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Biomedical subjects

X J Gao

Publications and source records attributed to X J Gao.

At least 19 recordsLinked to original sources
PubMed1998

Bioelectrical impedance analysis (BIA) using bipolar foot electrodes in the assessment of body composition in Type 2 diabetes mellitus.

The use of bioelectrical impedance analysis (BIA) for determining human body composition is widely accepted as a safe, rapid, and reliable technique. Although this technique has been validated in normal and obese individuals, only limited studies have been done in special populations. The use of BIA for the measurement of body composition in Type 2 (non-insulin dependent) diabetic patients would be of particular interest for both clinical and investigative studies. The aim of this study was to evaluate the validity of a new bipedal BIA device for the measurement of body composition in a population of individuals with Type 2 diabetes mellitus. The body composition of 48 male and 48 female Type 2 subjects was measured by BIA and dual energy X-ray absorptiometry (DXA). The percentage body fat determined by BIA was significantly correlated with % body fat determined by DXA (r = 0.89, p < 0.0001). Agreement analysis showed that BIA consistently overestimated % fat in female diabetic subjects by approximately 5% and underestimated % fat in male diabetic subjects by approximately 10% of the predicted value obtained with DXA. These differences were statistically significant but probably of minor clinical relevance. We conclude that BIA measurement by TBF 105 is a useful and reliable technique for measuring body composition in subjects with Type 2 diabetes mellitus.

Adult↗
PubMed1997

Comparison of methods for analyzing binary data arising from two-sample twin studies.

The study of twins is widely used for research into genetic and environmental influences on human outcome measurements. For the study design in which independent samples of monozygotic and dizygotic twins are compared with respect to their similarity on a binary trait, several statistical methods have been proposed. Using a Monte Carlo simulation, we compare the five following procedures: 1) goodness-of-fit method based on the common correlation model, 2) normal approximation of the maximum likelihood estimators of the common correlation coefficients, 3) Ramakrishnan et al. [(1992) Genet Epidemiol 9:273-282] method of odds ratio comparison, 4) generalized estimating equations method of odds ratio estimation, and 5) tetrachoric correlation method. The results show that the goodness-of-fit approach has similar or better performance in both type-one error rates and power than the other methods in all parameter settings. Its advantage with respect to type-one error rates is particularly clear under conditions of small sample sizes, extreme prevalences, or high values of the intraclass correlation coefficients. Therefore, the goodness-of-fit method is recommended for the two-sample twin study design.

Coronary Disease↗
PubMed1997

Serum immunoreactive leptin concentrations in a Canadian aboriginal population with high rates of NIDDM.

OBJECTIVE: To better understand the relationship between leptin and the anthropometric and physiological variables associated with diabetes, we measured this protein in an isolated Canadian aboriginal population with very high rates of NIDDM. RESEARCH DESIGN AND METHODS: There were 728 individuals aged 10-79 years who participated in a population-based survey to determine the prevalence of NIDDM and its associated risk factors. Fasting blood samples for glucose, insulin, triglyceride, and leptin were collected; a 75-g oral glucose tolerance test was administered and a second blood sample drawn after 120 min. Height, weight, and waist and hip circumference were determined, and percent body fat was estimated using biological impedance analysis. Fitness level was assessed in a subsample of individuals using a validated submaximal step test. The relationship between serum leptin and the other variables was assessed using Spearman's correlation coefficients and multiple linear regression. RESULTS: Serum leptin concentration was strongly correlated with adiposity, and levels were substantially higher in female subjects in all age-groups. For male subjects, percent body fat, fasting insulin level, and waist circumference were significant independent predictors of log serum leptin concentration in a multiple linear regression model (R2 = 0.582). For female subjects, these variables plus glucose tolerance status were included in the final model (R2 = 0.633). Fitness level, when included with the main effects of the above models, was a significant predictor for male subjects only. CONCLUSIONS: In an isolated aboriginal community with high rates of diabetes, we found significant independent relationships between leptin and percent body fat and between leptin and fasting insulin. As documented in other populations, the higher leptin concentration among female subjects may reflect differential leptin production from different adipose tissue beds, or leptin resistance. Independent relationships also existed among leptin and glucose tolerance status in female subjects and fitness level in male subjects.

Adolescent↗
PubMed1993

Scanning microradiographic study of the kinetics of subsurface demineralization in tooth sections under constant-composition and small constant-volume conditions.

The kinetics of subsurface demineralization of tooth sections has been studied in real-time by scanning microradiography (SMR). Demineralization was carried out: (1) with a large volume of solution buffered to pH = 4 to maintain a constant composition; and (2) in a small constant volume (approximately 3 mL), buffered initially at pH = 4, so that the degree of saturation at the tooth surface increased as the tooth dissolved. At constant composition, the change in lesion depth, Y, with time, T, followed a linear relation, Y = a + bT, for T > 44 +/- 5 h. Before this time, the relation could be approximated by a linear one with different a and b constants. At constant volume, Y = q(1-e-r(T + s)) for all T, where q, r and s are constants. Similar relations, with different constants, were found for the mineral loss per unit area of lesion exposed to acid. These results showed that the process of demineralization under the rather severe conditions used was essentially a surface-controlled process. The change of slope at approximately 44 h and the presence of the constant s in the exponential function were attributed to a change in kinetics after formation of the surface layer.

Dental Enamel↗
PubMed1991

A variant of HLA-DR4 determines susceptibility to rheumatoid arthritis in a subset of Israeli Jews.

HLA-DR4 is associated with risk for developing rheumatoid arthritis (RA) in most populations. In Israeli Jews, in whom the Dw10 subtype of DR4 predominates, no association of RA with DR4 has been found. The inability to detect an association could be due to the high frequency of DR4-Dw10. We used DNA typing with amplification by the polymerase chain reaction and dot-blotting with allele-specific oligonucleotides to determine DR4 variants in 131 Jewish RA patients living in Israel and 134 controls. In both Ashkenazi Jews and non-Ashkenazi Jews, the rare variant Dw15 (previously identified in Japanese populations and in Japanese patients with RA) was found to be the main allele associated with the risk of developing RA (relative risk = 9.2, corrected P less than 0.001). However, this low-frequency allele could be responsible for susceptibility in only 11.5% of the patients. Susceptibility for rheumatoid factor-positive RA was associated with Dw4 and Dw15; the risk for rheumatoid factor-negative RA was associated only with Dw14. The distribution of the HLA-DQ alleles associated with DR4 showed that more than half of the RA patients with Dw15 also had HLA-DQw2. The frequencies of DQw7 and DQw8 were not different in RA patients compared with controls. The results suggest that, as in other populations, susceptibility for the development of RA in Israeli Jews is associated with DRB1 locus alleles of the DR4 group.

Alleles↗
PubMed1991

Alleles at four HLA class II loci determined by oligonucleotide hybridization and their associations in five ethnic groups.

The use of polymerase chain reaction (PCR) and oligonucleotide hybridization offers a new approach for the definition of HLA class II alleles. It has been possible to determine 43 alleles of DRB1, four of DRB3, two of DRB4, four of DRB5, eight of DQA1, and 14 of DQB1. These alleles are inherited together in members of families and form closely associated groups which are found repeatedly and in characteristic patterns in different populations. We have determined the HLA class II alleles and analyzed their association in 431 healthy unrelated subjects including 161 North American Caucasians, 53 Latin Americans, 61 Blacks, 88 Chinese, and 68 Israeli Jews. For-locus haplotypes (DRB1; DRB3/4/5; DQA1; DQB1) were derived from 79 B cell lines and the analysis of segregation in 34 nuclear families. The B-cell lines yielded 37 and the families showed the same, and 20 other, haplotypic combinations. In addition to these 57 haplotypes, associated alleles were assigned in the unrelated panels following certain rules. The resulting haplotypes were assigned to groups known to share associated alleles. The groups were: 1) DR1, DR2, and DRw10 (13 haplotypes); 2) DR3 and DRw6 (26 haplotypes); 3) DR5 and DRw8 (24 haplotypes); 4) DR4, DR7, and DR9 (24 haplotypes). Their distribution in populations with different ethnic backgrounds was analyzed. The expressed DRB4 allele and its null mutant were determined by PCR and oligonucleotide hybridization. The different DR7 haplotypes resulting from these determinations were analyzed in a panel of 130 North American Caucasoids. This comprehensive analysis of class II HLA haplotypes in human populations should be useful in understanding the role of these genes and in various applications including anthropology, disease susceptibility, and transplantation of allogeneic organs and tissues.

Alleles↗
PubMed1991

Heterogeneity in HLA-DR2-related DR,DQ haplotypes in eight populations of Asia-Oceania.

The relative distributions of 480 DR2-related DR,DQ haplotypes have been determined in Australian Aborigines, Papua New Guinean Highlanders, coastal Melanesians, Micronesians, Polynesians, Javanese, and Southern and Northern Chinese. Using sequence-specific oligonucleotides (SSOs) for hybridization of polymerase chain reaction (PCR) products from DRB1, DRB5, DQA1, and DQB1 genes, 15 different DR2-related haplotypes were identified. The predominant DR2 haplotype in Oceania involved a novel combination of DRB1*1502, DRB5*0101 alleles; this haplotype occurred sporadically in Java, but not in China. In Southern China, the most frequent DR2 haplotype involved the unusual arrangement DRB1*1602,DRB5*0101; alternatively, DRB1*1602 was associated with a new DRB5 SSO pattern. This study has important implications for molecular HLA-typing protocols that assume particular DRB1, DRB5 or DR,DQ linkage relationships. Further, the novel DRB1, DRB5 haplotype in Oceania suggests that the mixed lymphocyte culture (MLC) determinants Dw2 and Dw12 are discriminated by codon 86 at the DRB1 locus.

Humans↗
PubMed1991

DNA typing for class II HLA antigens with allele-specific or group-specific amplification. V. Typing for subsets of HLA-DR1 and DR'Br'.

Three DRB1 alleles of the DR1 group including DRB1*0101, DRB1*0102, and DRB1*0103 are currently recognized. The first two of these are defined as HLA-DR1 by serologic typing and as either Dw1 or Dw20 by typing with T cells. DRB1*0103, previously called DR'Br' or DR'BON', is not detectable by serology. Little information exists about the population frequencies of DRB1*0102 and DRB1*0103. In the present study we have used the polymerase chain reaction (PCR) and allele-specific oligonucleotide probes to determine these alleles. To avoid cross-hybridization with other DRB genes having the same DNA sequences as those of the region to be analyzed, we performed group-specific PCR to amplify only DR1 DRB1 genes. This was accomplished using a 21-nucleotide-long primer, homologous to the first hypervariable region common to the DR1 DRB1 genes, and which under appropriate conditions amplified only DRB1 genes of the DR1 group. Five oligonucleotide probes, one matching the second hypervariable region, two spanning the third hypervariable region, and two covering codons 82 through 89, were used to determine the three alleles. DRB1*0101 (Dw1) was found to be the major type of DR1 in North American Caucasians. In North American black and Brazilian mestizo populations DRB1*0102 (Dw20) was more prevalent. DRB1*0103 (DR'Br') was detected in only six individuals in the present study.

Alleles↗
PubMed1991

DNA typing for HLA-DR, and -DP alleles in a Chinese population using the polymerase chain reaction (PCR) and oligonucleotide probes.

We have determined alleles of HLA-DRB1, DRB3, DRB5, DQA1, DQB1, and DPB1 loci in 91 unrelated healthy individuals from North China. Group-specific PCR primers were employed for the analysis of subsets of DR1, DR2, DR4, DRw52, and DPB. With allele-specific probes, 22 DRB1, 8 DQA1, 13 DQB1, and 12 DPB1 alleles were found in this panel. Allele frequencies showed that 25.3% of the subjects had DR7 and 26.4% had DR9, only 5.5% had DRB1*0301 (DRw17). In the DR4 group, DRB1*0405 (Dw15, 8.8%) and 0406 (KT2, 9.9%) were the most prevalent alleles. DRB1*0404 (Dw14.1), 0407 (Dw13.2) and 0408 (Dw14.2) were absent and the other alleles of the DR4 group were rare. The most common DRw6 subset was DRB1*1401 (8.8%). DRB1*0802 and 0803 were present (2.2%, 6.6%), and DRB1*0801 was not found. Associations with DQA1 and DQB1 were generally similar to those found in other populations. DPB1*0501 was the most frequent (60.2%) allele at the DPB1 locus. Overall our study shows that the distribution of class II alleles in a population from Mainland China is quite different from other ethnic groups. The high frequency of the KT2 subset of DR4. (DRB1*0406) and of DPB1*0501 are the most striking features found. A new type of DR4 was determined in one subject. It was like DR4-Dw15 (DRB1*0405) but, according to our hybridization patterns, it encoded valine instead of glycine in position 86. It is now called DRB1*0410.

Alleles↗
PubMed1991

Scanning and contact microradiographic study of the effect of degree of saturation on the rate of enamel demineralization.

The effect of degree of saturation with respect to hydroxyapatite (DSHA) on enamel section demineralization was studied by contact and scanning microradiography (CMR and SMR). Two aspects were studied: (1) the effect of different values of DSHA at constant pH, and (2) the effect of constant DSHA with variable pH. In the pH range (2.5-4.5) and time scale (0-120 h) studied, the DSHA was more important in determining the rate of enamel lesion progression than was the pH.

Adult↗
PubMed1991

[The observation of experimental respiratory distress syndrome and effects of anisodamine].

The respiratory distress syndrome (RDS) model induced by oleic acid injection in dogs and treated by anisodamine were observed. The clinical picture, blood gas parameters, Pap, Pwp, blood cells count, hemocoagulogram, CH50, and surface tension of BALF were studied in order to determine the pathophysiological mechanism and effects of anisodamine. According to the studies in our laboratory, it was suggested that the complement activation and neutrophil aggregation induced by C5a and mediators released by it and other way are likely to be the initiation factors. The lung injuries complicated diffuse intravascular coagulation with fibrinolysis occurred for whole 72 hours period. The anisodamine seems to exert certain therapeutic effects on RDS through preventing the complement activation and enable the lysosomal elimination decrease and stimulate the II-type epithelia to be repaired.

Animals↗
PubMed1990

HLA-DR alleles with naturally occurring amino acid substitutions and risk for development of rheumatoid arthritis.

To determine the HLA-DR4 subtypes associated with rheumatoid arthritis (RA), we performed amplification of DR4 DRB1 genes by the polymerase chain reaction and dot-blots with oligonucleotide probes. In 52 HLA-DR4+ RA patients, Dw4 was the predominant subtype. This subtype was found in 45 of 52 patients (86.5%) compared with 33 of 59 DR4+ controls (55.9%; P less than 0.001). In the whole population, Dw4 also gave the highest relative risk for RA (RR = 5.31). Relative risk was also associated with DR1.1, the common white DR1 (Dw1) type, which has a third hypervariable region amino acid sequence similar to some forms of DR4 and has glycine at position 86. Variants of DR1 (DR1.2) or DR4 (Dw13.1, Dw14.1) with valine at position 86 appeared less able to confer risk for RA. Substitution of residues in the third hypervariable region of the first domain of DRB1 appeared to correlate with relative risk for RA. Among subjects having 0-1 amino acid substitutions, RA developed in 53%, whereas in subjects with 2-4 amino acid changes, RA was present in only 17.4% (P less than 0.00001). DQw7 (formerly DQw3.1) was slightly increased in DR4+ RA patients compared with controls, but a striking excess of Dw4,DQw7 homozygous patients was observed. The results suggest that DQw7 may have an additional effect, possibly with a recessive mechanism, since it was observed only in DR4 homozygous patients.

Alleles↗
PubMed1990

DNA typing for class II HLA antigens with allele-specific or group-specific amplification. I. Typing for subsets of HLA-DR4.

DNA sequences that distinguish the subsets of HLA-DR4 are also found on several other alleles. This makes typing of heterozygotes with oligonucleotide probes quite impractical. We have therefore developed a procedure in which, in a first step, DNA of the genes to be analyzed is amplified selectively, using group-specific primers. In the case of DR4-DRB1, a primer matching codons 5 to 13 when used in the polymerase chain reaction resulted in products that were entirely suitable for typing for the DR4 subsets. Using appropriate probes, eight distinct subsets were identified. However, only six of them were represented in a normal North American Caucasian panel. In conjunction with a method for rapid DNA extraction, the procedure offers a simple, highly specific and reproducible method for determining subtypes of HLA-DR4 that at present cannot be recognized by serologic methods.

Alleles↗
PubMed1990

[Dental caries in 280 pairs of same-sex twins].

The dental caries in 280 pairs of like-sex twins (186 monozygotic, 94 dizygotic) were studied. Then, comparisons of variability of dental caries, missing and filled surface (DMFS), concordance, and correlation in the two types of twins were made. The heritability index (HI) was also calculated. There were less variance, higher concordance and higher correlation in monozygotic twins, but the results were not statistically significant. The HI of dental caries was 8.7% according to this study. It was suggested that environmental influence was dominant in caries initiation: whereas heredity was of little influence.

Adolescent↗
PubMed1988

Class II human leukocyte antigen genes and T cell receptor polymorphisms in patients with rheumatoid arthritis.

Human leukocyte antigen (HLA) typing was performed in 174 patients with rheumatoid arthritis and 222 white control subjects. Increases in HLA-DR4 and HLA-DR1 were observed as in previous studies. Each of these appeared to be inherited as dominant risk factors. Southern blotting with a DR-beta probe after digestion of genomic DNA with the restriction enzyme Bam HI showed seven bands. Three of them correlated with DR4 and were increased in rheumatoid arthritis patients. Subsets of DR4 were determined by polymerase chain reaction amplification followed by hybridization with oligonucleotide probes. Dw4 was increased in rheumatoid arthritis patients, and the frequency of the other subsets appeared to be similar in rheumatoid arthritis patients and control subjects. A polymorphism associated with the T cell receptor V-beta-8 gene family was significantly increased in rheumatoid arthritis patients.

Arthritis, Rheumatoid↗