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Biomedical subjects

S Zheng

Publications and source records attributed to S Zheng.

At least 127 records · Page 7Linked to original sources
PubMed1999

[INDO/CI studies on the electronic spectra of tetraphenylporphyrin and its derivatives].

MNDO calculations and group theory were carried out on tetraphenylporphyrine (TPP) to obtain its optimum molecular geometry. We employed an INDO/CI method to study the electronic structures of tetraphenylporphyrine and its derivatives and identify their main electonic absorption bands. Five-orbital model was advanced to explain the typical characteristics of electronic spectra of H2TPP and its derivatives. The calculated wavelengths were in good agreement with the experimental values. The effects of the substitution of variant group were discussed and some helpful conclusions were drawn.

Models, Molecular↗
PubMed1999

[TXRF technique and quantitative analysis of mollusc teeth].

Total reflection X-ray fluorescence (TXRF) analysis technique and the instrument with a short path, high efficiency, low power and small volume are briefly presented. The detection limit of the system are at pg-level for Cu and Mo target excitation. Teeth of a marine mollusc were measured quantitatively and the spectrum and analysis results were given.

Animals↗
PubMed1998

In search of the first flower: A jurassic angiosperm, archaefructus, from northeast china

Angiosperm fruiting axes were discovered from the Upper Jurassic of China. Angiosperms are defined by carpels enclosing ovules, a character demonstrated in this fossil. This feature is lacking in other fossils reported to be earliest angiosperms. The fruits are small follicles formed from conduplicate carpels helically arranged. Adaxial elongate stigmatic crests are conspicuous on each carpel. The basal one-third of the axes bore deciduous organs of uncertain affinities. No scars of subtending floral organs are present to define the individual fertile parts as floral units, but the leaf-like structures subtending each axis define them as flowers. These fruiting axes have primitive characters and characters not considered primitive.

Journal Article↗
PubMed1998

Pathologic features of initial adenomas as predictors for metachronous adenomas of the rectum.

BACKGROUND: Colorectal cancer is the third most common cancer in the world, arising mostly from pre-existing adenomatous polyps (adenomas) of the large bowel. Patients with colorectal adenomas are at increased risk of colorectal cancer because of a high recurrence rate for adenomas. We followed a cohort of 1490 patients with rectal adenomas to determine whether recurrence might be related to pathologic characteristics of the initial adenomas. METHODS: The patients were identified in Haining County, China, from 1977 through 1978 by means of examination with a 15-cm rigid sigmoidoscope. They were followed by endoscopic examination at years 2, 4, 6, 11, and 16 after their initial polypectomy. New adenomas in the rectum were identified in 280 patients in these follow-up examinations. RESULTS: Statistically significant twofold to threefold elevated risks of metachronous (recurrent) adenomas were observed for patients who had more than two initial adenomas or whose most advanced initial adenoma was more than 1.0 cm in size, was of villous/tubulovillous type, or showed moderate to severe dysplasia. Much stronger associations were observed for advanced metachronous neoplasms, which are defined as cancers or adenomas with severe dysplasia, with multivariate adjusted relative risks (95% confidence interval) of 4.2 (1.8-9.9) for a large initial adenoma (>1.0 cm), 8.1 (4.2-15.6) for villous/tubulovillous architecture, and 14.4 (5.0-41.3) for severe dysplasia. In particular, patients who had a large (>1.0 cm) adenoma with severe dysplasia at baseline had a relative risk of 37 (7.8-174.7) of developing advanced metachronous neoplasms compared with patients who had small adenoma(s) with mild dysplasia. CONCLUSIONS: The risk of metachronous adenomas is closely related to the pathology of initial adenomas, thus allowing identification of a high-risk group of adenoma patients for close surveillance after their initial polypectomy.

Adenoma↗
PubMed1998

Differential enantioselectivity of murine glutathione S-transferase isoenzymes in the glutathione conjugation of trans-3,4-dihydroxy-1, 2-oxy-1,2,3,4-tetrahydrobenzo[c]phenanthrene stereoisomers.

The kinetics of the glutathione (GSH) conjugation of (+)- and (-)-enantiomers of anti- as well as syn-3,4-dihydroxy-1,2-oxy-1,2,3, 4-tetrahydrobenzo[c]phenanthrene (B[c]PDE) catalyzed by murine GSH S-transferase (GST) isoenzymes has been investigated. Murine GSTs exhibited significant differences in their enantioselectivity toward B[c]PDE stereoisomers. For example, while pi class isoenzyme mGSTP1-1 was virtually inactive toward stereoisomers with 1S configuration [(-)-syn-and (+)-anti-B[c]PDE], these stereoisomers were good substrates for alpha class isoenzyme mGSTA1-2. When GST activity was measured as a function of varying B[c]PDE concentration (10-320 microM) at a fixed saturating concentration of GSH (2 mM), each isoenzyme examined obeyed Michaelis-Menten kinetics with all four B[c]PDE stereoisomers. Alpha class isoenzyme mGSTA4-4 exhibited negligible activity toward all four stereoisomers of B[c]PDE. The catalytic efficiency of mGSTA1-2 was approximately 1.5- to 15-fold higher than other murine GSTs in the GSH conjugation of (-)-anti-B[c]PDE, which among the four B[c]PDE stereoisomers is the most potent pulmonary carcinogen in the newborn mouse model and a potent skin tumor-initiator. While alpha class isoenzymes mGSTA3-3 and mGSTA1-2 were equally efficient in the GSH conjugation of (+)-anti-B[c]PDE, their catalytic efficiencies toward this stereoisomer were significantly higher than those of mGSTP1-1 and mGSTM1-1. Likewise, mGSTA1-2 was relatively more efficient than other GSTs in the GSH conjugation of both enantiomers of syn-B[c]PDE. In summary, our results indicate that (a) murine GSTs significantly differ in their enantioselectivity in the GSH conjugation of B[c]PDE stereoisomers, which may partially account for the observed differences in the carcinogenic potency of B[c]PDE stereoisomers, and (b) mGSTA1-2 and mGSTA3-3 play a major role in the detoxification of B[c]PDE.

Animals↗
PubMed1998

Impaired differentiation of HPRT-deficient dopaminergic neurons: a possible mechanism underlying neuronal dysfunction in Lesch-Nyhan syndrome.

Lesch-Nyhan syndrome is a hereditary disorder of purine metabolism causing overproduction of uric acid and neurological problems including spasticity, choreoathetosis, mental retardation, and compulsive self-mutilation. The syndrome is caused by a defect in the enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT), which converts guanine and hypoxanthine to the nucleotides GMP and IMP. There is evidence that the neurological problems are due to an adverse effect of the HPRT deficiency on the survival and/or development of dopaminergic neurons, specifically. Here we report that HPRT-deficient PC12 mutants that have a normal or near normal dopamine content (55-97% of that of wild-type cells) fail to undergo neuronal differentiation induced by nerve growth factor (NGF) when the de novo pathway of purine synthesis is partially inhibited. However, nerve growth factor-induced differentiation is near normal under these conditions in PC12 HPRT-deficient mutants containing much lower dopamine levels (<8% of that of wild type cells), indicating a neurotoxic effect of the endogenous dopamine in the mutants. The degree of inhibition of the de novo pathway of purine synthesis was the same in both classes of HPRT-deficient mutants. Expression of BCl-2 in a PC12 mutant that has a normal dopamine content allowed partial NGF-induced differentiation suggesting that the apoptotic pathway might be involved in the failure of differentiation when the de novo pathway of purine synthesis is partially inhibited.

Animals↗
PubMed1998

Experimental comparison between the conversion electron yield and X-ray fluorescence in catalyst analysis.

To evaluate the application of the conversion-electron-yield (CEY) method in catalyst analysis, the intensities of the CEY and X-ray fluorescence (XRF) as a function of glancing angle were measured simultaneously. The probing depth of the CEY method is shallower than that of the XRF method. The CEY method also shows potential application for the analysis of even a powder specimen of a low-concentration zeolite catalyst.

Journal Article↗
PubMed1998

Studies of multimerin in human endothelial cells.

Multimerin is a novel, massive, soluble protein that resembles von Willebrand factor in its repeating, homomultimeric structure. Both proteins are expressed by megakaryocytes and endothelial cells and are stored in the region of platelet alpha-granules resembling Weibel-Palade bodies. These findings led us to study the distribution of multimerin within human endothelial cells. Multimerin was identified in vascular endothelium in situ. In cultured endothelial cells, multimerin was identified within round to rod-shaped, dense-core granules, some of which contained intragranular, longitudinally arranged tubules and resembled Weibel-Palade bodies. However, multimerin was found primarily in different structures than the Weibel-Palade body proteins von Willebrand factor and P-selectin. After stimulation with secretagogues, multimerin was observed to redistribute from intracellular structures to the external cellular membrane, without detectable accompanied secretion of multimerin into the culture media. In early passage endothelial cell cultures, multimerin was associated with extensive, fibrillary, extracellular matrix structures, in a different distribution than fibronectin. Although multimerin and von Willebrand factor are stored together in platelets, they are mainly found within different structures in endothelial cells, indicating that there are tissue-specific differences in the sorting of these soluble, multimeric proteins.

Blood Proteins↗
PubMed1998

Germline mutations of hMLH1 and hMSH2 genes in patients with suspected hereditary nonpolyposis colorectal cancer and sporadic early-onset colorectal cancer.

PURPOSE: The present study was designed to determine the frequency of germline mutations in the hMLH1 and hMSH2 genes in 31 families suspected of having hereditary nonpolyposis colorectal cancer who do not fulfill the criteria of the International Collaborative Group on Hereditary Nonpolyposis Colorectal Cancer but in whom a genetic basis for colon cancer is strongly suspected and 45 patients with sporadic early-onset colorectal cancer who developed colorectal cancer before the age of 40 years without any family history of colorectal cancer. METHODS: Genomic DNAs were prepared from peripheral blood samples of patients who were tested. All coding exons and exon-intron borders of these two genes were screened, first with the polymerase chain reaction-single-strand conformation polymorphism method, followed by sequencing of the DNA fragments displaying an abnormal single-strand conformation polymorphism pattern. RESULTS: In 31 families with suspected hereditary nonpolyposis colorectal cancer, we found six different germline mutations in seven unrelated families, including one missense mutation and three frame-shift mutations in the hMLH1 gene and one missense mutation and one frame-shift mutation in the hMSH2 gene. Totally, frequency of mutation was 23 percent, 16 percent and 7 percent in the hMLH1 and hMSH2, respectively. Only one missense mutation of the hMSH2 gene was identified in 45 patients (2 percent) with sporadic early-onset colorectal cancer. The mutation detection rate in families with suspected hereditary nonpolyposis colorectal cancer was significantly higher than that of patients with sporadic early-onset colorectal cancer (P < 0.05). CONCLUSION: Our definition of suspected hereditary nonpolyposis colorectal cancer is useful in the diagnosis of hereditary nonpolyposis colorectal cancer and for identifying those families who need genetic presymptomatic diagnosis. Our results indicate that it may be important to perform DNA testing in families suspected of having hereditary nonpolyposis colorectal cancer. On the other hand, we only detected a low mutation rate (2 percent) in 45 patients with sporadic early-onset colorectal cancer.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Expression of vascular endothelial growth factor in hepatocellular carcinoma and its relationship to tumor growth and metastasis.

To understand the relationship between the expression of vascular endothelial growth factor (VEGF) and the growth, metastasis of hepatocellular carcinoma (HCC), immunohistochemistry and Northern blot were used to investigate VEGF protein and mRNA in 21 cases of HCC with and without metastasis. VEGF protein was found in 8 of 9 cases with metastasis, whereas only in 4 of 12 cases without metastasis. The positive rate of the former was significantly higher than that in the latter. VEGF mRNA was detectable in both carcinoma and its surrounding liver tissues, but its level in the former was 2-3 times higher than that in the latter. In carcinoma with metastasis, the mRNA level was 5-6 times higher than that without metastasis. It is concluded that VEGF is closely related to the growth of HCC as well as its metastasis and it might be a useful indicator for the metastatic potential of HCC.

Carcinoma, Hepatocellular↗
PubMed1998

Cellular distribution of retinoic acid receptor-alpha protein in serous adenocarcinomas of ovarian, tubal, and peritoneal origin: comparison with estrogen receptor status.

Retinoids are effective growth modulators of human ovarian carcinoma cell lines. Their effects are mediated by nuclear retinoic acid receptors (RARs) and retinoid X receptors (RXRs), which are transcriptional factors and members of the steroid/thyroid receptor superfamily. To our knowledge, until now, the cellular distribution of RAR proteins in human ovarian tumor specimens is unknown. This study provides new data on the differential cellular localization of RAR alpha protein in 16 serous adenocarcinomas originating from the ovaries, fallopian tubes, and the peritoneum. Using an affinity-purified antiserum specific for RAR alpha and a monoclonal antibody recognizing the full-length estrogen receptor molecule (clone 6F11), we performed immunohistochemistry on frozen tissue sections and examined the relationship between RAR alpha and estrogen receptor protein expression by comparing the percentage of immunostained tumor cells for either receptor. Our findings indicate a strong linear relationship between the percentages of RAR alpha- and estrogen receptor-labeled tumor cells as determined by linear regression analysis (P < 0.005, r = 0.825). A modest inverse relationship was found between the percentage of RAR alpha-positive tumor cells and histological grade, attesting to a differentiation-dependent trend (P < 0.04). No significant relationship was found between RAR alpha-labeled cells and clinical stage (P = 0.139), site of tumor origin (ovaries versus fallopian tubes versus peritoneum) (P = 0.170), and primary versus metastatic lesion (P = 0.561). Thus, serous adenocarcinomas are capable of expressing RAR alpha and estrogen receptor despite high histological grade and advanced stage of neoplastic disease. Compared with the heterogeneous localization of RAR alpha in cancer cells, there was widespread RAR alpha immunoreactivity in tumor-infiltrating lymphocytes, vascular endothelial cells, and stromal fibroblasts, underscoring the value of immunohistochemistry in the accurate determination of RAR/(RXR) content in tumor specimens.

Adenocarcinoma↗
PubMed1998

Utility of microdissection and polymerase chain reaction for the detection of immunoglobulin gene rearrangement and translocation in primary intraocular lymphoma.

OBJECTIVE: Primary intraocular lymphoma, a non-Hodgkin's lymphoma, is a primary central nervous system lymphoma (PCNSL). Diagnosis is usually made by identifying malignant, large B lymphocytes in the vitreous, eye, brain, and cerebral spinal fluid; however, these cells are few, friable, and difficult to recognize. Recently, clonal heavy chain immunoglobulin (IgH) gene rearrangement and bcl-2 gene translocation have been reported in systemic B-cell lymphoma and are used for the detection of malignant cells and in making a diagnosis. The authors investigated the molecular changes in three eyes and a chorioretinal biopsy specimen of four patients with PCNSL. DESIGN: Human tissue study. MATERIALS: Five ocular specimens of PCNSL were collected. INTERVENTION: The first patient had a diagnostic enucleation of the left eye. The second patient underwent diagnostic chorioretinal biopsy. In the third case, a pair of autopsied eyes with reactive lymphoplasmacytic infiltrates of a patient with acquired immune deficiency syndrome (AIDS) were studied. In the fourth case, an enucleated eye of a patient with AIDS-associated lymphoma was sampled. MAIN OUTCOME MEASURES: The bcl-2 and IgH genes of the lymphoma cells from routine, paraffin-embedded, formaldehyde-fixed, or frozen histologic tissue sections were analyzed using microdissection and polymerase chain reaction (PCR) technique. RESULTS: Lymphoma cells obtained from the above four cases showed IgH rearrangement gene in the third framework of the VH region. Bcl-2-associated translocation also was detected in three cases (cases 1, 2, and 4). CONCLUSION: Rearrangement of the IgH gene can serve as a molecular marker for PCNSL. Microdissection allows for procurement and analysis of specific, selected, minute cell populations that are obtained from histologic sections of the complex, heterogeneous tissue. Translocation of IgH and bcl-2, the apoptotic "survival" signal and proto-oncogene, could contribute to the pathogenesis of PCNSL. The combination of microdissection and PCR is a powerful tool for studies of small lesions and cell populations and for understanding disease mechanisms.

Adult↗
PubMed1998

Studies of multimerin in patients with von Willebrand disease and platelet von Willebrand factor deficiency.

In normal platelet alpha-granules von Willebrand factor (VWF) is stored with multimerin and factor V in an eccentric electron-lucent zone. Because the platelet stores of VWF are deficient in 'platelet low' type 1 and type 3 von Willebrand disease (VWD), we investigated their electron-lucent zone proteins. The patients with VWD had partial to complete deficiencies of plasma and platelet VWF but normal alpha-granular multimerin and factor V, and normal alpha-granular fibrinogen, thrombospondin-1, fibronectin, osteonectin and P-selectin. In type 3 VWD platelets, alpha-granular electron-lucent zones lacking VWF-associated tubules were identified and multimerin was found in its normal alpha-granular location. These findings indicate that the formation of the electron-lucent zone and the sorting of multimerin to this region occur independent of VWE The isolated abnormalities in VWF suggests a VWF gene mutation is the cause of 'platelet low' type 1 VWD.

Blood Platelets↗
PubMed1998

Suppression of peroxisomal membrane protein defects by peroxisomal ATP binding cassette (ABC) proteins.

X-Linked adrenoleukodystrophy (X-ALD) is a neurodegenerative disorder characterized by reduced peroxisomal very long chain fatty acid (VLCFA) beta-oxidation. The X - ALD gene product (ALDP) is a peroxisomal transmembrane protein with an ATP binding cassette (ABC). ALDP and three other ABC proteins (PMP70, ALDR, P70R) localize to the peroxisomal membrane. The function of this family of peroxisomal membrane proteins is unknown. We used complementation studies to begin analysis of their role in VLCFA beta-oxidation and on the peroxisomal membrane. Expression of either ALDP or PMP70 restores VLCFA beta-oxidation in X-ALD fibroblasts, indicating overlapping functions. Their expression also restores peroxisome biogenesis in cells that are deficient in the peroxisomal membrane protein Pex2p. Thus it is likely that complex protein interactions are involved in the function and biogenesis of peroxisomal membranes that may contribute to disease heterogeneity.

ATP Binding Cassette Transporter, Subfamily D, Mem↗
PubMed1998

Apolipoprotein AIV: a potent endogenous inhibitor of lipid oxidation.

Overexpression of apolipoprotein (apo) AIV in transgenic mice confers significant protection against atherosclerosis in apoE knockout animals even in the presence of a more severe atherogenic lipid profile. Because lipoprotein oxidation has been recognized to be pivotal in development of atherosclerosis, the antioxidative activity of apoAIV was investigated. Fasting intestinal lymph was used to mimic conditions in the interstitial fluid, the potential site for lipoprotein oxidation in vivo. ApoAIV (10 micrograms/ml) significantly inhibited copper-mediated oxidation of lymph. This inhibitory effect was further evaluated using purified low-density lipoprotein. Addition of apoAIV (2.5 micrograms/ml) increased the time of 50% conjugated diene formation by 2.4-fold, whereas apoE or BSA did not show such a protection even at 20 micrograms/ml. Addition of apoAIV during the propagation phase also resulted in a dose-dependent inhibition. ApoAIV also protected macrophage-induced oxidation of fasting lymph. These results provide the first evidence that apoAIV is a potent endogenous antioxidant.

Animals↗
PubMed1998

An experimental study on rat model of parkinsonism by gene therapy.

OBJECTIVE: To induce significant improvement of motor abnormalities and striatal dopamine (DA) levels in rat model of Parkinson's disease (PD), by intracerebral grafting of the genetically modified muscle cells expressing tyrosine hydroxylase (TH). METHODS: Primary myoblasts and myotubes from the rat were prepared by cell culture and a plasmid, pCMVTH, containing TH gene and a promoter of cytomegalovirus (CMV) was constructed by DNA recombination technique. The primary muscle cells were transfected with newly constructed pCMVTH DNA vector, by using lipofection. These genetically modified muscle cells were grafted into the caudate- putamen of 6-OHDA-lesioned rats, representing PD models. Before and after grafting, the rotational behaviour and the striatal levels of DA and its metabolities were tested at different postoperative survival times. In addition, the immunocytochemistry for showing TH activity was done both in vitro and in vivo. RESULTS: The newly constrcuted plasmid, pCMVTH was proved to contain TH gene and have correct direction of insertion. The cultured primary myoblasts and myotubes lipofected with pCMVTH were immunocytochemically shown to express TH activity in vitro. After grafting, these TH-expressing muscle cells showed to have a long-term survival cells in vivo and induced a marked decrease in abnormal locomotion and a increase in striatal DA levels for PD rat model. CONCLUSIONS: In experimental gene therapy for PD, the pCMVTH is a useful vector for carrying TH gene. The lipofection is a practical technique for transferring a target gene into eukaryotes and primary cultured muscle cells should be a good vehicle for DNA transfer and intracerebral grafting.

Animals↗
PubMed1998

[Effects of mifepristone on gene expression of epidermal growth factor in human uterine leiomyoma].

OBJECTIVES: To study the effects of mifepristone on epidermal growth factor gene expression in human uterine leiomyoma. METHODS: 20 patients with leiomyoma were divided into two groups. One was control group who underwent hysterectomy because of leiomyoma, the other was experimental group who underwent hysterectomy after pretreatment with mifepristone 10 mg/daily for 3 months. Epidermal growth factor (EGF) mRNA was semiquantified in samples of leiomyoma and adjacent normal myometrium from patients untreated in different phases of menostrual cycle and from those treated with mifepristone. Semiquantitative reverse transcriptase polymerase chain reaction, using beta-actin as internal standard, was applied to determine levels of EGF mRNA. RESULTS: Leiomyoma untreated with mifepristone had significantly greater amounts of EGF mRNA than adjacent normal myometrium of uterus only in the luteal phase, but not in the follicular phase of cycle. Similarly, leiomyoma untreated with mifepristone also had significantly larger amount of EGF mRNA than treated leiomyoma in the luteal phase of the cycle, whereas, no difference in the follicular phase of the cycle. CONCLUSION: These findings suggested that: (1) EGF mRNA levels in leiomyoma were increased only in the luteal phase, therefore, maybe mainly controlled by progesterone; (2) mifepristone inhibited EGF gene expression in leiomyoma. This may be one of regression mechanism of uterine leiomyoma in response to the antiprogesterone mifepristone.

Epidermal Growth Factor↗