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Biomedical subjects

Z Sheng

Publications and source records attributed to Z Sheng.

At least 109 records · Page 6Linked to original sources
PubMed1994

Type-specific immune response to human T cell lymphotropic virus (HTLV) type I and type II infections in Nigeria.

Type-specific antibody responses to human T cell lymphotropic virus type I (HTLV-I) and type II (HTLV-II) were studied in blood samples collected from 25 different locations in Nigeria between 1985 and 1991 and stored at the University College Hospital in Ibadan. A total of 4,153 sera were collected from participants in the National Immunity Survey of Viral Infections (n = 1,640), patients with tuberculosis (TB) (n = 140), patients with sexually transmitted diseases (STDs) (n = 876), patients with other medical conditions (n = 1,285), female prostitutes (n = 60), and health care workers (n = 152). The overall seroprevalence of HTLV was 5.6%, with similar rates among males and females. Using enzyme immunoassays that differentiated between antibodies to the two viruses, the seroprevalence rates were 2.5% for HTLV-I and 1.9% for HTLV-II, with an additional 1.2% of the samples dually reactive for both HTLV-I and HTLV-II. The seroprevalence rates for HTLV were low among children (0.8%) and adolescents (1.7%), with substantially higher rates among adults (range 5.0-7.4%). Age-specific patterns among adults appears to differ for HTLV-I and HTLV-II, with HTLV-I rates peaking above age 50 and HTLV-II rates peaking below age 50. The highest overall HTLV prevalence rates were observed for STD patients (16.3%), followed by female prostitutes (8.3%), TB patients (6.4%), health care workers (3.3%), patients with other medical conditions (3.2%), and immunity survey participants (1.8%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

[Carcinoma arising from postburn scars (report of 5 cases)].

Carcinoma arising from postburn scars is rare. We have encountered 5 patients suffering from this late complication of scars, accounting for 0.32% of 1563 admissions for late surgery after burn injuries. They were all males, with a mean age of 56 years. The mean latent period was 43.2 years, and it was apparently longer when the acute burn injury occurred earlier in life. The site of predilection was the lower extremity, and multiple biopsies of various sites of the lesion remained to be the measure of confirmation. Pathologically, they were all squamoon cell carcinoma, grade I in 4 cases and grade II in 1. Immunohistochemical staining with anti-proliferation cell nuclear antigen (PCNA) showed that PCNA positive nuclei of squamous cell carcinoma were more numerous, as compared with that in the neighboring pseudo -epitheliomatous hyperplasia (PEH) and in normal skin, denoting markedly augmented assimilation of DNA in malignant degeneration. On the contrary, the number of Langerhan's cells were smallest in cancer area, as compared with PEH and normal skin. The diagnosis, treatment and prevention of such malignant degeneration in postburn scars have been discussed.

Adult↗
PubMed1993

The baculovirus Autographa californica encodes a protein tyrosine phosphatase.

The genome of the baculovirus Autographa californica encodes a 19-kDa protein (BVP) containing an active site sequence motif ((I/V)HCXAGXXR(S/T)G) that characterizes a large family of protein tyrosine phosphatases (PTPs). The baculoviral protein was expressed in Escherichia coli and purified so that its enzymatic properties could be examined. We have demonstrated that recombinant BVP has intrinsic protein tyrosine phosphatase activity. Like VH1, a PTP encoded by vaccinia virus, BVP also dephosphorylates seryl or threonyl residues. However, the similarity of BVP to VH1 or the catalytic domains from PTPs of eukaryotic origin is restricted to a small region surrounding the active site motif. In contrast, the similarity of BVP to two putative PTPs encoded by the CDC14 gene of Saccharomyces cerevisiae and a gene of unknown function from Caenorhabditis elegans extends throughout its sequence. We postulate that BVP and its two homologs constitute a unique subfamily that may differ from other PTPs in having a specialized function, mode of regulation, or substrate preference.

Amino Acid Sequence↗
PubMed1993

Prevalence of human immunodeficiency virus types 1 and 2 infections in Nigeria.

The prevalence of human immunodeficiency virus (HIV) types 1 and 2 infections in Nigeria was estimated from 3854 serum samples collected at 21 locations from 1985 to 1990. Seventy-eight samples (2.0%) were reactive for HIV-1 and 49 (1.3%) for HIV-2 antibodies; 5 samples were reactive for both viruses. The prevalence of HIV-1 and -2 infections, respectively, was highest among 60 female prostitutes, with 10% and 6.7% positive. For other groups the respective rates of positivity were 4.1% and 3.4% in 610 patients with sexually transmitted diseases, 3.6% and 1.4% in 140 tuberculosis patients, 1.6% and 0.6% of 1253 other medical patients, and 1.2% and 0.9% of 1640 volunteer blood donors. Of 153 health care workers, 1.3% were positive for HIV-1 only. The age group from 20 to 29 years had the highest prevalences of HIV-1 (3.3%) and -2 (2.2%). In Nigeria, antibody prevalence for both viruses appears to have increased > 10-fold between 1986 and 1990.

Adolescent↗
PubMed1992

Isolation, expression, and mutation of a rabbit skeletal muscle cDNA clone for troponin I. The role of the NH2 terminus of fast skeletal muscle troponin I in its biological activity.

A cDNA for rabbit fast skeletal muscle troponin I (TnI) was isolated and sequenced. The clone contains a coding sequence predicting a 182-amino-acid protein with a molecular mass of 21,162 daltons. The translated sequence is different from that reported by Wilkinson and Grand (Wilkinson, J. M., and Grand, R. J. A. (1978) Nature 271, 31-35) in that Arg-153, Asp-154, and Leu-155 must be inserted into their original sequence. Amino acid sequencing of adult rabbit TnI confirmed this result. In order to investigate the role of the NH2 terminus of TnI in its biological activity, we have expressed a recombinant deletion mutant (TnId57), which lacks residues 1-57, in a bacterial expression system. Both wild type TnI (WTnI) and TnId57 inhibited acto-S1-ATPase activity and this inhibition could be fully reversed by troponin C (TnC) in the presence of Ca2+. Additionally both WTnI and TnId57 bound to an actin affinity column. Thus, both inhibitory actin binding and Ca(2+)-dependent neutralization by TnC were retained in TnId57. TnC affinity chromatography was used to compare the binding of TnI and TnId57 to TnC. Using this method, two types of interaction between TnC and TnI were observed: 1) one which is metal independent (or structural) and 2) one dependent on Ca2+ or Mg2+ binding to the Ca(2+)-Mg2+ sites of TnC. The same experiments with TnId57 demonstrated that the type 1 interaction was weakened, and type 2 binding was lost. This method also revealed an interaction between TnC and TnI which is dependent upon Ca2+ binding to the Ca(2+)-specific sites of TnC and which is retained in TnId57. Taken together, these results suggest that the NH2 terminus of TnI may constitute a Ca(2+)-Mg(2+)-dependent interaction site between TnC and TnI and play, in part, a structural role in maintaining the stability of the troponin complex while the COOH terminus of TnI contains a Ca(2+)-specific site-dependent interaction site for TnC as well as the previously demonstrated Ca(2+)-sensitive inhibitory and actin binding activities.

Actins↗
PubMed1992

Molecular cloning of the transmembrane component of the 13762 mammary adenocarcinoma sialomucin complex. A new member of the epidermal growth factor superfamily.

Ascites sublines of the 13762 rat mammary adenocarcinoma have a cell surface sialomucin complex composed of the sialomucin ascites sialoglycoprotein-1 (ASGP-1) and the membrane-associated glycoprotein ASGP-2. The sialomucin complex is synthesized as a high M(r) precursor, pre-sialomucin complex (pSMC-1). To characterize the structure of the membrane-associated component of this complex, a lambda gt11 cDNA expression library was constructed using mRNA from 13762 rat mammary adenocarcinoma cells and screened with polyclonal antibody against ASGP-2. The strongest antibody-binding clone, designated lambda ASGP2.9-1, had a 1.3-kilobase (kb) insert, and hybridized to a 9-kb transcript in 13762 cell mRNA. The large size of this transcript was expected, since the estimated molecular mass of pSMC-1 is greater than 250 kDa. To obtain the full sequence of ASGP-2, a longer cDNA (5.4 kb), designated pASGP1/2.1, was subsequently cloned by screening a plasmid library with an oligonucleotide complementary to the 5' end of the phage insert. The amino acid sequence derived from nucleotide sequence of pASGP1/2.1 showed a 12-amino acid identity with amino acid sequence obtained from the NH2 terminus of ASGP-2, indicating the entire ASGP-2 coding region was included in the cDNA. Furthermore, an 18-amino acid identity with the NH2 terminus of a 6-kDa CNBr fragment of ASGP-2 was also observed in the cDNA sequence. The polypeptide contains several distinct domains, including a hydrophobic transmembrane domain, a short (20 residue) COOH-terminal cytoplasmic tail, and a large extracellular domain with 24 potential N-glycosylation sites. These properties correspond to features of ASGP-2 and pSMC-1 predicted by previous biochemical studies. Most interestingly, the extracellular domain contains two cysteine-rich sequences, each of which has a segment with strong similarities to proteins with epidermal growth factor activity. Since our recent studies show that ASGP-2 can modulate epidermal growth factor receptor phosphorylation activity, these results provide structural evidence to support the role of the heterodimeric sialomucin complex as a bifunctional modulator of cellular interactions and cell proliferation.

Adenocarcinoma↗
PubMed1992

The role of endotoxin in the pathogenesis of experimental multiple system organ failure: a preliminary report.

In this study, an animal model of multiple system organ failure (MSOF) in rabbits, engendered by feeding E. coli prior to severe hemorrhagic shock, was used for the purpose of investigating 1) the relationship between lipopolysaccharide (LPS) and MSOF, and 2) the effectiveness of Re-LPS antiserum in preventing MSOF. The results showed that endotoxemia occurred very early, and its degree correlated well with that of organ dysfunction. Re-LPS antiserum administration abated the toxic effects and lowered the incidence of MSOF. These results suggest that sequential analysis of circulating LPS levels may be useful for the early diagnosis of MSOF, and that gut-derived endotoxin might play an important role in the pathogenesis of experimental MSOF.

Animals↗
PubMed1992

[A computer simulated test for the long-time change of heterozygote. Analysis of possibility on preserving the heterozygote for long-time in population].

Under the conditions of random mating and selecting. The research by computer simulation analysed the possibility of long-time conserving heterozygote in colong. An important conclusion was obtained. It was impossible to conserve heterozygote for a long time in colong. Therefore it is not necessary to control inbreeding for conserving all genes of colong by reducing gene purity in the work of conserving breeds for farm animal and poultry.

Animals↗
PubMed1992

Multiple organ injuries after abdominal high energy wounding in animals and the protective effect of antioxidants.

Multiple organ injuries caused by high energy abdominal wounds were studied in 8 pigs and 24 dogs, and at the same time the protective effect of antioxidants in 14 dogs with multiple organ injuries was also studied. The experimental results showed that: 1) more than two organs (six organs at most) were wounded in each of the animals studied; 2) the injuries were characterized by hemorrhaging, tissue rupture and hematoma, and the main pathologic changes were local edema and necrosis; 3) the marked increase of lipid peroxide (LPO) levels in the vital organs indicated that multiple organ injuries could also involve the molecular level; 4) the injuries were due to the direct effect of pressure waves and ischemic reperfusion and not to shock or infection; and 5) antioxidants (vitamin E and Salvia miltiorrhiza Bge.) exhibited significant protective effects against multiple organ injuries through a free radical mechanism.

Abdominal Injuries↗
PubMed1992

[Multi-origin usage for chromosome replication of suppressive integration strain of dnaA46 mutant of Escherichia coli integrated with R6K].

The chromosome of temperature sensitive initiation mutant dnaA46 of Escherichia coli K-12 fails to replicate at 42 degrees C. Suppressive integration (Sin) strain integrated with the R6K plasmid was screened at 42 degrees C. Marker frequency determination of the Sin strain reveals that replication was initiated at the normal site of initiation at 30 degrees C, while at three different sites at 42 degrees C. Two of the sites have been reported in the stable DNA replication mutant, one of them is a novel site. Inhibition of chromosome replication was not observed for the recA derivative of Sin initiated at two of the initiation sites close to the normal initiation site. Inhibition was observed for chromosome replication initiated near the site where chromosome replication normally terminates. It indicates that chromosome replication initiated at sites close to the terminus is recA gene dependent.

Chromosomes, Bacterial↗
PubMed1990

Evidence that both Ca(2+)-specific sites of skeletal muscle TnC are required for full activity.

To investigate the role of the Ca2(+)-specific (I and II) sites of fast skeletal muscle troponin C (TnC) in the regulation of contraction, we have produced two TnC mutants which have lost the ability to bind Ca2+ at either site I (VG1) or at site II (VG2). Both mutants were able to partially restore force to TnC-depleted skinned muscle fibers (approximately 25% for VG1 and approximately 50% for VG2). In contrast, bovine cardiac TnC (BCTnC), which like VG1 binds Ca2+ only at site II, could fully reactivate the contraction of TnC-depleted fibers. Higher concentrations of both mutants were required to restore force to the TnC-depleted fibers than with wild type TnC (WTnC) or BCTnC. VG1 and VG2 substituted fibers could not bind additional WTnC, indicating that all of the TnC-binding sites were saturated with the mutant TnC's. The Ca2+ concentration required for force activation was much higher for VG1 and VG2 substituted fibers than for WTnC or BCTnC substituted fibers. Also, the steepness of force activation was much less in VG1 and VG2 versus WTnC and BCTnC substituted fibers. These results suggest cooperative interactions between sites I and II in WTnC. In contrast, BCTnC has essentially the same apparent Ca2+ affinity and steepness of force activation as does WTnC. Thus, cardiac TnC must have structural differences from WTnC which compensate for the lack of site I, while in WTnC, both Ca2(+)-specific sites are probably crucial for full functional activity.

Amino Acid Sequence↗
PubMed1990

Expression, purification and characterization of a 41 kDa insulin receptor tyrosine kinase domain.

An active 41 kDa cytoplasmic domain of the insulin receptor tyrosine kinase (CIRK-41) encompassing amino acid residues 946 and 1303 of the native protein with an additional three amino acids (HAI) at the N-terminus has been overexpressed using the baculovirus pAC 373 expression system. The recombinant protein termed CIRK-41 has been purified to homogeneity. CIRK-41 was capable of autophosphorylation and up to 1.9 moles of phosphate were incorporated per mole of enzyme when it was incubated in the presence of 10 mM manganese chloride and 0.5 mM ATP. Autophosphorylation resulted in stimulation of CIRK-41 activity towards its exogenous substrate, indicating that CIRK-41 may be used as a model molecule to study the role of phosphorylation and dephosphorylation in the control of the insulin receptor tyrosine kinase activity.

Animals↗
PubMed1990

Isolation and partial characterization of ascites sialoglycoprotein-2 of the cell surface sialomucin complex of 13762 rat mammary adenocarcinoma cells.

Sialomucins are the dominant components of the cell surfaces of some carcinoma ascites cells and have been postulated to inhibit recognition of tumours by the immune system. The sialomucin ASGP-1 (ascites sialoglycoprotein-1) of the 13762 rat mammary adenocarcinoma is associated with the cell surface as a complex with a concanavalin-A-binding glycoprotein called ASGP-2. This sialomucin complex has been purified from ascites cell microvilli by extraction with Triton X-100 and CsCl density-gradient centrifugation. ASGP-1 (which has been purified previously) and ASGP-2 were dissociated in 6 M-guanidine hydrochloride and separated by gel filtration. The molecular mass of the undenatured detergent complex of ASGP-2, estimated by gel filtration and velocity sedimentation in Triton X-100, was 148 kDa. Since the apparent molecular mass by SDS/polyacrylamide-gel electrophoresis was about 120 kDa, ASGP-2 must be a monomer as extracted from the membrane. Studies of its chemical composition indicate that it contains about 45% carbohydrate by weight, including both mannose and galactosamine. Alkaline borohydride treatment of ASGP-2 converted approx. half of the N-acetylgalactosamine to N-acetylgalactosaminitol, demonstrating the presence of O-linked oligosaccharides. Analyses of mannose-labelled Pronase glycopeptides from ASGP-2 by lectin-affinity chromatography on concanavalin A and leucocyte-agglutinating phytohaemagglutinin suggested that 40% of the label was present in high-mannose/hybrid oligosaccharides, 20% in triantennary oligosaccharides substituted on the C-2 and C-4 mannose positions and 40% in tri- or tetra-antennary oligosaccharides substituted on C-2 and C-6. The presence of polylactosamine sequences on these oligosaccharides was suggested by lectin blots and by precipitation from detergent extracts with tomato lectin. From chemical analyses and lectin-affinity studies, we estimate that ASGP-2 contains four high-mannose and 13 complex N-glycosylated oligosaccharides, plus small amounts of polylactosamine and O-linked oligosaccharides. The presence of four different classes of oligosaccharides on this glycoprotein suggests that it will be an interesting model system for biosynthetic comparisons of the different glycosylation pathways.

Adenocarcinoma↗
PubMed1990

[Cloning and study on the replication origin of the integrated F plasmid in Escherichia coli].

The replication origin of the integrated F' plasmid was cloned by means of marker rescue. No difference in incompatibility and acridine orange sensitivity was found between the mini-F plasmid constructed from such an origin and the autonomous F' plasmid. Subcloning and comparative restriction enzyme analysis were carried out with the replication origin from the integrated F' plasmid and that from the autonomous F plasmid. No structural difference was found between them. These results suggest that the difference for the dependence of recA gene between the F and F' plasmids dose not come from any difference in structure of their replication origin, but probably from their site of integration on the chromosome.

Cloning, Molecular↗
PubMed1990

[Construction of promoter probe vector pFDC4 and gene expression vector pFDC11 with high transformation efficiency in Bacillus stearothermophilus].

A 0.5kb fragment from Sau3A-digested total DNA of Bacillus stearothermophilus CU21 was cloned with the vector pPGV5, a derivative of pPL703. The insertion of this fragment can activate the expression of the promoteless cat-86 gene on the cloning vector in both B. stearothermophilus and Bacillus subtilis hosts. When the 0.54 kb fragment is present in pPGV5 in either orientation, the transformation efficiency of the plasmid is increased about 10(3) to 10(4) fold in CU21 protoplasts. Southern hybridization showed this 0.54 kb fragment was homologous with a 1.6kb fragment, which was shown by Imanaka et al. (1984, J. Gen. Microbiol. 130, 1399-1408) to originate in a cryptic plasmid resident in CU21 and to enhance the transformat on efficiency of another plasmid. With this 0.54kb fragment a new promoter probe vector pFDC4 and a gene expression vector pFDC11 were constructed. Both can transform the CU21 recipient with high efficiency.

Gene Expression↗
PubMed1990

[Survey of Bacillus thuringiensis and Bacillus sphaericus from soils of four provinces of China and their principal biological properties].

A number of isolates of Bacillus thuringiensis and Bacillus sphaericus were obtained from soils of Southwestern Area and Shaanxi Province of China. Among isolates of B. thuringiensis were under 13 sorts of serotype in total of 23 sorts of B. thuringiensis and about 20% of auto-agglutinate strains. Rules of ecologic distribution of two sorts of bacteria were analysed. Toxicities on six species of insects, morphology and crystal proteins of B. thuringiensis, as well as toxicities, morphology and crystal proteins of B. sphaericus, were investigated. 22 strains of more efficient of B. thuringiensis and 2 strains of more efficient of B. sphaericus were obtained. It was shown that B. thuringiensis is actually soil microorganism, and resource of B. thuringiensis is much fruitful in Southwestern Area of China.

Bacillus↗
PubMed1989

Topography and microfilament core association of a cell surface glycoprotein of ascites tumor cell microvilli.

Membrane-microfilament interactions are being investigated in microvilli isolated from 13762 rat mammary ascites tumor cells. These microvilli are covered by a sialomucin complex, composed of the sialomucin ascites sialoglycoprotein-1 (ASGP-1) and the associated concanavalin A (Con A)-binding glycoprotein ASGP-2. Limited proteolysis of the microvilli releases large, highly glycosylated fragments of ASGP-1 from the microvilli and increases the association of ASGP-2 with the Triton-insoluble microvillar microfilament core (Vanderpuye OA, Carraway CAC, Carraway, KL: Exp Cell Res 178:211, 1988). To analyze the topography of ASGP-2 in the membrane and its association with the microfilament core, microvilli were treated with proteinase K for timed intervals and centrifuged. The pelleted microvilli were extracted with Triton X-100 for the preparation of microfilament cores and Triton-soluble proteins or with 0.1 M carbonate, pH 11, for the preparation of microvillar membranes depleted of peripheral membrane proteins. These microvilli fractions were analyzed by dodecyl sulfate gel electrophoresis, lectin blotting with Con A and L-phytohemagglutinin, and immunoblotting with anti-ASGP-2. The earliest major proteolysis product from this procedure was a 70 kDa membrane-bound fragment. At longer times a 60 kDa released fragment, 30-40 kDa Triton-soluble fragments, and 25-30 kDa membrane- and microfilament-associated fragments were observed. Phalloidin shift analysis of microfilament-associated proteins on velocity sedimentation gradients indicated that the 25-30 kDa fragments were strongly associated with the microfilament core. From these studies we propose that ASGP-2 has a site for indirect association with the microfilament core near the membrane on a 15-20 kDa segment.

Actin Cytoskeleton↗