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Biomedical subjects

B S Hu

Publications and source records attributed to B S Hu.

At least 19 recordsLinked to original sources
PubMed1999

A human cell line constitutively expressing HIV-1 Gag and Gag-Pol gene products.

A human cell line constitutively expressing the HIV-1 gag and pol genes products was established. The cell line was established by stably transfecting 293 cells with a plasmid construct that expresses the HIV Gag and Pol and can confer the transfectants resistant to mycophenolic acid. Particles generated from transient expression of the plasmid construct were noninfectious when pseudotyped with HIV envelope or with amphotropic murine leukemia virus envelope proteins. However, virus-like Gag particles produced by the stable cell line were appropriately processed, exhibited a wild-type retrovirus particle density, and possessed significant reverse-transcriptase (RT) activities. Continuous passage of the cell line either in the presence or absence of mycophenolic acid had no major effects on the Gag processing efficiency, particle assembly, or RT activity release. It was also demonstrated that the proteolytic processing of the virus-like particles released from the cell line was inhibited by an HIV protease inhibitor, saquinavir. The establishment of a stable cell line producing noninfectious but proteolytically processed HIV Gag particles offers a safe, convenient tool for biochemical and immunological analysis of virus-like particle assembly and is very useful for the development of anti-HIV protease drugs.

Blotting, Western↗
PubMed1998

Interactive coronary MRI.

The acquisition of complete three-dimensional (3D), segmented gradient-echo data sets to visualize the coronary arteries can be both time consuming and sensitive to motion, even with use of multiple breath-holding or respiratory gating. An alternate hybrid approach is demonstrated here, in which real-time interactive imaging is first used to locate an optimal oblique coronary scan plane. Then, a limited number of contiguous slices are acquired around that plane within a breath-hold with use of two-dimensional (2D) segmented gradient-echo imaging. Dual inversion nulling is used to suppress fat and myocardium. Finally, if needed, a limited reformat of the data is performed to produce images from relatively long sections of the coronaries. This approach yields relatively rapid visualization of portions of the coronary tree. Several different methods are compared for interactively moving the scan plane.

Coronary Angiography↗
PubMed1998

One-shot spatially resolved velocity imaging.

For quantitative velocity measurement, we have developed a technique that acquires full velocity spectra without cardiac gating. After a cylindrical excitation restricts imaging to one spatial dimension, data are acquired while an oscillating gradient is played out. After each excitation, an image of velocity versus spatial location is obtained. For a given spatial location, a series of these images can be used to form an image of velocity versus time. Acquisition times are much shorter than for phase-contrast imaging or Fourier-encoded velocity imaging, obviating the need for cardiac gating. Although a two-shot version of this technique has been presented previously, we have developed a one-shot version that offers higher temporal resolution for a given velocity resolution and superior off-resonance properties.

Aorta, Thoracic↗
PubMed1998

3D MR coronary artery segmentation.

Coronary arteries are segmented from the blood pool using mathematical morphology operations from a 3D magnetic resonance spiral acquisition on a continuously breathing healthy volunteer. The segmented volume is maximal intensity projected at different views to yield coronary angiograms showing the left anterior descending artery (LAD), right coronary artery (RCA), and left circumflex artery (LCX). Magnetic resonance coronary angiography provides a retrospective rotating view of the coronary artery tree that complements oblique reformatted sections.

Algorithms↗
PubMed1998

Molecular epidemiology of penicillin-resistant Streptococcus pneumoniae isolated in central Taiwan.

Previous studies have suggested that penicillin-resistant pneumococcal isolates (especially those with MIC > 1 microgram/mL) usually are clonally related. To test this hypothesis, the molecular epidemiology of 29 clinical isolates of penicillin-resistant pneumococci (of which 83% were also resistant to either cefotaxime or ceftriaxone) collected in central Taiwan was investigated by pulsed field gel electrophoresis. Twenty-seven distinct patterns were identified. Our results indicate that an increase in penicillin-resistant S. pneumoniae between April 1993 and June 1994 in central Taiwan is not due to the clonal dissemination of a limited number of epidemic strains.

Cefotaxime↗
PubMed1998

New real-time interactive cardiac magnetic resonance imaging system complements echocardiography.

OBJECTIVES: We conducted an initial clinical trial of a newly developed cardiac magnetic resonance imaging (CMRI) system. We evaluated left ventricular (LV) function in 85 patients to compare the clinical utility of the CMRI system with echocardiography, the current noninvasive gold standard. BACKGROUND: Conventional CMRI systems require cardiac-gating and respiratory compensation to synthesize a single image from data acquired over multiple cardiac cycles. In contrast, the new CMRI system allows continuous real-time dynamic acquisition and display of any scan plane at 16 images/s without the need for cardiac gating or breath-holding. METHODS: A conventional 1.5T Signa MRI Scanner (GE, Milwaukee, Wisconsin) was modified by the addition of an interactive workstation and a bus adapter. The new CMRI system underwent clinical trial by testing its ability to evaluate global and regional LV function. The first group (A) consisted of 31 patients with acceptable echocardiography image quality. The second group (B) consisted of 31 patients with suboptimal echocardiography image quality. The third group (C) consisted of 29 patients with severe lung disease or congenital cardiac malformation who frequently have suboptimal echo study. Two independent observers scored wall motion and image quality using the standard 16-segment model and rank-order analysis. RESULTS: CMRI evaluation was complete in less than 15 min. In group A, no significant difference was found between ECHO and CMRI studies (p = NS). In group B, adequate visualization of wall segments was obtained 38% of the time using ECHO and 97% of the time using CMRI (p < 0.0001). When grouped into coronary segments, adequate visualization of at least one segment occurred in 18 of 30 patients (60%) with ECHO and in all 30 patients (100%) with CMRI (p < 0.0001). In group C, adequate visualization of the wall segments was obtained in 58% (CI 0.53-0.62) of the time using echocardiography and 99.7% (CI 0.99-1.0) of the time using CMRI (p < 0.0001). CONCLUSIONS: The new CMRI system provides clinically reliable evaluation of LV function and complements suboptimal echocardiography. In comparison with the conventional CMRI, the new CMRI system significantly reduces scan time, patient discomfort and associated cost.

Adolescent↗
PubMed1997

Real-time interactive MRI on a conventional scanner.

A real-time interactive MRI system capable of localizing coronary arteries and imaging arrhythmic hearts in real-time is described. Non-2DFT acquisition strategies such as spiral-interleaf, spiral-ring, and circular echo-planar imaging provide short scan times on a conventional scanner. Real-time gridding reconstruction at 8-20 images/s is achieved by distributing the reconstruction on general-purpose UNIX workstations. An X-windows application provides interactive control. A six-interleaf spiral sequence is used for cardiac imaging and can acquire six images/s. A sliding window reconstruction achieves display rates of 16-20 images/s. This allows cardiac images to be acquired in real-time, with minimal motion and flow artifacts, and without breath holding or cardiac gating. Abdominal images are acquired at over 2.5 images/s with spiral-ring or circular echo-planar sequences. Reconstruction rates are 8-10 images/s. Rapid localization in the abdomen is demonstrated with the spiral-ring acquisition, whereas peristaltic motion in the small bowel is well visualized using the circular echo-planar sequence.

Abdomen↗
PubMed1997

Comparison of polymerase chain reaction and pulsed-field gel electrophoresis for the epidemiological typing of Alcaligenes xylosoxidans subsp. xylosoxidans in a burn unit.

Eighteen isolates of Alcaligenes xylosoxidans subsp. xylosoxidans were collected from clinical specimens of 15 patients in a burn unit and a plastic surgery ward over a 16-month period. Pulsed-field gel electrophoresis and polymerase chain reaction (PCR) were compared for the epidemiologic typing of these 18 isolates and fifteen epidemiologically unrelated strains. These 18 isolates demonstrated an identical fingerprint pattern and were easily distinguished from the 15 epidemiologically unrelated strains by pulsed-field gel electrophoresis typing and both enterobacterial repetitive intergenic concensus and repetitive extragenic palindrome-primed PCR fingerprinting. We conclude that pulsed-field gel electrophoresis analysis of XbaI-digested genomic DNA is a highly discriminatory and reproducible method for epidemiological typing of A. xylosoxidans subsp. xylosoxidans isolates. However, poor resolution due to frequent cutting in the smaller fragments (< 145.5 Kb) may lead to difficulty in interpretation. PCR is a rapid and highly discriminatory, but less reproducible, technique with occasional loss of major bands. The fingerprints produced by repetitive extragenic palindrome primed PCR had more intense bands and were easier to read than those produced by enterobacterial repetitive intergenic concensus-primed PCR in this study.

Alcaligenes↗
PubMed1997

In vitro antimicrobial activity of levofloxacin against Streptococcus pneumoniae.

BACKGROUND: Infections caused by Streptococcus pneumoniae continue to be a significant cause of mortality and morbidity in humans. Diseases caused by multi-resistant pneumococci are increasing rapidly worldwide. The fluoroquinolones have been widely used clinically to treat infectious diseases. The results of a study here on the five fluoroquinolones susceptibilities of S. pneumoniae are reported from the Taichung Veterans General Hospital. METHODS: Minimum inhibitory concentrations (MICs) of five quinolones (enoxacin, norfloxacin, ofloxacin, levofloxacin and ciprofloxacin) were determined for 106 strains of S. pneumoniae. All MICs were determined by the agar dilution method utilizing Mueller-Hinton agar supplemented with 5% sheep blood. RESULTS: MIC90 of levofloxacin was 1 microgram/ ml, and was unaffected by penicillin-susceptibility. MIC90 of ofloxacin and that of ciprofloxacin were 2 and 4 micrograms/ml, respectively, with 90.6% sensitive to ofloxacin. MIC90 of enoxacin and that of norfloxacin were higher than other compounds. CONCLUSIONS: The in vitro activity of levofloxacin is twice that of ofloxacin, 4-fold of ciprofloxacin, 16-fold of norfloxacin, and 64-fold of enoxacin. MICs of these five quinolones were unaffected by penicillin-susceptibility. The antibacterial activity of levofloxacin was better than that of ofloxacin and ciprofloxacin, norfloxacin, or enoxacin against S. pneumoniae.

Anti-Infective Agents↗
PubMed1997

Forward-looking catheters.

Current intravascular ultrasound catheters provide a cross-sectional view of the blood vessel that limits their ability to visualize severely stenosed or occluded vessels. Forward-looking ultrasound catheters can overcome these limitations. Development of a practical forward-looking ultrasound catheter requires solutions to address the need for improved lateral resolution and depth of penetration presented by the forward-looking format. Methods are also needed to generate the forward-looking scan within the space constraints of a catheter. New developments using mechanical scanning methods suggest that a practical device appears achievable. Two-dimensional, as well as three-dimensional imaging, may be possible. Early efforts towards a phased array scanner have also begun.

Animals↗
PubMed1996

Antimicrobial susceptibility of clinical isolates of Acinetobacter baumannii.

The in-vitro activity of 18 antimicrobial agents alone or in combination against 248 clinical isolates of Acinetobacter baumannii from Taiwan were tested by agar dilution. The MIC90S of ampicillin, amoxicillin, piperacillin, cefuroxime, cefotaxime, ceftriaxone, gentamicin, and amikacin were at least 128 mu g/ml. Ceftazidime, cefepime, sulbactam, clavulanic acid, and tazobactam presented moderate activity with MIC90S of 32, 16, 16, 32, and 32 mu g/ml, respectively. The increased activity of ampicillin/sulbactam, amoxicillin/clavulanic acid, and piperacillin/tazobactam was due to the intrinsic effect of sulbactam, clavulanic acid, and tazobactam, respectively. Imipenem, meropenem, and ciprofloxacin were the most active antimicrobial agents with MIC90S of 1, 1, and 0.5 mu g/ml, respectively. Nineteen isolates (7.7%) were resistant to all aminoglycosides and beta-lactam antibiotics, except carbapenems and ciprofloxacin. We are concerned about the multidrug resistance of A. baumannii in this study.

Acinetobacter↗
PubMed1996

Accuracy of biplane and multiplane transesophageal echocardiography in diagnosis of typical acute aortic dissection and intramural hematoma.

OBJECTIVES: The purpose of this study was to evaluate the diagnostic accuracy of biplane and multiplane transesophageal echocardiography in patients with suspected aortic dissection, including intramural hematoma. BACKGROUND: Transesophageal echocardiography is a useful technique for rapid bedside evaluation of patients with suspected acute aortic dissection. The sensitivity of transesophageal echocardiography is high, but the diagnostic accuracy of biplane and multiplane transesophageal echocardiography for dissection and intramural hematoma is less well defined. METHODS: We studied 112 consecutive patients at a major referral center who had undergone biplane or multiplane transesophageal echocardiography to identify aortic dissection. The presence, absence and type of aortic dissection (type A or B, typical dissection or intramural hematoma) were confirmed by operation or autopsy in 60 patients and by other imaging techniques in all. The accuracy of transesophageal echocardiography for ancillary findings of aortic dissection (intimal flap, fenestration and thrombosis) was assessed in the 60 patients with available surgical data. RESULTS: Of the 112 patients, aortic dissection was present in 49 (44%); 10 of these had intramural hematoma (5 with and 5 without involvement of the ascending aorta). Of the remaining 63 patients without dissection, 33 (29%) had aortic aneurysm and 30 (27%) had neither dissection nor aneurysm. The overall sensitivity and specificity of transesophageal echocardiography for the presence of dissection were 98% and 95%, respectively. The specificity for type A and type B dissection was 97% and 99%, respectively. The sensitivity and specificity for intramural hematoma was 90% and 99%, respectively. The accuracy of transesophageal echocardiography for diagnosis of acute significant aortic regurgitation and pericardial tamponade was 100%. CONCLUSIONS: Biplane and multiplane transesophageal echocardiography are highly accurate for prospective identification of the presence and site of aortic dissection, its ancillary findings and major complications in a large series of patients with varied aortic pathology. Intramural hematoma carries a high complication rate and should be treated identically with aortic dissection.

Acute Disease↗
PubMed1996

Use of restriction endonuclease analysis of plasmids and pulsed-field gel electrophoresis to investigate outbreaks of methicillin-resistant Staphylococcus aureus infection.

We used restriction endonuclease analysis of plasmids (REAP) and pulsed-field gel electrophoresis (PFGE) to investigate clusterings of methicillin-resistant Staphylococcus aureus (MRSA) infections in our orthopedic unit, neurosurgery unit, intensive care unit, and burn unit. Fourteen different strain types were identified by REAP and 10 different strain types were identified by PFGE among 25 MRSA isolates collected during these incidents of infection. Though neither technique was clearly superior to the other for typing MRSA isolates, REAP is recommended as a relatively simple and reproducible technique for the preliminary investigation of MRSA infection outbreaks in clinical settings.

Bacterial Typing Techniques↗
PubMed1996

Epidemiological typing of Flavimonas oryzihabitans by PCR and pulsed-field gel electrophoresis.

Flavimonas oryzihabitans has emerged as a potential nosocomial pathogen in recent years. The typing method for characterization of this species has never been reported before. Pulsed-field gel electrophoresis (PFGE) and enterobacterial repetitive intergenic consensus (ERIC)-based PCR were used to generate DNA fingerprints for 14F. oryzihabitans isolates obtained from eight episodes of nosocomial infections during a 2-year period. Both techniques successfully classified these clinical isolates into eight distinct genotypes, thus indicating that all of these episodes of infections were independent. In contrast, repeated isolates from the same patient were assigned to identical genotypes. The reproducibility of both techniques was good. Therefore, we conclude that both PFGE and ERIC-PCR have comparable reproducible and discriminatory powers for the typing of F. oryzihabitans and may be useful for clarifying the epidemiology of this species; however, ERIC-PCR has the advantages of both speed and simplicity.

Bacterial Typing Techniques↗
PubMed1996

Epidemiological typing of isolates from an outbreak of infection with multidrug-resistant Enterobacter cloacae by repetitive extragenic palindromic unit b1-primed PCR and pulsed-field gel electrophoresis.

An outbreak of multidrug-resistant Enterobacter cloacae infection lasted for 4 months in a neonatal intensive care unit (NICU). Forty-six isolates from the NICU and 20 epidemiologically unrelated strains were characterized by pulsed-field gel electrophoresis (PFGE) and repetitive extragenic palindromic unit b1-primed PCR (REPUb1-PCR) typing. The PFGE patterns after XbaI restriction of the bacterial DNA were analyzed by computer software (Gelcompar) using the UPGMA (unweighted pair group method with arithmetic averages) clustering method and the Dice coefficient. The 46 isolates from the NICU were classified by PFGE typing into five clusters: A (further classified into 7 subtypes, A1 to A7), B, C, D, and E. This outbreak was attributed to multiple genetically related strains of cluster A which had a similarity of 85.8% +/- 4.6%. The minor band differences among strains of cluster A were probably due to minor genetic mutations. The type A1 and A3 strains were isolated from the clinical specimens of patients and hands of nurses. It was probable that these outbreak strains were transmitted among patients via the hands of personnel. REPUb1-PCR typing of the 46 isolates also demonstrated five types, in agreement with results obtained by the PFGE technique, but could not detect the minor mutations among the cluster A strains. Twenty epidemiologically unrelated strains were well distinguished by both PFGE and REPUb1-PCR typing. We conclude that PFGE is a highly discriminatory but time-consuming method for epidemiological typing of E. cloacae and that REPUb1-PCR is a more rapid method with good reproducibility and discriminatory power comparable to that of PFGE.

Bacterial Typing Techniques↗
PubMed1995

Coronary angiography with magnetization-prepared T2 contrast.

A magnetization-prepared, T2-weighted sequence (T2 Prep) is used to suppress muscle and venous structures. When combined with lipid suppression, this technique improves the visualization of the coronary arteries. T2 Prep was designed to be rebust in the presence of flow as well as B0 and B1 inhomogeneities and may be combined with virtually any imaging technique. Here, it is implemented with both a single-slice spiral acquisition and a multi-slice spiral method that acquires up to 15 slices in a single breath-holding interval.

Arteries↗