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Biomedical subjects

C Cheng

Publications and source records attributed to C Cheng.

At least 181 records · Page 10Linked to original sources
PubMed1990

Identification of a major keratinocyte cell envelope protein, loricrin.

During epidermal cell cornification, the deposition of a layer of covalently cross-linked protein on the cytoplasmic face of the plasma membrane forms the cell envelope. We have isolated and characterized cDNA clones encoding a major differentiation product of mouse epidermal cells, which has an amino acid composition similar to that of purified cell envelopes. Transcripts of this gene are restricted to the granular layer and are as abundant as the differentiation-specific keratins, K1 and K10. An antiserum against a C-terminal peptide localizes this protein in discrete granules in the stratum granulosum and subsequently at the periphery of stratum corneum cells. Immunofluorescence and immunoelectron microscopy detect this epitope only on the inner surface of purified cell envelopes. Taken together, these results suggest that it is a major component of cell envelopes. On the basis of its presumed function, this protein is named loricrin.

Amino Acid Sequence↗
PubMed1990

The v-ras oncogene inhibits the expression of differentiation markers and facilitates expression of cytokeratins 8 and 18 in mouse keratinocytes.

Cultured mouse keratinocytes can be initiated in vitro by the introduction of a v-rasHa gene by viral transduction. Previous studies indicated that v-rasHa-transduced keratinocytes have a high proliferation rate in medium with 0.05 mM Ca2+ and resist terminal differentiation in medium with greater than 0.1 mM Ca2+, a culture condition in which normal cells mature into squames. The current studies demonstrate that v-rasHa keratinocytes do not express transcripts or protein for epidermal early differentiation markers keratins 1 and 10 when cells are challenged with 0.12 mM Ca2+, which is a signal for expression of these genes in normal cells. Both transcript and protein for the late differentiation marker loricrin are also diminished in v-ras keratinocytes, but filaggrin, also a late differentiation-related gene product, is expressed in nearly normal amounts but at a different Ca2+ optimum. Modification of intracellular Ca2+ with ionomycin failed to restore the expression of any suprabasal keratinocyte markers. In contrast to the effects on normal products of keratinocyte differentiation, the introduction of the v-rasHa gene facilitated the expression of keratins 8 (K8) and 18 (K18). These keratins are characteristic of embryonic cells and cells of simple adult epithelia but not stratified squamous epithelia such as skin. Like normal differentiation markers, the expression of K8 and K18 was dependent both on the v-ras oncogene and the Ca2+ concentration of the culture medium, with greater than 0.1 mM Ca2+ being optimal. At the optimal Ca2+ level, the majority of v-ras keratinocytes expressed K8 and K18 after 96 h, and many cells had reduced amounts of the normal keratinocyte cytokeratin K14. These studies indicate that the v-ras gene causes substantial reprogramming of epidermal physiology, producing an unusual phenotype devoid of early suprabasal markers but at least partially permissive for late marker expression. Furthermore, the Ca2(+)-dependent expression of K8 and K18 suggests that a normal signalling pathway used in keratinocyte differentiation is diverted to an abnormal endpoint.

Animals↗
PubMed1990

Response of Haemophilus somnus to iron limitation: expression and identification of a bovine-specific transferrin receptor.

Nine clinical isolates of Haemophilus somnus were screened for their ability to use different transferrins as a source of iron growth. All nine strains were capable of using bovine but not porcine, human or chicken transferrin. A screening assay for siderophore production did not show any evidence of siderophore production by these strains. When iron-deficient cells from these strains were screened for their ability to bind peroxidase-conjugated transferrin, binding was detected with conjugated bovine, but not human or porcine transferrin. Competition binding studies demonstrated that the binding of peroxidase-conjugated bovine transferrin was competitively inhibited by unconjugated bovine transferrin but not transferrin from other species. The induction of receptor expression by low iron conditions was inhibited by chloramphenicol and rifampicin but not ampicillin indicating that new protein and mRNA synthesis was required for expression of receptor activity. Affinity isolation of receptor proteins with biotinylated bovine transferrin, but not human or porcine transferrin, yielded three proteins from H. somnus strain H74. Two of the proteins were identified as 105 kDa and 73 kDa iron-regulated outer membrane proteins. A third protein of 85 kDa that was isolated did not co-migrate with any iron-regulated outer membrane protein. Affinity isolation of receptor proteins from other strains of H. somnus yielded a 73 kDa protein from all strains and a 105 kDa and 85 kDa protein in four of the six strains analysed.

Animals↗
PubMed1990

Cystoplasty: tubularisation or detubularisation?

Previous studies on substitution or augmentation cystoplasty have highlighted the profusion of surgical techniques available, but there is disagreement as to which is the best. We established an animal model to compare various types of cystoplasties, tubularised and detubularised, using ileum and caecum. Detubularisation did not abolish intrinsic bowel contractions but delayed their onset. No differences were noted in the frequency and amplitude of such contractions after detubularisation or between large and small bowel cystoplasties. Although intravenous urography did not demonstrate any abnormality in upper tract anatomy, a significant number of animals had some functional disturbance of the kidney after cystoplasty demonstrable on isotope renography, irrespective of the surgical technique. It may be possible to prevent these contractions with their associated harmful effects by preventing the bladder volume from building up excessively.

Animals↗
PubMed1990

[Preliminary probe into the cause of the black substance emerging in the course of the processing of sulfur with bean curd].

The author has probed into the reason why bean curd assumes a black green colour in the course of processing sulfur, and made an X-ray crystallographic and qualitative analysis of the substance which makes bean curd assume this colour during the processing. On the basis of these analyses, a discussion has been made on the processing conditions and container for sulfur.

Hot Temperature↗
PubMed1989

Anterior screw fixation of posteriorly displaced type II odontoid fractures.

Posteriorly displaced Type II odontoid fractures (Type II-P) are difficult to stabilize in an anatomic position with accepted methods of posterior atlantoaxial arthrodesis. Nine patients with Type II-P odontoid fractures with 4 to 15 mm displacement were treated with anterior odontoid screw stabilization. Seven of these patients had associated fractures or defects of the posterior arch of the first cervical vertebra (C1). Atlantoaxial posterior arthrodesis in these patients would not have been possible initially because of the lack of structural integrity of the posterior arch of C1. Two patients, later in the study, had no injury to the ring of C1. The odontoid fractures were stabilized with two 4.0-mm cancellous screws inserted through an anterior approach to the neck under fluoroscopic control with the skin incision at the C5 level. Preoperative reduction of the displaced odontoid process and immediate operative stability of the atlantoaxial complex were obtained in each case. No neurological complications related to the procedure occurred. Two patients died of causes unrelated to their cervical fracture surgery. The 7 patients who survived were followed for a minimum of 6 months. Fracture union and cervical stability were demonstrated in each of the surviving patients, without evidence of screw loosening or loss of fixation. Normal range of motion of the neck was documented at follow-up in all surviving patients. Although this series represents a limited experience with this treatment technique, anterior odontoid screw fixation has significant advantages over accepted methods of cervical stabilization for Type II-P odontoid fractures.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Progesterone receptor heterogeneity and endometrial tumour differentiation.

Progesterone binding components were isolated using fast protein liquid chromatography (FPLC) with a recovery efficiency of between 60-70%. In normal uterine cytosol, the two components were in about equal proportions. In endometrial cancer, the ratio of peak size between peaks 1 and 2 was 1.5 for Grade I, 3.7 for Grade II and 2.5 for Grade III. Whether estimation of the levels of the two progesterone components separately would enhance predictability of response to hormone therapy in endometrial cancer remains to be established.

Cell Differentiation↗
PubMed1987

Hydrolysis of stereoisomeric alpha-tocopheryl acetates catalyzed by bovine cholesterol esterase.

The kinetics of the bovine cholesterol esterase-catalyzed hydrolysis of three stereoisomers of alpha-tocopheryl acetate (alpha T-Ac) have been examined in vitro at 37 degrees C in the presence of dimyristoylphosphatidylcholine and sodium cholate. In contrast to in vivo results obtained earlier in rats (Ingold, K.U., Burton, G.W., Foster, D.O., Hughes, L., Lindsay, D.A. and Webb, A. (1987) Lipids 22, 163-172), 2R,4'R,8'R-alpha T-Ac (RRR-alpha T-Ac) is hydrolyzed (to form 'natural' vitamin E) more slowly (by a factor of approx. 7) than SRR- (and SSS-)alpha T-Ac. It is concluded that chirality at position 2 plays the dominant role in determining Vmax. The Km values show that RRR-alpha T-Ac is 2.1- and 2.7-times more strongly bound to the enzyme than are the SRR- and SSS-alpha T-Ac, respectively. The reaction is subject to competitive inhibition by the product with RRR-alpha T being 2.3-times as powerful an inhibitor as SRR-alpha T.

Animals↗
PubMed1987

Direct comparison of muscle force predictions using linear and nonlinear programming.

Estimating forces in muscles and joints during locomotion requires formulations consistent with available methods of solving the indeterminate problem. Direct comparisons of results between differing optimization methods proposed in the literature have been difficult owing to widely varying model formulations, algorithms, input data, and other factors. We present an application of a new optimization program which includes linear and nonlinear techniques allowing a variety of cost functions and greater flexibility in problem formulation. Unified solution methods such as the one demonstrated here, offer direct evaluations of such factors as optimization criteria and constraints. This unified method demonstrates that nonlinear formulations (of the sort reported) allow more synergistic activity and in contrast to linear formulations, allow antagonistic activity. Concurrence of EMG activity and predicted forces is better with nonlinear predictions than linear predictions. The prediction of synergistic and antagonistic activity expectedly leads to higher joint force predictions. Relaxation of the requirement that muscles resolve the entire intersegmental moment maintains muscle synergism in the nonlinear formulation while relieving muscle antagonism and reducing the predicted joint contact force. Such unified methods allow more possibilities for exploring new optimization formulations, and in comparing the solutions to previously reported formulations.

Algorithms↗
PubMed1986

Pro-opiomelanocortin messenger ribonucleic acid and posttranslational processing of beta endorphin in spleen macrophages.

We have previously demonstrated low levels of immunoreactive (ir)-beta-endorphin (beta-EP) and ir-ACTH in a subpopulation of mouse spleen macrophages, which is consistent with an involvement of opioid peptides in modulation of immune responses. Gel chromatography studies suggested the presence of an approximately 3.5,000-molecular weight (mol wt) species, putatively beta-EP, an approximately 11.5,000-mol-wt species, putatively beta-lipotropin, and a higher molecular weight species (putative beta-EP precursor, pro-opiomelanocortin (POMC). In this study we have extended our original findings by demonstrating the presence of messenger RNA for POMC by the use of a complementary DNA probe and Northern blot analysis of extracts of mouse and rat spleen. In addition, using high performance liquid chromatography (HPLC), we have shown that the major endorphin species in mouse spleen macrophages is beta-EP1-31, and that there are smaller amounts of each of the acetylated forms, N-acetyl-beta-EP1-16 (alpha-endorphin), N-acetyl-beta-EP1-17 (gamma-endorphin), N-acetyl-beta-EP1-27, and N-acetyl-beta-EP1-31. We interpret these studies as showing that (a) the spleen is an organ of POMC synthesis and that (b) the predominant COOH-terminal product of macrophage POMC is the opiate-receptor active species beta-EP1-31.

Animals↗
PubMed1986

Acute cholangitis in Singapore.

115 cases of acute calculous cholangitis were analysed for their presentations, treatment and complications. There were slightly more Chinese males than females (1.4:1) and the mean age was 62 years old. Though pain was the commonest symptom (95.7%), only 35.7% of patients had complete Charcot's triad. 21.7% presented in septicaemic shock. E. Coli and Klebsiella were the commonest organisms isolated. All patients had cholecystectomy and exploration of common bile ducts. Twenty patients had additional choledochontrostomy performed. 50.4% of patients developed complications and the overall mortality was 16.5%. Patients over 60 presented in shock carried a significantly higher mortality (40%).

Acute Disease↗
PubMed1983

Radionuclide angiocardiography: an improved deconvolution technique for improvement after suboptimal bolus injection.

Deconvolution is a mathematical technique used to improve radionuclide angiocardiography after suboptimal injection of radiopharmaceutical. A new deconvolution algorithm designed to be relatively insensitive to the random errors that occur in experimental data was tested. First-pass radionuclide angiocardiography using iridium-191m was performed to quantitate left-to-right shunting in normal dogs and dogs with atrial septal defects. Deconvolution was used to correct for injection shape. Four quantitation techniques were studied (good injection/no deconvolution, good injection/deconvolution, fragmented injection/no deconvolution, fragmented injection/deconvolution). The mean (p less than .001) and standard deviation (p less than .0001) of the fragmented injection/no deconvolution technique were significantly different from the other three techniques, which were not significantly different from each other (mean or standard deviation) at the p = 0.05 level. This deconvolution method made it possible to accurately quantitate left-to-right shunts even with fragmented injections.

Animals↗
PubMed1983

Characterization of certain minor monodispersed bands found on serum protein electrophoresis as C-reactive protein.

A monodispersed band is a dense, homogeneous band on serum protein electrophoresis (SPE), indicating the presence of a discrete protein. Minor monodispersed bands in the gamma region on SPE usually indicate minor monoclonal immunoglobulins that can be characterized by immunofixation. Occasionally, these minor monodispersed bands cannot be shown to be immunoglobulins. This report illustrates that elevated levels of C-reactive protein (CRP) may be detectable as an "M-spike" on SPE; therefore, if immunofixation is performed, anti-CRP could be included in the panel of antisera used to characterize the minor monodispersed band. The detection of CRP as an "M-spike" in the gamma region is, however, dependent upon the absence of a chelating agent in the SPE support medium. When EDTA is present, the electrophoretic mobility of CRP is altered to a beta mobility.

Blood Protein Electrophoresis↗