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Biomedical subjects

H Ji

Publications and source records attributed to H Ji.

At least 127 records · Page 7Linked to original sources
PubMed1996

[The surgical treatment for the epiglottic cancer extended to the base of tongue].

26 cases of the epiglottic cancer extended to the base of the tongue were studied retrospectively. Among them, 14 were male and 12 female. The age varied from 43 to 62. Besides two cases who underwent total laryngectomy, the other twenty-four were treated with supraglottic horizontal partial laryngectomy or horizontovertical subtotal laryngectomy and resection of part of base of the tongue. 11 cases received bilateral radical neck dissection (RND) and 10 cases unilateral RND simultenously. The results showed twenty-four cases had resumed speaking ability, twenty had been decannulated and restored the laryngeal functions. The 5-year survival rate was 57.9% (12/19). It was concluded that transpharyngeal approach was reasonable for supraglottic horizontal partial laryngectomy associated with the resection of the base of the tongue.

Adult↗
PubMed1995

Genetic transfer of a nonpeptide antagonist binding site to a previously unresponsive angiotensin receptor.

Mutational analysis based on the pharmacological differences between mammalian and amphibian angiotensin II receptors (AT receptors) previously identified 7 aa residues located in transmembrane domains (TMs) III (Val-108), IV (Ala-163), V (Pro-192, Thr-198), VI (Ser-252), and VII (Leu-300, Phe-301) of the rat AT receptor type 1b (rAT1b receptor) that significantly influenced binding of the nonpeptide antagonist Losartan. Further studies have shown that an additional 6 residues in the rAT1b receptor TMs II (Ala-73), III (Ser-109, Ala-114, Ser-115), VI (Phe-248), and VII (Asn-295) are important in Losartan binding. The 13 residues required for Losartan binding in the mammalian receptor were exchanged for the corresponding amino acids in the Xenopus AT receptor type a (xATa receptor) to generate a mutant amphibian receptor that bound Losartan with the same affinity as the rAT1b receptor (Losartan IC50 values: rAT1b, 2.2 +/- 0.2 nM: xATa, > 50 microM; mutant, 2.0 +/- 0.1 nM). To our knowledge, this is the first report of a gain-of-function mutant in which the residues crucial to formation of a ligand binding site in a mammalian peptide hormone receptor were transferred to a previously unresponsive receptor by site-directed mutagenesis. Ala substitutions and comparison of mammalian and amphibian combinatorial mutants indicated that TM III in the rAT1b receptor plays a key role in Losartan binding. Identification of residues involved in nonpeptide ligand binding will facilitate studies aimed at elucidating the chemical basis for ligand recognition in the AT receptor and peptide hormone receptors in general.

Amino Acid Sequence↗
PubMed1995

Synthesis, conformation and opioid activity of deltorphins.

A series of deltorphin analogues was prepared by solid-phase peptide synthesis. Their opioid activity was evaluated in rat opiatic assay and their conformation was determined by two-dimension Nuclear Magnetic Resonance Spectroscopy. The analogues containing D-alanine acid at position 2 were much more potent in the assay than their corresponding isomers containing L-alanine acid at this position. The conformational analysis on NMR study in DMSO showed that C-terminal tetrapeptides of both deltorphin II and its L-alanine analog might form a 3(10) helix, which confirms that the substitution of D-amino acid at position 2 decreased the opioid activity.

Analgesics↗
PubMed1995

Nonreducing two-dimensional polyacrylamide gel electrophoretic analysis of human colonic proteins.

Immunochemical detection of proteins with antigenic determinants that are dependent on the native spatial conformation of the protein can often pose problems with conventional two-dimensional polyacrylamide gel electrophoresis (2-DE). For example, many antigenic determinants are readily destroyed by reducing agents and/or urea, reagents which are critical components of many of the conventional isoelectric focusing and immobilized-pH-gradient (IPG) protocols used in the first electrophoretic dimension. Here we describe the use of commercially available precast 2-DE gels for performing nonreducing/non-urea 2-DE of proteins extracted from the human colon cancer cell line LIM 1215 with 0.3% Triton X-100 that permit the identification of antigens with conformational determinants by immunoblot analysis. Previous, related studies demonstrated the usefulness of peptide-mass fingerprinting for identifying 2-DE resolved proteins. Here we show how partial protein sequence data obtained by rapid peptide mapping, using capillary column liquid chromatography directly coupled with electrospray ionization tandem mass spectrometric methodologies, enhances the usefulness of this approach for identifying incompletely resolved proteins. The nonreducing 2-DE gel images reported in this study, along with our master 2-DE gel protein database for both normal human colonic crypts and several colon-cancer-derived cell lines, and information regarding microtechniques employed in this laboratory for obtaining structural data on 2-DE resolved proteins can be accessed over the Internet using World Wide Web (URL address: http:@www.ludwig.edu.au).

Amino Acid Sequence↗
PubMed1995

MeIQx (2-amino-3,8-dimethylimidazo [4,5-f]quinoxaline): metabolism in humans and urinary metabolites in human populations.

The metabolism of the heterocyclic amines has been extensively studied in rodents and limited studies have been conducted in nonhuman primates. A study has been undertaken on the metabolism of 2-amino-3,8-dimethylimadazo[4,5-f]quinoxaline (MeIQx) in human subjects consuming normal cooked foods. A variety of fish and meat products has been cooked in several ways and fed to human volunteers. Urine was collected and analyzed according to methods developed for this purpose. Earlier rodent studies using radioactive MeIQx had suggested that the principal urinary excretion products included unmetabolized MeIQx, MeIQx sulfamate and MeIQx N-glucuronide. Conditions were developed for HPLC analysis of the free amine and its conjugates in human urine and for total hydrolysis of the conjugates to the free amine. Extraction and cleanup from urine were made possible by the availability of suitable monoclonal antibodies to MeIQx which could be used for immunoaffinity chromatography. For sensitive detection of the amounts present in human urine, gas chromatographymass spectrometry (GC-MS) was used in the negative chemical ionization mode. These studies have demonstrated that the distribution of metabolites in humans strongly resembles that in the rat. The sulfamate and N-glucuronide appear to be predominant human metabolites, while no evidence could be found of N-acetyl MeIQx. Subsequent to the studies just described, the methods developed were applied to urines collected in an epidemiological study on aromatic amine metabolism in Los Angeles. The study includes African American, White, and Asian people who have been phenotyped for caffeine acetylator status.

Adult↗
PubMed1994

Differential structural requirements for specific binding of nonpeptide and peptide antagonists to the AT1 angiotensin receptor. Identification of amino acid residues that determine binding of the antihypertensive drug losartan.

The biphenylimidazole derivative losartan exemplifies a novel class of nonpeptide antagonists that selectively inhibit angiotensin II binding to the mammalian AT1 receptor and have potentially wide application as anti-hypertensive agents. In contrast to mammalian AT1 receptors, which have high affinity for both peptide antagonists and losartan, amphibian and avian angiotensin II receptors are pharmacologically distinct and recognize peptide but not nonpeptide antagonists. Mutant rat AT1 receptors in which non-conserved amino acids were replaced by the corresponding amphibian residues were constructed to identify specific sites in the AT1 receptor that determine losartan binding. Only minor changes in binding affinity for peptide antagonists were observed in COS-7 cells transiently expressing mutant receptors, indicating that the structural integrity of the receptor was maintained. However, analysis of receptors with single point and combined mutations revealed that specific residues in transmembrane domains III, IV, V, VI, and VII are involved in binding of the nonpeptide antagonist to the mammalian AT1 receptor. The most marked attenuation of losartan binding (IC50 > 50 microM) was observed in a mutant receptor containing amino acid substitutions at Val108, Ala163, Thr198, Ser252, Leu300, and Phe301. These results have demonstrated that the binding site of a potent nonpeptide antagonist of the AT1 receptor is defined by epitopes located within the membrane-spanning regions of the receptor and is distinct from the site at which peptide antagonists bind to the AT1 receptor.

Amino Acid Sequence↗
PubMed1994

Absence of transforming growth factor-beta responsiveness in the tamoxifen growth-inhibited human breast cancer cell line CAMA-1.

Tamoxifen has been an effective antiestrogen in suppressing breast cancer growth which is estrogen-responsive or dependent. Early studies have provided circumstantial evidence that transforming growth factor-beta (TGF-beta) may be an autocrine mediator of tamoxifen action. Therefore, it is both fundamentally important and clinically relevant to investigate the relationship between tamoxifen and TGF-beta. In this study, we demonstrated that CAMA-1 cells, which are sensitive to tamoxifen inhibition, did not respond to TGF-beta growth inhibition. The type I and II TGF-beta receptors were undetectable by the radio-ligand affinity labeling technique. Despite the presence of a normal TGF-beta type II receptor gene, the mRNA transcript of the gene was undetectable by the extremely sensitive Intron-differential RNA/PCR method. The possibility that the lack of TGF-beta receptors might be intimately linked to the absence of normal retinoblastoma (Rb) gene products, as suggested by previous studies of retinoblastoma cells, was further investigated. The lack of TGF-beta receptor expression was found due to reasons other than the absence, deletion or abnormality of the Rb gene because a normal Rb gene and its hyper- and hypo-phosphorylated protein products were detected in CAMA-1 cells. In conclusion, our results suggest that the TGF-beta system is not obligatory for antiestrogen growth inhibition of CAMA-1 cells.

Base Sequence↗
PubMed1994

Expression of E-cadherin (E-CD) as related to other prognostic factors and survival in breast cancer.

A series of 208 breast cancer biopsies were analysed immunohistochemically for expression of E-cadherin (E-CD). Altogether, 72 per cent of the tumours showed E-CD positivity in over 50 per cent of cells, the staining being heterogeneous in nearly all tumours. In only 16 per cent of ductal carcinomas was positive staining seen in less than 1 per cent of cells. Expression of E-CD was not related to tumour diameter, nodal status, metastasis at diagnosis, histological grade, DNA ploidy, S-phase fraction, nuclear area, mitotic frequency, or PR content. There was a significant relationship between expression of E-CD, histological type (P = 0.01), the proportion of intraductal growth (P = 0.008), the density of tumour-infiltrating lymphocytes (P = 0.0007), ER content (P = 0.012), and morphometric nuclear factors (P < 0.02). Expression of E-CD showed a weak association with a high survival probability (P = 0.02), while the relation to recurrence-free survival was not significant (P = 0.1). In axillary lymph node-negative tumours, E-CD expression was not related significantly to survival (P = 0.11) or to recurrence-free survival (P = 0.06). In multivariate analysis, E-CD expression had no independent prognostic value, while the axillary lymph node status, tumour diameter, patient age, and mitotic frequency were independent prognostic factors. The results indicate that E-CD expression is related to several histological features in breast cancer, but has no independent prognostic value over standard prognostic factors.

Adult↗
PubMed1994

Tumour vascularity and basement membrane structure in breast cancer as related to tumour histology and prognosis.

A series of 202 breast cancer biopsy specimens were analysed immunohistochemically for collagen IV to demonstrate basement membrane (BM) structures and blood vessels within tumour tissue. Integrity of the BM was graded into four categories and the number of vascular channels per square millimetre of tumour tissue were counted. Defective BM structures were significantly related to high grade, lack of tubule formation, invasive disease, high S-phase fraction and variability in nuclear size and shape. High vascular channel density was related to poor tumour differentiation and a high proliferation rate of cancer cells as well as to the absence of tubule formation, inconspicuous intraductal growth and low progesterone receptor content. High vascular density and defective BM structures were signs of poor prognosis and short recurrence-free survival in the entire cohort and also in local tumours. In multivariate analysis, the vascular density had independent prognostic value, as did the diameter, axillary lymph node status and mitotic rate. The counting of vascular channels within the tumour provides additional prognostic information in breast cancer, in contrast to analysis of the BM integrity which shows hardly any prognostic information additional to that provided by the special histological features, e.g. tubule formation and intraductal growth pattern.

Adult↗
PubMed1994

Characterization of a polymorphic family of integral membrane proteins in promastigotes of different Leishmania species.

Antibodies raised against a Leishmania major recombinant promastigote surface antigen 2 (PSA-2) fragment recognized three major polypeptides of approximate M(r) 96,000, 80,000 and 50,000 in promastigotes of three Israeli isolates of L. major including the cloned line LRC-L137-V121, but detected a different array of polypeptides in other L. major isolates. The pattern was different both in number of polypeptides detected and their molecular weight. The antibodies to L. major PSA-2 also recognized polypeptides in L. tropica, L. donovani and very weakly in L. mexicana promastigotes and in Crithidia lucilliae. The number and size of the polypeptides was different in each species. In addition to the membrane-bound PSA-2 polypeptides we identified water-soluble forms of PSA-2 released in promastigote culture supernatants. Peptide maps of the various L. major PSA-2 membrane polypeptides showed they were different from each other. N-terminal amino acid sequence of the three polypeptides expressed by L. major showed they are similar but distinct, consistent with being members of a polymorphic family. Because of the extensive sequence similarity between the PSA-2 genes it has been difficult to assign protein products to individual genes. As a first step towards solving this problem, we have transfected into L. mexicana a genomic clone of a L. major PSA-2 gene and shown that it produces a M(r) 35,000 polypeptide recognized by monoclonal and polyclonal antibodies to L. major PSA-2.

Amino Acid Sequence↗
PubMed1994

Rapid isolation of cosmid insert DNA by triple-helix-mediated affinity capture.

A simple and rapid method for the isolation of cosmid insert DNA was developed based on triple-helix-mediated affinity capture (TAC). A modified cosmid was constructed from the SuperCos 1 cosmid vector by flanking the cloning site with two homopurine-homopyrimidine triple-helix-forming sequences. The cosmid DNA is digested with NotI restriction enzyme to release the insert DNA. The NotI-digested cosmid DNA is then combined with a biotinylated homopyrimidine oligonucleotide in an acidic buffer solution to form a triple-helix complex. The triple-helix complex is captured with streptavidin-coated magnetic beads. Insert DNA is eluted by adding a pH 9 buffered solution to the captured complex. The purified insert DNA is recovered with a yield of up to 95% and a purity of at least 95%. The isolated insert DNA was directly digested with CviJI restriction endonuclease to generate random fragments for shotgun sequencing.

Base Sequence↗
PubMed1994

Reproducibility of five anorectal morphologic measurements in defecography.

RATIONALE AND OBJECTIVES: We evaluated the inter- and intraobserver reproducibility of measuring five morphologic parameters of the anorectum in defecography (evacuation proctography). METHODS: Measurements from 42 defecographic studies were statistically analyzed. The parameters measured during resting, squeezing, and straining included two anorectal angles (posterior and axis), maximal width of the anal canal, maximal width of the rectal lumen, and size of the rectocele. RESULTS: The results demonstrated only fair interobserver agreement (kappa = 0.22-0.38) for almost all measurements of the five morphologic parameters. There were high correlations (kappa = 0.62-1.00) among most intraobserver measurements. CONCLUSION: For defecographic measurement, the five parameters we studied have relatively poor clinical value because of high inter- and intraobserver inconsistency.

Adult↗