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Biomedical subjects

S K Hong

Publications and source records attributed to S K Hong.

At least 145 records · Page 8Linked to original sources
PubMed1988

Atrial natriuretic factor during head-out immersion at night.

The present investigation was undertaken to test the hypothesis that a circadian variation in the atrial natriuretic factor (ANF) response is responsible for the nocturnal inhibition of renal responses to head-out immersion (HOI). Plasma ANF responses to a 3-h HOI (water temperature 34.5 +/- 0.5 degrees C) were studied during day (1000-1300) and night (2400-0300) in six hydropenic male human subjects. In agreement with the previous observations, the renal responses, especially the diuresis, to HOI were attenuated at night compared with the day; furthermore, plasma renin activity decreased to the same low level during HOI at both day and night. Plasma ANF during time control periods was 30-40 pg/ml without showing any circadian variation. Moreover, plasma ANF showed a similar twofold increase within 1 h of HOI and was maintained at this elevated level throughout the 3-h HOI period in both the daytime and the nighttime series. On termination of HOI, plasma ANF decreased linearly to the pre-HOI level within 1 h. Hematocrit during time control periods was higher during the day compared with the night (P less than 0.05). Although HOI appears to induce a transient increase in plasma volume (as indicated by decreases in hematocrit) during the 1 h of HOI, the magnitude of the decrease in the latter parameters was not different between day and night. It is concluded that nocturnal inhibition of renal responses to HOI cannot be fully accounted for by circadian differences in the ANF and fluid shift response to HOI.

Adult↗
PubMed1988

Altered heart rate-arterial pressure relation during head-out water immersion in conscious dog.

The influence of head-out water immersion (WI) (37 degrees C) on baroreflex control of heart rate was studied in five trained, instrumented, conscious dogs. Arterial pressure was raised and lowered using occluder cuffs implanted around the aorta and inferior vena cava. Function curves relating transmural systolic arterial pressure (TSAP = systolic arterial pressure-pleural pressure) to heart rate (HR) were constructed to compare responses in air and during WI. The resting TSAP in air [142 +/- 8 mmHg (mean +/- SE) at 78 +/- 6 beats/min] increased significantly during WI (161 +/- 9 mmHg at 109 +/- 9 beats/min). During WI, the saturation TSAP at the bradycardia plateau of the relation increased significantly, by 19 mmHg, whereas the average gain (slope) of the relation decreased significantly, from -1.426 to -0.752 beats.min-1.mmHg-1. Therefore, WI elicits both a resetting and a decrease of the average gain of the TSAP-HR relation. The heart rate range increased during WI as well. After cholinergic blockade with atropine, WI did not elicit a resetting of the relation and the change in average gain was abolished. However, after beta 1-blockade with metoprolol, the resting TSAP increased significantly during WI and resetting persisted, but the decrease of average gain was abolished. Therefore, the alteration of the TSAP-HR relation in WI is achieved via a modulation of both adrenergic and cholinergic regulation of HR.

Animals↗
PubMed1988

Hormonal and electrolyte responses of conscious sheep to 96 h of hypoxia.

Hypoxia alters the relationship of aldosterone secretion to plasma renin activity. The potential role plasma electrolytes play in this modification is not clear. This study analyzed the interrelationships among renin, aldosterone, vasopressin (ADH), and plasma electrolytes during 96 h of normobaric hypoxia. Eight ewes were exposed, in discrete experiments, to hypocapnic hypoxia [arterial O2 tension (PaO2) 37-42 mmHg, arterial CO2 tension (PaCO2) 26-28 mmHg] and eucapnic hypoxia (PaO2 40-43 mmHg, PaCO2 28-31 mmHg) by N2 dilution in an environmental chamber. Urine output (24 h) was measured, and arterial plasma samples were collected during the normoxic control period and at 24-h intervals of hypoxia. Plasma Na+, K+, renin, and ADH levels did not change from the normoxic values during either hypocapnic or eucapnic hypoxia. However, urinary aldosterone excretion [critical significance (alpha) less than 0.046] and K+ excretion (alpha less than 0.046) decreased markedly during each type of hypoxia. All sheep developed a pronounced negative K+ balance by 96 h of hypoxia. These data suggest that plasma K+ concentration is preserved by movement of K+ out of the intracellular compartment; this change in K+ distribution may inhibit aldosterone secretion during hypoxia.

Aldosterone↗
PubMed1988

Effect of wearing gloves on the thermal balance of Korean women wet-suit divers in cold water.

Effect of wearing neoprene gloves on the thermal exchanges of wet-suited divers was studied in 8 Korean diving women. Subjects, clad with 5-6-mm-thick neoprene wet suits (jacket, pants, and boots) either with or without wearing 3-mm-thick neoprene gloves, were immersed for 3 h in water of critical temperature (17.3 degrees +/- 0.8 degree C) while the rectal and skin (chest, leg, arm, and hand) temperatures and oxygen consumption were measured. Overall thermal insulation of the subject plus suit was calculated from the rectal-to-water temperature difference divided by the estimated rate of skin heat loss. The skin heat loss was assumed to equal metabolic heat production minus respiratory heat loss, corrected for changes in heat storage when mean body temperature changed. All measurements were carried out in a resting condition. During the 3rd h of immersion, the rectal temperature was lower with gloves (delta Tre = 0.30 degree +/- 0.04 degree C; P less than 0.05) whereas metabolic heat production was not significantly different. Consequently, the total thermal insulation was nearly 16% lower with gloves than without gloves. In both the hands and forearms, the regional heat flux determined directly using a heat flux transducer was higher and the thermal insulation index was lower with gloves than without gloves. These results indicate that in wet-suited subjects resting in cold (17 degrees C) water gloves do not provide additional protection against heat loss, but rather decrease the efficiency of thermoregulatory mechanisms. We suggest that sensory input from cold receptors in the distal extremities is particularly important in thermoregulation during immersion in cold water.

Adult↗
PubMed1987

Renal effects of atrial natriuretic factor in domestic fowl.

The renal hemodynamic and tubular effects of ANF were investigated using the Sperber technique in chickens. This technique takes advantage of the unique portal circulation of the avian kidney and permits direct access to the renal peritubular space independent of renal arterial blood flow and glomerular filtration. Infusion of ANF into the avian renal portal system increased urine flow rate and sodium excretion by as much as 300% and 100%, respectively. These changes occurred in the absence of significant alterations in glomerular filtration rate or renal plasma flow. There was no significant difference in urine flow, sodium excretion or glomerular filtration rate between the ANF-infused kidney and the contralateral, non-infused kidney. We conclude that the diuretic and natriuretic effects of ANF do not depend on changes in glomerular filtration rate and that the site of action of ANF is the renal medulla.

Animals↗
PubMed1987

Deglycosylation of a native, protease-sensitive glycoprotein by peptide N-glycosidase F without protease inhibitors.

The glycoprotein fibrinogen was deglycosylated in its native state and in the absence of protease inhibitors by peptide N-glycosidase F following removal of protease contaminants from the enzyme by HPLC. Fibrinogen is sensitive both to proteolysis by contaminants which may constitute as little as 0.2% of the enzyme protein and to denaturation by 1,10-o-phenanthroline, the only substance known to inhibit the proteolysis. Thus removal of protease contaminants from the enzyme is a prerequisite for the deglycosylation of native fibrinogen. The starting material for the present method is the final material obtained from the purification described by A. L. Tarentino, C. M. Gomez, and T. H. Plummer (1985, Biochemistry 24, 4565). Three sequential passages over a PolyCAT A (20 X .46 cm) cation-exchange column and elutions with a linear gradient of NaCl from 0 to 0.4 M were necessary to completely overcome the tenacious but noncovalent association of peptide N-glycosidase F with contaminants that proteolyze fibrinogen. All three chromatographic runs could be completed in 1 day. Using this "protease-free" enzyme at up to a 1:20 molar ratio, fibrinogen that is completely deglycosylated and native has been generated in order to determine the role of the carbohydrate moieties in its function.

Amidohydrolases↗
PubMed1987

Thoracic duct lymph flow during head-out water immersion in conscious dogs.

Water immersion (WI) increases plasma volume in awake dogs. The contribution of lymph flow to this fluid shift was studied in six splenectomized conscious dogs with a side fistula of the thoracic duct. Lymph flow, hematocrit (Hct), and plasma (CP) and lymph (CL) protein concentration were measured during 60 min in air and 120 min of WI (37 degrees C). Lymph flow in air averaged 0.96 +/- 1.0 (SE) ml/min. Lymph flow tended to decrease immediately in WI and was maintained at a level averaging 0.66 ml/min. CP/CL did not change significantly, whereas Hct fell significantly by 1.51 +/- 0.2% (Hct units) at 40 min of WI. Urine flow increased significantly to a maximum value of 1.5 +/- 0.5 ml/min at 40-60 min of WI compared with a mean value in air of 0.3 +/- 0.1 ml/min. The Hct and urine flow responses indicate that fluid shifted into the intravascular space during WI. Since lymph flow tended to decrease, the fluid shift in WI occurs across the capillary wall and not via lymphatic channels.

Animals↗
PubMed1987

Extracellular fluid and plasma volumes during water immersion in nephrectomized dogs.

Extracellular fluid volume (ECF, [125I]iothalamate space), blood volume (BV, 51Cr-labeled erythrocyte space), and hematocrit were measured continuously to study the kinetics of fluid movements between intracellular, interstitial, and plasma compartments during water immersion (WI) at 38 degrees C in seven splenectomized and acutely nephrectomized dogs. ECF and plasma volume (PV) increased linearly during WI by 10 +/- 2 ml/kg (4% of initial ECF volume, P less than 0.05) and 12 +/- 2 ml/kg (33% of initial PV, P less than 0.05), respectively, above the control level by 120 min of WI. We estimate that 83% of the fluid entering the intravascular compartment is derived from the intracellular space at 120 min of WI. The results of this study indicate that WI leads to a sustained fluid movement of intracellular fluid toward the intravascular compartment. The increase in interstitial hydrostatic pressure (wick method) by 28.5 mmHg from the control level at 5 min of WI in response to the external water pressure exceeds the increase in mean capillary pressure by 10-11 mmHg relative to the control level. We postulate that this negative hydrostatic pressure gradient across the capillary wall leads to an increase in PV during WI.

Animals↗
PubMed1987

Role of cardiac nerves in response to head-out water immersion in conscious dogs.

The circulatory, renal, and hormonal responses during 100 min of thermoneutral (37 degrees C) head-out water immersion (WI) were investigated in conscious intact (INT) and cardiac-denervated (CD) dogs. In the INT group, both left and right atrial and aortic transmural distending pressures and left ventricular contractile performance (LV dP/dtmax) increased, and total peripheral resistance remained unchanged. Cardiac output (QCO) increased in association with an increase in heart rate and LV dP/dtmax. Urine flow (V), sodium excretion (UNaV), and osmolal clearance (Cosmol) all increased, whereas glomerular filtration rate, as indicated by creatinine clearance (CCr), remained constant. The diuresis and natriuresis occurred in the absence of any significant changes in plasma levels of antidiuretic hormone (ADH), aldosterone, or plasma renin activity. The CD animals showed a similar hemodynamic response except that the increase in QCO was now associated with an increase in stroke volume and no change in heart rate or LV dP/dtmax. Although the increase in V was similar in both magnitude and time course of the INT animals, there was no significant change in UNaV. Thus there is a striking change in the character of the response of the denervated group in that the natriuresis is abolished and, instead, a water diuresis occurred. Free water clearance increased, but no significant changes in Cosmol or CCr were observed. In addition plasma ADH levels significantly declined during WI in the CD group. These data indicate that cardiac receptors are important in determining the nature of the renal response to WI.

Animals↗
PubMed1987

Regional circulatory responses to head-out water immersion in conscious dogs.

We determined the regional blood flow responses to head-out water immersion (WI) in intact (INT) and cardiac-denervated (CD) conscious dogs. Immersing dogs in thermoneutral water (37 degrees C) in the quadruped position for 100 min resulted in significant increases in cardiac output (Qco) above control values by 38.7% in the INT dogs and 39.2% in the CD dogs (P less than 0.01). Arterial pressure increased by 32 and 34.7% in the INT and CD groups, respectively, during WI, with no significant changes occurring in the calculated total peripheral resistance. Regional blood flow responses were measured with 15-microns radiolabeled microspheres. Flows in the INT and CD groups increased significantly to the heart (40, 38%), skin (93, 96%), fat (79, 83%), diaphragm (44, 48%), and intercostal muscles (58, 55%), whereas there were no changes in renal cortical blood flows during WI. Total brain blood flows did not change significantly on immersion; however, blood flows in both INT and CD animals were increased to the cerebellum (19, 22%), but a significant decrease in pituitary flow (52%) was observed only in the CD group during WI. Gastrointestinal tissue flows increased only during early WI in both INT (45%) and CD (47%) animals. However, blood flows to the skeletal muscles increased only during late WI in the INT (53%) and CD (47%) groups. There were no significant differences between the INT and CD groups. Rectal temperatures and systemic O2 consumption (VO2) were unchanged during WI in both groups of animals. These observations indicate that WI leads to a sustained elevation of Qco accompanied by selective increases in regional tissue perfusion that may be accounted for in some tissues by an increase in metabolic demand or by local heating responses and produces a time-dependent redistribution of blood flow away from the gastrointestinal tissues toward skeletal muscle tissues, which may be due to a partial uncoupling of the normal Q/VO2 relationship. This may be caused by thermal or central neurohumoral mechanisms. These regional circulatory responses are not dependent on the presence of the cardiac nerves.

Animals↗
PubMed1987

Changes in thermal insulation during underwater exercise in Korean female wet-suit divers.

The present work was undertaken to examine the effect of wet suits on the pattern of heat exchange during immersion in cold water. Four Korean women divers wearing wet suits were immersed to the neck in water of critical temperature (Tcw) while resting for 3 h or exercising (2-3 met on a bicycle ergometer) for 2 h. During immersion both rectal (Tre) and skin temperatures and O2 consumption (VO2) were measured, from which heat production (M = 4.83 VO2), skin heat loss (Hsk = 0.92 M +/- heat store change based on delta Tre), and thermal insulation were calculated. The average Tcw of the subjects with wet suits was 16.5 +/- 1.2 degrees C (SE), which was 12.3 degrees C lower than that of the same subjects with swim suits (28.8 +/- 0.4 degrees C). During the 3rd h of immersion, Tre and mean skin temperatures (Tsk) averaged 37.3 +/- 0.1 and 28.0 +/- 0.5 degrees C, and skin heat loss per unit surface area 42.3 +/- 2.66 kcal X m-2 X h. The calculated body insulation [Ibody = Tre - Tsk/Hsk] and the total shell insulation [Itotal = (Tre - TW)/Hsk] were 0.23 +/- 0.02 and 0.5 +/- 0.04 degrees C X kcal-1 X m2 X h, respectively. During immersion exercise, both Itotal and Ibody declined exponentially as the exercise intensity increased. Surprisingly, the insulation due to wet suit (Isuit = Itotal - Ibody) also decreased with exercise intensity, from 0.28 degrees C X kcal-1 X m2 X h at rest to 0.12 degrees C X kcal-1 X m2 X h at exercise levels of 2-3 met.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Effect of head-out immersion on plasma atrial natriuretic factor in man.

This study was conducted to examine the role of atrial natriuretic factor (ANF) in the development of diuresis and natriuresis in response to the head-out immersion in 35 degrees C water. Six male subjects were hydrated (0.5% body wt), sat for 1 hr in air (preimmersion), were immersed in water to the neck for 3 hr, and then sat for 1 hr in air (postimmersion). In another series they were similarly hydrated and then sat for 5 hr in air for the time control. Urine and venous blood samples were collected hourly for creatinine and electrolyte measurements. In addition, the concentration of ANF was determined in unextracted plasma by a radioimmunoassay. The pattern of electrolyte excretion was evaluated on the basis of fractional excretion of filtered load. In the time control series, urine flow and fractional excretion of Na and K remained low throughout the 5-hr experimental period. On the other hand, urine flow increased significantly from the preimmersion level of approximately 2 to approximately 7 ml/min during the first hour of immersion (P less than 0.05), after which it decreased to approximately 5 ml/min during the second hour of immersion (P less than 0.05) and to approximately 2 ml/min during the third hour of immersion. Fractional excretion of Na increased continuously from preimmersion level of approximately 1.0 to approximately 1.8% during the second and third hours of immersion (P less than 0.05) and then decreased to 1.2% during the 1-hr postimmersion period. The plasma ANF remained low (approximately 75 pg/ml) during the 5-hr time control period. In the immersion series, plasma ANF increased significantly from the preimmersion level of approximately 80 to approximately 120 pg/ml during the entire 3-hr immersion period and then returned to the preimmersion level during 1 hr postimmersion. These results indicate that the immersion diuresis and natriuresis are indeed associated with the increased ANF release. However, it can not be ascertained from the present study if the increased ANF contributes directly to these renal responses to immersion or in concert with other mediators.

Atrial Natriuretic Factor↗
PubMed1987

Seadragon VI: a 7-day dry saturation dive at 31 ATA. III. Alterations in basal and circadian endocrinology.

Four male divers were exposed to an environment of 1 ATA air for 7 d, followed by 7 d of 31 ATA He-O2, and following decompression to a postdive 1 ATA air environment for 3 d. Urine and blood were collected for hormonal measurements. Divided 24-h urine collections were obtained during 3 consecutive d at predive 1 ATA conditions, and at 31 ATA conditions. Two consecutive day collections were obtained at early decompression (31-25 ATA), at late decompression (14-8 ATA), and at postdive 1 ATA. Two blood samples were obtained, at predive 1 ATA, at 31 ATA, and at postdive 1 ATA. Plasma antidiuretic hormone (ADH) concentration decreased about 45% (P less than 0.005), while plasma aldosterone concentration and urinary aldosterone excretion were doubled (P less than 0.005) after the subjects were at 31 ATA. Plasma cortisol concentration and plasma parathyroid hormone concentration were not significantly affected by hyperbaria. Urinary excretion of aldosterone was not significantly different between day (0700-1900) and night (1900-0700) at any time, and both day and night excretion rates were increased at 31 ATA through late decompression (P less than 0.005). Urinary ADH excretion was greater during daytime at predive 1 ATA (P less than 0.005), but not thereafter. Both daytime and nighttime ADH excretion rates were decreased from 31 ATA through late decompression (P less than 0.005). It is concluded that hyperbaria eliminates the circadian release pattern of ADH and that the overall reduction of ADH may contribute to the increased free water clearance observed at hyperbaria. Also, increased parathyroid hormone was not associated with the phosphaturia observed at hyperbaria, but increased aldosterone coexisted with the increased kaliuresis observed.

Adult↗
PubMed1987

Seadragon VI: a 7-day dry saturation dive at 31 ATA. VI. Hyperbaria enhances renin but eliminates ADH responses to head-up tilt.

Three male subjects were passively tilted from a supine to a 90 degree head-up standing position on 2 d each at 1 and 31 ATA, then on 1 d of the postdive period. On each day the subjects were tilted once in the morning (0800-1000) and once in the evening (2000-2200). Before each tilt experiment, the subjects were first intravenously cannulated for blood sampling, then assumed the supine position. A blood sample was taken after 10 min in the supine position, and another sample was taken after 15 min of motionless, supported standing. The plasma was analyzed for antidiuretic hormone (ADH), plasma renin activity (PRA), plasma cortisol, and aldosterone. ADH, PRA, and cortisol were significantly increased by tilt, but the responses varied with time of day or atmospheric pressure. Cortisol increased only in the morning tilt (P less than 0.005) and was not affected by pressure. At 1 ATA, PRA was elevated in the morning tilt experiment (P less than 0.005) and not the evening tilt, but the overall response to tilt was greater at 31 ATA than at 1 ATA (P less than 0.005). The ADH response to tilt (P less than 0.025) was unaffected by time of day, but was eliminated at 31 ATA. The basal levels of ADH were also lower at 31 ATA (P less than 0.005). The mechanism of these responses remains unclear, but the eliminated postural stimulation of ADH may account for the eliminated circadian excretory pattern of the hormones. The altered responses to body fluid shifts possibly contribute to the increased aldosterone and decreased ADH frequently observed at hyperbaria.

Adult↗
PubMed1987

Seadragon VI: a 7-day dry saturation dive at 31 ATA. I. Objectives, design, and scope.

Seadragon VI dive was designed to determine the effects on humans of a prolonged exposure to a 31 ATA, dry helium-oxygen environment. The specific objectives were to study a) circadian changes in renal-endocrine function, including a comprehensive characterization of nocturia; b) cardiovascular-endocrine responses to a 90 degree tilt; c) erythrocyte functions, including intracellular organic phosphates and the Donnan ratio for chloride; and d) blood enzyme profiles. The experiment was conducted over a period of 30 d in September and October 1984 at the Japan Marine Science and Technology Center, Yokosuka. Following a 5-d predive control period at 1 ATA in air, 4 male divers spent 7 d at 31 ATA in a helium-oxygen environment, and then returned to 1 ATA air after 12 d of decompression. They stayed an additional 3 d inside the chamber for postdive control measurements. The chamber temperature was maintained at 27-28 degrees C during pre- and postdive periods, 31-32 degrees C at 31 ATA, and 28-31 degrees C during decompression. At 31 ATA, PO2 and PCO2 of the chamber gas were maintained at approximately 225 and 2 mmHg, respectively. In this introductory paper, physical and physiologic characteristics of individual subjects, the major daily activity schedule, daily caloric intake, and the scope of investigation are presented.

Adult↗
PubMed1987

Seadragon VI: a 7-day dry saturation dive at 31 ATA. II. Characteristics of diuresis and nocturia.

Four male divers were exposed to a dry, 31 ATA, He-O2 environment for 7 d (Seadragon VI). Urine was collected diurnally (0700-2200 h) and nocturnally (2200-0700 h) before (predive 1 ATA air), during, and after (decompression and postdive 1 ATA air) exposure to 31 ATA. A typical hyperbaric diuresis associated with a reduction in urine osmolality was observed in the face of a constant creatinine clearance. A significant increase (P less than 0.05) in osmolal clearance (COSM) was observed with concomitant decrease (P less than 0.05) in negative free water clearance, indicating that the diuresis has both osmotic and free water components. Although urine flow increased at pressure during both day and night, its magnitude was twofold greater at night as compared to daytime. Moreover, the diurnal diuresis was entirely due to an increase in free water excretion, whereas the nocturnal diuresis was largely due to an increased COSM. These results indicate that hyperbaric diuresis is induced by inhibition of tubular reabsorption of free water during daytime and of certain solutes during the night. Approximately 80% of the nocturnal increase in the excretion of osmotic substances was accounted for by Na, K, Cl, and urea.

Adult↗
PubMed1987

Seadragon VI: a 7-day dry saturation dive at 31 ATA. IV. Circadian analysis of body temperature and renal functions.

Circadian rhythms of body temperature and daytime rhythms of urine flow and urinary excretion of electrolytes were investigated in 4 male subjects before, during, and after a 7-d stay in a dry heliox 31 ATA environment. The chamber temperature was maintained at about 28 degrees C during pre- and postdive 1 ATA periods and was raised to 31.5 degrees C at 31 ATA. The circadian rhythm of the rectal temperature, as analyzed by the cosinor fitting method, showed the same mesor (the mean level of fluctuation) and the amplitude at 31 and 1 ATA. However, a reversible phase shift was noted at 31 ATA in which the acrophase shifted to 1435 h at 31 ATA from 1540 h (predive) or 1610 h (postdive) at 1 ATA. This shift was attributed to an early rise of rectal temperature during night at 31 ATA. A similar phase shift was observed at 31 ATA for the skin temperature of the forehead, a region not covered by clothing or blanket. The daytime rhythms of urinary excretion of water, Na, Cl, urea, and total osmotic substances were similar, with the acrophase at 1300-1500 h at both 1 and 31 ATA. On the other hand, the daytime rhythm for urinary excretion of K, which was similar to the above at 1 ATA, disappeared at 31 ATA. The urinary excretion of endogenous creatinine remained constant during both daytime and nighttime at both 1 and 31 ATA. These results suggest that exposure to 31 ATA may alter the underlying pattern of circadian or daytime rhythms for thermoregulatory and certain renal functions.

Adult↗