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K Luo

Publications and source records attributed to K Luo.

81 records · Page 5Linked to original sources
PubMed1993

[Seroepidemiological investigations on hepatitis B virus infection in the populations of Han, Tibetan, Dai, Yao, Uygur, Mongol and Li nationalities].

Seroepidemiological investigations on the hepatitis B virus infection were carried out among populations of seven nationalities that could represent the main categories by the language system. The HBsAg prevalence, after sex- and age-adjustment, was 15.3% in Han in contrast, that was 26.2% in Tibetan and 24.0% in Yao, being significantly higher (P < 0.001); and on the other hand, 7.0% in Li and 5.3% in Uygur, being significantly lower than that in Han (P < 0.001). The age peaks of HBsAg prevalence in Uygur and Li declined much earlier than others. HBeAg was not detected in women during childbearing age. The ratios of anti-HBs/HBsAg were between 1.61 and 2.06 in general while they were only 0.82 in Tibetan and 1.09 in Yao.

Adolescent↗
PubMed1992

Activated lck tyrosine protein kinase stimulates antigen-independent interleukin-2 production in T cells.

p56lck, a member of the src family of cytoplasmic tyrosine kinases, is expressed predominantly in T cells where it associates with the T-cell surface molecules CD4 and CD8. Mutants of CD4 and CD8 that have lost the ability to associate with p56lck no longer enhance antigen-induced T-cell activation. This suggests that p56lck plays an important role during T-cell activation. In an effort to understand the function of p56lck in T cells, a constitutively activated lck gene (F505lck) was introduced into T-helper hybridoma cell lines by retroviral infection. In four T-cell lines we examined, the activated lck protein stimulated interleukin-2 (IL-2) production, a hallmark of T-cell activation, in the absence of antigenic stimulation. In addition, a marked increase in antigen-independent IL-2 production was apparent when T cells infected with a temperature-sensitive F505lck were shifted to the permissive temperature. Only one cell line expressing F505lck exhibited increased sensitivity to antigenic stimulation. The SH3 domain of p56lck was dispensable for the induction of antigen-independent IL-2 production. In contrast, deletion of the majority of the SH2 domain of p56F505lck reduced its ability to induce spontaneous IL-2 production markedly. Activated p60c-src also induced antigen-independent IL-2 production, whereas two other tyrosine kinases, v-abl and the platelet-derived growth factor receptor, did not. Tyrosine phosphorylation of a 70-kDa cellular protein was observed after cross-linking of CD4 in T cells expressing F505lck but not in cells expressing F527src.

Animals↗
PubMed1992

[Polymerase chain reaction in the detection of hepatitis B virus carriers with sole positive anti-hepatitis B core antigen].

To assess the prevalence of serum HBV DNA in the individuals with positive anti-HBc alone, seroepidemiologic investigations in three populations were carried out with polymerase chain reaction. The detection of sole anti-HBc were 21 of 294 (7.1%), 193 of 1995 (9.7%) and 23 of 377 (6.1%) individuals respectively. Among the anti-HBc positive sera, HBV DNA was detected in 6 (28.6%), 68 (35.2%) and 7 (30.4%) respectively. Follow-up observations showed that 83.8%, 93.1% and 71.4% still remained HBV DNA positive respectively. These might be reasonably regarded as chronic asymptomatic HBV carriers with undetectable HBsAg.

Carrier State↗
PubMed1992

[Asymptomatic hepatitis B virus infection among the elderly].

The hepatitis B virus (HBV) infection usually occurs during infancy and children. To elucidate how the infection changes during the elderly life, 2233 residents were surveyed and among them 440 individuals with the age of 60-96 years were centered for analysis. The infection in the elderly was decreasing. HBsAg prevalence (5.0%) and titer (3.5 +/- 2.3) were getting lower, nearly all HBeAg seroconverted to anti-HBe, and the infection might be cleared at last. However, the HBV antibody prevalence steadily maintained, implying frequent HBV exposure and antibody responses during aging in the endemic area. Among them no fresh HBsAg were detected at one year follow-up, but antibodies developed in 10.8% of 65 individuals without HBV markers initially, and more, in 79 with single anti-HBs or anti-HBc 6.3% developed another antibody in a year. Therefore, the elderly population might be in a hypo-infection and dynamic hyperimmune status of the hepatitis B virus.

Aged↗
PubMed1990

Strain differences in the ontogeny of estrogen receptors in murine uterine epithelium.

The expression of estrogen receptor (ER) in the reproductive tracts of neonatal mice was examined using immunocytochemical and autoradiographic methods. Two strains of mice used in previous studies that reported contradictory results showed different rates of uterine epithelial development. In the inbred strain, BALB/c, the epithelium was devoid of receptor from birth through 5 days of age, while uterine epithelial cells of the outbred strain, CD-1, expressed ER as early as 3 days of age. Oviductal epithelium and cervical epithelium expressed ER on the day of birth in CD-1 mice. Glandular ontogeny in the uteri of CD-1 animals was also advanced by 3 days compared to that of BALB/c mice. These observations reconcile the conflicting reports of ER ontogeny in the neonatal mouse. More importantly, these results confirm our earlier observations, indicating that the cells lining uteri of 2- and 4-day-old BALB/c mice lack ER at a time when estrogen induces their proliferation.

Aging↗
PubMed1990

Transfer of proteins to membranes facilitates both cyanogen bromide cleavage and two-dimensional proteolytic mapping.

We have found that the transfer of gel-fractionated proteins to membranes facilitates phosphopeptide mapping. Nitrocellulose proves to be an excellent matrix for both cyanogen bromide cleavage and proteolytic digestion. Digestion of p56lck bound to a nitrocellulose membrane with cyanogen bromide or trypsin generated patterns of phosphopeptides indistinguishable from those produced by digestion of p56lck eluted from a gel. Immobilon-P and nylon membranes can also be used for proteolytic mapping, but not for cyanogen bromide cleavage. Since the use of membrane-bound protein eliminates the need for elution and precipitation of the protein, analysis is rapid. In addition, the recovery of the peptides from proteins digested on membranes is better and more consistent than it is from eluted and precipitated proteins.

Animals↗
PubMed1989

Activators of protein kinase C induce dissociation of CD4, but not CD8, from p56lck.

The CD4 and CD8 T cell receptor accessory molecules can both be isolated from T lymphocytes in association with p56lck, a membrane-associated, cytoplasmic tyrosine protein kinase that is expressed exclusively in lymphoid cells. The enzymatic activity of p56lck may therefore be regulated by CD4 and CD8 and be important in antigen-induced T cell activation. Exposure of human T cells and some mouse T cells to the tumor promoter 12-O-tetradecanoyl phorbol-13-acetate (TPA), an activator of protein kinase C, caused the dissociation of p56lck and CD4. Activation of protein kinase C may therefore interrupt regulation of p56lck by CD4 and alter the ability of p56lck to interact with polypeptide substrates. In contrast, exposure of cells to TPA did not cause dissociation of p56lck and CD8. Regulation of p56lck by CD4 may therefore differ from regulation by CD8.

Animals↗
PubMedDate not supplied

The heliothis virescens 170 kDa aminopeptidase functions as "receptor A" by mediating specific Bacillus thuringiensis Cry1A delta-endotoxin binding and pore formation.

The relationship between Bacillus thuringiensis Cry1Aa, Cry1Ab and Cry1Ac delta-endotoxin binding and pore formation was investigated using a purified 170 kDa aminopeptidase N (APN) from Heliothis virescens brush border membranes. Aminopeptidases with molecular sizes of 110, 140 and 170 kDa were eluted from a Cry1Ac toxin affinity column using N-acetylgalactosamine. The 140 kDa aminopeptidase has a cross-reacting determinant typical of a cleaved glycosyl-phosphatidylinositol anchor. After mild base treatment to de-acylate the glycosyl-phosphatidylinositol linkage and incubation in phosphatidyl inositol phospholipase C, anti-cross-reacting determinant antibody recognized the 170 kDa protein. Kinetic binding characteristics of Cry1A toxins to purified 170 kDa APN were determined using surface plasmon resonance. Cry1Aa, Cry1Ab and Cry1Ac, but not Cry1C and Cry1E toxins recognized 170 kDa APN. Each Cry1A toxin recognized two binding sites: a high affinity site with KD ranging from 41 to 95 nM and a lower affinity site with KD in the 325 to 623 nM range. N-acetylgalactosamine inhibited Cry1Ac but not Cry1Aa and Cry1Ab binding to 170 kDa APN. When reconstituted into phospholipid vesicles, the 170 kDa APN promoted toxin-induced 86Rb+ release for Cry1A toxins, but not Cry1C toxin. Furthermore Cry1Ac, the Cry protein most toxic to H. virescens larvae, caused 86Rb+ release at lower concentrations, and to a greater extent than Cry1Aa and Cry1Ab toxins. The correlation between toxin-binding specificity and 86Rb+ release strongly suggests that the purified 170 kDa APN is the functional receptor A in the H. virescens midgut epithelial cell brush border membranes.

Acetylgalactosamine↗