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Biomedical subjects

S London

Publications and source records attributed to S London.

At least 37 records · Page 2Linked to original sources
PubMed1998

DXplain: a Web-based diagnostic decision support system for medical students.

DXplain is a diagnostic decision support program, with a new World Wide Web interface, designed to help medical students and physicians formulate differential diagnoses based on clinical findings. It covers over 2000 diseases and 5000 clinical manifestations. DXplain suggests possible diagnoses, and provides brief descriptions of every disease in the database. Not all diseases are included, nor does DXplain take into account preexisting conditions or the chronological sequence of clinical manifestations. Despite these limitations, it is a useful educational tool, particularly for problem-based learning (PBL) cases and for students in clinical rotations, as it fills a niche not adequately covered by MEDLINE or medical texts. The system is relatively self-explanatory, requiring little or no end-user training. Medical libraries offering, or planning to offer, their users access to Web-based materials and resources may find this system a valuable addition to their electronic collections. Should it prove popular with the local users, provision of access may also establish or enhance the library's image as a partner in medical education.

Clinical Clerkship↗
PubMed1998

Can shoulder dystocia be predicted? Preconceptive and prenatal factors.

OBJECTIVE: To evaluate the predictability of shoulder dystocia using preconceptive and prenatal risk factors. STUDY DESIGN: Data from 1,622 term patients with prenatal care prior to 20 weeks who delivered single, vertex fetuses during a consecutive 12-month period were analyzed. Two groups were chosen. The first group was patients whose fetuses experienced shoulder dystocia during delivery (cases). The second group (controls) consisted of the remaining patients, whose fetuses had not experienced shoulder dystocia. The two groups were compared with regard to demographics and pregnancy characteristics. RESULTS: Factors not significantly different between the two groups included were obesity, multiparity, history of diabetes, short maternal stature, postdatism and advanced maternal age. The incidence of macrosomia was significantly higher (P < .001) in cases (35.4%) than in controls (4.8%). Other factors associated with shoulder dystocia were previous shoulder dystocia, concurrent diabetes, prior delivery of a fetus > 4,000 g and excessive weight gain during pregnancy. Many factors previously associated with shoulder dystocia were found to be nonsignificant in our study. CONCLUSION: Macrosomia appears to be the single important factor associated with shoulder dystocia which, even in the presence of significant risk factors, remains largely unpredictable.

Adolescent↗
PubMed1998

Sports medicine across Missouri: interviews with Dr. Paul Meyer and Dr. Stanley London. Interview by Thomas D. Eppright, Shane Bradley, Maureen Alwood.

Paul Meyer and Stanley London are two Missourians who have led the way for many in the field of Sports Medicine. The careers of many professional athletes have been extended due to the clinical expertise of these exemplary physicians who both began their medical careers in the 1940s. Through this interview, they offer a historical perspective of Sports Medicine and baseball. They also share their life experiences, as well as their formulas for successful careers and long-lasting marriages.

Baseball↗
PubMed1997

A pilot study of urinary estrogen metabolites (16alpha-OHE1 and 2-OHE1) in postmenopausal women with and without breast cancer.

The two main pathways for metabolizing estrogen are via 16alpha-hydroxylation and 2-hydroxylation. The 16alpha-hydroxy metabolites are biologically active; the 2-hydroxy metabolites are not. It is suggested that women who metabolize a larger proportion of their endogenous estrogen via the 16alpha-hydroxy pathway may be at significantly elevated risk of breast cancer compared with women who metabolize proportionally more estrogen via the 2-hydroxy pathway. In particular, it is suggested that the ratio of urinary 2-hydroxyestrone (2-OHE1) to 16alpha-hydroxyestrone (16alpha-OHE1) is an index of reduced breast cancer risk. This pilot study compared this ratio in postmenopausal women diagnosed with breast cancer to those of healthy controls. Urinary concentrations of estrone (E1), 17beta-estradiol (E2) and estriol (E3) were also quantified. White women who were subjects in a previous breast cancer case-control study at our institution were eligible for inclusion. All participants provided a sample of their first morning urine. The results from the first 25 cases and 23 controls are presented here. The ratio of 2-OHE1 to 16alpha-OHE1 was 12% lower in the cases (p=0.58). However, urinary E1 was 30% higher (p=0.10), E2 was 58% higher (p=0.07), E3 was 15% higher (p=0.48), and the sum of E1, E2, and E3 was 22% higher (p=0.16) in the cases. These preliminary results do not support the hypothesis that the ratio of the two hydroxylation metabolites (2-OHE1/16alpha-OHE1) is an important risk factor for breast cancer or that it is a better predictor of breast cancer risk than levels of E1, E2 and E3 measured in urine.

Breast Neoplasms↗
PubMed1996

Gamma radiation effect on vascular smooth muscle cells in culture.

PURPOSE: Prior work in our laboratory demonstrated that external gamma irradiation administered within 48 h following balloon catheter carotid artery injury in rats produced a marked inhibition of intimal hyperplasia and restenosis. The current study used smooth muscle cells (SMC) in vitro to examine the radiation dose response and to investigate the cellular mechanism by which radiation inhibits SMC proliferation. METHODS AND MATERIALS: Quiescent rat aortic SMC in plasma were refed with whole blood serum to stimulate synchronous proliferation and immediately irradiated with single fraction doses of 1.25-20 Gy. RESULTS: Comparison between a micronucleus assay and a clonogenic assay indicated a dose-dependent inhibition of SMC growth, with an ED50 at 2-3 Gy. The micronucleus assay also demonstrated a dose-dependent increase in apparent chromosomal damage at 72 h after irradiation. Inhibition of SMC growth by radiation did not correlate with changes in intracellular or released mitogenic activity. Furthermore, there was no evidence of apoptosis in irradiated SMC up to 96 h after treatment. CONCLUSION: Radiation likely inhibits SMC proliferation after arterial injury by a dose-dependent mechanism of lethal and/or sublethal cellular injury leading to clonogenic cell death.

Animals↗
PubMed1996

Reduction of intracellular glutathione levels produces sustained arterial narrowing.

OBJECTIVE: Although lipid peroxidation and alterations in endogenous antioxidants have been hypothesized to contribute to cerebral vasospasm after subarachnoid hemorrhage, there has been no direct evidence demonstrating the relationship between oxidative stress and delayed arterial narrowing. To elaborate the role of the endogenous intracellular antioxidant and electron exchanger glutathione (GSH) in cerebral vasospasm, rat femoral arteries were treated with perivascular application of I-buthionine-(SR)-sulfoximine (BSO), which inhibits the synthesis of GSH. METHODS: To determine the dose-response relationship, BSO at doses of 10 to 100 mg/ml, in platelet-rich plasma, was applied for 7 days to rat femoral arteries in vivo. Vessels were then perfusion-fixed for morphometric analysis of luminal cross-sectional area. To determine the time course of arterial narrowing, BSO (75 mg/ml) was applied to femoral arteries for 1, 3, 7, or 21 days before histological analysis, as described above. With rats treated with 50 to 100 mg/ml BSO, exogenous GSH (100 mg/kg) was administered, by intraperitoneal injection, daily for 7 days. To demonstrate the mechanism of BSO effects in smooth muscle cells (SMCs), cultured rat aortic SMCs were treated with 1 mmol/l BSO for 24 hours and assayed for intracellular levels of GSH and two products of lipid peroxidation, malondialdehyde and 4-hydroxyalkenal. RESULTS: Compared with control arteries treated with platelet-rich plasma alone, perivascularly administered BSO applied for periods of 1 to 21 days produced sustained and reversible narrowing of rat femoral arteries with a time course, severity, and histological appearance analogous to those observed after perivascular application of whole blood. BSO-induced arterial narrowing was dose-dependent, with 60% reductions in the luminal cross-sectional area being noted at 75 and 100 mg/ml (P < 0.005). Systemic administration of exogenous GSH slightly inhibited the effect of BSO on arterial narrowing, although the inhibition was not statistically significant. Cultured rat aortic SMCs exposed to BSO for 24 hours showed a 70% decrease in intracellular GSH levels (P = 0.03); levels of two products of lipid peroxidation, malondialdehyde and 4-hydroxyalkenal, were increased by 25% (P = 0.24) and 38% (P = 0.09), respectively. CONCLUSION: These data support the hypothesis that diminished intracellular levels of GSH may produce delayed chronic arterial narrowing after subarachnoid hemorrhage. The specific mechanism by which GSH levels modulate vasoconstriction remains uncertain but may involve endogenous antioxidant capacity in SMCs.

Animals↗
PubMed1995

Proportional melanoma incidence and occupation among white males in Los Angeles County (California, United States).

A case-control analysis of cancer registry data was used to examine the hypothesis that occupational exposure to sunlight influences the risk of melanoma. Occupation at diagnosis was available for 3,527 cutaneous melanomas and 53,129 other cancers identified by the Los Angeles County (California, United States) Cancer Surveillance Program among non-Spanish-surnamed White males aged 20 to 65 years between 1972 and 1990. Occupational exposure to sunlight was assessed by blinded expert coding of job titles as indoor, outdoor, and mixed indoor/outdoor. Relative to indoor occupations, proportionate odds ratios (OR) adjusted for age, level of education, and birthplace were 1.16 (95 percent confidence interval [CI] = 1.07-1.27) for indoor/outdoor occupations and 1.15 (CI = 0.94-1.40) for outdoor occupations. However, increasing levels of the education or training required for the occupation was associated more strongly with increased melanoma occurrence (ORs adjusted for age, occupational sun exposure, and birthplace, were 1.0, 1.63, 2.09, 2.23, and 2.99 for low-skill occupation, high school, college, postgraduate, and doctoral levels, respectively). Analysis of melanoma occurrence by job titles confirmed a clear variation by the required education or training level but not by the category of occupational sunlight exposure. The findings suggest that lifestyle factors associated with higher levels of education may be more important determinants of melanoma risk than characteristics of the work environment.

Adult↗
PubMed1995

The time course of myosin light-chain phosphorylation in blood-induced vasospasm.

The phosphorylation of an M(r) 20,000 myosin light chain (MLC20) promotes the generation of contractile force through actin-myosin adenosine triphosphatase in most agonist-mediated vascular smooth muscle cell contraction. However, the role of calcium-mediated contractile processes in sustained arterial narrowing after subarachnoid hemorrhage remains unknown. In a femoral artery model of vasospasm, whole blood was applied to arteries in 54 rats for periods of 2 to 10 days; the contralateral artery treated with platelet-rich plasma served as matched control. During the early stage of vasospasm (Days 2-5), in the media of arteries exposed to blood, MLC20 phosphorylation (including diphosphorylated forms) increased significantly (30-38%; P < 0.05); total medial MLC20 during this interval was comparable to that in controls. After 5 days, however, total MLC20 decreased markedly (> 90%; P < 0.01) compared with controls; phosphorylated MLC20 was undetectable during this interval. MLC20-mediated contractile processes may be prominent in the early stages of arterial narrowing after subarachnoid hemorrhage; later stages are associated with the loss of MLC20 and the possible persistence of arterial narrowing by other mechanisms.

Animals↗
PubMed1995

Antioxidant and iron-chelating agents in cerebral vasospasm.

Prior work in our laboratory showed that the perivascular application of deferoxamine (an antioxidant and iron-chelating agent) inhibited delayed arterial narrowing after chronic blood exposure in a rat femoral artery model of vasospasm. To determine which of these mechanisms was operant in vasospasm, we compared deferoxamine with two agents (ascorbic acid and U74389F) that have antioxidant but not iron-chelating capacity. For the systemic application of drugs in 23 rats, whole blood encased in a silastic cuff was applied to the right femoral artery of each rat; whole-blood serum (lacking erythrocytes) was similarly applied to the left femoral artery. Deferoxamine (30 mg/kg/d), ascorbic acid (1000 mg/kg/d), U74389F (30 mg/kg/d), or pH-matched control vehicle was administered three times daily by intraperitoneal injection for 7 days. After exposure to whole blood, arteries treated with intraperitoneal vehicle showed an 85% reduction in the lumen, compared with vessels exposed to erythrocyte-free serum (P < 0.001). Intraperitoneal ascorbic acid and U74389F produced moderate amelioration in arterial narrowing (53 and 61% decrease, respectively, in the lumen versus controls; P < 0.05 versus vehicle); deferoxamine had no significant effect when administered intraperitoneally. To test the efficacy of these agents by the perivascular application of drugs, whole blood was applied to both femoral arteries in each of 25 rats. Solutions of deferoxamine (10 mg/ml), ascorbic acid (50 or 100 mg/ml), or U74389F (15 or 30 mg/ml) were directly applied to the perivascular thrombus surrounding the femoral arteries, compared with vehicle applied to contralateral vessels. The perivascular application of 50 mg of ascorbic acid (36% reduction, P < 0.05), 100 mg of ascorbic acid (31% reduction, P < 0.01), or 10 mg of deferoxamine (41% reduction, P < 0.05) significantly inhibited arterial narrowing, compared with vehicle. The application of U74389F at a dose of 15 or 30 mg directly into the perivascular thrombus produced nonsignificant reduction in arterial narrowing. These data suggest that mechanisms other than direct iron toxicity, such as generation of cytotoxic free radicals, may play an important role in cerebral vasospasm. In addition, the route of administration and concentration of drugs in the perivascular region adjacent to the thrombus may be critical to their efficacy.

Animals↗
PubMed1995

Radiation inhibition of intimal hyperplasia after arterial injury.

To demonstrate the effect of gamma radiation on proliferating smooth muscle cells in vivo, a standardized bilateral carotid balloon catheter arterial injury was produced in 45 rats and doses from 0-20 Gy were delivered to the right carotid artery at 24 h after injury. At 20 days after injury, cross-sectional area of intima was determined from axial histological sections. Compared to contralateral, nonirradiated balloon-injured arteries, radiation produced a significant dose-dependent reduction in intimal cross-sectional area, with a 50% decrease at 5-7.5 Gy. To determine the effect of timing of irradiation on intimal hyperplasia, 30 rats with bilateral carotid injury received unilateral cervical irradiation at doses of 1, 5 or 10 Gy administered at either 1, 3 or 5 days after injury. The radiation dose (P = 0.0002), timing of irradiation (P = 0.003) and an interaction between timing and dose (P = 0.0278) were significantly associated with reduction in neointimal cross-sectional area. To determine the effects of radiation on intimal hyperplasia at later intervals, rats irradiated with 15 (n = 5) or 20 Gy (n = 5) were euthanized at 3 months after injury. A significant persistent reduction in intimal cross-sectional area for irradiated arteries at 3 months was associated with minimal apparent radiation effects upon adjacent tissue. These data suggest that external gamma irradiation at the single doses used effectively inhibits smooth muscle proliferation and intimal hyperplasia in the rat balloon catheter injury model in a time- and dose-dependent manner.

Angioplasty, Balloon↗
PubMed1993

Endometriosis and ascites.

A 29-year-old black woman had increasing abdominal girth, dullness to percussion, and an irregular mass in the left adnexal region. At laparotomy, 6 L of dark brown fluid was removed, and the abdominal cavity had the appearance of extensive carcinomatosis. Subsequent histology was consistent with endometriosis. Fourteen cases of endometriosis producing symptoms resembling ovarian cancer have been previously reported. Of the 10 patients whose race was mentioned, 9 were black, as was our patient. The etiology of the ascites is unknown. Histologically, the endometrial implants show dense stroma and a slightly hyperplastic epithelium rather than the physiologic proliferative endometrium usually associated with endometriosis. This leads us to question the prognosis of the lesion despite its apparently benign histology.

Adult↗
PubMed1992

Reproductive factors, exogenous female hormones, and colorectal cancer by subsite.

The associations between reproductive factors, exogenous hormones, and colorectal cancer were examined among female subjects in a population-based case-control study in Sweden. The study was performed in Stockholm in 1986-88, and included 299 cases and 276 controls. There was little evidence that age at first birth, number of months of breast feeding, age at menarche, or age at menopause influenced the risk of colon or rectal cancer. However, the results indicate that postmenopausal hormone-replacement therapy might reduce the risk of colorectal cancer (age-adjusted relative risk [RR] = 0.4, 95 percent confidence interval [CI] = 0.2-0.9). Compared with nulliparous women, women with at least four births were at reduced risk for colon cancer (RR = 0.5, CI = 0.2-1.2) but not rectal cancer (RR = 1.0, CI = 0.4-2.6). However, no trend across increasing parity was observed. Adjustments for diet, body mass, and physical activity had little influence on the results.

Age Factors↗
PubMed1991

Parental occupational exposures and risk of childhood cancer: a review.

We reviewed the literature in order to summarize the present knowledge on the association between parental occupational exposures to chemicals and the risk of childhood malignancy. The 32 studies pertaining to this topic were evaluated by considering various study qualities such as sample size, specificity of outcome, confounding, exposure specificity, and control selection. When evaluating the findings from any epidemiologic study, the potential sources of bias have to be considered. The selection of subjects, misclassification of exposure or outcome, and confounding from extraneous factors can contribute to a biased estimate of effect. Studies done to minimize these potential biases will be more valid, and these studies should be given the most weight when parental occupational exposures are evaluated as risk factors for childhood malignancy. We conclude that the preponderance of evidence supports the hypothesis that occupational exposure of parents to chemicals increases the risk of childhood malignancy. The parental occupational exposures implicated in childhood malignancy risk are exposure to chemicals including paints, petroleum products, solvents (especially chlorinated hydrocarbons) and pesticides, and exposure to metals. The available data do not allow the identification of specific etiologic agents within these categories of compounds. Future epidemiologic and toxicologic studies should be designed to pursue these leads.

Chemical Industry↗
PubMed1991

Alcohol and other dietary factors in relation to serum hormone concentrations in women at climacteric.

The relationships between concentrations of endogenous hormones in serum and dietary intakes of alcohol, fats, fiber, and caffeine were examined in 325 healthy Massachusetts women aged 50-60 y who reported having a normal menstrual period within the previous 12 mo. Diet was assessed by a semiquantitative food frequency questionnaire. Hormones assayed were estrone, estradiol, percent free estradiol, sex-hormone-binding globulin (SHBG), cortisol, and gonadotropins. Alcohol intake was not associated with concentrations of estrogens or gonadotropins. Neither total fat intake nor the fat composition of the diet influenced hormone concentrations. Fiber intake was positively correlated with SHBG; no associations with estrogens were seen. Caffeine intake was inversely correlated with free estradiol and positively correlated with SHBG. These data suggest that fat, fiber, and alcohol intakes of US women at climacteric are not determinants of variations in estrone and either total or percent free estradiol.

Alcohol Drinking↗
PubMed1991

Lead exposure at uncovered outdoor firing ranges.

Excessive lead exposure in shooting instructors at indoor firing ranges and covered outdoor firing ranges has been documented. The City of Los Angeles assessed exposure of its full-time shooting instructors at uncovered outdoor ranges via air monitoring and blood lead-level measurements. Results of these tests revealed that significant lead exposure and absorption can occur at outdoor firing ranges. The use of copper-jacketed ammunition may decrease air lead levels and decrease lead absorption by range instructors.

Air↗