Biomedical subjects

M Polansky

Publications and source records attributed to M Polansky.

At least 73 records · Page 4Linked to original sources

PubMed1988

Protein-induced glomerular hyperfiltration: role of hormonal factors.

High protein diets acutely elevate the glomerular filtration rate. To characterize this response we administered 1 g of protein/kg body weight as a beef steak meal to nine, healthy male subjects and measured glomerular filtration rate (inulin clearance), renal plasma flow (p-amino hippurate clearance), plasma renin activity, aldosterone and plasma and urinary catecholamines. The subjects ingested the meal on three separate days and were pretreated with either placebo, 50 mg indomethacin (to inhibit renal prostaglandin synthesis), or 10 mg enalapril (to inhibit angiotensin II synthesis). Following placebo treatment protein feeding significantly increased the glomerular filtration rate, from a pre-meal level of 101 +/- 7 ml/min/1.73 m2 to a post-meal level of 130 +/- 6 ml/min/1.73 m2, P less than 0.005. A parallel rise in renal plasma flow and a fall in renal vascular resistance were noted. Indomethacin pretreatment attenuated the increase in glomerular filtration rate following the protein meal, 105 +/- 6 ml/min/1.73 m2 pre-meal level to 118 +/- 4 ml/min/1.73 m2 post-meal, P greater than 0.1. Enalapril pretreatment had no significant effect on protein-induced glomerular hyperfiltration. Protein feeding following placebo increased plasma aldosterone concentration while the concentrations were unchanged in the studies where enalapril or indomethacin was administered. Protein feeding following placebo or indomethacin did not alter plasma renin activity while plasma renin activity rose following enalapril administration. Urinary norepinephrine excretion rose while plasma norepinephrine concentration was unchanged in all three study groups. A decrease in urinary dopamine excretion was also noted four hours after the protein meal was ingested.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

Thermic effect of food in lean and obese men.

A systemic reappraisal of the thermic effect of food was done in lean and obese males randomly fed mixed meals containing 0, 8, 16, 24, and 32 kcal/kg fat-free mass. Densitometric analysis was used to measure body composition. Preprandial and postprandial energy expenditures were measured by indirect calorimetry. The data show that the thermic effect of food was linearly correlated with caloric intake, and that the magnitude and duration of augmented postprandial thermogenesis increased linearly with caloric consumption. Postprandial energy expenditures over resting metabolic requirements were indistinguishable when comparing lean and obese men for a given caloric intake. Individuals, however, had distinct and consistent thermic responses to progressively greater caloric challenges. These unique thermic profiles to food ingestion were also independent of leanness or obesity. We conclude that the thermic effect of food increases linearly with caloric intake, and is independent of leanness and obesity.

Adult↗

PubMed1987

A reappraisal of the caloric requirements of men.

The resting metabolic rates (RMR) of 60 lean and obese men, aged 18-82 y and weighing 60-171 kg, were measured and body compositions were determined. Body compositional variables reflecting active protoplasmic tissue were all highly interrelated. Body weight alone gave prediction values for RMR that were comparable to those of other variables of active protoplasmic tissue mass. Regional distribution of fat had no influence on the RMR and the influence of age on RMR was trivial. The classic prediction equations and tables overestimate RMR of men. The 95%-confidence limits for both lean and obese men were broad. This conclusively demonstrates that metabolic efficiency is not necessarily or exclusively related to obesity. New regression equations for predicting the RMR based on weight and fat-free mass were developed: RMR = 879 + 10.2 WT kg and RMR = 290 + 22.3 FFMD kg, where FFMD is fat-free mass from densitometry measurements.

Adult↗

PubMed1986

A reappraisal of caloric requirements in healthy women.

The caloric expenditure of 44 healthy, lean and obese women, 8 of whom were trained athletes, was measured by indirect calorimetry. Body composition was determined. Ages ranged from 18-65 yr and body weights from 43-143 kg. Stepwise, multiple-regression analysis was used to determine whether one or several variables best predicted the resting metabolic rate (RMR) of the women. The RMR and the thermic effect of food (TEF) were measured before and after the women consumed a mixed breakfast meal. The results showed that the currently available tables and regression equations overestimate the RMR of healthy women by 7-14%. Body weight was highly related to the RMR, and stepwise inclusions of various variables did not improve predictions of RMR. The slopes of the regression lines for nonathletes and athletes were significantly different. Regression equations for predicting RMR of women were developed: Nonathletes RMR = 795 + 7.18 kg WT; Athletes RMR = 50.4 + 21.1 kg WT. The range of RMR per kilogram body weight was wide for nonathletic, but narrow for athletic women. The metabolism of some lean and obese, nonathletic women was highly efficient, predisposing these women for developing and maintaining body fat. The TEFs were indistinguishable between nonathletic and athletic women, and formed a continuum from the lightest to the heaviest woman.

Adolescent↗

PubMed1986

Treatment of orthostatic hypotension with dihydroergotamine and caffeine.

Eight patients with orthostatic hypotension were treated with subcutaneous dihydroergotamine. Two doses of the drug (6.5 and 13 micrograms/kg) or placebo were given in a random sequence at 0600 h, and blood pressures were measured hourly throughout the day with patients in both supine and upright positions. To assess the effect of postprandial hypotension on the therapeutic response to dihydroergotamine, we gave breakfast, lunch, and supper on a fixed schedule at 0900 h, 1200 h, and 1700 h. Dihydroergotamine had a pressor effect in seven of the eight patients during the fasting period (0600 h to 0900 h), but this agent did not counteract the hypotensive effect of eating. Concomitant administration of caffeine (250 mg, 30 minutes before breakfast), however, maintained the beneficial effect of dihydroergotamine during the postprandial period. The combination of subcutaneous dihydroergotamine and caffeine represents a new therapeutic option for patients with severe autonomic neuropathy.

Adult↗

PubMed1985

Hepatic and renal metabolism before and after portasystemic shunts in patients with cirrhosis.

Hepatic cirrhosis with portal hypertension and gastroesophageal hemorrhage is a disease complex that continues to be treated by surgical portasystemic shunts. Whether or not a reduction or diversion of portal blood flow to the liver adversely affects the ability of the liver to maintain fuel homeostasis via gluconeogenesis, glycogenolysis, and ketogenesis is unknown. 11 patients with biopsy-proven severe hepatic cirrhosis were studied before and after distal splenorenal or mesocaval shunts. Hepatic, portal, and renal blood flow rates and glucose, lactate, pyruvate, glycerol, amino acids, ketone bodies, free fatty acids, and triglyceride arteriovenous concentration differences were determined to calculate net precursor-product exchange rates across the liver, gut, and kidney. The study showed that hepatic contribution of glucose and ketone bodies and the caloric equivalents of these fuels delivered to the blood was not adversely affected by either a distal splenorenal or mesocaval shunt. In addition to these general observations, isolated findings emerged. Mesocaval shunts reversed portal venous blood and functionally converted this venous avenue into hepatic venous blood. The ability of the kidney to make a substantial net contribution of ketone bodies to the blood was also observed.

Adult↗

PubMed1984

A classification for biomedical research reports.

Biomedical research uses a wide range of designs applied to problems in laboratory, clinical, and population settings. Whatever the nature of the study, a few key features--such as the admission rule, the method of allocating subjects to treatments, and the use of controls--largely determine the strength of scientific inferences. We used these and other features to classify the 332 Original Articles published in the New England Journal of Medicine during 1978-1979. This classification directs attention to critical aspects of study design and performance and can help in the choice of suitable research approaches and protocols. It emphasizes the critical role of the investigators' intent in performing and analyzing a study, and it alerts readers to important aspects of interpretation. We recommend that authors always report enough detail about their work for readers to apply this or a similar classification. Omission of such detail may limit the interpretation of a research study because a study that cannot be classified has probably been incompletely reported.

Clinical Trials as Topic↗

PubMed1984

Studies without internal controls.

Sometimes questions of clinical interest can be addressed only by investigations without concurrent controls that are under the supervision of the investigator (internal controls). Such studies nearly always make use of other types of comparisons (external controls), such as historical controls. In this paper we examine studies of clinical treatments that have weak internal controls or lack internal controls, as illustrated by recent examples from the Journal. These studies have a small but important and unique role in clinical investigation. Five interrelated features can add to the strength of such studies: (1) an intent by the investigator, expressed before the study, that the treatment will affect the outcomes reported; (2) planning of the analysis before the data are generated; (3) articulation of a plausible hypothesis before the results are observed; (4) a likelihood that the results would still have been of interest if they had been "opposite" in some sense; and (5) reasonable grounds for generalizing the results from the study subjects to a substantially broader group of patients. In spite of potential pitfalls, carefully selected and reported studies without internal controls can play a substantial part in the acquisition of scientific knowledge.

Animals↗

PubMed1984

Crossover and self-controlled designs in clinical research.

Crossover studies (clinical trials in which each patient receives two or more treatments in sequence) and self-controlled studies (in which each patient serves as his or her own control) can produce results that are statistically and clinically valid with far fewer patients than would otherwise be required. We investigated the use of the crossover design in the 13 crossover studies that appeared in the Journal during 1978 and 1979. We considered the following important features of design and analysis as they applied to these studies: the method by which patients were assigned to initial treatment (only 7 of 13 studies used random assignment); the determination of when to switch treatments (10 of the 13 used a time-dependent rule, and 3 a less appropriate disease-state-dependent rule); blinding of the crossover point (in only 3 of the 13 studies was the crossover point concealed, but in 4 of the remaining 10 concealment was impossible); assessment of the effects of the order of treatments (included in only 1 of the 13 studies); and the use of at least minimally acceptable statistical analysis (11 of the 13 studies had such an analysis). We also report briefly on 28 additional studies of a single treatment each, in which each patient served as his or her own control before or after treatment or both. The scientific issues were much the same as in crossover studies except that self-controlled comparisons of treatments tended to be less precisely designed and conducted and to focus on clinical problems and patient groups that are especially difficult to study.

Chronic Disease↗

PubMed1984

Inhibition of chemically induced mammary carcinogenesis in rats by short-term exposure to butylated hydroxytoluene (BHT): interrelationships among BHT concentration, carcinogen dose, and diet.

Dietary butylated hydroxytoluene (BHT) fed 14 days before and 14 days after carcinogen administration resulted in a dose-dependent inhibition of 7, 12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumor incidence in outbred Sprague-Dawley rats. In addition, the inhibitory effects of BHT were strongly influenced by the dose of initiating carcinogen and the type of diet in which BHT was administered. In animals fed the NIH-07 diet and receiving a low dose of DMBA (5 mg/rat), the inhibitory effect of BHT was manifested at all four BHT concentrations (6,000 leads to 300 ppm). Maximal inhibition was approximately 50% in animals given 5 mg DMBA and receiving 6,000 ppm BHT. However, in the group administered a high dose of DMBA (15 mg/rat), the inhibitory effect of BHT was expressed only at 6,000 ppm, the highest concentration given. Lower concentrations (300 and 1,000 ppm) of BHT had no detectable effect on tumor incidence. In animals fed the defined, semipurified AIN-76A diet during the 4-week treatment period and initiated with 5 mg DMBA, BHT at 6,000 ppm inhibited tumor development. However, at 15 mg DMBA animals fed the AIN-76A diet differed markedly from those fed the NIH-07 diet. In the former group, BHT at 6,000 ppm was unable to elicit any inhibitory response; in the latter group, BHT inhibited tumor development by 40%. Dietary BHT also inhibited DMBA-induced adrenocortical hyperplastic nodules in a dose-dependent fashion. These results indicate that short-term exposure to dietary BHT can inhibit experimental mammary tumor development at environmentally relevant concentrations.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1984

Analyzed vitamin B-6 intakes of pregnant and postpartum lactating and nonlactating women.

Daily dietary food composites were collected for three consecutive days from 36 women (23 who planned to breast feed their infants and 13 who planned to formula feed their infants) at approximately the 37th week of pregnancy and at one, three, and six months postpartum. When the food composites were collected, each woman also kept detailed food intake records. Daily protein and energy intakes were calculated from the records. Representative aliquots of the homogenized food composites were analyzed microbiologically for total vitamin B-6. The data from the composite analyses indicate that the daily dietary intakes of vitamin B-6 for both groups of women in late pregnancy through six months postpartum were substantially less than the Recommended Dietary Allowances (RDAs). During pregnancy, the women who planned to breast feed their infants consumed diets which provided 54% of the RDA. The women who planned to formula feed their infants consumed diets which provided only 44% of the RDA for vitamin B-6 for pregnant women. At one, three, and six months postpartum, the diets of the lactating women provided 61% of their RDA for vitamin B-6, and the diets of the nonlactating women provided a mean of 46%. Of the 402 daily dietary composites analyzed, only 6% met or exceeded the RDA for vitamin B-6 for the women while they were pregnant or postpartum, either lactating or nonlactating.

Adolescent↗

PubMed1983

Designs for experiments--parallel comparisons of treatment.

Clinical trials of medical treatments often compare two treated groups or a treated group with a separate but concurrent control group. We have examined a consecutive series of 47 such parallel studies reported in the Journal in 1978-1979, including 35 with random assignment to the treated or control group, to discover how this approach is actually used. A major strength of these studies as a group was the frequent use of randomized treatment assignment. Common problems included lack of sufficient detail about methods of randomization, failure to provide enough detail about patient sources, and insufficient use of multivariate statistical techniques and of statistical modeling. We emphasize the importance of avoiding bias by balancing prognostic factors when assigning patients to treatments, reducing bias by modeling the influence of prognostic factors on response, and increasing precision by modeling. We also advocate the careful consideration of the relevance of a treatment comparison within the study to the external world of clinical practice.

Adult↗

PubMed1983

Forms of vitamin B6 in human milk.

A previously developed high performance chromatographic method has been modified slightly and used to determine the forms of vitamin B6 in human milk. The chromatographic traces are free of compounds that would interfere with the two principal forms found, pyridoxal and pyridoxal phosphate. The method is fast and reliable; it yields recoveries of from 90 to 106% for the vitamers and agrees with results obtained on the same samples with the standard microbiological assay.

Biological Assay↗

PubMed1983

Epidemiology of coffee and pancreatic cancer.

The association between pancreatic cancer and putative risk factors was examined using 275 incident cases and 7994 controls interviewed in six United States cities for a major study of tobacco-related diseases. From the comparison population were excluded patients with other diseases postulated to be associated with pancreatic cancer (e.g., other pancreatic diseases and diseases of the gallbladder) and those admitted for disorders known to be associated with smoking. After carefully controlling for age, the data failed to indicate an association between coffee consumption and pancreatic cancer (odds ratio congruent to 1.0). This was true both before and after adjustment for cigarette smoking and in both males and females. There was a statistically significant association between pancreatic cancer and smoking in both males and females (odds ratio 3.0 for males who smoked more than 1.5 packs/day and 2.0 for females who smoked more than 1 pack/day).

Adult↗

PubMed1981

Toward understanding elders' health service utilization.

Providing appropriate health services to the elderly is emerging as one of the major challenges of this decade. Using the theoretical framework developed by Andersen and Aday, this study attempts to improve our understanding of those factors which inhibit or facilitate elders' use of health services. The data come from a 1974 statewide random probability sample of 1,625 noninstitutionalized elders 65 years of age or older living in Massachusetts. Regression analysis is used to study the effects of predisposing, enabling, and need characteristics on the use of five health services: hospitals, physicians, dentists, home care, and ambulatory care. The model explains from 5% to 27% of the variance in health service utilization. Need characteristics, in general, account for most of the explained variance.

Aged↗

PubMedDate not supplied

Resident education in transfusion medicine: a multi-institutional needs assessment.

A survey was conducted among resident physicians at nine academic medical centers to assess their perceptions of their knowledge of transfusion medicine (TM), their confidence in using various blood bank resources, and their ratings of the contribution of various learning resources to their knowledge of TM. A total of 320 residents completed the survey; nearly 90 percent were in an internal medicine, surgery, or anesthesiology residency. Respondents placed a high value on the relevance of TM to patient care, although they rated their knowledge and learning opportunities as only moderate. They rated senior residents as the most useful educational resource, with undergraduate medical school education, formal conferences, and journals and library resources being the three next most useful. Residents had the greatest confidence in using packed red cells, platelets, and fresh-frozen plasma. Surgery and anesthesiology residents generally had greater confidence in using blood bank resources than internal medicine residents. The findings of the survey can be used, along with the results of medical care evaluations of transfusion practice and opinions of education experts, to create an optimally relevant and effective curriculum for resident education in transfusion medicine.

Academic Medical Centers↗

PubMedDate not supplied

Effects of methylphenidate on attentional function after traumatic brain injury. A randomized, placebo-controlled trial.

Attention deficits after traumatic brain injury (TBI) are common and disabling. Many pharmacologic agents have been used to ameliorate attention deficits, and considerable interest has focused on methylphenidate (MP) because of its documented efficacy in attention deficit disorder. However, clinical studies of MP in subjects with TBI have yielded mixed results. We examined the effects of MP on attentional function in individuals with TBI referred specifically for attentional assessment and treatment. Subjects were studied in a double-blind, placebo-controlled, repeated crossover design, using five different tasks designed to measure various facets of attentional function. MP produced a significant improvement in the speed of mental processing. Orienting to distractions, most aspects of sustained attention, and measures of motor speed were unaffected. These results suggest that MP may be a useful treatment in TBI but is primarily useful for symptoms that can be attributed to slowed mental processing.

Adolescent↗

PubMedDate not supplied

Seroprevalence of human immunodeficiency virus type I (HIV-1) antibodies in a family-planning population.

Blind testing of 743 women who attended an inner-city hospital family-planning clinic showed 8 (1.1%) patients to have serum antibodies to human immunodeficiency virus type I (HIV-1). A retrospective chart survey did not show an association between HIV-1 antibody seropositivity and ethnicity, marital status, education, history of sexually transmitted diseases, drug and/or alcohol use, and contraceptive method. This failure to establish previously reported correlation may be a function of methods, sample size, or reflect a different population. Nonetheless, the seroprevalence the authors found shows that all patients in a family-planning clinic setting should be offered HIV-1 antibody testing.

Adult↗