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Biomedical subjects

S Chu

Publications and source records attributed to S Chu.

At least 91 records · Page 5Linked to original sources
PubMed1997

[Inherited defect of platelet nitric oxide synthase activity in essential hypertension].

The collagen-provocated platelet nitric oxide synthase (NOS) activity by the method of 3H-labelled L-arginine was compared between 19 essential hypertensives (EH) and 21 controls, and between 13 adolescents with their both parent hypertensives (FH+) and 12 adolescents without genetic hypertensive predisposition (FH-) as well. Results showed that the platelet NOS activity was lower significantly in EH group (4.76 +/- 2.01 vs 8.09 +/- 2.36 pmol.g-1.min-1, P < 0.001) and in FH+ group (3.64 +/- 2.07 vs 5.51 +/- 2.13 pmol.g-1.min-1, P < 0.05) comparing with their control groups respectively. It suggests that the inherited defect of some anti-hypertensive mechanisms like NO/NOS system may be implicated in the development of EH, which can be taken as a new "genetic marker" for detecting of specific clinic subtype. An useful data was thus presented of value in screening referred genes, for early prevention and rational remedy in essential hypertension.

Adolescent↗
PubMed1997

[Identification of photoproducts for PCB congeners by the new retention index system].

Polychlorinated biphenyls (PCBs) are a kind of priority pollutants, constituting a complex group of 209 congeners ranging from monochloro to decachlorobiphenyls. Because of the shortcomings of retention time data and the lack of suitable retention index systems, the congeners analysis of PCBs is one of the most challenging tasks in capillary column gas chromatography (GC), especially due to the fact that the isomers of PCBs can not be identified by GC-MS. A new retention index system, suitable for analysis of PCB congeners in the environmental samples by temperature-programmed capillary gas chromatography with ECD, has been developed recently by Chu et al. In this paper, retention indexes of all 209 PCB congeners were calculated according to the new retention index system from their respective retention times reported by other authors. The photoproducts of PCB87, PCB138 and PCB169 were identified with the new retention index system and confirmed by GC-MS. The deviations of retention indexes for all photoproducts were within 3 index units. It was testified that the above retention index system was reliable during the identification of PCB congeners and would have wide applicability. Based on the formations of coplanar PCB congeners (PCB77 and PCB126) during the photodegradations of PCB138 and PCB169, it was proposed that toxic equivalence (TEQ) should be used as a kind of quality indicator for the studies of the photolysis of PCBs.

Chromatography, Gas↗
PubMed1997

A novel protein shared by RNase MRP and RNase P.

We have isolated suppressors of the temperature-sensitive rRNA processing mutation rrp2-2 in Saccharomyces cerevisiae. A class of extragenic suppressors was mapped to the YBR257w reading frame in the right arm of Chromosome II. Characterization of this gene, renamed POP4, shows that the gene product is necessary both for normal 5.8S rRNA processing and for processing of tRNA. Immunoprecipitation studies indicate that Pop4p is associated with both RNase MRP and RNase P. The protein is also required for accumulation of RNA from each of the two ribonucleoprotein particles.

Amino Acid Sequence↗
PubMed1997

[Effects of captopril on the tissue nitric oxide synthase in off spring from treated pregnant SHRs].

OBJECTIVES: To further clarify the anti-hypertensive mechanism of captopril and explore a new method for earlier prevention and treatment of hypertension, we studied the effects on tissue nitric oxide/nitric oxide synthase (NO/NOS) of the descendants of spontaneously hypertensive rats (SHRs) by earlier captopril treatment. METHODS: After the pregnant SHR was treated by captopril (100 mg.kg-1.d-1), the systolic blood pressure (SBP), NOS activity and expression of inducible and constitutive NOS (iNOS and cNOS) in brain cortex, renal cortex, heart ventricle of their descendant were detected by tail-cuff sphyg-momanometer, liquid scintillation and reverse transcription-polymerase chain reaction method respectively. RESULTS: Compared with that of non-treated SHR, SBP of treated SHR was decreased (P < 0.01) and NOS activity of renal cortex, heart ventricle, iNOS expression of brain cortex, cNOS expression of renal cortex, heart ventricle significantly increased (P < 0.05). CONCLUSION: The results suggested that earlier captopril treatment could increase NOS activity and expression in different tissues of SHR, which might be a new anti hypertensiven mechanism.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1996

A short CIC-2 mRNA transcript is produced by exon skipping.

CIC-2 is a voltage- and volume-regulated chloride channel expressed in many tissues. We have shown that CIC-2 in rat lung airways is significantly down-regulated after birth [Murray,C.B. et al. (1995) Am. J. Respir. Cell Mol. Biol., 12, 597-604]. During PCR amplification from rat lung cDNA, a second transcript was identified which is 60 bp shorter than the full length sequence. The peptide translated from this 60 bp sequence contains many positively charged amino acid residues. Rat genomic DNA sequencing showed that the 60 bp sequence is an intact exon. A 71% pyrimidine content and an AAG 3'-end splice site in the intron immediately upstream from the 60 bp sequence were identified which may account for the alternative splicing of the following exon. Human genomic sequence analyses demonstrated similar intron-exon arrangement. A high CT content and an AAG 3' acceptor site were conserved in the intron corresponding to the rat upstream intron. The presence of the full length short form transcript was confirmed in rat kidney by RT-PCR, and the ratio of the long and the short form transcripts varied significantly according to the tissues examined, with the lowest long/short form ratio found in the lung among the tissues studied. Our data demonstrated that the alternatively spliced short form (CIC-2S) is transcribed in many rat tissues, the ratio of the long/short form transcripts is lower in the lung compared with the brain, and the genomic organization in this area is conserved in rat and human.

Alternative Splicing↗
PubMed1996

Non-ionic diffusion and carrier-mediated transport drive extracellullar pH regulation of mouse colonic crypts.

1. Extracellular pH (pHo) regulation within mouse colonic crypt lumens is stimulated by transepithelial gradients of short-chain fatty acids (SCFAs). Current work assesses underlying mechanisms contributing to pHo regulation. 2. Crypt luminal alkalinization was saturable by apical SCFA (substrate concentration activating half-maximal transport (KT) of isobutyrate = 45 mM). However, saturation was consistent with either carrier-mediated SCFA flux or non-ionic diffusion, because the non-ionized form was titrated by luminal alkalinization. Direct acidification of apical perfusates increased the magnitude of SCFA-induced luminal alkalinization, roughly in the same proportion to the increased concentration of non-ionized SCFA in the crypt lumen. 3. Transepithelial gradients of an alternative weak acid (CO2) produce pHo changes similar to SCFA. In contrast, a weak base (NH3) changes pHo with reverse dependence on the orientation of the transepithelial gradient compared with SCFA. Results implicate non-ionic diffusion in pHo regulation, and suggest that pHo changes may underly SCFA-stimulated bicarbonate secretion and ammonium absorption. 4. SCFA metabolism plays a minor role in extracellular pH regulation. An avidly metabolized SCFA (N-butyrate) augments crypt luminal alkalinization only slightly (0.08 pH units) versus a poorly metabolized SCFA (isobutyrate). 5. Apical addition of 1 mM 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) partially inhibits luminal alkalinization caused by apical SCFA. DIDS has no effect on luminal alkalinization caused by transepithelial CO2 gradients. Probenecid (1 mM), alpha-cyano-4-hydroxycinnamic acid (4 mM) or basolateral DIDS (1 mM) do not affect pHo regulation. Results suggest that DIDS-sensitive, SCFA-dependent transport in the colonocyte apical membrane contributes to pHo regulation.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1996

Quantitative measurements of force and displacement using an optical trap.

We combined a single-beam gradient optical trap with a high-resolution photodiode position detector to show that an optical trap can be used to make quantitative measurements of nanometer displacements and piconewton forces with millisecond resolution. When an external force is applied to a micron-sized bead held by an optical trap, the bead is displaced from the center of the trap by an amount proportional to the applied force. When the applied force is changed rapidly, the rise time of the displacement is on the millisecond time scale, and thus a trapped bead can be used as a force transducer. The performance can be enhanced by a feedback circuit so that the position of the trap moves by means of acousto-optic modulators to exert a force equal and opposite to the external force applied to the bead. In this case the position of the trap can be used to measure the applied force. We consider parameters of the trapped bead such as stiffness and response time as a function of bead diameter and laser beam power and compare the results with recent ray-optic calculations.

Biophysical Phenomena↗
PubMed1996

Comparison of males and females presenting with acute asthma to the emergency department.

OBJECTIVES: To determine the female:male ratio and compare the severity of asthma between female and male patients presenting with acute asthma to the authors' emergency department (ED). PATIENTS: Patients aged 15-50 years presenting with acute asthma. SETTING: Emergency department of a university-affiliated hospital. METHODS: Retrospective analysis of asthma surveillance data and medical records of all asthma-related visits to ED over 6 months (January 1992-June 1992). RESULTS: One hundred and thirty-seven patients aged 15-50 years made 196 consecutive visits to the authors' ED over 6 months. The ratio of female:male patients was 1.9 and the ratio of the number of visits made by female vs. male patients was 2.6. Initial peak expiratory flow rate (PEFR) and forced expiratory volume in 1 s (FEV1) were recorded in 94% and 49% of the visits, respectively. There was no statistically significant difference between the male and female patients in heart rate, respiratory rate or percentage of patients admitted to hospital. The mean (SD) initial FEV1 as a percentage of predicted was significantly higher in females compared to males (49% +/- 20% vs. 33% +/- 15%; P < 0.001). CONCLUSION: In the authors' institution there is a high female:male ratio among patients presenting with acute asthma, and males tend to present later or with more severe disease. These findings need to be confirmed by a prospective study looking at all the factors that may contribute to asthma patients presenting to the ED.

Acute Disease↗
PubMed1996

Gestational and tissue-specific regulation of C1C-2 chloride channel expression.

Chloride channels supply critical functions in epithelial cells throughout the body. Although function of the volume- and voltage-gated C1C-2 is uncertain, its wide tissue distribution of mRNA suggests C1C-2 has important housekeeping functions. This study's objective was to identify the extent of not only C1C-2 mRNA expression but also protein expression as a measure of the capacity for C1C-2 chloride secretion in epithelial tissues. Using quantitative ribonuclease protection assay, we found that C1C-2 mRNA transcripts were abundant in fetal and postnatal brain, fetal kidney, liver, intestine, and lung. In contrast to brain, C1C-2 mRNA transcripts were downregulated during late gestation in lung, kidney, and intestine. The lung expressed the least C1C-2 mRNA. Immunoblotting demonstrated similar tissue- and gestation-dependent variations in C1C-2 protein expression. To determine if there is a correlation between the sites of C1C-2 protein expression and cystic fibrosis transmembrane conductance regulator (CFTR), another epithelial chloride channel, a polyclonal COOH-terminal C1C-2 antibody and an anti-R domain CFTR anti-body were used. C1C-2 and CFTR were expressed in different sites in lung and kidney.

Aging↗
PubMed1995

Transformation of mammalian cells by overexpressing H2O2-generating peroxisomal fatty acyl-CoA oxidase.

Peroxisome proliferators induce qualitatively predictable pleiotropic responses, including development of hepatocellular carcinomas in rats and mice despite the inability of these compounds to interact with and damage DNA directly. In view of the nongenotoxic nature of peroxisome proliferators, it has been postulated that hepatocarcinogenesis by this class of chemicals is due to a receptor-mediated process leading to transcriptional activation of H2O2-generating peroxisomal fatty acyl-CoA oxidase (ACOX) in liver. To test this hypothesis, we overexpressed rat ACOX in African green monkey kidney cells (CV-1 cells) under control of the cytomegalovirus promoter. A stably transfected CV-1 cell line overexpressing rat ACOX, designated CV-ACOX4, when exposed to a fatty acid substrate (150 microM linoleic acid) for 2-6 weeks, formed transformed foci, grew efficiently in soft agar, and developed adenocarcinomas when transplanted into nude mice. These findings indicate that sustained overexpression of H2O2-generating ACOX causes cell transformation and provide further support for the role of peroxisome proliferation in hepatocarcinogenesis induced by peroxisome proliferators.

Acyl-CoA Oxidase↗
PubMed1995

Endogenous mutagenesis by an insertion sequence element identifies Aeromonas salmonicida AbcA as an ATP-binding cassette transport protein required for biogenesis of smooth lipopolysaccharide.

Analysis of an Aeromonas salmonicida A layer-deficient/O polysaccharide-deficient mutant carrying a Tn5 insertion in the structural gene for A protein (vapA) showed that the abcA gene immediately downstream of vapA had been interrupted by the endogenous insertion sequence element ISAS1. Immunoelectron microscopy showed that O polysaccharides did not accumulate at the inner membrane-cytoplasm interface of this mutant. abcA encodes an unusual protein; it carries both an amino-terminal ATP-binding cassette (ABC) domain showing high sequence similarity to ABC proteins implicated in the transport of certain capsular and O polysaccharides and a carboxyl-terminal potential DNA-binding domain, which distinguishes AbcA from other polysaccharide transport proteins in structural and evolutionary terms. The smooth lipopolysaccharide phenotype was restored by complementation with abcA but not by abcA carrying site-directed mutations in the sequence encoding the ATP-binding site of the protein. The genetic organization of the A. salmonicida ABC polysaccharide system differs from other bacteria. abcA also differs in apparently being required for both O-polysaccharide synthesis and in energizing the transport of O polysaccharides to the cell surface.

ATP-Binding Cassette Transporters↗
PubMed1995

Extracellular pH regulation in microdomains of colonic crypts: effects of short-chain fatty acids.

It has been suggested that transepithelial gradients of short-chain fatty acids (SCFAs; the major anions in the colonic lumen) generate pH gradients across the colonic epithelium. Quantitative confocal microscopy was used to study extracellular pH in mouse distal colon with intact epithelial architecture, by superfusing tissue with carboxy SNARF-1 (a pH-sensitive fluorescent dye). Results demonstrate extracellular pH regulation in two separate microdomains surrounding colonic crypts: the crypt lumen and the subepithelial tissue adjacent to crypt colonocytes. Apical superfusion with (i) a poorly metabolized SCFA (isobutyrate), (ii) an avidly metabolized SCFA (n-butyrate), or (iii) a physiologic mixture of acetate/propionate/n-butyrate produced similar results: alkalinization of the crypt lumen and acidification of subepithelial tissue. Effects were (i) dependent on the presence and orientation of a transepithelial SCFA gradient, (ii) not observed with gluconate substitution, and (iii) required activation of sustained vectorial acid/base transport by SCFAs. Results suggest that the crypt lumen functions as a pH microdomain due to slow mixing with bulk superfusates and that crypts contribute significant buffering capacity to the lumen. In conclusion, physiologic SCFA gradients cause polarized extracellular pH regulation because epithelial architecture and vectorial transport synergize to establish regulated microenvironments.

Acetates↗