield shift of at least 4 out of 14 phosphorus signals. The results are compared with those obtained on ditercalinium binding to the homologous sequences d(CGCG)2 and d(TTCGCGAA)2, and discussed in terms of sequence specificity.
    Additional Material: 24 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360310307
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    A sequence preference for nucleation of α-helix - crystal structure of Gly-L-Ala-L-Val and Gly-L-Ala-L-Leu: Some comments on the geometry of leucine zippers (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 397-407 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthetic peptide Gly-L-Ala-L-Val (C10H19N3O4·3H2O; GAV) crystallizes in the monoclinic space group P21, with a = 8.052(2), b = 6.032(2), c = 15.779(7) Å, β = 98.520(1)°, V = 757.8 Å3, Dx = 1.312 g cm-3, and Z = 2. The peptide Gly-L-Ala-L-Leu (C11H21N3O4·3H2O; GAL) crystallizes in the orthorhombic space group P212121, with a = 6.024(1), b = 8.171(1), c = 32.791(1) Å, V = 1614 Å3, Dx = 1.289 g cm-3, and Z = 4. Their crystal structures were solved by direct methods using the program SHELXS-86, and refined to an R index of 0.05 for 1489 reflections for GAV and to an R index of 0.05 for 1563 reflections for GAL. The tripeptides exist as a zwitterion in the crystal and assume a near α-helical backbone conformation with the following torsion angles: ψ1 = -150.7°; φ2, ψ2 = -68.7°, -38.1°; φ3, ψ31, ψ32, = -74.8°, -44.9°, 135.9° for GAV; ψ1 = -150.3°; φ2, ψ2 = -67.7°, -38.9°; φ3, ψ31, ψ32 = -72.2°, -45.3°, 137.5°, for GAL. Both the peptide units in both of the tripeptides show significant deviation from planarity [ω1 = -171.3(6)° and ω2 = -172.0(6)° for GAV; ω1 = -171.9(5)° and ω2 = -173.2(6)° for GAL]. The sidechain conformational angles χ21 and χ22 are -61.7(5)° and 175.7(5)°, respectively, for valine, and the side-chain conformations χ12 and χ23's are -68.5(5)° and (-78.4(6)°, 159.1(5)°) respectively, for leucine. Each of the tripeptide molecule is held in a near helical conformation by a water molecule that bridges the NH3+ and COO- groups, and acts as the fourth residue needed to complete the turn by forming two hydrogen bonds. Two other water molecules form intermolecular hydrogen bonds in stabilizing the helical structure so that the end result is a column of molecules that looks like an α-helix.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360310405
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    Mobility models for stiff and flexible macromolecules in dilute gels (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 435-447 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effective sphere approximation for modeling electrophoretic transport of macromolecules in highly porous gels (the “Ogston model”) is examined, and contrasted with similar mobility models for stiff and flexible solutes. Calculation of segmental depletion near gel obstacles of various shapes demonstrates the limited applicability of the effective sphere approach. For highly flexible chains, both theory and experiment reveal a nonunique mapping between mobility and molecular size when the molecular radius is comparable to that of gel fibers. Turning to mobility behavior in more concentrated gels, neither flexible or stiff macromolecules behave as spheres; for the particular case of flexible chains, the presence of entropic barriers in concentrated gels can be understood in terms of a simple random planes model for the gel structure.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360310409
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  • 96
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    Differential scanning calorimetry studies of NaCl effect on the inverse temperature transition of some elastin-based polytetra-, polypenta-, and polynonapeptides (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 465-475 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Differential scanning calorimetry studies of the effect of NaCl on protein-based polymer self-assembly has been carried out on six elastin-based synthetic sequential polypeptides- i.e., the polypentapeptide (L-Val1-L-Pro2-Gly3-L-Val4-Gly5)n and its more hydrophobic analogues (L-Leu1-L-Pro2-Gly3-L-Val4-Gly5)n and (L-Val1-L-Pro2-L-Ala3-L-Val4-Gly5)n; the polytetrapeptide (L-Val1-L-Pro2-Gly3-Gly4)n and its more hydrophobic analogue (L-IIe1-L-Pro2-Gly3-Gly4)n; and the polynonapeptide (a pentatetra hybrid), (L-Val1-L-Pro2-Gly3-L-Val4-Gly5-L-Val6-L-Pro7-Gly8-Gly9)n.Previous physical characterizations of the polypentapeptides have demonstrated the occurrence of an inverse temperature transition since increase in order of the polypentapeptide, as the temperature is raised from below to above that of the transition, has been repeatedly observed using different physical characterizations.In the present experiments, it is observed that the transition temperatures of the polypeptides studied are linearly dependent on NaCl concentration. The molar effectiveness of NaCl in shifting the transition temperature ΔTm/[N], is about 14°C/[N], with the dependence on peptide hydrophobicity being fairly small. Interestingly, however, the δΔQ/ [N] does depend on the hydrophobicity of a polypeptide.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/bip.360310502
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    Masthead (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991) 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310801
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  • 98
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    A molecular dynamics study of thermodynamic and structural aspects of the hydration of cavities in proteins (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 919-931 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure and activity of a protein molecule are strongly influenced by the extent of hydration of its cavities. This is, in turn, related to the free energy change on transfer of a water molecule from bulk solvent into a cavity. Such free energy changes have been calculated for two cavities in a sulfate-binding protein. One of these cavities contains a crystallo graphically observed water molecule while the other does not. Thermodynamic integration and perturbation methods were used to calculate free energies of hydration for each of the cavities from molecular dynamics simulations of two separate events: the removal of a water molecule from pure water, and the introduction of a water molecule into each protein cavity. From the simulations for the pure water system, the excess chemical potential of water was computed to be -6.4 ± 0.4 kcal/mol, in accord with experiment and with other recent theoretical calculations. For the protein cavity containing an experimentally observed water molecule, the free energy change on hydrating it with one water molecule was calculated as -10.0 ± 1.3 kcal/mol, indicating the high probability that this cavity is occupied by a water molecule. By contrast, for the cavity in which no water molecules were experimentally observed, the free energy change on hydrating it with one water molecule was calculated as 0.2 ± 1.5 kcal/mol, indicating its low occupancy by water. The agreement of these results with experiment suggests that thermodynamic simulation methods may become useful for the prediction and analysis of internal hydration in proteins.
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    URL: http://dx.doi.org/10.1002/bip.360310802
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    Electronic Resource
    Topographical requirements for δ-selective opioid peptidesAbbreviations: All amino acids are of the L variety unless otherwise stated. Abbreviations for amino acid residues follow those recommended by the IUPAC. Other abbreviations include the following: DPDPE. enkephalin, H-Tyr-D- Pen, penicillamine or β,β-dimethylcysteine; DCFPE, DRE, dermen kephalin, H-Tyr-D-Met-Phe-His-Leu-Met-Asp-NHg; DPLPE, DSLET, H-Tyr-D-Ser-Gly-Phe-Leu-Thr-OH; DSTBULET, H-Tyr-D-Ser(OtBu)-Gly-Phe-Leu-Thr-OH; BUBU, H-Tyr-D-Ser(OtBu)-Gly-Phe-Leu-Thr(OtBu)-OH; DAGO, [D -ala2, N-MePhe4, Gly5]enkephalin-OL. (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 941-955 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational possibilities of three different δ-selective opioid peptides, which are DPDPE , and DRE (Tyr-D-Met-Phe-His-Leu-Met-Asp-NH2, dermenkephalin), were explored using energy calculations. Sets of low-energy conformers were obtained for each of these peptides. The sets consisted of 61 structures for DPDPE, 32 for DCFPE, and 38 for DRE, including various types of rotamers of the Tyr and Phe side-chain groups. Comparison of the geometrical shapes of the conformers was performed for these sets using topographical considerations, i.e., examination of the mutual spatial arrangement of the N-terminal α-amino group, and of the Tyr and Phe side-chain groups. The results obtained suggest a model for the δ-receptor-bound conformer(s) for opioid peptides. The model suggests the placement of the Phe side chain in a definite position in space corresponding to the g- rotamer of Phe for peptides containing Phe4 and to the t rotamer for peptides containing Phe.3 The position of the Tyr1 side chain cannot be specified so precisely. The proposed model is in a good agreement with the results of biological testing of β-Me-Phe4-substituted DPDPE analogues that were not considered in the process of model construction.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310804
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    Electronic Resource
    Conformational analysis of two cyclic disulfide peptides (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 835-843 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complete nmr and CD studies of two cyclic tetrapeptides with disulfide bonds, 1 and 2 bonds have been carried out in different solvents to investigate the formation and stabilization of β-turn structures and to determine the stereochemistry of the disulfide linkage. Both peptides have three-dimensional structures with a type II β-turn, as derived from quantitative nuclear Overhauser effect data. The combined use of CD and nmr indicates that the dihedral angle of the disulfide bridge is different in the two peptides, although the chirality is maintained.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310704
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