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Biomedical subjects

T Lloyd

Publications and source records attributed to T Lloyd.

At least 55 records · Page 3Linked to original sources
PubMed1994

Supplementation trials with calcium citrate malate: evidence in favor of increasing the calcium RDA during childhood and adolescence.

The vast majority of peak adult bone mass is accumulated by the time longitudinal growth is complete. As peak bone mass is an important determinant of future fracture risk, the goal of the current calcium recommended dietary allowance during youth is to provide a calcium intake that allows individuals to reach their full genetic potential for acquiring skeletal mass. The advent of controlled trials of calcium supplementation and total body bone mass measurements in children and adolescents provide the first direct way of determining the amount of calcium necessary to achieve optimal skeletal accretion. These studies indicate that the current RDAs are insufficient to support optimal bone mass gain during growth and development. Based on the recent intervention trials, recommendations are made for an RDA of 1250 mg during childhood and 1450 mg during adolescence. These values are consistent with established calcium balance intake thresholds for growth during pre-adolescence and adolescence.

Adolescent↗
PubMed1993

Calcium supplementation and bone mineral density in adolescent girls.

OBJECTIVE: To evaluate the effect of calcium supplementation on bone acquisition in adolescent white girls. DESIGN: A randomized, double-blind, placebo-controlled trial of the effect of 18 months of calcium supplementation on bone density and bone mass. SUBJECTS: Ninety-four girls with a mean age of 11.9 + 0.5 years at study entry. SETTING: University hospital in a small town. INTERVENTIONS: Calcium supplementation, 500 mg/d calcium as calcium citrate malate; controls received placebo pills. MAIN OUTCOME MEASURES: Bone mineral density and bone mineral content of the lumbar spine and total body were measured by dual-energy x-ray absorptiometry and calcium excretion from 24-hour urine specimens. RESULTS: Calcium intake from dietary sources averaged 960 mg/d for the entire study group. The supplemented group received, on average, an additional 354 mg/d of calcium. The supplemented group compared with the placebo group had greater increases of lumbar spine bone density (18.7% vs 15.8%; P = .03), lumbar spine bone mineral content (39.4% vs 34.7%; P = .06), total body bone mineral density (9.6% vs 8.3%; P = .05), and 24-hour urinary calcium excretion (90.4 vs 72.9 mg/d; P = .02), respectively. CONCLUSIONS: Increasing daily calcium intake from 80% of the recommended daily allowance to 110% via supplementation with calcium citrate malate resulted in significant increases in total body and spinal bone density in adolescent girls. The increase of 24 g of bone gain per year among the supplemented group translates to an additional 1.3% skeletal mass per year during adolescent growth, which may provide protection against future osteoporotic fracture.

Absorptiometry, Photon↗
PubMed1993

Pneumoscrotum.

Pneumoscrotum is a rare condition that receives little discussion in standard texts of urology. The variety of possible etiologies for this condition include air accumulation from lung or retroperitoneal sources, surgical manipulations, or infection with gas-producing organisms. We report the case of a 79-year-old patient with pneumoscrotum who presented to the emergency department complaining of a swollen scrotum. Although Fournier's gangrene was suspected and the patient was taken to surgery, a small right apical pneumothorax that was not appreciated before surgery later was determined to have caused the pneumoscrotum. The process by which air may accumulate in the scrotum as well as differential diagnosis and treatment are discussed.

Aged↗
PubMed1992

Determinants of bone density in young women. I. Relationships among pubertal development, total body bone mass, and total body bone density in premenarchal females.

Bone mass accretion during puberty appears to be critical in the development of peak bone mass, which, in turn, is believed to be a major determinant of osteoporosis risk. Although genetics may be the primary determinant of peak bone mass, modifiable secondary factors, such as nutrition and hormone exposure, may significantly affect bone mass accretion during the second decade of life. As part of a longitudinal study of major determinants of bone development during puberty, we obtained cross-sectional measurements from 112 premenarchal caucasian females (mean +/- SD age, 11.9 +/- 0.49 yr at study entry). Total body bone mineral density (TBBMD) and total body bone mineral content (TBBMC) were measured by dual energy x-ray absorptiometry and compared to anthropometric, pubertal development, urinary steroid and gonadotropin levels, and nutrient intake. An integrated estrogen exposure index was developed and used to evaluate the cumulative effect of circulating estrogen levels on both development. Compared to normative reference data for adults, our subjects possessed 90% of adult height, 68% of adult weight, 83% of adult TBBMD, and 53% of TBBMC. The strongest combined predictors of prepubertal TBBMD and TBBMC were body weight, followed by height and pubertal development. Urinary estradiol levels were positively correlated with dietary intake of iron and vitamin B6.

Adolescent↗
PubMed1992

Measurement of bone mineral content and bone density in healthy twelve-year-old white females.

Bone mineral content (BMC) and bone mineral density (BMD) measurements were made by dual-energy x-ray absorptiometry (DEXA) in 112 healthy 12-yr-old white girls for the purposes of: (1) establishing reference data on total-body mineral content of 12-yr-old girls and (2) comparing the lumbar spinal bone density values from a dedicated scan with the lumbar region of interest bone density values from a whole-body scan. Total BMC ranged from 799 g to 2083 g with mean and median values of 1276 g and 1218 g. Total-body bone density ranged from 0.75 to 1.03 g/cm2 with mean and median values of 0.88 and 0.87 g/cm2. The mean and median lumbar bone density values from the lumbar scan mode were 0.74 and 0.73 g/cm2 and were not significantly different from the mean and median lumbar bone density values of 0.71 and 0.70 g/cm2 obtained from the region of interest data from the total-body scan. These results establish baseline bone mass and bone density values for our longitudinal study of bone accretion in young women and validate the use of lumbar vertebral bone density values obtained from whole-body scans.

Absorptiometry, Photon↗
PubMed1991

Menstrual differences due to vegetarian and nonvegetarian diets.

We studied 41 nonvegetarian and 34 vegetarian premenopausal women whom we closely screened. The two groups were indistinguishable with respect to height, weight, body mass index, and menarche. The incidence of menstrual irregularity was 4.9% among nonvegetarians and 26.5% among vegetarians (P = 0.009). The vegetarian group consumed significantly greater amounts of polyunsaturated fatty acids, carbohydrates, vitamin B-6, and dietary fiber whereas the nonvegetarians reported greater intakes of saturated fatty acids, protein, cholesterol, caffeine and alcohol. Logistic-regression analyses showed that the probability of menstrual regularity among all study subjects (n = 75) was positively associated with increasing protein/kJ and increasing cholesterol/kJ intakes. The probability of being menstrually regular was negatively associated with increasing dietary fiber/kJ and increasing magnesium/kJ intakes. These results are consistent with the notion that menstrual regularity can be influenced by specific dietary nutrients that may have direct effects or exert their effects by modulating circulating sex steroid status.

Adolescent↗
PubMed1991

Urinary hormonal concentrations and spinal bone densities of premenopausal vegetarian and nonvegetarian women.

We evaluated the relationships among nutrition, hormone concentrations, and bone density of the spine in 27 vegetarian and 37 nonvegetarian premenopausal women. The two groups were indistinguishable with respect to age, height, weight, menarche, years of formal education, and medical histories. The frequency of menstrual irregularity was significantly higher in the vegetarian group. The bone densities of the vegetarians and the nonvegetarians were not significantly different. Caffeine intake in both groups had a positive effect on urinary calcium excretion, but no association was observed between bone density and caffeine intake. Total fat, monosaturated fat, and oleic acid intake were positively associated with luteinizing hormone concentrations of the vegetarians only. Overall, the differences in dietary practices of these premenopausal vegetarian and nonvegetarian women did not appear to have major effects on bone biology or reproductive history.

Adult↗
PubMed1990

The association between students' research involvement in medical school and their postgraduate medical activities.

The authors examined the impact of students' research involvement during medical school on their postresidency medical activities. The three medical schools involved--The Pennsylvania State University College of Medicine (PSU), The University of Connecticut School of Medicine (UCONN), and The University of Massachusetts Medical School (UMASS)--have nearly indistinguishable applicant, matriculant, and curriculum profiles. However, at PSU a research project is a curriculum requirement for students who did not do medical research prior to entering medical school. Questionnaires were sent to all graduates from the classes of 1980, 1981, and 1982. A total of 567 graduates completed the questionnaires, an overall response rate of approximately 76%. Medical school research experience was reported by 83% (183) of the PSU graduates, 34% (52) of the UCONN graduates, and 28% (54) of the UMASS graduates. When compared on a school-by-school basis, the graduates from the three schools did not differ with respect to residency specialty training, fellowship training, academic appointments, career practice choices, or postgraduate research involvement. However, when all the graduates studied were examined as a single group, medical school research experience was found to be strongly associated with postgraduate research involvement.

Academic Medical Centers↗
PubMed1989

Long-term oral contraceptive use does not affect trabecular bone density.

To determine whether long-term exposure to exogenous estrogen in oral contraceptives influences trabecular bone mass in premenopausal women, we studied 25 closely matched, healthy, premenopausal women, who were recruited from an active obstetrics and gynecology practice. Eleven women had never used oral contraceptives, and 14 women had used oral contraceptives for a minimum of 67 months. All oral contraceptive users had used preparations that provided a minimum of 50 micrograms mestranol per day. Trabecular bone density was determined by quantitative single-energy computerized tomography of the L1-3 lumbar vertebral bodies. Trabecular bone density was similar for both the control group and the oral contraceptive users, 160.6 +/- 6.9 versus 161.2 +/- 7.4 mg/ml, respectively. The power to detect a 15% difference in bone density between these two samples was 0.87. We concluded that long-term, premenopausal oral contraceptive use has no effect on vertebral bone density.

Absorptiometry, Photon↗
PubMed1989

Determination of peak trabecular bone density: interplay of dietary fiber, carbohydrate, and androgens.

To elucidate mechanisms linking nutrition and sex hormones to magnitude of peak trabecular bone density, we studied 11 normal women aged 19-21 y. Trabecular bone density was related inversely to dietary fiber (r = -0.69, p = 0.02) and carbohydrate (r = -0.70, p = 0.02) and directly to serum free-and-albumin-bound testosterone (fab T) (r = -0.70, p = 0.02) and total testosterone (total T) (r = 0.66, p = 0.03). Dietary fiber was correlated negatively with fab T (r = -0.74, p = 0.009), total T (r = -0.70, p = 0.02), and androstenedione (Adione) (r = -0.72, p = 0.01). Controlling for the effect of fab T or Adione weakened the relationship between dietary fiber and bone density and the relationship was no longer statistically significant. Conversely, controlling for sex hormones did not abolish the effect of carbohydrate on bone density. The contributions of fab T and carbohydrate to bone density were independent. These results suggest that dietary fiber may depress serum androgens which in turn decrease trabecular bone density. Carbohydrate may also depress bone density but independently of sex steroid hormones.

Adult↗
PubMed1989

Designing and implementing a computer learning center in a college of medicine.

This report describes the approach taken at the Penn State College of Medicine to develop a central Computer Learning Center (CLC) and the use characteristics during the first 21 months of operation. A task force was created to establish the CLC, and a 12-month timetable was used from initial planning until the CLC was operational. In the first 21 months of operation, the CLC use increased linearly from 48 users per month to 388 users per month. More than half of the users were medical students, with the remainder distributed among faculty, staff, graduate students, nursing students, and medical residents. The growth of CLC use and the diversity of computer-assisted applications have occurred due to its central location within the medical center library and to CLC operation being shared by the library and the Department of Educational Resources.

Computer User Training↗
PubMed1988

Early vertebral trabecular bone loss in normal premenopausal women.

The precise timing for the onset of trabecular bone loss in women is a matter of controversy. To address this issue, we studied the relationship between age and vertebral trabecular bone density (measured by computed tomography) in 74 healthy premenopausal women from 18 to 48 years old. We also measured radial cortical bone density (by single photon absorptiometry) in 28 of these subjects. Trabecular bone density levels (milligrams per milliliter, mean +/- standard error of the mean, SEM) were significantly (p less than 0.05) higher in the second (178 +/- 8) and third (171 +/- 6) decades than in the fourth (158 +/- 4) or fifth (140 +/- 12) decades, and were inversely correlated with age (r = -0.39, p = 0.0006), diminishing at a rate of 1.3 mg/ml (0.73%) per year. Radial cortical bone density levels (grams per square centimeter) were similar in the third (0.711 +/- 0.021), fourth (0.721 +/- 0.012), and fifth (0.736 +/- 0.012) decades and were not related to age (r = 0.17, p = 0.39). We conclude that vertebral trabecular bone loss in women commences during or prior to the third decade. In contrast, radial cortical bone density does not decline during the premenopausal years.

Adolescent↗
PubMed1988

Determinants of peak trabecular bone density in women: the role of androgens, estrogen, and exercise.

To elucidate determinants of peak trabecular bone density, we studied the role of androgens, estrogen, and aerobic exercise in 30 women from 18 to 22 years old. The women were divided into three groups: Sedentary, 11 normal women who did not exercise regularly; eumenorrheic, 10 athletes with normal menstrual function; and oligomenorrheic, 9 athletes with exercise-induced oligomenorrhea. All athletes participated in aerobic sports that did not involve selective resistance loading of the back. Serum free and albumin-bound testosterone (fab T), androstenedione (A), and estradiol (E2) were measured on four separate occasions at consecutive 7 day intervals and averaged. Trabecular density was measured by quantitative computed tomography of the lumbar spine. Peak trabecular bone density was related to fab T (r = 0.48, p = 0.007), A (r = 0.40, p = 0.03), and E2 (r = 0.40, p = 0.04). When taken in combination, androgens and estrogen each accounted independently for significant portions of the variance in bone density [fab T and E2 (R2 = 0.38, p = 0.002) and A and E2 (R2 = 0.27, p = 0.01)]. Bone density (mg/ml, mean +/- standard error of the mean, SEM) in the sedentary group (174 +/- 6) was not significantly different from that in the eumenorrheic (183 +/- 12, p = 0.47) or oligomenorrheic (161 +/- 11, p = 0.32) subjects. We conclude that androgens and estrogen function as independent and additive determinants of peak trabecular bone density in young women. The quantitative impact of aerobic exercise (without resistance loading) and exercise-induced menstrual dysfunction appears to be less important than that of the hormones.

Adolescent↗
PubMed1988

Collegiate women athletes with irregular menses during adolescence have decreased bone density.

We studied six eumenorrheic and 13 oligomenorrheic collegiate women athletes who were matched in all respects other than menstrual histories. There was a significant (P less than .05) association between menstrual regularity and bone density. The severely oligomenorrheic subjects had modestly decreased plasma estrogen levels. These findings support the notion that plasma estrogen levels during adolescence play a significant role in the development of peak adult bone density in women.

Adolescent↗
PubMed1987

Adrenal androgens, sex-hormone binding globulin and bone density in osteoporotic menopausal women: is there a relationship?

The relationships among sex steroids, sex hormone binding globulin (SHBG) and vertebral bone density as measured by computerized tomography were studied in 18 post-menopausal women. A significant negative correlation was found between SHBG binding capacity (SHBG-BC) and bone density. Bone density and the adrenal androgen dehydroepiandrosterone sulfate (DHEAS) declined with age, and SHBG-BC was correlated significantly with DHEAS concentrations. The relationship between SHBG-BC and bone density may be affected by adrenal androgen output.

Adrenal Cortex Hormones↗
PubMed1987

Interrelationships of diet, athletic activity, menstrual status, and bone density in collegiate women.

We undertook a case-control study to examine the effect of nutritional factors on menstrual function and bone density in collegiate athletes. Three groups, matched with respect to age, height, and weight, were studied: eumenorrheic collegiate athletes, oligomenorrheic collegiate athletes, and eumenorrheic sedentary collegiate control subjects. Menarche was delayed in the eumenorrheic (13.1 y) and oligomenorrheic (14.3 y) athletic groups compared with the sedentary control subjects (12.2 y) (p less than 0.05). Average bone density tended (p = 0.10) to be lower in the oligomenorrheic athletes (158 mg/mL) compared with the eumenorrheic athletes (184 mg/mL) or sedentary control subjects (173 mg/mL). Dietary fiber intake was significantly elevated (p less than 0.05) in the oligomenorrheic athletes (5.74 g/d) compared with the eumenorrheic athletes (3.62 g/d) or sedentary control subjects (2.97 g/d). We conclude that increased dietary fiber intake is associated with menstrual dysfunction of these collegiate athletes. These factors may contribute to decreased bone density.

Adult↗
PubMed1987

The effect of age and hair colour on human hairbulb tyrosinase activity.

We studied tyrosinase activity from human hairbulbs from 51 subjects, aged 5-72 years. We used anagen hairbulbs and grouped the subjects according to hair colour. We did not observe an age-dependent fall in hairbulb tyrosinase activity. We observed considerable inter-individual variation in activity, with a range of 8-342 pmol DOPA formed/three hairbulbs/30 min. The mean tyrosinase activity from red hairbulbs was significantly higher than the mean for the other hair colours. White hairbulbs did not express tyrosinase activity, and specific antibodies to tyrosinase were used to establish that tyrosinase antigen was absent from white hairbulbs.

Adolescent↗