Biomedical subjects

L Zeng

Publications and source records attributed to L Zeng.

At least 181 records · Page 10Linked to original sources

PubMed1996

[The effect of gamma-interferon on hepatic fibrosis in schistosomiasis japonica].

OBJECTIVE: To study the effect of gamma-IFN on hepatic fibrosis in schistosomiasis japonica. METHODS: The amount and distribution of gamma-IFN and extracellular matrix, including fibronectin (FN), laminin (LN), I and II collagen which were used to judge the suppressing effect of gamma-IFN on hepatic fibrosis as markers of dynamics of extracellular matrix after administration of recombinant gamma-IFN, in liver obtained at different stages from S. japonicum-infected mice were determined by immunohistochemical streptavidin biotin-peroxidase complex method. RESULTS: The amount of gamma-IFN in liver reached a peak (3 mice respectively reached 2, 3 and 4 grade) at the 16th week after infection, which was higher than the levels of control groups and infected-mice at the 8-12th week (chi 2 = 15.39, 7.50, P < 0.01), and the majority of gamma-IFN was distributed round egg granuloma. FN and LN, and I and II collagen increased to 1 grade, individual 2 grade, at the 8th week after infection, which were higher than control (chi 2 = 12.44-15.39, P < 0.01), and were lineally distributed round egg granuloma. With chronicity and decrease of gamma-IFN, however, FN, LN and I, II collagen gradually increased, and reached a peak (over 70% infected mice reached 3-4 grade) respectively at the 20th week and 24th week, became wide, thick and retiform and deposited round and in egg granuloma. After administration of gamma-IFN, only 3 infected mice had 2 grade of FN at the 20th week, two mice had respectively 3 grade of type I and II collagen at the 24th week, and none of them reached 4 grade, which were significantly less than those in the untreated group at the same stage (chi 2 = 10.77, 5.05, 7.20, P < 0.01-0.05). CONCLUSION: The results indicate that gamma-IFN may play an important role in opposing the inflammatory response of egg granuloma, decreasing secretion and deposition of extracellular matrix in liver and suppressing hepatic fibrosis.

Animals↗

PubMed1996

[The effect of interferon in combination with ribavirin on the plus and minus strands of hepatitis C virus RNA in patients with hepatitis].

The effect of interferon in combination with ribavirin on the plus and minus strands of hepatitis C virus (HCV) RNA in patients with chronic hepatitis C (CHC) was studied by means of nested RT-PCR. The results showed that in those who respond to the combination of antiviral therapy, their increased serum ALT levels decreased to normal range, but more than half (55.56%) of these patients relapsed 24 weeks after cessation of the antiviral therapy. The positive rate of the plus strand HCV RNA in serum (92.31%) decreased significantly to 38.46% (P < 0.005) and that of the minus strands HCV RNA in peripheral blood mononuclear cells (PBMC, 76.92%) to 38.46% (P < 0.05) at the end of the treatment, but little effect on the plus strand HCV RNA in PBMC in these patients was found. Relapse occurred in patients whose plus and minus strands of HCV RNA in PBMC remained positive during treatment. These data indicated that absence of HCV RNA in serum do not mean complete clearance of HCV and can not predict a sustained therapeutic response. For evaluating the antiviral effect and prognosis it is essential to measure the plus and minus strands of HCV RNA in serum and PBMC simultaneously. The results of the combined antiviral therapy were similar to that of single interferon treatment; it seems that rib-a-virin do not enhance the antiviral effect of interferon.

Adult↗

PubMed1996

[Analysis of human hair lead and zinc during various physiological periods].

Hair specimens were collected from 1,477 healthy persons at various physiological periods in different areas of Henan Province and determined for their lead and zinc contents, to study systematically the trend of their changes, correlationship between them and their intrinsic connection. Results showed hair lead level was higher in persons, except neonates and the elderly, living in urban area than in rural one. Hair lead level correlated inversely with hair zinc level in logarithmic scale during various physiological periods, with a coefficient of correlation of 0.971. It suggested there possibly is antagonism between lead and zinc in human bodies. Theoretical explanation of the above results and the possibility to use zinc to prevent and treat the hazard caused by lead were provided.

Adolescent↗

PubMed1996

[Quadrant pattern visual evoked potential in normal eyes].

OBJECTIVE: The study was designed to approach the difference in pattern visual evoked potential (PVEP) among quadrants of the normal eye. METHODS: Quadrant transient PVEP method was used to record quadrant PVEP for 70 eyes of 35 normal subjects. RESULTS: The latency of P100 in lower temporal and lower nasal fields was significantly shorter than that in upper temporal and upper nasal fields; the amplitude of P100 in lower temporal and lower nasal fields was significantly higher than that in upper temporal and upper nasal fields. Generally, in lower field, the P100's latency is shorter and its amplitude higher. CONCLUSION: The difference in P100 between upper and lower field of normal person is possibly related to the fact that the lower field is used more frequently than the upper in ordinary human or animal life, and to the differences in distribution of retinal ganglion cells and in retina-cortex pathway between the upper and lower retina.

Adult↗

PubMed1996

[A review of 10 patients of nephrectomy through laparoscope video].

Ten patients were subjected to nephrectomy through laparoscope video. Compared with routine nephrectomy, it has such merits as slight trauma, less bleeding and pain during the operation as well as quick recovery and short hospitalization. In 6 male patients and 4 female patients the oldest one was 75 years old, and the youngest one was 15 years old. Seven patients suffered from nephrohydrosis and 3 from polycystic kidney. Before the operation, the patients were found the loss of function of the diseased kidney. The video scope was inserted into the abdominal cavity through an operating hole under the navel making the exploration in the cavity; the other operations are as basical as routine operations. The ill kidney was cut off and put into a special pocket, then it was cut into pieces, and taken out. The abdominal membrane was enclosed by the emanometer, the drainage tube kept. In the 10 patients the operations were successful and satisfactory.

Adolescent↗

PubMed1995

Insulin and vasopressin elicit inhibition of cholera-toxin-stimulated adenylate cyclase activity in both hepatocytes and the P9 immortalized hepatocyte cell line through an action involving protein kinase C.

Incubation of hepatocytes or the SV40-DNA-immortalized hepatocyte P9 cell line with cholera toxin led to a time-dependent activation of adenylate cyclase activity, which occurred after a defined lag period. When added together with cholera toxin, each of the hormones insulin and vasopressin was capable of attenuating the maximum stimulatory effect achieved by cholera toxin over a period of 60 min through a process which could be blocked by the compounds staurosporine and chelerythrine. Attenuating effects on cholera-toxin-stimulated adenylate cyclase activity could also be elicited by using either the protein kinase C (PKC)-stimulating phorbol ester PMA (phorbol 12-myristate 13-acetate) or the protein phosphatase inhibitor okadaic acid. Alkaline phosphatase treatment of membranes reversed the inhibitory effect of PMA. Cholera toxin also stimulated the adenylate cyclase activity of intact CHO (Chinese-hamster ovary) and NIH-3T3 cells, but this activity was insensitive to the addition of PMA. Overexpression of various PKC isoforms in CHO cell lines did not confer sensitivity to inhibition by PMA upon cholera-toxin-stimulated adenylate cyclase activity. Rather, overexpression of the gamma isoform of PKC allowed PMA to stimulate adenylate cyclase activity in CHO cells. It is suggested that the PKC-mediated phosphorylation of a membrane protein attenuates cholera-toxin-stimulated adenylate cyclase activity in hepatocytes and P9 cells. The cellular selectivity of such an action may be due to the target for this inhibitory action of PKC being a particular isoform of adenylate cyclase which provides the major activity in hepatocytes and P9 cells, but not in either CHO or NIH-3T3 cells.

3T3 Cells↗

PubMed1995

Resistance to transformation by insertionally activated c-erbB is a dominant phenotype in fibroblasts.

Tissue-specific factors influence whether cells are susceptible to transformation by erbB oncogenes. Avian fibroblasts resist transformation by insertionally activated c-erbB (IAc-erbB), whereas erythroblasts are transformed by this mutant of the epidermal growth factor receptor. In studies presented here, NIH/3T3 cells resisted transformation by IAc-erbB. This finding indicates that the nonpermissiveness of fibroblasts is conserved between avian and murine species. Surprisingly, expression of IAc-erbB blocked transformation by a v-erbB allele. The trans-dominant interference by IAc-erbB occurred despite expression at levels lower than for v-erbB. Together with previous reports, the results indicate that IAc-erbB can exert opposite growth effects in different tissues. The switch from positive to negative growth regulation, which depends on the cellular context, provides novel insight into tissue-specific regulation of receptor tyrosine kinases. Evasion of cell-specific inhibition apparently contributes to the distinct tissue tropisms of various erbB mutants.

3T3 Cells↗

PubMed1995

A role for protein kinase C-mediated phosphorylation in eliciting glucagon desensitization in rat hepatocytes.

An immobilized hepatocyte preparation was used to show that both vasopressin and glucagon could desensitize the ability of glucagon to increase intracellular cyclic AMP concentrations. This process was not dependent on any influx of extracellular Ca2+ and was not mediated by any rise in the intracellular level of Ca2+. The protein kinase C-selective inhibitors chelerythrine, staurosporine and calphostin C acted as potent inhibitors of the desensitization process but with various degrees of selectivity regarding their ability to inhibit the desensitizing actions of glucagon and vasopressin. The protein phosphatase inhibitor okadaic acid was just as potent as vasopressin and glucagon in causing desensitization. Treatment of hepatocyte membranes with alkaline phosphatase restored to near control levels the ability of glucagon to stimulate adenylate cyclase activity in membranes from both glucagon- and vasopressin-treated (desensitized) hepatocytes. It is suggested that the desensitization of glucagon-stimulated adenylate cyclase activity involves a reversible phosphorylation reaction with the likely target being the glucagon receptor itself.

Adenylyl Cyclases↗

PubMed1995

Analysis of simian hemorrhagic fever virus (SHFV) subgenomic RNAs, junction sequences, and 5' leader.

Full-length simian hemorrhagic fever virus (SHFV) genome RNA (about 15 kb in length) and six subgenomic RNAs, ranging in size from 0.65 to 4.7 kb, were detected by Northern blot hybridization in MA104 cytoplasmic extracts with a 3' genomic antisense probe. The 5' regions of the two smallest subgenomic RNAs (RNAs 6 and 7) were cloned and sequenced. Sequence analysis indicated that these two RNAs contained a common 5' leader sequence joined to the subgenomic RNA bodies via a highly conserved junction sequence; the junction sequence of RNA 7 was 5'-TTAACC-3', while that of RNA 6 was 5'-TCAACC-3'. The complete 5' leader sequence (208 nt) was obtained from genomic RNA. The genomic 5' junction sequence is identical to that of RNA 7. Northern blot hybridization with an antisense 5' leader probe confirmed the presence of the complete leader sequence in all six species of subgenomic RNA. In its virion morphology, genome size, gene order, and replication strategy, SHFV is most similar to viruses such as equine arteritis virus, lactate dehydrogenase-elevating virus, and Lelystad virus/porcine respiratory and reproductive syndrome virus.

Animals↗

PubMed1995

Specific suppression by prostaglandin E2 of activation-induced apoptosis of human CD4+CD8+ T lymphoblasts.

Receptors (Rs) for prostaglandin E2 (PGE2) of the EP2 subtype are expressed at high levels in rodent and human thymuses, with preferential localization on immature thymocytes. Human cultured lymphoblasts of the Tsup-1 line express CD4 and CD8 but only a low level of CD3, typical of immature thymocytes, and bear EP2-type Rs for PGE2 that were identified by binding of [3H]PGE2 and Ab to recombinant EP2Rs, and by cAMP responses to PGE2. PGE2 protected Tsup-1 cells from apoptosis initiated by diverse stimuli, including mitogenic lectins and anti-Fas or anti-CD3 plus anti-CD28 Abs, but not ionomycin, as assessed by suppression of both fragmentation of [3H]thymidine-labeled DNA and appearance of free 3'-OH ends of cleaved DNA. An EP2R-selective synthetic agonist also significantly suppressed lectin-induced apoptosis of Tsup-1 cells. Phosphodiesterase inhibition synergistically enhanced PGE2-induced increases in cAMP and decreases in apoptosis in parallel, which suggests that the EP2R-specific protective effect of PGE2 is mediated predominantly by cAMP suppression of apoptosis. Dibutyrylcyclic AMP alone protected Tsup-1 cells against lectin-induced apoptosis, but the maximal effect was less than that for PGE2. The thromboxane A2 mimetic U46619 initiated apoptosis of Tsup-1 cells that was suppressed significantly by PGE2. Immune negative selection of immature thymocytes thus may be regulated by opposing effects of endogenous eicosanoids that include destruction by thromboxane A2 and protection by PGE2.

Antibodies, Monoclonal↗

PubMed1995

Human malignant mesothelial cells: variability of ultrastructural features in established and nude mice transplanted cell lines.

The aim of this study was to determine, by transmission electron microscopy, the differentiation features of 21 human malignant mesothelioma cell lines (HMCLs) established from 13 specimens of 12 confirmed human malignant mesotheliomas, and of tumours induced in nude mice injected with 16 HMCLs. Fifty per cent of HMCLs showed typical mesothelial differentiation (long and slender microvilli, desmosomes, perinuclear intermediate filaments); 29 per cent did not show differentiation; and the remainder were poorly differentiated. Three human tumour specimens gave several different HMCLs; the cell lines obtained from a given tumour exhibited variable mesothelial differentiation. Eleven HMCLs were compared with the native tumour. Four were similar to the tumour and seven were less well differentiated, in most cases in relation to their microvilli. With six HMCLs, tumours induced in nude mice were less well differentiated than the corresponding cell lines, whereas with four HMCLs, tumours were equally or better differentiated. However, in most nude mice tumours, typical mesothelial microvilli were present. These results show that cell lines established from malignant mesothelioma may exhibit dedifferentiated features. However, while the variability in ultrastructural differentiation may result from the culture microenvironment, it could also be related to the state of differentiation, of the native tumour sample and to tumour cell heterogeneity.

Animals↗

PubMed1995

New bioactive adjacent bis-THF annonaceous acetogenins from Annona bullata.

Five new adjacent bis-THF annonaceous acetogenins, 32-hydroxybullatacin, 31-hydroxybullatacin, 30-hydroxybullatacin, and (2,4-cis and trans)-28-hydroxybullatacinones, were isolated from the ethanolic extract of the bark of Annona bullata Rich. (Annonaceae). The absolute configurations of the above five compounds, as well as those of (2,4-cis and trans)-32-, 31-, and 30-hydroxybullatacinones and (2,4-cis and trans)-bulladecinones, previously isolated from the same extract, were defined by the application of the advanced Mosher ester [methoxy(trifluoromethyl)phenyl acetate or MTPA] methodology. The determination of the absolute configuration of C-20 of (2,4-cis and trans)-bulladecinones to be S supports our hypothesis that the cyclization of the THF rings of (2,4-cis and trans)-bulladecinones starts from C-12 (the right side). The first five compounds listed above showed potent bioactivities in the brine shrimp lethality test (BST) and among six human solid tumour cell lines.

Animals↗

PubMed1995

Stable SV40-transformation and characterisation of some DNA repair properties of fibroblasts from a trichothiodystrophy patient.

To characterize nucleotide excision repair properties of cells from trichothiodystrophy (TTD) patients genetically-related to the xeroderma pigmentosum (XP) group D, TTD skin fibroblasts from two unrelated patients (TTD1VI and TTD2VI) belonging to the TTD/XPD group were transformed with a plasmid containing SV40 large T antigen-coding sequences and some DNA repair properties, such as unscheduled DNA synthesis (UDS), UV-survival, in vitro repair synthesis of cell extracts and reactivation of UV-irradiated reporter plasmid were studied. Results showed that: a) both untransformed and transformed TTD cells present a reduced UV-survival, compared to wild-type cells, but at significantly less reduced levels than XP-D cells; b) reduced repair activities were detected in both TTD and XP-D transformed cells by using in vitro cell free extract repair and reactivation of UV-irradiated plasmid procedures, and these relative reduced extents correlated with respective UV-survival; c) surprisingly, near wild-type UDS levels were detected in TTD2VILas transformed cells at different passages after the crisis, suggesting a phenotypic reversion of this transformed cell line; d) fluoro-cytometric analysis of TTD2VILas cells revealed a strong increase of a cell population containing a DNA amount more than twice as high than that of untransformed cells; finally, e) when UDS data were normalized to the DNA content in TTD2VILas cells, it appeared that the repair efficiency was only slightly higher than in untransformed cells. This implies that in transformed cells DNA repair properties should be evaluated, taking into account additional parameters. We obtained an immortalized TTD cell line which maintains DNA repair properties similar to those of parental untransformed cells and may be used to characterize the TTD defect at genetic, molecular and biochemical levels.

Cell Extracts↗

PubMed1995

Meliavolkenin, a new bioactive triterpenoid from Melia volkensii (Meliaceae).

Meliavolkenin, a new triterpene with an apotirucallane skeleton, has been isolated from the root bark of Melia volkensii (Meliaceae) by bioactivity-directed fractionation using the brine shrimp lethality test. The structure has been elucidated using spectral and chemical data. The relative stereochemistries were determined by reduction and acetonide derivations, and the ring conformations were analyzed using the results of NOESY experiments. Meliavolkenin was bioactive in the brine shrimp lethality test and gave moderate cytotoxicities against three human solid tumor lines.

Acetone↗

PubMed1995

A new cytotoxic dihydroxy sterol from the soft coral Alcyonium patagonicum.

A new sterol, 24-methylenecholest-4-ene-3 beta,6 beta-diol [1] was isolated from the soft coral Alcyonium patagonicum collected from the South China Sea. Its structure was determined by spectral analysis. Compound 1 was cytotoxic against the P-388 cell line with an IC50 value of 1 microgram/ml.

Animals↗

PubMed1995

Venezenin: a new bioactive Annonaceous acetogenin from the bark of Xylopia aromatica.

Asimicin and a new cytotoxic Annonaceous acetogenin, venezenin [1], were isolated from the bark of Xylopia aromatica by bioactivity-directed fractionation using lethality to brine shrimp. Compound 1 represents an unusual type of C37 Annonaceous acetogenin, lacking either tetrahydrofuran (THF) or epoxide rings and possessing a double bond located two methylenes away from a vicinal diol in the hydrocarbon chain. The structure of 1 was elucidated by 1H- and 13C-nmr, COSY, single-relayed COSY, and by HMBC techniques, and derivatization. Annomontacin 10-one [6] and 18/21-cis-annomontacin-10-one [7], two semi-synthetic mono-THF acetogenins were prepared from 1. These acetogenins showed cytotoxicity, comparable or superior to adriamycin, against three human solid tumor cell lines. Reduction of the 10-keto of 1 to the racemic OH-10 derivative enhanced the bioactivity, as did the conversion of 1 to 6 and 7. Venezenin [1], like other Annonaceous acetogenins, showed inhibition of oxygen uptake by rat liver mitochondria and demonstrated that the THF ring may not be essential to this mode of action.

Animals↗

PubMed1995

Two new cytotoxic monotetrahydrofuran Annonaceous acetogenins, annomuricins A and B, from the leaves of Annona muricata.

The leaves of Annona muricata have yielded eight monotetrahydrofuran Annonaceous acetogenins. Two of them, annomuricins A [1] and B [2], whose chemical structures were deduced by ms, nmr, ir, and uv spectral and chemical methods, are novel and unusual. Compounds 1 and 2 each possess five hydroxyl groups; two hydroxyl groups are vicinal, with the vicinal group of 1 threo and that of 2 erythro. The absolute configurations of 1 and 2 were determined by Mosher ester methodology. Six monotetrahydrofuran acetogenins, previously described in the seeds, were found in the leaves; these are gigantetrocin A, annonacin-10-one, muricatetrocins A and B, annonacin, and goniothalamicin.

4-Butyrolactone↗

PubMed1995

Muricatocins A and B, two new bioactive monotetrahydrofuran Annonaceous acetogenins from the leaves of Annona muricata.

The leaves of Annona muricata have yielded the novel monotetrahydrofuran Annonaceous acetogenins, muricatocins A [1] and B [2]. Each compound possesses five hydroxyl groups, with two hydroxyl groups at the C-10 and C-12 positions. The absolute configurations of 1 and 2 (except for positions C-10 and C-12) were determined by Mosher ester methodology. The C-10, C-12 acetonides (1c, 2c) suggested relative stereochemistry and significantly enhanced cytotoxicity against the A-549 human lung tumor cell line. Three known monotetrahydrofuran acetogenins, annonacin A, (2,4-trans)-isoannonacin, and (2,4-cis)-isoannonacin, were also found.

4-Butyrolactone↗