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Biomedical subjects

C Abraham

Publications and source records attributed to C Abraham.

13 recordsLinked to original sources
PubMed1992

Health beliefs and promotion of HIV-preventive intentions among teenagers: a Scottish perspective.

Beliefs concerning the spread of the human immunodeficiency virus (HIV) and preventive behaviors were examined in a sample of 351 sexually active Scottish teenagers. A postal questionnaire, including measures of variables specified by the health belief model (HBM) and preventive intentions, was employed. The relation between HBM measures and reported endorsement of HIV-preventive intentions was investigated. Results indicated that, in general, respondents intended to use condoms with new sexual partners. The majority also intended to carry condoms if they thought they might have sex with a new partner and to ask potential partners about their previous sexual history. Multiple-regression analyses showed that measures of health beliefs, gender, age, sexual experience, and previous condom use accounted for 17.8% to 24.3% of the variance in reported preventive intentions. Perceived barriers to preventive behaviors were found to be important predictors. However, the overall pattern of results raised questions concerning the adequacy of the HBM as a model of the determinants of HIV-preventive intentions, and the need for an extended model is discussed. Separate analyses were conducted for men and women and for 16- and 18-year-olds, and the implications for modeling intention formation in these subgroups are considered. The relevance of these findings to HIV-preventive campaigns is also discussed.

Adolescent↗
PubMed1992

Context and content: the impact of school-leaving and school-based health education on AIDS-relevant cognitions.

A survey examined health beliefs and intentions among 690 16-18 year-olds in Dundee. Respondents in the younger cohort (n = 363) were classified according to their educational situation (at school vs left) and self-reports of having received AIDS/HIV-relevant health education. Both remaining in school and receiving AIDS/HIV-relevant health education had independent beneficial effects, but the effects of leaving school also interacted with sex of respondent and with amount of relevant education received prior to leaving. Males' and females' reliance on mass media and other information sources diverged once they left school, indicating that males who leave school early are most likely to disregard useful or important information regarding AIDS. Consistent with this finding, leaving school reduced the difference between males' and females' intention to use condoms with a new partner. The beneficial impact of having previously received AIDS/HIV-relevant education on beliefs concerning the controllability of the epidemic and on feeling worried about everyday contact with a person with HIV/AIDS, was most marked among those who had left school. The results are discussed in terms of their implications for health education strategies.

Adolescent↗
PubMed1990

Ca2+ channel inhibition by a new dihydropyridine derivative, S11568, and its enantiomers S12967 and S12968.

Biochemical and electrophysiological techniques were used to describe the Ca2+ channel blocking properties of a new dihydropyridine derivative, S11568 (+/-)- ([(amino-2-ethoxy)-2-ethoxy]methyl)-2-(dichloro-2',3'-phenyl)-4- ethoxy-carbonyl-3-methoxycarbonyl-5-methyl-6-dihydro-1,4-pyridine and its enantiomers S12967 ((+)-S11568) and S12968 ((-)-S11568). In binding studies, S11568 and S12968 displaced specifically bound [3H]PN 200-110 from cardiac and vascular smooth muscle preparations with potencies of 5.6-51 nM, respectively. S12967 was 6- to 18-fold less potent than S12968. A good correlation was found between the IC50 value for the inhibition of 45Ca2+ uptake by A7r5 aortic smooth muscle cells and binding data. Whole-cell patch clamp studies in both guinea-pig ventricular myocytes and A7r5 cells yielded similar results. At holding potential (VH) -50 mV, S12968 inhibited L-type Ca2+ current with an IC50 value near 70 nM, 2- to 3-fold more potently than S11568 and 30-fold more potently than S12967. With VH -100 mV, all three compounds were less potent, with IC50 values ranging from 500 nM to 3 microM. These results demonstrate conclusively that S12968 is the more active enantiomer. Furthermore, the pronounced voltage dependence of its actions in vitro suggests that in vivo it could exhibit good selectivity for vascular smooth muscle over cardiac muscle.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1988

Surgical alternatives in the treatment of life-threatening ventricular arrhythmias.

We present our experience in the treatment of life-threatening ventricular tachycardia using electrophysiologically guided surgery (97 patients), automatic implantable cardioverter defibrillator (AICD) (42 patients), and orthotopic heart transplantation (15 patients). Eighty-three percent of these patients had ischemic and 17%, nonischemic heart disease. Our results of electrophysiologically directed surgery show an early mortality of 10% and a recurrence of 5% in the ischemic group. In the nonischemic group, the recurrence was 45%. The AICD was implanted in 31 patients with ischemic heart disease, in 5 with ventricular dysplasia, and in 6 with dilative cardiomyopathy, the ejection fractions ranging from 12% to 65%, with a mean of 30%. Early and late mortalities were 5% and 19%, respectively. The AICD was effective in all patients. Survival rate at 1 year was 83% +/- 6.4%. Thirteen of 15 patients have survived heart transplantation for 3-20 months (mean: 11 months). Ejection fractions prior to transplantation ranged from less than 10% to 34% (mean: 16%). We conclude that electrophysiologically guided surgery is highly effective in most cases of ischemia-related ventricular tachycardia. The AICD is considered a palliative alternative in patients with either poor ventricular function, no electrophysiological substrate, or multimorphological tachycardia. Heart transplantation has to be considered especially in young patients in whom progression of the underlying disease can be anticipated. Bridging by AICD is possible when transplantation is not immediately available or recommendable.

Adolescent↗
PubMed1986

X-ray diffraction from intraneuronal paired helical filaments and extraneuronal amyloid fibers in Alzheimer disease indicates cross-beta conformation.

Information about the structure of the paired helical filaments (PHF) that accumulate within human neurons and the amyloid fibers that accumulate in the extracellular spaces between neurons in Alzheimer disease has so far depended on electron microscopy of thin-sectioned or negatively stained material. To determine the protein conformation of these abnormal fibers, we have obtained x-ray diffraction patterns from unfixed human brain fractions highly enriched in PHF and from purified amyloid cores isolated from senile plaques. The predominant x-ray scatter evident from both types of samples, either wet or dry, is a sharp reflection at 4.76-A spacing and a diffuse one at about 10.6-A spacing. These features are characteristic of a beta-pleated sheet type of protein conformation. In doubly oriented dried pellets of PHF fractions, the two reflections are accentuated at right angles to each other and the arc at 4.76-A spacing is in the fiber direction indicating a cross-beta conformation. From the integral widths of the reflections we estimate the cross-beta crystallite to be about 80 A long in the fiber direction and about 40 A thick. These dimensions correspond to approximately four pleated sheets, each of which consists of approximately 16 hydrogen-bonded polypeptide chains running normal to the fiber direction. The cross-beta conformation of PHF and amyloid fibers that we have found from x-ray diffraction is in contrast to the predominant alpha-helical coiled-coil conformation of the neurofilaments with which they share epitopes and from which they have been postulated to derive.

Alzheimer Disease↗
PubMed1986

Intravenous treatment of autoimmune hemolytic anemia with very high dose gammaglobulin.

Autoimmune hemolytic anemia (AIHA) has been considered to be unresponsive to intravenous gammaglobulin (IVGG) at the doses that are effective in immune thrombocytopenic purpura and autoimmune neutropenia (usually 2 g/kg total dose). This study reports the use of a higher dose (5 g/kg total dose over 5 days) in four severe cases of AIHA which resulted in a sustained remission in two patients, a transient response in the third, and a failure in the forth patient. These data suggest that larger quantities of IVGG may be needed in this disease, possibly because the reticuloendothelial system appears to be enlarged in AIHA patients.

Adult↗
PubMed1979

T-cell division and aging.

The age-dependent drop in mixed lymphocyte reactivity and responsiveness to concanavalin A of lymph node and spleen cells of C57Bl/6J female mice were studied. The relative decrease in mixed lymphocyte reactivity was shown to be the same whether mounted against H-2 or Mls incompatibile stimulator cells. The time of peak response in vitro as well as the sensitivity to stimulator cell concentration are not altered with age. Cell cycle studies demonstrate that those cells which respond in vitro to alloantigens or to concanavalin A do so with a cell cycle which does not change with the age of the lymphocyte donor. In addition, regardless of the age of the donor, those cells which divide in vitro demonstrate identical capacities to redivide. These experiments suggest that the decline in observed T-cell proliferation in mixed lymphocyte and mitogen reactivity of senescent mice is not to a decreased cell generation time or to a reduced capacity to divide and redivide but rather to a smaller population of reactive cells.

Aging↗
PubMed1977

Reduced in vitro response to concanavalin A and lipopolysaccharide in senescent mice: a function of reduced number of responding cells.

The proliferative capacity of spleen cells from C57BL/6J female mice of various ages (3-28 months) to the polyclonal mitogens concanavalin A (Con A) and lipopolysaccharide (LPS) was examined. It was found that both the T and B cell population of the spleen demonstrate an age-related decrease in their capacity to respond in vitro. Peak responses to both mitogens occurs at about 1 year of age. This age-related reduction in response is expressed in the degree of incorporation of [3H]thymidine into DNA, the total number of cells generated in vitro, the number of labeled cells per culture and the number of blast cells per culture. The day of peak response in vitro does not change with age. Studies of the cell cycle of cells responding to Con A and to LPS from 12 and 28-month-old mice demonstrate that the generation time of individual proliferating cells does not alter with age. Nor does it differ for the B cells responding to LPS or the T cells responding to Con A. These studies also demonstrate that the proliferating cells from senescent mice are equally capable of repeated cell divisions as are the cells from the 1-year-old adult mouse. It is concluded that the defect in senescent mice which leads to a reduced in vitro response to the polyclonal mitogens LPS and Con A is a reduction in the number of responding cells and not an alteration in the capacity of those cells which do respond to divide.

Aging↗