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A Nichols

Publications and source records attributed to A Nichols.

66 records · Page 4Linked to original sources
PubMed1990

Tissue-specific trans-activation of the rabbit beta-globin promoter in Xenopus oocytes.

Identification of transcription factors regulating tissue-specific gene expression implies functional tests in transcription systems. In spite of its practical advantages, the Xenopus oocyte has only rarely been used for trans-activation studies, because some critical parameters inherent to the system may cause artefacts. Depending on the amount of DNA injected, even tissue-specific genes may be spontaneously transcribed. To develop a reliable trans-activation assay, we used the erythroid-specific rabbit beta-globin gene and, for comparison, the constitutively transcribed viral thymidine kinase gene. The viral gene is active over a wide range of injected DNA (0.2-10 ng), and addition of nuclear proteins from various cell types does not stimulate but often inhibits this activity. When large amounts of DNA are injected (greater than 10 ng), transcription is inhibited by self competition. Addition of nuclear proteins now re-establishes activity probably through increasing the pool of general transcription factors. By contrast, spontaneous activity of the beta-globin promoter occurs only within a narrow range of injected DNA (0.2-1 ng). At higher DNA concentrations (greater than 5 ng) spontaneous transcription becomes negligible. The addition of nuclear proteins from nonerythroid cells extracts has no or only a weak stimulatory effect on the beta-globin promoter. Only nuclear proteins isolated from erythroid tissues, bone marrow and spleen, bring about a strong transcriptional activation. Co-injection with either the polyoma virus, or the oviduct-specific chicken lysozyme gene shows that the beta-globin promoter is selectively activated by factors present in erythroid cell extracts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Echocardiographic and Doppler evaluation of left ventricular hypertrophy and diastolic function in black and white hypertensive patients.

Echocardiography including Doppler examination has been used to assess left ventricular hypertrophy and diastolic function in 24 patients: 12 black Negro patients and 12 white patients who were matched with respect to age, heart rate and systolic and diastolic blood pressure. Significant left ventricular hypertrophy was present with normal systolic function but impaired diastolic function with a decrease in peak E velocity, an increase in peak A velocity and reversal of the E/A ratio. In the combined groups LV mass and LVPW correlated with systolic blood pressure (P less than 0.05). In the blacks systolic and diastolic blood pressure correlated with LV mass and LVPW thickness (P less than 0.05). Septal thickness correlated only with systolic blood pressure (P less than 0.01). In contrast the indices of diastolic function did not correlate with blood pressure or with left ventricular hypertrophy. No morphological differences in the left ventricle have been shown between the two groups but both had significant left ventricular hypertrophy. Whilst diastolic function is abnormal, this appeared to be independent of either blood pressure or degree of left ventricular hypertrophy. A neurohumeral mechanism has not been discounted.

Adult↗
PubMed1984

Family history as an independent risk factor for coronary artery disease.

The risk of family history of ischemic heart disease independent of other well described risk factors has remained difficult to quantitate. Significant coronary artery disease was determined by coronary arteriography to be present in 223 patients and absent in 57 control subjects. Age, sex, blood pressure, serum cholesterol, cigarette smoking and the presence of diabetes and left ventricular hypertrophy on the electrocardiogram were tabulated for each patient and the data used to assign a risk score based on the American Heart Association multivariate model. Subjects were stratified and matched according to risk score to estimate risk of family history independent of familial aggregation of these seven other risk factors. Angina, myocardial infarction, cardiac death and any ischemic heart disease were ascertained in 1,319 first degree relatives. Odds ratios for overall, stratified and matched comparisons of these end points in relatives of patients and control subjects ranged between 2.0 and 3.9 (p less than 0.01 for all comparisons), indicating a higher frequency of all ischemic heart disease end points in relatives of patients with documented coronary artery disease. Life table comparison of patients at lowest risk with those at higher risk showed significantly greater cumulative frequency and earlier age of onset of all ischemic heart disease end points in relatives of low risk patients. These observations indicate that some of the risk associated with family history is independent of familial aggregation of other known risk factors and suggest that the independent effects of family history may be most important in individuals who otherwise are at low risk.

Adult↗
PubMed1975

Parallel radioimmunoassay for plasma cortisol and 11-deoxycortisol.

We describe a direct, rapid, and specific procedure for the parallel radioimmunoassay for cortisol and 11-deoxycortisol in plasma. The plasma sample is used directly, after heat inactivation of the natural cortisol-binding protein. The radioimmunoassay utilizes antibodies generated in rabbits by steroids congugated at their 3-oxo position to thyroglobulin. Ammonium sulfate is used to separate bound and free steroids. Our cortisol antibody and an 11-deoxycortisol antibody obtained elsewhere cross reacted negligibly with each other or with other steroids that might be present in plasma. Radioimmunoassays were therefore developed for both steroids in only 1.25 mul of plasma. The intra- and inter-assay coefficients of variation for both steroids were less than 10%, with a sensitivyt of 4 mug/liter. Steroid values obtained by a competitive protein binding method were consistently higher than those of the present method, suggesting that the former is measuring total corticosteroids. This simple approach requires only 4 h for the specific measurement of both cortisol and 11-deoxycortisol in 20 samples of plasma.

17-Hydroxycorticosteroids↗
PubMedDate not supplied

In someone else's shoes.

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Administrative Personnel↗
PubMedDate not supplied

AIDS in perspective.

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Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Utilization of health services along the Arizona-Sonora border: the providers' perspective.

Under the proposed North American Free Trade Agreement between Mexico, Canada, and the United States, issues of health policy and health care delivery will have to be addressed. People at the U.S.-Mexico border have been using health care providers on either side of the border for many years. Studying how the movement of patients has been taking place, and how it has affected health care providers' practices, is the first step towards the understanding and organization of health care services for the border region. This paper reports on the results of a health care provider survey conducted between 1987 and 1989 in Arizona and Sonora border towns. The paper includes information on the characteristics of border health care providers (98 residing on the U.S. side of the border and 249 on the Mexican side) and the demographics and diagnosis of patients who engage in border crossing behavior. The opinions of health care providers about why patients from the neighboring country come to their offices; the existing communication system between providers in both nations; and some of the problems that result from attending patients residing in the neighboring nation are also reported. Results from the survey demonstrate that although the border constitutes a region in itself, health services at the border are not structured to recognize this regional orientation. Improved communication between health care providers on both sides of the border, the establishment of health care protocols with quality assurance programs, and suitable health care financing mechanisms are some of the issues that require immediate attention if the health care delivery system at the border is to function more efficiently and to the satisfaction of health care providers and consumers.

Adolescent↗