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Biomedical subjects

S K Hong

Publications and source records attributed to S K Hong.

At least 163 records · Page 9Linked to original sources
PubMed1987

Seadragon VI: a 7-day dry saturation dive at 31 ATA. VII. Erythrocyte functions.

Organic phosphates and the Donnan ratio (cell to plasma Cl ratio) were measured in man during a dry saturation dive to 31 ATA for 7 d. 2,3-DPG increased significantly with a concomitant decrease in ATP and the molar ratios of ATP and ADP on Day 5 at 31 ATA (P less than 0.05). Inorganic phosphate did not change during the dive. The Donnan ratio was relatively high at 31 ATA and the value was significantly different on Day 3 at 31 ATA (0.731 at 1 ATA vs. 0.895 at 31 ATA, P less than 0.05). This suggests a rise in intracellular pH, resulting from a change in the net charge of hemoglobin. It is speculated that an increase in oxygen affinity of hemoglobin occurs during the early phase at 31 ATA and is followed by an increase in 2,3-DPG in response to the resulting tissue hypoxia.

Adenosine Diphosphate↗
PubMed1987

Seadragon VI: a 7-day dry saturation dive at 31 ATA. VIII. Plasma enzyme profiles.

This report summarizes serum profiles of liver enzymes of divers during 2 dry saturation dives to 31 ATA. In both dives, serum glutamic pyruvic transaminase (SGPT), serum glutamic oxaloacetic transaminase (SGOT), and alkaline phosphatase were significantly elevated at 31 ATA when compared to predive control levels. SGPT and SGOT levels returned to control levels during the postdive period. These data provide strong evidence for compromised liver function at high pressure and are consistent with similar observations in other saturation dives. The reason for the parenchymal dysfunction at high pressure remains unknown.

Adult↗
PubMed1986

Effect of ethanol on organic ion transport in rabbit kidney.

The effect of ethanol on the transport of organic ions in rabbit kidney cortical slices was studied. Ethanol at a concentration of 4 to 10% (v/v) reversibly inhibited the slice uptake of the organic anion, p-aminohippurate (PAH), in a dose-dependent manner, but had no significant effect on that of the organic cation, tetraethylammonium (TEA). Overall, the inhibitory effect on PAH uptake increased with the length of the hydrocarbon chain, with an I50 of 7.7, 0.9, and 0.05% for ethanol, butanol, and heptanol, respectively. The efflux of PAH was significantly decreased in the presence of 8% ethanol. Kinetic analysis indicated that ethanol decreased Vmax without a significant change in Km. Lowering the Na concentration in the incubation medium from 130 to 20 mM resulted in a disappearance of the above described inhibitory effect of ethanol on PAH uptake. Although Na-K-ATPase activity of renal cortical microsomes was significantly inhibited by ethanol (6-10%), butanol (1%), and heptanol (0.1%), there was no clear correlation between the effects of alcohols on PAH transport and/or Na-K-ATPase. Nevertheless, the results suggest that ethanol inhibits reversibly the Na-dependent transport of PAH from the medium into the cell across the basolateral membrane through a mechanism yet to be elucidated. The high degree of correlation between I50 and the partition coefficients of the alcohols suggested that their interaction with membrane lipids is important for the inhibition of PAH uptake, and also that PAH (but not TEA) transport is affected by alteration of the lipid environment of the membrane.

1-Butanol↗
PubMed1986

Plasma volume changes during head-out water immersion in conscious dogs.

Blood volume (51Cr-erythrocyte dilution method), hematocrit, and arterial (Pa), central venous (Pv), plasma colloid osmotic (IIpl), and interstitial fluid hydrostatic (Pcps, Guyton's capsule method) pressures were measured continuously to determine the kinetics of the transvascular fluid shift during 100 min of water immersion (WI) at 37 degrees C in six splenectomized dogs. Urine flow increased by 180% above control levels (P less than 0.05) by 30 min of WI. Plasma volume (PV) started to increase at 5 min of WI and rose by 7.2% (P less than 0.05) above control levels by 35 min of WI, and then it decreased gradually. PV returned to control levels immediately after WI. Plasma protein concentration and IIpl decreased significantly by 0.2 g/100 ml and 1.2 mmHg, respectively, at 35 min of WI, while plasma osmolality and Na+ concentration were constant. Pa and Pv increased (P less than 0.05) by 25 and 12 mmHg, respectively. Mean capillary pressure, which was calculated from Pa, Pv, and an estimated pre-to-postcapillary resistance ratio of 5-12, increased by 13-14 mmHg while Pcps increased (P less than 0.05) by 17 and 26 mmHg at upper hindlimb and lower forelimb, respectively. The changes in mean capillary pressure and IIpl tend to promote capillary filtration in WI; however, the greater elevation of Pcps more than offsets these forces and leads to a net transvascular shift into the plasma compartment.

Animals↗
PubMed1986

Atrial natriuretic factor and renal function during head-out water immersion in conscious dogs.

The potential role of atrial natriuretic factor (ANF) in the renal response to head-out water immersion (WI) was studied. Five female mongrel dogs, trained to stand for 100 min in air followed by 100 min of thermoneutral WI at 37 degrees C or 200 min in air (timed control, TC), were chronically instrumented with arterial and venous catheters. The animals were hydrated with a volume of 0.45% NaCl solution equivalent to 2% of their body weight. Prehydration levels of arterial ANF were 243 +/- 15 (SE), and venous ANF levels were 211 +/- 21 pg/ml. WI resulted in an increase in urine flow from 0.7 +/- 0.1 ml/min to a peak flow of 2.2 +/- 0.3 ml/min (P less than 0.05). On immersion, plasma venous and arterial ANF levels increased significantly by 29 and 21% from the preimmersion values of 183 +/- 14 and 222 +/- 20 pg/ml, respectively. The arterial-venous difference for plasma ANF was maintained at 35 +/- 14 pg/ml (P less than 0.05) during WI; therefore venous sampling may suffice as a measure of circulating ANF levels. Sodium excretion increased linearly during WI to a peak value of 228 +/- 32 mu eq/min from a base line of 52 +/- 12 mu eq/min (P less than 0.05). These data indicate that peripheral tissues extract ANF and that WI is a physiological stimulus for the release of ANF. However, the time course and magnitude of the changes in plasma ANF and urine sodium excretion during WI are not comparable, and other mechanisms are likely responsible for the WI natriuresis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Cardiorenal-endocrine responses to head-out immersion at night.

Cardiorenal-endocrine responses to 3-h head-out immersion (HOI) (water temperature = 34.5 +/- 0.5 degrees C) were studied during day (0900-1400 h) and night (2300-0400 h) in six hydropenic male human subjects. Although HOI induced a reversible increase in urine flow in all subjects, the response was faster and greater in magnitude during the day compared with night (P less than 0.05). Na excretion and osmolal clearance (Cosm) also followed the identical response pattern as urine flow, and in fact, the HOI-induced diuresis was entirely accounted for by the increased Cosm. Endogenous creatinine clearance was not different between the day and the night and remained unchanged during HOI. Both plasma renin activity and aldosterone concentration and urinary aldosterone excretion were nearly twofold greater during the day compared with night before HOI but decreased to the same level during HOI in both daytime and the nighttime series (P less than 0.05). There was no correlation between the Na excretion rate and renin-aldosterone levels either before or during HOI. Plasma antidiuretic hormone (ADH) level was comparable between day and night before HOI and decreased to a similar level during HOI in both daytime and nighttime series (P less than 0.05 for nighttime HOI). Cardiac output increased from 3.3 1/min before HOI to 5-6 1/min during HOI without showing any significant circadian difference. Hematocrit, hemoglobin, and plasma concentrations remained unchanged under all conditions. It is concluded that the renal response to HOI is subject to nocturnal inhibition, which cannot be attributed to circadian differences in the degree of HOI-induced central blood pooling, renin-aldosterone, or ADH responses.

Adult↗
PubMed1986

Fluid conservation in athletes: responses to water intake, supine posture, and immersion.

The roles of antidiuretic hormone (ADH) and aldosterone in the elicited diuretic responses of trained and untrained men to seated, supine, and head-out water immersed conditions were studied. Volunteers were comprised of groups of six untrained individuals, six trained swimmers, and six trained runners. Each subject underwent three protocols, six hours in a seated position, supine position, or immersion (35 degrees C water). The last two protocols were preceded and followed by 1 h of seated position. After 10 h of fasting, 0.5% body wt of water was drunk. One hour later the trained groups had higher urine osmolalities (P less than 0.05) and urinary excretion rates of ADH (P less than 0.05) and lower urine flow rates (P less than 0.05) than untrained subjects. Throughout the sitting protocol, urinary ADH was also higher in both trained groups (P less than 0.05). Both supine posture and immersion resulted in significant decreases in urinary ADH in the untrained subjects (P less than 0.05) but no changes wer noted in swimmers and only during the second hour of immersion in the runners (P less than 0.05). The natriuresis and kaliuresis were greater during immersion than in the supine position but plasma renin activity, measured only in trained groups, and plasma aldosterone, measured in the untrained group, were decreased similarly with both protocols. The increases in urinary sodium excretion and urine flow rate were lower in trained than untrained subjects during the supine and immersion protocols (P less than 0.05). The data are compatible with an increased osmotic but decreased volume sensitivity of ADH control in trained men.

Adult↗
PubMed1986

Energetics of wet-suit diving in Japanese male breath-hold divers.

The present study was undertaken to investigate energy balance in professional male breath-hold divers in Tsushima Island, Japan. In 4 divers, rectal (Tre) and mean skin (Tsk) temperatures and rate of O2 consumption (VO2) were measured during diving work in summer (27 degrees C water) and winter (14 degrees C water). Thermal insulation and energy costs of diving work were estimated. In summer, comparisons were made of subjects clad either in wet suits (protected) or in swimming trunks (unprotected), and in winter, they wore wet suits. The average Tre in unprotected divers decreased to 36.4 +/- 0.2 degrees C at the end of 1-h diving work, but in protected divers it decreased to 37.2 +/- 0.3 degrees C in 2 h in summer and to 36.9 +/- 0.1 degree C in 1.5 h in winter. The average Tsk of unprotected divers decreased to 28.0 +/- 0.6 degrees C in summer and that of protected divers decreased to 32.9 +/- 0.5 degrees C in summer and 28.0 +/- 0.3 degrees C in winter. Average VO2 increased 190% (from 370 ml/min before diving to 1,070 ml/min) in unprotected divers in summer, but in protected divers it rose 120% (from 360 to 780 ml/min) in summer and 110% (from 330 to 690 ml/min) in winter. Overall thermal insulation (tissue and wet suit) calculated for protected divers was 0.065 +/- 0.006 degree C X kcal-1 X m-2 X h-1 in summer and 0.135 +/- 0.019 degree C X kcal-1 X m-2 X h-1 in winter.(ABSTRACT TRUNCATED AT 250 WORDS)

Acclimatization↗
PubMed1986

Lack of interaction between atrial natriuretic factor and renal organic anion transport system.

The aim of the present investigation was to test the hypothesis that atrial natriuretic factor (ANF) is secreted into the proximal tubule lumen by the organic anion transport mechanism. The rationale for this hypothesis was the reported probenecid attenuation of the natriuretic effect of ANF. Probenecid is widely regarded as an inhibitor of organic acid transport in the proximal tubule. ANF was prepared in varying degrees of purity ranging from a relatively crude extract to a highly purified form. A commercially available form was also used. All forms were bioassayed using the anesthetized rat and a diuresis and natriuresis was observed in each case which was comparable to literature reports. Interaction of ANF with the organic acid transport system was evaluated using the renal cortical slice technique. Over a wide range of concentrations, there was no effect of ANF on cortical slice accumulation of either p-aminohippurate (PAH), the classical substrate of the organic anion transport system or tetraethylammonium (TEA), a typical organic cation. It is concluded that although ANF may indeed exert its effect at the luminal membranes of the nephron, access to the lumen is not mediated by the organic cation or anion transport system in the proximal tubule.

Aminohippuric Acids↗
PubMed1986

Ionic basis of short-circuit current in toad skin at high hydrostatic pressure.

The toad skin and urinary bladder are widely used for the study of water and Na+ transport under high pressure. These tissues can be mounted in Ussing type chambers and ion transport can be measured by evaluating electrical properties of the preparation, e.g., short-circuit current (Isc). The tacit assumption in these experiments is that the preparation behaves in the same manner at high pressure as at 1 ATA; namely, that net Na+ flux is equivalent to Isc. The purpose of the experiments described here was to test that assumption. Toad skins were mounted in an Ussing chamber and Isc was measured as an index of active net Na+ transport under hydrostatic pressures up to 100 ATA. The chamber was modified so that isotopic Na+ flux from the mucosal to serosal compartments could be measured in conjunction with Isc, without decompression. A linear regression of JNa+ms on Isc was computed and found to be described by the equation, JNa+ms = 3.83 + 0.83 Isc; n = 18; r = 0.92. The slope of the line was not significantly different from unity. No correlation was made for JNa+sm because of the difficulty in measuring JNa+sm and JNa+ms in the same skin simultaneously. Independent measurement of JNa+sm demonstrated that this flux accounted for less than 2% of JNa+net. In a second set of experiments, the influence of amiloride on Isc with and without pressure was tested. 10(-4) M amiloride abolished Isc under both circumstances. It is concluded that Isc can be wholly accounted for by net Na+ flux under pressures up to 100 ATA.

Amiloride↗
PubMed1986

Cardiac output by impedance cardiography during head-out water immersion.

This study was undertaken to ascertain the suitability of impedance cardiography for qualifying cardiac output during water immersion where the electrodes were wet. The cardiac output was compared during wet and dry immersion with the head above water by breath holding briefly at 3 lung volumes. For dry immersion, the subjects were protected from contacting water during immersion by enveloping the whole body in a thin plastic bag. For wet immersion, the subject went into the water wearing only trunks. Eleven healthy males served as subjects. Both basal thoracic impedance and the minimum rate of impedance change decreased during wet immersion. These changes were specific, which insignificantly influenced the computation of stroke volume as compared to dry immersion. Our results showed no statistical differences between wet and dry immersions, and between measurements made at total lung capacity functional residual capacity, or residual volume. It is concluded that impedance cardiography is applicable directly in wet conditions without having to protect the subject from getting wet.

Adult↗
PubMed1985

Hyperbaric diuresis and nocturia--a review.

Human divers are now able to engage in a multi-day dive to a considerable depth using the mixed gas saturation diving technique, however their daily activities are somewhat limited in the depth. One of the major problems that has not been generally appreciated is the potential for body fluid disturbances at high pressure due to the development of a sustained diuresis. In addition, a marked nocturia has been observed in recent saturation dives at 26-31 atmospheres absolute (ATA), which disturbs divers' sleep during the night. In this review, we will briefly discuss the basic characteristics and mechanisms of these disturbances of renal functions observed during hyperbaric exposure.

Adult↗
PubMed1985

Cardio-renal responses to a stimulated gravity-free state induced by water immersion.

HOI induces a significant increase in the cardiac output, which is accompanied by increases in the urinary excretion of water, Na and K. However, the renal responses are not always associated with the cardiac response, suggesting a possible dissociation of two events. Although the urinary excretion of both ADH and aldosterone decreases during HOI, the mechanism for these changes is not clearly understood. The renal responses to HOI, especially the natriuresis, is considerably attenuated in endurance-trained athletes, which may be related to the more moderate inhibition of both ADH and renin-aldosterone systems. The exact role of the cardiac receptors in inducing the renal responses to HOI is still not defined, although the latter receptors are involved in inducing the natriuresis. Finally, important diurnal variations have been demonstrated for the renal responses to HOI, and elucidation of the mechanism for this interesting phenomenon may help understand the overall mechanisms for the development of cardiorenal-endocrine responses to HOI.

Aldosterone↗
PubMed1985

Proximal tubule function in chronic serum sickness glomerulonephritis of rats.

Fatal immune complex glomerulonephritis can be induced in rats by chronic intravenous administration of bovine serum albumin. There are three distinct stages, mild, moderate, and severe, in the development of renal immunopathology and pathophysiology in this model of chronic serum sickness. The work described here was undertaken to evaluate aspects of proximal tubule function in those different stages. Tissue water distribution, oxidative metabolism, and transport of representative organic anions and cations were measured in renal cortical slices. In mild chronic serum sickness all functions were normal except the transport of p-aminohippurate (PAH, organic anion), which was significantly decreased. This decrease appeared to be attributable to immunization with Freund's adjuvant. In the moderate stage of chronic serum sickness, proximal tubule functions and morphology appeared essentially normal. Only Na-K-ATPase activity was somewhat lower than in controls. However, proximal tubule dysfunction was a feature of severe chronic serum sickness. A significant inhibition of anion and cation transport was observed. Reduction in transport functions occurred together with impaired oxidative metabolism and severe reduction in Na-K-ATPase activity. Abnormalities of mitochondrial structure, a decrease in number of mitochondria, and a significant increase in intracellular H2O content provided additional evidence of degenerative changes in proximal tubule cells during the severe stage of chronic serum sickness. It was concluded that decreased transport of organic ions by the basolateral membrane in proximal tubules of rats with severe chronic serum sickness resulted from a breakdown in the metabolic machinery of the tubule epithelium rather than a specific injury to organic ion transport systems.

Animals↗
PubMed1985

Renal transport of gossypol in the rabbit.

The present work was carried out to investigate the transport characteristics of gossypol, a toxic weak organic acid (pK = 7.2) contained in cottonseed, into the rabbit renal cortical slice. The uptake of gossypol increased linearly during a 2-hr incubation after which it leveled off with the average slice-to-medium concentration ratio (S/M) slightly above 20. In the presence of metabolic inhibitors, the S/M gossypol leveled off at about 9, suggesting an extensive binding of gossypol to tissue proteins. The uptake of gossypol was significantly inhibited by p-aminohippurate (PAH), probenecid, ouabain, and DIDS, all of which are known inhibitors of renal organic anion transport. However, the gossypol uptake was not affected by tetraethylammonium (TEA), a prototypical organic cation. Kinetic studies indicated that the apparent Km for gossypol transport is 0.28 mM, and also that probenecid inhibits gossypol transport in a competitive manner. It is concluded that gossypol is transported by the renal tubule through the classic organic anion system.

2,4-Dinitrophenol↗
PubMed1985

Impaired organic ion transport in proximal tubules of rats with Heymann nephritis.

Organic ion transport across the basolateral membrane of proximal tubules was measured by means of the tissue slice technique in each of the four different stages of Heymann nephritis. Impairment of both organic anion and cation transport was detected early in Stage 2, and became more severe in Stage 3 of Heymann nephritis. The decreased transport function was associated with extensive damage to proximal tubule cells, including loss of brush border microvilli and basal infoldings. Despite these abnormalities of structure and function, oxygen consumption of proximal tubule cells remained essentially normal. Partial recovery of organic cation transport was noted late in Heymann nephritis (Stage 4). Recovery of the cation transport function was associated with a partial restoration of brush border microvilli and basal infoldings to proximal tubule cells. However, organic anion transport remained depressed throughout the entire course of disease. Impairment of organic ion transport in rats with Heymann nephritis appeared to result from damage to basolateral membrane transport elements rather than general deterioration of the metabolic machinery of proximal tubule cells. Decreased organic cation transport appeared to be the consequence of a reduction in the number of carrier sites, a phenomenon that could have resulted from decreased membrane surface area. However, the depression of organic anion transport was associated with decreased substrate affinity of the anion carrier, indicating that qualitative, rather than quantitative changes, were primarily responsible for that defect. Specific antibody-mediated damage to the anion transport elements in basolateral membranes of proximal tubules is postulated to occur in Heymann nephritis.

Adjuvants, Immunologic↗