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  • 1
    Electronic Resource
    Electronic Resource
    Tachyphylaxis of juxtaglomerular epithelioid cells to angiotensin II (1987)
    Springer
    Pflügers Archiv 410 (1987), S. 55-62 
    Details
    ISSN: 1432-2013
    Keywords: Renin-Angiotensin II ; Tachyphylaxis ; Kidney vessels ; Epithelioid cells ; Mesangial cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A study has been made of desensitization of the depolarizing response to angiotensin II of juxtaglomerular epithelioid and vascular smooth muscle cells in the mouse kidney afferent arteriole, of media cells from the mesenteric artery as well as of cultured smooth muscle and mesangial cells. In all cell types, desensitization to this effect of angiotensin II was observed. There was no cross-desensitization between angiotensin II and other depolarizing agonists. Hence, it is concluded that this desensitization is specific, i. e. of the tachyphylaxis type. Substances interfering with receptor recycling, such as chloroquin and monensin, did not block the recovery of the cells from desensitization after removal of the octapeptide. Desensitization to the action of angiotensin II was also observed with respect to its vasoconstrictor effect in the isolated perfused rat kidney. In contrast there was no desensitization of renin secretion in the isolated perfused rat kidney, nor in isolated hydronephrotic mouse tissue, nor in microdissected rat glomeruli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581896
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  • 2
    Electronic Resource
    Electronic Resource
    Ultrastructure, renin status, contractile and electrophysiological properties of the afferent glomerular arteriole in the rat hydronephrotic kidney (1986)
    Springer
    Virchows Archiv 410 (1986), S. 31-42 
    Details
    ISSN: 1432-2307
    Keywords: Hydronephrotic kidney ; Renin-angiotensin system ; Microcirculation of the kidney ; Juxtaglomerular cells
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Histological, ultrastructural, immunohistochemical, intravital microscopic and electrophysiological techniques have been applied to study experimental hydronephrosis in rats in order to assess its value as a preparation for the investigation of renal microcirculation and of the electrophysiological properties of the renin-containing juxtaglomerular (JG) cells of the afferent glomerular arteriole. As hydronephrosis develops, the kidney parenchyma becomes progressively thinner owing to tubular atrophy. Twelve weeks after ureteral ligature, this process results in a transparent tissue sheet of about 150–200 μm in thickness. In this preparation, the renal arterial tree as well as the glomeruli can be easily visualized for intravital microscopic studies, e.g. the determination of kidney vessel diameters, or the identification of JG cells for penetration with an intracellular microelectrode. In contrast to the tubular atrophy, the vascular system is well preserved, and the JG cells and the sympathetic axon terminals are ultrastructurally intact. This is also true for the glomeruli, except for a certain confluence of the podocyte foot processes and a thickening of the basal laminae. Renin immunostaining and kidney renin content in the hydronephrotic organ correspond to those in control kidneys. In addition, there are no differences in the plasma renin levels of hydronephrotic and control rats. Intravital microscopic observations reveal that the renal vascular tree reacts in a typical, concentration dependent manner to the vasoconstrictor agent angiotensin II, mainly at the level of the resistance vessels. Electrophysiological recordings from juxtaglomerular granulated cells show a high membrane potential (−60 mV), and spontaneous depolarizing junction potentials, owing to random transmitter release from the nerve terminals. Angiotensin II, an inhibitor of renin release, depolarizes JG cells reversibly. Hence, we may infer that the hydronephrotic rat kidney is a suitable model for in vivo studies of the renal microcirculation as well as for in vitro investigations of the electrophysiological properties of the media cells of the afferent glomerular arteriole.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00710903
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  • 3
    Electronic Resource
    Electronic Resource
    Development of membrane- and calcium-gradients during pollen germination of Lilium longiflorum (1985)
    Springer
    Planta 163 (1985), S. 84-90 
    Details
    ISSN: 1432-2048
    Keywords: Calcium ; Lilium ; Membrane distribution ; Pollen germination ; Proton microprobe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chlorotetracyclin (10-4M) has been used to observe the distribution of membrane-associated calcium during pollen germination of Lilium longiflorum. For comparison, the general membrane distribution has been determined with 4·10-5 M fluorescamine. The pollen grains show a calcium gradient with either weak or strong chlorotetracycline-fluorescence intensity, but always increasing toward the germination colpus. This gradient intensifies during germination, reaching a maximum before the pollen tube emerges. The typical tip-to-base calcium gradient of the tube does not change during growth. Independent of the developmental stage, the pollen grains show a flat fluorescamine-fluorescence gradient with the highest intensity in one half of the grain. Pollen tubes reveal a tip-to-base membrane gradient, independent of their length. As an additional marker for membrane distribution, the distribution of phosphorus, measured by proton-induced X-ray emission in chemically fixed tubes, has been used. A tip-to-base phosphorus gradient, distinct from the calcium gradient measured with the same method, was detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00395901
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  • 4
    Electronic Resource
    Electronic Resource
    Wave of free calcium at fertilization in the sea urchin egg visualized with fura-2 (1988)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 9 (1988), S. 271-277 
    Details
    ISSN: 0886-1544
    Keywords: fertilization ; Ca2+ wave ; fura-2 ; sea urchin egg ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: A wave front of increased free calcium traversing the egg at fertilization is demonstrated in the sea urchin Lytechinus pictus. The use of the fluorescent calcium chelator fura-2 in combination with low-light-level TV microscopy and image processing allows the visualization of the Ca2+ wave front with high spatial and temporal resolution. Such a wave is demonstrated as increased fluorescence after an excitation of 340-nm wavelength and as the reciprocal image in form of a reduced fluorescence when excited at 380 nm. The band-like appearance of the wave resembles the Ca2+ wave described for larger eggs of other species. In a dispermic egg the high resolution of the system used allows us to recognize two waves of Ca2+ originating from the respective points of sperm entry.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970090309
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  • 5
    Electronic Resource
    Electronic Resource
    Plasticity of postganglionic sympathetic neurons in the rat superior cervical ganglion after axotomy (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Microscopy Research and Technique 29 (1994), S. 120-130 
    Details
    ISSN: 1059-910X
    Keywords: Galanin ; Vasoactive intestinal polypeptide ; Tyrosine hydroxylase ; Nerve regeneration ; Immunohistochemistry ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: The neuropeptides galanin (GAL) and vasoactive intestinal polypeptide (VIP) are upregulated in spinal and vagal sensory as well as in cranial motor neurons after axonal transection. In this study an increase of both peptides is demonstrated in axotomized principal ganglionic neurons (PGN) of the rat sympathetic superior cervical ganglion by use of double-labeling immunofluorescence. Compared to control ganglia that do not contain more than 1% GAL- or VIP-positive cells, about 26% of all PGN exhibit GAL immunoreactivity by day 1 after transection of the major postganglionic branches. The proportion of immunoreactive neurons reaches its maximum after 30 days (40%) and decreases to about 27% within the second month after axotomy. The percentage of VIP-positive neurons is much lower than for GAL: 2% of the PGN exhibit VIP immunoreactivity at day 1 and about 7% are observed 30 and 60 days after axotomy. In order to further characterize newly GAL- and VIP-positive PGN, their cell diameters were determined 12 days after axotomy. Compared to the mean overall neuron diameter of 24.8 μm, GAL-immunoreactive neurons are predominantly of small and intermediate size (22.2 μm), whereas VIP occurs mainly in larger neurons (26.1 μm). Besides cell bodies, many intraganglionic nerve fibers stain positive for GAL or VIP, particularly at day 6. Most likely, these fibers represent axons, as indicated by the absence of MAP2, a cytoskeletal protein found in neuronal somata and dendrites. They establish direct membrane contacts with postganglionic perikarya, as revealed by pre-embedding immuno-electron microscopy. Some cell bodies and fibers contain both peptides. Colocalization of GAL or VIP with tyrosine hydroxylase (TH), the rate-limiting enzyme of catecholamine synthesis, reveals a reduced immunoreactivity for TH in intensely GAL- or VIP-positive cells, and vice versa at day 6. However, no difference in staining intensity for VIP or GAL, and TH, is observed after 30 and 60 days. Possible implications of GAL and VIP for peripheral nerve regeneration and their regulation by target-derived factors are discussed. © 1994 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1070290209
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  • 6
    Electronic Resource
    Electronic Resource
    Ultrastructure of the kidney of a South American caecilian, Typhlonectes compressicaudus (Amphibia, Gymnophiona) (1988)
    Springer
    Cell & tissue research 252 (1988), S. 589-600 
    Details
    ISSN: 1432-0878
    Keywords: Glomerulus ; Nephron (neck segment, proximal tubule, intermediate segment) ; Mesonephros ; Typhlonectes compressicaudus (Amphibia, Gymnophiona)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The ultrastructure of the renal corpuscle, the neck segment, the proximal tubule and the intermediate segment of the kidney of a South American caecilian, Typhlonectes compressicaudus (Amphibia, Gymnophiona) was examined by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and freezefracture technique. The glomerular filter apparatus consists of the podocyte epithelium, a distinct basement membrane, a subendothelial space and the capillary endothelium. Emanating from the podocyte cell body, several long primary processes encircle neighboring capillaries. The short slender foot processes originating from the primary processes interdigitate with those from other primary processes, thereby forming the meandering filtration slit. Thick bundles of microfilaments are found in the primary processes, but absent in the foot processes. The basement membrane consists of a lamina rara externa and a rather thin lamina densa (50 nm thickness). The wide subendothelial space contains abundant microfibrils, a few collagen fibrils and many thin processes of mesangial cells. The endothelium is flat and fenestrated (compared to mammals displaying relatively few fenestrations); some of the fenestrations are bridged by a diaphragm. The glomerular mesangium is made up of the mesangial cells and a prominent mesangial matrix containing microfibrils and collagen fibrils. The cells of the neck and intermediate segments display numerous cilia with their microtubules arranged in the typical 9+2 pattern. The basal bodies of the cilia are attached to thick filaments with a clear crossbanding pattern of 65 nm periodicity. The proximal tubule is composed of cells typical for this segment (PT cells) and light cells lacking a brush border (bald-headed cells). The PT cells measure 10–25 μm in height and 15–30 μm in width and do not interdigitate at their lateral borders with each other. Their basolateral cell membrane is amplified by many folds projecting into lateral intercellular spaces and into basal recesses. The brush border is scarce and composed of loosely arranged short microvilli.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00216646
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  • 7
    Electronic Resource
    Electronic Resource
    In vivo fluorescence microscopy of corneal neovascularization (1998)
    Springer
    Graefe's archive for clinical and experimental ophthalmology 236 (1998), S. 390-398 
    Details
    ISSN: 1435-702X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  · Purpose: The purpose of our study was to establish an animal model to study the microcirculation in corneal neovascularization in the living animal atraumatically. · Methods: Corneal neovascularization was induced in New Zealand white rabbits by a standard micropocket assay utilizing pellets with 250 ng basic fibroblast growth factor. Anesthesia consisted of intramuscular injections of ketamine and xylazine. Intravital microscopy was performed without preparation of the cornea. Rhodamine 6G was used as fluorescent dye to stain leukocytes. Fluorescein-isothiocyanate-dextran served as plasma marker. Microcirculation analysis was done off-line by digital video imaging with special analysis software and included the following parameters: vessel diameters, blood velocity, and differentiation of leukocytes according to their interaction with endothelium into free-floating, rolling and sticking leukocytes. · Results: Vessel diameters in venular trunk vessels showed diameters of 54.0 ± 13.3 μm with 1.1 ± 0.5 mm/s flow; 29.4 ± 16.3% of all leukocytes were attached to the vascular wall. The number of sticking leukocytes was found to be 17.8 ± 36.0 cells/mm2 endothelial surface. Values are given for arteriolar trunk and branch as well as venular branch vessels. · Conclusions: This method for in vivo microscopic observation and quantification of the vasculature of the ocular surface seems to be suitable for evaluation of microhemodynamic and leukocyte measurements in mature neovascular vessels. It allows atraumatic experiments without corneal preparation procedures which disturb the microcirculation. The results concerning microhemodynamics and adherence of leukocytes are in a range comparable to other microcirculation studies. This new model could provide insight into the pathophysiology of microcirculatory disorders of the anterior eye segment, e.g. during angiogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004170050095
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