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R Jahn

Publications and source records attributed to R Jahn.

At least 199 records · Page 11Linked to original sources
PubMed1987

Synaptophysin immunoreactivity and small clear vesicles in neuroendocrine cells and related tumours.

Synaptophysin (protein p38) immunoreactivity has been detected immunohistochemically in neuroendocrine cells of the human adrenal medulla, carotid body, skin, pituitary, thyroid, lung, pancreas and gastrointestinal mucosa as well as in 87 out of 93 neuroendocrine tumours investigated, including pheochromocytomas, chromaffin and non-chromaffin paragangliomas, ganglioneuromas, pituitary adenomas, thyroid medullary carcinomas, parathyroid adenomas, lung carcinoids and neuroendocrine carcinomas, pancreatic and gut endocrine tumours and cutaneous merkelomas. Parallel ultrastructural investigation of synaptophysin-reactive cells and tumours revealed the presence, in addition to dense-cored, secretory granules, of a population of pleomorphic, small, clear vesicles resembling synaptic vesicles of nerve terminals as well as the synaptophysin immunoreactive vesicles already described in rat adrenal medullary and pituitary cells. Synaptophysin immunoreactivity showed several differences in its distribution among tumour and non-tumour endocrine cells when compared to chromogranin A immunoreactivity, a well known marker of the core of endocrine granules. Synaptophysin represents a reliable general marker of neuroendocrine cells and tumours, which may be useful in diagnostic histopathology.

Chromogranin A↗
PubMed1986

Characterization of synapsin I binding to small synaptic vesicles.

The binding of synapsin I, a synaptic vesicle-associated phosphoprotein, to small synaptic vesicles has been examined. For this study, synapsin I was purified under nondenaturing conditions from rat brain, using the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), and characterized. Small synaptic vesicles were purified from rat neocortex by controlled pore glass chromatography as the last purification step, and binding was characterized at an ionic strength equivalent to 40 mM NaCl. After removal of endogenous synapsin I, exogenous dephospho-synapsin I bound with high affinity (Kd, 10 +/- 6 nM) to synaptic vesicles. The binding saturated at 76 +/- 40 micrograms synapsin I/mg of vesicle protein, which corresponded to the amount found endogenously in purified vesicles. Synapsin I binding exhibited a broad pH optimum around pH 7. Other basic proteins, specifically myelin basic protein and histone H2b, did not compete with synapsin I for binding to vesicles. Other membranes purified from rat brain and membranes derived from human erythrocytes did not show the high affinity binding site for synapsin I found in vesicles. The binding of three different forms of phosphosynapsin I to vesicles was investigated. Synapsin I, phosphorylated at sites 2 and 3 by purified calcium/calmodulin-dependent protein kinase II, bound with a 5-fold lower affinity to the vesicles than did dephospho-synapsin I. In contrast, synapsin I, phosphorylated at site 1 by purified catalytic subunit of cAMP-dependent protein kinase, bound with an affinity close to that of dephospho-synapsin I. Synapsin I phosphorylated on all three sites bound to the vesicles with an affinity comparable to that of synapsin I phosphorylated on sites 2 and 3. Under conditions of higher ionic strength (150 mM NaCl equivalent), synapsin I bound with a 5-fold lower affinity to vesicles, and no effect of phosphorylation on binding was observed under these conditions.

Animals↗
PubMed1986

A solid-phase assay for the phosphorylation of proteins blotted on nitrocellulose membrane filters.

A new procedure for the phosphorylation and assay of phosphoproteins is described. Proteins are solubilized from tissue samples, separated by polyacrylamide gel electrophoresis, transferred onto nitrocellulose membrane filters, and the blotted polypeptides are phosphorylated with the catalytic subunit of cyclic AMP (adenosine 3':5'-monophosphate)-dependent protein kinase. The method was developed for the assay of dephosphosynapsin I, but it has also proven suitable for the phosphorylation of other proteins. The patterns of phosphorylation of tissue samples phosphorylated using the new method are similar to those obtained using the conventional test tube assay. Once phosphorylated, the adsorbed proteins can be digested with proteases and subjected to phosphopeptide mapping. The phosphorylated blotted proteins can also be analyzed by overlay techniques for the immunological detection of polypeptides.

Animals↗
PubMed1986

Protein p38: an integral membrane protein specific for small vesicles of neurons and neuroendocrine cells.

An intrinsic membrane protein of brain synaptic vesicles with Mr 38,000 (p38, synaptophysin) has recently been partially characterized (Jahn, R., W. Schiebler, C. Ouimet, and P. Greengard, 1985, Proc. Natl. Acad. Sci. USA, 83:4137-4141; Wiedenmann, B., and W. W. Franke, 1985, Cell, 41:1017-1028). We have now studied the presence of p38 in a variety of tissues by light and electron microscopy immunocytochemistry and by immunochemistry. Our results indicate that, within the nervous system, p38, like the neuron-specific phosphoprotein synapsin I, is present in virtually all nerve terminals and is selectively associated with small synaptic vesicles (SSVs). No p38 was detectable on large dense-core vesicles (LDCVs). p38 and synapsin I were found to be present in similar concentrations throughout the brain. Outside the nervous system, p38 was found in a variety of neuroendocrine cells, but not in any other cell type. In neuroendocrine cells p38 was localized on a pleiomorphic population of small, smooth-surfaced vesicles, which were interspersed among secretory granules and concentrated in the Golgi area, but not on the secretory granules themselves. Immunoblot analysis of endocrine tissues and cell lines revealed a band with a mobility slightly different from that of neuronal p38. This difference was attributable to a difference in glycosylation. The finding that p38, like synapsin I, is a component of SSVs of virtually all neurons, but not of LDCVs, supports the idea that SSVs and LDCVs are organelles of two distinct pathways for regulated neuronal secretion. In addition, our results indicate the presence in a variety of neuroendocrine cells of an endomembrane system, which is related to SSVs of neurons but is distinct from secretory granules.

Animals↗
PubMed1986

Applications of hand-arm models in the investigation of the interaction between man and machine.

The mode of vibration of hand-held tools cannot be considered without knowledge of the influence of the operator's hand-arm system. Therefore some technical applications of hand-arm models were realized for drill hammers by the University of Dortmund. These applications are a software program to simulate the motion of machine components, a horizontal drilling jig, and a chucking device in a drilling rig.

Arm↗
PubMed1985

Regulation of protein kinases in exocrine secretory cells during agonist-induced exocytosis.

Stimulation of exocytosis in exocrine glands is associated with an increased phosphorylation of several particulate proteins. Irrespective of the type of secretagogue (cAMP-dependent agonists, calcium-dependent agonists, calcium ionophores, phorbol esters) exocytosis is always accompanied by an enhanced phosphorylation of the ribosomal protein S6. It is shown by an analysis of the phosphopeptide pattern of the in vivo and the in vitro phosphorylated S6 protein that the protein kinase responsible for phosphorylation of the S6 protein during enhanced exocytosis is protein kinase C. This is so irrespective of whether the agonist uses cAMP or calcium as second messenger. Experiments with isolated guinea pig parotid gland lobules reveal that not only the acetylcholine analog carbamoylcholine, but also the beta-agonist isoproterenol lead within seconds to an increased formation of diacylglycerol. As diacylglycerol increases the affinity of protein kinase C for calcium this finding would explain why the phosphorylation pattern of the S6 protein reflects activation of protein kinase C also under conditions where (as in the case of stimulation with beta-agonists) cAMP is the primary second messenger. It would further explain why the changes of the phosphorylation of individual histones observed during agonist-induced exocytosis in the parotid gland are quite similar for isoproterenol on one hand and carbamoylcholine on the other. A 22 K protein which becomes phosphorylated only when cAMP serves as second messenger is located in the membrane of the endoplasmic reticulum. A possible relationship of this protein with the calcium transport ATPase of the endoplasmic reticulum is under investigation.

Animals↗
PubMed1985

A 38,000-dalton membrane protein (p38) present in synaptic vesicles.

A protein with an apparent molecular mass of 38,000 daltons designated p38 was found in synaptic vesicles from rat brain. The subcellular distribution of p38 and some of its properties were determined with the aid of polyclonal and monoclonal antibodies. The subcellular distribution of p38 was similar to that of synapsin I, a synaptic-vesicle specific phosphoprotein. p38 in the synaptic vesicle fraction purified by controlled-pore glass bead chromatography showed an enrichment of more than 20-fold over the crude homogenate. Immunostaining of sections through various brain regions revealed an intense labeling of most, and possibly all, nerve terminals. Only faint reaction in the region of the Golgi apparatus and no detectable labeling of axons and dendrites was observed. Two-dimensional electrophoresis revealed that p38 has an acidic pI. Solubilization experiments, as well as phase separation experiments using Triton X-114, indicated that p38 is an integral membrane protein. Binding of antibodies to intact synaptic vesicles, as well as controlled proteolytic digestion of intact and detergent-treated vesicles, revealed that p38 has a domain exposed on the cytoplasmic surface.

Animals↗
PubMed1985

[Ergotism--a risk in the prevention of thrombosis?].

In a 28 years old female who had undergone osteosynthesis for treating a pilon tibial fracture we postoperatively observed a spasm of the equilateral superficial femoral artery, followed by gangrene of the lower leg. The only therapy which was still possible as a life saving procedure consisted in amputating the lower leg. For prophylactic reasons the woman was postoperatively administered dihydroergotamin in combination with heparin. The author emphasises the fact that patients suffering from chronic liver diseases are particularly endangered by ergotism.

Adult↗
PubMed1984

Specific phosphorylation of a protein in calcium accumulating endoplasmic reticulum from rat parotid glands following stimulation by agonists involving cAMP as second messenger.

Stimulation of secretion in exocrine cells by agonists involving cAMP as second messenger is associated with the phosphorylation of a specific membrane-associated 22.4-kDa protein (protein III) (Jahn et al.). Here it is shown by subcellular fractionation of rat parotid gland lobules that protein III is associated with the endoplasmic reticulum. The submicrosomal fractions containing protein III, also contain the ATP-dependent microsomal calcium pump activity. Protein III in microsomal subfractions can be phosphorylated in vitro with catalytic subunit from cAMP-dependent protein kinase. Phosphorylated protein III contains exclusively P-serine. Protein III can be removed from ER-membranes with acid chloroform-methanol or Triton X-114, but not by high salt wash indicating that it is tightly associated with the membranes. Protein III is smaller than phospholamban and, in contrast to phospholamban, resistant to heating in SDS. A relationship between phosphorylation of protein III and microsomal calcium sequestration is discussed.

Animals↗
PubMed1984

[Vascular injury problems in childhood and adolescence].

Because of the marked elasticity of healthy blood vessels in children and adolescents, vascular trauma is very rare. In penetrating injuries, arteriography is not usually necessary but this procedure is essential in cases of blunt trauma to the blood vessels. The type of reconstructive procedure depends on the injury and its extent and can be performed by direct vascular anastomosis, by the insertion of a vein patch or by the transplantation of an autogenic venous segment. General anaesthesia is usually essential. Interrupted one-layer end-to-end anastomosis is advocated. The surgical technique of vascular repair must be meticulous. 12 children and adolescents (most of them had severe multiple injuries including vascular injuries) were followed up clinically and via arteriography. In 11 patients, the reconstructed vessels were found to be functioning normally.

Adolescent↗
PubMed1984

A quantitative dot-immunobinding assay for proteins using nitrocellulose membrane filters.

An immunoassay method is described for the quantitative determination of synapsin I (protein I) and of a 36,000-dalton membrane protein from rat brain synaptic vesicles. The samples are spotted on nitrocellulose membrane filters, incubated sequentially with specific antibodies and 125I-labeled protein A, and assayed for radioactivity in a gamma scintillation counter. Conditions have been established to prevent losses of protein from the sheets during processing, to quench background radioactivity, and to adjust the sensitivity to the range desired. A large number of samples can be handled in parallel. The assay does not require iodination of the antigen and is accurate even with crude tissue samples. Standard curves were linear over a 20- to 50-fold range. The sensitivity of the method is such that 10 pmol of synapsin I and 50 ng of total vesicle membrane protein could be measured with accuracy. The method should prove useful for a wide range of proteins.

Animals↗
PubMed1983

Phosphopeptide patterns of the ribosomal protein S6 following stimulation of guinea pig parotid glands by secretagogues involving either cAMP or calcium as second messenger.

Stimulation of secretion in exocrine cells is associated with the incorporation of up to 3 to 4 phosphates into the ribosomal protein S6. This occurs with secretagogues involving either cAMP or free calcium as second messenger. An analysis of the phosphorylation pattern of S6 from stimulated guinea pig parotid glands reveals 3 phosphopeptides (termed A,B,C). The phosphopeptide pattern was identical for cAMP- or calcium-mediated stimulation, whereas phosphorylation of the S6 protein in vitro with catalytic subunit of cAMP-dependent protein kinase resulted only in the formation of phosphopeptides A and C. Therefore, secretagogue-mediated phosphorylation is not or not exclusively catalyzed by cAMP-dependent protein kinase even when cAMP is the second messenger.

Animals↗
PubMed1983

Radioenzymatic determination of CMP-N-acetylsialic acid and free N-acetylsialic acid in biological material.

Free N-acetylsialic acid (NeuNAc) and CMP-N-acetylsialic acids (CMP-NeuNAc) are extracted from freeze-clamped or liquid nitrogen-frozen biological material by sequential extraction with cold acetone and acetone/water. [14C]NeuNAc and [14C]CMP-NeuNAc (20,000 dpm each) are added to the frozen material to correct for small losses occurring during the subsequent steps. NeuNAc and CMP-NeuNAc are separated by anion-exchange chromatography. CMP-NeuNAc is hydrolyzed with formic acid and again chromatographed on an ion-exchange column. The NeuNAc-containing fractions (representing free NeuNAc and CMP-NeuNAc) are converted to [14C]CMP-NeuNAc in the presence of [14C]CTP and CMP-NeuNAc synthetase. [14C]CMP-NeuNAc is separated by paper chromatography and the radioactivity measured by liquid scintillation counting. The amount of NeuNAc is calculated from a calibration curve obtained with NeuNAc standards. The small amounts of [14C]NeuNAc and [14C]CMP-NeuNAc added initially do not interfere with the final assay. The method gives reliable values down to 50 pmol/assay, but the sensitivity can be easily increased by a factor of 10. Recoveries, with NeuNAc and CMP-NeuNAc added to biological extracts, were 98.3 and 98.5% for NeuNAc and CMP-NeuNAc, respectively. With this method values of 61.2 +/- 12.8 and 24.4 +/- 5.2 nmol/g wet wt were found in rat liver for free NeuNAc and CMP-NeuNAc, respectively. Values for free NeuNAc found in human blood plasma were 600 +/- 476 and 373 +/- 180 pmol/g plasma for healthy persons and patients with breast cancer, respectively. Free CMP-NeuNAc could not be found in plasma.

Animals↗