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B Chu

Publications and source records attributed to B Chu.

At least 55 records · Page 3Linked to original sources
PubMed1998

Partial liquid ventilation with perfluorocarbon in the treatment of rats with lethal pneumococcal pneumonia.

BACKGROUND: Partial liquid ventilation with perfluorocarbon is a new therapeutic strategy to treat various lung disorders. The current study was undertaken to determine the efficacy of partial liquid ventilation with a perfluorocarbon (FC-77) in the treatment of pneumococcal pneumonia in rats. METHODS: Male Wistar rats (weight, 275-300 g; n, 75) were infected via direct intratracheal inoculation with ca 10(9) colony-forming units of viable Streptococcus pneumoniae, serotype 3, and 24 h after infection were placed into one of five groups, each containing 15 rats. The groups were (1) no treatment, (2) one intramuscular injection of penicillin G benzathine (200,000 U), (3) partial liquid ventilation with FC-77, (4) partial liquid ventilation with FC-77 and a single intramuscular dose of penicillin G benzathine (200,000 U), and (5) gas ventilation. Animals were observed every 24 h for survival. RESULTS: All untreated or gas-ventilated animals or animals that received only partial liquid ventilation were dead by 7 days. Those receiving only partial liquid ventilation survived longer than untreated controls, but ultimately all succumbed by day 7. Survival was 40% for penicillin-treated rats compared with controls (P < 0.05) and 80% for animals treated with both partial liquid ventilation and penicillin versus antibiotic alone (P < 0.05). CONCLUSIONS: These observations suggest that partial liquid ventilation with perfluorocarbon in combination with antibiotic administration may be an effective therapeutic modality in pneumococcal pneumonia.

Animals↗
PubMed1998

Ethanol potentiation of calcium-activated potassium channels reconstituted into planar lipid bilayers.

We examined the actions of ethanol on the single channel properties of large conductance Ca2+-activated K+ (BK) channels isolated from skeletal muscle T-tubule membranes and incorporated into planar lipid bilayer membranes. We have taken advantage of this preparation, because it lacks most elements of cellular complexity, including cytoplasmic constituents and complex membrane lipid composition and architecture, to examine the minimum requirements for the effects of alcohol. Clinically relevant concentrations (25-200 mM) of ethanol increased the activity of BK channels incorporated into bilayers composed of phosphatidylethanolamine (PE) alone or PE and phosphatidylserine. The potentiation of channel activity by ethanol was attributable predominantly to a decrease in the average amount of time spent in closed states. Ethanol did not significantly affect the current amplitude-voltage relationship for BK channels, indicating that channel conductance for K+ was unaffected by the drug. Although base-line characteristics of BK channels incorporated into bilayers composed only of PE differed from those of channels in PE/ phosphatidylserine in a manner expected from the change in bilayer charges, the actions of ethanol on channel activity were qualitatively similar in the different lipid environments. The effects of ethanol on single channel properties of BK channels in the planar bilayer are very similar to those reported for the action of ethanol on neurohypophysial BK channels studied in native membrane, and for cloned BK channels expressed in Xenopus laevis oocytes, which suggests that ethanol's site and mechanism of action are preserved in this greatly simplified preparation.

Animals↗
PubMed1997

p107 and p130 associated cyclin A has altered substrate specificity.

We demonstrate that p107 and p130 immune complexes exhibit kinase activity. We have tested such immune complexes with four substrates commonly utilized to assay Cdk activity, including all three known members of the retinoblastoma family. Immunodepletion revealed this kinase activity could be abolished by removal of either cyclin A or Cdk2 but was unaffected by removal of Cdk4 or any D-type cyclin. The appearance of p107 associated activity followed the accumulation of p107 protein. In contrast, the kinase activity associated with p130 immune complexes became apparent after mid-G1, coincident with p130 hyperphosphorylation. GST-Rb, GST-p107, and GST-p130 (where GST indicates glutathione S-transferase) were equally suitable substrates in p107 and p130 immune complex kinase assays, yielding activity equal to 25% of the cyclin A activity present. The p107 and p130 associated activity was unable to phosphorylate histone H1, suggesting the p107 and p130 associated cyclin A/Cdk2 may represent a distinct pool with a distinct substrate specificity. The p107 and p130 associated activity was released from the immune complexes upon incubation with ATP and Mg2+ and exhibited the same substrate preference observed with the untreated immune complex. Our data suggest that p107 and p130 recognize, or form by association, a distinct pool of cyclin A/Cdk2 that preferentially phosphorylates retinoblastoma family members.

3T3 Cells↗
PubMed1997

Heat shock inhibits release of the signal recognition particle from the endoplasmic reticulum in barley aleurone layers.

When barley (Hordeum vulgare) aleurone layers are subjected to heat shock there is a selective degradation of the normally stable mRNAs encoding secreted proteins. Messages for nonsecreted proteins are not degraded. The synthesis of heat shock proteins is not required for this selective message degradation. Our hypothesis explaining this phenomenon is that a component of the early steps in the synthesis of secreted proteins is damaged by heat shock, resulting in a selective halt in translation on secretory mRNAs, which may in turn lead to degradation of those messages. The first committed step in the synthesis of secreted proteins is the binding of the nascent signal sequence to the signal recognition particle. We have obtained cDNA clones and antibodies for the barley 54-kDa subunit of the signal recognition particle. In cell fractionation experiments, more signal recognition particle was bound to the endoplasmic reticulum membranes and less was in the free particle fraction following a heat shock. The results suggest that heat shock inhibits the release of the signal recognition particle from the endoplasmic reticulum. This would, in turn, inhibit the resumption of translation and may be the underlying cause of the secretory message degradation.

Amino Acid Sequence↗
PubMed1997

adg2-1 represents a missense mutation in the ADPG pyrophosphorylase large subunit gene of Arabidopsis thaliana.

Arabidopsis mutants affecting ADPG pyrophosphorylase (ADGase) activity can be divided into two complementation groups, adg1 and adg2. Previous biochemical studies of adg2-1 mutant indicated that mutant plants do not accumulate ADGase large subunit protein and that ADGase small subunits assemble as homotetramers. This suggested that the ADG2 gene may encode the large subunit of ADGase. In this paper, it is shown that adg2-1 mutant plants accumulate near wild-type levels of transcripts encoding both the large and small subunits of ADGase. However, by RFLP analysis and complementation of adg2-1 with the ADGase large subunit gene, we show that the adg2-1 mutant does represent a mutation of the ADGase large subunit gene. Sequence analysis of the adg2-1 allele revealed a missense mutation. The results therefore suggest either that the missense mutation affects the stability of the ADGase large subunit protein or that it prevents assembly of the large subunit into holoenzyme.

Amino Acid Sequence↗
PubMed1997

[A study on the action of tang niao kang decoction].

Experiments have verified that Tang Niao Karg (a preparation from Chinese medicinal herbs) taken orally does not decrease the blood sugar of empty stomach in mice, but markedly helps lower high levels of blood sugar and lipid induced by epinephrine and glucose in mice. For rat models of diabetes induced by 4-o-pyrincidine Tang Niao Kang can significantly lower the content of blood sugar, raise the insulin level of blood serum, and enhance the tolerance to sugar.

Animals↗
PubMed1997

Modulation of two cloned potassium channels by 1-alkanols demonstrates different cutoffs.

It is not known whether alcohols modulate ion channels by directly binding to the channel protein or by perturbing the surrounding membrane lipid. Cutoff describes the phenomenon where the potency of 1-alkanols monotonically increases with alkyl chain length until a loss of efficacy occurs. Determination of the cutoff for a variety of channels can be important, because similar and/or dissimilar cutoffs might yield information regarding the nature of ethanol's site of action. In this study, the two-electrode voltage clamp technique was used to determine the cutoffs for the 1-alkanol potentiation of cloned Ca(2+)-activated-K+ (BK) channels and for the inhibition of cloned Shaw2 K+ channels, expressed in Xenopus oocytes. Ethanol, butanol, hexanol, and heptanol reversibly enhanced BK currents, whereas octanol and nonanol had no effect. In contrast, Shaw2 currents were potently inhibited by both octanol and decanol, but not by undecanol. Taken together, data demonstrate that the modulation of K+ channels by long chain alcohols is channel-specific. Interestingly, ethanol was a less potent activator of BK currents in the intact oocyte in comparison with its effect on this channel in excised membrane patches. The decrease in potency could not be attributed to an ethanol-dependent change in Ca2+ influx through endogenous voltage-gated channels, an effect that would alter the concentration of Ca2+ available to activate BK channels.

Alcohols↗
PubMed1996

Sequential phosphorylation by mitogen-activated protein kinase and glycogen synthase kinase 3 represses transcriptional activation by heat shock factor-1.

Mammalian heat shock genes are regulated at the transcriptional level by heat shock factor-1 (HSF-1), a sequence-specific transcription factor. We have examined the role of serine phosphorylation of HSF-1 in the regulation of heat shock gene transcription. Our experiments show that mitogen-activated protein kinases (MAPKs) of the ERK-1 family phosphorylate HSF-1 on serine residues and repress the transcriptional activation of the heat shock protein 70B (HSP70B) promoter by HSF-1 in vivo. These effects of MAPK are transmitted through a specific serine residue (Ser-303) located in a proline-rich sequence within the transcriptional regulatory domain of human HSF-1. However, despite the importance of Ser-303 in transmitting the signal from the MAPK cascade to HSP70 transcription, there was no evidence that Ser-303 could be phosphorylated by MAPK in vitro, although an adjacent residue (Ser-307) was avidly phosphorylated by MAPK. Further studies revealed that Ser-303 is phosphorylated by glycogen synthase kinase 3 (GSK3) through a mechanism dependent on primary phosphorylation of Ser-307 by MAPK. Secondary phosphorylation of Ser-303 by GSK3 may thus repress the activity of HSF-1, and its requirement for priming by MAPK phosphorylation of Ser-307 provides a potential link between the MAPK cascade and HSF-1. Our experiments thus indicate that MAPK is a potent inhibitor of HSF-1 function and may be involved in repressing the heat shock response during normal growth and development and deactivating the heat shock response during recovery from stress.

Calcium-Calmodulin-Dependent Protein Kinases↗
PubMed1996

Polyacrylamide solutions for DNA sequencing by capillary electrophoresis: mesh sizes, separation and dispersion.

Two preparations of linear polyacrylamide with average molecular weights of 0.37 million and 1.14 million Da, and a deuterated preparation with an average molecular weight of 1.71 million Da, were used to study the effects of molecular weight, polydispersity, and concentration on the mesh size of entangled polymers in a DNA sequencing buffer solution and their ability to resolve DNA sequencing reactions by capillary electrophoresis. The polyacrylamide concentrations were above the overlap threshold C*, the concentration above which an entangled polymer network is expected to form. Small angle neutron scattering experiments showed that between 1% and 8% polyacrylamide, the mesh size ( xi ) can be expressed by the relation xi = 2.09C-0.76, where xi is in A and C is the polymer concentration in g/mL. The mesh size depended only on the concentration and was independent of the average molecular weight of the polyacrylamide. Consistent with this result, electrophoretic mobilities of DNA moving through the polymer network depended almost entirely on the polyacrylamide concentration and not on its molecular weight or polydispersity. Although separation was little affected, band sharpness persisted to longer DNAs when the polymer network contained a higher fraction of larger polyacrylamide molecules. We postulate a dispersive effect that depends on the size of the DNA and the resiliency of the polymer network. This interpretation provides a rationale for optimizing the design of polymer solutions to sieve DNA for sequencing by capillary electrophoresis.

Acrylic Resins↗
PubMed1996

Field studies on the preventive effect of oral artemether against schistosomal infection.

OBJECTIVE: To study the preventive effect of oral artemether (Art) against schistosomal infection in the field. METHODS: In Minglang District of Yiyang City, Hunan Province, there is an islet with embankment type endemic area in the southern Dongting Lake region. From August to October 1994 the residents who frequently contacted the infested water were selected for study and allocated to the Art group and the control group. About one month before the preventive Art administration, all the residents understudied were examined by stool hatching technique, and then treated orally with praziquantel at a single dose of 40 mg/kg in stool egg-negative residents and 50 mg/kg in stool egg-positive ones. In the Art group, the first dose of 6 mg/kg was given at the end of August, followed by 3 repeated doses every 15 days. Placebo (starch) was given to the control group at the same time as in the Art group. The preventive efficacy was evaluated by stool examination 25-32 days after the last medication. RESULTS: In the Art group, 20 out of 365 studied residents became stool positive with an infection rate of 5.5%, while in the control group, 51 out of 376 studied residents were stool positive with an infection rate of 13.6%. The egg count per gram of feces (EPG) determined by the Kato-Katz method was 122 +/- 79 in the Art group and 681 +/- 909 in the control group. Meanwhile, two cases of acute schistosomiasis were found in the control group, but none was observed in the Art group. No apparent adverse side effect was seen during the treatment with Art. CONCLUSION: Oral Art exhibited apparent preventive effect on the residents who contacted the infested water in schistosomiasis endemic area.

Administration, Oral↗
PubMed1996

[The significance of detecting Epstein-Barr virus DNA and latent membrane protein I in Hodgkin's disease from a high incidence area of nasopharyngeal carcinoma].

To study the EBV DNA and expression of latent membrane protein I (LMP1) in patients with Hodgkin's disease from high incidence area of nasopharyngeal carcinoma, hot starting PCR and microwave treatment of LSAB immunohistochemistry methods were used to detect EBV DNA and LMP1 from biopsy specimens from 40 cases of Hodgkin's disease (HD) and 20 cases having benign lymph node lesions, randomly selected from a high incidence area of nasopharyngeal carcinoma. EBV DNA was detected in 65.0% of the HD cases and 50.0% of the benign lymph node cases, the difference was not of statistical significance. LMP1 of EBV was detected in 52.5% of HD cases and its expression was restricted to tumor cells. In addition, the detection rates of LMP1 and DNA of EBV in patients under 20 years of age (84.6% and 76.9% respectively) was much higher than that in patients over 20 years of age (56.0% and 40.0% respectively) P < 0.05. The results suggest that there was latent EBV infection in at least half of HD patients, which may have a role in the genesis and development of HD, and HD occurring in youth was more closely correlated with EBV latent infection and LMP1 expression.

DNA, Viral↗
PubMed1995

Aggregation behavior of fosinopril sodium--a new angiotensin-converting enzyme inhibitor.

Fosinopril sodium is an effective new angiotensin-converting enzyme (ACE) inhibitor that is very useful for the clinical treatment of hypertension. After oral administration, fosinopril sodium is only partially absorbed (about one third of the drug). We studied the solution behavior of fosinopril sodium in aqueous media by a combination of high-resolution nuclear magnetic resonance (NMR) spectroscopy and laser light scattering (LLS). LLS characterizes the self-association properties of fosinopril sodium in solution, and NMR chemical shifts provide information on molecular conformation and interactions. The results revealed that fosinopril sodium has a micelle-like self-association behavior with a critical micelle concentration (cmc) approximately 1.5 mg/mL. Hydrophobic interactions could induce formation of micellar aggregates, which had a narrow hydrodynamic size distribution, with an average diameter of approximately 150 nm at concentrations above the cmc. The surface activity and self-association of fosinopril sodium may be responsible for its early observed concentration-dependent stability in aqueous solution, unexpected decrease in solubility in the presence of metal ions, as well as the limited absorption in clinical studies.

Fosinopril↗
PubMed1995

Evidence for the thiamine biosynthetic pathway in higher-plant plastids and its developmental regulation.

Thiamine or vitamin B-1, is an essential constituent of all cells since it is a cofactor for two enzyme complexes involved in the citric acid cycle, pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase. Thiamine is synthesized by plants, but it is a dietary requirement for humans and other animals. The biosynthetic pathway for thiamine in plants has not been well characterized and none of the enzymes involved have been isolated. Here we report the cloning and characterization of two cDNAs representing members of the maize thi1 gene family encoding an enzyme of the thiamine biosynthetic pathway. This assignment was made based on sequence homology to a yeast thiamine biosynthetic gene and by functional complementation of a yeast strain in which the endogenous gene was inactivated. Using immunoblot analysis, the thi1 gene product was found to be located in a plastid membrane fraction. RNA gel blot analysis of various tissues and developmental stages indicated thi1 expression was differentially regulated in a manner consistent with what is known about thiamine synthesis in plants. This is the first report of cDNAs encoding proteins involved in thiamine biosynthesis for any plant species.

Amino Acid Sequence↗
PubMed1995

Ethanol inhibition of recombinant heteromeric NMDA channels in the presence and absence of modulators.

The NMDA receptor/channel has been shown to be inhibited by ethanol in the clinically relevant range 25-100 mM. We studied heteromeric assemblies (NR1b/NR2) of the NMDA receptor, expressed in oocytes, to address three questions regarding this inhibition, and discovered the following: (1) The inhibition was nearly equivalent when ethanol was coapplied with the agonist, and when ethanol was introduced after steady-state current was established, suggesting that ethanol does not act by interfering with the activation process of the NMDA receptor. (2) The degree of inhibition was controlled by the NR2 subunit, with both NR2A and NR2B significantly more sensitive to ethanol than NR2C and NR2D. (3) Manipulation of the NMDA receptor with a number of agents that normally modulate it did not alter the degree of inhibition produced by ethanol. The presence of Mg2+ (3 and 12.5 microM), Zn2+ (1 and 10 microM), or the glycine antagonist 7-chlorokynurenic acid (1.25 or 5 microM), did not alter the ethanol sensitivity of heteromeric (NR1b/NR2A, NR1b/NR2B, NR1b/NR2C) NMDA receptors. Redox modulation of the NMDA receptor by dithiothreitol (2 mM) or 5,5'-dithiobis(2-nitrobenzoic acid) (1 mM) also did not alter the degree to which ethanol inhibits NMDA receptors. Taken together, these results indicate that the ethanol sensitivity of native NMDA receptors, which likely exist in heteromeric form, results from actions at a site different from those of known modulators of the receptor.

Animals↗
PubMed1995

[Field studies on preventive effect of artemether against infection with Schistosoma japonicum].

From August to October 1994, a field trial of preventive treatment with artemether (Art) was carried out in Minglang District of Yiyang City, Hunan Province, an islet with embankment type endemic area nearby southern Donting Lake region. The residents who frequently contacted with the infested water were selected for study and allocated to the Art group and the control group in reference to paired methods of randomization table. About one month before administration of Art, all residents under study were examined by stool hatching technique after nylon-bag concentration to determine the infection rate of each group, and then treated with praziquantel at a single dose of 40 mg/kg in stool egg-negative residents and 50 mg/kg in stool egg-positive ones. In Art group, the first dose of 6 mg/kg was given in late August, followed by repeated dosing every 15 days for 3 times. Placebo (starch) was given to the study residents in the control group at the same time as in Art group. The efficacy was evaluated by stool examination 25-32 days after the last medication. The results showed that after the preventive administration of Art, 20 out of 365 study residents in Art group revealed stool positive with an infection rate of 5.5%, while in the control group 51 out of 376 study residents showed stool positive with an infection rate of 13.6%. The difference between the two groups was statistically significant. Meantime, two cases of acute schistosomiasis were seen in the control group, but none was observed in Art group. The egg per gram of feces (EPG) determined with the Kato-Katz method was 122 +/- 79 (range 12-192) in Art group and 681 +/- 909 (range 12-2,760) in the control group. No apparent adverse side effect was seen during the treatment with Art, and no abnormal change in liver and renal function was detected after the last medication. The preliminary study indicates that application of the preventive administration of Art in the endemic area during the transmission season may effectively reduce both the infection rate and intensity of schistosomiasis.

Adolescent↗
PubMed1994

Dynamic laser light scattering studies of the effects of pyrophosphate on cyclic motions of cross-bridges in isolated thick myofilaments from Limulus striated muscle.

Pyrophosphate (PPi) is a non-hydrolyzable ATP analogue known to affect the binding between myosin heads and actin. By using a dynamic laser light scattering method, we have shown that 1-2 mM PPi enhances the increase in gamma values induced by Ca2+ in isolated thick myofilaments from Limulus striated muscle. However, similar treatment has no effect on the gamma values of filaments suspended in either relaxing solution or ATP-free solution. gamma is the average linewidth of the photoelectron count autocorrelation function of the light scattered. PPi had no effect on the increase of gamma values by Sr2+ but it substantially increased the gamma values of the thick myofilaments suspended in Ba(2+)-substituted Ca2+ activating solution. The results show that PPi also affects the energy-requiring cyclic cross-bridge motions.

Actin Cytoskeleton↗
PubMed1994

Arabidopsis thaliana expresses three divergent Srp54 genes.

The Arabidopsis thaliana Srp54 gene family was determined to consist of three genes, all of which were cloned and sequenced. In addition, cDNAs corresponding to two of the genes were obtained. To our knowledge this is the first description of multiple Srp54 genes within an organism. In contrast to the situation in mammals, where there are only three amino acid differences between the mouse and canine sequences, there was significant amino acid sequence diversity among the genes, particularly in the methionine-rich region of the protein, which is the region responsible for binding to the 7S RNA of the signal recognition particle and to the signal sequence of newly synthesized proteins. The amino acid sequences of the GTP-binding domains of the three clones were 86% identical, whereas the methionine-rich domains were only 65% identical. RNA gel blots of various tissues and developmental stages hybridized with gene-specific probes revealed that all three genes were expressed in all the tissues investigated. There were, however, quantitative differences in expression levels.

Amino Acid Sequence↗