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Biomedical subjects

D Kim

Publications and source records attributed to D Kim.

At least 433 records · Page 24Linked to original sources
PubMed1990

Effect of histidine on histidinol-induced heat protection in Chinese hamster ovary cells.

The possible mechanism for heat protection by the protein synthesis inhibitor histidinol was investigated in CHO cells. Histidinol (HST, 5 mM), an analogue of the essential amino acid L-histidine, added for 2 hr before and during heating at 43 degrees C, protected cells from killing at 43 degrees C. Treatment with HST produced a 600-fold increase in survival from 3 x 10(-4) to 1.8 x 10(-1) after 2.5 hr at 43 degrees C. Although the cells were washed after HST treatment, substantial protective effect was still observed during heating at 43 degrees C. This protective effect gradually decreased with increased incubation time after the drug treatment. However, the protective effect was immediately reduced by treatment with histidine (HIS, 0.25-5 mM) during heating. The amount of reduction was dependent upon HIS concentration: five millimolar HIS completely inhibited HST-induced heat protection. Furthermore, protein synthesis which was inhibited by 95% by 5 mM HST, resumed immediately with 5 mM HIS treatment. In addition, when cells were labeled during or after HST treatment, neither preferential accumulation of heat shock protein families nor phosphorylation of 28 kDa protein was observed. Therefore, these results suggest that the cessation of protein synthesis itself is one of the events involved in protection.

Animals↗
PubMed1990

Mathematical modeling of mass transfer in microvascular wall and interstitial space.

A one-dimensional, unsteady-state mathematical model was developed to describe the transfer of macromolecules across a microvascular wall and into the interstitial space. The proposed theoretical model accounts for both molecular diffusion and convective transfer through the microvascular wall as well as in the interstitial space. The resulting partial differential equations were simultaneously solved using the Laplace transform method. The inversion of the Laplace transformed equations was obtained by using contour integration in the complex region. The final solution is represented by two equations expressing the macromolecule concentration in the microvascular wall region and in the interstitial space, respectively, as functions of time, spatial coordinate, macromolecule concentration in the microvascular wall at the plasma-wall interface, wall thickness, wall-interstitial space equilibrium constant for the macromolecules, ratio of the cross-sectional area of the two regions, sieving coefficients, diffusivity coefficients, and average fluid velocity terms in the two regions. Plots of the macromolecule concentration in both regions as a function of time are presented and discussed for selected values of the parameters. An analytical expression for the total amount of mass which has accumulated in a portion of the interstitial space at any given time was also derived and used to determine the average fluid velocity term and the diffusivity coefficient for each of the two regions from published experimental data (A. Y. Bekker, A. B. Ritter, and W. N. Durán, 1989, Microvasc. Res. 34, 200-216). A numerical nonlinear regression method was used for this purpose. The values for the diffusivity coefficients found in this work for this particular data set compare favorably with the results previously obtained by other workers in similar systems. It is expected that our model will be used in the future to describe the dynamics of mass transfer across a microvascular wall and into the interstitial space, on the basis of the molecular diffusion and/or convective transport mechanisms, thus contributing to the solution of the controversy regarding the nature of the transfer mechanism controlling macromolecule transport in living systems.

Animals↗
PubMed1990

Ultrasonic imaging of the nonlinear parameter B/A: simulation studies to evaluate phase and frequency modulation methods.

This paper presents a method for imaging the nonlinear parameter B/A. It is based on measuring phase shift and frequency shift of a high frequency acoustic probe wave by a low frequency acoustic pump wave. These measurements yield the real and the imaginary parts of the Fourier component of the distribution B/A at the wave number of the pump wave. We also derive the necessary set of wave numbers of the pump wave which must be employed to accurately image the B/A parameter. We show that these wave numbers are a function of sampling period and sampling number. Simulations of the imaging method show that the proposed method in this paper leads to more accurate imaging of B/A than the earlier method.

Animals↗
PubMed1990

Intracellular regulation of ion channels in cell membranes.

Cells communicate with their environment through receptor proteins on the cell membrane. Some ion channels are receptors, whereas others are linked to receptors through guanine nucleotide-binding proteins (G proteins). Ion channels control intracellular concentrations of ions such as calcium, and these concentrations control cell functions such as secretion and cell division. This review summarizes the current state of knowledge about the control of ion channels.

Cell Communication↗
PubMed1990

Cell wall and enzyme changes during the graviresponse of the leaf-sheath pulvinus of oat (Avena sativa).

The graviresponse of the leaf-sheath pulvinus of oat (Avena sativa) involves an asymmetric growth response accompanied by several asymmetric processes, including degradation of starch and cell wall synthesis. To understand further the cellular and biochemical events associated with the graviresponse, changes in cell walls and their constituents and the activities of related enzymes were investigated in excised pulvini. Asymmetric increases in dry weight with relatively symmetric increases in wall weight accompanied the graviresponse. Starch degradation could not account for increases in wall weight. However, a strong asymmetry in invertase activity indicated that hydrolysis of exogenous sucrose could contribute significantly to the increases in wall and dry weights. Most cell wall components increased proportionately during the graviresponse. However, beta-D-glucan did not increase symmetrically, but rather increased in proportion in lower halves of gravistimulated pulvini. This change resulted from an increase in glucan synthase activity in lower halves. The asymmetry of beta-D-glucan content arose too slowly to account for initiation of the graviresponse. A similar pattern in change in wall extensibility was also observed. Since beta-D-glucan was the only wall component to change, it is hypothesized that this change is the basis for the change in wall extensibility. Since wall extensibility changed too slowly to account for growth initiation, it is postulated that asymmetric changes in osmotic solutes act as the driving factor for growth promotion in the graviresponse, while wall extensibility acts as a limiting factor during growth.

Avena↗
PubMed1990

Abdominal aorta and renal artery stenosis: evaluation with MR angiography.

A blinded, prospective study with magnetic resonance (MR) angiography was performed to study patients who had undergone abdominal aortography. In 55 renal arteries among 25 patients, MR angiography had a sensitivity of 100% for detecting renal artery stenosis of 50% or greater and a specificity of 92%. With MR angiography, the degree of renal artery stenosis was overgraded in four of 55 renal arteries: Mild stenosis was overgraded as moderate stenosis in two arteries and as a severe stenosis in one, and a moderate stenosis was overgraded as a severe stenosis in one. The number of renal arteries was correctly determined in all cases. The renal arteries could be well evaluated only in the proximal third of the vessel, precluding detection of more distal stenoses. Atherosclerotic plaque uniformly appeared dark on gradient-echo images and was easily differentiated from bright, flowing blood in the aortic lumen. MR angiography enabled correct grading of the presence of atherosclerotic plaque and stenoses of the abdominal aorta in 22 of 25 patients (88%). The authors conclude that MR angiography has the potential to be a useful screening technique for patients with suspected renal artery stenosis and disorders of the abdominal aorta, but further clinical studies are warranted.

Angiography↗
PubMed1990

Regulation of K+ channels in cardiac myocytes by free fatty acids.

Using rat ventricular cells, we studied the actions of free fatty acids and their ability to modulate the ATP-sensitive K+ channel and to activate a new type of ATP-insensitive K+ channel previously identified in rat atrial cells. Perfusion of the cytoplasmic face of the membrane with unsaturated fatty acids (10-50 microM) such as arachidonic, linoleic, and eicosatrienoic acids inhibited the ATP-sensitive K+ channel almost completely; lysophospholipids also markedly inhibited this channel. Inhibition was due to decreases in the frequency and the burst duration of channel openings. Arachidonic acid activated the ATP-insensitive K+ channel with an outwardly rectifying property. Since the level of free fatty acids rises after longer periods of ischemia, we speculate that the ATP-insensitive K+ channel contributes to the late or secondary phase of extracellular K+ accumulation.

8,11,14-Eicosatrienoic Acid↗
PubMed1990

Beta-adrenergic regulation of the muscarinic-gated K+ channel via cyclic AMP-dependent protein kinase in atrial cells.

Cholinergic and beta-adrenergic stimulations of ionic currents are major physiological mechanisms in the regulation of heart rate and contractility. Muscarinic receptor stimulation is known to reduce beta-adrenergic effects on calcium current via reduction of cyclic AMP. Whether the beta-adrenergic stimulation affects the muscarinic response is not known. I report here that the beta-adrenergic agonist isoproterenol enhanced the muscarinic-activated K+ channel activity in rat atrial cells. Application of cyclic AMP-dependent protein kinase or its catalytic subunit to the cytoplasmic side of the membrane augmented the acetylcholine-activated K+ channel activity twofold to threefold. Increases in channel activity produced by isoproterenol or cyclic AMP-dependent protein kinase were associated with fourfold to fivefold and approximately twofold increases in the mean open and closed time durations, respectively. Alkaline phosphatase treatment reversed these effects. These results suggest that cyclic AMP-dependent phosphorylation of the K+ channel or associated regulatory proteins modulates the gating kinetics of the channel. This mechanism may be important in the regulation of pacemaker activity and, thus, the heart rate during beta-adrenergic stimulation.

Alkaline Phosphatase↗
PubMed1990

Alcohol dependence and withdrawal: a genetic animal model.

Using the techniques of selective breeding, mouse lines have been developed that express severe (Withdrawal Seizure Prone: WSP) or mild (Withdrawal Seizure Resistant: WSR) handling induced convulsions after cessation of chronic ethanol exposure. These lines differ at least ten-fold in severity of withdrawal after identical ethanol treatment. One feature of the genetic model is that other traits which distinguish these lines are presumably influenced by those genes determining ethanol withdrawal severity. WSP and WSR mice do not differ markedly in the metabolism of ethanol. In addition to handling induced convulsions, they also differ in other withdrawal signs: for example, WSP mice show more pronounced tremor. WSP and WSR mice do not differ in sensitivity to ethanol's hypothermic, anesthetic, or locomotor stimulant effects, nor in the magnitude of tolerance development to these responses. This suggests that sensitivity, tolerance and dependence are distinct genetic entities. WSP mice also display more severe withdrawal from diazepam, phenobarbital, and nitrous oxide than WSR mice, suggesting that some genes generally predispose mice to withdrawal from depressants. WSP mice display withdrawal handling induced convulsions after a single dose of ethanol, pentobarbital, or diazepam. The effective dose for producing drug seizures is not markedly different between WSP and WSR mice for a number of compounds with varied mechanisms of action. However, WSP mice are more sensitive than WSR mice to the effects of acute doses of convulsants to elevate handling induced convulsions. WSP mice have more binding sites in hippocampus for the N-methyl-D-aspartate antagonist MK 801. Binding of this ligand is increased during ethanol dependence in both mouse lines.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcoholism↗
PubMed1990

Antibody response of mouse splenocytes using mixture of supernatants of thymocytes, adherent and non-adherent splenocytes: in-vitro immunization-II.

We adapted one of the in-vitro immunization methods to induce antibody responses and confirmed the success of the immunization by enzyme-linked immunosorbent assay (ELISA) without hybridization. We have previously reported several methods of in-vitro immunization using different conditioned media. Here we introduce another method of in-vitro immunization using a mixture of three types of supernatant (thymocytes, and adherent and non-adherent splenocytes of mouse). Splenocytes were immunized in-vitro by a recombinant human growth hormone (rhGH) with the above conditioned media, and the results by ELISA showed a much higher optical density than the other in-vitro immunization methods that we had previously reported. Humoral responses as a result of in-vitro immunization to soluble antigens were easily confirmed by ELISA using the above-conditioned media. This finding indicates that any other conditions thought to be critical by other researches may not be essential for in-vitro immunization.

Animals↗
PubMed1990

Simultaneous occurrence of superficial and deep thrombophlebitis in the lower extremity.

Forty-two consecutive patients diagnosed with superficial phlebitis were seen during a 5-year period. Thirty-five of the 42 patients were outpatients. The diagnosis of superficial phlebitis was made by the presence of palpable subcutaneous cords in the course of the greater saphenous vein or its tributaries in association with tenderness, erythema, and edema. The presence of concurrent deep venous thrombosis (DVT) was assessed by impedance plethysmography in 37 patients, compression venous ultrasonography in 3 patients, and venography in 8 patients. Five of the 42 patients (12%) had DVT. Four of these five patients had a positive impedance plethysmographic or ultrasonographic test result followed by a confirmatory venogram. The fifth patient had a positive ultrasonographic test result, but no venogram was performed. Two of the five patients had clots that involved the popliteal or femoral veins. Four of 23 patients (17%) with superficial phlebitis at or above the knee had DVT. Only 1 of the 19 patients (5%) with superficial phlebitis below the knee had DVT. Three of the five patients with both superficial phlebitis and DVT had undergone surgery recently. All but 3 of the 42 patients (93%) had varicose veins. No patients had clinically apparent pulmonary emboli. DVT occurred in 17% of the patients with above-knee extension of the superficial phlebitis. In the clinical management of superficial lower-limb thrombophlebitis, noninvasive tests should be performed to guide therapy. When superficial phlebitis develops after recent surgery or the superficial phlebitis extends above the knee, diagnostic surveillance should be especially strict. When the noninvasive test results are equivocal, phlebography is indicated to rule out DVT.

Female↗
PubMed1990

The effect of parathyroid hormone on the acutely ischemic myocardium.

UNLABELLED: Parathyroid hormone (PTH) is reported to be a potent vasodilator. To determine if this action is beneficial in acute myocardial infarction (AMI) and is due to changes in prostacyclin or thomboxane, thirty dogs were anesthetized and instrumented (left atrial, coronary sinus, left main coronary, pulmonary artery and femoral artery catheters). AMI was induced by ligating the left anterior descending coronary artery. Either pentobarbital or alpha chloralose anesthesia was randomly assigned. Following LAD ligation, animals were randomized to receive PTH 0.008 nm/kg over 10 minutes every 30 minutes during the ischemic period or an equal volume of saline. Cardiac index, regional myocardial blood flow, O2 consumption and lactate production were measured. Infarct size was determined by computerized planimetry. PTH bioactivity was verified by adenyalate cyclase stimulating activity in rat osteosarcoma cells. Myocardial blood flow ranged from 81.5 to 155.2 ml/min/kg for normal myocardium. Cardiac index, O2 consumption, lactate production and myocardial perfusion was unaltered by the PTH administration. PTH reduced infarct size in dogs receiving pentobarbital but was deleterious in those receiving alpha chloralose. There was no difference in prostacyclin and thromboxane levels among groups. CONCLUSION: PTH is not beneficial in acute myocardial infarction.

Anesthetics↗
PubMed1989

Potassium channels in cardiac cells activated by arachidonic acid and phospholipids.

Two types of potassium-selective channels activated by intracellular arachidonic acid or phosphatidylcholine have been found in neonatal rat atrial cells. In inside-out patches, arachidonic acid and phosphatidylcholine each opened outwardly rectifying potassium-selective channels with conductances of 160 picosiemens (IK.AA) and 68 picosiemens (IK.PC), respectively. These potassium channels were not sensitive to internally applied adenosine triphosphate (ATP), magnesium, or calcium. Lowering the intracellular pH from 7.2 to 6.8 or 6.4 reversibly increased IK.AA channel activity three- or tenfold, respectively. A number of fatty acid derivatives were tested for their ability to activate IK.AA. These potassium-selective channels may help explain the increase in potassium conductance observed in ischemic cells and raise the possibility that fatty acid derivatives act as second messengers.

Animals↗