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Biomedical subjects

R E Hall

Publications and source records attributed to R E Hall.

At least 91 records · Page 5Linked to original sources
PubMed1982

Monocyte cytotoxicity: evidence for multiple mechanisms of in vitro erythrocyte target killing. Trypan blue can both inhibit and enhance target lysis.

Four systems of human monocyte-mediated cytotoxicity against chicken erythrocyte targets were studied using a panel of cellular inhibitors. Monocyte synergistic cytotoxicity (MSC), spontaneous monocyte-mediated cytotoxicity (SMMC), antibody-dependent cellular cytotoxicity (ADCC), and mitogen-induced cellular cytotoxicity (MICC) each had a different pattern of inhibition with these agents. Monocyte synergistic cytotoxicity, a system in which monocytes and certain complement components cooperate in the lysis of target cells, was inhibited only by trypan blue, a known inhibitor of lysosomal enzymes and macrophage cytolysis of tumor cells. In marked contrast, spontaneous monocyte-mediated cytotoxicity, a system in which monocytes become spontaneously cytotoxic after a 5- to 10-day incubation in culture, was enhanced by trypan blue, whereas MICC and ADCC were not affected. Agents which deplete cellular hydrogen peroxide and superoxide were most inhibitory for SMMC and had no effect on ADCC, MICC, and MSC. Inhibitors of protein synthesis only blocked MICC, having no effect on the other systems. These data support the hypothesis that monocytes possess multiple mechanisms by which they may inflict damage on erythroid targets, which may depend on oxidative intermediates (SMMC), protein synthesis (MICC), microfilament function (SMMC, MICC, ADCC), in addition to other mechanisms which have not yet been clearly defined (MSC). Trypan blue can thus both inhibit and enhance different forms of monocyte-mediated cytotoxicity. Further studies with this agent revealed that preincubation of cells with trypan blue depleted the ability of the cells to kill by SMMC but not by ADCC or MICC. Such studies suggest that trypan blue, like certain other compounds, has more than one mechanism of action on cellular processes important for the mediation of cytotoxicity.

Animals↗
PubMed1979

A modification of the dialytrode for simultaneous CNS recording and chemical stimulation.

Currently, chemical stimulation of the brain is done either with a single cannula that is inserted at the time the drug is delivered or with two cannulae that permit perfusion of the area of interest. The dialytrode is a push-pull cannula consisting of two concentric tubes, a porous membrane covering the tip of the tubing and a platinum wire loop that extends around the membrane and is used for EEG recordings. Studies with the dialytrode indicate that while the membrane is relatively impermeable to bacteria, molecules the size of neurotransmitters pass easily through the membrane. Therefore, the dailytrode is well suited for chronic chemical stimulation studies.

Amygdala↗
PubMed1979

Vascular responses in canine subcutaneous adipose tissue to hypothalamic stimulation.

The present studies investigated vascular responses to electrical stimulation of the posterior hypothalamus in isolated but perfused and innervated subcutaneous adipose tissue in adult dogs. Three groups of dogs were distinguished: in one, electrical stimulation elicited vasodilation; in another, vasoconstriction, and in a third, neither significant vasodilation nor vasoconstriction occurred. Histological examination revealed that electrode placements were in the medial posterior hypothalamus, the lateral posterior hypothalamus, and the medial septal region, respectively. Hypothalamic stimulation failed to alter concentrations of free fatty acids or glycerol in venous blood from subcutaneous fat. Local beta-adrenergic block (propranolol) reversed the vasodilation to vasoconstriction while local alpha-adrenergic block (dihydroergotamine) abolished the vaso constrictor response. These results suggest that selective stimulation of the posterior hypothalamus results in neurogenic activation of both alpha- and beta-adrenergic mechanisms in adipose tissue vasculature. beta-Adrenergic vasodilation appears to predominate if the electrode is located medially, and alpha-adrenergic vasoconstriction appears to predominate if the electrode is located in the lateral posterior hypothalamus.

Adipose Tissue↗
PubMed1979

Abolition of hypoxic vagal bradycardia by lateral mesencephalic lesions in spinal cats.

To examine central sites that integrate the vagal bradycardia induced by hypoxia, heart rates were recorded continuously in spinal, precollicular, decerebrated cats during transient hypoxia induced by ventilation with 100% nitrogen. Bilateral lesions in the lateral mesencephalic reticular formation either decreased the extent of bradycardia or caused a reversal to tachycardia; anesthesia induced the same change. In contrast, bilateral lesions in the medial mesencephalic reticular formation failed to alter the bradycardia. Hence, the lateral mesencephalic reticular formation is essential for the appearance of hypoxia-induced vagal bradycardia.

Anesthesia↗
PubMed1977

Biosynthesis of pro-C3, a precursor of the third component of complement.

A precusor of the third component of complement, pro-C3, was detected in studies of cell-free synthesis and intracellularly in homogenates of liver tissue cultures. The molecular weight of pro-C3 was indistinguishable from that of intact native C3 secreted in vitro by liver or peritoneal macrophages, but its structure was different. Pro-C3 is a single polypeptide chain, whereas C3 secreted by cells in culture consists of two polypeptide chains (mol wt 120,000 and 76,000) linked by disulfide bonds.

Animals↗
PubMed1977

Cell-free synthesis of the fourth component of guinea pig complement (C4): identification of a precursor of serum C4 (pro-C4).

Polysomes (S-20) from homogenates of guinea pig liver synthesized serum albumin and a precursor of the fourth component of guinea pig complement (C4) in vitro. The C4 precursor (pro-C4) accounted for approximately 0.2% and albumin 4% of the radiolabeled protein precipitable by trichloroacetic acid and not bound to polysomes. Pro-C4 is a single polypeptide chain (molecular weight 200,000) which is then converted to C4, a three-chain (molecular weights 95,000, 78,000 and 31,000) structure linked by interchain disulfide bridges. Pro-C4 was also detected intracellularly in short-term tissue cultures of guinea pig liver. C4 was found in the medium harvested from these cultures.

Animals↗
PubMed1977

Orbital cortical influences on cardiovascular dynamics and myocardial structure in conscious monkeys.

The posterior orbital cortex of the frontal lobes in conscious monkeys was stimulated electrically to study the influence of this structure on cardiovascular hemodynamics and cardiac morphology. Stimulating electrodes, cardiac output flow probes, and arterial blood pressure transducers were chronically implanted by aseptic procedures into eight Macaca fascicularis monkeys. Cardiovascular changes induced by stimulating the orbital cortex included both biphasic and unidirectional alterations in cardiac output, blood pressure, heart rate, stroke volume, and total systemic resistance. Electrode position and the rate (Hz) of applied stimulation were the primary determinants of the direction and magnitude of the response. All animals stimulated demonstrated acute, discrete interventricular septal myocytolysis, characteristic of early ischemic lesions. Since the orbital cortex is a part of the limbic system, changes induced by its stimulation suggest a pathophysiological mechanism whereby emotional expression may effect dynamic shifts in cardiovascular functions and may thus induce permanent and manifest myocardial lesions.

Animals↗
PubMed1975

Hospital committee proceedings and reports: their legal status.

This Article examines the legal status of hospital committee proceedings and reports, focusing on how they may be used in a medicolegal context. Specific topics dealt with include the hospital medical staff in legal perspective, the concept of institutional responsibility, liability considerations arising from committee work, and the discovery and admissiblity of committee records in litigation cases. The author concludes that the danger of committee members facing liability for their activities is slight and that the fear that these reports and proceedings may be subject to discovery or be admissible into evidence in subsequent litigation is remote because candid and conscientious evaluations of clinical practices within every institution are essential and, therefore, public policy must encourage such evaluations by maintaining the confidentiality of committee activities.

Jurisprudence↗