bluuebunny/crossref_metadata_2025 huggingface dataset:
The Complex Genetics of Kallmann Syndrome: KAL1, FGFR1, FGF8, PROKR2, PROK2, et al.
Authors: Hardelin J.-P. , Dodé C.
Published: November 2008

Kallmann syndrome (KS) combines hypogonadotropic hypogonadism and anosmia. Anosmia is related to the absence or hypoplasia of the olfactory bulbs and tracts. Hypogonadism is due to gonadotropin-releasing hormone (GnRH) deficiency, which presumably results from a failure of the embryonic migration of neuroendocrine GnRH cells from the olfactory epithelium to the forebrain. This failure could be a consequence of the early degeneration of olfactory nerve and terminal nerve fibres, because the latter normally act as guiding cues for the migration of GnRH cells. Defects in GnRH cell fate specification, differentiation, axon elongation or axon targeting to the hypothalamus median eminence may, however, also contribute to GnRH deficiency, at least in some genetic forms of the disease. To date, five KS genes have been identified, namely, FGFR1, FGF8, PROKR2, PROK2, and KAL1. Mutations in these genes, however, account for barely 30% of all KS cases. Mutations in FGFR1, encoding fibroblast growth factor receptor 1, underlie an autosomal dominant form of the disease. Mutations in PROKR2 and PROK2, encoding prokineticin receptor-2 and prokineticin-2, have been found in heterozygous, homozygous or compound heterozygous states. These two genes are likely to be involved both in monogenic recessive and digenic or oligogenic KS transmission modes. Finally, KAL1, encoding the extracellular glycoprotein anosmin-1, is responsible for the X chromosome-linked form of the disease. It is believed that anosmin-1 acts as an enhancer of FGF signalling and perhaps of prokineticin signalling too.
WNT4 and Sex Development
Authors: Biason-Lauber A. , Konrad D.
Published: November 2008

Although factors involved in male sexual differentiation have been well studied, the pathways regulating female sexual differentiation remain incompletely defined. To date, no genes have been identified to play a similar role in ovarian development as was shown for the SRY or SOX9 genes in testicular development. In mice, Wnt4 regulates the development of the female reproductive tract, antagonizes the production of testosterone, and is important for oocyte development. The recent demonstration of heterozygous WNT4 defects in patients with Müllerian agenesis and signs of ovarian hyperandrogenism added WNT4 to the growing list of genes such as SRY, SOX9, WT1, DAX1, and SF-1 contributing to human sexual development. In particular, WNT4 was the first human gene to be identified to direct development of the bipotential gonad towards ovaries. From a more clinical point of view, it seems that the absence of a uterus (and not other Müllerian abnormalities) and the androgen excess are the pathognomonic signs of WNT4 defects, suggesting that WNT4 deficiency might be a clinical entity distinct from the typical Mayer-Rokitansky-Kuster-Hauser syndrome.
Recent Developments in Identifying Genetic Determinants of Premature Ovarian Failure
Authors: Skillern A. , Rajkovic A.
Published: November 2008

Premature ovarian failure (POF) is defined as cessation of menstruation and associated elevation of gonadotropin levels (FSH >40 IU/l) as a result of decreased ovarian function prior to the age of 40. An estimated 1% of the population is affected before age 40, with 0.1% affected prior to age 30. Although the causes for POF are many, the majority of POF cases have idiopathic etiologies. In an effort to investigate potential mechanisms of the disease, genetic determinants of POF have received particular attention in recent years. Transgenic mouse models have been instrumental in the discovery of novel genetic determinants of gonadal development and failure and have informed research identifying mutations in women with POF. Here, we review recent developments in identifying genetic determinants of POF.
Primary Fibrosarcoma of the Liver: We Don’t Know Much
Authors: Ali Sadaf , Shah Parveen , Shah Umer Javed , Shah Azra , Zargar Showkat , Bashir Atthar , Dhar Sunil , Ali Muzzafar
Published: November 2008

A 60-year-old lady presented to us with a right upper abdominal mass. With a clinical diagnosis of liver tumor, she was evaluated with abdominal CT, MRI, nuclear scan, tumor markers, USG guided FNAC and other baseline investigations. On evaluation she had a massive right lobe tumor crossing the midline. In view of the ambiguous diagnosis she was subjected to laparotomy where the lesion was judged unresectable and a biopsy was taken. Histopathological examination showed the rare pathology of primary fibrosarcoma of the liver with features of homogeneous, spindle-shaped cells with abundant collagen fibers showing a classic herringbone pattern. Tissue samples were then sent to another referral cancer hospital for immunohistochemistry and immunoreactive vimentin was found in the tumor cells. Electron microscopically, the tumor cells were rich in rough endoplasmic reticulum without a basement membrane, and were surrounded by large amounts of collagen fibers. The fibroblastic character of the tumor cells was suggested by light and electron microscopy.
Regulatory T Cells Participate in 4-1BB-Mediated Suppression of Experimental Allergic Conjunctivitis
Authors: Sumi Tamaki , Ishida Waka , Mittler Robert S. , Yagita Hideo , Taguchi Osamu , Fukushima Atsuki
Published: November 2008

Background: We showed previously that treatment with an agonistic anti-4-1BB Ab during the induction phase of murine experimental allergic conjunctivitis (EC) suppresses the development of this model disease. It was reported that 4-1BB promotes the expansion of regulatory T cells. Here we asked whether the suppression of EC by agonistic anti-4-1BB Ab treatment is mediated by regulatory T cells. Methods: Neonatal BALB/c mice were thymectomized and intraperitoneally injected with anti-CD25 Ab. At 6 weeks of age, these mice were immunized with ragweed (RW) in alum. As a control, immunocompetent BALB/c mice were immunized. Ten days later, the mice were challenged with RW in eye drops and 24 h later, the conjunctivas and spleens were harvested for histological and flow-cytometric analyses, respectively. The agonistic anti-4-1BB Ab or control normal rat IgG was injected intraperitoneally during the induction phase of EC. Results: With regard to immunocompetent mice, anti-4-1BB Ab treatment significantly suppressed the severity of EC as evaluated by conjunctival eosinophil numbers. In contrast, in thymectomized and anti-CD25 Ab-treated mice in which CD4+CD25+ regulatory T cells were efficiently depleted, anti-4-1BB Ab treatment did not affect the severity of EC. Conclusions: These results indicate that CD4+CD25+ regulatory T cells play a critical role in the suppression of EC by anti-4-1BB Ab treatment.
First-Episode ‘Coenesthetic’ Schizophrenia Presenting with Alien Hand Syndrome and Partial Agenesis of the Corpus Callosum
Authors: Simon Andor , Walterfang Mark , Petralli Carlo , Velakoulis Dennis
Published: November 2008

We describe the case of a 23-year-old Caucasian woman who presented with alien hand syndrome and a first episode of the coenesthetic subtype of schizophrenia. ‘Alienness’ of her non-dominant hand was intimately phenomenologically associated with the onset of first-psychosis. Cerebral MRI revealed a partial agenesis of the corpus callosum with a complete absence of the rostrum, hypoplastic anterior and inferior genu, and a hypoplastic splenium. This case suggests that this syndrome can occur with the development of a functional disconnection syndrome involving the anterior callosum, and in this case the ‘second hit’ proposed to occur in early adulthood in schizophrenia may have interacted with her earlier neurodevelopmental lesion to result in a combination of psychosis and alien hand syndrome.
Effect of the TNFα-308 G/A Polymorphism on the Changes Produced by Atorvastatin in Bone Mineral Density in Patients with Acute Coronary Syndrome
Authors: Pérez-Castrillón José Luis , Vega Gemma , Abad Laura , Sanz-Cantalapiedra Alberto , Gonzalez Sagredo Manuel , de Luis Daniel , Duenas-Laita Antonio
Published: November 2008

Aims: To evaluate the effect of atorvastatin on bone mass and markers of bone remodeling in patients with acute coronary syndrome depending on the tumor necrosis factor-α (TNFα)-308 G/A polymorphism. Methods: Sixty-two patients with acute coronary syndrome (35 males and 27 females), average age 60 ± 10 years, were included. Patients were given low (10–20 mg) and high doses (40–80 mg) atorvastatin according to their baseline levels of cholesterol and triglycerides and their index of vascular risk. Patients were studied during hospital admission (baseline) and at 12 months of follow-up. Cholesterol, triglycerides, total calcium, phosphorus, magnesium, osteocalcin and urinary deoxypyridinoline were determined in all patients at baseline and at 12 months of follow-up. Densitometric studies were conducted in the lumbar spine (L2–L4), femoral neck and trochanter using an X-ray densitometer. The TNFα-308 G/A polymorphism was determined by the polymerase chain reaction.Results:Forty-five patients were homozygous for G/G (72.5%) and 17 were heterozygous for G/A (27.5%). The prevalence of osteoporosis (T score ≤2.5 in the lumbar spine and/or hip) was 33% for the G/G genotype and 35% for the G/A genotype, with no statistically significant differences between groups. There was a statistically significant increase in bone mineral density (BMD) in the lumbar spine (1.107 ± 0.32 vs. 1.129 ± 0.23; p = 0.0001) in patients with the G/G genotype. No changes were observed in patients with the G/A genotype. Conclusion: In patients with acute coronary syndrome, atorvastatin increases lumbar spine BMD solely in patients with the G/G genotype of the TNFα-308 G/A polymorphism.
The Natural Compound Ascorbigen Modulates NADPH-Quinone Oxidoreductase (NQO1) mRNA and Enzyme Activity Levels in Cultured Liver Cells and in Laboratory Rats
Authors: Wagner Anika E. , Hug Hubert , Gössl Richard , Riss Georges , Mussler Bernd , Elste Volker , Rimbach Gerald , Barella Luca
Published: November 2008

Ascorbigen (ABG) is a natural compound that represents a breakdown product of the glucosinolates that are present in Brassica vegetables. It is postulated that ABG may have anticarcinogenic activity; however, the underlying molecular and cellular mechanisms are largely unknown. In the present study we investigated the effect of ABG on the mRNA and enzyme activity levels of NADPH-quinone oxidoreductase (NQO1), which is centrally involved in the detoxification of xenobiotics, in cultured liver cells and in rats. The mRNA levels of NQO1 showed an increase of up to 100% in cultured liver cells (HepG2) following incubation with different concentrations of ABG (3–100 µmol/l) compared to control cells. Furthermore, NQO1 activity was elevated (up to 20%) by ABG treatment. The in vitro results were confirmed in rats who received either 5 mg/day ABG or vehicle for 7 days. Significantly higher mRNA (a 90% increase) and enzyme activity levels (a 40% increase) of NQO1 were detected in the liver of ABG-treated rats as compared to control animals. Current data indicate that ABG is a moderate inducer of the phase II enzyme NQO1, both in cultured hepatocytes and in vivo.
Micropuncture Study of Renin Release at the Single Nephron Level
Authors: Leyssac P.P.
Published: November 2008

Measurements of renin concentration in nanolitre samples of efferent arteriolar (Re), renal venous (Rv) and arterial (Ra) plasma showed that Re equalled Rv and was significantly higher than Ra at low and moderate net secretion rate. Net addition of renin directly into the circulating blood from the juxtaglomerular apparatus was insignificant at low rates of renin secretion (Rv/Ra < 1.3). At higher secretion rates (Rv/Ra ≧ 1.3) at least 37% of net secretion was released directly into the blood (p < 0.05). The haematrocrit (Hct) of collected efferent arteriolar blood was artifactually increased (72.3%) above the value calculated from the arterial Hct (48%) and the filtration fraction of 0.24.
Precise Quantitation of Glomerular Basement Membrane Morphology
Authors: Gundersen Hans Jørgen G. , Østerby Ruth
Published: November 2008

Quantitative microscopical methods for studying the glomerular capillary basement membrane are described, mainly in terms of precision and overall experimental efficiency. The methods provide absolute data for basement membrane thickness, total surface and total volume, and for glomerular capillary dimensions, namely total length, total surface and average diameter, as well as for mesangial cell and matrix volumes. The impact of these methods on current research in glomerular structure and pathology is illustrated by results from a number of recent studies of human and experimental diabetes.
Lipid Peroxidation – An Initial Event in Experimental Acute Renal Failure
Authors: Joannidis Michael , Bonn Günther , Pfaller Walter
Published: November 2008

A method was developed to monitor the occurrence of lipid peroxidation (LPO) during ischemia and Na-maleate-induced acute renal failure (ARF) on male rats in vivo by measuring malondialdehyde (MDA) levels in arterial and renal venous blood and in urine. No signs of LPO could be detected under control conditions. In ischemic ARF produced by 45 min of renal artery clamping a steep increase of MDA was found in the renal venous effluent immediately after starting reperfusion. This effect was nearly abolished after 5 min of blood reflow while glomerular filtration remained at 5% of control value during a 90-min postischemic observation period. Intoxication with Na-maleate leads to enhanced LPO in combination with an impaired renal function 2 h after administration. These findings would well explain cellular damage and some aspects of renal dysfunction associated with the initation phase of ARF.
Action of Aldosterone on Citrate Synthase in Cultured Renal Collecting Duct Cells
Authors: Minuth Will W. , Struck Michael , Zwanzig Marianne , Gross Peter
Published: November 2008

Cultured renal collecting duct cells from neonatal rabbit kidney were used to examine the influence of aldosterone on enyzmatic activity of citrate synthase during increase in Na+ transport. Control epithelia showed citrate synthase activity of 71 ± 3 mU/mg protein (n=28), while after aldosterone treatment citrate synthase activity was significantly increased to 79 ± 6 mU/mgat 1 h(n=5), to 88 ± 6 mU/mg at 2 h(n=6) and to 93 ± 8 mU/mg protein at 3 h (n=5). Citrate synthase activity subsequently decreased to basal values. Spironolactone fully blocked the aldosterone-induced increase in citrate synthase activity. The time course of enzyme stimulation after aldosterone administration indicates that the hormone activates citrate synthase during the physiological early response phase.
Ca2+ Antagonists and db-cAMP Sustain a Rise in Renal Blood Flow Induced by Acetylcholine in Indomethacin-Treated Dogs
Authors: Dehkordi Ozra , Yun John C.H. , Ho Sai-Sun , Gill, Jr. John R. , Keiser Harry
Published: November 2008

Renal arterial infusion of acetylcholine (ACh) in the dog normally produces a sustained rise in sodium excretion (UNaV) and in renal plasma flow (RPF). When prostaglandin (PG) synthesis is inhibited, ACh induces only a transient increase in UNaV and RPF followed by a progressive decline in UNaV and RPF, and a rise in renin secretory rate (RSR). Renal arterial infusion of PGE2 but not a vasodilator such as bradykinin restored the response to ACh to normal in indomethacin (Indo)-treated dogs. During renal arterial infusion of dibutyryl cyclic AMP (6 mg/min), ACh also produced a sustained increase in UNaV and RPF despite an inhibition of PG synthesis by Indo. Renal arterial infusion of verapamil (60 µg/min) or diltiazem (60 µg/min) also prevented the subsequent fall in RPF when ACh was infused; RSR, however, did not show a rise. The results suggest that synthesis of PGE2 with stimulation of cAMP is required for sustained ACh action. When PGE synthesis is inhibited, ACh may produce renal vasoconstriction by increasing intracellular Ca2+ concentration. The partial effect of calcium channel blockers suggests that release of calcium from intracellular stores as well as calcium entry may mediate the response.
Effects of Impermeant Medium Ions on the Composition of Rabbit Renal Cortical Slices
Authors: Macknight Anthony D.C. , Scott Robert J.
Published: November 2008

When incubated in isosmotic oxygenated medium in which chloride was completely replaced by gluconate, rabbit renal cortical slices lost chloride with sodium, potassium and water before reaching a new steady-state composition after 15–30 min. When corrected for extracellular space, there was an electroneutral loss of alkali metal cations (Na+K) with chloride, accompanied by isosmotic loss of water from the cells. The losses of chloride and water were independent of medium pH over the range of 6.4–8.2, and were the same with potassium rather than sodium as the dominant medium cation. Incubation in isosmotic sodium chloride medium restored tissue composition of slices transferred from gluconate medium. This recovery was not dependent specifically upon medium chloride, for slice water content also recovered when nitrate rather than chloride was substituted for medium gluconate. With sodium completely replaced by n-methyl d-glucamine (nmdG+), cells in slices lost far more sodium and potassium than chloride before reaching a new steady-state composition after some 30 min. However, the loss of water was as predicted from the total losses of measured inorganic ions. With sodium and chloride completely replaced by nmdG+ and gluconate, there was a greater loss of water than found with unilateral substitutions. Again, the combined loss of diffusible inorganic cations exceeded the loss of chloride but the water loss was that expected for isosmotic loss accompanying the measured losses of ions. These results reveal that both gluconate and nmdG+ behave as impermeant ions in this tissue preparation. It is suggested that, in the absence of medium sodium, sodium-hydrogen exchange is inhibited. Retained hydrogen ions are buffered on charged cellular non-diffusible solutes and the associated hydroxyl (or bicarbonate) ions are lost from the cells accompanied by the inorganic univalent cations lost in excess of chloride in nmdG+ medium.
23Na, 19F, 35Cl and 31P Multinuclear Nuclear Magnetic Resonance Studies of Perfused Rat Kidney
Authors: Gupta Raj K. , Dowd Terry L. , Spitzer Adrian , Barac-Nieto Mario
Published: November 2008

The concentration of intracellular sodium [Na+]i has been measured in the perfused rat kidney using 23Na nuclear magnetic resonance (NMR) in combination with the extracellular shift reagent Dy(PPPi)72-. The data show 100% visibility of Na+ in interstitial spaces. A measurement of the resonance intensities of intra- and extracellular 23Na ions along with a knowledge of the extracellular space as a fraction of the total kidney water space yielded an average [Na+]i of 27 ± 2 mM for the kidney at 37°C. After prolonged ischemia [Na+]i rose to approach that in the external medium. In the absence of 5% albumin in the perfusion medium, the linewidth of the 35Cl resonance of an adult kidney (45 Hz) was about twofold larger than that of the medium alone (25 Hz). In contrast, the linewidth of 35Cl resonance of an adult kidney perfused with an albumin-containing medium (82 Hz) was only about 27% of that from the medium alone (300 Hz). We interpret this effect to be due to compartmentation of albumin in the extracellular space such that the interstitial space is not freely accessible to albumin. However, for a developing, immature kidney from a growing animal, perfused with an albumin-containing medium, the linewidth of the 35Cl resonance (233 Hz) was only slightly less than that of the medium alone (300 Hz) indicating a much greater albumin permeability of the capillary walls. 19F NMR of a perfused adult kidney, loaded with the membrane-impermeant intracellular calcium indicator 5FBAPTA, yielded a value of 256 nM for [Ca2+]i. Induction of ischemia for 10 min caused the [Ca2+]i to rapidly rise to 660 nM, which could not be fully reversed by reperfusion, suggesting irreversible injury.
Early Metabolic Effects of Hypotension on Rat Kidney
Authors: Freeman Dominique M. , Chan Laurence , Yahaya Haliru , Holloway Paul , Ross Brian D.
Published: November 2008

Saturation-transfer phosphorus nuclear magnetic resonance (STNMR) has been applied to the rat kidney in vivo. The rate of renal metabolism determined by this method compares favorably with the renal oxygen consumption, assuming an ATP:oxygen ratio of 2. Hemorrhagic hypotension resulted in a 20% fall in renal blood flow and a significant fall in oxygen consumption. The rate of renal metabolism fell by 50%. This rate of ATP synthesis was below that required to maintain a normal [ATP], but renal [Pi] was not increased. When renal perfusion was reduced by 60%, intrarenal [Pi] rose. When [Pi] was elevated, the method os STNMR no longer gave a reliable measure of the rate ATP synthesis, indicating that this new Pi pool was not in rapid chemical exchange with ATP. STNMR represents a useful noninvasive means of monitoring renal metabolic rate, with limitations due to insensitivity and the existence of multiple pools of intrarenal Pi.
Alterations of Lithium Clearance in Rats by Different Modes of Lithium Administration
Authors: Shalmi Michael , Thomsen Klaus
Published: November 2008

This study examines the effects of acute versus dietary lithium administration on proximal tubular fluid output (Vprox) and sodium clearance in 6 groups of unrestrained, conscious rats. Vprox was estimated on the basis of the renal lithium clearance. The aim was to find the mode of lithium administration which least influences the proximal and distal reabsorption of sodium. The lithium doses used resulted in serum lithium concentrations between 0.2 and 0.3 mmol/l with no difference between the groups. Acute intravenous lithium administration increased lithium clearance by 40% and sodium clearance by 109%. Administration by gastric tube increased lithium clearance by 22% and sodium clearance by 78% in comparison to dietary administration of lithium. Potassium excretion did not change by acute lithium administration. The data presented indicate that prior to measurements of lithium clearance, lithium should be administered in the diet for 2 days, since acute lithium administration, intravenously or by gastric tube, causes great changes in renal tubular reabsorption.
Intranephron Distribution of Purine-Metabolizing Enzymes in Rats
Authors: Takahashi Takeshi , Kakuno Katsuhiko , Yamada Hideo , Endou Hitoshi
Published: November 2008

The activities of purine-metabolizing enzymes, 5’-nucleotidase, adenosine deaminase, and purine nucleoside phosphorylase in microdissected rat nephron segments were measured. The specific activity of 5’-nucleotidase was highest in the proximal tubules and the cortical collecting duct, but low in the glomerulus. In contrast, the highest activity of adenosine deaminase was found in the glomerulus. The distribution pattern of purine nucleoside phosphorylase was similar to that of adenosine deaminase. These results suggest that various nephron segments can form adenosine and that the glomerulus exhibits highest capacities to metabolize this nucleoside.
Suppression of Ouabain-Insensitive K-ATPase Activity in Rabbit Nephron Segments during Chronic Hyperkalemia
Authors: Garg Lai C. , Narang Neelam
Published: November 2008

Recently, we demonstrated that an ATPase stimulated by K (and not inhibited by ouabain, Na-K-ATPase inhibitor) is present in the connecting tubule (CNT) and collecting duct segments of the rabbit. In this study, we determined the effects of high- and low-K diet on K-ATPase activity in the CNT and collecting duct segments of rabbit. One group of animals was given a low-K diet (34 mEq/kg diet) and the other group was given a high-K diet (700 mEq/kg diet) for 1 week. K-ATPase activity was measured by a microfluorometric assay in which ATP hydrolysis is coupled to oxidation of NADH. Low-K animals had plasma K = 3.1 ± 0.2 as compared with 5.5 ± 0.5 mEq/1 in high-K animals. Low-K animals had significant K-ATPase activity in CNT, CCD (cortical collecting duct) and MCD (medullary collecting duct). On the other hand, K-ATPase activity in all 3 segments from high-K animals was not significantly different from zero. These results support a hypothesis that chronic K loading suppresses the ouabain-insensitive K-ATPase in the distal nephron.
Immunohistochemical Localization of 11-Hydroxysteroid Dehydrogenase in Rat Kidney with a Monoclonal Antibody
Authors: Castello R. , Schwarting R. , Müller C. , Hierholzer K. , Lichtenstein I.
Published: November 2008

Monoclonal antibody (MAb) against 11-hydroxysteroid dehydrogenase (11-HSD) has been raised by immunization of female balb/c mice. 11-HSD from solubilized rat renal microsomal protein could be bound in a modified ELISA using antimouse IgG and MAb against 11-HSD. On Western blots of solubilized rat renal microsomes the MAb recognized a single protein band of an approximate molecular weight of 35 kD. Immunohistochemical staining of rat renal tissue with the above MAb and the APAAP staining technique displayed a heterogenous reginal and subcellular distribution: glomeruli and arterioles were practically devoid of specific staining, as were epithelial cells in inner and outer medulla. Intense immunostaining was observed in PCT and particularly in PST, appearing granular with highest density around the nuclei. Here the enzyme bound to intracellular membranes may exert an autocrine function such as signal inactivation. In contrast to cortex, staining of interstitial cells was observed in renal medulla. The latter localization is compatible with the concept of a paracrine function of 11-HSD which might prevent corticosterone from gaining access to collecting duct cells.
Volume-Regulatory Potassium Release from Isolated Perfused Rat Kidney
Authors: Joannidis Michael , Völkl Harold , Pfaller Walter , Lang Florian
Published: November 2008

The present study has been performed to test for cell volume regulatory potassium release from the isolated perfused rat kidney exposed to hypotonic perfusate and for its sensitivity to potassium channel blocker barium and calcium channel blocker verapamil. Replacement of 25 mmol/l NaCl with 50 mmol/l mannitol has little effect on effluent potassium activity, whereas subsequent omission of mannitol from the perfusate leads to a transient increase of effluent potassium activity, reflecting volume regulatory potassium release. Barium (1 mmol/l) leads to a marked transient decrease of effluent potassium activity, pointing to net cellular uptake of potassium. Verapamil (1 µmol/l) leads to a slight decrease of effluent potassium activity. Both barium and verapamil virtually abolish the rapid, transient increase of effluent potassium activity upon exposure to hypotonic perfusates. Thus, the substances either block or markedly retard volume regulatory potassium release. The apparent renal vascular resistance is transiently increased by exposure to hypotonic perfusates and by barium, but is reduced by verapamil. Cell volume regulation of isolated perfused mouse straight proximal tubules is retarded but not abolished by verapamil (0.1 mmol/l). In conclusion, cellular potassium release from rat kidney can be determined by continuous measurement of effluent potassium activity. The volume regulatory potassium release and cell volume regulation are impaired by both barium and verapamil. The persisting cell volume regulation could be due either to slow potassium release and/or some mechanism independent of potassium.
Metabolic Regulation of Organic Osmolytes in Tubules from Rat Renal Inner and Outer Medulla
Authors: Schmolke Michael , Guder Walter G.
Published: November 2008

Glycerophosphorylcholine (GPC), sorbitol and inositol were quantitated in renal tubule suspensions from inner and outer medulla of untreated Sprague-Dawley rats to study the regulation of organic osmolyte concentrations under different metabolic conditions and varying extracellular osmolalities in vitro. Inner medullary tubules prepared in hypertonic saline (550 mosm/kg) contained osmolyte concentrations comparable to those found in the kidney in vivo. Incubation for up to 8 h at 5 mmol/l glucose increased sorbitol in the inner medullary tubules and medium in an osmolality-dependent fashion, whereas GPC and inositol remained constant. At a given glucose concentration the rate of sorbitol formation decreased linearly with increasing tubular sorbitol concentration, which was regulated by an osmolality-dependent export mechanism. Perturbation of tubular mechanisms by inhibition of glycolysis or oxidative phosphorylation did not change the tubular osmolyte content. In contrast to papilla outer medullary tubules contained only inositol. Lactate added as a metabolic substrate to the outer medullary tubules did not change the cellular inositol levels. In outer medullary tubules osmolality changes (320-710 mosm/kg) had no effect on tubular inositol. Addition of furosemide was without effect, when added in vitro. The results indicate that tubular sorbitol formation is regulated by glucose concentration, the level of tubular sorbitol, and an osmolality-dependent export mechanism. In contrast, cellular inositol and GPC levels seem to be independent of acute changes in tubular metabolism.
Ion Channels in Opossum Kidney Cells
Authors: Kolb Hans-Albert
Published: November 2008

This review discusses the activation of ion transport pathways during regulatory volume decrease in opossum kidney (OK) cells. OK cells regulate their volume when exposed to a hypotonic medium. The changes in cell volume are caused by activation of ion transport pathways and the accompanying osmotically driven water movement so that the increased cell volume returns toward physiological levels. The reshrinking of hypotonically swollen cells is termed regulatory volume decrease. In OK cells separate K+ and Cl- conductances are activated. The Na+/H+ cotransport system seems not to be involved. The potassium pathway is mediated by a K+ channel with a slope conductance of about 12 pS. The occasionally observed widely distributed Ca2+- and voltage-dependent K+ channel of large unit conductance (120 pS) seems not to be involved. The volume regulatory decrease is accompanied by a cell depolarization from a resting potential of about -60 mV to about -20 mV followed by a repolarization. It will be discussed whether the depolarization is caused by the observed activation of stretch-sensitive ion channels of about 30 and 40 pS, respectively. The transient behavior of the cell volume parallels the time-dependent change of the total membrane current. For both recording techniques the volume regulatory decrease can be blocked by quinine. In addition an inward rectifying K+ channel of about 80 pS has been observed in high KCl solution.
Ion Channels in the Thick Ascending Limb of Henle’s Loop1
Authors: Greger R. , Bleich M. , Schlatter E.
Published: November 2008

The thick ascending limb of Henle’s loop (TAL) is polarized with respect to its conductances. The luminal membrane contains a K+ conductance which is made up by the synchronous operation of 60- to 80-pS K+ channels. The basolateral membrane contains a chloride conductance. This conductance corresponds most likely to a 30- to 60-pS Cl- channel present in this membrane. Our knowledge on the properties of the K+ channels of these cells has been increased rapidly by patch clamp studies: these K+ channels are inwardly rectifying. They are highly selective for K+ over Na+, Li+ and many other cations. They do not conduct Rb+, Cs+, NHf or other larger cations. In fact, all these three cations as well as choline, tetraethylammonium, lidocaine, verapamil, diltiazem, quinine, quinidine and Ba2+ inhibit these K+ channels. As apparent from kinetic studies the mechanisms of inhibition are different for the various blockers. The TAL K+ channels are downregulated by increasing cytosolic Ca2+ activity. Cytosolic adenosine trisphosphate (ATP) has a similar effect. This ATP inhibition is Ca2+ dependent. The affinity to ATP is augmented by increasing Ca2+. Cytosolic alkalinity increases the open probability of these channels, and cytosolic acidification has the opposite effect. This pH dependence is very marked. A change by 0.2 pH units leads to a more than twofold change in the open-channel probability. The basolateral chloride conductance reflects the properties of an outwardly rectifying 30- to 60-pS Cl- channel. This channel behaves, in many respects, like the Cl- channels of a multitude of Cl-transporting epithelia. It is characterized by two open and two closed states. It is highly selective for Cl- as compared with larger anions, and it is inhibited reversibly by Cl- channel blockers such as 5-nitro-2-(3-phenylpropylamino)-benzoate.
Epithelial Na Channels: The Nature of the Conducting Pore
Authors: Palmer Lawrence G.
Published: November 2008

Na-selective, amiloride-sensitive ion channels are a crucial component of the system for controlled NaCl reabsorption across tight epithelia. A kinetic model for the process of Na conduction through the channel is presented. The model is based on a view of the possible geometry of the pore obtained from an analysis of voltage-dependent block of Na currents by impermeant cations. It is also consistent with the known electrophysiological properties of the channel, including single-channel currents, current-voltage relationships and saturation. The model, while not a unique explanation of the available data, may serve as a starting point for more detailed experimental and theoretical studies.
K+ Channels of the Mammalian Collecting Duct
Authors: Geibel John , Zweifach Adam , White Stanley , Wang Wenhui , Giebisch Gerhard
Published: November 2008

Fine control of renal water and electrolyte excretion takes place in the collecting duct, a tubule segment which is also a major site of K+ secretion and hormone action. With the introduction of patch clamp techniques it has been possible to define the contribution of ion channels to K+ transport. Two types of channels have been identified in the cortical collecting tubules of the rabbit and rat: (1) a maxi- or high conductance K+ channel (single channel conductance > 80pS) found only in the apical membrane, and (2) smaller conductance K+ channels (single channel conductance < 60 pS) found in both apical and basolateral membranes. The gating properties of the K+ channels with smaller conductances differ in the apical and basolateral cell membranes; whereas the open probability of the small conductance K+ channel in the apical membrane is not voltage-sensitive, that of the basolateral channel increases with hyperpolarization. The maxi-K+ channel, so far only found in the apical cell membrane, is voltage-gated but its open probability increases with cell depolarization. The possible role of these K+ channels in different states of the K+ transport system in collecting ducts is discussed.
Natriuretic Response to Saline Load in One-Kidney/One-Clip Hypertensive Rats
Authors: Mac Laughlin Myriam , Altenberg Guillermo , Gioioso Enzo , Amorena Carlos E. , Taquini Alberto C.
Published: November 2008

Parameters of renal function were studied in conscious and anesthetized one-kidney (1K) and one-kidney/one-clip (1K-1C) rats. Effective renal blood flow (ERBF) was significantly lower in anesthetized 1K-1C rats than in conscious ones (12.1 ± 1.6 vs. 16.4 ± 1.2 ml/min). Renal function was evaluated in two-kidney (2K), 1K and 1K-1C unanesthetized rats. ERBF was lower in 1K and 1K-1C animals than in 2K rats. Glomerular filtration rate (GFR) and urinary sodium excretion (UNa · V) were not affected by uninephrectomy with or without clipping the renal artery. In 1K-1C rats, mean arterial pressure (MAP) increased from 100 ± 2 to 140 ± lmm Hg. Subsequently, the renal ability of unanesthetized rats to handle Na was studied by a sustained extracellular fluid volume expansion (EFVE) in all groups. During EFVE, MAP remained unchanged in the 2K and 1K groups and decreased significantly in the 1K-1C group, ERBF did not change and GFR increased to the same extent in all groups. The increase in UNa · V was 40% higher in 2K than in 1K or 1K-1C rats. These findings indicate that the relatively smaller natriuretic response to a saline load of 1K rats with or without a clip in the renal artery, as compared with 2K rats, could be ascribed to renal mass reduction. Finally, the study shows the advantage of performing studies of renal function in hypertension in conscious rather than anesthetized rats.
Progressive Hypervolemia Despite Hypoproteinemia and Massive Edema Formation in Rats with Nephrotoxic Serum Nephritis
Authors: Fujihara Clarice Kazue , Marcondes Marcello , Zatz Roberto
Published: November 2008

Blood volume and whole kidney and single nephron function were evaluated 2 and 10 days after nephrotoxic serum nephritis (NSN) induction in Wistar rats. Progressive proteinuria, hypervolemia and edema were observed in NSN rats. Sodium retention was associated with a progressive depression of single nephron glomerular filtation rate and elevated fractional tubular reabsorption rates. Since hypervolemia rather than hypovolemia was observed in this study, edema formation must have been a consequence of intrarenal rather than extrarenal phenomena.
Effects of Rat Bile Infusion on Renal Function in Rats
Authors: Shen Y.S. , Chen C.F. , Liu H.M. , Fang H.S.
Published: November 2008

The influence of rat bile infusion on renal function in rats and the possible role of bile-induced hemolysis in these effects were examined. The hemolytic action of rat bile and some bile salts were determined in vitro. After the i.v. infusion of rat bile (70 mg freeze-dried powder/2.55 ml) into pentobarbitone-anesthetized rats, the urine, sodium and potassium excretion rates were reduced more than half, which was due to the decrease of glomerular filtration rate and increase of tubular water and sodium reabsorption. A fall in blood pressure, a rise in hematocrit, and hemolysis were also found. Infusion of hemolysed (30 µl RBC) solution produced by distilled water and then made isotonic caused a short-duration increase in renal excretion and glomerular filtration rate, and the blood pressure was unchanged. Infusion of a rat bile-hemolysed solution after removal of bile acids with cholestyramine increased renal excretions at first with reduction thereafter. Infusion of the rat bile-hemolysed solution treated with barium sulfate produced a renal response very similar to rat bile alone. It is proposed that two factors are involved in the renal response after bile infusion, namely bile acid-induced hemolysis producing diuresis with natriuresis, and bile acid-induced antidiuresis and antinatriuresis, possibly due to a direct renal effect.
Morphological and Biochemical Changes of LLC-PK1Cells during Adaptation to Glucose-Free Culture Conditions
Authors: Gstraunthaler Gerhard , Gersdorf Elisabeth , Fischer Walter M. , Joannidis Michael , Pfaller Walter
Published: November 2008

The established renal epithelial cell line LLC-PK1 retained in tissue culture several differentiated properties of renal proximal tubular cells. By adapting LLC-PK1 cells to glucose-free culture conditions, we recently succeeded in isolating a gluconeogenic strain of LLC-PK1 cells capable of growing in the absence of hexoses. In contrast to the parental wild type, the isolated strain expressed fructose-1,6-bisphosphatase activity and was, therefore, designated LLC-PK1-FBPase+. Besides the differences in glucose metabolism, the isolated gluconeogenic substrain differs form the parental wild type with respect to morphological appearance and the expression of apical membrane marker enzymes. LLC-PK1-FBPase+ cells display a drastic accumulation of autophagic vacuoles, disappearance of apical membrane alkaline phosphatase activity, and increased γ-glutamyltranspeptidase activity. In order to find out whether or not a low alkaline phosphatase activity in combination with the enhanced formation of autophagic vacuoles is related to a change in apical membrane surface, we utilized a combined light and electron microscopic morphometric procedure to determine the absolute amount of organelle volumes and membrane surface areas. This stereologic approach shows that LLC-PK1-FBPase+ cells display a tenfold increase in the volume of autophagic vacuoles and the lysosomal compartment. Analysis of lysosomal enzyme activities, however, revealed no changes as compared to wild-type cells. The apical membrane surface of gluconeogenic cells was found to be increased by 80%. Karyotype analysis revealed that LLC-PK1 wild-type cells were diploid, whereas FBPase+ cells exhibited polyploidy with a high percentage of tetraploid nuclei. Culturing LLC-PK1-FBPase+ cells in the presence of 5 mM glucose does not abolish the morphological and biochemical changes described, indicating the stability of the FBPase+ strain.
Adaptive Ammoniagenesis in Chronic Renal Failure
Authors: Dass P.D. , Martin D.
Published: November 2008

The role of γ-glutamyltransferase (γ-GT) in renal ammoniagenesis, glutamine (Gin), and glutathione (GSH) utilization was evaluated in the intact functioning rat kidney of subtotal nephrectomy (SNX) model of chronic renal failure (CRF). NK+4derived from extracellular γ-GT hydrolysis of Gin and GSH was differentiated from the intramitochondrial phosphate-dependent glutaminase by using acivicin, a γ-GT-specific inhibitor. In the control (C) group Gin extraction accounted for 61% of total NH+4 production (sum of renal venous and urinary NH+4, but only 41% in SNX group. In the SNX group GSH extraction accounted for 10% of total NH+4 production, but only 1% in the C group. Acivicin inhibited 44% and 33% of total NH+4roduction in SNX and C group respectively, as compared to baseline before acivicin. In CRF, γ-GT a key enzyme of the γ-glutamyl cycle plays a significant role in adaptive ammoniagenesis.
Action of Aldosterone on Cultured Renal Collecting Duct Cells during the Latent Period
Authors: Zwanzig Marianne , Minuth Will W. , Gross Peter
Published: November 2008

The effects of aldosterone on protein synthesis in the latent period were investigated on cultured renal collecting duct cells from neonatal rabbit kidneys. Tissue was incubated with radioactively labelled uridine and amino acids and then precipitated with trichloroacetic acid in order to determine the intracellular precursor pool and identify new synthesis of RNA and protein. During the latent period, aldosterone increased the intracellular radioactive uridine pool and total radioactive RNA content already 20 and 60 min after its application; conversely 40 min after aldosterone introduction, no stimulation was found. Further experiments revealed that the intracellular radioactive amino acid pool was generally increased by aldosterone after 20, 40 and 60 min, while a distinct increased radioactive protein content was found to be induced by aldosterone only after 40 min. This indicates that aldosterone increases the uptake of RNA and protein precursors and the new synthesis of RNA and proteins. These events seem to to be regulated not continously but intermittently. The induced proteins possibly take part in the mediation of the early hormone response. Experiments with the aldosterone antagonist, spironolactone, provide evidence for the specificity of the described hormone effects. The results after application of the Na+ channel blocker, amiloride, and the Na+/K+-ATPase inhibitor, G-strophanthin, indicate that the aldosterone effects are controlled by Na+ channels and Na+ pumps and therefore by the intracellular Na+ content. The inhibitory effect of cycloheximide on the aldosterone-induced protein synthesis indicates the role of these proteins on the hormone-stimulated Na+ transport.
Association of Calcium and Sodium Handling in the Rabbit Nephron
Authors: Wong Norman L.M. , Quamme Gary A.
Published: November 2008

Two-phase recollection micropuncture experiments were performed on female New Zealand rabbits to investigate the effect of flow rate (volume-expansion) compared to reabsorptive rate (furosemide) on calcium and sodium handling along the nephron. Group 1 (n = 6) rabbits represented nonvolume-expanded animals. Each experiment was conducted with a control phase followed by a second phase of furosemide administration (lmg/kg/min). Group 2 rabbits (n = 6) were initially volume-expanded to 3% body weight with modified Ringers. The fractional excretion of sodium and calcium in the control phase of group I and II was 3 ± 1 and 22 ± 6% and 4 ± 1 and 26 ± 2%, respectively. Fractional excretion of sodium, calcium and magnesium rose after furosemide administration. The effect of volume expansion on sodium, calcium and magnesium remaining in the proximal tubule was relatively modest and not affected by furosemide. Our distal micropuncture data reveal that volume expansion has a greater inhibitory effect on fluid reabsorption at a site beyond the proximal micropuncture site (group 1, 9 ± 2%, group 2, 22 ± 2%). After furosemide infusion, the amount of electrolytes remaining rose similarly in both groups; however, additional sodium and calcium reabsorption did not occur in the volume-expanded group in the final segment of the nephron. These results indicate that calcium reabsorption by the cortical terminal segment of the rabbit is passive similar to that suggested by the in vitro perfused study since no additional calcium reabsorption is seen in the volume-expanded rabbit.
Post-Ischaemic Administration of Hyperosmolar Mannitol Enhances Erythrocyte Trapping in Outer Medullary Vasculature in the Rat Kidney
Authors: Hellberg O. , Nygren A. , Hansell P. , Fasching A.
Published: November 2008

Mannitol is widely used as a therapeutic agent in the management of acute renal failure. We sought to determine whether mannitol influences the trapping of red blood cells (RBCs) in renal microvasculature, as measured from the distribution of 51Cr-labelled RBCs, in the rat kidney after ischaemia. The results indicate that administration of hyperosmolar mannitol after an ischaemic insult increases RBC trapping in the outer renal medulla in a dose-dependent manner. This was found to occur even though parameters of nephron function were unaffected or even improved.
Two Patterns of Dopa Decarboxylase Immunoreactivity in Sympathetic Axons Supplying Rat Renal Cortex
Authors: Ferguson Meredith , Bell Christopher
Published: November 2008

Three ultrastructural cytochemical methods have been used to classify the innervation of the rat renal cortex. Every axon seen contained chromaffin-reactive, dense core vesicles and stained for tyrosine hydroxylase, indicating that they were all catecholaminergic. About 10% of the axons associated with smooth muscle and juxtaglomerular cells of the arteriolar vessels also contained dopa decarboxylase, but this enzyme was not present in any of the peritubular axons. Our results are compatible with the possibility that, in the rat, the juxtaglomerular blood vessels, but not the renal tubules, are supplied by dopaminergic as well as by noradrenergic nerves.