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Biomedical subjects

Z Vogel

Publications and source records attributed to Z Vogel.

At least 91 records · Page 5Linked to original sources
PubMed1987

Angiotensin-converting enzyme associated with Torpedo california electric organ membranes.

Torpedo electric organ contains high concentrations of angiotensin converting enzyme (ACE) like activity, cleaving [Leu5]enkephalin at the Gly3-Phe4 peptide bond. Most of the activity cosediments with the cell membranes. The enzymatic preparation from membranes is inhibited by low concentrations of the ACE inhibitors, SQ 14225 and SQ 20881 (IC50 of 0.6 and 15 nM, respectively), and is weakly inhibited by the neutral endopeptidase inhibitors, phosphoramidon and thiorphan (IC50 of 30 microM and ca. 70 nM, respectively). The enzyme degrades hippuryl-His-Leu and is activated by NaCl. Hippuryl-His-Leu and [Leu5]enkephalin are degraded with Km of 93 and 41 microM, and Vmax of 21 and 10 nmol/mg protein/min, respectively. The specific activity of the ACE-like activity in homogenates of Torpedo electric organ is relatively high (6.3 nmol hippuryl-His-Leu/mg protein/min); this value is similar to that obtained for rat lung and rat striatum.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1987

Molecular and cellular aspects of axon-glia interaction in CNS regeneration.

The relationships of neurons and non-neuronal cells are vital for the maintenance and function of neurons. Trauma alters these relationships causing proliferation of non-neuronal cells and, in adult mammalian CNS, presumably disturbs the environmental support needed for regeneration. A supportive environment can be restored by introducing a regenerating nerve to injured mammalian CNS. This response is probably due, at least in part, to diffusible substances secreted by the non-neuronal cells. We have obtained diffusible substances from either regenerating fish optic nerves or neonatal rabbit optic nerves and applied them around crushed adult rabbit optic nerves. This manipulation caused the adult nerve to show regenerative changes: a general increase of protein synthesis in the retinas; selective increase in synthesis of a few polypeptides in the retinas; sprouting from the retinas in vitro; increased viability of nerve fibers as shown by HRP staining; and the appearance of growth cones adjacent to glial limitans in the injured nerves. We termed these diffusible, active substances "Growth Associated Triggering Factors" (GATFs). In addition to the phenomena described above, the active substances (obtained in the form of media conditioned by regenerating fish optic nerve or neonatal rabbit optic nerve) caused various other changes in the injured nerve itself: acceleration of non-neuronal cell proliferation; changes in the protein pattern, e.g. an increase in a 12 kDa polypeptide which might be a second mediator in the cascade of events leading to regeneration; increased laminin immunoreactive sites in the nerve; and the acquisition of growth supportive activity in media conditioned by the implanted injured nerves.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Inhibition of adenylate cyclase and induction of heterologous desensitization by kappa agonists in rat spinal cord.

Using crude P2 membranes of adult rat spinal cord we were able to show that the K opiate agonist U50488 significantly and dose-dependently inhibited the basal cyclase activity, while mu (DAGO) and delta (DADL) agonists were ineffective. The regulatory action was stereospecific and required the presence of GTP plus Na+ as well as Ca2+ ions. This inhibitory effect of K agonists was also observed when the cyclase activity was stimulated by forskolin. Similar inhibition was observed in spinal cord-dorsal root ganglion cocultures. Following chronic exposure of cultured cells to etorphine or U50488, the K agonists lost their ability to inhibit the cyclase. Furthermore, the desensitization process appeared to be heterologous, since the alpha 2 adrenergic agonist, norepinephrine and the muscarinic agonist, carbachol exhibited significant lower potency for inhibiting cyclase activity when compared to control cultures. These data suggest that in spinal cord, opiate receptors of the K type are negatively coupled to adenylate cyclase and the induction of tolerance produced by K agonists is related to alterations of post-receptor regulatory components.

Adenylyl Cyclase Inhibitors↗
PubMed1986

Expression and regulation of kappa opiate receptors in rat spinal cord-dorsal root ganglion cocultures.

We have been using rat spinal cord-dorsal root ganglion primary cocultures (SC-DG) as a model system for exploring K receptor regulation. During the first 10 days in culture, the total number of opiate receptors increased markedly, reaching a Bmax of 180 fmoles/mg protein for K sites and a Bmax of 50 fmoles/mg protein for mu sites. Following this period of development, the K and mu receptor number did not change significantly. No detectable delta sites were observed at any time of culture. The binding of [3H]diprenorphine to K sites was found to be saturable, of high affinity and stereospecific. After chronic agonist treatment of cultured cells, K receptors did not down-regulate, whereas more than 50% of the mu receptor sites did. Following chronic antagonist treatment, mu receptors were markedly up-regulated (260% of control), while K sites exhibited a weaker up-regulation response (160% of control). These data demonstrate that K opiate receptors are expressed at high concentrations in SC-DG cultures and that contrary to mu receptors in spinal cord and delta receptors in NG10815 cells, K binding sites are less susceptible to modulation following chronic agonist or antagonist treatment. This suggests that K receptors may be regulated by different control mechanisms.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1985

Ciliary ganglia and spinal cord explants release an ascorbate-like compound which stimulates proline hydroxylation and collagen formation in muscle cultures.

A low-molecular-weight factor from embryonic rat brain stimulates collagen production in rat muscle cultures. This effect is associated with increased hydroxylation of proline residues in collagenous proteins produced by the cells. Here, we show that increased hydroxylation (22-and 7.5-fold) was also observed with extracts of rat embryonic spinal cord and extracts of the rat pheochromocytoma cell line PC12. A 5-25-fold stimulation in proline hydroxylation was obtained when muscle cells were cocultured with chick ciliary ganglia or with embryonic rat spinal cord explants. Medium conditioned by rat spinal cord explants also increased prolyl hydroxylation. Incubation of the muscle-nerve cocultures with ascorbate oxidase markedly reduced the observed increase in proline hydroxylation. These results show that the cultured explants release a factor which promotes proline hydroxylation and collagen production by muscle. This factor seems to be ascorbic acid or an ascorbate-like compound.

Animals↗
PubMed1985

Collagen-stimulating factor from embryonic brain has ascorbate-like activity and stimulates prolyl hydroxylation in cultured muscle cells.

Embryonic rat-brain extract contains a collagen-stimulating factor which enhances the production of collagen types I, III, IV and V by cultured rat muscle cells. Here we report on the partial characterization and possible mechanism of action of a low-molecular-mass fraction with ascorbate-like activity isolated from embryonic rat brain extracts. This activity eluted very close to ascorbate when filtered through Bio-Gel P-2 and Sephadex G-10. The peak of biological activity showed properties of a reducing agent. Both the biological and reducing activities were lost when the fraction was treated with the enzyme ascorbate oxidase. This factor enhanced in a time-dependent manner, the secretion of procollagen, pulse-labeled with [3H] proline. Incubation of the muscle cultures with the factor increased by 15-fold the ratio of hydroxyproline to proline residues in secreted macromolecules over controls. A fourfold increase in the above ratio was obtained for the cellular proteins. Crude homogenates from control and factor-stimulated cultures were tested for prolyl hydroxylase activity using [3H](Pro-Gly-Pro)n as a substrate. Cultures treated with the collagen-stimulating factor showed a 5-50-fold increase in prolyl hydroxylation activity compared to controls. No effect on prolyl hydroxylation was found when the factor was added in vitro to either control or stimulated enzyme preparations. Our results suggest that the collagen-stimulating factor contains ascorbate-like activity which promotes the secretion of collagenous proteins by increasing hydroxylation of proline residues in their polypeptide backbone.

Animals↗
PubMed1984

Enkephalin degrading enzymes are present in the electric organ of Torpedo californica.

Two proteolytic activities that degrade [Leu5]enkephalin were found in Torpedo californica electric organ. One is a soluble aminopeptidase that degrades enkephalin at the Tyr1-Gly2 peptide bond, and the second is an endopeptidase that degrades enkephalin at the Gly3-Phe4 peptide bond. The aminopeptidase is inhibited by low concentrations of puromycin and bestatin. More than 60% of the endopeptidase is associated with the particulate fraction and is almost completely inhibited by low concentrations of captopril (SQ 14225) or SQ 20881 (potent inhibitors of angiotensin converting enzyme). Thiorphan and phosphoramidon (potent enkephalinase inhibitors) are much less effective. The pattern of cleavage and inhibition of the particulate endopeptidase thus resembles that of angiotensin converting enzyme.

Aminopeptidases↗
PubMed1983

Characterization and localization of collagens synthesized by cultured muscle cells stimulated with collagen-inducing factor from embryonic brain extracts.

A low molecular weight fraction (Mr = 500-1500) was isolated by membrane and gel filtration from rat embryonic brain extract. This fraction was shown to stimulate collagen production in muscle cultures. Procollagen, intermediate collagenous proteins, and collagens of types I, III, and V were identified by analysis on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and DEAE- and Cm-cellulose chromatography and by selective degradation by pepsin, bacterial collagenase, and cyanogen bromide. Immunofluorescent staining with antisera to collagen types I, III, IV, and V of muscle cultures treated with the collagen-inducing factor revealed a large increase in staining compared to control cultures and a distinct pattern of staining on the surface of the treated myotubes.

Animals↗
PubMed1983

Protection of enkephalins from enzymatic degradation utilizing selective metal-chelating inhibitors.

Metal ion-chelating agents inhibited enkephalin degradation by a rat striatal membrane-associated endopeptidase termed 'enkephalinase'. The combination of a hydrophobic dipeptidyl moiety and a transition metal-chelating moiety in the same molecule resulted in very efficient and selective inhibitors of enkephalinase. The mercaptoacetyl dipeptides (2-mercaptoacetyl-Leu-Phe and 2-mercaptoacetyl-Phe-Leu) and the N-phosphorylated dipeptides (phosphoryl-Leu-Phe and phosphoramidon) inhibited enkephalinase with IC50 values of 15, 70, 0.3 and 1 nM respectively, but were much less potent against the aminopeptidase and angiotensin converting enzyme, two other metalloenzymes implicated in the degradation of the enkephalins in brain. The inhibition of enkephalinase, using phosphoryl-Leu-Phe as a selective inhibitor, resulted in a 4 fold increase in the amount of enkephalin recovered following K+ depolarization of rat striatal slices.

Aminopeptidases↗
PubMed1983

Laminin induces acetylcholine receptor aggregation on cultured myotubes and enhances the receptor aggregation activity of a neuronal factor.

The effect of several basement membrane components on the aggregation of acetylcholine (ACh) receptors on cultured myotubes was studied. Cultures were incubated for 16 to 24 hr with laminin, a heparan sulfate proteoglycan, collagen types IV and V, or fibronectin, alone, or together with medium conditioned by NG108-15 neuroblastoma X glioma hybrid cells (NCM). The number of ACh receptor aggregates per myotube was assayed by fluorescence microscopy of cultures stained with tetramethylrhodamine-labeled alpha-bungarotoxin. Laminin induced ACh receptor aggregation on primary rat myotubes and on myotubes formed by G8-1 clonal rat muscle cells. Laminin enhanced the receptor-aggregating activity of NCM in a concentration-dependent manner (0.6 to 6.0 micrograms/ml) and the number of aggregates formed in the presence of laminin and NCM together was greater than the sum of the aggregates induced by NCM and laminin separately. The aggregation factor in NCM is probably not laminin, since less than 10 ng/ml of laminin-like immunoreactivity was detected in NCM, and antiserum against laminin blocked the effects of laminin but had little effect on NCM aggregation activity. Collagen type V enhanced the receptor aggregation activity of NCM, but less strongly than laminin, and had little or no effect by itself. The other basement membrane components did not induce receptor aggregation or enhance the effect of NCM. Experiments in which ACh receptors were labeled before exposure of cultures to NCM and laminin indicated that laminin enhanced the rearrangement of receptors at the cell surface. Immunofluorescence microscopy indicated that laminin binds to the myotubes within 30 min and forms patches on the cell surface over a period of hours. Laminin bound to the myotube surface enhanced receptor aggregation as well as laminin continuously present in the culture medium. The results suggest the possibility that laminin could enhance the receptor aggregation activity of a neuronal factor(s) released at the developing neuromuscular junction.

Animals↗
PubMed1982

Involvement of collagen in the aggregation of acetylcholine receptors on cultured muscle cells.

The role of collagen macromolecules in the aggregation of acetylcholine receptors on the surface of cultured rat muscle cells was investigated. Both the synthesis and secretion of collagen, as well as acetylcholine receptor aggregation were stimulated by treatment of muscle cultures with an embryonic brain extract. Treatments with cis-hydroxyproline or monensin, which interfere with collagen synthesis and secretion, significantly reduced the number of acetylcholine receptor aggregates detected. Incubation of the cultures with embryonic brain extract induced a decrease in extractability of acetylcholine receptors. This effect could be reversed by treating the cells with bacterial collagenase. In addition, affinity purified antibodies against collagen of types I and IV inhibited the aggregation of acetylcholine receptors by stimulated brain extract. These data suggest that neurotrophic factor(s) present in embryonic nerve tissue have the ability to induce collagen production; the collagen formed plays a role in the formation and/or stabilization of acetylcholine receptor aggregates and possibly also of synaptic connections.

Animals↗
PubMed1982

Aggregation of acetylcholine receptors in nerve-muscle cocultures is decreased by inhibitors of collagen production.

Coculturing of rat embryonic muscle cells with spinal cord explants resulted in the formation of large numbers of acetylcholine receptor aggregates on the myotube surface, compared to those found on muscle cells grown in the absence of nervous tissue. Remarkably fewer receptor aggregates were formed when, upon addition of nerve explants, these cocultures were treated with either cis-hydroxyproline (a specific inhibitor of collagen production) or collagenase. The possibility is raised that collagen participates in the aggregation of acetylcholine receptors and in synapse formation.

Animals↗
PubMed1982

Embryonic brain extract induces collagen biosynthesis in cultured muscle cells: involvement in acetylcholine receptor aggregation.

The involvement of extracellular matrix components in induction of the aggregation of acetylcholine (AcCho) receptors by factor(s) present in embryonic brain extract was investigated. Embryonic brain extract induced a three-fold increase in the number of AcCho receptor aggregates on the surface of cultured myotubes and a 5- to 10-fold increase in the synthesis of procollagen, which was secreted into the medium and converted to collagen. Adult brain extract, embryonic serum, and embryonic liver extract were less active in stimulating both collagen synthesis and AcCho receptor aggregation. A physiological connection between the two processes is suggested, since the number of AcCho receptor aggregates could be reduced to control levels by treating brain extract-stimulated myotubes with purified bacterial collagenase. In addition, stimulation of collagen secretion by ascorbic acid (50 micrograms/ml) promoted a 1.6-fold increase in AcCho receptor aggregation. When ascorbic acid was added together with the brain extract, further increases in both collagen synthesis and AcCho receptor aggregation were observed.

Animals↗
PubMed1982

Inhibition of enkephalin degrading enzymes by metal chelating reagents.

The N-phosphorylated dipeptide K2PO3-Leu-Phe (P-Leu-Phe) and the mercaptoacetylated dipeptides SHCH2CO-Leu-Phe and SHCH2CO-Phe-Leu are potent inhibitors of the enkephalin carboxydipeptidase (enkephalinase) activity from rat striatal synaptosomal membranes; IC50, 0.3 nM, 15 nM, and 70 nM, respectively. These metal chelating compounds also inhibit the enkephalin degrading aminopeptidase activity present in the soluble fraction of rat striatum, although higher concentrations of inhibitors are needed; IC50, 100 microM, 80 microM and 150 microM, respectively. The binding of Leu-enkephalin (Leu-Enk) to rat striatal synaptosomal membranes is enhanced when the enkephalinase activity or the aminopeptidase activity present in these membranes is inhibited. Higher binding is obtained when both enzymes are inhibited. Similarly, the inhibition of these activities in rat striatal slices, using either puromycin or secobarbital which inhibit the aminopeptidase and enkephalinase, respectively, increases the amount of enkephalin recovered following K+ depolarization by about 100 percent. P-Leu-Phe at 1 mM, a concentration which inhibits both enzymatic activities, increased the amount of enkephalin recovered by 10-fold. The intracerebroventricular administration of 60 micrograms P-Leu-Phe with 200 micrograms of Leu-Enk induced analgesia in 4 out of 5 rats while Leu-Enk alone was not effective.

Aminopeptidases↗
PubMed1981

Benzodiazepine receptors in chick retina: development and cellular localization.

Benzodiazepine receptors are present in high concentration in the chick retina. Their pharmacological properties are similar to those of the benzodiazepine receptors present in the brain. The retina receptors appear prior to, as well as during, the period of synaptogenesis. In the newborn chick retina the receptors are localized in the inner synaptic layer, probably on or close to synaptic connections.

Aging↗