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Biomedical subjects

L Cheng

Publications and source records attributed to L Cheng.

At least 55 records · Page 3Linked to original sources
PubMed1989

Desensitization to parathyroid hormone in renal cells from aged rats is associated with alterations in G-protein activity.

Parathyroid hormone (PTH)-stimulated Na+/Ca2+ exchange activity, but not forskolin-sensitive Na+-dependent Ca2+ efflux, was blunted in renal cortical cells from aged rats. PTH-sensitive adenylate cyclase activity in renal membranes from senescent rats also declined, but forskolin-stimulated activity did not change. In addition, cholera toxin- and pertussis toxin-stimulated Na+-dependent Ca2+ efflux and cAMP formation were blunted in cells from aged animals. Further, cells from aged rats had decreased Gs-alpha and Gi-alpha proteins, as detected by ADP-ribosylation. These findings would be consistent with the proposal of an age-associated heterologous desensitization that involved the G-proteins. Serum concentrations of iPTH were increased in the old rat, suggesting that the desensitization to PTH in the aging rat represented an adaptive response to prolonged stimulation by the hormone. This hypothesis was supported by the findings that the attenuated PTH-sensitive Na+/Ca2+ exchange activity, cAMP formation, and adenylate cyclase activity in cells from old rats could be reversed by parathyroidectomy. The decreased label in cholera toxin-catalyzed ADP-ribosylated Gs-alpha and pertussis toxin catalyzed ADP-ribosylated Gi-alpha found in cells from aged rats was also largely negated by the surgery. In conclusion, the results suggest that the age-related blunting in the responses of renal cells to PTH was associated with a deficit in G-protein function and that this alteration could be reversed by removal of the parathyroid gland.

Adenosine Diphosphate Ribose↗
PubMed1989

An investigation of the polymerization of orthodontic adhesives by the transillumination of tooth tissue.

Prepared samples of light-activated composite were cured by transillumination of tooth tissue in healthy volunteers. Positioning of the samples and the direction of illumination was designed to simulate curing during direct bonding. The effectiveness of curing was investigated by determination of surface microhardness. The degree of polymerization of the specimens cured by transillumination was found to be reduced compared to the control samples cured by direct exposure to the light source.

Adult↗
PubMed1989

DNA ploidy analysis of cervical condyloma and intraepithelial neoplasia in specimens obtained by punch biopsy.

This study analyzed the feasibility of, and the strategy for, DNA ploidy analysis of cervical condyloma and intraepithelial neoplasia by a computerized digital imaging system. Paraffin-embedded tissue provided satisfactory single-cell preparations for DNA ploidy analysis after enzyme digestion and additional procedures. Negative endocervical curettings and normal squamous mucosa were used as internal diploid controls. With suitable controls, 21 (81%) of the 26 aneuploid lesions were identified as such in the single-cell preparations. The remaining five lesions (not recognized as aneuploid in the single-cell preparations) had ploidy levels between 2.08n and 2.30n and required DNA measurements on 12-microns sections. Criteria for these DNA measurements were defined: specimens intended for DNA ploidy analysis should contain abnormal epithelium of at least 3 mm to 4 mm in greatest dimension and should be accompanied by diploid controls, such as endocervical curettings or normal ectocervical squamous mucosa. With a combination of single-cell preparations and 12-microns tissue sections, it was possible to accurately determine the DNA ploidy patterns of the cervical lesion specimens obtained by punch biopsies. Available evidence suggests that ploidy analysis can provide useful diagnostic and prognostic information.

Biopsy↗
PubMed1988

Alpha-2-adrenergic modulation of the parathyroid hormone-inhibition of phosphate uptake in cultured renal (OK) cells.

Parathyroid hormone enhances the formation of cAMP and decreases the Na+-dependent uptake of phosphate in cultured renal cells derived from the American opossum (OK cells). Epinephrine, acting as an alpha 2-adrenergic agonist, inhibits the PTH-induced synthesis of cAMP by a pertussis toxin-sensitive mechanism and blunts the inhibition of phosphate transport by PTH. Na+-dependent alpha-methylglucoside and Na+ uptakes by the cells are unaffected by PTH and epinephrine. These findings suggest that alpha 2-adrenergic agonists may selectively modulate PTH-sensitive phosphate transport in the renal proximal tubule.

Animals↗
PubMed1988

Malondialdehyde-altered protein occurs in atheroma of Watanabe heritable hyperlipidemic rabbits.

It has been proposed that chemically reactive lipids released during lipid peroxidation convert low density lipoprotein (LDL), the major carrier of plasma cholesterol, to an abnormal form and that receptor-mediated clearance of this altered LDL produces cholesteryl ester deposition in macrophage-derived foam cells of atheroma. Immuno-cytochemical analyses now reveal the presence of protein modified by malondialdehyde, a peroxidative end product, which colocalizes with the extracellular deposition of apolipoprotein B-100 protein of LDL in atheroma from Watanabe heritable hyperlipidemic rabbits. These findings provide direct evidence for the existence in vivo of protein modified by a physiological product of lipid peroxidation within arterial lesions.

Animals↗
PubMed1988

Asymmetric distribution of gangliosides in rat renal brush-border and basolateral membranes.

Highly enriched brush-border and basolateral membranes isolated from rat renal cortex were used to study the distribution of endogenous gangliosides in the two distinct plasma membrane domains of epithelial cells. These two membrane domains differed in their glycolipid composition. The basolateral membranes contained more of both neutral and acidic glycolipids, expressed on a protein basis. In both membranes, the neutral glycolipids corresponding to mono-, di-, tri- and tetraglycosylceramides were present. The basolateral membranes contained more diglycosylceramide than the brush-border membranes. The major gangliosides found were GM4, GM3, and GD3 with minor amounts of GM1 and GD1a. The latter were identified and quantified by sensitive iodinated cholera toxin binding assays. When the distribution of individual gangliosides was calculated as a percent of total gangliosides, the brush-border membranes were enriched with GM3, GM1 and GD1a compared to the basolateral membranes, which were enriched with GD3 and GM4. The observation of a distinct distribution of glycolipids between brush-border and basolateral membranes of the same epithelial cell suggests that there may be a specific sorting and insertion process for epithelial plasma membrane glycolipids. In turn, asymmetric glycolipid biogenesis may reflect differences in glycolipid function between the two domains of the epithelial plasma membrane.

Animals↗
PubMed1988

Keratin immunoreactivity in fine-needle aspiration of the prostate: an aid in the differentiation of benign epithelium from well-differentiated adenocarcinoma.

The efficacy of utilizing immunocytochemical staining of prostatic basal cells in separating benign from malignant prostatic epithelium was tested by staining fine-needle aspiration smears of prostatic lesions with the monoclonal antibody EAB-903. This antibody has been shown to stain keratin subtypes present in the prostate only in basal cells. The study utilized 12 benign, nine malignant, and four suspicious-for-carcinoma cases. Ten of 12 benign cases showed an intermingled pattern of staining, which was not found in the malignant cases. Our findings indicate that this distinctive pattern of staining may assist in distinguishing benign epithelium from well-differentiated prostatic adenocarcinoma.

Adenocarcinoma↗
PubMed1988

Cranial base and cleft lip and palate.

Previous studies do not agree on relationships between cleft palate and the cranial base. This study comparing normal and cleft lip-and-palate samples finds no significant difference in cranial base angle, but significantly shorter clivus length in the cleft sample.

Adolescent↗
PubMed1988

Detection of Mycoplasma pneumoniae-DNA within diseased gingiva by in situ hybridization using a biotin-labeled probe.

Isolation of Mycoplasma pneumoniae was accomplished in gingival biopsies of four patients exhibiting chronic inflammatory periodontal disease using in situ hybridization with biotin-labeled DNA probes. The distribution of the M. pneumoniae organisms was mainly cytoplasmic and evenly spread around the nuclei of connective tissue cells. Controls of nondisease sites in the same patients showed no infection with M. pneumoniae. Since M. pneumoniae is the only Mycoplasma known to be pathogenic, their role in the pathogenesis of periodontal disease needs further study.

Biotin↗
PubMed1988

Demonstration of estrogen receptors by monoclonal antibody in formalin-fixed breast tumors.

An immunohistochemical technique using a commercially available monoclonal antibody to the estrogen receptor in formalin-fixed breast tumors is described. The author's technique is compared to three other recently published techniques in 27 case studies. The authors' method using pronase enzyme pretreatment and alkaline phosphatase as the third antibody yielded the best results. Comparison with the standard dextran-coated charcoal cytosolic assay results from the cases selected yielded a 100% sensitivity and 89% specificity for the authors' technique. The advantages of the immunohistochemical method over the biochemical assay are discussed and clinical implications are suggested. A step-by-step procedure for the authors' technique follows the text.

Adult↗
PubMed1987

Monoclonal antibodies to human malignant mesothelioma.

Murine monoclonal antibodies were used to identify tumor-cell membrane antigens on a new human mesothelioma cell line. Hybridomas were constructed by fusing SP2/0 mouse myeloma cells with spleen cells from Balb/C mice immunized by the human mesothelioma cell line MT-1. Hybridoma antibody was detected in 55/672 microculture wells that reacted to these MT-1 tumor cells by an indirect 125I-protein A binding assay. Six cultures produced antibody binding selectively to the MT-1 tumor cells but not to a human lymphoblastoid cell line. These six hybridomas were cloned: three were IgG and three were IgM antibodies. One monoclonal, MAb 45, reacted with 4 of 7 human mesothelioma cell lines but with only 1 of 11 carcinomas, 1 of 3 sarcomas, 4 of 11 melanomas, and 0 of 5 lymphoid lines. The other five monoclonals had a much broader cross-reactivity. Using an immunoperoxidase technique, MAb 45 bound to mixed-type malignant mesotheliomas but not to normal lung and pleura. The specificity of MAb 45 for diffuse mesotheliomas and the low cross-reactivity with carcinomas and normal adjacent tissues suggest that this monoclonal may be clinically useful.

Antibodies, Monoclonal↗
PubMed1987

Direct in situ hybridization for rapid detection of cytomegalovirus in bronchoalveolar lavage.

Rapid detection of cytomegalovirus (CMV) from pulmonary specimens in immunosuppressed persons may provide an origin for pneumonia. In situ DNA hybridization has been effective for detection of CMV in otherwise nondiagnostic histologic material. Studies comparing bronchoalveolar lavage (BAL) with open-lung biopsy have shown the former to be superior in detecting most pulmonary pathogens affecting immunocompromised patients. Fifty consecutive BAL specimens were studied to compare direct in situ DNA hybridization, routine tissue culture, and conventional cytologic examination to assess the efficacy of the hybridization technic to rapidly detect CMV. Using tissue culture as the standard, a sensitivity of 90% (28 of 31) and specificity of 63% (12 of 19) were observed with the CMV probe. Discrepant results between the probe and tissue culture were present in ten cases. There were seven probe-positive, culture-negative cases, three of which had systemic CMV infection, including two patients with inclusions noted by conventional cytologic examination. Three probe-negative, culture-positive cases were found. In the authors' laboratory, the predictive value of a positive CMV probe is 80% (28 of 35). In contrast to the probe, conventional cytologic examination revealed CMV inclusions in only 23% (7 of 31) of the culture-positive cases. An average of 21 days was required for CMV cultures to become positive; probe results were available within 24 hours. The authors conclude direct in situ DNA hybridization is a useful rapid method for the detection of CMV in BAL specimens submitted for cytologic examination.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Reactivity of neoplastic cells of hairy cell leukemia with antisera to S-100 protein.

Rabbit antibodies to bovine S-100 protein were tested by immunoperoxidase technics against fresh hairy cell leukemia (HCL) cells obtained from nine patients (peripheral blood in six and spleen in three), as well as lymphoblastoid cell lines derived from three patients with HCL. Peripheral mononuclear cells from three normal persons and two patients with chronic lymphocytic leukemia (CLL) and cells from two melanoma lines were used as controls. The melanoma cell lines, cell lines derived from patients with HCL, and fresh HCL cells displayed cytoplasmic and nuclear positivity after exposure to anti-S-100 protein sera. By contrast, normal peripheral blood lymphocytes and CLL cells were negative for S-100 protein. Additional studies were performed by immunoperoxidase technics on representative sections of formalin-fixed splenic tissues from eight patients who had splenectomies. The cause of splenectomy was HCL in three, traumatic rupture in one, CLL in one, Hodgkin's disease in one, and hypersplenism in two patients. Sections from all three HCL patients showed moderate to marked positivity with antisera to S-100 protein. These results strongly suggest the presence of S-100 protein in HCL cells.

Animals↗
PubMed1987

Na+-H+ exchange and Na+-dependent transport systems in streptozotocin diabetic rat kidneys.

The streptozotocin-induced diabetic rat was used to test the hypothesis that Na+-H+ exchange activity in the proximal tubule luminal membrane would be increased in association with renal hypertrophy, altered glomerular hemodynamics, enhanced filtered load and tubular reabsorption of Na+, and stimulated Na+ pump activity in the basolateral membrane, previously reported characteristics of this experimental animal model. Amiloride-sensitive H+ gradient-dependent Na+ uptake and Na+ gradient-dependent H+ flux were increased in brush-border membrane vesicles from the streptozotocin-treated animals. Na+ gradient-dependent uptakes of phosphate, D-glucose, L-proline, and myoinositol were decreased in the drug-induced diabetic animals. These membrane transport alterations were not found when the streptozotocin-diabetic animals were treated with insulin.

Animals↗
PubMed1986

Virus-neutralizing activity, serologic heterogeneity, and retrovirus isolation from homosexual men in the Los Angeles area.

Human retroviruses have been causally associated with the development of the acquired immune deficiency syndrome (AIDS) in groups of individuals at high risk including intravenous drug users, hemophiliacs, and homosexual men. Aside from classic AIDS, homosexual men also develop persistent generalized lymphadenopathy (PGL) which is considered a part of the AIDS-related complex (ARC). We have isolated 70 strains of retroviruses related to human T-lymphotropic viruses type III (HTLV-III) from patients with PGL, AIDS, or ARC. analyses of sera from these patients indicated a high degree of serologic heterogeneity in the antibody titers and their reactivities toward various HTLV-III viral proteins. In addition, we have detected virus-neutralizing antibodies in approximately 50% of the serum samples tested from patients with PGL or AIDS. This is the first comprehensive virologic and serologic report on more than 100 patients studied at one institution in Los Angeles.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Neuroendocrine carcinoma of the skin: an immunohistochemical study of tumor markers and neuroendocrine products.

Fifteen neuroendocrine carcinomas of the skin (Merkel cell tumors) were stained within the constraints of tissue availability by the Grimelius method and immunohistochemically for keratin, neuron-specific enolase (NSE), carcinoembryonic antigen (CEA), S-100, common leukocyte antigen (CLA), met-enkephalin, bombesin, calcitonin, ACTH, gastrin, and somatostatin. Focal argyrophilia was present in 5 of 12 tumors. All tumors tested demonstrated immunoreactivity for NSE and 5 tumors were positive for keratin. One tumors appeared to demonstrate focal ACTH-like immunoreactivity, but otherwise no immunoreactivity for the above mentioned polypeptide hormones was noted in 11 completely studied tumors. One tumor contained histologically obvious areas of squamous differentiation in addition to areas of Merkel cell tumor. In various tumors, keratin immunoreactivity was present either in areas of histologically obvious squamous differentiation, in randomly scattered single cells not histologically identifiable as squamous, or in a paranuclear dot-like distribution. Immunoreactivity for CEA, S-100 and CLA was not present in any tumors. The lack of met-enkephalin and the presence of squamous differentiation in these tumors indicates multidirectional differentiation in a fashion not phenotypically typical of Merkel cells.

Adenocarcinoma↗