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Biomedical subjects

M Wei

Publications and source records attributed to M Wei.

At least 91 records · Page 5Linked to original sources
PubMed1997

Serum leptin levels in Mexican Americans and non-Hispanic whites: association with body mass index and cigarette smoking.

Leptin is the protein product of the obesity (OB) gene in humans. To date, no study has correlated serum leptin levels with ethnicity, cigarette smoking, or other cardiovascular risk factors. In this study, serum leptin levels were measured in 100 Mexican Americans and 50 non-Hispanic whites who participated in the San Antonio Heart Study. Mexican Americans had higher levels of serum leptin than age- and sex-matched non-Hispanic whites (21 vs. 16 ng/mL). However, the leptin levels were similar in the two groups after controlling for body mass index (BMI). Women had higher levels of serum leptin than did men (24 vs. 9 ng/mL; P < .0001). There was a strong association between leptin levels and BMI (r = 0.91 in non-Hispanic white men; r = 0.77 in non-Hispanic women; r = 0.81 in Mexican American men; and r = 0.78 in Mexican American women). A model containing age, sex, and BMI explained 79% of the variance in serum leptin levels. After adjustment for age, sex, and BMI, current cigarette smokers had significantly lower leptin levels than never-smokers (p < 0.05). The results suggested that human obesity was associated with leptin-resistance rather than leptin-deficiency. Leptin levels were positively associated with BMI in this cross-sectional analysis. Cigarette smoking may increase sensitivity to leptin, since cigarette smokers had lower leptin levels than did nonsmokers with the same BMI.

Adipose Tissue↗
PubMed1997

[Prophylactic effects of magnesium sulfate and ligustrazin on the hypoxic-ischemic brain damage in neonatal rats].

OBJECTIVE: A model in neonatal rats was established to study pathophysiology of perinatal hypoxic-ischemic brain damage. METHODS: 7-9 day old Wistar rats were subjected to unilateral carotied artery ligation followed by hypoxic state for 3 hours (10% O2 + 90% N2, at 37 degrees C). Magnesium sulfate (0.5 mg/gBW) and ligustrazin (0.1 mg/gBW) was separately given a 30 min before hypoxia. Superoxide dismutase (SOD) and malonic dialdehyde (MDA) in the cerebral cortex and serum MDA were measured immediately after hypoxia. Neuropathologic examination was made in 4 weeks after hypoxia. RESULTS: It was found that SOD and MDA in the cerebral cortex and serum MDA in the hypoxicischemic group were significantly increased in comparision with the normal control group (P < 0.01), and that all these parameters either in the magnesium sulfate group or in the ligustrazin group were lower than in the hypoxic-ischemic group (P < 0.05). The hypoxic-ischemic group showed that there were neuronal degenerations in the gray matter, hippocampus and cerebellum which were reduced in the two treatment groups. CONCLUSION: Our results indicate that oxide free radical formation is one of the pathogenic factors of perinatal hypoxic-ischemic brain damage and magnesium sulfate and ligustrazin reduce hypoxicischemic brain damage due to indirect anti-oxidation.

Animals↗
PubMed1997

[Regeneration of functionally active rat brain muscarinic receptor in vitro after inhibition with methylmercury chloride].

The effect of methylmercury on muscarinic receptors and the regeneration of functionally active muscarinic receptor in vitro by antagonists were investigated. The result showed that methylmercury chloride (MMC) inhibited the binding of [3H] QNB to muscarinic receptor of rat brain-lysed synaptosomes, with IC50 values of 4.18 mmol/L. Regeneration of functionally active rat brain muscarinic receptors after inhibition with methylmercury was achieved by 2,3-dimercapto-1-propanesulfonc acid, Na salt (DMPS) dithiothreitol (DTT), glutathione (GSH) and Cysteine. Blocking the sulfhydryl groups is suggested to be the molecular mechanism of inhibition of brain muscarinic receptors by methylmercury. Our results provide evidence that thiols chelate out mercuric cations that tightly bound to sulfhydryl groups in muscarinic receptor binding sites and regenerate [3H] QNB binding activity.

Animals↗
PubMed1997

High responsiveness of cytosolic free calcium concentration to angiotensin II in cultured pulmonary arterial myocytes from pulmonary hypertensive rats.

Pulmonary arterial myocytes were cultured from normotensive and pulmonary hypertensive rats. Microfluorimetry of Ca2+ signals in fluo-3-loaded single myocytes at day 7 of culture was performed by a laser-scanned confocal imaging system. The resting level of cytoplasmic Ca2+ concentration ([Ca2+]i) in vascular myocytes obtained from hypertensive rats was higher than that in cultured myocytes obtained from normotensive rats. Angiotensin II elevated [Ca2+]i in the vascular myocytes cultured from both normotensive and hypertensive rats. However, a rise of [Ca2+]i induced by angiotensin II in the vascular myocytes obtained from pulmonary hypertensive rats was higher than that obtained from normotensive rats. On the other hand, the response of [Ca2+]i to A23187 did not differ between the vascular myocytes cultured from normotensive and hypertensive rats. The present results suggest that the resting and angiotensin II-responsive levels of [Ca2+]i in pulmonary arterial myocytes cultured from pulmonary hypertensive rats are higher than those cultured from normotensive rats.

Angiotensin II↗
PubMed1997

Responsiveness of cytosolic free calcium concentration in cultured rat pulmonary arterial smooth muscle cells: confocal microscopic measurement.

Rat pulmonary arterial smooth muscle cells were primarily cultured. alpha-actins in pulmonary arterial smooth muscle cells at day 7 of culture were observed by an immunofluorescence staining method using anti-alpha-actin antibody. Microfluorimetry of Ca2+ signals in fluo-3-loaded single smooth cell at day 7 of culture was performed by a laser-scanned confocal imaging system. The effects of several kinds of Ca(2+)-mobilizing drugs on cytoplasmic Ca2+ concentration ([Ca2+]i) were examined. KCl, a depolarizing agent, and norepinephrine, an alpha-adrenergic agonist, equally increased [Ca2+]i. Angiotensin II, a receptor agonist, and caffeine, a Ca(2+)-induced Ca2+ releaser, elevated [Ca2+]i in the same manner but was more potent than KCl and norepinephrine. Br-A23187, a Ca2+ ionophore, most potently increased [Ca2+]i. The present results suggest that drug receptors on plasma membrane, Ca2+ entry pathways and Ca(2+)-releasing mechanisms act normally, and that our cultured pulmonary arterial smooth muscle cells may be a good model for the study on the essential role of Ca2+ in vasoconstriction.

Adrenergic alpha-Agonists↗
PubMed1997

[Alternating optokinetic nystagmus (OKN) elicited by dichoptically presented moving grating stimuli in normal and unilateral labyrinthectomized rabbits].

Optokinetic responses to two dichoptically presented grating moving in opposite directions were investigated in normal and unilateral labyrinthectomized rabbits. In normal rabbits, OKN took place alternatively, while in unilateral labyrinthectomized rabbits, alternating OKN still took place only with some irregularity. These results indicate that OKN in rabbit to dichoptic stimulation is alternately controlled by the velocity information coming from the left and the right eye, a fact suggesting that the switching center of the control system locates somewhere behind the point of binocular summation in the central nervous system.

Animals↗
PubMed1996

Cultured melanocytes from dilute mutant mice exhibit dendritic morphology and altered melanosome distribution.

Mutant alleles at the dilute unconventional myosin heavy chain locus cause diluted coat color, opisthotonic seizures, and death. The dilute coat color phenotype is caused by irregular clumping of pigment in the hair, but amounts of melanin are unchanged from wild-type controls. The melanocyte phenotype has been described as adendritic, since hair bulb and Harderian gland melanocytes appear to be rounded in tissue sections. These observations do not exclude the possibility that the processes lack pigment, since the melanocyte shape was judged by the distribution of melanin. We have tested this hypothesis by culturing primary melanocytes from dilute mutant and wild-type mice. The mutant melanocytes do not lack processes; instead, they exhibit a concentrated perinuclear distribution of melanosomes, while wild-type melanocytes have a very uniform cytoplasmic distribution of melanosomes. Electron micrographs show no detectable differences in melanosome morphology or maturation between dilute and wild-type melanocytes. Immunofluorescence experiments indicate that the dilute protein is concentrated in regions of the cytoplasm that contain melanosomes. These experiments show that the dilute myosin is necessary for the localization of melanosomes, either by active transport or tethering.

Animals↗
PubMed1996

Effects of cigarette smoking, diabetes, high cholesterol, and hypertension on all-cause mortality and cardiovascular disease mortality in Mexican Americans. The San Antonio Heart Study.

Despite high levels of cardiovascular risk factors, Mexican Americans paradoxically have a lower prevalence of cardiovascular disease. A possible explanation is that conventional cardiovascular risk factors have a lesser impact on this ethnic group. In the present study, a 7- to 8-year follow-up of the San Antonio Heart Study cohort was used to estimate total and cardiovascular disease mortality and their association with baseline risk factors. A total of 2,629 Mexican Americans form the basis of this study, and 1,136 non-Hispanic whites from the same cohort served as the comparison group. The age- and sex-adjusted rates for total death and cardiovascular disease death were somewhat higher in Mexican Americans than non-Hispanic whites (rate ratio for total mortality = 1.4, 95% confidence interval 1.0-2.0; and rate ratio for cardiovascular mortality = 1.3, 95% confidence interval 0.7-2.4). After adjustment for sex, age, and socioeconomic status in multivariate analyses, current smoking, diabetes, high cholesterol, and hypertension were positively associated with all-cause mortality and cardiovascular disease mortality in Mexican Americans. Overall, these risk factors accounted for 45% of all-cause mortality and 55% of cardiovascular disease mortality in this ethnic group. In comparison, the risk factors accounted for 46% of all-cause mortality and 46% of cardiovascular disease mortality in non-Hispanic whites. The authors conclude that cigarette smoking, diabetes, high cholesterol, and hypertension are important predictors of both all-cause and cardiovascular disease deaths in Mexican Americans. There was no evidence for a diminished effect of these risk factors in Mexican Americans.

Adult↗
PubMed1996

Class I-like CD1A-C do not protect target cells from NK-mediated cytolysis.

Previous studies have validated the capacity of classical (HLA-A,B,C) and nonclassical (HLA-G) MHC class I antigens expressed by target cells to influence natural killer (NK) cell-mediated cytolysis. Generally, elevated expression of these HLA class I molecules is correlated with enhanced resistance to lysis by NK cells. In this study, we have evaluated the effect of transfected class I-like CD1A, CD1B, and CD1C molecules on C1R (HLA-A,B null) target cell sensitivity to natural killing. We report that while each of these molecules was expressed at physiologically relevant levels on the cell surface of clonal transfectants, no change was observed in target cell susceptibility to fresh or lymphokine-activated NK-mediated lysis.

Antigens, CD1↗
PubMed1996

Migration status, socioeconomic status, and mortality rates in Mexican Americans and non-Hispanic whites: the San Antonio Heart Study.

It has been claimed that Mexican Americans have a favorable mortality experience despite their low socioeconomic status (SES). The present study compared all-cause mortality of non-Hispanic whites with that of United States-born and foreign-born (i.e., born in Mexico) Mexican Americans. Subjects were 3735 residents of San Antonio, TX, who were followed-up for 7-8 years. The sex-age adjusted death rates per 1000 person-years were higher for United States-born Mexican Americans (5.7) than for non-Hispanic whites (3.8) or for foreign-born Mexican Americans (3.6). Foreign-born Mexican Americans had the lowest socioeconomic status (SES), and non-Hispanic whites had the highest SES. After adjustment for SES, the mortality ratio for United States-born Mexican Americans compared with foreign-born Mexican Americans was 1.9 (95% confidence interval, 1.0-3.5), while the ratio for United States-born Mexican Americans compared with non-Hispanic whites was 1.0 (95% confidence interval, 0.7-1.6). Stratified analysis revealed that those in the lowest SES tertiles had threefold greater risk of death than those in the highest tertiles among both United States-born Mexican Americans and non-Hispanic whites (test for trend, P < 0.001). These data suggest that lower SES is strongly associated with increased mortality. After adjustment for SES, mortality rates were similar for United States-born Mexican Americans and non-Hispanic whites. Foreign-born Mexican Americans had the lowest mortality rates of the three groups.

Adult↗
PubMed1996

Selection response in finite populations.

Formulae were derived to predict genetic response under various selection schemes assuming an infinitesimal model. Account was taken of genetic drift, gametic (linkage) disequilibrium (Bulmer effect), inbreeding depression, common environmental variance, and both initial segregating variance within families (sigma AW02) and mutational (sigma M2) variance. The cumulative response to selection until generation t(CRt) can be approximated as [equation: see text] where Ne is the effective population size, sigma AW infinity 2 = Ne sigma M2 is the genetic variance within families at the steady state (or one-half the genic variance, which is unaffected by selection), and D is the inbreeding depression per unit of inbreeding. R0 is the selection response at generation 0 assuming preselection so that the linkage disequilibrium effect has stabilized. beta is the derivative of the logarithm of the asymptotic response with respect to the logarithm of the within-family genetic variance, i.e., their relative rate of change. R0 is the major determinant of the short term selection response, but sigma Me2 Ne and beta are also important for the long term. A selection method of high accuracy using family information gives a small Ne and will lead to a larger response in the short term and a smaller response in the long term, utilizing mutation less efficiently.

Animals↗
PubMed1996

The relationship between ethnicity and advance directives in a frail older population.

OBJECTIVE: To assess the relationship between ethnicity and Health Care wishes, including Advance Directives, in a group of frail older persons in PACE (Program For All Inclusive Care Of The Elderly). DESIGN: Retrospective chart review of 1193 participants in the PACE program. SETTING: Program of All Inclusive Care Of The Elderly (PACE), a comprehensive managed care demonstration program serving frail older participants at 10 sites across the nation. PARTICIPANTS: A total of 1193 older adults, all of whom met state criteria for nursing home level of care. There were 385 non-Hispanic whites, 364 blacks, 156 Hispanics, and 288 Asians. MEASUREMENTS: Presence or absence of advance directives, type of health care wishes selected including living will, durable power of attorney, and health care proxy. RESULTS: Frail older white, black, Hispanic and Asian Americans differ significantly in their health care wishes and how they choose to express them. Blacks were significantly more likely to select aggressive interventions and less likely than non-Hispanic whites and Hispanics to utilize a written instrument for expressing health care wishes. Whites were significantly more likely to utilize written documents for advance directives, whereas Asians were more likely to select less aggressive interventions but were unlikely to use written advance directives. CONCLUSIONS: In this population, we found significant ethnic variations in choice of health care wishes. Although health care wishes are an individual decision, an awareness of cross cultural patterns can assist practitioners in addressing the concerns of their patients, as well as assisting Health Care Policy Development.

Advance Directives↗
PubMed1996

Ultrasonographically assessed maximum carotid artery wall thickness in Mexico City residents and Mexican Americans living in San Antonio, Texas. Association with diabetes and cardiovascular risk factors.

Measurements of carotid artery wall thickness are often used as a surrogate for atherosclerosis. However, few studies have performed these measurements in populations of Mexican origin. Since Mexicans in Mexico City consume high-carbohydrate diets and have carbohydrate-induced dyslipidemia (high triglyceride and low HDL cholesterol levels) compared with Mexican Americans living in San Antonio, Tex, we questioned whether they also had more atherosclerosis than San Antonio Mexican Americans. Mean maximum intimal-medial thickness (IMT) of the common (CCA) and internal (ICA) carotid arteries were measured in 867 subjects aged 35 to 64 years (40% men) in two Mexican-origin populations, one from San Antonio (n = 202) and the other from Mexico City (n = 665). IMT's in the two cities were compared, and their associations with cardiovascular risk factors were analyzed. Older age, male sex, high levels of total cholesterol, low levels of HDL cholesterol, and high systolic blood pressure were positively associated with both CCA IMT and ICA IMT. Cigarette smoking was significantly associated with ICA IMT. CCA and ICA IMTs in diabetic subjects were thicker than in nondiabetic subjects in both men and women (all P < = .05). CCA IMT was thicker in the San Antonio than the Mexico City subjects after adjustment for cardiovascular risk factors (0.81 versus 0.76 mm in men and 0.77 versus 0.71 mm in women; P < .001 for city difference). San Antonio men also had thicker ICA IMT than their counterparts in Mexico City (0.88 versus 0.83 mm), but the reverse was true for women (0.73 versus 0.77 mm; interaction between sex and city, P < .05). Our results indicate that men had higher carotid IMTs than women. CCA IMT was thicker in San Antonio Mexican Americans than in Mexico City residents. The differences in ICA IMTs between San Antonio and Mexico City were inconsistent. Thus, since Mexico City residents consume high-carbohydrate diets, the data do not support an atherogenic effect of such diets. The interaction between sex and city on ICA IMT deserves further study.

Cardiovascular Diseases↗
PubMed1996

Leptin concentrations in diabetic and nondiabetic Mexican-Americans.

Leptin, the product of the OB gene, is increased in obese individuals, suggesting resistance to its effect. We questioned whether subjects with NIDDM have an altered regulation of serum leptin levels. We used a radioimmunoassay to measure serum leptin levels in three groups from the San Antonio Heart Study: 1) 50 Mexican-Americans with NIDDM; 2) 50 nondiabetic Mexican-Americans matched by age and sex to the diabetic Mexican-Americans; and 3) 50 nondiabetic Mexican-Americans matched by age, sex, and BMI to the diabetic Mexican-Americans. Leptin concentrations did not differ significantly by diabetic status. Leptin concentrations were significantly correlated with BMI in all groups (NIDDM women: r = 0.637; nondiabetic women: r = 0.772; NIDDM men: r = 0.849; and nondiabetic men: r = 0.686; all P < 0.001). Leptin levels were higher in women than in men regardless of diabetic status. We concluded that the leptin concentrations were not different in diabetic and nondiabetic subjects and that the association of leptin with obesity was similar in diabetic and nondiabetic subjects.

Age Factors↗
PubMed1996

[Changes in brain monoamine neurotransmitter in iron deficiency nonanemic rats].

An iron deficiency nonanemic rat model was established by feeding with low-iron diet (11.9 mg/kg) to study if there exists biochemical abnormality in brain tissues. Iron contents of the brain, activities of monoamine oxidase (MAO) in the corpus striatum, and the contents of monoamine neurotransmitter and its metabolite in the cerebral cortex and hippocampus were determined by DCP-AES technique, enzyme histochemical method, and high performance liquid chromatography with electrochemical detection (HPLC-ECD), respectively. Results showed that iron contents and activities of MAO in brain tissues of iron deficiency nonanemic rats reduced significantly, and contents of norepinephrine (NE) and 5-hydroxytryptamine (5-HT) in cerebral cortex were significantly higher than those of controls, while 5-hydroxydroxytryptamine acid (5-HIAA) metabolite of 5-HT in the hippocampus was lower than that of controls. It indicated that there existed metabolic abnormality of monoamine neurotransmitter in the brain tissues of iron deficiency nonanemic rats. Also, this study laid a biochemical basis for abnormal mental and behavioral development caused by iron deficiency.

Animals↗
PubMed1995

Sintering effects on the strength of hydroxyapatite.

Mechanisms underlying temperature-strength interrelations for dense (> 95% dense, pores closed) hydroxyapatite (HAp) were investigated by comparative assessment of temperature effects on tensile strength, Weibull modulus, apparent density, decomposition (HAp:tricalcium phosphate ratio), dehydroxylation and microstructure. Significant dehydroxylation occurred above approximately 800 degrees C. Strength peaked at approximately 80 MPa just before the attainment of closed porosity (approximately 95% dense). For higher temperatures (closed porosity), the strength dropped sharply to approximately 60 MPa due to the closure of dehydroxylation pathways, and then stabilized at approximately 60 MPa. At very high temperatures (> 1350 degrees C), the strength dropped catastrophically to approximately 10 MPa corresponding to the decomposition of HAp to tricalcium phosphate and the associated sudden release of the remaining bonded water.

Chemistry, Physical↗