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Biomedical subjects

D Kim

Publications and source records attributed to D Kim.

At least 397 records · Page 22Linked to original sources
PubMed1992

A mechanosensitive K+ channel in heart cells. Activation by arachidonic acid.

Mechanosensitive ion channels have been described in many types of cells. These channels are believed to transduce pressure signals into intracellular biochemical and physiological events. In this study, the patch-clamp technique was used to identify and characterize a mechanosensitive ion channel in rat atrial cells. In cell-attached patches, negative pressure in the pipette activated an ion channel in a pressure-dependent manner. The pressure to induce half-maximal activation was 12 +/- 3 mmHg at +40 mV, and nearly full activation was observed at approximately 20 mmHg. The probability of opening was voltage dependent, with greater channel activity at depolarized potentials. The mechanosensitive channel was identical to the K+ channel previously shown to be activated by arachidonic acid and other lipophilic compounds, as judged by the outwardly rectifying current-voltage relation, single channel amplitude, mean open time (1.4 +/- 0.3 ms), bursty openings, K+ selectivity, insensitivity to any known organic inhibitors of ion channels, and pH sensitivity. In symmetrical 140 mM KCl, the slope conductance was 94 +/- 11 pS at +60 mV and 64 +/- 8 pS at -60 mV. Anions and cations such as Cl-, glutamate, Na+, Cs+, Li+, Ca2+, and Ba2+ were not permeant. Extracellular Ba2+ (1 mM) blocked the inward K+ current completely. GdCl3 (100 microM) or CaCl2 (100 microM) did not alter the K+ channel activity or amplitude. Lowering of intracellular pH increased the pressure sensitivity of the channel. The K+ channel could be activated in the presence of 5 mM intracellular [ATP] or 10 microM glybenclamide in inside-out patches. In the absence of ATP, when the ATP-sensitive K+ channel was active, the mechanosensitive channel could further be activated by pressure, suggesting that they were two separate channels. The ATP-sensitive K+ channel was not mechanosensitive. Pressure activated the K+ channel in the presence of albumin, a fatty acid binding protein, suggesting that pressure and arachidonic acid activate the K+ channel via separate pathways.

Adenosine Triphosphate↗
PubMed1992

Changes in the ultrastructure of cell walls, cellulose synthesis, and glucan synthase activity from gravistimulated pulvini of oat (Avena sativa).

Ultrastructural analyses of the cell walls from top and bottom halves of gravistimulated pulvini from oat leaves show a decrease in the density of material within the cell walls from the lower halves of pulvini after 24 h of gravistimulation. Assays of cellulose synthesis with a 14C-sucrose pulse-chase experiment indicate no difference in the amount of new cellulose synthesized in top compared with bottom halves of gravistimulated pulvini. The highest rate of cellulose synthesis occurs with 12-24 h of gravistimulation. Treatment of graviresponding pulvini with 2,6-dichlorobenzonitrile (DCBN) had only a minor effect on segment gravitropic curvature. We also found that there is no difference in the activities of either glucan synthase I or glucan synthase II in top halves as compared with bottom halves of gravistimulated pulvini. We conclude that the graviresponse in oat stems is not driven by new cell wall synthesis but, rather, by changes in cell wall plasticity and osmotic potential.

Avena↗
PubMed1992

Mixed handedness and features of schizotypal personality in a nonclinical sample.

Using a nonclinical, noncollege sample, this study set out to confirm and extend previous findings of a relationship between the cognitive-perceptual features of schizotypal personality and mixed handedness using the Schizotypal Personality Questionnaire (SPQ). Based on previous findings of relationships between nondextrality and thought disorder in schizophrenia, it was predicted that the odd speech subscale of the SPQ would have the strongest relationship with mixed handedness. Mixed-handed adults did have significantly higher scores than right-handed and left-handed adults on the cognitive-perceptual factor and its subscale of odd speech. Similar trends were also observed for the cognitive-perceptual subscales of suspiciousness, eccentric behavior, and unusual perceptual experiences. These results support and extend previous findings, and are broadly consistent with the association between thought disorder and nondextrality in schizophrenia.

Adolescent↗
PubMed1992

Peripheral directional atherectomy: 4-year experience.

Directional atherectomy alone or with supplemental percutaneous transluminal angioplasty was used to treat peripheral vascular lesions in 77 patients (85 procedures). Lesions involved 17 iliac arteries, 45 infrainguinal arteries, and 23 laser extremity vein bypass grafts. Technical success, defined as reduction of stenosis diameter to 30% or less of the normal vessel diameter, was achieved in 78 of 85 (92%) cases. The complication rate was 21% (18 of 85 procedures). Most complications were minor and were related to puncture sites. Patients underwent noninvasive follow-up studies, including measurement of ankle-brachial index and segmental pressures, plethysmography, and clinical examination. The mean follow-up period was 13.5 months. The probability of 1-, 2-, and 3-year patency for lesions treated with atherectomy alone was 92%, 84%, and 84%, respectively. Kaplan-Meier survival analysis revealed no difference in 2- to 3-year patency rate on the basis of lesion location or presence of calcification, eccentricity, or ulceration. Diabetic patients, however, had a higher restenosis rate than did patients who were not diabetic (P less than .03).

Aged↗
PubMed1992

The Simon nitinol filter: evaluation by MR and ultrasound.

In this prospective blinded study of inferior vena caval (IVC) patency, 18 patients underwent 25 duplex ultrasound (US) and magnetic resonance (MR) angiography examinations over an eight-month period following Simon nitinol filter placement. Clinical examination for lower extremity venous stasis and plain abdominal radiography were also performed. Twenty-three of 24 MR examinations and 11 of 24 US examinations were judged technically adequate by the blinded observers. One technically adequate US exam was false positive for intraluminal caval thrombus. Thirteen technically inadequate US examinations missed 3 complete caval occlusions and 2 partial occlusions. MR identified all patients with complete or partial caval occlusion. The authors conclude that duplex US reliably confirms IVC patency only when strict criteria for technical adequacy and interpretation are met (good visualization of filter and IVC above and below filter). MR, although expensive, more reliably identifies nonoccluding intraluminal thrombus and caval occlusion. It should be the noninvasive study of choice in symptomatic patients with venous stasis and patients with recurrent pulmonary emboli.

Adult↗
PubMed1992

Green and non-green callus induction from excised rice (Oryza sativa) embryos: effects of exogenous plant growth regulators.

Calli were induced either from excised rice embryos or from whole seeds in the presence of 1 to 5 mg l-1 NAA. After 12 days of culture, calli were induced only from excised rice embryos. We found that excised embryos accumulated NAA up to 6 times higher concentration than did whole seeds. In the presence of 1 to 5 mg l-1 NAA and 2 to 10 mg l-1 kinetin, chlorophyllous calli were induced from excised rice embryos. Chlorophyll contents in the callus tissue increased with increasing kinetin concentration while percent callus induction decreased. The total chlorophyll content was linearly correlated with the ratio of kinetin to NAA in the medium.

Cell Division↗
PubMed1992

Delayed massive hemobilia following percutaneous liver biopsy: treatment by embolotherapy.

A patient developed delayed life-threatening hemobilia after apparently uncomplicated percutaneous needle liver biopsy. An arteriobiliary fistula demonstrated by arteriography was successfully treated by selective transcatheter arterial embolization, with Gelfoam and a Gianturco coil. The diagnosis of liver biopsy-induced hemobilia should be suspected when a postprocedure fall in hematocrit is associated with abdominal pain, hyperbilirubinemia, or unexplained gastrointestinal bleeding. A review of the diagnosis and management of liver biopsy-related hemobilia is presented.

Abdominal Pain↗
PubMed1991

Subunit structure of deglycosylated human and swine trachea and Cowper's gland mucin glycoproteins.

The oligosaccharide chains in human and swine trachea and Cowper's gland mucin glycoproteins were completely removed in order to examine the subunit structure and properties of the polypeptide chains of these glycoproteins. The carbohydrate, which constitutes more than 70% of these glycoproteins, was removed by two treatments with trifluoromethanesulfonic acid for 3 h at 3 degrees and periodate oxidation by a modified Smith degradation. All of the sialic acid, fucose, galactose, N-acetylglucosamine and N-acetylgalactosamine present in these glycoproteins was removed by these procedures. The deglycosylated polypeptide chains were purified and characterized. The size of the monomeric forms of all three polypeptide chains were very similar. Data obtained by gel filtration, release of amino acids during hydrolysis with carboxypeptidase B and gel electrophoresis in the presence of 0.1% dodecyl sulfate showed that a major fraction from each of the three mucin glycoproteins had a molecular size of about 67 kDa. All of the deglycosylated chains had a tendency to aggregate. Digestion with carboxypeptidases showed that human and swine trachea mucin glycoproteins had identical carboxyl terminal sequences, -Val-Ala-Phe-Tyr-Leu-Lys-Arg-COOH. Cowper's gland mucin glycoprotein had a similar carboxyl terminal sequence, -Val-Ala-Tyr-Leu-Phe-Arg-Arg-COOH. The yield of amino acids after long periods of hydrolysis with carboxypeptidases showed that at least 85% of the polypeptide chains in each of the deglycosylated preparations have these sequences. These results suggested that the polypeptide chains in these deglycosylated mucin glycoprotein preparations were relatively homogeneous. The deglycosylated polypeptide chains as well as the intact mucin glycoproteins had blocked amino terminii. The purified polypeptide chains were digested with trypsin-TCPK, and S. aureus V8 protease and the resulting peptides were isolated by gel electrophoresis in the presence of 0.1% dodecyl sulfate and by HPLC. Two partial amino acid sequences from swine trachea mucin glycoprotein, two partial sequences from human trachea mucin glycoprotein and three partial sequences from Cowper's gland mucin glycoprotein were determined. The partial amino acid sequences of the peptides isolated from swine trachea mucin glycoprotein showed more than 70% sequence homology to a repeating sequence present in porcine submaxillary mucin glycoprotein. Five to eight immunoprecipitable bands with sizes ranging from about 40 kDa to 46 kDa were seen when the polypeptide chains were digested with S. aureus V8 protease. All of the bands had blocked amino terminii and differed by a constant molecular weight of about 1.5 kDa.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1991

Copy number and chromosomal location of Saccharomyces cerevisiae tRNA(Trp)-encoding genes.

Yeast tRNA(Trp)-encoding genes have been identified by Southern-blot analysis of chromosomal DNA. Seven copies of this gene are detected in blots of both restriction endonuclease digests and intact chromosomal DNA. Electrophoretic mapping of tDNA(Trp) indicates one copy is located on each of chromosomes X, XI, XIII, and XVI. The remaining three copies are localized to chromosomes VII and/or XV. Three different yeast strains gave identical results indicating this multi-gene family is relatively stable.

Base Sequence↗
PubMed1991

Effect of tunicamycin on glycosylation of a 50 kDa protein and thermotolerance development.

We investigated whether or not a 50 kDa glycoprotein might play an important role in protein synthesis-independent thermotolerance development in CHO cells. When cells were heated for 10 min at 45.5 degrees C, they became thermotolerant to a heat treatment at 45.5 degrees C administered 12 hr later. The thermotolerance ratio at 10(-3) isosurvival was 4.4. The cellular heat shock response leads to enhanced glycosylation of a 50 kDa protein. The glycosylation of proteins including a 50 kDa glycoprotein was inhibited by treatment with various concentrations of tunicamycin (0.2-2 micrograms/ml). The development of thermotolerance was not affected by treatment with tunicamycin after the initial heat treatment, although 2 micrograms/ml tunicamycin inhibited glycosylation by 95%. However, inhibiting protein synthesis with cycloheximide (10 micrograms/ml) after the initial heat treatment partially inhibited the development of thermotolerance. Nevertheless, there was no further reduction of thermotolerance development by treatment with a combination of 2 micrograms/ml tunicamycin and 10 micrograms/ml cycloheximide. These data suggest that development of thermotolerance, especially protein synthesis-independent thermotolerance, is not correlated with increased glycosylation of the 50 kDa protein.

Animals↗
PubMed1991

Inhibition of protein synthesis and heat protection: histidinol-resistant mutant cell lines.

The mechanism of histidinol (HST)-induced heat protection was investigated to test the hypothesis that the cessation of protein synthesis itself is one of the events involved in heat protection. For this study, we isolated three HST-resistant mutant strains. HST (5 mM), which inhibited protein synthesis by 88% in the wild type, caused only 0, 9, and 25% inhibition in three mutants, respectively. The drug, which afforded heat protection, (i.e., a 125-fold increase in survival from 4 x 10(-3) to 5 x 10(-1) after 2 hr at 43 degrees C in wild type), did not protect mutant cells from heat killing. In contrast, cycloheximide (10 micrograms/ml) which inhibited protein synthesis by 95% in both wild type and mutant cell types, protected both cell types from heat killing. Therefore, these results suggest that the cessation of protein synthesis, per se, preventing synthesis of nascent polypeptides, is a major event leading to heat protection.

Animals↗
PubMed1991

Calcitonin-gene-related peptide activates the muscarinic-gated K+ current in atrial cells.

A high density of nerve fibers containing calcitonin-gene-related peptide (CGRP) is present in the atria. Recently CGRP was reported to open ATP-sensitive K channels in arterial smooth muscle cells. This study examines whether CGRP activates a similar K+ channel in cardiac cells. In voltage-clamped whole cells loaded with GTP and ATP, CGRP reversibly evoked an inwardly rectifying K+ current. To identify the K+ channel that gives rise to this current, three types of K+ channel (resting, ATP-sensitive and acetylcholine-activated) were examined. CGRP failed to activate or inhibit the ATP-sensitive or the resting K+ channel. However, CGRP (0.1-1 microM) caused activation of single channels with kinetics similar to that of the muscarinic K+ channel (35-40 pS conductance and approx. 1 ms mean open time in symmetrical 140 mM K+). In excised, inside-out (CGRP in pipette) or in outside-out (GTP in pipette) patches, the K+ current was activated by perfusion with GTP or CGRP, respectively, suggesting that CGRP activated the muscarinic K+ channel via GTP-binding protein. Treatment with pertussis toxin inhibited the activation of the K+ channel, suggesting that CGRP receptor may be coupled to a Gi or a Go type of GTP-binding protein. Together with previous findings, these results suggest that CGRP modulates several types of ion channels to produce its cellular effects.

Adenosine Triphosphate↗