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Biomedical subjects

M Wong

Publications and source records attributed to M Wong.

At least 163 records · Page 9Linked to original sources
PubMed1995

Outburst of Jupiter's synchrotron radiation after the impact of comet Shoemaker-Levy 9.

Jupiter's nonthermal microwave emission, as measured by a global network of 11 radio telescopes, increased dramatically during the Shoemaker-Levy 9 impacts. The increase was wavelength-dependent, varying from approximately 10 percent at 70 to 90 centimeters to approximately 45 percent at 6 and 36 centimeters. The radio spectrum hardened (flattened toward shorter wavelengths) considerably during the week of impacts and continued to harden afterward. After the week of cometary impacts, the flux density began to subside at all wavelengths and was still declining 3 months later. Very Large Array and Australia Telescope images of the brightness distribution showed the enhancement to be localized in longitude and concentrated near the magnetic equator. The evidence therefore suggests that the increase in flux density was caused by a change in the resident particle population, for example, through an energization or spatial redistribution of the emitting particles.

Astronomical Phenomena↗
PubMed1995

Secretion of yeast aspartic protease 3 is regulated by its carboxy-terminal tail: characterization of secreted YAP3p.

Yeast aspartic protease 3 (YAP3p), a basic-residue specific proprotein processing enzyme, was shown to be a membrane-associated protease. The membrane association of YAP3p was demonstrated to be through a glycophosphatidylinositol anchor situated in the carboxy terminus of the enzyme. Carboxy-terminal truncation of YAP3p by 37 amino acids resulted in secretion of YAP3p into the growth medium. Western blot analysis after sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed two secreted forms of YAP3p with apparent molecular masses of approximately 180 and approximately 90 kDa. YAP3p has an isoelectric point of approximately 4.5 as determined by isoelectric focusing gel electrophoresis. Treatment of YAP3p with endoglycosidase H reduced the size of both forms of the protein to approximately 65 kDa, consistent with the presence of 10 potential N-linked glycosylation sites in the deduced amino acid sequence of this protein. Removal of the N-linked sugars did not affect the enzymatic activity of YAP3p. Analysis of the effect of temperature on the stability and the rate of enzymatic activity of YAP3p showed that the enzyme retained 100% of its activity when incubated for 1 h at 37 degrees C, while incubation at 50 degrees C for 1 h resulted in approximately 80% loss of activity. The dependence of activity on temperature demonstrated a calculated Q10 of 1.95.

Amino Acid Sequence↗
PubMed1995

Divergent effects of chronic amiodarone administration on systolic and diastolic function in patients with heart disease.

The purpose of this study was to determine the effects of chronic amiodarone treatment on systolic and diastolic function in patients with cardiac disease undergoing treatment for resistant ventricular arrhythmias. Previous studies have shown that chronic amiodarone treatment either has no effect or increases left ventricular ejection fraction, but the effects on diastolic properties of the ventricle have not been defined. Twelve male patients were given loading doses of amiodarone followed by a maintenance regimen. Serial measurements of heart rate, blood pressure, and indexes of systolic and diastolic function were measured by Doppler echocardiographic techniques at baseline conditions and at 2, 8, and 12 weeks of drug therapy. Changes in altered thyroid state were excluded by serial determinations of thyroid function. Amiodarone increased left ventricular ejection fraction (+16%, p < 0.01 by 8 weeks), decreased presystolic ejection period/left ventricular ejection time (-12%, p < 0.01 by 8 weeks), and increased velocity of circumferential fiber shortening (+22%, p < 0.05 by 8 weeks). Amiodarone decreased mitral inflow velocity peak E/peak A (-7%, p < 0.01 by 12 weeks), and increased deceleration and isovolumic relaxation times incrementally (+36% [p < 0.001] and +23% [p < 0.001], respectively, at 12 weeks). Chronically administered amiodarone can improve systolic function and exert a negative lusitropic action in patients with heart disease.

Aged↗
PubMed1995

Homologs of Drosophila Fushi-Tarazu factor 1 map to mouse chromosome 2 and human chromosome 9q33.

SF-1, a nuclear receptor that regulates gene expression of the cytochrome P450 steroid hydroxylases, and ELP, an embryonal protein that suppresses expression of the Moloney murine leukemia virus LTR, are isoforms transcribed from the same gene by alternative promoter usage and splicing. This gene is the mammalian homolog of the Drosophila fushi-tarazu factor 1 (FTZ-F1) gene. We have mapped the mouse gene Ftzf1 to the proximal quarter of Chr 2 by a linkage analysis using interspecific backcross mice, and its human homolog FTZ1 to Chr 9q33 by fluorescence in situ hybridization. The mouse and human genes are located in the homologous regions of mouse Chr 2 and human Chr 9, respectively.

Adrenal Insufficiency↗
PubMed1995

Effect of surface topology on the osseointegration of implant materials in trabecular bone.

The importance of surface topology and implant material composition on osseointegration in trabecular bone was investigated using three commericially used implant materials and surface-texturing procedures which included blasting, high temperature acid etching, and hydroxyapatite (HA) coating. Surface roughness and spacing parameters were measured for each implant group with a laser interferometric profilometer. Cylindrical implants were press-fit into trabecular bone sites in the knee of mature miniature pigs. After 12 weeks in situ, osseointegration was evaluated by (1) mechanical pushout tests to measure bone-implant interface strength and (2) quantitative morphometric measurements of the percent implant surface covered by bone. We found that HA-coated implants showed superior osseointegration in terms of both pushout failure load and surface coverage by bone measurements. An excellent correlation (r2 = .90) was found between the average roughness of the implant surface and pushout failure load. New methods for altering the local topologic and/or chemical state of the implant surface (i.e., by acid etching) may provide an important new avenue of research for improving the osseointegrative properties of orthopedic materials.

Alloys↗
PubMed1995

Interactive cellular modulation of chondrogenic differentiation in vitro by subpopulations of chick embryonic calvarial cells.

The embryonic chick calvarium normally develops into an intramembranous bone without an intermediate cartilage stage, although cartilage-like calvarial cells have been observed in calcium-deficient chick embryos (Dev. Biol. 115, 215, 1986; Dev. Biol. 133, 221, 1989). To analyze the cellular basis of calvarial development, Incubation Day 14 embryonic chick calvarial cells were fractionated by Percoll gradient isopycnic centrifugation; after 12 days in monolayer culture, a subpopulation of cells (fraction F) was observed to differentiate into a rounded cellular morphology with refractile extracellular matrix. The cartilaginous nature of the extracellular matrix produced by fraction F cells was strongly suggested by the immunodetection of aggrecan and type II collagen, and Alcian blue staining. The other calvarial cell fractions (C, D, E) showed predominantly osteoblastic morphology, expressed alkaline phosphatase activity, and elaborated a collagen type I extracellular matrix. These findings suggest that a "chondrocyte-like" subpopulation of cells exist in the embryonic calvarium. To investigate how cellular interactions may influence the expression of osteogenic versus chondrogenic phenotypes by calvarial cells in vitro, the following cell type combinations were tested in high-density (20 x 10(6) cells/ml) micromass cultures: (1) total, unfractionated calvarial cells; (2) Percoll fractions (C to F) of calvarial cells; and (3) a highly chondrogenic cell type, Hamburger-Hamilton stage 23/24 chick limb bud mesenchymal cells. The micromass cocultures were set up either by mixing and plating two cell types to form the initial, single micromass or by plating the two cell types as separate, side-by-side cultures in the same culture well. The effects of interactions between cocultured calvarial and limb mesenchymal cells upon their respective differentiation fates were separately analyzed, on the basis of the number of Alcian blue-staining cartilage nodules in limb mesenchymal cells and [35S]-sulfate incorporation in both cell types. In cocultures with unfractionated or "osteoblast-like" fraction C and D calvarial cells, limb mesenchymal cells had decreased chondrogenesis. In separate cocultures with "chondrocyte-like" fraction F cells, limb mesenchymal cells exhibited enhanced chondrogenesis. Conditioned media from fraction C and D cells, and from fraction F cells, inhibited and enhanced limb mesenchymal cell chondrogenesis, respectively. Q35S]Sulfate incorporation was greater in (1) unfractionated and fractionated calvarial cells cocultured separately with limb mesenchymal cells, compared to calvarial cells cultured alone, and (2) fraction F cells, compared to other fractions or unfractionated calvarial cells. Interestingly, [35S]sulfate incorporation in fraction F cells was decreased when cocultured with fraction C, D, and E cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Allograft heart valve sterilization: a six-year in-depth analysis of a twenty-five-year experience with low-dose antibiotics.

At the Prince Charles Hospital, from a 25-year experience with allograft heart valves (1969 to 1994), a 6-year analysis from March 1988 to August 1994 of the contamination rates and efficiency of a short-duration, low-dose antibiotic sterilization protocol was made. This analysis covered 642 collections and 680 aortic and pulmonary valve implants. Tissue samples obtained at collection, valve trimming, postantibiotic incubation, and implant provided the raw data. At collection, valves retrieved in open mortuaries produced the highest contamination rate of 54%. Minimal exposure to antibiotics during transport and trimming reduced the contamination rate to 11% (p < 0.05). This was similar to the contamination rate at trimming for valves collected in the "sterile" operating room from multiorgan donors (12%). Antibiotic incubation at 37 degrees C for 6 hours reduced the contamination rate to 4% (p < 0.05). Only valves that showed no contamination at cryopreservation were implanted. However, at implant, resected tissue from valves that had been incubated in antibiotics showed a contamination rate of 3%, presumably from the theater environment, compared with 15% (p < 0.05) for tissue from valves that had not been incubated. A residual antibiotic effect appears present at the time of implant in valves that have been incubated in antibiotics and may assist in the reduction of and resistance to infection in the immediate postoperative period. This is supported by the low incidence of endocarditis in the first 3 postoperative months. The simple and effective protocol of collection within 24 hours of death combined with low-dose antibiotic sterilization is sufficient to produce pathogen-free valves in the majority of cases (> 95%).

Anti-Bacterial Agents↗
PubMed1995

Macrosocial and environmental influences on minority health.

Ethnic minority populations show patterns of health, health care use, and mortality that differ from the overall U.S. population. Each of the broad groups of minorities (Asian Hispanic, Native, and African Americans) has a unique background of sociocultural factors that influence these patterns. Thus, the larger social environment for ethnic populations, including political, environmental, historical, and economic factors, is a major variable in possible health outcomes. The individual portions in this panel report of the conference seek to identify such factors for each ethnic group and to suggest those macrosocial influences that are most important for observed health effects.

Black or African American↗
PubMed1995

A case of fulminant human immunodeficiency virus dementia.

Human immunodeficiency virus (HIV) dementia is characterized by cognitive, motor, and behavioral abnormalities that develop over weeks or months. Fulminant presentations are not well described in the literature. In this report we describe a patient with HIV dementia who presented with acute changes in mental status that occurred over 2 days, resulting in rapid deterioration and death in 1 month.

AIDS Dementia Complex↗
PubMed1995

Mouse macrophage metalloelastase expressed in bacteria absolutely requires zinc for activity.

Mouse macrophage metalloelastase was expressed in Escherichia coli. This recombinant enzyme (rMME) was present in the inclusion bodies that were solubilized in 7 M guanidine HCl. After removal of guanidine HCl, rMME was purified with a Q-Sepharose column. Degradation of [3H]elastin by rMME absolutely required Ca2+; the optimal Ca2+ concentration was 5 mM. NaCl stimulated the enzyme activity; maximal stimulation was obtained at 400 mM. The rMME activity was inhibited by metalloprotease inhibitors, but not by serine, aspartyl, or thiol protease inhibitors. Among the divalent cations tested, only Ba2+ and Sr2+ exhibited marginal stimulation of rMME activity in the absence of Ca2+. Cu2+, Zn2+, or Cd2+ strongly inhibited rMME activity with IC50 values between 68 and 180 microM, while Mg2+, Ba2+, Mn2+, Co2+, and Sr2+ had no effect. The requirement of Zn2+ for rMME activity was determined. Significant enzyme activity was present in rMME treated with EDTA followed by Q-Sepharose column chromatography. Only when the inclusion bodies were solubilized in the presence of 20 mM EDTA, did an enzyme preparation which was absolutely dependent on exogenous Zn2+ for activity result. The optimal Zn2+ concentration for rMME activation was 100 microM. These results indicate that Zn2+ is tightly bound to rMME.

Amino Acid Sequence↗
PubMed1995

Clinical and diagnostic features of osteomyelitis occurring in the first three months of life.

We report a retrospective study of 94 infants, ages < 4 months, who underwent investigation for possible osteomyelitis during a 9-year period. Of the 30 babies with proven osteomyelitis (radiographic changes or positive bone cultures or positive blood cultures plus a compatible clinical picture), 17 were preterm artificially ventilated babies and 4 were full term infants receiving intensive care. An etiologic organism was isolated from 28: methicillin-susceptible Staphylococcus aureus, 16; methicillin-resistant S. aureus (MRSA), 7; Escherichia coli, 3; and group B Streptococcus, 2. MRSA occurred exclusively in the preterm group. Osteomyelitis was multifocal in 40% and associated with septic arthritis in 47%. The long bones were frequently affected (80%) whereas the flat bones were often sites of clinically silent disease. Twenty-five (83.3%) of the 30 babies with proven osteomyelitis had focal clinical signs or evidence of disseminated staphylococcal disease. Only 10 were febrile. Four of 27 babies investigated because of positive blood cultures for S. aureus but no focal signs had osteomyelitis, as did only 1 of 27 babies with suspected sepsis but no focal signs. The sensitivity of 99mTc bone scanning was 84%, specificity 89%, positive predictive value 79% and negative predictive value 92%. The addition of gallium scanning (in 39 of the 94 infants) improved the respective figures to 90, 97, 93 and 95% and was useful in interpreting equivocal bone scans.

Arthritis, Infectious↗
PubMed1995

The use of the handgrip maneuver to identify left ventricular diastolic function abnormalities by Doppler echocardiography in patients with coronary artery disease.

Doppler echocardiography accurately identifies diastolic dysfunction through the assessment of transmitral flow patterns during the application of the handgrip (HG) maneuver. In this study, 45 normal control patients (mean age 46 +/- 9, group A) and 13 patients with coronary artery disease (CAD) (mean age 51 +/- 6, group B) were involved. The effects of handgrip maneuver on transmitral flow patterns were studied by Doppler echocardiography. Group B patients had higher peak late diastolic filling velocities (A), lower peak early (E) to late diastolic filling velocity ratios (E/A) and longer isovolumic relaxation times (IVRT) compared to group A. On the other hand, systolic blood pressure (SBP), heart rate (HR) and peak E velocity (E) did not change significantly (p > 0.05) in either group, at rest. During the supine handgrip maneuver, NR (mean +/- standard error of mean, +21 +/- 13%, p < 0.05) and SBP (+21 +/- 9%, p < 0.05) increased significantly in both group A and group B (+21 +/- 13%, p < 0.05, +22 +/- 15%, p < 0.05, respectively). In group B, E/A ratio (-28 +/- 7%) decreased significantly (p < 0.05) compared to group A (-20 +/- 6%), as a consequence of significantly increased peak A velocity in group B (+7 +/- 5%) compared to group A (+6 +/- 3%, p < 0.05). Deceleration time decreased significantly in both groups (-10 +/- 6% vs -9 +/- 6%, p < 0.05). Isovolumic relaxation time (IVRT) significantly increased in both groups (+18 +/- 7% vs +16 +/- 6%, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Determination of tissue endothelin levels.

A methodology for the quantitation of tissue endothelin levels has been developed. About 85% of authentic endothelin-1 added to the tissue extract was recovered. Using this protocol, the levels of endothelin in various rat tissues were determined. In Wistar-Kyoto rats, the kidney was found to have the highest level of endothelin, 1120 pg/gm wet weight, followed by the spleen and liver. The brain contained only half as much of endothelin when compared with the kidney. This method can be utilized to assess the pathological role of endothelin in cardiovascular or renal diseases.

Animals↗
PubMed1995

Clinical hypnosis.

Clinical hypnosis is now an available tool for general practitioners. Hypnotists do not possess any magical powers. It is the patient who possess the magic; the hypnotist merely unlocks this power.

Family Practice↗
PubMed1994

Inhibition of peptidylglycine alpha-amidating monooxygenase by N-substituted homocysteine analogs.

C-terminal amidation is a posttranslational modification found in many neuropeptides. Peptidylglycine alpha-amidating monooxygenase (PAM) catalyzes the synthesis of the biologically essential C-terminal amide from a glycine-extended precursor peptide. Reported herein are the first potent inhibitors of PAM. Dipeptides containing a C-terminal homocysteine and an N-acylated hydrophobic amino acid were found to inhibit PAM with IC50s in the low nanomolar range. Inhibition potency was dependent on both the carboxylate and the thiolate functionalities of the homocysteine and on the hydrophobic groups of the second amino acid. The thiolate was postulated to produce high binding affinities through coordination with the active-site copper. The compound series also exhibited potent inhibition of PAM in rat dorsal root ganglion cells as demonstrated by a dose-dependent increase in the substance P-Gly/substance P ratio. These results indicate that the compounds have sufficient potency and intracellular bioavailability to aid future studies focused on neuropeptide function and the contributions of neuropeptides to various disease processes.

Animals↗
PubMed1994

Molecular and pharmacological characterization of the human CCKB receptor.

The human cholecystokinin B (CCKB) receptor has been isolated from a human temporal cortex cDNA library. Transient transfection of the receptor into COS-M6 cells resulted in high specific binding of 125I-sulphated CCK-8 labelled with Bolton and Hunter Reagent (KD = 31 pM). Competition experiments yielded the expected CCKB receptor ligand binding profile for agonists and antagonists. Similar results were obtained in human small cell lung carcinoma cells, which express an endogenous CCKB receptor. Extensive functional characterization of the receptor was performed in stably transfected HeLa cells using intracellular calcium imaging and microphysiometry techniques. Molecular analysis of the human CCKB receptor using Southern blotting of genomic DNA suggests the presence of a single gene for the CCKB receptor with no closely related homologues. This was confirmed by the polymerase chain reaction cloning of identical receptor coding sequences from human small cell lung carcinoma cells and human gastric enterochromaffin-like cell-oma (ECLoma) tissue.

Animals↗