Biomedical subjects

Z Liu

Publications and source records attributed to Z Liu.

At least 847 records · Page 47Linked to original sources

PubMed1997

A rapid fluorescence bioassay for the determination of selenium on agar plates.

The essential trace element selenium (Se) is involved in the form of selenocysteine at the active site of several prokaryotic and eukaryotic proteins called selenoproteins. These proteins have recently attracted attention particularly in relation to their application to human health and new characteristics of the genetic code. We have recently described a selenium bioassay based on a recombinant DNA construct in which the expression of the lac' Z gene in Escherichia coli is proportionally and specifically driven by UGA-directed selenocysteine incorporation. Here we have further developed this bioassay for more rapid and sensitive detection and measurement of selenium that permits screening of the selenium status on agar plates. Again, the inclusion of selenium into the lac'Z-fusion product is reflected by the level of beta-galactosidase activity, which in turn is reflected by the intensity of fluorescence on agar plates. This fluorescing agent is a 4-methylumbelliferyl moiety which is released through the cleavage by the enzyme of 4-methylumbelliferyl-beta-D-galactoside. The intensity of the fluorescence is easily detected by uv irradiation and photographed by polaroid or video cameras.

Agar↗

PubMed1997

Allopeptide-specific T cell reactivity altered by peptide analogs.

Recent evidence indicates that indirect allorecognition plays a key role in initiating and sustaining graft rejection. This self-restricted T cell response is generally limited to a restricted set of dominant immunogenic peptides derived from allogeneic HLA molecules. Here, we have examined whether peptide analogues of the dominant determinant of HLA-DRbeta1*0101 molecule (peptide DR1/22-35), recognized in the context of HLA-DRbeta1*1101 protein, are able to modulate the T cell response against the wild-type peptide Ag. The peptide analogues were generated by introducing single amino acid substitutions at putative MHC and TCR contact positions. Two analogues, 25R/A and 28E/Q, which bound to soluble DR11 protein, but did not stimulate an anti-DR1-specific T cell clone, inhibited the response of the clone to the wild-type peptide by TCR antagonism. Analogs 25R/A and 28E/Q were also able to inhibit the differentiation of Th precursors specific for peptide DR1/22-35. Two other peptides, 26L/I and 27L/V, acted as powerful TCR agonists, inducing a higher proliferative response of the DR1-specific T cell clone, compared with the wild-type peptide. At high concentrations, these peptides induced hyporesponsiveness of TCC-ZL36 in a manner similar to the wild-type peptide. Taken together, the results of this study indicate that specific suppression of indirect allorecognition can be achieved by using structural variants of the dominant allodeterminant.

Amino Acids↗

PubMed1997

Detection of DNA gains and losses in primary endometrial carcinomas by comparative genomic hybridization.

Comparative genomic hybridization (CGH) was used in a retrospective analysis of chromosomal imbalances in frozen primary tumor specimens from 14 endometrial carcinoma patients. Chromosome changes were detected in nine cases (64%), and tumor stage and grade tended to parallel the degree of genomic imbalances. Gain of the entire long arm of chromosome 1 was observed in six cases (43%), three of which displayed only this chromosome change. Other common sites of copy number increases included 8q21-->qter (4 cases), 10p15 (4 cases), 10q11-->q24 (3 cases), and 13q21-->qter (3 cases, each with stage III disease). Two of the tumors with gains of chromosome 10 involved the whole chromosome, and this was the sole abnormality in one case. DNA amplification at 5p14-->p15 was identified in one specimen, a stage III tumor having numerous imbalances. DNA microsatellite analysis revealed multiple replication errors (RER), indicative of the RER+ phenotype, in four of 13 (31%) cases evaluated. The RER+ phenotype was observed in four of six stage la tumors but in none of seven stage Ib or stage III tumors. Multiple genomic imbalances detected by CGH were not observed in RER+ tumors but were detected in five of nine tumors without the RER+ phenotype. These investigations demonstrate the feasibility of CGH for the retrospective assessment of chromosomal changes in endometrial carcinoma specimens. Moreover, these data suggest that the etiologies in tumors with and without the RER+ phenotype may differ.

Aged↗

PubMed1997

Combined chromosome microdissection and comparative genomic hybridization detect multiple sites of amplification DNA in a human lung carcinoma cell line.

Chromosome microdissection-fluorescence in situ hybridization and comparative genomic hybridization (CGH) were performed in parallel to identify the native location of amplified DNA in a human non-small cell lung cancer (NSCLC) cell line exhibiting a homogeneously staining region (hsr) and double minutes (dmin). The native locations of microdissected DNA from the hsr and dmin were 7p12-13 and 8q24, respectively. Southern analysis revealed coamplification of EGFR (7p12) and MYC (8q24). CGH detected amplification of DNA not only from 7p12-13 and 8q24, but also from 9p24 and 10q22.

Blotting, Southern↗

PubMed1997

Effects of amino acids and alpha-amanitin on bovine embryo development in a simple protein-free medium.

Five experiments, utilizing 3741 embryos produced in vitro, were designed to test the effects of Eagle's nonessential amino acids, and combinations of Eagle's essential amino acids and the RNA polymerase inhibitor alpha-amanitin on the development of preimplantation bovine embryos in a modified protein-free KSOM medium. Embryos were cultured in 5% O2:5% CO2:90% N2 at 39 degrees C for the first 40-44 hr in modified KSOM, and embryos with > or = 4 cells were cultured in modified KSOM-PVA with different amino acids in experiments 1-4, and with the addition of alpha-amanitin in experiment 5. In experiment 1, addition of 0.5x of the essential amino acids, with different concentrations of nonessential amino acids significantly increased hatching of blastocysts and decreased blastocyst degeneration, but increasing the nonessential amino acids from 1x to 5x, did not stimulate embryo development. In experiments 2-4, increasing only the glycine concentration, or adding each of the 12 essential amino acids singly or several in combination to the medium containing nonessential amino acids, did not significantly improve embryo development. Taurine (0.4 mM) in the modified KSOM medium reduced blastocyst degeneration. In experiment 5, alpha-amanitin (20 microM) completely inhibited further embryo development when it was added at several stages from 4-cell embryos to morulae. The study with protein-free KSOM plus amino acids provided a completely defined simple medium for culturing bovine embryos, with evidence that continuous mRNA activity and presumed protein synthesis was obligatory to meet the complex and continuous requirements for proteins by the developing blastocyst.

Amanitins↗

PubMed1997

Mechanisms of acantholysis in pemphigus foliaceus.

Pemphigus foliaceus (PF) is a dermatosis characterized by subcorneal vesicles and pathogenic IgG autoantibodies against desmoglein 1. PF IgG passively transferred into neonatal mice induces a blistering disease that duplicates the key findings of PF. In this study we have used this animal model to investigate the role of complement and IgG valence in triggering blister formation. In the passive transfer experiments, we found that PF IgG, as well as the F(ab')2 and Fab fragments, was capable of inducing the typical subcorneal blistering disease in both complement-deficient and complement-sufficient mice. Moreover, the disease activity in these mice correlated well with the dose of IgG or its proteolytic fragments injected in the animals. We conclude that neither complement activation nor IgG-mediated cell surface antigen crosslinking is required for the induction of acantholysis in the experimental PF model.

Acantholysis↗

PubMed1997

Mechanisms of acantholysis in pemphigus vulgaris: role of IgG valence.

Pemphigus vulgaris (PV) is a dermatosis mediated by autoantibodies against desmoglein 3 (Dsg3). It was known that intraperitoneal (i.p.) injections of PV IgG and PV F(ab')2, but not of PV Fab, into neonatal mice reproduced the key features of the disease in these animals. It was proposed that crosslinking of antigen by bivalent PV autoantibodies may trigger acantholysis in PV. In the present study, we have used subcutaneous (s.c.) injections of PV IgG and its proteolytic fragments into neonatal mice to test equimolar amounts of these autoantibody fractions. Mice developed clinical and histological features of PV in a dose-dependent manner following a similar time course. PV IgG and Fab fractions induced acantholysis as early as 2 hr after the injection. It was also demonstrated that sc injections of PV Fab were more effective in inducing disease than ip injections. PV autoantibodies may bind an "adhesive site" of Dsg3 and impair its function, thus triggering acantholysis.

Acantholysis↗

PubMed1997

Retrieval of overtrained place navigation during occlusion of one eye and ipsi- or contralateral blockade of relevant brain centers in rats.

Place navigation engrams acquired with intact brain can be retrieved with either eye and are stored in both hemispheres. The retrieval circuitry was examined by testing an overtrained rat under lidocaine inactivation of the hippocampus, visual cortex, and superior colliculus. Thirty-three hooded rats with implanted cannulae aimed at the above structures were trained to find a target in the southwest quadrant of the pool. Retrieval was tested during occlusion of one eye alone or combined with ipsi- or contralateral blockade (1 microliter 4% lidocaine) of hippocampus, hippocampus and visual cortex, or hippocampus, visual cortex, and superior colliculus. The intact brain escape latencies (9.8 s) were only slightly prolonged by occlusion of one eye (to 12.6 s). Blockade of centers ipsi- or contralateral to the occluded eye increased escape latencies to 12.7 or 15.2 s for hippocampus, to 16.8 or 16.9 s for hippocampus and visual cortex, and to 23.6 or 17.4 s for hippocampus, visual cortex, and superior colliculus, respectively. Significant asymmetry appearing in the last case indicates that the superior colliculus plays an important role in mediation of the crossed visual input supporting place navigation. Residual goal-finding capability in rats with blockade of centers ipsilateral to the occluded eye is probably due to uncrossed visual projections to the intact hemisphere.

Animals↗

PubMed1997

Studies on buffalo babesiosis in Hubei Province, China.

The present paper summarises our recent studies on buffalo babesiosis in the Hubei province of China. It describes the pathogen and the epidemiology of the disease, the tick vector and its biology, control, immunological diagnosis, methods of in vitro cultivation of the pathogen and their practical applications. The identify of the pathogen is discussed in detail.

Animals↗

PubMed1997

Studies on the in vitro cultivation of Babesia from buffaloes.

This paper summarizes a recent study on the in vitro cultivation of Babesia from buffaloes. Buffalo Babesia parasites were cultured many times by the microaerophilous stationary phase (MASP) method of Levy and Ristic (1980) with some modifications. The culture-derived Babesia organisms were similar to forms seen in the blood of infected buffaloes and the pathogenicity of these organisms was unchanged. Factors influencing the in vitro cultivation are discussed in detail.

Animals↗

PubMed1997

Studies on the pathogenicity of Babesia bovis in water buffaloes after cryopreservation and resuscitation.

Packed erythrocytes infected with Babesia bovis were mixed with an equal volume of 16% dimethyl sulphoxide (DMSO) in Alsever's solution and dispensed into 1.5 or 5 ml cryotubes. The vials were kept in liquid nitrogen (-196 degrees C) for 26, 78, 142 or 149 days. The samples were removed from the liquid nitrogen container and rapidly thawed in a 40 degrees C water bath. The thawed blood successfully infected splenectomised buffalo calves by injection via subcutaneous or intravenous or via intravenous and subcutaneous routes. The parasites, typical B. bovis, were discovered in red blood cells 5, 8 or 9 days after inoculation. The highest percentage of parasitised erythrocytes (PPE) was 15%. The babesiosis resulting from cryopreserved parasites was the same as that resulting from fresh parasites inoculated by ticks. Typical clinical signs were found, such as continuous fever (the highest temperature was 41.3 degrees C), anaemia, icterus and haemoglobinuria. Infected calves, which were not treated, died. Cryopreservation is a simple and reliable method for longterm preservation of B. bovis of water buffaloes.

Animals↗

PubMed1997

The cure of acute Babesiasis perroncitoi in swine.

From June to August in 1988, a total of 64 pure-bred Landrace, Yorkshire (large white) and Inner Mongolian Black Swine from a farm in Huhehot were affected with a disease, 13 died. The pathogen was confirmed primarily to be Babesia perroncitoi. The drugs used for treatment were Berenil and Acaprin. The intramuscular dose for Berenil was 3 mg per kilogram weight. The subcutaneous dose for Acaprin was 0.8 mg per kilogram weight. All of which had satisfactory results. In the same season in the second year and the third year, the disease was also reported, but all sick animals were cured.

Animals↗

PubMed1997

The effect of levobunolol hydrochloride on the calcium and potassium channels in isolated ventricular myocytes of guinea pig.

The effects of levobunolol hydrochlorid (Bun) on the type L calcium channel currents (ICA) and delayed rectifier potassium channel currents (IK) in isolated ventricular myocytes of guinea pig were studied by using patch clamp whole cell recording techniques. The results were showed that: 1) Bun caused a dose dependent decrease in ICA and a dose-dependent increase in IK of the ventricular myocytes. The threshold concentrations of Bun for ICA and IK were 10(-8) mol/L and 10(-7) mol/L respectively. The maximum effective concentration of Bun for bot ICA and IK was 3x10(-5) mol/L, and half-maximal concentration was 3x10(-6) mol/L; 2) IK was blocked by 2x100(-6) mol/L tetraethylammonium (TEA). A concentration of 3x10(-6) mol/L Bun showed a decreasing effect on the ICA as revealed by the current-voltage relationship curve, i.e., Bun caused an elevation of the curve;3) When ICA was blocked by 2x10(-6) mol/L Isoptin (Verapamil), at a concentration of 3x10(-6) mol/L Bun showed an increasing effect on IK and the effect could be blocked by TEA. The above-mentioned results indicated that Bun had an inhibitory effect on ICA and a fascilitatory effect on IK. The results suggested that the molecular mechanisms of antihypertensive, heart rate slowing the beta -receptor blocking effects of Bun might be due to decrease of ICA and increase of IK.

Adrenergic beta-Antagonists↗

PubMed1997

Effects of propranolol on beta-adrenergic receptor of experimental acute myocardial infarction in rats.

By using receptor autoradiography to observe the distribution and density of receptors, the effects of propranolol, a beta-blocker, on beta-adrenergic receptor of experimental acute myocardial infarction (AMI) were studied. One week after ligation of proximate left anterior descend (LAD) coronary artery, [3H] DHA binding sites were markedly decreased in both infarct region and non-infarct region. After treatment of propranolol (100 micrograms/kg), the [3H] DHA binding sites were obviously increased in the infarct region, and they were further decreased in the non-infarct region. The ratio of [3H] DHA binding sites of the infarct region to non-infarct region was from 0.24 at LAD ligation to 0.87 after propranolol treatment, which was close to 0.97 of control group (sham operation). The results indicated that the propranolol acted directly on myocardial beta- adrenergic through the receptor regulation of the balance of beta-receptors between the infarct region and non-infarct region, and improvement of the myocardial consonation and contraction synergism, thereby protecting the heart affected by AMI.

Adrenergic beta-Antagonists↗

PubMed1997

Effect of amlodipine on the growth of vascular smooth muscle cells of spontaneously hypertensive rats.

The effect of anti-hypertensive drug amlodipine on regression of cardiovascular hypertrophy due to hypertension was studied by using cultured smooth muscle cells derived from arteries of spontaneously hypertensive rats (SHR) and measuring [3H]-TdR and [3H]-Leucine binding. 48 h after adding amlodipine, [3H]-TdR binding in arterial smooth muscle cells from SHR in vitro was reduced by 50.5% and [3H]-Leucine binding was reduced by 56.2% as compared with neuropeptide Y (NPY)-treated group. However, there was no significant change in cell number. The results showed that amlodipine could effectively inhibit increase of DNA and protein synthesis of vascular smooth muscle cell (VSMC) due to NPY. It indicates that amlodipine is of great significance on regression of genesis and development of cardiovascular hypertrophy due to hypertension.

Amlodipine↗

PubMed1997

Clinical study of epidural analgesia with clonidine and sumatriptan in posthysterectomy.

A clinical study was conducted to compare the analgesic effect of clonidine with those of sumatriptan and their mixture and their effects on hemodynamics. 40 patients undergoing elective total hysterectomy were randomly divided into 4 groups in terms of the epidurally administered drugs with 10 patients in each group (group C1: clonidine 150 micrograms, group C2: clonidine 75 micrograms, group S: sumatriptan 6 mg and group S + C: clonidine 75 micrograms + sumatriptan 3 mg). MAP, HR, SpO2, VT VAS, VRS and ePDT were measured in the initial 4 h. The demographic data and the doses of intraoperative local anesthetics among the 4 groups were not statistically different. It was found that no significant difference in the pre- and postadministration values of HR, SpO2 and VT. A obvious reduction of MAP appeared in the groups of C1 and C2, but in the other groups the hemodynamical parameters were stable. The groups of C1, C2 and S + C showed significant increase in VAS and VRS, along with increase of ePDT when compared with the pre-drug level. There was no obvious alteration in group S after the drug administration. It was concluded that (1) single use of sumatriptan is ineffective in the dose given in this study; (2) small dose (150 micrograms and 75 micrograms) of clonidine has epidurally analgesic effects; (3) combined use of sumatriptan and clonidine is an acceptable way in epidural analgesia, in terms of its analgesic effect and hemodynamic changes.

Adult↗

PubMed1997

Characterization of hydroxyapatite film with mixed interface by Ar+ ion beam enhanced deposition.

Ar+ ion beam enhanced deposition (IBED) was used to produce a hydroxyapatite (HA) film on polished titanium substrates. In this study, the HA ceramic target was sputtered by an argon-ion beam with an energy of 1.5 KeV, and the sputtered film was intermittently bombarded by energetic argon-ions at 60 KeV. An effective Ca-Ti mixed layer produced by the energetic argon-ion bombardment was confirmed by using Auger electron spectroscopy. The characteristics of the deposited films were evaluated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses. XRD analysis revealed that the as-deposited film was amorphous, and a hydroxyapatite-type structure was obtained from the post-heat treatment of the deposited films. SEM observations showed that no distinct difference in surface morphology was found between the as-deposited and heat-treated samples for Ar+ IBED films, suggesting a strongly bonded HA film on the titanium substrate. In comparison with the HA target, some chemistry alterations were brought about in the deposited films, such as the incorporation of CO3, the loss of the OH groups and some distortion of the phosphate lattice.

Argon↗

PubMed1997

Elevated cerebrospinal fluid level of substance P and decreased undecapeptidase activity at term pregnancy.

This paper reports a study of substance P and its converting enzyme substance P endopeptidase (SPE) in cerebrospinal fluid (CSF) collected from women at term pregnancy. A method was developed to assess the CSF levels of substance P itself with minimum contribution from prestages or fragments of the undecapetide. The measured activity was compared with that detected in CSF from control, non-pregnant, non-puerperal women. The result indicates a significant increase in substance P-like immunoreactivity at term pregnancy (19.9 +/- 3.9 fmol/ml, n = 10) compared with that of control subjects (12.3 +/- 2.8 fmol/ml, n = 9; P < 0.001). This elevation was suggested to reflect an increased activity in spinal sensory neurons at this stage of pregnancy. The activity of SPE was assessed by measuring the product substance P1-7 by a radioimmunoassay specific for this fragment. It was found that the enzyme activity was significantly decreased in CSF from pregnant women (11.2 +/- 0.71 pmol/h.ml), compared with control samples (18.4 +/- 0.73 pmol/h.ml; P < 0.05). Moreover, a significant negative correlation was found to exist between the level of substance P and the activity of SPE (P < 0.05, r2 = 0.65), suggesting that the enzyme may be involved in a mechanism regulating the level of substance P concentration.

Case-Control Studies↗