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Biomedical subjects

S Kim

Publications and source records attributed to S Kim.

At least 1,225 records · Page 68Linked to original sources
PubMed1989

Effects of valinomycin on calcium mobilization in vascular smooth muscle cells induced by angiotensin II.

The effect of the specific potassium (K+) ionophore valinomycin on increase in intracellular calcium concentration [( Ca2+]i) was studied in vascular smooth muscle cells (VSMC). Valinomycin at more than 10(-9) M dose-dependently suppressed phasic increase in [Ca2+]i in VSMC induced by angiotensin II (AII) in both control and Ca2+-free solution, indicating that it suppressed the release of Ca2+ from intracellular Ca2+ stores. Nicorandil and cromakalim, which are both K+ channel openers, also suppressed the increases in [Ca2+]i induced by AII in the Ca2+ free solution. However, valinomycin did not suppress AII-induced production of inositol 1,4,5-trisphosphate (IP3), which is known to mediate the release of Ca2+. These results indicate that decrease of intracellular K+ induced by valinomycin suppressed the release of Ca2+ from intracellular Ca2+ stores induced by IP3.

Angiotensin II↗
PubMed1989

DNA looping generated by DNA bending protein IHF and the two domains of lambda integrase.

The multiprotein-DNA complexes that participate in bacteriophage lambda site-specific recombination were used to study the combined effect of protein-induced bending and protein-mediated looping of DNA. The protein integrase (Int) is a monomer with two autonomous DNA binding domains of different sequence specificity. Stimulation of Int binding and cleavage at the low affinity core-type DNA sites required interactions with the high affinity arm-type sites and depended on simultaneous binding of the sequence-specific DNA bending protein IHF (integration host factor). The bivalent DNA binding protein is positioned at high affinity sites and directed, by a DNA bending protein, to interactions with distant lower affinity sites. Assembly of this complex is independent of protein-protein interactions.

Bacterial Proteins↗
PubMed1989

Small molecular weight GTP-binding proteins in human platelet membranes. Purification and characterization of a novel GTP-binding protein with a molecular weight of 22,000.

When guanosine 5'-(3-O-[35S]thio)triphosphate (GTP gamma S)-binding activity was assayed in the particulate and cytosol fractions of human platelets, most activity was found in the particulate fraction. GTP-binding proteins (G proteins) were extracted from the particulate fraction by sodium cholate and purified by several column chromatographies. At least three G proteins with Mr values of about 21,000, 22,000, and 24,000 (21K G, 22K G, and 24K G, respectively) were separated in addition to the stimulatory (Gs) and inhibitory (Gi) regulatory GTP-binding proteins of adenylate cyclase. Among them, the amount of 22K G was more than 10-fold of those of other G proteins. 22K G was purified to near homogeneity and characterized. 22K G specifically bound GTP gamma S, GTP, and GDP, with a Kd value for GTP gamma S of about 50 nM. [35S]GTP gamma S binding to 22K G was inhibited by pretreatment with N-ethylmaleimide. 22K G hydrolyzed GTP to liberate Pi, with a turnover number of 0.01 min-1. 22K G was not copurified with the beta gamma subunits of Gs and Gi and was not recognized by the antibodies against the ADP-ribosylation factor for Gs and the ras protein. The peptide map of 22K G was different from those of the smg-25A and rho proteins, which we have purified from bovine brain membranes. 21K G was identified to be the c-ras protein, but 24K G was unidentified. These results indicate that there are multiple G proteins in platelet membranes and that a novel G protein (22K G) is a major G protein in platelets.

Blood Platelets↗
PubMed1989

Implications of hyperechoic lesions in small hepatocellular carcinoma.

Of 34 solitary small hepatocellular carcinomas (HCC) 2 cm in diameter or less, 13 with hyperechoic lesions were observed serially by sonography, and 11 of these were examined histologically. Serial examination showed that hypoechoic areas appeared at the periphery of or within, the hyperechoic tumor, and that these areas expanded more with tumor growth than the hyperechoic areas as if compressing or displacing the existing hyperechoic areas. Histologically, the hyperechoic lesions were composed mostly of well-differentiated cancer cells containing fat droplets, whereas the hypoechoic lesions were composed of cancer cells without fat droplets. In the two tumors that were formed almost completely of cancer cells showing fatty metamorphosis, cancer cells without fat droplets proliferated mainly in the periphery of the tumor. These findings suggest that, in hyperechoic HCC, cancer cells with fat droplets appear in the early stage of HCC, and probably change into concer cells without fat droplets by the time that a certain tumor size is reached, with gradual displacement by the latter type of cell during tumor growth.

Biopsy↗
PubMed1989

Studies on protein methyltransferase in human cerebrospinal fluid.

Protein methyltransferases, rich in most mammalian brains, were studied in human cerebrospinal fluid (CSF). Among several well-characterized groups of methyltransferases, protein methylase I (S-adenosylmethionine:protein-arginine N-methyltransferase, EC 2.1.1.23) was found in significant amounts in human CSF samples. Both myelin basic protein (MBP) -specific and histone-specific protein methylase I activities were observed, the latter being generally higher in most CSF. S-Adenosyl-L-homocysteine, a potent product inhibitor for the methyltransferase, inhibited approximately 90% of MBP-specific protein methylase I activity at a concentration of 1 mM. The optimum pH of the MBP-specific protein methylase I was found to be around 7.2. Identity of exogenously added MBP as the methylated substrate for CSF enzyme was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. An amino acid analysis of the [methyl-3H]protein hydrolysate showed two major radioactive peaks cochromatographing with monomethyl- and dimethyl (symmetric)-arginine. Human CSF contained relatively high endogenous protein methylase I activity (activity measured without added substrate protein): The endogenous substrate can be immunoprecipitated by antibody raised against calf brain MBP. Finally, CSF from several neurological patients were analyzed for protein methylase I, and the results are presented.

Humans↗
PubMed1989

Quantitative assessment of microcirculation in the rat dental pulp in response to alpha- and beta-adrenergic agonists.

Responses to intra-arterial injections of the alpha-agonist, norepinephrine, the beta-agonist, isoproterenol, and to selected blockers were investigated in vivo by intravital microscopy. Luminal diameters (D) of pulpal microvessels and red cell velocities (Vrbc) were measured simultaneously to facilitate calculation of volumetric blood flow (Q). Norepinephrine caused a decrease in D, mean red cell velocity (Vm) and Q within individual microvessels. These responses were blocked by the alpha-antagonist, phenoxybenzamine. In response to the arteriolar D increase and venular D and Q decrease with isoproterenol, a transient increase in arteriolar Q was followed by a decrease within the first 60 s. No such effects were observed when the beta-antagonist, propranolol, was administered before the isoproterenol injection. The biphasic response in Q in response to isoproterenol is most likely related to the low compliance of the pulp. In the low-compliance environment a passive compression of venules could result from an active dilation of arterioles with an attendant rise in extravascular tissue pressure.

Animals↗
PubMed1989

Effect of enzymatic methylation of apocytochrome c on holocytochrome c formation and proteolysis.

1. Methylation of the lysine at residue 72 of yeast apocytochrome c increases its import into mitochondria. 2. Using methylated and unmethylated apocytochrome c as substrate and intact yeast mitochondria and a solubilized mitochondrial fraction as a source of cytochrome c heme lyase, the results show that the methylation state of the apoprotein has no significant effect on its conversion to holoprotein. 3. The above result suggests that the import mechanism is separate from the heme-attaching activity. 4. Unmethylated apocytochrome c was less resistant to a yeast homogenate fraction that methylated apocytochrome c, suggesting that methylation of apocytochrome c alters the conformation of the whole protein.

Apoproteins↗
PubMed1989

Site-specificity of histone H1 methylation by two H1-specific protein-lysine N-methyltransferases from Euglena gracilis.

1. The histone H1 fractions from rat spleen and liver were used as substrates for two H1-specific protein-lysine N-methyltransferases, V-A and V-B (protein methylase III) from Euglena gracilis. 2. When the enzymatically [methyl-3H]labeled H1 fractions were resolved by two-dimensional gel electrophoresis, four subtypes were found to be methylated (H1b, H1c, H1d and H1e). Both enzymes methylated H1c and H1b to approximately the same extent; H1d and H1e were methylated preferentially by enzyme V-B and V-A, respectively. 3. Histone H1c, [methyl-3H]labeled by the methyltransferase V-A, which had been digested by arginine-specific protease (Arg C protease), showed a single radioactive peptide on HPLC, indicating methylation site specificity of the enzyme. 4. Arg C protease-digestion of [methyl-3H]labeled H1c labeled by methyltransferase V-B indicated that this enzyme methylated two sites on the histone molecule. 5. The histone H1c methylation sites of these two enzymes did not overlap, indicating the two enzymes have different site specificity. 6. In combination with the other results, this suggests that the two enzymes serve discrete purposes, possibly involving the presumed different actions of histone H1 subtypes.

Amino Acids↗
PubMed1989

Association of increased intracellular free Ca2+ by platelet-derived growth factor with mitogenesis but not with proteoglycan synthesis in chondrocytes--effect of suramin.

The effects of platelet-derived growth factor (PDGF) on the intracellular free Ca2+ concentration [( Ca2+]i) in chondrocytes were studied with a fluorescent Ca2+ indicator, fura 2, and compared with the effects of PDGF on mitogenesis and proteoglycan synthesis. PDGF evoked phasic and then tonic increase in [Ca2+]i dose-dependently in quiescent cultures of chondrocytes, and it also stimulated both DNA and proteoglycan syntheses dose-dependently similar to somatomedins. Suramin, which inhibits the interaction of PDGF with its receptors, caused dose-dependent inhibition of both the PDGF-evoked increase in [Ca2+]i and stimulation of DNA synthesis by PDGF. However, suramin rather enhanced the proteoglycan synthesis induced by PDGF without affecting the basal level of proteoglycan synthesis directly. These results suggest that [Ca2+]i may be an important signal for the action of PDGF on cell proliferation in chondrocytes, and that the initial signal for proteoglycan synthesis is different from that for DNA synthesis induced by PDGF after the activation of PDGF receptor.

Animals↗
PubMed1989

Intrasynaptosomal distribution of the ras, rho and smg-25A GTP-binding proteins in bovine brain.

We have purified to near homogeneity and characterized three small molecular weight (Mr) GTP-binding proteins, the c-Ki-ras protein (c-Ki-ras p21), the rho protein (rho p20) and a novel smg-25A protein (smg p25A), from bovine brain crude membranes. In the present studies, the intrasynaptosomal distribution of these 3 small Mr G protein has been investigated using bovine brain. ras p21 and rho p20 are found in the synaptosomal membrane fraction but not in the synaptosomal soluble fraction. In contrast, smg p25A is found in both the synaptosomal membrane and soluble fractions. These results indicate that the intrasynaptosomal distribution of these small Mr G proteins is different and suggest that they are involved in different neuronal functions.

Animals↗
PubMed1989

Hemodynamic regulation of the dental pulp in a low compliance environment.

Pulpal hemodynamic regulation has been investigated in experimental animals using 133Xe washout, 15-microns radioisotope-labeled microsphere injection, and intravital microscope methods. Three distinct types of pulp blood flow reductions were observed. Type I was characterized by reduction in response to direct stimulation of the sympathetic nerve; intraarterial infusion of norepinephrine, 5-HT, or prostaglandin F2 alpha; and indirect stimulation of the sympathetic nerve. The Type II response, an initial increase in flow followed by a decrease, was observed with isoproterenol, prostaglandin E2, substance P, and bradykinin. This biphasic flow response is caused by the low compliance environment of the tooth and may play a role in pulp inflammatory processes. The Type III response follows administration of histamine and is characterized by a gradual decrease in pulpal blood flow.

Animals↗
PubMed1989

Olfactory discrimination of estrous condition by the male golden hamster (Mesocricetus auratus).

After repeated exposure to receptive and nonreceptive females, male golden hamsters were tested for olfactory preferences in a four-choice olfactometer. Males discriminated between the odor of anesthetized females in different stages of their estrous cycle when the airstreams carrying the stimulus odors were diluted. Previous failures to demonstrate such an ability were probably due to ceiling effects resulting from laboratory testing. Males preferred the odor of females on the day before receptivity (a day coincident with maximal scent marking by the female) and least preferred the odor of females on diestrus-1 (the day on which females attacked and chased males during pretesting encounters). Detection and quick response to an impending estrus would be especially important for males of a solitary and promiscuous species in which there is a first male mating advantage.

Animals↗
PubMed1989

Pathological effects of Echinostoma caproni (Trematoda) in the domestic chick.

Domestic chicks experimentally infected with Echinostoma caproni for 2 weeks showed a dilated ileum, unkempt feathers, watery diarrhoea, and weight loss. The ileum from infected and control chicks was fixed in 10% neutral buffered formalin, and prepared as 10 microns paraffin sections stained in haematoxylin and eosin, Papanicolau, periodic acid-Schiff, picro-ponceau, and alcian blue. The infected ileum showed atrophic villi, hypertrophied circular musculature with collagen-like fibres and haemorrhagic zones. The brush borders of epithelial cells and goblet cells were absent in the mucosa of the infected ileum. Worms in contact with host mucosa showed tissue plugs in the suckers. The cephalic spines of worms abraded the host mucosa.

Animals↗
PubMed1989

Lack of a negative influence on viral growth by the nef gene of human immunodeficiency virus type 1.

Human immunodeficiency virus type 1 (HIV-1) contains an open reading frame called nef at the 3' end of its genome. The nef gene product has been reported to down-regulate viral growth by suppressing viral transcription through interaction with the long terminal repeat region. We have compared two isogenic HIV-1 (HIV-1-WI3) strains, one of which lacks nef expression, and found little difference between them in in vitro growth. We tested effects on viral entry, DNA synthesis, and RNA expression by measuring HIV-specific low molecular weight DNA and RNA after infection. The qualitative and quantitative aspects of DNA and RNA synthesis were comparable between the nef+ and nef- strains. The effects on viral growth were also examined by following changes in reverse transcriptase activity during the course of infection. The presence of the nef gene product failed to slow viral growth in several different cell types tested, including the human T-lymphocyte cell lines H9 and CEM-SS, human primary T cells enriched for CD4+ cells, and human monocytic cell lines U-937 and THP-1. On the contrary, the nef+ strain grew more efficiently in some cell types than the nef- strain. The same results were obtained with nef+ and nef- strains of a different virus, HIV-1-432, whose Nef had been reported to have a negative effect on viral growth. Our data suggest that the Nef protein does not act as a negative factor, at least in the experimental systems employed in our studies.

Cell Line↗
PubMed1989

Scintigraphic patterns of the reflex sympathetic dystrophy syndrome of the lower extremities.

Thirty-two patients with clinical signs and symptoms of the reflex sympathetic dystrophy syndrome (RSDS) of the lower extremities underwent Tc-99m MDP bone scintigraphy. Twenty-three patients had abnormal scan findings consistent with RSDS, while the scans of the remaining nine patients were normal. Of the 23 patients with abnormal scans, 19 demonstrated increased periarticular activity on early and delayed images, while 4 patients demonstrated decreased activity in the affected limb.

Adolescent↗