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Biomedical subjects

C Xu

Publications and source records attributed to C Xu.

At least 271 records · Page 15Linked to original sources
PubMed1996

[Kindling of rat epilepsy by intracerebroventricular injection of norfloxacin and ultrastructural changes of brain].

AIM: To study the toxic effects of norfloxacin (Nor) on EEG and ultrastructure of the brain. METHODS: EEG was recorded in the sensorimotor area of rat cortex after Nor 150 and 300 micrograms.kg-1 were injected into the right ventricle of the brain. RESULTS: Spike waves occurred, first at the ipsilateral side and then bilaterally. The seizure spike appeared at 168 +/- 129, 51 +/- 35 s, and 276 +/- 138, 118 +/- 65 s in the right and left cerebral cortices in 150 and 300 micrograms.kg-1 groups, respectively. The wave forms were variable, the wave amplitude and frequency increased gradually, accompanied with limb twitching. Neuron degeneration was seen in both cerebral hemispheres, hippocampus, and cerebellum 120 min after the i.c.v. of Nor 300 micrograms.kg-1: myeloid degeneration of Golgi complex, rough endoplasmic reticulum, and neuropils; swelling of cytoplasm; dissolution of nuclears and chromatin; necrosis of gliocytes and the appearance of changes in both the light and dark neurons, especially the dark ones. CONCLUSION: Rat brain was widely damaged after the kindling by Nor.

Animals↗
PubMed1995

The human papilloma virus 16E6 gene sensitizes human mammary epithelial cells to apoptosis induced by DNA damage.

Programmed cell death (apoptosis) is a normal physiological process, which could in principle be manipulated to play an important role in cancer therapy. The key importance of p53 expression in the apoptotic response to DNA-damaging agents has been stressed because mutant or deleted p53 is so common in most kinds of cancer. An important strategy, therefore, is to find ways to induce apoptosis in the absence of wild-type p53. In this paper, we compare apoptosis in normal human mammary epithelial cells, in cells immortalized with human papilloma virus (HPV), and in mammary carcinoma cell lines expressing wild-type p53, mutant p53, or no p53 protein. Apoptosis was induced with mitomycin C (MMC), a DNA cross-linking and damaging agent, or with staurosporine (SSP), a protein kinase inhibitor. The normal and HPV-transfected cells responded more strongly to SSP than did the tumor cells. After exposure to MMC, cells expressing wild-type p53 underwent extensive apoptosis, whereas cells carrying mutated p53 responded weakly. Primary breast cancer cell lines null for p53 protein were resistant to MMC. In contrast, two HPV immortalized cell lines in which p53 protein was destroyed by E6-modulated ubiquitinylation were highly sensitive to apoptosis induced by MMC. Neither p53 mRNA nor protein was induced in the HPV immortalized cells after MMC treatment, although p53 protein was elevated by MMC in cells with wild-type p53. Importantly, MMC induced p21 mRNA but not p21 protein expression in the HPV immortalized cells. Thus, HPV 16E6 can sensitize mammary epithelial cells to MMC-induced apoptosis via a p53- and p21-independent pathway. We propose that the HPV 16E6 protein modulates ubiquitin-mediated degradation not only of p53 but also of p21 and perhaps other proteins involved in apoptosis.

Alkaloids↗
PubMed1995

On the distribution of amino acid residues in transmembrane alpha-helix bundles.

The periodic distribution of residues in the sequence of 469 putative transmembrane alpha-helices from eukaryotic plasma membrane polytopic proteins has been analyzed with correlation matrices. The method does not involve any a priori assumption about the secondary structure of the segments or about the physicochemical properties of individual amino acid residues. Maximal correlation is observed at 3.6 residues per period, characteristic of alpha-helices. A scale extracted from the data describes the propensity of the various residues to lie on the same or on opposite helix faces. The most polar face of transmembrane helices, presumably that buried in the protein core, shows a strong enrichment in aromatic residues, while residues likely to face the fatty acyl chains of lipids are largely aliphatic.

Amino Acids↗
PubMed1995

Alternative methods of preparing whole-cell DNA from fungi for dot-blot, restriction analysis, and colony filter hybridization.

There is a large and increasing number of methods for preparing whole-cell DNA from fungi. Modifications have evolved for two reasons. This first is to simplify the protocol as much as possible to allow processing of large sample numbers, in some cases for very specific uses, e.g., dot-blots. The second is to increase the quality of the DNA. Most preparations are contaminated with varying amounts of polysaccharides and unknown wall contaminants that can inhibit subsequent restriction or ligation. The extent of contamination varies with the species, the individual isolate, and at least in Neurospora, with the method or extent of growth. This paper offers three new methods. The first is a simplified procedure for isolating denatured DNAs from filamentous fungi for dot-blot analysis. The second is a rapid method for isolating DNAs from large numbers of small- to medium-scale cultures of filamentous fungi. These preparations are sufficiently pure for a variety of enzymatic reactions. The third is a nonenzymatic method for yeast colony filter hybridization that is simple, inexpensive, and efficient and results in uniform signals for a variety of species.

Aspergillus↗
PubMed1995

Translocation of dopamine and binding of 2 beta-carbomethoxy-3 beta-(4-fluorophenyl) tropane (WIN 35,428) measured under identical conditions in rat striatal synaptosomal preparations. Inhibition by various blockers.

Translocation of [3H]dopamine and binding of 2 beta-carbomethoxy-3 beta-(4-fluorophenyl)[3H]-tropane ([3H]WIN 35,428) were measured in crude synaptosomal preparations from rat striatum under identical conditions of assay buffer (phosphate-Krebs) and temperature (25 degrees). [3H]Dopamine uptake as a function of time was close to linear for at least 8 min, whereas [3H]WIN 35,428 binding had reached equilibrium within 1 min and remained at its plateau value for at least 20 min. The following inhibitors were tested in uptake and binding assays run in parallel with the same synaptosomal preparation: cocaine, WIN 35,428, benztropine, nomifensine, mazindol, methylphenidate, N-[1-(2-benzo[b]-thiophenyl)cyclohexyl]piperidine (BTCP), Lu 19-005 (Indatraline), 1-(2-(di(4-fluorophenyl)-methoxy)-ethyl)-4-(3-phenyl-2-propyl)piperazine (GBR 12909), 1-(2-(diphenylmethoxy)-ethyl)-4-(3-phenyl-2-propyl)piperazine (GBR 12935) and 7-trifluoromethyl-4-(4-methyl-1-piperazinyl)-pyrrolo [1,2-a]quinoxaline (CGS 12066B). When present together with [3H]dopamine or [3H]WIN 35,428 for 8 min, the observed binding IC50 values were generally higher (average 1.4-fold) than the uptake IC50 values, with a significant y-axis intercept in linear regression analysis of binding on uptake IC50. For slowly equilibrating inhibitors, estimates of uptake IC50 values were overestimates, and relatively lower values were obtained by monitoring [3H]dopamine uptake for 1 min only during the last minute of the 8-min presence of inhibitor; under these conditions, binding over uptake IC50 ratios were on the average 2.3. Kinetic calculations, taking into account both radioligand and inhibitor equilibration kinetics, indicated that the latter comparison between binding and uptake measurements was most relevant, and suggested the involvement of complexities beyond simple competitive inhibition of dopamine transport, such as different binding domains for substrate and blocker recognition, or spare receptors for blockers. The present data indicate that binding over uptake IC50 ratios should be interpreted with caution, depending on the experimental conditions used to measure these ratios.

Animals↗
PubMed1995

The improved Allium/Vicia root tip micronucleus assay for clastogenicity of environmental pollutants.

The meristematic mitotic cells of plant roots are appropriate and efficient cytogenetic materials for the detection of clastogenicity of environmental pollutants, especially for in situ monitoring of water contaminants. Among several cytological endpoints in these fast dividing cells, such as chromosome/chromatid aberrations, sister-chromatid exchanges and micronuclei, the most effective and simplest indicator of cytological damage is micronucleus formation. Although the Allium cepa and Vicia faba root meristem micronucleus assays (Allium/Vicia root MCN) have been used in clastogenicity studies about 12 times by various authors in the last 25 years, there is no report on the comparison of the efficiency of these two plant systems and in different cell populations (meristem and F1) of the root tip as well as under adequate recovery duration. In order to maximize the efficiency of these bioassays, the current study was designed to compare the Allium and the Vicia root MCN assays on the basis of chromosome length, peak sensitivity of the mitotic cells, and the regions of the root tip where the MCN are formed. The total length of the 2n complement of Allium chromosomes is 14.4 microns and the total length of the 2n complement of Vicia is 9.32 microns. The peak sensitivity determined by serial fixation at 12-h intervals after 100 R of X-irradiation is 44 h. The slope of the X-ray dose-response curve of Allium roots derived from the meristematic regions was lower than that derived from cells in the F1 region. Higher efficiency was also demonstrated when the MCN frequencies were scored from the F1 cells in both Allium and Vicia treated with formaldehyde (FA), mitomycin C (MMC), and maleic hydrazide (MH). The results indicated that scoring of MCN frequencies from the F1 cell region of the root tip was more efficient than scoring from the meristematic region. The X-ray linear regression dose-response curves were established in both Allium and Vicia cell systems and the coefficients of correlations, slope values were used to verify the reliability and efficiency of these two plant cell systems. Based on the dose-response slope value of 0.894 for Allium and 0.643 for Vicia, the Allium root MCN was a more efficient test system. The greater sensitivity of the Allium roots is probably due to the greater total length of the diploid complement and the higher number of metacentric chromosomes.(ABSTRACT TRUNCATED AT 400 WORDS)

Allium↗
PubMed1995

Effect of monoisoamyl meso-2,3-dimercaptosuccinate on the pathology of acute cadmium intoxication.

The ability of monoisoamyl meso-2,3-dimercaptosuccinate (Mi-ADMS) to offset the characteristic organ pathology of intraperitoneally administered cadmium chloride (CdCl2) and that of the cadmium-cysteine complex has been examined in male Wistar rats. The tissues examined for damage were the testes, kidney, liver, pancreas, and bone marrow. At a high dose of CdCl2 (0.03 mmol/kg, ip) testicular damage was completely prevented by Mi-ADMS (0.50 mmol/kg, ip) given immediately. A decrease in the protective ability of the antagonist was observed following delayed administration of Mi-ADMS given at 1, 2, 4, and 24 h post CdCl2. At a lower dose of CdCl2 (0.006 mmol/kg, ip), Mi-ADMS furnished essentially full protection from testicular damage when given (0.50 mmol/kg, sc) at 0 and 1 h after CdCl2. The administration of cadmium-cysteine complex (0.01 mmol/kg, ip) induced notable renal tubular damage, which was antagonized by the administration of Mi-ADMS (0.50 mmol/kg, ip) as late as 4 h after the complex. At a 24-h delay, extensive tubular necrosis was found on sacrifice after 4 d. The administration of cadmium-cysteine complex ip reduced, but did not eliminate, the characteristic damage of the seminiferous tubules found for cadmium alone. There is a progressive reduction of testicular weight as the interval between cadmium and antagonist administration increases. The average kidney weights of the animals given CdCl2-cysteine complex were increased in comparison to normal controls. The antagonistic effects of Mi-ADMS treatment on cadmium intoxication in the kidneys and the testes of rats is very similar to that found for effective dithiocarbamate antagonists. In order to obtain complete protection of the testes from the deteterious effects of cadmium, such antagonists must be administered no later than about 1 h after the cadmium.

Acute Disease↗
PubMed1995

[Analyses of the prevalences for neural tube defects and cleft lip and palate in China from 1988 to 1991].

This paper reports the monitoring results of two main categories of birth defects-neural tube defects (NTD) and cleft of lip and palate (CLP) in China during the period of continuous monitoring (1988-1991). The method of hospital-based monitoring was adopted for data collection. From Jan. 1988 to Dec. 1991, a total of 2,750,588 births were monitored, and 28,168 cases of congenital malformations were identified. The prevalence of total birth defects was 102.4 per 10,000. 6885 cases of NTD were identified during this period, the prevalence of NTD being 25.0 per 10,000. The prevalence of NTD varied geographically; it declined gradually from the north to the south of China with the highest rate of NTD in the Taihang Mountain Regions. A total of 4548 cases of CLP were identified, and the provincial prevalence of CLP varied from 11.2 to 25.7 per 10000 with a mean of 16.5 per 10000. The prevalence of NTDs varied seasonally with the peak in winter (January). The sex ratio of NTD was 0.59, the prevalences in female births (32.1 per 10,000) being higher than that in male births (17.4 per 10,000) (P < 0.01). The sex ratio of CLP was 1.33. A significant difference was noted between the sex ratio of cleft palate (0.80) and that of the total cleft lip (1.46) (P < 0.01). The prevalence of NTD in rural areas (44.3 per 10,000) was 3 times as high as that in urban areas (14.4 per 10,000), but no difference in occurrence of CLP was observed between the urban and rural areas (P > 0.05).

China↗
PubMed1995

[Variant gap phenomenon in A-V conduction].

In 361 consecutive patients 4 with variant gap phenomenon (VGP) underwent intracardiac electrophysiological studies. The premature atrial response initially delayed in His-Purkinje system (HPS) which had a long relative refractory period (RRP), and H-V interval was prolonged. However, as atrial responses were more premature, the atrioventricular node (AVN) showed RRP and slowed down the conduction, that made HPS get rid of RRP before the response arriving. Thus the conduction resumed, and H-V interval became normal. It was different from the classic gap phenomenon. We call it variant gap phenomenon.

Adult↗
PubMed1995

[14C-urea breath test in the diagnosis of Helicobacter pylori infection in the stomach].

We developed a modified 14C-urea breath test (14C-UBT) to diagnose Helicobacter pylori (Hp) infection in 70 patients in which subjects were given 92.5 kBq (2.5 microCi) 14C-urea with 25 mg nonradioactive urea, without nutrient-dense meal. Using the mean value +3s as a cutoff value, the 20 min sample gave a sensitivity of 97.36%, a specificity of 90.00%, a positive predictive value of 97.36%, and a negative predictive value of 90.0%. Our data showed: (1) A satisfying accuracy of the modified 14C-UBT for the detection of Hp infection was obtained. (2) Taking 92.5 kBq (2.5 microCi) 14C-urea and 20 min collected sample may be of great use and to replace the previous big dose and long time methods. (3) This test may be applied routinely as a noninvasive, accurate, low cost, safe and rapid method. (4) It played an important role in reflecting the susceptibility of Hp to various drugs in vivo and monitoring the recurence of Hp.

Adult↗
PubMed1995

[A clinical study on limitation of infarct size by ischemic preconditioning in 100 cases of acute myocardial infarction].

The protective effect of ischemic preconditioning has been confirmed in animal models. In this study we analyzed the clinical data of 110 cases of acute myocardial infarction (77 male, 33 female). Sixty-nine cases (group A) had ischemic manifestations prior to myocardial infarction, while forty one (group B) did not have. Our data showed that the clinical features in group B were quite different as compared with those in group A: (1) larger infarct size (ratio between necrotic size and ischemic size: 71.55 +/- 3.70 to 41.65 +/- 3.96, P < 0.0001); (2) higher peak level of serum cardiac enzymes (CPK: 2085.78 +/- 265.57 to 1329.80 +/- 189.44, P < 0.01; CK-MB: 102.73 +/- 12.47 to 47.38 +/- 8.83, P < 0.01); (3) poorer cardiac function [LVEF < 0.45: 12/41 (29.3%) to 6/69 (8.7%), P < 0.05]; (4) higher incidence of left ventricular aneurysm [9/41 (22.0%) to 3/69 (4.3%), P < 0.05] and (5) higher mortality rate in 4 weeks [6/41 (14.6%) to 2/69 (2.9%), P < 0.05]. The difference between the two groups is statistically significant. In addition, the effect of the duration of preconditioning on protection of myocardium, the potential mechanism of preconditioning and its clinical significance were discussed.

Aged↗
PubMed1995

Cholecystokinin octapeptide reverses mu-opioid-receptor-mediated inhibition of calcium current in rat dorsal root ganglion neurons.

Cholecystokinin octapeptide (CCK-8) is reported to antagonize the analgesic effect produced by mu- and kappa- but not delta-opioid agonist in spinal cord. However, the mechanisms of interaction remain obscure. In the present study, whole-cell patch-clamp recording was performed on acutely isolated rat dorsal root ganglion (DRG) neurons to evaluate the effects of the highly specific mu-opioid agonist ohmefentanyl and the delta-opioid agonist DPDPE on voltage-gated calcium channels and the possible interaction between CCK-8 receptor and mu- or delta-opioid receptor. The results indicated that ohmefentanyl, but not DPDPE, can suppress the voltage-gated calcium currents elicited in DRG neurons, an effect readily reversed by naloxone or by the antiopioid peptide CCK-8. The effect of CCK-8 can in turn be abolished by the CCK-B receptor antagonist L365,260. CCK-8 used by itself has no enhancing effect, but rather a depressant effect, on calcium currents. However, used simultaneously with ohmefentanyl, CCK-8 shows a clear-cut reversal of depression of the mu-opioid. We conclude that the depressant effect produced by mu-opioid on voltage-gated calcium current in DRG neurons can be antagonized by CCK-8 through CCK-B receptor located in the same neuron. The delta-opioid DPDPE has no direct effect on the voltage-gated calcium current in DRG neurons.

Animals↗
PubMed1995

[Value of dobutamine technetium-99m-MIBI SPECT in detecting coronary artery disease].

The value of dobutamine 99mTc-MIBI SPECT (Dobu-ECT) for detecting coronary artery disease (CAD) was assessed in 39 patients. Compared with coronary angiography, the overall sensitivity and specificity of Dobu-ECT for detecting CAD were 92.9% and 90.9%. Of 13 patients with CAD without myocardial infarction, the sensitivity of Dobu-ECT was 84.6%. In detecting CAD with single, double or triple vessel diseases, the sensitivity of Dobu-ECT was 90.9%, 87.5% and 100% respectively. Furthermore, 88.2% of the patients (15/17) with multivessel (two or three vessels) diseases were correctly identified as having multivessel involvement. For detecting CAD, the sensitivity and specificity of dobutamine ECG were 53.5% and 82%. No serious side effects were observed in the study. The results showed that Dobu-ECT is a feasibie, safe and noninvasive method for diagnosing CAD.

Adult↗
PubMed1995

[The role of substance P in immunosuppression induced by Tripterygium wilfordii].

The effects of T II (extracted from Tripterygium wilfordii) and substance P (SP) on imunoregulation were investigated. It has been shown that Tripterygium wilfordii is an immunosuppresive. In order to assess the immunosuppression elicited by T II was mediated by SP in spinal dorsal horn, Wistar rats were injected intrathecally with capsaicin (CAP) to deplete SP in spinal dorsal horn prior to T II given orally. The level of interleukin 2 (IL-2) produced by splenic lymphocytes of rats and the contents of SP in some brain areas and spinal cord in mice were assayed after T II treatment. Our findings were as follows: 1. The level of IL-2 was decreased significantly after T II treatment only. However the level of IL-2 was increased markedly after CAP was given intrathecally. Moreover, CAP administration also enhanced the level of IL-2 even in immunosuppression group induced by T II treatment. 2. SP contents in spinal cord, hypothalamus and brain stem of mice were increased dramatically during immunosuppression produced by T II. The results suggested that SP in spinal dorsal horn was involved in regulation of cellular immunity, the suppressive effect of T II on cellular immunity might be mediated by SP in spinal dorsal horn.

Animals↗
PubMed1995

[Shape memory angioembolus for varicocele].

Seven target veins (in 5 dogs) were embolized with nitinol conical rugby embolus (NT-CRE). The pathological examination showed firm impact between NT-CRE and intravenous membrane without misembolization from retrograde flow. Compact collagenous fibrous tissue was seen in and out NT-CRE on spaces. On the basis of animal experiment, 10 patients with varicocele were treated with NT-CRE. After the operation, the varicocele and symptoms disappeared and venae spermatica collapsed. The follow-up for 1.5-2.3 years showed no recurrence in the 10 patients. We consider that the therapeutic method is simple and effective for varicocele.

Adolescent↗
PubMed1995

[Chemical constituents of Cyclocarya paliurus (Batal.) Iljinsk].

Four compounds were isolated from the leaves of Cyclocarya paliurus. They were identified as daucosstero, beta-L-arabopyranose, steraric acid and palmitic acid on the basis of spectral data and chemical properties. All of them were isolated from this plant for the first time.

Drugs, Chinese Herbal↗