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Biomedical subjects

G Zheng

Publications and source records attributed to G Zheng.

At least 91 records · Page 5Linked to original sources
PubMed1998

[A stereological study of the remaining parotid gland of rat after duct-preserved partial parotidectomy].

The remaining parotid glands of rats after duct-preserved partial parotidectomy were sectioned and examined randomly by stereological methods which determine acinararea and proportional volumes (PV) of the component tissues. The volume of the remaining glands were measured at the same time. Results showed that: 1. there were no difference of the above quota 1-3 days after the operation (P > 0.05); 2. 1-2 weeks after the operation, the gland volume decreased (P < 0.05) with the PV of acini decreasing (P < 0.05); 3. 4-7 weeks after the operation, the acinar area increased (P < 0.05), the PV of acini and gland volume regained (P > 0.05). All the results indicate, with the duct preserved, the remaining parotid glands after partial parotidectomy do have the regenerating ability and significant function.

Animals↗
PubMed1998

[The effect of internal irradiotherapy with 32P glass microspheres on tumor vasculature in mouse sarcoma 180].

In order to investigate the effect of internal irradiotherapy on tumor microvasculature, the vascular changes of tumor S180 following internal irradiotherapy with 32P glass microspheres were observed microscopically with vessel casts of resin perfusion and ink perfusion. The results showed that the microvessels expanded with the endothelial cells swelling and the amount of microvessels and new vessels decreased, which led to peritumoral vascular density descended. It suggests that internal irradiotherapy destroying the tumor microvasculature as external irradiation is an important influence on the efficiency of internal irradiotherapy.

Animals↗
PubMed1998

[Effect of taixian tablet on hamster buccal pouch carcinogenesis].

Eighty syrian hamsters were divided into 4 equal groups. The right buccal pouches of hamsters in group I and group II were painted three times weekly with 0.5% DMBA dissolved in acetone, but the hamsters in group I received 0.45 g Taixian tablet daily by mouth. The animals in group III only received 0.45 g Taixian tablet daily and group IV was control group. After 9, 12 weeks, animals were killed with their pouches excised, and tumors were counted and measured. The results showed; 1. Comparing with group II, the malignant rate of group I was lower after 9 weeks and the tumor volume was smaller after 12 weeks (P < 0.01); 2. It was found histologically many inflammatory cells locating in the epithelial layer and lamina propria of group I after 9 weeks, while only a few inflammatory cells in group II. The high differentiated squamous cell carcinoma could be seen in group I and group II after 12 weeks, but no abnormal changes in cervical lymphnodes and organs (lung, liver, spleen, et al) of all animals in 4 groups. It suggests that Taixian tablet can restrain the development of oral carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1997

High affinity dimerization by Ski involves parallel pairing of a novel bipartite alpha-helical domain.

c-Ski protein possesses a C-terminal dimerization domain that was deleted during the generation of v-ski, and has been implicated in the increased potency of c-ski in cellular transformation compared with the viral gene. The domain is predicted to consist of an extended alpha-helical segment made up of two motifs: a tandem repeat (TR) consisting of five imperfect repeats of 25 residues each and a leucine zipper (LZ) consisting of six heptad repeats. We have examined the structure and dimerization of TR or LZ individually or the entire TR-LZ domain. Using a quenched chemical cross-linking method, we show that the TR dimerizes with moderate efficiency (Kd = 4 x 10(-6) M), whereas LZ dimerizes poorly (Kd > 2 x 10(-5) M). However, the entire TR-LZ domain dimerizes efficiently (Kd = 2 x 10(-8) M), showing a cooperative effect of the two motifs. CD analyses indicate that all three proteins contain predominantly alpha-helices. Limited proteolysis of the TR-LZ dimer indicates that the two helical motifs are linked by a small loop. Interchain disulfide bond formation indicates that both the LZ and TR helices are oriented in parallel. We propose a model for the dimer interface in the TR region consisting of discontinuous clusters of hydrophobic residues forming "leucine buttons."

Amino Acid Sequence↗
PubMed1997

DNA binding and transcriptional activation by the Ski oncoprotein mediated by interaction with NFI.

The Ski oncoprotein has been found to bind non-specifically to DNA in association with unindentified nuclear factors. In addition, Ski has been shown to activate transcription of muscle-specific and viral promoters/enhancers. The present study was undertaken to identify Ski's DNA binding and transcriptional activation partners by identifying specific DNA binding sites. We used nuclear extracts from a v-Ski-transduced mouse L-cell line and selected Ski-bound sequences from a pool of degenerate oligonucleotides with anti-Ski monoclonal antibodies. Two sequences were identified by this technique. The first (TGGC/ANNNNNT/GCCAA) is the previously identified binding site of the nuclear factor I (NFI) family of transcription factors. The second (TCCCNNGGGA) is the binding site of Olf-1/EBF. By electophoretic mobility shift assays we find that Ski is a component of one or more NFI complexes but we fail to detect Ski in Olf-1/EBF complexes. We show that Ski binds NFI proteins and activates transcription of NFI reporters, but only in the presence of NFI. We also find that homodimerization of Ski is essential for co-activation with NFI. However, the C-terminal dimerization domain of c-Ski, which is missing in v-Ski, can be substituted by the leucine zipper domain of GCN4.

Animals↗
PubMed1997

Synthesis, photophysical properties, in vivo photosensitizing efficacy, and human serum albumin binding properties of some novel bacteriochlorins.

The synthesis, photophysical characteristics, in vivo photosensitizing efficacy, human serum albumin (HSA) binding properties, and skin phototoxicity of some stable bacteriochlorins were investigated. The novel bacteriochlorins, obtained from chlorophyll-a, have long-wavelength absorptions in the range lambda max = 734-758 nm. Preferential migration of ethyl over methyl substituents among ketobacteriochlorins obtained in the pinacol-pinacolone rearrangements of vic-dihydroxybacteriochlorins was confirmed by NOE studies. The bacteriochlorins show relatively low fluorescence quantum yields. Among all the bacteriochlorins the triplet states were quenched by ground state molecular oxygen in a relatively similar manner, yielding comparable singlet oxygen quantum yields. In preliminary in vivo studies (DBA/2 mice, transplanted with SMT/F tumors), ketobacteriochlorins were found to be more photodynamically active than the related vic-dihydroxy analogues. Replacement of the methyl ester functionalities with di-tert-butylaspartic acids enhanced the in vivo efficacy. Site specific human serum albumin (HSA) binding studies indicated a direct correlation between the ability of the compound to bind to the diazepam binding site (albumin site II) and the in vivo photosensitizing efficacy.

Animals↗
PubMed1997

Identification of a core functional and structural domain of the v-Ski oncoprotein responsible for both transformation and myogenesis.

The v-ski oncogene promotes cellular transformation and myogenic differentiation. In quail embryo fibroblasts the two properties are displayed simultaneously and terminal muscle differentiation occurs only among cells already transformed by v-ski. To understand how the two phenotypes are derived from a single gene, we have undertaken to identify functionally important regions in v-ski and to test whether these regions can promote one phenotype without the other. We have generated both random and targeted mutations in v-ski and evaluated the effects of these mutations on expression, intracellular location, transformation, and myogenesis. Among a total of 26 mutants analysed, we have not found complete separation of the myogenic and transforming properties. Mutations in the region of v-Ski encoded by exon 1 of c-ski frequently abolish both its transformation and muscle differentiation activities, whereas mutations outside of this region are always tolerated. When expressed in cells from a minigene containing only the exon 1 sequence, the protein displays the transforming and myogenic activities similar to v-Ski. These results argue that the amino acid sequence encoded by exon 1 contains the core functional domain of the oncoprotein. To determine whether this functional domain has a structural counterpart, we have fragmented the v-Ski protein by limited proteolysis and found a single proteolytically stable domain spanning the entire exon 1-encoded region. Physical studies of the polypeptide encoded by exon 1 confirms that it folds into a compact, globular protein. The finding that both the transforming and myogenic properties of v-Ski are inseparable by mutation and are contained in a single domain suggests that they are derived from the same function.

Cell Transformation, Neoplastic↗
PubMed1997

Determination of rate and equilibrium constants for the reactions between electron transfer mediators and proteins by linear sweep voltammetry.

Redox proteins undergo measurable charge transfer at electrodes only under special circumstances, while they readily take part in electron transfer reactions with mediators in solution. Advantage was taken of the latter fact to develop a new method to study the kinetics and equilibria of protein-mediator electron transfer reactions. It was shown that rate and equilibrium constants for the electron exchange between electron transfer mediator and the protein can be obtained from the analysis of the perturbation of the linear sweep voltammetry (LSV) response of the mediator due to the presence of the protein. The experiments were carried out under conditions where the protein does not interact with the electrode. Theoretical data obtained by digital simulation are presented to show the conditions under which rate and equilibrium constants are accessible by the LSV technique. The electron transfer reactions between ferri- and ferrocytochrome c and N,N,N',N'-tetramethylphenylenediamine and the corresponding radical cation in phosphate-buffered saline (0.04 M phosphate, pH 7.4, 0.1 M NaCl) buffer were selected to demonstrate the technique. These studies resulted in an equilibrium constant equal to 1.0 and forward and reverse rate constants equal to 1.6 x 10(4) M-1 s-1. The data available from this method include forward and reverse rate constants for electron transfer and the formal potential for the protein redox couple.

Animals↗
PubMed1997

The effects of voluntary exercise and immobilization on humoral immunity and endocrine responses in rats.

This research examined the effect of type of stressor (physical vs. psychological) on humoral immunity and neuroendocrine responses in male and female rats. Eighty adult Sprague-Dawley rats were assigned to one of the four stress conditions (n = 20 animals/group): 1. Voluntary running (high physical/low psychological stress); 2. immobilization (low physical/high psychological stress); 3. mixed stress (running and immobilization); and 4. cage control group. The experimental manipulations were conducted over a 6-week period for 4 h/day. Five weeks after the start of the study, all animals were immunized with 1 ml of a 10% suspension of sheep red blood cells (SRBC) in saline and sacrificed 1 week later. Data analyses revealed no main effect of stress on any of the immune or endocrine parameters. However, strong gender differences emerged within the stress conditions on these physiological parameters. The stressed female rats displayed an enhanced antibody response to SRBC and a higher percentage of peripheral blood lymphocytes than their male counterparts. However, there were no significant differences between the male and female control animals with respect to these variables. Female rats consistently displayed elevated levels of plasma corticosterone and adrenal norepinephrine across all conditions. In addition, female rats displayed heavier relative organ weights (adrenal and spleen). Taken together, the notion of differential immunity with respect to physical or psychological stress is not supported by the present study.

Animals↗
PubMed1997

Endothelium-independent relaxation of aortic rings by the nitric oxide synthase inhibitor diphenyleneiodonium.

1. The flavoprotein binder diphenyleneiodonium (DPI) is a potent, irreversible inhibitor of nitric oxide synthase (NOS), but produces only a transient pressor response following systemic administration to animals, despite evidence of persistent NOS inhibition. To characterize further the effects of DPI on vascular tone, isometric tension was recorded from rat isolated aortic rings mounted between steel wires in an organ bath. 2. The NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME, 1 mM) initiated an additional contraction of prostaglandin F2 alpha-preconstricted rings with endothelium which was sustained throughout the period of L-NAME exposure (+234 +/- 39% at 15 min). In contrast, addition of DPI (5 microM) to rings with endothelium produced a transient initial contraction (+111 +/- 27% at 2 min) followed by a more sustained relaxation (-27 +/- 19% at 15 min, P < 0.001 vs L-NAME). 3. The contraction to DPI was also observed in rings without endothelium, was abolished by L-NAME pretreatment, and was unaffected by the alpha-adrenoreceptor inhibitor prazosin. Relaxation in response to DPI was not inhibited by endothelium removal or by pretreatment with either L-NAME or with the ATP-sensitive potassium channel blocker glibenclamide. 4. The endothelium-independent relaxation to DPI was inhibited at 23 degrees C and its time course was delayed by pretreatment with the guanylate cyclase inhibitor methylene blue. 5. Thus, in addition to a transient initial contraction due to NOS inhibition, DPI produces an endothelium-independent, temperature-dependent relaxation which appears in part due to activation of guanylate cyclase. This relaxant effect of DPI may explain the transient nature of its pressor effect in vivo despite sustained NOS inhibition.

Adrenergic alpha-Antagonists↗
PubMed1997

Correlation between site II-specific human serum albumin (HSA) binding affinity and murine in vivo photosensitizing efficacy of some Photofrin components.

Human serum albumin (HSA) is one of the key components in human blood that may influence drug distribution. As such, it is important to know the affinity of any drug for albumin. Previously, Photofrin, a mixture of monomeric, dimeric and oligomeric porphyrins, has been subjected to HSA binding studies. However, due to its complex nature, binding studies on Photofrin or other hematoporphyrin derivatives with HSA are inconclusive. In this report, the binding properties of some components (dimers and trimers) of Photofrin and the relationship between murine photosensitizing efficacy and those binding properties were investigated. The interaction of these porphyrins with HSA was investigated by direct ultrafiltration and fluorescent titration techniques with fluorescent probes such as dansyl-L-proline (DP), which is known to interact selectively with site II on HSA. Porphyrins also were tested for antitumor activity in a mouse model following intravenous administration and exposure to laser light. Together, the results suggest that the photosensitizers that were preferentially bound to site II of HSA were most effective at controlling murine tumor regrowth.

Animals↗
PubMed1997

[Effect of cigarette smoking on lipid peroxidation and antioxidation in rat lens].

The effects of cigarette smoking on lipid peroxidation, the activities of antioxidases, and the level of non-protein sulphydryl group in the rat lenses were investigated. The results showed that compared with the control group, MDA contents were significantly higher, while the wet weight of lenses, the concentration of non-protein sulphydryl group, the activities of superoxide dismutase and glutathione peroxidase were significantly decreased in the smoking rats. This study suggested that cigarette smoking might be involved in the development of cataract.

Animals↗
PubMed1997

[Drug resistance mechanism of doxorubicin-resistant human gastric cancer cells BGC-823/DOX].

To further investigate drug resistance mechanism of BGC-823/DOX, we analysed the amplication, transcription and overexpression of genes associated with drug resistance by Southern blot, RT-PCR, immunohisto clogical assay and the concentration of Doxorubicin in the cells by flow cytometry. The results showed that parent cells of BGC-823 were cell line with intrinsic drug resistance similar to the gastrointestinal tumors. Multidrug resistance was the main mechanism of drug resistance in BGC-823/DOX. There was a significant difference between the doxorubicin-resistant cells line from parent cells with intrinsic drug resistance and from parent cells without intrinsic drug resistance in drug resistance.

ATP-Binding Cassette Transporters↗
PubMed1997

[Establishment and characterization of doxorubicin-resistant BGC-823/DOX of human gastric cancer cell line].

To study drug resistance mechanism of gastrointestinal tumor, doxorubicin resistant cell line of human gastric cancer, we developed BGC-823/DOX, by increasing doses of doxorubicin. We completed chromosomal analysis, double time of cell grow, cell cycle distributions, drug resistance and cross-resistance, and studied reversing drug resistance. The results showed that chromosome of BGC-823/DOX was subtriploid karyotype. Cell morphology, double time, cell cycle distributions were different from its parent cells and 6.35 times more resistant to cytotoxic action of doxorubicin, cross-resistant to VP-16. Verapamil showed modified effect on doxorubicin resistance. BGC-823/DOX with doxorubicin resistance has many characteristics of gastrointestinal tumors.

Adenocarcinoma↗
PubMed1997

[Evaluation of oral glucose tolerance test in the assessment of reserved function of liver for patients with hepatocellular carcinoma].

The aim of this study was to evaluate oral glucose tolerance test(OGTT)in the assessment of reserved function of liver for predicting the tolerability of patients to hepatectomy and hence provided a criteria for selecting the candidates for undergoing hepatectomy, since the majority of hepatocellular carcinoma (HCC) patients were associated with posthepatitis cirrhosis. The preoperative and postoperative OGTT and liver biopsy for pathological investigation were carried out in 62 cases of hepatecomized patients and 49 cases of unresected patients for comparison. The results revealed that the patients whose preoperative OGTT curve was of P type recovered uneventfully after hepatectomy, but those whose curve was of L type of tolerated poorly to hepatectomy and were liable to postoperative hepatic failure and complications. The severity of cirrbosis in those poor risk patients fell to C III or C IV histological degree. 29 patients with intermediate feature of OGTT curve between P type and L type, i.e. I type underwent regional vascular occlusion at hepatic hilus as hepatectomy, and infusion of Danshen extract solution before vascular occlusion to prevent hepatocytes from reperfusion injury. Of them, 20 recovered uneventfully, 8 suffered from complications such as ascites and/or juandice, and 1 died within 1 month after operation. The followup study showed that the survival time of patients with P type OGTT curve was longer than that of I type, and the latter was longer than that of L type. The pattern of OGTT curve could change from preoperative P type to postoperative L type, depending on the severity of vascular interruption of liver and the ischemic injury to hepatocytic mass in operation.

Adolescent↗
PubMed1997

Magnesium status and risk of coronary artery disease in rural and urban populations with variable magnesium consumption.

This survey was conducted to determine the association between amount of magnesium intake and prevalence of coronary artery disease (CAD) and coronary risk factors in north India. There were 3575 subjects aged 25-64 years including 1769 rural (894 men, 875 women) and 1806 urban (904 men, 902 women) subjects. The survey methods were questionnaires for 7-day food intake record, physical examination and electrocardiography using World Health Organization criteria. The overall prevalence of CAD was three-fold greater in urban compared to rural subjects (9.0 vs 3.3 per cent, p < 0.001). The prevalence of CAD was significantly higher among subjects consuming lower dietary magnesium. Lower magnesium status was inversely associated with risk of CAD in both rural and urban subjects in both sexes. Among subjects with low magnesium status, there was a higher prevalence of hypertension, hypercholesterolemia and diabetes mellitus showing a significant increasing trend with decrease in magnesium status. Multivariate logistic regression analysis after pooling of data from rural and urban subjects and after adjustment of age showed that magnesium intake had an inverse association with prevalence of CAD. Serum magnesium (odds ratio: men 1.14, women 1.05), dietary magnesium (men 1.21, women 1.12), serum cholesterol (men 1.15, women 1.15), blood pressure (1.26 men, women 1.21), diabetes mellitus (men 1.20, women 1.18) in both sexes and smoking in men (1.05) were significant risk factors of CAD. Lower consumption of dietary magnesium and low serum Mg level in north India have a higher prevalence of CAD and of the coronary risk factors hypertension, hypercholesterolemia and diabetes mellitus. It is possible that increased intake of magnesium to about 500 mg/day may be of benefit in the prevention of CAD.

Adult↗