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Biomedical subjects

A Mason

Publications and source records attributed to A Mason.

At least 91 records · Page 5Linked to original sources
PubMed1988

The in vitro slice preparation for combined morphological and electrophysiological studies of rat visual cortex.

The morphological condition of slices of rat visual cortex, maintained in vitro in an interface-type recording chamber, was assessed. In addition, neurones in these slices were impaled with glass micropipettes for intracellular recording and horseradish peroxidase (HRP) injection. After fixation and embedding, slices were examined by light and electron microscopy. Slices sectioned orthogonally to the original plane of cutting showed a vertical zonation of tissue preservation. The upper zone contained dense and flattened neuronal somata, although the neuropil appeared normal. The central zone was well preserved, with the appearance of most somata, dendrites, axons and synapses comparing favourably with perfusion-fixed material. The lower zone contained many abnormal, vacuolated somata. The morphology of HRP-injected neurones was assessed by light microscopy. Dendrites could be visualised in great detail and spines were clearly visible. Local axon arbors were well represented. There was good correlation between electrophysiological and morphological criteria for the assessment of the condition of the slice. We conclude that, provided the extent of degeneration within the slice is monitored and appreciated, slices of visual cortex can provide both electrophysiological and morphological data of high quality.

Animals↗
PubMed1988

Electrocardiographic monitoring of cardiac transplants in mice.

In the murine cardiac model for vascularised transplantation graft function may be monitored by direct palpation, electrocardiography, and graft histology. To assess the merits of these methods, and to measure ischaemic damage, isografts and allografts were examined at regular intervals from 0 to 60 days after grafting. Heart transplants were vascularised from the abdominal great vessels, using microsurgical techniques, with ischaemic times of less than 60 min. Isografts showed no decrease in heart rate over 60 days, as measured by palpation and electrocardiography, but the voltage of the ventricular complex fell progressively over the first 28 days after grafting then remained stable for more than 60 days. The voltage drop was associated with atrophy of myocardial tissue. Allografts in recipients treated with rabbit antimouse antilymphocyte serum were maintained for more than 60 days with little change in palpation rate or recorded heart rate but with significant falls in ventricular complex voltage, reflecting myocardial atrophy and fibrosis. Untreated allografts were rejected in 10-14 days and showed a rapid fall in palpated heart rate, measured heart rate, and ventricular complex voltage. Thus, in this study, palpation of the heart graft gave an accurate measure of the pulse rate and correlated with electrical activity in acutely rejecting grafts, but in long surviving grafts measurement of ventricular complex voltage showed myocardial damage that was not detectable by direct palpation.

Animals↗
PubMed1988

The replacement effect and comparisons of per capita income across countries: a short note.

This article is intended to clarify two aspects of Leibenstein's replacement effect that have not been adequately addressed in print. First, formal analysis of the replacement effect demonstrates that it is not determined by the quality of entering and departing workers alone but, rather, by the entire age schedule of labor quality. Second, a simple model is used to demonstrate the absence of welfare implications associated with the replacement effect and to quantify the magnitude of the replacement effect.

Humans↗
PubMed1987

Occult (non-surface expression) of T, B and monocyte markers in human large granular lymphocytes.

Human large granular lymphocytes were examined for non-surface expression with a panel of monoclonal antibodies to T cell, B-cell and monocyte markers. T101, antibody to the T65 antigen, showed binding to crude fractions containing intracellular membranes but not to immobilized whole cells. Non-surface expression of T65 was also demonstrated by flow cytometry using lysolecithin to transiently permeabilize cells. With the latter technique nonsurface expression was also demonstrated with monoclonal antibodies B2 and MO-2. T65 was shown to be synthesized by large granular lymphocytes by metabolic labeling, indirect immunoprecipitation and SDS-PAGE. T65 from large granular lymphocytes was the same mol. wt as antigen for T cells derived from the same donor. These results indicate that human large granular lymphocytes synthesize, but do not express on the surface, certain monoclonal antibody-derived markers heretofore considered specific for other cell lineages.

Antibodies, Monoclonal↗
PubMed1987

Power and affiliation motivation, stress, and abuse in intimate relationships.

The associations among n Power, n Affiliation, inhibition, stressful life events, and infliction and receipt of psychological and physical abuse in intimate relationships were investigated in a sample of 48 male and 107 female college undergraduates. Results indicated that life events that were perceived as being negative were associated with both the infliction and the receipt of abuse for women but not for men. Individual personality characteristics determined the tactics used in resolving intimate interpersonal conflicts. High n Power was significantly associated with the infliction of physical abuse on their partners by men, but not by women. For women, n Affiliation and activity inhibition moderated the effect that stress has on the infliction of abuse. Highly stressed women with high n Affiliation and low activity inhibition were the most likely to inflict abuse. Length and status of relationship were also found to be related to abuse, with abuse occurring most often between more committed couples. Sex differences were found for the relation between infliction and receipt of abuse. That is, receipt of abuse was highly correlated with infliction of abuse for women but not for men, suggesting that when women strike out they are struck in return.

Adolescent↗
PubMed1987

Tinkering with successful synapse regeneration in the leech: adding insult to injury.

In the leech, synapse regeneration in adults and synapse formation during embryonic development can be studied in single, identifiable cells that make precise connections with their targets. Certain cellular components, such as synaptic targets and glia, were selectively destroyed to study how the regenerating axons locate their targets, what triggers axons to start growing and what stops them. The results showed that glia and targets play only a limited role in synapse regeneration and in axon degeneration. For example, contact with the synaptic target may inhibit sprouting and availability of targets may promote it. Comparative studies on axon growth and synapse formation by interneurones in embryos showed that regeneration does not simply recapitulate embryonic development. There are clearly separate constraints on the two processes. Axon survival is a different problem. Although isolated axon segments can survive for up to a year in the leech, temperature is a major factor in survival. Axon segments in a tropical leech that regenerates synapses well at 31 degrees C degenerated within 2-3 weeks at this elevated temperature, even when regeneration was prevented. In similar leeches at room temperature (22 degrees C), segments survived for months. Overall, results in the leech support the idea that degeneration as well as regeneration share fundamental mechanisms with other invertebrates and the vertebrates, including mammals. Perhaps long-lived axon segments and other features of the leech that speed or encourage functional regeneration can now be made to operate in repair of the mammalian nervous system.

Animals↗
PubMed1987

Making medical records professional(s).

In 1986 a joint medical records project group was set up by the Institute of Health Services Management, the Association of Health Care Information and Medical Records Officers and the NHS Training Authority, with Mr Vic Peel as chairman. The group was supported by Arthur Andersen & Co, management consultants. The following is a shortened and edited version of an interim report drafted for the group by Dr Alastair Mason. It is intended for discussion and does not yet represent the definitive views of the sponsoring bodies.

Computers↗
PubMed1987

The effect of operative ischemia in murine cardiac transplantation: isograft control studies.

Isograft studies were performed in the murine model of cardiac transplantation to investigate the morphologic effects of operative ischemia. Primarily vascularized CBA mouse hearts were grafted heterotopically into the recipient CBA mouse's abdomen with standard microsurgical techniques. After ischemia times of 30 and 60 minutes, histologic examination showed minimal myocardial damage, with necrosis or scarring occupying less than 5% of the cross-sectional area of hearts bisected from apex to base after grafts had been removed on the seventh day after transplantation. Maximal ischemic damage was seen at 7 days after transplantation after 120 minutes of ischemia, with more than 30% myocardial necrosis or scarring of myocardial tissue. Isografts performed with ischemia times of less than 60 minutes were followed for more than 100 days. All hearts showed a fine, generalized, perimyocytic fibrosis, which was maximal at 28 days after transplantation and did not progress thereafter. These results will serve as important control measures for future studies in this model because ischemic damage must be considered in examining histologic samples from long-surviving cardiac allografts maintained in immunosuppressed recipients.

Animals↗
PubMed1986

Lymphokine-activated killer cells. Analysis of progenitors and effectors.

IL-2 has been examined for its ability to regulate lymphokine-activated killer (LAK) activity. IL-2 is a potent activator of cytolytic activity against a wide array of tumor cells, including those from fresh autologous and allogeneic tumors. Using subpopulations of lymphoid cells that were separated on Percoll density gradients, and subsequently purified by immunoadsorbance, studies were performed to examine the phenotypes of progenitor and effector cells of human LAK cells and to compare them with the phenotype of activated NK cells. From these studies, it was evident that several lymphoid subsets, including CD3+, CDw16- and CD3-, CDw16+ cells could mediate LAK lysis of fresh tumor cells. Our examination of the kinetics of activation revealed that CDw16+, NKH1+ (NK-active) cells were maximally activated by 1-2 d. In contrast, CD3+ cells appeared not to achieve maximal cytolytic activity against fresh and cultured tumor cells until days 2-3. Using limiting-dilution frequency analysis, we showed that a large percentage of cytolytically active progenitors was present among the CDw16+, NKH1+ cells. The progenitor and effector cell frequencies appear to be 10-50 times higher in these populations compared to CD3+ cells. In addition, the selective blockage by mAb to the CD3 determinant of the T cell receptor complex indicated that these two effector cell phenotypes relied on different receptors to mediate their cytotoxic activity against tumor cells. Therefore, the accumulated data suggest that there is not a single unique progenitor of LAK activity, but rather that multiple subsets of lymphocytes become cytotoxic in response to IL-2. However, the NK cell population forms the largest single component of LAK cell activity in human peripheral blood.

Antigens, Differentiation, T-Lymphocyte↗