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Biomedical subjects

D Kim

Publications and source records attributed to D Kim.

At least 487 records · Page 27Linked to original sources
PubMed1987

Retraining of functional gait through the reduction of upper extremity weight-bearing in chronic cerebellar ataxia.

Patients with chronic ataxia resulting from traumatic central nervous system (CNS) damage frequently attain a gait pattern dependent upon upper extremity weight-bearing (UEWB). Traditional attempts to train these patients may perpetuate UEWB dependency, by not allowing optimal facilitation of balance and associated movement control required for independent ambulation. In the present study an ambulation retraining approach designed to facilitate coordination and balance while minimizing UEWB was used. This approach can allow the patient to train outside of the clinic; only about 5% of the actual therapy hours involved a therapist.

Adult↗
PubMed1986

Isolated external iliac artery aneurysm secondary to cystic medial necrosis.

The computed tomographic and angiographic findings of an isolated external iliac artery aneurysm secondary to cystic medial necrosis in a patient without Marfan's disease are demonstrated. A review of the differential diagnosis and surgical treatment of iliac artery aneurysms is presented. The dramatic surgical sequelae in this patient underscore the importance of preoperative consideration of this rare diagnosis.

Adult↗
PubMed1986

Effect of growth in low-Na+ medium on transport sites in cultured heart cells.

Increases in intracellular Na+ concentration ([Na+]i) lead to an increase in the number of Na+ pump sites in the cell membrane. To investigate further the role of [Na+]i in the regulation of Na+-K+-ATPase sites, we studied the effect of reduced [Na+]i on the number of Na+ pump sites and Na+-K+ pump activity using spontaneously beating cultured chick ventricular cells. Cells incubated in medium containing 60, 80, 100, or 140 mM Na+ for 24 or 48 h showed an extracellular [Na+]-dependent alteration in cellular Na+ content. The number of Na+ pump sites identified by [3H]ouabain binding binding declined with decreasing levels of Na+ in the medium in a time-dependent manner over 48 h, with a concomitant increase in cellular Na+ content. Verapamil (1 microM) or tetrodotoxin (1 microM) significantly reduced cellular Na+ content by 30 min of exposure and the number of Na+ pump sites by 48 h of incubation. Na+ pump activity determined from the ouabain-sensitive 42K+ uptake rate was significantly reduced in cells grown in low Na+ for 48 h, as was pump capacity, determined in Na+-loaded cells. These results support the view that [Na+]i exerts a long-term modulating effect on the number of physiologically functional Na+ pump sites.

Animals↗
PubMed1986

Inhibition of multiple trans-sarcolemmal cation flux pathways by dichlorobenzamil in cultured chick heart cells.

Dichlorobenzamil, an analog of amiloride, has been reported to inhibit Na-Ca exchange in sarcolemmal vesicles of guinea pig heart. To examine further the effect of the drug on Na-Ca exchange in intact cardiac cells and the pharmacological specificity of this action, we determined in cultured chick heart cells the effects of dichlorobenzamil on the following: contractile state, Nai-dependent Ca uptake, Ca uptake via slow Ca channels (defined as verapamil-inhibitable Ca uptake), Ca efflux via the sarcolemmal Ca pump, monovalent cation transport, and cellular Ca and Na content. Dichlorobenzamil produced a concentration-dependent decrease in the amplitude of cell motion (EC50 = 5 X 10(-7) M) and abolished the development of ouabain-induced rhythm disturbances and contracture. In normal or Na-loaded cells, dichlorobenzamil inhibited the Ca uptake rate, also in a concentration-dependent manner (EC50 = 6 X 10(-7) M). Dichlorobenzamil (6 X 10(-7) M) also caused a significant inhibition of the isoproterenol-induced elevation of Ca uptake. At 5 X 10(-5) M, dichlorobenzamil blocked completely Ca influx via slow Ca channels. Ca efflux rate was also reduced by dichlorobenzamil (EC50 = 10(-6) M). Replacement of Na with choline in the efflux medium to prevent Ca efflux via Na-Ca exchange did not alter the ED50 of the drug's inhibition of Ca efflux rate. Dichlorobenzamil caused concentration-dependent inhibition of sodium pump activity as judged by ouabain-sensitive 42K uptake (EC50 approximately 2 X 10(-6) M), and, at concentrations above 5 X 10(-7) M), produced an increase in steady state cellular Na content. These results indicate that dichlorobenzamil has several sites of action in intact heart cells and that the negative inotropic action of the drug is due, in part, to inhibition of Ca influx via both Na-Ca exchange and slow Ca channels.

Amiloride↗
PubMed1986

Effects of amiloride and ouabain on contractile state, Ca and Na fluxes, and Na content in cultured chick heart cells.

Amiloride has been reported to reduce the positive inotropic and toxic actions of cardiac glycosides in patients as well as in experimental animals. To investigate the mechanism by which amiloride interacts with glycosides at the cellular level, we examined the effect of amiloride and ouabain on cellular Na content and uptake, Ca flux via Na-Ca exchange, and contractile state. Amiloride (1 mM) reduced cellular Na content by 16% (p less than 0.05) under normal conditions and by 45% in the presence of 1 mM ouabain compared to respective control values observed in the absence of amiloride. Amiloride (1 mM) reduced the initial rate of 45Ca uptake by 40% in ouabain (1 mM)-treated cells. This reduction of 45Ca uptake could be mimicked by lowering cellular Na content by 42%. Amiloride (1 mM) did not alter significantly the initial rate of 24Na uptake under normal conditions but reduced it by 32% in the presence of 3 microM ouabain. Amiloride (1 mM) produced a transient increase followed by a gradual decrease in the amplitude of cell motion over 60 min to 10% of control level. At other concentrations between 0.1 and 3 mM, amiloride produced negative inotropic effects only. Amiloride increased the concentration of ouabain needed to produce rhythm disturbances and contracture, and reduced Na-free contracture amplitude by 18%. These results are consistent with the view that amiloride antagonizes the arrhythmogenic effects of ouabain by inhibiting the glycoside-induced elevation in cellular Na content and, consequently, the increases in [Ca]i that occur via Na-dependent pathways. The reduced cellular Na content appears to be due to decreased Na influx via Na-H exchange.

Amiloride↗
PubMed1985

Nd-YAG laser fusion of human atheromatous plaque-arterial wall separations in vitro.

The hypothesis that thermal fusion of disrupted layers of atheromatous arterial wall can be achieved with a neodymium-yttrium aluminum garnet (Nd-YAG) laser was tested. Fresh postmortem human atheromatous plaque was separated from the underlying arterial wall to simulate a dissection in 1-cm2 arterial wall sections. With the plaque and underlying arterial wall subsequently compressed between glass slides, 17 W of continuous-wave Nd-YAG laser radiation were delivered through an optical fiber to the luminal surface of the plaque over a 4-mm2 area. Fusion of the plaque to the underlying arterial wall invariably occurred when tissue compression was applied during lasing and a thin blood film was present between the tissues. The load supported by tissue welds depended on plaque thickness, plaque composition, and exposure duration and was as great as 25 g. In postmortem, blood-filled, whole-artery segments, in which plaque had been completely separated from the media, this technique was applied intraluminally during angioplasty with a prototype balloon catheter. Lateral dispersion of Nd-YAG radiation from the termination of an optical fiber within the balloon allowed fusion of plaque to the underlying arterial wall during balloon inflation to 2 atm. Histologic examination of laser-treated tissues showed coagulation of tissues at the junction between the intimal plaque and media. It is concluded that thermal fusion of separated layers of atheromatous arterial wall can be achieved with Nd-YAG laser irradiation. This concept may be useful in the treatment of arterial dissections.

Arteries↗
PubMed1985

Effects of thyroid hormone on calcium handling in cultured chick ventricular cells.

Mechanisms underlying thyroid hormone-induced changes in myocardial contractile state were investigated by studying the effects of triiodothyronine (T3) on Ca2+ fluxes across the sarcolemmal membrane and Ca2+ handling by the sarcoplasmic reticulum, using spontaneously contracting monolayers of cultured chick embryo ventricular cells. Cells were grown in serum-free medium containing either no T3 or 10(-8) M-T3 for 48 h. At [Ca2+]o levels of 0.6 and 1.2 mM, the velocity of cell contraction was significantly greater in cells grown in 10(-8) M-T3 than in its absence. At higher [Ca2+]o, no differences in the velocity of contraction were noted. 45Ca2+ exchange kinetic studies showed a biexponential pattern with a rapid and a slow component of uptake in cells grown both with and without 10(-8) M-T3. The rate of the rapid phase of uptake and total Ca2+ content were higher in cells grown in T3, with the increment in content ascribable to the rapidly exchangeable Ca2+ pool. Verapamil partially inhibited the T3-induced increase in the rapidly exchangeable pool. 45Ca2+ uptake in response to a step change to Na+-free medium in the presence of 1 microM-verapamil was significantly greater in cells grown in 10(-8) M-T3 than in T3-free medium. Cells grown in T3 showed 20% greater beating rate than cells grown in its absence. A similar increase in beating rate achieved by lowering [K+]o from 4.0 to 3.0 mM or by electrical stimulation failed to affect the rate of 45Ca2+ uptake or the size of the rapidly exchangeable pool; pacing-induced increases in rate resulted in reduction rather than augmentation of contractile state. Ca2+ efflux rate was greater in cells grown in 10(-8) M-T3 than in T3-free medium, whereas cells loaded with various levels of Ca2+ acutely by incubation at selected [Ca2+]o levels had similar efflux rates. Replacement of Na+ by choline in the efflux medium resulted in elevated Ca2+ efflux rates in cells grown both with and without T3; however, it remained greater in cells grown in 10(-8) M-T3 than in its absence. Caffeine (20 mM) in the efflux medium increased Ca2+ efflux to a greater degree in cells grown in T3 than without it. Caffeine also produced a greater tonic contraction in T3-treated cells than in cells grown in absence of T3 in Na+- and Ca2+-free medium.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Comparative recognition of left ventricular thrombi by echocardiography and cineangiography.

Studies performed in 47 patients, 11 of whom underwent surgery for aneurysmectomy and 36 of whom underwent cardiac transplantation, were reviewed to assess the diagnostic accuracies of cross sectional echocardiography and cineangiography in detecting left ventricular mural thrombi and the effect of anticoagulation treatment on the incidence of such thrombi. Cross sectional echocardiography in 37 patients and cineangiography in 26 (16 patients were examined by both methods) were analysed independently by sets of two observers experienced in the respective methods. All four observers were blinded to the pathological or surgical findings regarding mural thrombus. Mural thrombus was confirmed by pathological investigation in 14 of 47 (30%) cases; 11 of these 14 patients had intra-aneurysmal thrombi. The negative predictive value was quite good for both methods, but cross sectional echocardiography had a superior positive predictive value. This was due both to detailed soft tissue resolution by cross sectional echocardiography and to overdetection of mural thrombi by cineangiography in cases of aneurysms without mural thrombi. Mural thrombi were present in three of 20 patients with preceding anticoagulation and in 10 of 19 patients without anticoagulation. The results emphasise that cross sectional echocardiography is more reliable than cineangiography in recognising thrombi.

Adult↗
PubMed1985

Inotropic effect, binding properties, and calcium flux effects of the calcium channel agonist CGP 28392 in intact cultured embryonic chick ventricular cells.

CGP 28392 is a recently described dihydropyridine derivative with positive inotropic properties. To study the mechanism of action of this putative calcium channel agonist, we have related the effects of CGP 28392 on contraction (measured with an optical video system) and radioactive calcium uptake to ligand-binding studies in cultured, spontaneously beating chick embryo ventricular cells. CGP 28392 produced a concentration-dependent increase in amplitude and velocity of contraction (EC50 = 2 X 10(-7) M; maximum contractile effect = 85% of the calcium 3.6 mM response). Nifedipine produced a shift to the right of the concentration-effect curve for CGP 28392 without decreasing the maximum contractile response, suggesting competitive antagonism (pA2 = 8.3). Computer analysis of displacement of [3H]nitrendipine binding to intact heart cells by unlabeled CGP 28392 indicated a KD = 2.2 +/- 0.95 X 10(-7) M, in good agreement with the EC50 for the inotropic effect. CGP 28392 increased the rate of radioactive calcium influx (+39% at 10 seconds) without altering beating rate, while nifedipine decreased radioactive calcium influx and antagonized the CGP 28392-induced increase in calcium influx. Our results indicate that, in intact cultured myocytes, CGP 28392 acts as a calcium channel agonist and competes for the dihydropyridine-binding site of the slow calcium channel. In contrast to calcium channel blockers, CGP 28392 increases calcium influx and enhances the contractile state.

Animals↗
PubMed1985

Mechanisms of beta-adrenergic receptor regulation in cultured chick heart cells. Role of cytoskeleton function and protein synthesis.

To examine mechanisms by which cardiac tissue regulates the beta-adrenergic receptor and physiological response to beta-adrenergic agonists, we studied the effects of cytoskeletal disrupting agents and inhibition of protein synthesis on receptor properties and contractile response to isoproterenol in intact cultured ventricular cells from embryonic chick heart. Thirty minutes of exposure of intact cells to 1 microM isoproterenol produced loss of the high-affinity state (KD = 4.5 +/- 1.5 nM) of the receptor found in cell membranes with no loss of total receptor number, whereas there was concomitant decline in the contractile response to 1 microM isoproterenol to 41 +/- 16% (SD) of control. Contractile response recovered within 60 minutes of agonist removal to 78 +/- 11% of initial response. There was concomitant recovery of the high-affinity state of the receptor, so that 1 hour after agonist removal there was 72% of the initial proportion of high-affinity receptors. This desensitization of the contractile response, as well as recovery after agonist removal, was markedly blunted by preincubation with cytochalasin B so that contractile responsiveness to isoproterenol was maintained at 77 +/- 13% of the initial response. Colchicine (10 microM) was without effect on the first 30 minutes of agonist-induced desensitization. More prolonged agonist exposure (1 microM isoproterenol for 24 hours) produced colchicine-sensitive loss of receptors from intact cells to 40% of control levels. Full recovery of receptor number occurred over 72 hours; this was completely blocked by cycloheximide (P less than 0.01). Thus, rapid desensitization and resensitization of the beta-receptor-mediated contractile response is associated with alterations in high-affinity agonist binding and appears to be modulated by microfilaments. Receptor down-regulation is dependent on functional microtubules, and recovery of these receptors after agonist removal requires protein synthesis.

Adrenergic beta-Antagonists↗
PubMed1985

The efficacy and adequacy of continuous ambulatory peritoneal dialysis.

Since it was introduced in 1976, continuous ambulatory peritoneal dialysis (CAPD) has won acceptance in many centres and it is now regarded as an important alternative to haemodialysis. CAPD patients have comparable and, in some circumstances, better survival than those on chronic haemodialysis. It is indicated particularly in patients with diabetes mellitus, cardiovascular instability and at the extremes of life. The success of kidney transplantation is similar in those maintained on CAPD and on haemodialysis. CAPD also achieves satisfactory physical and psychological rehabilitation, and the quality of life, including the level of sexual function, is similar during CAPD and haemodialysis. Women on CAPD menstruate more often than those on haemodialysis. CAPD provides adequate clearance of metabolic wastes, maintains fluid balance and ameliorates neurotoxic cognitive dysfunction. CAPD gives control of hypertension and anaemia which is superior to that on haemodialysis. Neuropathy remains stable but osteitis fibrosa seems to progress. CAPD is the most economical of the various forms of dialysis. We conclude that CAPD is an adequate form of replacement and should be made available in every nephrology centre providing treatment for patients with end-stage renal disease.

Adolescent↗