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Biomedical subjects

S Lu

Publications and source records attributed to S Lu.

At least 307 records · Page 17Linked to original sources
PubMed1995

Expression cloning of the cDNA for a polypeptide associated with rat hepatic sinusoidal reduced glutathione transport: characteristics and comparison with the canalicular transporter.

Using the Xenopus oocyte expression system, we previously identified an approximately 4-kb fraction of mRNA from rat liver that expresses sulfobromophthalein reduced glutathione S-conjugate (BSP-GSH)-insensitive and an approximately 2.5-kb fraction expressing BSP-GSH-sensitive reduced glutathione (GSH) transport. From the former, a 4.05-kb cDNA was cloned and characterized as the putative rat canalicular GSH transporter. Starting with a cDNA library constructed from the approximately 2.5-kb fraction, we have now isolated a single clone that leads to expression of a BSP-GSH- and cystathionine-inhibitable GSH transporter activity with Km approximately 3 mM characteristic of the sinusoidal GSH transporter. The cDNA for the rat sinusoidal GSH transporter-associated polypeptide (RsGshT) is 2733 bases with an open reading frame of 1059 nucleotides encoding a polypeptide of 353 amino acids (39,968 Da) with two putative membrane-spanning domains. No identifiable homologies were found in searching various data bases. An approximately 40-kDa protein is generated in in vitro translation of cRNA for RsGshT. Northern blot analysis revealed a single approximately 2.8-kb transcript in rat and human liver with negligible hybridization signal in other organs. The abundance of mRNA for RsGshT did not increase with phenobarbital treatment. Cis-inhibition by BSP-GSH and trans-inhibition by cystathionine and lack of induction by phenobarbital are characteristic of sinusoidal GSH secretion and thus indicate that RsGshT either encodes the sinusoidal GSH transporter itself or a regulatory subunit of the transporter that determines its liver-specific activity.

Amino Acid Sequence↗
PubMed1995

No evidence of human papillomavirus DNA in actinic keratosis.

Human papillomaviruses (HPVs) are involved in premalignant and malignant skin diseases as well as in a variety of benign cutaneous and mucosal lesion disease. Its association with HPV infection has recently been evaluated in a few studies, but the results are contradictory. For further assessment of the role of HPVs in AK, a series of 100 paraffin-embedded biopsy specimens taken from subjects with AK were studied for the presence of HPV types 1, 2, 3, 4, 5, 7, 12, 15, 26, 36, 37 and 59 DNA using in situ hybridization (ISH) under high stringency conditions (Tm -10 degrees C). All specimens were definitely negative for all bion specimens were definitely negative for all biotinylated HPV DNA probes tested. One fifth of the specimens were studied using the polymerase chain reaction (PCR) with general primers to confirm the negative results. All cases were also in the PCR. Our results suggest that HPVs are not directly involved in the aetiology of AK.

Adult↗
PubMed1995

Parametric phase-delay estimation of sound transmitted through intact human lung.

Sonic noise between 300 and 1600 Hz is introduced into the mouths of 11 healthy adult male subjects at resting lung volume and is detected over the anterior extrathoracic trachea and at three sites on the right posterior chest wall. To overcome the difficulties associated with non-parametric phase unwrapping due to thoracic anti-resonances, the phase delay tau(f) of propagation between the trachea and the chest wall is estimated using a linear parametric ARX-type statistical model with the non-parametric magnitude spectra as a guide. The resulting tau(f) estimates are unambiguous and reliable, and show a clear trend of decreasing tau(f) with increasing frequency, indicating that sound at higher frequencies reaches the chest wall faster than that at lower frequencies. This finding indicates that respiratory sound transmission is highly dispersive, most probably owing to frequency-dependent airway and parenchymal wavespeeds.

Acoustics↗
PubMed1995

Sonic phase delay from trachea to chest wall: spatial and inhaled gas dependency.

A parametric phase delay estimation technique is used to determine the spatial and inhaled gas composition dependencies of sound propagation time through an intact human lung at frequencies of 150-1200 Hz. Noise transmission measurements from the mouth to the extrathoracic trachea and six sites on the posterior chest wall are performed in 11 healthy adult subjects at resting lung volume after equilibration with air, an 80% helium-20% oxygen mixture, and an 80% sulfurhexafluoride-20% oxygen mixture. The phase delay, tau(f), exhibits a bilateral asymmetry with relatively decreased delays to the left posterior chest as compared with the right. The phase delay to lower lung sites is greater than to upper sites at frequencies below 300 Hz; yet the opposite is found at higher frequencies, indicating changing propagation pathways with frequency. There is no measurable effect of inhaled gas composition on tau(f) below 300 Hz. At higher frequencies, changes in tau(f) that reflect the relative sound speed of the particular inhaled gas are observed. These findings support and extend previous measurements and hypotheses concerning the strong frequency dependence of the acoustical properties of the intact respiratory system.

Acoustics↗
PubMed1995

Sporulation protein SpoIVFB from Bacillus subtilis enhances processing of the sigma factor precursor Pro-sigma K in the absence of other sporulation gene products.

Processing of inactive pro-sigma K to active sigma K in the mother cell compartment of sporulating Bacillus subtilis is governed by a signal transduction pathway emanating from the forespore and involving SpoIVFB in the mother cell. Coexpression of spoIVFB and sigK (encoding pro-sigma K) genes in growing B. subtilis or Escherichia coli enhanced pro-sigma K processing in the absence of other sporulation-specific gene products. The simplest explanation of these results is that SpoIVFB is a protease that processes pro-sigma K.

Bacillus subtilis↗
PubMed1995

Mechanisms of cyclic nucleotide-induced relaxation in canine tracheal smooth muscle.

The effects of exogeneous cyclopiazonic acid (CPA, 10 microM), a selective inhibitor of the sarcoplasmic reticulum (SR) Ca2+ adenosinetriphosphatase, on cyclic nucleotide-induced relaxations of canine airway smooth muscle were examined. Strips of tracheal muscle were precontracted with carbachol (50% median effective concentration, 0.1 microM) or with 60 mM KCl. The beta-agonist isoproterenol (ISO, 10 microM) relaxed the tissue by approximately 50%. The relaxation was reduced in the presence of CPA when L-type Ca2+ channels were available but not when these were blocked by 0.1 microM nifedipine. Forskolin (1.0 microM), an adenylate cyclase activator, was less effective at inhibiting the contraction than ISO, and addition of CPA did not block its inhibitory effect as effectively as when ISO was used. Radioimmunoassay indicated that both these agents raised adenosine 3',5'-cyclic monophosphate (cAMP) levels to the same degree. Very little relaxation of the precontracted smooth muscle was elicited by 3 mM 8-bromo-adenosine 3',5'-cyclic monophosphate (8-BrcAMP), and addition of CPA had no effect. Sodium nitroprusside (100 microM) and 8-bromo-guanosine 3',5'-cyclic monophosphate (10 mM) inhibited contraction to a greater degree than any agent that raised cAMP. These inhibitions were greatly reduced in the presence of CPA when L-type Ca2+ channels were available. We conclude that pumping of Ca2+ into SR plays a major role guanosine 3',5'-cyclic monophosphate-produced but not cAMP-induced relaxation; L-type Ca2+ channels must be available for the relaxant role of Ca2+ pumping into the SR to be expressed; and ISO-induced relaxation may not involve primarily elevation of the cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1995

The renal medulla and hypertension.

We review evidence supporting the conclusion that renal dysfunction underlies the development of all forms of hypertension in humans and experimental animals. Indexes of global renal function are generally normal in the early stages of most genetic forms of hypertension, but renal function is clearly impaired in long-established hypertension. Studies in our laboratory over the past decade summarized below have established that the renal medulla plays an important role in sodium and water homeostasis and in the long-term control of arterial pressure. Development of implanted optical fibers for measurement of cortical and medullary blood flows with laser-Doppler flowmetry and techniques for delivery of vasoactive compounds into the medullary interstitial space enabled us to examine determinants of medullary flow (nitric oxide, atrial natriuretic peptides, kinins, eicosanoids, vasopressin, renal sympathetic nerves, etc). We have shown in spontaneously hypertensive rats that the initial changes of renal function begin as a reduction of medullary blood flow in the absence of changes of cortical flow. Long-term medullary interstitial infusion of captopril, which preferentially increased medullary blood flow, resulted in a lowering of arterial pressure. In normal Sprague-Dawley rats, selective reduction of medullary flow with medullary interstitial or intravenous infusion of small amounts of NG-nitro-L-arginine methyl ester resulted in hypertension. These and other studies we review show that although blood flow to the inner renal medulla comprises less than 1% of the total renal blood flow, changes in flow to this region can have a major effect on sodium and water homeostasis and on the long-term control of arterial blood pressure.

Animals↗
PubMed1995

Direct in vivo observation of subendocardial arteriolar response during reactive hyperemia.

To study the vasodilatory capacity of subendocardial (ENDO) arterioles, we evaluated the reactive hyperemic responses of ENDO as well as subepicardial (EPI) arterioles in 40 dogs by our needle-probe intravital microscope. We also examined the individual and combined effects of an ATP-sensitive K+ channel blocker (glibenclamide, 200 micrograms/kg), an inhibitor of nitric oxide synthase (NG-monomethyl-L-arginine [L-NMMA], 2 mumol/min, 20 minutes), and an adenosine-receptor antagonist (8-phenyltheophylline [8PT], 0.75 mumol/min, 15 minutes). The percent increase in end-diastolic diameter of ENDO arterioles was larger (P < .01) than that of EPI arterioles during reactive hyperemia, especially for the arterioles larger than 120 microns (P < .01). The diastolic-to-systolic vascular pulsation amplitude at the peak flow was greater in ENDO than EPI arterioles (25% versus 6%, P < .05). Compared with control conditions, the presence of both glibenclamide and L-NMMA suppressed the vasodilation responses of ENDO arterioles (P < .01 for both) and EPI arterioles (P < .05 for both). The effect of L-NMMA was greater in ENDO arterioles (P < .01), but that of glibenclamide was not different between ENDO and EPI arterioles. 8PT influenced the hyperemic response, although statistical significance was found only in the flow response. The effect of combined infusion of L-NMMA and glibenclamide with or without 8PT was greater than that of individual infusions in both ENDO and EPI arterioles. Conclusions are as follows: (1) The vasodilatory response of ENDO arterioles was even larger than that of EPI arterioles. Thus, the smaller flow reserve of ENDO arterioles may be caused by other factors, including the greater effects of myocardial compression and nitric oxide on the ENDO arterioles. (2) The vascular responses of ENDO and EPI arterioles were modulated by both endothelium-independent and -dependent vasodilative factors, and the effect of each factor including adenosine was associated with the effects of others.

Adenosine↗
PubMed1995

Abstracting capacity in cirrhotic alcoholics: negative findings.

OBJECTIVE: Alcoholic and nonalcoholic cirrhotics and normal controls were compared to determine the extent to which the cognitive deficits frequently observed in alcoholics are attributable to hepatic encephalopathy. METHOD: A battery of neuropsychological tests was administered measuring verbal and nonverbal abstracting capacity. RESULTS: No significant differences between the three groups were observed. Both the alcoholic (n = 43) and nonalcoholic (n = 63) subjects performed comparably to normal controls (n = 21) and the former two groups performed comparably to each other on seven indicators of abstracting capacity. CONCLUSIONS: Deficits in reasoning ability are not invariably associated with chronic alcoholism. In addition, low grade hepatic encephalopathy concomitant to cirrhosis in both alcoholics and nonalcoholics does not impact adversely on abstracting capacity.

Adult↗
PubMed1995

[Correlation studies on the alterations of multiple tumor suppressor genes in human esophageal cancer and in human and monkey esophageal epithelial cells treated with N-methyl-N-benzyl nitrosamine].

The correlation between the mutation spectra of tumor suppressor genes Rb, p53, APC and MCC in human esophageal cancer (EC) and in human and monkey esophageal epithelium treated with N-Methyl-N-Benzyl nitrosamine (NMBzA) was studied using PCR amplification and direct sequencing methods. The results showed that in 40.9% (9/22) of the specimen examined, the mutation spectrum of p53 in primary EC was similar to that in the esophageal epithelium of human fetus (in vitro) and monkey (in vivo) treated with NMBzA. The same mutational spectra of tumor suppressor genes Rb, APC, MCC in esophageal epithelium cells of human and monkey treated with NMBzA were also found in some human primary EC. The correlation observed in the mutation spectra of multiple tumor suppressor genes between human primary EC and the esophageal epithelia of human and monkey origin treated with NMBzA wouldsuggest that NMBzA may be the esophageal etiological agent for human esophageal cancer in China.

Animals↗
PubMed1995

[The regulation of estradiol and progesterone in tumor necrosis factor production in vitro].

The production of tumor necrosis factor (TNF) induced by lipopolysaccharide (LPS) in peripheral blood mononuclear cells (PBMC) from normal woman were determined. The study investigated the role of regulation of estradiol (E2) and progesterone (P) in the production of TNF in-vitro. The results showed that PBMC would produce TNF when stimulated by E2 or P in culture in-vitro. The appropriate dosages were 125 pmol/L in E2 and 10-20 nmol/L in P. The findings suggested that some sex hormones could play a regulating role in the production of TNF by PBMC. E2 and P may be endogenous substances capable of inducing TNF production. The results revealed a beneficial aspect of sex hormones in anti-cancer treatment.

Adult↗
PubMed1995

[Over expression of alpha-hANP in two kinds of expression systems of Escherichia coli].

Two kinds of expression plasmids carried Ref-Adaptor-(alpha-hANP) hybrid gene have been constructed. The adaptor GAA is the codon of glutamic acid which is a recognition site of the endoproteinase Glu-C. The expression of the heterologous fusion gene was controlled by the bacteriophage lambda PL promoter in the Escherichia coli expression system which is affected by the cIts857 repressor. These overproduced proteins were found in the form of inclusion bodies and constituted 35% and 48% of the total cellular protein respectively. The fusion protein was isolated and cleaved with Glu-C to liberate mature alpha-hANP, which demonstrated significant activities for reduction of blood pressure and vasorelaxation comparable to that of the chemically synthesized hormone. In this paper, the comparison between the two kinds of expression systems is also discussed.

Animals↗
PubMed1995

[Mutation of tumor suppressor genes APC and MCC in human esophageal cancer].

The mutation and deletion of APC, MCC genes in human esophageal cancer were analyzed by PCR amplification and direct sequencing assay. In PCR amplification analysis, one of 10 cases of esophageal cancer was found to have APC gene deletion in exon 11; one of 10 cases of EC was found to have MCC gene deletion in exon 12; one case of EC was found to have MCC gene deletion in exon 12. One of adjacent non-tumor tissue was also found to have deletion at exon 12 of MCC. In PCR direct sequencing analysis, two of 10 cases of EC were found to contain APC gene mutation in exon 11, two of 7 cases of EC were found to contain MCC genes mutation in exon 12. The results confirmed that mutation of APC and MCC genes exists in human esophageal cancer. It gives new clues to the understanding of carcinogenesis of human esophageal cancer. The mechanism of mutation or deletion of APC and MCC genes in EC needs further study.

Base Sequence↗
PubMed1995

[Multiple tumor suppressor genes in esophageal carcinoma induced in human fetus esophageal epithelium by NMBzA].

Results of epidemiological studies have shown that nitrosamine-induced carcinogensis is involved in esophageal cancer in China. In order to demonstrate the mechanism at molecular level, Multiple tumor suppressor genes Rb, p53, APC and MCC in human fetus esophageal epithelium treated with NMBzA (in vitro) for 24 hours or three weeks and esophageal carcinoma induced by NMBzA were analyzed with PCR amplification and direct sequencing. In PCR amplification analysis. Rb, p53, APC and MCC deletions in esophageal carcinoma of human fetus induced by NMBzA were found, but no deletions of these genes was demonstrated in NMBzA-treated human fetal esophageal epithelium. PCR direct sequencing analysis revealed mutation of p53, Rb and MCC genes in human fetal esophageal epithelium treated with NMBzA for three weeks. The results first confirmed (in vitro) that nitrosamine can cause mutations and deletions of multiple tumor suppressor genes in human esophageal epithelium. The mutations of tumor suppressor genes in nitrosamine-induced esophageal carcinoma may occur in the early stage, while deletions in late stage of carcinogenesis.

Carcinogens↗
PubMed1995

[Pharmacological studies of Polygonum capitatum Buch-Ham. ex D. Don].

The pharmacological effect of aqueous extract of Polygonum capitatum has been studied. The experimental results show that Polygonum capitatum markedly decreases WBC and RBC in urine of pyelonephritis mode in rats, the death rate of Escherichia coli infected mice, and the temperature of feverish rabbits. It has also been found that after oral administration of Polygonum capitatum the animal urine markedly inhibits the growth of Escherichia coli, but diuretic action of the herb has not been observed.

Animals↗
PubMed1995

[Effect of NMBzA on the oncogene and multiple tumor suppressor genes in monkey esophageal epithelium].

Mutations of ras oncogene and multiple tumor suppressor genes p53, Rb and APC in esophageal epithelium of rhesus monkey fed with one dose of N-methyl-N-benzylnitrosamine (NMBzA 30mg/kg), which was found in high incidence areas of esophageal cancer in China, were analysed by PCR and direct sequencing. Mutation at codon 12 of Ha-ras gene was not found in esophageal epithelium of monkey fed with NMBzA. Some mutations of p53 gene were found in esophageal epithelium of monkey after being fed with NMBzA for 24-48 hours. Some mutation of Rb and APC were found in esophageal epithelium of monkey after being fed with NMBzA for 48 hours. The mutation fingerprints of these genes disappeared in esophageal epithelium of monkey after being fed with NMBzA for 5 days. The results demonstrated that chemical carcinogen NMBzA can induce mutations of multiple tumor suppressor genes in monkey (in vivo) and indicated that the alteration of tumor suppressor genes in the initial stage of carcinogenesis needs many hits by chemical carcinogen. These alterations of p53, Rb, APC genes were similar to the changes of these genes in some reported previously primary esophageal cancer.

Animals↗
PubMed1995

[High purification of human thrombin].

A highly purified human thrombin was prepared from plasma. The procedure involved the adsorption of prothrombin from human plasma by barium chloride and precipitation by using ammonium sulfate. The partially purified prothrombin was activated by tissue thromboplastin and followed by chromatography on Amberllte and SP-Sephadex. The purified enzyme is homogeneous on SDS-PAGE and has a specific activity toward fibrinogen of 2000 NIH U/mg. The recovery is about 30% approximately 40%. This highly purified human thrombin can be used as a tool enzyme in the downstream procedure of fused recombinant proteins expressed by genetic engineering.

Amino Acid Sequence↗