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Biomedical subjects

C Zhang

Publications and source records attributed to C Zhang.

At least 649 records · Page 36Linked to original sources
PubMed1994

Differential regulation of the two xGATA-1 genes during Xenopus development.

Xenopus laevis provides an established developmental system to study the regulation of cell lineage establishment and the generation of tissue-specific patterns of gene expression. We have isolated from Xenopus erythroid cell RNA two distinct cDNA clones encoding the xGATA-1 transcription factor. We have identified, in erythroid nuclear extracts, the sequence-specific DNA-binding protein they encode. By characterizing the expression patterns for RNA derived from two distinct homologues, we find that the two xGATA-1 genes are differentially regulated. The xGATA-1a mRNA predominates in embryos prior to terminal differentiation of erythroid cells, while the differentiated cells contain RNA derived predominantly from the xGATA-1b gene. Both proteins activate a target globin promoter in transient transfection assays. During early development, GATA-1 transcripts are localized to ventral regions of the embryo. GATA-1 should therefore provide a useful early marker for studying signalling pathways which result in the generation of ventral mesoderm. The differentially regulated genes may be distinct markers for targets of ventral mesoderm induction.

Animals↗
PubMed1994

Urinary excretion of thyroid hormones in rainbow trout, Oncorhynchus mykiss.

Urinary excretion of the thyroid hormones (TH) L-thyroxine (T4), and 3,5,3'-triiodo-L-thyronine (T3) and their derivatives was studied in urinary-catheterized rainbow trout (mean wt. 227 g) fasted for 2 days under a 12-hr L:12-hr D photocycle in running water (12 degrees). Catheterized trout were intracardiac-injected with [125I]T4 (*T4) or [125I]T3 (*T3) and urine was collected as 2-hr fractions over 48 hr. The 125I corresponding to I-, TH conjugates (sulfates and glucuronides), or TH was separated by LH-20 column chromatography and HPLC. Urine production (daily mean, 72.5 ml/kg/day) was lowest during the scotophase and doubled at the start of photophase, causing acute fluctuations in excretion of 125I-labeled materials, and implying dependence on glomerular filtration rate. During the first 48 hr, 8.2% of *T4 (I-, 3.6%: TH conjugates, 1.7%; TH, 2.9%) and 6.7% of injected *T3 (I-, 1.8%; TH conjugates, 2.5%; TH, 2.4%) was excreted in urine; 32.6% (*T4) and 26.4% (*T3) was in the gall bladder; 45.5% (*T4) and 45.7% (*T3) were in the remaining carcass; and 13.7% (*T4) and 23.7% (*T3) were lost via other routes. We extrapolate that about 15% of *T4-injected and 12% of *T3-injected total radioactivity would be excreted ultimately in urine, with 8.4% (*T4) and 9.0% (*T3) as TH or their conjugates. Neither a T4 nor a T3 challenge (20 ng/g) influenced the amount of radioactive loss in urine over 48 hr. We conclude that the urine is a significant route for excretion of TH and their conjugates, and that urinary TH loss depends to a large extent on the rate of urine production.

Animals↗
PubMed1994

Estimating the risks and prevalence of hypertension in a suburban area of Beijing.

Community-oriented primary care (COPC) provides a framework for identifying and addressing a defined community's health and health care needs. The research reported upon here is based on a community health survey in a new suburban neighborhood (Tayuan region) in the Haidian district of Beijing, conducted by the Beijing Medical University Department of Preventive Medicine and Health Care, to serve as a basis for planning health care services for the residents in that community. The analyses focus on the prevalence and predictors of hypertension among older adult residents (those 45 years of age and older). Based on logistic regression analyses, the odds ratios (in parentheses) confirm that individuals with a family history of cardiovascular disease were more likely to have been diagnosed as hypertensive (1.57). Hypertensives were also more likely to have uncontrolled systolic (3.85) or diastolic (4.75) blood pressure and associated behavioral and biologic risks, such as obesity (1.87) and renal damage (2.60). These risks were even greater among current or former smokers. These analyses will inform the design of community-oriented primary care interventions in that particular community in the People's Republic of China. They also signal important implications and highlight practical methods for assessing and targeting interventions in U.S. communities facing comparable, but unexamined, risks.

Aged↗
PubMed1994

Effect of template size on accumulation of defective interfering RNAs in protoplasts.

A turnip protoplast system has been used to study the effects of template size and sequence on the replication and/or stability of a small defective interfering (DI) RNA associated with turnip crinkle virus. Our results indicated that as little as a single base difference in the size of the molecule in some regions, rather than the specific sequence, affected the level of DI RNA accumulating in protoplasts.

Cloning, Molecular↗
PubMed1994

Excitation-contraction coupling and relaxation in porcine carotid arteries are specifically dependent on glucose.

Vascular metabolism is compartmentalized, such that aerobic glycolysis is associated with membrane energy-dependent functions and oxidative metabolism correlates with vascular contractility. We investigated the importance of glucose, a primary substrate for glycolysis, in maintenance of resting tension and excitation-contraction (EC) coupling in porcine carotid artery. All arteries were precontracted with 80 mM KCl and exposed to hypoxia in the absence of glucose (6 min) to deplete stored glycogen, an alternative substrate for glycolysis. After depletion, sensitivity to agonists was substantially increased. The concentration of norepinephrine (NE) that induced half-maximal response (EC50) was significantly decreased under glucose-free conditions, and the maximal response was unchanged. The decrease in EC50, or increase in sensitivity, was reversed by glucose, but not by beta-hydroxybutyrate, a substrate for oxidative metabolism. Similar results were obtained in concentration-isometric force responses of histamine and KCl. Importantly, measurements of high-energy phosphagen content in freeze-clamped arteries indicate that these substrate perturbations were not associated with significant changes in global energy stores. Responses to a single dose of NE or histamine in Ca(2+)-free medium were significantly lower if intracellular Ca2+ stores were loaded in the presence of beta-hydroxybutyrate than in the presence of glucose, suggesting that normal maintenance of intracellular Ca2+ stores also depends specifically on glucose. Furthermore 14 of 26 rings exhibited an increase in resting tension and/or oscillation in the absence of glucose, despite near-normal force responses to KCI. This phenomenon was reversed by nifedipine or glucose.(ABSTRACT TRUNCATED AT 250 WORDS)

3-Hydroxybutyric Acid↗
PubMed1994

Adenosine-mediated inhibition of platelet aggregation by acadesine. A novel antithrombotic mechanism in vitro and in vivo.

Inhibition of platelet aggregation by acadesine was evaluated both in vitro and ex vivo in human whole blood using impedance aggregometry, as well as in vivo in a canine model of platelet-dependent cyclic coronary flow reductions. In vitro, incubation of acadesine in whole blood inhibited ADP-induced platelet aggregation by 50% at 240 +/- 60 microM. Inhibition of platelet aggregation was time dependent and was prevented by the adenosine kinase inhibitor, 5'-deoxy 5-iodotubercidin, which blocked conversion of acadesine to its 5'-monophosphate, ZMP, and by adenosine deaminase. Acadesine elevated platelet cAMP in whole blood, which was also prevented by adenosine deaminase. In contrast, acadesine had no effect on ADP-induced platelet aggregation or platelet cAMP levels in platelet-rich plasma, but inhibition of aggregation was restored when isolated erythrocytes were incubated with acadesine before reconstitution with platelet-rich plasma. Acadesine (100 mg/kg i.v.) administered to human subjects also inhibited platelet aggregation ex vivo in whole blood. In the canine Folts model of platelet thrombosis, acadesine (0.5 mg/kg per min, i.v.) abolished coronary flow reductions, and this activity was prevented by pretreatment with the adenosine receptor antagonist, 8-sulphophenyltheophylline. These results demonstrate that acadesine exhibits antiplatelet activity in vitro, ex vivo, and in vivo through an adenosine-dependent mechanism. Moreover, the in vitro studies indicate that inhibition of platelet aggregation requires the presence of erythrocytes and metabolism of acadesine to acadesine monophosphate (ZMP).

Adenosine↗
PubMed1994

Expression of plasminogen activator genes and enzymatic activities in rat preimplantation embryos.

Plasminogen activator has been implicated in tissue invasion and remodelling because of its role in the degradation of the extracellular matrix. Its activity can be detected in mouse embryos as early as day 6 of pregnancy, suggesting that plasminogen activator is involved in the process of implantation. The present study determined the time course of expression of the genes encoding tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA) during the preimplantation period in rats by the sensitive mRNA phenotyping procedure of reverse transcription-PCR. The tPA mRNA was present in rat oocytes and two-cell embryos, but was not detected between the four-cell and blastocyst stages. The uPA mRNA was first detected in two-cell rat embryos, and was present through to the blastocyst stage. In chromogenic assays, plasminogen activator activity was detected in oocytes and embryos between two-cell and blastocyst stages. Most plasminogen activator activity present in preimplantation embryos appeared to be uPA, as it could be inhibited by anti-uPA antibody and a specific uPA inhibitor, amiloride, but not by anti-tPA antibody. The present data demonstrate the expression of uPA gene and uPA activity in preimplantation rat embryos, suggesting that embryonic uPA may be involved in early embryo development and implantation.

Amino Acid Sequence↗
PubMed1994

Airway provocation test with ragweed pollen extract in Chinese asthmatics.

As ragweed becomes widespread over China, ragweed pollenosis tends to be more frequent. Incidence of ragweed pollenosis is about 1.04% in Qingdao district. To elucidate ragweed as an allergen in the development of bronchial asthma, ragweed pollen extract inhalation airway provocation tests (APT) were studied in 55 patients with ragweed pollenosis. A single dosage of 9,000 PNU ragweed pollen extract was applied and positive response was defined as more than 35% fall in SGrs at the dose of PT35-Grs. Among 55 patients, positive APTs were found in 27 cases (49%), dual late-phase responses in 11 patients, single late-phase responses in 2 patients in the complicated asthma group. Late-phase responses were related to the increased specific IgE and strong positive skin test response (wheal > 11 mm). The results suggested ragweed pollen was one of the important allergens causing bronchial asthma. There was airway hyperresponsiveness to ragweed pollen in some patients (20%) with ragweed pollenosis without asthmatic symptoms.

Adolescent↗
PubMed1994

[Studies on triterpenoids of total glucosides of tripterygium wilfordii].

Three more triterpenoids were isolated from total glucosides of tripterygium wilfordii (T1). T16 and T17 were identified as salaspermic acid and as wilforlide B. T18 was a new compound. The structure of T18 was determined, as 3-oxo-22 alpha-hydroxy-delta 12-oleanen-29-oic acid by detail spectroscopic and chemical analysis, and named triptotriterpenonic acid A.

Drugs, Chinese Herbal↗
PubMed1994

Effect of albendazole on the larvae and eggs of Necator americanus in golden hamster.

When golden hamsters infected with adult Necator americanus were treated ig with albendazole(Alb) 75 or 150 mg/kg, the efficacy rates were 83.8% and 100%, respectively. Three days before treatment, the mean numbers of larvae recorded from the incubation of feces from 2 treated groups were 29,716 +/- 3,299 and 28,256 +/- 118 per gram of feces, while in the control group, it was 8,828 +/- 2,659. Within 3 days after treatment, no larva was detected in the 2 treated groups, but in the control group the mean larva number was 9,066 +/- 7,416. Furthermore, in 2 treated groups none or only a few degenerated eggs could be found using saturated saline solution method. when infected golden hamsters were treated ig with Alb at a single dose of 150 or 300 mg/kg on day 3, 7 or 14 after infection with the third stage larvae, the egg positive rates in the feces were 0-9.1%, while the worm reduction rates were 96.8-100%.

Albendazole↗
PubMed1994

Effect of albendazole on Ancylostoma caninum larvae migrating in the muscles of mice.

When mice inoculated with 1,000 third-stage larvae of Ancylostoma caninum for 1 week were treated intragastrically (ig) with albendazole (Alb) 75, 150 or 300 mg/kg.d for 3 days, the mean larva numbers collected from the muscles of each group were 2.7 +/- 1.7, 2.0 +/- 1.5 and 1.0 +/- 1.0, respectively, being much less than that 205 +/- 68 of the control group. In mice treated ig with Alb 150 mg/kg.d for 3 days, the concentrations of Alb and its effective metabolite, albendazole sulfoxide (AlbSO), were determined in plasma and the muscles at different intervals after the last medication using high performance liquid chromatography. The results showed that only low concentrations of Alb were detected in both plasma and the muscles. However, higher concentrations of AlbSO were found not only in the plasma (5.4-10.5 micrograms/ml), but also in the muscles (2.2-4.6 micrograms/g). The higher contents of AlbSO in the muscles would be helpful for killing the Ancylostoma larvae migrating in the muscles of mice.

Albendazole↗
PubMed1994

Inhibition of the transforming ability of cigarette smoking condensate-treated human fetal lung DNA induced by oltipraz.

Rat-1 cells transfected by genomic DNA of human fetal lung explants treated with 100 micrograms/ml of oltipraz (5-(2-pyrazimyl)-4-methyl-1, 2-dithiol-3-thione) for 14 hr or 100 micrograms/ml of cigarette smoking condensate for 6 hr formed 0 to 8 transformation foci, respectively. If 100 micrograms/ml of oltipraz was added to culture of human fetal lung explants 8 hr prior to the treatment of cigarette smoking condensate, the Rat-1 cells transfected by genomic DNA of human fetal lung explants formed only two foci. In addition, the growth speed of Rat-1 cells transfected by genomic DNA of human fetal lung treated with both oltipraz and cigarette smoking condensate was lower than that transfected by cigarette smoking condensate-treated human fetal lung DNA. Our results indicate that oltipraz can block the irreversible change of human fetal lung DNA caused by cigarette smoking condensate, and the results suggest the possibility of using oltipraz as control in the experimental initiation of human lung carcinogenesis.

Animals↗
PubMed1994

[Chromosome abnormality and dominant lethality among the F1 generation of mice after gamma-ray irradiation].

This paper reports on the relationship between chromosome abnormality or dominant lethality and dosage of 0.15-1.56 Gy 60Co gamma-ray irradiation in the F1 generation of mice. The irradiated female mice were mated at 7-12 days after irradiation with unirradiated or irradiated at 22-28 days after irradiation. The fetuses aged 9.5-11 days were recovered from the uterus and lethality and chromosome aberrations were investigated. Results suggested that the rate of fetus with chromosome abnormality increased with dose, and so did dominant lethality rate, and both could fit linear relationship. Increase of translocation carriers in the F1 mice was observed at the dose level of over 1.0 Gy.

Animals↗
PubMed1994

Survey of cellular radiosensitivity parameters.

A model of the formation of particle tracks in emulsion has been extended through the use of biological target theory to formulate a theory of the response of biological cells and molecules of biological importance to irradiation with energetic heavy ions. For this purpose the response to gamma rays is represented by the single-hit, multitarget model with parameters m and D0, while additional parameters kappa (or a0) and sigma 0 are required to represent the size of internal cellular targets and the effective cross-sectional area of the cell nucleus, respectively, for heavy-ion bombardments. For one-or-more-hit detectors, only the first three of these parameters are required and m = 1. For cells m is typically 2 or more. The model is developed from the concept that response to secondary electrons follows the same functional form for gamma rays and for the gamma rays surrounding an ion's path. Originally applied to dry enzymes and viruses in 1967, the model of the one-hit detector has been extended to emulsions, to other physical and chemical detectors, to single- and double-strand breaks in DNA in EO buffer and to three E. coli strains. The two-hit response has been observed for "track core" effects in radiation chemistry, for supralinearity in thermoluminescent dosimeters and for desensitized nuclear emulsions, where hit numbers up to 6 have been observed. In its extension to biological cells, additional concepts are required relating to the character of the track, namely the grain-count and track-width regimes, and to the ability of multitarget systems to acquire damage from intertrack delta rays (called gamma kill) as well as from intratrack delta rays (called ion kill). The model has been applied to some 40 sets of radiobiological data obtained from gamma, track-segment heavy-ion and neutron irradiations. Here we elaborate on the meaning of these concepts, tabulate the cellular parameters, and display their systematic behavior and the relationships among them. In particular the parameter kappa, which serves to determine the location in Z*2/beta 2 of the maximum value of the RBE, shows little variation among cell types, while D0, which describes the response to gamma rays and sigma 0, which appears to indicate the target size, varies over many orders of magnitude.

Animals↗
PubMed1994

[The alteration of histidase catalytic activity and the expression of the enzyme protein in rat primary hepatomas].

The catalytic activity of histidase and the expression of the enzyme protein were investigated in rat hepatomas induced by diethylnitrosamine. The results indicated that the activities of histidase in the hepatomas were significantly diminished as compared with normal rat livers (P < 0.01). Western blot analysis revealed that enzyme protein levels in hepatomas were markedly reduced. It is thus inferred that some factors which control expression of histidase protein may be altered during carcinogenesis. These findings lay a foundation for studying the relationship between the regulation and expression of the histidase gene and hepato carcinogenesis.

Animals↗