Biomedical subjects

G Tang

Publications and source records attributed to G Tang.

At least 73 records · Page 4Linked to original sources

PubMed1999

Assessment of total body stores of vitamin A in Guatemalan elderly by the deuterated-retinol-dilution method.

BACKGROUND: Deuterated retinol dilution (DRD) gives quantitative estimates of total body stores of vitamin A. OBJECTIVES: In elderly people, we studied 1) the time when an oral dose of deuterated vitamin A equilibrates with body stores, 2) whether serum ratios of deuterated to nondeuterated retinol (D:H) at 3 or 6 d postdosing predicted body stores, and 3) the ability of DRD to detect changes in the size of the body vitamin A pool. DESIGN: A 10-mg oral dose of [2H4]retinyl acetate was administered to 60-81-y-old Guatemalans (n = 47); percentage enrichment of serum retinol with deuterated retinol was determined at 1-3 time points per subject at 3, 6, 7, 14, 20, 21, and 54 d. In subjects from whom blood was obtained at 3 and 21 d (n = 15) and at 6 and 20 d (n = 9), total body stores were calculated by using the formula of Furr et al (Am J Clin Nutr 1989;49:713-6) with 21- or 20-d data and correlated with serum D:H at 3 or 6 d postdosing. Nine subjects received diets containing 982+/-20 microg RE (x+/-SEM) plus 800 microg RE as retinyl acetate supplements for 32 d. DRD, serum retinol, and relative dose response were used to assess vitamin A status before and after the intervention. RESULTS: Deuterated retinol equilibrated with the body pool by 20 d postdosing. Vitamin A supplementation for 32 d increased body stores, although unexplained exaggerated increases were seen in some subjects. An inverse linear relation was found between estimates of body stores and serum D:H at 3 d postdosing (r = -0.75, P = 0.002); at 6 d postdosing, the correlation was weaker. CONCLUSIONS: DRD can detect changes in total body stores of vitamin A, although factors affecting serum D:H need to be elucidated. Serum D:H 3 d postdosing might be used as an early indicator of total body stores of vitamin A, although a predictive equation will need to be developed.

Administration, Oral↗

PubMed1999

Green and yellow vegetables can maintain body stores of vitamin A in Chinese children.

BACKGROUND: Vitamin A activity of plant provitamin A carotenoids is uncertain. OBJECTIVE: The objective was to determine whether plant carotenoids can sustain or improve vitamin A nutrition during the fall season in kindergarten children in the Shandong province of China. DESIGN: The serum vitamin A concentration of 39% of the children was <1.05 micromol/L and of 61% of the children was > or = 1.05 micromol/L. For 5 d/wk for 10 wk, 22 children were provided approximately 238 g green-yellow vegetables/d and 34 g light-colored vegetables/d. Nineteen children maintained their customary dietary intake, which included 56 g green-yellow vegetables/d and 224 g light-colored vegetables/d. Octadeuterated and tetradeuterated vitamin A were given before and after the interventions, respectively, and their enrichments in the plasma were determined by gas chromatography-mass spectrometry. Serum retinol and carotenoid concentrations were measured by HPLC. RESULTS: Carotenoid nutrition improved after consumption of green-yellow vegetables. Serum concentrations of retinol were sustained in the group fed green-yellow vegetables but decreased in the group fed light-colored vegetables (P < 0.01). The isotope-dilution tests confirmed that total-body vitamin A stores were sustained in the group fed green-yellow vegetables, but decreased 27 micromol (7700 microg retinol) per child, on average, in the group fed light-colored vegetables (P < 0.06). CONCLUSION: Green-yellow vegetables can provide adequate vitamin A nutrition in the diet of kindergarten children and protect them from becoming vitamin A deficient during seasons when the provitamin A food source is limited.

Analysis of Variance↗

PubMed1999

An analysis of breastfeeding patterns and menses returning in Chengdu, China.

OBJECTIVE: To study the relationship between infant feeding practices and the duration of lactational amenorrhea, WHO conducted a multi-centered prospective study in 7 countries from 1989. This paper reports the preliminary results based on the data collected in Chengdu center in China. METHODS: A detailed follow-up survey was conducted among 541 pairs of mothers and infants from delivery to the returning of menses of mothers at the interval of every 2 weeks. RESULTS: The results showed that the mean number of breastfeeding episodes and mean duration of breastfeeds had little correlation with the time since delivery. Within 6 months since delivery, the percentage of infants' feeds consisting of breastmilk was over 90%, and this percentage dropped to 70% at 1 year's age of infants. The time to the start of regular supplementation was 153 days postpartum. The proportion of women in exclusive breastfeeding at 2 weeks postpartum was 73.4%, and these figures at 3 and 6 months postpartum were about 60% and 40%, respectively. Until 18 months postpartum, nearly 80% mothers were partial breastfeeding their infants. The cumulative probabilities of menses returning were 0.0150, 0.0395, 0.2345 and 0.6820 at 61, 89, 187 and 369 days postpartum respectively. The median duration of lactational amenorrhea was 282 days. CONCLUSION: These results indicated that the duration of lactational amenorrhea would be prolonged if the time of exclusive/predominant breastfeed was extended and the supplementary food was introduced later. The paper concluded that the first menses returning was the signal for initiating contraceptive methods for women.

Adult↗

PubMed1999

Proteasome activity is required for anthrax lethal toxin to kill macrophages.

Anthrax lethal toxin (LeTx), consisting of protective antigen (PA) and lethal factor (LF), rapidly kills primary mouse macrophages and macrophage-like cell lines such as RAW 264.7. LF is translocated by PA into the cytosol of target cells, where it acts as a metalloprotease to cleave mitogen-activated protein kinase kinase 1 (MEK1) and possibly other proteins. In this study, we show that proteasome inhibitors such as acetyl-Leu-Leu-norleucinal, MG132, and lactacystin efficiently block LeTx cytotoxicity, whereas other protease inhibitors do not. The inhibitor concentrations that block LF cytotoxicity are similar to those that inhibit the proteasome-dependent IkappaB-alpha degradation induced by lipopolysaccharide. The inhibitors did not interfere with the proteolytic cleavage of MEK1 in LeTx-treated cells, indicating that they do not directly block the proteolytic activity of LF. However, the proteasome inhibitors did prevent ATP depletion, an early effect of LeTx. No overall activation of the proteasome by LeTx was detected, as shown by the cleavage of fluorogenic substrates of the proteasome. All of these results suggest that the proteasome mediates a toxic process initiated by LF in the cell cytosol. This process probably involves degradation of unidentified molecules that are essential for macrophage homeostasis. Moreover, this proteasome-dependent process is an early step in LeTx intoxication, but it is downstream of the cleavage by LF of MEK1 or other putative substrates.

Adenosine Triphosphate↗

PubMed1999

Expression of voltage-dependent K(+) channel genes in mesenteric artery smooth muscle cells.

Molecular basis of native voltage-dependent K(+) (Kv) channels in smooth muscle cells (SMCs) from rat mesenteric arteries was investigated. The whole cell patch-clamp study revealed that a 4-aminopyridine-sensitive delayed rectifier K(+) current (I(K)) was the predominant K(+) conductance in these cells. A systematic screening of the expression of 18 Kv channel genes using RT-PCR technique showed that six I(K)-encoding genes (Kv1.2, Kv1.3, Kv1.5, Kv2.1, Kv2.2, and Kv3.2) were expressed in mesenteric artery. Although no transient outward Kv currents (I(A)) were recorded in the studied SMCs, transcripts of multiple I(A)-encoding genes, including Kv1.4, Kv3.3, Kv3.4, Kv4.1, Kv4.2, and Kv4.3 as well as I(A)-facilitating Kv beta-subunits (Kvbeta1, Kvbeta2, and Kvbeta3), were detected in mesenteric arteries. Western blot analysis demonstrated that four I(K)-related Kv channel proteins (Kv1.2, Kv1. 3, Kv1.5, and Kv2.1) were detected in mesenteric artery tissues. The presence of Kv1.2, Kv1.3, Kv1.5, and Kv2.1 channel proteins in isolated SMCs was further confirmed by immunocytochemistry study. Our results suggest that the native I(K) in rat mesenteric artery SMCs might be generated by heteromultimerization of Kv genes.

4-Aminopyridine↗

PubMed1999

[The relation between alpha1-antichymotrypsin gene polymorphism and epsilon4 allele of apolipoprotein E gene in Alzheimer disease in Chinese].

OBJECTIVE: To detect the relation between alpha1-antichymotrpsin(AACT)gene polymorphism and epsilon4 allele of apolipoprotein E (ApoE) gene in Alzheimer disease (AD) in Chinese. METHODS: The gene polymorphisms of ApoE and AACT were genotyped in 125 AD cases and 140 controls with PCR methods and RFLP typing. Then the association between AACT polymorphism and ApoE epsilon4 was analysed. RESULTS: There was no association between AD and any allele or genotype of AACT polymorphism; AACT polymorphism was not associated with AD ApoE epsilon4 or without ApoE epsilon4. In AACT*AT and AACT*TT genotypes, ApoE epsilon4 allele was associated with AD, but no association was observed in AACT*AA genotype. CONCLUSION: AACT may not be associated with AD in Chinese, and this effect can not be influenced by ApoE epsilon4, but AACT gene polymorphism may affect the association between ApoE epsilon4 allele and AD.

Adult↗

PubMed1999

[A study of genetic epidemiology on child bronchial asthma].

OBJECTIVE: To examine the relationship between child bronchial asthma and genetic fastor. METHODS: A case-control study including 372 pedigree was carried out. RESULTS: Child bronchial asthma had obvious familiar clustering (chi 2 = 24.8, P < 0.01). The prevalence rate of the first and the second degree relatives of proband was significally higher than that of the controls. The segregation ration of asthma was 0.14 (95% CL 0.098-0.18). The h2 of the first and second degree relatives of asthma were 78.18% and 55.02%, of which 83.64% for female and 73.48% for male. CONCLUSION: The genetic model of asthma belonged to polygenetics. Genetic fastor was a main risk fastor for asthma, especially for female patients.

Adolescent↗

PubMed1999

[The association between microsatellite polymorphism of alpha 1-antichymotrypsin gene and Alzheimer's disease].

OBJECTIVES: To examine the relation between the microsatellite polymorphism of alpha 1-antichymotrypsin (AACT) gene and Alzheimer's disease (AD) in Han population of Shanghai area, and to detect the influences of apolipoprotein E (ApoE) gene epsilon 4 allele on this relation. METHODS: The polymorphism of AACT and ApoE gene were genotyped in 63 AD cases, 62 controls with amplified fragment length polymorphism typing (Amp-FLP). RESULTS: The frequencies of A6 and A10 alleles of the microsatellite polymorphism of AACT gene polymorphism were decreased markedly (ZA6 = 2.2357, ZA10 = 1.9668, P < 0.05), but only A6 allele was negatively associated with AD (RR = 0.4, chi 2 = 4.683, P < 0.05). When the data were split into ApoE * epsilon 4-positive and ApoE * epsilon 4-negative groups, the drop of AACT * A6 allele frequency was only associated with AD with non-ApoE epsilon 4 (RR = 0.29, chi 2 = 3.197, P < 0.05). CONCLUSION: AACT * A6 allele may be associated with AD negatively in Shanghai area, and this effect only exists in non-ApoE * epsilon 4 AD.

Aged↗

PubMed1999

[Age changes in CT values of human major salivary glands].

OBJECTIVE: To investigate CT values ranges of normal major salivary gland in different age groups and regularity of age changes. METHODS: CT values of normal parotid and submandibular glands, comparing with those of masseter and sterocleidomastoid muscles, were measured and analyzed in 100 cases with 4 different age groups. RESULTS: CT values of parotid and submandibular gland decreased with aging, whereas no significant age change in CT values occurred in the masseter and sterocleidomastoid muscles. The CT values of parotid and submandibular gland showed big differences in different age groups. This difference, however, became smaller after the case were divided in 4 groups reference to age. CONCLUSION: CT value ranges of normal major salivary gland should be determined according to the age. It is possible to take the contralateral gland as the control gland for CT diagnosis.

Adolescent↗

PubMed1999

[Application of high performance liquid chromatography to the study on the production of maltooligosaccharide by synergistic action of two-enzymes].

This paper describes the application of high performance liquid chromatograpy to the study on the production of maltooligosaccharide by synergistic action of two-enzymes. Seven sugars in products were separated on a column of Nucleosil C18 with water as the mobile phase and determined refractometrically. Meanwhile, for the preparation of maltooligosaccharide, the effect of supplementing rate of the two enzymes on the content of maltooligosaccharide in products is examined in this paper. The optimun technological conditions were obtained by using the orthogonal design and the amount of the two enzymes added was determined. Thus more than 70% of M3-M6 maltooligosaccharide in product was obtained.

Chromatography, High Pressure Liquid↗

PubMed1999

[A method of preparing the section of eye tissue for transmission electron microscopy].

A method of preparing the section of eye tissue for transmission electron microscopy (TEM) is recommended. The tissue was prefixed with a mixed solution of 4% paraformaldehyde and 2.5% glutaraldehyde and followed by softening in 3% EDTA solution for 20 minutes, then the tissue was fixed in 1% osmium tetroxide, dehydrated in series acetone, infiltrated in Epox 812 for a longer, and embeded. Ultrathin sections were cut with glass knives or diamond knife, stained with uranyl acetate and lead citrate and examined with H600-IV. The advantage of this method is that the ultrastructures of tissues are well preserved without any damage and distortion. The main points of the procedure of preparation have been discussed.

Animals↗

PubMed1999

[Studies on degradation of poly-(propyl,3-hydroxypropyl)-DL-asparamide and release of conjugate linking aspirin in vivo and in vitro].

Two polyasparamide derivants having different hydrophilicities were selected to be degraded in vivo and in vitro. The results demonstrate that the degradation process of polyasparamide is enzymatic hydrolysis. Materials with different hydrophobicities are different in degradation rate and the same material has different metabolic rates in the planting position, kidney and liver. The release results of two polymeric drugs indicate that protease is of advantage to release of drug, and hydrophobicity of material is also an advantage to the release.

Animals↗

PubMed1999

[A water-soluble synthetic polymer, alpha,beta-poly(hydroxyalkyl)-DL-asparamide, and conjugating drug].

A water-soluble polymer alpha,beta-poly (hydroxyalkyl)-DL-asparamide was synthesized by polysuccinimide(PSI) and different lengths of hydroxyalkyls, including alpha,beta-poly(hydroxyethyl)-DL-asparamide(PHEA), alpha,beta-poly(hydroxypropyl)-DL-asparamide(PHPA), and alpha,beta-poly(hydroxybutyl)-DL-asparamide(PHBA). These polymers were characterized by differential scanning calorimetry(DSC) and infrared spectrophotometry(IR). Stability and acutetoxicity of these polymers were studied. The experiment indicated that these materials were of low-toxicity and high stability. Acetylsalicylic acid, as a model drug, was conjugated into polymers; the drug loadings were 38.63%, 37.68% and 38.70% respectively. Polymer drugs were made into cylinder, and in-vivo release in rabbits was set out. It showed that the longer the spacer was linked into the polymer, the faster the drug was released.

Animals↗

PubMed1998

Pro region C-terminus:protease active site interactions are critical in catalyzing the folding of alpha-lytic protease.

alpha-Lytic protease is encoded with a large (166 amino acid) N-terminal pro region that is required transiently both in vivo and in vitro for the correct folding of the protease domain [Silen, J. L. , and Agard, D. A. (1989) Nature 341, 462-464; Baker, D., et al. (1992) Nature 356, 263-265]. The pro region also acts as a potent inhibitor of the mature enzyme [Baker, D., et al. (1992) Proteins: Struct.,Funct., Genet. 12, 339-344]. This inhibition is mediated through direct steric occlusion of the active site by the C-terminal residues of the pro region [Sohl, J. L., et al. (1997) Biochemistry 36, 3894-3904]. Through mutagenesis and structure-function analyses we have begun to investigate the mechanism by which the pro region acts as a single turnover catalyst to facilitate folding of the mature protease. Of central interest has been mapping the interface between the pro region and the protease and identifying interactions critical for stabilizing the rate-limiting folding transition state. Progressive C-terminal deletions of the pro region were found to have drastic effects on the rate at which the pro region folds the protease but surprisingly little effect on inhibition of protease activity. The observed kinetic data strongly support a model in which the detailed interactions between the pro region C-terminus and the protease are remarkably similar to those of known substrate/inhibitor complexes. Further, mutation of two protease residues near the active site have significant effects on stabilization of the folding transition state (kcat) or in binding to the folding intermediate (KM). Our results suggest a model for the alpha-lytic protease pro region-mediated folding reaction that may be generally applicable to other pro region-dependent folding reactions.

Amino Acid Sequence↗

PubMed1998

Sonographic localization of abdominal vessels in Chinese women: its role in laparoscopic surgery.

Trauma to abdominal wall blood vessels occurs following 0.2-2% of laparoscopic operations. This prospective observational study assessed the possible role of sonographic localization of abdominal blood vessels prior to laparoscopic surgery in Chinese women and compared the findings reported in a Western group. The inferior epigastric and superficial circumflex iliac vessels were located by color Doppler imaging. Ultrasonography was 100% and 80% successful in locating the inferior epigastric and the superficial circumflex iliac vessels, respectively. The positions of the inferior epigastric vessels were similar to those reported in the Western population whilst the superficial circumflex iliac vessels were found to be situated 1 cm more medially. In our study population, a safe area for entry of lateral ports appeared to be 7 cm from the midline and 5 cm above the pubic symphysis. Sonographic localization of abdominal blood vessels is a potentially useful clinical tool in the prevention of blood vessel trauma.

Adult↗

PubMed1998

[Study on the relationship between DNA topoisomerase II activity and multidrug resistance in leukemic cells].

OBJECTIVE: To explore the relationship between DNA topoisomerase II (Topo II) activity and multidrug resistance in acute leukemia(AL). METHODS: Topo II activities were measured in peripheral blood or bone marrow leukemia cells from 17 pretreated patients and 20 after combination chemotherapy by fluorometric assay. In the same time, multidrug resistant p-glycoprotein expression was detected by immunohistochemistry using JSB-1 monoclonal antibody and mdr-1 gene expression was assayed by RT-PCR in 18 post-chemotherapy patients. RESULTS: Topo II activities were significantly higher in pretreated AL patients (0.6415 +/- 0.0561) than in healthy blood donors (0.2304 +/- 0.0591)(P < 0.005) and significantly lower in post-chemotherapy patients (0.3563 +/- 0.1011) than in pretreated ones (P < 0.005). Among 15 poorly responsed patients, 12 were p170 positive and mdr-1 overexpression, 3 case were p170 negative. Topo II activity was also decreased in these poor responsers. CONCLUSION: Decreased Topo II activity may be another factor in multidrug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1998

[Determination of vitamin D3 in health-care foods fortified with calcium by reversed-phase high performance liquid chromatography].

"Bu Gai Bao" and "Gaoxiao Man Gai" are health-care foods fortified with calcium for people of all ages. This paper describes a method of reversed-phase high performance liquid chromatography for quantitating vitamin D3 in these products. The method is simple, sensitive, and suitable for routine analysis of vitamin D3 in a variety of health-care foods fortified with calcium. Shimadzu LC-4A high performance liquid chromatograph with SPD-2AS UV detector and C-R2AX data processor were used. The vitamin D3 in products was extracted with chloroform and separated with mu-Bondapak C18 column(300 mm x 3.9 mm i.d.) and methanol water(87:13, V/V) mobile phase with detection at UV-264 nm. Regression coefficient of correlation of calibration curves in the range of 10-50 mg/L was 0.9998. Average recoveries of vitamin D3 added to the products was 95.63%. The coefficients of variation of vitamin D3 in both products were 0.24%-0.49%.

Calcium↗

PubMed1998

[Isotope tracer combined with trichloroacetic acid precipitation method for determination of nerve growth factor concentration in mouse plasma].

OBJECTIVE: To establish the radioisotope (125I) tracer method combined with trichloroacetic acid (TCA) precipitation for the determination of nerve growth factor (NGF) in mouse plasma. METHODS: Radioisotope tracer labelling method combined with TCA precipitation was used to determine NGF in mouse plasma. RESULTS: The detection limit of the method for NGF in plasma was 2.0 ng/ml. The intra-assay cv (CV) and the inter-assay CV were all less than 10%. The assay linearity was determined over the range of 12.5-400 ng/ml in plasma and the correlation coefficient was 0.9990. The average recovery of the method for NGF was 95.21%. CONCLUSIONS: The radioisotope tracer method combined with TCA precipitation is stable, sensitive and reliable. It is suitable for the determination of NGF concentration in mouse plasma.

Animals↗