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Biomedical subjects

S Y Cheng

Publications and source records attributed to S Y Cheng.

At least 109 records · Page 6Linked to original sources
PubMed1989

Biphasic recovery in n-hexane polyneuropathy. A clinical and electrophysiological study.

We studied the course of recovery in n-hexane polyneuropathy in 4 patients by quantitatively assessing clinical and electrophysiological features. The electrophysiological study included measures of motor conduction of the median, ulnar, tibial and peroneal nerves and sensory conduction of the median, ulnar and sural nerves. After cessation of exposure, there was an initial worsening in muscle strength, sensory deficit and nerve conduction for up to 2-5 months. This deterioration was more severe and prolonged in the lower limbs than in the upper limbs. The period of deterioration was followed by a slow recovery studied for 1 year.

Adolescent↗
PubMed1989

Application of nasopharyngoscopy and videofluoroscopy in the fabrication of a speech aid for soft palate defects.

Conventional methods of speech aid fabrication have little control over the pharyngeal extension or over the adequacy of the velopharyngeal closure. These limitations can be overcome by using a nasopharyngoscope, which provides the operator with direct vision during the molding of the pharyngeal section. Likewise, the use of a videofluoroscope also permits visualization of the prosthesis in relation to the surrounding structures during various activities, and is equally valuable in the evaluation of the velopharyngeal mechanism. In both instances, the evidence of inadequate closure could be seen as mucus bubbling or refluxing of barium from the junction of the prosthesis with the soft palate defect. Also the standard Mandarin phrases used in the speech test and the advantages of nasal endoscopy over oral endoscopy are discussed.

Adult↗
PubMed1988

Antibodies against the human cellular 3,3',5-triiodo-L-thyronine-binding protein (p 58).

High-titer antibodies against a cellular thyroid hormone-binding protein (Mr 58,000, p58) were developed by a special immunization method. To enhance immune responses, this method uses a boosting protocol in which repeated injections of small amounts of antigen are administered at 2-day intervals. Antibodies were detected 1 week after the last injection of antigen by ELISA, Western dot blotting and immunoprecipitation. The anti-p58 antibodies recognized p58 which is bound to the thyroid hormone. With the availability of anti-p58 antibodies, it has become possible to study cellular localization and function.

Animals↗
PubMed1988

Thyroid hormone down-regulates p55, a thyroid hormone-binding protein that is homologous to protein disulfide isomerase and the beta-subunit of prolyl-4-hydroxylase.

We have previously characterized a cellular thyroid hormone-binding protein (p55) that is found concentrated on the lumenal face of the endoplasmic reticulum and nuclear envelope (Cheng, S.-y., Hasumura, S., Willingham, M.C., and Pastan, I. (1986) Proc. Natl. Acad. Sci. U.S.A. 83, 947-951). To understand the role p55 plays in thyroid hormone action, we examined the regulation of p55 by 3,3',5-triiodo-L-thyronine (T3). Rat pituitary tumor GH3 cells cultured in regular medium, thyroid hormone-depleted medium (Td medium), or Td medium supplemented with 50 nM T3 (Td + T3 medium) were metabolically labeled with [35S]methionine and immunoprecipitated with antibodies against p55. Treatment with T3 caused a fall in p55 levels. Poly(A+) RNA from cells cultured in regular, Td, or Td + T3 medium was hybridized to a cDNA from p55. T3 withdrawal or addition had no effect on p55 mRNA levels. Furthermore, the initial rates of synthesis of p55 from cells cultured in regular, Td, and Td + T3 were found to be similar. However, analysis of the decay curves from cells in which p55 was pulse-labeled with [35S]methionine indicated that p55 is 2-fold less stable in T3 containing medium. These results indicated that down-regulation of p55 by T3 occurs at the post-translational level. Since DNA sequence analysis indicates that p55 is identical to protein disulfide isomerase and the beta-subunit of prolyl-4-hydroxylase, T3 may mediate its effects on the synthesis, secretion, and/or transport of proteins via p55.

Animals↗
PubMed1988

Antipeptide antibodies recognize c-erbA and a related protein in human A431 carcinoma cells.

Peptides corresponding to the deduced amino acid residues 15-29 of the amino-terminal region and 445-456 of the carboxyl-terminal region of the human placental c-erbA protein (hc-erbA-beta) were synthesized and used to produce site-specific rabbit polyclonal antipeptide sera. Antibodies to the carboxyl-terminal peptide (C-91) and the amino-terminal peptide (N-98) specifically immunoprecipitated the hc-erbA-beta proteins synthesized in vitro. Furthermore, 68% and 48% of the T3-binding activity of the hc-erbA-beta protein were immunoabsorbed by antibodies C-91 and N-98, respectively. These results indicate that C-91 and N-98 recognized hc-erbA-beta proteins. These antibodies were used to study the subcellular distribution of hc-erbA-beta protein in human cultured cells. Nuclear extracts were prepared from human A431 carcinoma cells; C-91 immunoabsorbed 50% of the specific T3-binding activity in these extracts. These results provide structural evidence to confirming that hc-erbA-beta is the T3 nuclear receptor. Cells were metabolically labeled with [35S]methionine, and the cytosolic extracts were immunoprecipitated by C-91 or N-98. A protein with a mol wt of 58,000 (Cp58) was specifically immunoprecipitated by N-98 or C-91. Peptide mapping by V8 digestion and cyanogen bromide cleavage showed that the Cp58 molecules immunoprecipitated by N-98 or C-91 was identical. Indirect immunofluorescence using N-98 or C-91 indicated that Cp58 is present exclusively in the cytoplasm. Other human cultured cells, HepG2, MCF-7, IM-9, and KB, were also evaluated, and similar results were found. These results raised the possibility that a precursor of hc-erbA-beta may be present in the cytosol. The functional significance of the hc-erbA-beta-related cytosolic Cp58 remains to be established.

Antibodies↗
PubMed1988

Intracranial phycomycosis: case reports.

Cerebral phycomycosis is a rare disease. We describe two patients with unusual features of focal intracranial phycomycosis: a diabetic patient with chronic epidural abscess and a healthy individual with an isolated intracerebral abscess. Biopsy established the diagnosis in both patients. Treatment was successful in the patient with intracerebral abscess.

Adult↗
PubMed1988

Chromosomal localization of the gene for a human thyroid hormone-binding protein.

A cDNA for the gene that encodes for a human cellular thyroid hormone-binding protein (p55) has recently been isolated and sequenced. The sequence of p55 indicates that it is identical to the protein disulfide isomerase and the beta-subunit of prolyl 4-hydroxylase. By in situ hybridization, the gene for p55 was localized on chromosome 17 at band q25. This localization shows that the p55 gene is not linked to either erbA1 or erbA2; two other thyroid hormone-binding protein genes are located at 17q 11-21 and 3p21-pter, respectively. The localization of p55 gene will permit the evaluation of the possible effects of chromosome changes on the structure and activity of the p55 gene in chromosome syndromes or neoplasms.

Carrier Proteins↗
PubMed1987

The nucleotide sequence of a human cellular thyroid hormone binding protein present in endoplasmic reticulum.

A cDNA clone encoding a human cellular thyroid hormone binding protein (p55) has been isolated. The cDNA sequence contains a single open reading frame of 1524 nucleotides which encodes a polypeptide of 491 amino acids and a signal sequence of 17 amino acids. Two partial protein sequences determined from the purified protein correspond to the deduced amino acid sequence. In vitro translation of mRNA prepared by transcription of the cDNA clone yielded a protein of the size of an unprocessed precursor (Mr 57,000) as well as smaller fragments which were immunoprecipitated by antibodies against p55. The isolation of the cDNA clone should allow elucidation of the cellular function of this thyroid hormone binding protein which is present in the endoplasmic reticulum and nuclear envelope.

Amino Acid Sequence↗
PubMed1987

A cellular 3,3',5-triiodo-L-thyronine binding protein from a human carcinoma cell line. Purification and characterization.

A cellular binding protein for 3,3',5-triiodo-L-thyronine (T3) was solubilized with 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate (CHAPS) from A431 human epidermoid carcinoma cells. The binding activity is T3 specific. Analysis of the equilibrium binding data indicated that the binding protein has one class of binding sites for T3 with a Kd of (17 +/- 3) nM and Bmax of (1.8 +/- 0.6) pmol/50 micrograms of protein. The pH optimum for binding is 6.8. The T3 binding protein elutes from Sephadex G-200 in an included peak which has a Stokes radius of 40 A and sediments on glycerol gradients at 3.7 S. By affinity labeling with [3,5-125I]thyroxine a protein with a molecular weight of 58,000 was specifically labeled. Its isoelectric point was determined to be 7.1, which is different from the reported pIs of other thyroid hormone binding proteins. p58 was successively purified to apparent homogeneity by chromatography on Sephadex G-200, QAE-Sephadex, SP-Sephadex, and hydroxylapatite. Approximately 50 micrograms of purified protein was obtained from 2.5 X 10(9) cells with a yield of 1.1%. The purified protein retains its binding activity. The specific binding activity is enriched by approximately 1000-fold. With the availability of a purified protein with T3 binding activity, it becomes possible to study its cellular function.

Carcinoma, Squamous Cell↗
PubMed1987

Immunohistochemical localization of a thyroid hormone-binding protein (p55) in human tissues.

We have localized p55, a thyroid hormone-binding protein found in the endoplasmic reticulum in cultured cells, in samples of normal human and monkey tissues, using a monoclonal antibody with cryostat sections and immunoperoxidase histochemistry. Large amounts of p55 were found in many tissues, generally corresponding to the amount of endoplasmic reticulum contained in each cell type. Intense localization of p55 was found in cells of the anterior and intermediate pituitary lobes, in epithelial cells of thyroid follicles, in the glandular epithelium of mammary gland, in hepatocytes, in Paneth cells and Brunner's glands in duodenum, in acinar cells of pancreas, in adrenal cortical cells, and in scattered interstitial fibroblastic cells in many tissues. These results suggest a potential role for thyroid hormone and p55 in regulating protein synthesis or secretion in multiple organs.

Animals↗
PubMed1987

Thyroid hormone action: induction of morphological changes and stimulation of cell growth in rat pituitary tumor GH3 cells.

The effects of thyroid hormones on morphology and growth were studied in rat pituitary tumor GH3 cells using medium containing serum depleted of thyroid hormones. T3 and T4 induce the cells to change from a flattened fibroblastic morphology to a rounded or spindle-shaped morphology. The induction in morphological changes is T3 and T4 specific and dose dependent. Thyronine and rT3 are ineffective in inducing morphological changes; the half-maximal effective concentrations for T3 and T4 are 0.3 and 2 nM, respectively. Concomitantly, T3 stimulates cell growth, as indicated by a 2-fold reduction in doubling time and a 2-fold increase in mitotic rate. The growth-stimulating effect has the same analog specificity and dose dependency as the morphological changes. The morphological changes could be potentially useful for evaluating the biological effects of T3 and its analogs and in studying the mechanism of thyroid hormone action.

Animals↗
PubMed1986

Purification and characterization of a membrane-associated 3,3',5-triiodo-L-thyronine binding protein from a human carcinoma cell line.

A membrane-associated binding protein for 3,3',5-triiodo-L-thyronine (T3) was purified to apparent homogeneity from A431 human epidermoid carcinoma cells. A431 cells were specifically labeled with the N-bromoacetyl derivative of T3 labeled with 125I at the 3' position (BrAc[125I]T3) and were extracted with 3-[3-(cholamidopropyl)dimethylammonio]-1-propanesulfonate (CHAPS), a zwitterionic detergent. The solubilized BrAc[125I]T3-labeled protein was successively purified by chromatography on Sephadex G-200 and QAE-Sephadex followed by NaDod-SO4/PAGE. Approximately 0.2 mg of purified protein was obtained from 2.5 X 10(9) cells, which represents a 3000-fold purification. The membrane-associated T3 binding protein is an acidic protein with a pI of 5.1 and an apparent molecular mass of 55,000 daltons determined by NaDodSO4/PAGE. Polyclonal antibodies against the 55-kDa protein were prepared and used in indirect immunofluorescence to show that the 55-kDa protein was mainly found in the nuclear envelope and endoplasmic reticulum.

Carcinoma, Squamous Cell↗
PubMed1986

The identification of a plasma membrane 3,3',5-triiodo-L-thyronine binding protein on the cultured Swarm rat chondrosarcoma chondrocyte and the lack of its up-regulation by insulin in vitro.

Primary cultures of Swarm rat chondrosarcoma chondrocytes were examined for the presence of T3 plasma membrane binding proteins and their possible regulation by insulin. Incubation of this tumor cell with [125I]T3 at 4 C yielded saturable and reversible binding of the radioligand. As assessed by LIGAND computer analysis, the binding data in one experiment revealed two classes of [125I]T3 binding sites with association constants of 2.2 X 10(9) M-1 and 4.8 X 10(6) M-1, and binding capacities of 4.9 X 10(3) and 1.9 X 10(6) sites per cell, respectively. Whole cells and a preparation enriched for plasma membrane were affinity labeled with N-bromoacetyl-[125I]T3 (N-BrAc-[125I] T3), and the molecular weights of the radiolabeled proteins were analyzed both by sodium dodecyl sulfate polyacrylamide gel electrophoresis and by Sephadex G-200 gel filtration chromatography. One major chondrosarcoma protein of 55,000 mol wt and two minor proteins of 47,000 and 33,000 mol wt bound N-BrAc-[125I]T3, suggesting that the mol wt of the T3 binding protein was 55,000. As assessed by isoelectric focusing, the 55,000 mol wt protein had an isoelectric point of 5.1. The radiolabeled 55,000 mol wt chondrosarcoma protein was immunoprecipitated with anti-T3 and anti-GH3 plasma membrane T3 antisera. The high degree of homology between this chondrocyte N-BrAc-[125I]T3 binding protein and the protein on rat GH3 cells was demonstrated by a comparison of the peptide maps of Staphylococcus aureus V8 protease and elastase digested radiolabeled binding protein. Although culture of the chondrocytes in medium containing insulin resulted in an approximate 400% increase in plasma membrane [125I]insulin binding, no significant increase in [125I]T3 binding was observed. Thus, expression of the T3 plasma membrane binding protein was similar to that observed previously for the insulin-like growth factor-II receptor on these chondrosarcoma chondrocytes in not being influenced by the concentration of insulin in the culture medium.

Affinity Labels↗