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Biomedical subjects

Z Xu

Publications and source records attributed to Z Xu.

At least 523 records · Page 29Linked to original sources
PubMed1994

Effects of dietary zinc deficiency on the hepatic microsomal cytochrome P450 2B in rats.

This study was conducted to investigate whether the effects of zinc deficiency on the in vitro and in vivo drug metabolism in rats results from an altered expression of hepatic microsomal P450, particularly P450 2B (2B), in rats. Three-week-old, male Wistar rats were randomly assigned to three groups: a zinc-adequate ad libitum (ZnAL), zinc-adequate pair-fed (ZnPF), and zinc-deficient (ZnDF) group. After 3 weeks on the diet, each dietary group was further divided into drug control and phenobarbital (PB, 100 mg/kg, 3 days, ip) group. Within the drug control group, total microsomal P450 concentration was lower in both ZnPF and ZnDF than in ZnAL. Zinc deficiency resulted in a decreased aminopyrine N-demethylase (AD) activity expressed per milligram protein, with no effect on benzphetamine N-demethylase (BD) activity. The constitutive level of 2B protein and mRNA was not affected by dietary treatments. The level of NADPH--P450 reductase in ZnDF was significantly higher than in ZnAL and ZnPF. PB treatment significantly induced total microsomal P450 concentration, AD and BD activities expressed per milligram protein, 2B protein and mRNA levels, and NADPH-P450 reductase level in all dietary groups. In summary, the constitutive level of AD activity, but not BD activity, was decreased in dietary zinc deficient rats. The constitutive levels of 2B protein and mRNA were not affected by dietary zinc deficiency. PB-induced expression of 2B, both transcriptionally and translationally, and the induction of AD and BD activity by PB were not affected by zinc deficiency in rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Aminopyrine N-Demethylase↗
PubMed1994

Incomplete processing of progastrin expressed by human colon cancer cells: role of noncarboxyamidated gastrins.

Gastrin is mitogenic for several colon cancers. To assess a possible autocrine role of gastrin in colon cancers, we examined human colon cancer cell lines for expression of gastrin mRNA and various forms of gastrin. Gastrin mRNA was not detected in the majority of colon cancer cell lines by Northern hybridization but was detected in all human colon cancer lines by the sensitive method of reverse transcriptase-polymerase chain reaction (PCR). Gastrin mRNA was quantitated by the competitive PCR method. The majority of cell lines expressed very low levels of gastrin mRNA (< 1-5 copies/cell); only one cell line expressed > 20 copies/cell. The mature carboxyamidated form of gastrin was not detected in any of the cell lines by radioimmunoassay or immunocytochemistry. Results suggested that either gastrin mRNA expressed by colon cancer cells was altered (mutated) or posttranslational processing of progastrin was incomplete. Gastrin cDNA from all the colon cancer cell lines had an identical sequence to the published sequence of human gastrin cDNA. Specific antibodies against precursor forms of gastrin were used, and significant concentrations of nonamidated (glycine-extended) and prepro forms of gastrin were measured in tumor extracts of representative colon cancer cell lines. The presence of precursor forms of gastrin suggested a lack of one or more of the processing enzymes and/or cofactors. Significant concentrations of the processing enzyme (peptidylglycine alpha-amidating monooxygenase) were detected in colon cancer cells by immunocytochemistry. Therefore, lack of other cofactors or enzymes may be contributing to incomplete processing of precursor forms of gastrin, which merits further investigation. Since low levels of gastrin mRNA were expressed by the majority of human colon cancer cell lines and progastrin was incompletely processed, it seems unlikely that gastrin can function as a viable autocrine growth factor for colon cancer cells. High concentrations of glycine-extended gastrin-17 (GG) (> 10(-6) M) were mitogenic for a gastrin-responsive human colon cancer (DLD-1) cell line in vitro. It remains to be seen if GG or other precursor forms of gastrin are similarly mitogenic in vivo, which may then lend credibility to a possible autocrine role of gastrinlike peptides in colon cancers.

Base Sequence↗
PubMed1994

Expression of IGF-II and IGF-binding proteins by colon cancer cells in relation to growth response to IGFs.

We previously reported that even though virtually all human colon cancers were positive for IGF-I receptors, only 50% responded to growth effects of insulin-like growth factor (IGF)-I (1-100 nM). The present studies were undertaken to determine whether expression and secretion of IGFs (IGF-I, IGF-II) and IGF-binding proteins (BPs; 1-6) were perhaps different in IGF-responsive (COLO 205, COLO 320, Caco-2) and IGF-nonresponsive (HCT 116, HT-29, DLD-1) cells. Several bands (2.0-6.0 kb) of IGF-II mRNA transcripts were detected in all the cell lines; none expressed IGF-I. Significant concentrations of IGF-II (0.2-0.9 ng/10(6) cells) were measured in the conditioned media (CM) of the cells. All cell lines expressed BP2 and/or BP4 mRNA and secreted BP4 (24 kDa) and/or BP2 (32.5 kDa); BP1 was not detected in any cell line. Interestingly, BP3 mRNA was measured only in the responsive cell lines. The relative concentration of total BPs tended to be higher in the CM of nonresponsive cells. Interestingly, a large concentration of 44- to 48-kDa BP (BP3?) was associated with the membranes of only the responsive cell lines. Our present studies thus demonstrate that human colon cancers do not secrete IGF-I and BP1. Of all the IGF-related factors examined, the quantity and the type of BPs expressed by the human colon cancer cell lines (especially BP2, BP4, and BP3) may significantly dictate the growth response of the cells to exogenous IGF-I.

Animals↗
PubMed1994

Organ-specific autoantigens induce interferon-gamma and interleukin-4 mRNA expression in mononuclear cells in multiple sclerosis and myasthenia gravis.

T cells recognizing the myelin components myelin basic protein (MBP) and proteolipid protein (PLP) are increased in multiple sclerosis (MS), and there are elevated numbers of T cells recognizing the nicotinic acetylcholine receptor (AChR) in myasthenia gravis (MG). However, the cytokine repertoires in these diseases are largely unknown. We adopted in situ hybridization with radiolabeled complementary DNA oligonucleotide probes to enumerate mononuclear cells that expressed the T-helper type 1 (Th1) cell-related interferon-gamma (IFN-gamma) and Th2-associated interleukin-4 (IL-4) after short-term culture in the presence of autoantigen. High numbers of IFN-gamma and IL-4 mRNA-expressing cells in response to MBP and PLP were detected in patients with untreated MS, and to AChR in MG. The levels of IFN-gamma and IL-4 mRNA-positive cells in MS after culture in the presence of AChR, and in MG after culture in the presence of MBP or PLP, did not differ from those detected after culture without antigen. The CSF of MS patients contained four- to eightfold more myelin protein-reactive IFN-gamma and IL-4 expressing cells. The findings imply that MS and MG are associated with mixed Th1- and Th2-like cell responses directed to organ-specific target antigens.

Adult↗
PubMed1994

Involvement of inositol 1,4,5-trisphosphate-mediated Ca2+ release in early and late events of mouse egg activation.

Sperm-induced activation of mammalian eggs is associated with a transient increase in the concentration of intracellular Ca2+. The role of inositol 1,4,5-trisphosphate (IP3)-mediated release of Ca2+ from intracellular stores during mouse egg activation was examined in the present study by determining the effects of microinjected monoclonal antibody (mAb) 18A10, which binds to the IP3 receptor and inhibits IP3-induced Ca2+ release, on endpoints of egg activation following insemination. The antibody inhibited in a concentration-dependent manner the ZP2 to ZP2f conversion that is involved in the zona pellucida block to polyspermy, as well as the ZP2 to ZP2f conversion promoted by microinjected IP3 in non-inseminated eggs. As anticipated, inseminated eggs that had been microinjected with the antibody were polyspermic. In addition, the antibody inhibited the fertilization-associated decrease in H1 kinase activity and pronucleus formation, and the concentration dependence for inhibition of these events was similar to that observed for inhibiting the ZP2 to ZP2f conversion. Last, the antibody inhibited the fertilization-induced recruitment of maternal mRNAs and post-translational modifications of proteins. In each case, eggs microinjected with the mAb 4C11, which also binds to the IP3 receptor but does not inhibit IP3-induced Ca2+ release, had no inhibitory effect on fertilization and egg activation. Results of these studies suggest that IP3-mediated Ca2+ release is essential for both early and late events of mouse egg activation.

Animals↗
PubMed1994

Human monoclonal anti-idiotypic antibodies bearing the internal image of hemorrhagic fever with renal syndrome virus antigen.

A human hybridoma cell line C8 secreting human monoclonal anti-idiotypic antibodies (alpha Id) was established by fusing Epstein-Barr virus transfected peripheral blood lymphocytes from a hemorrhagic fever with renal syndrome (HFRS) patient with interspecific myeloma SHM-D33 cells. The alpha ID human monoclonal antibody (hMAb) could react with anti-HFRSV Ab1 from different species, and the reaction could be inhibited by HFRSV antigen, indicating that anti-idiotype hMAb bears the internal image of HFRSV antigen. Anti-HFRSV antibodies (Ab3) with neutralizing and hemagglutination inhibition activities in BALB/c mice or rabbits induced by the alpha Id h MAb were produced, suggesting that the internal image beared by anti-idiotype antibodies may be related to neutralizing and hemagglutinating epitopes on HFRSV antigen.

Animals↗
PubMed1994

[The role of TNF-alpha in the growth and differentiation of U937 cells induced by PMA and IFN-gamma].

The effects of PMA and IFN-gamma on regulation of growth and differentiation of human monoblastic leukemic cell U937 were examined. U937 cells were stimulated by different concentrations of PMA and IFN-gamma respectively and NBT reduction assay was used to detect the differentiation of the cells. The results showed that both PMA and IFN-gamma dose-dependently induced differentiation of U937 cells into mature macrophage-like cells. The data also revealed a time-course response in the differentiation induction. Moreover, the U937 cell growth was significantly inhibited by the treatment of PMA and IFN-gamma. These results suggest that PMA and IFN-gamma coupled the regulation of U937 cell growth and differentiation. It was found that tumor necrosis factor-alpha (TNF-alpha) was expressed by the stimulated U937 cells. The specific monoclonal antibody against TNF-alpha diminished the effects of PMA and IFN-gamma on the growth and differentiation of U937 cells. Thus the endogenous TNF-alpha may involved in the mechanism of the effects of PMA and IFN-gamma on the differentiation of U937 cells. The regulatory action of the endogenous TNF-alpha on U937 cells was not due to its cytotoxic effect.

Cell Transformation, Neoplastic↗
PubMed1994

[Experimental and clinical observation on wrinkle correction by medical cosmetic collagen injection].

Medical cosmetic collagen is a new biomaterial for soft tissue augmentation, such as wrinkle correction, It consists of highly purified human collagen. The ratio of type I and type III collagen is 44/56. The persistence of collagen in rats is more than one year. Rat cells and capillaries grew into the injections. Fibroblasts synthesized rat collagen. Capillaries established blood supply. The clinical observation on 123 cases proved the safety of this product. No adverse reactions developing from the use of the collagen were found. It was effective in correcting contour deformities of the skin. More than 90% correction results were excellent or good.

Adult↗
PubMed1994

[Iontophoretic atropine attenuates the inhibitory effect of stimulating SmI on nociceptive responses of pf neurons].

Using the techniques of multimicropipette and iontophoresis, we observed whether ACh was involved in the cortical descending modulation of Pf neurons in rats. It was shown that the inhibition elicited by stimulation of the sensorimotor area (SmI) was attenuated after microiontophoretic atropine and that the nociceptive responses of Pf neurons were obviously reduced by microiontophoretic ACh. Therefore, it suggests that ACh may be considered as one of the neurotransmitters involved in the descending modulation of pain.

Acetylcholine↗
PubMed1994

Short-term ex vivo activation of splenocytes with anti-CD3 plus IL-2 and infusion post-BMT into mice results in in vivo expansion of effector cells with potent anti-lymphoma activity.

We investigated the proliferation and therapeutic utility of anti-CD3 activated splenocytes infused into mice following BMT. Using congenic mouse strains we demonstrated that splenocytes activated briefly ex vivo with anti-CD3 plus IL-2 (T-activated killer cells or T-AK) and infused intravenously following BMT had a greater expansion in blood, spleen and BM compared with splenocytes stimulated with IL-2 alone. T-AK cells recovered from blood, spleen and BM consisted predominantly of CD8+ T cells. A single infusion of T-AK cells given on day +1 post-syngeneic BMT and sustained in vivo with liposomal encapsulated IL-2, significantly increased survival of mice with BDL-2 lymphoma when compared with mice receiving saline and those treated with IL-2 liposomes alone. The anti-tumor effect of T-AK cells was significantly enhanced when IL-2 was given by continuous infusion compared with bolus injections. Depletion studies confirmed that the CD8+ T-AK cells were mainly responsible for the anti-tumor effect against BDL-2 lymphoma. Our findings demonstrate that brief ex vivo activation of splenocytes with anti-CD3 plus IL-2 results in in vivo proliferation of effector cells with potent anti-tumor activity following BMT.

Animals↗
PubMed1994

[Dynamic study on relationship between serum SEAIC level and hepatic pathological changes in mice infected with Schistosoma japonicum].

Using purified rabbit polyclonal antibodies to SEA, avidin-biotin system and capture ELISA technique, we observed the dynamic changes in the level of the circulating soluble egg antigen-antibody complex (SEAIC) in murine sera at various weeks post infection. Simultaneously, the diameter and area of liver egg granuloma were measured by using profile analytical technique. Serum SEAIC was first detected 4 weeks post infection (p.i.), reaching peak level at 6-7th week, and then gradually dropped, and maintained at moderately high level till the end of the observation (12 weeks p.i.). Schistosome eggs appeared in liver tissue at 4 weeks p.i. No egg granuloma could be found until 6 weeks p.i. The peak of the average diameter and area of liver egg granuloma was noted at 7 weeks p.i., then dropped gradually. Its dynamic changes were consistent with that of the serum SEAIC level. It is therefore suggested that the serum SEAIC level could be a reference index reflecting the extent of the pathological changes of the liver. Moreover, SEAIC might play an important role in the pathogenesis of schistosomiasis japonica.

Animals↗
PubMed1994

[A community cohort study on risk factors of strokes in Shanghai: a Cox regression analysis on 15,885 subjects].

Baseline investigation on 15,885 subjects who were over thirty-five years old had been launched since July 1987. All of them were selected from eighteen neighbourhoods of three districts in Shanghai by using multiple stage cluster sampling procedure. All of them were followed up till the end of 1989. Each new case of stroke was randomly matched with about twenty controls by age and sex. The total 2,682 controls together with 127 new cases of strokes were analyzed by using Cox regression model for risk factors. The population attributable risk proportion (PARP) of factors was also estimated.

Acute Disease↗
PubMed1994

Regional modulation of neurofilament organization by myelination in normal axons.

Previous studies in the hypomyelinating mouse mutant Trembler have suggested that demyelinating axons are smaller in caliber compared to normal axons, and that there are differences in the organization of axonal neurofilaments. In the normal PNS, however, the relationship between neurofilament organization and myelination has not been investigated extensively. In normal axons, only the initial segments, the nodes of Ranvier (approximately 1 micron), and the terminals are not covered by myelin. We took advantage of an unusual feature of the primary sensory neurons in the dorsal root ganglion, the relatively long nonmyelinated stem process (up to several hundred micrometers), to determine if the presence of myelination correlates with differences in cytoskeletal organization and neurofilament phosphorylation. Axonal caliber and neurofilament numbers were substantially greater in the myelinated internodes than in the stem process or nodes of Ranvier. Neurofilament spacing, assessed by measuring the nearest-neighbor neurofilament distance, was 25-50% less in the stem processes and nodes of Ranvier than in the myelinated internodes. In the myelinated internodes, neurofilaments had greater immunoreactivity for phosphorylated epitopes than those in the stem process. These findings indicate that interactions with Schwann cells modulate neurofilament phosphorylation within the ensheathed axonal segments, and that increased phosphorylation within myelinated internodes leads to greater interfilament spacing. Lastly, the myelinated internodes had three fold more neurofilaments, but the same number of microtubules. Both the increased neurofilament spacing and the increase in neurofilament numbers in myelinated internodes contribute to a greater axonal caliber in the myelinated internodes.

Animals↗
PubMed1994

Hypocotyl protoplast culture in Brassica napus L.

Protoplasts were isolated from the hypocotyls of two oilseed rape (Brassica napus L.) cultivars, Yunbei 2 and Ningyou 7. Light treatment during seed germination could apparently increase their cell division frequency. The purified protoplasts were cultured with three different methods. The method called "agarose island" was found superior to two others ("thin liquid layer" and "agarose solid layer"). The protoplasts cultured in the "agarose island" divided more rapidly and developed into calli more frequently. Shoot regeneration occurred soon after the transfer of protoplast-derived calli onto the differentiation medium. Individual shoots were rooted on the rooting medium. Whole plants were transplanted into pots, and grew well in the phytotron. The "agarose island" method might be suitable for genetic transformation of protoplasts because the liquid medium surrounding the "island" could be conveniently replaced without strong disturbing the microenvironment of protoplasts plated.

Biotechnology↗
PubMed1994

Mouse antibody response following repetitive injections of gamma-irradiated human placenta collagen.

Injectable bovine collagen has been used clinically for years. But both the necessity of repeated injections to maintain corrections and the question of adverse allergic reactions developing from the use of a xenogenic collagen have been an area of serious concern. To overcome these adverse effects, we have developed injectable collagen preparations from human placenta. Gamma irradiation was used for sterilization and crosslinking of the collagen. We observed the mouse immune response to gamma-irradiated human placenta soluble and insoluble collagen following multiple injections. After six injections of these materials, no total IgG level increase was found, nor was antibody specifically directed against human collagen found. Mouse antibody levels were also observed following Zyderm II and Zyplast repetitive injections and following repetitive implantations of coated vicryl and chromic gut. No humoral immune response was found in this heterologous type system.

Animals↗
PubMed1994

[Changes of cardiac function and hemodynamics in peripartum period].

Doppler's echocardiography was used to measure the changes of cardiac function and hemodynamics in peripartum period of 30 healthy women. The results showed that heart rate, body weight, body surface area, left ventricular mass (LVM), stroke volume (SV), cardiac output (CO), ejection fraction (EF), fractional shortening (delta D%), diastolic dimension (Dd), end-diastolic volume (EDV) and A/E ratio were significantly lowered within the first few postpartum days. However, the mean blood pressure (MBP) and systemic vascular resistance (SVR) were markedly increased (P < 0.01) in contrast to that of antepartum. Aorta diastolic dimension (AODd), aorta systolic dimension (AODs), maximum velocity (Vmax) and velocity time integral (VTI) were significantly different between before and after delivery. It may result from eliminated weight load, decreased blood volume load, and low circulating estrogen and progestogen levels and reduced physiological effects. It showed a great adaptability of cardiovascular system in healthy women to physiological load.

Adult↗