Biomedical subjects

K W Cho

Publications and source records attributed to K W Cho.

At least 127 records · Page 7Linked to original sources

PubMed1989

Phylogenetic study on the immunoreactive atrial natriuretic peptide in the heart.

Using two antisera against atriopeptin III (AP III) which had different characteristics in cross-reactivities with atrial natriuretic peptide (ANP) analogs, we have measured an immunoreactive ANP (ir-ANP) in the heart extracts of several species. ir-ANP in atrial extracts showed both high and low molecular weights. Serial dilutions of atrial extracts from chickens, turtles, frogs, and fish yielded competition curves which were parallel to the standard curve of AP III with antiserum No. 4. In comparison with two serial dilution curves of atrial extracts made using two antisera, No. 4 and No. 9, we suggest that the amino acid at position 12 of ir-ANP in the atrial extracts of chicken, turtle, frog, and fish is not isoleucine but is some other amino acid.

Animals↗

PubMed1989

Presence of immunoreactive atrial natriuretic peptide in follicular fluid, ovary and ovarian perfusates.

Immunoreactive atrial natriuretic peptide (ir-ANP) was measured in the follicular fluid of pig ovarian follicle, and rabbit ovarian homogenates and perfusates using a specific radioimmunoassay (RIA). Serial dilution curves made with the extracts of follicular fluid, ovarian homogenates and perfusates using SepPak C18 cartridges were parallel with the RIA standard curve. On gel filtration chromatography and reverse phase HPLC, all extracted materials showed high and low molecular weight forms of ir-ANP. The amount of ir-ANP in rabbit ovary was 40.70 +/- 0.39 pg/mg and that in follicular fluid of pig ovarian follicle was 18.88 +/- 2.49 pg/ml.

Animals↗

PubMed1989

Vertebrate homeodomain proteins: families of region-specific transcription factors.

Vertebrate homeodomain proteins are transcription factors whose genes can be isolated via a conserved DNA-binding domain called the homeobox. We review recent studies suggesting that one function of these genes is the early subdivision of the embryo along the antero-posterior axis into 'fields' of cells with different developmental potential.

Amino Acid Sequence↗

PubMed1989

Duplicated homeobox genes in Xenopus.

Multiple kinds of clones and restriction fragment polymorphisms are frequently encountered when analyzing genes of the tetraploid frog Xenopus laevis. Two types of cDNA clone have been isolated for homeobox gene 2. Analysis of their corresponding genomic clones confirmed the existence of clearly distinct restriction maps; in addition the nearby presence of two additional homeoboxes suggests that this region is homologous to the Hox 2 gene complex of mammals. We asked whether the genetic polymorphism in Xenopus results from increased allelic differences due to tetraploidy or from having duplicated Hox 2 complexes. Using X. laevis/Xenopus borealis interspecies hybrids we show that the two types of X. laevis homeobox gene 2 transcripts result from two different genetic loci. They cannot represent alleles of the same gene because they do not segregate independently in the F1 hybrid progeny. Most other X. laevis homeobox genes studied so far are also found in two versions. Thus X. laevis seems to have two homeobox genes, both of which are expressed, for each one present in mammals or other vertebrates.

Alleles↗

PubMed1989

Stimulation of renin secretion by non-diuretic sulfhydryl reagents.

Organomercurial diuretics stimulate renin secretion although the underlying cellular mechanisms remain undefined. Since organomercurials are also known to react with sulfhydryl groups, the present studies determined the effects of sulfhydryl reagents on renin secretion. The effects of the non-diuretic mercurial agent, parachloromercuriphenyl-sulfonate (PCMPS), as well as that of other sulfhydryl reagents, N-ethylmaleimide (NEM), N-phenylmaleimide (NPM) and monobromotrimethylammoniobimane (qBBR), on renin secretion were determined in rabbit renal cortical slices. All four reagents stimulated renin secretion. NEM, which has a high membrane permeability, stimulated secretion to a relatively small extent and its effects were not apparent for at least one hour. Conversely, PCMPS, which is much less permanent than NEM, produced the largest stimulation and these effects were apparent within one hour. The stimulation of secretion by sulfhydryl reagents was independent of the concentration of Ca2+, Na+, and K+ in the incubation media, suggesting that the stimulation is not secondary to alterations of intracellular ion concentrations. These results raise the possibility of direct involvement of sulfhydryl groups of particular membrane protein(s) of the juxtaglomerular (JG) cells in some steps leading to renin secretion, and raise the possibility that sulfhydryl reactivity might in part account for the stimulatory effects of organomercurial and other diuretics.

Animals↗

PubMed1989

Reduction volume dependence of immunoreactive atrial natriuretic peptide secretion in isolated perfused rabbit atria.

A new technique to permit gradual changes in atrial distension has been developed in an isolated perfused rabbit atrium preparation. Graded volume reduction in the atrium was induced by changing the elevation of the outflow catheter tip. Pressure reduction from 6 cm H2O atrial distension resulted in a decrease in atrial distension volume. Atrial distension by 6 cmH2O did not change the release of immunoreactive atrial natriuretic peptide (irANP). The graded reduction in atrial distension from 0.11 +/- 0.03 (1.5 cm H2O) to 1.36 +/- 0.19 microliters/mg wet weight (6.0 cm H2O) resulted in 1.7 (6.76 +/- 2.05 versus 3.83 +/- 1.18 pg/mg per min, n = 9, P less than 0.025) to 40.1-fold (77.66 +/- 17.82 versus 3.0 +/- 1.14 pg/mg per min, n = 11, P less than 0.025) increases in irANP release. IrANP release in response to the reduction of atrial distension was volume dependent. The relation of percentage increase in irANP release with the percentage reduction of atrial distension was exponential. The data suggest that the atrial muscle shortening, but not stretch per se, may be a potent direct stimulus for the regulation of irANP secretion.

Animals↗

PubMed1989

Growth and luminescence of the bacterium Xenorhabdus luminescens from a human wound.

Xenorhabdus luminescens, a newly isolated luminous bacterium collected from a human wound, was characterized. The effects of ionic strength, temperature, oxygen, and iron on growth and development of the bioluminescent system were studied. The bacteria grew and emitted light best at 33 degrees C in a medium with low salt, and the medium after growth of cells to a high density was found to have antibiotic activity. The emission spectrum peaked at 482 nm in vivo and at 490 nm in vitro. Both growth and the development of luminescence in X. luminescens required oxygen and iron. The isolated luciferase itself exhibited a temperature optimum at about 40 degrees C; after purification by affinity chromatography, it showed two bands (52 and 41 kilodaltons) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, indicative of an alpha and beta subunit structure. Reduced flavin mononucleotide (Km of 1.4 microM) and tetradecanal (Km of 2.1 microM) were the best substrates for the luciferase, and the first-order decay constant under these conditions at 37 degrees C was 0.79 s-1.

Chromatography, Affinity↗

PubMed1989

Plasma concentration of atrial natriuretic peptide in different phases of Korean hemorrhagic fever.

Korean hemorrhagic fever (KHF) is an epidemic viral disease characterized by high fever, hemorrhagic tendency and renal failure, and by hemorrhages of right atrium and renal medulla as well as necrosis of anterior hypophysis. Plasma immunoreactive atrial natriuretic peptide (irANP) levels of 15 patients in the oliguric phase was 94.8 +/- 8.4 pg/ml (mean +/- SEM), 80% higher than of the normal control group (53.0 +/- 4.7 pg/ml; n = 28). In the diuretic phase it declined to 63.7 +/- 5.3 pg/ml (n = 26). Plasma renin activity (PRA) in the oliguric phase was 19.0 +/- 1.3 ng AI/ml/h, and in the diuretic phase 5.3 +/- 0.9 ng AI/ml/h, significantly higher than the control value (2.5 +/- 0.1 ng AI/ml/h). Elevations of irANP and PRA were not correlated in each group. Also systemic blood pressure as well as heart beats were significantly increased in the oliguric phase. These findings suggest that the increased irANP may have resulted from increased circulatory volume and that the ANP secretory process may not be affected by the disease.

Acute Kidney Injury↗

PubMed1988

Epicardial release of immunoreactive atrial natriuretic peptides in inside-out perfused rabbit atria.

An easy and convenient isolated atrial perfusion technique was developed. The effect of stretch of the atrial subpericardial myocytes was investigated in the inside-out perfused rabbit atria. Graded distension of the inverted atria was induced by changing the elevation of the atrial catheter tip. Intra-luminal volume expansion resulted in an increase in release of immunoreactive atrial natriuretic peptides (irANPs). The response was volume, or pressure dependent. Distension-induced release of irANPs occurred at the reduction of the distension. IrANPs in epicardial perfusate showed both high and low molecular weights. The major peak of irANP was observed at the corresponding fraction to the rat ANP-(1-28) in the Sephadex G-50 gel chromatography. The data suggest that the epicardial release of irANP is stretch-induced response and that the release may be involved in the regulation of cardiac function.

Animals↗

PubMed1988

Differential utilization of the same reading frame in a Xenopus homeobox gene encodes two related proteins sharing the same DNA-binding specificity.

Xenopus XlHbox 1 produces two transcripts during early development. One encodes a long open reading frame (ORF) and the other a short ORF sharing the same homeodomain, but differing by an 82 amino acid domain at the amino terminus. The long protein amino terminus is conserved with many other homeodomain proteins, and its absence from the short protein could have functional consequences. Some viral genes also utilize a single ORF to encode transcription factors of antagonistic functions. The overall organization of the homologous genes in frog and man is similar, supporting the notion that both transcripts are of functional significance. Studies on XlHbox 1 function show that the region common to the long and short proteins has a sequence-specific DNA-binding activity, and that microinjection of specific antibodies into embryos results in the loss of structures derived from cells normally expressing XlHbox 1.

Amino Acid Sequence↗

PubMed1988

Characteristics of distension-induced release of immunoreactive atrial natriuretic peptide in isolated perfused rabbit atria.

Atrial pressure- or distension-induced release of atrial natriuretic peptide (ANP) has been considered as an important regulatory mechanism of ANP release in cardiac atria. A new technique to permit graded continuous atrial distension has been developed in an isolated perfused single rabbit atrium. Graded atrial distension was induced by changing the elevation of the outflow catheter tip. Intra-atrial volume expansion resulted in an increase in immunoreactive ANP release. The graded increase in atrial distension from 43.9 +/- 10.2 to 207.7 +/- 29.1 microliter resulted in 6.2-27.1-fold increases in volume-dependent immunoreactive ANP release. A rise in immunoreactive ANP release induced by increasing atrial distension did not occur in the state of atrial distension but occurred only after return to the reduced distension. However, in the case of atrial distension with pacing, an increase in immunoreactive ANP release was observed during atrial distension with pacing and after return to the basal level. The present study shows that the new technique is applicable to the study of the 'stretch-secretion coupling' mechanism of ANP release in vitro, and that the more important factor involved in the release of immunoreactive ANP induced by atrial distension may be the atrial reduction to basal level after distension rather than the stretch itself.

Animals↗

PubMed1987

A Xenopus laevis gene encodes both homeobox-containing and homeobox-less transcripts.

A cDNA clone (p52) that contains all the protein-coding region from the maternally expressed XlHbox 2 locus of the frog Xenopus laevis has been isolated and sequenced. A probe containing the exon preceding the homeobox detected transcripts which arise from a splicing event in which the homeobox-containing exon is replaced by another exon lying 5' to it in the genome. Both the homeobox-containing and homeobox-less splicing event occur in the same tissues, with the homeobox-less RNA representing the minority of mRNA from this gene. There may therefore be a function for two types of transcript, and hence protein, from this locus. This phenomenon may not be exclusive to the XlHbox 2 gene of Xenopus, but might occur more generally in other homeobox-containing genes. The protein deduced from the homeobox-containing cDNA is significantly similar to the yeast mating type factor a1 (MAT-a1) gene product. In addition to the previously described homology of the homeodomains, the amino-terminal domains of XlHbox 2 and MAT-a1 are similar to each other; thus essentially all of the MAT-a1 protein corresponds to some part of the XlHbox 2 protein. In the case of XlHbox 2, the protein coded for by the homeoboxless mRNA would contain all of the non-homeobox homology to yeast MAT-a1.

Amino Acid Sequence↗

PubMed1987

Circannual changes in renin concentration, plasma electrolytes, and osmolality in the freshwater turtle.

Seasonal changes in heart rate, blood pressure, plasma and renal renin concentrations, plasma electrolyte concentrations, and osmolality were studied in freshwater turtles (Amyda japonica) exposed to the natural environment. Seasonal changes in heart rate and blood pressure showed a marked increase in summer and a decrease in winter, which correlated directly with that of an environmental temperature. Two peaks in plasma renin concentration were observed in November and May and correlated with the preparation for hibernation and arousal periods. Renal renin content exhibited a marked seasonal variation characterized mainly by an increase in summer, fall, and winter and a decrease in spring. Plasma sodium concentration and osmolality were the highest in summer, the lowest in winter, and intermediate during spring and fall. A change in plasma osmolality correlated closely with that of temperature. However, no marked seasonal variations in the concentrations of plasma potassium, chloride, and calcium were observed. On the basis of these data, we suggest that a circannual rhythm of renin concentration may be related to hibernation. We also suggest that seasonal changes in sodium concentration and osmolality relate closely to environmental temperature, although the mechanisms are not clear.

Animals↗

PubMed1987

Characterization of angiotensin I-converting enzyme activity in the freshwater turtle, Amyda japonica.

1. Angiotensin I-Converting Enzyme (ACE) activity has been characterized in the freshwater turtle, Amyda japonica. 2. Peak activity of ACE in plasma from the freshwater turtle was shown at pH 9.0, which was more alkaline compared to that of mammals. 3. Chloride requirements for the optimal ACE activity were different from species. 4. ACE inhibitors, EDTA, teprotide (SQ 20,881), Captopril (SQ 14,225) showed dose-dependent inhibitions of ACE activity in plasma from the freshwater turtle as well as mammals. 5. ACE activity was found in several different tissues with a different activity showing the highest activity in kidney homogenate from the freshwater turtle, Amyda japonica.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1987

Unilateral renal arterial infusion and renal vein catheterization in rabbits. Study of renal function and renin release.

This study evaluates the direct effects of verapamil and furosemide infused into the unilateral renal artery on renal function and the renin secretion rate in renal vein-catheterized rabbits. Catheterization did not alter the renal function parameters of the kidney. Verapamil and furosemide increased renal blood flow, urine flow, and urinary sodium, potassium and chloride excretions confined to the infused kidney. Verapamil increased the glomerular filtration rate and free water clearance. The renin secretion rate was increased by furosemide but not by verapamil. The present study shows that the technique is applicable to renal function studies in which unilateral renal arterial infusion of the agents studied is required. The contralateral kidney can be a reliable control for the infused kidney. It also provides a useful technique for the study of renin release in rabbits.

Animals↗

PubMed1987

Renal and renin effects of sodium thiopental in rabbits.

Unilateral renal arterial infusion of sodium thiopental on renal function and renin secretion were investigated in unanesthetized rabbits. Sodium thiopental infusion in doses of less than 0.3 mg/kg/min into unilateral renal artery caused dose-dependent increases in urine flow, urinary excretion of electrolytes, fractional excretion of sodium and free water clearance with no changes in systemic blood pressure and clearance of p-aminohippuric acid (renal blood flow). An anesthetic dose of sodium thiopental administered intravenously caused decreases in systemic blood pressure, renal hemodynamics, urine flow and free water clearance during the early period of anesthesia followed by increases in urinary excretion of sodium and fractional excretion of sodium. Unilateral renal arterial infusion of sodium thiopental decreased the renin secretion rate and plasma norepinephrine concentration in renal vein, whereas an anesthetic dose of sodium thiopental administered intravenously increased the renin secretion rate. These observations suggest that the diuretic, natriuretic and renin suppressive effects of sodium thiopental may be due to an inhibition of intrarenal sympathetic nervous system or due to a direct tubular action.

Animals↗

PubMed1986

The gene encoding the large subunit of human RNA polymerase II is located on the short arm of chromosome 17.

We have used chromosomal in situ hybridization and Southern blot analysis of DNA from somatic cell hybrids to determine the chromosomal localization of the subgenomic DNA fragment that encodes part of the large subunit of human RNA polymerase II. The results of our analysis demonstrate localization of the human RNA polymerase II large subunit gene to the short arm of chromosome 17.

Animals↗

PubMed1985

The gene encoding the large subunit of human RNA polymerase II.

As a first step to approach the structural and functional analysis of DNA-dependent RNA polymerase II (EC 2.7.7.8), we have isolated genomic sequences for the large subunit of the human enzyme. The sequences homologous to Drosophila RNA polymerase II large subunit sequences are present in the genome as single copy genes, when assayed at high stringency. The polypeptide information is encoded in a mRNA of 7.35 kilobases, as determined by Northern blot analysis. In vitro translation reveals a polypeptide of 220 kDa, similar in electrophoretic mobility to the largest subunit of the enzyme. A fusion-polypeptide synthesized in bacteria contains a region that cross-reacts with anti-RNA polymerase II antiserum. Antiserum directed against the purified fusion protein reacts with the large subunit of RNA polymerase II, whether in the intact IIA (220 kDa) or in the degraded IIB (180 kDa) forms. Moreover, the antifusion protein antibody inhibits not only the purified calf thymus RNA polymerase II activity but also specific RNA polymerase II transcription in a HeLa cell extract. Thus, the DNA fragment isolated contains structural and functional domains of the human RNA polymerase II large subunit.

Cell Line↗