Bibliothek

Notizen: Abstract A five-year-old domestic cat with generalised toxoplasmosis and severe leukaemia (145 × 109 WBC/1) is described. The liver was necrotic with tissue cysts and a localised lymphoma.Toxoplasma gondii organisms were found in all organs investigated. Tumour cells containing large cytoplasmic, azurophilic granules were observed in the blood. Erythrophagocytosis by tumour cells was also seen.

Notizen: Summary Three cases of rhabdoid tumour of the central nervous system arising in a supratentorial location are reported. The patients were 18, 14, and 7 years old. All three tumours showed a common morphology. The neoplastic cells were usually globoid with round nuclei and prominent nucleoli and large acidophilic, cytoplasmic inclusions were present in many of them. These inclusions showed strong immunoreactivity for vimentin, weak immunoreactivity for epithelial membrane antigen and focal immunoreactivity for cytokeratins. Ultrastructurally they were made up of whorls of intermediate filaments, 8–10 nm in thickness. Rhabdoid tumours of the central nervous system, whatever the cell of origin, appear to be an independent entity with identifiable histology and aggressive behaviour.

Notizen: Abstract An ultrastructural study of amyloid deposits in four cases of squamous cell carcinoma of uterine cervix was performed. The amyloid deposits reacted with anti-keratin antiserum on frozen sections. Amyloid deposits showed nodular (4 cases) and star-like forms (3 cases). Nodular amyloid deposits were composed of slightly whorled fibrils, measuring 7–10 nm in width. Some of them contained cellular debris and thicker, more electron-dense filaments than amyloid fibrils. In three cases, filamentous tumour cells and filamentous masses were observed together with amyloid. Star-like amyloid deposits were composed of bundles of straight amyloid fibrils. Some of the tumour cells in contact with star-like amyloid deposits had deep cytoplasmic invaginations, where closely packed amyloid fibrils were arrayed in parallel fasion. In addition, a few tumour cells had membrane-bound amyloid fibrils in the cytoplasm. It is suggested that nodular amyloid deposits are derived from the tumour cells through filamentous degeneration. Amyloid fibrils in star-like amyloid deposits are thought to be formed within the cytoplasm or in the vicinity of invaginated cytoplasmic membranes of the tumour cells.

Notizen: Abstract Morphological and morphometric studies of glomeruli were carried out in streptozotocin-induced diabetic rats using improved tissue processing and computerized morphometry. Increased mesangial matrix, occupying the enlarged diabetic mesangium, contained an abundance of dark granular material in addition to the microfibrils which were usually found in the control glomeruli. In the diabetic glomeruli, the lamina densa was thick and heterogeneous showing a dense layer both on its epithelial and endothelial aspects, and the lamina rara externa contained more fibrils than in control rats. Detailed estimation of the absolute values of the various compartments of the diabetic glomeruli by using perfusion-flxed materials and a computer-assisted digitizer revealed that the volume and surface area of the mesangium were increased more extensively than those of the capillary; the enlargement of the mesangial-capillary interface area was the most pronounced among the morphometric changes of the diabetic glomeruli; and that the moderate increase in capillary volume was associated with an increased radius. Our quantitative results showed that capillaries in the diabetic glomeruli had an extensively wider neck which may be the first sign of structural damage to the glomerular tuft.

Notizen: Abstract Experimental obstruction of the fetal small intestine resulted in massive hypertrophy of the segment proximal to the site of obstruction. Villus morphology was grossly abnormal. Enterocytes developed many irregular features, most notably cytoplasmic extensions (pseudopods, or blebs) from their apical surface. Distal to the site of obstruction, morphological anomalies which resembled those seen after experimental oesophageal ligation were found. These included delayed disappearance of the apical endocytic network, disrupted or absent microvilli, glycogen accumulation and inappropriate cell extrusion. Proximal to the obstruction, where stasis of swallowed fluid occurs, distension and abnormal intestinal development ensues. Distal to the obstruction where the intestine develops in the absence of swallowed fluid, development is also abnormal. The anomalies resemble those noted after oesophageal ligation in utero, and possibly are the results of reduced cellular nutrition. These results suggest that fetal ingestion provides the developing gastrointestinal tract with an important stimulus for normal growth.

Notizen: Abstract Yersinia enterocolitica is an invasive pathogen capable of causing a wide spectrum of gastrointestinal diseases in man. While there is a considerable body of data on the invasiveness ofY. enterocolitica in vitro, little is known about the events in vivo leading to the translocation of the bacteria from the intestinal lumen into the ileal tissue. There is no detailed ultrastructural information describing the course of infection of pathogenicY. enterocolitica in comparison with an avirulent strain. We compared a virulent plasmid-bearing strain and an isogenic avirulent plasmid-free derivative strain ofY. enterocolitica serotype O∶8 at the ultrastructural level, in the established model of murine yersiniosis. At 12 h postinoculation we found no indications of an active invasion of the intestinal epithelium, although microcolonies of the pathogenic strain were detectable closely under the follicle-associated epithelium of the Peyer's patches. The plasmid-bearing strain ofY. enterocolitica affected the gut-associated lymphoid tissue which was destroyed 36 h post-infection. Unlike the pathogenic strain ofY. enterocolitica, the nonpathogenic plasmid-free strain caused no detectable morphological alterations in the ileal tissue by this time. Morphological evidence is provided thatYersinia does not invade the ileal epithelium in an active manner, as has been observed in vitro, but appears to be transported across the epithelial barrier by M-cells.

Notizen: Summary We report a case of sarcoma botryoides of the uterine cervix occurring in a 19-year-old woman. By light microscopy the tumor showed round and spindle cells with hyperchromatic nuclei and, focally, a cambium layer subjacent to the surface epithelium and surrounding endocervical glands. Strap-shaped cells with and without cross-striations and small foci of immature cartilage were also present. Immunohistochemical studies showed positive staining within the tumor cells for myoglobin, desmin, vimentin, muscle-specific actin and CD56. By electron microscopy, tumor cells showed cytoplasmic filaments in an alternating pattern of thick and thin filaments. Chromosomal analysis demonstrated deletion of the short arm of chromosome 1, and trisomies 13 and 18. To our knowledge, this is the first reported case of sarcoma botryoides of the endocervix with chromosomal analysis.

Notizen: Abstract The aim of the present work was to analyse, at the ultrastructural level, the action of heroin of 150 centrilobular sinusoids from liver biopsies of five intravenous drug abusers, who presented clinical and biological manifestations of hepatic impairment. A comparative study of 90 sinusoids from liver biopsies of three control patients was performed. Electron microscopic observations showed a thickening of the sinusoidal wall related to endothelial cell hypertrophy and to fibrosis of the space of Disse. This was generally associated with basement-membrane-like material and hepatocyte microvilli flattening. In addicts, hepatic vascular pole changes were a constant finding, accompanied by interhepatocyte space disjunction and perisinusoidal collagenization. Morphometric assessment confirmed a significant increase of sinusoidal wall surface, endothelial cell body and processes and Ito cell process surface was significantly different between the patient groups. This cellular hypertrophy may represent hyperactivation of the sinusoidal cell functional capacity, triggering the fibrogenesis in the space of Disse. While this mechanical barrier might hinder the free exchange through the space of Disse, it may equally well protect the liver against heroin toxicity.

Notizen: Abstract The three-dimensional ultrastructure ofCryptococcus neoformans was studied by quick-freezing and deep-etching (QF-DE) method.C. neoformans, strain CDC551, was cultured on agar. The viable yeast cells (107 cells) were inoculated into each mouse from the tail vein. Three weeks after the inoculation, the brains of the mice were perfused with fixatives, quickly frozen, freeze-fractured, deeply etched and rotary shadowed with platinum and carbon. In addition, the viable cells ofC. neoformans on agar were picked up and quickly frozen, and replica membranes were prepared as described above. The ultrastructure ofC. neoformans was three-dimensionally demonstrated by the QF-DE method. The capsule was composed of fine meshworks of microfibrils (10–13 nm in diameter), which were directly attached to the cell walls. The capsule of the in vivo yeasts (yeast cells in the brain lesion) was thicker than that of the in vitro yeasts (yeast cells on agar culture). At the outer part of the cell wall, a particle-accumulating layer was observed. This layer in vivo was thicker than that in vitro. Occasionally, the yeast cells were ingested by phagocytes in the mouse brain. Although the cytoplasm of such yeast cells was destroyed, the capsular meshworks were well preserved. The ultrastructure of the capsule was the same both in cultured and phagocytized yeasts in the cystic lesions of the brains. This lack of morphological changes of the capsular meshworks suggests that they are resistant to the digestion by phagocytes. This stability of capsular structures may provide one of the important pathogenic factors in cystic lesions byC. neoformans.

Notizen: Summary Foetal rat brain reaggregate cultures have been employed to investigate the morphological changes associated with the neurotoxic action of ethylcholine mustard aziridinium (ECMA). In a companion study we provided evidence for apparent selective cholinergic neurotoxicity. Exposure of 9-day-old cultures to 12.5 μM ECMA for 3 days produced dilatation of selected axon preterminals and terminals in the outer core tissue layer. Axoplasm in these dilated terminals was electron lucent and contained a flocculent, plasma-like material with remnants of the smooth endoplasmic reticulum. Their synaptic vesicle content was much reduced or, absent. Microglial cells were engaged in phagocytosis of these effete structures and a few necrotic neurons were enveloped by glial processes. Exposure to 50 μM ECMA produced widespread necrosis with some surviving neurons, surrounded by the still-persisting capsular layer. Treatment with 100 μM ECMA generated a greater extent of tissue necrosis, with only a few surviving neurons and glial cells being contained within the necrotic tissue mass. Reaggregates frequently disintegrated following capsule loss. Our results indicate that the initial morphological manifestation of ECMA-induced toxicity is dilatation of axon terminals, that are probably of cholinergic origin and are targeted due to their possession of the high-affinity choline transport system which is unique to these neurons.

Notizen: Summary The neuropathological findings in a Japanese male with nephrosialidosis are reported. Clinically, coarse face, psychomotor retardation, macular cherryred spot and proteinuria were noted at 1 year and 7 months. He was diagnosed to have nephrosialidosis on the basis of a deficiency of α-neuraminidase activity in both lymphocytes and cultured skin fibroblasts, and of severe glomerular and tubular involvement on renal biopsy. He died of multiple organ failure at 8 years and 6 months. There were numerous vacuoles and storage materials in visceral organs, particularly in the glomerular and tubular epithelial cells of the kidney and Kupffer cells as well as hepatocytes in the liver. Neuropathological examination revealed severe neuronal storage in the selected part of the central nervous system; lower motor neurons of the brain stem and spinal anterior horn cells, as well as neurons in the basal nucleus of Meynert. In the peripheral nervous system, sympathetic ganglia were severely affected. There was little or no neuronal storage in the basal ganglia, cerebral cortex or cerebellum, and demyelination was not found. Electron microscopic examination showed fine wavy multilamellar structures in the spinal anterior horn cells or Zebra body-like structures in the neurons of the Meynert's basal nucleus. Lectin histochemistry was positive for wheat germ agglutinin, Ricinus communis agglutinin-1 and peanut agglutinin within distended neurons. We conclude that the neuropathological feature in nephrosialidosis is not specific except for the selectiveness of the anatomical sites of involvement. It shares some aspects found in other types of sialidosis or galactosialidosis.

Notizen: Abstract A simple and reproducible method for cryo-preservation of brain tissue from patients with Alzheimer's disease is described. Fresh brain slices (1 cm thick) obtained less than 6 h postmortem are placed in sealed plastic bags, sandwiched between 0.3-cm-thick aluminium sheets, and frozen by placing the entire “sandwich” between layers of dry ice pellets. The frozen brain slices are stored at −85 °C. Specific anatomic areas can be retrieved at any time for light and electron microscopic, immunocytochemical, autoradiographic and neurochemical studies.

Notizen: Abstract Intrinsic connections in the cat primary auditory field (AI) as revealed by injections Phaseolus vulgaris leucoagglutinin (PHA-L) or biocytin, had an anisotropic and patchy distribution. Neurons, labelled retrogradely with PHA-L were concentrated along a dorsoventral stripe through the injection site and rostral to it; the spread of rostrally located neurons was greater after injections into regions of low rather than high characteristic frequencies. The intensity of retrograde labelling varied from weak and granular to very strong and Golgi-like. Out of 313 Golgi like retrogradely labelled neurons 79.6% were pyramidal, 17.2% multipolar, 2.6% bipolar, and 0.6% bitufted; 13.4% were putatively inhibitory, i.e. aspiny or sparsely spiny multipolar, or bitufted. Individual anterogradely labelled intrinsic axons were reconstructed for distances of 2 to 7 mm. Five main types were distinguished on the basis of the branching pattern and the location of synaptic specialisations. Type 1 axons travelled horizontally within layers II to VI and sent collaterals at regular intervals; boutons were only present in the terminal arborizations of these collaterals. Type 2 axons also travelled horizontally within layers II to VI and had rather short and thin collateral branches; boutons or spine-like protrusions occurred in most parts of the axon. Type 3 axons travelled obliquely through the cortex and formed a single terminal arborization, the only site where boutons were found. Type 4 axons travelled for some distance in layer I; they formed a heterogeneous group as to their collaterals and synaptic specializations. Type 5 axons travelled at the interface between layer VI and the white matter; boutons en passant, spine-like protrusions, and thin short branches with boutons en passant were frequent all along their trajectory. Thus, only some axonal types sustain the patchy pattern of intrinsic connectivity, whereas others are involved in a more diffuse connectivity.

Notizen: Summary Bone marrow transplantation (BMT) has been used therapeutically in several types of mucopoly-saccharidoses (MPS) and other inherited metabolic disorders. Fibroblasts are severely affected in MPS due to the intralysosomal accumulation of glycosaminoglycans. We report a stereological and morphometric study at light and electron microscopy levels of dermal fibroblasts before and 21 months after BMT in a young girl with MPS I Scheie phenotype (MPS I-S). Dermal fibroblasts showed remarkable morphological changes although their density, expressed as number of fibroblasts per unit volume of dermis (number density), was not modified in the post-BMT samples as compared to pre-BMT ones. Stereological and morphometric parameters referring to cell characteristics of post-BMT fibroblasts (nuclear and cell surface densities, and both nucleus/cell and cell/nucleus volume densities) showed significant differences when compared with pre-BMT fibroblasts, and non-significant differences regarding control cells. On the other hand, quantitative parameters of the lysosomal compartment from post-BMT fibroblasts showed intermediate values between pre-BMT and control fibroblasts. These results, at cellular level, are in agreement with previous biochemical and clinical results, and clearly showed a progressive course to a non-pathological state. All parameters estimated may be considered useful tools in evaluating the success of BMT. These parameters provide quantitative data which can be statistically compared, showing the changes due to the reduction of storage material after BMT. Cell/nucleus volume density is especially interesting since not only is it easy to estimate, even by automatic procedures, but it could also constitute a numerical expression of skin anatomopathological analyses performed post-BMT.

Notizen: Summary In this report we describe a glioblastoma multiforme with focal granular cell change. In most astroglial tumors with granular cells, the granular appearance is due to the presence of periodic acid-Schiff-positive, membrane-bound cellular debris. In the present case the granular appearance was due to the presence of many small Rosenthal fibers, which were immunoreactive for glial fibrillary acidic protein, vimentin, ubiquitin, and heat-shock protein 27, but not for α-B crystallin. The ultrastructural characteristics are described. These findings demonstrate that granulofilamentous inclusions with the appearance of Rosenthal fibers in glial tumors are a structurally heterogeneous feature.

Notizen: Abstract An extraskeletal myxoid chondrosarcoma in the pineal region was studied by light and electron microscopy. The immunohistochemical positivity for S-100 protein, vimentin and collagen type II favored a chondrocytic origin of the tumor. In addition to the well-described ultrastructural features suggestive of a cartilagenous nature, this tumor had unusual lamellar inclusions in the rough endoplasmic reticulum. To the best of our knowledge, this is the first report of these special inclusion bodies in a myxoid chondrosarcoma.

Notizen: Abstract The effects of permanent focal cerebral ischaemia on Alz-50 and ubiquitin antibody immunohistochemical staining were investigated in vivo in the cat. Alz-50 and ubiquitin antibody staining was compared to the distribution of ischaemic cell damage. Six hours following permanent occlusion of one middle cerebral artery, Alz-50 immunoreactivity was present in neurones in the ipsilateral ischaemic cerebral cortex and caudate nucleus but not in any region of the contralateral hemisphere or in sham-operated cats. Only a proportion of neurones were stained with Alz-50 and these did not have the shrunken, pyknotic appearance characteristic of irreversible ischaemic cell damage. Ubiquitin immunoreactivity was also increased in the ischaemic hemisphere, again only a proportion of neurones were stained. The Alz-50 antibody recognises the microtubule-associated protein tau and stains neurofibrillary tangles as well as neurones vulnerable to neurofibrillary change in tissue sections of Alzheimer brain. The results indicate that there are changes in tau protein in response to an ischaemic insult, but only in some neurones, which may reflect an early stage of the degenerative process. Increased ubiquitin immunoreactivity may be a response to the presence of abnormal proteins, including tau, which are induced by an ischaemic challenge.

Notizen: Abstract The significance of the development of polyglucosan bodies (PBs) in the CNS is incompletely understood. We present the clinicopathological features of three autopsy cases with numerous PBs other than the common corpora amylacea or Lafora bodies. The first patient had pleomorphic PBs in the neuronal processes of pallidum and substantia nigra which, thus, are consistent with Bielschowsky bodies. Bielschowsky bodies involved also the hypothalamus and tegmentum of midbrain and medulla. The present case was the first not associated with any clinical symptoms. The second patient also had incidental Bielschowsky bodies in the external pallidum, substantia nigra, and pallidothalamic, pallidonigral and nigrostriatal tracts. Additionally, unique clusters of small PBs appeared in the cerebral cortex, putamen, pallidum, and caudate nucleus. Immunostaining suggested that these small clustered PBs were located in the cytoplasm and processes of astrocytes. Ultrastructurally, these clustered PBs were in agreement with previous descriptions of PBs. The third patient had adult polyglucosan body disease. Most PBs in the white matter were corpora amylacea situated in astrocytic processes or axons. In the gray matter, many pleomorphic PBs resembling Bielschowsky bodies occurred in neuronal processes. In the peripheral nervous system, a few PBs were seen in myelinated axons. The following conclusions may be drawn from this study: (1) each type of PBs develops in distinct cell types of the human brain in variable distribution; (2) Bielschowsky bodies may not manifest clinically; (3) PBs other than corpora amylacea or Lafora bodies may be distributed in localized or diffuse patterns; (4) in the localized pattern (patients 1 and 2), PBs occur as Bielschowsky bodies or clustered PBs, and tend to involve certain systems (pallidum, striatum, and substantia nigra); and (5) in the diffuse pattern (patient 3), PBs develop as corpora amylacea and Bielschowsky-like bodies of adult polyglucosan body disease.

Notizen: Summary The development of the intermediate lobe of the rabbit pituitary was investigated by light and electron microscopy and by using immunocytological techniques. The first immunoreactive melanotrophic cells were detected at the fetal day 17 in the dorsal zone of Rathke's pouch epithelium facing the neural lobe; this coincided ultrastructurally with the appearance in this area of a few cells exhibiting secretory vesicles and granular condensations in the Golgi saccules. The differentiation of the gland probably required an infundibular inductive effect. Secretory cells increased in number following a dorsoventral gradient during the next fetal and neonatal stages until postnatal day 20, the stage at which the intermediate lobe exhibited its definitive organization. The gland innervation occurred during the first days after birth. The advent of these oxytocin- and neurophysin-immunoreactive fibres coincided with an obvious stimulation of the synthetic activity of the melanotrophic cells. The possible neurotrophic effect of these cells on their innervating system remains to be established.

Notizen: Abstract The ciliary ganglia of eight healthy adult cats were studied by light and electron microscopy. The ganglion, measuring about 2 mm in length, was consistently found to be attached to the branch from the oculomotor nerve supplying the inferior oblique muscle. The number of neurons varied from 2773 to 3794 after applying Abercrombie's correction. The mean of average somal diameter of the neurons was 36.5 μm (SD = 5.0 μm) and the mean of somal cross-sectional area was 904.2 μm2 (SD = 262.8 μm2). The mean of average nuclear diameter was 13.9 urn (SD = 1.8 μm) and the mean of nuclear cross-sectional area was 142.2 μm2 (SD = 37.1 μm2). The mean of the aspect ratios of the soma and nucleus were 1.2 (SD = 0.1) and 1.1 (SD = 0.1) respectively. The frequency distributions of these parameters were all unimodal. Under the light microscope, the Nissl granules in the neurons were prominent and were distributed peripherally, perinuclearly or randomly in the cytoplasm. Under the electron microscope, the rough endoplasmic reticulum showed a similar pattern of distribution in the cytoplasm. In some neurons, glycogen-like granules were present; these were either distributed randomly throughout the cell, or aligned in single rows in relation to sub-surface cisterns and between the cisterns of smooth and rough endoplasmic reticulum. Most of the dendrites were short protrusions from the cell body; some contained glycogen-like granules. Occasionally, the dendritic protrusions were electron-dense. All the synapses encountered were axodendritic. In most axon terminals, the synaptic vesicles were spherical and measured 30–50 nm in diameter; in some, they were flattened, measuring 50 nm by 20 nm. Some axon terminals containing either spherical or flattened synaptic vesicles also contained large dense-cored vesicles that measured 80–100 nm, while their dense core measured 40–60 nm.

Notizen: Abstract The histological and ultrastructural aspect of normal human hair follicles maintained ex vivo for 12 days was evaluated. Anagen hair follicles, dissected free of contaminating connective tissue, were maintained for up to 12 days in a serum-free medium. Macroscopic observations revealed continued viability for 12 days, at which time some follicles involuted in a manner morphologically similar to catagen. Increased growth of maintained follicles was measured from the abrupt ending of the connective tissue sheath (CTS), as no increase in this component was observed from initiation of culture. In general follicles maintained up to 8 days exhibited little divergence from normal in vivo morphologies including the persistence of functional hair bulb melanocytes — a marker of anagen. After this time melanin granules were present in dermal papilla cells, as occurs during impending involution in vivo. Heterotypic cell contact occurred in the middle to upper follicle between outer root sheath (ORS) keratinocytes and disorganized CTS. Herniation of some ORS cells away from the follicle and the occurrence of loose desmosomal junctions between ORS keratinocytes reflected loss of normal follicular cell interactions in upper follicles maintained after 8 days. Continued follicle growth correlated with the presence of mitotic matrix keratinocytes even at 12 days. After 12 days in culture most follicles involuted displaying apoptotic-like keratinocytes and hair bulb melanocytes and the presence of highly keratinized hair ‘club’ structures. While most follicles exhibited this orderly sequence of events, a few follicles involuted after 24 h with synchronous degeneration of all cells. Two follicles exhibited upregulated cortical cell differentiation at the level of the dermal papilla (DP). Normal cell cytoplasmic constituents were replaced with ribosomes and keratin bundles. This study reveals for the first time the histology and ultrastructure of normal hair follicles in culture for up to 12 days in serum-free medium. Although involuted hair follicles may exhibit some features of catagen, it is possible that the mechanisms involved are entirely different.

Notizen: Abstract Germ line cell cluster formation in ovarioles of three different stages, each from a different mayfly species, was studied using ultra-thin serial sectioning. In the analysed ovariole of Cloeön sp., only one linear, zigzag germ line cell cluster was found, consisting of sibling cells connected by intercellular bridges which represent remnants of preceding synchronized mitotic cycles followed by incomplete cytokinesis. A polyfusome stretched through all sibling cells. At the tip of the ovariole, cytokinesis occurred without preceding division of nuclei; thus, intercellular bridges were lined up but the remaining cytoplasm between the bridges had no nuclei. The analysed Siphlonurus armatus vitellarium contained five oocytes at different stages of development. Each oocyte in the vitellarium was connected via a nutritive cord to the linear cluster of its sibling cells in the terminal trophic chamber. Each cluster had the same architecture as was found in Cloëon. The 3-dimensional arrangement and distribution of closed intercellular bridges strongly suggest that all five clusters are derived from a single primary clone. The position of oocytes within each cluster is random. However, each oocyte is embraced by follicular or prefollicular cells whilst all other sibling cells are enclosed by somatic inner sheath cells, clearly distinguishable from prefollicular cells. In the analysed ovariole of Ephemerella ignita, two small linear clusters were found in the tropharium beside two single cells, two isolated cytoplasmic bags with intercellular bridges but no nuclei, and some degenerating aggregates. One cluster was still connected to a growing oocyte via a nutritive cord. In all species the nurse cells remained small and no indications of polyploidization were found. We suggest that this ancient and previously unknown telotrophic meroistic ovary has evolved directly from panoistic ancestors.

Notizen: Abstract Cutaneous facial inputs influencing head movement were examined in the conscious and anaesthetised cat. EMG recordings were made in neck muscles of conscious, unrestrained cats in which an unexpected light cutaneous stimulus was applied to the glabrous skin of the planum nasale (PN). These observations established that head aversion movements were associated with synchronised activation of both deep and superficial dorsal neck muscles. In anaesthetised cats in which activity in the motoneurons of the large dorsal neck muscles was examined, mechanical stimulation of the PN or electrical stimulation of the infraorbital nerve (ION) produced a short latency, reflex activation. The reflex could be elicited by excitation of low threshold, rapidly conducting fibres in the ION. Intracellular recording from neck motoneurons showed that there is a short latency, probably disynaptic, excitatory pathway from low threshold nerves in the ION to neck motoneurons, but discharge of neck motoneurons occurred several milliseconds later, presumably as a result of activity in a longer multisynaptic pathway.

Notizen: Abstract The motoneurons (MNs) in the ventrolateral nucleus (VLN) of the upper sacral spinal cord segments in the cat supply the external sphincters and the ischiocavernosii muscles. The dendrites of the MNs in the VLN are arranged into rostro-caudally oriented bundles (ventrolateral dendritic bundle, VLB). In this study we describe the distribution and synaptic arrangement of γ-aminobutyric acid-immunoreactive (GABA-IR) axonal bouton profiles innervating the VLB. This was accomplished using the peroxidase-antiperoxidase technique and a polyclonal antibody raised against glutaraldehydeconjugated GABA. The VLN receives an extensive innervation of GABAIR axonal bouton profiles that surround both cell bodies and dendrites. Twenty-five per cent of the total number of vesicle-containing axonal profiles in the VLN neuropil were estimated to be GABA-IR. On cell bodies in the α-motoneuron size-range, the membrane covering of GABA-IR bouton profiles was about 18% and they constituted about 29% of the total membrane covering of axonal bouton profiles. Quantitative analysis of GABAIR bouton profiles on dendrites revealed membrane covering figures rather similar to those on the cell bodies. They were not randomly distributed within the dendritic arborisations. Instead, they were very infrequent (2.5% of the covering) on small calibre dendrites (〈 1 μm) as compared to larger dendrites (〉 1 μm, 14–18.5% of the covering), although the total membrane covering of axonal bouton profiles was rather similar for all dendrites (42–52%). The data on membrane covering by GABA-IR boutons presented here may be low estimates due to technical limitations, indicating that the GABAergic input to this region might be even more extensive. A frequent finding was that one and the same GABAIR bouton made synaptic contact with two to three adjacent dendrites. This type of synaptic arrangement among the VLN MNs indicates a divergence of the GABAergic input at the terminal level. In addition, the postsynaptic dendrites involved in such arrangements often disclosed dendro-dendritic contacts. In total, 44% of the bundled dendrites in the VLN disclosed direct dendro-dendritic contact regions. These contacts were most often of the puncta adherentia type, while desmosome-type contacts were less frequent. None of the dendro-dendritic contacts studied had the characteristics of a gap junction. Taken together, the present results indicate that GABA may be a transmitter substance in a large fraction of the synaptic input to the VLN MNs. Furthermore, the location of GABA-IR bouton profiles on the cell bodies and more proximal regions of the dendritic trees implies that they could exert a considerable influence on MN activity pattern.

Notizen: Abstract The effects of electrical stimulation within the midbrain on fusimotor output to the jaw elevator muscles were studied in anaesthetized cats. Muscle spindle afferents recorded in the mesencephalic trigeminal nucleus were categorised as primary or secondary by their responses to succinylcholine during sinusoidal or rampand-hold stretches. Changes in their stretch responses during midbrain stimulation were then assessed by changes in bias and in dynamic sensitivity. Problems were encountered in interpreting changes in sine wave stretch responses of primary afferents, in some of which a very small change in firing pattern produced large changes in estimates of the reponse amplitude. Sine wave testing also sometimes over-estimated static effects and under-estimated dynamic effects relative to ramp responses. On other occasions a small amount of static fusimotor activity caused a marked increase in sine response amplitude, which could be wrongly interpreted as a dynamic effect. Consequently, ramp responses only were used for diagnosing fusimotor changes. The most effective region for producing pure dynamic fusimotor excitation was directly rostral to the red nucleus, extending dorsally and ventrally approximately in the course of the retroflex bundle. Stimulation of regions caudal and dorso-caudal to the red nucleus, previously designated as the mesencephalic area for dynamic fusimotor control of leg muscles, gave static or mixed static and dynamic effects on jaw spindles. The use of midbrain stimulation to identify fusimotor neurones of jaw muscles as static or dynamic would be most reliable with stimulation just rostral to the red nucleus and would require spindle afferent behaviour to be monitored at the same time with ramp stretches.

Notizen: Abstract Forelimb movements and motor skills were studied in adult cats in order to determine the effect of brain damage inflicted at different postnatal ages. The unilateral lesion included the cortical areas from which the pyramidal tract originates in cat: areas 4 and 6 corresponding to the motor cortex; areas 3, 2 and 1 corresponding to the primary somatosensory cortex; and part of area 2 prae-insularis corresponding to the secondary somatosensory cortex. Forelimb performance of a food-retrieving task requiring proximal as well as distal muscles was assessed by comparing the limb contralateral to the damaged hemisphere (affected limb) with the limb contralateral to the intact hemisphere (non-affected limb) that appeared to perform the task as well as both limbs of control animals. In simple task-related movements, all operated animals were rapidly able to achieve the goal with the affected limb, whatever the age at lesion. In complex tasks, the ability to achieve the goal with the affected limb decreased with increasing age at lesion. Recovery of distal skills, i.e. grasping and wrist rotation, did not occur in animals operated on after the 23rd postnatal day (PND), and recovery of proximal skills, i.e. amplitude and precision of the reaching movement, did not occur in animals operated on after the 45th PND. The critical time for the recovery of distal skills lies somewhere between the 23rd and 30th PND, whereas for the recovery of proximal skills it lies somewhere between the 45th and 60th PND. These critical dates for the recovery of motor skills support the Kennard doctrine. Different critical times for proximal and distal skills may be explained in terms of different stages of sensorimotor development in kitten. It is hypothesised that recovery only occurs if brain damage is inflicted before maturation of the nervous system underlying a given motor skill.

Notizen: Abstract Latencies of normal and adapted feline vestibulo-ocular reflex (VOR) were studied in five cats by applying ± 20°/s horizontal head velocity steps (4000°/s2 acceleration) and measuring the elicited horizontal or vertical reflex eye responses. Normal VOR latency was 13.0 ms ± 1.9 SD. Short-term adaptation was then accomplished by using 2 h of paired horizontal sinusoidal vestibular stimulation and phase-synchronized vertical optokinetic stimulation (cross-axis adaptation). For long-term adaptation, cats wore ×0.25 or ×2.2 magnifying lenses for 4 days. The cats were passively rotated for 2 h/day and allowed to walk freely in the laboratory or their cages for the remainder of the time. The latency of the early (primary) adaptive response was 15.2ms±5.2 SD for crossaxis adaptation and 12.5 ms±3.9 SD for lens adaptation. This short-latency response appeared within 30 min after beginning the adaptation procedure and diminished in magnitude overnight. A late (secondary) adaptive response with latency of 76.8 ms±7.0 SD for cross-axis adaptation and 68.1 ms±8.8 SD for lens adaptation appeared after approximately 2 h of adaptation. It had a more gradual increase in magnitude than the primary response and did not diminish in magnitude overnight. These data suggest that brainstem VOR pathways are a site of learning for adaptive VOR modification, since the primary latency is short and has a similar latency to that of the normal VOR.

Notizen: Abstract The spatial distribution of neuronal responses to frequency-modulated (FM) sweeps was mapped with microelectrodes in the primary auditory cortex (AI) of barbiturate-anesthetized cats. Increasing and decreasing FM sweeps (upwardand downward-directed FM sweeps, respectively) covering a range of 0.25–64.0 kHz were presented at three different rates of frequency change over time (i.e., sweep speed). Using multiunit recordings, the high-frequency domain (between 3.2 and 26.3 kHz) of AI was mapped over most of its dorsoventral extent (as determined by the distribution of the excitatory bandwidth, Q10dB) for all six cases studied. The spatial distributions of the preferred sweep speed and the preferred sweep direction were determined for each case. Neuronal responses for frequency sweeps of different speeds appeared to be systematically distributed along the dorsoventral axis of AI. In the dorsal region, cortical cells typically responded best to fast and/or medium FM sweeps, followed more ventrally by cells that responded best to medium — then slow-, then medium-speed FM sweeps. In the more ventral aspect of AI (which in some cases may also have included cells located in the dorsal region of the second auditory field, AII), neurons generally preferred fast FM sweeps. However, a comparison of maps from different animals showed that there was more variability in the distribution of preferred speed responses in the ventral region of the cortex. The directional preference of units for FM sweeps was determined for the sweep speed producing the strongest response. Direction selectivity appeared to be nonrandomly distributed along the dorsoventral axis of AI. In general, units that responded best to upward-directed FM sweeps were located in the more dorsal and ventral aspects of AI while units that responded best to downward-directed FM sweeps were usually located in the mid-region of AI. Direction selectivity was also determined for multiunit responses at each of the three FM sweep speeds. In general, there was a relatively close agreement between the spatial distributions of direction selectivity determined for the strongest response with those calculated for the fast and medium speeds. The spatial distribution of direction selectivity determined for slow FM sweeps deviated somewhat from that determined for the strongest response. Near the dorsoventral center of the mapped areas, the distribution of units that responded best to downward sweeps tended to overlay the distribution of units that responded best to slow speeds, suggesting some spatial covariance of the two parameters. However, when the analysis was extended over the entire region of cortex examined in this study, the point-by-point correlation between preferred speed and direction selectivity was not statistically significant. In addition, when neural responses obtained from the dorsal and ventral subregions were analyzed separately, no significant correlation was observed between these two response parameters. This suggests that, for a given cortical location, the response properties of direction selectivity and preferred speed are derived from distinct neural processing mechanisms. Significant observations were also made between preferred FM sweep speed and excitatory bandwidth (i.e., Q10dB and Q40dB) such that units that responded best to slower FM speeds also seemed to have higher Q10dB and Q40dB (i.e., were narrowly tuned) and vice versa. In addition, units that responded well to a broadband transient stimlus in general preferred faster FM sweeps and vice versa. Although these correlations were significant across the entire dorsoventral extent of AI investigated in this study, they were stronger for responses in the dorsal subregion of AI. For direction selectivity, statistically significant correlations with these response parameters were observed more often in the dorsal than the ventral regions of AI. The apparent spatial segregation of neuronal responses to different FM sweep speeds and sweep directions distributed along the isofrequency domain of AI suggests that the global aspects of cortical function are compatible with psychophysically derived notions of parallel streams of processing for different aspects of FM signals.

Notizen: Abstract Trajectory formation of unrestrained forelimb target-reaching was investigated in relation to the effect of a change in target location. Sagittal displacement of the target (6 cm in each direction) gave a selective change of velocity in the x direction (protraction) with an increase or decrease at larger and shorter distances, respectively. In the case of a double-peaked x velocity profile, the change was mainly with respect to the first major component. The shape of the y (sideways) and of the z (lifting) velocity profiles were both almost unchanged, but the onset of the movement in the z direction changed with the x distance. Vertical displacement (4 cm up or 5 cm down) gave increased velocity in the z direction (lifting) when the target was above the normal mid-position and decreased velocity when the target was lower. The velocity was changed with constant rate of rise, so that the rise time increased when the target was elevated and shortened when the target was lowered (pulse width control policy). The change in the z velocity was not selective. In cats with a double-peaked x velocity profile, the second component decreased when the target was elevated and increased when it was lowered. With excessive lowering of the target (14 cm down), the first x velocity component was very much reduced in amplitude so that protraction depended mainly on the second x velocity component. In the cat with a unimodal x velocity profile, a second component appeared in the x and net velocity profiles when the target was excessively lowered. The velocity profile in the y direction changed when the target was lowered so that the horizontal movement path became straighter. Sideways displacement (10–13 cm) produced adduction/abduction, with only moderate changes in x and z velocity profiles. The results are discussed with reference to the angular movements in the elbow and shoulder.

Notizen: Abstract This study examined changes in the performance of a single-joint, elbow task produced by reversible inactivation of local regions within the proximal forelimb representation in area 4γ of motor cortex (MCx) and the red nucleus (RN) of the cat. Inactivation was carried out by microinjecting lidocaine, γ-aminobutyric acid, or muscimol into sites where microstimulation evoked contraction of elbow muscles. Reaction time, amplitude, and speed (velocity or dF/dt) of position and force responses elicited during inactivation were compared to control values obtained immediately prior to inactivation. In addition, we assessed qualitatively the effects of inactivation on reaching, placing reactions, and proprioceptive responses to imposed limb displacement. In the single-joint task, injections in MCx did not increase reaction time (simple or choice) and produced modest and inconsistent reductions in response amplitude (mean-8%) and speed (mean -19%). In contrast, injections of the same amounts of inactivating agents in the forelimb representation of RN consistently increased reaction time (34.4%), and increased the reaction time coefficient of variability (32%). There were small reductions in response amplitude (-4%) and speed (-10%) which were less than those produced by MCx inactivation. During reaching, however, these same injections in MCx and RN produced a substantial loss of accuracy. For MCx, this was due, in part, to systematic hypometria: for RN, inaccuracy resulted from increased variability in paw paths. Placing reactions and corrective responses to imposed limb displacements were also depressed by the cortical and rubral injections. Our results suggest that the forelimb representation in RN plays a role in the initiation of the single-joint, elbow tracking response examined here. The RN may mediate cerebellar regulation of response timing, a function that is likely to be important for interjoint coordination. Although neurons in the forelimb representations of MCx may contribute to force generation in single-joint movements, their contribution to multijoint control appears to be more important and is examined in the subsequent report (Martin and Ghez 1993).

Notizen: Abstract The purpose of this study was to test our hypothesis that the serotoninergic system plays a significant role in airway obstruction during sleep, by focusing on patterns of serotoninergic innervation of the medullary motoneurons involved in upper airway control. We used the combined techniques of retrograde labelling of motoneurons with unconjugated cholera toxin B and immunohistochemistry with antiserum against serotonin (5-HT). The retrograde tracers were injected into posterior cricoarytenoid (PCA), cricothyroid (CT), and genioglossal (GG) muscles of the cat. Motoneurons retrogradely labelled from PCA were identified ipsilateral to the injection site in the caudal part of nucleus ambiguus (NA). Serotonin immunoreactive terminals surrounded their somata and proximal dendrites, suggesting a strong influence of serotonin on the PCA-labelled motoneurons. Motoneurons retrogradely labelled from CT were located ipsilaterally in two distinct groups in the rostral NA and in the retrofacial nucleus (RFN). Selective peripheral nerve section revealed that the CT-labelled motoneurons in the NA had axons in the recurrent laryngeal nerve, whereas the other CT-labelled motoneurons in the RFN were innervated through the superior laryngeal nerve. In the RFN, the pattern of 5-HT innervation in relation to the CT-labelled motoneurons was analogous to that observed with the PCA-labelled motoneurons. In the NA, however, 5-HT terminals made few contacts with the CT-labelled motoneurons, although a dense network of 5-HT terminals was present in the surrounding region. In the GG-labelled motoneuron region of the hypoglossal nucleus, 5-HT terminals were apposed to distal dendrites, not to the soma, indicating less effect of serotonin on GG than on PCA activity. The present results demonstrated that the patterns of 5-HT innervation vary according to the type of motoneurons and their projections to the upper airway.

Notizen: Abstract A retinotopic map can be described by a magnification function that relates magnification factor to visual field eccentricity. Magnification factor for primary visual cortex (VI) in both the cat and the macaque monkey is directly proportional to retinal ganglion cell density. However, among those extrastriate areas for which a magnification function has been described, this is often not the case. Deviations from the pattern established in V1 are of considerable interest because they may provide insight into an extrastriate area's role in visual processing. The present study explored the magnification function for the lateral suprasylvian area (LS) in the cat. Because of its complex retinotopic organization, magnification was calculated indirectly using the known magnification function for area 19. Small tracer injections were made in area 17, and the extent of anterograde label in LS and in area 19 was measured. Using the ratio of cortical area labeled in LS to that in area 19, and the known magnification factor for area 19 at the corresponding retinotopic location, we were able to calculate magnification factor for LS. We found that the magnification function for LS differed substantially from that for area 19: central visual field was expanded, and peripheral field compressed in LS compared with area 19. Additionally, we found that the lower vertical meridian's representation was compressed relative to that of the horizontal meridian. We also examined receptive field size in areas 17, 19, and LS and found that, for all three areas, receptive field size was inversely proportional to magnification factor.

Notizen: Abstract We have investigated the expression of messenger RNA (mRNA) encoding substance P receptor (SPR) in the visual cortex of adult cats and 17-day-old kittens, using in situ hybridization histochemistry with two digoxigenin-labeled oligodeoxynucleotides complementary to the SPR mRNA. In the adult cortex, a subset of large pyramidal neurons of layer V and layer III is heavily labeled. Other, mainly pyramidal neurons in layers II, III and V are less intensely labeled, but most neurons in these layers appear unlabeled. Neurons in layer IV and VI, and in the white matter do not show hybridization signals above background levels. In the 17-day-old kitten, SPR mRNA-expressing cells are confined to layer V and to the upper white matter (subplate zone), whereas supragranular neurons do not yet contain SPR mRNA. A few neurons in layer VI display moderate labeling. Astrocytes, identified with anti-glial fibrillary acid protein antibodies, did not express detectable levels of SPR mRNA in both adult and kitten visual cortex. These results indicate that SPR mRNA expression is transient in neurons of the white matter, and is developmentally regulated in supragranular layers. In addition, the localization of SPR mRNA in a subset of pyramidal cells suggests that substance P modulates the excitability of certain projection neurons which are the origin of extrinsic connections.

Notizen: Summary We examined whether transient projections in the developing central nervous system of Mammalia form functional synapses on their target neurons, using transient ipsilateral interpositorubral (iIR) projection in kittens as a model system. Intracellular recordings were made from red nucleus (RN) neurons in 26 kittens aged 6–26 postnatal days (PD6-26). RN neurons were identified by monosynaptic excitatory postsynaptic potentials (EPSPs) evoked by stimulation of contralateral nucleus interpositus (IN), and additionally by intracellular staining in a few cells. Sixty-nine out of 362 RN neurons responded to stimulation of the ipsilateral IN. Of the 69 cells, 25 showed depolarizing responses with relatively short latency (2.1–6.7 ms) in kittens up to PD20. Such responses were not observed in older animals. Varying stimulus strength revealed that the potentials were unitary. Paired-pulse facilitation of the potential was observed, suggesting that the depolarizations are EPSPs. Several lines of evidence were obtained suggesting that the EPSPs are evoked monosynaptically. They followed high-frequency stimulation up to 50 Hz, and their latencies remained constant with varying stimulus strength. The latencies of ipsilaterally induced EPSPs were always longer than those of contralateral ones, evidence consistent with the longer course of ipsilaterally projecting axons than that of contralateral ones (Song and Murakami 1990). The age of disappearance of the monosynaptic EPSPs, i.e., PD20, also corresponds roughly with that of the anatomically demonstrable iIR fibers (PD15–PD25; Song and Murakami 1990). It is thus concluded that the transient iIR fibers in kittens form functional synapses on RN neurons.

Notizen: Summary Short-latency excitatory postsynaptic potentials (EPSPs) evoked by stimulation in the medial longitudinal fasciculus (MLF) were recorded intracellularly from motoneurons in the cat lumbosacral spinal cord. Monosynaptic and disynaptic EPSPs occurred in most flexor and extensor motoneurons studied. These EPSPs resulted from the activation of fast (〉 100 m/s) descending axons from the MLF to the spinal cord. Several features distinguished monosynaptic and disynaptic MLF EPSPs. Disynaptic EPSPs exhibited temporal facilitation during short trains of stimulation, whereas monosynaptic EPSPs did not. Disynaptic EPSPs, but not monosynaptic EPSPs, were also facilitated by stimulation of the pyramidal tract and the mesencephalic locomotor region. However, disynaptic MLF EPSPs exhibited little or no facilitation when conditioned by short-latency cutaneous pathways. During fictive locomotion, the amplitude of disynaptic MLF EPSPs was modulated, with maximal amplitudes during the step cycle phase when the recorded motoneuron was active, resulting in reciprocal patterns of modulation of flexors and extensors. No comparable change was seen in the amplitude of monosynaptic MLF EPSPs during fictive stepping. These data suggest that the central pattern generator for locomotion modulates disynaptic MLF excitation at a premotoneuronal level in a phase-dependent manner. The effects of lesions made in the MLF and thoracic cord suggest that the interneurons in the disynaptic pathway from the MLF to motoneurons reside in the lumbosacral cord.

Notizen: Summary Visual response properties were examined in the superficial layers of the superior colliculus (SC) of anesthetized, paralyzed cats before and after i.v. administration of d-amphetamine. Receptive fields (RFs) of single SC units were plotted using small spots of light presented to the contralateral eye. Within the first hour following d-amphetamine injections, RF size gradually increased, reaching a maximum 86 min post-injection. On average, the area of the RF increased by 5.6 times and RF expansion was observed in all single units examined in the superficial layers. Over the subsequent 4–8 h following the injection, RF area gradually decreased and returned to control dimensions. Most RFs displayed asymmetrical patterns of expansion, showing relatively more horizontal than vertical growth. As RF expansion developed, responses to stimuli flashed “on” and “off” at various locations both inside and outside the borders of the control RF became progressively more vigorous. In contrast, no significant changes were noted in directionselective responses at any time after d-amphetamine injections. Using an array of light bar stimuli of different lengths, the strength of surround suppression was found to be significantly diminished by d-amphetamine. The reduction in surround suppression was especially clear for bar lengths which exceeded the diameter of the control RF. No RF expansion was observed in the superficial layers of the SC when d-amphetamine was injected intravitreally. Furthermore, d-amphetamine had no discernable effect on the RF sizes of cells in the visual cortex. These results suggest that the RF changes in the SC were not of either retinal or cortical origin. We conclude that the mean retinal area which can potentially influence the activity of RFs in the superficial layers of the SC may be on average over 5 times greater than the RF area determined using conventional methods and criteria. These findings raise the interesting possibility that the relatively small size and sharp borders characteristic of RFs in the superficial layers arise from local inhibitory networks which delimit a broader field of excitatory activity supplied by retinal and cortical afferent terminals. Thus, in order to generate the RF changes observed here, either these local inhibitory circuits are amphetamine sensitive, or more likely, these inhibitory networks are dynamically modulated by an, as yet unidentified, amphetamine-sensitive input affecting visual RFs in the superficial layers.

Notizen: Abstract The activity of cells in the magnocellular red nucleus (RNm) was recorded extra and intracellularly in the curarized thalamic cat performing fictive locomotion. The locomoter episodes were detected from the rhythmic activity recorded in the motor nerves of the contralateral hindlimb. It was confirmed that, during fictive locomotion, a large proportion of the rubrospinal cells (56% in our sample) exhibit a rhythmic pattern of activity which is synchronized with the efferent spinal motor nerve activity. On the basis of the intracellular recordings it was established that phases of intense synaptic activity with mixed excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) are involved in this rhythmicity. After eliminating the cerebellar input to the RNm, it was observed that the cells still received intense excitatory and inhibitory inputs, resulting in a continuous modulation of their membrane potential, due to the occurrence of EPSPs and IPSPs. During fictive locomotor like activity and after elimination of the cerebellar afferents to the RNm, it was observed that the spontaneous PSPs in RNm cells (in the case of 45% of the cells) were organized in repetitive subthreshold bursts occurring in phase relationships with the activity recorded in the motor nerves. Some extracellularly recorded cells (12%) showed a rhythmic firing pattern. It is generally recognized that, in the thalamic cat preparation, the locomotor pattern observed in efferent nerves originates from the central pattern generator (CPG) of the spinal cord. It therefore seems likely that the rhythmicity observed here in the RNm may originate from the spinal CPG and be transmitted through the spino rubral pathway ascending in the ventral part of the cord. It is concluded that the spino rubral pathway may transmit both somatosensory information and corollary discharges relating to the activity of the spinal CPG for locomotion.

Notizen: Abstract The contribution of the lateral suprasylvian cortex to pattern recognition was studied by behavioural detection experiments in combination with bilateral lesions of different parts of the lateral suprasylvian areas (LSA) and area 7 in seven cats. In a two-alternatives forced choice task the cats had to discriminate simple outline patterns which were additively superimposed on a structured visual background made up of broadband Gaussian noise. For various stimulus conditions (moving or stationary patterns and/or background) the detection probability (P D) of the cats was measured as a function of the signal to noise ratio (S/N). Each cat was tested before and after the lesion. Four different types of lesion could be distinguished depending on their extent: (1) lesion of parts of the (LSA); (2) lesion of parts of the LSA with undercutting of areas 17, 18 and 19; (3) lesion of area 7; (4) lesion of area 7 and parts of the LSA. 1. We found that a large bilateral lesion of the LSA led to significant deficits in all test situations which were dependent on the existence of relative velocity of moving patterns against a structured background. The ability of the cats to discriminate simple outline patterns which were kept stationary was not reduced. On the contrary, when they were tested with stationary and moving patterns on unfocused (empty) backgrounds, we found, to our great surprise, that the performance of the lesioned cats was significantly improved compared with intact animals. As these lesioned cats had no deficits with moving patterns on a uniformly grey background, we conclude that the deficits with the moving patterns must have been caused by interactions between patterns and background, and not by movement of a pattern per se. 2. As soon as the lesion of the LSA was extended by a bilateral undercutting of areas 17, 18 and 19 we found very severe deficits in all test situations, regardless of whether the patterns were moving or kept stationary, or whether they were superimposed on a background or not. The most substantial deficits occurred when the patterns were moving on a stationary background. In these situations the cats were no longer able to reach the 84% correct criterion. Again, the cats were able to reach criterion with moving patterns on a uniformly grey background indicating that this deficit is probably caused by the interaction of patterns and background and not by motion of the patterns per se. 3. A large lesion of area 7 led to modest but significant deficits of more or less the same degree in all test situations with the exception of quickly moving patterns on a structured background. In contrast, a much smaller lesion of area 7 yielded significant deficits only when the background was moved and there was a low relative velocity between the patterns and the background. 4. In brief, the combination of a lesion of area 7 with that of the LSA roughly provoked a combination of the effects of the two lesions (1 and 3) alone. We found significant deficits in all test situations. We did not find evidence for any type of functional recovery in any of the lesions described. All deficits were permanent. Our results support the idea of a functional segregation between the LSA and area 7. They confirm that the LSA are involved in pattern recognition whenever it is associated with motion in combination with object-background interactions. This suggests an involvement of the LSA in the analysis of object- and self-induced motion. An interpretation of the results of lesioning area 7 is based on the conjecture that the mechanism of vergence movements or of binocular fusion of both retina images might be impaired. Under this condition it seems conceivable to expect double images or a reduced visual acuity because the images are out of focus. This would have a similar effect on the detection performance in each stimulus configuration. In addition, the results of lesion 4 provide evidence that both functional subunits (LSA and area 7) are not able to compensate for one another. Finally, we conclude from the results after lesion 2 that the LSA is part of a system which is based on the cooperation with striate cortex and requires intact primary cortex for its full function.

Notizen: Abstract Focal blockade of restricted regions in layer V of area 18 was used to assess the contribution of this region to the responses to high-velocity stimuli of cells in retinotopically matched, layer V in area 17. In 40% of cases, blockade within area 18 revealed responses of area 17 cells to high-velocity stimuli to which they previously showed only poor responses. Stimulus specificity of the cells in area 17 was otherwise unaltered. All effects were reversible and repeatable. We suggest that a component of the output of layer V from area 18 normally suppresses the responses of retinotopically matched cells within area 17 to stimuli of high velocity, thereby enhancing the specificity of those cells to stimuli of low velocity

Notizen: Abstract This study investigated the topographical organization of mesodiencephalic areas for monosynaptic activation of vertical eye movement-related oculomotoneurons (OMNs) in anaesthetised cats. Systematic mapping of effective sites for inducing monosynaptic, excitatory field potentials in vertical OMN pools was performed bilaterally using one concentric bipolar stimulating electrode. These OMN pools included superior rectus, inferior oblique, inferior rectus and superior oblique pools of the oculomotor and trochlear nuclei. All the field potentials induced in each OMN pool were negative and had a latency of 0.8–1.2 ms, indicating monosynaptic activation of the OMNs. Effective stimulating sites for inducing the field potentials were distributed at a rostrocaudal level of A 7.0–9.0 and 1.0–4.0 mm lateral from the midline, but especially at A 7.0–8.0 and 2.0–3.0 mm lateral from the midline. Histologically, they were located within and near the medial part of the Forel's field H. Stimulation at a more caudal level of A 5.0–6.0 and 1.0–2.0 mm from the midline was also particularly effective. This area correspond to the interstitial nucleus of Cajal and the nearby reticular formation. For each OMN pool, the above field potentials were induced bilaterally, but predominantly ipsilaterally. These results suggest the existence of a bilateral, but ipsilaterally predominant, monosynaptic excitatory pathway from Forel's field H to each vertical OMN pool.

Notizen: Abstract The distribution of optic chiasm input to different types of neurons in pericruciate cortex of cats agreed with previous work using light flashes. Neuron response times served to differentiate the input pathways to pericruciate cortex, and the types of neurons they influence. Input from the optic chiasm arrived in three distinct surges: the first via the superior colliculus, the second via an unidentified pathway, and the third via the visual cortex. A fourth, diffuse surge arrived in the postcruciate cortex via some unidentified pathway. Stimulation of the contralateral side of the optic chiasm had a weaker effect than stimulation of the ipsilateral side; it evoked activity at a higher threshold, with fewer spikes per response, and at a longer latency. The difference in response latency between the two sides was largest on neurons responding to the first surge, decreasing in later surges, and being least on those neurons responding to the last surge. About 2.3% of the postcruciate and 15% of the precruciate neurons responded only to optic chiasm stimulation; they were isolated in the granular layers, and their responses could not be influenced by prior cutaneous input. It is suggested that much of the visual input to pericruciate cortex serves to modulate on-going cortical output and, thereby, the behavior of the animal.

Notizen: Abstract Trajectory formation of unrestrained forelimb target-reaching was investigated in six cats. A Selspotlike recording system was used for three-dimensional recording of the position of the wrist every 3 ms with the aid of two cameras detecting infrared light emitted from diodes taped to the wrist. These measurements allowed reconstruction of movement paths in the horizontal and sagittal planes and velocity profiles in the direction of the cartesian x, y and z co-ordinates. Horizontal movement paths were smoothly curved, segmented or almost linear. Sagittal movement paths were sigmoid. The net velocity profile was usually bell-shaped with longer deceleration than acceleration, but for some slow movements the velocity profile had a plateau. When the net velocity profile was bell-shaped, the averaged sagittal movement paths and normalized x (protraction) and z (lifting) velocity profiles were virtually superimposable for fast and slow movements: thus, movement speed was changed by parallel scaling of protraction and lifting. Comparison of movement paths and velocity profiles amongst the different cats revealed considerable differences. The ż profile was unimodal in one cat and double peaked in five cats: the second component was pronounced in two cats and small in the other three. The ż profile was unimodal and, except for one cat, it had later onset and summit than the first component of the x profile. In contrast to the interindividual differences, there was a high degree of intraindividual constancy over 6–12 months. It is postulated that the interindividual variability depends on chance differences established early during learning of the task and that the imprinted pattern remains, resulting in intra-individual constancy.

Notizen: Abstract To assess speed- and gait-related changes in semitendinosus (ST) activity, EMG was recorded from three cats during treadmill locomotion. Selected step cycles were filmed, and hip and knee joint kinematics were synchronized with EMG records. Swing-phase kinetics for trot and gallop steps at 2.25 m/s were compared for gait-related differences. Also, swing kinetics for different gallop forms were compared. With few exceptions, ST-EMG was characterized by two bursts for each step cycle; the first preceded paw off (STpo), and the second preceded paw contact (STpc). The two-burst pattern for the walk was defined by a high-amplitude STpo burst and a brief, low-amplitude STpc burst; at the slowest walk speeds, the STpc burst was occasionally absent. For the trot, the STpo burst was biphasic, with a brief pause just after paw off. With increasing walk-trot speeds, the duration of both bursts (STpo, STpc) remained relatively constant, but recruitment increased. Also, the onset latency of the STpo burst shifted, and a greater proportion of the burst was coincident with knee flexion during early swing. At the trot-gallop transition, there was an abrupt change in the two-burst pattern, and galloping was characterized by a high-amplitude STpc burst and a brief, low-amplitude STpo burst. At the fastest gallop speeds, the STpo burst was often absent, and the reduction in or elimination of the burst was associated with a unique pattern of swing phase kinetics at the knee. Knee flexion during the gallop swing was sustained by two inertial torques related to hip linear acceleration (HLA) and leg angular acceleration (LAA); correspondingly, muscle contraction was unnecessary. Conversely, knee flexion at the onset of the trot swing relied on a flexor muscle torque at the knee acting with an inertial flexor torque (LAA). Rotatory and transverse gallops at 4.0 m/s had similar swing phase kinetics and ST-EMG. Gait-related changes in ST-EMG, particularly at the trot-gallop transition, are not congruent with neural models assuming that details of the ST motor pattern are produced by a spinal CPG. We suggest that motor patterns programed by the spinal CPG are modulated by input from supraspinal centers and/or motion-related feedback from the hindlimbs to provide appropriate gait-specific activation of the ST.

Notizen: Abstract In kittens, callosally projecting neurons were labeled by retrograde transport of FITC- (fluorescein isothiocyanate)- and TRITC- (tetramethylrhodamine isothiocyanate)-conjugated latex microspheres injected in two different visual areas (17, 17/18, 19, or postero-medial lateral suprasylvian; PMLS) at postnatal day 3. At postnatal day 57 more than 1200 labeled neurons in visual cortical areas were intracellularly injected with 3% lucifer yellow (LY) in perfusion-fixed slices of the contralateral hemisphere. The distribution of labeled neurons was charted, and LY-filled neurons were classified on the basis of their area and layer of location, and dendritic pattern. The dendritic arbors of 120 neurons were computer reconstructed. For the basal dendrites of supragranular pyramidal neurons a statistical analysis of number of nodes, internodal and terminal segment lengths, and total dendritic length was run relative to the area of location and axonal projection. Connections were stronger between homotopic than between heterotopic areas. Overall tangential and laminar distributions depended on the area injected. Qualitative morphological differences were found among callosally projecting neurons, related to the area of location, not to that of projection. In all projections from areas 17 and 18, pyramidal and spinous stellate neurons were found in supragranular layers. In contrast, spinous stellate neurons lacked in projections from area 19, 21a, PMLS and postero-lateral lateral suprasylvian (PLLS). In all areas, the infragranular neurons showed heterogeneous typology, but in PMLS no fusiform cells were found. Quantitative analysis of basal dendrites did not reveal significant differences in total dendritic length, terminal, or intermediate segment length among neurons in area 17 or 18, and this was related to whether they projected to contralateral areas 17–18 or PMLS. All injections produced exuberant labeling in area 17. No differences could be found between neurons in area 17 (with transient axons through the corpus callosum) and neurons near the 17/18 border (which maintain projections to the corpus callosum). In conclusion, morphology of callosally projecting neurons seems to relate more to intrinsic specificities in the cellular composition of each area than to the area of contralateral axonal projection or the fate of callosal axons.

Notizen: Abstract Pattern visual evoked potentials (VEPs) were recorded from the pial surface of the cat primary visual cortex prior to and following the intravenous administration of physostigmine, an agent which blocks the enzyme responsible for the breakdown of synaptically released acetylcholine. The control VEP was composed of a small initial positive deflection (P1), a subsequent large negative wave (N1) and a second large positive wave (P2). Following physostigmine, the amplitude of P1-N1 was diminished whereas that of N1-P2 increased. These effects were long lasting and were blocked by prior treatment with scopolamine, a result consistent with mediation by a muscarinic cholinergic pathway. Waveform subtraction revealed that the physostigmine-sensitive component had a slow, negative polarity waveform while the physostigmine-insensitive component was also slow, but positive in polarity. The fundamental nature of these components remains to be assessed. Nevertheless, the results indicate that waveforms of different polarity combine algebraically to yield the conventional VEP.

Notizen: Abstract This study explored the locations and input output properties of a large population of putative premotor neurones of skin reflex pathways in the cat. These neurones, interneurones excited by forelimb skin afferents and antidromically from the T1 motor nucleus (MN) and/or the lateral funiculus (LF, C8/T1 border), termed antidromic cells, were extracellularly recorded at C6-8. Selection of this site was based on data showing that cells retrogradely HRP labelled from the T1 MN were most numerous in C6-8 and the observation that transection of LF at the C8/T1 border abolished most skinevoked postsynaptic potentials of T1 motoneurones. Antidromic cells were located in laminae IV–V, VI and VII. The latencies of antidromic excitation ranged from 0.4 to 1.8 ms, with a tendency for laminae IV–V cells to show longer latencies than laminae VI and VII cells. Latency of skinevoked excitation ranged from 0.6 ms (IV–V cells), 0.8 ms (VI) and 1.4 ms (VII) to greater than 5 ms. The sum of the ortho and antidromic latencies (estimated central latency) of individual cells explained the central latencies of skinevoked postsynaptic potentials in T1 motoneurones. Skin-evoked firing responses (average of eight to ten cells) were earliest and largest in laminae IV–V antidromic cells, and latest and smallest in lamina VII cells. The antidromic cells also received inputs from muscle afferents and descending tracts. The following three results support the suggestion that the sampled antidromic cells are mostly premotor neurones. (1) Projection to the T1 MN via LF was verified in six laminae IV–VII antidromic cells, as tested with threshold mapping for antidromic excitation. (2) Three skinexcited axons of the middle LF projected to T1 MN, as revealed by intra-axonal staining (HRP). (3) PHA-L injection in laminae I–V of C8 anterogradely labelled terminals in lamina IX and LF axons at T1. It is suggested that last order neurones of skin reflex pathways to T1 motoneurones are widely distributed in laminae IV–VII of C6-8 and consist of a variety of neurones with different locations and input patterns.

Notizen: Abstract We studied the modulatory actions of microiontophoretically applied acetylcholine (ACH), serotonin (5-HT, 5-hydroxytryptamine) and noradrenaline (NA), and those of the adrenoceptor agonists phenylephrine (PHE, α1), clonidine (CLO, α2) and isoprenaline (ISO, β) on spontaneous and visually induced activities in cat perigeniculate (PGN) and thalamic reticular (NRT) neurons (only spontaneous) during extracellular recordings performed in vivo. ACH and 5-HT were found to affect the ongoing (spontaneous) and visually evoked activity of PGN cells and also the spontaneous activity of NRT cells in an opposite fashion. ACH inhibited tonic firing and often induced burst activity. By contrast, 5-HT exerted an excitatory influence, which caused a long-lasting, very regular, high-frequency activity between about 35 and 120 Hz. Spontaneous as well as 5-HT-induced firing was found to prefer three distinct frequency ranges: 35–42 Hz, 60–67 Hz and 80–120 Hz. Opposite actions of ACH and 5-HT were also evident when applied simultaneously. ACH dampened the high-frequency activity elicited with 5-HT, and 5-HT could replace the burst activity induced with ACH application by a regular tonic activity. The absolute strength of visual responses (in spikes per second) was only slightly enhanced or reduced by ACH and 5-HT, respectively, but due to the strong effects on background activity, ACH clearly elevated the signal-to-noise ratio and 5-HT reduced it. Despite its excitatory action, 5-HT did not facilitate visual responses. Spontaneous changes in ongoing activity were found to affect the visual response amplitude in the same way. Noradrenaline, the α1-agonist PHE and the β-agonist ISO exerted a weak depressant action on high-frequency maintained activity, but during low-frequency single spike activity and/or burst activity a facilitatory effect was evident, which prevented the generation of burst discharges and slightly increased single spike firing. Visually evoked activity was little affected, but signal-to-noise ratio changed with changes in ongoing activity. The α2-agonist CLO clearly attenuated both spontaneous activity and visual responses. We suggest that, in addition to direct effects of ACH and 5-HT on geniculate relay cells, the balance between the opposite actions of ACH and 5-HT on PGN cells determines the mode of operation in the recurrent inhibitory circuit: either a global, tonic inhibition of relay cells during a dominating 5-HT influence or a less tonic but phasic inhibition during increased activity in the cholinergic system.

Notizen: Abstract We examined the influence of acetylcholine (ACh) on the visual response properties of lagged cells in the dorsal lateral geniculate nucleus of anaesthetised cats. By means of electrophysiological techniques, the response of single cells was recorded before, during and after ionophoretic application of ACh. ACh evoked a clear enhancement of the visual response. The initial suppression that a visual stimulus evokes in lagged cells was resistant to the effects of ACh. The characteristic anomalous response component of lagged cells was also present during application of ACh. The difference in latency to half-rise and to half-fall of the visual response that is found between lagged and non-lagged cells was maintained during application of ACh. Taken together, the results support previous evidence from experiments with brain stem stimulation that the fundamental visual response characteristics of lagged cells are state independent.

Notizen: Abstract In a previous study, we reported on a selective and long-lasting paradoxical sleep (PS) deprivation in cats following repeated administration of the Parkinson syndrome-inducing neurotoxin N-methyl-4-pheny11,2,3,6-tetrahydropyridine (MPTP). While the characteistic motor deficits occurred only from the 2nd to 3rdday of a 5-day long administration of 5 mg/kg per day MPTP i.p., the PS deprivation started immediately after the first injection and lasted altogether for 11–13 days. The motor deficiencies induced by repeated administration of MPTP are mainly due to the selective depletion of dopaminergic neurons in the nigrostriatal system as the histological and biochemical data show. The immediate onset of PS deprivation and the PS recovery, despite the definite cell loss, suggests a mechanism independent of cell destruction. In our present study we investigated the occasional histological and the PS-deprivatory effect of a single low dose of MPTP in cats. A single injection of 2 mg/kg MPTP i.p. resulted in PS deprivation lasting for 2.5–3.5 h. The duration of other sleep stages showed no significant change and PS recovery was without rebound phenomenon, as in the case of repeated administration. Even a higher single dose of MPTP (5 mg/kg) resulted in no visibly detectable nigrostriatal cell loss. We suggest that the changes in monoamine release and/or turnover are involved in the PS deprivatory effect of MPTP.

Notizen: Abstract We examined the orientation tuning curves of 86 cells located in layer V of area 17, before, during, and after focal blockade of a small (300-μm diameter) region of near-retinotopic register in layer V of area 18 of quantitatively established orientation preference. Such focal blockade revealed three distinct populations of area 17 layer V cells-cells with decreased responses to stimuli of some orientations (21%), cells with increased responses to stimuli of some orientations (43%), and cells unaffected by the focal blockade (36%). These effects were clearcut, reproducible, and generally directly related to the known receptive field properties of the cell recorded in area 18 at the center of the zone of blockade. These effects were also analyzed in terms of alterations in orientation bandwidth in the cells in area 17 as a result of the blockade-bandwidth increases (22%) and decreases (24%) were found; however, these changes were essentially unrelated to the measured receptive field properties. Inhibitory and excitatory effects were most pronounced when the regions in areas 17 and 18 were of like ocular dominance and were of similar orientation preference. Inhibitory effects (suggesting a normally excitatory input) were most dependent upon the similarity of receptive fields; excitatory effects (suggesting a normally inhibitory input) were less heavily dependent.

Notizen: Summary We studied in decerebrate, paralyzed cats, the effect of sinusoidal yaw rotation on upper cervical commissural neurons. The activity of some neurons was modulated by this stimulus, and they were classified as receiving input from the horizontal semicircular canal. The responses, which were mainly type II, were well correlated with the velocity of the stimulus. These commissural neurons, some of them propriospinal, transmit horizontal canal signals to the contralateral ventral horn, presumably to motoneurons, as well as to more caudal levels of the spinal cord.

Notizen: Abstract We are studying the response to injury within the brainstem trigeminal nucleus following trigeminal nerve lesions. We have previously shown with light microscopy and reduced silver stains that unilateral retrogasserian rhizotomy results not only in massive degeneration throughout the ipsilateral spinal trigeminal nucleus; in addition, degeneration is seen in a ventral position at the periobex region (involving caudal pars interpolaris and rostral pars caudalis) in the contralateral spinal trigeminal nucleus. In the present study, we have used electron microscopy to identify the source of the degenerating elements seen bilaterally after unilateral retrogasserian rhizotomy in eight adult felines with survival times ranging from 3 to 20 days. At short survival times (3–7 days) degenerating terminals with round synaptic vesicles (R terminals) and type 1, asymmetric contacts predominate bilaterally, while fewer degenerating terminals with flattened synaptic vesicles (F terminals) and type 2, symmetric contacts are seen. At longer survival times more F terminal degeneration is seen, especially on the contralateral side. Postsynaptic sites and dendrites show minimal alterations. These findings suggest that the degenerating R terminals seen on the contralateral side originate from primary afferents while the degenerating F terminals seen on the contralateral side originate from intrinsic sources involving a crossed internuclear pathway. In addition, the finding of degenerating F terminals may represent a novel form of selective transynaptic change of intrinsic neurons, associated with minimal dendritic or somatic alterations.

Notizen: Abstract It has been suggested for a number of years that ganglion cells inform the rest of the brain about contrast in the retinal image. The purpose of the work undertaken here was to demonstrate this fact explicitly. Extracellular recordings were made from X- and Y-cell axons of the optic tracts of anesthetized cats. Responses of these cells to gratings that were near optimal in spatial and temporal frequency were measured for a range of contrasts. For each cell, similar measurements were made at a number of light levels, spanning the photopic to high scotopic (inclusive) ranges. A monotonie relationship between response and contrast was found at all light levels studied, and the same relationship was retained to a good approximation across all light levels. A similar result was also found when nonoptimal spatial frequencies were used as stimuli. These results indicate strongly that X and Y cells inform the cat's brain about contrast in the retinal image. It was also observed that the mean discharge rate of X and Y cells did not change with light level, indicating that no information is relayed to the brain by these cells on the mean light level.

Notizen: Abstract To study the biomechanics of the calcaneal ten-don's complex insertion onto the calcaneus, we measured torque-time trajectories exerted by the triceps surae and tibialis anterior muscles in eight unanesthetized decerebrate cats using a multi-axis force-moment sensor placed at the ankle joint. The ankle was constrained to an angle of 110° plantarflexion. Muscles were activated using crossed-extension (XER), flexion (FWR), and caudal cutaneous sural nerve (SNR) reflexes. Torque contributions of other muscles activated by these reflexes were eliminated by denervation or tenotomy. In two animals, minia-ture pressure transducers were implanted among tendon fibers from the lateral gastrocnemius (LG) muscle that insert straight into the calcaneus or among tendon fibers from the medial gastrocnemius (MG) that cross over and insert on the lateral aspect of calcaneus. Reflexively evoked torques had the following directions: FWR, dorsiflexion and adduction; SNR, plantarflexion and abduction; and XER, plantarflexion and modest abduction or adduction. The proportion of abduction torque to plantarflexion torque was always greater for SNR than XER; this difference was about 50% of the magnitude of abduction torque generated by tetanic stimulation of the peronei. During SNR, pressures were higher in regions of the calcaneal tendon originating from MG than regions originating from LG. Similarly, pressures within the MG portion of the calcaneal tendon were higher during SNR than during XER, although these two reflexes produced matched ankle plantarflexion forces. Selective tenotomies and electromyographic recordings further demonstrated that MG generated most of the torque in response to SNR, while soleus, LG, and MG all generated torques in response to XER. Previous studies have shown that interneurons processing afferent information from both XER and SNR differentially excite the MG and LG motoneuron pools. Further, our data demonstrate that forces produced by this differential activation are preserved throughout the calcaneal tendon. We conclude that selective activation of the gastrocnemei permits the animal to take advantage of the complex mechanical insertion of MG and LG at calcaneus and, specifically, to generate different torques at the ankle joint in response to different reflex activations.

Notizen: Abstract Electrical stimulation of the thalamic nucleus pulvinar was found to influence unit activity in the feline caudate nucleus. Twenty-six (18.3%) units were encountered, in this subcortical region of the brain, that responded to activation of the pulvinar input in anesthetized cats and 41 (54%) in awake animals. In the two types of experiments, stimulation of the pulvinar induced mainly an initial excitatory reaction (81% and 78% of responsive cells, respectively). A latency analysis indicated that the majority of responses occurred at a long latency, while 9 (34.6%) cells in anesthetized cats and 5 (12%) in awake animals were excited at a short latency. The short latency is compatible with the involvement of a monosynaptic pathway between the pulvinar and the caudate nucleus. Units that responded to thalamic stimulation were found predominantly in the posterior regions of the caudate nucleus. These results confirm previous neuroanatomical findings of a direct projection from the pulvinar to the feline caudate nucleus. In awake animals, neurons activated by pulvinar stimulation were also tested, using visual stimuli of various orientations. Out of 41 units, 63% were classified as having “visual responses”. Of these, 5 cells were found to respond selectively to a particular orientation of the visual stimulus. Three of these were excited at a short latency by pulvinar stimulation. The possible involvement of a direct pathway from the pulvinar to the caudate nucleus in the processing of visual information is discussed.

Notizen: Abstract The distribution of immunoreactivities to six amino acids, possibly related to synaptic function, was investigated in the motor nucleus of the cat L7 spinal cord (laminae VII and IX) using a postembedding peroxidase-antiperoxidase technique. Consecutive 0.5 μm transverse sections of plastic-embedded tissue were incubated with antisera raised against protein-glutaraldehyde conjugates of γ-aminobutyric acid (GABA), glycine, aspartate, glutamate, homocysteate, and taurine. This method allowed localization of the different immunoreactivities in individual cell profiles. The results showed that all these amino acids, except homocysteate, could be clearly detected in either neuronal or glial elements in the ventral horn. In cell bodies of neurons in lamina VII, immunoreactivity was observed for aspartate, glutamate, GABA, and glycine. Adjacent section analysis revealed that combinations of immunoreactivity for glycine/glutamate/aspartate, GABA/glycine/glutamate/aspartate and glutamate/aspartate, respectively, may occur in one and the same cell. In the motor nuclei (lamina IX), immunoreactivity to amino acids was observed in two types of neuron. Large cells, probably representing α-motoneurons, were harboring immunoreactivity to both glutamate and aspartate, while a few small neurons in this area displayed a colocalization of glycine, glutamate, and aspartate. Dendrites and axons in the motor nuclei cocontained glycine/glutamate/aspartate, GABA/glycine/glutamate/aspartate, and glutamate/aspartate immunoreactivities. In both laminae VII and IX, taurine-like immunoreactivity was absent in neuronal cell bodies, but highly concentrated in perivascular cells and small cells with a morphology resembling that of glial cells. A punctate immunolabeling, in all probability representing labeling of nerve terminals, could be demonstrated in the ventral horn for GABA, glycine, and glutamate, but not with certainty for aspartate or taurine. A quantitative estimate of the covering of cell bodies of α-motoneuron size by immunoreactive puncta revealed that glycine immunoreactive terminal-like structures were most abundant (covering 26–42% of the somatic membrane), while glutamate immunoreactive terminals were seen least frequently (5–9% covering). GABA-immunoreactive terminals covered from 10 to 24% of the soma surface. A colocalization of GABA and glycine immunoreactivities in putative nerve terminals could be shown both in the neuropil and in close relation to cell bodies of motoneurons. These results suggest that among the studied amino acids probably only three, namely GABA, glycine, and glutamate, can be considered to be neurotransmitter candidates in the ventral horn of the cat spinal cord.

Notizen: Summary The effects of β -phorbol 12, 13-dibutyrate (PDBu) on the discharge properties of slowly conducting knee joint afferents (group III and group IV fibers) were studied to determine the role of protein kinase C in nociception. Extracellular single unit recordings were made from small filaments dissected from the medial articular nerve in cats anesthetized with alphachloralose. PDBu was applied intra-arterially close to the joint in concentrations of 10-6 up to 10-4 M. The afferents were classified as low-threshold and high-threshold units with regard to their sensitivity to passive noxious and innocuous movements of the knee joint. Following PDBu application, an excitation occurred in 28% of the group III and in 40% of the group IV fibers. An enhancement of responses to passive movements of the joint (sensitization) occurred in 37% of group III and 19% of group IV afferents. In summary, 37.5% of the low-threshold and 50% of the high-threshold fibers proved to be sensitive to PDBu. Most of the PDBu-positive units responded also to bradykinin, whereas only a few PDBu-positive units were sensitive to prostaglandin I2 and E2. We conclude from these results that, in a distinct population of slowly conducting joint afferents, protein kinase C is likely to be involved in the process of transduction. Thus, pain and hyperalgesia may be mediated at least partly by intracellular mechanisms that are linked to protein kinase C.

Notizen: Abstract In a previous study, we have shown that the corticofugal projection to the dLGN enhances inhibitory mechanisms underlying length tuning. This suggests that the inhibitory influences deriving from the corticofugal feedback should exhibit characteristics that reflect the response properties of orientation-tuned layer VI cells. Here we report data obtained from experiments using a bipartite visual stimulus, with an inner section over the dLGN cell receptive field centre and an outer section extending beyond it. For both X and Y cells there was a modulation of the strength of the surround antagonism of centre responses that was dependent on the orientation alignment of contours in the two components of the stimulus. Layer VI cells showed maximal responses when the two components were aligned to the same orientation; dLGN cells showed a minimal response. Varying the orientation alignment of the inner and outer components of the stimulus in a randomised, interleaved fashion showed that bringing the stimulus into alignment resulted in a 24.28% increase in the surround antagonism of the centre response. Blocking cortical activity showed this effect of alignment to be strongly dependent on corticofugal feedback. This effect of orientation alignment appears to apply for any absolute orientation of the alignment condition and supports the view that an entire subset of cortical orientation columns generate the feedback influencing any given dLGN cell. This mechanism makes dLGN cells sensitive to the orientation domain discontinuities in elongated contours moving across their receptive field.

Notizen: Abstract Experiments were performed to determine whether the receptors of the glabrous skin of the cat planum nasale (PN) could function in tactile analysis. Trigeminal projection sites of the PN were first identified using transganglionic transport of wheat germ agglutin-in-horseradish peroxidase and horseradish peroxidase. Restricted projection sites were identified in this way among the interstitial neurons of the trigeminal tract, in the dorsal horn of the medulla, in subnucleus interpolaris and to a lesser extent in subnucleus oralis. Electrophysiological recording in the trigeminal spinal nucleus confirmed the major neuroanatomical findings and confirmed the paucity of PN projections to the trigeminal system. Most neurons innervated from the PN have small receptive fields, are rapidly adapting and responsive to PN vibration at amplitudes as low as 10 μm. Neurons could be entrained at frequencies below 80 Hz. This upper limit for entrainment presumably reflects the lack of pacinian corpuscles in the PN. A limited number of slowly adapting neurons were found, but only responded to PN displacements of 400 μm and above. The data suggest that the PN can function in tactile analysis to a limited degree. The significance of these findings is considered with respect to the organization of neural systems controlling head movement.

Notizen: Abstract The activity of tectoreticulospinal neurons (TRSN) during orienting gaze shifts was studied in alert, head-fixed cats by intra-axonal recordings. The scope of the study was to evaluate the role of this class of superior colliculus neurons in the generation of slow eye movements (drifts) which often follow main-sequence saccades and sometimes appear as an independent motor event of orienting. The parameters of such movements are described in the first part of the paper. The organization of underlying pathways in the lower brainstem has been studied by intra-axonal horseradish peroxidase (HRP) tracing. The mean amplitude of postsaccadic drifts (PSD) is 1.21° (SD 0.63), but it can eventually reach 6–8°. PSDs have mean velocity of 14.9°/s (SD 4.28) and mean duration of 104.2 ms (SD 50.8). These two parameters are positively correlated with PSD amplitude. The presence of PSDs is usually associated with an increased neck muscle activity on the side toward which the eyes move. The durations of these two motor events show a reliable positive correlation. PSDs appear to occur when gaze error persists after a saccade and a correction is attempted by means of a slow eye movement and a head turn. The durations of TRSN bursts are, on average, longer than the sum of the lead time and the saccade duration. Bursts associated with combinations of saccades and PSD are significantly longer than those recorded in the absence of PSDs. The probability of occurrence of PSDs is higher when firing of TRSNs continues after saccade termination. Such prolonged discharges usually coincide with a combination of PSDs and phasic activation of the neck electromyogram. The mean firing rate of TRSNs during PSDs is 62% of that during saccade-related portions of the burst and declines to 45% after the end of PSDs. According to its timing and intensity, postsaccadic firing of TRSNs is appropriate as a signal underlying slow, corrective eye movements and later portions of phasic neck muscle contractions during orienting. Intraaxonal HRP labeling showed that visuomotor TRSNs of the X type (n = 3) terminate in the abducens nucleus, with 145–331 boutons terminaux and en passant. Average bouton densities in the nucleus are lower than in the periabducens reticular formation, but higher than in more rostral paramedian pontine reticular formation (PPRF) regions. Terminal fields in the PPRF match the locations of “eye-neck” reticulospinal neurons (RSNs) and exitatory burst neurons. Termination densities comparable with those in the caudal PPRF are found also in the rostral nucleus reticularis gigantocellularis, which contains phasic RSNs (“neck bursters”) and inhibitory burst neurons. Morphological observations alone do not exclude firing rate modulation of abducens motoneurons through the monosynaptic tectal pathway. However, the available physiological data point to a major role of a multiple convergent connection involving the eye-neck RSNs. In conclusion, the signals of X type TRSNs, reinforced by parallel connection through RSNs, encode mainly the intended head movement. Collateral actions of these two populations may be sufficient to induce slow, orienting eye movements, independently of the burst output from the classic saccadic generator.

Notizen: Abstract Intrapontine microinjections of serotonin in acutely decerebrated cats resulted in the bilateral augmentation of the postural muscle tone of the hindlimbs. Optimal injection sites were located in the dorsomedial part of the rostral pontine reticular formation corresponding to the nucleus reticularis ponds oralis (NRPo). In this study, attempts were made to elucidate the cellular basis for the serotoninergically induced augmentation of postural muscle tone by recording the electromyographic (EMG) activity of hindlimb extensor muscles, the monosynaptic reflex responses evoked by electrical stimulation of group Ia muscle afferent fibres and the membrane potentials of hindlimb alpha-motoneurons (MNs). Serotonin injections resulted not only in the augmentation of the EMG activity of gastrocnemius soleus muscles, but also in the restoration of EMG suppression, which was induced by previous injection of carbachol into the NRPo. Extensor and flexor monosynaptic reflex responses were facilitated by serotonin injections into the NRPo. Such reflex facilitation was not induced by serotonin injections into the mesencephalic or the medullary reticular formation. Intrapontine serotonin injections resulted in membrane depolarization of extensor and flexor MNs with decreases in input resistance and rheobase. Spontaneous depolarizing synaptic potentials (EPSPs) increased in both frequency and amplitude. Peak voltage of Ia monosynaptic EPSPs also increased. Serotonin injections which followed carbachol injections resulted in membrane depolarization of MNs along with an increase in the frequency of spontaneous EPSPs and a decrease in carbachol-induced inhibitory postsynaptic potentials. Following pontine carbachol injections, antidromic and orthodromic responses in MNs were suppressed. Discharges of MNs evoked by intracellular current injections were also suppressed, but were restored following serotonin injections. These results indicate that postsynaptic excitation, presynaptic facilitation and disinhibition (withdrawal of postsynaptic inhibition) simultaneously act on the hindlimb MNs during serotonin-induced postural augmentation and restoration.

Notizen: Abstract This study analyzed changes in the performance of a reaching task and its adaptive modification produced by reversible inactivation of three sites within the forelimb representation of the motor cortex (MCx, area 4γ) in five cats by microinjections of muscimol. Two sites were located in the lateral MCx, rostral (RL-MCx) and caudal (CL-MCx) to the end of the cruciate sulcus, where intracortical microstimulation (ICMS) produced contraction of the most distal muscles. The third site was located more medially, in the anterior sigmoid gyrus (RM-MCx) where ICMS primarily produced contraction of more proximal muscles. The task required the animals to reach into a horizontal target well, located in front of them at one of three possible heights, to grasp and retrieve a small piece of food. The height of the reach was primarily achieved by elbow flexion. Grasping consisted primarily of digit flexion, and food retrieval consisted of forearm supination and shoulder extension. In some blocks of trials, an obstacle was placed in the path of the limb to assess the animal's ability to adaptively adjust the kinematic characteristics of their response trajectory. In normal animals, contact with the bar on the first trial triggered a corrective response at short latency that allowed the paw to circumvent the bar. On all subsequent trials, the trajectory was adapted to prevent contact with the obstacle, with a safety margin of about 1 cm. Inactivation at all sites produced a slowing of movement, a protracted and extended forelimb posture, and increased variability of initial limb position. In addition, inactivation of RL-MCx immediately produced systematic reaching errors, consisting of hypermetric movements, as well as impaired grasping and food retrieval. The degree of hypermetria was similar for all target heights and was not associated with alterations in trajectory control. During inactivation, animals did not compensate for the hypermetria by reducing paw path elevation, suggesting a defect in kinematic planning or in adaptive control. This was confirmed by finding that trajectory adaptation to avoid bar contact was impaired during RL-MCx inactivation. The short latency corrective response, triggered by contact of the limb with the obstacle was, however, preserved. Inactivation of CL-MCx did not impair aiming, grasping, or adaptation immediately after injection. However, impairments occurred after about 1 h postinjection, and at that time mimicked the effects of RL-MCx inactivation. This delay suggests that the drug was acting indirectly on the RL-MCx. Inactivation of RM-MCx did not impair the control of distal muscles, but the reaches became hypometric. The hypometria was greater for higher targets, suggesting that it resulted from weakness. Our results suggest that both rostral regions of the forelimb area of MCx play a more important role in the planning and execution of the prehension response than the caudal portion. We hypothesize that (1) the slowing of movement, forelimb postural changes, hypometria, and grasping and food retrieval impairments are due to defective control of muscles represented locally at each site in MCx and that (2) aiming and adaptation defects, which are produced only by RL-MCx inactivation, result from disruption of integrative mechanisms underlying sensorimotor transformations that normally assure movement accuracy.

Notizen: Abstract Synchronised oscillatory population events (35–80 Hz; 60–300 ms) can be induced in the visual cortex of cats by specific visual stimulation. The oscillatory events are most prominent in local slow wave field potentials (LFP) and multiple unit spikes (MUA). We investigated how and when single cortical neurons are involved in such oscillatory population events. Simultaneous recordings of single cell spikes, LFP and MUA were made with up to seven microelectrodes. Three states of single cell participation in oscillations were distinguished in spike triggered averages of LFP or MUA from the same electrode: (1) Rhythmic states were characterised by the presence of rhythmicity in single cell spike patterns (35–80 Hz). These rhythms were correlated with LFP and MUA oscillations. (2) Lock-in states lacked rhythmic components in single cell spike patterns, while spikes were phase-coupled with LFP or MUA oscillations. (3) During non-participation states LFP or MUA oscillations were present, but single cell spike trains were neither rhythmic nor phase coupled to these oscillations. Stimulus manipulations (from “optimal” to “suboptimal” for the generation of oscillations) often led to systematic transitions between these states (from rhythmic to lock-in to non-participation). Single cell spike coupling was generally associated with negative peaks in LFP oscillations, irrespective of the cortical separation of single cell and population signals (0–6 mm). Our results suggest that oscillatory cortical population activities are not only supported by local and distant neurons with rhythmic spike patterns, but also by those with irregular patterns in which some spikes occur phase-locked to oscillatory events.

Notizen: Abstract Several studies have suggested that the caudal hypothalamus modulates responses to hypercapnia and hypoxia. In addition, this area of the hypothalamus contains neurons that have a sympathoexcitatory discharge. The purpose of the present study was to determine whether the basal discharge of caudal hypothalamic neurons that are stimulated by hypercapnia or hypoxia is related to cardiovascular (sympathetic discharge and/or the cardiac cycle) and/or respiratory activity (phrenic nerve discharge). Hypothalamic single unit activity, phrenic nerve activity, and cervical sympathetic nerve activity were recorded in anesthetized cats. Computer averaging techniques were used to compare temporally the discharge of hypothalamic neurons with cardiovascular and/or respiratory activity. Cardiorespiratory and hypothalamic neuronal responses to ventilation with hypoxic (10% O2/90% N2) and hypercapnic (5% CO2/95% O2) gases were determined in intact and in peripherally-chemodenervated, barodenervated cats. Thirty-two percent of hypothalamic neurons were stimulated by a hypercapnic stimulus in intact cats; of those that were stimulated by hypercapnia, all had a basal discharge related to cardiovascular and/or respiratory activity. Hypoxia significantly increased the discharge rate of 21% of hypothalamic units in intact animals; 90% of those had a cardiovascular and/or respiratory-related rhythm. Only 13% of the neurons were stimulated by both hypoxia and hypercapnia. Similar results were found in barodenervated, peripherally chemodenervated cats. Neurons excited by these stimuli in both the intact and denervated cats were found to be concentrated in the posterior hypothalamic area. The results of this study suggest that a group of caudal hypothalamic neurons contribute to the cardiorespiratory responses to hypoxia and hypercapnia, but via separate subpopulations of neurons. In addition, input from peripheral baroreceptor and chemoreceptor afferents is not required for this modulation.

Notizen: Abstract The main input of the lateral part of the cat's lateralis posterior-pulvinar complex (LP-P) comes from the primary visual cortex. We investigated the response properties of cells in area 17 projecting to the striate-recipient zone (LPl) of the cat's LP-P complex. The cells' receptive fields were stimulated with drifting sine-wave gratings. Cells whose fibres terminate in the superior colliculus were also recorded, to determine how their properties compare with those of cortico-LPl cells and to investigate the possibility that LPl is innervated by collaterals of cortico-tectal units. A total of 26 cells in the striate cortex were identified by antidromic activation from the LPl (mean latency 2.2 ms) and 22 from the colliculus (mean latency 2.5 ms). Only six cortical cells could be activated from the LPl and the colliculus. All cortico-LPl cells except for two responded to drifting sinusoidal gratings with unmodulated discharges (AC/DC ratios 〈1). On the basis of their modulation index, these units were classified as complex cells. All cortico-LPl cells were selective for the orientation of gratings (mean bandwidth of 28°). There was a tendency for cortico-LPl cells to prefer vertical and horizontal orientations. More than half of these cells (57%) were direction selective. Strong orientation anisotropies were also found in the receptive fields of cortico-tectal cells, since almost all units responded preferentially to horizontally oriented gratings. The mean preferred spatial and temporal frequencies of cortico-LPl cells were 0.74 c/deg (bandwidth 2.03 octaves) and 2.7 Hz (bandwidth 2.5 octaves), respectively. These properties did not differ significantly from those of cortico-tectal cells. Most cortico-LPl cells (72%) exhibited contrast-response curves with saturation at low contrast (mean half-saturation 0.2). For the remaining units, the responses increased linearly with contrast without clear saturation. For more than half of cortico-tectal cells (60%), the contrast function was also characterised by a response saturation. Almost all cortico-LPl cells responded to moving random dot patterns with mean tuning functions of 43.6°. “Standard” as well as “special” complex cells were found to be equally responsive to the motion of visual noise. Similar properties were recorded for cortico-tectal cells (mean bandwidth of 44.2°). Cortico-LPl and cortico-tectal cells were either binocularly or monocularly driven by the contralateral eye and their mean spontaneous firing rates were 11.7 and 10.9 spikes/s, respectively. These cells were presumably located in layer V. Stimulation of LPl and colliculus also evoked trans-synaptic responses in area 17. The average latency of the orthodromic responses from LPl was much shorter than that from the colliculus (medians 3.5 and 50 ms, respectively). The findings indicate that almost all cortico-LPl units have complex receptive fields and that their overall properties differ from those of recipient cells in LPl. These results also indicate that LPl is not likely to be innervated by collaterals of fibres of cortico-tectal cells. While cortico-LPl and cortico-tectal cells appear to form two distinct populations, there is no significant difference between the overall properties of these two cell groups.

Notizen: Summary The development of microspore mother cells (MMC) and tapetum in male-fertile and male-sterile anthers of Beta vulgaris L. was compared at the electron microscope level. These studies were complemented by morphometric analyses of mitochondria in both tissues through successive stages of microsporogenesis. The earliest irregularities in the ultrastructure of male-sterile anthers were noted within the tapetum at the tetrad stage. These disturbances were initially expressed by a slight reduction in mitochondrial size and the appearance of concentric configurations of endoplasmic reticulum. As development proceeded, a further decrease in mitochondrial size become more conspicuous and was accompanied by a reduction in ribosome population and a failure of the tapetum to produce Ubisch bodies. This failure to produce Ubisch bodies is reflected in the underdevelopment of sterile microspore exine.

Notizen: Summary Structures have been found in the locular space between the tapetal cells and megaspores in Selaginella argentea and S. kraussiana that enter the megaspore wall and extend to the plasma membrane of the megaspore cytoplasm. We have called these structures “wicks”. Unless special fixation procedures are used wicks are either very poorly preserved or not apparent. Wicks appear to be routes for the transport of materials from the tapetum to developing megaspores. The entry of the wicks into the megaspore wall and their passage throughout the wall implies that the megaspore wall of Selaginella is a three-dimensional mesh-work of inter-connecting spaces. Wicks have several macromolecular-sized subunits, and the results of our histochemical reactions indicated the presence of glycoprotein and/or mucopolysaccharide. X-ray microanalysis of the S. convoluta exospore showed that silicon is present in rod-shaped structures between units of the exospore in mature megaspores. Because of the size and form of the structures between the exospore units we consider that they are remnants of wicks stabilized by silicon.

Notizen: Summary Phenylcinnoline carboxylate compounds SC-1058 and SC-1271 cause complete male sterility in wheat when applied at suitable dosages at the pre-meiotic stage of anther development. Anthers from treated and untreated plants were compared using light and electron microscopy from the pre-meiotic stage through the formation of nearly mature pollen. Overall anther development is gradually slowed in treated plants and pollen development is generally arrested in the late prevacuolate or early vacuolate microspore stage, although the first pollen mitosis does sometimes occur. The sporopollenin-containing exine walls are thinner, and show abnormally developed foot and tectum layers with sparse connecting baculi. Microspore cytoplasm degenerates and the cells eventually collapse. At the early, prevacuolate, free microspore stage treated tapetal cells hypertrophy, expanding into the locule. They contain abnormally large vacuoles that appear to form from the fusion of secretory vesicles, and some vacuoles contain electrondense deposits. The sporopollenin-containing orbicular wall and Ubisch bodies are retarded in their development and are structurally deformed. Acetolysis of whole anthers and of thick sections shows that the sporopollen-in-containing structures of treated materials are greatly reduced in thickness and are less rigid than in the control. We conclude that application of these compounds causes interference with the secretory function of tapetal cells which supplies sporopollenin cell-wall polymers to the exine of the microspores and to the tapetal orbicular wall and associated Ubisch bodies. Interference with the tapetal secretion of other nutrients required for microspore development is strongly suggested.

Notizen: Summary Several kinds of outgrowth from the grass ovule are known. Attention is focused here on one outgrowth that occurs within or around the micropyle and is of nucellar origin. Grass species in which it is currently known to occur are listed and examples of variants briefly described. Attention is concentrated upon Pennisetum, where the cell structure is described in detail with a series of electron photomicrographs. The tissue representing an aggregation of these transfer cells is newly named with the term ‘embellum’, and its significance for pollen tube growth is considered.

Notizen: Summary The ultrastructure of the epidermal and sub-epidermal cells of the appendix of the Sauromatum guttatum inflorescence reveals developmental changes during anthesis. These changes precede, and probably make possible, heat and odor production. Two days before D-day (the day of heat production and inflorescence-opening) the mitochondria of the epidermis divide; apparent division of the amyloplasts was observed at the same time. The presence of lipid bodies and peroxisomes in the epidermis was clearly evident. On D-day, the epidermis becomes a continuous layer in which the cell walls separating two adjacent cells disappear. At the same time, in the sub-epidermal cells, the mitochondria and the amyloplasts undergo division. The mitochondria become electron-dense, and their DNA is clearly visible. On that day, lipids as well as starch are being depleted. The peroxisomes change in structure every day, from D-2 to D-day. It has also been demonstrated by histochemical techniques that during anthesis the activity of cytochrome c oxidase (3,3-diaminobenzidine as a substrate) decreases whereas the activity of NADH dehydrogenase [tetrazolium salts: nitro-blue tetrazolium chloride (NBT) or neotetrazolium chloride (NT) in the presence of NADH], increases. Oxygen consumption of isolated mitochondria from the D-day appendix was inhibited in the presence of the two tetrazolium salts to a different degree: oxidation of NADH in the presence of NBT was the most sensitive to inhibition, more so than the oxidation of malate and succinate. NT was less effective as an inhibitor in the presence of those three respiratory substrates.

Notizen: Abstract Diazepam (5 mg/kg) increased the number of shocks accepted by rats on two successive trials in the punished drinking test. Thus, the phenomenon of “one trial tolerance” to the anxiolytic effects of benzodiazepines in the elevated plus-maze does not generalise to this other animal test of anxiety. FG 7142 (20 mg/kg) and prior exposure to the odour of a cat had significant anxiogenic effects on two successive trials in the plus-maze. Thus the phenomenon of “one trial tolerance” does not generalise to these anxiogenic effects in the plus-maze. Furthermore, chlordiazepoxide retained its ability to counteract the anxiogenic effects in the plus-maze of prior exposure to cat odour, over successive trials. On the basis of these and previous experiments it is suggested that the state of anxiety generated on trial 2 in the plus-maze is close to a phobic state, against which benzodiazepines are relatively ineffective. Chlordiazepoxide (5 and 10 mg/kg) was also ineffective against the behavioural responses of rats during exposure to cat odour, another possible animal test of phobia. This contrasted with its efficacy against the anxiogenic effects of cat odour that subsequently generalised to and could be detected in the plus-maze.

Notizen: Abstract 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is known for inducing cortical atrophy in the rat thymus. The present study was conducted to provide ultrastructural evidence for the cortical epithelium to be a target for TCDD in vivo. Juvenile male Wistar rats were orally intubated once with either 50 or 150 μg/kg TCDD and killed 4 or 10 days thereafter. Major changes were found in the cortical thymic epithelium. First, a relative shift occurred from “pale” to darker cortical epithelial cell types, as judged by their nuclear and cytoplasmic electron density. This effect was most prominent at 10 days after exposure to 150 μg/kg TCDD. The increased electron density of the cortical epithelium indicates an altered state of cellular differentiation. Secondly, at the 150 μg/kg dose level focal epithelial cell aggregates were seen both at day 4 and day 10 after administration. This aggregation may either be compound induced or represent a secondary event to the collapse of the thymic stroma. Thirdly, increased vacuolation of cortical epithelial cells was apparent. This effect is interpreted as a consequence rather than a cause of thymocyte depletion from the cortex. This study indicates that TCDD exposure affects the cortical epithelium of the rat thymus at a high dose level. Electron microscopy reveals that the differentiation of epithelial cells is altered. In addition, epithelial cell aggregates are formed.

Notizen: Abstract Cultural investigations revealed that Naemacyclus minor, Lophodermium seditiosum and Cenangium ferruginosum were the most frequent colonizers of asymptomatic and symptomatic Pinus sylvestris needles. Since ultrastructural observations showed that morphological features were not suitable to differentiate hyphae of N. minor from hyphae of other isolates, the on-section immunogold labelling technique was applied in combination with an anti-N. minor specific immunoserum. The specificity of this serum was tested against culture hyphae of all isolates. Anti-N. minor specific immunoserum was then used to identify N. minor hyphae in thin sections of green P. sylvestris needles. The infection loci identified were restricted to small tissue areas located in the vicinity of stomata. In the hypodermis, hyphae and endocell-containing hyphae were located within the lumina of host cells but outside the protoplast. The growth of hyphae from cell to cell occurred through pits. The hyphae spreat into the mesophyll intercellularly and continued with the intracellular colonization of moribund and dead mesophyll cells in a later stage of infection. The observed host-parasite interactions at cellular and ultrastructural level are discussed in connection with the still controversial interpretation of the pathogenicity of N. minor.

Notizen: Abstract The ultrastructure of vegetative cells and spores of Bacillus pulvifaciens was studied by CTEM and SEM methods. The vegetative cells are rods, 1.6–4.5 μm long and 0.4–0.6 μm wide, exhibiting typical ultrastructural features of Gram-positive bacteria. The spores are of ellipsoidal shape, 0.6×1.2 μm in size, with six longitudinal ribs reaching up to 130 nm in height. There are satelite ribs on both sides of the longitudinal ribs, reaching up to 20 nm in height. Between the longitudinal ribs, additional transversal ribs were observed in SEM. A special tubular layer, separating the outer and inner coat of the spores, was revealed in ultrathin sections. This layer seems to be a typical ultrastructural feature of Bacillus pulvifaciens spores.

Notizen: Abstract The formation of quasi-multicellular bodies of Treponema denticola was analysed using different electron microscopical methods. These bacteria could develop four different conformations: (i) normal helical forms; (ii) twisted spirochetes, forming plaits; (iii) twisted spirochetes, forming club-like structures; (iv) spherical bodies in different size. Treponemes within spherical bodies, plaits, and clubs proved to be enclosed in a common outer sheath in which the normal arrangement of their axial flagella was lost. The development of the quasi-multicellular bodies starting from the monoforme spirochetes was elucidated and this morphogenetic process is illustrated by a schematic drawing. Factors which might be involved in the induction of the structures are discussed and their possible pathogenetic importance is considered.

Notizen: Summary The occurrence of cells resembling mammalian Langerhans cells in the avian epidermis was studied by ATPase histochemistry, Ia immunoreactivity and electron microscopy. The existence of MHC class II antigen-(Ia) expressing, ATPase-positive dendritic cells, which are ultrastructurally similar to mammalian Langerhans cells except for the absence of Birbeck granules, was demonstrated. These cells may be a basic component of the immune system of birds.

Notizen: Summary The development of endocrine cells in the chicken proventriculus has been investigated using light-and electron-microscopy in conjunction with silver and immunocytochemical techniques. The first morphologically detectable endocrine cells were found in 5-day-old embryos by electron microscopy. From the 9th to the 13th day, endocrine cells in contact with the lumen of the organ could be detected both by electron and light (silver impregnation) microscopy. The number of open-type endocrine cells progressively decreased and the number of closed-type increased after this stage. Until the 16th day, endocrine cells were located exclusively in the luminal epithelium, but afterwards they appeared in progressively greater numbers in the compound glands. After hatching, long cytoplasmic processes could be seen in the endocrine cells. Immunoreactivities to regulatory substances appeared in the following order: serotonin (day-14), avian pancreatic polypeptide, glucagon and somatostatin (day-16), bombesin and neurotensin (day-18), and finally, met-enkephalin (day-21).

Notizen: Abstract Neurofilament immunoreactivity was examined in spinal cords of rats and cats with antibodies to all three subunits (68 kD, 155 kD and 200 kD) and to different phosphorylation states of 200 kD. NFHP-, an antibody against non-phosphorylated 200 kD, labelled all rat neuronal perikarya but failed to labet cat neurofilaments. In both species, the perikarya and processes of motoneurones were immunoreactive for all three subunits but most dorsal horn neuronal perikarya were not immunoreactive for 68 kD and 155 kD. Motoneuronal perikarya and proximal processes showed filamentous labelling for 68 kD but not for 155 kD in the rat, while in neither species did these show labelling with RT97, an antibody against a highly phosphorylated form of 200 kD; immunoreactivity for 200 kD was present in both filamentous (probably partially phosphorylated) and non-filamentous (non-phosphorylated) forms, but in dorsal horn neurones only the latter was present. Interpretations consistent with this data are: in rat and possibly also cat, motoneuronal neurofilaments consist of a 68 kD backbone with partially phosphorylated 200 kD sidearms, with both 155 kD and 200 kD (non-phosphorylated) subunits in a non-filamentous form; this neurofilament becomes more highly phosphorylated along the proximal processes. The dorsal horn neurones probably contain 200 kD in a non-filamentous form but may lack the other subunits.

Notizen: Abstract This investigation concerns the natural history of microlith in the salivary glands of cat. Microliths were detected in more sublingual than submandibular glands and were almost absent in the parotid. They were found intraparenchymally, intraluminally and interstitially, and ultrastructurally in phagosomes of acinar, ductal and myoepithelial cells, intermixed with the cytoplasm of degenerate acinar cells, and in intraparenchymal macrophages and a multinuclear giant cell. They appear to form in healthy acinar cells during autophagocytosis, and possibly to be discharged luminally, laterally or basally, and to form in the debris of degenerate cells intraparenchymally and intraluminally. They appear to be removed by expulsion in the saliva, scavenging macrophages, and possible eventual degradation in the parenchymal phagosomes. The greater occurrence of microliths in the sublingual gland may relate to a low level of secretory activity, and the near absence of microliths in the parotid to a low level of calcium. The feline salivary glands were found to be an outstanding model for the investigation of microlithiasis.

Notizen: Abstract The distribution of GABAA receptors in the inner plexiform layer of cat retina was studied using monoclonal antibodies against the β2/β3 subunits. A dense band of receptor labeling was found in the inner region of the inner plexiform layer where the rod bipolar axons terminate. Three forms of evidence indicate that the GABAA receptor labeling is on the indoleamine-accumulating, GABAergic amacrine cell that is synaptically interconnected with the rod bipolar cell terminal. (1) Electron microscopy showed that the anti-GABAA receptor antibody (62-3G1) labeled profiles that were postsynaptic to rod bipolar axons and made reciprocal synapses. (2) Indoleamine uptake (and the subsequent autofluorescence) combined with GABAA receptor immunohistochemistry showed co-localization of the two markers in half of the receptor-positive amacrine cells. (3) Double labeling demonstrated that half of the receptor-positive somata also contained GABA. These results indicate that a GABAergic amacrine cell interconnected with the rod bipolar cell, most likely the so-called A17 amacrine cell, itself bears GABAA receptors.

Notizen: Abstract The effects of dietary thyroxine on the immunoreactivity of cells in the pars distalis of the adenohypophysis in dwarf (dw/dw) mice were determined by ultrastructural immunocytochemistry. In nontreated dwarfs only adrenocorticotropic hormone (ACTH) cells and luteinizing hormone (LH) cells showed positive reactions to their respective antibodies, whereas no cells showed immunoreactivity to antibodies to growth hormone (GH), thyroid-stimulating hormone (TSH), or prolactin (Prl). In dwarfs supplemented postnatally with dietary thyroxine for 9 wks, the treatment failed to produced immunoreactive GH, TSH or Prl cells. However, LH cells became more prominent and fully developed, with denser concentrations of immunoreactive particles overlying the secretory granules than occurred in nontreated dwarfs. In thyroxine-treated dwarfs, ACTH cells were similar in ultrastructural features and immunoreactivity to those in nontreated dwarfs.

Notizen: Summary The proliferation rate of differentiating fetal rat adrenocortical cells was studied in primary culture. In this system, stimulation with ACTH induces differentiation of zona glomerulosa-like cortical cells into zona fasciculata-like cells. Incorporation of bromodeoxyuridine (BrdU) was studied immunocytochemically by use of anti-BrdU antibody, and the proliferation rate was counted from the monolayer colonies of adrenocortical cells. After 21 days of cultivation in the absence of ACTH, the proliferation rate of zona glomerulosa-like cells was 10%. The rate slowly declined to 1% at the age of 100 days during continuous cultivation in the absence of ACTH. Stimulation with ACTH induced a strong inhibition in the proliferation rate (down to 2% during the first 24 h). Treatment with ACTH during the following 48 h led to an extremely intense proliferation of adrenocortical cells at a proliferation rate of 25%. Continuous treatment with ACTH up to 100 days led to a persistent growth of adrenocortical cells, and a proliferation rate over 2-fold higher than in control cells cultivated in the absence of ACTH. Thus, ACTH is the principal growth-promoting factor also in vitro, as has been found in in vivo studies. This growth effect is mediated by a biphasic course; at the beginning of differentiation the effect is inhibitory and is followed by a persistent stimulation of the growth of adrenocortical cells.

Notizen: Abstract The ultrastructure of testicular interstitium in young and aged adult rats was analysed using morphometric methods, and the plasma testosterone concentration was measured. With increasing age there was an augumentation in the volume of collagen fibrils in the intercellular matrix and in blood vessels. During the aging process (approximately two years) the average volume of the Leydig cell decreased from 1364 μm3 to 637 μm3, but the number of Leydig cells in paired testes increased from 53x106 to 113x106. The absolute volume of smooth surfaced endoplasmic reticulum (SER) per Leydig cell amounted in aged rats to 78% of that in young adult rats. The total amount of SER in paired testes increased by 62% with aging. The present analysis suggests that the ability of SER to maintain peripheral testosterone concentration decreases with age. In young adult rats the absolute volume of peroxisomes per Leydig cell correlated significantly with the concentration of testosterone in blood and also with the absolute volume of SER per Leydig cell. These results combined with ultrastructural observations of close apposition of peroxisomes and SER suggest that peroxisomes have a role in testosterone secretion by Leydig cells.

Notizen: Abstract The histamine-producing enterochromaffinlike (ECL) cells in the acid-producing portion of the rat stomach responded to long-standing hypergastrinemia (omeprazole treatment daily for 8–10 weeks) with hypertrophy (and hyperplasia) and with a reduced number of granules and vesicles per unit cytoplasm. There was a reduction in the ratio of electron-dense granules versus vesicles and an increase in the profile diameter of the vesicles. Also, portacaval shunting (PCS) induced changes in the ECL cells, manifesting (i) as an increase in cell number and size, and (ii) as a reduced number of granules and vesicles per unit area. The cytoplasmic granules and vesicle profiles were enlarged, and the ratio of granules versus vesicles was reduced. The combination of PCS and long-standing hypergastrinemia (omeprazole treatment) produced a greatly enhanced ECL cell hypertrophy (and hyperplasia) and a marked reduction in the number of granules. The ratio of granules versus vesicles was markedly reduced while the profile diameters of both granules and vesicles were increased. The relative predominance of very large vesicles (vacuoles) was a prominent feature of the ECL cells in these rats.

Notizen: Abstract The distribution of nerve fibres in the mucosa of the nasal septum of the rat was investigated by means of transmission electron microscopy on transverse and tangential ultrathin sections. Near the basement membrane of respiratory and squamous epithelium, a rather dense network of unmyelinated nerve fibres occurs. Some fibres in the respiratory epithelium ascend between the epithelial cells to reach up to the tight junctions. These fibres appeared in transverse sections to end as hooks or boutons, sometimes with branches. These shapes resemble the free nerve endings that are considered to act as nociceptors. The small intraepithelial fibres, with diameters of about 0.5–1 μm, contain both dense granules and clear vesicles comparable to synaptic vesicles. Substance P was found in dense granules in basal fibres; vasoactive intestinal peptide was absent throughout the epithelium. Acetylcholinesterase activity was observed closely associated with the basal fibres; the apical fibres showed little if any activity. Membrane specializations pointing to an efferent function as well as structures usually associated with mechanoreceptive functions were lacking in both respiratory and squamous epithelium.

Notizen: Abstract Galanin is a 29 amino acid residue neuropeptide. In mammalian airways, galanin is found in nerve fibers associated with airway smooth muscle, bronchial glands, and blood vessels, and in nerve cell bodies of airway ganglia. The present study was conducted to determine if galanin-containing fibers in the walls of feline airways originate from the nerve cell bodies of airway ganglia. The colocalization of galanin with vasoactive intestinal peptide was also investigated. Organotypic cultures of cat airways were held in culture for 0 (nonculture control), 3, 5, and 7 days. After each culture period, the distribution of galanin and the colocalization of galanin with vasoactive intestinal peptide were determined by immunocytochemistry. Galanin-containing fibers were found in bronchial smooth muscle, around bronchial glands and in the walls of bronchial arteries and arterioles throughout the culture period. Nerve fibers and cell bodies containing both galanin and vasoactive intestinal peptide were observed after all culture periods. Nerve fibers and cells bodies that contained galanin frequently contained vasoactive intestinal peptide as well, but nerve fibers with only galanin or vasoactive intestinal were also observed. Galanin- and vasoactive intestinal peptide-containing nerve fibers and cell bodies were both well maintained throughout the culture period. The findings show that galanin-containing nerve fibers associated with bronchial smooth muscle, bronchial glands, and bronchial arteries, originate from nerve cell bodies of intrinsic airway ganglia, and that galanin and vasoactive intestinal peptide are frequently colocalized in these neurons.

Notizen: Abstract The effects of gonadectomy and testosterone treatment on the fine structure of the Harderian gland in male and female green frogs were investigated in different periods of the year. Gonadectomy, carried out when the glands are in the lowest secretory phase (September), causes degenerative changes consisting of a reduction of the rough endoplasmic reticulum, the appearance of autolysosomes, and an increase of nuclear heterochromatin. These effects can be prevented by testosterone treatment. No castration effects are found during the recovery (November) and enhancement (April-May) phases of secretory activity. The results suggest that the frog Harderian gland's sensitivity to testosterone changes during the annual cycle. The androgen dependence of the Harderian gland is correlated with the presence of androgen receptors in both male and female forgs.

Notizen: Abstract To determine whether lipid-secreting cells have cytosolic Ca2+ concentration ([Ca2+]c)-related secretory mechanisms, morphological changes and intracellular calcium dynamics of Harderian glands of guinea pigs stimulated by secretagogs were studied by electron microspy and Fura-2/AM digital image analysis. Control glandular cells contained large lipid vacuoles that were bordered by multi-layered membranes. Rough-surfaced endoplasmic reticulum, mitochondria, and smooth-surfaced endoplasmic reticulum may be involved in lipid vacuole formation. Myoepithelial cells surrounded alveoli. After carbamylcholine (CCh, 10−6, 10−5, and 10−3 M) stimulation, lipid materials within the membranous structures were frequently discharged by an exocytotic mechanism. Conspicuous deformation of glandular cells caused by vigorous contraction of myoepithelial cells was observed in isolated alveoli after 10−6M CCh stimulation, whereas the deformaties of glandular tissues perfused via vessels were small even after 10−3M CCh stimulation. Connective tissue between glandular alveoli inhibited unbridled myoepithelial-cell contraction. Fura-2/AM digital imaging analysis revealed that CCh stimulation caused an increase in [Ca2+]c in isolated alveoli. The morphological reactions and changes in [Ca2+]c were prevented by atropine. When extracellular calcium ions were absent, enhanced extrusion of lipid vacuoles, myoepithelial-cell contraction, and a rise in [Ca2+]c after CCh stimulation were not observed. Nicotine and catecholamines had no effect on the secretion or on the dynamics of [Ca2+]c. It can be concluded that acetylcholine elicits exocytosis in glandular cells and contraction of the myoepithelial cells of Harderian glands, accompanied by an increase in [Ca2+]c. The dynamics of [Ca2+]c of the gland alveoli are mostly dependent on extracellular Ca2+.

Notizen: Abstract Insulin (B)-, somatostatin 25 (SST-25) (D1)-, somatostatin 14 (SST-14) (D2)-, glucagon (A)-, and glucagon PP/PYY/NPY (PP-like)-immunoreactive cells in islets of sea bass (Dicentrarchus labrax) were characterized according to their ultrastructure and immunogold labeling. Cells labeled with antisera to bonito and salmon insulin had numerous secretory granules with a small halo and round core, and a few with wide halo and round or crystalloid core. Gold particles were found throughout the granule in tissue labeled with the former but only in the core in tissue labeled with the latter. D1 cells had large granules with a medium electron-dense content and some with a darker core. D2 had smaller medium or high electron-dense secretory granules than D1 cells, located mainly in cell periphery. Glucagon-immunoreactive cells contained some granules with a polygonal core that was heavily labeled and other granules with a round core with no or hardly any labeling. Glucagon and PP-like immunoreactivity were co-localized in secretory granules, in which the gold particles showed no different distribution with the various antisera used. PYY-immunoreactive granules were also found in nerve endings. All the pancreatic endocrine cell types showing involutive characteristics are found.

Notizen: Abstract The integument of the hagfish Myxine glutinosa is described with respect to the topography and the fine structural organization of the dermal and hypodermal nerve fiber plexus. Both nerve fiber plexuses contain small ganglion cells with axodendritic and axosomatic synapscs. The six barbels of the head (4 nasal and 2 oral barbels) are supplied with about 5600 afferent trigeminal nerve fibers via the right and left ophthalmic nerve. With respect to the topography of the sensory nerve terminals in the barbels different types of receptors are termed the external cuff receptor, internal cuff receptor, and perichondrial receptor. Free nerve terminals occur within the epidermal layer, especially at the tip region of the barbels and in the glassy membrane of the dermis. The hypodermal edge receptor organ extends from the ventral nasal barbel to the oral barbel. A mechanoreceptive function of the different receptor types is discussed. The innervation pattern of the barbel is similar to the innervation of the mammalian sinus hair. In this context, the barbel is a highly differentiated receptor organ able to explore the nearest surroundings with high stereognostic perception. The ganglion cells of the skin seem to represent a part of the peripheral autonomic nervous system, which is involved in the control of secretion mechanisms.

Notizen: Abstract We have previously shown that an antibody against neuron-specific enolase (NSE) selectively labels Müller cells (MCs) in the anuran retina (Wilhelm et al. 1992). In the present study the light- and electron-microscopic morphology of MCs and their distribution were described in the retina of the toad, Bufo marinus, using the above antibody. The somata of MCs were located in the proximal part of the inner nuclear layer and were interconnected with each other by their processes. The MCs were uniformly distributed across the retina with an average density of 1500 cells/mm2. Processes of MCs encircled the somata of photoreceptor cells isolating them from each other by glial sheath, except for those of the double cones. Some of the photoreceptor pedicles remained free of glial sheath. Electron-microscopic observations confirmed that MC processes provide an extensive scaffolding across the neural retina. At the outer border of the ganglion cell layer these processes formed a non-continuous sheath. The MC processes traversed through the ganglion cell layer and spread beneath it between the neuronal somata and the underlying optic axons. These processes formed a continuous inner limiting membrane separating the optic fibre layer from the vitreous tissue. Neither astrocytic nor oligodendrocytic elements were found in the optic fibre layer. The significance of the uniform MC distribution and the functional implications of the observed pattern of MC scaffolding are discussed.

Notizen: Abstract The tertiary component of the myenteric plexus consists of interlacing fine nerve fibre bundles that run between its principal ganglia and connecting nerve strands. It was revealed by zinc iodide-osmium impregnation and substance P immunohistochemistry at the light-microscope level. The plexus was situated against the inner face of the longitudinal muscle and was present along the length of the small intestine at a density that did not vary markedly from proximal to distal. Nerve bundles did not appear to be present in the longitudinal muscle as judged by light microscopy, although numberous fibre bundles were encountered within the circular muscle layer. At the ultrastructural level, nerve fibre bundles of the tertiary plexus were found in grooves formed by the innermost layer of longitudinal smooth muscle cells. In the distal parts of the small intestine, some of these nerve fibre bundles occasionally penetrated the longitudinal muscle coat. Vesiculated profiles in nerve fibre bundles of the tertiary plexus contained variable proportions of small clear and large granular vesicles; they often approached to within 50–200 nm of the longitudinal smooth muscle cells. Fibroblast-like cells lay between strands of the tertiary plexus and the circular muscle but were never intercalated between nerve fibre varicosities and the longitudinal muscle. These anatomical relationships are consistent with the tertiary plexus being the major site of neurotransmission to the longitudinal muscle of the guinea-pig small intestine.

Notizen: Summary Elastase (ELA) is an enzyme catalyzing the digestion of elastin, an essential constituent of elastic fibers. Using isolated guinea pig papillary muscles, we examined the effect of ELA (3 × 10−7 −3 × 10−4 g/ml) on resting tension (RT) and twitch tension (TT). The effects of ELA on elastic fibers located in the subendocardium were examined histologically. A relatively high concentration of ELA (3 × 10−4 g/ml) increased TT transiently, with progressive decreases in RT. In contrast, a relatively low concentration (3 × 10−5 g/ml) decreased both TT and RT straightforwardly. Much lower concentrations (3 × 10−6 −3 × 10−7 g/ml) did not reveal significant effects. The ELA-induced increases in TT were unaffected in the presence of atenolol (10−5 g/ml), ouabain (10−7M) or ryanodine (10−6M). ELA did not increase the maximum rate of rise of slow action potentials recorded using standard microelectrodes.ELA (3 × 10−5 g/ml) decreased the maximum TT obtained at optimal RT or Lmax, and decreased the slope of the ascending and descending limbs of the TT-RT relation curve (Frank-Starling's). Electronmicroscopic findings revealed that subendocardial elastin was mostly digested at ELA concentrations of 3 × 10−5 −3 × 10−4 g/ml. These findings suggest that the decrease of RT by ELA may be, at least in part, caused by a decomposition of the elastic fibers. On the other hand, the increase of TT by ELA could not be attributed to a release of endogenous catecholamine, an inhibition of Na+, K+-pump, a release of Ca2+ from sarcoplasmic reticulum, or an increase of slow inward current.

Notizen: Summary The sub-cellular localization of some nitrogen compounds within the leaf cavities ofAzolla filiculoides Lam. was obtained by means of electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS). The analyses were performed on ultrathin unstained sections of differentAzolla leaf cavities which contain epidermal hairs,Anabaena azollae Strasb. and bacteria. Net nitrogen distributions were visualized by image analysis, and nitrogen peaks were evidenced in spectra recorded in the same areas. Different distributions of nitrogen compounds were observed within the leaf cavities along the stem, in particular inside the epidermal hairs ofAzolla and the vegetative cells and heterocysts ofA. azollae.

Notizen: Summary Actin distribution and ultrastructure of the fission yeastSchizosaccharomyces pombe treated with cytochalasin A (CA) were investigated by fluorescence microscopy using rhodamine-conjugated phalloidin (rh-ph) and freeze substitution electron microscopy. Among the cytochalasins tested, CA was most effective and at 5 μg/ ml inhibited the appearance of the actin ring at the cell equator at the stage prior to septum formation and the accumulation of actin dots at the septum-forming site both in wild-type cells and the mutantcdc 11, which is defective in septum formation at restrictive temperature. Freeze substitution electron microscopy of CA-treated cells revealed the displacement and morphological alteration of cytoplasmic vesicles and dictyosomes within 30 min and the appearance of dense bodies in the cytoplasm. A sub-population of cytoplasmic vesicles and dictyosomes were insensitive to CA and maintained their original structure. An electron less dense layer containing filamentous material was noted beneath the plasma membrane and thought to be the area of heavy actin patches stained with rh-ph at the cells ends. These results suggest that CA disrupted an actin network that normally maintains the organization of the secretory pathway involving dictyosomes and vesicles.

Notizen: Summary High-pressure freezing/freeze-substitution/TEM were employed for studying plasma membrane coatings in mature pollen grains. Data are presented on 6 species belonging to 4 not closely related orders. Two sorts of coatings were observed at the cytoplasmic face of the vegetative plasma membrane bordering the generative cell: (i) A dense, uniform layer with an average thickness of 10 nm (“fluffy coating”). (ii) “Strip-shaped projections” protruding rectangularly into the vegetative cytoplasm. They are 25 to 35 nm in height and set at a constant distance of about 30 nm from each other. Their maximum length, estimated from grazing sections, is about 400 nm. This is the first description of periodically arranged plasma membrane protrusions in freeze-substituted plant cells. Both kinds of membrane coatings are species-and age-dependent features. Especially “strip-shaped projections” are frequently intimately associated with polymorphic endoplasmic reticulum surrounding the generative cell, a hitherto unreported pattern. It is presumed that “strip-shaped projections” are similar to, or even identical with, “ordered ridges” observed in freeze-fracturedPhoenix dactylifera pollen.

Notizen: Summary The development of the generative cell (GC) was examined in the bicellular pollen ofCyrtandra pendula. The essential stages are: (1) GC attached to the inline, (2) GC detached and spheroidal in shape, (3) GC mature and elongated. Cisternae of the endoplasmic reticulum (ER) of the vegetative cell are in close contact with the GC at all stages of development. In stages (1) and (2) the entire, slightly undulated surface of the GC is surrounded by tightly appressed, single ER tubules or short stacks. In mature pollen grains (stage 3) the shape of the GC as well as the arrangement of the surrounding ER changes conspicuously. The GC is now spindleshaped and its surface is wrinkled. An ER tubule is present in each invagination. These ER tubules form a cage-like framework around the GC. In the cytoplasm of the generative cell, 6 to 7 microtubular bundles with longitudinal orientation can be observed. They seem to be responsible for maintaining the elongate shape of the GC. During all stages of development vegetative ER cisternae are the only elements intimately associated with the GC wall. This feature indicates that the ER may contribute to the formation of the undulated outer shape of the GC. Also discussed is the possibility that energy-carrying substances are conveyed into the GC through the channels of ER.

Notizen: Summary Brassica napus cv. Topas microspores isolated and cultured near the first pollen mitosis and subjected to a heat treatment develop into haploid embryos at a frequency of about 20%. In order to obtain a greater understanding of the induction process and embryogenesis, transmission electron microscopy was used to study the development of pollen from the mid-uninucleate to the bicellular microspore stage. The effect of 24 h of high temperature (32.5 °C) on microspore development was examined by heat treating microspore cultures or entire plants. Mid-uninucleate microspores contained small vacuoles. Late-uninucleate vacuolate microspores contained a large vacuole. The large vacuole of the vacuolate stage was fragmented into numerous small vacuoles in the late-uninucleate stage. The late-uninucleate stage contained an increased number of ribosomes, a pollen coat covering the exine and a laterally positioned nucleus. Prior to the first pollen mitosis the nucleus of the lateuninucleate microspore appeared to be appressed to the plasma membrane; numerous perinuclear microtubules were observed. Microspores developing into pollen divided asymmetrically to form a large vegetative cell with amyloplasts and a small generative cell without plastids. The cells were separated by a lens-shaped cell wall which later diminished. At the late-bicellular stage the generative cell was observed within the vegetative cell. Starch and lipid reserves were present in the vegetative cell and the rough endoplasmic reticulum and Golgi were abundant. The microspore isolation procedure removed the pollen coat, but did not redistribute or alter the morphology of the organelles. Microspores cultured at 25 °C for 24 h resembled late-bicellular microspores except more starch and a thicker intine were present. A more equal division of microspores occurred during the 24 h heat treatment (32.5 °C) of the entire plant or of cultures. A planar wall separated the cells of the bicellular microspores. Both daughter cells contained plastids and the nuclei were of similar size. Cultured embryogenie microspores contained electron-dense deposits at the plasma membrane/cell wall interface, vesicle-like structures in the cell walls and organelle-free regions in the cytoplasm. The results are related to embryogenesis and a possible mechanism of induction is discussed.

Notizen: Summary Ornithogalum virens is a bicellular pollen species. In mature pollen, the generative nucleus is at advanced prophase. Mitosis of the generative cell is resumed just after pollen rehydration and prometaphase occurs within 10 min of germination. Prometaphase is manifested by nuclear envelope breakdown and the appearance of spindle microtubules in the nucleoplasm region. At this stage the number of cytoplasmic microtubules located in the generative cell periphery appears to decrease. Endoplasmic reticulum-like cisternae originating from the nuclear envelope tend to be spaced around the chromosomes, outside the area of the forming mitotic spindle. Some also begin to penetrate the spindle area. The results are discussed in terms of the generative cell cycle in bicellular pollen.

Notizen: Summary Spontaneous nodules were formed on the primary roots of alfalfa plants in the absence ofRhizobium. Histologically, these white single-to-multilobed structures showed nodule meristems, cortex, endodermis, central zone, and vascular strands. Nodules were devoid of bacteria and infection threads. Instead, the larger cells were completely filled with many starch grains while smaller cells had very few or none. Xylem parenchyma and phloem companion cells exhibited long, filiform and branched wall ingrowths. The characteristic features of both types of transfer cells were polarity of wall ingrowths, high cytoplasmic density, numerous mitochondria, abundant ribosomes, well-developed nucleus and nucleolus, and vesicles originated from rough endoplasmic reticulum. These results were compared with normal nodules induced byRhizobium. Our results suggest that xylem parenchyma and phloem companion transfer cells are active and probably involved in the short distance transport of solutes in and out of spontaneous nodules. Since younger nodules showed short, papillate, and unbranched wall ingrowths, and older tissue showed elongated, filiform and branched wall ingrowths, the development of wall ingrowths seemed to be gradual rather then abrupt. The occurrence of both type-A and -B wall ingrowths suggests that phloem companion transfer cells may be active in loading and unloading of sieve elements. Since there were no symbiotic bacteria and thus no fixed nitrogen, it is tempting to speculate that xylem parenchyma transfer cells may be re-transporting accumulated carbon from starch grains to the rest of the plant body by loading xylem vessels. Fusion of ER-originated vesicles with wall ingrowth membrane indicated the involvement of ER in the membrane formation for elongating wall ingrowths. Since transfer cells were a characteristic feature of both spontaneous andRhizobium-induced nodules, their occurrence and development is controlled by the genetic make-up of alfalfa plant and not by a physiological source or sink emanating from symbiotic bacteria.