Search PubMed⌕ Search

Biomedical subjects

Y N Wu

Publications and source records attributed to Y N Wu.

15 recordsLinked to original sources
PubMed1992

Anti-(14-3-3 protein) antibody inhibits stimulation of noradrenaline (norepinephrine) secretion by chromaffin-cell cytosolic proteins.

Incubation of digitonin-permeabilized bovine chromaffin cells in the absence of Ca2+ results in a loss of both cytosolic proteins and Ca(2+)-dependent secretion. Addition of these leaked proteins prevents this loss of secretory activity. We have purified a protein from an extract of bovine adrenal medulla which can partially prevent this loss of Ca(2+)-dependent secretion. Antibody against this protein inhibited the ability of leaked chromaffin-cell proteins to prevent the loss of Ca(2+)-dependent secretion. Sequence analysis showed it to have sequence identity with bovine brain 14-3-3 protein. These results demonstrate that 14-3-3 protein makes a significant contribution to the ability of leaked chromaffin-cell proteins to maintain secretory activity.

14-3-3 Proteins↗
PubMed1992

Modification of chromaffin cells with pertussis toxin or N-ethylmaleimide lowers cytoskeletal F-actin and enhances Ca(2+)-dependent secretion.

In an attempt to identify proteins involved in the secretory response, bovine chromaffin cells were modified with N-ethylmaleimide (NEM). NEM concentrations less than 30 microM enhanced norepinephrine secretion evoked by nicotine or by K+ depolarization and increased Ca(2+)-dependent secretion from digitonin-permeabilized cells. Higher concentrations of NEM inhibited secretion. The protein modified by NEM which was responsible for the enhancement of secretory activity appeared to rapidly diffuse out of the digitonin-permeabilized cells. When proteins which diffuse from control digitonin-permeabilized cells were incubated with pertussis toxin and [32P]NAD, several proteins were ADP-ribosylated. However, when proteins from cells preincubated with 30 microM NEM were incubated with pertussis toxin and [32P]NAD, these GTP-binding proteins (G-proteins) were not ADP-ribosylated, which suggests that they were modified in the cell by NEM. Stimulation of norepinephrine secretion by NEM was not additive with that caused by pertussis toxin. Modification of chromaffin cells with pertussis toxin or with 30 microM NEM caused a 40-50% decrease in the amount of cytoskeletal F-actin. This decrease in cytoskeletal F-actin may account for the increase in secretory activity.

Actins↗
PubMed1992

Cloning, functional expression, and developmental regulation of a neuropeptide Y receptor from Drosophila melanogaster.

Neuropeptide Y, peptide YY, and pancreatic polypeptide are homologous 36-amino acid peptides that differ from most other peptide transmitters by having a relatively rigid conformation in aqueous solutions, defined as the pancreatic polypeptide fold, and a critical C-terminal tyrosine amide. These peptides serve as gastrointestinal hormones and neurotransmitters. A cDNA encoding a novel G protein-coupled receptor activated by neuropeptide Y was cloned from Drosophila by use of degenerate oligonucleotide primers and polymerase chain reaction amplification of cDNA prepared from transcripts expressed early in embryogenesis. The cDNA encodes a protein of 449 amino acids with the characteristics of a G protein-coupled receptor and shares significant amino acid identity with mammalian tachykinin receptors. When expressed in Xenopus oocytes, the PR4 protein is activated by mammalian neuropeptides in the order: peptide YY greater than neuropeptide Y much greater than pancreatic polypeptide. Northern analysis showed that PR4 receptor is expressed at equivalent levels in adult Drosophila head and body and that the expression of the PR4 receptor is regulated during development. The molecular characterization of this receptor should lead to a better understanding of the functional role of this important family of hormone receptors in adult organisms and during development.

Amino Acid Sequence↗
PubMed1992

Calcium-activated potassium channels expressed from cloned complementary DNAs.

Calcium-activated potassium channels were expressed in Xenopus oocytes by injection of RNA transcribed in vitro from complementary DNAs derived from the slo locus of Drosophila melanogaster. Many cDNAs were found that encode closely related proteins of about 1200 aa. The predicted sequences of these proteins differ by the substitution of blocks of amino acids at five identified positions within the putative intracellular region between residues 327 and 797. Excised inside-out membrane patches showed potassium channel openings only with micromolar calcium present at the cytoplasmic side; activity increased steeply both with depolarization and with increasing calcium concentration. The single-channel conductance was 126 pS with symmetrical potassium concentrations. The mean open time of the channels was clearly different for channels having different substituent blocks of amino acids. The results suggest that alternative splicing gives rise to a large family of functionally diverse, calcium-activated potassium channels.

Amino Acid Sequence↗
PubMed1992

Detection of varicella-zoster virus DNA in the oropharynx and blood of patients with varicella.

The polymerase chain reaction (PCR) was used to detect varicella-zoster virus (VZV) DNA in respiratory epithelial cells and in peripheral blood leukocytes from adults with varicella. VZV DNA was detected in oropharyngeal epithelium in 62% of patients early in the course of varicella; the amount of VZV DNA declined with time and was detectable in only 22% of patients for greater than 6 days. VZV DNA was also detected in peripheral blood leukocytes in 74% of patients early in disease and was detected in both polymorphonuclear and mononuclear leukocytes. PCR demonstrated the presence of VZV DNA in the oropharynx and blood of most patients during varicella, in contrast to the ability to detect VZV in these tissues by viral culture.

Adult↗
PubMed1992

Variables affecting electronic root canal measurement.

This study was conducted in two parts. In the first part, 20 single-rooted teeth that had been scheduled for extraction were investigated. The electronic root canal lengths were measured in vivo with a Dental Sono-Explorer type Y-III, and the actual canal lengths were measured after extraction of the teeth. The rate of agreement of the two measurements was 77.5% within a range of +/- 0.5 mm, while it was 100% at +/- 2.0 mm, which is acceptable clinically. In the second part, there were 19 simulated canals whose lengths and apical foramen sizes were known beforehand. Experiments revealed a negative correlation between the areas of the apical foramina and the difference between the electronic and the actual root canal lengths. This relationship was shown by the linear regression equation: ŷ = 0.6-1.6x. With the exception of the smallest areas of foramina, electronic root canal length measurements were less than the actual lengths.

Analysis of Variance↗
PubMed1991

Transmitter regulation of voltage-dependent K+ channels expressed in Xenopus oocytes.

Voltage-dependent K+ channels (RBK1, RBK2 and RGK5) were co-expressed in Xenopus oocytes with 5-hydroxytryptamine (5-HT2) receptors. K+ currents measured 2-4 days later were inhibited by 5-HT (100 nM-10 microM, 20-30 s application) by up to 90%. The effect of 5-HT was mimicked by intracellular injection of Ins(1,4,5)P3. Increasing the Ca2+ concentration at the inner surface of excised membrane patches did not decrease the K+ current.

Animals↗
PubMed1991

Effects of phosphatase inhibitors and a protein phosphatase on norepinephrine secretion by permeabilized bovine chromaffin cells.

A protein phosphatase and phosphatase inhibitors were used to examine the role of protein phosphorylation in the regulation of norepinephrine secretion in digitonin-permeabilized bovine chromaffin cells. Addition of okadaic acid, a potent inhibitor of type 1 and type 2A protein phosphatases, or 1-naphthylphosphate, a more general phosphatase inhibitor, to digitonin-permeabilized chromaffin cells caused about a 100% increase in the amount of norepinephrine secreted in the absence of Ca2+ (in 5 mM EGTA) without affecting the amount of norepinephrine secreted in the presence of 10 microM free Ca2+. This stimulation of norepinephrine secretion by protein phosphatase inhibitors suggests that in the absence of Ca2+ there is a slow rate phosphorylation and that this phosphorylation triggers secretion. Addition of an exogenous type 2A protein phosphatase caused almost a 50% decrease in Ca(2+)-dependent norepinephrine secretion. Thus, the amounts of norepinephrine released both in the absence of Ca2+ and in the presence of Ca2+ appear to depend upon the level of protein phosphorylation.

Adrenal Medulla↗
PubMed1991

Calpactin-depleted cytosolic proteins restore Ca(2+)-dependent secretion to digitonin-permeabilized bovine chromaffin cells.

Incubation of digitonin-permeabilized bovine chromaffin cells results in a loss of Ca(2+)-dependent catecholamine secretion. The addition of cytosolic proteins prevents this loss of secretory activity. It has been proposed that calpactin might be the protein which is responsible for preventing this loss of activity. The experiments described in this paper show that cytosolic proteins which have been depleted of calpactin are as effective as control cytosolic proteins in preventing the loss of Ca(2+)-dependent secretion. Thus, a cytosolic protein(s) other than calpactin appears to be responsible for preventing this loss of secretory activity.

Adrenal Glands↗
PubMed1991

Cloning, heterologous expression and developmental regulation of a Drosophila receptor for tachykinin-like peptides.

We identified clones encoding a Drosophila receptor for tachykinin-like peptides by low stringency screening of an embryonic cDNA library with probes from the bovine substance K receptor. The cDNAs encode a seven transmembrane domain protein (DTKR) of 519 amino acids with 40-48% amino acid identity to mammalian tachykinin receptors within transmembrane regions. Xenopus oocytes injected with DTKR cRNAs showed selective responses to vertebrate substance P, its agonists and not to other vertebrate tachykinin peptides. These responses were eliminated by treatment of oocytes with pertussis toxin. In the adult fly, Northern and PCR analysis demonstrated preferential expression of DTKR in the head; in situ hybridization indicated that DTKR is accumulated in the cell bodies of neurons in the adult CNS. The levels of DTKR transcript are regulated during development. Northern and PCR amplification analysis showed that while DTKR transcripts are present at all stages, high levels of expression occur in later stages of embryogenesis (starting at 10-14 h), coinciding with the beginning of major periods of neural development. Whole mount embryo in situ hybridization demonstrated that DTKR is expressed at these later stages of embryogenesis (11-15 h) in the brain and in a specific subset of neurons in each neuromere of the developing ventral ganglion. The gene encoding DTKR was mapped by in situ hybridization to a single location at 99D on the right arm of chromosome 3. These observations demonstrate that the tachykinin family of peptide transmitters and their receptors represent an evolutionarily ancient form of cellular communication within the nervous system.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1989

Relationship between selenium and protein synthesis in cells and subcellular fractions in rat liver.

In order to determine the effect of selenium supplementation on protein synthesis in rat liver, the rate of incorporation of (3H)-leucine into protein by isolated hepatocytes, liver mitochondria and post-mitochondrial supernatant derived from four groups of rats fed diets supplemented with 0, 0.25, 0.35 and 0.40 mg/kg selenium as selenite were investigated. In addition, the alteration in nucleic acid, lipid peroxides and glutathione peroxidase in hepatocytes from the same liver were also examined. By the end of feeding, the rates of amino acid incorporation, ribonucleic acid contents and glutathione peroxidase activities were significantly higher in hepatocytes from the 0.25, 0.35 and 0.40 mg/kg Se diet groups compared with the unsupplemented group. With increasing selenium supplementation, the increments of amino acid incorporation activity, RNA content as well as glutathione peroxidase all together plateau at approximately 0.25 mg/kg Se level of selenium supplementation. The rates of amino acid incorporation into protein in liver mitochondria and post-mitochondrial supernatant and RNA/DNA ratio in liver homogenates derived from the 0.25 mg/kg Se group were increased as compared to that from the unsupplemented group; concomitantly the increment of glutathione peroxidase activities and the reduction of malondialdehyde in liver were also found in the 0.25 mg/kg Se group. The results suggested that selenium supplementation at a 0.25 mg/kg level was sufficient to stimulate amino acid incorporation into protein in hepatocytes, mitochondria and post-mitochondrial supernatant from rat liver, and the increases in incorporation were also consistent with increments of glutathione peroxidase activities and decrease of malondialdehyde.

Animals↗
PubMed1985

IgA nephropathy.

Explore the source record for details and available documents.

Adolescent↗
PubMedDate not supplied

Rupture of chordae tendineae in acute rheumatic carditis: report of one case.

Acute rheumatic carditis is a rare cause of ruptured chordae tendineae of the mitral valve. Such rupture could result in severe mitral regurgitation and in fatality. Surgical valvuloplasty or valve replacement is usually necessary. A 12-year old boy presented with acute rheumatic carditis, complicated with rupture of the chordae tendineae of the mitral valve leading to intractable congestive heart failure and cardiogenic shock. He was successfully treated by a simple repair of the chordae and by mitral valvuloplasty.

Acute Disease↗