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Biomedical subjects

R Weiler

Publications and source records attributed to R Weiler.

At least 55 records · Page 3Linked to original sources
PubMed1991

Synaptin/synaptophysin, p65 and SV2: their presence in adrenal chromaffin granules and sympathetic large dense core vesicles.

The subcellular distribution of three proteins of synaptic vesicles (synaptin/synaptophysin, p65 and SV2) was determined in bovine adrenal medulla and sympathetic nerve axons. In adrenals most p65 and SV2 is confined to chromaffin granules. Part of synaptin/synaptophysin is apparently also present in these organelles, but a considerable portion is found in a light vesicle which does not contain significant concentrations of typical markers of chromaffin granules (cytochrome b-561, dopamine beta-hydroxylase or the amine carrier). An analogous finding was obtained for sympathetic axons. The large dense core vesicles contain most p65 and also SV2 but only a smaller portion of synaptin/synaptophysin. A lighter vesicle containing this latter antigen and some SV2 has also been found. These results establish that in adrenal medulla and sympathetic axons three typical antigens of synaptic vesicles are not restricted to light vesicles. Apparently, a varying part of these antigens is found in chromaffin granules and large dense core vesicles. On the other hand, the light vesicles do not contain significant concentrations of functional antigens of chromaffin granules. Thus, the biogenesis of small presynaptic vesicles which contain all three antigens as well as functional components like the amine carrier is likely to involve considerable membrane sorting.

Adrenal Medulla↗
PubMed1991

Protein kinase C mediates transient spinule-type neurite outgrowth in the retina during light adaptation.

Light and dark adaptation of the teleost retina is accompanied by a remarkable morphological rearrangement of the synaptic connections between photoreceptors and second-order neurons: during light adaptation, numerous new neurites, the so-called spinules, arise from the terminal dendrites of horizontal cells invaginating the cone pedicle, and during dark adaptation, these spinules are retracted. The formation of these spinules is paralleled by the appearance of color opponency in horizontal and ganglion cells, which led to the suggestion that these spinules are the site of the inhibitory synapses in the negative feedback loop between cones and horizontal cells. The formation of the spinules in the light and their disappearance in darkness have a time course of minutes and are modulated by the neurotransmitters dopamine and glutamate, respectively. Neurotransmitters can modulate neuronal processing through a variety of second messengers that activate protein kinases, resulting most commonly in protein phosphorylation. Herein we report that activation of protein kinase C by phorbol esters promotes the formation of new horizontal-cell spinules in animals kept in the dark. Partial inhibition of protein kinase C activation with sphingosines prevents the formation of new spinules during light adaptation but does not affect established spinules. The spinule-forming effect of phorbol esters is not mediated by dopaminergic neurons, since the effect is also seen in retinas depleted of dopaminergic neurons. Phorbol esters also initiate the formation of spinules in synaptically isolated horizontal cells, demonstrating that they have a direct action on these cells. In addition, isolated horizontal cells have substrate proteins that are phosphorylated in a protein kinase C-dependent manner.

Adaptation, Physiological↗
PubMed1991

Short-term potentiation of off-responses in turtle horizontal cells.

Depolarizing responses to light off were studied in turtle horizontal cells using intracellular recording in the everted eyecup preparation. In many cells the off-response showed two components (fast and slow) which could overshoot beyond the steady-state dark level. The peak amplitudes of the fast and slow components increased with increasing duration of the light stimulus. A similar enhancement of the off-responses could also be produced by repetitive stimulation with brief flashes. However, the degree of enhancement produced by repetitive stimulation was greater than could be produced by increasing stimulus duration, and the latency of the onset of depolarization was longer, suggesting that the enhancement produced by repetitive stimulation involves an additional mechanism. Dramatic enhancement of the off-response by stimuli which did not affect the on-response during light indicates that the off-response may contain information not present in the on-response. The fast component of the off-response was suppressed to a greater degree than other components by reducing extracellular calcium or in the presence of 500 microM cobalt, suggesting that this component may involve a calcium current.

Animals↗
PubMed1991

Stimulation of rat adrenal medulla can induce differential changes in the peptide and mRNA levels of chromogranins, neuropeptides and other constituents of chromaffin granules.

The levels of various components of chromaffin granules were determined in rat adrenals after treatment with several stimulants. After reserpine the levels of calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY) and chromogranin B but not those of chromogranin A and secretogranin II were elevated. On the other hand, the mRNA of chromogranins A, B and secretogranin II were significantly increased. Treatment with oxotremorine or nicotine (multiple injections for 2 or 3 days) induced analogous changes for peptide and mRNA levels, however, the increases were smaller and for the mRNA less consistent. A single injection of oxotremorine or nicotine raised only the levels of CGRP and NPY and of the NPY mRNA whereas those of the chromogranins and their respective mRNAs remained unaltered. Amongst the membrane proteins only the levels of dopamine beta-hydroxylase are increased after prolonged stimulation, whereas those of cytochrome b-561, carboxypeptidase H and synaptin/synaptophysin (SYN) remain unaltered. Thus, the biosynthesis of chromaffin granules can be regulated in quite sophisticated patterns.

Adrenal Medulla↗
PubMed1991

Undegraded chromogranin A is present in serum and enters the endocytotic lysosomal pathway in kidney.

Analysis of human and bovine serum by immunoblotting revealed the presence of the proprotein chromogranin A. By the same method chromogranin A was also found in rat, bovine and human kidney. However this organ did not contain any chromogranin A mRNA arguing against a synthesis within this organ. By immune-electron microscopy chromogranin A immunoreactivity was found in proximal tubule cells of rat kidney. Positive immunostaining was present in small vesicles within and in close proximity to the brush border and closer to the nucleus in typical lysosomal structures. These results make it likely that chromogranin A from serum reaches kidney tubule cells by glomerular filtration and is taken up into the endocytotic lysosomal pathway.

Animals↗
PubMed1991

[Ethical viewpoints on cryopreservation of human embryos].

In the introduction the author describes how moral judgements are being formed in the pluralistic structures of today's societies. Moral relativism and subjectivism are the wide spread consequences of empirical anthropological theories. In this situation the necessity of an objective and normative moral theory (Christian natural law theory) is being stressed. Neither biology nor medicine can pronounce final judgements on the value of human life. The arguments in favour of cryoconservation (medical progress, parents wish to have children, cost-reduction) are outweighed by those arguments which maintain that man cannot dispose of human life through the manipulation of the progenitive act outside marriage and of the juman act of procreation. There are also the risks and the endangering of the human value of the embryo, up to prolicide which is considered to be permissible in some cases, on these moral grounds the author objects to the cryoconservation of embryos as does the relevant instruction of the papal magisterium of the Roman Catholic Church (Donum vitae 1987). He does not, however, take a final stance on how the subjective decision of the physician is to be judged in the individual case.

Embryo Transfer↗
PubMed1990

Glycoprotein II from adrenal chromaffin granules is also present in kidney lysosomes.

Glycoprotein II (GP II) is a protein found in the membranes of chromaffin granules from adrenal medulla. Immunoblotting (one- and two-dimensional) revealed that this antigen is also present in liver and in kidney. Subcellular fractionation of the latter organ indicated that GP II was present in lysosomes. This was confirmed by immunoelectron microscopy. The antiserum against GP II immunolabelled the membranes of organelles which could be identified as lysosomes by the labelling of their contents with an antiserum against cathepsin D. Thus GP II is an antigen common to secretory vesicles and lysosomes.

Adrenal Medulla↗
PubMed1990

Chromogranins in rat brain: characterization, topographical distribution and regulation of synthesis.

The properties and distribution of chromogranins A, B and secretogranin II in rat brain were analyzed by quantitative immunoblotting. In contrast to endocrine tissues brain contains a significant amount of the proteoglycan form of chromogranin A. For secretogranin II a significant degree of endogenous proteolytic processing is apparent. Chromogranin A and secretogranin II had a similar topographical distribution with the highest concentrations found in the hypothalamus, amygdala/piriform cortex and hippocampus, whereas for chromogranin B by far the highest concentration was found in the cerebellum. Compared with adrenal medulla the concentration of all three proteins is low, however, secretogranin II appears relatively enriched. The synthesis of chromogranin A in brain does not depend on glucocorticoids since neither adrenalectomy nor dexamethasone treatment changed its levels. This is in contrast to adrenal medulla and to the anterior pituitary. Three days after kainic acid-induced seizures the levels of chromogranin A in frontal cortex and hippocampus were significantly elevated. For frontal cortex there was also an increase of the respective mRNA. This result establishes that the synthesis of chromogranin A can be regulated like that of neuropeptides.

Animals↗
PubMed1990

Divergent changes of chromogranin A/secretogranin II levels in differentiating human neuroblastoma cells.

Human neuroblastoma cells were cultured either in the absence or presence of 12-O-tetradecanoylphorbol-13-acetate (TPA) known to induce neuronal differentiation. This treatment led to a marked increase in the concentration of secretogranin II but to a decrease of chromogranin A. Analogous changes were observed for the respective mRNAs. Thus during differentiation of these cells the biosynthesis of two vesicle constituents of large dense core vesicles is differentially regulated as determined both at the mRNA and the protein level. Levels of both synaptin/synaptophysin large dense core vesicles is differentially regulated as determined both at the mRNA and the protein level. Levels of both synaptin/synaptophysin and SV2 were also elevated but to a smaller degree than that of secretogranin II.

Cell Differentiation↗
PubMed1990

A high ratio of chromogranin A to synaptin/synaptophysin is a common feature of brains in Alzheimer and Pick disease.

Chromogranin A and synaptin/synaptophysin were characterized by immunological methods in human autopsy brain tissue from patients with Alzheimer's and Pick's disease. In immunoblots there was no qualitative difference between the antigens in control and diseased brain, but significant quantitative differences were found. In all Alzheimer cases there was a significantly lower level of synaptin/synaptophysin, whereas chromogranin A was higher in 4 out of 5 cases and in all cases relative to synaptin/synaptophysin. An analogous finding was obtained for Pick's disease. Immunohistologically a consistent staining of neuritic plaques for chromogranin A, but not for secretogranin II was found in Alzheimer cases. In Pick's disease the characteristic Pick bodies showed an analogous specific immunostaining.

Aged↗
PubMed1990

Evaluation of horseradish peroxidase as an intracellular stain in electrophysiological recording.

Iontophoresis of horseradish peroxidase into cells during intracellular electrophysiological recording to visualize the neurons recorded from is a powerful technique, but its success depends on a number of critical factors. The described agar injection technique is a simple method for the evaluation of several parameters at once, using procedures which closely resemble recording from, fixing, and processing to visualize the HRP in experimental tissue.

Electrophysiology↗
PubMed1990

Endogenous dopamine and cyclic events in the fish retina, I: HPLC assay of total content, release, and metabolic turnover during different light/dark cycles.

In this study, we investigated the potency of dopamine for being an intrinsic signal for cyclic events in the fish retina. Dopaminergic activity was measured during different light/dark cycles, during continuous darkness, and during short-term light and dark adaptation within 1 h. During a 12-h light/12-h dark cycle, the total content of endogenous dopamine was high during the dark phase and low during the light phase. The potassium-induced release of endogenous dopamine followed a parallel time course. The concentration of the dopamine breakdown product 3,4-dihydroxyphenylacetic acid (DOPAC), which reflects the endogenous dopaminergic activity, was high during the light phase and low during the dark phase. Similar alterations occurred in accelerated 6-h light/6-h dark cycles, again indicating a strong coupling of dopaminergic activity with light. The cyclic alterations in the total endogenous dopamine content persisted during continuous darkness after an entrainment of the fish to a 12-h light/12-h dark cycle. Although the magnitude of the change was weaker, changes in dopamine content, potassium-induced dopamine release, and DOPAC were also measured during 1 h of light or dark adaptation. During a 1-h period of dark adaptation, the total content of dopamine and the potassium-induced release of endogenous dopamine increased, while DOPAC values decreased. These values changed in the opposite direction during 1 h of light adaptation. Our findings strongly suggest that dopamine is the intrinsic signal for light during both the light and dark phases and during short-term adaptation. Light seems to be the major trigger for dopaminergic activity within the fish retina.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1990

Endogenous dopamine and cyclic events in the fish retina, II: Correlation of retinomotor movement, spinule formation, and connexon density of gap junctions with dopamine activity during light/dark cycles.

In the fish retina, retinomotor movement, spinule formation, and alteration of connexon density within gap junctions occur in response to changes in ambient light conditions. All of these morphological parameters can also be influenced by the application of dopamine. This study examines whether the morphological alterations of these structures are correlated with the activity of endogenous dopamine during an entrained 12-h light/12-h dark cycle and after 1-h sort-term adaptation periods. The two measured parameters of retinomotor movement, cone inner segment length and pigment dispersion, were well-correlated with endogenous cyclic dopamine activity. However, retinomotor movement was initiated already at the end of the entrained dark period, before the onset of light and before the onset of dopamine turnover. Furthermore, a 1-h dark-adaptation period in the middle of the light phase reduced dopamine activity but did not affect retinomotor movement. At the switch from light to dark and after a 1-h light period at midnight retinomotor movement correlated exactly with dopamine turnover and illumination conditions. The formation of spinules was correlated with dopaminergic activity during all phases of the light/dark cycle and during short-term adaptation periods. Spinules were expressed in the light when dopamine activity was high and they were retracted when dopamine activity was reduced during darkness. Connexon density of horizontal cell gap junctions showed a weaker correlation with the endogenous dopamine turnover. In this case, a high activity of endogenous dopamine was paralleled by a high density of connexons. Our results suggest that endogenous dopamine is involved in the cyclic regulation of the observed morphological alterations and that dopamine is part of the light signal for these mechanisms.

Animals↗
PubMed1990

Chromogranins A and B are co-localized with atrial natriuretic peptides in secretory granules of rat heart.

We investigated the occurrence and subcellular localization of chromogranins A and B in atrial myoendocrine cells of rat heart, using immunological methods. Immunoblotting revealed the presence of both chromogranin A and B in an extract from large granules isolated from this tissue by subcellular fractionation. Immunohistochemistry at the ultrastructural level demonstrated the presence of chromogranin A and B in secretory granules. These organelles also immunostained for atrial natriuretic peptides (ANP). Within a given section, all granules were labeled with immunogold for these three antigens. This apparent co-localization of the three antigens was confirmed by double immunostaining with immunogold particles of different sizes. We conclude that, in agreement with their endocrine nature, the secretory organelles of rat atria contain both chromogranins A and B. Apparently these acidic peptides, which have a widespread distribution in the endocrine system, are co-stored and therefore also co-secreted with ANP.

Animals↗
PubMed1990

Chromogranin A and B gene expression in carcinomas of the breast. Correlation of immunocytochemical, immunoblot, and hybridization analyses.

Chromogranins (Cg) are regarded as specific neuroendocrine (NE) markers in cells and tumors. Expression of CgA and CgB genes has been demonstrated by correlative immunocytochemical, immunoblotting, in situ hybridization, and Northern blot procedures in seven argyrophilic breast carcinomas, while eight control cases of ductal carcinomas, not otherwise specified, were negative. A high degree of correlation was observed between the various techniques revealing CgA and/or CgB gene expression at different levels; minor discrepancies might be related to tumor heterogeneity or to technical factors. The present study, confirming previous investigations, establishes NE differentiation in a group of human breast cancers. The identification of this type of tumors, especially by testing chromogranin(s) production, appears to be of both biologic and clinical interest.

Biomarkers, Tumor↗
PubMed1989

Adrenal chromaffin granules and secretory granules from thyroid parafollicular cells have several common antigens.

The presence of various antigens in two types of isolated endocrine vesicles (chromaffin granules and secretory vesicles of thyroid parafollicular cells) was investigated by immunoblotting. The two types of vesicles have three common secretory proteins: chromogranin A, chromogranin B and secretogranin II. Furthermore, six common membrane antigens were found: cytochrome b-561, carboxypeptidase H, glycoprotein II, glycoprotein III, synaptin/synaptophysin and SV 2. These results demonstrate that vesicles obtained from neural crest-derived endocrine cells not only share several common secretory peptides and proteins, but also have common properties as far as their membrane antigens are concerned.

Adrenal Medulla↗