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Biomedical subjects

D W Kim

Publications and source records attributed to D W Kim.

195 records · Page 11Linked to original sources
PubMed1991

Changes of cardiac output during treadmill exercise by impedance cardiography.

Nine athletes and ten nonathletes were selected randomly to study the changes of cardiac function during exercise by impedance cardiography. The speed of the treadmill was maintained at 3.4 mph, and its grade was increased by 1% (Balke protocol). The exercise was continued until the target heart rate (THR), 85% of maximum oxygen uptake (VO2max). The measured parameters for pre- and post-exercise were stroke volume (SV), heart rate (HR), and cardiac output (CO). Average stroke volume of athletes at pre-exercise, 71.1 ml, was higher than that of nonathletes, 64.6 ml, and stroke volume of the former at post-exercise, 97.0 ml, was also higher than that of the latter, 85.2 ml. Therefore, despite the lower heart rate, cardiac outputs of athletes at pre- and post-exercise, 4.98 and 16.3 L/min, were higher than those of nonathletes, 4.87 and 14.2 L/min. For the second phase of the study, cardiac outputs of three subjects were measured during the continuous treadmill exercise with newly developed electrodes and shoes for minimizing motion artifact. Though there were several studies measuring cardiac output during continuous bicycle exercise, this is thought to be the first study in the world measuring cardiac output during continuous treadmill exercise without aid of ensemble averaging.

Adult↗
PubMed1990

Use of the human elongation factor 1 alpha promoter as a versatile and efficient expression system.

We have characterized the promoter region of the human elongation factor 1 alpha-encoding gene (EF-1 alpha) and developed a versatile expression system which has a wide host range and a high efficiency of gene expression. To identify the promoter region of the EF-1 alpha gene necessary for efficient gene expression, we constructed four pEF-CAT plasmids that have the bacterial cat gene fused to four different sites of the human EF-1 alpha gene: (i) ligated to the end of the TATA box (pEF220-CAT); (ii) ligated in exon 1 (pEF204-CAT and pEF233-CAT), and (iii) ligated in exon 2 (pEF321-CAT). All the pEF-CAT plasmids were highly expressed in all the cell types tested, including fibroblasts and lymphoid cells. Plasmid pEF321-CAT, which contains the first exon and the first intron, gave the highest level of cat expression. Plasmids pEF204- and pEF233-CAT, which contain part of the first exon but do not contain the first intron, were less efficient in cat expression than was pEF321-CAT. Plasmid pEF220-CAT, which lacks both the first exon and the first intron, was the least efficient. Plasmid pEF321-CAT was several- to 100-fold more efficient in cat expression than plasmid pSV2-CAT depending on the recipient cell types. The promoter of pEF321 plasmid also directed the stable expression of the bacterial neo gene more efficiently than the promoter of the simian virus 40 (SV40) early gene or the long terminal repeat of Rous sarcoma virus. Using this system, the SV40 early gene and the cDNA encoding human CD4 were also expressed efficiently.

Animals↗
PubMed1990

A case of methimazole-induced acute hepatic failure in a patient with chronic hepatitis B carrier.

We report a case of methimazole-induced acute hepatic failure, which occurred 17 weeks after initiation of the drug in a 43-year-old man with hyperthyroidism and hepatitis B surface antigenemia. Postmortem needle autopsy of the liver revealed an established micronodular cirrhosis secondary to hepatitis B with moderate septal/portal inflammation, marked cholestasis and scattered acidophilic bodies. The serum hepatitis B surface antigen (HBsAg) was positive, but reactivation of hepatitis B was unlikely in view of the absence of a serum hepatitis B e antigen (HBeAg) and hepatitis B virus deoxyribonucleic acid (HBV-DNA) and negative stain for HBsAg and hepatitis B core antigen (HBcAg) in the liver tissue.

Acute Disease↗
PubMed1989

Patterns of endothelial microfilament distribution in the rabbit aorta in situ.

The available data on F-actin microfilament distribution in vascular endothelial cells in vivo is limited. In this study, the appearance and distribution of endothelial cell microfilaments in the rabbit thoracic aorta, the abdominal aorta and its major arterial branch points, and the aortic bifurcation were examined. Perfusion fixed rabbit aortas were stained in situ for F-actin by infusing rhodamine phalloidin via a peristaltic pump into the aortas at a slow flow rate. This new technique resulted in excellent visualization of branch points and allowed for a precise description of the actin microfilament bundles in endothelial cells along flow dividers. In the thoracic and abdominal aorta, away from branch ostia, actin microfilaments were localized in two regions of the endothelial cells, as a prominent band that completely outlined the cell periphery, and also as short central stress fibers. The central stress fibers were more frequent and prominent in cells of the abdominal aorta. At branch sites and at the aortic bifurcation, long, thick microfilament bundles were present in endothelial cells extending from the tip of the flow divider to a few millimeters along the branch arteries, the aorta, and the iliac arteries. Peripheral actin, however, no longer completely surrounded the cells. The thick bundles were not prominent in endothelial cells located adjacent to the proximal lip of branches or at the iliac arteries opposite the flow divider. This study shows that endothelial cell F-actin microfilament distribution in vivo is well defined along the aortic-arterial system. The prominent central microfilament bundles and the reduced peripheral microfilaments seen at localized regions may reflect an adaptive response to elevated shear stress at these sites.

Actin Cytoskeleton↗
PubMed1989

Detection of physiological events by impedance.

The current emphasis on the acquisition of physiological data by noninvasive means for mass medical screening and patient monitoring has increased interest in the use of electrical impedance for the measurement of physiological events. The technique has gained some degree of acceptance for monitoring respiration (Baker & Geddes, 1970), and much interest has been displayed recently in use of the technique to measure cardiac output including studies by Kubicek et al. (1966) Judy et al. (1969), and Mohapatra (1981). Other applications using the impedance technique include thoracic fluid accumulation, peripheral blood flow, cerebral blood flow, muscle contraction, eye movement, and uterine contraction, etc. The purpose of this article is to introduce the various impedance techniques for the measurement of physiological variables.

Cardiography, Impedance↗
PubMed1989

Structural analysis of phleboliths and salivary calculi.

Three phleboliths and ten salivary calculi in the submandibular duct were studied with scanning electron microscopy (SEM) and computer aided microanalyser (CMA). The surface of the phleboliths was rather even with some irregularity. According to their surface structure the salivary calculi were divided into three types: the rock-like type, the granular type, and the globular type. The phleboliths were classified into two types according to their cut surface: the calcified-core type, and the uncalcified-core type. The core structure was similar to the surface structure in the calcified-core type of phleboliths, but in the salivary calculi the core structure was different from the surface structure in that the cut surface of the core was an accumulation of circular or polygonal structures forming a honey-comb pattern which was surrounded by small projections distributed radially. On the basis of these results some etiological factors of phleboliths and salivary calculi are discussed.

Electron Probe Microanalysis↗
PubMed1989

[Experimental studies of the effect of direct electric micro-current on the healing processes of bone defects].

As a procedure to accelerate healing of the bone defect, the electric micro-current has attracted much attention in the field of clinical application and experimental research. However, investigation of the calcifying process and comparison of the elements of the newly formed bony callus have not yet been carried out. In order to get deeper understanding of the callus formation and calcifying process in bone defects, this experiment aimed at comparing the healing processes of bone defects in the rabbit humerus between stimulated and non-stimulated control group. The bone specimens were surgically removed, on the 4th postoperative day and 1st, 2nd, 3rd, and 4th postoperative weeks. The specimens were examined by the use of the computer aided microanalyser, the energy dispersive spectrometer, and the scanning electron-microscope (JCMA-733). Histological examination was also made. In the stimulated group, on the 4th day, Ca and P of low concentration were observed around the inner periosteum indicating initiation of the calcification with callus formation. On the 1st week Ca and P were distributed diffusely in the bone defect. On the 2nd and 3rd weeks, the bone defect was almost filled with new bony callus and the calcification became more intense. After the 4th week, the distribution and concentration of Ca and P in the bony callus were similar to those of the surrounding cortical bone. Furthermore, the molar ratio of Ca/P of the new bony callus was much greater in the stimulated group than in the control group, and was rather similar to the molar ratio of Ca/P in the surrounding cortical bone. The results showed that the electric micro-current facilitated not only callus formation but also calcification, thus shortening the healing period of the bone defect.

Animals↗
PubMedDate not supplied

A partially duplicated discoid lateral meniscus.

Partially duplicated discoid lateral meniscus has not been previously reported. We present a case of a partially duplicated discoid lateral meniscus with a peripheral tear of the meniscus and a concomitant cartilage lesion of the lateral femoral condyle.

Arthralgia↗
PubMedDate not supplied

In vivo modulation of endothelial F-actin microfilaments by experimental alterations in shear stress.

F-actin microfilament reorganization in response to alterations in shear stress has not been experimentally tested in vivo. In the current study, we analyzed changes in F-actin distribution in endothelial cells around the site of a coarctation performed in the midabdominal aorta of rabbits. The coarctation caused a 60% decrease in luminal diameter and produced three distinct zones: 1) a high shear region immediately upstream of the coarct (Zone I); 2) a region of low, fluctuating shear immediately downstream of the coarct (Zone II); and 3) an annular vortex characterized by high shear extending 0.5 to 3 mm downstream of the coarct (Zone III). Endothelial cells of control abdominal aortas were ellipsoid in shape and aligned in the direction of blood flow. They displayed a prominent circumferential band of microfilaments and short, thin stress fibers. Near coarctations, cells of Zone I were much more elongate, and stress fibers were markedly thicker and longer than in control abdominal aortas. In Zone II, cells were polygonal in shape and showed a prominent peripheral band of microfilaments and central stress fibers. Zone III cells were similar in shape to control abdominal aortic endothelial cells but showed very striking central stress fibers. These findings indicate that in vivo F-actin microfilament distribution can be modulated by experimentally altering flow conditions. F-actin redistribution in response to elevated shear stresses may increase cell-substrate adhesion and thus maintain endothelial integrity.

Actin Cytoskeleton↗
PubMedDate not supplied

Angiogenesis and fibroblast proliferation precede formation of recurrent tumors after radiation therapy in nude mice.

Recently, the combination of ionizing radiation with inhibitors of angiogenesis has been reported to improve tumor eradication compared to treatment with irradiation alone. However, the mechanisms of this effect have not been defined. For this purpose [corrected] we established a non-small cell lung cancer model in nude mice. Tumor vascularization was visualized in vivo by MRI using gadolinium-DTPA as contrast agent. Further, cryosections were produced as close as possible to the MRI slice positions. Since we were interested in examining the formation of a recurrent tumor, irradiation was performed with a single fraction of 4 Gy. This dose caused a partial remission followed by recurrent tumor growth 25 to 35 days after therapy. The process of partial remission as well as formation of the recurrent tumor was examined in 28 nude mice analysing the following parameters: (i) contrast agent enhancement using high-resolution MRI, (ii) proliferation of tumor cells and fibroblasts using Ki-67 immunohistochemistry and (iii) formation of microvessels using CD31 immunohistochemistry. The latter analyses led to differentiation of three stages. Stage 1 (day 1 to day 15 after irradiation) was characterized by increasing areas of dead cell mass in hematoxylin-eosin-stained slides that corresponded to a decrease in tumor cell proliferation as well as contrast agent enhancement in MRI. The percentage of Ki-67-positive tumor cells decreased from initially 45.1% +/- 6.0% (mean +/- standard deviation) to 1.4% +/- 1.2% (mean +/- standard deviation) on day 15. Stage 2 (day 6 to day 20 after irradiation; overlapping with stage 1) was characterized by proliferation of fibroblasts leading to formation of fibrotic septae with abundant microvessels. Already during late stage 2, MRI identified new contrast agent enhancing areas. Stage 3 (day 20 to day 40 after irradiation) was characterized by new tumor cell proliferation. Interestingly, tumor cells almost exclusively proliferated in the direct neighbourhood of the fibrotic septae that had been formed in stage 2. Obviously, proliferation of fibroblasts and blood vessels was a condition prior to formation of recurrent tumor tissue. Thus, our results are in contrast with the view that tumors or recurrent tumors begin as avascular masses that later induce neovascularization. With respect to clinical practice, our results suggest that: (i) adjuvant anti-angiogenic therapy should not be limited to the day of irradiation but should cover a critical period until day 5 to day 20 after radiotherapy, (ii) adjuvant therapy should also include inhibition of fibroblast proliferation and (iii) MRI can identify a recurrent tumor 10 to 15 days before occurrence of new tumor growth.

Animals↗