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S Cohen

Publications and source records attributed to S Cohen.

At least 361 records · Page 20Linked to original sources
PubMed1993

Epidermal growth factor stimulates the tyrosine phosphorylation of SHC in the mouse.

Previous studies have demonstrated that the administration of epidermal growth factor (EGF) to neonatal mice results in the tyrosine phosphorylation of multiple substrates in all organs examined (Donaldson, R. W., and Cohen, S. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 8477-8481). One of these substrates, a 55-kDa protein, was shown to associate with the receptor for EGF (EGFR). We now report the identification of this receptor-associated protein as SHC. Immunoprecipitation and Western blotting analyses have revealed that SHC associates only with the activated EGFR. In the absence of EGF stimulation, SHC exists in the liver as a cytoplasmic monomer. Intraperitoneal injection of EGF results, within minutes, in the translocation of 50-80% of SHC to the liver plasma membrane. The membrane-associated SHC was found to be tyrosine-phosphorylated; the subsequent release of SHC from the membrane correlated with a tyrosine dephosphorylation. We conclude that SHC is a physiological substrate that appears to participate in the in vivo signaling response to EGF.

Animals↗
PubMed1993

Regulation of VCAM-1 expression and involvement in cell adhesion to murine microvascular endothelium.

The present studies were undertaken to examine the regulation of murine VCAM-1 expression and the involvement of this molecule in adhesive processes occurring on the surface of microvascular endothelium. Flow cytometric analyses revealed that murine microvascular endothelium (MME) in culture constitutively expresses VCAM-1 and that stimulation of MME by TNF, IL-1, or LPS, but not by PMA or staurosporine, strongly increased the surface expression of this cell adhesion molecule. Stimulation of VCAM-1 expression by TNF may be diminished by ionomycin as well as by inhibitors of protein kinases (H-7 and sangivamycin). However, TGF-beta, which strongly inhibited the adhesiveness of endothelium, had little effect on the expression of VCAM-1. A newly developed adhesion assay, based on the rosette technique, allowed us to distinguish between the adhesive properties of an individual endothelial cell and those of endothelial cell monolayers and demonstrated that inhibition of binding by TGF-beta resulted primarily from its influence on the adhesive properties of individual cells. Studies on the inhibition of cell binding by monoclonal antibodies against mouse VCAM-1 and mouse VLA-4 indicated that VCAM-1 plays a dominant role in mediating the adherence of a variety of cell types, including murine splenocytes and thymocytes, P815 mastocytoma cells, PT 18 mast/basophil cells, human Molt-4 cells, and human eosinophils, to cytokine-activated MME.

Alkaloids↗
PubMed1993

Glutamate-like immunoreactivity in retinal terminals of the mouse suprachiasmatic nucleus.

With a view to identifying the neurotransmitter content of retinal terminals within the mouse suprachiasmatic nucleus, a highly specific antiserum to glutaraldehyde-coupled glutamate was used in a postembedding immunogold procedure at the ultrastructural level. Retinal terminals were identified by cholera toxin--horseradish peroxidase transported anterogradely from the retina and reacted with tetramethyl benzidine/tungstate/H2O2, or by their characteristically pale and distended mitochondria with irregular cristae. Controls included model ultrathin sections containing high concentrations of various amino acids. Alternate serial sections were labelled with anti-glutamate and anti-gamma-aminobutyric acid (GABA). Data were analysed by computer-assisted image analysis. Density of glutamate labelling (gold particles per micron2) on whole retinal terminals was > 3 times higher than that on postsynaptic dendrites, and > 5 times higher than that on miscellaneous non-retinal non-glutamatergic terminals in the suprachiasmatic nucleus. The overall density of gold particles over retinal terminals was approximately 3 times higher than that over GABAergic terminals, in which glutamate-like immunoreactivity was mainly mitochondrial. Labelling of vesicles in retinal terminals was almost 5 times greater than the apparent labelling of vesicles in GABAergic terminals, underscoring the location of transmitter glutamate within synaptic vesicles in retinal terminals. In the retino-recipient region of the suprachiasmatic nucleus there was also a small population of non-retinal glutamatergic terminals. Their overall immunoreactivity was similar to or exceeded that of retinal terminals, but morphological features clearly distinguished between these two types of glutamate-containing terminals. The present results indicate that the vast majority of retinal terminals may use glutamate as a transmitter, in keeping with electrophysiological and neuropharmacological data from other sources. The possibility of cotransmitters within retinal terminals, suggested by the presence of dense-core vesicles among the glutamate-containing synaptic vesicles, has still to be addressed.

Animals↗
PubMed1993

Olfactory receptors: transduction, diversity, human psychophysics and genome analysis.

The emerging understanding of the molecular basis of olfactory mechanisms allows one to answer some long-standing questions regarding the complex recognition machinery involved. The ability of the olfactory system to detect chemicals at sub-nanomolar concentrations is explained by a plethora of amplification devices, including the coupling of receptors to second messenger generation through GTP-binding proteins. Specificity and selectivity may be understood in terms of a diverse repertoire of olfactory receptors of the seven-transmembrane-domain receptor superfamily, which are probably disposed on olfactory sensory neurons according to a clonal exclusion rule. Signal termination may be related to sets of biotransformation enzymes that process odorant molecules, as well as to receptor desensitization. Many of the underlying molecular components show specific expression in olfactory epithelium, with a well-orchestrated developmental sequence of emergence, possibly related to sensory neuronal function and connectivity requirements. A general model for molecular recognition in biological receptor repertoires allows a prediction of the number of olfactory receptors necessary to achieve efficient detection and sheds light on the analogy between the immune and olfactory systems. The molecular cloning and mapping of a human genomic olfactory receptor cluster on chromosome 17 provides insight into olfactory receptor diversity, polymorphism and evolution. Combined with future genotype-phenotype correlation, with particular reference to specific anosmia, as well as with computer-based molecular modelling, these studies may provide insight into the odorant specificity of olfactory receptors.

GTP-Binding Proteins↗
PubMed1993

Characteristics of DNA replication in isolated nuclei initiated by an aprotinin-binding protein.

Isolated cell nuclei were used as the source of template DNA to investigate the role of a cytosolic aprotinin-binding protein (ADR) in the initiation of eukaryotic DNA replication. Computerized image cytometry demonstrated that the DNA content of individual nuclei increased significantly following incubation with ADR-containing preparations, and the extent of DNA synthesis is consistent with that allowed by the limiting concentration of dTTP. Thus, dTTP incorporation into isolated nuclei represents DNA synthesis and not parent strand repair. We found that dTTP incorporation into the isolated nuclei is dependent on DNA polymerase alpha (a principal polymerase in DNA replication) but that DNA polymerase beta (a principal polymerase in DNA repair processes) does not play a significant role in this system. Finally, neither aprotinin nor a previously described cytosolic ADR inhibitor can block the replication of nuclease-treated calf thymus DNA, while both strongly inhibit replication of DNA in isolated nuclei. This result, coupled with the relative ineffectiveness of nuclease-treated DNA compared with nuclear DNA to serve as a replicative template in this assay, argues against a significant contribution from repair or synthesis which initiates at a site of DNA damage. These data indicate that ADR-mediated incorporation of 3H-dTTP into isolated nuclei results from DNA replicative processes that are directly relevant to in vivo S phase events.

Aprotinin↗
PubMed1993

Dose and temporal parameters in delaying injured optic nerve degeneration by low-energy laser irradiation.

Low-energy laser irradiation has been reported to postpone the degenerative processes in crushed optic nerves of rats, which are part of the nonregenerable mammalian central nervous system. In the present study, we evaluated the optimal irradiation parameters for this purpose. Optic nerves of 141 rats were subjected to crush injury and then irradiated through the eye, starting at different points of time before or after the injury, for different durations and periods, using various intensities of either helium-neon laser or noncoherent infrared light (904 nm). The effect was evaluated by measurements of the compound action potentials of the nerve segments between the site of injury and the optic chiasm. The compound action potential amplitude of the crushed nonirradiated nerves, as measured 2 weeks after the injury, was found to be 0.51 +/- 0.30 mV, in contrast to 3.10 +/- 1.03 mV measured in 232 normal nerves. Irradiation with a 10.5 mW helium-neon laser for 2 and 3 min once a day for 14 consecutive days resulted in maximal preservation of action potentials (1.78 +/- 0.72 and 1.95 +/- 0.71 mV, respectively). Irradiations beginning immediately prior to the injury were as effective as irradiations beginning soon after it. Irradiations for longer than 3 min or twice a day aggravated the damage. Noncoherent infrared light was ineffective or adversely affected the injured nerves. Our experiments suggest that optimal delay of posttraumatic optic nerve degeneration in rats is attainable with 10.5 mW helium-neon laser irradiations for 2 or 3 min once a day for 14 consecutive days.

Action Potentials↗
PubMed1993

A cytosolic activator of DNA replication is tyrosine phosphorylated in its active form.

Cytosolic extracts from actively dividing lymphoid cells have been shown to induce DNA synthesis in isolated, quiescent nuclei. An initiating factor in such extracts (activator of DNA replication; ADR) is a > 90-kDa aprotinin-binding protein whose activity is inhibitable not only by aprotinin, but also by several other protease inhibitors as well. Although cytosol from non-proliferating lymphocytes is devoid of ADR activity, we have shown that these preparations can be induced to express ADR activity by brief exposure to a membrane-enriched fraction of spontaneously proliferating MOLT-4 cells via a kinase-dependent mechanism. In the present study, we examine the role of tyrosine kinases in this process. Three inhibitors of tyrosine kinases (genistein, kaempferol, and quercetin) can inhibit the in vitro generation of ADR activity. In vitro generation of ADR activity is associated with the de novo phosphorylation of several proteins, many of which are detectable using anti-phosphotyrosine monoclonal antibodies. ADR itself may be tyrosine phosphorylated in active form as immunoprecipitation using such monoclonal antibodies leads to the depletion of its activity. Moreover, immunoprecipitation results in the removal of several de novo tyrosine-phosphorylated proteins, including species at approximately 122, 105, 93, 86, 79, and 65 kDa. A subset of de novo-phosphorylated proteins, migrating at approximately 105, 93, and 70 kDa, also bound to aprotinin, suggesting that at least one of these proteins may represent ADR itself.

Aprotinin↗
PubMed1993

In vitro replication of plasmids containing human ribosomal gene sequences: origin localization and dependence on an aprotinin-binding cytosolic protein.

We previously investigated the role of an aprotinin-binding protein (ADR) in the initiation of DNA replication in isolated quiescent nuclei. In the present study, we have used a cell-free DNA replication system to test the ability of plasmid vectors which contain sequences from the human ribosomal RNA gene to serve as replicative templates in vitro when exposed to ADR-containing preparations. Significant dTTP incorporation was seen using DNA from either a 7-kb sequence in the 5' spacer region (CHE) or a 7-kb sequence which begins near the end of the 28S coding region and extends into the 3' spacer region (ADBB), while sequences from other regions of the rRNA gene mediated little or no dTTP incorporation. The characteristics of plasmid-directed dTTP incorporation indicate that most incorporation is due to DNA replication and not repair or damage-initiated processes. To conclusively demonstrate origin-dependent replication in the plasmid system and to further map replication origins, an approach was developed using ddGTP to restrict the length of daughter strands followed by hybridization of these replication products to restriction fragments spanning the putative origin region. This approach allowed us to identify replication origin activity apart from parent strand repair or synthesis initiated at random damaged sites. One of the origins was localized to a 1375-bp fragment within the 5' spacer region, and this fragment contains sequences homologous to those found in other replication origins.

Aprotinin↗
PubMed1993

Complications during pneumatic dilation for achalasia or diffuse esophageal spasm. Analysis of risk factors, early clinical characteristics, and outcome.

UNLABELLED: A retrospective cohort study was performed to assess risk factors, early clinical characteristics, and outcome of complications in patients undergoing pneumatic dilation. Of 178 patients with achalasia or diffuse esophageal spasm who underwent 236 dilations with a Browne-McHardy dilator, 16 patients experienced a complication (9.0%). Nine major complications developed: perforations (4), hematemesis (2), fever (2), and angina (1). A prior pneumatic dilation and use of inflation pressure > or = 11 PSI were independent risk factors by multivariate analysis for developing a complication. An esophagram immediately following the dilation identified three of the four perforations. Three postdilation findings were identified as indicators of patients with an increased risk of having developed a perforation: blood on the dilator, tachycardia, and prolonged chest pain lasting > 4 hr after dilation. In all patients incurring a major complication, one of the three indicators, or the complication itself was recognized within 5 hr of dilation. All patients with complications, including the four with perforation who received prompt surgical repair and esophagomyotomy, recovered uneventfully. The symptomatic relief of dysphagia in patients with perforation undergoing emergent surgical repair and esophagomyotomy was similar to patients undergoing elective esophagomyotomy. CONCLUSIONS: (1) Pneumatic dilation is a safe treatment of achalasia, with a 1.7% risk of perforation. (2) The risk of developing a complication is increased by having had a previous pneumatic dilation or by use of inflation pressures > or = 11 psi. (3) All patients with a major complication were identified within 5 hr after dilation. (4) Complications following pneumatic dilation, if recognized and treated promptly, were not associated with adverse, long-term sequelae.

Catheterization↗
PubMed1993

Pneumatic dilatation or esophagomyotomy treatment for idiopathic achalasia: clinical outcomes and cost analysis.

The choice between pneumatic dilatation and surgical esophagomyotomy as the initial treatment for achalasia is controversial. The aims of this study were to determine the long term clinical outcome and costs of treating achalasia initially with pneumatic dilatation as compared to esophagomyotomy. Of 123 patients undergoing an initial pneumatic dilatation for achalasia at our institution from 1976 to 1986, 71 (58%) received no further treatment for achalasia during a mean follow up of 4.7 +/- 2.8 years. Only 15 of these 123 patients (12%) eventually underwent surgical esophagomyotomy (two for perforation during pneumatic dilatation, 13 for persistent or recurrent symptoms). The degree of dysphagia at follow up was improved to a similar degree in patients treated with an initial pneumatic dilatation as compared to patients treated with an initial esophagomyotomy. Patients with age > or = 45 years at time of initial pneumatic dilatation had fewer subsequent treatments for persistent or recurrent symptoms and had less dysphagia on follow up as compared to patients < 45 years. Subsequent pneumatic dilatations to treat persistent or recurrent symptoms were less beneficial than an initial pneumatic dilatation. The cost of esophagomyotomy was 5 times greater than the cost of pneumatic dilatation. When costs were analyzed to include subsequent treatments of symptomatic patients, the total expectant costs of treating with an initial esophagomyotomy remained 2.4 times greater than treating with an initial pneumatic dilatation. This study suggests that an initial pneumatic dilatation will be the only treatment needed for the majority of patients with achalasia. A treatment regimen starting with pneumatic dilatation has less overall costs than starting with esophagomyotomy. For each subsequent pneumatic dilatation, however, the clinical benefit leans toward surgery.

Catheterization↗
PubMed1993

Intensive one-week orientation for foreign medical graduates entering an internal medicine residency program.

The authors describe an intensive week-long introduction to hospital-based medical practice for foreign medical graduates (FMGs) entering an internal medicine residency program. The intensive orientation helps the FMGs function more effectively in the American hospital environment and reduces the frequency of personal and professional adjustment problems. The program is easily adaptable to other hospitals with large numbers of FMG residents.

Foreign Medical Graduates↗
PubMed1993

Design of synthetic polymeric structures for cell transplantation and tissue engineering.

Two approaches for cell transplantation and new tissue constructions are discussed. In one case, a novel synthetic polyphosphazene has been synthesized that can be gelled by simply adding ions to it at room temperature under aqueous conditions. This polymer has been shown to be compatible for several different cell types. Microcapsular membranes based on the complex of this polymer with poly (L-lysine) allow the inward diffusion of nutrients to nourish the encapsulated cells, but are impermeable to antibodies. In a second approach, biodegradable polyesters have been designed as scaffolds for liver cells and cartilage cells to aid in organ regeneration. Design of the polymer scaffold including the characterization of the surface chemistries for cell attachment, as well as in-vitro and in-vivo data on cell behavior are presented.

Animals↗
PubMed1993

Signs and symptoms in common colds.

The patterns of disease caused by five common viruses which infect the respiratory tract are described. The viruses were strains of rhinovirus types 2, 9, and 14, a strain of coronavirus type 229E and of respiratory syncytial virus. Volunteers were given nasal drops containing a low infectious dose of one of the viruses, quarantined from 2 days before to 5 days after inoculation, and examined daily by a clinician using a standard checklist of respiratory signs and symptoms. Only subjects who developed clinical illness accompanied by viral shedding and/or specific antibody production were analysed [n = 116]. The results confirm indication from earlier studies that the main difference between colds induced by different viruses is in duration of the incubation period. Patterns of symptom development were not substantially different with different viruses. Analyses of signs and symptoms in different categories, e.g. nasal symptoms v. coughing, justify treatment with different drugs either successively or simultaneously.

Adolescent↗
PubMed1993

Determinants of release rate of tetanus vaccine from polyester microspheres.

Controlled-release formulations based on poly(lactic) (PLA) and poly(lactic/glycolic) acid (PLGA) microspheres containing tetanus vaccine were designed. The polymers forming the microspheres were L-PLA of different molecular weights and DL-PLGA, 50:50. These microspheres were prepared by two solvent elimination procedures, both using a double emulsion, and were characterized for size, morphology, and toxoid release kinetics. The influence of formulation variables such as polymer type, vaccine composition, and vaccine/polymer ratio was also investigated. Both techniques yielded microspheres with similar size, morphology, and release properties. Microsphere size was dependent on the type of polymer and the presence of the surfactant L-alpha-phosphatidylcholine, which led to a reduction in microsphere size. On the other hand, the release kinetics of encapsulated protein were affected by the polymer properties (ratio lactic/glycolic acid and molecular weight) as well as by the vaccine composition, vaccine loading, and microsphere size. Moreover, for some formulations, a decrease in microsphere size occurred simultaneously, with an increase in porosity leading to an augmentation of release rate. The changes in the PLA molecular weight during in vitro release studies indicated that release profiles of tetanus toxoid from these microspheres were only marginally influenced by polymer degradation. A significant fraction of protein (between 15 and 35%) was initially released by diffusion through water-filled channels. In contrast, the decrease in the PLGA molecular weight over the first 10 days of incubation suggested that erosion of the polymer matrix substantially affects protein release from these microspheres. Among all formulations developed, two differing in microsphere size, polymer hydrophobicity, and release profile were selected for in vivo administration to mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Negative life events, perceived stress, negative affect, and susceptibility to the common cold.

After completing questionnaires assessing stressful life events, perceived stress, and negative affect, 394 healthy Ss were intentionally exposed to a common cold virus, quarantined, and monitored for the development of biologically verified++ clinical illness. Consistent with the hypothesis that psychological stress increases susceptibility to infectious agents, higher scores on each of the 3 stress scales were associated with greater risk of developing a cold. However, the relation between stressful life events and illness was mediated by a different biologic process than were relations between perceived stress and illness and negative affect and illness. That these scales have independently relations with illness and that these relations are mediated by different processes challenges the assumption that perceptions of stress and negative affect are necessary for stressful life events to influence disease risk.

Adaptation, Psychological↗
PubMed1993

Depression and immunity: a meta-analytic review.

A meta-analysis indicated that clinical depression was associated with several large alterations in cellular immunity. Analyzing only methodologically sound studies, reliable immune alterations included lowered proliferative response of lymphocytes to mitogens (effect size rs = .24-.45), lowered natural killer cell activity (r = .28), and alterations in numbers of several white blood cell populations (rs = .11-.77). Immune alterations were greater in both older and hospitalized samples. There was also evidence of a linear relation between intensity of depressive affect and indicators of cellular immunity. Estimates of sample sizes needed to detect reliable effects for each immune outcome are provided. How neuroendocrine mechanisms or health practices might link depression to immunity is discussed, and design features needed to better understand these pathways are specified.

Adult↗
PubMed1993

Postcesarean delivery epidural patient-controlled analgesia. Fentanyl or sufentanil?

BACKGROUND: The highly lipid-soluble opioids, fentanyl and sufentanil, frequently are used in combination with local anesthetic agents and/or epinephrine to provide postoperative epidural analgesia. The authors compared the incidence of side effects and patient satisfaction during prolonged epidural patient-controlled analgesia (PCA) infusions of these opioids in combination with bupivacaine and epinephrine. METHODS: Using a double-blind study design, 250 patients scheduled for elective cesarean delivery were, on arrival in the postanesthesia care unit, randomized into two epidural PCA infusion groups: group I (n = 125) received fentanyl 2 micrograms/ml with bupivacaine 0.01% and epinephrine 0.5 micrograms/ml and group II (n = 125) received sufentanil 0.8 micrograms/ml with bupivacaine 0.01% and epinephrine 0.5 microgram/ml. The initial infusion rate was 16 ml/h with self-administered 3-ml boluses every 15 min by PCA as desired. At intervals after discontinuation of the infusion, plasma samples were obtained to determine opioid concentrations. RESULTS: The median overall satisfaction scores were 9.0 for group I and 10.0 for group II (difference not significant). Pain relief was satisfactory and comparable in both groups, and all patients could ambulate easily. The total number of times PCA requests were made was greater (P < 0.05, by Wilcoxon rank-sum test) for group I than for group II (106.7 +/- 312 vs. 70.8 +/- 138). There were no differences between the groups with respect to incidence of pruritus, sedation, and nausea; however, vomiting occurred more frequently with sufentanil than with fentanyl (12% vs. 4.8%, respectively; P < 0.05). At approximately 1-2 h after discontinuation of the infusion, 1 patient receiving fentanyl and 42 patients receiving sufentanil complained of lightheadedness and dizziness (P < 0.0001). CONCLUSIONS: Epidural PCA in both groups had no serious side effects and achieved a high level of patient satisfaction. Those receiving sufentanil made fewer PCA requests but had a significantly greater incidence of vomiting during the infusion and dizziness after the termination of the infusion. Epidural sufentanil offered no advantages over epidural fentanyl.

Adult↗