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Biomedical subjects

J Hu

Publications and source records attributed to J Hu.

At least 505 records · Page 28Linked to original sources
PubMed1995

Methods for the estimation of failure distributions and rates from automobile warranty data.

We consider the occurrence of warranty claims for automobiles when both age and mileage accumulation may affect failure. The presence of both age and mileage limits on warranties creates interesting problems for the analysis of failures. We propose a family of models that relates failure to time and mileage accumulation. Methods for fitting the models based on warranty data and supplementary information about mileage accumulation are presented and illustrated on some real data. The general problem of modelling failures in equipment when both time and usage are factors is discussed.

Automobiles↗
PubMed1995

Quantitative analysis of the tomographic technetium-99m MIBI (99mTc-MIBI) myocardial bullseye display: application to diagnosis of coronary artery disease.

In this study, the 99mTc-MIBI myocardial bullseye display of 31 healthy persons and 34 patients with myocardial ischemia and 17 patients with myocardial infarction were analyzed quantitatively; and compared with the results of myocardial tomography analysis and qualitative bullseye analysis. The sensitivities of the three methods were 88.2%, 91.2% and 94.1% respectively (P > 0.05), and the specificities were 93.5%, 83.9% and 83.9% respectively (P < 0.05). On the other hand, the quantitative analysis obviously outperformed the other two methods in the detection of ischemic segments of myocardium near infarction zone (P < 0.01). The quantitative analysis of 99mTc-MIBI myocardial bullseye (quantitative bullseye) was an objective, specific and sensitive method for diagnosis of coronary artery disease.

Adult↗
PubMed1995

Anomalous increase in nitric oxide synthase activity by certain nitric oxide-generating compounds in intact neuronal cells.

It has been shown that nitric oxide (NO) regulates NO synthase (NOS) activity through negative feedback in cytosolic enzyme preparations in various cell types. We compared the effects of the NO-generating compounds S-nitroso-N-acetylpenicillamine (SNAP), 3-morpholinosydnonimine (SIN-1), and sodium nitroprusside (SNP) on NOS activity in intact neuroblastoma N1E-115 cells and in the cytosol obtained from the same cells. Enzyme activity was measured by the conversion of L-[3H]arginine into L-[3H]citrulline. At concentrations that elicit almost complete inhibition of NOS activity in cytosolic enzyme preparations of these cells, SIN-1 and SNP did not cause significant attenuation of enzyme activity measured at 45 min in intact cells. It is surprising that SIN-1 and SNP markedly stimulated L-[3H]citrulline formation in a time- and concentration-dependent manner when cells were incubated with the compounds for > 1.5 h. Neither inhibitory nor stimulatory effects of SNAP on NOS were observed in intact N1E-115 cells. This is in contrast to the inhibitory effects of SNAP in cytosolic preparations of the enzyme. The increased NOS activity by SIN-1 or SNP in intact cells was dependent on the presence of extracellular Ca2+, suggesting that it might be due to increased Ca2+ influx. On the other hand, measurements of the activity of lactate dehydrogenase showed that there was no generalized increase in cell permeability in response to SIN-1 or SNP. There was no agreement in the rank order of potencies of these compounds in activating guanylate cyclase and in affecting NOS activity, both in broken-cell preparations and in intact cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗
PubMed1995

Redox-active chalcogen-containing glutathione peroxidase mimetics and antioxidants inhibit tumour promoter-induced downregulation of gap junctional intercellular communication between WB-F344 liver epithelial cells.

Evidence is mounting supporting a role for oxidative stress in the mechanism of tumour promotion in response to agents such as 12-O-tetradecanoylphorbol-13-acetate (TPA). In this paper we demonstrate that glutathione peroxidase-mimetic xenobiotics, ebselen, ebselen-glutathione, alpha-(phenylselenenyl) acetophenone and bis-(4-aminophenyl) telluride (at concentrations between 10 microM and 50 microM) all demonstrate protective effects on TPA-induced downregulation of gap-junctional intercellular communication (GJIC) between WB-F344 rat liver epithelial cells. These effects were, in each case, diminished if the cells were depleted of their intracellular glutathione, and potentiated if glutathione was supplemented into the incubations. Additionally, bis-(4-aminophenyl) selenide and several N-substituted analogues, possessing potent antioxidant activity but being devoid of GSH peroxidase-mimetic activity, demonstrated remedial activity against TPA-induced downregulation of GJIC. Structure-activity relationships between these molecules showed a strong correlation to the oxidation potential of the selenium atom in the compound as the bis-(4-nitrophenyl)- and bis-(4-cyanophenyl)- derivatives, which possess poor antioxidant capacity and a half-wave redox potential well above +1.0 V, did not affect TPA-induced effects on GJIC. Examination of the mechanism of action of these redox-active compounds demonstrated correlations between their abilities to (i) prevent TPA-induced downregulation of GJIC, (ii) abolish the accumulation of intracellular oxidants and (iii) prevent the hyper-phosphorylation and internalization of connexin 43 in the cells. The active compounds were also able to prevent the rapid, TPA-induced translocation of protein kinase C to the particulate fraction of the cells, without affecting phorbol ester binding. These data support a synergistic role for oxidants and other TPA-dependent responses within the cell in mediating the downregulation of GJIC. Such oxidative metabolism may play a role in the control of translocation of protein kinase C from the cytosol to membranes in response to TPA within these cells. Despite the nature of the in vitro test system studied, the data also clarify the molecular basis for a potential anti-tumour promotive effect of antioxidants, based on established redox chemistries of several series of structurally-related molecules.

Animals↗
PubMed1995

Development of an ELISA to detect MX virus, a human calicivirus in the snow Mountain agent genogroup.

MX virus is a Snow Mountain agent (SMA) genogroup human calicivirus (HuCV) identified in a Mexican child with diarrhoea. An ELISA using hyperimmune antisera to the recombinant MX virus (rMX) capsid was developed to detect SMA genogroup HuCVs in stool specimens. The rMX ELISA detected the prototype MX virus, SMA, and Hawaii agent (HA), but not Norwalk virus (NV) or Sapporo virus. Twenty-three diarrhoea stool specimens from children attending day care centres in Norfolk, Virginia, were positive by the rMX ELISA and results were confirmed by reverse transcription-polymerase chain reaction (RT-PCR). Eight of 20 diarrhoea stool specimens from children in the United Kingdom previously shown to contain small round structured viruses (SRSVs) or HuCVs by electron microscopy were also positive by the rMX ELISA and RT-PCR. Sequence analysis of the RT-PCR products showed that all the rMX ELISA-positive viruses belong to the SMA genogroup. These data also showed that the SMA genogroup can be further divided into two subgroups: subgroup 1 includes prototypes SMA and HA, and subgroup 2 includes MX virus, minireovirus, Oth-25 and Bristol virus.

Animals↗
PubMed1995

Generation of DNA-based markers in specific genome regions by two-primer RAPD reactions.

Random amplified polymorphic DNA (RAPD) markers offer quick screening of different regions of the genome for genetic polymorphisms. The standard RAPD procedure uses a single 10-base-long random oligonucleotide as a primer to amplify short stretches of the genome by PCR. We modified the procedure by using two primers in each reaction in a Brassica napus mapping project. We found that the two-primer RAPD tends to amplify more and smaller fragments than the standard RAPD technique. These new bands were always amplified in the two-primer reactions, and Southern analysis revealed that they had no homology to the bands amplified in single-primer reactions involving the same primers. Furthermore, these new markers were not linked to markers amplified with the same primers in the standard RAPD reactions, suggesting that they were amplified from different genomic regions. The advantage of the two-primer RAPDs is that it allows more reactions to be carried out with a limited number of primers to generate more markers. Using a single primer, the number of reactions is equal to the number of primers (n), which in turn limits the total number of markers. When using two primers in all possible combinations, the total number of reactions increases to n x (n-1/2). This method could be useful in conjunction with bulked segregant analysis to develop high density maps of certain chromosomal regions. We used this approach to map a second marker linked to a gene governing low linolenic acid concentration in a B. napus F2 population.

Brassica↗
PubMed1995

Expression, self-assembly, and antigenicity of a snow mountain agent-like calicivirus capsid protein.

Virus-like particles were produced in insect cells infected with a recombinant baculovirus containing the capsid gene of MX virus, a Mexican strain of human calicivirus. These recombinant MX (rMX) particles were morphologically similar to recombinant Norwalk virus (rNV) particles as observed under an electron microscope and contained a single capsid protein with a molecular weight of 57,000, which was slightly smaller than that of rNV. This protein was immunoprecipitated by sera from volunteers infected with the Snow Mountain agent, but it reacted weakly with sera from volunteers infected with NV. This protein did not react with hyperimmune antisera from animals immunized with rNV in the rNV antigen enzyme immunoassay (EIA). Seroresponses were detected from volunteers infected with Snow Mountain agent and Hawaii agent when the rMX particles were used as antigen in an EIA. This EIA also detected an immune response in the sera of child from whom the MX virus was isolated, and a high prevalence of antibody to MX virus was found in the sera of a cohort of Mexican children.

Animals↗
PubMed1995

Mutational analysis of Saccharomyces cerevisiae U4 small nuclear RNA identifies functionally important domains.

U4 small nuclear RNA (snRNA) is essential for pre-mRNA splicing, although its role is not yet clear. On the basis of a model structure (C. Guthrie and B. Patterson, Annu. Rev. Genet. 22:387-419, 1988), the molecule can be thought of as having six domains: stem II, 5' stem-loop, stem I, central region, 3' stem-loop, and 3'-terminal region. We have carried out extensive mutagenesis of the yeast U4 snRNA gene (SNR14) and have obtained information on the effect of mutations at 105 of its 160 nucleotides. Fifteen critical residues in the U4 snRNA have been identified in four domains: stem II, the 5' stem-loop, stem I, and the 3'-terminal region. These domains have been shown previously to be insensitive to oligonucleotide-directed RNase H cleavage (Y. Xu, S. Petersen-Bjørn, and J. D. Friesen, Mol. Cell. Biol. 10:1217-1225, 1990), suggesting that they are involved in intra- or intermolecular interactions. Stem II, a region that base pairs with U6 snRNA, is the most sensitive to mutation of all U4 snRNA domains. In contrast, stem I is surprisingly insensitive to mutational change, which brings into question its role in base pairing with U6 snRNA. All mutations in the putative Sm site of U4 snRNA yield a lethal or conditional-lethal phenotype, indicating that this region is important functionally. Only two nucleotides in the 5' stem-loop are sensitive to mutation; most of this domain can tolerate point mutations or small deletions. The 3' stem-loop, while essential, is very tolerant of change. A large portion of the central domain can be removed or expanded with only minor effects on phenotype, suggesting that it has little function of its own. Analysis of conditional mutations in stem II and stem I indicates that although these single-base changes do not have a dramatic effect on U4 snRNA stability, they are defective in RNA splicing in vivo and in vitro, as well as in spliceosome assembly. These results are discussed in the context of current knowledge of the interactions involving U4 snRNA.

Base Sequence↗
PubMed1995

Cardioselective derivatives of 2,2-diphenyl-2-ethylthioacetate do not discriminate between m2 and m3 muscarinic receptors expressed in CHO cells.

Characteristics of interaction of two derivatives of 2,2-diphenyl-2-ethylthioacetate with muscarinic receptors were studied in Chinese hamster ovary (CHO) cells stably transfected with the genes of human m2 and m3 muscarinic receptors. Data from radioligand-receptor binding assays and measurements of m2 receptor-inhibited cyclic AMP formation and m3 receptor-stimulated phosphoinositide (PI) hydrolysis showed that this new series of muscarinic receptor antagonists exhibited a middle range of affinities in binding to muscarinic receptors (Ki = 0.2-0.7 mumol/l), without being able to discriminate between m2 and m3 receptors. They completely displaced [3H]N-methylscopolamine ([3H]NMS) binding at equilibrium and inhibited receptor-mediated increase in PI turnover in m3 CHO cells and decrease in cyclic AMP synthesis in m2 CHO cells in an apparent competitive manner. However, higher concentrations of the compounds (> 10 mumol/l) decelerated the kinetics of atropine-induced dissociation of [3H]NMS at m2 and m3 receptors, indicating an allosteric interaction. Collectively, our results demonstrate that these derivatives of 2,2-diphenyl-2-ethylthioacetate display a mixed mechanism of interaction with muscarinic receptors, being competitive at low concentrations and allosteric at higher concentrations. In contrast to previous reports of a significantly higher affinity at cardiac M2 as compared to ileal M3 receptor, these compounds do not exhibit such selectivity when the two receptor subtypes are expressed in the same type of cells.

Animals↗
PubMed1995

[Establishment and biological characteristics of the nude mice xenograft model from human hepatocellular carcinoma].

The human hepatocellular carcinoma was successfully heterotrasplanted into nude mice and 10 passages were made seriously during 11 months. Initial take rate was 14.3% and then the take rate increased to 100% after the 3rd passage. Histological, morphological, ultrastructural and biological investigation and chromosome analysis showed that the characteristic of transplanted tumor was identical to that of characteristics of human donor tumor. Through serial passages no metastatic signs were found grossly and under the microscope in the lymph nodes, liver and lung of the nude mice. Result also showed that the model retained some functions of the original tumor. The transplanted tumor could secret a-fetoprotein (AFP), r-glufamyl transpeptidase (r-GT). Acidic isoferritin (AIF) also could be detected. The tumor tissue of xenograft model was cultured in vitro in order to develop a permanent cell line. We found that the tumor specimen of the later passages grew more rapidly than the earlier ones. Up to now 3 cell passages were made. In this paper, a reliable animal model of human hepatocellular carcinoma is provided for studies of clinical diagnosis, treatment, antitumor drug screen test, etc.

Aged↗
PubMed1995

Quantitative cleaning efficacy evaluation methods with protein and lipid lens soiling models.

We developed a nondestructive, quantitative method for evaluating the cleaning efficacy of rigid gas permeable contact lens care systems. Simulated tears prepared with lysozyme, albumin, and calcium ions were applied to rigid gas permeable lenses as a protein soiling model, and a mixture of grease and unsaturated fat was applied as a lipid soiling model. The ComfortCare system (Pilkington Barnes Hind) and the Boston Cleaner and Boston Conditioning Solution (Polymer Technology) were evaluated for their efficacy in removing protein deposits; water was used as a control. The ComfortCare system and the Boston Advance Cleaner and Boston Advance Conditioning Solution were evaluated for their effectiveness in removing lipid deposits; saline was used as a control. Protein deposit level was detected by a densitometer at the absorbance of 280 nm. The lipid deposit level was evaluated by the absorbance of the fluorescence at 430 nm using the same densitometer with a fluorescence accessory. The two test systems demonstrated a significantly higher cleaning efficacy than the control for both soiling models. The methods provide quantitative measurements and therefore can be analyzed statistically for screening or comparison purposes.

Contact Lens Solutions↗
PubMed1995

Gentle Touch, a lens material resistant to protein deposition.

We investigated the ability of the Gentle Touch, a non-ionic contact lens material containing 35% netrafilcon A and 65% water, to repel protein deposits. Studies were conducted in vivo (lenses worn by patients) and in vitro (lenses coated by artificial tears). Acuvue soft contact lenses, an ionic lens material containing 42% etafilcon A and 58% water, were used as controls. After 1 to 2 weeks of wear, protein deposits on Gentle Touch lenses averaged 1.5-2.8 micrograms per lens versus 338-444 micrograms per lens for Acuvue. Gentle Touch lenses that were heat-coated with an FDA tear solution recommended for testing protein deposition averaged 6.5 micrograms of protein deposits per lens, whereas almost 100 micrograms of protein was deposited on each Acuvue lens. Lenses treated with an artificial tear solution deposited a non-detectable amount of protein on each Gentle Touch lens versus more than 358 micrograms on each Acuvue lens. These studies demonstrated that Gentle Touch lenses are highly resistant to protein deposits.

Biocompatible Materials↗
PubMed1995

The central region of the yeast U4 snRNA is not important for hammerhead catalysis, but may act as a domain spacer.

Several distinct domains of U4 small nuclear (sn)RNA interact with other components of the spliceosome and are essential for pre-mRNA splicing. We have previously shown that single point mutations (Hu et al., 1995) in the central domain of the yeast U4 snRNA do not effect cell growth. In contrast to our results, this region has been reported to possess metal-binding or catalytic activity in vitro (Yang et al., 1994). In order to test if large mutations in the central domain effect cell growth and/or in vivo splicing, we have carried out further mutational analyses of this domain. A deletion of nucleotides from 62 to 88, including all those corresponding to the invariable positions of the hypothetical hammerhead, does not affect cell growth at/or above 25 degrees C. In addition, the central region (nucleotides 69-88) can be replaced by two copies of a 38-nt spacer inserted in the same orientation without any effect on cell growth or nuclear RNA splicing. These results suggest that the central domain of U4 snRNA functions primarily to separate the 5'- and 3'- domains of the snRNA by an optimal distance.

Base Sequence↗
PubMed1995

Polymorphism of phosphoglucomutase 1 (PGM1) in five Han subpopulations in China.

PGM1 polymorphism in five Han subpopulations in China was investigated by polyacrylamide gel isoelectric focusing. The frequency of PGM1*1A was 0.6256 for Xi'an Han, 0.5982 for Zhengzhou Han, 0.6429 for Huhhot Han, 0.6232 for Lanzhou Han, and 0.6000 for Hakka in Guangdong Province. There was a north to south cline of PGM1*1A frequency.

Alleles↗
PubMed1994

Synergy in the spectral tuning of retinal pigments: complete accounting of the opsin shift in bacteriorhodopsin.

UV-visible and solid-state NMR studies of a series of 6-s-trans protonated Schiff bases of retinal with aniline show that the bathochromic shift induced by weakening the imine counterion is significantly greater in the 6-s-trans conformation than in the 6-s-cis conformation. Based on the observed magnitude of this coupling between the electronic effects of 6-s isomerization and imine counterion strength in the model compounds, the large opsin shift and unusual chemical shifts in light-adapted bacteriorhodopsin can be fully explained. These phenomena therefore do not require a negative point charge or polarizability effects in the chromophore binding pocket. The results are consistent with an effective center-to-center distance between the Schiff base and its counterion of about 4 A in light-adapted bacteriorhodopsin.

Aniline Compounds↗