Biomedical subjects

H L Cheng

Publications and source records attributed to H L Cheng.

At least 55 records · Page 3Linked to original sources

PubMed1995

The XRCC4 gene encodes a novel protein involved in DNA double-strand break repair and V(D)J recombination.

The XR-1 Chinese hamster ovary cell line is impaired in DNA double-strand break repair (DSBR) and in ability to support V(D)J recombination of transiently introduced substrates. We now show that XR-1 cells support recombination-activating gene 1- and 2-mediated initiation of V(D)J recombination within a chromosomally integrated substrate, but are highly impaired in ability to complete the process by forming coding and recognition sequence joins. On this basis, we isolated a human cDNA sequence, termed XRCC4, whose expression confers normal V(D)J recombination ability and significant restoration of DSBR activity to XR-1, clearly demonstrating that this gene product is involved in both processes. The XRCC4 gene maps to the previously identified locus on human chromosome 5, is deleted in XR-1 cells, and encodes a ubiquitously expressed product unrelated to any described protein.

Amino Acid Sequence↗

PubMed1995

Characterization of the ovine-lens plasma-membrane protein-kinase substrates.

The cAMP-dependent protein-kinase-catalyzed phosphorylation of the two major intrinsic lens fiber cell plasma membrane proteins, MP20 and MP26, is likely restricted to the inner cortical and nuclear regions of the lens in vivo. The ovine-lens-specific connexin, MP70, that has been identified as Cx50 in mice and Cx45.6 in the chick, is also a protein kinase substrate although it does not appear to be phosphorylated by a number of protein kinases including cAMP-dependent protein kinase, calmodulin-dependent protein kinase or protein kinase C. Rather, an extrinsic lens membrane fraction was isolated which contained protein kinase activity that catalyzed the phosphorylation of MP70; this protein kinase activity was cAMP-independent, Ca(2+)-independent, Mg(2+)-dependent, phosphorylated MP70 on a serine residue(s) and migrated with a molecular mass of 35 kDa on a gel filtration column. Both MP70 phosphorylation and the endogenous protein kinase activity were restricted to the lens outer cortical region. This membrane-associated protein kinase activity represents the first reported partial characterization of an endogenous lens fiber cell protein kinase activity that catalyzes the phosphorylation of a lens connexin protein. The phosphatase-induced shift in the electrophoretic mobility of MP70 is not reversed by this protein kinase, indicating that MP70 is likely phosphorylated on different residues by two or more protein kinases.

Alkaline Phosphatase↗

PubMed1995

CD3 epsilon and CD3 zeta cytoplasmic domains can independently generate signals for T cell development and function.

To determine whether CD3 epsilon and CD3 zeta proteins have unique roles in TCR-dependent functions, chimeric genes encoding the extracellular and transmembrane domains of the human IL-2 receptor alpha chain (Tac) fused to a cytoplasmic domain of either the CD3 epsilon or CD3 zeta chain were introduced as transgenes into both normal and RAG2-deficient (RAG2-/-) mice. Developmental arrest of T lineage cells at the CD4, CD8 double-negative stage in the transgenic RAG2-/- thymus was released to the CD4, CD8 double-positive (DP) stage by in vivo cross-linking of TT epsilon or TT zeta with anti-Tac antibody. In TT epsilon + or TT zeta +, RAG2-/- mice, in vitro cross-linking of TT epsilon and TT zeta induced DP thymocyte cell death and proliferation of mature single-positive T cells. Overall, no qualitative differences were observed between TT epsilon- and TT zeta-mediated functions, suggesting that different CD3 components deliver qualitatively similar signals in inducing TCR-dependent functions.

Animals↗

PubMed1995

Effects of transforming growth factor-beta on bone marrow macrophage Ia expression induced by cytokines.

The initiation of the immune response is regulated, in part, by the effect of cytokines on the level of expression of major histocompatibility complex (MHC) class II antigens on antigen-presenting cells (APC). The expression of class II antigens on B cell and macrophage APC is induced by IFN-gamma and IL-4, and GM-CSF induces class II expression on macrophages (M phi). Our results show that transforming growth factor-beta (TGF-beta) inhibits IL-4- and GM-CSF-induced Ia gene expression on bone marrow macrophages but enhances IFN-gamma-induced gene expression. Nuclear run-on experiments demonstrated that the inhibitory effects of TGF-beta on GM-CSF- and IL-4-induced Ia antigen expression were primarily posttranscriptional and augmentation of IFN-gamma by TGF-beta was largely transcriptionally regulated.

Animals↗

PubMed1994

A class switch control region at the 3' end of the immunoglobulin heavy chain locus.

We replaced the IgH 3' enhancer (3'EH) region with a neomycin resistance gene in ES cells and generated chimeric mice in which all mature lymphocytes were either heterozygous (3'EH+/-) or homozygous (3'EH-/-) for the mutation. In vitro activated 3'EH-/- B cells responded similarly to 3'EH+/- B cells with respect to proliferation and secretion of IgM and IgG1 but were specifically deficient in IgG2a, IgG2b, IgG3, and IgE secretion. These isotype deficiencies correlated with a deficiency in accumulation of transcripts from and class switching to affected CH genes. In vivo, chimeric mice containing only 3'EH-/- B cells were deficient in serum IgG2a and IgG3. We propose that the 3'EH-/- mutation disrupts the activity of a regulatory region that influences heavy chain class switching to several different CH genes that lie as far as 100 kb upstream of the mutation.

Animals↗

PubMed1994

A DNA repair defect in Chinese hamster ovary cells affects V(D)J recombination similarly to the murine scid mutation.

Lymphocyte antigen receptor variable regions are encoded by gene segments that are assembled by the site-specific variable (diversity) joining (V(D)J) recombination process. We have assayed the V-3 Chinese hamster ovary cell line, which has a double-strand DNA break repair (dsbr) defect, for the ability to carry out V(D)J recombination following transfection of constructs that encode the RAG-1 and RAG-2 proteins necessary to confer V(D)J recombination activity to non-lymphoid cells. The V-3 cells had substantially impaired ability to undergo V(D)J recombination of transiently introduced test substrates. Although these cells can initiate V(D)J recombination by introducing endonucleolytic scissions at the junctions of V(D)J recombination signal sequences and the flanking coding sequences, they have a greatly impaired ability to rejoin the coding sequences. Detailed characterization of attempted coding joins recovered from these cells indicated that the V(D)J recombination defect in V-3 is similar in phenotype to the murine severe combined immunodeficient (scid) defect and quite distinct from that found in other Chinese hamster ovary dsbr mutant cell lines. Somatic cell complementation analyses between homozygous scid mutant fibroblasts and V-3 cells confirmed that these mutations fall into the same genetic complementation group.

Animals↗

PubMed1994

Near-diploid transitional cell carcinoma: a preliminary report.

DNA ploidy analysis has been accepted as an important prognostic factor for patients with transitional cell carcinoma (TCC). However, there was few information dealing with the clinical relevance of slightly aberrant DNA content by flow cytometry (FCM). Here we present five cases of near-diploid (ND) tumours, with DNA index (DI) varying from 0.92 to 1.14, obtained from a prospective study of fifty-one cases (9.8%). The frequency of ND tumours showed a tendency to decrease with increasing tumour stage. Higher fraction of tumour proliferation, defined by Ki-67 index, showed a steady increment from 3.4 to 23.5% with occurrence of gross chromosomal changes. In contrast, the expression of epidermal growth factor receptor (EGFR) decreased from 48.3 to 35.3% for diploid (n = 29) through aneuploid (n = 17) tumours. All three ND bladder cancers had recurrence of one to three times with median follow-up of 36 months. The incidences of tumour recurrence (60%) and cancer death (20%) in ND tumours were intermediate between the aneuploid and diploid TCCs. But, flow DNA analysis of paraffin-embedded ND tumours revealed wide and symmetrical G0/G1 peak with DI varying from 5.6 to 13.0. Our limited experience suggests the necessity of special treatment for G0/G1 peaks having CV values greater than 5.5% from paraffin-embedded urothelial carcinomas.

Aneuploidy↗

PubMed1994

Anions that potentiate excitation-contraction coupling may mimic effect of phosphate on Ca2+ release channel.

Perchlorate is one of a group of inorganic anions that potentiate excitation-contraction coupling in skeletal muscle. We have compared the effect of perchlorate on the sarcoplasmic reticulum (SR) Ca(2+)-release channel with the effect of inorganic phosphate (Pi), an anion which accumulates in skeletal muscle during exercise. Perchlorate and Pi (10-20 mM) stimulated Ca2+ release from SR vesicles 2- to 3-fold, respectively, and increased ryanodine binding to SR vesicles 1.5-fold. Stimulation of SR Ca(2+)-release channel activity by both perchlorate and Pi was maximal in the presence of micromolar Ca2+ and was associated with an increased affinity of the channel for ryanodine. Other anions known to potentiate muscle contraction (thiocyanate, iodide, and nitrate) also stimulated skeletal muscle SR Ca2+ release and ryanodine binding, as did the Pi analogue vanadate. However, none of the inorganic anions examined altered ryanodine binding to cardiac muscle SR. These results confirm that the SR Ca(2+)-release channel may be a primary site at which perchlorate and other potentiating anions affect skeletal muscle excitation-contraction coupling. In addition, these results demonstrate that the action of these anions on the SR Ca(2+)-release channel resembles that of Pi, a potential endogenous regulator of this channel.

Animals↗

PubMed1994

Urinary cytodiagnosis: can it have a different prognostic implication than a diagnostic test?

In order to assess the clinical implications of the cytology of voided urine we analyzed 65 patients among 147 cases of transitional cell carcinoma (TCC) in relation to the cytohistologic correlation and prognostic significance. Urinary cytology detected 42.6% of bladder tumors, 59% of renal pelvic tumors, and 35.3% of ureteral carcinomas. None of the 3 cases of grade-1 upper urinary tract tumors was detected by preoperative urinary cytology. Tumors with positive cytology were associated with epidermal growth factor receptor expression (p = 0.0009) and a higher fraction of tumor proliferation as defined by Ki-67 immunohistochemistry (p = 0.0038). Anaplastic tumor cells in urine correlated fairly well with muscular invasion (p = 0.018) and the DNA aneuploidy of the tumor (p = 0.0038). Tumors with muscular invasion were more likely to be detected by cytologic examination (p = 0.013). In urinary bladder carcinoma (n = 107), patients with positive cytology had a higher incidence of tumor recurrence (p = 0.004), and had an unfavorable prognosis (p = 0.0001) with a median follow-up of 46 months. In Ta-T1 tumors (n = 87), urinary cytology had prognostic value in terms of risk of recurrence (p = 0.0001), and poor patient outcome (p = 0.0001). Our data suggest that urinary cytology can offer important biological information on TCC and may be used as a simple and effective short-term prognostic indicator.

Adult↗

PubMed1993

Distinct IL-4 response mechanisms of the MHC gene A alpha in different mouse B cell lines.

Interleukin-4 (IL-4) is a multipotent cytokine which stimulates proliferation of B and T lymphocytes, induces B lymphocyte expression of major histocompatibility complex (MHC) class II molecules and Fc epsilon R II (CD23) molecules, and promotes immunoglobulin class switching to IgE and IgG1. The mechanisms by which IL-4 induces these changes are unclear. To study the basis for heterogeneity in induction of class II MHC proteins observed in splenic B cells, three mouse B cell lines were treated with IL-4, and the response of MHC class II A alpha mRNA was analyzed. Each of the three cell lines responded with a distinctive profile. In one line, 70Z/3, A alpha mRNA was induced greater than 10 fold by 65 hr of IL-4 stimulation. Additional studies showed that A alpha mRNA was stabilized by IL-4 treatment of 70Z/3 cells, and that changes in gene transcription accounted for little of the increase in mRNA levels. A second line, WEHI.231, was shown to increase A alpha mRNA levels 4 fold after 48 hr of IL-4 treatment. In contrast to 70Z/3, when A alpha mRNA stability in the IL-4 treated WEHI.231 cells was compared to untreated cells, no difference was observed, IL-4 treatment induced A alpha transcription. The third cell line, M12.4.1, expressed high basal levels of A alpha, and these levels increased only slightly following IL-4 stimulation. The small increase correlated with a comparable transcriptional response. These data shown that the nature of the A alpha gene response to IL-4 differs among B cell lines. This heterogeneity of response is consistent with responses in total splenic B cells, and with the existence of functionally distinct subpopulations of B cells.

Animals↗

PubMed1993

TGF-beta 2 gene and protein expression in maternal and fetal tissues at various stages of murine development.

The transforming growth factor beta family of peptides have diverse actions on the reproductive tracts of primates and rodents. In this study we report the expression of high levels of mRNA of one member of this superfamily, TGF-beta 2, in the pregnant mouse uterus. Using Northern blot analysis and in situ hybridization techniques, we have examined the pattern of expression of TGF-beta 1, TGF-beta 2 and colony-stimulating factor (CSF-1) in mouse maternal and fetal tissue at specific days of gestation. We report here that TGF-beta 2 is synthesized primarily in maternal decidual and uterine epithelial tissues. We observed a shift in the major site of synthesis from decidua to uterus between days 8.5 and 10.5 of gestation. These data demonstrate that the expression of TGF-beta 2 is differentially regulated in the decidua and uterine epithelial cells at various times during gestation. Small amounts of TGF-beta 2 mRNAs were detected in the fetus, and none was detected in placenta, yolk sac, or amniotic membrane. The uterus is likely the major site of synthesis of the TGF-beta 2 found in mouse amniotic fluid. TGF-beta 1 mRNAs are expressed in the uterus at markedly lower levels when compared to TGF-beta 2 mRNAs in both the decidua and uterus. Our results suggest that there is a unique regulation of TGF-beta 2 during pregnancy which may depend on pregnancy hormone(s) and differentiates it from the other mammalian isoforms of the TGF-beta s. TGF-beta 2 may play an important, albeit unknown, role at the maternal/fetal interface.

Amniotic Fluid↗

PubMed1990

A transforming growth factor beta 2 (TGF-beta 2)-like immunosuppressive factor in amniotic fluid and localization of TGF-beta 2 mRNA in the pregnant uterus.

This report describes a murine amniotic fluid (MAF) immunosuppressive factor that has properties similar to transforming growth factor beta (TGF-beta). The MAF factor exhibits TGF-beta-like activity in stimulating soft agar colony formation by AKR-2B cells and inhibiting thymidine uptake by Mv1Lu cells. We demonstrate that both the immunosuppressive and TGF-beta-like activities of the MAF factor are completely neutralized by anti-TGF-beta 2-specific antibodies and not by anti-TGF-beta 1-specific antisera. The immunosuppressive factor in MAF is novel in that it appears to be identical or very closely related to TGF-beta 2 and is active in its native state. This active and anti-TGF-beta 2-neutralizable factor chromatographs at approximately 70 kD on Sephadex at neutral pH and appears to be able to complex with alpha-fetoprotein in native amniotic fluid. Chromatography of native MAF under acidic conditions demonstrates a lower molecular mass protein that chromatographs on BioGel in the same position as the mature 25-kD TGF-beta. This protein has the biological properties of TGF-beta and is immunosuppressive. Both of these activities are neutralizable with anti-TGF-beta 2 but not with anti-TGF-beta 1 or other antisera. By Northern analysis, we find high levels of TGF-beta 2 mRNA (with little or no TGF-beta 1) in the pregnant uterus that peak around day 15 of gestation and then fall rapidly by day 19 as birth approaches. The TGF-beta 2-like factor could possibly play a role in maternal immunity, in the retention of the fetal allograft, as well as in regulating fetal and neonatal immunological competence.

Amniotic Fluid↗

PubMed1990

Quality control in the flow cytometric measurement of T-lymphocyte subsets: the multicenter AIDS cohort study experience. The Multicenter AIDS Cohort Study Group.

Since 1984, the Multicenter AIDS Cohort Study (MACS) has utilized four flow cytometry laboratories to measure T-lymphocyte subset levels semiannually in a large cohort of homosexual men. This report summarizes the steps taken in the MACS laboratories to attain comparability of lymphocyte subset determinations across the centers and over time. Identical flow cytometers, monoclonal antibodies, and analytic procedures have been used, and over a period of time, the procedure for sample preparation was also standardized. Interlaboratory proficiency testing utilizing identical specimens analyzed in the four laboratories was performed to evaluate the comparability of the data among the laboratories. Our results verify that such testing can identify technical bias in flow cytometric evaluations performed at different laboratories. Temporal laboratory consistency in flow cytometric measurements was evaluated using data from each site's HIV-seronegative homosexual reference group. Both sequential 95% confidence intervals (mean +/- 2 x SEM) and the within-person standard deviations of the immune measurements were considered. Significant variation in CD3, CD4, and CD8 lymphocyte subset percentages over time in the seronegative reference population was observed. Our observations indicate that the lymphocyte subset values of this seronegative group should be used to adjust those obtained on the seropositive study participants during a particular time period, thereby allowing improved discrimination of the effects of HIV on T cells in infected individuals. The data presented are of use for designing epidemiologic and intervention studies in HIV-1-infected individuals, especially for calculating sample sizes. The methods we have used to assess the quality of data in the MACS have general application to quality control programs in flow cytometry laboratories. In particular, comparison of sequential confidence intervals and within-person standard deviations for lymphocyte subset determinations on control populations are essential to a comprehensive proficiency testing program because they permit assessment of consistency within a laboratory over time.

Acquired Immunodeficiency Syndrome↗

PubMed1990

Assessing the quality of life--a study in newly-diagnosed breast cancer patients.

Quality of life (QL) assessment is an increasingly important component of clinical research, especially with cancer patients. The literature strongly supports the view that QL should be assessed by the patient rather than the clinician. While clinical parameters such as performance status or toxicity ratings may bear some relationship to QL, they are not a substitute for its measurement. In spite of these observations, clinicians have been reluctant to accept the need for patient-rated measures of QL. In this paper, data from a sample of 109 newly-diagnosed breast cancer patients were used to examine the relationship between expert-rated measures and a patient-rated measure of QL; to determine whether the Cancer Rehabilitation Evaluation System (CARES), an instrument for assessing the rehabilitation needs of cancer patients, is a measure of QL; to explore whether there are any medical, social or demographic variables which the clinician can use to predict how patients assess their QL; and to determine which variables (expert-rated scales, medical, social or demographic variables, or rehabilitation needs) have the most effect on how patients evaluate their QL. In this sample, patient ratings of QL were widely distributed and were only moderately correlated with the expert-rated Karnofsky Performance Status (r = 0.53) and Global Adjustment to Illness Scale (r = 0.59). In addition, there were no significant correlations between important clinical variables (axillary node status, type of surgery, receipt of chemotherapy) and patient-rated QL. Among the clinical variables and instruments studied, the Global CARES score demonstrated the best correlation (r = -0.74) with the patient-rated assessment of QL. A stepwise multiple linear regression procedure was performed with QL as the dependent variable in order to identify which factors accounted for the most variance in patient assessment of QL. The potential predictor variables used in this procedure were chosen from among those that would be available to a clinician. The Global CARES score was the best single predictor of QL, accounting for 55% of the variance, followed by Karnofsky Performance Status, the Medical Interaction and Sexual summary scales of the CARES, and the patient's educational status. Data from the CARES provided additional descriptive information about the type and frequency of rehabilitation problems experienced by these patients in relation to their ratings of QL.(ABSTRACT TRUNCATED AT 400 WORDS)

Activities of Daily Living↗

PubMed1988

Structural basis of stimulatory anti-idiotypic antibodies.

In order to design and produce effective vaccines based upon the idiotype network hypothesis of Jerne, a thorough understanding of the biological and structural aspects underlying the stimulating activities of anti-idiotypic antibodies is needed. Here we determined the nucleotide sequence of the variable heavy and light chain regions of two monoclonal anti-idiotypic antibodies which induce different anti-phosphorylcholine responses. The nucleotide sequences of the variable domains of two monoclonal anti-TEPC 15 (T15) antibodies (F6-3 and 4C11) were determined by the primer extension and Maxam-Gilbert techniques. The nucleotide sequence data show that 4C11 and F6-3 have homologous VH segments and JH segments, but different D regions. The VH segments of both clones belongs to the J558 VH family. Most of the differences among the VH segments are located in CDR2. The VK segments of 4C11 and F6-3 are homologous to the VK gene group 4 and group 8, respectively. Comparison of the sequences of 4C11 and F6-3 with other published anti-idiotype antibodies shows that there is no preferential utilization of immunoglobulin genes. An analysis of the distribution of charged residues and hydropathic comparison studies were used to interpret the sequence of 4C11 in terms of the biological mimicry of antigenic stimulation.

Amino Acid Sequence↗

PubMed1987

Early effects of HIV on CD4 lymphocytes in vivo.

Low circulating CD4 cell numbers and CD4 cell dysfunction are distinguishing features of HIV-mediated disease. The current study delineates the in vivo effects of HIV on distinct functional subsets of CD4 cells in homosexually active men who have been infected with HIV for different lengths of time, and examines the capacity of lymphocytes from these men to proliferate in vitro in response to soluble antigen. Although peripherial blood mononuclear cells from most acquired immune deficiency syndrome (AIDS) patients did not proliferate in response to either tetanus toxoid or Candida albicans, cells from most HIV seropositive men without AIDS, many of whom had been infected for more than 18 mo, responded normally to both. Non-responsiveness in HIV-infected men without AIDS was a late event and was associated with longer duration of infection, lower CD4 cell numbers, and subsequent development of AIDS. A defect in this response was observed in only one of 19 HIV seropositive men whose CD4 levels were greater than 300/mm3, but in eight of 10 with levels less than 300/mm3. The defect could not be attributed to a selective depletion of defined CD4 subpopulations that respond to soluble antigen. Dual-color immunofluorescent flow cytometry indicated that 4B4+, 2H4-, and HB-11- CD4 cells were not lost at a faster rate than other CD4 subsets.

Acquired Immunodeficiency Syndrome↗

PubMed1987

Idiotypic self binding of a dominant germline idiotype (T15). Autobody activity is affected by antibody valency.

We have previously described (1-3) an IgM antibody that binds to PC, expresses the T15 idiotype, and binds also to itself or T15 if insolubilized. Because of the simultaneous presence of complementary idiotopes and paratopes this type of antibody has been termed autobody. The self binding involves the antigen-binding site because the F(ab')2 fragment of T15, PC, and no other haptens inhibit the self binding. DNA sequence analysis of 11E7-1 using primer extension cDNA sequencing showed that the variable sequences of H and L chains of 11E7-1 are identical to the germline sequence of the prototype T15 idiotype. Furthermore, monomeric and dimeric T15 IgA were shown to bind to insolubilized T15 and other T15+ antibodies including 11E7-1. Thus, the self-binding activity is an inherent property of the T15 germline sequence. The self binding is highly dependent on the polymeric state of the binding antibody since the IgM pentamer of 11E7-1 is about three fold more effective than the T15 dimer and 50 times more than the T15 monomer. These data suggest that the self-binding activity of a germline-encoded idiotype may play an important role in the biology of its expression, and more specifically, may be responsible for the establishment of its dominant expression.

Amino Acid Sequence↗

PubMed1987

Selective alterations in immunoregulatory lymphocyte subsets in early HIV (human T-lymphotropic virus type III/lymphadenopathy-associated virus) infection.

In order to characterize the effects of HIV (human T-lymphotropic virus type III/lymphadenopathy-associated virus) on the immune system, Leu8- and Leu8+ subsets of CD4 and CD8 cells were studied in seropositive homosexually active men without acquired immune deficiency syndrome (AIDS). Controls included both heterosexual men and HIV-seronegative homosexually active men. The decrease in CD4 levels, observed in HIV-seropositive men who were asymptomatic, as well as in those who had persistent generalized lymphadenopathy or constitutional symptoms of HIV infection, occurred proportionally in both the Leu8- and the Leu8+ CD4 subsets. This observation, that HIV infection does not selectively diminish either subset of CD4 cells, indicates that the selective loss of T cell-mediated functions which accompanies the development of AIDS is not related to preferential loss of the Leu8+ CD4 subset. Among CD8 cells, however, HIV infection resulted in a threefold elevation in the number of Leu8- CD8 cells, while the number of Leu8+ CD8 cells remained constant. The increase in Leu8- CD8 cells was present in recent seroconverters, persistently seropositive men, and patients with AIDS. We propose that the increase in Leu8- CD8 cells represents an HIV-specific cytotoxic T-cell response. These cells may operate by killing infected CD4 cells, thereby partially controlling viral infection while simultaneously contributing to the destruction of the immune system.

Acquired Immunodeficiency Syndrome↗