Biomedical subjects

Y Kim

Publications and source records attributed to Y Kim.

At least 793 records · Page 44Linked to original sources

PubMed1990

Feasibility study of monitoring temperature rise in muscle phantoms by the Electrical Impedance Tomography system during hyperthermia treatment.

A simulation study of monitoring temperature rises during hyperthermia treatment was conducted on an Electrical Impedance Tomography (EIT) system developed at the University of Washington. A 2,450 MHz microwave generator was used to induce heat on muscle phantoms. Reconstructed temperature distributions by the EIT system showed hot spots with temperature rises of 2 to 8 degrees in the phantoms. The locations of the temperature rises were verified by infrared pictures and a thermistor probe. From repeated experiments, the results consistently revealed comparable temperature rises within the area underneath the rectangular aperture of the microwave applicator. These results are encouraging, and warrant further study of using the EIT technique to monitor the temperature patterns in actual clinical hyperthermia treatment.

Body Temperature↗

PubMed1990

Trichloroethylene degradation by two independent aromatic-degrading pathways in Alcaligenes eutrophus JMP134.

The bacterium Alcaligenes eutrophus JMP134(pJP4) degrades trichloroethylene (TCE) by a chromosomal phenol-dependent pathway and by the plasmid-encoded 2,4-dichlorophenoxyacetic acid pathway. The two pathways were independent and exhibited different rates of removal and capacities for quantity of TCE removed. The phenol-dependent pathway was more rapid (0.2 versus 0.06 nmol of TCE removed per min per mg of protein) and consumed all detectable TCE. The 2,4-dichlorophenoxyacetic acid-dependent pathway removed 40 to 60% of detectable TCE.

2,4-Dichlorophenoxyacetic Acid↗

PubMed1990

Effects of nifedipine and enalapril on glomerular injury in rats with deoxycorticosterone-salt hypertension.

Male Munich-Wistar rats underwent right nephrectomy and were given weekly injections of deoxycorticosterone acetate (DOCA) and 1% saline (salt) to drink. Two studies were performed. In the first, rats given enalapril (ENP) were compared with controls. In the second, rats ingested either standard chow or chow to which the calcium-entry blocker nifedipine (NIF) had been added. Six to eight weeks after nephrectomy, both control DOCA-salt rats and those given ENP had severe hypertension and significant proteinuria. Rats given NIF excreted less protein, and glomerular lesions were not observed in this group. The effects of NIF on several parameters that have been associated with glomerular injury were examined. Micropuncture studies revealed that glomerular capillary pressure was increased in DOCA-salt rats and was not reduced by NIF. Platelet aggregation was also similar in NIF-treated and control rats. Morphometric studies revealed a tendency toward lower glomerular volume of NIF-treated rats; however, kidney weight and glomerular capillary radius were unaffected by therapy. Thus NIF, but not ENP, prevents DOCA-salt rats from developing hypertension and glomerular injury. This effect does not depend on reduction in glomerular pressure or inhibition of platelet aggregation.

Animals↗

PubMed1990

Polymorphonuclear leukocytes induced vasoconstriction in isolated canine coronary arteries.

To assess how polymorphonuclear leukocytes (PMNs) act on coronary vasoactivity, we measured the changes in isometric tension of isolated rings of canine coronary arteries upon addition of autologous PMNs to organ chambers in which the rings were suspended. When PMNs isolated by the colloidal polyvinylpyrrolidone-coated silica (Percoll) gradient method were added to the chambers, ring preparations of left circumflex coronary arteries developed isometric tension. The increase in tension was dependent on the amount of PMNs (1 X 10(4) to 5 X 10(6) cells/ml). Maximal tension obtained by an optimal amount of PMNs (5 X 10(5) cells/ml) was almost comparable to that produced by prostaglandin F2 alpha (5 microM). Integrity of endothelial cells was not disrupted after the addition of PMNs because the developed tension could be reversed by the addition of acetylcholine in an endothelium-dependent manner. Mechanical rubbing of endothelium abolished the PMN-induced vasoconstriction, which was regained by placing an endothelium-unrubbed ring inside a rubbed ring ("sandwich preparation"). When PMN suspensions were pretreated with 5-lipoxygenase inhibitors of arachidonate, PMN-induced vasoconstriction was greatly suppressed, although the pretreatment of vascular preparations did not alter the development of isometric tension. These findings indicate that PMNs induce the contraction of coronary arterial rings in the presence of intact endothelial cells. The mechanism by which PMNs induce the contraction is the release of vasoconstrictive substances by metabolic interaction between PMNs and endothelial cells. Vasoconstrictive substances produced by the PMN-endothelial system, such as 5-lipoxygenase metabolites through a "leukotriene A4 steal" mechanism, may contribute to the contraction of vascular smooth muscle.

Animals↗

PubMed1990

Detection of oxygen-derived free radical generation in the canine postischemic heart during late phase of reperfusion.

To define the relation between oxygen-derived free radical (oxy-radical) generation in the reperfused ischemic myocardium and the progression of myocardial damage, we measured oxy-radical generation in the ischemic myocardium and the propagating infarct size in a model of canine coronary occlusion (90 minutes) and reperfusion. We used electron paramagnetic resonance spin-trapping techniques (5,5-dimethyl-1-pyrroline N-oxide [DMPO]) to detect oxy-radicals in the rapidly frozen myocardial samples taken by needle biopsy. There was no detectable generation of DMPO adducts in the normal myocardium before or after reperfusion. In the reperfused ischemic myocardium, electron paramagnetic resonance signals of DMPO-OOH (superoxide anion) and DMPO-OH (hydroxyl radical) were detected, with peak concentrations at 1 hour after reperfusion for DMPO-OOH and at 3 hours after reperfusion for DMPO-OH, respectively. These DMPO adducts were also detected during the early phase (15 seconds) of reperfusion, but the concentrations of these signals were much less than those during the late phase of reperfusion. Treatment with human recombinant superoxide dismutase (2.5 mg/kg/hr) and catalase (2.5 mg/kg/hr) during the course of experiments abolished DMPO-OOH formation but had little effect on DMPO-OH formation. Infarct size (percent of risk area infarcted), quantified by a dual staining method with Evans blue dye and triphenyltetrazolium chloride, was 18.3 +/- 4.8% (mean +/- SEM) at 90 minutes of occlusion. After 5 hours of reperfusion, infarct size increased to 43.6 +/- 7.2%. These results indicate that a greater magnitude of oxy-radical generation was sustained in the ischemic myocardial tissue during the late phase (1-3 hours) of reperfusion, associated with the progression of myocardial infarction. The concurrent appearance of oxy-radicals and progressive infarction may support the view that a chain reaction of oxy-radicals contributes to the propagation of myocardial cell damage in the postischemic heart.

Animals↗

PubMed1990

Effect of cyclosporin on generalized Shwartzman reaction in diabetic rats.

The effect of cyclosporin (CsA) on the endotoxin-induced generalized Shwartzman reaction (GSR) was studied in diabetic and nondiabetic rats. After 4.5 wk of diabetes, CsA (20 mg/kg) or intralipid as a control substance was given intraperitoneally daily for 10 days. Next, diabetic rats were given either high-dose (2 mg/kg or low-dose (0.1 mg/kg) endotoxin (Escherichia coli 026:B6 lipopolysaccharide B) as a single injection. The rats were killed at intervals of 1, 4, 8, and 24 h. No significant glomerular thrombi were seen in the nondiabetic control animals, whereas the severity of glomerular thrombi in the diabetic animals was dependent on the presence or absence of CsA, endotoxin dose, and degree of glycemic control. In the diabetic rats, glomerular thrombi occurred maximally at 4 h but were no longer present at 24 h. The CsA/high-dose-endotoxin rats had fewer glomerular thrombi than rats receiving the intralipid/high-dose endotoxin, but this difference was not statistically significant. The CsA/low-dose-endotoxin rats had increased glomerular thrombi compared with the intralipid/low-dose-endotoxin rats (P less than 0.01). Insulin treatment reduced the glomerular capillary thrombi in the CsA/low-dose-endotoxin diabetic animals. Thus, CsA aggravates the GSR with low-dose endotoxin but has no significant effect when high-dose endotoxin is given. Improved glycemic control reduces the GSR in CsA-treated rats. Thus, the interrelationships of diabetes, endotoxin, and CsA on the GSR are complex, and the pathogenesis of these events is unclear.

Animals↗

PubMed1990

Head size as a basis of gender difference in the latency of the brainstem auditory-evoked response.

In order to discuss the source of gender difference in the latencies of the brainstem auditory-evoked response (ABR), correlation analysis between head size (nasion to inion, ear to ear and circumference) and ABR latencies were investigated in 107 adults (57 males and 50 females) with normal hearing. Wave III and wave V latencies and I-III and I-V interpeak latency intervals (IPL) were significantly shorter in females than in males. Moreover, head size of the male subjects was significantly larger than the female subjects' head size with respect to all three parameters. Significant positive correlations were obtained between head size and the above-mentioned ABR wave latencies and IPLs, even when each gender was analyzed separately. These results suggest that head size, which may reflect brain size, is one of the important factors for the basis of gender difference in ABR latencies.

Adolescent↗

PubMed1990

Modification of mucin gene expression in the airways of rats exposed to sulfur dioxide.

The molecular mechanisms mediating mucous cell metaplasia and hypersecretion in the respiratory tract are unknown. Previous work suggests that mucous metaplasia requires the induction of mucin gene expression. We are investigating this possibility by monitoring steady state levels of mucin mRNA in a model of mucous cell metaplasia induced by SO2 exposure. Male Sprague Dawley rats were exposed to 400 ppm SO2 gas in air for 3 h per day, 5 days per week for 0,1,2, or 3 weeks. Sham controls were exposed to air under similar conditions. After 3 weeks, morphological changes were apparent in the epithelium of SO2 exposed rats at all levels from the trachea to the distal airways. The epithelial thickness increased, as well as the number and size of glands in the trachea. Epithelial mucous (goblet) cells increased from 0 to 4.5 per mm in the trachea, 0.2 to 6.2 per mm in the main stem bronchi, and 0.2 to 22.7 per mm in the distal airways (mean values obtained for 3-6 tissue blocks per airway level per condition). In parallel experiments, we used SMUC41, a 950 bp human intestinal cDNA to isolate a human airway cDNA, HAM-1 from a cDNA library constructed in bacteriophage from human bronchial poly A+RNA. HAM-1 is a 90 bp cDNA encoding a threonine- and proline-rich peptide with 96% homology to the human intestinal cDNA SMUC-41. Next we probed total and poly A+ airway RNA from rats in each exposure condition with SMUC-41 or HAM-1. Blots were then stripped and reprobed with cDNA encoding beta actin. Densitometry values normalized for the amount of RNA loaded per lane (as determined by actin hybridization intensity) showed that mucin mRNA increased 8-9 fold as a function of SO2 exposure. This is consistent with the possibility that mucin gene transcription is induced by SO2 exposure, and may represent a primary event in the development of mucous metaplasia and hypersecretion.

Animals↗

PubMed1990

[A six-year follow-up study of childhood behavior problems].

In order to study the outcome of childhood behavior problems and to investigate relationships between those behavior problems and mental health problems in later years, a survey which was conducted in 1977 was repeated after six years. Subjects were randomly selected children aged from three to seven years living in Bunkyo-ku in Tokyo in 1977. Out of 279 children, responses to the questionnaire were obtained for 201 children, with 39 refusing to co-operate and 39 having left the area. The main results were as follows: 1. Comparison of prevalence rates of individual behavior problems occurring in early childhood (from 3 to 7 years old), showed that behaviors such as overactivity, "difficult to control", persistence, stubbornness and poor relations with unfamiliar persons decreased rapidly with age. On the other hand, hypoactivity, withdrawal and shyness increased. For problems occurring in late childhood (from 9 to 13 years old), the prevalence of poor concentration and passive behavior problems increased with age, while aggressive behaviors decreased. Behaviors such as thumb-sucking, nail-biting, bed-wetting and tics decreased. 2. Over the six years of this study, many behavior problems in areas of activity, mood, volition, human relations and abnormal symptoms showed significant persistence, although the degree of the persistence was not very strong. 3. Significant relationships between behavior problems observed at age three to seven years and mental health problems such as refusal to attend school and antisocial behaviors after six years were not seen.

Adolescent↗

PubMed1990

Uniformity of current density under stimulating electrodes.

This work examines all the factors that go into designing, simulating, implementing, and experimentally testing high-current bioelectrodes. It reviews previous work on the properties and risks of electrodes used to interface high currents to the human body. It is a self-contained presentation covering all aspects of the design, test, and implementation of high-current stimulating bioelectrodes. Inherent properties derived from theoretical work are pointed out. The tools to design and evaluate electrodes are introduced and discussed. Analytical methods provide insights into inherent characteristics, but lack generality and are often very difficult to use. Numerical methods overcome the difficulties of analytical procedures and are capable of quantitatively evaluating existing electrode designs, or can be used to find a design that is optimal in certain properties and specific applications. Experimental studies have verified and provided knowledge of the mechanisms that can potentially cause damage to the patient. They are also used to test the validity as well as the limitations of numerical models and their predictions, and to point out which aspects of the numerical methods need to be improved. Experimental measurements are in good agreement with the analytical predictions and simulation results. For example, all three approaches pinpoint that the edge effect (the current density at the electrode-body interface increases toward the perimeter of the electrode) is an inherent property of a low-impedance electrode attached to a body of higher resistivity. Also, several optimal stimulating electrode designs to obtain the uniformity of current density under the electrodes are presented.

Animals↗

PubMed1990

Dense intramembranous deposit disease: a clinical comparison of histological subtypes.

The accumulation of osmiophilic dense deposits in glomerular mesangial and basement membranes (dense intramembranous deposit disease, or DIDD) is associated with variable histologic alterations of the kidneys. We compared clinical features and long-term renal outcome in 21 patients representing two histologic subtypes of DIDD, namely membranoproliferative glomerulonephritis (MPGN) and focal segmental glomerulonephritis (FSGN). We found that MPGN-type DIDD in 12 patients was associated with nephrotic syndrome in 12, persistent hypocomplementemia in 10 and progression to chronic renal insufficiency in 8. In 9 patients with the focal segmental variety of DIDD, nephrotic syndrome was observed in 3, persistent hypocomplementemia in none, and progression to renal insufficiency in 2 (significance: nephrotic syndrome, p = 0.001; persistent hypocomplementemia, p = 0.0001; chronic renal insufficiency, p = 0.02). In one patient transition from focal segmental to MPGN-type DIDD was observed. We conclude that DIDD is a heterogeneous disorder, and that certain clinical and histologic features may be useful in predicting ultimate outcome.

Adolescent↗

PubMed1989

A dynamic model for the structure of acyl carrier protein in solution.

The determination of solution structures of proteins using two-dimensional NMR data is commonly based on the assumption that the structure can be represented by a single rigid conformer. We present here a procedure whereby this assumption can be relaxed and illustrate its application to acyl carrier protein from Escherichia coli, a small negatively charged protein with no internal disulfide bonds. The methodology rests on a model having two distinct conformers in dynamic equilibrium. Use of this two-state model results in a dramatic improvement in fit to cross-relaxation-derived distance constraints and a substantial lowering of molecular mechanics energies for individual conformers of acyl carrier protein. The two-state model retains the three-helix motif previously identified on the basis of a one-state structure, but substantial motion of loop regions and the C-terminal peptide, as well as partial disruption of the second helix, is suggested to occur. Support for the existence of these motions can be found in amide exchange rate and spin relaxation time data.

Acyl Carrier Protein↗

PubMed1989