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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
PubMed1984

Production of leukocyte migration inhibitory factor (LIF) in human lymphocyte subsets exposed to polyclonal activators.

Lymphocyte subsets separated on the basis of nylon-wool adherence and E and EA rosetting, and characterized for the presence of esterase-positive phagocytic cells were investigated for production of leukocyte migration inhibitory factor (LIF) in response to polyclonal T- and B-cell activators, PHA, ConA, PWM, and Epstein-Barr virus (EBV). In the nylon-passed population only the high avidity E+EA+ cells responded to ConA, PHA-induced LIF production in all E-rosetting subsets. The nylon-adherent E+ subset, which contains activated T cells, produced LIF spontaneously. B cells produced LIF when exposed to PWM or uv-inactivated EBV. In accordance with the known T-cell dependence of PWM activation, LIF was detected only in supernatants of reconstituted populations containing both B and T cells. In contrast, uv-inactivated EBV, devoid of transforming potential, elicited LIF production in the pure B-cell population. LIF production in response to polyclonal activators seemed to be independent of accessory cells since reconstitution with autologous macrophages or semipurified monokine, high-molecular-weight Interleukin 1 (IL-1), did not alter the results.

B-Lymphocytes↗
PubMed1984

Demonstration of uronic acid capsular material in the cerebrospinal fluid of a patient with meningitis caused by mucoid Pseudomonas aeruginosa.

A 39-year-old female with insulin-dependent diabetes mellitus developed Rhizopus infection of the maxillary sinus. Subsequent to successful treatment with amphotericin B and surgical debridement, she developed purulent meningitis due to a mucoid strain of Pseudomonas aeruginosa. Analysis of cerebrospinal fluid documented the presence of a uronic acid polymer at a concentration of 40 micrograms/ml. In spite of parenteral and intrathecal antibiotic therapy, the patient died. This case illustrates that mucoid strains of P. aeruginosa may result in fatal infection and that alginate capsule is produced in vivo in humans.

Adult↗
PubMed1984

Relationship between glucose and 20 alpha-hydroxysteroid dehydrogenase in fetal sheep erythrocytes.

We have examined whether glucose supply to fetal sheep erythrocytes limits the rate of 20 alpha-reduction of progesterone in blood and as such is associated with the progressive loss of 20 alpha-hydroxysteroid dehydrogenase activity which has been observed from 30 days before term. Enzyme activity in erythrocytes depleted of glucose by washing was regained in the presence of at least 0.167 mmol glucose/1. The cofactor NADPH was necessary to support the reaction in lysed cells. Addition of glucose to whole blood diluted 20-fold for assay of 20 alpha-hydroxysteroid dehydrogenase did not increase the rate of reaction. Infusion of dextrose to increase fetal plasma glucose concentrations had no effect on 20 alpha-hydroxysteroid dehydrogenase activity. Over the period from 114 to 137 days of gestation, both dextrose- and saline-infused fetuses showed a decline in enzyme activity from a combined mean of 1.45 +/- 0.21 (S.E.M.) to a mean of 0.78 +/- 0.18 mumol/ml erythrocytes per h. Fetal leucocytes did not contribute significantly to the activity of 20 alpha-hydroxysteroid dehydrogenase in whole blood. The rate of 20 alpha-reduction of progesterone in the blood of eight fetuses with indwelling carotid catheters declined from 2.31 +/- 0.09 mumol/ml erythrocytes per h at 90-95 days of gestation to 0.73 +/- 0.04 mumol/ml per h at 141-145 days. However, a consistent decline was only observed after 116-120 days. The apparent equilibrium position for progesterone reduction to 20 alpha-dihydroprogesterone varied between 83.9 +/- 1.8 and 65.7 +/- 4.2%.(ABSTRACT TRUNCATED AT 250 WORDS)

20-Hydroxysteroid Dehydrogenases↗
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↗