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B Chu

Publications and source records attributed to B Chu.

At least 73 records · Page 4Linked to original sources
PubMed1993

Detection of the (--SEA) double alpha-globin gene deletion by a simple immunologic assay for embryonic zeta-globin chains.

Homozygous alpha-thalassemia [alpha-thal-1], with loss of all four alpha-globin genes, causes lethal hydrops fetalis. The most common mutation producing this syndrome is the Southeast Asian (--SEA) double alpha-globin gene deletion. Erythrocytes from adults heterozygous for the (--SEA) deletion have minute amounts of embryonic zeta-globin chains detectable by anti-zeta-globin monoclonal antibodies. Among 225 peripheral blood samples tested by a simple anti-zeta-immunobinding tetrazolium dye test, 81 were positive and 144 were negative. The majority of subjects were of Filipino, Chinese, or Laotian ancestry. All 81 positive samples were confirmed by Bam HI digests and a zeta-cDNA probe to have the (--SEA) mutation. The (--SEA) double alpha-deletion was the only abnormality in 58. In the others, it was combined with alpha-globin or beta-globin mutations, or coincidental iron deficiency. Four other samples from (--SEA) heterozygotes were negative by this immunologic assay. Anti-zeta negative samples included 78 deletions of the total alpha-globin region, (--Tot), 23 single alpha-globin deletions, and a variety of beta-globin mutations; 16 normocytic samples with normal alpha-genes were also negative. Ten anti-zeta positive and 25 anti-zeta negative samples had benign triplicated zeta-globin genes. In this population, the sensitivity of this test was 95%; and specificity for the (--SEA) mutation was 100%. Anti-zeta immunobinding testing provides rapid, simple, and reliable screening for the (--SEA) double alpha-globin deletion, although it does not detect the (--Tot) total alpha-deletions.

Antibodies, Monoclonal↗
PubMed1993

Isolation and characterization of an Arabidopsis thaliana gene for the 54 kDa subunit of the signal recognition particle.

The first step in the routing of newly synthesized proteins into the secretory pathway is the binding of the nascent signal sequence to the signal recognition particle. The mammalian signal recognition particle is a complex consisting of 6 proteins and a single 7S RNA molecule. Signal recognition particle-like complexes have been described from wheat and maize but none of the protein components have yet been described from any plant species. Here we report the cloning and characterization of an Arabidopsis thaliana gene encoding the 54 kDa protein subunit of the signal recognition particle. This is the first report of a SRP-54 sequence for any plant species and the first genomic sequence for any multicellular organism.

Amino Acid Sequence↗
PubMed1993

Radial and ulnar artery repairs: assessing patency rates with color Doppler ultrasonographic imaging.

This study was undertaken to evaluate the patency rate of radial and ulnar artery repairs performed with use of the magnification afforded by the operative microscope. Color Doppler ultrasonographic imaging was chosen as a reproducible, noninvasive technique to evaluate patency and graphically display vascular flow characteristics. Twenty-eight consecutive patients with 35 arterial injuries form the study group. Twenty-four patients with 31 arterial lacerations were available for enrollment in the protocol. Follow-up ranged from 1 to 40 months (average, 10 months). Eighteen male and six female patients sustained 13 radial and 18 ulnar artery lacerations, all sharp. Four patients required interposition vein grafting. Overall patency after repair was found to be 84%, with 82% of single vessels and 86% of double vessels patent. The patency of single vessels repaired without the use of vein grafts was 100%. These results indicate that microscope-assisted repairs of the radial and ulnar arteries remain patent at a higher rate than is commonly cited.

Color↗
PubMed1993

The effect of dextran on microvascular thrombosis in an experimental rabbit model.

Although low molecular weight dextran is commonly utilized in clinical microsurgery, few experimental data are available documenting its efficacy. Bilateral 2-mm arterial inversion grafts were constructed in the femoral arteries of New Zealand White rabbits. The experimental group (n = 40 grafts) received a 5-day constant infusion of intravenous dextran 40 at 2.1 ml/hour, and the control group (n = 50 grafts) received no infusion. Whereas 85 percent (34/40) of the dextran grafts were patent at 1 week, only 48 percent (24/50) of the control grafts were patent (p = 0.0003). Scanning electron micrographs revealed a decrease in both platelet and fibrin deposition in the patent dextran arterial inversion grafts versus the patent control specimens. As a marked diminution in microvascular thrombosis was demonstrated at a clinically relevant dose, the continued use of intravenous dextran 40 in clinical microsurgery is supported by this study.

Animals↗
PubMed1992

Suppression of crossbridge motions of isolated thick myofilaments in ATP-free medium by thiourea.

Thiourea is known to suppress the contractile response of Mytilus anterior byssus retractor muscle and toad sartorious muscle following electrical or chemical stimulation without abolishing of the electrical responses. In addition, it blocks the shortening of glycerinated sartorious muscle induced by Ca2+. With dynamic laser light scattering method we found that thiourea suppresses the increase of the average linewidth of the photoelectron count autocorrelation function, gamma, of isolated thick filaments of Limulus striated muscle induced by depletion of ATP. The results obtained suggest that thiourea prevents the crossbridges from moving away from the thick myofilament backbones which will, in turn, prohibit the crossbridges from interacting with the thin myofilaments.

Adenosine Triphosphate↗
PubMed1992

Movement of fluorescence pattern after photobleaching: an accelerated procedure for DNA electrophoretic mobility analysis.

A new approach which is compatible with many of the existing procedures for the analysis of DNA species in gel electrophoresis is being demonstrated. It takes advantage of fluorescence photobleaching in order to create a sharp boundary between the stained and the (partially) photobleached DNA. By arbitrarily creating a stained DNA band of narrower width, the sensitivity to detect (averaged) DNA band movements has been increased. This feature permits measurements of time-dependent electrophoretic mobility over very short time periods. The approach can be used to shorten the running time of gel electrophoresis experiment and to increase the resolution because of the sharper boundary and narrower band width. With faster running time, diffusion of both DNA and dye in the gel also becomes less serious. Movement of fluorescence pattern after photobleaching also permits measurements of localized motions when the gel pores are small in comparison with DNA sizes. Experiments demonstrating some aspects of the proposed technique, as well as the anticipated limitations, are presented and discussed.

Autoanalysis↗
PubMed1992

Seasonal changes in the activation of crossbridge motions of isolated thick filament from Limulus striated muscle.

In dynamic light scattering, measurements of the intensity-intensity time correlation function from a suspension of rod-like particles of length L could reveal dynamical information related to translational and internal motions of those particles. For a suspension of thick filaments isolated from the myosin-regulated, striated muscles of Limulus at KL greater than 1 (where K is the scattering vector), the average characteristic linewidth (gamma) increased with the addition of Ca2+ or with the depletion of ATP. The increase in the gamma with the addition of Ca2+ could be due to the presence of energy-requiring, high-frequency motions of the crossbridges activated by Ca2+. The increase in gamma which occurred with the depletion of ATP was assumed to be mainly due to the thermal motions of the crossbridges after they had moved radially away from the filament backbone. The percentage increase in gamma following the addition of Ca2+ was found to be seasonal, i.e., values of gamma obtained from thick filaments isolated between the middle of June and the middle of September were smaller than those obtained during the rest of the year. The effect of temperature on the percentage increase in gamma was also different. The increase showed a maximum at about 35 degrees C during the summer and at about 25 degrees C at other times. However, the percentage increase in gamma developed under ATP-depleted conditions showed no temperature-related maximum. The number of bound Ca2+ per myosin molecule was 1 during the summer and 2 at other times.

Adenosine Triphosphate↗
PubMed1990

Neurotoxicity induced by the D-1 agonist SKF 38393 following microinjection into rat brain.

Microinjection of the D-1 agonist R-SKF 38393 into rat striatum resulted in extensive neurotoxic damage as revealed by the presence of large lesions upon histological analysis. These lesions were observed following a single injection of the drug into the ventrolateral striatum (30 micrograms/0.5 microliters) or nucleus accumbens (3.0 or 30 micrograms/0.5 microliters). This neurotoxic damage was also observed following microinjection of the inactive isomer S-SKF 38393. The mechanisms underlying these effects are presently unknown. The use of this compound for intracerebral microinjection studies should be re-evaluated. In view of the usefulness of central microinjections in studying the role of D-1 and D-2 receptors in behavior, it is suggested that alternative D-1 agonists, or ways of minimizing the toxicity of SKF 38393, should be considered.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1990

Electrophoresis and movements of fluorescence pattern after photobleaching of large DNA fragments in agarose gels.

By combining electrophoresis with movements of fluorescence pattern after photobleaching (MOFPAP), which is abbreviated as EMOFPAP, we are able to measure electrophoretic mobilities of large DNA fragments in an agarose gel within a fairly short time scale (about 10 min or even down to 1 min). The new method represents a significant improvement in experiment time when compared with the time (typically on the order of hours) required to determine the average electrophoretic mobility of large DNA fragments in agarose gels by means of either conventional gel electrophoresis or pulsed-field gel electrophoresis. In this article, we present the EMOFPAP experimental setup and consider optical conditions, including beam profile geometry and fluorescence pattern formation. A realistic formula that can explain the parameters governing the EMOFPAP method using our present optical setup has been derived. A comparison of results between experimental and computer simulation data is made, and an optimization of the EMOFPAP method is proposed.

DNA↗
PubMed1987

Effect of ATP depletion on the isolated thick filament of limulus striated muscle.

With the dynamic light scattering method, we have shown that calcium ions increase the high-frequency internal motions of isolated thick filaments of Limulus striated muscle in the presence of ATP (Kubota, K., B. Chu, Shih-fang Fan, M.M. Dewey, P. Brink, and D. Colflesh. J. Mol. Biol. 1983. 166:329 and Fan, S.-f., M.M. Dewey, D. Colflesh, B. Gaylinn, R. Greguski, and B. Chu. Biophys. J. 1985. 47:809). If ATP is removed from the suspending medium, an increase of high-frequency internal motions also has been observed with characteristics different from those of filaments suspended in a medium containing ATP and calcium ions. These internal motions appear whether calcium ions are present or not and are suppressed by trifluoperazine (TFP). The motions differ from the calcium ion-induced motions in that (a) an energy supply is not required; (b) they are insensitive to heat treatment (42 degrees C, 10 min) and (c) they are also insensitive to phenylmethylsulfonyl fluoride which blocks the motions in the presence of ATP and calcium ions (Fan, Shih-fang, M.M. Dewey, D. Colflesh, B. Gaylinn, R. Greguski, and B. Chu. 1985. Biochim. Biophys. Acta. 827:101). Electron micrographs of negatively stained thick filaments in an ATP-free medium show that the majority of crossbridges extend out from the backbone of the filament and optical diffraction patterns from these filaments lack layer lines arising from the crossbridges. The flexibility of the thick filaments suspended in ATP-free media increases.

Adenosine Triphosphate↗
PubMed1985

Suppression of active cross-bridge motions of isolated thick myofilaments in suspension by phenylmethylsulfonyl fluoride.

Studies of photoelectron count autocorrelation function of light scattered from suspensions of thick filaments of Limulus telson muscle and scallop striated adductor muscle reveal that Ca2+ can activate cross-bridge motions of these isolated filaments. By treating suspensions of activated filaments with phenylmethylsulfonyl fluoride (PMSF), we can suppress active cross-bridge motions but not affect the Ca2+-dependent ATPase activity.

Adenosine Triphosphatases↗
PubMed1985

The active cross-bridge motions of isolated thick filaments from myosin-regulated muscles detected by quasi-elastic light scattering.

Intensity fluctuation spectroscopy has been used successfully as a probe that can detect an increase in high-frequency internal motions of isolated thick filaments of Limulus muscle upon the addition of calcium ions. We have attributed such motions to cross-bridge motion instead of to an increase in the flexibility of the filament backbone. Here we show that after cleavage of the S-1 and then the S-2 moieties with papain, cross-linking the myosin heads to the filament backbone, or heat denaturation (42 degrees C, 10 min), the increase in the high frequency internal motions in the thick filaments no longer occurs. Congo Red, which has been shown to induce shortening of isolated myofibrils, also increases the high-frequency motions of the isolated filaments. Furthermore, the increase is suppressed by treating the filaments with a myosin ATPase inhibitor such as vanadate ions (10 mM) or by replacing ATP with either an equimolar CrADP or the nonhydrolyzable ATP analogue beta, gamma-imido-adenine-5'-triphosphate (AMP-PNP). Calcium ions have a similar effect on isolated thick filaments from scallop muscle, where the myosin is known to be regulatory. Calcium ions have no such effect on thick filaments isolated from frog muscle, which is believed not to be regulated by calcium binding to myosin. These results confirm our earlier supposition that the additional high frequency internal motions of the thick filaments isolated from striated muscle of Limulus are related to the energy dependent, active cross-bridge motions.

Adenosine Triphosphatases↗