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Biomedical subjects

S M Guo

Publications and source records attributed to S M Guo.

At least 19 recordsLinked to original sources
PubMed2001

The variation of heat transfer coefficient, adiabatic effectiveness and aerodynamic loss with film cooling hole shape.

The heat transfer coefficient and adiabatic effectiveness of cylindrical, fan shaped holes and a slot are presented for the region zero to 50 diameters downstream of the holes. Narrow-band liquid crystals were used on a heated flat plate with heated air coolant. These parameters have been measured in a steady state, low speed facility at engine representative Reynolds number based on hole diameter and pressure difference ratio (ideal momentum flux ratio). The aerodynamic loss due to each of the film cooling geometries has been measured using a traverse of the boundary layer far downstream of the film cooling holes. Compared to the cylindrical holes, the fan shaped hole case showed an improvement in the uniformity of cooling downstream of the holes and in the level of laterally averaged film cooling effectiveness. The fan effectiveness approached the slot level and both the fan and cylindrical hole cases show lower heat transfer coefficients than the slot and non film cooled cases based on the laterally averaged results. The drawback to the fan shaped hole was that the aerodynamic loss was significantly higher than both the slot and cylindrical hole values due to inefficient diffusion in the hole exit expansion.

Journal Article↗
PubMed2000

A randomized controlled trial of kurorinone versus interferon-alpha2a treatment in patients with chronic hepatitis B.

It has recently been shown that a Chinese traditional medicine, kurorinone, extracted from Sophora Flavescens Ait, possesses antiviral properties. We evaluated the efficacy and safety of kurorinone treatment in patients with chronic hepatitis B. Ninety-four patients with abnormal alanine transaminase (ALT) levels and hepatitis B e antigen (HBeAg) and/or hepatitis B virus (HBV) DNA-positivity were randomly assigned to receive either kurorinone 400 mg daily (45 patients) or 3 million units (MU) of interferon-alpha (IFN-alpha) (49 patients, daily for 1 month, every other day for 2 months) for 3 months. Patients were followed-up for 12 months. At baseline, both groups were comparable regarding age, gender and serological parameters. At the end of treatment, complete response (defined as ALT normalization and HBeAg and/or HBV DNA loss) occurred in 50% of the kurorinone group and in 61.3% of the IFN-alpha-treated group (P > NS). At the end of the 12-month follow-up period, a complete response (sustained response) occurred in 26.7-36.7% of kurorinone-treated patients with moderate or mild liver damage and in 44.4-46.7% of IFN-alpha-treated patients with similar liver injury. In kurorinone- as well as in IFN-alpha-treated patients, there was no statistical significant difference with respect to complete response rates between HBeAg-positive and hepatitis B e antibody-positive subgroups. Kurorinone had no untoward side-effects except for local pain at injection sites. The results of this trial suggest that kurorinone is able to inhibit HBV replication and improve disease remission in patients with chronic hepatitis B.

Adolescent↗
PubMed2000

[Establishment and its application of a reporter-based screening model for discovering new ligands of estrogen receptor alpha subtypes].

AIM: To establish a sensitive and efficient reporter gene based screening model and use it to screen compounds for discovering new ligands of estrogen receptor alpha subtype. METHODS: A recombinant Epstein-Barr virus episomal vector (pMT/ERE-CAT) was constructed by inserting a synthetic sequence composed of five estrogen response elements upstream of promoter and a chloramphenicol acetyltransferase (CAT) gene downstream of promoter. pMT/ERE-CAT was transfected into HepG2 cells expressing estrogen receptor alpha subtype (ER +HepG2). Hygromycin (200 micrograms.mL-1) was added 48 h after transfection for selection. One stably transfected clone was isolated and used to screen compounds for activity of stimulating CAT gene expression using colorimetric CAT assay. RESULTS: In the ER +HepG2 cells, the expression of CAT gene was induced by estradiol. A dose-dependent expression of CAT gene with half-maximal induction at 0.07 nmol.L-1 was observed. The ER +HepG2 cell was used to screen compounds for activity of stimulating CAT gene expression. Resveratrol was found to produce a maximal level of induction (1.75 times of estradiol). In vitro radiation survival experiment showed that the radioprotection activity of resveratrol (D0 = 3.18 Gy) is stronger than that of estradiol (D0 = 2.59 Gy). CONCLUSION: Vector pMT/ERE-CAT was used to generate stably transfected ER +HepG2 cell lines. The cell lines can be used to screen compounds for estrogen activity by testing extracts of cells grown in microtiter wells directly using colorimetric CAT assay. This system should provide an efficient method for screening and analyzing the activity of large numbers of ligands of estrogen receptor.

Chloramphenicol O-Acetyltransferase↗
PubMed1998

Effects of sex hormones on action potential and contraction of guinea pig papillary muscle.

AIM: To study the effects of sex hormones, estradiol (Est), progesterone (Pro) and testosterone (Tes) on the action potential (AP) and contraction of guinea pig papillary muscle. METHODS: Using conventional glass microelectrode and mechanical recording of myocardial contraction. RESULTS: Est slowed down the maximal rate of rise of phase 0 (Vmax) of AP at low concentration (1 mumol.L-1). At 10 mumol.L-1 and above, Est also prolonged AP duration (APD50 and APD90), effective refractory period (ERP) and decreased the maximal isometric tension (Pmax) and velocity of tension development (dT/dt) of contraction. Tes (100 mumol.L-1 - 1 mmol.L-1) prolonged APD90 and ERP with decreased Pmax and dT/dt. But Pro (1 mumol.L-1 - 1 mmol.L-1) had no effects on both AP and contraction. CONCLUSION: Est prolonged AP and depressed contraction of guinea pig papillary muscle.

Action Potentials↗
PubMed1996

Effects of sodium pentobarbital on electric and mechanical activities of guinea pig papillary muscle.

AIM: To study the effects of sodium pentobarbital (SP) on the action potential (AP) and contraction of guinea pig papillary muscle. METHODS: Using conventional glass microelectrode and mechanical recording of myocardium contraction. RESULTS: SP (> or = 10 mumol.L-1) prolonged the AP duration (APD) and effective refractory period (ERP), while amplitude (APA) and Vmax of phase 0 showed no changes. The effects of SP were abolished by pretreatment with cromakalim, an agonist of ATP-sensitive K+ channel. The maximal isometric tension (Pmax) and velocity of tension development (dT/dt) were decreased to 51% and 48% of control, respectively. The first postrest beat (B1) and second postrest beat (B2) were also depressed. CONCLUSION: SP affected the action potential by reducing activities of the K+ channels and reduced the contraction of guinea pig myocardium.

Action Potentials↗
PubMed1991

Reference data on gains in weight and length during the first two years of life.

Serial data from studies of infants at the University of Iowa and from the Fels Longitudinal Study were used to develop sex-specific percentiles for increments in weight and recumbent length for selected intervals during the first 24 months of life. Weight increments are presented for 1-month intervals from birth to 6 months, 2-month intervals from birth to 12 months, and 3-month intervals from birth to 24 months. Length increments are presented for 2-month intervals from birth to 6 months, and for 3-month intervals from birth to 24 months of age. Weights and lengths at the target ages were obtained for the Iowa data by simple interpolation, and for the Fels data by fitting families of three-parameter mathematical functions to the serial data from ages 1 to 24 months. The tabular presentations are based on the Iowa data from birth to 3 months of age, on the combined Iowa and Fels data from 3 to 6 months of age, and on the Fels data from 6 to 24 months of age. We believe that these reference data will be useful in screening for deviations from normal growth and may aid in early detection of failure to thrive or excessive weight gain during early life.

Age Factors↗
PubMed1991

Patterns of change in weight/stature2 from 2 to 18 years: findings from long-term serial data for children in the Fels longitudinal growth study.

Serial weight/stature2 (W/S2) data recorded semi-annually from 2 to 18 years in the Fels longitudinal study were analyzed to establish an approach for the investigation of long-term serial changes in body fatness during childhood and adolescence in individuals. To describe patterns of change in body fatness during childhood and adolescence, a family of mathematical models was fitted to individual serial W/S2 data recorded from 250 boys and 246 girls. The selected models fitted the W/S2 data well as judged by the root mean square errors. Based on the fitted models, variables representing patterns of change in an individual were derived. These included estimated value of W/S2 at 2 years of age (W/S(2)2yr), minimum value of W/S2 (W/S2min), age at minimum value of W/S2 (Amin), maximum velocity of W/S (Vmax), age at maximum velocity of W/S2 (AVmax), maximum value of W/S2 (W/S2max), and age at maximum value of W/S2 (Amax). There were highly significant correlations between observed W/S2 at 18 years and all the derived variables except AVmax indicating, for example, that in both sexes about 25 percent of the variation in W/S2 at 18 years could be explained by when Amin occurs or by the value of W/S2min. The negative correlations (r = -0.5) between Amin and W/S2 at 18 years suggested that the earlier children reach their nadir in W/S2, the earlier they began to increase in adiposity and the fatter they were at 18 years. Likewise, the positive correlations (r approximately 0.3 and 0.5, respectively) between the W/S(2)2yr or W/S2min and W/S2 at 18 years indicated that increased childhood adiposity may lead to increased adult adiposity.

Adipose Tissue↗
PubMed1990

Capillary blood gases in the neonate. A reassessment and review of the literature.

Heel puncture capillary blood gas (CBG) measurements continue to be used in neonates for estimating arterial blood gas values. Review of the literature reveals general agreement that CBG PO2 values are of little use in predicting arterial PO2 and that CBG pH values are reliable predictors of arterial pH; opinion varies regarding CBG PCO2. We conducted a two-part study comparing postductal arterial and CBG values. First, 50 infants were studied, each only once. All infants had umbilical arterial catheters in place. Blood was obtained simultaneously from the umbilical artery catheter and the warmed heels. Results demonstrated poor predictability of arterial values from CBG pH and PCO2 as well as for PO2. Second, to determine if variation both within and among individuals was similar, repeated measurements were made in 27 additional infants comparable to the first group. We obtained 3 to 28 simultaneous postductal arterial and CBG samples from each infant. A random-effects nested analysis of variance indicated that for pH, variation was largely the result of between-subject or within-subject replicates effects, while for PO2 and PCO2, most variation was explained by differences between the two techniques (umbilical artery catheter vs CBG). The results indicate that CBG measurements do not accurately predict arterial values in neonates. Extreme caution should be used when management decisions are based on CBG values.

Blood Gas Analysis↗
PubMed1989

Fat-free mass in children and young adults predicted from bioelectric impedance and anthropometric variables.

Fat-free mass (FFM) values calculated from densitometry by using a multicomponent model were significantly (p less than 0.05) larger than those from the Siri two-component model (465 males, 441 females), especially in children and females. The multicomponent model assumes the density of FFM varies by age and sex because of differences in its constituents. With FFM values from the multicomponent model as the dependent variable and impedance and anthropometry as the independent variables, prediction equations were derived by all possible subsets of regression (140 males, 110 females). These equations had RMSEs of 2.2-2.3 kg and CVs of 5.0-5.8%. Cross-validation results were excellent for young adults but less satisfactory for children for whom a different calf skinfold had been measured. The selected equations are applicable to healthy white individuals aged 7-25 y.

Adipose Tissue↗
PubMed1987

Doubling time of human chorionic gonadotropin (hCG) in early normal pregnancy: relationship to hCG concentration and gestational age.

There is controversy regarding whether the doubling time of human chorionic gonadotropin (hCG) in early normal pregnancy is constant or rises with increasing gestational age (GA) and hCG concentration. To clarify the influence of these variables on hCG doubling time, we obtained serial blood specimens every 2 to 4 days between postovulatory day 12 and 70 from 16 women who conceived while monitoring basal body temperature. The serum concentration of beta-hCG was determined by radioimmunoassay. Serial doubling time of hCG was calculated in all subjects and correlated with GA and hCG concentration. Least-squares estimates of 95% confidence bands were established from regression analysis given the second hCG concentration for each pair of samples or GA. For elimination of the need for calculation and thus improvement of the clinical utility of doubling time determinations, a nomogram relating the concentrations of hCG in paired serum samples to doubling time was constructed. We observed a significant correlation of doubling time with hCG concentration and GA, both in the group overall and within each individual pregnancy. These data support the recommendation that doubling time determinations should be evaluated with reference to normal values for a given GA or hCG concentration and suggest that previously proposed normal values of doubling time in early normal pregnancy may be low.

Chorionic Gonadotropin↗
PubMed1987

Head circumference reference data: birth to 18 years.

Highly reliable data from a sample of 888 white US children, measured serially in a single study, have been used to provide reference data for head circumference from birth to 18 years of age. The present data differ little from those already available for the age range from birth to 36 months of age, but they are considerably higher (about 0.5 cm) at older ages for boys and tend to be slightly higher for girls. These new reference data are smoother across age than those used currently for screening and evaluation. Percentiles for 6-month increments from birth to 6 years have been provided.

Cephalometry↗
PubMed1986

Quantitative structure-activity relationship of the mutagenicity of substituted N-nitroso-N-benzylmethylamines: possible implications for carcinogenicity.

The relative mutagenicities of substituted N-nitroso-N-benzylmethylamines have been reexamined from a quantitative structure-activity relationship point of view. Most of the compounds were mutagenic toward Salmonella typhimurium TA 1535 with Aroclor-induced male hamster liver S9 activation. The dose-response data were subjected to a multiple linear regression equation calculated in a stepwise manner, which found that the differences in mutagenicities could be explained primarily by differences in the three-bond path molecular connectivity index, with smaller contributions from sigma and pi. Moreover, a polynomial regression analysis showed that the maximum mutagenicity could be explained by an optimal amount of electron withdrawal by the substituent which would cause a weakening, or activation, of the methylene C-H bond. The possible relevance of these observations to carcinogenesis is discussed.

Animals↗