Response properties of hypogastric afferent fibers supplying the uterus in the cat

The present study was undertaken to examine the sensory function of uterine afferent fibers in cats at unknown stages of the estrous cycle. Single unit activity was recorded from strands of the hypogastric nerve of the anesthetized cat. Once a unit was found, the conduction velocity was determined and the mechanical receptive field localized on the uterus. The response properties of the unit to mechanical stimuli applied to the receptive field and to chemical stimuli applied by intra-arterial injection of algesic chemicals (bradykinin, KCl and capsaicin) into the uterine artery were studied. Single unit activity from a total of 52 units was examined in this study. Based on the conduction velocities, about 2/3 of these fibers were found to be unmyelinated C fibers and the remaining 1/3 were thinly myelinated A delta fibers. The receptive fields of most of these fibers were located at different parts of the uterine horn and body while a few were at the uterine cervix. Mechanical thresholds, as determined by von Frey filaments applied to the external surface of the uterus, varied more than 150-fold among mechanically sensitive units, ranging from extremely low to high thresholds. In addition, most of these afferents were activated by intra-arterially injected algesic chemicals, often by more than one chemical. The data in the present study suggest that a large portion of the cat uterus is innervated by the hypogastric nerve and that these afferents originate from sensory receptors that have potentially a wide range of functions. Their potential functions as low threshold mechanoreceptors and nociceptors are discussed.

Arterial blood gas tensions during breath-hold diving in the Korean ama

Korean female unassisted divers (cachido ama) breath-hold dive > 100 times to depths of 3-7 m during a work day. We sought to determine the extent of arterial hypoxemia during normal working dives and reasonable time limits for breath-hold diving by measuring radial artery blood gas tensions and pH in five cachido ama who dove to a fixed depth of 4-5 m and then continued to breath hold for various times after their return to the surface. Eighty-two blood samples were withdrawn from indwelling radial artery catheters during 37 ocean dives. We measured compression hyperoxia [arterial PO2 = 141 +/- 24 (SD) Torr] and hypercapnia (arterial PCO2 = 46.6 +/- 2.4 Torr) at depth. Mean arterial PO2 near the end of breath-hold dives lasting 32-95 s (62 +/- 14 s) was decreased (62.6 +/- 13.5 Torr). Mean arterial PCO2 reached 49.9 +/- 5.4 Torr. Complete return of these values to their baseline did not occur until 15-20 s after breathing was resumed. In dives of usual working duration (< 30 s), blood gas tensions remained within normal ranges. Detailed analysis of hemoglobin components and intrinsic oxygenation properties revealed no evidence for adaptive changes that could increase the tolerance of the ama to hypoxic or hypothermic conditions associated with repetitive diving.

Assay of inert gas contamination in studies of hydrostatic pressure effects

In hyperbaric tissue studies it is common to use gas pressure as a means for increasing the hydrostatic pressure of the preparation. When this is done, one must take the necessary precautions to avoid gas contamination of the tissue. In the present study, we demonstrate a) methods for calculating the gas contamination using particular materials in the perfusion system, and b) a technique for isolating the fluid environment from contamination by the compressing gas in a flow-through tissue chamber. The present work is exemplified with a specific apparatus, but the general principle is applicable to other studies.

Effects of protein kinase inhibitors on in vitro protein phosphorylation and cellular differentiation of Streptomyces griseus

In vitro phosphorylation reactions using extracts of Streptomyces griseus cells and gamma-[32P]ATP revealed the presence of multiple phosphorylated proteins. Most of the phosphorylations were distinctly inhibited by staurosporine and K-252a which are known to be eukaryotic protein kinase inhibitors. The in vitro experiments also showed that phosphorylation was greatly enhanced by manganese and inhibition of phosphorylation by staurosporine and K-252a was partially circumvented by 10 mM manganese. A calcium-activated protein kinase(s) was little affected by these inhibitors. Herbimycin and radicicol, known to be tyrosine kinase inhibitors, completely inhibited the phosphorylation of one protein. Consistent with their in vitro effects the protein kinase inhibitors inhibited aerial mycelium formation and pigment production by S. griseus. All these data suggest that S. griseus possesses several protein kinases of eukaryotic type which are essential for morphogenesis and secondary metabolism. In vitro phosphorylation of some proteins in a staurosporine-producing Streptomyces sp. was also inhibited by staurosporine, K-252a and herbimycin, which suggests the presence of a mechanism for self-protection in this microorganism.

Nitrogen tensions in brachial vein blood of Korean ama divers

Intravascular bubble formation and symptoms of decompression sickness have been reported during repetitive deep breath-hold diving. Therefore we examined the pattern of blood N2 kinetics during and after repetitive breath-hold diving. To study muscle N2 uptake and release, we measured brachial venous N2 partial pressure (PN2) in nine professional Korean breath-hold divers (ama) during a 3-h diving shift at approximately 4 m seawater depth and up to 4 h after diving. PN2 was determined with the manometric Van Slyke method. Diving time and depth were recorded using a backpack computer-assisted dive longer that allowed calculating the surface-to-depth time ratio to derive the effective depth. With the assumption that forearm muscle N2 kinetics follow the general Haldanian principles of compression and decompression, i.e., forearm muscle is a single compartment with a uniform tissue PN2 equal to venous PN2, PN2 data were fitted to monoexponential functions of time. In the early phase of the diving shift, PN2 rapidly increased to 640 Torr (half time = 6 min) and then slowly declined to baseline levels (half time = 36 min) after the work shift. Peak PN2 levels approximated the alveolar PN2 derived from the effective depth. We conclude that forearm muscle N2 kinetics are well described by a Haldanian single-compartment model. Decompression sickness is theoretically possible in the ama; it did not occur because the absolute PN2 remained low due to the shallow working depth of the ama we studied.

Urinary vasopressin and aldosterone and plasma volume during a saturation dive to 450 m

Urinary vasopressin (VP), aldosterone (ALDO), osmotic substances, sodium excretion, and plasma volume were assessed in 4 healthy male divers during 2 predive control days, 2 compression days, 6 days at 46 atm abs, and 26 days of decompression with stops at 37 and 27 atm abs. At pressure the ambient gas was trimix (0.5 atm abs O2:5% N2:remainder He). All urine was collected throughout the dive. Samples were divided into daytime (0700-1900) and nighttime (1900-0700). Indocyanine green dye dilution was used to determine plasma volume at predive 1, 46, and 24 atm abs. In agreement with previous dives at 31 atm abs, there was a decrease in VP excretion during compression lasting until return to 1 atm abs (P less than 0.05). Also similar to the shallower dives at 31 atm abs, the normal diurnal pattern of VP excretion, daytime higher than nighttime (P less than 0.05), disappeared at pressure. Urine osmolality showed alterations compatible with responses to VP. In contrast to previous studies at 31 atm abs, but in agreement with a previous study at 49.5 atm abs, there was no sustained increase in urinary ALDO excretion and only a transient natriuresis during the compression phase, followed by a reduced sodium excretion. In confirmation of earlier conclusions from indirect evidence, direct measurements of plasma volume indicated a reduction of about 20% (P less than 0.05) at 46 atm abs which remained reduced after decompression to 24 atm abs.

Renal responses during a dry saturation dive to 450 msw

Four subjects were compressed to a simulated depth of 450 msw (46 bar) for 37 days in the main research chamber of the German underwater simulator diving facility at the GKSS Research Center, Geesthacht. The ambient gas was trimix. Urine was collected at 0700, 1300, and 1900 h each day for analysis of Na+, K+, volume, osmolality, and creatinine. Urine, antidiuretic hormone (ADH), and aldosterone were analyzed separately. Daily fluid, Na+, and K+ intake were analyzed throughout the dive. The aim of the investigation was to confirm the existence of a diuresis and natriuresis which had been observed in earlier saturation dives to 31 atm abs using He-O2. A significant diuresis was observed during compression despite a decrease in fluid intake. After compression the diuresis decreased somewhat but remained significantly above precompression control levels during the entire hyperbaric exposure. No significant change in fluid intake was observed. Daily Na+ and K+ excretion increased significantly during compression, which was accompanied by a significant increase in nocturnal excretion of Na+ and K+. Daily intake of Na+ and K+ decreased throughout the dive. Daily urine ADH decreased immediately upon compression and was associated with a parallel decrease in urine osmolality. In contrast, urinary aldosterone excretion exhibited no change during the dive despite the increase in Na+ and K+ excretion and decrease in Na+ intake.

Plasma and urinary concentrations of methamphetamine after oral administration of famprofazone to man

1. To obtain further evidence for the metabolic formation of methamphetamine from famprofazone in man, concentrations of methamphetamine in plasma, as well as in urine, were measured by g.l.c. In addition, intact famprofazone and famprofazone N-oxide were analysed in the urine. 2. Methamphetamine appeared in plasma 1 h after a single 100 mg dose of the drug to two male subjects, and the concentration maintained between 24 and 44 ng/ml over 2-12 h, declining to 10 ng/ml and an undetectable level respectively after 24 h. 3. Total urinary excretion of methamphetamine over 72 h was 1.9 mg for a 25 mg dose and 2.2 mg for a 50 mg dose. After a 100 mg dose, 4.6 mg of methamphetamine was excreted over 36 h. Neither intact famprofazone nor famprofazone N-oxide were detected when the urine samples after the 100 mg dose were examined. 4. The results provide further evidence that methamphetamine is a bona fide human metabolite of famprofazone and suggest that at least 20% dose may be broken down via the pathways leading to the formation of methamphetamine. This could have significant clinical implications as the result of pharmacological activity of this metabolite.

Takayasu arteritis in Korea: Clinical and angiographic features

Clinical and angiographic features of Takayasu arteritis were investigated in 129 Korean patients. This disease affects females more frequently than males, in a ratio of 6.6 to 1. Of the total number of patients, 51 were in the third decade, 27 in the fourth decade, and 23 in the second decade. Common clinical symptoms were headache (60%), exertional dyspnea (42%), dizziness (36%), and malaise or weakness (34%). Takayasu arteritis affected the abdominal aorta (46%) and descending thoracic aorta (37%) more frequently than the ascending aorta (1%) and aortic arch (2%) According to Ueno's classification based on aortographic findings, the 129 patients were divided into type I (37), type II (25), and type III (67). Among the 48 patients who had coronary angiography, 11 (23%) showed coronary arterial involvement. Because the clinical features are determined by the extent and severity of the specific artery involved in the occlusive phase of the disease, total aortography including coronary angiography is very important in the initial evaluation of Takayasu arteritis.

Effects of methylguanidine on sodium and organic ion transport

We studied the acute effect of methylguanidine (MG), a suspected uremic toxin that accumulates in renal failure, on p-aminohippurate (PAH) and tetraethylammonium (TEA) uptake in rabbit kidney slices, on Na+,K+ ATPase activity in the microsomal fraction of rabbit kidneys, and on transepithelial active Na transport across toad skin. MG at concentrations ranging from 0.05 (similar to that reported in uremic patients) to 1.0 mM does not affect the organic anion (PAH) uptake, although it exhibits a concentration-dependent inhibition of organic cation (TEA) uptake. MG at concentrations from 0.05 to 5 mM had no effect on kidney Na+,K+ ATPase activity or on active transepithelial Na transport across toad skins when applied to the outside bathing solution; however, MG (greater than 1 mM) stimulated Na transport when applied to the inside bathing solution. These results are not consistent with the hypothesis that MG is a potential uremic toxin that causes the natriuresis and other toxic effects. However, long-term toxic effects of MG on the kidney were not assessed in the present study.

Daily diving pattern of Korean and Japanese breath-hold divers (ama)

Daily diving patterns and thoracic skin and sea-water temperatures were recorded during the entire work shift of Korean female unassisted (cachido) and Japanese male unassisted and partly assisted (funado) divers using Underwater Physiological Data Loggers developed in Buffalo and Japan. All 3 groups of divers were studied during the summer of 1989 and 1990. Additional studies were conducted during the winter of 1991 on Korean female divers who, unlike Japanese divers, dive all year round. The water temperature of the diving grounds in summer was 24 degrees C in both Korea and Japan, and 10 degrees C during winter in Korea. Both Korean female and Japanese male cachido divers made 113-138 dives a day and stayed in the water a total of 170-200 min.day-1, of which only 52-63 min were spent diving submerged, and the remaining time at the water surface. These diving patterns were not different between female and male cachido divers. Compared with Japanese male divers, Korean female divers dived to a shallower depth (3.7 vs. 6.9 m) with shorter dive time (29 vs. 37 s) and shorter bottom time (14 vs. 18 s). Velocities of descent (0.72 vs. 0.47 m.s-1) and ascent (0.77 vs. 0.56 m.s-1) were also slower in female divers than in male divers. The diving pattern of Korean female divers was similar in both summer and winter. Although all cachido divers wore wet suits and thus were protected from severe cold stress, thoracic skin temperature decreased during a work shift by 7 degrees C in winter (vs. 1 degree C in summer) in Korean divers. Compared with Japanese male cachido divers, Japanese male funado divers stayed in the diving ground (including time in the boat) longer (201 vs. 305 min.day-1) but performed only 23 dives per day. The average diving depth (9.7 m), duration (69 s), and bottom time for each dive (45 s), however, were significantly greater in funados. The velocity of vertical descent (1.0 m.s-1) was also significantly greater in funados because they descend with a weight (8-12 kg). The rate of ascent was not different.

Identification of an A-factor-dependent promoter in the streptomycin biosynthetic gene cluster of Streptomyces griseus

A-factor (2-isocapryloyl-3R-hydroxymethyl-gamma-butyrolactone) is a microbial hormone controlling streptomycin (Sm) production, Sm resistance and sporulation in Streptomyces griseus. In order to identify A-factor-dependent promoters in the Sm biosynthetic gene cluster, a new promoter-probe plasmid with a low copy number was constructed by using an extremely thermostable malate dehydrogenase gene as the reporter. Of the three promoters in the Sm production region that includes strR, aphD and strB, only the promoter of strR, which codes for a putative regulatory protein, was found to be directly controlled by A-factor. This was also confirmed by S1 nuclease mapping. The region essential for its A-factor-dependence was determined to be located 430-330 base pairs upstream of the transcriptional start point. Increase in the copy number of the strR promoter region did not lead to a corresponding increase in the total promoter activity, probably due to titration of a putative activator which binds to the enhancer-like region and controls the expression of the strR promoter. This putative activator is apparently distinct from the A-factor-receptor protein. The aphD gene, which encodes the major Sm resistance determinant, Sm-6-phosphotransferase, was transcribed mainly by read-through from the A-factor-dependent strR promoter; this accounts for the prompt induction of Sm resistance by A-factor.

Renal, hormonal, and fluid shift responses to ANP during head-out water immersion in awake dogs

Renal responses to low doses of atrial natriuretic peptide (ANP) may be potentiated during water immersion-induced central hypervolemia. To test this hypothesis, ANP was infused in awake dogs in doses of 0, 5, and 25 ng.kg-1.min-1 either when the dogs were in air or during head-out water immersion (WI) under thermoneutral conditions (37 degrees C). In general, there were greater diuretic (V) and natriuretic responses (UNaV) at the same level of plasma ANP in WI, with the slopes (or sensitivities) of V and UNaV in relation to plasma ANP levels being significantly increased during WI. Plasma renin activity decreased only during WI and was significantly correlated with both V and UNaV only during WI. Plasma and urinary arginine vasopressin levels were unchanged during WI. Infusion of ANP prevented the usual decline of hematocrit that occurs during WI. These results support the view that the renal sensitivity to ANP is augmented during the plasma volume expansion of WI. In addition, ANP may attenuate the transcapillary fluid shift that occurs during WI.

Phosphorylation of the AfsR product, a global regulatory protein for secondary-metabolite formation in Streptomyces coelicolor A3(2)

The AfsR protein is essential for the biosynthesis at the wild-type level of A-factor, actinorhodin, and undecylprodigiosin in Streptomyces coelicolor A3(2) and Streptomyces lividans. Because overexpression of the afsR gene caused some deleterious effect on these strains, a multicopy plasmid carrying the whole afsR gene was introduced into Streptomyces griseus, from which a crude cell lysate was prepared as a protein source. The AfsR protein was purified to homogeneity from the cytoplasmic fraction through several steps of chromatography, including affinity column chromatography with ATP-agarose and use of anti-AfsR antibody for its detection. The molecular weight of AfsR was estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by gel filtration to be 105,300, which is in good agreement with that deduced from the nucleotide sequence of afsR. The purified AfsR protein was found to be phosphorylated through the transfer of the gamma-phosphate group of ATP in the presence of the cell extracts of S. coelicolor A3(2) and S. lividans. This phosphorylation proceeded very rapidly, and no competition was observed with CTP, GTP, UTP, or cyclic AMP. In the cell extract of S. griseus, no activity phosphorylating the AfsR protein was detected, suggesting that this activity is not generally present in Streptomyces spp. but is specific to certain species. It is conceivable that the extent of phosphorylation of the AfsR protein modulates its regulatory activity which, in turn, regulates expression of some target gene(s) involved in the secondary-metabolite formation in S. coelicolor A3(2).

Interaction of heptanol and pressure on sodium and chloride transport by toad skin

We examined the interaction of heptanol and hydrostatic pressure on Na+ and Cl- transport in isolated toad skin. In the presence of Cl-, heptanol decreased short-circuit current (Isc) and total transepithelial resistance (Rt). However, in the absence of Cl- in the mucosal bath, heptanol increased Rt, although it retained the same inhibitory effect on Isc. When transepithelial active Na+ transport was blocked by amiloride, heptanol had no effect on Isc whether or not Cl- was present, whereas it decreased the shunt resistance (Rs) only in the presence of Cl- in the mucosal bath. Moreover, this effect of heptanol on Rs was significantly smaller in the presence of diphenylamine-2-carboxylate (DPC), a known Cl- channel blocker. Pressure also decreased Isc through inhibition of active Na+ transport, but it increased Rs. When heptanol and pressure were applied together, their inhibitory effects on Isc were additive, but their effects on Rs were antagonistic. Furthermore, when a transepithelial Cl- current was produced by reducing the Cl- concentration of the serosal bath, heptanol stimulated this current, which was reversibly inhibited by pressure or DPC addition to the mucosal bath. When the heptanol-stimulated Cl- current was first inhibited by pressure, subsequent DPC addition had less or no effect. These results suggest that one site of an antagonistic interaction of heptanol and pressure in toad skin is an apical membrane Cl- conductance.

Primary structure of AfsR, a global regulatory protein for secondary metabolite formation in Streptomyces coelicolor A3(2)

The afsR gene of Streptomyces coelicolor A3(2) complements afsB mutations affecting production of pigmented antibiotics. It also directs pigment production in Streptomyces lividans when carried on a plasmid vector. Nucleotide sequencing of the afsR gene revealed that it codes for a 993-amino acid protein (Mr 105,600) with A- and B-type ATP-binding consensus sequences at its N-terminal portion and two DNA-binding consensus sequences with a helix-turn-helix motif at its C-terminal portion. Each of the N- and C-terminal halves was capable of conferring pigment production, to some extent, in S. lividans, when carried separately on a multicopy plasmid. In addition, expression in trans of the two regions on the same plasmid conferred pigment production to almost the same extent as did the intact afsR gene. Mutations at the two ATP-binding consensus sequences, that were generated by in vitro site-directed mutagenesis, revealed their functional importance. Disruption of the S. coelicolor A3(2) chromosomal afsR gene in either the N- or C-terminal half using phage phi C31 KC515 resulted in significant, but not complete, loss of pigment production. These data suggest that the AfsR protein comprises two domains, viz., an ATP-binding and a DNA-binding domain, each of which could function as a positive regulator for pigment production. These afsR mutants sporulate normally. In addition to an internal promoter, which we previously detected in the middle of the AfsR coding region, S1 nuclease mapping revealed two tandem transcriptional start points, separated by 64 bp, upstream from a putative ATG start codon of the AfsR product.

Effect of hydration state on renal responses to head-out water immersion in conscious dogs

Renal responses to head-out water immersion (WI) (37 degrees C, WI 100 min) were studied in conscious, instrumented dogs during volume repletion (R), when all blood and urine losses were replaced with 0.9% NaCl, or without volume repletion (NR), to determine the influence of hydration state. The lithium clearance method was used to estimate the locus of the renal tubular fractional sodium excretion (FENa) responses. WI in the R condition increased urine flow (V) from 0.9 (+/- 0.1 SE) to 4.2 (+/- 0.6) ml/min and FENa from 0.7 (+/- 0.1) to 3.2 (+/- 0.8)%. Fractional proximal sodium reabsorption (FPRNa) decreased from 0.82 (+/- 0.03) to 0.69 (+/- 0.1)% and fractional distal sodium reabsorption decreased from 0.96 (+/- 0.01) to 0.88 (+/- 0.04)%. By comparison, WI in the NR condition elicited smaller increments in V and FENa, no change in FPRNa and a significant decrease of FDRNa from 0.97 (+/- 0.01) to 0.93 (+/- 0.01). Although there were quantitative differences in the renal responses in the R and NR conditions, there were similar increments in both arterial and atrial pressures as well as plasma atrial natriuretic peptide concentration; plasma arginine vasopressin was unaltered in either situation, and plasma renin activity was depressed in both conditions. Since plasma protein concentration was significantly lower during the R condition, the differing renal responses are probably related to differing levels of volume expansion in the R vs. NR condition.

Splenic contraction during breath-hold diving in the Korean ama

Major increases of hemoglobin concentration and hematocrit, possibly secondary to splenic contraction, have been noted during diving in the Weddell seal. We sought to learn whether this component of the diving response could be present in professional human breath-hold divers. Splenic size was measured ultrasonically before and after repetitive breath-hold dives to approximately 6-m depth in ten Korean ama (diving women) and in three Japanese male divers who did not routinely practice breath-hold diving. Venous hemoglobin concentration and hematocrit were measured in nine of the ama and all Japanese divers. In the ama, splenic length and width were reduced after diving (P = 0.0007 and 0.0005, respectively) and calculated splenic volume decreased 19.5 +/- 8.7% (mean +/- SD, P = 0.0002). Hemoglobin concentration and hematocrit increased 9.5 +/- 5.9% (P = 0.0009) and 10.5 +/- 4% (P = 0.0001), respectively. In Japanese male divers, splenic size and hematocrit were unaffected by repetitive breath-hold diving and hemoglobin concentration increased only slightly over baseline (3.0 +/- 0.6%, P = 0.0198). Splenic contraction and increased hematocrit occur during breath-hold diving in the Korean ama.

Absence of diuresis during a 7-day saturation dive at 2.5 ATA N2-O2

Three male divers were studied for 2 days during each of the predive and postdive 1 ATA air control periods and for 7 days at 2.5 ATA (2.3 ATA N2 and 0.2 ATA O2). The chamber temperature was always maintained at a comfort level. Average urine flow remained at 1500 ml.day-1 during both predive and 2.5 ATA periods; urine osmolality also remained constant at around 700 mOSM/kg. On the other hand, daily excretion of Na increased significantly from 139 mEq during the predive period to 178 mEq at 2.5 ATA (P less than 0.05) but returned to the predive level during the postdive period. In contrast, daily K excretion decreased progressively with a significant decrease during the postdive period (P less than 0.05). Plasma osmolality, Na, and K remained unchanged, whereas a 6% reduction of total protein concentration at 2.5 ATA (P less than 0.05) was observed. A quantitatively similar decrease (8%) was observed for hematocrit during the 2.5 ATA period, which did not recover at postdive. These changes were accompanied by a significant increase in urinary excretion of antidiuretic hormone (P less than 0.05) and by decreases in both plasma renin and aldosterone (P less than 0.05) level and urinary excretion of aldosterone (P less than 0.05). Plasma atrial natriuretic factor remained unchanged throughout the entire dive period.

Hyperbaric oxygen effect on active Na+ transport across isolated toad skin

The effect of hyperbaric oxygen (HBO) on Na+ transport across the isolated toad (Bufo marinus) skin was studied by measuring the transepithelial short-circuit current (ISC) and resistance (R) at 5, 8, and 10 ATA PO2 and 15 ATA normoxia during steady state conditions. The imposition of 5, 8, and 10 ATA PO2 for 2 h resulted in 45, 52, and 85% decrease in ISC, respectively. This decrease in ISC was always accompanied by an increase in R. When amiloride (10(-4) M) was added to the bathing medium, ISC decreased to zero within 15 min regardless of the PO2 level, indicating that the HBO-induced decrease in ISC is caused by an inhibition of amiloride-sensitive Na+ transport. Addition of both superoxide dismutase (SOD) and catalase to the medium bathing both sides of the skin markedly attenuated the HBO effect on ISC and R. Applying HBO to the serosal or mucosal surface independently produced similar effects on ISC. However, the presence of antioxidant enzymes (SOD and catalase) with 10 ATA PO2 prevented the toxic HBO effect only from the serosal side; no protection by these antioxidant enzymes was observed from the mucosal side. These findings are consistent with a view that free radicals are involved in the HBO-induced inhibition of ISC. However, further studies involving the site(s) of radical generation as well as site(s) of toxic action are needed to understand the cellular and molecular mechanism of HBO toxicity.

Characteristics of increased urine flow during a dry saturation dive at 31 ATA

Three male divers were subjected to a 7-day dry saturation dive at 31 ATA (New Seatopia). Urine samples were collected for measurements of electrolytes and creatinine for glomerular filtration rate (GFR) 5 times daily, at 3-h intervals during daytime (0700-2200 h) and once at night (2200-0700 h). Collections were taken for 2 days before (predive 1 ATA air), 7 days during 31 ATA exposure, and during 10 days of decompression and for 2 days at postdive 1 ATA air. Blood samples were taken after overnight fasting at each of the dive periods for measurements of atrial natriuretic factor (ANF), electrolytes, and other blood constituents. Compression to 31 ATA resulted in a twofold increase in urine flow accompanied by increases in excretion of osmotic substances (+40%) and sodium (+54%), and a reduction in urine osmolality (-32%). The increase in urine volume was greater (P less than 0.05) at night than day with no change in GFR between day and night, confirming the earlier findings. However, no change in plasma ANF was observed in spite of a sustained increase in daily sodium and water excretion at high pressure. These results suggest that the hyperbaric diuresis-natriuresis may not be directly mediated by the ANF release.

Size selected mRNA induces expression of P-aminohippurate transport in Xenopus oocytes

Xenopus oocytes were injected with size-fractionated mRNA isolated from the renal cortex of rabbit kidney and after 4 days incubation, PAH uptake in oocytes injected with mRNA (0.7-1.3 kb) was 8 to 45 fold that of the water injected controls. The oocyte to medium ratio of accumulated PAH was 1.95. The Km and Vmax for transport were 333 microM and 66.6 nmoles.oocyte-1.min-1, respectively. This Km is similar to that reported for PAH transport in intact kidneys and slices. The uptake of PAH was unaffected by the absence of Na+ or the presence of probenecid. Expression of the transport represents the first step in an effort to clone and identify the gene for PAH transport.

Mechanism of tolerance to renal ischemia in harbor seal: role of membranes

Many diving animals are capable of engaging in long breath-hold dives. Investigations were undertaken to compare the active tubular transport of organic ions between kidney slices from harbor seals (Phoca vitulina) and rats (control) under anoxia or low pH or both. Para-aminohippurate (PAH) and tetraethylammonium (TEA) were used as a representative organic anion and cation, respectively. The slice-to-medium concentration ratios (S:M) of PAH (congruent to 2.5) in the harbor seal was not altered (unlike in the rat) after 60 min of incubation in a nitrogen atmosphere but was reduced to congruent to 1.0 in the presence of 10(-4) M 2,4-dinitrophenol. Subsequent studies also demonstrated that PAH uptake in the harbor seal was not influenced by pH of the incubation medium over a range of 6.0 to 7.4. In contrast, PAH uptake was very sensitive to the medium pH in the rat, decreasing significantly with reduction in pH. Although the TEA uptake decreased in anoxia in both species, it decreased considerably less in the harbor seal than in the rat (40 vs. 70%). However, TEA uptake decreased significantly at low pH in both species. The magnitudes of increase in intracellular Na and of decrease in intracellular K in anoxia were consistently less in the harbor seal than in the rat, especially at low pH. On the basis of these and other findings reported in the literature, cellular mechanisms for the remarkable ischemic tolerance of the seal kidney are discussed.

Interstitial and intravascular pressures in conscious dogs during head-out water immersion

Water immersion (WI) causes an increase in plasma volume in humans and dogs. To determine the mechanism for this fluid movement, the transmission of external water hydrostatic pressure to the interstitial and vascular compartments was studied in six conscious dogs. Systemic arterial, central venous, peripheral arterial (ulnar artery) and venous (cephalic vein), pleural, intra-abdominal, and interstitial fluid hydrostatic (by Guyton's capsule and wick catheter method) pressures and external reference water pressure were measured at three different levels of WI: 1) extremities only, 2) midchest, and 3) midcervical levels at 37 degrees C. There was a significant linear relationship between interstitial fluid hydrostatic pressure (X) and external water pressure (Y): (Y = 0.86X + 1.4, r = 0.93 by Guyton's capsule; Y = 0.85X + 2.4, r = 0.93 by wick catheter. However, vascular pressures did not change when dogs were immersed at the level of the extremities. These pressures increased only during WI at the midchest and midcervical levels. Therefore the pressure gradient that develops between the interstitial and intravascular compartments is probably the major reason for the transcapillary fluid shift during WI.