Biomedical subjects

X Zheng

Publications and source records attributed to X Zheng.

At least 289 records · Page 16Linked to original sources

PubMed1994

Injecting drug use and HIV infection in southwest China.

OBJECTIVES: To determine the prevalence of drug injection among drug users, the seroprevalence of HIV and risk factors for HIV infection among injecting drug users (IDU), and to determine heterosexual transmission of HIV among IDU and their spouses in southwest China. METHODS: Using a cross-sectional design, we conducted an HIV seroprevalence and behavioral survey in three rural counties of Yunnan province, Ruili, Longchuan and Luxi in southwest China, bordering Myanmar (Burma). A total of 860 drug users were recruited in randomly selected communities at the three study sites (response rate, 97%). In addition, a random sample of 62 wives of HIV-infected IDU were assembled from 460 known HIV-positive IDU in Ruili and Longchuan (response rate, 81%). RESULTS: In the sample of 860 drug users, 33% reported injecting drugs. Among the 282 subjects who injected drugs, 82% began intravenous drug use after 1988; 64% injected drugs at least once every day. All subjects shared needles but none cleaned the injection equipment with alcohol or bleach. Overall, 49% tested HIV-positive. HIV seropositivity was independently correlated with a longer history of drug injecting, daily injecting, frequent needle-sharing, being younger, and living in Ruili county. Among the 62 wives of HIV-positive IDU, none used condoms during sex and 10% tested HIV-positive. CONCLUSIONS: We conclude that the introduction of HIV into drug-using communities and the rapid increase in heroin injecting in this population appear to have triggered an explosive HIV epidemic among IDU in southwest China. We recommend that AIDS prevention efforts should begin immediately and focus on discouraging the shift from opium smoking to heroin injecting, needle-sharing, and unprotected sex among drug users and their partners.

Adult↗

PubMed1994

Ureaplasma urealyticum biovar specificity and diversity are encoded in multiple-banded antigen gene.

Ureaplasma urealyticum is a commensal organism of the lower genital tract of females, but in a subpopulation of individuals, it can invade the upper genital tract. It is a significant cause of chorioamnionitis and neonatal morbidity and mortality. There are 14 recognized serovars of U. urealyticum; these can be divided into two distinct clusters or biovars. Biovar 1 is composed of serovars 1, 3, 6, and 14, Biovar 2 is composed of serovars 2, 4, 5, 7, 8, 9, 10, 11, 12, and 13. We previously identified a surface antigen, the multiple-banded (MB) antigen, which contains both serovar-specific and cross-reactive epitopes. Genotypic characterization of the C-terminal region of the MB antigen of serovar 3 indicates that serovar specificity and MB antigen size variation reside in that domain. In the present study, we used PCR analysis with primers derived from the serovar 3 MB antigen gene DNA sequence to determine if the MB antigen gene was present in the remaining 13 reference serovars as well as in invasive clinical isolates. The results indicated that not only was the MB antigen gene present in all serovars but that the genes' 5' regions were markers of biovar specificity and diversity. Further analysis of this region should reveal the phylogenetic relationship among serovars of U. urealyticum and, possibly, their invasive potential.

Antigenic Variation↗

PubMed1994

Inhibition of acrosin by protein C inhibitor and localization of protein C inhibitor to spermatozoa.

Protein C inhibitor (PCI) is synthesized by cells throughout the male reproductive tract and is present in high concentrations (220 micrograms/ml) in seminal plasma. Seminal plasma as well as the acrosome of spermatozoa are rich in possible target proteases for PCI. We analyzed the interaction of PCI with acrosin, a serine protease stored in its zymogen form in the acrosome of spermatozoa. Purified human PCI inhibited the amidolytic activity of purified boar acrosin with an apparent second-order rate constant of 3.7 x 10(4) M-1.s-1. Inhibition was paralleled by the degradation of PCI from its 57- to its 54-kDa form. Human PCI also inhibited the amidolytic activity of activated human sperm extracts and formed complexes with acrosin as determined by an enzyme-linked immunosorbent assay. Immunocytochemistry revealed that morphologically abnormal spermatozoa stained for PCI antigen, whereas morphologically normal spermatozoa were negative. In immunoelectron microscopy, PCI was exclusively localized in the immediate vicinity of disrupted acrosomal membranes of sperm heads. These data suggest that PCI might function as a scavenger of prematurely activated acrosin, thereby protecting intact surrounding cells and seminal plasma proteins from possible proteolytic damage.

Acrosin↗

PubMed1994

Induction of nasal and nasopharyngeal tumours in Sprague-Dawley rats fed with Chinese salted fish.

Epidemiological studies have implied that Chinese salted fish is a human nasopharyngeal carcinogen. In the present study, 162 Sprague-Dawley rats were randomly assigned to one of four experimental groups. Rats in groups 1 (n = 41) and 3 (n = 40) were exposed to salted fish from birth through the breast feeding period by giving the maternal rats a diet containing 10% and 5% salted fish, respectively, later feeding the rats with pellets containing 10% and 5% of salted fish respectively. In group 2, the rats (n = 41) were given pellets containing 10% of salted fish from 6 weeks of age. Rats in group 4 (n = 40), serving as controls, were only given ordinary pellets. Three rats had nasopharyngeal tumours, 2 from group 1 had a poorly differentiated carcinoma and a squamous cell carcinoma. One rat from group 2 had a squamous cell carcinoma. Four rats had nasal tumours, one fibrosarcoma and one adenocarcinoma were found in rats from group 1. One rhabdomyosarcoma was found in group 2, and one soft tissue sarcoma was found in a rat in group 3. No nasal or nasopharyngeal tumours appeared in the control group. The difference in the occurrence of malignant nasal and nasopharyngeal tumours among the four experimental groups was statistically significant (one tailed p for trend = 0.041). The frequency of tumours appearing in other organs such as the breast, kidney, lung, liver and brain was not significantly different between the salted fish treated groups and the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗

PubMed1994

Antigen expression of epithelial markers, collagen IV and Ki67 in middle ear cholesteatoma. An immunohistochemical Study.

The expression of epithelial markers (cytokeratins, Filaggrin, BerEp4 and EMA), collagen IV and Ki67 was studied immunohistochemically in cholesteatoma and compared with that in epidermis of meatal skin, squamous epithelium of eardrum and simple epithelium of middle ear mucosa. MNF116 (cytokeratin 10, 17, 18) stained the full layer of normal epithelium and all cholesteatoma specimens. CK10 and Filaggrin were expressed in the upper layer of epidermis but more diffusely in cholesteatoma. BerEp4 was found in the basal layer of normal epithelium but was detected in most epithelial cells in cholesteatoma matrix. Variability was observed in EMA and CK14 immunostaining. Collagen IV was localized in the basement membrane of normal epithelium with a continuously staining pattern, an observation also made in the cholesteatomas studied. However, in one of these small areas the basement membrane was not stained with collagen IV. Ki67 was expressed in nuclei of the cells in the basal layer of normal epithelium but extended to epithelial cells in the upper layers of cholesteatoma matrix. The results of the present study indicate that the expression pattern of epithelial markers in cholesteatoma corresponds to that in normal epidermis. The increasing expression of BerEp4 and Ki67 confirms the hyperproliferative nature of cholesteatoma. Whether or not the lack of expression of collagen IV in one of the cholesteatomas reflects a true degradation of the basement membrane needs further investigation in extended materials.

Cholesteatoma↗

PubMed1994

Epstein-Barr virus infection, salted fish and nasopharyngeal carcinoma. A case-control study in southern China.

Two hundred and five histologically confirmed cases of nasopharyngeal carcinoma (NPC) in southern China, and an equal number of matched controls, were investigated for their dietary habits, occupational exposure, use of tobacco and alcohol, history of relatives with NPC, and IgA against Epstein-Barr virus (EBV) capsid antigen (IgA/VCA). Positive IgA/VCA and intake of salted fish were associated with a strong excess risk of NPC. The association persisted after adjustment for other factors. The combination of salted fish and EBV was strongly associated with NPC, and more so than EBV or salted fish per se. Multivariate analyses showed that IgA/VCA was the most important predictor of NPC, and salted fish the second most important. These results suggest that EBV has a strong effect on the development of NPC. The exclusion of EBV and genetic factors in earlier epidemiological studies may have resulted in an overestimation of salted fish as important etiological factor causing NPC.

Adult↗

PubMed1994

[Prevalence of HIV and HCV among injecting drug users (IDUs) in Yunnan, China].

Prevalence of HIV and HCV was studied among 507 IDUs in Yunnan Province. The results reveal that sharing needles with other IDUs is one of the primary pathways to transmit both HIV and HCV. The rates of HIV and HCV infection in the IDU group is 66.5% and 94.9% respectively, which is significantly higher than those in the non-IDU group. There is a direct correlation between the rates of HIV and HCV antibody positive. 97.5% HCV (+) subjects are also HIV (+); and 57% HIV (+) subjects are HCV (+). It is suggested that all IDUs should be encouraged to stop using drugs to prevent HIV and HCV transmission.

Adult↗

PubMed1994

[Influence of cooling motor cortex on the inhibitory effect of stimulation of SII on nociceptive responses in ILN neurons].

Fibers from the cortical somatosensory area II (SII) or motor cortex (MCtx) to intralaminar nuclei (ILN) have been proven to exist, and SII was found to be connected with MCtx by cortico-cortical fibers. The present work was undertaken to study whether MCtx participated in SII producing descending modulation of ILN. All experiments were performed on sodium pentobarbitone anaesthetised cats. Single unit activities of ILN neurons were extracellularly recorded by glass microelectrodes. The effects of stimulating SII on nociceptive responses of ILN neurons were observed before and after cooling MCtx. The nociceptive responses of ILN neurons were attenuated by stimulating SII. There was a statistically significant difference at 0'-2' after the stimulation (n = 14, P < 0.05). The inhibitory effect of stimulating SII was reduced after cooling MCtx (19 degrees C-20 degrees C) in 8 neurons, and abolished in other neurons when the temperature was below 18 degrees C. MCtx was involved in SII producing descending modulation of ILN.

Animals↗

PubMed1994

[Involvement of glutamate in corticofugal modulation of intralaminar nuclei from SII via motor cortex in acupuncture analgesia].

The present experiments were designed to study the effect of glutamate on cortical somatosensory area II (S II) producing descending modulation of intralaminar nuclei (ILN) via the motor cortex (MCtx) in acupuncture analgesia. The glutamate antagonist glutamate diethylester (GDEE) or saline was topically applied at MCtx in 17 cats. Single unit activities of ILN neurons were extracellularly recorded. The results were as follows: 1. The nociceptive responses of ILN neurons were attenuated by stimulating S II after topical administration of saline at MCtx. However, the inhibitory effect of stimulating S II in the same neurons was reduced after application of GDEE. There was a significant difference at 0'-1' after the stimulation between the two groups (n = 10, P < 0.05). 2. The inhibitory effect of electroacupuncture (EA) on nociceptive responses was reduced after topical application of GDEE, while marked inhibition was shown at 0'-10' after cessation of EA in the saline control group (n = 11, P < 0.05). The results, together with the finding that the majority of S II neurons could be activated by EA, showed that glutamate released from S II to MCtx might be involved in corticofugal modulation of ILN from S II via MCtx in acupuncture analgesia.

Acupuncture Analgesia↗

PubMed1994

The connexins and their family tree.

The connexins, gap junction forming proteins, are encoded by a gene family. Sequence comparisons reveal regions of conservation with functional implications for voltage dependence of junctional conductance, junction formation and regulation by phosphorylation. The best connexin tree shows that most gene duplications giving rise to the family occurred early in or before vertebrate divergence. The topology of most deep branches of the tree is uncertain. Evolutionary rates vary for different paralogous connexin genes.

Amino Acid Sequence↗

PubMed1994

[Cohort study of HIV infection among drug users in Ruili and other counties in Yunnan Province, China].

In 1993, a second survey was conducted in Ruili City and other two counties, where a cohort study field was established last year. Seven hundred and fifty five drug users and one hundred and two spouses of HIV infected IDUs were interviewed. Nine samples among 54 from 89 IDUs in cohort were tested as seroconversion. The seroconversion rate (incidence rate) in IDUs (per hundred person years) in Ruili, Longchuan, and Luxi as well were 40.0, 12.2 and 0, respectively in 1993, comparing to 43.2, 12.2 and 0 in 1992. Thirty eight were tested as positive among 108 samples from 116 newly recruited IDUs. The seroprevalence rates in this three counties were 85.7%, 40.0% and 0 in 1993, comparing to 81.8%, 44.6% and 5.1% in 1992. A coordination of the level between seroconversion and seroprevalence was observed. A increasing trend of seroprevalence among the spouses of HIV positive IDUs was found, the seroprevalence rate were 3.1% in 1990, 9.8% in 1992 and 7.4% in 1993. More attention should be paid to Luxi where the ratio of intravenous drug using increased rapidly, although fewer positives and later starting of drug using was found in this county.

China↗

PubMed1993

Plasma levels of cyclic nucleotides in chronic congestive heart failure and their clinical implication.

Plasma levels of cyclic nucleotides were determined by radioimmunoassay in 196 cardiac patients and 50 normal persons. Plasma levels of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) increased with the deterioration of cardiac function. The level of cGMP was correlated with the cardiothoracic ratio, ratio of pre-ejection period and left ventricular ejection time, the intracardiac diameter, left ventricular ejection fraction and left ventricular short axis shortening (r = 0.55, r = 0.50, r = 0.55, r = -0.53 and r = -0.50, respectively; P < 0.001). There were only weak correlations between the level of cAMP and the cardiothoracic ratio, the ratio of pre-ejection period and the left ventricular ejection time, left ventricular ejection fraction, and left ventricular short axis shortening (r = 0.35, r = 0.38, r = -0.28 and r = -0.31, respectively; P < 0.01). The correlations between cGMP and mean pulmonary artery pressure (r = 0.48; P < 0.05) and mean left atrial pressure (r = 0.55; P < 0.01) were also significant. In patients who had received cardioversion and valve replacement the plasma cGMP level decreased significantly. During the follow-up period, 29 of 108 patients died (26.9%), the initial plasma levels of cAMP and cGMP in the dead group were significantly higher than those in the survival group (27.41 +/- 1.13 and 31.11 +/- 3.33 vs. 21.56 +/- 0.60 and 17.45 +/- 1.05 nmol/l, respectively; P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

GroEL, GroES, and ATP-dependent folding and spontaneous assembly of ornithine transcarbamylase.

When purified rat liver ornithine transcarbamylase (OTC), a trimer of 36 kDa subunits, was denatured in 6 M guanidine hydrochloride and then diluted 50-100-fold, no activity was recovered, and the OTC subunits aggregated. In contrast, when the chaperonin groEL was included in the dilution buffer, OTC did not aggregate but instead comigrated in a sucrose density gradient with the groEL oligomer, indicating that a complex had been formed. Upon addition of the cochaperonin groES and ATP to the isolated OTC-groEL complex, OTC monomers were folded, released, and assembled into active trimer. Neither groES nor ATP alone was sufficient to release active OTC from groEL. The extent of recovery of activity was proportional to the concentration of the complex, reaching approximately 80-90% at monomer concentrations above 0.6 microM. At low complex concentrations, kinetic studies revealed an initial lag in the reconstitution reaction, suggesting that assembly is the rate-limiting step under these conditions. We could trap folded, released, inactive OTC monomers at early times that assembled into active trimers with longer incubation. A nonhydrolyzable ATP analog could release bound OTC from groEL in the presence of groES, but the OTC monomers were not competent for assembly. These data show that recovery of OTC activity in vitro can be efficiently directed by the bacterial chaperonins in the presence of ATP and suggest that the mechanism of reconstitution involves ATP and groES-dependent folding and release of OTC monomers from groEL, followed by spontaneous assembly of trimers.

Adenosine Triphosphate↗

PubMed1993

A cellular automaton model of cancerous growth.

A cellular automaton model describing immune system surveillance against cancer is furnished. In formulating the model, we have taken into account the microscopic mechanisms of cancerous growth, such as the proliferation of cancer cells, the cytotoxic behaviors of the immune system, the mechanical pressure inside the tumor and so forth. The model may describe the Gompertz growth of a cancer. The results are in agreement with experimental observations. The influences of the proliferation rate of cancer cells, the cytotoxic rate and other relevant factors affecting the Gompertz growth are studied.

Humans↗

PubMed1993

Structural variations and phenotypic switching of mycoplasmal antigens.

It is becoming apparent that a high rate of variability of surface structures is a ubiquitous property among mycoplasmas. The present study demonstrates how variations in the size of the V-1 antigen (a major surface antigen of Mycoplasma pulmonis thought to be associated with virulence) are reflected by phenotypic differences (cytadherence) that may play a role in virulence of the organism. Furthermore, a similar antigen is described for the human pathogen Urea-plasma urealyticum, and data are presented on the analysis of clinical isolates that demonstrate the potential for variation in the size of this antigen in vivo. Although no direct connection of antigen variation to natural disease has yet been presented, the data further document the tremendous potential for virulence-related diversity possessed by these organisms and emphasize the importance of a valid animal model for discerning the true relationship between variation and virulence.

Animals↗

PubMed1993

Studies on etiological factors of nasopharyngeal carcinoma.

A case-control study of nasopharyngeal carcinoma (NPC) was performed in Guangzhou, southern China in 1987 to 1989. We investigated 205 cases and an equal number of matched controls. Epstein-Barr virus (EBV) infection with positive IgA against viral capsid antigen (VCA-IgA) was shown to be the most important predictor in NPC. Consumption of salted fish was also strongly associated with NPC but not to the same extent as EBV. In order to investigate the possible carcinogenic effect of salted fish, Sprague-Dawley rats were given a diet containing salted fish for 2 years. Three rats with nasal and 3 with nasopharyngeal tumors were found in the experimental groups of 122 rats but none in the control group. Nitrosodimethylamine (NDMA) was found in kidney and liver but not in urine in the rats fed with salted fish. In a non-tumorigenic human keratinocyte line, RHEK-1, transfection of EBV latent membrane protein (EBV-LMP, originated from NPC cell line) induced alterations of morphology and immunophenotype. The LMP expressing sublines showed higher proliferative capacity and lower differentiation in vitro and some of the sublines produced tumors in SCID mice. When cultured in media containing salted fish extract in vitro parental RHEK-1 cells died after 12 weeks. In contrast, LMP expressing sublines survived indicating that exposure to some chemical compounds in salted fish and expression of EBV-gene may be of importance for the transformation of epithelial cells and thus for the pathogenesis of NPC.

Animals↗

PubMed1993

[Influence of lesion of motor cortex on second somatosensory area emanating descending modulation on thalamic intralaminar nuclei].

The present study was undertaken to verify further the participation of motor cortex (MCtx) in the somatosensory area II(SII) emanating descending modulation of thalamic intralaminar nuclei (ILN). Neuronal responses in ILN to noxious stimulation of the superficial peroneal nerve were extracellularly recorded in 34 cats. The effects of electrical stimulating SII on nociceptive responses of neurons in ILN before and after lesion of MCtx were observed and compared. It was shown that electrical stimulation of SII obviously inhibited the nociceptive responses in the majority of neurons recorded (11/13) in ILN in the cats with MCtx intact (P < 0.05). After lesion of MCtx the inhibitory effect still remained (n = 10, P < 0.05), but weakened to a certain extent compared with that before lesion. In the animals with the lesion involving MCtx and the underlying subcortical structures electrical stimulating SII facilitated the nociceptive responses of ILN neurons (n = 7, P < 0.05). The results further support the idea that SII emanating descending modulation on ILN is in part fulfilled via MCtx.

Animals↗

PubMed1993

[Changes in plasma neuropeptides before and after clonidine in patients with essential hypertension].

Plasma concentrations of beta-endorphin (beta-EP), leucine enkephalin (LEK), arginine vasopressin (AVP), neurotensin (NT), renin activity (PRA) and angiotensin II (AT-II) were determined before and after the treatment with clonidine in 117 patients with essential hypertension. Before the treatment, the patient group had lower levels of beta-EP and LEK (P < 0.001), higher levels of AVP, PRA and AT-II (P < 0.05-0.01), as compared with those in control group. After 14 days of the treatment, plasma levels of beta-EP, LEK increased significantly (P < 0.001), and correlated negatively with the decrease of the mean artery pressure (r = -0.369 and r = -0.441, respectively, P < 0.01). PRA and AT-II decreased significantly (P < 0.05, P < 0.01). Decrease of AVP level was also observed, but did not reach the statistical significance. NT did not change both before and after the treatment. These data suggest that beta-EP and LEK may be involved in pathogenesis of hypertension and in hypotensive action of clonidine.

Adult↗