Mating patterns of female Leon Springs pupfish Cyprinodon bovinus.

In a field study of Leon Springs pupfish Cyprinodon bovinus, two questions about female promiscuity were investigated. First, were females selective in the males with whom they spawned or were they unselective, spawning randomly among males? Second, how promiscuous were the females, i.e. with how many males did they spawn? If simply spawning with many males maximized a female's reproductive success, then females might be expected to spawn randomly with as many males as possible. Alternatively, if females were selective but engaged in multiple mating, they would limit their spawning to preferred males. In the only wild population of this endangered fish, breeding males defend closely associated territories in the shallow margins of a single desert pool. No territories were observed elsewhere in the pool. Therefore, all territorial males were present simultaneously and females could survey all of them, depositing any number of eggs with one, a few or many males. Rather than spawning randomly, females surveyed many males first, visited relatively few males and ultimately spawned with a small fraction of those available males. With increasing numbers of spawns, however, females increased the number of different mates with whom they spawned. Thus, females showed a bet-hedging tactic of having a narrow mate preference while also laying eggs in the territories of other males, possibly to reduce egg predation and to avoid inbreeding.

Erythropoietin requirements increase following hospitalization in end-stage renal disease patients.

UNLABELLED: The effect of hospitalization on an ESRD patient's hemoglobin (Hgb) level and erythropoietin (Epo) requirement has not been investigated. We postulated patients with end stage renal disease required an increased Epo dose to maintain stable Hgb during hospitalization and for a period following discharge. To evaluate this hypothesis, we conducted a retrospective chart review on 65 hemodialysis patients. All hemodialysis patients admitted for more than 2 days who did not have more than the index hospitalizations for 2 months prior to and following discharge were included. Multiple parameters including Hgb, Epo dose, intravenous iron dose, serum iron, TIBC, and ferritin during the 2 months before and the two months after hospitalization, Hgb at admission and discharge, Hgb trough, surgery, blood transfusions and co-morbid factors were evaluated. Statistical significance was evaluated using ANOVA or rank-sum testing, as appropriate. In 65 hemodialysis patients (24 M/41 F, age 58 +/- 2.2 years, mean +/- SEM), Hgb levels following discharge and for 2 subsequent months were significantly lower than 2 months prior to admission (11.4 +/- 0.25 vs. 10.7 +/- 0.22 g/dl, p < 0.01). This occurred in spite of an increase in Epo dose (128 +/- 14 vs. 185 +/- 21 U/kg/week, p < 0.0001) over this 2-month period. There was no difference in the iron saturation before and after hospitalization (22 vs. 23%,p > 0.05). There were also no apparent effects of comorbid factors, including surgery, or discharge diagnosis on the changes in Hgb or Epo requirements. However, patients who required a blood transfusion during the hospitalization had lower Hgb levels and higher Epo doses both prior to and after hospitalization, as well as lower Hgb trough levels. In addition, females had lower Hgb levels than males both prior to and after hospitalization, and were receiving a higher Epo dose 191 +/- 18 vs. 129 +/- 20 U/kg/week at 1 month and 215 +/- 18 U/kg/week vs. 134 +/- 22, p < 0.005 at 2 months after hospitalization. CONCLUSION: This study points out that hemodialysis patients experience a significant and prolonged decrease in Hgb levels after hospitalization, even despite a moderate increase in Epo dosing.

Adverse effect of peritonitis on peritoneal membrane function in children on dialysis.

The effect of peritonitis on peritoneal membrane solute transport characteristics was determined as part of a multicenter study in children on continuous ambulatory/cycling peritoneal dialysis. Ninety-three children each underwent a 4-h peritoneal equilibration test (PET) with 1,100 ml/m2 2.5% Dianeal for determination of mass transfer area coefficients (MTAC), dialysate to plasma ratios (D/P) for creatinine and urea at 0, 30, 60, 120, 180, and 240 min and dialysate glucose levels at 0, 30, 60, 120, 180, and 240 min for calculation of D/Do. The mean age of the study cohort was 10.1 +/- 5.6 years (range 0.1-19 years). There were 162 historical episodes of peritonitis; at the time of the PET tests, 36 children had never had an episode of peritonitis (group I) while 57 children had a history of one or more episodes of peritonitis (group II). In group II children, the 4-h glucose D/Do was significantly lower and the 4-h D/P creatinine ratio, the creatinine MTAC, and the glucose MTAC were significantly higher (each P < 0.05) than in group I. In children with a history of peritonitis caused by Gram-negative organisms, the 4-h glucose D/Do (P < 0.05) and the creatinine MTAC (P < 0.05) were significantly lower and the glucose MTAC (P = 0.07) nearly significantly lower than in children without a history of peritonitis. Linear regression analysis did not demonstrate a correlation between any of the variables and duration of peritoneal dialysis, while the rate of peritonitis was weakly correlated with glucose MTAC (r = 0.34, P < 0.05) and with 4-h glucose D/Do (r = -0.222, P < 0.01). We conclude that children with a history of peritonitis have peritoneal membranes that are more permeable to glucose and creatinine than children without a history of peritonitis, and that the peritoneal membranes of children who have had peritonitis caused by Gram-negative organisms are also more permeable to creatinine and glucose. Such changes are likely to have an adverse effect on membrane function and could eventually contribute to ultrafiltration failure.

The impact of vesicoureteral reflux on contralateral renal length in infants with multicystic dysplastic kidney.

PURPOSE: The purpose of our study was to determine the influence of vesicoureteral reflux (VUR) on contralateral renal length in neonates and young infants with unilateral multicystic dysplastic kidney (MCDK). MATERIAL AND METHODS: We reviewed the imaging findings in 48 term neonates and infants (27 boys; 21 girls) who had unilateral MCDK (mean age at diagnosis 0.09 years; range 0-0.64 years). Each had renal ultrasonography (RUS), renal scintigraphy, and voiding cystourethrography before 1 year of age. The diagnosis of MCDK was based on characteristic imaging findings (i. e., an echogenic, cystic kidney at RUS that did not function at scintigraphy). None had contralateral hydronephrosis or cysts. We calculated an age-corrected z-score for contralateral renal length (at RUS) in each patient based on published standards. We examined the effects of gender, ipsilateral or contralateral VUR, and age at RUS on the contralateral renal length using multifactor ANOVA. RESULTS: Nine patients (19 %) had VUR into the contralateral kidney. The refluxing kidneys were significantly shorter (renal length: median 5.1 cm, mean 5.07 cm; z-score: median - 0.43, mean - 0.58) than the nonrefluxing kidneys (renal length: median 6.2 cm, mean 6. 08 cm; z-score: median 1.03, mean 1.04; P < 0.001). The contralateral kidney was more than 1 SD longer than the mean for age in none of the 9 patients with VUR on that side. By comparison, the contralateral kidney was more than 1 SD longer than the mean for age in 21 (54 %) of 39 patients with no VUR on that side, and more than 2 SD longer than the mean in 5 (13 %). CONCLUSION: VUR into the kidney contralateral to a MCDK is associated with smaller size of that kidney during the first year of life.

Aminoglycoside antibiotics traffic to the Golgi complex in LLC-PK1 cells.

Aminoglycoside antibiotics are known to be internalized via endocytosis and have been associated with subcellular organelle dysfunction; however, the route of intracellular trafficking and their distribution remain largely unknown. To address these questions, a Texas Red conjugate of gentamicin (TRG) was synthesized for dual-labeling experiments with the endoplasmic reticulum, Golgi, and lysosomal markers DiOC6-3, C6-NBD-ceramide, and fluorescent dextrans, respectively. Confocal images were overlaid to determine areas of colocalization. Initial characterization studies of the fluorescent gentamicin analogue revealed that both internalization and accumulation were inhibited by excess unlabeled gentamicin. Furthermore, the fluorescent gentamicin label was colocalized with unlabeled gentamicin, using immunologic techniques. LLC-PK1 cells were exposed to the fluorescent gentamicin in media containing 1 mg/ml labeled gentamicin for 8 h and then either fixed or chased with gentamicin-free media for an additional 16 or 40 h (24 to 48 h total). Studies with fluorescent dextrans revealed rapid intracellular colocalization within the endosomal and lysosomal systems. Neither endoplasmic reticulum nor mitochondrial colocalization could be detected. However, Golgi colocalization was revealed using both confocal and electron microscopic techniques at 8 h of TRG incubation, and continued to be present for an additional 40 h. Protein synthetic rates were quantified and revealed decreased synthesis at the 24-h chase mark. These results suggest that TRG can serve as a fluorescent tracer for aminoglycoside trafficking within cells. The fluorescent marker remained associated with vesicular structures at all times and colocalized with the Golgi apparatus. It is postulated that this early association of gentamicin with the Golgi complex may be an avenue for delivery of aminoglycosides to other intracellular compartments.

Response of crescentic Henoch-Schoenlein purpura nephritis to corticosteroid and azathioprine therapy.

The benefits of treating severe Henoch-Schoenlein Purpura (HSP) glomerulonephritis have not been established. In this study, we evaluate the outcome of 21 children with severe HSP nephritis treated with corticosteroids and azathioprine. Between 1977 and 1995, 78 children (age range 1 to 16 years) were seen for evaluation of HSP. Thirty-one underwent kidney biopsy; indications included nephritic and/or nephrotic onset (15 patients), persistently decreased creatinine clearance (5 patients), or proteinuria > 4 g/24 h (11 patients). Twenty treated patients had diffuse mesangial proliferation with crescents in 6-100% (mean 40%) of glomeruli. One treated patient, not biopsied due to extreme obesity, had a creatinine clearance of 49 ml/min/1.73 m2 and proteinuria of 21.3 g/24 h. These 21 patients were initially treated with azathioprine and daily oral prednisone (13 patients) or i.v. methyl-prednisolone (8 patients), followed by azathioprine and alternate-day prednisone for 9-24 (mean 15) months. The average follow-up was 32 months. Over the course of follow-up, 19 treated patients showed a decline in hematuria (> 5 red blood cells/high power field) from 100% to 16% (p < 0.01), a fall in the serum creatinine from 1.71 +/- 2.20 to 0.78 +/- 0.25 mg/dl (p < 0.01), an increase in creatinine clearance from 76 +/- 43 to 122 +/- 26 ml/min/1.73 m2 (p < 0.01), and a reduction in proteinuria from 8.8 +/- 7.5 to 0.47 +/- 0.39 g/24 h (p < 0.01). Two treated patients progressed to end-stage renal failure. There was no difference in outcome comparing patients initially treated with prednisone versus methyl-prednisolone. These observations suggest that corticosteroid and azathioprine therapy is effective in crescentic HSP nephritis.

Role of the actin cytoskeleton in ischemia-induced cell injury and repair.

This paper reviews the role of the actin cytoskeleton in the establishment and maintenance of surface membrane structure and function in all epithelial cells. It describes in detail certain interactions between the actin cytoskeleton and the surface membrane. Recent studies show that ischemia and/or ATP depletion will rapidly disrupt the actin cytoskeleton, an important event in ischemia-induced cell injury. Finally, the review examines specific functional and structural interactions between the actin cytoskeleton and the surface membrane.

Calcitriol and the parathyroid hormone-ionized calcium curve: a comparison of methodologic approaches.

Investigations of the effects of calcitriol on the inverse sigmoidal relationship between parathyroid hormone (PTH) and ionized calcium (iCa) have yielded contradictory conclusions, possibly because of variations in experimental and analytical approaches. To clarify the existing literature, PTH-iCa curves were constructed by inducing hypo- and hypercalcemia through alterations in dialysate calcium concentration in eight hemodialysis patients with mild to moderate secondary hyperparathyroidism. The effects of low (metabolic acidosis) versus normal bicarbonate dialysis were compared before and after 4 wk of intravenous calcitriol, in a cross-over design. The PTH-iCa curves were primarily evaluated by using a four-parameter model. In addition, a variety of alternative published analytic approaches were examined and PTH-iCa curve slopes were further evaluated after normalization by (maximum - minimum PTH). The latter partially corrects for gland mass and cell-secretory capacity, and therefore yields a purer measure of the sensitivity of secretory activity to changes in iCa. The results of the study indicate that calcitriol decreased basal, maximal, and minimal PTH and non-normalized slope (all P < 0.05), but did not affect set point or normalized slope, independent of the specific analytic approach. Acute metabolic acidosis did not affect the PTH-iCa curve. Thus, intravenous calcitriol appears to decrease parathyroid gland functional mass, as reflected by decreases in maximal and minimal PTH levels, but does not affect the sensitivity of the parathyroid gland to changes in iCa, as set point and normalized slope were unaffected.

Disease processes in epithelia: the role of the actin cytoskeleton and altered surface membrane polarity.

The establishment and maintenance of cell polarity is essential for normal epithelial function. Disruption of the underlying processes, either as a primary inborn defect or as a secondary result of other pathologic processes, can lead to loss of epithelial polarity and further cellular and organ-level dysfunction. Continued elucidation of the processes involved may prove fruitful both in the understanding of basic cell biology and in the understanding and treatment of a variety of disease states.

On the analysis of substrate cycles in large metabolic systems.

The simultaneous operation of paired, opposing reactions (substrate cycles) or parallel reactions (dual pathways) with seeming wastage of ATP is widespread in cellular metabolism. Analysis of such "futile" pathways has hitherto been limited to loci with only two or three interconnecting fluxes. We introduce here a method that allows straightforward analysis of more complex systems. The method involves the linear superposition of "fundamental" modes, one or more of which may be energetically wasteful. Decomposition of a flux pattern into such modes allows computation of the amount of free energy "wasted" at any locus. Appropriate normalizations of energy wastage yield a number of indices useful for assessing the energetic impact of futile pathways on the cell and for comparing the degree of regulation of substrate cycles or dual pathways under different metabolic conditions. This approach is applied to steady-state flux data obtained in the protozoan Tetrahymena pyriformis and in isolated rat hepatocytes under a variety of conditions.

Interpretation of dose-response curves for luteinizing hormone release by gonadotropin-releasing hormone, related peptides, and leukotriene C4 according to a hormone/receptor/effector model.

The dose-response curves for pituitary luteinizing hormone (LH) release in response to gonadotropin-releasing hormone and its agonists are unusually broad. It appears, however, that these ligands bind to a single class of receptors. It is shown that these dose-response data can be explained by either of two models in which ligand-receptor complexes stimulate LH secretion by interacting with either of two different effector systems or by interacting with a single effector system but forming monomeric and dimeric active effector complexes. A combination of these two basic models can account for the very broad, biphasic dose-response curve reported for LH release in response to leukotriene C4.

Effects of VIP and forskolin on alanine metabolism in isolated hepatocytes.

The effects of vasoactive intestinal polypeptide (VIP) and of forskolin on alanine metabolism in hepatocytes isolated from fed and fasted rats were examined. VIP and 17 microM forskolin stimulated glucose production, gluconeogenesis from alanine, and ureagenesis, and inhibited glyconeogenesis to comparable degrees. However, combination of 17 microM forskolin with a maximal dose of VIP significantly augmented only the inhibition of glyconeogenesis. At 100 microM, forskolin induced metabolic responses comparable to those induced by glucagon, but similarly, in combination with maximal doses of VIP or glucagon, augmented only inhibition of glycogen synthesis. In addition to demonstrating modulation of alanine metabolism by VIP and forskolin, these results raise questions about the nature of the coupling between VIP receptor occupancy and metabolic response.