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Biomedical subjects

P C Hsieh

Publications and source records attributed to P C Hsieh.

14 recordsLinked to original sources
PubMed2001

Successful resuscitation of acute massive pulmonary embolism with extracorporeal membrane oxygenation and open embolectomy.

Acute massive pulmonary embolism is usually fatal if not treated aggressively, but the management is not standardized. Open pulmonary embolectomy retains a role in the treatment of this disastrous disease. Extracorporeal membrane oxygenation has been used for cardiopulmonary support in some patients with life-threatening pulmonary embolism. This article details our experience of a 58-year-old woman suffering from acute cardiopulmonary collapse caused by massive pulmonary embolism. Under extracorporeal membrane oxygenation support, the patient received pulmonary angiography and underwent open embolectomy for a definitive treatment.

Acute Disease↗
PubMed2001

A series of enediynes as novel inhibitors of topoisomerase I.

A series of acyclic enediynes, 2-((6-substituted)-3-hexen-1,5-diynyl)benzonitriles (8--11), display potent inhibition against topoisomerase I without the formation of active biradical intermediates and show inhibitory activity against topoisomerase I at 10 microM, which is five times that of camptothecin from the results of agarose gel electrophoresis.

Camptothecin↗
PubMed2000

Cloning, expression, and purification of a thermostable nonhomodimeric restriction enzyme, BslI.

BslI is a thermostable type II restriction endonuclease with interrupted recognition sequence CCNNNNN/NNGG (/, cleavage position). The BslI restriction-modification system from Bacillus species was cloned and expressed in Escherichia coli. The system is encoded by three genes: the 2,739-bp BslI methylase gene (bslIM), the bslIRalpha gene, and the bslIRbeta gene. The alpha and beta subunits of BslI can be expressed independently in E. coli in the absence of BslI methylase (M.BslI) protection. BslI endonuclease activity can be reconstituted in vitro by mixing the two subunits together. Gel filtration chromatography and native polyacrylamide gel electrophoresis indicated that BslI forms heterodimers (alphabeta), heterotetramers (alpha(2)beta(2)), and possibly oligomers in solution. Two beta subunits can be cross-linked by a chemical cross-linking agent, indicating formation of heterotetramer BslI complex (alpha(2)beta(2)). In DNA mobility shift assays, neither subunit alone can bind DNA. DNA mobility shift activity was detected after mixing the two subunits together. Because of the symmetric recognition sequence of the BslI endonuclease, we propose that its active form is alpha(2)beta(2). M.BslI contains nine conserved motifs of N-4 cytosine DNA methylases within the beta group of aminomethyltransferase. Synthetic duplex deoxyoligonucleotides containing cytosine hemimethylated or fully methylated at N-4 in BslI sites in the first or second cytosine are resistant to BslI digestion. C-5 methylation of the second cytosine on both strands within the recognition sequence also renders the site refractory to BslI digestion. Two putative zinc fingers are found in the alpha subunit of BslI endonuclease.

Amino Acid Sequence↗
PubMed1999

Case mix adjustment in nursing systems research: the case of resident outcomes in nursing homes.

Case mix indicates, for a resident population, the degree of risk for developing favorable or unfavorable outcomes. In a study of 164 nursing homes, we explored two methods for combining resident assessment data into a case mix index (CMI). We compared a facility-level, composite CMI to a prevalence-based CMI comprised of 22 separate resident characteristics for their adequacy in explaining resident outcomes. The prevalence-based CMI consistently explained more variance in outcomes than the facility level, composite CMI. This study indicates a reasonable method for using administrative databases containing resident assessment data to adjust for the influence of case mix on nursing home resident outcomes.

Fractures, Bone↗
PubMed1999

Computerized tomography-guided stereotactic aspiration of brain abscesses: experience with 28 cases.

BACKGROUND: Computerized tomography (CT)-guided stereotactic techniques allow accurate identification of brain abscesses and provide promising results for the management of brain abscesses. METHODS: We reviewed the results of stereotactic aspiration of brain abscesses in 28 consecutive patients from 1984 to 1995. In all patients, the diagnosis of brain abscess was made by computerized tomography (CT). All patients underwent stereotactic aspiration of abscesses as the primary surgical therapy. Intravenous antibiotics were administered preoperatively and adjusted according to organism type and sensitivity to antibiotics. In patients with multiple lesions, aspirations were performed on abscesses larger than 2 cm in diameter or on those causing significant mass effects. CT was performed weekly to monitor abscess growth or failure to resolve. Patients were followed on an outpatient basis. This report is a retrospective review of clinical features, diagnostic methods, treatment and postoperative results. RESULTS: A total of 19 patients had good recoveries and six patients had mild neurologic sequelae. One patient had persistent conscious impairment. Intracranial hemorrhage occurred in one patient. Two deaths occurred during hospitalization. One patient with a fungal infection underwent additional surgical excision of the abscess. Most patients had resolution of abscesses after stereotactic treatment within two months. The cure rate was 92% in patients with bacterial brain abscesses treated with stereotactic aspiration and intravenous antibiotics for six weeks. CONCLUSIONS: Stereotactic surgery is a procedure with minimal morbidity and mortality, and can be the treatment of choice for brain abscesses when combined with appropriate antibiotic therapy.

Adult↗
PubMed1998

Bacteria lacking a multidrug pump: a sensitive tool for drug discovery.

Microorganisms express multidrug resistance pumps (MDRs) that can confound antibiotic discovery. We propose the use of mutants deficient in MDRs to overcome this problem. Sensitivity to quinolones and to amphipathic cations (norfloxacin, benzalkonium chloride, cetrimide, pentamidine, etc.) was increased 5- to 30-fold in a Staphylococcus aureus mutant with a disrupted chromosomal copy of the NorA MDR. NorA was required both for increased sensitivity to drugs in the presence of an MDR inhibitor and for increased rate of cation efflux. This requirement suggests that NorA is the major MDR protecting S. aureus from the antimicrobials studied. A 15- to 60-fold increase in sensitivity to antimicrobials also was observed in wild-type cells at an alkaline pH that favors accumulation of cations and weak bases. This effect was synergistic with a norA mutation, resulting in an increase up to 1,000-fold in sensitivity to antimicrobials. The usefulness of applying MDR mutants for natural product screening was demonstrated further by increased sensitivity of the norA- strain to plant alkaloid antimicrobials, which might be natural MDR substrates.

Anti-Bacterial Agents↗
PubMed1998

Resource allocation and resident outcomes in nursing homes: comparisons between the best and worst.

The purpose of this study was to identify patterns of resource allocation that relate to resident outcomes in nursing homes. Data on structure, staffing levels, salaries, cost, case mix, and resident outcomes were obtained from state-level, administrative databases on 494 nursing homes. We identified two sets of comparison groups and showed that the group of homes with the greatest percentage of improvement in resident outcomes had higher levels of registered nurse (RN) staffing and higher costs. However, comparison groups based on best-worst average outcomes did not differ in resource allocation patterns. Additional analysis demonstrated that when controlling for RN staffing, resident outcomes in high- and low-cost homes did not differ. The results suggest that, although RN staffing is more expensive, it is key to improving resident outcomes.

Aged↗
PubMed1996

Kinetic mechanisms of polyphosphate glucokinase from Mycobacterium tuberculosis.

Polyphosphate glucokinase from Mycobacterium tuberculosis catalyzes the phosphorylation of glucose using inorganic polyphosphates [poly(P)] or ATP. The steady-state kinetic mechanisms of the poly(P)- and ATP-dependent glucokinase reactions were investigated using initial velocity, product inhibition, and dead-end inhibition analyses. In the poly(P)-dependent reaction, the enzyme follows an Ordered Bi Bi sequential mechanism with poly(P) binding to the enzyme first and glucose 6-phosphate dissociating last. Polyphosphate is utilized nonprocessively with a preference for longer chains due to higher kcat/K(m) values. The lack of inhibition at high poly(P) concentrations suggests that binding of poly(P) as a product is not favorable. In the ATP-dependent glucokinase reaction, the data are also consistent with an Ordered Bi Bi sequential mechanism, with ATP binding to the enzyme first and glucose 6-phosphate leaving last. At high concentrations, ATP displays competitive substrate inhibition with respect to glucose, which is consistent with the formation of an enzyme.ATP.ATP nonproductive complex. The overall catalytic efficiencies (kcat/KiaK(b)) of the poly(P)- and ATP-dependent reactions are approximately 10(11) M-2 s-1 and approximately 10(8) M-2 s-1, respectively. The higher catalytic efficiency, high value of the substrate specificity constant (kcat/K(a)) approaching a diffusion-controlled limit, and the absence of substrate inhibition in the poly(P)-dependent reaction suggest that poly(P), rather than ATP, is the major phosphate donor for poly(P)-glucokinase in M. tuberculosis.

Adenosine Triphosphate↗
PubMed1996

Cloning, expression, and characterization of polyphosphate glucokinase from Mycobacterium tuberculosis.

Polyphosphate glucokinase from Mycobacterium tuberculosis catalyzes the phosphorylation of glucose using polyphosphate or ATP as the phosphoryl donor. The M. tuberculosis H37Rv gene encoding this enzyme has been cloned, sequenced, and expressed in Escherichia coli. The gene contains an open reading frame for 265 amino acids with a calculated mass of 27,400 daltons. The recombinant polyphosphate glucokinase was purified 189-fold to homogeneity and shown to contain dual enzymatic activities, similar to the native enzyme from H37Ra strain. The high G+C content in the codon usage (64.5%) of the gene and the absence of an E. coli-like promoter consensus sequence are consistent with other mycobacterial genes. Two phosphate binding domains conserved in the eukaryotic hexokinase family were identified in the polyphosphate glucokinase sequence, however, "adenosine" and "glucose" binding motifs were not apparent. In addition, a putative polyphosphate binding region is also proposed for the polyphosphate glucokinase enzyme.

Adenosine↗
PubMed1995

Multicentric plasma cell granuloma of spinal cord meninges.

A 37-year-old man had multicentric meningeal plasma cell granuloma of the spinal cord. The presenting symptoms were back pain and progressive numbness and weakness of both legs for 6 months. Through physical examination, hypoesthesia below the inguinal region and decreased muscle power of both legs with bilateral ankle clonus was seen. Computed tomographic myelogram and magnetic resonance imaging showed 2 extramedullary intradural masses at the T5 and T12-L1 levels. The latter produced all the neurologic deficits. The patient underwent 2 consecutive operations: laminectomy with removal of the tumor at the T12-L1 level, and thoracotomy with partial corpectomy and removal of the tumor at T5 level. Findings from both operations showed that the tumors arose from the dura and grew inward compressing the spinal cord. Microscopically, these 2 tumors showed identical pictures of plasma cell granuloma and were characterized by numerous granulomas formed by mature plasma cells with Russell bodies and histiocytes set in a fibrotic background. The patient was discharged with complete recovery of sensory and motor functions of both legs.

Adult↗
PubMed1993

Involvement of tryptophan(s) at the active site of polyphosphate/ATP glucokinase from Mycobacterium tuberculosis.

The glucokinase (EC 2.7.1.63) from Mycobacterium tuberculosis catalyzes the phosphorylation of glucose using inorganic polyphosphate (poly(P)) or ATP as the phosphoryl donor. The nature of the poly(P) and ATP sites was investigated by using N-bromosuccinimide (NBS) as a probe for the involvement of tryptophan in substrate binding and/or catalysis. NBS oxidation of the tryptophan(s) resulted in fluorescence quenching with concomitant loss of both the poly(P)- and ATP-dependent glucokinase activities. The inactivation by NBS was not due to extensive structural changes, as evidenced by similar circular dichroism spectra and fluorescence emission maxima for the native and NBS-inactivated enzyme. Both phosphoryl donor substrates in the presence of xylose afforded approximately 65% protection against inactivation by NBS. The Km values of poly(P) and ATP were not altered due to the modification by NBS, while the catalytic efficiency of the enzyme was decreased, suggesting that the essential tryptophan(s) are involved in the catalysis of the substrates. Acrylamide quenching studies indicated that the tryptophan residue(s) were partially shielded by the substrates against quenching. The Stern-Volmer quenching constant (KSV) of the tryptophans in unliganded glucokinase was 3.55 M-1, while KSV values of 2.48 and 2.57 M-1 were obtained in the presence of xylose+poly(P)5 and xylose+ATP, respectively. When the tryptophan-containing peptides were analyzed by peptide mapping, the same peptide was found to be protected by xylose+poly(P)5 and xylose+ATP against oxidation by NBS. The two protected peptides were determined to be identical by N-terminal sequence analysis and amino acid composition.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1993

Purification of polyphosphate and ATP glucose phosphotransferase from Mycobacterium tuberculosis H37Ra: evidence that poly(P) and ATP glucokinase activities are catalyzed by the same enzyme.

Polyphosphate [poly(P)n]:D-(+)-glucose-6-phosphotransferase (EC 2.7.1.63) from Mycobacterium tuberculosis H37Ra was purified to homogeneity using an improved method which yielded a 634-fold purification with higher recovery. The purified enzyme migrated as a single band with M(r) 33 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The native enzyme was shown to be a dimer by gel filtration using high-performance liquid chromatography (HPLC). The purified enzyme fractionated as a single peak on a C8 reverse-phase HPLC column and was found to display both polyphosphate- and ATP-dependent glucokinase activities. Further evidence that a single protein was responsible for both activities was shown by nondenaturing PAGE, in which the two activities (as determined by an activity stain in dual experiments) were found to comigrate. The C-terminal analysis yielded a single sequence while the N-terminus which was blocked also yielded a single sequence after deblocking. The two activities were found to have the same temperature optimum of 50 degrees C. The pH optima were 9.5 and 8.6-9.5 with poly(P)32 and ATP as the phosphoryl donors, respectively. The apparent Km for poly(P)32 was 18.4 microM while the Km for ATP was 1.46 mM. In addition, the nucleotide analogue, Reactive Blue 4, was found to be a competitive inhibitor with ATP in the ATP-dependent glucokinase reaction, while it displayed noncompetitive inhibition patterns with poly(P) in the poly(P)-dependent glucokinase reaction. It is concluded that the poly(P) and ATP glucokinase activities are catalyzed by the same enzyme but that the two substrates may have different binding sites.

Amino Acid Sequence↗