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Biomedical subjects

D Kim

Publications and source records attributed to D Kim.

At least 325 records · Page 18Linked to original sources
PubMed1995

Heat shock protein hsp70 accelerates the recovery of heat-shocked mammalian cells through its modulation of heat shock transcription factor HSF1.

The role of mammalian 70-kDa heat shock protein (hsp70) in regulating cellular response to heat shock was examined by using three closely related rat cells: control Rat-1 cells, thermotolerant Rat-1 (TT Rat-1) cells, and heat-resistant M21 cells, a derivative of Rat-1 cells that constitutively overexpress human hsp70. In all these cells, after a prescribed heat shock, the level of the phosphorylated form of heat shock transcription factor HSF1 and that of HSF1 capable of binding to its cognitive DNA sequence heat shock element (HSE) exhibit similar time dependence. The amount of a constitutive HSE-binding activity (CHBA), on the other hand, inversely correlates with those of the two aforementioned forms of HSF1. The recovery kinetics from heat shock are different for the three cell lines, with the thermal-resistant TT Rat-1 and M21 cells showing faster recovery in terms of the state of phosphorylation of HSF1 and its ability to bind HSE or in terms of the reappearance of CHBA. Treatment with okadaic acid, a serine/threonine phosphatase inhibitor, delays the recovery kinetics of Rat-1 cells but not that of thermal-resistant M21 cells. These results are interpreted in terms of a role for hsp70 in the recovery of heat-shocked mammalian cells.

Animals↗
PubMed1995

Ontogeny of microvascular permeability to macromolecules in the chick chorioallantoic membrane during normal angiogenesis.

Chick embryos were incubated using standard shell-less techniques for microscopic observations at Days 4.5, 5.0, and 5.5 of the normal 21-day gestation. The chorioallantoic membrane (CAM) was prepared for intravital fluorescence confocal microscopy. A graded series of FITC-dextrans (20, 40, 70, and 150 kDa) was injected via vitelline vein. The changes in interstitial optical intensity due to FITC-dextran extravasation were evaluated by computer-assisted image analysis. Apparent permeability coefficients (Ps) were calculated for first order postcapillary vessels from the changes in intensity as a function of time. On Day 4.5, Ps values (means +/- SE x 10(-7) cm/sec) in the CAM microvessels for FITC-Dextran 20, 40, 70, and 150 were 11.8 +/- 1.0, 6.4 +/- 0.4, 3.1 +/- 0.5, and 1.5 +/- 0.5, respectively. The respective Ps values fell dramatically on Day 5.0 to 2.2 +/- 0.5, 0.7 +/- 0.2, 0.6 +/- 0.2, and 0.6 +/- 0.2. On Day 5.5, Ps values for all these FITC-dextrans were equal to 0.7 +/- 0.3. The evaluation of FITC-Dextran 10 on Day 5.5 yielded a Ps value of 1.9 +/- 0.3. Our data demonstrate a rapid reduction in microvascular permeability to macromolecules during normal angiogenesis in the early stages of CAM development. Our data also suggest that these changes in permeability may reflect functional adaptations of the CAM. A comparison of our data to those available in the literature for adult and tumoral tissues demonstrates that microvascular permeability properties in these tissues are different from those of the CAM.

Allantois↗
PubMed1995

Polyarginine and eosinophil-derived major basic protein increase microvascular permeability independently of histamine or nitric oxide release.

We tested the hypothesis that cationic peptides (polyarginine; poly-argn) and eosinophil-derived major basic protein (MaBP) increase permeability by stimulating the release of histamine and/or nitric oxide. We used intravital microscopy, clearance, and integrated optical intensity (IOI), using FITC-dextran 150 (FITC-dx 150) as a tracer, to evaluate changes in microvascular permeability in the hamster cheek pouch. Poly-argn at 1 microM (topical) increased the clearance of FITC-dx 150 from 610 to 3240 nl/60 min/g. In contrast, 1 microM polyglutamic acid (poly-glun; and anionic peptide) did not affect the clearance of FITC-dx 150 (605 nl/60 min/g). At 0.5 and 1.0 nM, poly-argn increased the clearance of FITC-dx 150 from 610 to 1722 and 2396 nl/60 min/g (P < 0.05). Similarly, 0.5 nM MaBP increased clearance from 591 +/- 38 to 1967 +/- 168 nl/60 min/g. L-NAME at 10(-4) M did not prevent the 0.5 nM MaBP-induced elevation in clearance (1784 +/- 350). Poly-argn at 1 nM increased net mean IOI by 21.5 +/- 7.2 units. This elevation was not inhibited by topical 10(-4) M L-NMMA (27.5 +/- 8.4). Using 0.5 nM poly-argn as agonist, we assayed suffusate samples for their histamine concentration using a competitive enzyme immunoassay and found no detectable histamine. Pyrilamine, an H1 antagonist, did not inhibit the 0.5 nM poly-argn-induced elevation in clearance of FITC-dx 150. We conclude that (1) cationic peptides and MaBP increase microvascular permeability and (2) the increase in microvascular permeability produced by low concentrations of poly-argn and by MaBP is independent of the release of histamine and does not require nitric oxide.

Animals↗
PubMed1995

Platelet activating factor modulates microvascular permeability through nitric oxide synthesis.

Biochemical signaling determines the specific action of vasomediators in the control of microvascular permeability and tone. We tested the hypothesis that nitric oxide (NO) synthesis is involved in the biochemical signaling pathway of platelet activating factor (PAF). The cheek pouch of anesthetized male Syrian hamsters was used as a microvascular model. Vessel diameter [expressed as the ratio of the experimental to the control (e/c) diameter, with control diameter normalized to 1] and extravasation of FITC-dextran 150 by integrated optical intensity (IOI) were determined using intravital fluorescent microscopy and computer-assisted digital image analysis. N-Nitro-L-arginine methyl ester (L-NAME) at 10(-5) and 10(-6) M and N-nitro-L-mono-methyl arginine (L-NMMA) at 10(-4) and 10(-5) M were used as inhibitors of NO synthase (NOS). Acetylcholine (ACh) and bradykinin were used as indirect indices of NOS activation. L-NAME and L-NMMA attenuated both ACh and bradykinin vasodilatory effects as well as the bradykinin-induced increase in vascular permeability. Topical PAF (10(-7) M) caused vasoconstriction (mean +/- SEM e/c ratio = 0.3 +/- 0.1) and increased IOI from a normalized baseline of 0 to 67.4 +/- 12.8. Topical administration of L-NAME produced differential effects on the series-arranged arterioles but had no effect on postcapillary venular permeability. L-NMMA did not influence the basal arteriolar diameter, but at 10(-5) M it caused a small increase in permeability (IOI = 14.3 +/- 4.2). In the presence of NOS inhibitors, PAF caused a reduced arteriolar constriction (e/c ratio = 0.6 +/- 0.1) relative to PAF alone. Both NOS inhibitors reduced the PAF-stimulated increase in vasopermeability. At 10(-5) M L-NMMA, the PAF-stimulated IOI mean value was 26.1 +/- 5.2, while at 10(-4) M L-NMMA the PAF-stimulated IOI was 15.2 +/- 2.6 compared to 10(-7) M PAF (67.4 +/- 12.8). These results support our hypothesis that NO synthesis is a step in the biochemical signaling pathway of the postcapillary cellular responses to PAF.

Animals↗
PubMed1995

Modulation of the serotonin-activated K+ channel by G protein subunits and nucleotides in rat hippocampal neurons.

In hippocampal neurons, 5-hydroxytryptamine (5-HT) activates an inwardly rectifying K+ current via G protein. We identified the K+ channel activated by 5-HT (K5-HT channel) and studied the effects of G protein subunits and nucleotides on the K+ channel kinetics in adult rat hippocampal neurons. In inside-out patches with 10 microM 5-HT in the pipette, application of GTP (100 microM) to the cytoplasmic side of the membrane activated an inwardly rectifying K+ channel with a slope conductance of 36 +/- 1 pS (symmetrical 140 mM K+) at -60 mV and a mean open time of 1.1 +/- 0.1 msec (n = 5). Transducin beta gamma activated the K5-HT channels and this was reversed by alpha-GDP. Whether the K5-HT channel was activated endogenously (GTP, GTP gamma S) or exogenously (beta gamma), the presence of 1 mM ATP resulted in a approximately 4-fold increase in channel activity due in large part to the prolongation of the open time duration. These effects of ATP were irreversible and not mimicked by AMPPMP, suggesting that phosphorylation might be involved. However, inhibitors of protein kinases A and C (H-7, staurosporine) and tyrosine kinase (tyrphostin 25) failed to block the effect of ATP. These results show that G beta gamma activates the G protein-gated K+ channel in hippocampal neurons, and that ATP modifies the gating kinetics of the channel, resulting in increased open probability via as yet unknown pathways.

Adenosine Triphosphate↗
PubMed1995

Membrane stretch augments the cardiac muscarinic K+ channel activity.

Arachidonic acid has been shown to activate K(+)-selective, mechanosensitive ion channels in cardiac, neuronal and smooth muscle cells. Since the cardiac G protein (GK)-gated, muscarinic K+ (KACh) channel can also be activated by arachidonic acid, we investigated whether the KACh channel was also sensitive to membrane stretch. In the absence of acetylcholine (ACh), KACh channels were not active, and negative pressure failed to activate these channels. With ACh (10 microM) in the pipette, applying negative pressure (0 to -80 mm Hg) to the membrane caused a reversible, pressure-dependent increase in channel activity in cell-attached and inside-out patches (100 microM GTP in bath). Membrane stretch did not alter the sensitivity of the KACh channel to GTP. When GK was maximally activated with 100 microM GTP gamma S in inside-out patches, the KACh channel activity could be further increased by negative pressure. Trypsin (0.5 mg/ ml) applied to the membrane caused activation of the KACh channel in the absence of ACh and GTP; KACh channel activity was further increased by stretch. These results indicate that the atrial muscarinic K+ channels are modulated by stretch independently of receptor/G protein, probably via a direct effect on the channel protein/ lipid bilayer.

Acetylcholine↗
PubMed1995

Differentiation of the microvascular endothelium during early angiogenesis and respiratory onset in the chick chorioallantoic membrane.

The present study served to determine the extent of microvascular endothelial differentiation during early stages of morphogenesis (days 4.5-5.5 of the 21-day incubation) in the chick chorioallantoic membrane (CAM). CAM's, which serve as the embryonic lung, were prepared for intravital injections of a graded series of FITC-dextrans and subsequent ultrastructural morphometric analyses of the microvascular units. The precapillary, capillary, and postcapillary microvascular segments presented a continuous endothelium that was substantially thicker than that of adult lung endothelia (DeFouw, 1988). Further, plasmalemmal vesicles were uniformly sparse, while endothelial vacuoles, of variable diameters, were present continuously in the proliferating microvascular units. Average widths and depths of the interendothelial clefts were uniform and suggested complete structural differentiation from the onset of CAM morphogenesis. Based on our recent estimates of CAM microvascular permeability coefficients (Rizzo et al., 1995), the observed endothelial ultrastructure was associated with microvascular selectivity comparable to that of adult pulmonary microvessels (Lanken et al., 1985). Therefore, despite incomplete ultrastructural differentiation of the early CAM microvascular endothelium, these angiogenic microvessels presented adult-like barrier properties. Further they were less permeable than (Wu et al., 1993; Yuan et al., 1993) and ultrastructurally distinct from (Kohn et al., 1992) certain tumorigenic microvessels. Thus, angiogenesis is likely not a routinely homogeneous process, and CAM microvascular permeability characteristics may be teleologically significant.

Allantois↗
PubMed1995

Basis for changes in the auxin-sensitivity of Avena sativa (oat) leaf-sheath pulvini during the gravitropic response.

During the gravitropic response, auxin-sensitivity of the lower flanks of leaf-sheath pulvini of Avena sativa (oat) is at least 1000-fold higher than those of the upper flanks and non-gravistimulated pulvini. When the pulvini are treated with 1 mM Ca2+, a 10-fold increase in auxin-sensitivity of the pulvini is observed. Related to this difference in auxin-sensitivity, in vitro activation of the vanadate-sensitive H(-)-ATPase by IAA was observed. Results show that the activation of the H(+)-ATPase by IAA is probably mediated by soluble protein factors and that the H(+)-ATPase prepared from the lower flanks is activated by IAA with a 1000-fold higher auxin-sensitivity as compared with that from the upper flanks of the graviresponding pulvini. Ammonium sulfate fractionation experiments show that these soluble protein factors are in the 30 to 60% fraction. Auxin-binding assays reveal that lower flanks contain more high-affinity soluble auxin-binding sites (kD; on the order of 10(-9) M) and less low-affinity soluble auxin-binding sites (kD; on the order of 10(-6) M) than upper flanks. It is concluded that differential auxin-sensitivity of graviresponding oat-shoot pulvini is achieved by the modulation of affinities of auxin-binding sites in upper and lower flanks of the pulvini, that Ca2+ is involved in such modulation, and that one of the probable cellular functions of these auxin binding sites is the activation of the proton pump on the plasma membranes.

Avena↗
PubMed1995

L-type calcium channel blockers modulate the microvascular hyperpermeability induced by platelet-activating factor in vivo.

PURPOSE: Platelet-activating factor (PAF) is a potent phospholipid mediator of the microvascular dysfunction associated with ischemia-reperfusion injury. Because changes in cytosolic-free Ca2+ concentration are essential in PAF cellular signaling, we formulated the hypothesis that blockade of Ca2+ entry may inhibit the PAF-induced microvascular dysfunction. METHODS: To investigate this hypothesis two L-type calcium channel blockers, verapamil and nifedipine, were applied to the hamster cheek pouch before the topical PAF challenge was undertaken. Permeability was assessed by measurement of the plasma clearance of fluorescein isothiocyanate dextran, 150,000 mol wt. The arteriolar diameter was measured simultaneously to evaluate the effects of L-type calcium channel blockers on PAF-induced vasoconstriction. RESULTS: Baseline clearance was 498.7 +/- 225.0 nl/60 min/gm (mean +/- SE). PAF at 10(-8) mol/L (n = 5) increased clearance to 3753.8 +/- 572.8 nl/60 min/gm (p < 0.01). Pretreatment with verapamil (2 mg/kg; n = 5) significantly reduced the increase in permeability caused by 10(-8) mol/L PAF (1909.1 +/- 620.2 nl/60 min/gm; p < 0.05). Nifedipine (5-10(-6) mol/L; n = 5) also significantly attenuated the impact of 10(-8) mol/L PAF (2037.2 +/- 427.5 nl/60 min/gm; p < 0.05). Neither verapamil nor nifedipine affected PAF-induced vasoconstriction. CONCLUSION: The significant inhibition of the increase in permeability by the L-type calcium channel blockers suggests that these compounds may be useful in the management of PAF-induced hyperpermeability.

Animals↗
PubMed1995

Anticoagulants and hematomas in free flap surgery.

A review of systemic anticoagulant use in 517 free flap procedures was performed to determine the associated risk of hematoma formation. Patients were divided retrospectively (not randomly) into five groups: no anticoagulation (227 flaps, 5.3 percent hematomas), low-dose heparin bolus of 2000 to 3000 units and postoperative infusion at a rate of 100 to 400 units/hr for 5 to 7 days (192 flaps, 6.7 percent hematomas), intraoperative bolus of 5000 units of heparin without postoperative anticoagulation (46 flaps, 6.5 percent hematomas), high-dose heparin infusion at a rate of 500 to 1200 units/hr (30 flaps, 20 percent hematomas), and dextran 40 infusion at a rate of 25 ml/hr (22 flaps, 9.1 percent hematomas). Intraoperative blood loss was similar for all groups. The flap loss rate was lower in the bolus (1.0 percent) and low-dose (1.0 percent) heparin groups than in the no-anticoagulation group (4.4 percent), but this difference was not statistically significant. The pedicle thrombosis rate also was lower in the bolus (2.2 percent) and low-dose (2.1 percent) heparin groups than in the no-anticoagulation group (6.2 percent). A cause-and-effect relationship between the use of anticoagulants and flap loss or prevention of thrombosis could not be established. We can conclude, however, that the use of low-dose heparin does not increase significantly the risk of hematoma or intraoperative bleeding.

Blood Loss, Surgical↗
PubMed1995

Isolation of a dextranase constitutive mutant of Lipomyces starkeyi and its use for the production of clinical size dextran.

A derepressed and partially constitutive mutant for dextranase of Lipomyces starkeyi was selected after ethyl methane sulphonate mutagenesis by zone clearance on blue dextran agar plates. The mutant produced dextranase when grown on glucose, fructose and sucrose as well as on dextran, and more enzyme was produced by the mutant than by the parental strain when grown on 1% dextran. The pH and temperature optima for the mutant dextranase were 5.5 and 55 degrees C, respectively. Dextranase produced on sucrose produced more isomaltose and less glucose after dextran hydrolysis than the equivalent enzyme produced on dextran. The clinical size dextran (average mol. wt of 75,000 +/- 25,000) yield of mixed culture fermentation with the mutant and Leuconostoc mesenteroides was 94% of the total dextran produced.

Dextranase↗
PubMed1995

Caulonemal gravitropism and amyloplast sedimentation in the moss Funaria.

Caulonemata of the moss Funaria were examined to determine whether they are gravitropic. Funaria and Physcomitrella were also evaluated to compare amyloplast sedimentation with that of Ceratodon. Protonemata were either chemically fixed in place or examined alive using infrared timelapse videomicroscopy. Funaria caulonemata were found to be negatively gravitropic, i.e., they grew upwards in the dark. Upward curvature reversed temporarily before cytokinesis in Funaria, a phenomenon already known for Ceratodon and Physcomitrella. Most horizontal and upward-curving Funaria tip cells contained a broad subapical zone where plastid sedimentation occurred. In dark-grown Physcomitrella caulonemata, sedimentation was detected by the presence of a thin, amyloplast-free strip of cytoplasm at the top of the cell. These results suggest that gravitropism and subapical amyloplast sedimentation may be relatively common in moss caulonemata.

Bryopsida↗
PubMed1995

Lower extremity spiral CT angiography versus catheter angiography.

Both catheter and spiral computed tomography (CT) angiography of the lower extremity vasculature were performed in six patients with clinically symptomatic peripheral vascular disease. Forty-eight arteries were studied and were independently evaluated for arterial stenoses and occlusions. Compared with catheter arteriography, CT angiography correctly depicted segmental occlusions and significant stenoses (> 50%) in 26 of 28 arteries, yielding a sensitivity of 92.9%, a specificity of 96.2%, and an overall accuracy of 95.5%.

Aged↗
PubMed1995

Dynamic contrast-enhanced subtraction MR angiography of the lower extremities: initial evaluation with a multisection two-dimensional time-of-flight sequence.

PURPOSE: To determine the clinical feasibility of a contrast material--enhanced two-dimensional (2D) magnetic resonance (MR) angiographic sequence in lower extremity arteries. MATERIALS AND METHODS: Four healthy volunteers and 12 patients underwent dynamic contrast-enhanced MR angiography; all patients also underwent conventional angiography. A 2D multisection gradient-echo sequence with image subtraction was used for all MR imaging examinations. RESULTS: Oblique-coronal contrast-enhanced MR angiography was completed in less than 4 minutes, with a 256 x 512 matrix. The arterial contrast enhancement ratio was 2.0 +/- 0.8 (standard deviation), and the pre- and post-contrast contrast-to-noise ratios were 2.1 +/- 13.8 and 46.2 +/- 18.7, respectively. The sensitivity for MR angiography was 100% and specificity was 69% for distinction of vessels with greater than 50% stenoses from normal or mildly stenotic vessels. CONCLUSION: Dynamic contrast-enhanced 2D MR angiography is capable of increasing intraarterial signal intensity and depicting small vessel anatomy of the lower extremities over a large field of view in a short imaging time.

Adult↗
PubMed1995

Platelet-activating factor stimulates protein tyrosine kinase in hamster cheek pouch microcirculation.

We studied the interactions between platelet-activating factor (PAF) and protein tyrosine kinase (PTK) in the modulation of microvascular responses in the hamster cheek pouch using intravital microscopy and computer-assisted image analysis. Changes in arteriolar diameter and in integrated optical intensity (IOI; an index of vascular permeability) were measured. Fluorescein isothiocyanate-labeled dextran 150 (FITC-Dx 150) served as a tracer for macromolecular transport. Genistein and tyrphostin 25, two PTK inhibitors, were applied topically in separate experiments. Pretreatment with 10(-4), 10(-6), and 10(-8) M genistein and with tyrphostin 25 at 10(-5) and 10(-7) M attenuated the maximal increment in mean IOI (+/- SE) induced by PAF at 10(-7) M (19.9 +/- 5.3, 21.5 +/- 4.5, 58.5 +/- 11.4, 28.7 +/- 7.6, and 35.0 +/- 10.9 vs. 70.7 +/- 8.9 units, respectively). Pretreatment with PTK inhibitors resulted in vasodilation but did not inhibit PAF-induced vasoconstriction. Our results suggest that PTK represents a biochemical pathway involved in the PAF modulation of microvascular permeability but not PAF modulation of arteriolar tone.

Amino Acid Oxidoreductases↗