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Biomedical subjects

A Chu

Publications and source records attributed to A Chu.

At least 55 records · Page 3Linked to original sources
PubMed1997

G alpha(i-2) mediates renal LLC-PK1 growth by a Raf-independent activation of p42/p44 MAP kinase.

The protooncogene G alpha(i-2) plays a pivotal role in signaling pathways that control renal cell growth and differentiation. Mitogen-activated protein kinases (MAPKs) are potential downstream effectors for G alpha(i-2) in these pathways. In predifferentiated LLC-PK1 renal cells, the temporal maximal expression of G alpha(i-2) coincided with maximal activation of MAPK(p42/p44). By contrast, pertussis toxin treatment of these cells inhibited cell growth and reduced MAPK(p42/p44) activity by 30%. These findings reflected upstream activation of MAPK kinase (MEK1), as transient transfection of cells with a plasmid encoding a constitutively active form of MEK1 increased MAPK(p42/p44) activity and cell growth, whereas treatment with PD-098059, an inhibitor of MEK1 activity, reduced MAPK(p42/p44) activity and cell growth. Expression of a guanosinetriphosphatase (GTPase)-deficient G alpha(i-2) in these cells increased MAPK(p42/p44) activity and correspondingly reduced cell doubling time from 24 to 10 h without altering the activity of Raf-1 or c-Jun/stress-activated protein kinases (SAPKs). By contrast, expression of a GTPase-deficient G alpha(i-3) in these cells reduced both their cell doubling time by 30% and MAPK(p42/p44) activity by 60%. As the known MEKK isoforms (MEKK1, -2, and -3) can also activate SAPKs, these findings suggest the GTP-charged G alpha(i-2) subunit transduces growth signals in renal cells via activation of MAPK(p42/p44) and that such activation may be linked to pathways containing novel MEKK isoforms that preferentially activate MEKs.

Animals↗
PubMed1997

The comparative efficacy of benzoyl peroxide 5%/erythromycin 3% gel and erythromycin 4%/zinc 1.2% solution in the treatment of acne vulgaris.

This randomized 10-week study compared the efficacy of benzoyl peroxide 5%/erythromycin 3% gel with erythromycin 4%/zinc 1.2% solution in 72 acne vulgaris patients. Physician global evaluations were significantly more improved (P < or = 0.05) in the benzoyl peroxide 5%/erythromycin 3% gel treatment group compared to erythromycin 4%/zinc 1.2% solution at week 2 and at each subsequent biweekly clinical visit. Inflammatory lesions (papules/pustules) were significantly more reduced (P < or = 0.005) in the benzoyl peroxide 5%/erythromycin 3% gel treatment group than the erythromycin 4%/zinc 1.2% solution at weeks 4 and 10. Comedones were significantly more reduced (P < or = 0.001) in the benzoyl peroxide 5%/erythromycin 3% gel treatment group than in the erythromycin 4%/zinc 1.2% solution group at weeks 8 and 10. Patient efficacy evaluations significantly (P < or = 0.001) favoured benzoyl peroxide 5%/erythromycin 3% gel to erythromycin 4%/zinc 1.2% solution.

Acne Vulgaris↗
PubMed1996

(+)-Pinoresinol/(+)-lariciresinol reductase from Forsythia intermedia. Protein purification, cDNA cloning, heterologous expression and comparison to isoflavone reductase.

Lignans are a widely distributed class of natural products, whose functions and distribution suggest that they are one of the earliest forms of defense to have evolved in vascular plants; some, such as podophyllotoxin and enterodiol, have important roles in cancer chemotherapy and prevention, respectively. Entry into lignan enzymology has been gained by the approximately 3000-fold purification of two isoforms of (+)-pinoresinol/(+)-lariciresinol reductase, a pivotal branchpoint enzyme in lignan biosynthesis. Both have comparable ( approximately 34.9 kDa) molecular mass and kinetic (Vmax/Km) properties and catalyze sequential, NADPH-dependent, stereospecific, hydride transfers where the incoming hydride takes up the pro-R position. The gene encoding (+)-pinoresinol/(+)-lariciresinol reductase has been cloned and the recombinant protein heterologously expressed as a functional beta-galactosidase fusion protein. Its amino acid sequence reveals a strong homology to isoflavone reductase, a key branchpoint enzyme in isoflavonoid metabolism and primarily found in the Fabaceae (angiosperms). This is of great evolutionary significance since both lignans and isoflavonoids have comparable plant defense properties, as well as similar roles as phytoestrogens. Given that lignans are widespread from primitive plants onwards, whereas the isoflavone reductase-derived isoflavonoids are mainly restricted to the Fabaceae, it is tempting to speculate that this branch of the isoflavonoid pathway arose via evolutionary divergence from that giving the lignans.

Amino Acid Sequence↗
PubMed1996

A gene map of the human genome.

The human genome is thought to harbor 50,000 to 100,000 genes, of which about half have been sampled to date in the form of expressed sequence tags. An international consortium was organized to develop and map gene-based sequence tagged site markers on a set of two radiation hybrid panels and a yeast artificial chromosome library. More than 16,000 human genes have been mapped relative to a framework map that contains about 1000 polymorphic genetic markers. The gene map unifies the existing genetic and physical maps with the nucleotide and protein sequence databases in a fashion that should speed the discovery of genes underlying inherited human disease. The integrated resource is available through a site on the World Wide Web at http://www.ncbi.nlm.nih.gov/SCIENCE96/.

Amino Acid Sequence↗
PubMed1996

Heteroduplex analysis in hemophilia B: detection of two novel factor IX gene mutations.

Heteroduplex analysis of polymerase chain reaction (PCR)-amplified factor IX (FIX) sequences in eight hemophilia B pedigrees localized the causative hemophilia mutation to a single exon in each case. Subsequent PCR-based direct DNA sequence analysis identified two novel FIX mutations and six recurrent mutations. Three of the eight pedigrees represent sporadic hemophilia B, and direct mutation analysis facilitated hemophilia carrier diagnosis in each case.

DNA Mutational Analysis↗
PubMed1996

A proliferation analysis of arterial neointimal hyperplasia: lessons for antiproliferative restenosis therapies.

Medial smooth muscle cell proliferation is frequently implicated as the major cause of coronary restenosis. Although antiproliferative agents have shown efficacy in animal studies, they are ineffective in human trials. To better understand these discrepancies, we performed a mathematical kinetic analysis of cellular proliferation in the neointimal hyperplasia of rats, pigs, and patients. A model was derived using a differential expression for proliferation, proportional to the number of cells present. Additional terms were included for inhibition of proliferation proportional to neointimal mass and time. The resulting equation was solved in closed form for the number of cells and proliferation rate. These equations were validated in the rat carotid artery injury model from published data. The model was then applied to the porcine coronary injury model, and then to clinical data obtained from angiographic human studies. Peak cellular proliferative activity in patients occurs at 16 days and continues at lower levels for much longer periods of time. Less than 10 generations of cells are sufficient to develop clinically significant restenosis. Conversely, proliferation rates in the two animal models (rats and pigs) are maximal at roughly 2 and 6 days, respectively, also continuing at low levels for extended time periods. Cell proliferation in restenosis is a highly controlled process, with comparatively few cell generations causing enough neointima for arterial obstruction to occur. Substantial cell kinetic differences occur across species. The rat exhibits high proliferation rates and rapid doubling times compared to patients and pigs, and is thus a highly 'proliferative' model. Such differences may be responsible for discrepant animal model and clinical trial results. These data may help determine the timing and strategy of therapy against clinical restenosis.

Animals↗
PubMed1995

Coding changes in the 3a cell-to-cell movement gene can extend the host range of brome mosaic virus systemic infection.

The M1 and M2 strains of brome mosaic virus (BMV) both systemically infect the monocot host barley, but only the M2 strain systemically infects the dicot cowpea line TVu-612. We have shown previously that this difference in host range maps primarily to RNA3. To further characterize the role of RNA3 in host specificity, a series of RNA3 hybrids were tested, in inoculations with M1 RNA1 and RNA2, for ability to systemically infect TVu-612 cowpea. Although all hybrids were amplified well in cowpea protoplasts and all supported systemic infection in barley plants, only those with the 3a cell-to-cell movement gene of BMV-M2 supported systemic infection of cowpea. The sequences of the M1 and M2 3a proteins differ at four positions. Introducing these four coding differences individually or in various combinations into M1 RNA3 revealed that all four influenced BMV adaptation to cowpea and that these four differences were sufficient to account for the difference in ability between M1 and M2 RNA3s to support systemic infection of this legume. These coding changes were also associated with faster spread of infection in inoculated cowpea leaves, suggesting that they influence the ability to systemically infect TVu-612 cowpea through effects on the rate of cell-to-cell spread.

Base Sequence↗
PubMed1995

Ryanodine receptor-ankyrin interaction regulates internal Ca2+ release in mouse T-lymphoma cells.

In this study, we have identified and partially characterized a mouse T-lymphoma ryanodine receptor on a unique type of internal vesicle which bands at the relatively light density of 1.07 g/ml. Analysis of the binding of [3H]ryanodine to these internal vesicles reveals the presence of a single, low affinity binding site with a dissociation constant (Kd) of 200 nM. The second messenger, cyclic ADP-ribose, was found to increase the binding affinity of [3H]ryanodine to its vesicle receptor at least 5-fold (Kd approximately 40 nM). In addition, cADP-ribose appears to be a potent activator of internal Ca2+ release in T-lymphoma cells and is capable of overriding ryanodine-mediated inhibition of internal Ca2+ release. Immunoblot analyses using a monoclonal mouse antiryanodine receptor antibody indicate that mouse T-lymphoma cells contain a 500-kDa polypeptide similar to the ryanodine receptor found in skeletal muscle, cardiac muscle, and brain tissues. Double immunofluorescence staining and laser confocal microscopic analysis show that the ryanodine receptor is preferentially accumulated underneath surface receptor-capped structures. T-lymphoma ryanodine receptor was isolated (with an apparent sedimentation coefficient of 30 S) by extraction of the light density vesicles with 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid (CHAPS) in 1 M NaCl followed by sucrose gradient centrifugation. Further analysis indicates that specific, high affinity binding occurs between ankyrin and this 30 S lymphoma ryanodine receptor (Kd = 0.075 nM). Most importantly, the binding of ankyrin to the light density vesicles significantly blocks ryanodine binding and ryanodine-mediated inhibition of internal Ca2+ release. These findings suggest that the cytoskeleton plays a pivotal role in the regulation of ryanodine receptor-mediated internal Ca2+ release during lymphocyte activation.

Adenosine Diphosphate Ribose↗
PubMed1995

Bleeding injuries in professional football: estimating the risk for HIV transmission.

OBJECTIVE: To determine the risk for bleeding injuries in professional football and to estimate the risk for transmission of the human immunodeficiency virus (HIV) through such injuries. DESIGN: A prospective, observational study. PARTICIPANTS: Professional football players from 11 teams of the National Football League were observed during 155 regular season games from September through December 1992. MEASUREMENTS: The frequencies of bleeding injuries were calculated in association with environmental and athletic factors. Using this information, HIV prevalence, and data on transmission of HIV in other circumstances, the risk for transmission of HIV during football games was estimated. RESULTS: 575 bleeding injuries (average, 3.7 per game for each team) involving 538 players (average, 3.5 players on each team per game) were observed. Approximately 88% of the bleeding injuries were abrasions; the remainder were lacerations. Bleeding injuries were markedly more frequent during games played on artificial surfaces, during games played in domed stadiums, and on teams with a final win/loss percentage of 0.500 or lower. Using data on the prevalence of HIV among college men and rates of HIV transmission in the health care setting, the risk for HIV transmission to each player was estimated to be less than 1 per 85 million game contacts. CONCLUSIONS: Although injuries occur in professional football competitions, bleeding injuries, especially lacerations, occur infrequently. We estimate that the risk for HIV transmission during such competition is extremely remote. The role of artificial playing surfaces on the incidence or severity of bleeding injuries should be investigated.

Chi-Square Distribution↗
PubMed1995

Reliability and validity of tympanic temperature measurement in persons with high spinal cord injuries.

Tympanic temperature measurements in the able bodied have been well studied and validated in previous investigations. This validation has not been studied in individuals with high spinal cord injuries where autonomic control is different above and below the level of the lesion, which makes the accuracy of this measurement for core body temperature questionable. In this correlational study we look at the reliability and validity of tympanic temperature measurement in individuals with high spinal cord injuries in comparison to oral and rectal temperature measures. The rectal measurement proved to be the most reliable with an r value of 0.975 overall. The oral was minimally better than the tympanic with r values of 0.88 and 0.86, respectively. The validity of the oral measure in predicting changes in the rectal temperature (gold standard) was slightly better than the tympanic with r values of 0.88 and 0.77, respectively. Both the oral and tympanic measures accurately reflected changes in the rectal (core) temperature.

Body Temperature↗
PubMed1995

Ca2+ release channels in rat denervated skeletal muscles.

Sarcoplasmic reticulum (SR) Ca2+ release channel-ryanodine receptors (RYR1) from rat fast-twitch skeletal muscle were studied by incorporating heavy sarcoplasmic reticulum membranes into a lipid bilayer. Channels from normal and denervated muscles had the same conductance as that reported for rabbits (about 500 pS) in 250:250 mM cis:trans caesium methanesulphonate. Caffeine (0.1 mM) induced a larger increase in the open probability (Po) in denervated than in normal channels. The caffeine effect was caused by changes in mean open and burst time distributions. Longer opening and burst events were detected in the presence of caffeine. High caffeine concentrations (4 mM) gave similar results in channels from normal and denervated muscles. In denervated muscle, unlike intact muscle, the Ca2+ release channel was not activated at millimolar Ca2+ concentrations; this is similar to the cardiac isoform of the channel. Maximal channel activation was shifted to higher Ca2+ concentrations (pCa 4) and the channel remained activated at millimolar Ca2+ concentrations. The main effect of millimolar Ca2+ concentrations upon Ca2+ release channels from denervated muscles was an increase in the mean open time, with a concomitant increment of the mean burst duration. Alterations in channel gating properties in calcium and caffeine account for changes in the mechanical response after skeletal muscle denervation.

Animals↗
PubMed1994

Solvent-dependent influences on skeletal muscle sarcoplasmic reticulum calcium uptake and release.

The organic cosolvents propylene glycol (PG) and polyethylene glycol 400 (PEG 400) have previously been shown to differ in their potential to cause muscle damage following im injection. PG was found to be more myotoxic than PEG 400, with indirect implications of the role of cytosolic calcium in mediating this damage. In the present study, the direct effects of these cosolvents were investigated on the sarcoplasmic reticulum (SR), the major intracellular muscle membrane that mobilizes calcium. The passive permeability of isolated SR microsomal vesicles to calcium was not affected by 5.3 and 10.5% (v/v) PG and PEG 400. At 10.5% (v/v), a concentration of the organic cosolvent that would not be unexpected at the injection site, PEG 400 stimulated calcium uptake by 40 and 140% in longitudinal tubular-derived and terminal cisternal-derived vesicles, respectively, without significantly altering the ATP hydrolytic activity of the calcium pump. The calcium pumping efficiency (Ca2+/ATP coupling ratio) was therefore also enhanced. On the other hand, 10.5% (v/v) PG did not significantly alter either calcium uptake or ATPase activity of the pump. PG stimulated calcium efflux from only the terminal cisternae vesicles via a pathway indicative of the ryanodine-sensitive calcium channel, as demonstrated by inhibition of PG-induced efflux by millimolar Mg2+. These results are consistent with multiple interactions of cosolvents with proteins in the membrane bilayer, with the distinction that the two cosolvents differentially influence the calcium pump and release channel, particularly at the terminal cisternae, where there is rapid change of calcium level during excitation-contraction coupling. These data provide further evidence for the role of calcium in mediating organic cosolvent-induced muscle damage. In addition, they provide a possible explanation for the myoprotective effect of PEG 400 (compared to PG) as a result of increased myoplasmic calcium removal and reduced calcium release.

Adenosine Triphosphate↗
PubMed1994

Genetically engineered antibodies for diagnostic pathology.

Antibody genes can be cloned, genetically manipulated, and expressed in both homologous and heterologous expression systems to produce viable antigen-binding proteins complete with natural effector functions. Manipulation of antibody genes permits the expression of fusion proteins or truncated proteins that retain antigen-binding activity. The new antibody technologies are becoming increasingly sophisticated, permitting the alteration of antigen-binding responses, the transfer of antigen specificity between antibodies, and the expression of minimal-size antigen-binding protein domains. These new molecules have been made mostly for studies on function or to provide molecules suited for in vivo diagnosis and therapy; very few have been specifically designed for, or used for, diagnostic histopathology. We describe here the adaptation of small antibody derivatives for use in immunohistochemistry. Molecules suitable for this purpose need only to possess specific antigen-binding ability and some means of detection of antigen-bound material. Detection could be by recognition of a genetically fused flag or tag epitope, by the fusion of an enzyme whose activity can be assayed, or by fusion with a protein that can interact with pre-existing histopathological reagents.

Animals↗
PubMed1993

Stereospecificity of (+)-pinoresinol and (+)-lariciresinol reductases from Forsythia intermedia.

Pinoresinol/lariciresinol reductase catalyzes the first known example of a highly unusual benzylic ether reduction in plants; its mechanism of hydride transfer is described. The enzyme was found in Forsythia intermedia and catalyzes the presumed regulatory branch-points in the pathway leading to benzylaryltetrahydrofuran, dibenzylbutane, dibenzylbutyrolactone, and aryltetrahydronaphthalene lignans. Using [7,7'-2H2]-pinoresinol and [7,7'-2H3]lariciresinol as substrates, the hydride transfers of the highly unusual reductase were demonstrated to be completely stereospecific (> 99%). The incoming hydrides were found to take up the pro-R position at C-7' (and/or C-7) in lariciresinol and secoisolariciresinol, thereby eliminating the possibility of random hydride delivery to a planar quinone methide intermediate. As might be expected, the mode of hydride abstraction from NADPH was also stereospecific: using [4R-3H] and [4S-3H]NADPH, it was found that only the 4 pro-R hydrogen was abstracted for enzymatic hydride transfer.

Lignin↗
PubMed1993

Cyclic ADP-ribose as an endogenous regulator of the non-skeletal type ryanodine receptor Ca2+ channel.

The skeletal and cardiac isoforms of the ryanodine receptor Ca2+ channel (RyRC) constitute the Ca2+ release pathway in sarcoplasmic reticulum of skeletal and cardiac muscles, respectively. A direct mechanical and a Ca(2+)-triggered mechanism (Ca(2+)-induced Ca2+ release) have been respectively proposed to explain the in situ activation of Ca2+ release in skeletal and cardiac muscle. In non-muscle cells, however, where the RyRC also participates in Ca2+ signalling, the mechanism of RyRC activation is unknown. Cyclic adenosine 5'-diphosphoribose (cADPR), which is present in many mammalian tissues, has been reported to induce Ca2+ release from ryanodine-sensitive intracellular Ca2+ stores in sea urchin eggs. Here we provide evidence that cADPR directly activates the cardiac but not the skeletal isoform of the RyRC. This, together with results on sea urchin eggs, suggests that cADPR is an endogenous activator of the non-skeletal type of RyRC and may thus have a role similar to inositol 1,4,5-trisphosphate in Ca2+ signalling.

Adenosine Diphosphate Ribose↗
PubMed1993

A comparison of a new polypropylene suture with Prolene.

The purpose of this paper is to examine the performance of the newly available monofilament polypropylene suture (Surgipro) manufactured by U.S. Surgical and compare it with commercial Prolene sutures for determining the merit of this new suture. Two different sizes of Surgipro sutures were used. They were 4/0 and 0 sizes and were tested in terms of their fundamental properties: level of crystallinity, melting temperature, fiber morphology, and mechanical properties including knot strength and knot security. The effect of three different sterilization methods on the mechanical and fundamental properties of the new polypropylene (PP) sutures was also examined. In general, the new Surgipro sutures performed as good as Prolene sutures in terms of mechanical properties; but there were some differences in fundamental properties between these two types of PP sutures, particularly in finer size PP sutures. The major differences were in interior fiber morphology, level of crystallinity, and melting temperature. Surgipro suture fibers showed homogeneous interior morphology, while Prolene fibers exhibited two distinctive fiber morphologies. These two types of PP suture fibers also responded differently to the three sterilization methods tested. Surgipro sutures are less affected by different sterilization methods than the same size Prolene control. Except for the Co 60 gamma sterilization, Surgipro suture fibers did not exhibit statistically significant differences in tensile breaking strength between sterilized and control. Ethylene oxide and autoclave sterilized Prolene suture fibers, however, showed statistically (p less than 0.05) consistently lower tensile breaking strength than their unsterilized controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Crystallization↗