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Biomedical subjects

G Cheng

Publications and source records attributed to G Cheng.

At least 235 records · Page 13Linked to original sources
PubMed1991

Lipoprotein receptor activity of peritoneal macrophages from insulin-deficient mice.

Binding, uptake and degradation of 125I-labeled normal very low density lipoprotein (125I-n-VLDL) from normal swine plasma and 125I-labeled beta-migrating VLDL (125I-beta-VLDL) from hypercholesterolemic rabbit plasma by peritoneal macrophages of mice rendered insulin-deficient by streptozotocin (250 mg/kg) were studied. It was found that the amount of binding, uptake and degradation of 125I-n-VLDL by macrophages from the diabetic mice was 2-fold or 2.5-fold higher than by macrophages from normal mice, resulting from an increase in the binding capacity of VLDL receptors on the macrophages from the insulin-deficient rodents. In contrast, the binding, uptake and degradation of 125I-beta-VLDL by macrophages from diabetic mice were reduced to only about 45% of normal levels because of a decrease in the number and affinity of the receptors for beta-VLDL. These experimental results indicate that n-VLDL is more important than beta-VLDL in the pathogenesis of atherosclerosis in insulin-dependent diabetes.

Animals↗
PubMed1990

Molecular characterization of beta-thalassaemia in 174 Greek patients with thalassaemia major.

The mutations producing beta-thalassaemia in 174 Greek patients with thalassaemia major were investigated by dot-blot hybridization of oligonucleotide probes to genomic DNA amplified by the polymerase chain reaction procedure, by direct sequencing of amplified DNA, and by gene mapping. beta-thalassaemia in Greeks was found to be very heterogeneous at the molecular level as 17 different mutations were observed: 86.6% of the beta-thalassaemic genes, however, could be identified with five probes: IVS-I-110 (G----A) (42.5%), codon 39 (C----T) (17%), IVS-I-1 (G----A) (13.2%), IVS-I-6 (T----C) (7.2%) and IVS-II-745 (C----G) (6.9%). Several mutations which had not previously been reported in the Greek population and which occurred at an incidence of 2% or lower were observed in this study. The information obtained will facilitate the prenatal diagnosis of beta-thalassaemia in Greece.

Adolescent↗
PubMed1989

[The role of lipoxygenase and cyclooxygenase metabolites in acute hypoxic pulmonary vasoconstriction in piglets].

The role of lipoxygenase and cyclooxygenase metabolites in acute hypoxic pulmonary vasoconstriction (HPV) was studied in piglets. It has been found that acute alveolar hypoxia induced remarkable pulmonary vasoconstriction, associated with an increase in cardiac output. The hypoxic pulmonary vasoconstriction response was insignificantly attenuated after infusion of DEC. Indomethacin potentiated markedly the increase in pulmonary artery pressure and pulmonary vascular resistance and thus augmented HPV. It is inferred that hypoxic pulmonary vasoconstriction in piglet may be mediated by other important mediators in addition to leukotrienes, but modulated by prostaglandins to prevent an excessive rise in pulmonary artery pressure.

Animals↗
PubMed1986

Accessory cells in immune suppression. III. Evidence for two distinct accessory cell-dependent mechanisms of T lymphocyte-mediated suppression.

Suppression of antibody secretion by the 2,4,6-trinitrophenol (TNP)-binding BALB/c myeloma, MOPC 315, by idiotype- and hapten-reactive suppressor T cells is mediated by secreted factors (TsF) and requires the presence of accessory cells (AC). Idiotype-specific TsF functions only in the presence of Ia+ AC and is completely idiotype specific. Moreover, no suppression is observed when myeloma targets and AC are separated by cell-impermeable membranes, indicating that the role of AC may be to bind, focus, and/or present TsF to the myeloma cells. In contrast, TNP-specific TsF inhibits myeloma function in the presence of TNP-protein and activated macrophages that are not Ia+. This form of suppression is nonspecific at the effector stage; i.e., anti-TNP TsF inhibits a non-TNP binding cell line, TEPC 15, as long as TNP-protein and activated macrophages are present. Moreover, suppression occurs even when myeloma targets and AC are separated by cell-impermeable membranes. These results are consistent with the view that hapten-reactive TsF binds to antigen on the surface of macrophages and induces these cells to secrete nonspecific immunosuppressive molecules. Thus, different types of AC may play fundamentally different roles in TsF-mediated suppression; they may either bind and present TsF to targets (as in the case of idiotype-specific TsF) or secrete nonspecific immunosuppressants as a consequence of a TsF-antigen interaction (hapten-specific TsF). Autonomous, suppressible targets provide valuable experimental systems for analyzing the cellular interactions in T cell-mediated suppression.

Animals↗
PubMed1985

A methodological basis for SEM autoradiography: biosynthesis and radioligand binding.

A method is described for scanning electron microscope (SEM) autoradiography whereby preservation of high resolution cell surface details is retained together with degelatination of the emulsion without gross loss or redistribution of silver grains. This method should provide a convenient medium-sized marker for SEM (using secondary, backscattered electron and X-ray imaging) topographic studies of biosynthesized molecules, and of cell surface receptors and antigens, using indirect or direct labelling procedures with radio-labelled ligands.

Autoradiography↗
PubMed1985

Multiple myeloma with initial presentation in the jaw: a clinical-pathologic discussion.

A 39-year-old white female presented with jaw pain initially interpreted as a manifestation of an odontogenic infection. Mandibular radiographs revealed lytic lesions suggesting a diagnosis of myeloma, which was subsequently confirmed by abnormalities in serum and urinary proteins and in bone marrow. Chemotherapy produced a transient response, but eventual relapse with extramedullary plasmacytomas and plasma cell leukemia led to death. The clinicopathologic implications of this case are presented and discussed.

Adult↗
PubMedDate not supplied

Vitamin B12 deficiency--need for a new guideline.

OBJECTIVES: Many patients with vitamin B12 deficiency do not have anemia or macrocytosis, but the prevalence of B12 deficiency in patients without macrocytosis is not known. METHODS: We investigated the prevalence of B12 deficiency among patients with normocytosis and microcytosis and recommended a screening strategy. All patients (n = 3714) with serum B12 measured at the Prince of Wales Hospital in 1996 were reviewed. The prevalence of serum B12 less than 140 pmol/L was determined for the following patient subgroups: younger than 70 y, older than 70 y, anemic, non-anemic, macrocytic, normocytic, microcytic, documented iron deficiency, and documented thalassemia. RESULTS: The prevalence of B12 deficiency (<140 pmol/L) ranged from 4.8% to 9.8% among the different subgroups. CONCLUSIONS: Whatever screening criteria were used, a significant number of B12-deficient patients will be missed. Therefore, there may be a case for universal vitamin B12 screening.

Age Factors↗
PubMedDate not supplied

Role of alpha- and beta-calcitonin gene-related peptide in postoperative small bowel ileus.

Ablation of a-calcitonin gene-related polypeptide (CGRP) containing neurons with the afferent neurotoxin capsaicin improves postoperative foregut transit in a rodent model. Similarly, administration of a selective alpha-CGRP antibody or hCGRP((8-37)), a CGRP receptor antagonist, improves postoperative gastric emptying. Unlike the stomach, which contains only alpha-CGRP, the small bowel additionally contains beta-CGRP. The role of the latter in postoperative small bowel transit is unknown. The purpose of this study was to evaluate the effect of an alpha-CGRP antibody and hCGRP((8-37)) on postoperative small bowel transit. Male Sprague-Dawley rats underwent placement of duodenal catheters and were randomly assigned to 1 of 11 groups. Four groups were pretreated with 1% capsaicin. One week later, all animals underwent standardized laparotomy following administration of a control antibody or the alpha-CGRP mono-clonal antibody, or during infusion of hCGRP((8-37)) at varying doses. Small bowel transit was measured 25 minutes postoperatively. The alpha-CGRP antibody sped postoperative transit when given alone or in combination with capsaicin. In contrast, animals treated with hCGRP((8-37)) showed no significant improvement in postoperative transit, and the beneficial effect of capsaicin was blocked. Unlike their similar effects on postoperative gastric emptying, we found that hCGRP((8-37)) and the alpha-CGRP antibody had differing effects on postoperative small bowel transit. The reason for this is unknown but may be related to their differing specificities for alpha- and beta-CGRP.

Animals↗
PubMedDate not supplied

The I-antigens of Ichthyophthirius multifiliis are GPI-anchored proteins.

The parasitic ciliate Ichthyophthirius multifiliis has abundant surface membrane proteins (i-antigens) that when clustered, trigger rapid, premature exit from the host. Similar antigens are present in free-living ciliates and are GPI-anchored in both Paramecium and Tetrahymena. Although transmembrane signalling through GPI-anchored proteins has been well-documented in metazoan cells, comparable phenomena have yet to be described in protists. Since premature exit of Ichthyophthirius is likely to involve a transmembrane signalling event, we sought to determine whether i-antigens are GPI-anchored in these cells as well. Based on their solubility properties in Triton X-114, the i-antigens of Ichthyophthirius are amphiphilic in nature and partition with the detergent phase. Nevertheless, following treatment of detergent lysates with phospholipase C, the same proteins become hydrophilic. Concomitantly, they are recognized by antibodies against a cross-reacting determinant exposed on virtually all GPI-anchored proteins following cleavage with phospholipase C. Finally, when expressed in recombinant form in Tetrahymena thermophila, full-length i-antigens are restricted to the membrane, while those lacking hydrophobic C-termini are secreted from the cell. Taken together, these observations argue strongly that the i-antigens of Ichthyophthirius multifiliis are, in fact, GPI-anchored proteins.

Amino Acid Sequence↗
PubMedDate not supplied

Yuehchukene, a bis-indole alkaloid, and cyclophosphamide are active in breast cancer in vitro.

Yuehchukene (YCK) is a novel bis-indole alkaloid with weak estrogenic activity. Biochemical studies showed that YCK could attenuate estrogenic action. In this study, the response of MCF-7, an estrogen-receptor-positive breast cancer cell line, under different combinations of estradiol, cyclophosphamide and YCK, was tested. From the dose-response curve, we discovered that 10(-2) M cyclophosphamide, even in its so-called 'bio-inert' form, could inhibit MCF-7 cell growth. However, the cytotoxic effect of cyclophosphamide was lost by reducing its concentration to approximately 1 x 10(-3) M. On the other hand, a low concentration ( approximately 10(-8)-10(-9) M) of YCK was found to potentiate the cytotoxic effect of cyclophosphamide on the MCF-7 cell line. Such an effect was absent in the estrogen-receptor-negative cell line MDA-MB-231. These findings, together with the dual role of a mixed estrogen and anti-estrogen effect, suggested that YCK and cyclophosphamide can be a potential combination in chemo-hormonal therapy for breast cancer.

Alkaloids↗