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Biomedical subjects

T Clausen

Publications and source records attributed to T Clausen.

190 records · Page 11Linked to original sources
PubMed1968

Membrane potential of brown adipose tissue. A suggested mechanism for the regulation of thermogenesis.

Membrane potentials were recorded in isolated segments of interscapular brown adipose tissue from rats. After equilibration at 29 degrees C in Krebs-Ringer bicarbonate buffer a mean value of -51 +/- 4 mv (SD) was found. This level could be maintained for up to 5 hr. The mean effective membrane resistance was 1.35 +/- 0.45 megohm. The membrane potential was a function of the extracellular potassium concentration. Ouabain (10(-6)-10(-3)M) and incubation in K-free buffer produced progressive depolarization. Epinephrine and norepinephrine in concentrations as low as 10(-8) g/ml produced a prompt depolarization. Cooling of the tissue and lowering of the oxygen tension caused a marked and reversible decrease in the membrane potential. In tissue obtained from cold-adapted rats, the membrane potential was considerably diminished. 6Assuming that the membrane potential is some function of the Na permeability of the plasma membrane it is suggested that an increase in the rate of active Na-K transport and ensuing ADP formation might contribute to the increase in respiration seen during exposure to thermogenic stimuli.

Adaptation, Physiological↗
PubMedDate not supplied

Ouabain binding and Na+ content in resistance vessels and skeletal muscles of spontaneously hypertensive rats and K+-depleted rats.

The possible role of Na+ in the development of hypertension in rats was explored in measurements of intracellular Na+, 22Na efflux, and 3H-ouabain binding sites in resistance vessels and skeletal muscles. In resistance vessels obtained from 13-week-old spontaneously hypertensive rats (SHR) or age-matched Wistar-Kyoto rats (WKY), (Na)i, total or ouabain-resistant 22Na efflux, and the concentration of 3H-ouabain binding sites showed no significant differences. Soleus muscles obtained from 6-week-old and 13-week-old SHR contained 5 to 11% more 3H-ouabain binding sites than those of WKY. The small difference in ouabain binding probably was related more to variations in growth rate and strain than to the hypertension. In SHR and WKY the Na+ and K+ contents of gastrocnemius muscles were almost identical at 6 and 13 weeks of age. By contrast, in Wistar rats in which the (Na)i of skeletal muscle was increased sixfold by K+ depletion, the systolic blood pressure was decreased by 10%. The K+ depletion was associated with a 35 to 55% decrease in the concentration of 3H-ouabain binding sites in both resistance vessels and skeletal muscles. The results provide no support for any simple cause-effect relationships between either elevated (Na)i or altered concentration of 3H-ouabain binding sites and hypertension in SHR.

Animals↗
PubMedDate not supplied

Chronic diseases and health inequalities in older persons in Botswana (southern Africa): a national survey.

OBJECTIVES: To evaluate the health status of older persons in Botswana, to report on the prevalence of common health conditions--typically chronic diseases, to assess the socio-demographic correlates of morbidity in this population, and to assess the associations between physical functioning and self-reported health and the common health problems presented. DESIGN: National, cross-sectional survey (12 rural areas, 3 urban centres), inclusive of clinical examinations. SAMPLE: 372 individuals (183 females, 189 males) aged 60-109 years. RESULTS: 68% of respondents reported musculoskeletal pain in two or more locations; 42% were found to be hypertensive; 36% reported dental problems; 32% had dermatological problems; 11% were blind (as defined); 9% had cognitive impairment; 7% were depressed. Multinomial regression analyses showed poor self reported health to be significantly associated with musculoskeletal pain (OR = 15.5), depression (OR = 9.7), incontinence (OR = 3.9), dermatological problems (OR = 3.0) and dental problems (OR = 2.3); hypertension, blindness and cognitive impairment did not show significant associations. CONCLUSION: A large number of older persons in Botswana suffer from one or more age-associated chronic diseases that may impair function and quality of life. Several of the conditions may be diagnosed and treated to optimise the individuals' functioning. Poor self reported health was associated with "painful conditions" which are commonly poorly managed or untreated.

Activities of Daily Living↗
PubMedDate not supplied

Nutritional status, tobacco use and alcohol consumption of older persons in Botswana.

AIM: To describe body mass index (BMI) distribution according to patterns of tobacco use, alcohol consumption and sociodemographic factors of older persons in Botswana. MATERIAL AND METHODS: Data were collected in 1998 as part of a national household survey of 1085 subjects aged 60 years and older. For the purpose of this analysis, data are utilised from a representative 50 % sub-sample (n=393; response rate = 72 %), in which weight and height were measured as part of a medical examination in the subjects' homes. RESULTS: A high prevalence of underweight (BMI < 18.5) was found in men (20.1 %), while overweight (BMI = 25-29.9) and obesity (BMI > or = 30) were common in women (21.3 % and 27.9 %, respectively). Thirty-four percent of the subjects reported alcohol consumption and 39 % reported tobacco use. Half of the sample used either one or both of the stimulants. Underweight was significantly associated with low socioeconomic status (OR=3.3; 95 % CI=1.3-8.2) and the use of a combination of alcohol and tobacco (OR=2.2; 95 % CI=1.1-4.4). Obesity was significantly associated with female gender (OR=4.9; 95 % CI=2.5-9.7) and younger age (60-69 years, compared to older groups; OR=3.2; 95 % CI=1.3-7.7). A higher than expected clustering of the three health-related risk factors (underweight, tobacco use and alcohol consumption) was found at 6.7 % (observed:expected ratio = 2.9). CONCLUSION: A double burden of undernutrition and overnutrition was found in this sample of older persons in an African country. A clustering of the three risk factors for increased morbidity (tobacco use, alcohol consumption and underweight) was evident. These findings indicate a need for health education to effect lifestyle behavioural change in older adults in the subregion.

Age Factors↗
PubMedDate not supplied

Mode of action of cystathionine beta-lyase.

Cystathionine beta-lyase (CBL) is a member of the gamma-family of pyridoxal-5'-phosphate (PLP)-dependent enzymes (Alexander et al., 1994) that cleave C(beta,gamma)-S bonds of a broad variety of substrates. Recently, we reported the X-ray crystal structures of CBL and the CBL-trifluoroalanine inactivation complex at 1.83 A and 2.3 A resolution, respectively. The structures explicitly reveal the cofactor and substrate binding pockets. Spectral analysis of substrate turnover indicates a change of hydrophobicity in the microenvironment of the aldimine bond. In combination with further spectroscopic data, crystallographic evidence permits the formulation of a likely reaction mechanism.

Chemical Phenomena↗