Role and integration of mechanisms controlling gastric emptying.
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Animals↗
Biomedical subjects
W Sun
Publications and source records attributed to W Sun.
Sodium channel mutations in paramyotonia congenita uncouple inactivation from activation.
Mutations in the adult human skeletal muscle Na+ channel alpha subunit cause the disease paramyotonia congenita. Two paramyotonia congenita mutations, R1448H and R1448C, substitute histidine and cysteine for arginine in the S4 segment of domain 4. These mutations, expressed in a cell line, have only small effects on the activation of Na+ currents, but mutant channels inactivate more slowly with less voltage dependence than wild-type channels and exhibit an enhanced rate of recovery from inactivation. Increase of extracellular pH made the rate of inactivation of R1448H similar to that of R1448C, suggesting that this residue has an extracellular location and that its charge is important for normal inactivation. Analysis of single-channel data reveals that mutant channels inactivate normally from closed states, but poorly from the open state. The data suggest a critical role for the S4 helix of domain 4 in coupling between activation and inactivation.
Base Sequence↗
The M2 transmembrane segment as a molecular determinant of the ion permeation properties in the superfamily of ligand-gated ion channels.
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Animals↗
Forage and splanchnic tissue mass in growing lambs: effects of dietary forage levels and source on splanchnic tissue mass in growing lambs.
Forty-two crossbred lambs (33.4 kg initial body weight; twenty-four wethers and eighteen ewes) were used in a 42 d experiment with a 2 x 3 factorial treatment arrangement to determine effects of forage level and source on splanchnic tissue mass. Diets were 250 and 750 g/kg of chopped lucerne (Medicago sativa) (A), ryegrass (Lolium multiflorum)-wheat (Triticum aestivum) (RW) or bermudagrass (Cynodon dactylon) (B) hay, with the remainder being maize-based concentrate. Five lambs per treatment were slaughtered at the end of the experiment and measurements made of internal organs and contents of the gastrointestinal tract (GIT). Digestible organic matter intake (DOMI) on the 7 d preceding slaughter was 0.89, 0.83, 0.90, 0.83, 0.77 and 0.61 (SE 0.05) kg/d, and live-weight gain was 0.20, 0.17, 0.18, 0.10, 0.10 and 0.07 (SE 0.02) kg/d for diets A-25, RW-25, B-25, A-75, RW-75 and B-75 respectively. Total GIT mass (fresh) was higher (P < 0.05) for 750 than 250 g forage/kg and for B than RW (4.80, 4.57, 5.55, 5.84, 5.99 and 6.91 kg for diets A-25, RW-25, B-25, A-75, RW-75 and B-75 respectively). Non-fat organic matter was 259, 295, 292, 303, 277 and 264 g for the total GIT; 93, 102, 103, 106, 95 and 97 g for the reticulo-rumen (forage level x type (diet A v. diets RW and B) interaction; P < 0.05); and 204, 196, 202, 177, 156 and 127 g for the liver (SE 10) with diets A-25, RW-25, B-25, A-75, RW-75 and B-75 respectively. In summary, differences in properties of forage A and the grasses at 250 g/kg diet may have influenced GIT mass independent of energy intake and digesta mass. Conversely, with 750 g dietary forage/kg, higher digesta mass for diet B than diet RW appeared responsible for high reticulo-rumen mass relative to DOMI. Greater digesta mass for 750 than 250 g forage/kg may have elevated intestinal tissue mass/DOMI with diets A and B but not with diet RW, for which NDF digestibility was highest.
Animal Feed↗
Voltage-dependent regulation of modal gating in the rat SkM1 sodium channel expressed in Xenopus oocytes.
The TTX-sensitive rat skeletal muscle sodium channel (rSkM1) exhibits two modes of inactivation (fast vs slow) when the alpha subunit is expressed alone in Xenopus oocytes. In this study, two components are found in the voltage dependence of normalized current inactivation, one having a V1/2 in the expected voltage range (approximately -50 mV, I(N)) and the other with a more hyperpolarized V1/2 (approximately -130 mV, IH) at a holding potential of -90 mV. The I(N) component is associated with the gating mode having rapid inactivation and recovery from inactivation of the macroscopic current (N-mode), while IH corresponds to the slow inactivation and recovery mode (H-mode). These two components are interconvertible and their relative contribution to the total current varies with the holding potential: I(N) is favored by hyperpolarization. The interconversion between the two modes is voltage dependent and is well fit to a first-order two-state model with a voltage dependence of e-fold/8.6 mV and a V1/2 of -62 mV. When the rat sodium channel beta 1-subunit is coinjected with rSkM1, IH is essentially eliminated and the inactivation kinetics of macroscopic current becomes rapid. These two current components and their associated gating modes may represent two conformations of the alpha subunit, one of which can be stabilized either by hyperpolarization or by binding of the beta 1 subunit.
Animals↗
Common distribution of antigenic determinants and complementation activity on matrix proteins of two vesicular stomatitis virus serotypes.
To compare the antigenic and functional domains of the matrix (M) proteins of vesicular stomatitis virus (VSV) serotypes Indiana (VSV-Ind) and New Jersey (VSV-NJ), deletion mutants and chimeras were cloned in pBSM13 and expressed as in-frame lacZ fusion proteins in Escherichia coli. Non-cross-reactive monoclonal antibodies directed to the two antigenically distinct M proteins were tested by Western blot analysis to map three epitopes of VSV-Ind M protein and four epitopes of VSV-NJ M protein. Epitope 1 of the VSV-Ind M protein and epitope II of the VSV-NJ M protein both mapped to the highly basic N-terminal 34 amino acids of each homotypic M protein. Epitopes 2 and 3 of the VSV-Ind M protein and epitopes III and IV of the VSV-NJ M protein mapped to a region spanning amino acids 35 to 74. Epitope I of the VSV-NJ M protein mapped to a region between amino acid 75 and the C terminus. The similarity in location of the serotypically unique antigenic determinants of the two M proteins suggested that they may have a common functional domain. This hypothesis was substantiated by the finding that the two M proteins and various chimeras expressed in CV-1 cells by a recombinant vaccinia virus system were able to rescue M gene temperature-sensitive mutants of both VSV serotypes.
Antibodies, Monoclonal↗
Order and disorder in fully hydrated unoriented bilayers of gel-phase dipalmitoylphosphatidylcholine.
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Journal Article↗
Membrane-binding domains and cytopathogenesis of the matrix protein of vesicular stomatitis virus.
The membrane-binding affinity of the matrix (M) protein of vesicular stomatitis virus (VSV) was examined by comparing the cellular distribution of wild-type (wt) virus M protein with that of temperature-sensitive (ts) and deletion mutants probed by indirect fluorescent-antibody staining and fractionation of infected or plasmid-transfected CV1 cells. The M-gene mutant tsO23 caused cytopathic rounding of cells infected at permissive temperature but not of cells at the nonpermissive temperature; wt VSV also causes rounding, which prohibits study of M protein distribution by fluorescent-antibody staining. Little or no M protein can be detected in the plasma membrane of cells infected with tsO23 at the nonpermissive temperature, whereas approximately 20% of the M protein colocalized with the membrane fraction of cells infected with tsO23 at the permissive temperature. Cells transfected with a plasmid expressing intact 229-amino-acid wt M protein (M1-229) exhibited cytopathic cell rounding and actin filament dissolution, whereas cells retained normal polygonal morphology and actin filaments when transfected with plasmids expressing M proteins truncated to the first 74 N-terminal amino acids (M1-74) or deleted of the first 50 amino acids (M51-229) or amino acids 1 to 50 and 75 to 106 (M51-74/107-229). Truncated proteins M1-74 and M51-229 were readily detectable in the plasma membrane and cytosol of transfected cells as determined by both fluorescent-antibody staining and cell fractionation, as was the plasmid-expressed intact wt M protein. However, the expressed doubly deleted protein M51-74/107-229 could not be detected in plasma membrane by fluorescent-antibody staining or by cell fractionation, suggesting the presence of two membrane-binding sites spanning the region of amino acids 1 to 50 and amino acids 75 to 106 of the VSV M protein. These in vivo data were confirmed by an in vitro binding assay in which intact M protein and its deletion mutants were reconstituted in high- or low-ionic-strength buffers with synthetic membranes in the form of sonicated unilammelar vesicles. The results of these experiments appear to confirm the presence of two membrane-binding sites on the VSV M protein, one binding peripherally by electrostatic forces at the highly charged NH2 terminus and the other stably binding membrane integration of hydrophobic amino acids and located by a hydropathy plot between amino acids 88 and 119.
1,2-Dipalmitoylphosphatidylcholine↗
Coordinated expression of a 45 kD protein and ozone toxicity in a human bronchial epithelial cell line.
The human bronchial epithelial cell line, BEAS-2B, which was immortalized by transformation with SV40 virus, when grown biphasically between 0.1 and 1.0 ppm of ozone and liquid medium showed increased release of Cr, decreased synthesis of various macromolecules, and decreased cell viability. Cell injury was a function of the concentration of ozone to which the cells were exposed. Furthermore, in proportion to the extent of cell injury, ozone exposure also induced and/or enhanced synthesis of a 45 kD protein but not any of the well-characterized heat shock proteins, e.g., HSP 70. Actinomycin D prevented enhanced synthesis of the 45 kD protein in cells exposed to ozone, suggesting transcriptional regulation of expression of the 45 kD protein. Enhanced synthesis of the 45 kD protein was not observed in cells treated with heat, cigarette smoke condensate, hydrogen peroxide, or bleomycin. High concentrations of glutathione added to the culture medium reduced ozone toxicity and ozone-enhanced synthesis of the 45 kD protein. These results suggest that ozone injury and enhanced expression of a gene encoding a 45 kD protein of as yet unknown function are coordinated in the SV40-immortalized bronchial epithelial cells.
Bleomycin↗
The combined method of transplantation of foetal substantia nigra and stereotactic thalamotomy for Parkinson's disease.
Five cases with late Parkinson's disease improved following treatment with a combination of foetal substantia nigra grafts and stereotactic thalamotomy. The average Webster's score decreased from 21 to 11 points. This modified method is simple, safe and effective.
Female↗
A study of histology and enzymatic histochemistry on rabbit's retina in acute ocular hypertension.
The changes of activities of enzymes relating to energy metabolism in rabbit's retina in acute ocular hypertension were observed. The activities of succinate dehydrogenase and adenosine triphosphatase were found to be reduced, while the activities of the lactatic dehydrogenase and glucose-6-phosphatase increased. The results revealed the metabolic disturbance of energy in retina after acute ocular hypertension might be the underlying factors relating to the defects of the functions and structures of the retina.
Adenosine Triphosphate↗
Studies on the condition of fermentation of pullulan by Aureobasidium pullulans.
Studies on optimal conditions for pullulan fermentation based on the results obtained from a shaking flask were carried out in a 16-L auto-controlling fermentor. It found that the optimal DE value of starch hydrolyzate was 40-50 when 10% starch hydrolysate was used as carbon source. The optimal concentration of ammonium sulfate in the medium for fermentation was different from that of the shaking flask. The fermentation kinetics and effects of seed age, seed volume, airflow rate, pressure of tank, agitation speed and number of vane group on the production of pullulan were investigated.
Biomass↗
[The changes in the summating potential and morphology in the cochlea of guinea pigs with anoxia].
The dynamic changes in the CAP, SP and EP in the scale media were examined with single micropipet during anoxia and reventilation with oxygen. Also, the morphologic changes in the IHC, OHC and synapse were observed in this experiment. It was found that the amplitude of the SP and EP values declined with alteration in polarity of these value. The changes in polarity and amplitude of the SP followed the changes of CAP threshold induced by anoxia. The histologic examinations revealed no evidence of acetylcholinesterase (AChE) alteration in the synapse and no succinic dehydrogenase (SDH) changes in IHC appeared. However, the activity of SDH in the OHC decreased. The results suggest that the polarity and amplitude of SP were influenced passively by the changes of EP value. In addition, the changes of SP polarity from positive to negative during anoxia is due to the loss of modulation process of OHC to IHC, while the SP polarity from negative to positive during the supply of oxygen is caused by regain of the modulation process of OHC.
Acetylcholinesterase↗
Studies on isolation and purification of penicillin acylase by adsorption on bentonite.
When bentonite I as an absorbent according to 0.6% (w/v) was added to the supernatant of the fermentation broth for adsorption of penicillin acylase from Bacillus megatherium, 100% activity of penicillin acylase and about 10% protein in the supernatant were adsorbed. The adsorption of enzyme was not obviously changed with different pH and salt concentration of the supernatant. Various kinds of buffer with different pH were used to wash the enzyme-adsorbent complex. Only 1% enzyme activity adsorbed was washed out; however, it can wash out about 15% protein adsorbed. When phosphate buffer containing 10% PEG and NaCl as an eluent was used to elute the complex, 100% of enzyme activity adsorbed on the complex would be eluted, and purification and concentration times of enzyme could achieve about 25 and 6, respectively. The isolation and purification process can be carried out at room temperature. Its characters were very simple and showed a high recovery yield of enzyme activity, and it can be directly used for isolation and purification of penicillin acylase from the fermentation broth.
Adsorption↗
Ultrastructural observations of the anterior chamber angle tissues in congenital glaucoma.
Eighteen trabeculectomy specimens of congenital glaucoma were examined by light and transmission electron microscopy. The results showed that the primary anomalies in congenital glaucoma included the developmental defects of trabecular meshwork, excessive collagen fibrils in the trabecular matrix, shifting forward of ciliary muscle fibres and persistent mesenchymal tissues in the anterior-chamber angle. The authors also pointed out the importance of the secondary lesions of the trabecular meshwork in the pathogenesis of congenital glaucoma.
Anterior Chamber↗
The potential antiarrhythmic effects of exogenous and endogenous bradykinin in the ischaemic rat heart in vivo.
BACKGROUND: Recent studies have shown that bradykinin decreases the incidence of ischaemic arrhythmias in dogs and may also mediate the antiarrhythmic effects of preconditioning in this species. We investigated the effects of exogenously administered bradykinin on the severity of ischemic arrhythmias and the role of endogenously released bradykinin, acting on B2-receptors, in preconditioning in anaesthetized rats. METHODS: In protocol 1, male rats were subjected to a single 30 min occlusion of the left main coronary artery and received left ventricular infusions of bradykinin (30 ng to 10 micrograms/kg/min) or saline. In protocol 2, rats were pretreated with the B2-receptor antagonist HOE 140 (40 and 400 micrograms/kg intravenous bolus) 10 min before coronary artery occlusion. In protocol 3, rats were preconditioned by a 3 min coronary occlusion followed by 10 min of reperfusion before a sustained 30 min occlusion. Saline or HOE 140 was given 10 min before the preconditioning protocol. In all groups, the number and severity of ventricular arrhythmias were determined during the 30 min coronary occlusion. RESULTS: In protocol 1, none of the doses of bradykinin had any significant effect on the total number of ventricular ectopic beats (1512 +/- 252 in saline-treated controls versus 1337 +/- 302 with the highest dose of bradykinin tested) or on the incidence of ventricular tachycardia or ventricular fibrillation. The two higher doses of bradykinin (1 and 10 micrograms kg/min) caused a reduction in blood pressure soon after infusion began, although this was not maintained for the duration of the experiment. In protocol 2, HOE 140, in doses that produced a sustained antagonism to the depressor response to bradykinin, had no effect on either arrhythmia count or the incidence of ventricular fibrillation in rats subjected to a single 30 min coronary occlusion. In protocol 3, a 3 min preconditioning occlusion in saline-treated rats reduced arrhythmia counts from 1046 +/- 196 in non-preconditioned rats to 76 +/- 44 in preconditioned rats, and reduced the incidences of ventricular tachycardia and ventricular fibrillation from 100 to 50% and from 75 to 7%, respectively. Neither dose of HOE 140 tested reversed these antiarrhythmic effects of preconditioning. CONCLUSION: These results suggest that bradykinin is not protective against ischaemic arrhythmias in rats in vivo, whether given exogenously or released endogenously. Furthermore, in contrast to other species, bradykinin does not appear to play a role in the antiarrhythmic effect of ischaemic preconditioning.
Adrenergic beta-Antagonists↗
Kinetics of Trolox C oxidation by lactoperoxidase compound II.
The lactoperoxidase (LPO) compound II catalyzed oxidation of Trolox C, a vitamin E water-soluble derivative, was studied by rapid scan spectral analysis and stopped-flow kinetic measurements. Our rapid scan spectral analysis clearly indicates that LPO compound II is reduced to native enzyme by Trolox C; hence the reaction is a one-electron redox process. The reaction was investigated at pH's ranging from 3.0 to 7.0. Trolox C is more reactive with LPO-II in acidic solutions. Kinetic and spectroscopic studies demonstrate that LPO has a binding site in the vicinity of the heme for Trolox C. Trolox C exhibits a quantitative 1:1 binding to native LPO in acidic solutions. The binding ability of Trolox C to native LPO decreases with increasing pH. The same trend is observed when the second order rate constants kapp for the reaction are plotted against pH. A mechanism of Trolox C oxidation by LPO-II has been proposed in which protonation of an amino acid residue on LPO-II with a pKe of 2.3 is essential and ionization of the carboxylic acid group on Trolox C accelerates the reaction rate. The second-order rate constants were determined to be (4.1 +/- 0.5) x 10(6) M-1s-1 for protonated Trolox C oxidation and (1.9 +/- 0.3) x 10(7) M-1s-1 for deprotonated Trolox C.
Chromans↗
Molecular cloning, functional expression, and pharmacological characterization of an N-methyl-D-aspartate receptor subunit from human brain.
A cDNA encoding a full-length N-methyl-D-aspartate (NMDA) receptor subunit 1, hNR1, was isolated from a human brain cDNA library. The hNR1 cDNA encodes an open reading frame of approximately 2.7 kb that shares high homology with the rat brain NMDA receptor subunit 1 and the mouse zeta 1 subunit. The hNR1 sequence, however, diverges from the rodent and murine homologs near the C terminus, suggesting that they represent alternatively spliced messages of the same gene. Oocytes injected with cRNA synthesized from the hNR1 cDNA express glutamate and NMDA-activated currents in the presence of glycine. Currents are blocked by the NMDA-receptor-specific antagonists 2-amino-5-phosphovaleric acid and 7-chlorokynurenate, and the open channel blockers MK-801 and phencyclidine, by Mg2+ ions in a voltage-dependent manner, and by Zn2+. Expressed hNR1 homomeric receptor channels exhibit the high Ca2+ permeability characteristic of neuronal NMDA receptors. Therefore, the cDNA clone hNR1 codes for a human brain NMDA receptor subunit cognate to the rodent and murine brain NR1 subunits.
2-Amino-5-phosphonovalerate↗