Search PubMed⌕ Search

Biomedical subjects

S Hansen

Publications and source records attributed to S Hansen.

440 records · Page 25Linked to original sources
PubMedDate not supplied

Temperature effects on the breeding distribution of grey seals (Halichoerus grypus).

The metabolic rates of six female grey seal (Halichoerus grypus) pups were measured during their postweaning fast at air temperatures between -15 degrees and 30 degrees C. The composite of their individual thermal neutral zones extended from a mean lower critical temperature of -7.1 degrees +/- 0.7 degree C to a mean upper critical temperature of 23.0 degrees +/- 0.4 degree C. Within the thermal neutral zone, mean standard metabolic rate of the fasting animals was 1,265 +/- 82 kcal d-1, or about 1.1 times the value predicted for an adult animal of similar body mass (mean mass = 40.9 +/- 1.2 kg). For those grey seal populations that reproduce during winter months in the eastern and western Atlantic and in the Baltic Sea, the lower critical temperature of fasting pups corresponds closely with the coldest mean monthly air temperature at the northern end of their breeding ranges. This observation supports the hypothesis that cold ambient air temperatures limit the northern breeding distribution of grey seals, primarily through their thermoregulatory effects on small, fasting pups before they enter the water.

Animals↗
PubMedDate not supplied

Ontogeny of the thermal limits in the harbor seal (Phoca vitulina).

We measured metabolic rates (mL O2 h-1, converted to kcal d-1), deep body temperatures (degree C), and skin temperatures (degree C) and calculated whole-animal thermal conductances (mL O2 g-1 h-1 degree C-1) of five 3-yr-old harbor seals (Phoca vitulina concolor) at air temperatures between -20 degrees and 35 degrees C. The mean thermal neutral zone of these seals extended from a lower critical temperature of -12.9 degrees +/- 1.6 degrees C (SD) to an upper critical temperature of 28.6 degrees +/- 1.7 degrees C. Hyperthermia was observed at an ambient air temperature of 35 degrees C. Mean standard metabolic rate was 1,553.6 +/- 168.2 kcal d-1, about 1.2 times the value expected for adult animals of similar body mass (mean mass = 49.2 +/- 7.5 kg). Mean deep body temperature increased from 37.5 degrees +/- 0.30 degrees C at an ambient temperature of 30 degrees C and reached 39.3 degrees +/- 0.33 degrees C at an ambient temperature of 35 degrees C. Skin temperature decreased with decreasing ambient temperature but remained well above ambient temperature. Mean whole-animal thermal conductance decreased from an ambient temperature of 35 degrees C until it reached a minimum value of 0.007 mL O2 g-1 h-1 degree C-1 at -4.0 degrees C; it then increased with a further decrease in ambient temperature. In comparison to the thermal limits of the same seals during their first year of life, the results indicate a broadening of the thermal neutral zone with age: an 11 degrees C decrease in the lower critical temperature and a 3.5 degrees C increase in the upper critical temperature. These findings suggest that warm ambient air temperatures should not pose any particular thermoregulatory problems for larger and older harbor seals, even beyond the limits of their current annual distribution.

Animals↗
PubMedDate not supplied

Effect of local intracerebral corticosterone implants on alcohol intake in the rat.

Corticosterone acts within the brain to stimulate alcohol consumption in the rat. The experiments reported here were aimed at identifying where in the brain corticosterone acts to facilitate ethanol drinking. The daily fluid intake of male Wistar rats with simultaneous access to 6% ethanol and water was determined during a 1-week pre-operative baseline period and following implantation of corticosterone in various brain areas. Animals bearing unilateral or bilateral implants of corticosterone in the ventral striatum showed increased ethanol consumption compared to cholesterol-treated controls. Ethanol intake was not affected when corticosterone was implanted into septum, hippocampus, or thalamus. Neither were changes in fluid intake detected in animals bearing ventral striatal implants of two related steroid hormones, aldosterone and testosterone. These results indicate that corticosterone partly acts within the ventral striatopallidal system to facilitate alcohol consumption in the rat.

Alcohol Drinking↗
PubMedDate not supplied

Increased novelty seeking and decreased harm avoidance in rats showing Type 2-like behaviour following basal forebrain neuronal loss.

Previous research has shown that excitotoxic lesions of the septum, ventral striatum and adjacent areas increase alcohol intake and defensive aggression in the rat. This behavioural constellation resembles that observed in early-onset Type 2 alcoholism. Due to the fact that the prototypical Type 2 alcoholic scores high on novelty seeking and low on harm avoidance, we studied these temperamental traits in rats with basal forebrain lesions. In comparison with controls, such rats showed more exploration (nose-poking) of a hole-board (indicating increased novelty seeking) and less risk assessment behaviour (stretched attend posturing) in an unfamiliar arena (indicating reduced harm avoidance). In both tests the experimental rats showed signs of motor restlessness. The results obtained indicate that basal forebrain neuronal loss may be associated with an enhanced exploratory responsiveness to novel stimuli together with a relative freedom of anticipatory anxiety.

Adult↗
PubMedDate not supplied

Pafenolol in hypertension: a double-blind randomized trial of a new beta 1-selective adrenoceptor blocker.

The antihypertensive effect of pafenolol, a new beta 1-selective adrenoceptor blocker without intrinsic sympathomimetic activity and three times more selective than metoprolol, was evaluated. Twenty-three patients with essential hypertension, mean age 49 years (range 21-62), were randomized after a 4-week placebo run-in period (double-blind) to 4 weeks of either placebo, pafenolol 50 mg or 100 mg once daily. A submaximal exercise test was performed before and at the end of the treatment period. Pafenolol 50 mg and 100 mg significantly reduced recumbent and standing blood pressure compared with baseline with a mean reduction of 17/14 and 10/12 mm Hg on pafenolol 50 mg and 15/10 and 14/10 mm Hg on pafenolol 100 mg, respectively. Heart rate, both at rest and during exercise, was significantly reduced (p less than 0.05) on pafenolol 100 mg compared with placebo. The reduction in exercise heart rate (percent) was dose dependent and significantly correlated to the log plasma concentration of pafenolol (r = 0.60; p less than 0.05). It can be concluded that pafenolol had a clinically relevant antihypertensive effect when given once daily. No difference between 50 and 100 mg could be demonstrated, thus suggesting that 50 mg may be the preferred dose for antihypertensive treatment.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

On the complication risk of early amniocentesis versus standard amniocentesis.

In the last 6 years early amniocentesis for the prenatal diagnosis of chromosome aberrations has been established in many centers worldwide, but knowledge about the gynecological safety of the procedure is sparse. From 1990 to 1995 at the Evangelisches Krankenhaus Oberhausen (Germany) 3,277 early amniocenteses (between weeks 11 and 14) and 1,808 standard amniocenteses were performed in low-risk indication groups (advanced maternal age and anxiety). A complete follow-up including reports of fetal outcome was obtained in 4,444 cases (87.5%). A pregnancy age-related abortion rate was determined with a slightly higher rate of abortions up to week 28 of gestation in early amniocentesis. The total abortion rate up to week 28 after the procedure for cases with complete follow-up was 2% in early amniocentesis. Compared to standard amniocentesis performed under the same clinical conditions with an abortion rate of 1.3%, there is no statistical difference between early and standard amniocentesis (p = 0.0971). Hip and foot dislocations (22 cases) and pulmonary distress syndromes (8 newborns) showed no significant correlation with the gestational week. Given the high normal background rate of spontaneous abortions in the early period of pregnancy without an invasive procedure, early amniocentesis can be considered as a safe alternative to chorionic villus sampling and standard amniocentesis.

Abortion, Induced↗
PubMedDate not supplied

A reexamination of the association between HOME scores and income.

This study, which represents another look at the relationship between the HOME Inventory and income, uses data from the Infant Health and Development Program (IHDP), a multisite, longitudinal study of low-birth-weight preterm infants. Two versions of the HOME Inventory were used: The Infant/Toddler (IT-HOME), at 12 months of age, and the Early Childhood (EC-HOME), at 36 months of age. Predictor variables were income, ethnicity, maternal education, parity, gestational age, marital status, maternal age, and site. HOME scores were positively correlated with income. However, after controlling for the other variables in the models, the portion of the variance in HOME scores uniquely explained by income was quite low (IT-HOME, 5.1%; EC-HOME, 4.2%). Finally, the relationship between HOME scores and four child characteristics (cognitive development, growth, maladaptive behavior, and social competence) measured when the child was 36 months old were investigated using correlation. The results indicated that the quality of the home environment, as measured by the HOME Inventory, is related to children's development.

Adult↗