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Biomedical subjects

S Gordon

Publications and source records attributed to S Gordon.

At least 325 records · Page 18Linked to original sources
PubMed1991

An outbreak of cryptosporidiosis in a day-care center in Georgia.

Diarrhea among the 11 million children attending day-care centers in the United States is common, but infection control of enteric pathogens in the day-care center setting remains a challenge. In August 1989, an outbreak of cryptosporidiosis was investigated at a day-care center in Georgia. A total of 49% (39/79) of children and 13% (3/23) of staff members who submitted stool specimens were found to be infected with Cryptosporidium. A total of 77% (30/39) of infected children had mild-to-moderate diarrhea (median duration, 5 days). Children were at highest risk if they were less than age 36 months, in diapers, and not toilet trained. Serial stool specimens were collected from 12 infected children. After diarrhea had ceased, oocyst shedding continued in all children for a mean duration of 16.5 days. It is concluded that the prevalence of asymptomatic infections and the duration of shedding after the end of symptoms may previously have been underestimated. Cohorting or exclusion from the day-care center of children who are asymptomatic shedders is not practical, and the management of cryptosporidiosis in day-care centers remains a major challenge.

Adult↗
PubMed1991

Regulation of tumor necrosis factor (TNF) release by murine peritoneal macrophages: role of cell stimulation and specific phagocytic plasma membrane receptors.

In spite of the physiologic and pathologic importance of tumor necrosis factor (TNF), the cellular factors that govern its release by macrophages (M phi) are poorly understood, in comparison with other secretory products. We have studied the role of M phi heterogeneity and of plasma membrane receptors in regulating TNF release in vitro. Resident and various exudate murine peritoneal M phi populations were challenged with lipopolysaccharide (LPS) or different phagocytic particles, and TNF release assayed by cytotoxicity for L-929 fibroblasts. Resident peritoneal M phi (RPM phi) released a small amount of TNF in response to LPS whereas thioglycollate-elicited M phi (TPM phi) released high levels of TNF (5000 U/3 x 10(5) M phi/ml). M phi elicited by Bio-Gel polyacrylamide beads (BgPM phi), another nonspecific inflammatory stimulus, or early in the course of intraperitoneal Bacillus Calmette-Guérin infection, before recruited cells become immunologically activated, released tenfold less TNF after the same stimulus. By contrast, TNF release in response to various phagocytic triggers was similar (approximately 300-600 U/3 x 10(5) M phi/ml) in all M phi populations including RPM phi. The response by BgPM phi to LPS was enhanced by pre-treatment in vitro with interferon-gamma or thioglycollate broth. With respect to phagocytic receptor triggering we found that complement receptor type 3 (CR3) ligation or latex uptake did not mediate release of significant quantities of TNF (less than 48 U/3 x 10(5) M phi/ml) by any M phi, whereas ligation of the Fc receptor for IgG1/IgG2b subclasses or of receptors for zymosan particles sufficed, in the absence of ingestion, to induce release of circa 500 U/3 x 10(5) M phi/ml TNF by all M phi tested. Our studies show that M phi vary in respect to priming for TNF release and that heterogeneity should be related to a particular triggering stimulus. Furthermore, the capacity of some M phi populations to release unusually high levels of TNF depends on immune or nonspecific stimuli subsequent to the process of inflammatory recruitment.

Acrylic Resins↗
PubMed1991

Purification and properties of sialoadhesin, a sialic acid-binding receptor of murine tissue macrophages.

Macrophage subpopulations in the mouse express a lectin-like receptor, sialoadhesin (originally named sheep erythrocyte receptor, SER), which selectively recognizes sialoglycoconjugates and is likely to be involved in cellular interactions of stromal macrophages in haematopoietic and lymphoid tissues. In this report we describe the purification and ligand specificity of sialoadhesin isolated from mouse spleen. Purified sialoadhesin, a glycoprotein of 185 kd apparent Mr, agglutinated sheep or human erythrocytes at nanomolar concentrations in a sialic acid-dependent manner. Low angle shadowing and electron microscopy showed that sialoadhesin consisted of a globular head region of approximately 9 nm and an extended tail of approximately 35 nm. To investigate the specificity for sialic acid, we studied the interaction of sialoadhesin with derivatized human erythrocytes, glycoproteins, and glycolipids. In conclusion, sialoadhesin specifically recognizes the oligosaccharide sequence Neu5Ac alpha 2----3Gal beta 1----3GalNAc in either sialoglycoproteins or gangliosides. These findings imply that specific sialoglycoconjugates carrying this structure may be involved in cellular interactions between stromal macrophages and subpopulations of haematopoietic cells and lymphocytes.

Animals↗
PubMed1991

The CNS acute inflammatory response to excitotoxic neuronal cell death.

Acute inflammation is a stereotyped non-specific response to tissue injury which results in the recruitment of neutrophils and monocytes within minutes. In this study the myelomonocytic and microglial reaction to neuronal destruction following unilateral hippocampal injection of kainic acid neurotoxin was investigated. Despite extensive acute neuronal necrosis and notwithstanding a leaky blood-brain-barrier, there is no neutrophil recruitment and a 2-day delay before any increase in macrophage-microglial cell numbers. Resident microglia are capable of reversible upregulation to an activated morphology and the macrophage-microglial reaction is seen not only at the injection site, but also at distant sites related to the axonal pathways and synaptic terminals of the killed neurons.

Animals↗
PubMed1991

The kinetics and morphological characteristics of the macrophage-microglial response to kainic acid-induced neuronal degeneration.

Outside the nervous system myelomonocytic cells are known to play an important role in the inflammatory response and tissue repair after injury. In this study we have examined the myelomonocytic response to neuronal destruction following unilateral injection of the excitotoxin kainic acid into the mouse hippocampus. Intrahippocampal injection of kainate induces rapid, synchronous neuronal death. There is no neutrophil recruitment and a delay of at least 48 h before macrophage-microglial cell numbers increase. The microglial reaction in the injected hippocampus consists of altered morphology, a 6-9-fold increase in mononuclear phagocyte cell numbers and enhanced expression of the macrophage-specific plasma membrane antigen, F4/80, assessed immunohistochemically and by Western blotting. Microglia also respond at distant sites related to the projection pathway and terminals of killed pyramidal cells but the reaction varies in cell numbers, kinetics and morphology. The absence of neutrophil recruitment and the delay in an increase in macrophage or microglial cells shows that the CNS differs from other sites in the body with regard to the kinetics and nature of the myelomonocytic cell inflammatory response. The role of mononuclear phagocytes in tissue repair in the CNS remains to be defined.

Animals↗
PubMed1991

Macrophage dependence of peripheral sensory nerve regeneration: possible involvement of nerve growth factor.

The levels of NGF and NGF receptor mRNA, the degree of macrophage recruitment, and the ability of sensory and motor axons to regenerate were measured in C57BL/Ola mice, in which Wallerian degeneration following a nerve lesion is very slow. Results were compared with those from C57BL/6J and BALB/c mice, in which degeneration is normal. We found that in C57BL/Ola mice, apart from the actual lesion site, recruitment of macrophages was much lower, levels of mRNA for both NGF and its receptor were raised only slightly above normal, and sensory axon regeneration was much impaired. Motor axons regenerated quite well. These results provide in vivo evidence that macrophage recruitment is an important component of NGF synthesis and of sensory (but not motor) axon maintenance and regrowth.

Animals↗
PubMed1991

Macrophages in haemopoietic and other tissues of the developing mouse detected by the monoclonal antibody F4/80.

Macrophages are widely distributed in lymphohaemopoietic and other tissues of the normal and diseased adult, where they play an important role in host defence and repair. Although the development of haemopoiesis has been well studied in several species, the ontogeny of the mononuclear phagocyte system remains poorly understood. We have used a highly specific mAb, F4/80, to examine the distribution of mature macrophages in the developing mouse, with special reference to their presence in the haemopoietic microenvironment. Monocytes and macrophages were first seen in embryos on day 10 in the yolk sac and liver as well as in mesenchyme. In liver, spleen and bone marrow, there was expansion of this population associated with the initiation of haemopoiesis on days 11, 15 and 17, respectively. Macrophages in these sites formed part of the haemopoietic stroma and their extensively spread plasma membrane processes could be seen making intimate contacts with clusters of differentiating haemopoietic cells. F4/80+ cells were widely dispersed in undifferentiated mesenchymal tissue in organs such as lung, kidney and gut. Numbers of F4/80-labelled cells increased concomitantly with organ growth and local mitoses were evident, as well as actively phagocytic macrophages. Our studies establish that macrophages are among the earliest haemopoietic cells to be produced during development and that they are relatively abundant in fetal tissues in the absence of overt inflammatory stimuli. Their distribution is correlated with the sequential migration of haemopoiesis and they constitute a prominent component of the stroma in fetal liver, spleen red pulp and bone marrow. Apart from a role in haemopoietic cellular interactions, their highly developed endocytic and biosynthetic activities suggest that macrophages contribute major undefined functions during growth, turnover and modelling of fetal tissues.

Animals↗
PubMed1991

Expression of a divalent cation-dependent erythroblast adhesion receptor by stromal macrophages from murine bone marrow.

Stromal macrophages in haemopoietic organs express novel surface receptors that are implicated in trophic interactions with developing blood cells. Macrophages isolated from foetal liver bind erythroblasts (Eb) by a divalent cation-dependent receptor (EbR), whereas stromal macrophages in adult bone marrow and lymphoid organs express a lectin-like receptor, sialoadhesin, which interacts with sialylated structures on sheep erythrocytes and murine haemopoietic cells. In order to learn more about the regulation of these haemagglutinins, we examined binding of Eb by stromal macrophages that had been isolated from adult murine tissues or generated in Dexter-type cultures of bone marrow. Macrophages were purified from bone marrow by collagenase digestion, adherence to a substratum and detachment of clustered haemopoietic cells, and tested for their ability to bind Eb from foetal liver or anaemic adult spleen. Freshly isolated bone marrow macrophages bound Eb mainly by a divalent cation-dependent activity that was not inhibited by neuraminidase treatment of Eb or by specific anti-sialoadhesin monoclonal antibodies, although these macrophages express sialoadhesin and Eb bear a potential ligand for this receptor. Macrophages obtained by digestion from other adult lymphoid tissues also bound Eb by a divalent cation-dependent activity, whereas blood monocytes and lavaged peritoneal macrophages failed to do so. Peritoneal macrophages could be induced to express high levels of sialoadhesin by cultivation in homologous mouse serum, but such macrophages did not acquire sialoadhesin-independent EbR activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Exercise prescription for hypertensive patients.

Physical conditioning has been suggested as a useful adjunct or alternative to pharmacologic therapy in the treatment of borderline or mild hypertension. This recommendation stems from numerous studies that have demonstrated modest decreases in blood pressure in hypertensive individuals. Exercise guidelines should be based on preliminary exercise testing and modified to accommodate those patients who are taking a variety of antihypertensive medications. Although pure isometric exercise is generally contraindicated in hypertensive patients, potentially valuable training activities that involve a substantial static component, including arm crank ergometry and mild-to-moderate load weight training, probably requires individual assessment.

Blood Pressure↗
PubMed1991

Coach/player relationships in tennis.

The present study examined the variables that predict coach/athlete compatibility. Compatibility among a sample of 52 elite tennis coach/player dyads was assessed using a sport adapted version of Schutz's (1966) Fundamental Interpersonal Relations Orientation-Behaviour (FIRO-B), a sport adapted version of Fiedler's (1967) Least Preferred Co-worker scale (LPC), and Chelladurai and Saleh's (1980) Leadership Scale for Sport (LSS). Self-ratings of the quality of the interaction were obtained from both coach and athlete. Multiple-regression analyses using self-rating scores as the dependent measure were carried out to determine which variables best predicted the degree of compatibility. The sole inventory that significantly predicted compatibility was the LSS. More specifically, the discrepancy between the athlete's preferences and perceptions on the autocratic dimension was the best predictor. Implications for tennis coaches and recommendations for future research in this area are discussed.

Achievement↗