Search PubMed⌕ Search

Biomedical subjects

J Stevens

Publications and source records attributed to J Stevens.

At least 361 records · Page 20Linked to original sources
PubMed1976

The effect of anaesthesia of the airway in dog and man: a study of respiratory reflexes, sensations and lung mechanics.

1. The effect of breathing an anaesthetic aerosol of 5% bupivacaine hydrochloride has been assessed in dog and man. 2. In the dog, the cough reflex was abolished and the Hering-Breuer inflation reflex severely impaired or abolished; breathing became slower and deeper; no pathological changes were found in the lungs of these dogs. 3. In man, no untoward effects resulted from a 10 min period of aerosol inhalation; there were no systematic effects on airway resistance or lung volumes and the cough reflex in response to either tactile or chemical (citric acid aerosol) stimulation was invariably abolished. The Hering-Breuer inflation reflex was impaired, but this was not associated with any change in resting ventilation. The Ve/CO2 response was enhanced after aerosol anaesthesia; subjects felt an exaggerated dyspnoea. The aerosol anaesthesia abolished the afferent pathway of a reflexly elicited bronchoconstriction in one subject. There was no effect on the ability to hold the breath, or on the quality of the associated sensation. 4. Control aerosols of sodium chloride solution or phosphate buffer produced no effects. Control experiments with intravenous infusions of bupivacaine proved that none of the effects could have been produced by systemic effects of the absorbed anaesthetic. 5. Plasma concentrations of bupivacaine in man did not exceed a recognized toxic level. The experiments demonstrate a safe reversible anaesthesia of the airways in man lasting for a period of 10-20 min.

Aerosols↗
PubMed1976

Quality of the meat after the application of anabolic agents in young calves.

Experiments were carried out to test the effect of implantation of Implix¿ (20 mg estradiol + 200 mg testosterone) or Revalor¿ (140 mg trienbolone acetate + 20 mg estradiol) on growth, feed conversion, slaughter quality, and residue levels in black Friesian bull calves at 4, 8, or 4 and 8 weeks before slaughtering. Weighings and calculations of feed conversion were carried out weekly. The control group of weight gain and feed conversion consisted of 22 calves; the chemical analyses of the control group was restricted to 8 animals. Implantation of the hormones at 4 or 8 weeks before slaughtering resulted in a significant beneficial effect on weight gain, feed conversion and carcass index over the control. This effect was improved (up to 15%) by implanting the hormones at 8 and 4 weeks before slaughter. The effects obtained with Revalor seemed to be superior to those obtained with Implix. In 75% of the treated animals, some remainder of implants was found. No effect was found on water binding capacity and colour of raw meat. Carcass quality was not significantly improved as judged from water, fat, ash, and protein content of the M. Longissimus Dorsi. The collagen content of the animals treated with Revalor was slightly, though not significantly, increased. There is a slight decrease in the relative bone content of the treated animals over the control resulting in higher meat percentages. Residues were determined in meat obtained from rib and neck by biological and chemical methods. Oestrogenic activity was found in only 7 samples from the neck; all samples from the rib were negative. Chemical examination indicates the presence of oestradiol in these samples. No residues of trienbolone could be detected in the meat samples. The Pars Dissiminata of the prostate was examined histologically on frozen and paraffin sections. Although the latter permitted a sharper interpretation, both methods indicated an increased activity of the prostates induced by hormone treatment. Compared to Implix, Revalor treatment provoked a more pronounced mucous activity. In recent years, the administration of estrogens in combination with testosterone or with trenbolone acetate (androst-4,9[10]-11-trien-3-one 17-acetate)2,3,4,17 has been shown to improve the growth rate and feed conversion5,14,17 in farm animals. However, there is a lack of information on carcass quality, which is of interest to the producer as well as to the consumer. Moreover, there are sample data14 about the residue levels remaining in the carcass following hormone implantation. These experiments were carried out to test the effect of the implantation of Implix¿ (20 mg estradiol + 200 mg testosterone) or Revalor¿ (140 mg trienbolone acetate + 20 mg estradiol) on growth, feed conversion, slaughter quality, and residue levels in black Friesian bull calves.

Anabolic Agents↗
PubMed1975

Estriol concentrations in plasma of normal, non-pregnant women.

Using a rabbit antisera directed against estriol-3-0-carboxy methyl ether complexed to BSA, an immunoassay for estriol (1) was developed. The mean plus or minus SE concentration of estriol in 18 women in days 5-7 of their cycle was 7.9 plus or minus 0.6 pg/ml which was significantly (P less than 0.01) less than the mean value of 11.1 plus or minus 0.8 pg/ml in 15 women in days 20-22 of the cycle. In 3 of 6 women in whom plasma samples were drawn frequently during their cycle, an estriol peak occurred coincident with the estradiol peak. In 3 women from whom plasma was obtained several times during the course of a day estriol levels did not appear to vary significantly. In 8 women who were on oral contraceptives the mean level of estriol was 7.6 plus or minus 1.5 pg/ml. In 8 post-menopausal women the mean level was 6.0 plus or minus 1.2 pg/ml which is significantly (P less than 0.01) less than the mean luteal phase value but not less (P greater than 0.1) than the follicular phase or oral contraceptive user values. We conclude that some of the circulating estriol is directly secreted by the ovary of normal women.

Adult↗
PubMed1975

Sequential irreversible, actinomycin D-sensitive, and cycloheximide-sensitive steps prior to cortisol inhibition of uridine utilization by P1798 tumor lymphocytes.

Events preceeding the cortisol inhibition of uridine utilization by corticoid-sensitive P1798 lymphocytes have been investigated. When tumor cells were incubated with 1 muM cortisol for 15 min and then washed free of steroid and reincubated in the absence of hormone, the expected decrease of uridine uptake failed to appear 1.5 hr later. In contrast, the removal of cortisol after 30 or 60 min did not prevent subsequent development of the steroid effect. Addition of actinomycin D with cortisol, or 15 min after hormone treatment was started, blocked steroid action. However, when actinomycin D was added 30 or 60 min after the initial exposure to cortisol, hormone-induced depression of uridine uptake was no longer prevented. To study the role of protein synthesis, cycloheximide was added to the tumor cell suspensions at various times after cortisol treatment was started. Cortisol suppression of uridine utilization was blocked when cycloheximide was added with the hormone or 30 min after the start of hormone treatment. Cycloheximide added together with cortisol and washed out with the steroid after 30 min did not prevent subsequent appearance of decreased nucleoside uptake. Hydroxyurea, an inhibitor of DNA synthesis, did not prevent cortisol action, even when present throughout a 2 hr exposure to the steroid. Hormone removal or actinomycin D addition after 1.5 to 2 hr (when uridine uptake was already inhibited about 25%) did not prevent intensification of the steroid effect during a subsequent 1.5- to 2-hr incubation period, while addition of cycloheximide at this time completely prevented its progression. These results suggest aht: (a) cortisol inhibition of uridine uptake by P1798 lymphocytes involves an early irreversible step and appears to require continuing RNA but not protein synthesis during the first 15 to 30 min of hormone action; (b) protein synthesis but not RNA synthesis is required between 30 and 60 min; and (c) continuing protein synthesis but not RNA synthesis or hormone presence is necessary for the preestablished cortisol effect to progress.

Animals↗