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Biomedical subjects

M Kahan

Publications and source records attributed to M Kahan.

At least 37 records · Page 2Linked to original sources
PubMed1989

T-cell clone anti-clone interactions. Effects on suppressor and helper activities.

An experimental model of two interacting clones of T cells is described, which may be used for defining and exploring the T-cell immunoregulatory network. Mx9/9 is a CD4 clone bearing an antigen receptor recognized by the Mx9 anti-V beta 8 monoclonal antibody (MoAb). Anti-V beta 8 MoAbs activate and induce cell proliferation of this clone. Autologous clones were raised against Mx9/9 cells using the peripheral blood mononuclear (PBM) cells of the Mx9/9 clone donor (PBMjm). Some of these cloned anti-clone cells proliferated after stimulation with irradiated Mx9/9 cells, but not after stimulation with other autologous cloned T cells or heterologous PBM, suggesting that these clones recognize the T cell receptor (TCR) of the Mx9/9 cells. The proliferation of the Mx9/9 stimulated cloned anticlone cells was blocked by anti-class II MoAbs, indicating that the autoreactive clones recognize their target antigen in conjunction with HLA Class II products. The ability of clone Mx9/9 to proliferate after stimulation with anti-V beta 8 MoAb was inhibited when clone 121 cells were added to the cultures. However, clone 121 lost its suppressor function after 4 months in culture and instead gained the ability to enhance the proliferation of Mx9/9 cells in the presence of anti-V beta 8 MoAb. In contrast, clone 18 lacked suppressor activity at the early stage of the study but later acquired this function. We conclude that some autoreactive clones are not fully committed and may express more than a single function. Such cells cannot therefore be designated as 'suppressor cells', although they expressed suppressor potential at certain stages.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1988

The majority of the activated T cells in the blood of insulin-dependent diabetes mellitus (IDDM) patients are CD4+.

Twenty-five recently diagnosed insulin-dependent diabetic patients were screened for the presence of activated T lymphocytes using the anti-IL-2 receptor monoclonal antibody; thirteen had elevated levels of activated T lymphocytes. The activated cells were mostly confined to the CD4 subset, with the CD4/CD8 ratio in IL-2 receptor expressing cells averaging 5 +/- 1 (s.d.) compared with 1.3 +/- 0.3 for all T cells. In recent onset insulin-dependent diabetes blood there was no lack of CD4 CD45R+ (suppressor/inducer) T cells. The activated IL-2 receptor, expressing cells belonged to both CD4 subsets, 'helper inducer' (CD44B4) and 'suppressor inducer', (CD42H4).

Adolescent↗
PubMed1987

The health of children of low-income families.

Childhood poverty is common in Canada: 1,114,000 children under 16 years of age live below the poverty line. The incidence is highest among children of single mothers, unemployed parents, Canadian native peoples and recent immigrants, particularly refugees. Compared with the national average, the infant mortality rate is twice as high, deaths from infectious diseases are 2.5 times more common and accidental deaths are twice as common among children of low-income families. Other problems associated with poverty are iron deficiency anemia, dental caries, chronic ear infections, mental retardation, learning disabilities, poor school performance and increased suicide rates. Health care professionals can help address the poor physical and mental health associated with poverty in children by promoting a broad range of public policies.

Adolescent↗
PubMed1985

Use of medical care by children during a physicians' strike.

From March through June 1983 the almost 8,000 physicians in the public sector in Israel were on strike. While emergency hospital care was assured, primary care options were severely limited, and the Alternative Medical Service set up by the Israel Medical Association involved a significant payment at the time of visit. This constituted a radical change from the no-charge physician care regularly provided to the insured population in the community clinics. A study was conducted in the third month of the strike to assess the utilization of care for children. The results of interviews with 253 families registered in eight Sick Fund clinics showed that the majority of parents who reported a child's illness did not defer seeking care. The first sources of care were the nurses in the community clinic and the hospital emergency room, while care from physicians working privately was used to the same extent as the Alternative Medical Centers. These results indicate that the relatively high utilization patterns of this population were not significantly changed. Differences in the first source of care by clinic suggest that socioeconomic factors and the availability of the various options are related to use in each area. These factors, as well as the threshold for seeking care and the influence of selection, should be examined in more detail to develop appropriate utilization patterns and a more rational use of resources.

Adolescent↗
PubMed1985

Ambulatory care of the aged in Kupat Holim clinics.

The use of ambulatory services by the elderly was studied, using data recorded on a daily diary in primary care practices. The number and content of visits to primary care practices in Kupat Holim (Health Insurance Institute of the General Federation of Labor) community clinics in the Sharon and Tel Aviv regions is presented. The rates of use by the total adult population and by those greater than or equal to 65 years old treated by the same physicians are compared for the two regions. As expected, the elderly have the higher visit rates, with 8.4 annual visits as compared with 5.1 for the total adult population in the Sharon region clinics. For Tel Aviv practices, there were 11.7 and 6.8 visits, respectively. The proportion of visits by the elderly in the daily load is around 60% greater than is their proportion in the patient populations. These data do not permit any qualitative analysis, but have implications for the planning, staffing and management of ambulatory care for the elderly.

Adult↗
PubMed1983

[Secondary neoplastic subacute constrictive pericarditis disclosing a bronchial cancer].

In a fifty-three-year-old man, constrictive metastatic carcinoma of the pericardium revealed a bronchial carcinoma. The subacute course was rapidly progressive. Only partial pericardiectomy could be performed. Death occurred 16 days after the peripheral signs of compression of the heart became patent. In such cases early diagnosis, before signs of constrictive pericarditis become obvious, is very important.

Adenocarcinoma↗
PubMed1977

Interactions of yeast tRNAPhe with ribosomes from yeast and Escherichia coli. A fluorescence spectroscopic study.

The interaction of ethidium-labeled tRNAPhe from yeast with ribosomes from yeast and Escherichia coli was studied by stead-state measurements of fluorescence intensity and polarization. The ethidium label was covalently inserted into either the anticodon or the dihydrouridine loop of the tRNA. The codon-independent formation of a tRNA-ribosome complex led to only a moderate increase of the observed fluorescence polarization indicating a considerable internal mobility of the labeled parts of the tRNA molecule in the ribosome complex. When the ribosome complex was formed in the presence of poly(U), the probes both in the dihydrouridine loop and in the anticodon loop were strongly immobilized, the latter exhibiting a substantial increase in fluorescence intensity. A smaller intensity change was observed when E. coli ribosomes were used, although the extent of immobilization was found to be similar in this case. Competition experiments with non-labeled tRNAPhe showed that the labeled tRNAPheEtd was readily released from the complex with yeast ribosomes when poly(U) was absent, whereas in the presence of poly(U) it was bound practically irreversibly. The finding that the mobility of a probe in the dihydrouridine loop is affected by the codon-anticodon interaction on the ribosome suggests a conformational change of the ribosome-bound tRNA which may involve opening of the tertiary structure interactions between the dihydrouridine and the TpsiC loop.

Binding Sites↗
PubMed1977

Studies on the immune response to fixed antigens. II. Optimal conditions for inducing and eliciting helper function by fixed antigens and the mechanism responsible for this effect.

Heavily trinitrophenylated sheep red blood cells (RBC) (TNP128SRBC) and glutaraldehyde-treated SRBC (G-SRBC) induced helper function. This helper function could accelerate anti-SRBC and anti-TNP secondary responses to subsequent challenge with TNP0.14SRBC in different strains of mouse. Preferential induction of helper function over primary antibody response was obtained with fixed antigens only. High doses of fixed RBC (4 X 10(7) or 4 x 10(8)/mouse) could induce optimal helper function and high doses of the challenger TNP0.14SRBC (4 X 10(7) or 4 x 10(8)/mouse) could optimally recall this function and stimulate secondary responses. G-SRBC was a better inducer of helper function than low doses of nonmodified SRBC. TNP128SRBC-primed mice produced a significant anti-SRBC response after subsequent challenge with TNP0.14 mouse RBC. Reverse help was suggested as one of the possible mechanisms of this response. Early helper function which developed four days after priming with TNP128SRBC or G-SRBC could be transferred to irradiated recipients with T, but not B, cells. Late immunologic memory which appeared 18 days after priming with TNP128SRBC could be transferred to irradiated recipients only with a mixture of T and B cells.

Animals↗
PubMed1976

Countercurrent immunoelectrophoresis on cellulose acetate.

A technique for the detection and demonstration of antigens or antibodies by means of countercurrent immunoelectrophoresis on cellulose acetate (CAM) is described. The method is simple, sensitive and rapid. There is no need for preliminary preparation. The samples are contained in wells punched in the CAM. The equipment required is commonly available in routine laboratories, and the whole procedure can be performed and the results obtained within 90 min.

Acetates↗
PubMed1976

Studies on the immune response to fixed antigens. Preferential induction of helper function with heavily trinitrophenylated sheep erythrocytes, and glutaraldehyde-treated sheep erythrocytes.

Mice primed with heavily trinitrophenylated sheep red cells (TNP128SRC) or glutaraldehyde-treated sheep red cells (G-SRC) developed an early helper function mediated by thymus-derived cells. Such mice were able to produce high secondary responses to both hapten and carrier after challenge 2 days after priming, with lightly trinitrophenylated SRC (TNP0.14SRC). However, the primary response of the TNP128SRC or G-SRC-primed mice were very low to undetectable, and their secondary responses were also low when the challenge antigen was administered 4 days after priming or later. Inhibitory humoral factor(s) which were induced in the primed animals appeared responsible for the decreased capacity of primed mice to mount a secondary response when challenged later than 2 days after priming. Transfer of spleen cells from TNP128SRC-primed mice to sublethally irradiated recipients circumvents their exposure to inhibitory humoral factor(s) present in intact animals allowing them to react with challenge antigen. Enriched populations of T cells, but not B cells, were able to transfer this early immunologic memory to irradiated recipients. The theoretical and practical implications of these results are discussed.

Aldehydes↗