Biomedical subjects

Z Yan

Publications and source records attributed to Z Yan.

At least 163 records · Page 9Linked to original sources

PubMed1997

Regulation of tumor antigen presentation by urocanic acid.

Urocanic acid (UCA) accumulates in the epidermis after deamination of histidine. UCA isomerizes from the trans to the cis form upon exposure to environmental UV radiation. Cis-UCA is immunosuppressive in several models. Topically applied cis-UCA was reported to enhance the cutaneous tumor yield in chronically UV-irradiated mice, suggesting involvement of cis-UCA in photocarcinogenesis. Since Langerhans cells (LC) are capable of presenting tumor-associated Ags (TAA) for primary and secondary tumor-immune responses, we examined the effects of trans- and cis-UCA on LC tumor Ag presentation in a model of immunity to the S1509a spindle cell tumor (H-2a). In this system, induction of immunity requires exposure of LC to granulocyte-macrophage CSF. Naive CAF1 (H-2(a/d)) mice were immunized against S1509a by injection with granulocyte-macrophage CSF-exposed and TAA-pulsed epidermal cells (EC), as assessed by growth inhibition of inoculated tumor cells. Incubation of EC in cis-, but not trans-UCA completely inhibited Ag presentation in this system. Neither histamine antagonists nor indomethacin reversed these effects of cis-UCA. The ability of trans- and cis-UCA to modulate EC presentation of TAA for secondary immune responses was also examined. EC were pulsed with TAA in vitro and then injected into hind footpads of tumor-immune mice. After 24 h, footpad swelling was assessed as a measure of delayed-type hypersensitivity. Incubation with cis-, but again not trans-UCA before TAA exposure significantly inhibited elicitation of delayed-type hypersensitivity. These data indicate that cis-UCA may be an important regulator of LC Ag-presenting function in tumor-immune responses, and thus may play a role in photocarcinogenesis.

Animals↗

PubMed1997

Kinetics and metabolism of chloral hydrate in children: identification of dichloroacetate as a metabolite.

Chloral hydrate was introduced into therapeutics more than 100 years ago, and since then a number of kinetic and metabolic studies have been conducted on this drug. Trichloroethanol, its glucuronide and trichloroacetic acid have been identified as the metabolites of chloral hydrate. We now report the identification of dichloroacetate as a major product of chloral hydrate metabolism in children, in addition to trichloroethanol and trichloroacetic acid. Furthermore, pretreatment of children with chloral hydrate appears to retard the plasma clearance of dichloroacetate.

Acidosis, Lactic↗

PubMed1997

Significance of proliferating cell nuclear antigen expression in liver metastasis of colorectal cancer.

PURPOSE: The study contained herein was aimed at finding some possible pathologic factors that have significance for the prediction of liver metastasis in colorectal cancer. METHOD: Resected specimens of colorectal cancer from 23 patients with liver metastasis and 30 patients without liver metastasis were subjected to pathologic study, including microscopic characteristics and proliferating cell nuclear antigen immunohistochemistry assay. RESULTS: Strongly positive expression of proliferating cell nuclear antigen was present in 65.21 percent (15/23) of the liver metastasis group, whereas it was found in only 20 percent (6/30) of the group without liver metastasis (P < 0.005). Deeper invasion to the muscularis propria or serosa and less infiltration of lymphocytes surrounding the tumor were more frequently found in the liver metastasis group than in the other group (P < 0.025). CONCLUSION: Extent of proliferating cell nuclear antigen expression, depth of invasion, and reaction of lymphocyte infiltration of the primary tumor could have predictive significance of colorectal cancer in liver metastasis.

Adult↗

PubMed1997

D5 dopamine receptors enhance Zn2+-sensitive GABA(A) currents in striatal cholinergic interneurons through a PKA/PP1 cascade.

Cholinergic interneurons have been implicated in striatally mediated associative learning. In classical conditioning paradigms, conditioned stimuli trigger a transient suppression of neuronal activity that is dependent upon an intact dopaminergic innervation. Our hypothesis was that this suppression reflected dopaminergic enhancement of sensory-linked GABAergic input. As a test, the impact of dopamine on interneuronal GABA(A) receptor function was studied by combined patch-clamp recording and single-cell reverse transcription PCR. Activation of D5 dopamine receptors reversibly enhanced a Zn2+-sensitive component of GABA(A) currents. Although dependent upon protein kinase A (PKA) activation, the modulation was blocked by protein phosphatase 1 (PP1) inhibition, suggesting it was dependent upon dephosphorylation. These results establish a novel mechanism by which intrastriatally released dopamine mediates changes in GABAergic signaling that could underlie the initial stages of associative learning.

Animals↗

PubMed1997

Influence of dehydroepiandrosterone on the expression of insulin-like growth factor-1 during cystogenesis in polycystic rat ovaries and in cultured rat granulosa cells.

This study was designed to investigate the expression of insulin-like growth factor-1 (IGF-1) during cystogenesis in the dehydroepiandrosterone (DHEA)-induced rat polycystic ovarian syndrome (PCO) model. IGF-1 expression patterns in DHEA-treated rat ovaries were compared with those in control ovaries. In situ hybridization revealed a similar distribution of IGF-1 mRNA in DHEA-treated and control ovaries: in both, IGF-1 mRNA expression was confined to the granulosa cells of preantral and small antral follicles. Some hybridization signals for IGF-1 mRNA were also found in theca and infrequently in the interstitial cells. No signal was observed in larger antral follicles, atretic follicles, or cysts. This similarity indicates that there might be a shared mechanism in the early follicular development of normal folliculogenesis and DHEA-induced cystogenesis. The effects of DHEA on granulosa cells were analyzed in vitro in their quiescent, proliferative, differentiative, and preovulatory stages. Northern analysis revealed three transcripts for IGF-1 (7.5 kilobases [kb], 1.6 kb, and a group of signals between 0.4 and 0.9 kb) in cells at all stages except the preovulatory. The strongest signal was observed in cells of the proliferative stage of control cultures, while expression of IGF-1 increased only in the DHEA-treated cells cultured in the differentiative stage (when they secrete estrogen). Increase in IGF-1 expression may contribute to the hypersteroidogenism observed in the DHEA-treated rat PCO model.

Animals↗

PubMed1997

Expression of neurotrophic factors and neuropeptide receptors by Langerhans cells and the Langerhans cell-like cell line XS52: further support for a functional relationship between Langerhans cells and epidermal nerves.

Epidermal Langerhans cells are frequently anatomically associated with calcitonin gene-related peptide-containing nerves. Furthermore, calcitonin gene-related peptide inhibits Langerhans cells antigen-presenting function in several assays. Studies were performed to further explore the hypothesis that Langerhans cells and nerves have a functional relationship. To examine whether Langerhans cells may produce factors that influence nerve cell differentiation, we utilized the Langerhans cell-like cell line XS52 as a surrogate for Langerhans cells and compared it with Langerhans cells enriched to 90%. Supernatants conditioned by lipopolysaccharide-stimulated XS52 cells were able to induce the differentiation of the pheochromocytoma line PC12 into sympathetic neuron-like cells. This was also the case with enriched Langerhans cells stimulated by lipopolysaccharide. Pretreatment of conditioned supernatants with specific neutralizing anti-sera indicated that most of the differentiation-inducing activity was due to interleukin-6 and a small amount was due to nerve growth factor and basic fibroblast growth factor. By reverse transcriptase polymerase chain reaction, three clones of the XS52 cell line, XS52-4D, XS52-11D, and XS52-8B, were found to express mRNA for interleukin-6 and expression was markedly augmented by lipopolysaccharide. mRNA for nerve growth factor and basic fibroblast growth factor was detected in XS52-4D and XS52-11D, but not in XS52-8B. The expression of these neurotrophic factors by enriched Langerhans cells was quite similar to that of XS52-4D. In order to examine whether Langerhans cells may express receptors for nerve-derived peptides, reverse transcriptase polymerase chain reaction was employed to look for pituitary adenylate cyclase activating polypeptide type I, type II, and type III, and gastrin-releasing peptide receptors. All clones examined, as well as enriched Langerhans cells, expressed pituitary adenylate cyclase activating polypeptide type II and type III, and gastrin-releasing peptide receptors. These results suggest bi-directional signalling between Langerhans cells and nerves; nerve cells may regulate Langerhans cell function by elaboration of certain neuropeptides whereas Langerhans cells may promote the differentation of nerves by elaboration of interleukin-6 and, possibly, other factors.

Animals↗

PubMed1997

In vitro stabilization and in vivo solubilization of foreign proteins by the beta subunit of a chaperonin from the hyperthermophilic archaeon Pyrococcus sp. strain KOD1.

The gene encoding the beta subunit of a molecular chaperonin from the hyperthermophilic archaeon Pyrococcus sp. strain KOD1 (cpkB) was cloned, sequenced, and expressed in Escherichia coli. The cpkB gene is composed of 1,641 nucleotides, encoding a protein (546 amino acids) with a molecular mass of 59,140 Da. The enhancing effect of CpkB on enzyme stability was examined by using Saccharomyces cerevisiae alcohol dehydrogenase (ADH). Purified recombinant CpkB prevents thermal denaturation and enhances thermostability of ADH. CpkB requires ATP for its chaperonin function at a low CpkB concentration; however, CpkB functions without ATP when present in excess. In vivo chaperonin function for the solubilization of insoluble proteins was also studied by coexpressing CpkB and CobQ (cobryic acid synthase), indicating that CpkB is useful for solubilizing the insoluble proteins in vivo. These results suggest that the beta subunit plays a major role in chaperonin activity and is functional without the alpha subunit.

Adenosine Triphosphate↗

PubMed1997

D2 dopamine receptors reduce N-type Ca2+ currents in rat neostriatal cholinergic interneurons through a membrane-delimited, protein-kinase-C-insensitive pathway.

Dopamine has long been known to regulate the activity of striatal cholinergic interneurons and the release of acetylcholine. Yet, the cellular mechanisms by which this regulation occurs have not been elucidated. One way in which dopamine might act is by modulating voltage-dependent Ca2+ channels. To test this hypothesis, the impact of dopaminergic agonists on Ca2+ channels in neostriatal cholinergic interneurons was studied by combined whole cell voltage-clamp recording and single-cell reverse transcription-polymerase chain reactions. Cholinergic interneurons were identified by the presence of choline acetyltransferase mRNA. Nearly, all interneurons tested (90%, n = 17) coexpressed D2 (short and long isoforms) and D1b (D5) dopamine receptor mRNAs. D1a receptor mRNA was found in only a small subset (20%) of the sample and D3 and D4 receptor mRNAs were undetectable. D2 receptor agonists rapidly and reversibly reduced N-type Ca2+ currents. D1b/D1a receptor activation had little or no effect on Ca2+ currents. The D2 receptor antagonist sulpiride blocked the effect of D2 agonists. Dialysis with guanosine-5'-O-(2-thiodiphosphate) or brief exposure to the G protein (Gi/o) alkylating agent N-ethylmaleimide also blocked the D2 modulation. The reduction in N-type currents was neither accompanied by kinetic slowing nor significantly reversed by depolarizing prepulses. The D2 receptor effects were mediated by a membrane-delimited pathway, because the modulation was not seen in cell-attached patches when agonist was applied to the bath and was not disrupted by perturbations in cytosolic signaling pathways known to be linked to D2 receptors. Activation of M2 muscarinic receptors occluded the D2 modulation, suggesting a shared signaling element. However, activation of protein kinase C attenuated the M2 modulation without significantly affecting the D2 modulation. Taken together, our results suggest that activation of D2 dopamine receptors in cholinergic interneurons reduces N-type Ca2+ currents via a membrane-delimited, Gi/o class G protein pathway that is not regulated by protein kinase C. This signaling pathway may underlie the ability of D2 receptors to reduce striatal acetylcholine release.

Animals↗

PubMed1997

[Comparison between the effects of rhCNTF on sensory and motor neuron of chicken embryo].

The effects of rhCNTF on dorsal root ganglia (DRG) sensory neurons and spinal cord (SC) motor neurons of 10-day chicken embryos were observed with serum-free culture. The results indicated that rhCNTF supported the survival and differentiation of these neurons and showed certain dose-dependent manners. No effect was found at 0.5 ng/ml rhCNTF concentration, a little survival promotive effect at 1.0-1.5 ng/ml, peak effect at 4 ng/ml and no more effects from 8.0 to 100 ng/ml. The survival number of neurons on 7th day was compared, and results showed higher sensitivity of sensory neuron to CNTF shortage than that of motoneuron. This suggests that survival effect of CNTF on motoneuron is only small part of its neurotrophic effects.

Animals↗

PubMed1997

[Topographical evaluation of centration of excimer laser photorefractive keratectomy].

OBJECTIVE: To evaluate the situation of centrality of excimer laser photorefractive keratectomy (PRK). METHODS: Eyesys Corneal Analysis System was used for the computer-assisted analysis of corneal differential topographical maps gained preoperatively and 10 days postoperatively in 158 eyes of 98 patients with at least six months of follow-up to determine the direction and the distance of the center of ablation zone relative to the center of the entrance pupil, and a comparison in decentration difference was made between one-zone ablated eyes and multi-zone ablated eyes. RESULTS: Concerning the centration of ablated zone relative to the center of entrance pupil: 100 eyes (63.3%) were centered within 0.50 mm, 55 eyes (34.8%) were decentered more than 0.50 mm with 3 eyes (1.9%) being decentered more than 1 mm, and the mean decentration amount was 0.45 mm. 38 eyes were performed by multi-zone ablation and 120 eyes by one-zone ablation, their mean amount of decentration was 0.55 mm and 0.44 mm respectively, the difference being significant (P < 0.05). 4 eyes with decentration greater than 0.50 mm lost one to two lines of their best corrected visual acuity postoperatively due to the decentered ablation. CONCLUSION: Many factors contribute to decentration of the ablated zone. Great decentration will affect the recovery of the postoperative visual acuity. The Passive Eye Tracking System (PET) will contribute to precise centration and reduction of displacement.

Adolescent↗

PubMed1997

[The study and manufacture of spinning counter for experimental animals].

The single-chip microcomputer technique is used in the present study of spinning counter, which has 4 observation tunnels, the spinning behave of four experiment animals can be recorded at same time. The function of this instrument has four selections according to different experiment, and the recording data can be compute processed.

Animals↗

PubMed1997

[Synthesis and bioactivity of some 3,4-diacyloxybenzopyrans].

Considerable attention is now being given to the potassium channel openers of benzopyrans as potential therapeutical agents for hypertension. In order to search for novel antihypertensive with high efficacy and low toxicity, integrating structural features of cromakalim and praeruptorin C, twenty-four compounds of 3,4-diacyloxybenzopyrans were designed and synthesized. Some of them exhibited hypotensive activity in Sprague Dawley rats.

Animals↗

PubMed1997

[The effect of a new cholinolytic-[3H] tricyclopinate on human brain muscarinic receptors].

The binding characteristics of the novel cholinergic antagonist [3H] tricyclopinate with muscarinic receptors from human cerebral cortex were investigated in comparison with [3H] QNB by performing radioligand binding assays. As revealed by saturation experiments, the binding parameters of [3H] tricyclopinate (Kd = 0.044 nmol.L-1, Bmax = 514 fmol.mg-1) were almost identical with those of [3H]QNB (Kd = 0.040 nmol.L-1, Bmax = 508 fmol.mg-1). Both ligands fit a one site model of receptor-ligand interaction. Tricyclopinate showed a potency comparable to QNB on muscarinic receptors in inhibition experiments. However, some differences also existed between tricyclopinate and QNB. Kinetic experiments showed that both the association and dissociation of tricyclopinate (K1 = 1.40 (nmol.L-1)-1.min-1, K2 = 0.39 min-1) with muscarinic receptors were quicker than QNB (K1 = 0.65 (nmol.L-1)-1.min-1, K2 = 0.005 min-1). In addition, tricyclopinate behaved differently from QNB in the response of the dissociation profile to the allosteric modulation of gallamine. These results demonstrated that tricyclopinate has comparable affinity to muscarinic receptors with QNB but might interact with them in a different way. The introduction of [3H] tricyclopinate might complement the use of [3H] QNB in the study of central muscarinic receptors.

Cerebral Cortex↗

PubMed1997

[Expression of foreign genes in adult rats' central nervous system by use of defective herpes simplex virus type 1 vectors].

We developed a defective herpes simplex virus (HSV) vector system that permitted the introduction of virtually any gene into mammalian central nervous system neurons. The HSV-1 amplicon plasmid, pHSL, contained a beta-galactosidase transcription cassette directed by HSV-1 IE68 promoter and two elements from HSV-1 genome: the origin of HSV-1 replication and its packaging site sequence. Being transfected into immortalized cells such as Vero cells in the present of HSV-1 to provide the helper virus function, (in our tests, a temperature-sensitive mutank tsK strain with permissive temperature at 31 degrees C was used), the prototype vector pHSL could be packaged into HSV-1 particles as a head-to-tail concatemer with the size of about the genome of HSV-1. A mixed HSV-1 stocks obtained were called dvHSL. Infection of cultured embryonic spinal cord motor neurons and forebrain cortex neurons of rats with dvHSL showed that beta-galactosidase was expressed up to twelve days. Via corneal inoculation, the trigeminal ganglia of rats were infected by dvHSL and the expression of beta-galactosidase could be detected there at different times after inoculation for at least two months. Infection of the forebrain cortex of rats with dvHSL through stereotactic injection showed that the expression of beta-galactosidase was restricted to the injection site for up to two months.

Animals↗

PubMed1997

[Preliminary study on the inhibition of hepatitis B viral expression in vitro via specific receptors mediated ribozyme transfer].

Comparing with liposome and transferrin receptors (Tf-R) mediated transfection, a plasmid harboring foreign gene with hepatic specificity could be transfected via asialoglycoprotein receptors (ASGP-R) mediated endocytosis. A recombination plasmid pCMV-Ripc harboring a hammerhead ribozyme which aim at the pregenome RNA of HBV ayw subtype at the 1796 site in the genome was delivered into HepG2 cells (HBV transient transfected system) and 2.2.15 cells (HBV permanent transfected system) via receptors mediated gene transfer methods. ELISA results showed that the inhibition of HBsAg and HBeAg expression is 55.29% and 68.73% respectively when pCMV-Ripc is co-transfected with pUC-2HBV in HepG2 cells via ASGP-R mediated DNA transfer method. The result indicated that pCMV-Ripc is efficient to inhibit the expression of HBV antigen and ASGF-R method is a safe, liver-targeted delivery system, therefore it is possible to develop an in vivo gene therapy strategy aiming to the treatment of hepatic infectious disease.

Cell Line↗

PubMed1997

Glutathione-dependent conversion to glyoxylate, a major pathway of dichloroacetate biotransformation in hepatic cytosol from humans and rats, is reduced in dichloroacetate-treated rats.

Although it has been postulated that glyoxylate is an intermediate in the biotransformation of DCA to oxalate, CO2, and glycine, there has been no positive identification of glyoxylate as a metabolite of DCA. We have demonstrated that a GSH-dependent pathway in dialyzed hepatic cytosol from rats and humans converts a mixture of 1-14C- and 1,2-13C-DCA to isotopically labeled glyoxylate. The reaction does not occur in the presence of NADPH or NADH or in the absence of GSH. The identity of the glyoxylate was demonstrated by HPLC with radiochemical detection and confirmed by GC/MS of the methylated glyoxylate, which showed the 13C-labeled product. The apparent Km for GSH was 0.075 mM in rat hepatic cytosol. Pretreatment of rats with NaDCA, 50 mg/kg, p.o. (by mouth) for 2 days prior to preparation of hepatic cytosol on the third day affected the cytosolic metabolism of DCA. With 0.2 mM DCA as substrate, in the presence of 1 mM GSH, control rats formed 1.45 +/- 0.13 nmol glyoxylate/min/mg cytosolic protein, whereas the rate in DCA-treated rats was 0.45 +/- 0.10 nmol glyoxylate/min/mg protein (mean +/- SD, N = 4 in each group). The mechanism of this reduction in the rate of DCA biotransformation in DCA-treated rats is unknown but is consistent with in vivo observations that the elimination of DCA from plasma of humans and rats is slowed by prior administration of DCA.

Animals↗

PubMed1997

Studies on multiple forms of maltotetraose-forming amylase from Alcaligenes sp.

Zymograms of the cultural supernatant of Alcaligenes sp. showed three bands, the major one being G4A-1 and the minor two, G4A-2 and G4A-3. Based on the electrophoretic homogeneity of the purified three bands and the enzymatic activities identified by a thin layer chromatography of the soluble starch hydrolysates, all the three bands were confirmed to be maltotetraose-forming amylase but in multiple forms. Neither glycosidase nor protease activities could be detected in the culture (only very weak protease activities were observed at 48 hours after cultivation), which indicate that the two enzymes were not involved in the amylase multiple-form formation. Only the relative amount of the two minor bands (but not the multiple-form pattern) was changed when the initial pH of the medium varied from 6.5-8.5. An addition of 0.3% glucose raised the yield of G4A-2 and G4A-3.

Alcaligenes↗

PubMed1997

[Study on the inactivated vaccine of Gardnerella vaginalis of fox. VI. Experimental development of the inactivated vaccine of Gardnerella vaginalis of fox].

The aluminum hydroxide gel, propolis and oil adjuvant inactivated vaccines were developed by silecting good immunity, representing principal epidemic serotype I GVF44 of Gardnerella vaginalis of fox in civil. The results showed that the aluminum hydroxide gel vaccine in safety was better than propolis and oil adjuvant vaccines, the most optimal inactivated concentration of formalin is 0.1%. Efficient immunity doses are 4 billon bacteria/1 ml. There were on any bad influences to occur for fox after the aluminum hydroxide gel of three times immunity doses were injected. The inoculated foxes could resist challenge of a hundred ID50 virulent strains after the vaccine was injected to foxes for 21 d. Immunity period of the vaccine is 6 months storage period is 10 months at 4-10 degrees C. The field experiments confirmed that the vaccine possessed accuracy, stability and reliability.

Animals↗