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Biomedical subjects

D Stevens

Publications and source records attributed to D Stevens.

At least 91 records · Page 5Linked to original sources
PubMed1983

Respiratory pressures and function in young adults.

The relationships of lung functions to maximal respiratory pressure relative to the role of other recognized determinants (height, weight, age, and smoking status) were examined in 924 healthy Caucasian urban residents, 369 males 15 to 35 yr of age and 555 females 13 to 35 yr of age. In subjects no longer thought to be growing in stature, height was the main determinant of most functions. After height, respiratory pressures were the main determinant of forced vital capacity (FVC), forced expiratory volume in one second (FEV), and peak flow in men and women, with weight also an important determinant in women. Age had no consistent effect, and, although functions in smokers were lower than in nonsmokers for several tests, the effects were only significant for FEV and forced expiratory flow during the middle half of the FVC in women. These findings indicate that, if required, between-subject variation in this age group can be reduced by taking into account the relatively simple measurement of maximal inspiratory and expiratory pressures.

Adolescent↗
PubMed1981

Use of cryopreserved lymphocytes for the indirect leukocyte migration inhibition assay.

Production of leukocyte migration inhibitory factor (LIF) by fresh and cryopreserved lymphocytes from the same donors was detected by indirect leukocyte migration inhibition (LMI) assay. The same results were obtained when fresh and frozen lymphocytes were tested in parallel. This indicates that cryopreservation does not impair the ability of lymphocytes to produce LIF.

Freezing↗
PubMed1980

Sympathetic innervation and the development of structure and function of brown adipose tissue: studies on lambs chemically sympathectomized in utero with 6-hydroxydopamine.

Fetal sheep were injected intramuscularly with 25-100 mg/kg of 6-hydroxydopamine HBr on 3-4 occasions between the 94th and 136th day of pregnancy. Following birth, which took place normally, the metabolic response to cold (summit metabolism) was found to be lower in treated than in control lambs, by an amount that approximated the thermogenic potential of brown fat. Under thermo-neutral conditions, the dose of infused noradrenaline (10 microgram kg-1 min-1) that stimulates maximum non-shivering thermogenesis in control lambs failed to stimulate thermogenesis in treated lambs unless accompanied by a dose of the alpha-blocker, phentolamine. This failure was apparently due to vasoconstriction induced by hypersensitivity to noradrenaline; hypersensitivity was also indicated when one-tenth of this dose was found to be fully effective in stimulating metabolism and substrate mobilization of the treated lambs. Examination of the perirenal adipose tissue of treated lambs with the electron microscope and by a monoamine fluorescence technique that visualizes catecholamine-containing structures, revealed that the tissue possessed the histological characteristics of brown fat, but there was little or no evidence of sympathetic innervation, in contrast with profuse innervation in control lambs. This is consistent with the observed hypersensitivity to noradrenaline. Similar histological findings were made in lambs that had received weekly intraperitoneal injections of 6-hydroxydopamine from day 70 of gestation, after which time sympathetic innervation normally begins to appear. It is probable that an intact sympathetic innervation is unnecessary for normal development of brown adipose tissue. This chemical sympathectomy appears to be long-lasting since treated lambs 8-months old were unable to vasoconstrict their extremities effectively in response to cold, and significant monoamine fluorescence could not be demonstrated in the various tissues examined.

Adipose Tissue, Brown↗
PubMed1980

The cardiovascular responses of conscious newborn lambs treated in utero with 6-hydroxydopamine.

Fourteen fetal sheep were treated in utero with a single intramuscular injection or three to four injections of 6-hydroxydopamine. After birth the cardiovascular responses of these lambs to adrenergic drugs were studied and compared with the cardiovascular responses of untreated newborn lambs. Lambs which received three to four injections of 6-hydroxydopamine were more sensitive to the pressor actions of noradrenaline and phenylephrine than were control lambs or lambs which received a single injection of 6-hydroxydopamine. The supersensitivity to noradrenaline persisted in multiple treatment lambs until at least 5 months of age. Lambs which received multiple injections of 6-hydroxydopamine were also subsensitive to the pressor action of tyramine. The sensitivity to the pressor actions of noradrenaline and phenylephrine in lambs which received a single injection of 6-hydroxydopamine lay between that of control and multiple treatment groups. Despite the pharmacological evidence of impairment of sympathetic innervation of peripheral blood vessels plus a lack of responsiveness of these lambs to alpha-adrenergic blockade with phentolamine, treated lambs had arterial pressures and heart rates similar to control lambs. As well, treated lambs showed no impairment in their ability to reflexly regulate heart rate in response to changes in arterial pressure, which is consistent with the recently reported vagal control of the cardiac baroreceptor reflex.

Animals↗
PubMed1979

Folic acid supplementation in low birth weight infants.

Low birth weight infants (246) entered a trial to folic acid supplementation from 3 weeks to 12 months of age. The folic acid group had significantly higher mean hemoglobin levels at 6 and 9 months of age but the differences were only about 0.5 gm/dl, there was no significant difference in hematocrit, and in both groups of infants the mean hemoglobin levels were higher than those of normal birth weight infants. The differences in hemoglobin, although statistically significant, are of uncertain clinical significance. Median red cell folate levels remained within the normal adult range in both groups of infants. A minority of infants in the untreated group had low red cell folate levels but this was usually temporary, corrected by dietary folate, and not associated with low hemoglobin. Weight gain was not affected by folic acid supplementation. The infants in this trial were fed with a milk preparation containing 3.5 microgram/100 ml of folic acid which is a similar concentration to that of human milk and we recommend that the folate content of milks fed to low birth weight infants should not fall below this level. We do not have sufficient grounds to recommend routine folic acid supplements for all low birth weight infants throughout the first year of life but there is a possibility that their folate intake may sometimes be suboptimal.

Anemia, Macrocytic↗
PubMed1978

Mycoplasma pneumoniae infections in children.

Details are given of all serologically confirmed Mycoplasma pneumoniae infections in children referred to Bristol hospitals during an epidemic lasting 18 months. 44 children, many below school age, had lower respiratory infections. The majority had cough and malaise which had failed to respond to antibiotics given before referral. Chest x-rays showed no pathognomonic features: segmental or patchy consolidation was common; 3 cases of lobar consolidation. Cold agglutinins were raised in 9 out of 12 cases. In the majority of cases the total leucocyte count was normal and the absolute neutrophil count raised. Mean duration of symptoms was 4.2 weeks (range 1-16). Treatment with erythromycin or tetracycline appeared to have little effect in most cases. Seven nonrespiratory manifestations were seen in 6 children. These were meningitis (2 cases), Stevens-Johnson syndrome (4 cases, 1 case complicated by toxic epidermal necrolysis), and acute haemolytic anaemia (1 case).

Adolescent↗