Biomedical subjects

S Liu

Publications and source records attributed to S Liu.

At least 955 records · Page 53Linked to original sources

PubMed1993

H(2)-CO(2)-Dependent Anaerobic O-Demethylation Activity in Subsurface Sediments and by an Isolated Bacterium.

The ability of microorganisms in sediments from the Atlantic Coastal Plain to biodegrade methoxylated aromatic compounds was examined. O-demethylation activity was detected in deep (121- and 406-m) sediments, as well as in the surface soil. A syringate-demethylating consortium, containing at least three types of bacteria, was enriched from a deep-sediment sample in a medium containing syringate as the sole organic carbon source and with a N(2)-CO(2) atmosphere. An isolate which demethylated syringate was obtained from the enrichment on an agar medium incubated under a H(2)-CO(2) but not a N(2)-CO(2) or N(2) atmosphere. O demethylation of syringate of this isolate was dependent on the presence of both H(2) and CO(2) in the gas phase. The metabolism of syringate occurred in a sequential manner: methylgallate accumulated transiently before it was converted to gallate. Mass balance analysis suggests that the stoichiometry of the reaction in this isolate proceeds in accordance with the following generalized equation: C(7)H(3)O(3)(OCH(3))(n) + nHCO(3) + nH(2) --> C(7)H(3)O(3)(OH)(n) + nCH(3)COO + nH(2)O.

Journal Article↗

PubMed1993

Vascular endothelial growth factor induces EDRF-dependent relaxation in coronary arteries.

Vascular endothelial growth factor (VEGF), also known as vascular permeability factor (VPF), has recently been shown to increase cytosolic free calcium in endothelial cells. In the present study, we investigated the coronary vascular effects of recombinant human and native guinea pig VEGF/VPF in isolated canine coronary arteries in the presence and absence of intimal endothelium, indomethacin, and NG-monomethyl-L-arginine, a competitive nitric oxide synthase inhibitor. Addition of recombinant VEGF/VPF (1-660 pM) in coronary arteries that had been previously contracted with prostaglandin F2 alpha induced a slow, dose-dependent relaxation, reaching a maximum of -59.1 +/- 6.7% (mean +/- SE, n = 19). Mechanical disruption of the intimal endothelium completely abolished the observed relaxation. No direct vascular effect of recombinant VEGF/VPF on the endothelium-disrupted coronary arteries was noted. Pretreatment of endothelium-intact coronary arteries with 5 microM of indomethacin did not alter the observed relaxation (-57.3 +/- 7.0%, n = 18), whereas pretreatment with either NG-monomethyl-L-arginine or 10 microM of genistein, a known inhibitor of tyrosine kinase, significantly inhibited the relaxation. Addition of native VEGF/VPF (1-100 pM) also induced an endothelium-dependent relaxation in the isolated coronary arteries. Heating of recombinant VEGF/VPF (70 degrees C, 25 min) or prior incubation with a specific antibody raised against a VEGF/VPF peptide completely abolished the relaxation. Finally, recombinant VEGF/VPF stimulated a slow rise in cytosolic free calcium in cultured human endothelial cells that was qualitatively similar to that of native VEGF/VPF.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Costal diaphragm curvature in the dog.

The curvature of the midcostal region of the diaphragm in seven dogs was determined at functional residual capacity (FRC) and end inspiration during spontaneous breathing and mechanical ventilation and at total lung capacity in the prone and supine positions. Metallic markers were attached to muscle fibers on the abdominal surface of the diaphragm, and the dog was allowed to recover from surgery. The three-dimensional positions of the markers were determined by biplane videofluoroscopy. A quadratic surface was fit to the bead positions. The principal axes of the quadratic surface lie nearly along and perpendicular to the muscle fibers. In both the supine and prone positions, the values of the principal curvatures were similar at FRC and end inspiration during spontaneous breathing, when muscle tension and transdiaphragmatic pressure both increase with increasing lung volume, and during mechanical ventilation and passive inflation to total lung capacity, when both decrease relative to their magnitude at FRC. No abrupt change of curvature, which might be expected at the edge of the zone of apposition, was apparent. The curvature along the muscle fiber was 0.35 +/- 0.07 cm-1; the curvature perpendicular to the muscle fiber was much smaller, 0.06 +/- 0.01 cm-1. The costal region of the diaphragm displaces and shortens as lung volume increases, but its shape, as described by its curvatures, does not change substantially.

Animals↗

PubMed1993

Characterization and measurement of prostate-specific antigen using monoclonal antibodies.

Monoclonal and polyclonal antibodies were produced using a pure preparation of prostate-specific antigen (PSA) as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). By SDS-PAGE, the apparent molecular weight of PSA was about 33 kD. Eighty-four monoclonal antibodies were produced, 77 of which bind PSA with an affinity higher than 10(9) M-1. Use of these monoclonal antibodies to study the immunological characteristics of PSA revealed the presence of 4 epitopes. Injection of PSA into goats resulted in a production of polyclonal antibodies with high affinity. These polyclonal antibodies were purified by affinity chromatography and adsorbed on plastic tubes. By an immunometric assay, we have also demonstrated that polyclonal antibodies bind PSA at a fifth epitope that is different from those of monoclonal antibodies. Using an iodinated monoclonal antibody and polyclonal antibodies adsorbed on plastic tubes, a sensitive immunoradiometric assay could be developed, and a further increase in sensitivity could be achieved by using a mixture of 2 monoclonal antibodies. The serum PSA levels in 2,250 patients measured with this immunoradiometric assay were identical to the values determined by Tandem-R, although the present assay reached a minimum detectable value of 0.05 ng/ml compared with 0.2 ng/ml by Tandem-R.

Animals↗

PubMed1993

[Recording intracellular potentials of viscero-nociceptive neurons in posterior group of thalamic nuclei (PO) and their labeling with HRP intracellularly in cats].

Intracellular potentials (ICP) of the neurons in PO evoked by stimulating greater splanchnic nerve (GSN) were recorded in 42 cats. The resting potentials and action potentials induced by stimulating GSN were 53.74 +/- 11.68 mV and 29.44 +/- 9.22 mV respectively. Owing to intensity of the stimulation we can record EPSP and single spike or polyspikes on it. The action potentials derived from stimulating GSN (related action potentials) were inhibited by injection of morphine intravenously. On the basis of recording ICP, we also labeled 2 related neurons with stimulation of GSN and 2 unrelated ones. Differences between two kinds of the neurons were compared preliminarily. The ICP of the related neuron with stimulating GSN were inhibited by stimulating Amygdala too. Factors influencing amplitude of action potential in intracellular recording, criteria of determining nociceptive neuron and inhibition derived from stimulating Amygdala were also discussed.

Action Potentials↗

PubMed1993

[Purulent ventriculitis treated by continuous perfusion with antibiotic fluid].

24 cases of purulent ventriculitis were treated by perfusion with antibiotic fluid were reported. Two tubes were mounted, one for continuous drip in and the other for drain out. The results showed that it is more effective than ordinary antibiotic injection and/or single tube drainage. The cure rate may be promoted if effective antibiotic were used early.

Adolescent↗

PubMed1993

[Memory function of patients with cerebral arteriosclerosis evaluated by Rivermead behavioural memory test].

Using Rivermead behavioural memory test, we examined 142 patients with cerebral arteriosclerosis. The results showed that the rate of anomalies of screening score in patients with cerebral arteriosclerosis were significantly higher than that of the control group (P < 0.01). The patients and control scores were significantly different (P < 0.05) in all items except the picture and face recognition. Comparing the screening score with brain CT scan, we found a relationship between brain damage and behavioural memory declination. Also, many persons of control group got low scores with behavioural memory test, suggesting that the Rivermead behavioural memory test be sensitive to memory declination. With its simplicity and sensitivity the Rivermead behavioural memory test may have some practical value in China.

Aged↗

PubMed1993

[The isolation and identification of a Clostridium botulinum serotype A strain].

319 soil specimens were collected from different places of China for isolating Clostridium botulinum. A strain of Clostridium botulinum was isolated from a culture of soil specimens in Ruoergai of Sichuan Province, the strain was called As-3. The As-3 was identified as Clostridium botulinum serotype A according to its biological properties, biochemical serological and toxicological characteristics and DNA determination. Its DNA G + C mol is 24.9%. The toxin produced by As-3 strain can only be neutralized by type A antiserum.

Animals↗

PubMed1993

[Experimental method and clinical significance of hidden rheumatoid factors].

Hidden rheumatoid factor (HRF) was detected in rheumatoid arthritis (RA) serum with ELISA after separation and dissociation of immune complex (IC). It was found that 60% of the patients with active RA has positive latex fixation test, whereas 96% of them has been demonstrated to have IgM hidden rheumatoid factor (HIgMRF) and 70% of them IgG hidden rheumatoid factor (HIgGRF). When the disease was controlled, HIgMRF and HIgGRF was found in 24% and 12% respectively. The difference was significant with P < 0.01. Our results show that the presence of HRF in RA patients is related with the activity of the disease, but not with duration of disease, sex and age.

Adult↗

PubMed1993

Endoscopic variceal ligation. Experience in 78 patients.

Endoscopic variceal ligation (EVL) is a new alternative to sclerotherapy in the treatment of esophageal variceal hemorrhage, which results in strangulation, necrosis and scar formation of varices without systemic or local adverse effect. From May 1, 1991 through July 1, 1992, EVL was performed in 78 consecutive patients, in 35 of them it was performed during active massive bleeding, and active bleeding was controlled by the initial session in 31 patients. With repeated EVL treatment, 32 patients had their varices obliterated. The varices had reduced in size in other patients. No ligation-related complications were observed. This procedure is a safe, effective and rather simple method to treat esophageal varices, especially in patients with poor liver function and recurrent bleeding after devascularization or shunt surgery.

Adolescent↗

PubMed1993

[Study on estrogen and progesterone receptors in endometriosis and adenomyosis].

Estrogen and progesterone receptors (ER and PR) in 18 cases of ovarian endometriosis and 13 cases of adenomyosis were determined with dextran coated charcoal (DCC) method. The levels of ER and PR in those specimens were lower than those of normal endometrium. Among the 18 cases of ovarian endometriosis, 6 (33.4%) were negative for PR, which accounted for the unsatisfactory results of progesterone treatment for some endometriosis. In the 13 cases of adenomyosis there were 10 (76.9%) showing positive PR. It is suggested that the hormone therapy may be useful to treat those young patients with adenomyosis instead of surgery. The correlation of the ER and PR levels, the treatment and prognosis in endometriosis and adenomyosis are worth further studying.

Adult↗

PubMed1993

[Study on hydrolytic kinetics of metronidazole-phosphate in rabbit plasma by HPLC].

A HPLC method for the simultaneous determination of metronidazole and metronidazole-phosphate in rabbit plasma has been established. This method is simple, sensitive, reproducible and has a good linearity. It has been used to study the hydrolytic kinetics of metronidazole-phosphate in rabbit plasma. The results show that hydrolytic process of metronidazole-phosphate in vitro at 37 degrees C follows a first order kinetics with the rate constant 0.016 min-1 and half-life 43 min.

Animals↗

PubMed1993

[Determination of glycyrrhizin in glycyrrhiza and it's preparations by ion-pair HPLC].

Glycyrrhizin is the main component of glycyrrhiza. In this article an Ion-pair high performance liquid chromatography (HPLC) method is described for the determination of glycyrrhizin in two kinds of glycyrrhiza from different origins and twelve kinds of Chinese traditional patent medicine containing glycyrrhiza. A reversed phase system was used, including an ODS column with water and methanol (36:64) as the mobile phase which contained 5mmol/L tetra-n-butyl ammonium hydroxide and was adjusted to pH 6.0 by phosphoric acid. The column temperature was 35 degrees C; the detection was performed at 254 nm. Under this condition glycyrrhizin could be separated from other components. The limit of detection was 13ng, and the average recovery was 99.85%. During the experiments, we studied the concentration of counter-ion, the mixing ratio of methanol to water, the pH of the mobile phase and column temperature and their effect on the capacity factor of compound and resolution. We also studied the method of pre-treatment for the samples. The determination method is simple and accurate.

Chromatography, High Pressure Liquid↗

PubMed1993

[Microcomputer image analysis of surface parameters of the optic disk].

103 normal and 86 open-angle glaucoma optic disks were evaluated with the microcomputer image analyser. Except for the diameter and area, all other parameters of the normal disk differed significantly from those of the glaucomatous disk. The cup/rim area ratio in glaucoma was significantly larger, while the cup/disk area ratio was moderately so, indicating that the former was more useful in the early diagnosis of glaucoma. The microcomputer image analyser was reliable and accurate, also capable of processing blurred images from varying exposure and focussing. The quotient between the horizontal and vertical C/D ratios was a relatively stable value with changing glaucomatous cupping.

Adolescent↗

PubMed1993

Aging effects on stereoselective pharmacokinetics and pharmacodynamics of verapamil.

Pharmacokinetics and pharmacodynamics were studied after separate single 15-min infusions of each of verapamil's enantiomers (d, 10-11 mg/kg; l, 0.10-0.11 mg/kg) in 16 healthy non-smoking subjects ranging in age from 24 to 40 (young) and from 63 to 83 years (elderly). Verapamil clearance was found to be decreased in an age-related stereoselective manner, with significant reductions in l-verapamil clearance in older subjects (P < .03), but no age-related change in d-verapamil clearance. Greater l- vs. d-verapamil clearance rates were only seen in younger male subjects. Trends for increased elimination half-lives for both enantiomers were seen with increasing age (for d-, P < .09, l- P = .10). Protein binding was stereoselective, with greater binding of d- vs. l-verapamil in both age groups (P < .0001) with no age-related differences in binding detected. Vd beta was greater for d- vs. l-verapamil (P < .05). l-Verapamil was more potent than d-verapamil (P < .001) for all pharmacodynamic variables measured. Both verapamil enantiomers decreased blood pressure (P < .0001), increased P-R intervals during sinus rhythm (P < .0001) and atrioventricular Wenckebach block cycle lengths (P < .0001) and transiently increased heart rate (P < .0001) in both young and elderly subjects. Age-related differences in responses were seen for blood pressure (greater decreases in systolic pressure in the elderly after d-verapamil, P < .002), heart rate (smaller and only transient increases followed by decreases after d-verapamil) and P-R intervals during sinus rhythm (less prolongation in the elderly after both enantiomers, P < .02).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

[Molecular and clinical cytogenetic studies of a family with a 22p+ marker chromosome].

A male with gonadal dysgenesis and a 22p+ was observed. Molecular and Clinical Cytogenetic studies have been carried out on the members of the family. The results showed that there was a 22p+ marker chromosome transmitted from the maternal grandmother of the proband to 6 members of this family. Its short arm showed a homogeneously dull stained region in C-banded preparations and a narrow dark or light stained band in R-, G-banded preparations respectively. A large Ag-band or double NORs was also observed on p+. The chromosomal in situ hybridization with tritium labelled rRNA gene probe demonstrated that the distribution of the silver grains was along the entire p+ of the marker chromosome. The number of silver grains on the short arm of the p+ was 3.9 times as that of any other normal acrocentric chromosomes. Two cases of female with repeated spontaneous abortions and 2 cases of male with gonadal dysgenesis were found by family study. Our studies, combining with previous literatures suggested that these abnormalities were probably in association with p+ marker chromosome.

Adult↗

PubMed1992

Involvement of cysteine residues in catalysis and inhibition of human aldose reductase. Site-directed mutagenesis of Cys-80, -298, and -303.

In order to study the potential role of cysteinyl residues in catalysis and inhibition of human aldose reductase, mutants containing cysteine to serine substitution at positions 80 (ALR2:C80S), 298 (ALR2:C298S), and 303 (ALR2:C303S) were constructed. Mutation of Cys298 resulted in the most profound changes, as ALR2:C298S displayed 4- to 5-fold elevation in K'm(NADPH), K'm(DL-glyceraldehyde), and kcat(DL-glyceraldehyde) relative to wild type aldose reductase as well as a 10-fold higher Ki for the aldose reductase inhibitor sorbinil. Wild type and mutant reductases were equally sensitive to tolrestat, a structurally different reductase inhibitor. Carboxymethylation of the wild type enzyme or the C80S and C303S mutants led to a modest decrease in kcat as well as an increase in K'm(DL-glyceraldehyde) and Ki(sorbinil). These parameters were not significantly changed when ALR2:C298S was subjected to carboxymethylation. Lithium sulfate caused activation of ALR2:WT, C80S, and C303S but did not significantly affect the activity of ALR2:C298S. The differential sensitivity of wild type and mutant reductases to inhibition by sorbinil and tolrestat, before and after carboxymethylation, indicates that these inhibitors bind at different sites. These results suggest that Cys-298 is present near the active site and constitutes a regulatory group which controls the catalytic activity and inhibitor sensitivity of the enzyme.

Aldehyde Reductase↗

PubMed1992

Tissue-specific expression in mammalian brain, heart, and muscle of S1, a member of the elongation factor-1 alpha gene family.

Elongation factor-1 alpha (EF-1 alpha) is an ubiquitous protein that functions in peptide elongation during mRNA translation. We previously reported the isolation of a rat S1 protein that is antigenically related to statin, a nonproliferation-specific protein; this S1 gene shares a high degree of homology to EF-1 alpha. We constructed specific riboprobes to the two genes, based on the difference in the 3' noncoding regions of both S1 and EF-1 alpha mRNAs. Northern analysis and RNase protection assays have revealed that S1 mRNA is present only in brain, heart, and muscle, while EF-1 alpha mRNA has been detected in all tissues surveyed so far. The same tissue specificity has been observed in mouse, suggesting that S1 expression is conserved between these two mammalian species. S1 transcript was detected in late brain embryogenesis (day 20), but in lower amounts than in 3-month-old adult brain. We show that the relative levels of both S1 and EF-1 alpha transcripts and their respective tissue abundances remain unchanged during the aging process. The function of S1 is not yet known; but these results suggest that it may be involved in specific control mechanisms for protein synthesis in tissues where cells (i.e. neurons and myocytes) are permanently locked in a state of nonproliferation.

Aging↗