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Biomedical subjects

H Zhong

Publications and source records attributed to H Zhong.

At least 91 records · Page 5Linked to original sources
PubMed1999

Determination of trace elements in tissue of human uterine cancer by instrumental neutron activation analysis.

In this article, the low-temperature freeze-drying pretreated technique and instrumental neutron activation analysis were used to determine 29 trace elements in samples of human uterine cancer tissue. The content of these trace elements in uterine cancer tissue was compared with that in cervicitis tissue and in healthy tissue, respectively. Preliminary results indicated that significant differences in contents of Au, I, and Se were observed in these tissues.

Female↗
PubMed1999

Differential activation of mitogen-activated protein kinase pathways in PC12 cells by closely related alpha1-adrenergic receptor subtypes.

Coupling of the three known alpha1-adrenergic receptor (alpha1-AR) subtypes to mitogen-activated protein kinase (MAPK) pathways were studied in stably transfected PC12 cells. Subclones stably expressing alpha1A-, alpha1B-, and alpha1D-ARs under control of an inducible promoter, or at high and low receptor density, were isolated and characterized. Radioligand binding showed similar ranges of expression of each subtype. Norepinephrine (NE) increased inositol phosphate formation and intracellular Ca2+ level in these cells in a manner dependent on receptor density. However, alpha1A-ARs activated these second messenger responses more effectively than alpha1B-ARs, whereas alpha1D-ARs were least effective. NE stimulated activation of extracellular signal-regulated kinases (ERKs) in cells expressing all three alpha1-AR subtypes, although alpha1A- and alpha1B-ARs caused larger ERK activation than did alpha1D-ARs. Nerve growth factor (NGF) caused similar levels of ERK activation in all subclones. NE also activated p38 MAPK in alpha1A- and alpha1B- but not alpha1D-transfected cells and activated c-Jun NH2-terminal kinase (JNK) only in alpha1A-transfected cells. NE, but not NGF, strongly stimulated tyrosine phosphorylation of a 70-kDa protein only in alpha1A-transfected PC12 cells. NE caused neurite outgrowth only in alpha1A-expressing PC12 cells, but not in alpha1B- or alpha1D-transfected cells, whereas NGF caused neurite outgrowth in all cells. These studies show that alpha1A-ARs activate all three MAPK pathways, alpha1B-ARs activate ERKs and p38 but not JNKs, and alpha1D-ARs only activate ERKs. Only the alpha1A-AR-expressing cells differentiated in response to NE. The relationship of these responses to second messenger pathways activated by these subtypes is discussed.

Animals↗
PubMed1999

Identification of target sites of the alpha2-Mcm1 repressor complex in the yeast genome.

The alpha2 and Mcm1 proteins bind DNA as a heterotetramer to repress transcription of cell-type-specific genes in the yeast Saccharomyces cerevisiae. Based on the DNA sequence requirements for binding by the alpha2-Mcm1 complex, we have searched the yeast genome for all potential alpha2-Mcm1 binding sites. Genes adjacent to the sites were examined for expression in the different cell mating types. These sites were further analyzed by cloning the sequences into a heterologous promoter and assaying for alpha2-Mcm1-dependent repression in vivo and DNA-binding affinity in vitro. Fifty-nine potential binding sites were identified in the search. Thirty-seven sites are located within or downstream of coding region of the gene. None of the sites assayed from this group are functional repressor sites in vivo or bound by the alpha2-Mcm1 complex in vitro. Among the remaining 22 sites, six are in the promoters of known alpha-specific genes and two other sites have an alpha2-Mcm1-dependent role in determining the direction of mating type switching. Among the remaining sequences, we have identified a functional site located in the promoter region of a previously uncharacterized gene, SCYJL170C. This site functions to repress transcription of a heterologous promoter and the alpha2-Mcm1 complex binds to the site in vitro. SCYJL170C is repressed by alpha2-Mcm1 in vivo and therefore using this method we have identified a new a-specific gene, which we call ASG7.

Binding Sites↗
PubMed1999

No role for Ca++ or protein kinase C in alpha-1A adrenergic receptor activation of mitogen-activated protein kinase pathways in transfected PC12 cells.

We studied the role of Ca++ and protein kinase C (PKC) in alpha-1A adrenergic receptor (AR)-mediated activation of mitogen-activated protein kinase pathways in PC12 cells. In PC12 cells stably transfected with the human alpha-1A AR, norepinephrine (NE) strongly activated both extracellular signal regulated kinases (ERKs) and c-jun-NH2-terminal kinases (JNK). Ten nanomolar thapsigargin (TG) increased cytoplasmic Ca++ at least as much as NE but did not activate ERKs or JNK. Higher concentrations of TG caused a small activation of ERKs but not JNK. Emptying [Ca++]i stores by pretreatment with TG prevented the NE-stimulated increase in [Ca++]i but not ERK or JNK activation. The Ca++ chelator bis(2-aminophenoxy)ethane-N-N-N'-N'-tetraacetate (BAPTA) dose dependently abolished NE-stimulated Ca++ responses but not ERK or JNK activation. NE increased tyrosine phosphorylation of Pyk2, and this response was neither blocked by BAPTA nor mimicked by TG. The phorbol ester tumor promoting agent (TPA) caused a dose-dependent activation of ERKs that was potentiated by 10 nM TG. TPA caused only a small activation of JNK relative to that caused by NE, which was not affected by TG. The potent PKC inhibitor bisindolylmaleimide I dose dependently inhibited ERK and JNK activation by TPA, but not NE. ATP and UTP activated similar mitogen-activated protein kinase responses through endogenous P2Y2 receptors, and these responses were not blocked by BAPTA or bisindolylmaleimide I, suggesting that these results may be generalizable to other Gq/11-coupled receptors. The results suggest that Ca++ release and PKC activation are neither necessary nor sufficient for alpha-1A AR-mediated activation of mitogenic responses in PC12 cells.

Adrenergic alpha-Agonists↗
PubMed1999

The yeast a1 and alpha2 homeodomain proteins do not contribute equally to heterodimeric DNA binding.

In diploid cells of the yeast Saccharomyces cerevisiae, the alpha2 and a1 homeodomain proteins bind cooperatively to sites in the promoters of haploid cell-type-specific genes (hsg) to repress their expression. Although both proteins bind to the DNA, in the alpha2 homeodomain substitutions of residues that are involved in contacting the DNA have little or no effect on repression in vivo or cooperative DNA binding with a1 protein in vitro. This result brings up the question of the contribution of each protein in the heterodimer complex to the DNA-binding affinity and specificity. To determine the requirements for the a1-alpha2 homeodomain DNA recognition, we systematically introduced single base-pair substitutions in an a1-alpha2 DNA-binding site and examined their effects on repression in vivo and DNA binding in vitro. Our results show that nearly all substitutions that significantly decrease repression and DNA-binding affinity are at positions which are specifically contacted by either the alpha2 or a1 protein. Interestingly, an alpha2 mutant lacking side chains that make base-specific contacts in the major groove is able to discriminate between the wild-type and mutant DNA sites with the same sequence specificity as the wild-type protein. These results suggest that the specificity of alpha2 DNA binding in complex with a1 does not rely solely on the residues that make base-specific contacts. We have also examined the contribution of the a1 homeodomain to the binding affinity and specificity of the complex. In contrast to the lack of a defective phenotype produced by mutations in the alpha2 homeodomain, many of the alanine substitutions of residues in the a1 homeodomain have large effects on a1-alpha2-mediated repression and DNA binding. This result shows that the two proteins do not make equal contributions to the DNA-binding affinity of the complex.

Consensus Sequence↗
PubMed1999

Cloning and characterization of the merozoite surface antigen 1 gene of Plasmodium berghei.

Merozoite surface antigen 1 (MSA1) is a promising candidate for vaccine development against malaria parasites. Here, we report the complete nucleotide sequence of the gene encoding the precursor to this major surface antigen of Plasmodium berghei strain ANKA using cDNA library screening and polymerase chain reaction techniques. A single open reading frame of 5,376 basepairs encoding a protein with a calculated molecular mass of 197 kD was defined. The protein contains a putative signal peptide of 19 amino acids, a membrane anchor sequence of 18 residues, and shows two epidermal growth factor-like domains rich in Cys residues at the C-terminus. There are four repeat sequences of oligopeptides in the molecule: tetrapeptide (Ser-Thr-Thr-Thr), tripeptide (Pro-Thr-Pro and Pro-Ala-Ala), and dipeptide (Ser-Gly). Furthermore, three nine-residue stretches of a motif (Ala-Ser-Asn-Pro-Gly-Ala-Ser-Ala-Ser) are located near each other. All of these repeat sequences are unexceptionally located in the variable regions when compared with other MSA1 molecules. The molecule displays 79% overall identity to the analogous antigen of P. yoelii yoelii strain YM, 70% to that of P. chabaudi chabaudi strain AS, and 38% to that of P. falciparum strain Wellcome.

Amino Acid Sequence↗
PubMed1999

[Expression of tumor metastasis suppressor gene KAI1/CD82 in human cancer cell lines with different metastasis potential].

OBJECTIVE: To investigate the correlation of a newly-defined tumor metastasis suppressor gene KAI1/CD82 and metastatic potential of human cancer cell lines. METHODS: Expressions of KAI1/CD82 in eight human cancer cell lines of prostate, lung and melanoma with different metastasis potential were studied by Northern blot hybridization and the mutation were detected by PCR-SSCP. RESULTS: Expressions of KAI1 mRNA decreased in human prostate cancer cell lines PC3 and PC3M, and lung cancer cell line PG which were metastatic cancer cell lines (integral light density values: 0.0319, 0.0266 and 0.0549, respectively). Expression of KAI1 mRNA showed high level in PAa, a human lung cancer cell line with no metastasis (integral light density value: 0.7313). In human melanoma cell lines with different metastasis potential (WM35, WM1341b, WM983a and WM451), expression of KAI1 showed moderate expression (integral light density values are 0.1798, 0.1582, 0.1501, 0.1800 respectively). PCR-SSCP analysis indicated the existence of band shift in exon 7 of KAI1 gene in PC3, PG and PC3M. CONCLUSION: Decreased KAI1/CD82 expression may be associated with enhanced metastatic potential in prostate cancer cell lines and lung cancer cell line other than melanoma cell lines. The decreased expression may be partially nelaled with mutation of KAI1 gene.

Adenocarcinoma↗
PubMed1999

Molecular cytogenetic detection of trisomy 21 in interphase nuclei and metaphase chromosomes.

OBJECTIVE: To explore the potential application of molecular methodology in the detection of numerical chromosome aberration for clinical diagnosis and prenatal diagnosis of Down's syndrome. METHODS: The primed in situ labelling (PRINS) procedure was carried out by in situ annealing of specific oligonucleotide primers to chromosome 13, 16, 18, 21, X and Y, respectively, followed by primer elongation by a Taq polymerase in the presence of labelled nucleotides. Detection of the labelling sites was performed by immunocytochemistry and conventional fluorescence microscopy. RESULTS: Under the stringent annealing temperature, chromosomes 13, 16, 18, X and Y were specifically labelled at centromeres and the procedure was carried out successfully on interphase nuclei as well as on metaphase spreads with easily scorable signals. In 33 cases of uncultured peripheral blood lymphocytes and 11 cases of uncultured amniocytes tested, two fluorescence signals were shown on more than 87.6% interphase nuclei when chromosomes 13, 16, 18 were investigated. Sex chromosomes were correctly detected in the same way. Blind tests on peripheral blood lymphocytes from 14 cases of normal individuals and 12 cases of Down's syndrome patients and on 9 cases of amniocytes showed that when chromosome 21 was detected by PRINS, two fluorescence spots as positive signals were visible on 89.3% normal nuclei and three spots on 88.8% trisomic nuclei. The above results were fully compatible with karyotypic analysis. CONCLUSION: PRINS provides a rapid and efficient method for the clinical diagnosis or prenatal diagnosis of trisomy 21.

Amnion↗
PubMed1999

[Expression of membrane-type I matrix metalloproteinase and its correlation with gelatinase A activation in cancer cell lines].

OBJECTIVE: To study the expression of membrane-type I matrix metalloproteinase (MT1-MMP) and its correlation with gelatinase A (MMP2) activation. METHODS: Reverse transcription PCR, northern blots and western blots were employed to detect the expression levels of MT1-MMP mRNA and MMP2 protein in 4 human melanoma cell lines, 2 human lung cancer cell lines and 2 human prostate cancer cell lines. RESULTS: All the cancer cell lines expressed MT1-MMP mRNA, and the MT1-MMP mRNA level in the 4 melanoma cell lines was significantly higher than that in the lung and prostate cancer cell lines. Activated MMP2 proteins were only detected in the melanoma cell lines, whereas PG, a lung cancer cell line, which secreted pro-MMP2 and expressed low level of MT1-MMP, could not produce activated MMP2. CONCLUSIONS: The level of MT1-MMP expression was highly associated with MMP2 activation.

Blotting, Northern↗
PubMed1999

[The effect of mobile phase on the enantiomeric separation of cyfluthrin by chiral high performance liquid chromatography].

The enantiomeric separation of cyfluthrin on chiral stationary phase(CSP), derived from (R)-N-(3,5-dinitrobenzoyl) phenylglycine (Prikle type 1-A CSP) has been studied by using different hexane-alcohol mixtures as mobile phase. Mobile phase strength and composition have shown an important role in the chromatographic separation of eight isomers of cyfluthrin. Increase of the mobile phase strength reduces the retention of the eight isomers, while the diastereomeric selectivity is decreased and the enantiomeric selectivity remains almost unchanged. Also, the resolution varies in accordance with the steric hindrance of the alcohol. Secondary or tertiary alcohols impart a greater resultion to the CSP than primary alcohols. Peak shapes are better with the lower alcohols than the higher alcohols. For the enantiomeric separation of cyfluthrin on Pirkle type 1-A CSP, hexane-tert-butanol and hexane-2-propanol are better binary mobile phases.

Chromatography, High Pressure Liquid↗
PubMed1999

[Effect of dialysates on ultrastructure of mouse peritoneal mesothelium].

OBJECTIVE: To observe the effect of various peritoneal dialysates on the ultrastructure of the peritoneal mesothelium. METHODS: Continuous ambulatory peritoneal dialysis mice model was made by injecting domestic lactate, acetate, and American Baxter dialysates intraperitoneally. The diaphragmatic peritoneum of the mice was taken at 10th day and 21th day respectively after injection. RESULTS: After 10 day experiment, the mesothelial ultrastructure of Baxter group was normal, but some pathological changes occurred in the peritoneal mesothelium of both domestic lactate and acetate groups. And the injury of the peritoneal mesothelium was progressing with times, e.g. adhesion and exfoliation of the microvilli, shrinkage of the mesothelial cells and even fibrous adhesion. The extent of effects on the mesothelial cells varied in three groups, the least is Baxter group. After 21 day experiments, the diameters of the stomata were (6.96 +/- 2.46) microns and (6.98 +/- 2.16) microns in both domestic lactate and acetate dialysates groups respectively, which were much greater than those in physiological condition (1.47 +/- 0.88) microns (P < 0.01). The distribution density of the lymphatic stomata were significantly increased in acetate and lactate dialysate groups compared with the control group (P < 0.01). But little effects on the lymphatic stomata were showed after using Baxter dialysate. After discontinuing experiment for 10 days, the impairment of the peritoneal mesothelium recovered in Baxter group and improved to varying degrees in both domestic dialysate groups. The lymphatic stomata were still abnormal in both domestic dialysate groups. CONCLUSIONS: Our findings indicate that lactate and acetate dialysates are more like to elicit peritoneal fibrosis and the increase of distribution density and the enlargement of the lymphatic stomata can significantly enhance their absorption effects and increase their reabsorption quantity of dialysate from the peritoneal cavity during peritoneal dialysis. These changes of the lymphatic stomata and their lymphatic reabsorption are thought to be associated with deterioration of peritoneal function, and to cause ultrafiltration failure in the patients on long-term continuous ambulatory peritoneal dialysis (CAPD) therapy.

Acetates↗
PubMed1998

Increased expression of hypoxia inducible factor-1alpha in rat and human prostate cancer.

Hypoxia-inducible factor 1 (HIF-1) is a transcription factor that regulates genes involved in adaptation to hypoxia. Expression of HIF-1alpha was evaluated in rat and human prostate cancer cell lines. Increased expression of HIF-1alpha mRNA in rat prostate cancer cell lines and hypoxia-induced expression of HIF-1alpha protein in human prostate cancer cell lines are associated with increased cell growth rates and metastatic potential. HIF-1alpha mRNA was undetectable in the normal rat ventral prostate by Northern blot hybridization. HIF-1alpha protein expression and HIF-1 DNA binding activity were detected in normoxic PC-3 cells. Human prostate cancer cells plated at low density manifested higher functional HIF-1alpha expression than cells plated at high density independent of O2 tension. HIF-1alpha may become dysregulated in prostate cancer and thus drive the transcription of hypoxia-adaptive genes involved in tumor progression. This is also the first evidence that human cancer cells can express functional HIF-1alpha protein under normoxic conditions.

Animals↗
PubMed1998

Differential coupling of alpha1-, alpha2-, and beta-adrenergic receptors to mitogen-activated protein kinase pathways and differentiation in transfected PC12 cells.

Three adrenergic receptor families that selectively activate three different G proteins (alpha1/Gq/11, alpha2/Gi, and beta/Gs) were used to study mitogen-activated protein kinase (MAPK) activation and differentiation in PC12 cells. PC12 cells were stably transfected with alpha1A-, alpha2A-, or beta1-adrenergic receptors (ARs) in an inducible expression vector, and subclones were characterized. Norepinephrine stimulated inositol phosphate formation in alpha1A-transfected cells, inhibited cyclic adenosine 3'5'-monophosphate (cAMP) formation in alpha2A-transfected cells, and stimulated cAMP formation in beta1-transfected cells. Nerve growth factor activated extracellular signal-regulated kinases (ERKs) in all cell lines; however, norepinephrine activated ERKs only in alpha1A- and beta1-transfected cells but not in alpha2A-transfected cells. Norepinephrine also activated c-Jun NH2-terminal kinase and p38 MAPK in alpha1A-transfected cells but not in beta1- or alpha2A-transfected cells. Norepinephrine caused differentiation of PC12 cells expressing alpha1A-ARs but not those expressing beta1- or alpha2A-ARs. However, norepinephrine acted synergistically with nerve growth factor in promoting differentiation of cells expressing beta1-ARs. Whereas ERKs are activated by Gi- but not Gs-linked receptors in many fibroblastic cell lines, we observed the opposite in PC12 cells. The results show that activation of the different G protein signaling pathways has different effects on MAPKs and differentiation in PC12 cells, with Gq signaling pathways activating all three major MAPK pathways.

Adrenergic alpha-Agonists↗
PubMed1998

Apoptosis induction by the glucocorticoid hormone dexamethasone and the calcium-ATPase inhibitor thapsigargin involves Bc1-2 regulated caspase activation.

The requirement for caspases (ICE-like proteases) were investigated in mediating apoptosis of WEHI7.2 mouse lymphoma cells in response to two death inducers with different mechanisms of action, the glucocorticoid hormone dexamethasone (DX) and the calcium-ATPase inhibitor thapsigargin (TG). Apoptosis induction by these agents followed different kinetics, and was closely correlated with in vivo activation of caspase-3 (CPP32/Yama/Apopain) and cleavage of the caspase target protein poly(ADP-ribose) polymerase (PARP). Caspase activation and PARP cleavage were inhibited by Bcl-2 overexpression. Cell extracts from DX- and TG-treated cells cleaved the in vitro synthesized baculovirus p35 ICE-like protease target, producing 25 and 10 kDa fragments. p35 cleavage was inhibited by mutating the active site aspartic acid to alanine, and by a panel of protease inhibitors that inhibit caspase-3-like proteases, including iodoacetamide, N-ethylmaleimide, and Ac-DEVD-cho. Treatment of cells in vivo with two cell permeant peptide fluoromethylketone inhibitors of caspase activity, Z-VAD-fmk and Z-DEVD-fmk, inhibited DX- and TG-induced apoptotic nuclear changes and maintained plasma membrane integrity, whereas the cathepsin inhibitor, Z-FA-fmk, and two calpain inhibitors failed to inhibit apoptosis. An unexpected observation was that due to the delayed time course of DX-induced apoptosis, optimal preservation of plasma membrane integrity was achieved by adding caspase inhibitors beginning 8 h after DX addition. In summary, the findings indicate that two diverse apoptosis-inducing signals converge into a common Bcl-2-regulated pathway that leads to caspase activation and apoptosis.

Animals↗
PubMed1998

Training effects on soleus of cats spinal cord transected (T12-13) as adults.

Adult spinal cord transected (T12-13) cats were trained for 30 min/day, 5 days/week to either step on a treadmill (Stp-T) or stand (Std-T) for approximately 5 months. Training ameliorated soleus atrophy and enhanced maximum force capability compared to nontrained (N-T) spinal cats, with Stp-T being significantly different from N-T. Isometric twitch speed and maximum rate of shortening were unaffected by training; the soleus of all spinal groups was significantly faster than control. There was an elevation in myosin adenosine triphosphatase activity and a shift toward faster myosin heavy chain and fiber type compositions in N-T and Std-T, but not Stp-T cats. Thus, rhythmical activity involving muscle length and force changes (stepping) was more effective than a similar amount of a more static activity (standing). This specificity related to the type of training should be considered when developing rehabilitative strategies following spinal cord injury.

Animals↗
PubMed1998

Effects of inactivity on myosin heavy chain composition and size of rat soleus fibers.

Myosin heavy chain (MHC) and fiber size properties of the adult rat soleus were determined after 4-60 days of complete inactivity, i.e., lumbar spinal cord isolation. Soleus atrophy was rapid and progressive, i.e., 25% and 64% decrease in weight and 33% and 75% decrease in fiber size after 4 and 60 days of inactivity, respectively. Changes in MHC occurred at a slower rate than the atrophic response. After 15 days there was de novo expression of type IIx MHC (approximately 10%). By 60 days, type IIx MHC accounted for 33% of the total MHC content, and 7% of the fibers contained only type IIx MHC. The relative amount of type I MHC was reduced from 93% in control to 49% after 60 days of inactivity. Therefore, the effects of 60 days of inactivity suggest that during this time period at least 75% of fiber size and approximately 40% of type I MHC composition of the adult rat soleus can be attributed to activation-related events.

Animals↗