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Biomedical subjects

G Block

Publications and source records attributed to G Block.

At least 19 recordsLinked to original sources
PubMed1995

Cellular analysis of a molluscan retinal biological clock.

The eye of the opisthobranch mollusc Bulla gouldiana expresses a circadian rhythm in optic nerve impulse frequency. The circadian rhythm is generated among approximately 100 neurons at the base of the retina referred to as basal retinal neurons. These cells are electrically coupled to one another and fire spontaneous action potentials in synchrony. Basal retinal neurons recorded intracellularly exhibit a circadian rhythm in membrane potential that appears to be driven by a circadian modulation of membrane conductance. Membrane conductance is relatively high during the subjective night and decreases after subjective dawn. Recent experiments in our laboratory indicate that individual basal retinal neurons in culture can express circadian rhythms in membrane conductance. When completely isolated, these cells continue to show circadian conductance changes. These studies provide the first direct demonstration that individual neurons can act as circadian pacemakers. Although the precise details of the mechanism generating the circadian periodicity remain obscure, our research indicates that several transmembrane ionic fluxes are not involved in rhythm generation, but that a transmembrane Ca2+ flux is critical for entrainment. Both transcription and translation appear to play critical roles in generating the circadian cycle.

Animals↗
PubMed1995

Effects of treatment with lovastatin and pravastatin on daytime cognitive performance.

The HMG-CoA reductase inhibitors lovastatin and pravastatin have both proven to be effective and well tolerated in the treatment of hypercholesterolemia. To evaluate whether lovastatin or pravastatin might affect daytime cognitive function, a double-blind, placebo-controlled, two-period, incomplete block, crossover study was performed in 36 patients (24 per treatment) with primary hypercholesterolemia. Patients received placebo, lovastatin (40 mg), or pravastatin (40 mg) for 4 weeks. Following a 1-week washout period, patients were crossed over to either lovastatin, pravastatin, or placebo for an additional 4 weeks. Mental performance tests (digit symbol substitution, choice reaction time, auditory vigilance, selective reminding word recall, finger tapping), visual analogue rating scales, and the Profile of Mood States were administered before test drug administration and after 2 and 4 weeks of each treatment. After 4 weeks, no statistically significant differences between treatments in changes from baseline were observed on any parameter with the exception of digit symbol substitution, for which lovastatin and pravastatin were both significantly better than placebo but did not differ from each other. Low-density lipoprotein cholesterol was reduced 38% by lovastatin and 30% by pravastatin. In summary, neither of these chemically distinct HMG-CoA reductase inhibitors impaired daytime cognitive performance after 4 weeks of treatment in patients with primary hypercholesterolemia.

Adult↗
PubMed1995

[Intra-abdominal bleeding after myocardial infarction with cardiopulmonary resuscitation and thrombolytic therapy].

Adverse effects of resuscitation due to closed-chest cardiac massage are common, and the incidence is increased when an incorrect technique is used. Nevertheless, thrombolytic therapy of a myocardial infarction can become necessary even after cardiopulmonary resuscitation (CPR). In these patients, the risk of thrombolytic therapy-induced bleeding is immanent. CASE REPORTS. Within 9 months, two male patients aged 44 and 52 years were admitted to the intensive care unit after out-of-hospital CPR for myocardial infarction with cardiac arrest. In both cases, thrombolytic therapy was undertaken due to the cardiovascular situation or echocardiographic results. Thrombolytic therapy was successful with regard to the ECG changes, but a few hours later both patients demonstrated increasing cardiovascular instability. After abdominal sonography, intra-abdominal bleeding was suspected. Emergency laparotomy became unavoidable, although the coagulation profile was severely impaired in both patients (Tables 1 and 2). Anaesthetic management was characterised by introduction of central venous and intra-arterial catheters, replacement of volume and oxygen carriers using large-bore IV lines, restoration of coagulation factors with fresh frozen plasma, and the choice of "modified neuroleptanaesthesia" with blood pressure-adjusted, small doses of fentanyl, midazolam, and pancuronium. Intraoperatively, a liver injury due to closed-chest cardiac massage was found in both cases. The postoperative courses were complicated by respiratory problems, which led to prolonged mechanical ventilation, but both patients survived without remarkable neurological deficits. CONCLUSION. In patients with thrombolytic therapy after CPR and persisting cardio-vascular instability, a resuscitation injury with consequent haemorrhagic shock should be suspected. For diagnosis, chest X-ray films and abdominal and thoracic sonography are useful and practicable, even at the bedside. Anaesthetic management should focus on adequate monitoring, replacement of volume and oxygen carriers, fast restoration of plasma coagulation, and careful, blood pressure-adjusted maintenance of anaesthesia.

Abdomen↗
PubMed1995

Sources of energy and six nutrients in diets of low-income Hispanic-American women and their children: quantitative data from HHANES, 1982-1984.

OBJECTIVE: Identification of important food sources of energy, protein, fat, vitamin A, vitamin C, calcium, and iron for low-income Hispanic women and their children. DESIGN: A subset of 24-hour recalls from the Hispanic Health and Nutrition Examination Survey (HHANES), a sample representing 76% of the Hispanic-origin population, provides the most comprehensive examination of Hispanic food habits in the United States. SUBJECTS/SAMPLES: The sample, which approximates the population of the Special Supplemental Food Program for Women, Infants, and Children (WIC), included 1,046 17- to 34-year-old women with household income less than 185% of poverty level and their 1- to 5-year-old children (n = 1,063). MAIN OUTCOME MEASURES: Tables show the percentage that each food contributes to total intake of energy and six nutrients for women and for children and percentage of persons who reported consuming each food during a 24-hour period. RESULTS: Cultural foods contributed less to the energy and nutrient intake of the population than expected, with few exceptions, notably beans, rice, tortillas, and salsa. Major sources of energy and nutrients were similar to those seen for blacks and whites in the second National Health and Nutrition Examination Survey (1976-1980). APPLICATIONS: The data presented should be useful to researchers designing dietary assessment instruments and to nutrition educators designing or adapting educational materials. The data may be of particular interest to WIC staff who work with low-income Hispanic populations.

Adolescent↗
PubMed1995

Food choices of whites, blacks, and Hispanics: data from the 1987 National Health Interview Survey.

Dietary guidelines posit an association between diet and cancer. Different cancer mortality rates among whites, blacks, and Hispanics may be related to differences in diet. Food frequency data from the 1987 National Health Interview Survey on 20,143 adults were used to estimate the percentage of adults, by gender and race/ethnicity, who consume some 59 foods six or more times per year, median number of servings for consumers, and frequency of consumption of skin on poultry and fat on red meat. On the basis of percent consumption of these foods, women appear to have a more diverse diet than men. Women eat more fruits and vegetables, less meat, and fewer high-fat foods and drink fewer alcoholic beverages. Whites eat a more varied diet than blacks and Hispanics; blacks eat more fried and high-fat food; consumption of high-fat foods is lowest among Hispanics. Public health messages, especially those aimed at cancer prevention, should be targeted at increasing the overall consumption of fruits and vegetables, decreasing consumption of high-fat foods, especially among white and black men, and increasing consumption of those healthful foods already consumed by particular race/ethnicity groups.

Black or African American↗
PubMed1995

Are clinical trials really the answer?

It has been asserted that clinical trials hold the answer to questions about the role of nutrients in preventing chronic diseases. This is not the case. Clinical trials give us rigorous answers to restricted questions. Rarely can more than one or two substances be tested, usually at a single dose. Subjects usually have to be persons with precancerous conditions or an extremely high risk of the disease in question. Rarely can any diseases other than the most common ones be studied. Most important, clinical trials test the efficacy of an agent that is administered for a limited time, beginning fairly late in life. Few trials will tell us anything about whether dietary amounts of nutrients might contribute to prevention of long-term chronic diseases. They also tell us nothing about whether agents at high doses might reduce disease risk if taken throughout the lifetime. Furthermore, they tell us nothing about other antioxidants, other combinations, or other doses. Clinical trials were developed for therapeutic situations to determine which treatment was better for curing a specific disease. However, the questions about prevention that are of interest may involve persons with no unusual risk of disease, lifetimes of exposure, enormously complex interactions among nutrients, and the effects of these nutrients on hundreds of often uncommon disease conditions. Clinical trials simply cannot answer these questions. Only a solid examination of the laboratory and epidemiologic evidence can approximate the answers to most of the questions of interest.

Carotenoids↗
PubMed1995

Effects of treatment with simvastatin and pravastatin on cognitive function in patients with hypercholesterolaemia.

The effects of equi-efficacious doses of the cholesterol-lowering drugs simvastatin (20 mg day-1) and pravastatin (40 mg day-1) on tests of cognitive function were investigated in a double-blind, placebo-controlled, 2-period (4 weeks per period), incomplete block, crossover study of 36 patients (24 per treatment) with hypercholesterolaemia. After 4 weeks neither of the active treatments differed significantly from placebo on any cognitive measure.

Adult↗
PubMed1994

Revision of dietary analysis software for the Health Habits and History Questionnaire.

The software for analysis of the Health Habits and History Questionnaire (HHHQ) has been revised and is available to researchers. As in earlier versions of the software, questionnaires other than the standard National Cancer Institute versions can be analyzed. Foods can be added or dropped, nutrients can be added or changed, and many other revisions and options are facilitated. Estimates of 33 nutrients and up to 20 user-defined food groups are produced. The validity is unchanged from the previous software. Other features include a data entry key-and-verify system, standardized editing, a computer-assisted interview, and the calculation of health indices including pack-years of smoking and social network index.

Data Collection↗
PubMed1994

Comparison of effects on sleep of lovastatin and pravastatin in hypercholesterolemia.

The effects on sleep of lovastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor administered as a lipophilic lactone prodrug, and pravastatin, an inhibitor administered in its active, hydrophilic, open-acid form, were compared by polysomnographic sleep monitoring. Twenty-four men with primary hypercholesterolemia (low-density lipoprotein 4 to 7 mmol/liter) each received 2 of the following 3 treatments in a randomized, incomplete block, crossover design study: lovastatin (40 mg/day), pravastatin (40 mg/day), and placebo. Test drug was administered once daily for 4 weeks during each half of the crossover study. Subjective sleep assessments were obtained throughout each treatment period, and polysomnographic recordings were obtained at the end of the 4-week treatment periods. Treatment periods were separated by a 1-week washout. Lovastatin did not differ from placebo regarding any polysomnographic parameter except "number of entries to wake," for which it produced fewer entries (i.e., change was in the direction of improvement). Pravastatin did not differ from placebo regarding any polysomnographic measures, but was associated with worsening in relation to lovastatin in the following parameters: sleep efficiency, entries to wake, percent rapid eye movement sleep, wake time during sleep, and total wake time. For each of these 4 parameters, although neither drug showed marked differences from placebo, the mean change in the lovastatin group was in the direction of improved sleep, whereas the change in the pravastatin group was in the direction of disturbed sleep. Neither lovastatin nor pravastatin had any effect on subjective, qualitative sleep ratings.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Summary of the round table discussion on strategies for cancer prevention: diet, food, additives, supplements, and drugs.

A Round Table Discussion was held at the Fourth International Conference on Anticarcinogenesis and Radiation Protection. Scientists from government and academia were brought together to discuss the evidence for the preventive effect of foods, specific nutrients and drugs against cancer, and the most appropriate methods of initiating nutritional cancer prevention activities to improve the health of the public. The panel reviewed the epidemiological evidence of the role of diet and specific micronutrients for the prevention of cancer, the doses of specific micronutrients required for preventive effects and their safety, the evidence for aspirin as a chemopreventive agent, the issue of foods versus specific micronutrients in the prevention of cancer, food safety, and approaches to prevention such as food fortification or dietary supplements. The remarks of the panel members are summarized.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1994

Nutrient sources of provitamin A carotenoids in the American diet.

The food sources of provitamin A carotenoids were estimated from data from the Second National Health and Nutrition Examination Survey (NHANES II) carried out in 1976-1980. Carrots contribute over 30% of total population intake. Dark green leafy vegetables and sweet potatoes are also major contributors. However, several items often omitted from questionnaires to assess carotenoids are also major contributors, including salad, orange juice, beef stew, and milk. Conversely, many foods often included on such questionnaires are unimportant contributors, including papayas, plums, okra, and grapes. Recent changes in databases or food habits might change some rankings, but are unlikely to change the items in a list covering the top 90% of provitamin A intake. Questionnaires should include the important sources and exclude trivial sources, to minimize misclassification.

Adult↗
PubMed1994

Supplement use, other dietary and demographic variables, and serum vitamin C in NHANES II.

OBJECTIVE: Our objective was to evaluate the effect of regular use of nutritional supplements on serum vitamin C levels in a multivariable regression model, taking into account other dietary and demographic variables which may affect nutritional status. METHODS: We analyzed NHANES II data for subjects age 3 to 74. Analysis was limited to regular supplement users and nonusers, excluding irregular users. Multivariable regression analysis was performed with SUDAAN, incorporating sample weights and accounting for the complex survey design. RESULTS: Regular supplement users had substantially higher serum vitamin C levels than nonusers (p < 0.001). The magnitude of the effect of supplement use on serum vitamin C was 0.23-0.33 mg/dL in children and teens, and 0.36-0.46 mg/dL in adults. In adults who smoked, bottom quartile vitamin C levels were 0.3 mg/dL in men and 0.4 mg/dL in women who did not use supplements, compared to 0.9 and 1.1 mg/dL in regular supplement users. There was a significant interaction of smoking and supplement use in men (p < 0.001). CONCLUSION: Regular supplement use has a strong impact on serum vitamin C levels, independent of other dietary and demographic characteristics of supplement users which may favor improved nutritional status.

Adolescent↗
PubMed1994

Collection of dietary-supplement data and implications for analysis.

The role of nutrient intake in disease outcome is often examined in epidemiologic studies. Most such studies conducted in the United States, however, have not included fortified foods or vitamin supplements. In the United States, these are important sources of vitamins C and E, but not of beta-carotene. In addition, the importance of these nutrient sources varies by race, sex, and age. Failure to include these sources produces errors in nutrient estimates, notable misclassification of individuals with regard to their total intake, and rankings of intake that bear little or no relationship to blood concentrations of those nutrients. Implications for statistical analysis are also considered. Risk analyses in which nutrients from supplements are handled as control variables or are analyzed separately may impair the ability to detect associations between total nutrient intake and disease risk. The additional source of misclassification of nutrient status for vitamins C and E and other nutrients derived from fortified foods or supplements would make it more difficult to obtain significant and consistent results in etiologic studies of these nutrients; this has not been a factor for beta-carotene, which is derived almost exclusively from fruits and vegetables.

Adult↗
PubMed1994

The Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study in Finland.

The U.S. National Cancer Institute and the Finnish National Public Institute jointly sponsored a large double-blind, placebo-controlled primary-prevention trial to examine the effects of vitamin E and beta-carotene supplementation on reducing the incidence of lung cancers in male smokers, ages 50-69 years. Supplementation did not result in a significant reduction in lung cancer, and a higher incidence of lung cancer was observed in the group receiving beta-carotene. These results should be examined within the context of the population studied before they are cited as definitive.

Aged↗
PubMed1993

Vitamin and mineral status of women of childbearing potential.

Increasing data suggest a role for micronutrients in pregnancy outcome, and in some cases nutritional status must be adequate in the first weeks of pregnancy. We examined nationally representative survey data on women of childbearing age: the NHANES II data for serum measures of iron status and the CSFII four-day data for dietary measures of intake of protein, iron, zinc, folic acid, and vitamins A, C, and B6. For those nutrients, women below or near poverty had consistently lower levels, with median intakes below the RDA for all but protein (e.g., folic acid, 150 micrograms in contrast with the RDA of 180 for nonpregnant and 400 for pregnant women; for B6, 0.96 mg instead of 1.6 or 2.2). Even among women with incomes as high as three times the poverty level or more, large segments of the population had very low intakes. For example, the 25th percentile in that group was only 142 micrograms/day of folic acid, 4.6 alpha-tocopherol equivalents of vitamin E, 6.7 mg zinc, and 433 mg of calcium. Approximately 15% of women had low transferrin saturation.

Adolescent↗