Biomedical subjects

S Wong

Publications and source records attributed to S Wong.

At least 163 records · Page 9Linked to original sources

PubMed1994

Analysis of the peripheral T-cell receptor V beta repertoire in newly diagnosed patients with type I diabetes.

Type I diabetes is an autoimmune disease characterised by a marked activation of peripheral T cells around the time of clinical diagnosis. Studies of T-cell antigen receptor V beta (TCRBV) gene usage in type I diabetes have been conflicting. Using a semi-quantitative polymerase chain reaction technique and flow cytometry we have investigated the TCRBV gene usage of 13 newly diagnosed patients with type I diabetes and 11 normal healthy controls. No preferential TCRBV gene usage was found between patients and controls even after matching for HLA-DR3 and/or -DR4. In addition, no significant differences in TCRBV gene usage were found between sequential samples taken over a period of up to 7 months following diagnosis. These results suggest that the TCR repertoire of these patients is heterogeneous and it is unlikely that a single 'pathogenic' T-cell clone is dominant at the clinical onset of the disease.

Adult↗

PubMed1994

Roaming yuppies: Hong Kong migration to Australia.

"Hong Kong has been the top source for Asian migration to Australia in recent years. The majority of the Hong Kong migrants are young, educated professionals. Using survey data conducted in Hong Kong on emigration tendencies, this article analyzes why they are leaving Hong Kong, what attracts them to Australia, and what impact this influx has on Australian society. It is speculated that this movement may create an enduring change in the identity of emigrant Hong Kongers and have a wider significance in the contradictory currents of geopolitics and geoeconomics which are simultaneously encouraging and resisting migration."

Asia↗

PubMed1994

Ofloxacin eardrop treatment for active chronic suppurative otitis media: prospective randomized study.

This report presents a prospective randomized study of 0.3 percent ofloxacin eardrops for the treatment of active chronic suppurative otitis media. Twenty-nine patients were treated with ofloxacin eardrops for 1 week, and another 27 patients were treated with Augmentin for 1 week. One week after completion of treatment, 22 (76%) patients of the group treated with ofloxacin had dry ears, and only seven (26%) patients treated with Augmentin had dry ears. Ofloxacin eardrops were effective in the initial treatment of active chronic suppurative otitis media.

Administration, Oral↗

PubMed1993

Isolation and characterization of an intracellular serine proteinase inhibitor from a monkey kidney epithelial cell line.

A recent report described a thrombin inhibitory activity in the soluble fraction of human placenta and the cytosolic fraction of K562 cells. Isolation and characterization of the functionally inactive 35-38-kDa placental form of this protein revealed that it was a novel serine proteinase inhibitor (Coughlin, P. B., Tetaz, T., and Salem, H. H. (1993) J. Biol. Chem. 268, 9541-9547). In the present study, we observed a 67-kDa sodium dodecyl sulfate (SDS)-stable complex when 125I-thrombin was incubated with the cytosolic fraction of a monkey kidney epithelial cell line, BSC-1. This complex was not observed in either the particulate cell fraction extracted with 0.2% Triton X-100 or medium conditioned by cells, suggesting that the thrombin-complexing factor is confined to the cytoplasm. The cytoplasmic antithrombin activity was purified to apparent homogeneity from the cytosol of BSC-1 cells previously pulsed with [35S]methionine by a combination of heparin-agarose chromatography, Mono Q fast protein liquid chromatography, and anhydrotrypsin-Affi-Gel 10 affinity chromatography. Analysis of the affinity-purified preparation by SDS-polyacrylamide gel electrophoresis and fluorography revealed a single protein with an apparent molecular mass of 38 kDa. The purified 38-kDa protein inhibited the amidolytic activities of thrombin, trypsin, urokinase, and factor Xa but not that of elastase. Incubation of the 38-kDa protein with excess thrombin identified approximately 60% of the labeled 38-kDa protein in an SDS-stable 67-kDa complex. The purified 38-kDa inhibitor was cleaved with cyanogen bromide and the isolated peptides subjected to microsequencing. Amino acid sequence obtained for a region within this protein exhibited significant homology with human antithrombin III and plasminogen activator inhibitors 1 and 2. This homologous peptide contained the full complement of residues designated as highly conserved in helix F of the greater serine proteinase inhibitor superfamily. In addition, an internal sequence of GGGGDIHQGF was found in the monkey cytoplasmic inhibitor, which is identical to that reported for an internal sequence of the human placental inhibitor. These findings confirm the existence of a novel cytoplasmic serine proteinase inhibitor in mammalian cells and provide additional details of its molecular properties. The physiological function of this novel serine proteinase inhibitor in cytoplasm is unknown.

Amino Acid Sequence↗

PubMed1993

A phantom for beam positioning and visualization.

PURPOSE: A system was developed which uses the light field on the simulator to allow easy visualization of the treatment field in the sagittal plane of a phantom for complex treatment geometries. METHODS AND MATERIALS: The phantom consists of a plastic shell with a vertical metallic plate in the sagittal plane. Magnetic strips attach to the plate to mark the lateral field while the anterior field is marked by a special pointer. CONCLUSION: This method is useful for teaching and technique development by showing how the field is distorted after gantry, collimator, and couch rotations, as well as any overlap or gap in field matching for certain treatment techniques. It could be modified for actual patient setup.

Humans↗

PubMed1993

Epigenetic mechanisms of drug resistance: drug-induced DNA hypermethylation and drug resistance.

In a model system employing Chinese hamster V-79 cells, the DNA synthesis inhibitor 3'-azido-3'-deoxythymidine (BW A509U, AZT) was shown to induce genome-wide DNA hypermethylation, low-frequency silencing of thymidine kinase (TK; EC 2.7.1.21) gene expression, and resistance to AZT. Twenty-four hours of exposure of V-79 cells to 150 microM AZT led to > 2-fold enhancement of genomic 5-methylcytosine levels and produced TK- epimutants at a rate approximately 43-fold above background. Such AZT-induced TK- epimutants were shown to be severely reduced in their capacity to activate AZT to its proximate antiviral form, AZT 5'-monophosphate, as compared with the TK+ parental cell line from which they were derived. TK- clones isolated under these conditions were shown to be 9- to 24-fold more resistant to the cytotoxic effects of AZT than the parental TK+ cell line and showed collateral resistance to 5-fluoro-2'-deoxyuridine. Three of four TK- epimutants could be reactivated at very high frequency (8-73%) to the TK+ AZT-sensitive phenotype by 24 hr of exposure to the demethylating agent 5-azadeoxycytidine (5-azadC), implying that drug-induced DNA hypermethylation, rather than classical mutation, was involved in the original gene-silencing event in these three clones. These 5-azadC-induced TK+ revertants concomitantly regained the ability to metabolize AZT to its 5'-monophosphate. RNA slot blot analyses indicated that the four AZT-induced TK- clones expressed 8.9%, 15.6%, 17.8%, and 11.1% of the parental level of TK mRNA. The three clones that were reactivatable by 5-azadC showed reexpression of TK mRNA to levels 84.4%, 51.1%, and 80.0% that of the TK+ parental cell line. These experiments show that one potential mechanism of drug resistance involves drug-induced DNA hypermethylation and resulting transcriptional inactivation of cellular genes whose products are required for drug activation.

Animals↗

PubMed1993

Forskolin inhibits platelet-activating factor binding to platelet receptors independently of adenylyl cyclase activation.

The effect of forskolin on platelet-activating factor (PAF) receptor was investigated. Rabbit platelets treated with forskolin showed approximately a 9-fold increase in cAMP levels over the control. After treatment of platelets with forskolin prior to PAF binding, a 30-40% (P < 0.005) decrease in PAF binding was observed. The decrease in PAF binding caused by forskolin was concomitant with a decrease in the physiological responses of platelets induced by PAF. However, this forskolin-induced decrease in PAF binding was not a consequence of cAMP formation as the addition of a cAMP analog could not mimic the action of forskolin. Additionally, the inactive analog of forskolin, dideoxyforskolin, which does not activate adenylyl cyclase, also reduced PAF binding to its receptor. Reduction of PAF binding by forskolin and dideoxyforskolin was also observed with isolated platelet membranes. To understand the mechanism of forskolin induced changes in PAF binding, the involvement of a G-protein in this process was investigated. Cells treated with GTP gamma S showed approximately a 25% reduction in PAF binding. Addition of forskolin to the GTP gamma S treated cells resulted in a further reduction in PAF binding, suggesting the action of forskolin was independent of G-protein activation. The data suggests that the action of forskolin was independent of adenylyl cyclase or G-protein involvement. It is speculated that the action of forskolin on PAF binding was due to a direct effect of this molecule and its analog on the PAF receptor itself or to components of the post-receptor signalling for PAF.

Adenylyl Cyclases↗

PubMed1993

Functional characteristics of QT prediction formulas. The concepts of QTmax and QT rate sensitivity.

A community-based population sample of 14,379 North American children and adults aged from birth to 75 years with normal ECG was used to investigate functional properties of 13 QT prediction formulas over a wide range of heart rates (HR) in normal sinus rhythm. QT measurements were made by a computer program from simultaneously sampled standard 12-lead or orthogonal XYZ leads and all QT measurements were visually verified using a high-resolution display terminal. New concepts of QT rate sensitivity (dQT/dHR) and maximum predicted QT after a long pause (QTmax) are introduced. Drastically diverging functional behavior is documented for different QT prediction formulas regarding QT rate sensitivity and QTmax. The simplest formula for predicted QT (QTp) meeting reasonable physiological constraints regarding QTmax and functional behavior of QT rate sensitivity while producing the best QT prediction accuracy was a function with only one independently adjusted parameter (QTmax) of the form: QTp = QTmax/(1 + 0.01HR), with QTmax = 656 ms. This formula also suggests that QT rate sensitivity is inversely proportional to the square of HR and that individual values of QTmax can be predicted from ambulatory or exercise ECGs using the formula QTmax = 2 x QT100, where QT100 is QT at HR = 100/min.

Adolescent↗

PubMed1993

Early and late gene expression in UT-7 cells infected with B19 parvovirus.

UT-7, a human megakaryocytoblastoid cell line, can be persistently infected with B19 parvovirus. We performed detailed serial analysis of parvovirus DNA replication and RNA transcription of synchronized cells. RNA transcription appeared as an early event following infection, with viral RNA detected about 6 hr after infection. In contrast, dimer-replicative intermediate forms of parvovirus DNA did not appear until more than 16 hr after infection. Northern analysis of specific transcripts showed an earlier appearance of nonstructural protein RNA (6 hr) compared to capsid protein RNA (24 hr). The addition of an inhibitor of protein synthesis to block synthesis of nonstructural protein abolished capsid protein RNA transcription as well as DNA replication. Primer extension analysis confirmed the initiation of all transcription from the single P6 promoter. RNA transcription precedes DNA replication of B19 parvovirus in these cells, and RNA processing may have a major role in regulating gene expression.

Base Sequence↗

PubMed1993

Organization of mini-exon and 5S rRNA genes in the kinetoplastid Trypanoplasma borreli.

Mini-exon gene repeats from Trypanoplasma borreli, which belongs to the Cryptobiidae family of the Bodonina suborder of the Kinetoplastida, were isolated by PCR amplification and cloning. The presence of kinetoplastid-like mini-exon genes in T. borreli is consistent with the taxonomic status of this organism as a kinetoplastid protozoan. Two families of repeats were found: 597 nt (T1) and 794 nt (T2), each of which encodes an approximately 95-nt medRNA transcript. The T1 repeats also contain a complete 5S rRNA gene on the complementary strand. The T2 repeats contain a defective copy of a 5S gene, in which the 5' portion is absent. The intergenic regions between the 5'-ends of the mini-exon genes and the 5S rRNA genes in the T1 and T2 repeats are highly diverged. All or most mini-exon genes and 5S genes are located within either the T1 or the T2 repeats. The T1 repeats were localized to a megabase-size chromosome, while the T2 repeats were localized within at least 4 large chromosomes.

Animals↗

PubMed1993

Changes in 17 beta,20 alpha-hydroxysteroid dehydrogenase activity supporting an increase in the estrogen/progesterone ratio of human fetal membranes at parturition.

OBJECTIVE: Our purpose was to measure the activity of the reversible enzyme 17 beta,20 alpha-hydroxysteroid dehydrogenase around parturition with estrogen and progestogen substrates. STUDY DESIGN: Classic kinetic studies and explant cultures were used to determine kinetic parameters and net enzyme activities in both oxidative and reductive directions for both sets of substrates. RESULTS: Affinity constant values for estrone, estradiol, and 20 alpha-dihydroprogesterone were 1 to 8 mumol/L. Affinity constant for progesterone was 9 to 25 mumol/L. Maximal velocities for all substrates in the chorion were 20- to 70-fold higher than in amnion and severalfold higher for estrogen substrates compared with the progestins. Around parturition there was a significant change toward net formation of the stronger estrogen (estradiol) and the weaker progestin (20 alpha-dihydroprogesterone), suggesting an increase in the local estrogen/progesterone ratio. CONCLUSION: The enzyme 17 beta,20 alpha-hydroxysteroid dehydrogenase may be an important regulator of the local estrogen/progesterone ratio in fetal membranes around the time of parturition.

20-Hydroxysteroid Dehydrogenases↗

PubMed1993

Categorization of clinical isolates of Helicobacter pylori on the basis of restriction digest analyses of polymerase chain reaction-amplified ureC genes.

Restriction endonuclease analyses of a 1.1-kb polymerase chain reaction-amplified portion of the ureC gene from Helicobacter pylori were used to group or to differentiate 21 clinical isolates. Isolates were placed into 4 groups after HindIII digestion alone, and placement was expanded into 15 groups after isolates were digested with AluI and PvuI.

Bacterial Typing Techniques↗

PubMed1993

Genomic and transcriptional linkage of the genes for calmodulin, EF-hand 5 protein, and ubiquitin extension protein 52 in Trypanosoma brucei.

We report genomic linkage of a pair of tandem, identical ubiquitin-extension protein 52 (EP52) genes, a novel EF-hand superfamily member gene (EFH5), and the calmodulin gene cluster in Trypanosoma brucei. The intergenic regions of these four genes are short: about 108 bp between the calmodulin gene C and the EFH5 gene, about 111 bp between the EFH5 gene and the ubiquitin-EP52/1 gene, and about 116 bp between the ubiquitin-EP52/1 and -EP52/2 genes. RNA molecules that span these three intergenic regions have been detected by polymerase chain reaction, which suggests that the genes are transcribed in a polycistronic manner. Transcription of the calmodulin, EFH5, and ubiquitin-EP52 genes in isolated nuclei is rapidly inactivated by UV irradiation, which further strengthens the hypothesis that this cluster of three different genes is transcribed in a polycistronic manner and suggests that they are under the control of a single distant upstream promoter. These results suggest that polycistronic transcription is common in trypanosomes and will probably be found for most, if not all, protein-encoding genes. The presence of at least three housekeeping genes with different known or potential regulatory functions within a polycistronic unit suggests that regulation of transcription initiation plays an important role in the coordinated expression of housekeeping genes in trypanosomes.

Amanitins↗

PubMed1993

The dynamics of prostaglandin metabolism in human fetal membranes and decidua around the time of parturition.

To address whether prostaglandins (PGs) produced in the amnion can gain access to the myometrium, we used three in vitro systems to determine the characteristics of PG secretion, metabolism, and transfer in amnion, chorion, and decidua around the time of parturition. PG metabolism, measured in explant cultures or cytosol preparations, occurs predominantly by the enzyme PG dehydrogenase, which was highest in chorion and was 2- to 3-fold more active for PGE2 than PGF2 alpha. The activity increased significantly around the time of labor onset. The activity of PG-9-ketoreductase, which interconverts the E and F series of PGs, was 2-3 orders of magnitude less than that of PG dehydrogenase. Using a dual chamber perfusion apparatus, we demonstrated that similar amounts of PGE2 were secreted from the fetal (amnion) and maternal (chorio-decidua) surfaces, and this ratio did not change with labor. Using radiolabeled PGE2, radioactivity traversed full thickness membranes at the rate of 4%/h. Only approximately 12% of the transferred radioactivity remained as intact PGE2, and very little conversion to PGF2 alpha was detected. No changes in transfer were detected around the onset of labor. We conclude that it is unlikely that PGE2 produced in the amnion acts directly on the myometrium.

Amnion↗

PubMed1993

Familial isolated hyperparathyroidism: a distinct genetic entity with an increased risk of parathyroid cancer.

Familial isolated hyperparathyroidism (FIHP) is a rare heritable disorder characterized by hypercalcemia, inappropriately high PTH levels, and isolated parathyroid tumors with no evidence of hyperfunction of any other endocrine tissues. To establish whether FIHP exists as a distinct disease entity or represents a variant of any of the known multiple endocrine neoplasia (MEN) syndromes, we tested 19 members of a large, well characterized family with FIHP in which the disease is transmitted through 4 generations in an autosomal dominant fashion. Fourteen DNA markers at 10 polymorphic loci closely linked to the MEN1 locus on the long arm of chromosome 11 and 5 markers close to the MEN2A gene on chromosome 10 were tested using Southern blot analysis and polymerase chain reaction-based techniques. Additionally, two polymorphic markers (Mir1 and Mir2) within the prepro-PTH gene on the short arm of chromosome 11 were analyzed using denaturant gradient gel electrophoresis. Linkage was clearly excluded between FIHP and the MEN1 and MEN2A loci as well as to the PTH gene. Comparison of constitutional and tumor genotypes showed that constitutional heterozygosity was retained for markers in the MEN1 and MEN2A regions as well as to the PTH gene in 4 tumors from 3 affected members. In 1 individual, a parathyroid carcinoma was found after recurrence of hypercalcemia. We, therefore, propose that autosomal dominant FIHP can occur as a genetically and clinically distinct entity with an increased risk of malignant transformation of parathyroid tumors.

Adolescent↗

PubMed1993

Comparison of the efficacy and metabolic effects of nicardipine and hydrochlorothiazide in hypertensive black men and women.

A double-blind, randomised, parallel study compared the BP and metabolic responses in black hypertensive patients following monotherapy with nicardipine or hydrochlorothiazide (HCTZ). Following a single-blind placebo wash-out period of 1-4 weeks, the study drug, nicardipine 20-40 mg three times daily or HCTZ 25-100 mg four times daily, was administered in a double-blind fashion for 12 weeks. Doses were titrated to control sitting DBP (< or = 90 mmHg). Both drugs were effective in reducing sitting SBP and DBP as compared with baseline values (nicardipine: 152.5 +/- 1.6/102.0 +/- 0.6, HCTZ: 152.5 +/- 1.5/101.4 +/- 0.5 mmHg). DBP responses (reduction from baseline; nicardipine: -10.9, HCTZ: -12.7 mmHg), and the percentage of patients achieving a response < or = 90 mmHg (nicardipine: 54%, HCTZ: 63%) to the two drugs were similar. Although SBPs at baseline and endpoint (137.3 +/- 1.6 on nicardipine and 132.1 +/- 1.4 mmHg on HCTZ), and the percentage of patients achieving a response < or = 140 mmHg (nicardipine: 70%, HCTZ: 79%), were comparable between the two treatments, the SBP reduction with HCTZ was statistically greater (P = 0.026). A comparison of the metabolic responses in the two treatment groups showed significant differences. Nicardipine caused no significant changes in blood chemistry, whereas HCTZ caused statistically significant decreases (P < 0.001) in sodium and potassium and increases (P < or = 0.01) in glucose, BUN, creatinine, uric acid, cholesterol and LDL compared with baseline. In 12.7% of the patients in the HCTZ group, serum potassium dropped to levels < 3.5 meq/l, which occurred in only 1.4% of the patients who used nicardipine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Establishment of a Chinese hamster ovary cell line that expresses grp78 antisense transcripts and suppresses A23187 induction of both GRP78 and GRP94.

GRP78, a 78,000 dalton protein residing in the endoplasmic reticulum, is postulated to play important roles in protein folding and cell survival during calcium and other physiological stress. Here we describe the construction of an eukaryotic expression vector for the constitutive expression of grp78 antisense RNA and the creation of a CHO cell line, 78WO, which expresses high levels of the grp78 antisense RNA through amplification of the stably transfected antisense vector. We observed that whereas 78WO maintains a basal level of GRP78 similar to that of control cells, GRP78 is no longer inducible by A23187. The 78WO cells have undergone a compensatory increase in grp78 transcription such that the effects of antisense are cancelled out at the protein level under nonstressed conditions. In these same cells, GRP94, a 94,00 dalton ER protein, is also rendered noninducible by A23187. This provides the first evidence that the regulation of two ER proteins might be coupled such that the failure to induce GRP78 results in the down-regulation of GRP94. The 78WO cell line grows with a doubling time of about 26 hr and exhibits decreased tolerance to A23187, suggesting the GRPs contribute to cell viability under calcium stress. The establishment of this cell line, which can be stably maintained, will provide a useful tool for testing whether the induction of the GRPs is important for protein folding or transport and whether their enhanced synthesis is the cause or consequence of a variety of physiological adaptations.

Animals↗

PubMed1992

Identification of a new EF-hand superfamily member from Trypanosoma brucei.

We identified several open reading frames between the regions encoding calmodulin and ubiquitin-EP52/1 in the genome of Trypanosoma brucei. One of these, EFH5, encodes a protein 192 amino acids long. The EFH5 transcript is present in poly(A)+ mRNA and is present at similar levels in the mammalian bloodstream form and the insect procyclic form. EFH5 contains four EF-hand homolog domains, two of which are inferred to bind Ca2+ ions. We expressed EFH5 as a fusion protein in Escherichia coli and demonstrated calcium-binding activity of the fusion protein using the 45Ca-overlay technique. The function of EFH5 remains unknown; however, as the fourth EF-hand homolog identified in trypanosomes, it attests to the broad range of functions assumed by calcium functioning as a second messenger. EFH5, which is most closely related to LAV1-2 from Physarum, represents a distinct subfamily among the EF-hand-containing proteins.

Amino Acid Sequence↗