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H Louie

Publications and source records attributed to H Louie.

At least 19 recordsLinked to original sources
PubMed2004

FlaC, a protein of Campylobacter jejuni TGH9011 (ATCC43431) secreted through the flagellar apparatus, binds epithelial cells and influences cell invasion.

Type III secretion systems identified in bacterial pathogens of animals and plants transpose effectors and toxins directly into the cytosol of host cells or into the extracellular milieu. Proteins of the type III secretion apparatus are conserved among diverse and distantly related bacteria. Many type III apparatus proteins have homologues in the flagellar export apparatus, supporting the notion that type III secretion systems evolved from the flagellar export apparatus. No type III secretion apparatus genes have been found in the complete genomic sequence of Campylobacter jejuni NCTC11168. In this study, we report the characterization of a protein designated FlaC of C. jejuni TGH9011. FlaC is homologous to the N- and C-terminus of the C. jejuni flagellin proteins, FlaA and FlaB, but lacks the central portion of these proteins. flaC null mutants form a morphologically normal flagellum and are highly motile. In wild-type C. jejuni cultures, FlaC is found predominantly in the extracellular milieu as a secreted protein. Null mutants of the flagellar basal rod gene (flgF) and hook gene (flgE) do not secrete FlaC, suggesting that a functional flagellar export apparatus is required for FlaC secretion. During C. jejuni infection in vitro, secreted FlaC and purified recombinant FlaC bind to HEp-2 cells. Invasion of HEp-2 cells by flaC null mutants was reduced to a level of 14% compared with wild type, suggesting that FlaC plays an important role in cell invasion.

Bacterial Adhesion↗
PubMed2000

Identification of Campylobacter jejuni, C. coli, C. lari, C. upsaliensis, arcobacter butzleri, and A. butzleri-like species based on the glyA gene.

Currently, the detection and identification of Campylobacter and Arcobacter species remains arduous, largely due to cross-species phenotypic similarities and a relatively narrow spectrum of biochemical reactivity. We have developed a PCR-hybridization strategy, wherein degenerate primers are used to amplify glyA fragments from samples, which are then subjected to species-specific oligodeoxyribonucleotide probe hybridizations, to identify and distinguish between Campylobacter jejuni, C. coli, C. lari, C. upsaliensis, Arcobacter butzleri, and an A. butzleri-like species. Evaluation of this strategy with genomic DNA from different type strains suggests that this approach is both specific and sensitive and thus may be applicable in a diagnostic assay to identify and differentiate these highly related species.

Arcobacter↗
PubMed1998

Expression of the flgFG operon of Campylobacter jejuni in Escherichia coli yields an extra fusion protein.

Two Campylobacter jejuni genes with homology to the Escherichia coli flgF and flgG genes encoding two of the basal body rod proteins were isolated, and the nucleotide sequence was determined and analyzed. These two C. jejuni genes were shown, by Northern hybridization analysis, to function as a single operon (flgFG). Two transcriptional start sites were detected upstream of flgF, corresponding to the two RNA transcripts detected in the Northern blot. Western blot immunoassays using anti-FlgF and anti-FlgG antibodies demonstrated the synthesis of FlgF and FlgG proteins in C. jejuni and in Escherichia coli containing the C. jejuni flgF and flgG genes. Maxicell analysis and Western immunoblots using anti-FlgF antibodies to probe flgFG-encoded proteins in E. coli revealed the presence of a protein with a molecular mass of approximately the combined mass of the FlgF and FlgG proteins. Anti-FlgF antibodies detected in C. jejuni cell extracts the native FlgF protein and also a higher-molecular-weight protein that is likely encoded by the flgF and part of the flgG sequences.

Amino Acid Sequence↗
PubMed1998

The need to step up the gonadotropin dosage in the stimulation phase of IVF treatment predicts a poor outcome.

PURPOSE: It is a common practice to increase the gonadotropin dose during ovarian stimulation when the estradiol (E2) rise is found to be inadequate. The prognostic impact of the use of this step-up regimen on the outcome of the affected in vitro fertilization (IVF) cycle is the subject of this study. METHODS: This is a retrospective analysis of IVF cycles in a series of consecutive patients who required an increase in the gonadotropin dosage during the stimulation phase because of inadequate E2 rise. Controls consisted of patients in whom the dose was not increased. After 4 days of stimulation, the gonadotropin dosage was increased if E2 levels failed to rise by 70% every 2 days. Outcome was defined in terms of maximum E2 level, number of follicles at aspiration, number of oocytes obtained, fertility rate, and pregnancy rate and was compared in study and control patients. Pregnancy was defined by sonographic demonstration of cardiovascular activity. RESULTS: One hundred forty-five patients were analyzed. A step-up regimen was used in 35 patients (24.1%). Patients who required the step-up dosing had significantly lower peak E2 levels (1373 vs 1828 pg/ml; P < 0.005), fewer follicles measuring greater than 16 mm (7.2 vs 9.7; P < 0.003), and fewer oocytes recovered (8.3 vs 11.2; P < 0.009). The fertilization rate (67.6 vs 64.2%) was not significantly different. The pregnancy rate (8.5 vs 32.7%; P < 0.004) was significantly lower in the group requiring the step-up regimen. CONCLUSIONS: The utilization of a step-up regimen during an IVF treatment cycle is a predictor of a poor outcome for the specific IVF cycle. As this information is available before retrieval, consideration of cycle cancellation may be appropriate.

Adult↗
PubMed1997

Infection of cats by injection with DNA of a feline immunodeficiency virus molecular clone.

Establishment of infection of animals with a viral clone will be important for investigating viral determinants of pathogenesis and monitoring sequence changes in the viral genome in vivo and may find utility as a means of immunization with live-attenuated virus. To test the efficiency of intramuscular (i.m.) injection of cloned proviral plasmid DNA for establishing feline immunodeficiency virus (FIV) infection in specific pathogen-free (SPF) cats, groups of cats were inoculated by the i.m. route with 300, 100, or 30 micrograms of plasmid DNA containing the infectious molecular clone, FIV-pPPR. A fourth group of cats was inoculated intradermally with 30 micrograms of FIV-pPPR plasmid DNA. For comparison, a fifth group received 10(3) TCID50 of a live virus stock of FIV-pPPR by intraperitoneal inoculation. Inoculation by i.m. injection with 100 to 300 micrograms of infectious FIV-pPPR proviral DNA produced infection detectable by both antiviral antibody and virus isolation from peripheral blood mononuclear cells. Inoculation by i.m. injection with 30 micrograms of proviral DNA resulted in infection in two of three inoculated cats. Intradermal injection with 30 micrograms of proviral DNA induced infection in one of three cats. Induction of antiviral antibody and viremia was delayed in cats inoculated with 30 micrograms compared to cats inoculated with either 100 or 300 micrograms of proviral DNA. This study indicates that cloned FIV proviral DNA may replace infectious virion preparations as inocula for pathogenesis and immunization studies.

Animals↗
PubMed1996

Guided bone regeneration to facilitate implant and prosthodontic therapy: three case reports.

In some patients, lack of bone at a desired fixture site has resulted, by necessity, in the placement of endosseous implants in less than favorable locations. The principles of guided bone regeneration can be used to restore lost alveolar bone and permit the placement of implants at more ideal locations, or to provide a more favorable ridge form to support a removable prosthesis. The advantages of a two-stage technique involving bone grafting followed by a healing period prior to implant placement are discussed. Different methods of membrane tenting to provide space for bone growth are illustrated by three case reports. Evidence of bone augmentation is provided by computed tomography.

Adult↗
PubMed1995

Cloning and transcription regulation of the ferric uptake regulatory gene of Campylobacter jejuni TGH9011.

A Campylobacter jejuni (Cj) TGH9011 (ATCC 43431) gene homologous to the Escherichia coli ferric uptake regulatory gene (fur) has been cloned and characterized. Cj fur encodes a polypeptide consisting of 157 amino acids (aa) (18.1 kDa). The 5'-flanking region of the Cj fur gene contains two putative catabolite activator protein (CAP)-binding sequences and four Fur boxes or Fur-binding sequences (FBS), implicating cAMP and autogenous regulation respectively. A major and a minor transcription start point (tsp) were active in Fe(+) and Fe(-) media and three tsp were suppressed in Fe(+) condition. The major transcript has an unusually short leader sequence. The homology of the Cj Fur to other Proteobacteria Fur proteins is moderately low with identity ranging from 36.3% for Yersinia pestis to 31.8% for Legionella pneumophila. Multiple alignments of the Fur sequences identified three conserved motifs, I [aGLKvTlpR1KiL], II [eiGlATvYR] and III [HHDHlvCldcGeviEf] (uppercase aa are identical in 12 or all 13 Fur sequences and lowercase aa are identical in six or more sequences). A truncated TGFH9011 Fur missing 18 aa of the N terminus but retaining all three conserved motifs was shown to bind all four FBS sequences. The binding and transcription studies support autoregulation of fur expression in Cj.

Amino Acid Sequence↗
PubMed1995

Physical and genetic map of the genome of Campylobacter upsaliensis.

A physical map of Campylobacter upsaliensis ATCC 43954 was constructed from DNA fragments generated by SalI (5' G/TCGAC), NarI (5' GG/CGCC) and BssHII (5' G/CGCGC) restriction digests separated using pulsed-field gel electrophoresis. The size of the C. upsaliensis genome was approximately 2000 kb, providing evidence of the largest Campylobacter genome sized to date. Twenty-one fragments created from these restriction digests were assembled into a physical map using a combination of complementary methods including cross-Southern hybridization, hybridization fingerprint analysis and hybridization with homologous and heterologous (from Campylobacter jejuni) gene probes. The position of ten genetic loci, including that of the iron-uptake regulatory (fur) gene, were localized to the physical map. A genomic library of C. upsaliensis ATCC 43954 was constructed in lambda Gem-11 vector. Fifty thousand recombinants with an average size of 16 kb represent a library about 200 times the size of the genome. Using C. jejuni DNA probes, clones representing C. upsaliensis flaA, fur and ftsZ genes were isolated and localized to the physical map.

Blotting, Southern↗
PubMed1993

Cloning and characterization of the gamma-glutamyl phosphate reductase gene of Campylobacter jejuni.

The gamma-glutamyl phosphate reductase gene, proA, of Campylobacter jejuni was isolated from a recombinant pBR322 clone. A HindIII fragment of the insert containing the gene was subcloned into pUC19 and sequenced in both orientations. The deduced amino acid sequence of gamma-glutamyl phosphate reductase (EC 1.2.1.41) of C. jejuni exhibits 36.4% identity to that of Escherichia coli and 36.0% identity to Serratia marcescens. Two highly conserved regions in the amino acid sequence were identified from the alignment of the three available gamma-glutamyl phosphate reductase gene sequences. The gene was expressed from its own promoter and the transcription start site was mapped. The proline biosynthetic genes of C. jejuni are not located tandemly and thus differ in this respect from those of E. coli and S. marcescens, where gamma-glutamyl phosphate reductase and gamma-glutamyl kinase (proB) are located in a single operon.

Aldehyde Oxidoreductases↗
PubMed1993

Fine mapping of the three rRNA operons on the updated genomic map of Campylobacter jejuni TGH9011 (ATCC 43431).

The three rRNA gene loci of Campylobacter jejuni TGH9011 (ATCC 43431) were cloned. All three rRNA operons were shown to possess a contiguous 16S-23S structure and contain intercistronic tRNA(Ala) and tRNA(Ile). The three RNA operons and additional 14 genetic markers were mapped in the updated genomic map of C. jejuni TGH9011, which now has a total of 24 genetic markers.

Campylobacter jejuni↗
PubMed1993

Experimental vaccine protection against homologous and heterologous strains of feline immunodeficiency virus.

More than 90% of cats immunized with inactivated whole infected-cell or cell-free feline immunodeficiency virus (FIV) vaccines were protected against intraperitoneal infection with 10 50% animal infectious doses of either homologous FIV Petaluma (28 of 30 cats) or heterologous FIV Dixon strain (27 of 28 cats). All 15 control cats were readily infected with either strain of FIV. Protection appears to correlate with antiviral envelope antibody levels by a mechanism yet to be determined.

Animals↗
PubMed1992

Physical map of Campylobacter jejuni TGH9011 and localization of 10 genetic markers by use of pulsed-field gel electrophoresis.

The physical map of Campylobacter jejuni TGH9011 (ATCC 43430) was constructed by mapping the three restriction enzyme sites SacII (CCGCGG), SalI (GTCGAC), and SmaI (CCCGGG) on the genome of C. jejuni by using pulsed-field gel electrophoresis and Southern hybridization. A total of 25 restriction enzyme sites were mapped onto the C. jejuni chromosome. The size of the genome was reevaluated and was shown to be 1,812.5 kb. Ten C. jejuni genetic markers that have been isolated in our laboratory were mapped to specific restriction enzyme fragments. Furthermore, we have accurately mapped one of the three rRNA operons (rrnA) and have demonstrated a separation of the 16S and 23S rRNA-encoding sequences in one of the rRNA operons.

Campylobacter jejuni↗
PubMed1992

Triggering by ATP of product release by mucous granules of the land slug Ariolimax columbianus.

The body wall of the pulmonate land slug Ariolimax columbianus secretes mucus packaged in granules bounded by two closely adjacent membranes. Newly secreted granules rupture in the presence of ATP (approximately 1 microM). This response is apparently mediated by an ATP receptor and is lost by granules held in osmotically balanced saline solutions with relatively low [K+] or [Cl-], but is retained for long periods in solutions with high [K+] and [Cl-]. Rupture by ATP is blocked by indomethacin, furosemide, nigericin, or verapamil, implicating in the ATP-rupturing process a cyclooxygenase product of arachidonic acid as well as activation of K(+)-Cl- transport and efflux of Ca2+ through activated channels according to a proposed electrical potential (proton) gradient. Mechanical stress, exposure to cold (e.g., 1 h at 0 degree C), and pertussis toxin also cause rupture that is blocked by the pharmacological agents that block ATP action. The results suggest that a single basic mechanism causes rupture of the granules, releasing mucins that form the mucous layer protecting the body wall.

Adenosine Triphosphate↗
PubMed1991

Preoperative duplex scan assessment of the inferior epigastric artery as a coronary bypass conduit.

The inferior epigastric arteries are currently being evaluated as alternative autologous arterial conduits for coronary artery bypass operations. The inferior epigastric arteries are variable in diameter and length and require harvesting through separate abdominal incisions. There is a need, therefore, for a method to preoperatively assess the diameter and length of the inferior epigastric arteries to determine their suitability as a coronary artery bypass graft. We have found that the duplex scan is a valuable noninvasive preoperative imaging modality to evaluate the inferior epigastric arteries.

Abdominal Muscles↗
PubMed1991

Experimental vaccine protection against feline immunodeficiency virus.

Infection of domestic cats with the feline immunodeficiency virus (FIV) represents an important veterinary health problem and a useful animal model for the development of vaccines against acquired immunodeficiency syndrome (AIDS). Two experimental FIV vaccines have been developed; one consisting of fixed infected cells (Vaccine 1), the other of inactivated whole virus (Vaccine 2). After 4-6 immunizations over 2-5 months, both vaccines induced a strong FIV-specific immune response including neutralizing antibody and T-cell proliferation. Vaccine 1 protected 6 of 9 and Vaccine 2 protected 5 of 6 recipient cats against any detectable infection with a low dose (10 animal ID50) of FIV given intraperitoneally 2 weeks after the final boost. One additional cat in each vaccine group had a transient infection at 5-7 weeks postchallenge following which virus could no longer be detected. Thus, a total of 13 of 15 vaccinated cats were protected against persistent infection. By contrast, 13 of 13 controls were persistently infected by this challenge. The infected cell vaccine failed to protect against a higher dose (5 x 10(4) ID50) of FIV. These results indicate that vaccine prophylaxis against natural FIV infection should be achievable and enhance optimism of the prospect of developing an effective AIDS vaccine for humans.

Animals↗
PubMed1991

Development of IL-2-independent feline lymphoid cell lines chronically infected with feline immunodeficiency virus: importance for diagnostic reagents and vaccines.

Two interleukin 2 (IL-2)-independent feline immunodeficiency virus (FIV) producer cell lines (FL-4 and FL-6) were produced by selecting cells from an IL-2-dependent culture of mixed peripheral blood lymphocytes infected with FIV. The new cell lines have been stable for over 1 year and spontaneously produce FIV with an average reverse transcriptase titer of 300,000 cpm/ml and an average sucrose gradient purified viral protein concentration of 1 mg/l. FIV produced from these cultures is highly infectious in vitro and in vivo. The FL-6 cell line was phenotyped as expressing the feline CD8 and Pan-T antigens, while the FL-4 cell line expressed the CD4, CD8, and Pan-T antigens. Both cell lines, however, express high levels of viral core and envelope proteins. Paraformaldehyde-inactivated whole virus and similarly inactivated whole-cell virus preparations induced a strong antibody response to core and envelope antigens in immunized cats. The establishment of FIV-producing feline IL-2-independent peripheral blood lymphocyte lines should be valuable for the development of FIV-diagnostic reagents and vaccines and also as a model for human acquired immunodeficiency syndrome vaccine development.

Animals↗