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Biomedical subjects

T Zhang

Publications and source records attributed to T Zhang.

At least 343 records · Page 19Linked to original sources
PubMed1995

Role of the Entamoeba histolytica cysteine proteinase in amebic liver abscess formation in severe combined immunodeficient mice.

Evidence from in vitro studies suggest that the Entamoeba histolytica cysteine proteinase plays a role in the tissue lysis and cytopathic effects seen in invasive amebiasis. We used affinity-purified antibodies against a recombinant E. histolytica cysteine proteinase to demonstrate that the proteinase is present extracellularly in amebic liver abscesses in mice with severe combined immunodeficiency (SCID mice). Treatment of E. histolytica trophozoites with specific cysteine proteinase inhibitor E-64 blocked or greatly reduced liver abscess formation at 48 h in SCID mice. Our study suggests an important role for a functional cysteine proteinase in amebic liver abscess formation.

Animals↗
PubMed1995

Intestinal peptide YY: ontogeny of gene expression in rat bowel and trophic actions on rat and mouse bowel.

The purpose of this study was twofold: 1) to characterize the profile of colonic peptide YY (PYY) gene expression in rats and 2) to examine for potential trophic effects of PYY on the intestine in rats and mice. Expression of PYY mRNA (analyzed by Northern blotting and in situ hybridization) and PYY (analyzed by high-performance liquid chromatography and radioimmunoassay) was detected initially at day 17 of gestation in colonic extracts of Sprague-Dawley and Fischer rats. Expression of colonic PYY mRNA increased until 7 days of age and remained at its highest level (approximately twofold greater than the adult level) through the end of the nursing period. After weaning (21 days of age), PYY mRNA levels declined quickly to adult levels. Colonic PYY concentrations followed, in a coordinated manner, with some temporal delay after birth, the increase and decrease of its mRNA. Administration of PYY increased the weight and DNA content of the duodenum significantly in nursing rats and adult mice. In mice, PYY treatment also increased weight and DNA content of the ileum and colon. The trophic effects of PYY were dose related, peptide specific, and independent of species and sex. From these findings, we hypothesize that PYY plays an important role in intestinal development and dietary adaptation.

Aging↗
PubMed1995

Phorbol ester-induced alteration in the pattern of secretion and storage of chromogranin A and neurotensin in a human pancreatic carcinoid cell line.

Brief phorbol ester treatment of BON cells results in a persistent release and cellular depletion of immunoreactive chromogranin A (CGA-IR) and neurotensin (NT-IR) cell contents. The purpose of the present study was to characterize the effects of 12-O-tetradecanoyl phorbol-13-acetate (TPA) on the secretion, biosynthesis, and steady-state messenger RNA (mRNA) levels of chromogranin A (CGA) and of a coresident peptide, neurotensin, by a novel human pancreatic carcinoid cell line, called BON. Acute TPA treatment (100 nM, 1 h) of BON cells resulted in 20- and 40-fold elevations in release of CGA-IR and NT-IR, respectively; and a 70-90% depletion of CGA-IR and NT-IR cell contents. TPA treatment also increased the biosynthetic rate of CGA-IR. Steady-state mRNA levels of CGA and NT/N (neurotensin/neuromedin N) were unchanged. Cell contents of CGA-IR and NT-IR were not replenished for a period of up to 6 days; secretion of CGA-IR and NT-IR persisted. In addition, BON cells failed to release CGA in response to stimulation by ionomycin and A23187 several days after acute TPA treatment. Our data indicate that the lack of replenishment of cell contents of CGA-IR and NT-IR is not due to decreases in steady-state CGA-IR and NT-IR mRNA levels, nor is it due to a decrease in biosynthesis of CGA-IR, but it is the result of a loss in the ability of TPA-treated BON cells to store and secrete CGA-IR and NT-IR in a regulated manner. These effects of TPA are mediated through the PKC pathway.

Analysis of Variance↗
PubMed1995

[Study on Xu Shuwei's Zhongjing's 36 kinds of maifatu].

The extant book titled Maifa Weizhi copied in the Ming Dynasty, is, in fact, an edition of the lost book of Zhongjing's 36 kinds of Maifatu written by Xu Shuwei of the Southern Song Dynasty. This is one of the earliest illustrative books on pulsolgy some one hundred years earlier than Shi Fa's Chabing Zhinan.

China↗
PubMed1995

A new approach to primer selection in polymerase chain reaction experiments.

We address the problem of primer selection in polymerase chain reaction (PCR) experiments. We prove that the problem of minimizing the number of primers required to amplify a set of DNA sequences is NP-complete, and show that even approximating solutions to this problem to within a constant factor times optimal is intractable. On the practical side, we give a simple branch-and-bound algorithm that solves the primers minimization problem within reasonable time for typical instances. We present an efficient approximation scheme for this problem, and prove that our heuristic always produces solutions no worse than a logarithmic factor times the optimal, this being the best approximation possible within polynomial time. Finally, we analyze a weighted variant, where both the number of primers as well as the sum of their "costs" is optimized simultaneously. We conclude by presenting the empirical performance of our methods on biological data.

Algorithms↗
PubMed1995

Insulin-like growth factor-II expression in carcinoma in colon cell lines: implications for autocrine actions.

BACKGROUND: In the gastrointestinal tract, insulin-like growth factor-II (IGF-II) messenger RNA (mRNA) is localized mainly in mesenchymal cells, and is more abundant in the fetus than in the adult. The purposes of this study are to characterize the gene expression of IGF-II at the mRNA and protein level in seven different epithelial cell lines derived from colon carcinomas and to determine the action of IGF-II and IGF-receptors on a colon carcinoma cell line. STUDY DESIGN: Insulin-like growth factor-II mRNAs were examined by Northern analysis; conditioned media from colon carcinoma cells were concentrated, chromatographed, and examined by a specific IGF-II radioreceptor assay. Insulin-like growth factor receptors were examined by radioligand binding assays. The mitogenic role of IGF-II was determined by a 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide assay. RESULTS: Multiple sizes of IGF-II mRNAs were expressed in all colon carcinoma cell lines tested (six human cell lines: HCT116, COLO 205, COLO 320 DM, LoVo, DLD-1, and HT29, and one mouse cell line: MC-26). In the conditioned media of COLO 205 and HCT116 cells, 7.5 kilodaltons IGF-II and high molecular form (IGF-II and IGF binding protein complex) were detected. Both Type I and Type II IGF receptors were present on COLO 205 cells whose growth was stimulated by IGF-II. Addition of anti-IGF-I receptor and anti-IGF-II antibody in the cell culture significantly depressed growth of the COLO 205 cell line in the presence or absence of exogenous IGF-II. CONCLUSIONS: Insulin-like growth factor-II mRNAs are expressed in human and mouse colon carcinoma cell lines, which may induce production of a significant amount of biologically active IGF-II protein. The IGF-II secreted by COLO 205 cells may stimulate cell growth in an autocrine fashion through the Type I IGF receptors.

Affinity Labels↗
PubMed1995

Comparison between conformational change and inactivation rates of aminoacylase during denaturation in urea solutions.

The kinetic method of the substrate reaction in the presence of inactivator previously described by Tsou has been applied to the determination of inactivation rates of aminoacylase during denaturation in urea solutions. The protective effect of substrate on the inactivation of aminoacylase by urea has been investigated. Simultaneously, the comparison between conformational change and inactivation rates of enzyme in the urea solutions of different concentrations has been studied. Results obtained show that the inactivation rate constants of the enzyme are larger than the rate constants of conformational changes. The present results show that the active site of metal enzyme-aminoacylase is also located in a limited and flexible region of the molecule that is more sensitive to denaturants than the enzyme as a whole.

Amidohydrolases↗
PubMed1995

[A seroepidemiologic survey on HCMV infection in pregnant women].

A survey on antibodies to HCMV-IgM was carried out with the solid-phase ELISA in 6,428 pregnant women who were given perinatal medical care in six regions of Henan Province. The positive rate was 1.1%. It was found that women of different ages, stages and numbers of pregnancy had the same positive rate. And the rate in autumn was slightly higher than those in other seasons.

Antibodies, Viral↗
PubMed1995

[Toxicity of vanadium to Leydig cells in vitro].

The levels of testosterone secreted by rat's Leydig cells in varied concentrations of V2O5 (0.125, 0.,25, 0.5, 2 and 3 mmol/L) were assayed. The result showed there was no obvious relation between the level of testosterone and the concentration of V2O5. This in vitro study in accord with the result of whole animal research indicates that Leydig cell is not the target of V2O5.

Animals↗
PubMed1995

[Medicinal plant resources of Berberis L. in Guizhou province].

Based on field investigation and identification of 19 species and one variety of medicinal plant of Berberis produced in Guizhou Province, it has been found out that among these species 3 is found to be new ,4 species and one variety are discovered for the first time in Guizhou province. Geographical distribution, perpendicular distribution and medicinal uses of these species are spelled out and a key for their identification is given.

China↗
PubMed1994

Diagnosis of freemartinism in cattle: the need for clinical and cytogenic evaluation.

A total of 727 blood samples from female calves born co-twin to male calves were examined cytogenetically for freemartinism between 1978 and 1992. Six hundred calves (82.5%) were determined to be freemartins, and 127 (17.5%) were determined not to be freemartins. The percentage of calves determined not to be freemartins was substantially higher than the 8% reported for an unselected population of female co-twins. We concluded that some obvious freemartins were eliminated prior to submission of samples for confirmatory cytogenetic diagnosis, and that only a small percentage of the estimated 93,000 female calves born co-twin to male calves annually are so examined. Therefore, probably a large number of female co-twins that are not truly freemartins are sold to slaughter every year. We propose that obvious freemartins be identified by use of the vaginal-length test and that the remaining clinically questionable calves be differentiated cytogenetically. This combination of procedures could prevent unnecessary economic losses and preserve important genetic material. Three animals with chromosomal anomalies were found during examination of samples for freemartinism. Cytogenetic evaluation for freemartinism thus offers the added value of simultaneous surveillance for cytogenetic aberrations in male and female cells of a sample.

Animals↗
PubMed1994

Naloxone-precipitated morphine withdrawal increases pontine glutamate levels in the rat.

Extracellular fluid (ECF) levels of glutamate (Glu) and aspartate (Asp) were measured in the locus coeruleus (LC) during morphine withdrawal by using microdialysis in conscious morphine-dependent Sprague-Dawley rats. Guide cannulae were implanted chronically and rats were given intracerebroventricular (i.c.v.) infusions of morphine (26 nmol/1 microliters/hr) or saline (1 microliters/hr) for 3 days. Microdialysis probes (2 mm tip) were inserted into the LC 24 hr before precipitation of withdrawal by i.c.v. injection of naloxone (12 or 48 nmol/5 microliters). Behavioral evidence of withdrawal (teeth-chattering, wet-dog shakes, etc.) was detected following naloxone challenge in morphine, but not in saline-infused rats. Increases (P < 0.01) in ECF levels of Glu (and Asp, to a lesser degree) were noted after naloxone-precipitated withdrawal only in the morphine group. The ECF Glu levels in the LC increased from 9.6 +/- 2.7 to 15.5 +/- 5.0 microM following 12 nmol/5 microliters naloxone, and from 9.5 +/- 1.9 to 20.5 +/- 3.3 microM following 48 nmol/5 microliters naloxone, before and in the first 15 min sample after the precipitation of withdrawal in the morphine-dependent rats, respectively. These results provide direct evidence to support the role of excitatory amino acids within the LC in morphine withdrawal.

Animals↗
PubMed1994

Cardiovascular and analgesic effects of a highly palatable diet in spontaneously hypertensive and Wistar-Kyoto rats.

Ingestion of highly palatable diets (HPDs), rich in sucrose and fat, has been shown to lead to obesity and alterations in cardiovascular function in animal models. A hypothesis has been advanced which suggests that ingestion of an HPD increases hypothalamic beta-endorphin release, an effect which results in an increase in sympathetic nerve outflow during the development of obesity. The hypothesis was tested by chronic (10 weeks) feeding of male spontaneously hypertensive rats (SHRs) and Wistar-Kyoto rats (WKYs) with the HPD or normal rat chow (ND). Cardiovascular function (systolic blood pressure, heart rate) and body weight gain were monitored during the feeding period. Pain sensitivity was tested weekly by measuring tail-flick latency. Body weight gain was greater in WKY rats than in SHRs, but ingestion of the HPD had no effect in either strain. Terminal organ analysis indicated differences between strains of SHRs and WKYs in the heart, the adrenal and pituitary glands, peri-testicular fat pad, and testis weights expressed by organ weight/body weight. The heart weight was greater in SHRs on the HPD than in SHRs on the ND. The ingestion of the HPD significantly increased blood pressure only in SHRs, following 10 weeks of dietary intervention. However, tail-flick latency was prolonged in both SHRs and WKYs during ingestion of the HPD. Increases in tail-flick latency suggest that the HPD increases brain opiate levels in both SHRs and WKYs. Exaggerated increases in heart weight and blood pressure were noted in SHRs following feeding with the HPD, indicating enhanced sensitivity of SHRs to HPD-induced hypertension.

Analgesia↗
PubMed1994

Brain atriopeptin mediates AV3V depressor response.

In urethane-anesthetized rats, sodium L-glutamate (Glu) microinjection into the anteroventral third ventricle region (AV3V) induced a depressor response, but the heart rate remained unchanged, whereas Glu injection into its surrounding areas or normal saline injection into the AV3V had no effect on the arterial pressure and heart rate. Bilateral preinjection of procaine or atriopeptin III antiserum into the nucleus paraventricularis (NPV) and methyl atropine (IV) markedly attenuated the AV3V depressor response, but the hypotensive response was not significantly affected by phentolamine or propranolol (IV), indicating that atriopeptin in the NPV mediates the AV3V depressor response, and excitation of the cardiac vagus is also involved in this response.

Animals↗
PubMed1994

Entropic effects of disulphide bonds on protein stability.

To measure the thermodynamic consequences of the reduction in the number of polypeptide-chain conformations that accompanies protein folding, we developed a method called loop permutation analysis. In this approach, the stabilizing contributions of three engineered disulphide bonds were compared in extended and circularly permutated mutants of phage T4 lysozyme. The observed differences in disulphide contributions, although qualitatively consistent with theoretical estimates, were not solely proportional to the differences in loop length. These findings suggest that in addition to the length of the chain, the polypeptide sequence may influence the energetic consequences of conformational restrictions.

Amino Acid Sequence↗