Biomedical subjects
Publications and source records attributed to W Cao.
A campaign against lymphatic filariasis began in China's Shandong Province during 1956. Epidemiological surveillance since 1984 indicates that the transmission of infection has been interrupted. The factors accounting for this are discussed and the continuing challenges presented by the disease are outlined.
In single cells, isolated by enzymatic digestion from the circular muscle layer of the lower esophageal sphincter (LES), acute experimental esophagitis (AE) alters signal transduction in response to a maximally effective dose of acetylcholine. In normal LES contraction was inhibited by M3 >> M1 or M2 antagonists. In AE inhibition by M2 antagonists increased significantly so that contraction was inhibited by M3 > M2 > M1 antagonists. In normal cells permeabilized by saponin, contraction was antagonized by antibodies against Gq/11, by the phosphatidylinositol-specific phospholipase C (PI-PLC) antagonist U 73122, but not by the phosphatidylcholine-specific phospholipase C (PC-PLC) inhibitor D609, or by the phospholipase D pathway inhibitor propranolol. In AE contraction was reduced by Gq/11 and Gi3 antibodies and by U73122, propranolol and D609. After thapsigargin treatment of normal cells to reduce intracellular Ca++ stores, contraction was inhibited by M2 and M3 antagonists, by antibodies against Gq/11 and Gi3, by U73122, D609 and propranolol, suggesting that depletion of Ca++ stores reproduces the changes induced by AE. We conclude that in normal LES smooth muscle cells acetylcholine-induced contraction is mediated by M3 receptors linked to Gq/11 and PI-PLC, whereas in AE, contraction through this pathway is reduced, perhaps because of reduction in Ca++ stores, and a second pathway is activated by M2 receptors linked to Gi3, PC-PLC and phospholipase D.
The splicing reaction that removes introns from pre-messenger RNAs requires the assembly of the spliceosome on the nascent transcript, proper folding of the substrate-enzyme complex, and finally, two transesterification reactions. These stages in the splicing reaction must require careful orchestration. Here we show data that suggest that the sequential phosphorylation and dephosphorylation of SR proteins mark the transition between stages in the splicing reaction. Many data had already led to the idea that phosphorylation of SR proteins could modulate their activity, when we showed that dephosphorylation of these proteins abrogates their activity in a reaction measuring conversion of pre-spliceosomes to spliceosomes (Roscigno RF, Garcia-Blanco MA, 1995, RNA 1:692-706). Subsequently, Xiao and Manley (1997, Genes & Dev 11:334-344) showed that phosphorylated ASF/SF2, but not mock-phosphorylated ASF/SF2, activates the splicing of HIV tat pre-mRNA in reactions challenged with excess random RNA. Here we confirm and extend these two findings. Phosphorylated ASF/SF2 efficiently complemented an SR protein-deficient HeLa S100 extract in promoting the splicing of an adenovirus-2-derived pre-messenger RNA, whereas unphosphorylated ASF/ SF2 did not. Moreover, we show that, whereas unphosphorylated ASF/SF2 inhibited splicing in HeLa nuclear extracts, phosphorylation of the ASF/SF2 reversed the inhibition and enhanced splicing. We also present data that shows that dephosphorylation of ASF/SF2 is required for the first transesterification reaction once the spliceosome has assembled. Thiophosphorylated ASF/SF2, which cannot be readily dephosphorylated, can promote spliceosome assembly, but cannot promote the first transesterification reaction. These data, together with other observations, indicate for the first time a requirement for SR protein dephosphorylation in pre-messenger RNA splicing in vitro.
Explore the source record for details and available documents.
We observed an induction of basic fibroblast growth factor (bFGF) mRNA in the rat retina after systemic administration of the alpha 2-adrenergic agonists xylazine and clonidine. A single injection of xylazine or clonidine transiently increased bFGF mRNA. Preinjection of yohimbine, an alpha 2-adrenergic antagonist, completely inhibited this increase. Higher dosage of yohimbine inhibited the baseline expression of bFGF. Of particular interest is the finding that the induced bFGF expression occurred almost exclusively in the inner segment region of photoreceptors. No increase in bFGF mRNA was found in the brain after either xylazine or clonidine injection. Xylazine or clonidine given systemically before and during constant light exposure also reduces photoreceptor degeneration in albino rats. These results indicate that regulation of bFGF expression in photoreceptors is unique in the CNS and suggest that endogenous bFGF promotes photoreceptor survival.
Most proteins synthesized in cytoplasm target to mitochondria through sequences at their amino termini. However, a previous study suggests that the native carboxyl terminus of ISP6 might be critical of its specific delivery. Here we investigated the sequence directing ISP6 to yeast mitochondrial outer membrane. Unlike mitochondrial presequences, a region at the amino terminus of ISP6 is dispensable for importing the rest of the protein. The carboxyl-terminal end and the nearby transmembrane region of ISP6 are essential to direct the protein exclusively to its correct membrane destination. ISP6 thus may be directed to mitochondria by an unusual sequence.
One of the two class I MHC (H-2Kd)-restricted immunogenic regions identified on the influenza virus strain A/Japan/57 (H2N2) hemagglutinin (HA) encompasses two distinct, partially overlapping epitopes. These epitopes map to residues 204 to 212 (JHA 204-212) and 210 to 219 (JHA 210-219), respectively. When we investigated the magnitude of the CTL responses of H-2d BALB/c mice to these two epitopes, we found that the JHA 204-212 nonamer epitope is immunodominant, eliciting vigorous CTL responses in BALB/c mice immunized with A/Japan/57 virus. In contrast, the CTL response to the JHA 210-219 decamer epitope was weak and variable. The subdominance of the JHA 210-219 was not due to low affinity binding of JHA 210-219 to H-2Kd or to inefficient processing of this epitope in vivo. Rather, an analysis of CTL precursor (pCTL) frequency by limiting dilution showed that the frequency of pCTL to the JHA 210-219 epitope was at least 10-fold lower than the frequency of pCTL to the JHA 204-212 epitope, implying that the low and variable response to the JHA 210-219 epitope was due to a limited number of CD8+ T cell precursors directed to JHA 210-219. This hypothesis was further supported by the finding of limited heterogeneity in reactivity pattern displayed by short term bulk cultures of the JHA 210-219-specific CTLs for cross-reactive epitopes. Implications of these findings for vaccine design and for T lymphocyte function and repertoire development are discussed.
BACKGROUND: The cardiac muscle cell ceases to divide shortly after birth; this cessation is followed by a limited period when DNA synthesis and karyokinesis occur without cytokinesis. The regulation of this process is not known. The purpose of this study is to explore the possible events that could lead to the cessation of cardiac muscle cell division. One protein requisite for DNA synthesis is proliferating cell nuclear antigen (PCNA). This protein is the auxiliary protein of DNA polymerase delta. METHODS: Rats of fetal age day 18 or days 0, 4, 8, 12, and 16 after birth were obtained. In addition, adult hearts were used for this study. Hearts from the fetal day-18 rats and the day-0 neonatal rats were digested. Cardiac myocytes were isolated and placed in culture for an analysis of DNA synthesis by using tridiated thymidine. Ventricular muscle tissue was isolated from hearts of all ages and frozen in liquid nitrogen for Northern and Western blot analyses. RESULTS: Tridiated thymidine analysis revealed that, although serum stimulation significantly increased the number of labeled fetal cardiac muscle cells, it did not have that effect on neonatal cardiac muscle cells in culture. Northern blot analysis revealed that the steady state levels of mRNA for PCNA remained constant from fetal day 18 through day 4 after birth. Steady state levels declined during the second postnatal week and then reached basal levels by day 16. PCNA message was still present in adult heart tissue. By using indirect immunofluorescence and Western blotting, PCNA protein could be located in the nucleus of cardiac muscle cells during the first 2 weeks after birth. At 16 days after birth, the protein was found in the cytoplasm in very low amounts but was not found in the nucleus. The protein was barely detectable by Western blotting in the cytoplasmic fraction from the adult myocardium. CONCLUSIONS: The results of this study suggest that the PCNA message and protein product declined after birth, but both were present at low levels in the adult myocardium. However, the PCNA protein was not translocated to the nucleus in adult myocardial cells. The events involving PCNA correlated closely with the time period when cell division and then DNA synthesis ceased in these cells.
T cell interaction with antigenic peptides leads to signal transduction and activation events in the effector cells. Recent studies of T cell responses to subtle variants of antigenic peptides can lead to alterations in the activation state of T cells. A variety of physiological roles for altered peptide ligands have recently been postulated, and their potential therapeutic applications have generated considerable interest. This review summarizes progress made in understanding the T cell signal transduction pathways and the nature of T cell responses to altered peptide ligands. Our recent observation of a self peptide as a partial agonist for a cytotoxic T cell clone directed to a foreign antigen suggests that naturally occurring altered peptide ligands may be important in regulating T cell mediated immune response.
The protein product of the mouse preimplantation embryo development (Ped) gene, which controls the rate of preimplantation embryonic cleavage division and subsequent embryo survival, is the Qa-2 antigen. This major histocompatibility complex (MHC) class I b protein is encoded by four genes, Q6, Q7, Q8, and Q9. The present study was undertaken to begin to elucidate which of the four Qa-2-encoding genes are responsible for the Ped gene phenotype in the C57BL/6 mouse (H2(b)). First, restriction maps of the four genes, using 25 restriction enzymes, were created. The RE maps confirmed that Q6 is similar to Q8 and Q7 is similar to Q9, but that the Q6/Q8 gene pair differs from the Q7/Q9 gene pair. The genomic DNA sequences of Q6 and Q8 were determined, as well as the DNA sequences of exons 4 - 8 of Q9, and the 5' regulatory regions of Q6, Q8, and Q9. This DNA sequence information, combined with the published DNA sequence information for the entire Q7 gene and exons 1 - 3 of Q9, allowed us to design primers for reverse transcription-polymerase chain reaction that could distinguish which of the four genes were transcribed in mouse lymphocytes and embryos. It was found that all four genes are transcribed in lymphocytes, but only Q7 and Q9 are transcribed in mouse embryos. Thus, both Q7 and Q9 are candidates for the genes responsible for the Ped gene phenotype.
Finite element method (FEA) has been used to calculate the thickness resonance frequency and electromechanical coupling coefficient kt for 2-2 piezocomposite transducers. The results are compared with that of the effective medium theory and also verified by experiments. It is shown that the predicted resonance frequencies from the effective medium theory and the unit cell modeling using FEA deviate from the experimental observations for composite systems with a ceramic aspect ratio (width/length) more than 0.4. For such systems, full size FEA modeling is required which can provide accurate predictions of the resonance frequency and thickness coupling constant kt.
PURPOSE: To assess the effects of systemic hypoxia and hyperoxia on the volume of the subretinal space (SRS). METHODS: The authors measured the concentration of the extracellular space marker tetramethylammonium (TMA+) in the intact cat eye using double-barreled ion-selective microelectrodes. The retina was loaded with TMA+ by a single intravitreal injection. Systemic hypoxia was induced by adding nitrogen to the breathing mixture, and hyperoxia was induced by adding oxygen. RESULTS: Hypoxia produced a slow increase in dark- adapted [TMA+]0, which was prominent in amplitude in the distal portion of the retina, suggesting a shrinkage of the SRS. This effect was essentially proportional to the decrease in arterial oxygen tension (PaO2) below the normoxic level. Dark-adapted (TMA+)0 began to increase at a PaO2 of 60 to 80 mm Hg and was enhanced by 13% to 15% at a PaO2 of 40 mm Hg. Because of its slow onset, the size of the increase also was related to the duration of hypoxia. The light-evoked decrease in (TMA+)0 in the SRS was larger in amplitude during hypoxia than in normoxia. This difference increased with severity of hypoxia, beginning at approximately the same PaO2 as the increase in dark-adapted (TMA+)0. Interestingly, the hypoxic increase in amplitude depended on light intensity, i.e., it was proportionally greater at lower intensities versus higher ones. Background illumination suppressed the hypoxia-induced increase in (TMA+)0 in SRS, inhibiting it by approximately 50% at levels of hypoxia down to a PaO2 of 40 mm Hg. Systemic hyperoxia produced the reverse effect of hypoxia. Between two extreme states, e.g., illumination during hyperoxia (PaO2 > 200 mm Hg) versus severe hypoxia in darkness (PaO2 approximately 40 mm Hg), extracellular volume may change more than 4-fold. CONCLUSIONS: The observations of this study indicate that the space surrounding photoreceptors shrinks in response to hypoxia. This shrinkage should affect concentrations of all ions and metabolites located in the subretinal space.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The method of multilevel full-thickness eyelid resection combined with plication of the levator aponeurosis Müller's muscle was used to correct severe acquired ptosis. The 19 eyes of 13 patients treated with this method included neurogenic ptosis (3 eyes of 3 cases), myasthenia gravis ptosis (8 eyes of 4 cases), chronic progressive external ophthalmoplegia (4 eyes of 2 cases) and traumatic ptosis (4 eyes of 4 cases). All the patients had poor levator function. After operation their eyelids were elevated to an acceptable functional level without exposure keratopathy. The operative results were satisfactory. The operation procedure and indications were discussed.
The contents of armillarin and melleolid in different stages of development of Armillaria mellea were determined by means of HPLC. The results indicated that the content of armillarin was 0.0085% in mycelia 0.54 mg/L in fermenting liquor, 0.002% in fruit-body, 0.0008% in rhizomorph; melleolid 0.0002% in mycelia 0.0011% in fruit-body and 0.0011% in rhizomorph.
This study is aimed to investigate the effects of L-arginine, a precursor of the formation of nitric oxide, on acute hypoxic pulmonary hypertension in vivo and on production of endothelin-1 both in vivo and in cultured endothelial cells. In mechanically ventilated anesthetized dogs (n = 7), L-arginine (0.5 g/kg) reduced the mean pulmonary arterial pressure and femoral arterial pressure during hypoxic ventilation and its action lasted for about 30 minutes. Meanwhile, plasma endothelin-1 in the pulmonary and femoral artery had no remarkable change. In cultured endothelial cells from umbilical veins, different concentrations of L-arginine had no influence on endothelin-1 level of culture medium in 4 or 24 hours after the addition of L-arginine. These results indicate that L arginine can decrease the pulmonary arterial pressure during acute hypoxia, which may be associated with the increase of nitric oxide production.
We tested the effect of flupirtine against ischemic and excitotoxic neuronal damage as well as on the glutamate-induced rise in cytosolic calcium ion concentration (= [Ca2+]i). For in vivo experiments we used a model of focal cerebral ischemia in mice. The middle cerebral artery was permanently occluded and 48 h afterwards brain tissue was stained with neutral red, perfusion-fixed and the infarct surface was determined planimetrically. Pretreatment with flupirtine significantly reduced the infarct area (controls: 24.3 +/- 4.8 mm2, 1 mg/kg flupirtine: 20.1 +/- 3.6 mm2 and 10 mg/kg flupirtine: 19.5 +/- 3.9 mm2; P < 0.05), whereas postischemic application of flupirtine failed to reduce the infarct area. For in vitro studies, primary neuronal cultures were prepared from the hippocampi of newborn rats and excitotoxic damage was induced by exposing the cells to 500 mu M L-glutamate for 30 min. We could demonstrate that flupirtine (1-10 microM) was capable of protecting neurons against glutamate-induced cytotoxicity. In order to elucidate the underlying mechanism of action, we tested the effect of flupirtine on the glutamate-induced rise in [Ca2+]i using the Ca2+-indicator fura-2. L-Glutamate added in a final concentration of 100 microM to the cultured cells for 16 s caused a rise in [Ca2+]i from about 100 nM to 900 nM. Flupirtine (0.1-10 microM) reduced the glutamate-induced rise in [Ca2+]i concentration dependently.