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Biomedical subjects

L Shi

Publications and source records attributed to L Shi.

At least 271 records · Page 15Linked to original sources
PubMed1994

[Meta-analysis and its application in epidemiology].

Meta-analysis provides a powerful statistical tool for epidemiological study. The basic principle of meta-analysis is introduced in this paper, and some problems about its application in epidemiology are discussed. This method was used by the authors to study the relationship between exposure to extreme low frequency electromagnetic fields (ELF) and childhood leukemia, and the result showed that there is a significant association between them.

Electromagnetic Fields↗
PubMed1994

[Histochemical study of dopamine on rat substantia nigra--ventral tegmental area during status epilepticus].

We studied the amount of dopamine on the substantia nigra-ventral tegmental area during status epilepticus of male Wistar rats induced by coriaria lactone with fluorescence histochemical technique and autoexposuremeter of microscope. The intensity of dopamine fluorescence in the climax epileptic seizure group (10 rats) and postepileptic seizure group (8 rats) decreased significantly as compared with the control (10 rats), but the intensity of dopamine fluorescence in the pre-eileptic seizure group (10 rats) was not significantly different from that of the control group. The result indicated that epileptic seizure induces a decrease of the inhibitory neurotransmitter-dopamine. Therefore dopamine plays an important role in regulating the epileptic seizures.

Animals↗
PubMed1994

The study of health effects of vinyl chloride air pollution on population.

A series of indicators, including serum lysozyme activity, G-banding chromosome aberration (G-banding CA) analysis, sister chromatid exchanges (SCEs), chromosome aberration (CA), T-lymphocyte transformation rate (TcTR), gamma-GT, GPT and AKP, were employed in the present survey among occupationally vinyl chloride (VC) exposed workers and inhabitants living in VC polluted area in a polyvinyl chloride (PVC) factory. The results showed that the serum lysozyme (S-LZM) activities in Group 3 (adult inhabitants exposed to 0.20 mg/m3 VC for at least 8 years), Group 2 (workers exposed to 4.1 mg/m3 for at least 7 years occupationally), Group 1 (workers exposed to 25.7 mg/m3 for at least 2 years) were significantly higher than control. G-banding CA analysis showed that the total chromosome breakage rates in both Groups 1 and 2 were higher, but no difference existed between Group 3 and control. Only Group 1 was observed having higher SCEs, CA level and lower TcTR than control. AKP levels in Groups 1 and 2 were higher than control, but no gamm-GT and GPT differences were found among groups. The study also suggests that G-banding CA analysis is more sensitive than CA and SCEs.

Adolescent↗
PubMed1994

[Studies of the miotic chromosomes, meiosis and spermatogenesis of a macaque hybrid].

The mitotic and meiotic chromosomes, as well as the spermatogenesis of a male hybrid between Macaca fascicularis and M. assamensis have been studied using chromosome banding, microspreading, and tissue sectioning techniques. The band patterns of the parental chromosome complements are found highly homologous. The observation on meiosis and testis histology indicates that the hybrid should be fertile. It is suggested that the reproductive barrier between M. fascicularis and M. assamensis is not complete and may resulted from ecological isolation. The taxonomic status of M. fascicularis and M. assamensis is discussed also.

Animals↗
PubMed1994

[mtDNA polymorphism and differentiation of subspecies of Chinese raccoon dog (Nyctereutes procyonides)].

The mtDNA from 14 Raccoon dogs of 7 geographical populations was analyzed with 8 restriction endonucleases, and the restriction map was constructed. Furthermore, UPG molecular phylogenetic trees of the mtDNA were constructed based on the genetic distances. Our results indicated that the differentiation was obvious within geographical populations of the subspecies N. p. procyonoides, and that the event of divergence in Chinese Raccoon dog first occurred between the southern and northern populations, and then, between the western and the eastern populations. We proposed that both of the Huabei and Shanxi populations which had not been identified could be classified into two independent subspecies respectively.

Animals↗
PubMed1994

[Drinking water and leukemia].

A retrospective cohort study was conducted to investigate the relationship between drinking water contamination and risk of leukemia in human being. It was found that the leukemia incidence rate of group D who drank the tap-water from Donghu Lake was significantly higher than that of the groups C and H who drank the tap-water from Changjiang River and Hangjiang River, RR = 1.77, 95% CL = 1.36-2.30, P < 0.01. But the difference between group C and group H is not significant. By using the sex- age-strata analysis; trend and correlation analysis, the results showed that there was a significant positive correlation between the RR of incidence of leukemia and tap-water mutagenicity. It was also connected with pollution of halogenated hydrocarbons in drinking water.

Adolescent↗
PubMed1993

DnaK ATPase activity revisited.

It has recently been reported that the ATPase activity of DnaK, a 70 kDa heat shock protein from E. coli, is autostimulated by increasing protein concentration [(1993) FEBS Lett. 322, 277-279], suggesting that the DnaK dimer may be the enzymatically active species. In this paper we investigated the ATPase activity of different DnaK preparations; we found that the turnover number was very dependent on protein purification. With HPLC-purified DnaK we found a turnover number 20- to 50-fold lower than typical values previously published and no evidence of autostimulation, indicating that the monomer is the active species.

Adenosine Triphosphatases↗
PubMed1993

Identification of PECAM-1 in solid tumor cells and its potential involvement in tumor cell adhesion to endothelium.

PECAM-1 (CD31/EndoCAM) is an adhesion molecule in the immunoglobulin supergene family that is expressed on endothelial cells, platelets, and some hematopoietic lineage cells. In this paper, using several polyclonal and monoclonal antibodies against PECAM-1, we identified PECAM-1 molecules on human, rat, and murine solid tumor cell lines. Immunocytochemical labeling and flow cytometric analysis using either polyclonal, monoclonal, or Fab portion of the antibodies against PECAM-1 detected a distinct distribution on tumor cell surface. Immunoblotting revealed proteins ranging from 120 to 130 kDa in tumor cells derived from different species. Immunoprecipitation and subcellular fractionation studies indicated that PECAM-1 is constitutively expressed on the surface of human tumor cells (i.e. colon adenocarcinoma). The specificity of a major polyclonal anti-PECAM-1 used in the current study (i.e. SEW-3) was confirmed by the preabsorption studies. PECAM-1 molecules on tumor cells appear to bear terminal carbohydrate moieties (i.e. sialic acid residues) different from those on platelets, since neuraminidase treatment of tumor cells, unlike platelets, did not result in a mobility shift. Polymerase chain reaction (PCR) analysis of genomic DNA derived from tumor cell lines of different species revealed the presence of PECAM-1 gene in the genome. The mRNAs of PECAM-1 in tumor cells were detected by reverse transcription-PCR followed by Southern hybridization. Screening of more than 20 human, rat, and murine solid tumor cell lines indicated that PECAM-1 is widely expressed, although the level of expression varies considerably among different cell lines. The expression of PECAM-1 message in tumor cells was confirmed by Northern blotting. DNA sequencing of the PCR fragment revealed that human tumor cell PECAM-1 matches 100% to the human endothelial cell counterpart. Finally, it was demonstrated that tumor cell PECAM-1 is involved in mediating tumor cell adhesion to endothelium, as evidenced by the ability of anti-PECAM-1 antibodies to decrease the adhesion of unstimulated tumor cells to microvascular endothelial cells.

Amino Acid Sequence↗
PubMed1993

ATP-induced protein-Hsp70 complex dissociation requires K+ but not ATP hydrolysis.

The molecular chaperone proteins, particularly Hsp60 and Hsp70, have been implicated in essential cell functions under both normal and stress conditions (reviewed in refs 1-5). Members of the family of heat-shock proteins of M(r) 70K, Hsp70, bind to unfolded proteins and short peptides. Addition of Mg-ATP results in the dissociation of the substrate polypeptides from the chaperone, but as ATP-gamma S (an ATP analogue that is only slowly hydrolysable) cannot substitute for ATP in this reaction, it has been concluded that ATP hydrolysis is necessary to dissociate Hsp70-substrate protein complexes. By independently measuring the rates of ATP hydrolysis and substrate protein dissociation, we show here that Mg-ATP binding but not Mg-ATP hydrolysis is essential for substrate dissociation. We also show that there is an absolute requirement for K+ for the effect of Mg-ATP: only the combination of K+ and Mg-ATP will cause the conformational change in Hsp70 that is necessary for substrate dissociation. Moreover, in the absence of K+, Mg-ATP favours complex formation. We consider these results in terms of a G-protein-like model.

Adenosine Triphosphatases↗
PubMed1993

Three-state denaturation of DnaK induced by guanidine hydrochloride. Evidence for an expandable intermediate.

The denaturation of the heat shock protein DnaK induced by guanidine hydrochloride (Gdn-HCl) was investigated by circular dichroism, fluorescence, size-exclusion HPLC, and dynamic light scattering. DnaK unfolding takes place in two discrete steps. The midpoint (Cm) of the first transition (0.5 M) was shifted to higher denaturant concentrations (0.8 M) in the presence of Mg/ADP or Mg/ATP, whereas the second transition (Cm = 1.6 M) was unaffected by nucleotides. An intermediate state which continuously expands with increasing Gdn.HCl concentration was observed; its relation to molten globules is discussed. In addition, a direct correlation between molecular volume and ellipticity at 222 nm was found, regardless of the conformational state (native, intermediate, unfolded); the implications of these findings are discussed. The unfolding of DnaK is best explained by a hierarchical model of unfolding.

Chromatography, High Pressure Liquid↗
PubMed1993

The 4F9 antigen is a member of the tetra spans transmembrane protein family and functions as an accessory molecule in T cell activation and adhesion.

In this report, we describe a 43- to 50-kDa protein, which may function as a costimulatory molecule for full activation of human T cells. This Ag, defined by a mouse monoclonal antibody (mAb) anti-4F9, is primarily distributed on "helper/inducer" or "memory" CD4+CD45RO+ subset. Like mAbs against many other accessory/costimulatory molecules, coimmobilization of anti-4F9 with anti-CD3 resulted in synergistic T cell proliferation. In addition, immobilized anti-4F9 on plastic plates induced T cell spreading characterized by the development of prominent dendritic processes. A cDNA encoding the 4F9 Ag was isolated from a cDNA library constructed from PHA/PMA-activated T cells using a COS cell expression system. The sequence of the cDNA and a homology search revealed that the 4F9 Ag was identical to R2, a molecule recently cloned by subtractive hybridization. The 4F9/R2 Ag belongs to a newly identified supergene family (tetra spans transmembrane protein family) characterized by four putative transmembrane domains which are highly conserved between the members of this family. Based upon the phenotypical and functional studies described here, we propose that the 4F9 Ag is an integral membrane protein which can transmit signals involved in T cell proliferation and adhesion. The preferential distribution of this molecule on the CD4+CD45RO+ subset of T cells may contribute to the distinct activation profile and functional repertoire of these cells.

Animals↗
PubMed1993

DNA fragmentation induced by cytotoxic T lymphocytes can result in target cell death.

Cytotoxic T lymphocyte (CTL)-mediated lysis is accompanied by fragmentation of target cell DNA into an oligonucleosome ladder, a hallmark of apoptosis. Is this a fortuitous coincidence, or could CTL be inducing lysis by activation of the suicide signal? In this report we demonstrate that CTL-mediated target cell death can be blocked with the drug aurintricarboxylic acid (ATA). The abrogation of death correlates with the inhibition of DNA fragmentation. While ATA prevented DNA fragmentation, it failed to significantly alter protein, RNA, or DNA synthesis in the cell lines over the dose range used. In addition, there was no inhibition of cell-cell interaction or granule exocytosis during CTL-mediated killing. ATA also significantly inhibited the cytolysis and DNA fragmentation mediated by isolated cytolytic granules, as well as the granular protein fragmentin. We developed an assay in which target cells could be separated from CTL after binding and programming for lysis. Once they had received the "kiss of death," target cells could be rescued from lysis (as indicated by inhibition of DNA fragmentation and increased target cell viability) by treatment with ATA. These results suggest that ATA blocks target cell death by inhibition of DNA fragmentation, and further, that chromatin degradation is a cause rather than a result of cell death in CTL-mediated lysis.

Animals↗
PubMed1993

The origin and genetic differentiation of native breeds of pigs in southwest China: an approach from mitochondrial DNA polymorphism.

Mitochondrial DNA (mtDNA) of six breeds of native domestic pigs from Yunnan province, southwest China, and two wild boars obtained from Sichuan, China, and Vietnam was analyzed using 20 restriction endonucleases that recognize six nucleotides. Restriction maps were made by double-digestion methods and polymorphic sites were located on the map. According to their mtDNA restriction types, all the breeds were classified into six groups. Genetic distances among groups were calculated to define their phylogenetic relationships. The relationship between the Sichuan wild boar and domestic pigs is close, while the Vietnamese wild boar is relatively far from them, so the domestic pigs in southwest China are likely to have originated from a wild pig which distributed in west China. We compare our results with previous reports in literature and discuss the relationship among Chinese pigs, Japanese pigs, and European pigs. The mtDNA cleavage pattern of the Mingguang pig digested by EcoRV was identical to that of Duroc; mutations at the EcoRI site, detected in the mtDNA of two Dahe pigs, are the same as in the Vietnamese wild boar, suggesting that mutational hot spots exist in the mtDNA of pigs.

Animals↗
PubMed1993

Family financial and household support exchange between generations: a survey of Chinese rural elderly.

This study examines the pattern of social support exchange between Chinese elderly and their adult children, based on a 1989 rural Chinese household survey. Following social exchange theory, we found reciprocity in household support but not in financial support. Elderly with greater resource capacities (i.e., health, income, education, and social network) were more likely to provide than receive assistance, whereas those with fewer resources had the opposite patterns. The exchange of support was more likely to be related to affective and nonfinancial instrumental support than financial instrumental support. Because only 42% of elderly with one or two children were living with their children, a formal pension and elderly care system is needed to complement the informal support system.

Adult↗
PubMed1993

AIDS-related knowledge and attitudes of social workers in South Carolina.

This study examines the association between knowledge of acquired immune deficiency syndrome (AIDS) and skill among social workers in South Carolina and attitudes toward people with human immunodeficiency virus (HIV) and AIDS. A stratified random sampling method was used to obtain a representative sample of social workers in South Carolina. Findings show that AIDS-related knowledge and skill were significantly associated with improving the general attitudes of social workers toward HIV/AIDS clients. In addition to knowledge and skill-related measures, other significant covariates of attitudes include levels of contact with HIV/AIDS clients and sensitivity to minorities. As with previous studies, demographic variables such as age and gender were not found to be significantly related to variations in attitudes toward HIV/AIDS clients. Furthermore, locality of practice and supervisory position did not significantly correlate with attitudes. The implications of these findings for social services agencies are discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Incentives for physicians to treat HIV-seropositive patients: results of a statewide survey.

We asked primary care physicians in South Carolina about their knowledge, attitudes, and beliefs regarding patients with human immunodeficiency virus (HIV) infection and acquired immunodeficiency syndrome (AIDS) and the services they provide for these patients. In support of an effort to develop more effective state policies regarding HIV/AIDS, the survey focused on conditions under which physicians would provide additional services for such patients; 597 of 900 physicians (66%) responded. Among responding physicians, 40% had not seen a patient with HIV infection/AIDS during the past year and 50% had seen only one to nine. Respondents identified lack of specialty backup support, insufficient clinical knowledge, and lack of available community services as the major barriers to providing care for these patients. Gaps in their knowledge included state and federal policies, available community resources, and clinical issues. Respondents said they would provide additional services if they had specialty backup (54%), better community and social support services (50%), additional training (46%), and limited liability (44%). We concluded that policy changes in these areas could expand access to care for HIV/AIDS patients in South Carolina.

Acquired Immunodeficiency Syndrome↗
PubMed1993

The determinants of utilization of nonphysician providers in rural community and migrant health centers.

The use of nonphysician providers, such as nurse practitioners, physician assistants, and certified nurse midwives, in rural areas is critically important due to the continued primary care access problems. This study examines the major factors influencing the use of nonphysician providers in rural community and migrant health centers based on a 1991 national survey of the centers. This study demonstrates that the employment of nonphysician providers in rural community and migrant health centers is significantly influenced by both supply and demand factors. Among supply factors, there is a significant and positive relationship between the number of total staff and the number of nonphysician providers employed. There is a significant but inverse relationship between the number of physicians and the number of nonphysician providers employed, indicating nonphysician providers primarily serve as substitutes for physicians in rural community and migrant health centers. The supply of nonphysician providers, as measured by the number of affiliated training programs, is significantly related to the employment of nonphysician providers. The demand variable, geographic location, and the centers' staffing policies are also significant determinants of the use of nonphysician providers.

Community Health Centers↗