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Biomedical subjects

L Vaughan

Publications and source records attributed to L Vaughan.

68 records · Page 4Linked to original sources
PubMed1981

Pantothenic acid content of human milk.

One-day diets were recorded by 22 lactating women 1 to 6 months postpartum. Pantothenic acid content of the diets was estimated using a published table of pantothenic acid values for food. The mean pantothenic acid intake of the lactating women was 7.6 mg/day over the 6-month period. The day after diet recording, the women collected two samples of breast milk during the first feeding of the day after 5 AM. The first sample was obtained at the beginning of the feed (fore milk) and the second at the end of the feed (hind milk). The pantothenic acid in the milk was determined by microbiological assay using Lactobacillus plantarum, after prior treatment of the milk with intestinal phosphatase and pigeon liver extract to free bound pantothenic acid. There was no significance acid in the milk was 6.7 microgram/ml. No change occurred in the concentration of pantothenic acid in the milk from 1 to 6 months postpartum. There was a significant (p less than 0.005), positive correlation (r = 0.51) between the pantothenic acid in the diet of the mother the day preceding milk collection and the pantothenic acid content of the milk.

Adult↗
PubMed1980

Section of the pituitary stalk in the rhesus monkey. I. Endocrine studies.

The effects of pituitary stalk section on anterior pituitary secretion were studied in 20 female rhesus monkeys. Vascular connections between the hypothalamus and the pituitary gland were permanently interrupted in all but 4 animals. Prolactin levels rose rapidly and remained significantly elevated in all effectively stalk-sectioned animals for as long as the observation period (up to 3 years). Only smaller and transient elevations of prolactin were seen in the animals in which revascularization of the anterior pituitary gland had occurred. Growth hormone and cortisol were significantly decreased after stalk section, and were not released by insulin. Radioimmunoassayable luteinizing hormone (LH) levels decreased following surgery and, by bioassay, LH became undetectable within 5 weeks after stalk section, indicating that gonadotropin-releasing hormone is essential for the viability of the gonadotrope. The results indicate that plasma prolactin concentrations can be used to monitor completeness of pituitary gland isolation from direct hypothalamic influence. Stalk-sectioned monkeys provide good models to study direct pituitary effects of various hormones or drugs.

Animals↗
PubMed1980

The reliability of serum theophylline determinations from clinical laboratories.

Three aliquots of pooled serum containing theophylline and disguised as patient specimens were sent, one at a time, on different days, to 29 community hospital and referral laboratories serving Iowa. The mean +/- SEM concentration of 65 replications for the same serum pool was 15.7 +/- 0.1 microgram/ml. Twenty-eight per cent of the 85 measurements reported by the clinical laboratories were outside the acceptable range of 13.2 to 18.1 microgram/ml established by the 95% confidence limits of the assayed pool. Reliability of the results was not related to the type of facility, method of measurement, or fee charged. Therefore, variation in clinical laboratory performance was a result of technician error in handling or analyzing the specimens. We conclude that measurements of serum theophylline can only be relied on to adjust dosage when the accuracy of the laboratory has been established with blinded samples.

Double-Blind Method↗
PubMed1980

Effect of estrogen on thyrotropin-releasing hormone-induced release of prolactin in intact, ovariectomized, and stalk-sectioned female rhesus monkeys.

The effects of estrogen treatment on basal and TRH-induced serum PRL concentrations were studied in three groups of four female rhesus monkeys; intact monkeys, ovariectomized animals, and monkeys in which the pituitary gland had been isolated from direct hypothalamic influences by pituitary stalk section. The TRH tests (50 microgram, iv) were performed before and 7 and 21 days after the sc implantation of one or two 3-cm long silastic capsules containing 17 beta-estradiol. Treatment with estradiol significantly increased the PRL response to TRH in the three groups of animals. The highest PRL response to TRH was observed after stalk section. The estrogen treatment also increased basal PRL concentrations in stalk-sectioned monkeys but no statistically significant increase was observed in intact or ovariectomized animals. These results indicate that physiological amounts of estradiol increase the magnitude of TRH-induced PRL release in rhesus monkeys, and that this estrogen effect is probably enacted directly at the level of the anterior pituitary gland.

Animals↗
PubMed1975

Energy-dependent endocytosis in erythrocyte ghosts. IV. Effects of Ca2+, Na+ +K+, and 5'-adenylylimidodiphosphate.

The requirement of actual splitting of ATP for endocytosis in erythrocyte ghosts has been confirmed by use of the ATP analog, 5'-adenylylimidodiphosphate, (AMP-P(NH)P). This compound, in which the oxygen connecting the beta and gamma phosphorus atoms was replaced by an NH group, did not cause endocytosis nor was it a substrate for ATPase activity. AMP-P(NH)P was a competitive inhibitor both for the endocytosis and the Mg2+-ATPase activities. The K1 of AMP-P(NH)P for Mg2+ ATPase activity was 2.0 - 10-4 M and, while the Km of ATP for this activity was also 2.0 - 10-4 M indicating nearly identical affinities of ATP and AMP-P(NH)P for the active site. ADP, or ADP plus orthophosphate, did not cause endocytosis, showing that endocytosis was not due to binding of the products of ATP hydrolysis. Sodium or potassium ion or ouabain had no effect on endocytosis, which eliminated the possibility of involvement of the Na+, K+ ATPase in the endocytosis process. Calcium could not be substituted for magnesium; rather it inhibited endocytosis at the concentration of 1 - 10-3 M. EGTA relieved the inhibitory effect of Ca, which indicated that the binding of calcium to the membrane was reversible. These experimental results reaffirm the conclusion that ATP must be split to engender endocytosis under these conditions. Some characteristic parameters of the hemoglobin-free porcine erythrocyte ghosts were studied in order to characterize the system more adequately.

Acetates↗
PubMedDate not supplied

Dose dependency for absorption and elimination rates of theophylline. Implications for studies of bioavailability.

Dose dependency for absorption and elimination rates of theophylline were examined by administering 2-mg/kg and 6-mg/kg doses of a theophylline solution to 8 adult volunteers. The area under the concentration-time curve extrapolated to infinity after the lower dose was 84% of that calculated after the higher dose. This is associated with a decrease in the slope of the terminal portion of the elimination curve to varying degrees after the higher dose in all 8 patients (p less than 0.001). A significantly smaller fraction of the higher dose was absorbed at 15 minutes (0.46 vs. 0.77, p less than 0.002), but the differences were trivial by 30 to 45 minutes. Dose dependency for elimination may cause changes in a steady-state serum concentration during multiple dosing that is disproportionately larger than changes in dosage. In addition, the slower elimination at higher serum concentrations may confound the assessment of bioavailability of slow-release formulations when the doses used result in a substantial disparity in the range of serum concentrations attained for the slow-release formulation and the reference. The use of unequal doses adjusted to provide similar peak serum concentrations appears to minimize this potential error.

Absorption↗
PubMedDate not supplied

Preseason strength and flexibility imbalances associated with athletic injuries in female collegiate athletes.

One hundred thirty-eight female collegiate athletes, participating in eight weightbearing varsity sports, were administered preseason strength and flexibility tests and followed for injuries during their sports seasons. Strength was measured as the maximal isokinetic torque of the right and left knee flexors and knee extensors at 30 and 180 deg/sec. Flexibility was measured as the active range of motion of several lower body joints. An athletic trainer evaluated and recorded injuries occurring to the athletes in practice or competition. Forty percent of the women suffered one or more injuries. Athletes experienced more lower extremity injuries if they had: 1) a right knee flexor 15% stronger than the left knee flexor at 180 deg/sec; 2) a right hip extensor 15% more flexible than the left hip extensor; 3) a knee flexor/knee extensor ratio of less than 0.75 at 180 deg/sec. There was a trend for higher injury rates to be associated with knee flexor or hip extensor imbalances of 15% or more on either side of the body. These data demonstrate that specific strength and flexibility imbalances are associated with lower extremity injuries in female collegiate athletes.

Adolescent↗
PubMedDate not supplied

Red foxes (Vulpes vulpes) in Ireland as hosts for parasites of potential zoonotic and veterinary significance.

Intestinal washes, faecal flotations and serological examinations for antibodies to Toxoplasma gondii and Neospora caninum were used to assess the prevalence of parasites in carcases of foxes killed on roads or shot in the Dublin area and surrounding counties. The ascarids Uncinaria stenocephala and Toxocara canis were prevalent, as was the trematode Alaria alata. Taenia species, eggs of Capillaria species and sporocysts of Sarcocystis species were also found. Only one fox out of 70 examined was seropositive for N. caninum, whereas 24 of 51 were seropositive for T. gondii.

Ancylostomatoidea↗