Biomedical subjects

N Schechter

Publications and source records attributed to N Schechter.

At least 55 records · Page 3Linked to original sources

PubMed1990

Neuronal intermediate filament expression during neurite outgrowth from explanted goldfish retina: effect of retinoic acid.

Regulation of the goldfish neuronal intermediate filament proteins ON1 and ON2 was investigated in a retinal explant system. The synthesis of these proteins in explanted retina decreased with increasing time in culture, despite continuing neurite outgrowth. Thus, ON1/ON2 neurofilament expression is regulated independently from neurite outgrowth. During regeneration of the goldfish optic nerve in vivo, the expression of these proteins increased during the later phase of the process, when growing axons make contact with the optic tectum. The declining synthesis of ON1 and ON2 during neurite outgrowth in culture suggests that factors extrinsic to the retina are necessary to support synthesis of these proteins. Treating retinal explants with retinoic acid stimulated the synthesis of the ON1/ON2 proteins in a dose-dependent manner. This stimulation was effective during a period of declining synthesis of the ON1/ON2 proteins, restoring their synthesis towards initial levels of expression. These results show that retinoic acid serves as a modulator of neurofilament expression in this in vitro model of nerve regeneration.

Animals↗

PubMed1989

A type II keratin is expressed in glial cells of the goldfish visual pathway.

The predominant intermediate filament proteins of the goldfish visual pathway consist of neuronal and non-neuronal isoelectric variants (58 kd). We have isolated a cDNA clone for the glial intermediate filament protein (ON3) from an optic nerve expression library. The predicted amino acid sequence of this clone reveals that it codes for a type II keratin representing the goldfish equivalent of mammalian keratin K8. K8 has been shown to be associated with embryogenesis and development. Unlike the mammalian visual system, the goldfish visual pathway displays a remarkable capacity for functional regeneration. The expression of K8, a protein not usually expressed in glial cells but shown to be associated with development, in the goldfish optic nerve may be involved with the processes of growth and regeneration in the goldfish visual pathway.

Amino Acid Sequence↗

PubMed1989

Monoclonal antibodies differentiate neurofilament and glial filament proteins in the goldfish visual pathway: probes for monitoring neurite outgrowth from retinal explants.

The expression of the neurofilament proteins of the goldfish visual pathway reflects the degeneration and regeneration of the optic nerve after nerve crush. To monitor these processes, monoclonal antibodies (mAb) were generated to the intermediate filament proteins of this pathway. The predominant goldfish visual pathway intermediate filament proteins have a molecular weight of 58K and can be separated into 4 isoelectric variants, 2 of which are neuronal (ON1 and ON2) and 2 of which are non-neuronal (ON3 and ON4). The specificities of the mAbs were characterized biochemically and histologically. Immunoblot analysis demonstrated that 2 of the antibodies reacted specifically with the neurofilament proteins (ON1/ON2) and another antibody reacted specifically with the glial filament proteins (ON3/ON4) and with a 48K optic nerve protein of non-neuronal origin. Chymotrypsin digestion of the ON proteins and immunoblotting of the resulting fragments showed that the anti-ON1/ON2 mAbs were directed toward the variable domains of the filament proteins. In contrast, the anti-ON3/ON4 mAb was directed toward the 40K chymotrypsin-resistant region of the glial filament proteins containing the conserved intermediate filament core. When sections of optic nerve tissue were incubated with anti-ON1/ON2 or anti-ON3/ON4 mAbs, the staining resulted in either axonal or glial patterns, respectively. In retina, after optic nerve crush, anti-ON1/ON2 labeled retinal ganglion cells and Müller fibers. In contrast, prior to optic nerve crush, only Müller fibers were labeled. One of the neuronal-directed mAbs was used to decorate growing neurites from retinal explants; anti-ON1/ON2 reactivity appeared in a time-dependent manner that paralleled the expression of ON1/ON2 in vivo. Thus, the antibodies can differentiate these 2 types of goldfish intermediate filament proteins and can be used to monitor optic nerve regeneration in the goldfish visual pathway both in vivo and in vitro.

Animals↗

PubMed1989

Kidney transplantation in insulin dependent diabetic patients: improved survival and rehabilitation.

Between 1977 and 1986, 50 insulin-dependent diabetic patients received a kidney transplant, 19 from living related donors and 31 from cadaveric donors. Cumulative patient survival was 81% and graft survival was 64% and 33% for living related and cadaveric donor kidneys, respectively, at five years. These results are comparable to that of nondiabetic patients. While physical performance and visual acuity significantly improved after a successful kidney transplantation, neuropathies and angiopathies might not improve. Physical performance improved even in those patients whose nerve conduction time had deteriorated. These findings suggest that kidney transplantation is an effective means of improving survival and rehabilitation of diabetic patients with end-stage renal disease.

Adult↗

PubMed1988

Muscarinic receptors in preoptic area and hypothalamus: effects of cyclicity, sex and estrogen treatment.

Cholinergic muscarinic receptor binding was measured in the preoptic area (POA) and whole hypothalamus (HTH) of adult Sprague-Dawley rats using the tritiated antagonist quinuclidinyl benzilate ([3H]QNB) as the ligand. Binding of [3H]QNB expressed as fmol/mg protein was 30% higher in POA than in HTH from gonadectomized rats. Cyclic changes were observed in the POA with the highest binding at proestrus and the lowest binding at diestrus. In HTH, no significant changes occurred over the estrous cycle. Estrogen treatment (10 micrograms of estradiol benzoate (EB)/120 g b. wt./48 and 24 h before sacrifice) increased [3H]QNB binding by 42% in the POA and 17% in HTH, relative to the ovariectomized controls. The enhancement of [3H]QNB binding in POA as compared with controls was evident with both the filtration and the centrifugation methods, although binding levels were higher when centrifugation assay was used. A lower estrogen dose (2 micrograms EB/rat/48 and 24 h before sacrifice) which is routinely used to activate lordotic behavior in female rats increased muscarinic binding by 26% in the POA but had no appreciable effect in HTH. A significant sex difference was found in the ability of estrogen to induce [3H]QNB binding in the central nervous system (CNS). Estrogen was ineffective in altering [3H]QNB binding in either brain region of castrated males, although the level and pattern of cholinergic binding between untreated gonadectomized males and females were similar.2+ These data suggest that physiological changes in estrogen secretion over the estrous cycle are capable of modulating cholinergic muscarinic binding in the POA and these changes may be of physiological relevance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Distribution of specific intermediate-filament proteins in the goldfish retina.

The intermediate-filament proteins expressed in the goldfish retina were investigated by immunohistochemistry and by immunoblotting. Polyclonal antibodies that previously had been raised against the goldfish optic nerve neurofilament (ON1 and ON2) and glial filament (ON3 and ON4) proteins were used in this study. Anti-ON1/ON2 antiserum reacted on a retinal immunoblot with two proteins having molecular weights and isoelectric points corresponding to those of ON1 and ON2. Histologically, the most pronounced anti-ON1/ON2 reactivity was observed in the ganglion cell layer of the goldfish retina. The anti-ON3/ON4 antiserum reacted with a single protein on a retinal immunoblot. This protein had a molecular weight and isoelectric point which corresponded to the goldfish optic nerve glial filament proteins. This anti-serum labeled horizontal cells in retina sections. Three previously unidentified goldfish visual-pathway intermediate-filament proteins sharing a molecular weight of 60K were observed on two-dimensional gels of retinal cytoskeletal proteins and on retinal immunoblots which were probed with a monoclonal antibody which recognizes an epitope common to all intermediate filament proteins. The possible existence of homologs of mammalian GFAP and vimentin in the goldfish retina was also explored. Antibodies directed against mammalian GFAP and vimentin labeled the Müller fibers and the cone horizontal cells, respectively. However, immunoblot analysis and a comparison of the two-dimensional gel electrophoresis patterns of goldfish retinal and rat spinal cord cytoskeletal proteins demonstrated a lack of goldfish proteins identical to the mammalian intermediate-filament proteins.

Animals↗

PubMed1987

Optimization of donor specific blood transfusion in kidney transplantation.

1. One hundred milliliters of stored whole blood DST, three times at weekly intervals is a practical, less immunizing and effective approach to enhance graft survival in recipients of a living-related donor kidney. 2. This protocol could also be used in sibling donor/recipient pairs who do not share a haplotype as well as in those who share two haplotypes to enhance graft survival. 3. The use of a short course of Cs (6 mg/kg/d for three weeks) along with DST appears to reduce the sensitization rate even lower. The dose of Cs used in this study produced no clinically significant adverse reactions, whereas Aza (1 mg/kg/d) often produces leukopenia. 4. DST produces significantly suppressed donor specific MLC responses in the early post-DST period; however, it increases the response at a later time. DST modulates immune responses in such a way that secondary responses upon grafting are more readily reversible by immunosuppressive agents.

Adult↗

PubMed1986

Induction of rat E and chicken A-I apolipoproteins and mRNAs during optic nerve degeneration.

Apolipoprotein synthesis was measured in control optic nerves and optic nerves undergoing Wallerian degeneration. After short term organ culture with radiolabeled amino acid, optic nerve extracts were reacted with antiserum to rat or chicken apolipoproteins. Immunoprecipitates were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the degenerating rat optic nerve, apo-E synthesis increased from 0.30 to 0.90% of newly synthesized protein and from 0.45 to 1.4% of secreted protein. A DNA-excess solution hybridization assay was constructed to measure the absolute amount of apo-E mRNA in control and degenerating optic nerves. Paralleling the increase in apo-E protein synthesis, the absolute amount of apo-E mRNA was elevated 3- to 4-fold after enucleation. Similar to rat apo-E, apo-A-I synthesis was increased in degenerating chicken optic nerve. Chicken apo-A-I represented 0.65 and 3.5% of newly synthesized protein from control and enucleated optic nerves, respectively. Apo-A-I increased from 0.85 to 5.5% of secreted protein following enucleation. Using in vitro translation to quantitate relative amounts of chicken apo-A-I mRNA, enucleated optic nerve apo-A-I mRNA content was increased 5-fold. These results suggest that local apolipoprotein synthesis may be involved in the mobilization of myelin cholesterol which occurs during Wallerian degeneration. The similar response of the rat and chicken to increase optic nerve apolipoprotein synthesis during degeneration supports the idea that avian peripheral apo-A-I and mammalian peripheral apo-E may be performing functions common to both classes of animals.

Animals↗

PubMed1986

Immunohistochemical localization of intermediate filament proteins of neuronal and nonneuronal origin in the goldfish optic nerve: specific molecular markers for optic nerve structures.

The predominant proteins (58K) of the intermediate filament complex in the goldfish visual pathway consist of a series of isoelectric variants. Previous biochemical studies have shown that proteins ON1 and ON2 are of neuronal origin, whereas ON3 and ON4 are of nonneuronal origin. Polyclonal antibodies, purified by affinity chromatography, that are specific for ON1 and ON2 or ON3 and ON4 have been used to localize histologically the ON proteins within the normal and crushed optic nerve. Anti-ON1/ON2 antiserum presented a pattern consistent with intraaxonal staining. A nonneuronal staining pattern was observed with anti-ON3/ON4 antiserum. The two patterns were distinct from and complementary to each other. The data suggest that ON3 and ON4 represent a novel glial fibrillary acidic protein. The results are discussed in terms of the function of these proteins in development, plasticity, and regeneration.

Animals↗

PubMed1986

Elevated levels of retinal neurofilament mRNA accompany optic nerve regeneration.

RNA isolated from goldfish retinas before and during optic nerve regeneration, when translated in vitro, directed the synthesis of neurofilament proteins that are normally found in high levels in the optic nerve. The major neurofilament proteins of the goldfish optic nerve comprise a group of four isoelectric variants of molecular weight 58,000 (58K) which we have identified previously as ON1-ON4. The levels of ON1 and ON2 within the optic nerve had been shown to decrease shortly after optic nerve crush and then increase to precrush levels during the regeneration process. Employing two-dimensional electrophoretic analysis of in vitro translation products and immunoprecipitations with antibodies specific for the ON proteins and an anti-intermediate filament monoclonal antibody, we show that ON1 and ON2 are encoded by mRNA synthesized in the retinas. The synthesis of ON3 and ON4 by retina RNA was undetected. This confirms data from previous ex vivo experiments that indicated that ON1 and ON2 are of neuronal origin whereas ON3 and ON4 are nonneuronal. ON1 and ON2 synthesis increases dramatically during optic nerve regeneration to levels 10- and 30-fold over precrush levels, respectively. In addition to ON1 and ON2, the synthesis of a previously unidentified 52K protein is observed at relatively high levels 20 and 32 days after optic nerve crush, but is unobserved before regeneration. Thus, optic nerve regeneration can be correlated with specific changes in intermediate filament gene expression within the retina.

Animals↗

PubMed1986

Homology and diversity between intermediate filament proteins of neuronal and nonneuronal origin in goldfish optic nerve.

The predominant intermediate filament proteins of the goldfish optic nerve have molecular weights of 58K. They can be separated into a series of four major isoelectric variants of neuronal (ON1 and ON2) and nonneuronal (ON3 and ON4) origin. The extent of homology between the goldfish 58K intermediate filament proteins themselves and to rat optic nerve vimentin and glial fibrillary acidic protein (GFAP) was investigated. Unlabeled and [32P]orthophosphate-labeled proteins were subjected to partial hydrolysis by V8 protease, chymotrypsin, and CNBr. The results show that the goldfish intermediate filament proteins share with vimentin and GFAP a 40K chymotrypsin-resistant core fragment. Phosphorylated moieties appear to be located outside the core region since they are preferentially cleaved off by chymotrypsin and not found associated with the 40K core. In addition, the goldfish ON proteins contain the antigenic site within the core that is common to most intermediate filaments. V8 or CNBr digestion indicates that many fragments that are common to ON1 and ON2 are clearly distinct from fragments that are common to ON3 and ON4. In addition, structural variability is observed between the goldfish intermediate filament proteins and vimentin and GFAP. The results are discussed in terms of intermediate filament structure and their possible role in nerve growth.

Animals↗

PubMed1986

62K proteins constitute the major neurofilament proteins in the frog optic nerve.

The frog optic nerve contains a major group of proteins at a molecular weight of 62K. These proteins are insoluble in nonionic detergents, reactive with a general antibody to intermediate filament proteins, and not labeled by ex vivo incubations of optic nerve. They were therefore considered neurofilament proteins. Axonal transport and enucleation studies were performed to characterize further the origin of these proteins. The results show that the 62K proteins are transported into the optic nerve at a very slow rate (0.1 mm/day). After enucleation, these proteins are substantially reduced in concentration to 20% of the control value at 13 weeks. The predominant neurofilament proteins of the frog optic nerve are 62K in molecular weight. These results are discussed in terms of the anatomy of the frog optic nerve and also contrasted to findings obtained for the goldfish optic nerve.

Animals↗

PubMed1985

Variable expression of intermediate filament proteins during embryonic development of human optic nerve.

The intermediate filament protein composition of human optic nerve and tract was analyzed by two-dimensional gel electrophoresis. Optic nerves were analyzed at 15, 19, 22, and 24 weeks of embryonic development and the results were compared with the composition of adult optic nerve. The optic tract was analyzed at the later stages of development. The proteins were visualized by Coomassie blue staining and immunoblotting with specific antibodies to glial fibrillary acidic protein (GFAP) and vimentin. The 70K and 150K neurofilament proteins were first observed at 24 weeks. At 15 weeks of development, only trace amounts of GFAP were observed and vimentin was the predominant intermediate filament protein. In contrast, there was more than twice as much GFAP as vimentin in the adult optic nerve. The results also showed that the ratio of GFAP to vimentin is higher in the optic tract than in the optic nerve during development, whereas in adult tissue, the ratio is the same for the two regions. In pathological situations with axonal dropout, a complete loss of neurofilament proteins was observed. The amounts of both GFAP and vimentin were the same for both the normal and involved optic nerve. These results are discussed in terms of the development of the optic nerve.

Glial Fibrillary Acidic Protein↗

PubMed1985

Survey of intermediate filament proteins in optic nerve and spinal cord: evidence for differential expression.

The distribution of intermediate filament proteins in optic nerve and spinal cord from rat, hamster, goldfish, frog, and newt were analyzed by two-dimensional gel electrophoresis. General as well as specific monoclonal and polyclonal antibodies were reacted against putative intermediate filament proteins. In vitro incubations of excised optic nerve in the presence of [35S]methionine distinguished between neuronal and nonneuronal intermediate filament proteins. The proteins of the intermediate filament complex in the two tissues for rat and hamster were similar. The typical neurofilament triplet and glial fibrillary acidic protein (GFAP) were observed. Vimentin was more concentrated in the optic nerve than in the spinal cord. The goldfish, newt, and frog contained neurofilament proteins in the 145-150K range and in the 70-85K range. In addition, predominant neurofilament proteins in the 58-62K molecular-weight range were found in all three species. In contrast to mammalian species, the goldfish, newt, and frog displayed extensive heterogeneity between optic nerve and spinal cord in the expression of both neuronal and nonneuronal intermediate filament proteins. The distinctive presence of low-molecular-weight intermediate filament proteins and their high concentration in the optic nerve and spinal cord of these nonmammalian vertebrates is discussed in terms of neuronal development and regeneration.

Amphibians↗

PubMed1985

UV suppression of mast cell-mediated wealing in human skin.

Prior exposure of normal skin to subthreshold doses of UVR from a "UVA" phototherapy cabinet resulted in a small but significant reduction of the wealing response to intradermally injected codeine phosphate, a mast cell degranulating agent. The flare component of the reaction was not affected, nor were the responses to intradermally injected histamine. Both UVA and UVB from banks of filtered fluorescent tubes appeared to produce a similar but less pronounced effect. Dose-response studies revealed that the inhibition of mast cell-mediated wealing required a certain cumulative threshold dose of UVR (about 35 J/cm2 UVA + 20 mJ/cm2 UVB). The observed reduction in wealing could not be entirely explained by differences in the content of tissue histamine. It is concluded that repeated exposure to a broad range of UV wavelengths can depress the response of mast cells in vivo to degranulating agents by an unknown mechanism. This finding may have relevance to some of the observed therapeutic effects of phototherapy in certain inflammatory dermatoses and especially cutaneous mast cell disorders.

Adult↗

PubMed1984

Alpha-2-adrenergic receptors in avian spinal cord: increases in apparent density associated with the sympathetic preganglionic cell column.

Vertebrate spinal cord receives a dense and diversified catecholaminergic innervation from brainstem and diencephalon. Within the spinal gray, the densest terminations appear to be within the neuropil surrounding sympathetic preganglionic neurons (SPNs) in thoracic spinal cord. Results of recent iontophoresis investigations showed that several catecholamines and clonidine, an alpha-2 agonist, uniformly inhibited the maintained discharge activity of SPNs [19]. These experiments raised the possibility that the inhibitory effects might be mediated by activation of an alpha-2-adrenergic receptor. The present series of ligand binding studies provide biochemical evidence suggesting the presence of alpha-2-adrenergic receptors in the SPN cell column. Total specific binding (Bmax) of the radiolabeled agonists clonidine (CLO) and para-amino-clonidine (PAC) (at concentrations above and below apparent KDS) was significantly greater in thoracic spinal cord in comparison with cervical spinal cord (P less than 0.001). The elevated levels in thoracic spinal cord were entirely accounted for by increases in apparent receptor density in dorsal horn and the SPN cell column (inclusive of the adjoining intermediate spinal laminae) (P less than 0.005). Adrenergic receptor subtype specificity of [3H]PAC was tested in competitive inhibition experiments. The results confirmed that [3H]PAC is a preferential alpha-2 agonist in thoracic and cervical spinal cord, and indicated the following rank order of potency for its displacement: norepinephrine = yohimbine much greater than prazosin greater than propranolol.

Adrenergic alpha-Agonists↗

PubMed1984

Alpha 1- and alpha 2-adrenoceptor binding in the Dahl rat model of hypertension.

Dahl sensitive rats on a high salt diet (DSH group) developed significant elevations in blood pressure (BP). Sensitive rats maintained on a low salt diet (DSL group) and Dahl resistant rats on a high or low salt diet (DRH and DRL groups, respectively) remained normotensive. The DSH and DRH groups displayed a lower density of alpha 2-adrenoceptors (as measured with [3H]-clonidine) in the cerebral cortex than normotensive DSL and DRL groups. In contrast, the density of alpha 2-adrenoceptors in the medulla was significantly lower in the DSH group than the DSL group, but significantly higher in the DRH group compared to the DRL group. The density of alpha 1-adrenoceptors (as measured with [3H]-WB4101) in the hypothalamus was lower in the DSH group than the DSL group but greater in the DRH group than the DRL group. The results suggest that the sensitive and resistant lines can be distinguished by the density of alpha 1- adrenoceptors in the hypothalamus and medulla, respectively. The interactive effects of dietary NaCl and susceptibility to hypertension on adrenoceptors lend further support to the hypothesis that the genetic predisposition to hypertension is associated with a disruption in central adrenergic activity.

Adrenergic alpha-Antagonists↗

PubMed1984

Induction of immune alterations and successful renal transplantation with a simplified method of donor-specific blood transfusion.

We developed a new and simplified donor-specific blood transfusion (DSBT) protocol for prospective kidney transplant recipients from one-haplotype-mismatched related donors. Prospective kidney donors gave 450 ml of blood in a quad-pack unit, and the blood was stored in a blood bank. Twenty-five patients were transfused with 100 ml of the respective donor's whole blood at 1, 8, and 15 days after its storage. After DSBT, only three (12%) developed donor-specific lymphocytotoxic antibodies. Following DSBT, donor-specific mixed lymphocyte culture (MLC) was significantly suppressed, without any accelerated (secondary-type) response in early MLC. In addition, sera obtained after DSBT also suppressed donor-specific MLC significantly. Sixteen recipients subsequently received a kidney transplant from the donor, and all had functioning grafts at three months, but one lost the graft thereafter (graft survival rate: 94% at 12 months). This study indicates that (1) 100 ml of stored whole-blood DSBT three times at weekly intervals is a practical, less immunizing, and effective approach to enhance graft survival in recipients of a one-haplotype-mismatched graft; and (2) immune consequences of DSBT include induction of donor-specific cellular and humoral adaptive responses that might be conducive to successful graft outcome.

Adolescent↗