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B Wong

Publications and source records attributed to B Wong.

At least 73 records · Page 4Linked to original sources
PubMed1996

Transcriptional organization and regulation of the dnaK and groE operons of Chlamydia trachomatis.

The transcriptional organization and regulation of the dnaK and groE heat shock operons of Chlamydia trachomatis were studied and found to resemble those of the cognate operons of Bacillus subtilis and Clostridium acetobutylicum. The gene order is conserved (hrcA-grpE-dnaK), but no dnaJ homolog could be identified in this region. The dnaK operon was transcribed as a low-abundance polycistronic mRNA whose levels did not increase upon exposure to heat shock. In contrast, a more abundant 2.3-kb mRNA encoding only the dnaK sequence was detectable, and its steady-state level increased upon heat shock. The transcription initiation sites of the dnaK and groE operons were found to be preceded by sequences that resemble an Escherichia coli sigma70 consensus promoter. Upstream of each putative promoter is an inverted repeat sequence which resembles a similar element (CIRCE [controlling inverted repeat of chaperone expression]) found upstream of the dnaK and groE operons in at least 27 eubacterial species. In vitro transcription studies utilizing partially purified C. trachomatis RNA polymerase demonstrated that the regions containing the putative promoter elements of the dnaK and groE operons are functional, although heat shock-regulated expression could not be demonstrated.

Amino Acid Sequence↗
PubMed1996

Undetectable interleukin (IL)-10 and persistent IL-8 expression early in hyaline membrane disease: a possible developmental basis for the predisposition to chronic lung inflammation in preterm newborns.

We are interested in determining whether premature birth alters expression of counterregulatory cytokines which modulate lung inflammation. Production of proinflammatory cytokines tumor necrosis factor alpha. IL-1 beta, and IL-8 is regulated in part by the antiinflammatory cytokine IL-10. For preterm newborns with hyaline membrane disease, deficiencies in the ability of lung macrophages to express antiinflammatory cytokines may predispose to chronic lung inflammation. We compared the expression of pro- and antiinflammatory cytokines at the mRNA and protein level in the lungs of preterm and term newborns with acute respiratory failure from hyaline membrane disease or meconium aspiration syndrome. Four sequential bronchoalveolar lavage (BAL) samples were obtained during the first 96 h of life from all patients. All patients rapidly developed an influx of neutrophils and macrophages. Over time, cell populations in both groups became relatively enriched with macrophages. The expression of proinflammatory cytokine mRNA and/or protein was present in all samples from both patient groups. In contrast, IL-10 mRNA was undetectable in most of the cell samples from preterm infants and present in the majority of cell samples from term infants. IL-10 concentrations were undetectable in lavage fluid from preterm infants with higher levels in a few of the BAL samples from term infants. These studies demonstrate that 1) IL-10 mRNA and protein expression by lung inflammatory cells is related to gestational age and 2) during the first 96 h of life neutrophil cell counts and IL-8 expression decrease in BAL from term infants, but remain unchanged in BAL samples from preterm infants.

Bronchoalveolar Lavage↗
PubMed1996

Formation of p27-CDK complexes during the human mitotic cell cycle.

In eukaryotic cells, the coordinated activation of different cyclin-dependent kinases regulates entry into S-phase. In vitro and in nonproliferating cells, p27 associates with and inhibits cyclin/cycin-dependent kinase (CDK) holoenzymes containing either CDK4, CDK6, or CDK2. Although many different types of proliferating cells contain p27 protein, neither the interactions of p27 with cyclin/CDK complexes nor the consequences of this interaction during the mitotic cycle have been fully explored. We report that, in MANCA cells, the amount of p27 is constant during the cell cycle. In addition, p27 associates with three different CDKs: CDK2, CDK4, and CDK6. Furthermore, the amount of p27 is significantly lower than the amount of cyclin D3 in these cells. The amount of CDK4 and CDK6 associated with p27 does not change in a cell cycle-dependent fashion; in contrast, the amount of CDK2 associated with p27 is lowest in early G1 cells and increases to a maximum in mid-G1 phase, reaching a steady-state level in late G1-phase cells. After mid-G1 phase, the amount of each p27/CDK complex remains constant through the remainder of the cell cycle. p27-immunoprecipitates contain an Rb-kinase activity. The substrate specificity, the expression pattern of this kinase, and the ability to deplete 50% of this kinase activity with a CDK6-specific antibody suggest that the CDK6 protein mediates, in part, the p27-associated Rb-kinase activity. In contrast, p27 complexes containing CDK2 are incapable of phosphorylating histone H1. These data are consistent with a model wherein cyclin D/CDK complexes sequester the CDK2-dependent kinase inhibitory activity of p27.

Animals↗
PubMed1995

Isolation, characterization and expression of the gene that encodes D-arabinitol dehydrogenase in Candida tropicalis.

The gene (ARD) that encodes NAD-dependent D-arabinitol dehydrogenase (ArDH) in the pathogenic fungus Candida tropicalis (Ct) was cloned by transforming Escherichia coli (Ec) BW31M (araCc) with a plasmid library of Ct genomic DNA and selecting for D-arabinitol-utilizing (D-arab+) clones. Plasmid DNA from a D-arab+ clone retransformed fresh Ec BW31M cells to D-arab+; these cells produced both ArDH catalytic activity and a 31-kDa protein recognized by antibodies to native Ct ArDH. The plasmid contained an 846-bp open reading frame (ORF) that encoded a deduced protein of 282 amino acids (aa) (30,748 Da). Four partial aa sequences from Ct ArDH were present in the deduced aa sequence, thus verifying that Ct ARD had been cloned. Ct ArDH was 95% identical to ArDH from Candida albicans (Ca), 85% identical to a xylitol dehydrogenase (XDH) from Pichia stipitis (Ps) and 20-25% identical to many other short-chain dehydrogenases. Ct ArDH, Ca ArDH and Ps XDH were typical short-chain dehydrogenases except that they lacked an N-terminal Gly that is conserved in other members of this family. Thus, these enzymes may represent a subclass of closely-related fungal pentitol dehydrogenases. Large amounts of recombinant ArDH (re-ArDH) were produced in Ec and purified by dye ligand affinity chromatography. The physical and catalytic properties of re-ArDH were similar to those of native Ct ArDH, and re-ArDH and native ArDH performed similarly in an automated enzymatic assay for D-arabinitol in human serum.

Amino Acid Sequence↗
PubMed1995

D-arabitol metabolism in Candida albicans: construction and analysis of mutants lacking D-arabitol dehydrogenase.

Candida albicans produces large amounts of the acyclic pentitol D-arabitol in culture and in infected animals and humans, and most strains also grow on minimal D-arabitol medium. An earlier study showed that the major metabolic precursor of D-arabitol in C. albicans was D-ribulose-5-PO4 from the pentose pathway, that C. albicans contained an NAD-dependent D-arabitol dehydrogenase (ArDH), and that the ArDH structural gene (ARD) encoded a 31-kDa short-chain dehydrogenase that catalyzed the reaction D-arabitol + NAD <=> D-ribulose + NADH. In the present study, we disrupted both ARD chromosomal alleles in C. albicans and analyzed the resulting mutants. The ard null mutation was verified by Southern hybridization, and the null mutant's inability to produce ArDH was verified by Western immunoblotting. The ard null mutant grew well on minimal glucose medium, but it was unable to grow on minimal D-arabitol or D-arabinose medium. Thus, ArDH catalyzes the first step in D-arabitol utilization and a necessary intermediate step in D-arabinose utilization. Unexpectedly, the ard null mutant synthesized D-arabitol from glucose. Moreover, 13C nuclear magnetic resonance studies showed that the ard null mutant and its wild-type parent synthesized D-arabitol via the same pathway. These results imply that C. albicans synthesizes and utilizes D-arabitol via separate metabolic pathways, which was not previously suspected for fungi.

Alleles↗
PubMed1995

Hypocapnia and increased ventilatory responsiveness in patients with idiopathic central sleep apnea.

We previously demonstrated that central apneas during sleep in patients with idiopathic central sleep apnea (ICSA) are triggered by abrupt hyperventilation. In addition, baseline PCO2 at the time of augmented breaths which triggered central apneas was lower than for augmented breaths which did not trigger apneas. These observations led us to hypothesize that patients with ICSA chronically hyperventilate maintaining their PCO2 close to the threshold for apnea during sleep owing to increased chemical respiratory drive. To test these hypotheses, we recorded transcutaneous PCO2 (PtcCO2) during overnight sleep studies on nine consecutive patients with ICSA and nine sex-, age-, and body-mass-index-matched control subjects. Daytime PaCO2 as well as rebreathing and single breath ventilatory responses to CO2 were also measured. Compared with the control subjects, the patients had significantly lower mean PtcCO2 during sleep (37.8 +/- 1.2 versus 42.7 +/- 10.9 mm Hg, p < 0.01) and lower PaCO2 while awake (35.1 +/- 1.3 versus 38.8 +/- 0.9 mm Hg, p < 0.05). Furthermore, patients with ICSA had significantly higher ventilatory responses to CO2 for both the rebreathing (3.14 +/- 0.34 versus 1.60 +/- 0.32 L/min/mm Hg, p < 0.005) and single breath methods (0.51 +/- 0.10 versus 0.25 +/- 0.04 L/min/mm Hg, p < 0.05). We conclude that: (1) patients with ICSA chronically hyperventilate awake and asleep and (2) chronic hyperventilation is probably related to augmented central and peripheral respiratory drive which predisposes to respiratory control system instability.

Carbon Dioxide↗
PubMed1995

Experience in the development of a postmarketing surveillance network: the pharmacy medication monitoring program.

OBJECTIVE: To describe the pilot and early implementation phase of a system for assembling and recruiting cohorts of patients taking selected prescription medications and prospectively monitoring them for new health events. DESIGN: Prospective observational study, based on telephone interviews, of 1475 patients filling prescriptions for a nonsteroidal antiinflammatory drug (NSAID). Patients were interviewed by telephone using trained interviewers at a central site. Hospitalizations and deaths were followed up and reviewed by an independently physician. SETTING: Community setting in a region of Hamilton, Ontario, Canada. PARTICIPANTS: All consenting patients filling new or repeat prescriptions for NSAIDs at participating pharmacies. MAIN OUTCOME MEASURES: The authors report on the development and assessment of systems for: (1) ongoing recruitment of patients through community pharmacies; (2) data transfer from pharmacies to the coordinating center; (3) surveying patients; (4) classifying, coding, and evaluating new health events; and (5) following up on new serious adverse events. RESULTS: Fifty-one percent of patients approached were recruited, and 83% of these provided completed interviews. For patients picking up their own medications, pharmacy workload varied from 4 to 10 minutes per patient approached. Nineteen percent of patients reported having a new health problem or unusual symptom at the initial telephone interview. Reported health-related events were similar to those described in other studies of NSAIDs. CONCLUSIONS: Most aspects of the monitoring system performed well. One limitation was the low recruitment rate for patients who did not directly drop off or pick up their own prescriptions. Even so, this method of patient accrual may complement alternative monitoring programs.

Adverse Drug Reaction Reporting Systems↗
PubMed1994

Cloning, sequencing and transcriptional studies of the genes for cytochrome c-553 and plastocyanin from Anabaena sp. PCC 7120.

In some cyanobacteria and eukaryotic algae, cytochrome c-553 (c-552) and plastocyanin function as alternative electron carriers between the cytochrome b6-f complex and Photosystem I. In these organisms plastocyanin is the electron carrier under copper-replete conditions, and cytochrome c-553 is the electron carrier during copper deprivation. In this paper we report the cloning, sequencing and transcriptional analysis of the genes for cytochrome c-553 and plastocyanin from Anabaena sp. PCC 7120. The gene for cytochrome c-553 encodes a preprotein containing 111 amino acids with a predicted N-terminal transit peptide sequence of 25 amino acids. The gene for plastocyanin encodes a preprotein containing 139 amino acids with a N-terminal transit peptide sequence of 34 amino acids. RNA transcript analyses indicate that the expression of the genes for cytochrome c-553 (petJ) and plastocyanin (petE) are regulated in reciprocal ways in response to copper concentration. In copper-replete conditions, petJ is expressed at very low levels, but is transcribed at high levels under copper deprivation; petE is down-regulated in the absence of copper, but is rapidly up-regulated when copper is added back to the medium.

Amino Acid Sequence↗
PubMed1994

An automated enzymatic method for measurement of D-arabinitol, a metabolite of pathogenic Candida species.

An automated enzymatic method was developed for the measurement of D-arabinitol in human serum. The assay is based on a novel, highly specific D-arabinitol dehydrogenase from Candida tropicalis. This enzyme catalyzes the oxidation of D-arabinitol to D-ribulose and the concomitant reduction of NAD+ to NADH. The NADH produced is used in a second reaction to reduce p-iodonitrotetrazolium violet (INT) to INT-formazan, which is measured spectrophotometrically. The entire reaction sequence can be performed automatically on a COBAS MIRA-S clinical chemistry analyzer (Roche Diagnostic Systems, Inc., Montclair, N.J.). Replicate analyses of human sera supplemented with D-arabinitol over a concentration range of 0 to 40 microM demonstrated that the pentitol could be measured with an accuracy of +/- 7% and a precision (standard deviation) of +/- 0.4 microM. Serum D-arabinitol measurements correlated with those determined by gas chromatography (r = 0.94). The enzymatic method is unaffected by L-arabinitol, D-mannitol, or other polyols commonly found in human serum. Any of 17 therapeutic drugs potentially present in serum did not significantly influence assay performance. Data illustrating the application of the assay in patients for possible diagnosis of invasive candidiasis and the monitoring of therapeutic intervention are presented. The automated assay described here was developed to facilitate the investigation of D-arabinitol as a serum marker for invasive Candida infections.

Agranulocytosis↗
PubMed1994

Interaction of hyperventilation and arousal in the pathogenesis of idiopathic central sleep apnea.

Central apneas during sleep may arise as a result of reduction in PaCO2 below the apnea threshold. We therefore hypothesized that hyperventilation and arousals from sleep interact to cause hypocapnia and subsequent central apneas in patients with idiopathic central sleep apnea (ICSA). Accordingly, the relationships among preapneic ventilation, arousal from sleep, and the onset and duration of subsequent central apneas were examined during Stage 2 non-REM sleep in eight patients with ICSA (mean +/- SEM, 45.4 +/- 4.7 central apneas and hypopneas/h of sleep). During Stage 2 sleep, all episodes of periodic breathing with central apneas were triggered by hyperventilation. Minute ventilation (VI) was greater (6.3 +/- 0.7 versus 5.4 +/- 0.8 L/min, p < 0.05) and mean transcutaneous PCO2 (PtcCO2) was lower (37.8 +/- 1.3 versus 38.9 +/- 1.6 mm Hg, p < 0.05) during periodic breathing than during stable breathing. VI during the ventilatory phase of the periodic breathing cycle increased progressively with increasing grades of associated arousals from Grade 0 (no arousal) (10.3 +/- 1.4 L/min) to Grade 1 (EEG arousal) (12.6 +/- 1.6 L/min) to Grade 2 (movement arousal) (14.1 +/- 1.6 L/min, p < 0.01). There was a corresponding progressive increase in central apnea length following the ventilatory period from no arousal (14.1 +/- 2.0) to EEG arousal (16.4 +/- 1.8) to movement arousal (18.1 +/- 2.0 s, p < 0.01). We conclude that arousals and hyperventilation interact to trigger hypocapnia and central apneas in ICSA.

Aged↗
PubMed1994

Retinopathy of prematurity: incidence and severity in Hawaii.

Because survival of low birth-weight infants requiring intensive care has improved recently, particularly since the advent of exogenous surfactant therapy, we reviewed our experience at Kapiolani Medical Center for Women and Children (KMCWC) from 1989 to 1991 to determine if the incidence of retinopathy of prematurity (ROP), a serious long-term complication, had also increased. During this 3-year period, threshold disease, the ROP stage in which cryosurgery is recommended, occurred only in infants < or = 1000 grams. Seventy-four infants < or = 1000 grams were diagnosed with ROP of any stage. Sixteen eyes (9 infants) reached threshold; 14 were treated with cryosurgery. Six of these eyes have useful vision on follow up; 8 do not. Exogenous surfactant therapy had no significant effect on ROP incidence or severity in our series. Although ROP incidence did not increase during this review period, it remains a serious problem in high-risk premature infants in our Newborn Intensive Care Unit.

Cryosurgery↗
PubMed1993

Prevention of relapse of histoplasmosis with itraconazole in patients with the acquired immunodeficiency syndrome.

OBJECTIVE: To assess the efficacy and safety of itraconazole in preventing relapse of histoplasmosis after induction therapy with amphotericin B in patients with the acquired immunodeficiency syndrome (AIDS) and disseminated histoplasmosis. DESIGN: A prospective, multicenter, open-label clinical trial, with follow-up for at least 52 weeks. SETTING: Tertiary care hospitals participating in a clinical investigation sponsored by the National Institutes of Allergy and Infectious Diseases (AIDS Clinical Trial Group and Mycoses Study Group). PATIENTS: Forty-two patients with AIDS who had successfully completed induction therapy for disseminated histoplasmosis amphotericin B, at least 15 mg/kg body weight given over 4 to 12 weeks. INTERVENTIONS: Itraconazole, 200 mg given orally twice daily. MAIN OUTCOME MEASURES: Response to therapy, specifically prevention of histoplasmosis relapse, was the main outcome measure. Secondary end points were survival and the effect of therapy on Histoplasma capsulatum variety capsulatum antigen levels in urine and serum. Plasma itraconazole concentrations were measured to document drug absorption and compliance with therapy. RESULTS: The median follow-up was 109 weeks, and median survival was 98 weeks. Two relapses occurred (5%; 95% CI, 0.5% to 16%), one in a patient withdrawn from the study 18 weeks earlier and one in a patient who did not comply with the study therapy. Patients with elevated antigen levels at study entry showed clearance of antigen from urine and serum; urine specimens became negative in 43% of patients (CI, 26% to 59%), and serum specimens became negative in 75% of patients (CI, 56% to 94%). Only one patient discontinued treatment because of itraconazole toxicity (hypokalemia). CONCLUSIONS: Itraconazole, 200 mg twice daily, is safe and effective in preventing relapse of disseminated histoplasmosis in patients with AIDS. Antigen clearance from blood and urine correlates with clinical efficacy.

AIDS-Related Opportunistic Infections↗
PubMed1993

D-arabitol metabolism in Candida albicans: studies of the biosynthetic pathway and the gene that encodes NAD-dependent D-arabitol dehydrogenase.

Candida albicans produces large amounts of the pentitol D-arabitol in culture and in infected mammalian hosts, but the functional and pathogenic significance of D-arabitol in C. albicans is not known. In this study, we sought to elucidate the pathway by which C. albicans synthesizes D-arabitol and to identify and characterize key enzymes in this pathway. C. albicans B311 produced D-[14C-1]arabitol from [14C-2]glucose; this finding implies on structural grounds that D-ribulose-5-PO4 from the pentose pathway is the major metabolic precursor of D-arabitol. NAD- or NADP-dependent pentitol dehydrogenases catalyze the final steps in D-arabitol biosynthesis in other fungi; therefore, lysates of C. albicans B311 were tested for enzymes of this class and were found to contain a previously unknown NAD-dependent D-arabitol dehydrogenase (ArDH). The ArDH structural gene was cloned by constructing a new D-arabitol utilization pathway in Escherichia coli. The C. albicans ArDH gene expressed in E. coli and Saccharomyces cerevisiae an enzyme that catalyzes the reaction D-arabitol + NAD <-->D-ribulose + NADH; this gene was present as a single copy per haploid genome, and its deduced peptide sequence was homologous with sequences of several members of the short-chain dehydrogenase family of enzymes. These results suggest that (i) C. albicans synthesizes D-arabitol by dephosphorylating and reducing the pentose pathway intermediate D-ribulose-5-PO4 and (ii) ArDH catalyzes the final step in this pathway.

Amino Acid Sequence↗
PubMed1992

Identification of a membrane-associated 1-0-alkyl-2-arachidonoyl-sn-glycero-3-phosphocholine hydrolyzing phospholipase A2 in guinea pig 1 epidermis. Implications in the cutaneous biosynthesis of platelet-activating factor.

A membrane-associated 1-0-alkyl-2-arachidonoyl-GPC hydrolyzing phospholipase A2 was identified in guinea pig epidermis. It is regio-specific (associated with the particulate microsomal fraction) and specific for the hydrolysis of 1-0-alkyl-2-arachidonoyl-sn-glycero-3-phosphocholine. It is sensitive to low calcium concentrations suggesting that it may be activated by increasing intracellular calcium. Since ether-linked phospholipids are known to exist in the epidermis, further understanding of the properties of this 1-0-alkyl-arachidonoyl-hydrolyzing PLA2 may allow us to control the generation of 1-0-alkyl-2-lyso-sn-glycero-3-phosphocholine, a key substrate for the generation of the platelet-activating factor in the tissue.

Animals↗
PubMed1992

Spermine dialdehyde, a novel ex vivo purging agent for both allogenic and autologous bone marrow transplantations.

The use of ex vivo purging agents has shown to be beneficial for both allogeneic and autologous bone marrow transplantations. We have shown previously that spermine dialdehyde (SDA), an oxidized product of spermine, when used in phosphate-buffered saline (PBS) preferentially inhibits T-cell proliferation while sparing myeloid cells. Lethally irradiated mice were rescued by reconstitution with SDA-treated allogeneic marrow and showed no sign of graft-vs-host disease (GVHD). In this paper, we show by HPLC analysis that SDA degraded rapidly in PBS but remained intact in saline. Administered in saline, SDA was more inhibitory on leukemic cell lines than normal myeloid or T-cells. Lethally irradiated mice receiving a syngeneic bone marrow leukemic cell mixture treated ex vivo with SDA in saline did not manifest leukemia. Thus, the preferential inhibitory effect of SDA and its degraded products in different buffers suggest that SDA could act as a novel purging agent for both allogeneic and autologous bone marrow transplantations.

Acrolein↗