Search PubMed⌕ Search

Biomedical subjects

J Liu

Publications and source records attributed to J Liu.

At least 1,009 records · Page 56Linked to original sources
PubMed1999

Mechanism of prejunctional muscarinic receptor-mediated inhibition of neurogenic vasodilation in cerebral arteries.

Nitric oxide (NO) is a major transmitter in mediating cerebral neurogenic vasodilation in several species. Recent findings have suggested that acetylcholine, which is costored with NO in cerebral perivascular nerves, plays a role in modulating NO release, presumably by acting on muscarinic (M) receptors on nitric oxidergic nerve terminals. The present study was designed using an in vitro tissue bath technique to pharmacologically characterize the presynaptic muscarinic-receptor subtype(s) that mediate modulation of NO release and therefore neurogenic vasodilation and to investigate further the possible mechanisms involved in this presynaptic modulation in porcine basilar arteries. Transmural nerve stimulation (TNS) elicited a frequency-dependent, tetrodotoxin-sensitive relaxation. The relaxation was abolished by nitro-L-arginine (30 microM) and was completely reversed by L-arginine and L-citrulline, but not by their D-enantiomers. Atropine (0.01-1 microM), pirenzepine (an M1-receptor antagonist, 0. 01-1 microM), and methoctramine (an M2-receptor antagonist, 0.01-1 microM), but not 4-DAMP (an M3-receptor antagonist) or tropicamide (an M4-receptor antagonist) at concentrations as high as 10 mM, significantly increased the TNS-elicited relaxation. This relaxation, on the other hand, was significantly attenuated by arecaidine but-2-ynyl ester tosylate (an M2-receptor agonist, 0.1 microM) but was not affected by McN-A-343 (an M1-receptor agonist, 1 microM). Double-labeling immunohistochemical study demonstrated that perivascular M2 receptor-immunoreactive fibers were completely coincident with NADPH diaphorase fibers. Furthermore, the muscarinic receptor-mediated modulation of TNS-elicited relaxation was completely prevented by omega-conotoxin GVIA (0.1 microM), a specific N-type Ca2+ channel inhibitor, but was still observed in the presence of tetraethylammonium (1 mM), 8-bromo-cAMP (0.5 mM), and pertussis toxin. It is concluded that the presynaptic M2 receptors on porcine cerebral perivascular nitric oxidergic nerves mediate inhibition of NO release. The inhibition is due primarily to a decreased Ca2+ influx through N-type Ca2+ channels.

Animals↗
PubMed1999

Rhinovirus-16 colds in healthy and in asthmatic subjects: similar changes in upper and lower airways.

Rhinovirus (RV) infections appear to precipitate most asthma exacerbations. To investigate whether RV-16 induces different inflammatory changes in upper and lower airways of asthmatic and healthy subjects, we inoculated 10 nonatopic healthy and 11 atopic asthmatic adults with 2,000 TCID50 RV-16. Subjects recorded symptoms and peak flow daily; and they underwent spirometry, methacholine challenge (PC20), nasal lavage, and sputum induction at baseline and on Days 2, 4, 15, and 29 d after inoculation. One asthmatic subject developed an exacerbation requiring prednisone treatment 5 d after inoculation. The cold symptom severity (Jackson score) did not differ between groups. During the cold, asthma symptoms increased slightly from baseline in the asthmatic group; and PC20 decreased in the healthy group. However, peak flow, bronchodilator use, and spirometry did not change in either group. At baseline, asthmatics had higher neutrophils, eosinophils, and interleukin (IL)-6 in nasal lavage. After inoculation, both groups developed significant increases in nasal neutrophils, IL-6 and IL-8, and modest increases in sputum neutrophils and IL-6, but not IL-8. However, these changes did not differ between groups. IL-5, interferon-gamma, and RANTES were detected only in nasal lavages from two asthmatic subjects, who had the most severe colds. IL-11 was not detected in any sample. We conclude that inflammatory responses of upper and lower airways during RV-16 colds are similar in asthmatic and healthy subjects, and that RV-16 infection is not by itself sufficient to provoke clinical worsening of asthma.

Adolescent↗
PubMed1999

Chromatin recycling of glucocorticoid receptors: implications for multiple roles of heat shock protein 90.

Unliganded glucocorticoid receptors (GRs) released from chromatin after hormone withdrawal remain associated with the nucleus within a novel subnuclear compartment that serves as a nuclear export staging area. We set out to examine whether unliganded nuclear receptors cycle between distinct subnuclear compartments or require cytoplasmic transit to regain hormone and chromatin-binding capacity. Hormone-withdrawn rat GrH2 hepatoma cells were permeabilized with digitonin to deplete cytoplasmic factors, and then hormone-binding and chromatin-binding properties of the recycled nuclear GRs were measured. We found that recycled nuclear GRs do not require cytosolic factors or ATP to rebind hormone. Nuclear GRs that rebind hormone in permeabilized cells target to high-affinity chromatin-binding sites at 30 C, but not 0 C, in the presence of ATP. Since geldanamycin, a heat shock protein-90 (hsp90)-binding drug, inhibits hormone binding to recycled nuclear GRs, hsp90 may be required to reassemble the receptor into a form capable of productive interactions with hormone. Geldanamycin also inhibits GR release from chromatin during hormone withdrawal, suggesting that hsp90 chaperone function may play multiple roles to facilitate chromatin recycling of GR.

Adenosine Triphosphate↗
PubMed1999

pG2 gene expression and its regulation in human adrenocortical and medullary tumors.

The cDNA clone pG2 was originally isolated from a human pheochromocytoma. The respective gene was found to be strongly expressed in normal adrenal zona glomerulosa and medulla, as well as in Conn's adenomas and pheochromocytomas. To shed more light on the expression and regulation of the pG2 gene, we investigated its expression in a wide variety of different adrenal neoplasms and cultured adrenal cells. Northern blot analysis was used to determine the steady state level of pG2 mRNA. Besides normal adrenals, Conn's adenomas and pheochromocytomas, we found abundant expression of pG2 mRNA in Cushing's, virilizing and nonfunctional adrenocortical adenomas and carcinomas, as well as in hyperplastic adrenals. The relative levels of pG2 mRNA in various adrenocortical tumors were not significantly different from those in normal adrenals and pheochromocytomas. In primary cultures of normal adrenal cells, treatment with adrenocorticotropin induced a 3- to 15-fold increase in the expression of pG2 mRNA (P<0.01), and this effect was reproduced by incubation with (Bu)2cAMP. In cultured pheochromocytoma cells, treatment with (Bu)2cAMP and a protein kinase inhibitor, staurosporine, increased pG2 mRNA accumulation (2- to 4-fold over the control level, P<0.01, and 3- to 8-fold, P<0.01, respectively). These results indicate that pG2 is widely expressed in normal and pathological adrenal tissues from both cortical and medullary origin, which eliminates its usefulness as a specific marker for zona glomerulosa or medullary adrenal tumors. Accumulation of pG2 mRNA is regulated by multiple differentiating factors through different pathways in primary cultures of normal adrenal and pheochromocytoma cells.

Adenoma↗
PubMed1999

Regulation of neuropeptide Y mRNA expression in cultured human pheochromocytoma cells.

The expression of the neuropeptide Y (NPY) gene varies considerably in human pheochromocytomas, but the mechanisms for this variation have not been clarified. To investigate the regulation pattern of the NPY gene in human pheochromocytomas, we screened 16 pheochromocytomas and 9 normal adrenal tissues with Northern blots. The expression level of NPY mRNA in normal adrenal medulla was low and relatively constant, while the pheochromocytomas showed a very wide variation in NPY mRNA levels in both malignant and benign tumors. This indicates that NPY gene expression is not correlated with malignancy in pheochromocytomas. In primary cultures of human pheochromocytoma cells, nerve growth factor treatment (causing neuronal differentiation) increased NPY mRNA accumulation 2- to 5-fold (P < 0.05). NPY mRNA levels were also induced by protein kinase modulators (Bu)(2)cAMP and staurosporine in the cultures (P < 0.05). In contrast, treatment with dexamethasone and IGF-II (causing or linked with chromaffin differentiation) reduced NPY mRNA accumulation (P < 0.05). These data show that the regulation pattern of NPY mRNA expression in cultured human pheochromocytoma cells is different from that previously described in rat pheochromocytoma PC12 cells. Regulation of NPY mRNA expression in primary cultures by these differentiating factors suggests that the expression of NPY mRNA in pheochromocytoma tissues may be associated with the neuronal differentiation of the tumor cells affected by multiple factors.

Adrenal Gland Neoplasms↗
PubMed1999

Detection of virtually all mutations-SSCP (DOVAM-S): a rapid method for mutation scanning with virtually 100% sensitivity.

Dideoxy fingerprinting (ddF) was used as a tool to search for a generic set of conditions with sufficient power to detect virtually all mutations. For each condition tested, a very large sample of mutation-containing, single-stranded segments (about 1500) were analyzed with ddF. Correlation coefficients identified pairs of conditions in which single-strand conformation polymorphism (SSCP) mobilities were poorly correlated. The data strongly suggest that tertiary structure (e.g., base-sugar and sugar-sugar interactions) rather than secondary structure is the predominant determinant of mobility shifts by SSCP. Five conditions were selected with sufficient redundancy to detect all the mutations. The sensitivity of detection of virtually all mutations-SSCP (DOVAM-S) was determined by blinded analyses on samples containing additional mutations scattered throughout the eight exons and splice junctions in the factor IX gene. The factor IX gene sequence (2.5 kb) was scanned in one lane by 15 PCR-amplified segments (125 kb of sequence scanned per gel). All of the 84 single-base substitutions were detected in the blinded analyses, the first consisting of 50 hemizygous mutant and wild-type (WT) samples and the second consisting of 50 heterozygous mutant and WT samples. DOVAM-S is estimated to be five times faster than fluorescent DNA sequencing for the detection of virtually all mutations when the five conditions are applied.

Biotechnology↗
PubMed1999

Major DQ8-restricted T-cell epitopes for human GAD65 mapped using human CD4, DQA1*0301, DQB1*0302 transgenic IA(null) NOD mice.

The 65KD isoform of GAD is considered to be a major target autoantigen in many humans with autoimmune prediabetes or diabetes. The major histocompatibility complex class II allele DQA1*0301, DQB1*0302, which encodes HLA-DQ8, confers susceptibility to type 1 diabetes and occurs in up to 80% of affected individuals. To map T-cell epitopes for GAD65 restricted to the diabetes-associated DQ8 heterodimer, we generated transgenic NOD mice expressing HLA-DQ8 and human CD4 while having the mouse class II gene (IA(beta)) deleted. These mice were immunized with full-length purified recombinant GAD65, and the fine specificity of T-cell responses was mapped by examining recall responses of bulk splenocytes to an overlapping set of 20-mer peptides encompassing the entire GAD65 protein. Four different peptides (P121-140, P201-220, P231-250, and P471-490) gave significant T-cell recall responses. P201-220 and P231-250 have been shown previously to bind DQ8, whereas the other two peptides had been classified as nonbinders. Interestingly, the peptide giving the greatest response (P201-220) encompasses residues 206-220 of GAD65, a region that has been shown to be a dominant T-cell epitope in wild-type IA(g7) NOD mice. Overlap in this T-cell epitope likely reflects structural similarities between DQ8 and IA(g7). The fine specificity of antibody responses in the GAD65-immunized mice was also examined by testing the antisera by enzyme-linked immunosorbent assay (ELISA) against the same overlapping set of peptides. The two dominant B-cell epitopes were P361-380 and P381-400; P121-140 and P471-490 appeared to correspond to both B- and T-cell epitopes. Although the NOD human CD4, DQ8, IA(null) transgenic mice generated in these studies do not develop autoimmune diabetes either spontaneously or after cyclophosphamide treatment, they can be used to map DQ8-restricted T-cell epitopes for a variety of human islet autoantigens. They can also be used to test T-cell-specific reagents, such as fluorescently labeled DQ8 tetramers containing GAD65 peptides or other beta-cell peptides, which we believe will be useful in analyzing human immune responses in diabetic and prediabetic patients.

Amino Acid Sequence↗
PubMed1999

Precompetition anxiety in Chinese athletes.

Precompetition anxiety and self-confidence were investigated in a sample of 132 male and 103 female Shanghai college athletes. The participants were administered the Competitive State Anxiety Inventory-2 of Martens, et al. 30 to 40 min. before competing in important track and field events or basketball games. Analysis by independent t tests showed that there were no sex differences in scores on the Cognitive Anxiety, Somatic Anxiety, or Self-confidence subscales; however, compared to those in team sports (basketball), athletes competing individually (track and field) scored significantly higher on the Somatic Anxiety subscale and significantly lower on the Self-confidence subscale. Comparisons with data from comparable North American samples indicated that Chinese athletes reported lower scores on Cognitive Anxiety and Somatic Anxiety but similar scores on Self-confidence.

Anxiety Disorders↗
PubMed1999

Participation motives of young Australian and Chinese gymnasts.

Reasons for participating in gymnastics were investigated with 280 Australian and 103 Chinese youth. The participants, aged 8 to 15 years, completed modified versions of the Participation Motivation Questionnaire. Treatment of the scores by principal components analysis yielded seven factors. Further analyses showed that the samples differed significantly on six of these factors. Comparisons of individual items indicated that the Australian gymnasts rated having fun and liking the rewards as more important than did the Chinese respondents. Chinese athletes allocated higher ratings to being part of a club, having a good body, liking to win, and wanting to be popular. Both groups assigned high values to reasons associated with improving skills, being fit, and getting exercise. It was suggested that the findings reflected cultural differences between Australian and Chinese societies as well as particular characteristics of the Chinese sample.

Adolescent↗
PubMed1999

Reproducibility of fasting plasma leptin concentration in lean and obese humans.

We determined the reproducibility of plasma leptin levels in 20 healthy subjects (10 men, 10 women; 10 lean, 10 obese) at stable body weight. Blood samples were obtained, after an overnight fast, between 0700 and 0800 on days 1, 2, 3, 4, 5, 12, 19, and 26. Body weights were recorded on the same days. Plasma leptin was measured using a specific radioimmunoassay. The mean +/- SE baseline body weights (kg) were 65.8 +/- 3.6 (lean) and 96.4 +/- 7.1 (obese). The body mass indices (BMI) were 22.9 +/- 2.8 kg/m2 (lean) and 32.7 +/- 2.2 kg/m2 (obese). The mean daily fasting plasma glucose level was 98.7 +/- 3.7 mg/dl. Baseline plasma leptin levels (ng/ml) were 5.3 +/- 0.75 in lean men, 14.9 +/- 4.6 in obese men, 11.2 +/- 2.8 in lean women, and 27.1 +/- 8.4 in obese women. Fasting leptin levels on days 2 to 26 were highly correlated with the baseline levels on day 1 (r2 = 0.9, P<0.0001). Body weights remained within 98%-102% of baseline, whereas intra-individual leptin levels fluctuated between 80% and 120% of baseline values, throughout the 26 days of study. We conclude that fasting plasma leptin levels are reproducible, with a maximum day-to-day variation of approximately 20%, in healthy, free-living, lean and obese persons who maintain a stable body weight.

Adult↗
PubMed1999

Intravenous infusion ascitic fluid during hemodialysis: a study of 108 treatments in 13 uremic cases.

Nephrogenic ascites is a clinical diagnosis defined as persistent ascites in an uremic patient without evidence for a causative underlying disease. It imperils the patient's life with intradialytic hypotension, however there is no effective therapy other than renal transplantation so far. In 13 cases, 108 treatments with i.v. ascites infusion were performed with hemofilter alone or combined with plasmafilter during hemodialysis over past 7-years. The ascitic fluid was filtrated and dialyzed before it was intravenously infused into the blood compartment of the hemofilter. There were a mean of 8.38 treatments per patient in a period of 56 days and 3,275.9 +/- 1,359.5 ml of ascitic fluid were removed per treatment. The patients' appetite and physical ability were considerably improved and the intradialytic hypotensions disappeared immediately following the initiation of ascitic fluid infusions. In this study, one patient was transplanted successfully. The longest interval without ascitic fluid infusion was 127 days. Main side effect was light pyrogenic reaction, which was presented in 12.96% of the total treatments. It is concluded that this method permits to continue hemodialysis, improves the nutritional condition and prolongs the lifespan by conserving and reusing the ascites protein.

Adult↗
PubMed1999

Use of bioluminescent aequorin for the pharmacological characterization of 5HT receptors.

A convenient functional assay for 5HT2a and 5HT2c receptors is reported utilizing the bioluminescent aequorin to detect intracellular calcium changes. Using this assay, the pharmacological properties of many 5HT ligands can be determined in a 96-well format. The data indicate that the aequorin detection method is superior to the inositol phosphate assay with regard to speed and scope. This system is also appropriate for kinetic studies of receptor desensitization. We showed that the human 5HT2c receptor desensitizes in a biphasic manner, with a fast desensitization of approximately 90% of the total response occurring within 15 minutes while the remaining 10% response remains for at least 3 hours.

Aequorin↗
PubMed1999

Metallothionein-I/II knockout mice are sensitive to acetaminophen-induced hepatotoxicity.

The purpose of this study was to examine whether intracellular metallothionein (MT) protects against acetaminophen hepatotoxicity. MT-I/II knockout (MT-null) and control mice were given acetaminophen (150-500 mg/kg i.p.), and liver injury was assessed 24 h later. MT-null mice were more susceptible than controls to acetaminophen-induced lethality and hepatotoxicity, as evidenced by elevated serum enzyme activities and histopathology. Zinc pretreatment, a method of MT induction, protected against acetaminophen hepatotoxicity in control mice, but not in MT-null mice. The susceptibility of MT-null mice to acetaminophen hepatotoxicity was not due to the increased acetaminophen bioactivation, as cytochrome P-450 enzymes, and acetaminophen-reactive metabolites in bile and urine were not increased in MT-null mice. Western blots of liver cytosol indicated that acetaminophen covalent binding at 4 h increased with acetaminophen dose, but there was no consistent difference between control and MT-null mice. Acetaminophen injection depleted cellular glutathione similarly in both control and MT-null mice, but produced more lipid peroxidation in MT-null mice, as evidenced by the abundance of thiobarbiturate-reactive substances, and by immunohistochemical localization of 4-hydroxynonenal and malondialdehyde protein adducts. MT-null hepatocytes were more susceptible than control cells to oxidative stress and cytotoxicity produced by N-acetylbenzoquinoneimine, a reactive metabolite of acetaminophen, as determined by oxidation of 2', 7'-dichlorofluorescin diacetate and lactate dehydrogenase leakage. In summary, this study demonstrated that MT deficiency renders animals more vulnerable to acetaminophen-induced hepatotoxicity. The increased sensitivity does not appear to be due to increased acetaminophen activation, glutathione depletion, or covalent binding, but appears to be associated with the antioxidant role of MT.

Acetaminophen↗
PubMed1999

[An investigation of the polymorphism of HLA class II alleles in the Han population in Hubei Province of China].

OBJECTIVE: To investigate the polymorphism of HLA class II alleles in the Han population in Hubei province. METHODS: The alleles of DRB1*(n=168), DQB1*(n=160) and DPB1*(n=93) were typed by using the polymerase chain reaction/sequence specific primer(PCR/SSP) and polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) techniques. RESULTS: 39 HLA-DRB1, 15 DQB1 and 17 DPB1 alleles were found. Alleles with higher frequencies are DRB1*0901 (GF=14%), *1501(GF=11.3%), *0301(GF=7.1%), *0803(GF=4.8%); DQB1*0301(GF=18.8%), *0303(GF=18.4%), *0201(GF=10%), *0302(GF=8.4%); DPB1*0501(GF=31.2%), *0401(GF=15.1%), *0201(GF=14%), *0402(GF=11.8%), respectively. As compared with Caucasians, the Han people in Hubei province have higher gene frequencies of DRB1*0901, *1001, *0803; DQB1*0303, *0502 and DPB1*0501, *0202; and lower gene frequencies of DRB1*0301, *0401, *1301; DQB1*0201, *0603 and DPB1*0401, suggesting that Hubei Hans have their own layout of HLA class II allele frequencies. CONCLUSION: These data may serve as normal reference values for the Han population in south China.

Alleles↗
PubMed1999

Inhibitory effects of huperzine B on cholinesterase activity in mice.

AIM: To determine the anticholinesterase properties of huperzine B (Hup B) and compare with tacrine in vitro and in vivo. METHODS: Spectrophotometry was used to determine ChE activity. RESULTS: Hup B showed much more selective inhibition to acetylcholinesterase (AChE) than tacrine. The IC50 ratios of Hup B and tacrine for butyrylcholinesterase (BuChE): AChE were 65.8 and 0.54, respectively. Hup B ig exhibited higher efficacy on the inhibition of brain AChE than that of tacrine. Tacrine was more effective in the inhibition of serum BuChE in mice with severe concomitant peripheral adverse effects than Hup B. A single ig dose of Hup B produced steady state of AChE inhibition in 4 h. CONCLUSION: Hup B exhibits higher selectivity and efficacy in the inhibition of AChE, and lower toxicity in mice than tacrine.

Acetylcholinesterase↗
PubMed1999

Effects of electro-acupuncture on somatostatin and pancreatic polypeptide in ischemic cerebrovascular diseases.

The levels of somatostatin (SS) in CSF and blood and pancreatic polypeptide (PP) in plasma were measured by radioimmunoassay in 64 patients with acute ischemic cerebrovascular diseases (ICVD), randomly divided into two groups: group 1 (n = 31, both electro-acupuncture and routine treatments given) and group 2 (n = 33, routine treatment) and 26 non-ICVD patients were used as controls. The points of electro-acupuncture were Quchi (LI 12), Waiguan (SJ 5) and Huantiao (GB 30) and Zusanli (St 36). After a course of treatment, the SS levels in plasma and CSF were significantly increased in the patients of group 1 with good result and their plasma PP level had no significant change. In the patients with poor result, however, the PP level was significantly decreased. The results suggested that electro-acupuncture might play an active role in alleviating the SS metabolic disturbance in CNS of ICVD patients.

Adult↗