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Biomedical subjects

L Shen

Publications and source records attributed to L Shen.

At least 235 records · Page 13Linked to original sources
PubMed1994

Structure and genetics of the partially duplicated gene RP located immediately upstream of the complement C4A and the C4B genes in the HLA class III region. Molecular cloning, exon-intron structure, composite retroposon, and breakpoint of gene duplication.

The correlation of many HLA-associated autoimmune and genetic diseases with the polymorphic complement C4 genes may be attributed to the presence of disease susceptibility genes in the close proximity of C4. We have cloned and characterized a pair of partially duplicated genes, RP1 and RP2, located 611 base pairs upstream of the human C4A and C4B genes, respectively. The putative RP protein, consisting of 364 amino acid residues, is basic and highly hydrophilic. There is a bipartite nuclear localization signal at residues 114-131 and therefore RP may be a nuclear protein. Northern blot analysis suggested that RP is ubiquitously expressed. The 5' region of the RP1 gene is CpG rich, which is a characteristic of housekeeping genes. The RP1 gene contains nine exons. Located in the fourth intron is a cluster of Alu elements, and a newly defined composite retroposon SVA with a SINE, multiple copies of GC-rich VNTRs and an Alu element altogether enclosed by direct terminal repeats. Members of SVA are also present in the complement C2 gene located about 20 kilobases upstream of RP1 in the HLA and in the cytochrome CYP1A1 gene. Determination of the DNA sequences for RP2 from two different HLA haplotypes revealed identical hybrid sequences which resulted from fusion of RP with the tenascin-like Gene X and truncation of the 5' regions of both genes. Cumulative data suggest that the four tandemly arranged genes RP, complement C4, steroid 21-hydroxylase (CYP21), and Gene X altogether form a modular structure, RCCX. The number of RCCX modules varies from one to three or more in the population. Absence of the truncated genes RP2 and Gene XA have been detected in genomes with single RCCX modules. Duplication of the RCCX modules probably occurred before the speciation of great apes and humans as they contain the same breakpoint region of RP and Gene X gene duplication.

Alleles↗
PubMed1994

Unaggregated serum IgA binds to neutrophil Fc alpha R at physiological concentrations and is endocytosed but cross-linking is necessary to elicit a respiratory burst.

My43 is a monoclonal antibody directed against Fc alpha Rs on monocytes that also recognizes neutrophil (PMN) Fc alpha Rs and is able to elicit a respiratory burst in purified cells. It appears to be directed against the immunoglobulin A (IgA) binding site of Fc alpha Rs or an epitope in close proximity, since IgA and My43 compete for binding to PMNs. My43 immunoblotted Fc alpha R that had been affinity purified from PMN membranes and immunoprecipitated a 50-70 kDa protein from radiolabeled PMN membranes, apparently identical to that purified on IgA-Sepharose. These results suggest the presence of a single class of Fc alpha R on PMNs. Binding of unaggregated monomeric or dimeric serum IgA to Fc alpha Rs on PMNs occurs at physiological concentrations, suggesting that in vivo Fc alpha Rs are saturated with ligand. This binding does not elicit a respiratory burst. Purified PMNs do not express surface IgA, since receptor-bound IgA is lost from the cell surface by endocytosis at room temperature although not at 4 degree C. Rapid endocytosis of receptor-bound IgA has been demonstrated by flow cytometry and confocal microscopy. Unoccupied receptor that is able to bind IgA or My43 is subsequently reexpressed. Cross-linking of surface-bound IgA using F(ab')2 anti-alpha chain antibodies triggers an oxidative burst. After internalization of the surface IgA the same F(ab')2 anti-alpha chain antibodies do not trigger the burst.

Endocytosis↗
PubMed1994

Tumor necrosis factor receptor expression in HIV-1-infected CD4+ T cells.

We investigated whether HIV-1 can regulate tumor necrosis factor receptor (TNFR) expression in SupT-1, a CD4+ T-cell line. The cells were infected with HIV-1 containing 1,000 cpm RT activity, as early as day 3 after infection and all along the culture the supernatant level of core protein p24 was > 250 pg/ml, and on days 6 and 9 after infection, p24 was found in 10% of the cells as determined by indirect immunofluorescence assay. The cells were growing without loss of viability. The study of TNFR expression was based on a microassay for measurement of binding of 125I-TNF alpha to cells, in which free and cell-bound ligand separation was performed by centrifugation through oil. Scatchard analysis of TNF alpha binding on days 6 and 9 after infection revealed a 90% increase in the expression of high-affinity membrane receptors in HIV+SupT-1 culture compared with uninfected cells (mean +/- S.D. = 501 +/- 148.5 vs. 263 +/- 77.8 receptors/cell, n = 9, P < 0.001) with no change in dissociation constants (mean +/- S.D. = 4.36 +/- 1.06 vs. 4.00 +/- 1.12 x 10(-10) M).

CD4-Positive T-Lymphocytes↗
PubMed1994

Comparison of cytotoxic properties of neonatal and adult neutrophils and monocytes and enhancement by cytokines.

We studied cytotoxic capabilities of newborn polymorphonuclear leukocytes (PMNs) and monocytes and their enhancement by cytokines and antibodies. Umbilical cord PMNs were assessed for their ability to kill various target cells spontaneously, after activation with phorbol myristate acetate, in the presence of antiserum (antibody-dependent cellular cytotoxicity), and in the presence of dually specific antibody (heteroantibody-mediated cytotoxicity). Target cells included the K562 cell line (natural killer cell target), chicken erythrocytes (CRBCs), and herpes simplex virus-infected CEM cell lines. Newborn PMNs were equivalent to adult PMNs in their cytotoxic capacity in several cytotoxicity assays. Neither adult nor newborn PMNs lyse tumor cell targets (i.e., K562 cells) spontaneously, but both lyse K562 cells following activation with phorbol myristate acetate. Both adult and newborn PMNs lyse CRBCs and herpes simplex virus-infected CEM cells in antibody-dependent cellular cytotoxicity assays, and this lysis could be enhanced by the cytokines granulocyte-macrophage colony-stimulating factor and gamma interferon. PMN heteroantibody-mediated cytotoxicity, resulting from the use of an antibody with dual specificity to CRBCs and immunoglobulin G FcRII, was greater in newborn PMNs than in adult PMNs; however, monocyte heteroantibody-mediated cytotoxicity, resulting from the use of an antibody to CRBCs and monocyte immunoglobulin G FcRI, was lower in newborn monocytes than in adult monocytes. The percentage, but not the density, of PMNs expressing FcRII was significantly reduced in newborn PMNs compared with that in adult PMNs, while the percentages and densities of FcRI expression were equivalent in newborn and adult monocytes. We conclude that the cytotoxic capability in term newborn PMNs is equivalent to that in adult PMNs, that the activity of newborn PMNs can be enhanced by antibody and/or cytokines, and that PMNs can contribute to the newborn's ability to kill virus-infected cells.

Adult↗
PubMed1994

[Effect of xiaoyu pian on new platelet aggregation defect].

The Xiaoyu pian (XYP, mainly consisted of prunus persica, Carthamus tinctorius, Glycyrrhiza uralensis, etc) was used to treat patients with new platelet aggregation defect. Patients were divided into 2 groups, the TCM group (72 cases) treated with XYP and the control group (65 cases) treated with vitamin C and P and/or adrenosem for at least 3 months. The results showed that marked effective rate was 87.5% in TCM group and 35.4% in control group (chi 2 = 39.7, P < 0.01); the recovery rate of platelet was 91.8% in the former and 10.3% in the latter (chi 2 = 71.4, P < 0.01); the recurrence rate of follow-up (6 months after treatment) was 30.8% in the former and 82.1% in the latter (chi 2 = 19.2, P < 0.01). The difference between two groups was very significant. The results suggested that XYP could regulate the hemostatic action and the platelet aggregation function. It is worthwhile to use XYP as an hemostatic clinically.

Adolescent↗
PubMed1994

[Preliminary clinical study on prevention of bone loss in postmenopausal women with kidney invigoration].

The effect of Bushen Migu Ye (BSMGY) on preventing the bone loss in postmenopausal women was observed. 43 healthy women with the menopause within 5 years were randomly divided into the treated and control groups, which were basically similar in age and menopausal time. BSMGY and Rhizoma Dioscoreae decoction was given orally in two groups. Some biochemical parameters related to bone metabolism, serum estradiol and forearm bone density were taken before and after treatment. The results showed that 5 months after BSMGY treatment, the ulnar and radial bone mineral content was higher than that of pretreatmental value (P < 0.05), while in control group this index was continually decreased. The change in bone density were also significant different (P < 0.05). It seems that BSMGY is able to prevent the bone loss in postmenopausal women. In the treated group, ratio of fasting urinary calcium and hydroxyproline to creatinine was lower than that of before treatment and the control group (P < 0.05); the concentration of serum alkaline phosphatase had no significant difference (P < 0.05). This preliminary study suggested that one of the therapeutic mechanism of BSMGY was probably due to declining of bone resorption, without affecting the bone formation in postmenopausal women.

Bone Density↗
PubMed1994

Fc alpha-receptor expression on the myelomonocytic cell line THP-1: comparison with human alveolar macrophages.

Immunoglobulin A (IgA) and alveolar macrophages are two important components of the immune system in the respiratory tract. Fc alpha-receptors (Fc alpha R) are present on neutrophils, eosinophils and a series of human mononuclear phagocytes, including monocytes, alveolar macrophages and leukaemia cell lines (U-937). In the present study, using idiotypes and anti-idiotypic antibodies, we report that THP-1 cells, a myelomonocytic cell line, constitutively express Fc alpha R and that all IgA preparations used bind the receptor. Of the stimuli used (phorbol myristate acetate, retinoic acid, calcitriol), only calcitriol can induce differentiation of THP-1 cells, as assessed by CD14 expression. The expression of Fc alpha R appears to be independent of cell differentiation, since calcitriol pretreatment has no effect on IgA-binding. Finally, My43, a monoclonal antibody recognizing the Fc alpha R on U-937 cells, does not bind to THP-1 cells or to human alveolar macrophages. In addition, preincubation of THP-1 cells or human alveolar macrophages with My43 does not diminish IgA-binding to these cells. Ribonucleic acid (RNA) encoding the Fc alpha R isolated from U-937 is expressed, although possibly at a lower level, in alveolar macrophages and THP-1 cells. In conclusion, Fc alpha R are constitutively expressed on THP-1 cells and share some characteristics with the Fc alpha R described in human alveolar macrophages. THP-1 cells, therefore, may represent a reasonable model for further investigation of the interaction of immunoglobulin A and tissue macrophages.

Base Sequence↗
PubMed1993

Sonic hedgehog, a member of a family of putative signaling molecules, is implicated in the regulation of CNS polarity.

We have identified three members of a mouse gene family related to the Drosophila segment polarity gene, hedgehog (hh). Like hh, they encode putative secreted proteins and are thus implicated in cell-cell interactions. One of these, Sonic hh (Shh), is expressed in the notochord, the floor plate, and the zone of polarizing activity, signaling centers that are thought to mediate central nervous system (CNS) and limb polarity. Ectopic expression of Shh in the mouse CNS leads to the activation of floor plate-expressed genes. These results suggest that Shh may play a role in the normal inductive interactions that pattern the ventral CNS.

Amino Acid Sequence↗
PubMed1993

Conserved T-cell receptor repertoire in simian immunodeficiency virus-infected rhesus monkeys.

Studies to assess the possibility that the HIV may encode a superantigen that plays a role in the depletion of functional CD4+ lymphocytes in the infected individual have yielded discrepant results. The problem in performing conclusive examinations of this issue may be attributed, at least in part, to the difficulty of prospectively studying individuals from before their infection until the time of profound CD4+ lymphocyte loss. To determine whether the AIDS virus deletes particular subpopulations of V beta-expressing lymphocytes, we have employed an animal model of AIDS, the simian immunodeficiency virus (SIV)-infected macaque monkey. Rhesus monkeys were experimentally infected with SIVmac and studied prospectively. A PCR-based quantitative method for assessing TCR repertoire was employed to analyze the expression of 24 V beta and 30 V alpha gene families in the monkeys. Although circulating PBL were increased in number by 3 wk after SIVmac infection, the expanded lymphocyte populations exhibited no significant perturbation in their TCR V beta repertoires. PBL obtained from monkeys before and 0.5 to 3 years after infection displayed no significant change in V beta and V alpha gene family expression. Finally, no deletion of V beta-expressing cell subpopulations could be demonstrated in purified CD4+ lymphocytes from infected monkeys. This was true even for monkeys whose blood contained less than 200 CD4+ lymphocytes/microliters. These results indicate that the TCR repertoire is conserved in SIVmac-infected rhesus monkeys and suggests that mechanisms other than superantigen-induced deletion must be responsible for CD4+ lymphocyte loss in these animals.

Animals↗
PubMed1993

Immunohistochemical mapping of angiotensin AT1 receptors in the brain.

A new approach to study angiotensin receptor distribution in the brain has been taken by developing antibodies to partial sequence of the angiotensin II (AII) type-1 receptor subtype (AT1) and demonstrating the presence of receptors with immunohistochemical staining. The antibody to a portion of the 3rd cytoplasmic loop of the AT1 receptor revealed distinctive punctate immunoreactive staining on cell bodies. The cell bodies were distributed in the forebrain in paraventricular and supraoptic nuclei, the organum vasculosum lamina terminalis, median preoptic area and subfornical organ. In the brainstem, the entire locus coeruleus was stained, together with the adjacent mesencephalic and motor nuclei of the trigeminal nerve. The auditory system including the cochlear nucleus and superior olivary nuclei were stained. In the medulla, all the structures involved in blood pressure control were stained including the nucleus of the solitary tract, the 12th nerve nuclei, the rostroventral lateral area and the nucleus ambiguous. Sites where AT2 receptors are located were not stained or staining was limited to specific area such as the medial accessory nucleus of the inferior olive. Immunocytochemical staining of AT1 receptors provides a new and more precise approach to the cellular localization of AII receptors.

Amino Acid Sequence↗
PubMed1993

Recombinant soluble IgA Fc receptor: generation, biochemical characterization, and functional analysis of the recombinant protein.

We previously described the cloning of a human myeloid cell surface receptor for the Fc region of immunoglobulin A (Fc alpha R). In the present study, a soluble version of the Fc alpha R (solFc alpha R) was generated by removing the transmembrane and cytoplasmic coding regions from full-length Fc alpha R cDNA and ligating into a mammalian expression vector. COS-7 cells transfected with the solFc alpha R plasmid secreted a protein that inhibited both immunoglobulin A (IgA) and anti-Fc alpha R monoclonal antibody (mAb) binding to Fc alpha R+ U937 cells. Furthermore, the solFc alpha R bound specifically to and could be eluted from an anti-Fc alpha R mAb-immunoaffinity column, retaining biological activity. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that the recombinant full-length Fc alpha R migrates over a molecular mass range of approximately 40-60 kd, consistent with the reported size and heterogeneity of the naturally occurring myeloid cell surface Fc alpha R. The solFc alpha R ran on SDS-PAGE as a smaller band (37-55 kd) that reduced to two bands of 23 and 25 kd following N-glycanase treatment, indicating that the Fc alpha R is a heavily glycosylated protein. The biochemical data, coupled with flow cytometry studies showing that the recombinant Fc alpha Rs bind to five different anti-Fc alpha R mAbs, clearly demonstrate that the cloned Fc alpha R corresponds directly to the major Fc alpha R species expressed on human monocytes, neutrophils, and myeloid cell lines. The generation of soluble receptor protein will permit investigations of the role of Fc alpha R in IgA-mediated immunoregulation, effector functions, and disease.

Antigens, CD↗
PubMed1993

Simian immunodeficiency virus-specific cytotoxic T lymphocytes in rhesus monkeys: characterization and vaccine induction.

An effective HIV vaccine should be capable of eliciting virus-specific cytotoxic T lymphocytes (CTL). We have characterized the cellular and molecular features of a simian immunodeficiency virus of macaques (SIVmac) gag-specific CTL response in rhesus monkeys. We have shown that SIVmac-infected rhesus monkeys expressing the major histocompatibility complex (MHC) class I molecule Mamu-A*01 develop a SIVmac gag-specific CTL response which recognizes a 9 amino acid fragment of the gag protein in association with Mamu-A*01. Moreover, this peptide/MHC class I recognition is mediated by T cell receptors (TCR) employing a predominant V beta gene family and J beta gene. Using this understanding of a SIVmac-specific CTL response, we have shown that SIVmac-specific CTL can be elicited through three novel approaches to vaccination: a recombinant viral vector, a recombinant bacterial vector and a peptide vaccine. These studies illustrate the utility of the SIV/macaque model in AIDS vaccine research.

Animals↗
PubMed1993

Role of oxygen intermediates in cytotoxicity: studies in chronic granulomatous disease.

The ability of human neutrophils to lyse various target cells was investigated using cells from normal individuals and from patients with chronic granulomatous disease (CGD) whose cells lack the ability to form reactive oxygen intermediates (ROI). Cytolysis was stimulated by phorbol myristate acetate (PMA), rabbit antiserum, and a heteroantibody that binds to both the FcRII receptor of neutrophils and to the target. The PMA-activated CGD neutrophils were deficient compared to controls in killing both tumor and chicken erythrocyte (CRBC) targets at all effector-target ratios in 18-h assays. When CRBC were sensitized with rabbit antiserum, the normal cells still killed slightly more. When killing of CRBC was mediated by the heteroantibody, however, cytotoxicity of CGD neutrophils exceeded that of normal cells. CGD mononuclear cells (MNC) killed tumor cell targets as well as or better than normal MNC. Thus, PMA-mediated cytolysis appears to depend primarily upon the ability of the cell to generate ROI whereas antibody-mediated cytotoxicity and MNC-mediated lysis of tumor cells do not require ROI formation.

Animals↗
PubMed1993

Selenium content of sheep's milk and its distribution in protein fractions.

The selenium (Se) distribution in sheep's milk is reported. Skim milk was found to contain the major part (98%) of total milk Se. The Se distribution over casein and whey protein fractions depends on the separation method used, but irrespective of these methods, skim milk Se is mainly associated with the casein fraction (> 68%). Approximately 11%, 4% and 17% Se is removed by dialysis (molecular mass cut-off 10-12 kDa) from skim milk, casein and whey respectively, indicating a major association of Se with milk proteins. This observation is confirmed through Se analysis of individual caseins and whey proteins isolated through ion-exchange chromatography and gel filtration. Se concentrations of the different isolated milk proteins show considerable variations (caseins, 304-750 ng Se/g; whey proteins, 241-806 ng Se/g).

Animals↗
PubMed1993

Selenium distribution in egg white proteins.

The present studies were undertaken to characterize selenium distribution in egg white. Ion-exchange chromatography fast protein liquid chromatography (FPLC) and flow injection atomic (absorption) spectrometry (FIAS) were used to separate egg white proteins and to determine the selenium content of different fractions. After purification, nine different proteins were identified with sodium dodecyl sulphate-polyacrylamide gel electrophoresis and 56% of the total selenium content was found to be associated with ovalbumin-1 and -2 (+/- 500 ng/g), which is the main protein in egg white. Flavoprotein was determined to be the richest selenium-containing protein (1800 ng/g). The selenium content of the other proteins (lysozyme, conalbumin, globulins and ovomucoid) ranged from 359 to 1094 ng/g.

Animals↗
PubMed1993

Evaluation of an in vitro method for the estimation of the selenium availability from cow's milk.

The present study evaluates the application of an in vitro digestion procedure for estimating the selenium (Se) availability from cow's milk. The results obtained by this in vitro method indicate that only a small portion (< 10%) of milk Se can be estimated as available. The available fraction of whole milk (4.7%) was significantly lower compared to the Se availability of skim milk (7.3%). Investigations on the methodology of the in vitro method indicate that the portion of total potentially available Se, determined as total dialysable Se, increases simultaneously with protein digestibility along with the digestion process. Therefore it is concluded that protein digestibility might largely influence the Se availability from milk.

Animals↗