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Biomedical subjects

S Gao

Publications and source records attributed to S Gao.

At least 127 records · Page 7Linked to original sources
PubMed1999

[Raman spectra of complexes of rare earth nitrate with histidine].

Raman spectra of solid complexes RE(His)(NO3)3 x H2O (RE = La-Nd, Sm-Lu, Y; His = L-alpha-histidine ) have been investigated. The results indicate that RE3+ coordinates with one O atome of carboxyl group in the complex, while amino group and imidazole ring do not take part in coordination and NO3 is double coordination. The vibration peaks of carboxyl group delta(v)COO-(as-s) were plotted against the atomic number of the lanthanoids, which obeys Oddo-Harkins law.

Histidine↗
PubMed1998

Synthesis, assembly, and intracellular transport of the platelet glycoprotein Ib-IX-V complex.

The platelet glycoprotein Ib-IX-V complex plays critical roles in adhering platelets to sites of blood vessel injury and in platelet aggregation under high fluid shear stress. The complex is composed of four membrane-spanning polypeptides: glycoprotein (GP) Ibalpha, GP Ibbeta, GP IX, and GP V. Glycoprotein Ibalpha contains a binding site for von Willebrand factor through which it mediates platelet adhesion; GP V is required for the complex to bind thrombin with high affinity; and both GP Ibbeta and GP IX are necessary for efficient plasma membrane expression of the complex. To further define the roles of the individual polypeptide subunits in the biosynthesis and intracellular transport of the GP Ib-IX-V complex, we studied full and partial complexes expressed in heterologous mammalian cells. We found that the full complex was formed within minutes in the endoplasmic reticulum before being transported into the Golgi cisternae. Approximately 160 min were required for the complex to be fully processed and to appear on the plasma membrane. About 25% of GP Ibalpha expressed as part of either a GP Ib-IX complex or a GP Ib-IX-V complex was degraded through a nonlysosomal pathway. Over 60% of GP Ibalpha, however, was degraded when it was expressed in partial complexes with only GP Ibbeta or GP IX. The increased degradation was blocked by treating cells either with brefeldin A to prevent the transport of proteins from the endoplasmic reticulum to the Golgi or with lysosomal inhibitors, indicating that GP Ibalpha expressed in partial complexes was targeted to the lysosomes for degradation. These results indicate that the presence of both GP Ibbeta and GP IX, but not the presence of GP V, is required for efficient processing and targeting of GP Ibalpha to the plasma membrane. Absence of either GP Ibbeta or GP IX increased the rate of GP Ibalpha degradation, providing an explanation for why mutation of their genes leads to deficient GP Ibalpha expression and platelet adhesion in Bernard-Soulier syndrome, the deficiency disorder of the complex.

Biological Transport↗
PubMed1998

In vitro percutaneous absorption enhancement of a lipophilic drug tamoxifen by terpenes.

Tamoxifen is a highly lipophilic drug that is widely used in breast malignancies and also as a prophylactic therapy in women at high risk for the development of this disease. Recently, the terpenes have been reported to show an enhancement effect on percutaneous drug absorption. The effect of terpenes (e.g. carvone, 1,8-cineole, menthol, and thymol) was studied on the in vitro percutaneous absorption of tamoxifen through porcine epidermis. The above terpenes (5% w/v) in combination with 50% ethanol significantly (P < 0.01) increased the permeability coefficient of tamoxifen in comparison to the control (50% ethanol). The solubility of tamoxifen was determined in the control and enhancer solutions to correct the permeability enhancement by way of fractional solubility adjustment. Binding of tamoxifen to powdered stratum corneum from control and enhancer solutions was also determined. Binding studies reveal that the enhancement in the permeability coefficient of tamoxifen by menthol and thymol is due at least in part, to improvement in the partitioning of the drug to the stratum corneum. In conclusion, terpenes in combination with ethanol can be used to enhance the percutaneous absorption of the highly lipophilic drug tamoxifen.

Animals↗
PubMed1998

The relationships between age, sex, and the incidence of dementia and Alzheimer disease: a meta-analysis.

BACKGROUND: Prevalence studies on dementia and Alzheimer disease (AD) have reported a positive association with age. However, the trend of the association in the oldest-old categories has been the subject of discussion. The relationship between sex and AD has been inconsistent with these studies. Prevalence rates are influenced by the survival and disease incidence. Incidence rates provide a better measure of disease risk. METHODS: English-language articles identified through a MEDLINE search on "incidence dementia" and "incidence Alzheimer's disease" were examined and references from identified articles were reviewed. Population-based studies using personal interviews, standard clinical diagnosis criteria (DSM-III for dementia, National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorder Association for AD) and reporting age-specific incidence rates were included in the meta-analysis. Data from the selected studies were extracted and verified. Mixed-effect models were used in the meta-analysis to accommodate the heterogeneity of the studies. RESULTS: Incident dementia and AD are associated with a significant quadratic age effect indicating that the increase in incidence rates slows down with the increase in age, although there is no sign of a decline in the incidence rates themselves. The odds ratios for women to develop incidence of dementia and AD relative to men are 1.18 (95% confidence interval, 0.95-1.46) and 1.56 (95% confidence interval, 1.16-2.10), respectively. CONCLUSIONS: The acceleration of incidence rates for AD and dementia slows down with the increase in age, although we find no evidence of a rate decline. Women are at higher risk of developing AD than men.

Age Factors↗
PubMed1998

Mutagenesis of putative acylation sites alters function, localization, and accumulation of a Gi alpha subunit of the chestnut blight fungus Cryphonectria parasitica.

Targeted disruption of cpg-1, a gene encoding the G protein Gi alpha subunit, CPG-1, in the chestnut blight fungus, Cryphonectria parasitica, results in reduced mycelial growth, reduced orange pigmentation, loss of virulence, loss of asexual sporulation, and female infertility. We report the development of a complementation system for cpg-1 null mutants and its use to evaluate the in vivo consequences of mutating conserved putative CPG-1 myristoylation (G2) and palmitoylation (C3) sites. Independent mutations of the two putative acylation sites differentially altered complex fungal biological processes, including virulence, and modified CPG-1 membrane association. Results of combined Northern (RNA) and Western (immunoblot) analysis also indicated a role for lipid modification in post-transcriptional regulation of CPG-1 accumulation.

Acylation↗
PubMed1998

Use of 13C nuclear magnetic resonance and gas chromatography to examine methionine catabolism by lactococci.

Formation of methanethiol from methionine is widely believed to play a significant role in development of cheddar cheese flavor. However, the catabolism of methionine by cheese-related microorganisms has not been well characterized. Two independent methionine catabolic pathways are believed to be present in lactococci, one initiated by a lyase and the other initiated by an aminotransferase. To differentiate between these two pathways and to determine the possible distribution between the pathways, 13C nuclear magnetic resonance (NMR) performed with uniformly enriched [13C]methionine was utilized. The catabolism of methionine by whole cells and cell extracts of five strains of Lactococcus lactis was examined. Only the aminotransferase-initiated pathway was observed. The intermediate and major end products were determined to be 4-methylthio-2-oxobutyric acid and 2-hydroxyl-4-methylthiobutyric acid, respectively. Production of methanethiol was not observed in any of the 13C NMR studies. Gas chromatography was utilized to determine if the products of methionine catabolism in the aminotransferase pathway were precursors of methanethiol. The results suggest that the direct precursor of methanethiol is 4-methylthiol-2-oxobutyric acid. These results support the conclusion that an aminotransferase initiates the catabolism of methionine to methanethiol in lactococci.

Carbon Isotopes↗
PubMed1998

Intracranial stenosis in Chinese patients with acute stroke.

We studied 100 consecutive acute stroke patients in a Chinese population with transcranial Doppler and CT. Twenty patients had intracerebral hemorrhage and 14 patients did not have adequate temporal windows for transcranial Doppler examination. Among the remaining 66 patients, 22 patients (33%) had intracranial occlusive diseases and 3 (6%) had extracranial carotid stenosis. Our data showed that intracranial occlusive disease is the most commonly found vascular lesion in our acute stroke patients.

Adult↗
PubMed1998

Risk factors and Alzheimer's disease: a comparative study of two communities.

OBJECTIVE: To determine the association between demographic, lifestyle and medical history factors to Alzheimer's disease (AD), we studied samples of two community dwelling populations with significantly different prevalence rates of AD in Indianapolis, USA (6.24%) and Ibadan, Nigeria (1.4%). METHODS: The samples were drawn from African-American community dwelling residents 65 years of age and over in Indianapolis, and Yoruba community-dwelling residents 65 years of age and over in Ibadan. A two-stage epidemiological design was used in which diagnosis of AD was by National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association criteria. RESULTS: In Indianapolis, age (odds ratio [OR] = 1.16; 95% confidence interval [CI] = 1.11-1.21), family history of dementia (OR = 5.40; 95% CI = 1.99-14.62), low education (0-6 years, OR = 3.49; 95% CI = 1.06-11.48) and rural residence (OR = 2.49; 95% CI = 1.05-5.88) were associated with a higher risk of AD. In Ibadan, age (OR = 1.15; 95% CI = 1.12-1.18) and female gender (OR = 13.9; 95% CI = 3.85-50.28) were associated with a higher risk of AD. CONCLUSIONS: The remarkably similar odds ratios between age and AD between sites suggest that biological processes associated with ageing are essential elements in the development of AD but that genetic and environmental risk factors may alter age-specific rates. In our longitudinal study, we intend to investigate in more depth the interaction between these ageing, genetic and environmental factors.

Aged↗
PubMed1998

[The source of endogenous digitalis-like substance in normal pregnancy].

OBJECTIVE: To study the source of endogenous digitialis-like substance (EDLS) which increases in maternal vein plasma during normal pregnancy. METHODS: The EDLS concentrations in following samples: (1) villi in the 1st trimester (2) placenta, amnion and umbilical jelly of Wharton in the 3rd trimester, (3) plasma of normal non-pregnant women (4) maternal plasma in three trimesters, 24-48 hours post partum, (5) maternal plasma and umbilical blood in labour, were determined by radioimmunoassay. RESULTS: The concentration of EDLS in villi, placenta, amnion and jelly of Wharton was about 37, 33, 29 and 24 times higher respectively than the concentration of maternal blood. There was a significant positive correlation between the concentrations of EDLS in placenta or amnion and that in jelly of Wharton. Plasma EDLS levels in pregnant women of 1st and 2nd trimesters were similar to that in non-pregnant women, while in the 3rd trimester of pregnany they were significantly increased, and then significantly decreased in 24 to 48 hours post partum. There was a significant positive correlation between the plasma EDLS level and mean arterial pressure in the 3rd trimester. The EDLS concentration in plasma of umbilical vein and artery was about 3.1 and 2.9 times higher respectively than that in the maternal plasma. There were significant positive correlations between plasma EDLS levels of umbilical vein, artery or maternal vein and the weight of placenta or newborn. CONCLUSION: The fetal-placenta unit is the source of EDLS which increases in maternal vein plasma during normal pregnancy.

Adult↗
PubMed1998

[Observation and analysis on metabolism of serum calcium and phosphorus in patients with pregnancy-induced hypertension].

37 patients with obvious pregnancy-induced hypertension, 56 normal pregnant women and 40 nonpregnant women in the same age groups were tested on their serum calcium(Ca), phosphorus(P) alkaline phosphatase(AKP), parathyroid hormone(PHT) and calcitonin(CT). Results indicated that the respective means of serum Ca and CT were statistically lower (P < 0.05), while AKP and PTH were higher (P < 0.01) than that of normal pregnant women. It was also confirmed that Ca metabolism of patients with pregnancy-induced hypertension was obviously abnormal. In addition, pathogenesis of pregnancy-induced hypertension was also discussed.

Adult↗
PubMed1998

Mechanism of allyl chloride-induced cytoskeletal injury to nerve cells.

OBJECTIVE: To dissect the molecular mechanism of toxic neuropathy induced by allyl chloride (AC). METHODS: Fluorescence molecular probe (Fura-2/AM), electron probe X-ray microprobe analysis (EPMA) and biochemical methods were used to determine the concentrations of cytosolic free Ca2+, the contents of intracellular Ca2+ percentage, Ca(2+)-free calmodulin (CaM), the activity of Ca2+/CaM-dependent protein kinase II (Ca2+/CaM-PK II), and cytoskeletal protein synthesis in chicken embryo brain cells induced by AC. RESULTS: The contents of Ca2+ percentage, the concentrations of cytosolic free Ca2+, and the activities of Ca2+/CaM-PK II in the cells were increased significantly as AC was added (P < 0.01). However, the content of Ca(2+)-free CaM and the synthesis of cytoskeletal proteins were markedly decreased (P < 0.01). CONCLUSION: The results suggest that one of the mechanism of AC-induced cytoskeletal injury in vitro might be related to the elevation of intracellular Ca2+, activated CaM and Ca2+/CaM-PK II.

Allyl Compounds↗
PubMed1998

[Development condition of three dimensional ultrasonic imaging and analysis of some key technologies].

This paper introduces the value of three-dimensional ultrasonic imaging and it's different realizing approaches. It deliberately analyzes the key techniques used in three-dimensional ultrasonic imaging. These techniques include registration of two-dimensional images, accurate reconstruction of three-dimensional volume, projection of irregularly sampled plane and segmentation of three-dimensional image. The development status and future trend are also given in this paper.

Image Processing, Computer-Assisted↗
PubMed1997

Logistic regression models with missing covariate values for complex survey data.

Maximum likelihood methods are used to incorporate partially observed covariate values in fitting logistic regression models. We extend these methods to data collected through complex surveys using the pseudo-likelihood approach. One can obtain parameter estimates of the logistic regression model using standard statistical software and their standard errors by Taylor series expansion or the jackknife method. We apply the approach to data from a two-phase survey screening for dementia in a community sample of African Americans age 65 and older living in Indianapolis. The binary response variable is dementia and the covariate with missing values is a daily functioning score collected from interviews with a relative of the study subject.

Black or African American↗
PubMed1997

An empirical comparison of two semi-parametric approaches for the estimation of covariate effects from multivariate failure time data.

We conducted a simulation study to compare two semi-parametric approaches for the estimation of covariate effects from multivariate failure time data. The first approach was developed by Wei, Lin and Weissfeld (WLW) and the second by Liang, Self and Chang (LSC). Based on the simulation results we recommend Wei, Lin and Weissfeld's method for the situations with identical covariates and high correlations between the failure times. When the covariates are independent, LSC produces smaller mean squared errors than WLW, although at the expense of larger bias. We also compared four computer programs for implementing Wei, Lin and Weissfeld's approach: a FORTRAN program, MULCOX2; a SAS macro; the coxph function in S-plus, and a specialized software package for complex survey data (SUDAAN). Our comparison indicates that for large data sets, the speeds of the SAS macro and coxph are comparable, while MULCOX2- and SUDAAN took longer to run. However, MULCOX2 and coxph function in S-plus have the advantage of allowing time-dependent covariates, and SUDAAN has the advantage of handling complex survey data.

Adult↗
PubMed1997

Confidence intervals for the log-normal mean .

In this paper we conduct a stimulation study to evaluate coverage error, interval width and relative bias of four main methods for the construction of confidence intervals of log-normal means: the naive method; Cox's method; a conservative method; and a parametric bootstrap method. The simulation study finds that the naive method is inappropriate, that Cox's method has the smallest coverage error for moderate and large sample sizes, and that the bootstrap method has the smallest coverage error for small sample sizes. In addition, Cox's method produces the smallest interval width among the three appropriate methods. We also apply the four methods to a real data set to contrast the differences.

Bias↗
PubMed1997

Apolipoprotein E-associated risk for Alzheimer's disease in the African-American population is genotype dependent.

As a part of our ongoing study on Alzheimer's disease (AD) in elderly African Americans, we obtained clinical assessment and apolipoprotein E (ApoE) genotype data on 288 individuals (including 60 with AD). The ApoE epsilon4 allele frequency was significantly increased in AD patients compared with controls. The age-adjusted odds ratio (OR) for AD in epsilon4 homozygotes was 4.83 (95% confidence interval [CI], 1.71-13.64) compared with the epsilon3/epsilon3 genotype, but the OR for AD with the epsilon3/epsilon4 genotype did not reach significance (1.20; 95% CI, 0.58-2.45). These findings suggest that the association between ApoE epsilon4 and AD is weaker in African Americans than in whites.

Aged↗
PubMed1997

Effect of left ventricular outflow on flow convergence region on the left septal surface in ventricular septal defect.

The corrected shunt flow rate (Fc) and corrected defect orifice area (Ac) were calculated by modified equation F = 2 pi R2 (NL-VLVOT x Sin theta) in 23 patients with single membranous ventricular septal defect, in order to correct the effect of left ventricular outflow on flow convergence region on the left septal surface. The results indicated that Fc was closely correlated with Qp-Qs, and Qp/Qs measured by pulsed wave Doppler (r = 0.95 and r = 0.81 respectively, P < 0.001). And the correlation between Ac and the diameter of defect (Dd) measured directly in two-dimensional views was better than that between uncorrected defect orifice area (A) and the Dd (r = 0.98 and 0.69, respectively, P < 0.001). The shunt flow rate calculated by ideal equation F = 2 pi R2 x NL overestimated the actual shunt flow rate in ventricular septal defect, especially in membranous type. Our study concluded that Fc can be used for a more accurate evaluation of the shunt severity of ventricular septal defect.

Adolescent↗