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Biomedical subjects

M C Chu

Publications and source records attributed to M C Chu.

17 recordsLinked to original sources
PubMed2005

Phenotypic variation in hyperandrogenic women influences the findings of abnormal metabolic and cardiovascular risk parameters.

In hyperandrogenic women, several phenotypes may be observed. This includes women with classic polycystic ovary syndrome (C-PCOS), those with ovulatory (OV) PCOS, and women with idiopathic hyperandrogenism (IHA), which occurs in women with normal ovaries. Where other causes have been excluded, we categorized 290 hyperandrogenic women who were seen consecutively for this complaint between 1993 and 2004 into these three subgroups. The aim was to compare the prevalence of obesity, insulin resistance, and dyslipidemia as well as increases in C-reactive protein and homocysteine in these different phenotypes with age-matched ovulatory controls of normal weight (n = 85) and others matched for body mass index (BMI) with women with C-PCOS (n = 42). Although BMI affected fasting serum insulin and the Quantitative Insulin-Sensitivity Check Index, these markers of insulin resistance were greatest in C-PCOS (n = 204), followed by OV-PCOS (n = 50) and then IHA (n = 33). Androgen levels were similar in OV-PCOS and IHA but were higher in C-PCOS, whereas gonadotropins were similar in all groups. Lipid abnormalities were highest in C-PCOS and OV-PCOS and were normal in IHA. C-reactive protein was elevated in C-PCOS and OV-PCOS but not IHA. Homocysteine was elevated only in C-PCOS. Overall, the prevalence of obesity (BMI > 30) was 29% in C-PCOS, 8% in OV-PCOS, and 15% in IHA and insulin resistance (Quantitative Insulin-Sensitivity Check Index < 0.33) was 68% in C-PCOS, 36% in OV-PCOS, and 26% in IHA. The prevalence of having at least one elevated cardiovascular risk marker was 45% in C-PCOS 38% in OV-PCOS and was not increased on IHA (6%). These results suggest that among hyperandrogenic women the prevalence of abnormal metabolic and cardiovascular risk parameters is greatest in C-PCOS, followed by OV-PCOS and then women with IHA. Moreover, in that in OV-PCOS and IHA, ages and weights were similar yet the prevalence of metabolic and cardiovascular risk was greater in OV-PCOS, the finding of polycystic ovaries may be a significant modifying factor.

Body Mass Index↗
PubMed2005

A 12-case outbreak of pharyngeal plague following the consumption of camel meat, in north-eastern Jordan.

Between late January and early February 1997, an outbreak of plague, associated with cervical lymphadenopathy and fever, occurred in the Jordanian village of Azraq ad-Druze, which lies about 50 km west of the border with Saudi Arabia. The 12 cases who presented at hospital were initially assumed to have tularaemia, and all were successfully treated with gentamicin. When, however, their sera were tested for evidence of Yersinia pestis or Francisella tularensis infection (using haemagglutination, enzyme immuno-assays for specific IgM or the F1 antigen of Y. pestis, and micro-agglutination tests), all 12 were found to have anti-Y. pestis IgM. Three dogs shot near the Saudi Arabian border were also found seropositive for antibodies against Y. pestis. Eleven of the 12 patients reported that, 2-4 days before their symptoms appeared, they had eaten the meat cut from the carcass of the same camel, either raw (10 cases) or cooked (one case). All 12 patients were diagnosed as cases of pharyngeal plague (the first cases of plague reported in Jordan for more than 80 years), caused by Y. pestis that most had acquired when they ate raw meat from a camel that was infected with the pathogen.

Adolescent↗
PubMed2001

Role of gas density in the stability of single-bubble sonoluminescence.

Recent full hydrodynamic simulations of a sonoluminescing bubble interior have shown that the bubble content is compressed to a very dense state during the violent collapse. In this paper, we numerically studied the shape stability of a radially oscillating gas bubble by using Hilgenfeldt et al. theoretical model with corrections taking into account the gas density effect. Our results show that gas density variations not only significantly suppress the Rayleigh-Taylor instability, but also enhance the threshold of the parametric instability under sonoluminescence conditions.

Journal Article↗
PubMed2000

Complete DNA sequence and analysis of an emerging cryptic plasmid isolated from Yersinia pestis.

A 6-kb cryptic plasmid (pYC; 5919 bp) has been recovered from Yersinia pestis isolates originating from regions of Yunnan province in China. The sequence of pYC was determined, and analysis of the sequence has revealed that two of the plasmid DNA regions (ORFs 10 and 11) are similar to the DinJ1 and DinJ2 gene products encoded by Escherichia coli chromosomal DNA. This plasmid is increasingly harbored by Y. pestis isolates recovered from a domestic rodent cycle in the southern regions of the province. Further studies will determine the origin and function of pYC.

Base Sequence↗
PubMed1998

A cryptic 19-kilobase plasmid associated with U.S. isolates of Yersinia pestis: a dimer of the 9.5-kilobase plasmid.

Yersinia pestis, the etiologic agent of plague, carries three prototypic plasmids with sizes of 110 kb (pFra, pTox), 70 kb (pLcr, pVW, pCad), and 9.5 kb (pPla, pPst). Studies suggest that geographic isolates of Y. pestis may be differentiated by plasmid profiles. Yersinia pestis isolated from the western United States harbor an additional plasmid, estimated to be approximately 19 kb in size. This cryptic plasmid was characterized by restriction endonuclease digestion, amplification and sequencing of the plasminogen activator gene segment, Southern blotting, and visualized by electron microscopy. Results revealed that this cryptic plasmid is a supercoiled DNA plasmid, 18.85+/-0.59 (mean+/-SD) kb in length, and is a dimer of the 9.5-kb plasmid. The genetic reason for the appearance of this form of the 9.5-kb plasmid in Y. pestis from Arizona, California, Colorado, New Mexico, and Texas is under study.

Animals↗
PubMed1996

Identification of Yersinia pestis by BBL Crystal Enteric/Nonfermenter Identification System.

The BBL Crystal Enteric/Nonfermenter System (Crystal) was used to test 25 archived isolates of Yersinia pestis to obtain a unique biochemical profile code for Y. pestis. The revised Crystal system and the API 20E system were compared by using 12 clinical human isolates of Y. pestis. Crystal correctly identified 11 of the 12 isolates, while API correctly identified 7 of the 12 isolates.

Animals↗
PubMed1996

Adult croup.

Adult croup is a distinct disease entity that probably represents a heterogeneous clinical syndrome. Three cases of adult laryngotracheitis characterized by upper airway infection and progression to airway obstruction are illustrated. Close observation and prompt decisions regarding airway intervention are critical in effective management, and complete resolution is expected.

Adult↗
PubMed1993

Replication of Colorado tick fever virus within human hematopoietic progenitor cells.

Significant neutropenia, as well as thrombocytopenia and a mild anemia, occurs in patients infected with Colorado tick fever virus. In this study, human bone marrow CD34+ cells and KG-1a cells, a human hematopoietic progenitor cell line, were infected in vitro with Colorado tick fever virus. The time course and morphological appearance of viral replication in human progenitor cells were similar to those seen in erythroblasts and in HEL cells and suggest one possible mechanism for the clinical hematologic findings.

Animals↗
PubMed1991

Growth of dengue type 2 virus isolates in human peripheral blood leukocytes correlates with severe and mild dengue disease.

We tested three dengue type 2 (DEN-2) isolates from children with clinically apparent but mild secondary dengue infections, and 10 isolates from children with moderately severe dengue hemorrhagic fever, and noted significant growth differences in peripheral blood leukocytes, but not in C6/36 cells. We also observed cytopathic effects in C6/36 cells that correlated with disease severity. These preliminary observations suggest the possibility that viral factors, whether surface antigens, attachment sites for entry into leukocytes, or intrinsic replication properties in human mononuclear phagocytes, might contribute to enhanced DEN infection and to the severity of the disease.

Child↗
PubMed1990

Antibodies to dengue 2 virus E-glycoprotein synthetic peptides identify antigenic conformation.

Eighteen synthetic peptides have now been prepared from dengue (DEN) 2 virus, representing 80% of the extra-membranal domain of the DEN envelope (E)-glycoprotein. These peptides were selected based upon our previous results with Murray Valley encephalitis (MVE) virus, computer analysis of the DEN virus sequence, and the predicted E-glycoprotein secondary structure. Six of these peptides were "structural" peptides derived from either nonlinear amino acid sequences or predicted disulfide bridge-stabilized loop structures. As with MVE virus, some peptides could be recognized by antivirus hyperimmune ascitic fluids, but monoclonal antiflavivirus antibodies failed to react with any peptide. Immunogenicity of these peptides was tested in BALB/c or NIH-Swiss mice. Fourteen of these peptides elicited antipeptide antibody in one or both mouse strains. Eleven of these antipeptides reacted with virus. Peptides 35 (amino acids 35-55) and 17 (amino acids 352-368) elicited virus-neutralizing antibody. Four antipeptides were more efficient at binding to pH 5.0-treated virus. These antipeptides precisely defined a flavivirus group common sequence (amino acids 98-110) that has biochemical characteristics similar to previously defined viral fusion sequences.

Amino Acid Sequence↗
PubMed1989

Genetic relatedness among structural protein genes of dengue 1 virus strains.

The structural protein-coding genomic regions of dengue virus type 1 (DEN-1) strains representing three distinct topotypes (Thailand, Philippines and Caribbean) were cloned and sequenced. In addition the envelope (E) nucleotide sequences of two recent Caribbean topotype DEN-1 isolates were obtained by direct RNA sequencing. The nucleotide sequence of the DEN-1 viruses in the structural gene region was found to be highly conserved with greater than 95% nucleotide sequence homology and with less than 4% change in the amino acid sequence. Although there was a less than 2% change in the nucleotide sequence of DEN-1 E proteins, strains could be differentiated by the clusters of nucleotide changes. Furthermore, the deduced amino acid changes in the E protein were clustered primarily within the proposed immunologically reactive regions. Genomic nucleotide sequence comparisons did not define geographical or virulence markers but located unique clusters of nucleotide/amino acid changes for each of the three topotypes of DEN-1 viruses examined.

Amino Acid Sequence↗
PubMed1988

Association of toxic shock toxin-1 determinant with a heterologous insertion at multiple loci in the Staphylococcus aureus chromosome.

Most Staphylococcus aureus strains associated with toxic shock syndrome and producing toxic shock syndrome toxin 1 (TSST-1) require tryptophan because of a genetic defect in tryptophan biosynthesis. The association between TSST-1 production and tryptophan auxotrophy was not correlated with the phage type, the colonization site, or the disease status of the patient from whom the isolate came. Protoplast fusion and transformation mapping located the genetic determinant of TSST-1 production (tst) very close to the trp operon in such strains and very close to tyrB in a Trp+ TSST-1+ strain. Southern blot hybridization of ClaI-restricted chromosomal DNA with a tst-specific probe revealed a common homologous segment in all of the Trp+ strains with tst linked to tyrB. These results confirmed that the tst determinant in Trp- strains is located at one site, whereas in Trp+ TSST-1+ strains the determinant is located elsewhere on the S. aureus chromosome. It is suggested that the TSST-1 determinant is associated with the insertion of a transposonlike segment into several sites on the S. aureus chromosome.

Bacterial Toxins↗
PubMedDate not supplied

Growth of toxic shock syndrome toxin 1-producing, tryptophan-requiring strains of Staphylococcus aureus associated with the presence of Escherichia coli.

More than 80 percent of TSST-1-positive strains of Staphylococcus aureus are tryptophan auxotrophs (Trp-). Chromosomal mapping has located the genetic determinant for TSST-1 (tst) in the trp operon for strain S411 (Trp-) and near the tyrB site for strain FRI1169 (Trp*). Auxonographic screening on tryptophan-free medium of 28 strains of S. aureus (TSST-1-positive and -negative, Trp+ and Trp-) against Escherichia coli (strains 6094, 7603, and 7877) and other strains of Enterobacteriaceae showed that Trp- S. aureus strains responded only to E. coli and tryptophan. Neither E. coli nor tryptophan inhibited TSST-1 production. Cocultivation of strain FRI1169 or S411 with E. coli strain 7877 showed that TSST-1 production by FRI1169 was not enhanced. In contrast, TSST-1 production by S411 was equal to that of S. aureus alone (less than 640 ng/mL) or enhanced (greater than 12,000 ng/mL) if the input log10 cfu of S. aureus was of equal or greater ratio to input E. coli and if the recovered S. aureus was greater than log10 5 cfu. These results suggest that nutritionally deficient toxicogenic strains of S. aureus may overcome growth limitation by coexisting in dynamic balance with strains of E. coli.

Bacterial Toxins↗
PubMedDate not supplied

Effect of magnesium on in vitro production of toxic shock syndrome toxin 1.

Batch and chemostat culture of Staphylococcus aureus strain S411 was conducted in an investigation of the role of Mg++ in the control of production of toxic shock syndrome toxin 1 (TSST-1). Under both growth conditions, Mg++ influenced bacterial growth, and TSST-1 production was correlated with bacterial growth. The specific activity of TSST-1 (ng/mg yield, ng/mg total protein) increased with increasing concentrations of Mg++ and was maximal at physiologic levels of Mg++. No production of TSST-1 was observed under anaerobic conditions. In chemostat cultures in which valine nutrient limitation was used with various levels of tryptophan in the chemically defined medium, tryptophan concentration controlled the production of TSST-1 by strain S411, regardless of the concentration of Mg++.

Aerobiosis↗
PubMedDate not supplied

A serological survey of rural dogs and cats on the southwestern Canadian prairie for zoonotic pathogens.

A survey for antibodies against agents of plague, tularemia, and Rocky Mountain spotted fever (RMSF), and against Sin Nombre hantavirus (SNV), Bartonella henselae and B. clarridgeiae was conducted in the summer of 1995 using serum from rural dogs and cats living in the vicinity of four public parks in southeastern Alberta and southwestern Saskatchewan. Antibodies to all pathogens were detected in all survey areas. Overall prevalence rates were 0.075 for Yersinia pestis, 0.089 for Francisella tularensis, 0.025 for Rickettsia rickettsii (dogs only), and 0.029, 0.178 and 0.186 for SNV, B. henselae and B. clarridgeiae, respectively (cats only). This serological survey of rural dogs and cats was more sensitive and efficient than previous surveys based on collection and culture of rodents and ectoparasites. All six pathogens appear endemic to the region. Surveillance for plague, tularemia, RMSF and SNV, and management of associated public risks should be done in endemic regions.

Animals↗