An ikaros-containing chromatin-remodeling complex in adult-type erythroid cells

We have previously described a SWI/SNF-related protein complex (PYR complex) that is restricted to definitive (adult-type) hematopoietic cells and that specifically binds DNA sequences containing long stretches of pyrimidines. Deletion of an intergenic DNA-binding site for this complex from a human beta-globin locus construct results in delayed human gamma- to beta-globin switching in transgenic mice, suggesting that the PYR complex acts to facilitate the switch. We now show that PYR complex DNA-binding activity also copurifies with subunits of a second type of chromatin-remodeling complex, nucleosome-remodeling deacetylase (NuRD), that has been shown to have both nucleosome-remodeling and histone deacetylase activities. Gel supershift assays using antibodies to the ATPase-helicase subunit of the NuRD complex, Mi-2 (CHD4), confirm that Mi-2 is a component of the PYR complex. In addition, we show that the hematopoietic cell-restricted zinc finger protein Ikaros copurifies with PYR complex DNA-binding activity and that antibodies to Ikaros also supershift the complex. We also show that NuRD and SWI/SNF components coimmunopurify with each other as well as with Ikaros. Competition gel shift experiments using partially purified PYR complex and recombinant Ikaros protein indicate that Ikaros functions as a DNA-binding subunit of the PYR complex. Our results suggest that Ikaros targets two types of chromatin-remodeling factors-activators (SWI/SNF) and repressors (NuRD)-in a single complex (PYR complex) to the beta-globin locus in adult erythroid cells. At the time of the switch from fetal to adult globin production, the PYR complex is assembled and may function to repress gamma-globin gene expression and facilitate gamma- to beta-globin switching.

Circadian variation in the natriuresis produced by potassium intake in the rat

To determine if there was an endogenous circadian regulation of the renal natriuretic response to acute potassium loading, unanesthetized rats, either fed or fasted, were given an intragastric infusion of KCl over 100 min at the times of maximum and minimum circadian sodium excretion, i.e. in the early dark and early light phase of a 12 hour dark/light cycle. During KCl infusion plasma potassium concentration as well as sodium and potassium excretion progressively increased. Cumulative sodium excretion was greater in dark than light phase, and was greater in fed than fasted rats. Sodium excretion was greater at any given elevated level of plasma potassium in the dark than light phase. The results suggest that reported variations in the effects of high potassium diets on sodium excretion, blood pressure, or circulatory pathology in hypertension, may in part be explained by variations in the time of oral potassium intake.

Aldosterone and potassium homeostasis

The presently accepted regulators of the homeostatic excretion of potassium are the plasma concentrations of aldosterone and potassium. Evidence for a role of aldosterone is reviewed, and it is pointed out that aldosterone is kaliuretic at supraphysiologic levels but has little kaliuretic activity within its normal secretory range. Elevation of plasma potassium above its normal range enhances the kaliuretic action of aldosterone. Elevation of plasma potassium above, but not within, its normal range is strongly kaliuretic. In sheep the kaliuresis induced by intake of a potassium rich meal cannot be explained by changes in aldosterone or plasma potassium. A kaliuretic reflex arising from receptors in the gut, portal vein or liver has been proposed the explain the meal-induced kaliuresis. This putative reflex involves the central nervous system and efferent kaliuretic factors other than aldosterone and plasma potassium. Evidence for the involvement of the central nervous system and undetermined kaliuretic regulatory factors can be found in studies of the physiologic circadian rhythm of renal potassium excretion. This rhythmic excretion does not appear to depend on changes in either aldosterone or plasma potassium.

Early effects of uninephrectomy on K homeostasis in unanesthetized rats

Mechanisms underlying the change in K excretion (UKV) during the first 6 days after uninephrectomy (UNX) were examined in unanesthetized rats. Arterial plasma K concentrations (PK) were 0.55 meq/l above control values at 12 and 24 h after UNX but were not significantly different 36-72 h after UNX. To determine if there was an increased sensitivity of the distal K secretory mechanism to increases in PK, an intragastric KCl infusion was given. The delta UKV/delta PK per kidney values were in the following order: 6-day UNX > 2-day UNX > control. In the normal rats, an acute increase of 0.5 meq/l in PK increased UKV by an amount approximating 25% of the increase in UKV observed 12-24 h after UNX. Amiloride, administered 48 h after UNX, increased Na excretion per kidney and decreased UKV per kidney approximately twice as much in UNX as in control groups. Thus an adaptive increase of amiloride-inhibitable K secretion occurred within 2 days of UNX and continued to increase thereafter. This K adaptation may have been induced by transient increases in PK.

Kaliuresis in normal subjects following oral potassium citrate intake without increased plasma potassium concentration

Ingestion of potassium salts typically induces both a kaliuresis and an increase in the systemic plasma potassium concentration. In this study normal healthy adults undergoing water diuresis ingested potassium citrate or sodium citrate (0.5 mmol/kg body weight) or continued without ion ingestion (a time control group). Urine was collected over 20-min intervals and venous blood sampled at midinterval. Intake of potassium citrate led to a significant increase in potassium excretion that began during the first postingestion collection and peaked 60-80 min after intake with a maximal increase in potassium excretion above baseline of 1.60 mumol/min.kg-1. The kaliuresis occurred without changes in plasma potassium concentration, excretion of creatinine or calcium, or urine hypo-osmolality and was associated with a briefer, smaller, and less regular increase in sodium excretion and a pronounced but irregular increase in chloride excretion. Plasma aldosterone was insignificantly elevated above baseline, and the initial increase did not occur until 40-60 min after potassium intake. Intake of sodium citrate did not produce a kaliuresis. The cause of the kaliuresis does not appear to be an increased systemic plasma potassium concentration, an increased plasma level of aldosterone, intake of citrate, or an elevated excretion of sodium. The mechanism inducing the kaliuresis following oral potassium intake in the absence of changes in systemic plasma potassium may involve a reflex initiated at potassium sensors in gut, portal vein, or liver.

Circadian rhythms and time course of adaptive sodium and potassium excretion in rats after uninephrectomy

The relationship between renal circadian cyclic excretion and renal compensatory adaptation after uninephrectomy for K, Na, and water was studied. Rats in a 12:12-h light-dark environment were given a liquid diet, and urine was collected for 16 days with consecutive 90-min periods. Days 1-4 were control, 5-10 followed a sham operation, and 11-16 followed uninephrectomy. The major findings were 1) the circadian cycles in excretion were virtually unchanged after sham and uninephrectomy; 2) an adaptive increase in excretion of Na, K, and water by the remaining kidney occurred within 90 min after uninephrectomy; 3) after uninephrectomy the distribution of the 24-h increment in excretion for the remaining kidney closely followed the preexisting pattern of circadian excretion for Na but was evenly distributed between light and dark phases for K; and 4) after uninephrectomy the ratio of excretion to intake was unchanged. This is the first study to document the time course of adaptation to uninephrectomy using consecutive brief collections over several days in unanesthetized and undisturbed rats. Adaptation after uninephrectomy occurred essentially immediately; was maintained unchanged; and preserved Na, K, and water homeostasis. Uninephrectomy did not alter the circadian control of excretion.

The central nervous system in potassium homeostasis

There is considerable evidence that the central nervous system (CNS) is significantly involved in potassium homeostasis: (a) Potassium-specific receptors located in the liver or hepatic portal circulation initiate a reflex increase in potassium excretion via vagal afferents. This reflex is lost or diminished with hypophysectomy. (b) Oscillators, presumably located in the hypothalamus, determine a circadian rhythm in the renal excretion of potassium. The efferent control factors are unknown. (c) Exogenous hypophysial peptides (vasopressin, oxytocin, and alpha-, beta-, and gamma-MSH) stimulate increased potassium (and sodium) excretion. (d) Hypophysial gamma-MSH or a related hypophysial peptide stimulates an increase in the excretion of potassium (and sodium) following uninephrectomy in the rat. This adaptive response involves cerebral, naloxone-inhibitable opioid receptors. (e) Intra-third-ventricular infusion of hypertonic NaCl initiates an increased potassium (and sodium) excretion through undetermined humoral mechanisms and is blocked by prior hypophysectomy. (f) In rats depleted of potassium by low potassium intake or by production of DOCA hypertension, an inhibition of skeletal muscle Na+, K(+)-ATPase ion pump activity is directed by hypothalamic centers and involves inhibition by alpha-adrenergic activity of slow twitch fibers and inhibition by undetermined humoral factors of fast twitch fibers. (g) Potassium receptors, either demonstrated or inferred, initiate reflex increases in respiration, heart rate, blood pressure, and peripheral tissue potassium uptake as well as a reflex inhibition of skeletal muscle ion pumps. (h) Evidence for CNS regulation of potassium intake is equivocal. Major gaps exist in this emerging picture of neuroendocrine involvement in potassium homeostasis.

Do Splanchnic Potassium Receptors Initiate a Kaliuretic Reflex?

In sheep, acute oral intake of K causes a rapid and precisely regulated increase in urinary K excretion that is mediated by unidentified factors other than aldosterone, systemic plasma K, diuresis, or natriuresis. K receptors in gut, hepatic portal vein, or liver may initiate a reflex increase in K secretion.

Homeostatic regulation of potassium excretion

Multiple systems participate in the homeostatic regulation of potassium excretion. Changes in plasma potassium, above a baseline value, will directly stimulate potassium excretion. Acute variations in aldosterone may have only small and perhaps insignificant effects in stimulating potassium excretion when aldosterone is present within its normal plasma range, but may be highly significant in determining the kaliuretic response to changes in plasma potassium or tubular flow rate. Elevation of plasma aldosterone to supraphysiological levels appears to produce increases in potassium excretion. Chronic variations in aldosterone are important, but not unique in determining renal potassium adaptation to chronic variations in potassium uptake. New lines of evidence point to sensors of potassium intake located in the hepatic portal vein or liver, or in enteric locations. A reflex control of potassium excretion, first demonstrated by Aizman and Finkenshtein et al. [120-123] in the dog, and independently suggested in a more general form for the sheep, may be integral in the regulation of potassium excretion in response to intake. With this feedforward control system, potassium excretion may be regulated without changes in systemic plasma potassium concentration. From diverse lines of investigation we find that there is a compelling argument for an important role for the brain in regulating both potassium excretion and its ICF/ECF ratio. One may speculate, albeit on the basis of preliminary information, that separate but analogous systems exist for sodium and for potassium, each involving the brain and each acting through specific humoral factors. For sodium, evidence is accumulating for a ouabain-like humoral agent, perhaps originating in the brain, which modulates renal sodium excretion and the sodium concentration of ICF. Both of these actions have been proposed to have an important influence on blood pressure regulation. The evidence presented here is compatible with a similar system for potassium. On the basis of these studies reviewed here, it is intriguing to speculate that an analogous humoral factor is involved in the regulation of potassium homoeostasis, and that its effects, when understood, may help to resolve current debates regarding the role of potassium in blood pressure regulation.

Hemodynamic changes after nafcillin administration during coronary artery bypass surgery

The hemodynamic response to nafcillin administration was studied in 45 patients with good left ventricular function and no known history of hypersensitivity to penicillin during coronary artery bypass grafting (CABG). Group I (15 patients) received 1 gram of nafcillin in 10 mL of saline as an intravenous (IV) bolus, group II (15 patients) received 1 gram of nafcillin in 50 mL of saline as a slow IV infusion over 15 minutes, and group III (15 patients) did not receive nafcillin. Hemodynamic variables and plasma histamine and catecholamine levels were measured before and after nafcillin administration, after 500 mg of CaCl2, and after 0.1 mg of phenylephrine. Bolus nafcillin administration produced profound hypotension secondary to vasodilatation with significant increases in cardiac index and decreases in systemic and pulmonary vascular resistances. Cardiac index increased from 3.15 +/- 0.3 L/min/m2 to 5.75 +/- 0.25 L/min/m2 (P less than 0.005) one minute after nafcillin administration, and remained at 5.1 +/- 0.35 L/min/m2 after administration of CaCl2 (P less than 0.005). All hemodynamic parameters returned toward control values after administration of 0.1 mg of phenylephrine, IV. Plasma epinephrine, norepinephrine, and histamine levels increased more than 100%. In group II, cardiac index increased, while systemic and pulmonary vascular resistances and mean arterial pressure decreased. However, these changes were less significant than those found in group I.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiloride effect on diurnal cyclic Na and K excretion in rats

Amiloride was administered to rats during the peak and minimum of Na and K diurnal rhythmic excretion (i.e., during early dark phase and early light phase). In rats receiving a normal-K diet (2.34 meq/day) amiloride decreased K excretion from 186 to 37 mueq/h (dark phase) and from 31 to 4 mueq/h (light phase). Amiloride increased Na excretion from 91 to 344 mueq/h (dark phase) and from 35 to 164 mueq/h (light phase). Rats receiving a high-K diet (10.4 meq/day) showed a higher diurnal peak and minimum for K excretion. During high-K intake, amiloride decreased K excretion from 787 to 191 mueq/h (dark phase) and from 197 to 40 mueq/h (light phase) and increased Na excretion from 237 to 891 mueq/h (dark phase) and from 31 to 222 mueq/h (light phase). Whenever given, amiloride reduced K excretion to approximately 20% of control excretion. It is concluded that rhythmic changes in amiloride-sensitive distal transport are largely, but not entirely, responsible for the diurnal K cycle, but do not cause the concurrent Na cycle. Thus the diurnal cycles in Na and K are expressed through changes in different transport mechanisms. In rats maintained on a high-K diet there is an increase in rhythmic K secretion and Na reabsorption by amiloride-sensitive transport. To maintain Na excretion unchanged, Na reabsorption must be correspondingly depressed at an amiloride-insensitive site.

Survival time, causes of death, and tumor/treatment-related morbidity in 100 women with ovarian cancer

One hundred cases of ovarian cancer were studied at autopsy to determine the effect of morphologic and clinical factors on survival time, the primary cause of death, and tumor/treatment-related morbidity. The mean survival time was 19 months (0 to 174 months). Increasing neoplastic histologic grade and increasing clinical stage at diagnosis were each associated with decreased survival time. In grade I tumors, the mean survival time was 84 months; in grade II tumors, it was 18 months; and in grade III tumors, it was 12 months (P = .0008). Patients who presented in stage I or II had a better survival time (28 months) than those who presented in stage III or IV (15 months) (P = .02). The most common causes of death were disseminated carcinomatosis (48%), infection (17%), pulmonary embolus (8%), and combinations of infection and carcinomatosis (11%). In patients dying of infection, 43% had sepsis, 21% had pneumonia, and 25% had a combination of sepsis and pneumonia. Escherichia coli and Klebsiella were the most common pathogens identified postmortem. Intestinal obstruction (51%) and ureteral obstruction (28%) were the most common forms of tumor-induced morbidity. Bone marrow depression and resultant pancytopenia was the most common form of treatment-induced morbidity.

The effect of feeding four different formulae on stool weights in prolonged dehydrating infantile gastroenteritis

Prolonged diarrhea following an acute episode of dehydrating gastroenteritis in infants is often treated by the empirical removal of both cow's milk protein and lactose from the feed, as they both have been implicated in the prolongation of diarrhea. In order to assess the efficacy of this policy and to determine whether there are any advantages in using a lactose-free semi-elemental feed in this situation, infants with prolonged dehydrating gastroenteritis from a developing community in South Africa were studied. Male black children between the ages of 6 weeks and 2 years with prolonged dehydrating gastroenteritis (requiring intravenous fluids for longer than 72 h to maintain hydration) were randomly assigned to receive one of four feeds if the stool weight was greater than 30 g/kg body weight/24 h on the fourth day of admission. The four formula feeds were a partially modified cow's milk formula; a lactose-free, casein-containing formula; a lactose-free, soy-protein-containing formula; and a lactose-free, whey-hydrolysate-containing formula. Stool weights were measured for the following 3 days. Seventy-two children were enrolled into the study. Stool weights were similar in the four groups at the start of the trial, and fell significantly over the trial period in those groups receiving the lactose-free feeds. Mean stool weight in the cow's milk formula group did not change. Thus, it appears that the continued feeding of a cow's milk-based lactose-containing formulae to infants with prolonged dehydrating gastroenteritis adversely affects their recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

Model of homeostatic regulation of potassium excretion in sheep

Based on experimental observations on unanesthetized sheep, a hypothesis is proposed for the homeostatic control of potassium excretion in this ruminant. This hypothesis includes as a novel element a splanchnic sensor of potassium intake. Information provided by the splanchnic sensor contributes to the control of potassium excretion independently of the level of systemic plasma potassium or other conventional control factors. A mathematical model based on this hypothesis successfully simulates the relations between potassium excretion, plasma potassium, and oral and intravenous potassium input observed in sheep.

Homeostatic potassium excretion in fed and fasted sheep

In unanesthetized adult sheep, following intake of a daily meal, there was a peak in K excretion. The maximum and minimum rates of K excretion following meals were directly related to meal K content. On days without meals, no peak in K excretion occurred. Changes in K excretion on fed and fast days occurred without changes in the low levels of plasma aldosterone and were poorly correlated with urine or blood pH, urine flow rate, Na excretion, or the filtered load of K, but they correlated well with fractional K excretion. Plasma K did not change on fast days. Plasma K increased on some, but not all, fed days. Increases in plasma K that occurred on fed days were insufficient to account for the concurrent kaliuresis. Infusion of aldosterone or isotonic NaCl failed to alter K excretion in fed or fasted sheep. Infusion of isotonic NaCl + aldosterone hypertonic Na2SO4 + aldosterone increased K excretion in fasted but not fed sheep. Infusion of K in the rumen of fed and fasted sheep elevated rumen K concentration and led to increases in K excretion that could not be explained by increases in plasma K. The mechanisms responsible for the homeostatic changes in K excretion on fed and fast days were not ascertained but may importantly depend on sensors of enteric K content.

Aldosterone reverses potassium-induced food aversions in adrenalectomized rats

Young adult male rats were individually housed and given a standard ration (66 ml) of a liquid diet (Nutrament) each day. The animals were divided into 7 groups: five groups were bilaterally adrenalectomized (ADX) and given one of 5 doses of aldosterone and/or dexamethasone by continuous, osmotic minipump infusions. The remaining two groups served as intact and sham operated controls. Each of the seven groups were subdivided into 3 dietary groups: a basal potassium dietary group, a moderately potassium-supplemented dietary group, and a highly potassium-supplemented dietary group. All rats with intact adrenals as well as those ADX rats given basal or 10 X basal aldosterone treatment consumed all of their allotted 66 ml of diet each day, independent of the level of potassium supplementation. ADX rats given little or no aldosterone treatment that were given access to the moderately or highly supplemented diets became anorexic, eating little or none of the diet. These data are discussed with reference to the factors controlling the intake of ADX rats.

Distribution of disease at autopsy in 100 women with ovarian cancer

Clinical and morphologic factors that affected the distribution of disease are described in 100 cases of ovarian cancer at autopsy. In addition to the expected pattern of pelvic and abdominal peritoneal spread, extensive visceral parenchymal metastases were seen: liver parenchyma (45%), lung parenchyma (39%), small and large intestinal wall (52% and 55%), lymph nodes (70%), pancreas (21%), ureter (24%), bone (11%), and brain (6%). Liver parenchymal metastases replaced more than one third of the liver in 25% of cases, whereas lung metastases always involved less than one third of the lungs. When intestinal wall invasion was seen, bowel obstruction was present more often (71%) than when only intestinal serosa was involved (30%). Lymphatic invasion was predictive of lymph node, small intestinal wall, pancreatic, and liver as well as lung parenchymal metastases. Blood vessel invasion was predictive of pancreatic and ureteral metastases. Clinical stage I at diagnosis was associated with high incidences of liver parenchymal (56%), lymph node (56%), lung parenchymal (44%), large intestinal wall (33%), and bone (33%) metastases. Thus, ovarian cancer has parenchymal metastases similar to other carcinomas in addition to its peritoneal spread. Lymphatic and blood vessel invasion is predictive of such involvement. Intestinal wall invasion predicts bowel obstruction.

Plasma potassium and diurnal cyclic potassium excretion in the rat

The relation of the plasma potassium concentration to the daily cyclic variation in potassium excretion was examined in undisturbed, unanesthetized male Sprague-Dawley rats maintained on a liquid diet in a 12-h light-dark environment. Potassium excretion increased from a light-phase minimum of 16 mu eq/h to a peak of 256 mu eq/h 3 h after the beginning of the dark phase. Plasma potassium concentration in arterial blood, sampled in rats at 90-min intervals during these changes in potassium excretion, showed no significant change and was in the range 4.50-4.99 meq/liter. In adrenalectomized rats receiving aldosterone and dexamethasone at constant basal rates by implanted pumps, the daily cycle of potassium excretion was the same as in the intact rats, and plasma potassium was not significantly different when measured at the time of minimum and maximum rates of potassium excretion (4.79 +/- 0.42 vs 5.16 +/- 0.47 meq/liter, mean +/- SD). These results indicate that plasma potassium concentration is not the efferent factor controlling diurnal cyclic changes in potassium excretion in adrenal intact rats and may not be the only significant factor in adrenalectomized-steroid replaced rats.

Kaliuretic regulatory factors in the rat

To evaluate the role of aldosterone, plasma potassium, and sodium and urine excretion rates in controlling both total daily potassium excretion and the diurnal cyclic excretion of potassium, we performed experiments on unanesthetized, undisturbed rats kept in a 12-h light/12-h dark environment and fed a liquid diet. Independent variations were imposed on potassium intake, sodium intake, and, in groups of adrenalectomized rats, on aldosterone infusion rates. Potassium intake was 2.6, 10.6, and 18.7 meq/day. Sodium intake was 2.1, 6.7, and 17 meq/day. Aldosterone infusion was 0.1, 0.4, 1, and 10 times a basal rate of 1 microgram.day-1.100 g-1, with constant dexamethasone infusion at 1.43 micrograms.day-1.100 g-1. Twenty-four-hour excretion of potassium and sodium balanced 24-h intake of potassium and sodium regardless of the imposed combination of known regulatory factors. The amplitudes of potassium and sodium excretion during the diurnal cycle were each closely related to the ongoing levels of potassium and sodium intake. Plasma potassium was measured at the peak of the potassium cycle. It is suggested, based on analysis of the results, that when caloric balance was maintained, the amplitude of the diurnal potassium cycle was not importantly influenced by the rates of sodium and urine excretion, and, in addition to effects of aldosterone and plasma potassium concentration, the amplitude was importantly influenced by unspecified, homeostatically effective kaliuretic factors. Adrenalectomized rats receiving subbasal aldosterone replacement rejected the high potassium diet, were anuric, lost weight, and were severely hyperkalemic, observations indicating the necessity of adequate aldosterone for maintenance of potassium homeostasis.

Prediction of intra-uterine growth retardation using maternal glucose tolerance and anthropometric data

Maternal anthropometric data and the intravenous glucose tolerance test (IVGTT) were investigated as predictors of idiopathic intra-uterine growth retardation (IUGR). Eighty-three eligible subjects without known risk factors for IUGR were enrolled at 30.5 +/- 3.8 weeks' gestation and followed up until delivery at 39.3 +/- 1.9 weeks, at which stage the infants were assessed. There were no differences between the IVGTT profiles of mothers of infants which were appropriate for gestational age and those which were small for gestational age (SGA), irrespective of lenient or strict definitions of SGA. Third-trimester weight gain (grams per week) correlated well with both duration of pregnancy and birth weight (P less than 0.01). Correlations were also found between maternal weight and birth weight, between maternal height/weight ratio and birth weight, and between birth weight and maternal subscapular skinfold thickness.

Diurnal potassium excretory cycles in the rat

Diurnal potassium cycles (DPC) were measured in unanesthetized undisturbed rats fed a liquid diet and maintained in a 12-h light-dark environment. A fourfold step increase in diet potassium content increased DPC amplitude without altering phase. After presentation of the high-potassium diet, the initial adaptive increase in excretion occurred within 1.5 h (diet given during dark phase) and within 6 h (diet given during light phase). On a day when food was withheld (no potassium intake), DPC were present but with a lowered amplitude. The amount of potassium excreted on a fasting day exceeded gut and extracellular fluid potassium content and was only modestly increased when rats were previously fed a high-potassium diet. In adrenalectomized rats that received no steroid replacement or received constant infusions of low levels of aldosterone, dexamethasone, or aldosterone plus dexamethasone, potassium balance and DPC were normal. It is concluded that the amplitude of DPC in the rat is determined in part by the availability of potassium from both intracellular and extracellular potassium pools; mechanisms independent of potassium intake can generate the DPC; and the presence or the cyclic secretion of adrenal steroids is not necessary for the generation of DPC in the rat.

Effect of aldosterone on potassium excretion during potassium chloride infusion in sheep

Experiments were performed on normal mature ewes to quantitate the effect of acute variations in aldosterone activity on renal K excretion. Six-hour clearance studies were performed on three sheep. Treatments were control (no infusion), infusion of KCl (140 meq in 2 h) alone or with superimposed infusions of aldosterone (20 micrograms/h), or infusion of aldosterone antagonist potassium canrenoate (100 mg/h). During KCl infusion there were simultaneous increases in plasma K, K excretion, and Na excretion. Aldosterone treatment diminished the increase in plasma K and in Na excretion but increased the rate of K excretion. Canrenoate had opposite effects. The rate of change of K excretion relative to the change in plasma K was 417 for aldosterone and 102 microeq/min per meq/l for canrenoate treatments, P less than 0.05. Before KCl infusion aldosterone decreased the rate of Na excretion and the salivary Na-to-K ratio but did not alter plasma K or K excretion. Aldosterone has a potent kaliuretic action in sheep when plasma K is elevated.

Effects of KCl infusion on potassium excretion in sheep

To determine the quantitative relation of K excretion (UKV) to plasma K concentration (PK), three fasted, conscious, mature ewes were infused intravenously with 50 mmol KCl over 15, 30, and 60 min. Control experiments were without infusion. During KCl infusion PK was increased to 7.26 +/- 0.40 (15 min), 6.68 +/- 0.48 (30 min), and 5.59 +/- 0.3 meq/liter (60 min). During all three infusions the increase in UKV relative to the increase in PK was similar. The mean delta UKV/delta PK ratio was 160 +/- 30 (SD) mueq/min per meq/liter (range 102-203). On termination of each infusion PK decreased to control values, but UKV either remained elevated (60-min infusion) or first decreased and then increased (15- and 30-min infusions). The second, delayed kaliuresis began 30-45 min after initiation of KCl infusion and accelerated a return to the level of K balance of the control experiments. A plot of UKV against the corresponding period PK showed that, at a common value of PK, UKV was higher following KCl infusion when PK was dropping than during KCl infusion when PK was rising. The mechanisms responsible for this hysteresis phenomenon are not identified.

Intrapulmonary shunting during deliberate hypotension with nifedipine, diltiazem and labetalol in dogs

Pulmonary shunt (Qs/Qt) was calculated in 49 mongrel dogs weighing 18-20 kg during mechanical ventilation, before and during deliberate hypotension with either nifedipine (group N), diltiazem (group D), labetalol (group L), or ethyl alcohol and polyethylene glycol (group E). A 30 per cent decrease in mean arterial blood pressure occurred after two minutes of nifedipine infusion, two minutes after diltiazem, and three minutes after labetalol; these effects lasted two hours after nifedipine administration, 90 minutes after diltiazem and three hours after labetalol. There was an accompanying significant decrease in systemic and pulmonary vascular resistance. Qs/Qt and cardiac output increased significantly after nifedipine infusion. Shunt increased (mean +/- S.E.) from 9.7 +/- 0.8 to 18.25 +/- 1.05 per cent at two minutes (p less than 0.0005); 19.05 +/- 1.2 per cent at 30 minutes (p less than 0.005); 17.5 +/- 1.6 per cent at two hours (p less than 0.01); and 12 +/- 1.1 per cent at three hours (p less than 0.025). No increase in shunt occurred after the administration of diltiazem, labetalol or polyethylene glycol and ethyl alcohol. Arterial oxygen tension (PaO2) decreased significantly after nifedipine infusion from 146 +/- 11.5 to 105 +/- 3.5 mmHg two minutes after infusion; to 89.5 +/- 3 mmHg 30 minutes after; 115 +/- 4.75 mmHg two hours after; and 130 +/- 10.75 mmHg three hours later. PaO2 was not significantly different after diltiazem, labetalol, or polyethylene glycol and ethyl alcohol administration. With nifedipine cardiac output increased from 2.25 +/- 0.3 to 3.95 +/- 0.25 after two minutes (p less than 0.005) to 3.85 +/- 0.35 after 30 minutes (p less than 0.005), 3.7 +/- 3 after two hours (p less than 0.01) to 2.9 +/- 1.1 after three hours. No significant increase in cardiac output occurred in groups D or L. These results suggest that only nifedipine infusion significantly alters oxygenation in dogs and therefore its use warrants caution in the presence of a preexisting abnormal Qs/Qt.

Time course of adaptation to altered K intake in rats and sheep

The early time course of adaptation to large step increases in K intake was examined in sheep and rats. Fifteen 3-day experiments were performed on four mature ewes. They received on each day a single meal (730-930 meq K/day) and on days 2 and 3 a rumen KCl supplement (600 mM/day). Adaptation to the changed intake occurred within 47 h and was defined by the ratio of urinary K/K intake approximating normal preloading ratios. K excretion did not correlate significantly with plasma K or with Na excretion. Three groups of four rats, body wt 210 g, were studied over 19 days. Four rats fed a basal diet excreted 1.96 +/- 0.04 (n = 19) meq/day K. For four rats, the basal diet was supplemented with KCl on days 5-15, during which time K excretion was 9.34 +/- 0.36 (n = 11) meq/day; four rats with a higher KCl supplement on days 5-15 excreted 15.37 +/- 0.69 (n = 11) meq/day K. For rats, adaptation to increased and decreased intake was rapid, occurring on the first day of changed intake when urinary K excretion approximated intake. The rapid K adaptation was contrary to the generally accepted, but experimentally unverified, view that adaptation is a chronic process requiring 1 or more weeks to develop.

Sheep renal potassium excretion: efferent kaliuretic regulatory factors

The possibility that efferent factors in addition to aldosterone and plasma K may mediate the renal response to large variations in K intake in sheep was explored in experiments on four mature ewes. K supplementation of a normal diet provided a total K intake of 1,300-1,500 meq/day for 3 days and produced a high K excretion (737 +/- 34 mu eq/min) with plasma K 4.67 +/- 0.07 meq/liter. K deprivation by 83 h of fasting produced low K excretion (48 +/- 10 mu eq/min) with plasma K 3.60 +/- 0.14 meq/liter. Additional treatments during both K-supplemented and K-deprived states included: raising plasma K through the range 4-7 meq/liter by intravenous infusion of 45 meq KCl in 30 min; intravenous infusion of aldosterone (20 micrograms/h) or of an aldosterone antagonist, potassium canrenoate (100 mg/h). Na supplementation during fasting was by rumen infusion of Na acetate-Na propionate (1,000 meq Na/day). Results showed that the increase in plasma K during intravenous K infusion directly elevated K excretion, that aldosterone enhanced and canrenoate depressed the kaliuretic effect of K infusion, and that Na loading during fasting enhanced the kaliuretic effect of aldosterone. Comparisons, made at the same level of plasma K, indicated that differences in plasma K, aldosterone, or Na excretion were not sufficient individually or in combination to account for the large differences of 350-1,150 mu eq/min in K excretion that existed between K-supplemented and K-deprived states. Unidentified kaliuretic regulatory factors appear to play a major role in the homeostatic control of K excretion in sheep under the circumstances of these experiments.

Hyperglycaemia in infantile gastroenteritis

The prevalence and pathogenesis of hyperglycaemia were investigated in a consecutive series of 27 black infants admitted to hospital with gastroenteritis over a period of three months. Hyperglycaemia (plasma glucose concentration greater than 10 mmol/l) occurred in 15 (55%) of these patients. The pathogenesis was not clear but possible contributory factors included raised concentrations of the stress hormones pancreatic glucagon, growth hormone, and cortisol; hypokalaemia; and peripheral insulin resistance. Intravenous rehydration, without insulin, corrected the plasma glucose concentrations and restored the hormonal profile towards normal within 36 to 48 hours.

Effects of glucagon, insulin, propionate, acetate, and HCO3 on K excretion in sheep

The effects on renal K excretion of 1 h intravenous infusion of glucagon, insulin, Na propionate, Na acetate, or NaHCO3 were studied in mature, conscious fasted ewes. These treatments were compared with the fasted state without treatment (control) and with feeding a single daily meal. Renal K excretion was increased by feeding and by Na propionate and Na acetate treatments but not by infusion of glucagon, insulin, and NaHCO3. Since hormone levels were elevated more by specific hormone infusions than by feeding or Na propionate infusions, these results do not support a role for glucagon and insulin in mediating the increases in renal K excretion that occurred after meals or during acetate and propionate infusions. The mechanisms responsible for the acetate- and propionate-induced kaliuresis are not clear but do not appear to include changes in plasma K (PK), glucagon, and insulin (Pinsulin) or in urine flow and urine Na excretion. However, a relation between insulin and K was observed during infusion of KCl in fasting sheep. Above a PK threshold of 4 meq/l, Pinsulin (ng/ml) = 1.52 PK (meq/l) - 5.89. In other experiments, K excretion increased after an intravenous bolus injection of 1 mg of glucagon, indicating that sheep, like humans and dogs, respond to pharmacologic doses of glucagon with kaliuresis.

Urea and renal concentrating ability in the rabbit

The hypotheses of passive salt accumulation predict an enhancement of renal concentrating ability by urea. We tested this prediction in rabbits, a species whose nephons when studied in vitro show tansport properties that support these hypotheses. We used calm, unanesthetized, hydropenic, vasopressin-treated rabbits with intact kidneys fed a 16% protein diet, and we observed the effect of urea administration at two rates of solute excretion (60 and 190 microOsm/min . kg body wt; N = 10 and 5, respectively). After an i.v. mannitol infusion, when urea was infused, the i.v. solute excretion rate was unchanged, the changes in urine urea concentration were large (a change of 767 and 408 mumoles/ml), but only small and variable changes in urine osmolality occured (a change of 78 +/- 146, and 36 +/- 50 microOsm/g H20). In additional experiments, we removed the kidneys from antidiuretic, or urea- or mannitol-infused rabbits and measured the intrarenal distribution of sodium, potassium, urea, and chloride. When the urine urea level was greater than 400 mmoles, the urine-to-papilla ratios for urea were 1.6 to 3.6. This suggested that a low collecting duct permeability to urea could explain the absence of a marked enhancement of concentrating ability during urea administration. Further analysis, based on a model of inner medullary solute compartments, indicated that sodium chloride was the major (86%) osmotically active solute in the medullary central core of these rabbits and that it was not influenced by changes in urinary urea concentration. The results of tissue analysis were consonant with either active or passive sodium chloride reabsorption from the thin ascending limb of Henle's loop in these rabbits.

Renal sodium and potassium excretion in sheep given amiloride

When amiloride was given (IV) to unanesthetized ewes, potassium excretion decreased to one-third of baseline values, and sodium excretion increased 6- to 180-fold. Potassium excretion during amiloride administration was relatively invariant with respect to duration (0 to 270 minutes) or rate of amiloride administration (0.125 to 2.0 mg/minute), but sodium excretion clearly increased with both duration and dose rate in individual experiments. This increase was independent of the rate of concomitant saline administration. Thus, sheep fed a normal ration (about 600 mEq of potassium per day) respond to amiloride as do man, dogs, and rats. The relationship of sodium excretion to rate and duration of amiloride administration is not unique to sheep, but has not been stressed in previous studies on other species.

Epidemic listeriosis. Report of 14 cases detected in 9 months

During the period August 1977 to April 1978, 14 Black patients in Johannesburg area had systemic infections caused by Listeria monocytogenes. Nine of these patients were neonates who presented with septicaemia (5 cases) or septicaemia and meningitis (4 cases) and 5 were adults, all of whom had meningitis. The mortality rate was 43% (6/14), with 4 neonatal and 2 adult deaths. All isolates of L. monocytogenes were type 4b. Only sporadic cases of human listeriosis have previously been reported in South Africa, and the cases reported here constitute the first epidemic in this country.

Type I histiocytosis X presenting as biliary atresia. A case report

Histiocytosis X may present in a variety of ways. We report a patient who presented with the unusual feature of infiltration of the hepatic duct with histiocytes, manifesting as biliary atresia.

Renal potassium excretion in sheep during sodium sulfate, phosphate, and chloride infusion

The renal excretion of potassium by unanesthetized sheep was studied in clearance studies in which water and sodium excretion were elevated by intravenous infusion of isotonic sodium chloride, hypertonic sodium phosphate, or hypertonic sodium sulfate. Aldosterone was infused at 10 microgram/h in some experiments with sodium sulfate. Sodium excretion increased in all experiments, rising at times to equal 25% of the filtered load. Urine flow increased in most experiments. Glomerular filtration rate increased only with infusion of isotonic saline. No consistent change in potassium excretion occurred under any of these loading conditions. This finding contrasts with the increase in potassium excretion commonly seen in man, dogs, and rats intravenously loaded with sodium salts.

Renal concentrating ability in the uninephrectomized rat

To investigate the effects of uninephrectomy on renal concentrating ability, studies were performed on unanesthetized rats 5-11 days after uninephrectomy (UN) or a sham operation (SO). Female rats were deprived of water for 27 h prior to the infusion of inulin and para-aminohippurate and urine collection. They were also preconditioned to being handled and to the experimental locale. During a nondiuretic state urine osmolality was the same for all UN and SO groups (mean about 1,700 micro osmol/g H2O), whereas the mean solute excretion rate (micro osmol/min per kg body wt per kidney) was 74 in the UN and 35 in the SO rats. When SO rats were infused with mannitol or isotonic saline to increase their solute excretion rate per kidney to the level of the UN rats, urine osmolality dropped 200-1,000 micro osmol/g H2O; when urea was infused, urine osmolality did not drop. Thus, after uninephrectomy and a consequent doubling of the solute excretion rate per kidney, renal concentrating ability was higher than predicted on the basis of a comparable but acute elevation of the solute excretion rate. The glomerular filtration rate was about 17 ml/min per kg body wt in the SO rats and was 1.2 times greater (on a per kidney basis) in the UN rats. These exceptionally high glomerular filtration rats are attributed to preexperimental conditioning of the rats and the absence of stress during urine collection.

Aldosterone and postprandial renal excretion of sodium and potassium in sheep

When sheep rapidly eat a meal of dry feed a period of antinatriuresis and antidiuresis is rapidly initiated and lasts for 2-3 hrs. This is followed by a postprandial period of natriuresis and diuresis. This study tested the hypothesis that the postprandial natriuresis was due to a reduction in the secretion of aldosterone. In unanesthetized ewes of about 50 kg body wt, measurements were made of sodium and potassium excretion beginning in the terminal phase of the feed-induced antinatriuresis and continuing through the period of postprandial natriuresis. Aldosterone, given by constant infusion at a physiological dose (10 microgram/h), inhibited the natriuresis. Spironolactone, a competitive inhibitor of aldosterone given as a single intravenous injection of 5 mg/kg body wt, did not significantly increase the natriuresis. These results support the stated hypothesis. Neither aldosterone nor spironolactone had a significant effect on potassium excretion. This finding supports earlier view that aldosterone has only a small role in the homeostatic control of potassium excretion in sheep.

Leprechaunism. Case report in a black African child

A case of leprechaunism is described. This is thought to be the first reported in a black child.

Urea and sodium in sheep kidneys during ethacrynic acid diuresis

The possibility of uphill transport of urea from the collecting ducts of sheep fed diets containing 14% protein (HP) and 4.9% protein (LP) was explored by measuring cortex to papilla and urine to papilla gradients of urea during ethacrynic acid diuresis. Clearance studies were done on adult, unanesthetized, hydropenic, vasopressin infused sheep. Saline was given to compensate for urine loss during ethacrynic acid diuresis. Following a period of antidiuresis, ethacrynic acid administration caused and increase in fractional water excretion to 0.33 (HP) and 0.44 (LP), an increase in fractional sodium excretion to 0.28 (HP) and 0.41 (LP), and an average increase in glomerular filtration rate of 14.7%. Fractional potassium excretion showed no consistent change. Renal concentrating ability and medullary sodium accumulation were inhibited. Antidiuretic LP and HP medullary urea accumulation patterns were lost. However, identical but small ascending cortex to papilla urea gradients remained in the LP and HP animals. There was no significant difference between the urea concentration in urine and papilla tissue water. The results fail to provide support for the presence of active urea transport from the collecting ducts of sheep fed high or low protein diets.