The effect of β-adrenoceptor blockade on body temperature and plasma renin activity in heat-exposed man

1 The effect of propranolol (5 mg i.v.) on rectal and skin temperatures, heart rate, blood pressure, plasma renin activity (PRA) and plasma renin substrate concentration (PRS) was investigated in twelve men exercising in the heat. The effect of practolol (10 mg i.v.) on PRA was investigated in five men. 2 Body temperatures were insignificantly affected by propranolol, while heart rate elevation in response to exercise in the heat was 21% lower than in the same subjects receiving saline. Diastolic blood pressure during exercise was elevated by propranolol. 3 The normal increase in PRA seen in heat exposure was suppressed by propranolol to levels seen when the same exercise was carried out at 25°C. Practolol did not affect the renin response to heat exposure. 4 PRS was not altered significantly by exercise or heat. 5 The results indicate that the increase in PRA seen in the heat is largely a result of increased sympathetic activity.

Dermal angiopathy in hemodialysis patients: the effect of time

We studied skin biopsies from 14 patients after 6 months to 18 years on hemodialysis (HD) to discern any effect of duration of treatment on skin and dermal capillaries. Patients selected for biopsy were without evidence of other diseases known to affect vasculature such as diabetes mellitus. Pathological changes compared with duration of HD were: capillary wall thickening, endothelial proliferation and new capillary formation, lipid content, and epidermal atrophy. Severity of morphologic changes were graded from 0 to 4+ by a pathologist who had no knowledge of HD duration. The earliest change observed was reduplication of the capillary basement membrane. Narrowing of capillary lumina due to endothelial cell proliferation and new capillary formation were noted after five years of HD; lipid droplets were noted in capillaries by five years; and epidermal atrophy by 10 years. Progressive severity of each finding was associated with length of time on HD. Neither amyloid nor Ca++ deposits were observed in any specimens. By clinical observation, easy bruisability and increased skin fragility were worse the longer the patient was on HD. Capillary occlusion inducing tissue ischemia could be a cause of the atrophic skin changes noted. However, no patient manifested dermal necrosis. While pathogenesis of the capillary changes in uremic skin is unknown, the changes have been shown to stabilize following successful kidney transplantation.

Carbamylated hemoglobin in prerenal azotemia

Carbamylated hemoglobin (Carb Hb) levels were measured in 16 patients with a documented transient rise in BUN due to prerenal azotemia, in whom BUN levels before and after the episode were normal. They were compared with 13 controls. Carb Hb was expressed as carbamyl valine concentrations, which were significantly higher in the patients (166 micrograms/g Hb) than in controls (95.3 micrograms/g Hb, p < 0.01). The mean maximum BUN level in the patients was 51.8 +/- 23.9 mg/dl. There was a significant correlation between the product of mean BUN level times the number of days of BUN elevation, and the Carb Hb level (r = 0.5197; p < 0.05). There was no correlation between Carb Hb and either mean BUN level or maximum BUN level. Elevated Carb Hb was seen after a minimum of 4 days' BUN elevation. Four patients had no elevation of Carb Hb despite elevated BUN levels.

CONCLUSION

Carb Hb may be elevated after a minimum of 4 days' transient BUN elevation; Carb Hb is not useful in differentiating between mild acute renal failure and prerenal azotemia.

The effect of aluminum on the vanadium-mediated oxidation of NADH

Aluminum catalyzes the oxidation of NADH by vanadate both in the presence and absence of a reducing sugar. The effect of aluminum is concentration dependent and inhibitable with superoxide dismutase but not catalase. The fructose-6-phosphate-free reaction is characterized by an initial lag phase which can be eliminated by preincubating aluminum with NADH, but is not altered by preincubating aluminum with vanadate, suggesting that the effect of aluminum is not directly on vanadate. Aluminum also catalyzes vanadyl-mediated oxidation of NADH, and this effect is similarly inhibitable by superoxide dismutase as well as catalase. It is suggested that aluminum catalyzes the oxidation of NADH by vanadium though enhancing the production of superoxide radicals and that this effect may account in part of the biological toxicity associated with aluminum, particularly when associated with the accumulation of other trace elements such as vanadium.

Blood flow rate and access recirculation in hemodialysis

We studied the effect of extracorporeal blood flow rate (BFR) on access recirculation (recirc) in 19 hemodialysis patients. BUN was determined in simultaneous peripheral (P), arterial (A), and venous (V) blood obtained at BFRs of 200, 400, and 600 ml/min. Percent recirc was calculated for each BFR using the formula (P-A)/(P-V) x 100. Venous drip-chamber (VP) and pre-blood-pump (AP) pressures were measured at each BFR. Fistulograms were performed in 10 patients, and stenoses were identified in 5, all at the proximal (arterial) end of the access. Recirc increased with increasing BFR from 200 to 400 ml/min but increased little from 400 to 600 ml/min. At all BFRs recirc in the stenotic patients was higher than that of non-stenotic or unstudied patients. Urea clearance, corrected for recirc, rose with blood flow both in stenotic and non-stenotic patients. There were no differences in AP or in VP between stenotic and non-stenotic patients. At BFR greater than or equal to 400 ml/min, a recirc threshold of 15% identified stenoses with sensitivity 100% and specificity 71%. We conclude (1) recirc increases with increasing BFR but not enough to outweight the concomitant increase in urea clearance; (2) significant access stenosis and recirc may be present even with low VP; (3) recirc was associated with arterial side stenoses; (4) at BFR greater than or equal to 400 ml/min, access stenosis is associated with recirc greater than 15%.

Effect of chromium on oxygen free radical metabolism, inhibition of superoxide dismutase and enhancement of 6-hydroxydopamine oxidation

The effect of chromium on superoxide dismutase activity (SOD) as well as on the rate of hydroxydopamine oxidation was studied in vitro, since chromium is known as an environmental and occupational carcinogen and oxygen free radicals are implicated in carcinogenic processes. Chromium is a strong inhibitor of SOD activity in this system. The degree of inhibition is directly proportional to the chromium concentration (tested chromium range 0.166-0.33 mg/L in reaction mixture), to reaction time (tested range up to 10 minutes), and to substrate concentration. Autoxidation of 6-hydroxydopamine was increased by chromium concentration of 15 mg/L. The combination of excessive oxygen free radical production and inhibition of their elimination by inhibition of SOD activity may contribute to the toxic effects of chromium.

Effect of nickel on oxygen free radical metabolism. Inhibition of superoxide dismutase and enhancement of hydroxydopamine autoxidation

The effect of nickel on superoxide dismutase activity (SOD), as well as on rate of hydroxydopamine oxidation, was studied in vitro since lipid peroxidation has been implicated in cell damage by nickel, whose toxicity and carcinogenicity are well established. Nickel strongly inhibits SOD activity. The degree of inhibition is directly proportion to the nickel concentration (tested range 0.066 to 0.33 microgram/mL in the reaction mixture); to the substrate concentration (tested range 0.4 x 10 4M to 1.1 x 10 4M 6-hydroxydopamine); and to reaction mixture. Autoxidation of 6-hydroxydopamine was increased by nickel concentrations higher than 15 micrograms/mL. The combination of excessive oxygen free radical production and inhibition of their elimination by inhibition of SOD activity may contribute to the nickel toxicity that has been reported in industrial accidents, as well as to the high incidence of cancer occurring in nickel workers. It may also contribute to many complications in uremic patients, in whom increased serum nickel levels were reported to be in a similar range to those inhibiting SOD.

Inhibition of superoxide dismutase activity by silicon

Elevated silicon levels have been found in the serum of uremic patients, in the brain of patients with senile dementia and in neuroglial tangles of Alzheimer patients. The effect of silicon on superoxide dismutase was studied in vitro, since excessive superoxide production occurs in renal failure, in inflammatory conditions and in the aging process. Silicon in concentrations similar to those found in serum of uremic patients inhibits superoxide dismutase activity. The degree of inhibition is directly proportional to silicon levels. Depression of superoxide dismutase by Si is likely to result in a decrease in oxygen free radical destruction and thus an increase in excessive local availability of oxygen free radicals. The increased silicon levels in brain, kidney, lung and RBC which are especially sensitive to oxygenation damage may contribute to a variety of important clinical complications, by means of excess oxygen free radicals.

Transcapillary oncotic pressure in the edema of congestive heart failure

Tissue fluid and plasma oncotic pressure levels were measured in an unselected group of 13 patients presenting with congestive heart failure. Patients had a mean serum albumin of 3.6 g/dl +/- (SD) 0.35; serum oncotic pressure was 22.23 +/- 1.8 mm Hg; tissue fluid (lower leg) oncotic pressure was 0.985 +/- 0.34 mm Hg. The oncotic pressure gradient between plasma and tissue fluid was 21.25 Hg +/- 1.7. This is about 10 mm Hg greater than delta pi in normal man. The high value in congestive heart failure is a mechanism to protect against the formation of edema. The possible mechanisms responsible for the formation of edema in congestive heart failure are discussed.

Reduced superoxide dismutase activity in erythrocytes of dialysis patients: a possible factor in the etiology of uremic anemia

Superoxide dismutase (SOD) plays a major part in the destruction of oxygen-free radicals in the body. SOD activity is impaired by several trace elements including aluminium and silicon which are found in increased levels in plasma and tissues of uremic man. SOD activity was investigated in the erythrocytes of normal controls and of dialysis patients to determine if lack of SOD-protective activity could be a contributory cause to the increased hemolysis of uremia. It was found that SOD levels in red cell hemolysate were significantly lower in dialysis patients (41.4 +/- 9.1 units/100 ml) compared to control (49.3 +/- 7.2 units/100 ml) (U = 7.3; p less than 0.005). When expressed per 100 ml of whole blood SOD levels were 3.25 +/- 0.93 units/100 ml in dialysis patients and 6.46 +/- 0.99 units/100 ml in controls (U = 96; p less than 0.001). It is concluded that inhibition of SOD activity in the erythrocytes of dialysis patients may contribute to their anemia.

Effect of aluminium on superoxide dismutase

1. The effect of Al3+ on superoxide dismutase in vitro was studied, since in uraemia there is excessive superoxide production and frequently an elevated serum Al3+ level. Thus, the protective role of superoxide dismutase is particularly important. 2. Al3+ in concentrations similar to those found in the serum of uraemic patients inhibits superoxide dismutase activity. The degree of inhibition is directly proportional to the Al3+ level. 3. The combination of excessive oxygen free radical production with an increased Al3+ level may contribute to a variety of complications, including aluminium dementia or initiation and promotion of carcinogenic processes, which are known to be more common in uraemic patients.

Oedema protein concentrations for differentiation of cellulitis and deep vein thrombosis

The differentiation between cellulitis and deep vein thrombosis was investigated in a series of patients with acutely swollen, painful, red legs. Oedema-fluid protein concentrations (as mean [SD]) were significantly higher in patients with cellulitis than in those with deep vein thrombosis (19.8 g/l [5.0] vs 5.85 g/l [1.6]), and the oncotic pressure of oedema-fluid was also significantly higher in cellulitis (6.3 mm Hg [1.3] vs 2.1 mm Hg [0.6]). In hospitals where phlebography, plethysmography, or doppler ultrasound are not available, measurement of oedema-fluid protein concentrations may be a rapid and inexpensive guide to the cause of a red, swollen leg.

Effect of aluminum on bidirectional calcium flux in rat everted intestinal sacs

The effect of aluminum on intestinal calcium absorption was determined in male Sprague-Dawley rats using an everted intestinal sac technique. Bidirectional calcium flux in the duodena and ilea of normal rats was assessed by means of dual calcium isotopes. Two micromolar aluminum significantly inhibited net calcium absorption (J net) in the duodenum through suppression of mucosato-serosa flux (J m----s). Jm----s was reduced from 2.21 +/- 0.50 mumol Ca.h-1.g wet wt-1 in controls to 0.93 +/- 0.35 mumol Ca.h-1.g-1 in aluminum exposed sacs, and Jnet was reduced from 1.88 +/- 0.14 mumol Ca.h-1.g-1 to 0.55 +/- 0.41 mumol Ca.h-1.g-1 (P less than 0.001). Serosa-to-mucosa calcium flux (Js----m) was not similarly influenced by aluminum. Inhibition of Jm----s occurred whether aluminum was initially present on the mucosal or serosal side of the duodenal sac and inhibition of Jnet calcium by 2 muM A1 occurred at all ambient concentrations of calcium studied. In the ileum, aluminum had no effect on any component of calcium flux. Aluminum did not induce any suppression of glucose transport in either the duodenum or ileum, suggesting that the effect on calcium transport is relatively specific. These results suggest that aluminum inhibits calcium absorption in the duodenum through an effect on active mucosa-to-serosa transport, but has no effect on ileal calcium absorption, which in the rat is not mediated by an active process.

Heparin-free hemodialysis with a polyacrylonitrile membrane

The low in vitro thrombogenicity of polyacrylonitrile (AN-69) membrane may offer the possibility of performing hemodialysis (HD) with little or no heparin. The authors sought to reduce heparin dosage using AN-69 dialyzers at blood flows of 400 to 600 ml/min. Over a 90 day period, 2228 HDs were performed: 1531 (69%) with AN-69, 528 (24%) with regenerated cellulose (RC), and 169 (8%) with cellulose acetate (CA) dialyzers. Two hundred and eighty-three HDs were performed without systemic heparin; blood compartments were prerinsed with 2,000 U heparin in 1,000 ml of 0.9% saline. Saline flushes were used in cases of rising venous drip chamber pressures or visible clotting. Incidence of clotting overall in AN-69 HDs was 0.52% (8/1531), 2.8% (15/528) with RC, and 11.2% (19/169) with CA. In heparin-free HDs, incidence with AN-69 was 1.3% (3/230), 28.6% with RC (4/14), and 25.6% with CA (10/39). AN-69 remained less thrombogenic when HDs were stratified by blood flow rate and vascular access was used. Urea clearance was no different in conventional and heparin-free treatments. Blood flow rates of 400 ml/min or higher had an independent antithrombogenic effect. It was concluded that the combination of high blood flow with AN-69 membrane allows marked reduction of HD heparin dose and safe routine use of heparin-free HD.

Uptake, distribution, and excretion of 31silicon in normal rats

This study examines the uptake, distribution, and excretion of 31-labeled silicic acid in rat tissues at 1, 2, and 4 h after intracardiac injection of 31Si(OH)4. Plasma levels of 31Si decrease rapidly from 0.71 +/- 0.04% at 1 h to 0.07 +/- 0.06% of the dose administered per milliliter at 4 h. 31Si in plasma was found to be virtually entirely nonprotein bound. Kidney, liver, and lung accumulated the greatest amounts of 31Si per gram of wet weight, with concentrations at 4 h suggesting both relatively avid uptake and retention. Bone, skin, spleen, muscle, and testes also accumulated 31Si, but the levels were considerably lower than the aforementioned organs. Brain, however, contained negligible concentrations of 31Si throughout the study, indicating active exclusion by the blood-brain barrier. The major portion of the administered 31Si, 77 +/- 12%, was recovered in the urine within 4 h.

Distribution of(31)Silicon-Labeled silicic acid in the rat

Carrier-free(31)Silicon ((31)Si) prepared by neutron activation, was injected in the form of(31)Si-labeled silicic acid into five albino male rats, and the organ and tissue distribution of labeled silicic acid was determined at sacrifice after 30 min. The kidney was found to contain 0.85% of the injected dose (ID) per gram of tissue; skin had 0.3% ID/G; testes 0.29; bone 0.26; liver 0.22; and brain 0.13. When expressed as % ID/organ, voluntary muscle had 14.6%; skin 10.8; bone 3.4; liver 1.6; kidneys 1.5; testes 0.8, and brain 0.2. These results indicate the need for further research into silicon metabolism in kidney, skin, bone, and brain.

Silicon metabolism. II. Renal handling in chronic renal failure patients

In 36 patients suffering from chronic renal failure (mean creatinine clearance 26 ml/min), serum silicon levels were significantly increased (mean 0.52 microgram/ml compared with 0.265 microgram/ml in normals; p less than 0.005). Urinary silicon excretion per 24 h was significantly decreased (15.71 mg/24 h compared with 21.4 mg/24 h in normals; p less than 0.001). Fractional excretion of silicon (FESi) was significantly increased in chronic renal failure (p less than 0.001), with overall tubular secretion of silicon in 33% of patients. Urinary excretion of silicon was significantly related to urinary calcium excretion (p less than 0.0001) urinary magnesium excretion (p less than 0.0001) creatinine clearance (p less than 0.05) and sodium excretion (p less than 0.05). It is suggested that urinary silicon is in the form of orthosilicate, principally bound to calcium and magnesium; and that in chronic renal failure the increase in FESi, and the decrease in absorbed Si from the gastrointestinal tract, moderate the increase in plasma silicon levels and prevent excessive entry of silicon into the tissues.

Silicon metabolism. I. Some aspects of renal silicon handling in normal man

Renal silicon handling was investigated in 23 healthy adults using electrothermal atomic absorption techniques. The mean urinary silicon excretion was 33.1 +/- 3.85 mg/day; the mean renal silicon clearance was 88.6 +/- 7.94 ml/min; the mean fractional excretion of silicon was 86.35 +/- 8.1%, and the mean urine silicon concentration was 0.265 micrograms/ml. Using multiple correlation analysis, the urinary silicon was found to be highly significantly correlated with the urine magnesium concentration (p less than 0.001) and also with urinary sodium and urinary osmolality (p less than 0.01). 24-hour urinary silicon excretion was highly significantly correlated with fractional excretion of silicon (p less than 0.001), sodium (p less than 0.001), phosphorus (p less than 0.001), magnesium (p less than 0.001), and osmolar load. In split urine studies in 7 subjects urinary silicon was correlated highly significantly with urinary magnesium in all 7 and with urinary osmolality, urine calcium, and urine creatine concentration in 6 of 7. There was a highly significant correlation between renal silicon clearance and fractional excretion of silicon (p less than 0.0005), with magnesium excretion (p less than 0.01), and with sodium excretion. It is suggested that ion pairing of orthosilicate and magnesium may explain some of these urinary findings.

Effect of inorganic phosphate on serum ionized calcium concentration in vitro: a reassessment of the "trade-off hypothesis"

The development of secondary hyperparathyroidism in uremia is thought to be due, in part, to the retention of inorganic phosphate which, as proposed by the "trade-off hypothesis", lowers serum ionized calcium by means of CaHPO4 complex formation. To study this hypothesis, free from hormonal or physiological influence, the effect of changes in inorganic phosphate concentration on calcium ion concentration was examined in vitro in serum and protein-free aqueous solutions. The findings of this study demonstrate that the mean change in ionized calcium in aqueous solution is -0.019 +/- 0.001 mM per 1 mM change in inorganic phosphate, and is not significantly different in serum where the mean change in ionized calcium is -0.018 +/- 0.003 mM per 1 mM change in inorganic phosphate. The results in both aqueous solutions and sera agree closely with values predicted from the K'CaHPO4. Based on these results, the serum inorganic phosphate would have to increase by 1.2 mM (3.7 mg%) before the serum ionized calcium would fall sufficiently (0.025 mM) to stimulate the parathyroid glands. These results indicate that an increase in serum inorganic phosphate to as great as 1 mM/liter does not produce a fall in serum ionized calcium by means of direct physicochemical CaHPO4 complex formation great enough to account for the development of secondary hyperparathyroidism.

Effect of chronic alcohol intake on muscle composition and metabolic balance of calcium and phosphate in rats

Chronic alcoholism is associated with abnormalities of serum and muscle mineral metabolism. Decreased muscle phosphate and magnesium and increased muscle calcium have been proposed as significant factors in the development of alcoholic myopathy. As the mechanisms producing these abnormalities remain unknown, we sought to reexamine these findings and investigate the extent to which the kidney and gastrointestinal tract contribute to their pathogenesis. Serum and muscle from rats receiving 20% of their caloric intake as ethyl alcohol were analyzed for PO4, Ca, Mg, Na, and K at 0 and 20 wk and compared with isocalorically fed normals. In addition, individual metabolic balance studies were carried out over 72 h for Ca and PO4 in normal and alcohol-fed rats. The results of serum and muscle analyses did not reveal any differences among the groups for any of the minerals examined. Metabolic balance studies demonstrated that despite a significantly lower Ca and PO4 intake in the alcoholic rats (P less than 0.003) net balance remained the same as in controls. This was due to the retention of a significantly larger proportion of the ingested mineral and was achieved for both Ca (P less than 0.05) and PO4 (P less than 0.03) by means of greater gastrointestinal absorption and additionally for PO4 by a reduction in renal excretion (P less than 0.005). We conclude that in the rat chronic alcohol ingestion is not associated with abnormalities in serum or muscle mineral concentrations, normal adaptive mechanisms by the kidney and gastrointestinal tract compensate appropriately for differences in dietary Ca and PO4, and the rat may not be a suitable species for the study of metabolic effects of chronic alcoholism.

Duodenal aluminum absorption in the rat: effect of vitamin D

Aluminum absorption by the duodenum was studied with an in vivo isolated gut segment technique in vitamin D-deficient and vitamin D-replete rats. Aluminum uptake could be resolved into saturable and nonsaturable components. Both groups demonstrated an identical nonsaturable mechanism with an aluminum uptake of approximately 23% of the amount perfused per 100 mg dry intestinal weight. Saturable absorption was significantly lower in the vitamin D-deficient group (Jmax 6.9 +/- 1.4 microM X h-1 X 100 mg dry wt-1) than in the vitamin D-replete group (Jmax 13.0 +/- 2.7 microM X h-1 X 100 mg dry wt-1) (P less than 0.05). The presence of aluminum in the perfusion solutions reduced duodenal calcium absorption by 33% (P less than 0.02) in the vitamin D-replete group but not the vitamin D-deficient group. These results suggest that aluminum is absorbed in the duodenum by both a nonsaturable mechanism and a vitamin D-dependent saturable mechanism, for which it may compete with calcium.

Effect of chronic uremia in the rat on cerebral mitochondrial calcium concentrations

Whole cerebral and isolated mitochondrial calcium levels were determined in normal and chronically uremic Sprague-Dawley rats. Uremia was induced by a two-stage 5/6 nephrectomy 4 weeks prior to study. Serum was obtained for urea, calcium, magnesium, phosphate, and i-PTH. Mitochondria were isolated by gradient centrifugation and calcium was determined by flameless atomic absorption spectrophotometry. The results demonstrate that mitochondrial calcium levels in uremic rats are not different from normal (8.0 +/- 2.8 vs. 7.8 +/- 1.8 nmoles/mg protein) despite an 11% increase in whole cerebral calcium concentration (17.3 +/- 2.0 vs. 15.5 +/- 2.8 nmoles/mg protein; P less than 0.005) in 24 severely uremic rats (BUN greater than 18.0 mmoles/liter). Multiple regression analysis demonstrates a significant positive correlation between cerebral calcium concentrations and both serum calcium (P less than 0.005) and serum magnesium levels (P less than 0.005). No relationship was found for urea, serum phosphate, or i-PTH. Similar analysis of mitochondrial calcium concentration demonstrated a significant positive correlation with serum calcium (P less than 0.005) and i-PTH (P less than 0.05) suggesting that increased PTH may be necessary for maintaining normal intracellular calcium levels in uremia. We conclude that uremia in the rat is associated with a small rise in whole cerebral calcium but that intracellular calcium as reflected by mitochondrial levels is not elevated.

Uptake and distribution of 45Ca in the brain of chronically uremic rats

The exchange of calcium between serum, cerebrum and cerebral mitochondria was studied in chronically uremic rats. Chemical and radiocalcium assays were performed at periods from 1 to 48 h following intracardiac injection of 45Ca. The disappearance of 45Ca from the serum of uremic rats was identical to that observed in normals. Maximal uptake and equilibration with serum by both cerebrum and cerebral mitochondria were assessed in uremic rats by means of relative specific activities (RSAs) and found not to differ significantly from normal. Peak levels occurred at 6 h for cerebrum and between 4 and 6 h for mitochondria. These results indicate that in the rat, calcium uptake by the brain over a period of 48 h is not altered by chronic renal failure. Moreover, the findings in brain mitochondria suggest that the intracellular calcium burden may not be increased by uremia.

Rapid correction of severe lactic acidosis with massive isotonic bicarbonate infusion and simultaneous ultrafiltration

Patients with severe lactic acidosis and oliguria who receive large amounts of sodium bicarbonate may develop fluid overload and hyperosmolarity. We infused massive amounts of isotonic sodium bicarbonate and simultaneously removed the excess sodium and water with ultrafiltration if 2 patients with lactic acidosis. The first patient received 1,125 mmol of bicarbonate over 4.5 h with a rise in pH from 7.00 to 7.36 and in HCO3 from 3.5 to 15.7 mmol/l. The second received 968 mmol of bicarbonate over 5.25 h with a rise in pH from 7.00 to 7.27 and in HCO3 from 5.3 to 14 mmol/l. Blood pressure remained stable or rose, electrolytes normalized, excess fluid was removed, and a higher pH was maintained. Isotonic bicarbonate infusion with simultaneous ultrafiltration is a safe and rapid method of correcting the metabolic status of patients with severe lactic acidosis who have not responded to standard therapy.

Renal calcium and magnesium handling in water immersion in nephrotic patients

The effect of water immersion to the neck on renal calcium and magnesium handling was studied in 11 nephrotic patients. There was an increase in the urinary excretion of both calcium and magnesium on immersion, and a return towards preimmersion control values in the hour following immersion. Clearances of calcium and magnesium, and fractional excretion of calcium and of magnesium all increased significantly during water immersion, and decreased in the postimmersion hour. However, magnesium excretion was 10-50 times greater than calcium excretion. Fractional excretion of sodium was highly significantly related to fractional excretion of calcium (p less than 0.001) and magnesium (p less than 0.001). The relationship between fractional excretion of phosphate and fractional excretion of calcium was statistically significant (p less than 0.05), as was that between fractional excretion of phosphate and that of magnesium (p less than 0.01). Magnesium and calcium fractional excretions were significantly correlated (p less than 0.01). It was concluded that the increase in calcium and magnesium excretion on immersion is likely to be related to the sodium diuresis caused by central hypervolemia due to immersion.

Aluminum absorption in the rat everted gut sac

Intestinal absorption of aluminum was studied in rat everted gut sacs. Aluminum transport and aluminum uptake in the jejunum initially rose with increasing bath aluminum concentration, but reached a plateau with high bath aluminum concentrations. The aluminum transport was inhibited by dinitrophenol, absence of glucose, and a temperature of 4 degrees C. There was no change with acute renal failure, chronic renal failure, parathyroidectomy, or parathyroid hormone injection. The aluminum absorption from the rat jejunum appears to involve an energy-dependent, carrier-mediated mechanism.

Growth and bone mineralisation as affected by dietary calcium, phytic acid and vitamin D

1. Rats were fed various diets ranging from the normal chow, pure flour containing large amounts of phytic acid, Ca-enriched flour and mixtures of flour and normal food with various levels of calcium. 2. It was found that the animals eating the pure flour grew less and were smaller. 3. They suffered from hypocalcemia and had low plasma alkaline phosphatase and 25-HCC-vitamin D3 levels. 4. These animals had rib-cage deformities. 5. Additional calcium in the flour improved the animals' growth and calcification. 6. The mixed food did not greatly affect the animals and additional calcium did not improve growth or bone mineralisation. 7. The Bedouin eat large amounts of unleavened bread containing large amounts of phytates. 8. It is concluded that uptake of large amounts of phytates by the Bedouin eating unleavened bread is due to the flour and that the clinical manifestations are a direct result of the flour and not the lack of vitamin D due to covering the skin from sunlight.

Renal phosphate handling in nephrotic syndrome during water immersion

In 11 patients suffering from nephrotic syndrome, renal phosphate handling was studied in water immersion up to the neck. There was a rapid onset of phosphate diuresis which continued to increase throughout water immersion; and an increase in fractional excretion of phosphate (FEPO4) continuing throughout immersion and decreasing in the hour after immersion. TmPO4/GFR did not change on immersion. TmPO4/Inulin clearance gave higher figures than TmPO4/creatinine clearance due to secretion of creatinine in 9 of 11 patients. There was a transitory increase in PTH during immersion, but mean immersion plasma levels of PTH did not change when compared to preimmersion control values. FEPO4 was more frequently significantly correlated with FECL than to FENa in nephrotics.

The toxicity of guanidino compounds in the red blood cell in uremia and the effects of hemodialysis

The presence of creatine, guanidinopropionic acid (GPA) and guanidinobutyric acid (GBA) was demonstrated in red blood cells from uremic patients; they were found only in trace amounts in red blood cells of normal controls. The levels of creatine, GPA and GBA in the red cell did not change during dialysis in contrast to the simultaneous decrease in plasma level. Both creatine and GPA inhibited glucose-6-phosphate dehydrogenase (G6PD) in vitro in physiological concentration, while creatine also activated erythrocyte transketolase (ETK). These effects are consistent with the low red cell G6PD level and high ETK activity that were observed in our uremic patients. The unchanging levels of creatine and GPA in the red cell despite hemodialysis may explain the continuing autohemolysis in otherwise adequately hemodialyzed end-stage renal failure patients.

Renal salt and water handling in water immersion in the nephrotic syndrome

1. Eleven nephrotic patients were immersed up to the neck in 1.3 m of water at 34 degrees C for 4 h. 2. A diuresis began, within the first hour of, and continued throughout, immersion. The urine osmolality fell significantly and decreased to hypotonic levels in the first hour of immersion and increased gradually during the remainder of immersion and postimmersion. 3. Throughout immersion there was a steady increase in urinary sodium and chloride excretion and a sharp fall in the postimmersion hour. 4. Overall fractional excretion of sodium and of chloride increased steadily throughout immersion and fell during the post-immersion hour. 5. There was an increase in urinary potassium excretion on immersion but no change in fractional excretion of potassium. There was an initial increase in distally reabsorbed sodium/chloride on immersion, as expressed by positive values of CH2O in the first hour of immersion. 6. Plasma aldosterone levels were initially elevated in only two out of nine patients. There was a significant fall in plasma aldosterone levels on immersion, but there was no correlation between sodium/chloride handling and aldosterone levels on immersion.

Water immersion in nephrotic syndrome

Five adults suffering from nephrotic syndrome were immersed up to the neck in 1.3 m of warm water for four hours. There was a mean weight loss of 2 kg; 1 kg was lost through sweat and 1 kg was lost through urine. Thirty-five millimoles of sodium was excreted in the urine in four hours, 15 times more than on control days. The urine became hypotonic to plasma in the first two hours of immersion. Aldosterone levels did not change on immersion in three patients, but fell from elevated levels in two others. It is concluded that water immersion up to the neck in nephrotic patients warrants further investigation as a therapeutic agent in those cases that are not responding to conventional diuretic therapy.

Beta-thromboglobulin levels in the nephrotic syndrome

Beta-thromboglobulin (BTG), a platelet-specific protein released on platelet aggregation, was measured in 13 patients with clinical and biochemical evidence of the nephrotic syndrome. All 13 patients had increased concentrations of BTG compared to both 10 normal controls and to 12 non-nephrotic azotemic patients (p < 0.001). In five patients with the nephrotic syndrome in remission, the BTG levels returned to normal. These results support the contention that the nephrotic syndrome is associated with a state of hypercoagulability and suggest that increased platelet aggregation may be the primary underlying mechanism.