bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructural Localisation of Substance P, Vasoactive Intestinal Polypeptide, Somatostatin and Neuropeptide Y Immunoreactivity in Perivascular Nerve Plexuses of the Gut
Authors: Fehér Erzsébet , Burnstock G.
Published: November 2008

Substance P, vasoactive intestinal polypeptide, somatostatin and neuropeptide Y-like immunoreactivity was studied by immunocytochemistry in the wall of the blood vessels of the small intestine of the cat, rat and guinea-pig. Immunoreactive nerve fibres were localized by means of the peroxidase-antiperoxidase (PAP) procedure, by use of antisera raised against these peptides. These neuropeptide-containing nerve fibres were widespread in association with the blood vessels and especially with the dense network of perivascular nerves supplying arterioles. At the ultrastructural level, immunoreactive nerve fibres were found very close to the basement membrane of the capillary walls. No immunoreactive nerve fibres were found in the wall of the veins. The anatomical findings of the present study are consistent with the proposal that several neuropeptides could function as neurotransmitters or neuromodulators in the control of blood flow in the small intestine.
Automatic Recognition of Pathological Phoneme Production
Authors: Wielgat Robert , Zieliński Tomasz P. , Woźniak Tomasz , Grabias Stanisław , Król Daniel
Published: November 2008

Objective: Proper diagnosis and therapy of pathological pronunciation of phonemes play an important role in modern logopedics. To enhance the efficiency of diagnosis and therapy an automatic recognition of pathological phoneme pronunciation is addressed in this paper. The authors focus on the therapy of phoneme substitution disorders. Patients and Methods: Recognized speech samples come from speech-impaired Polish children and partially from persons imitating speech disorders. Recognized speech disorders were substitutions in pairs {s, Ê‚}, {É•, Ê‚}, {Ê¦, tÊ‚+}, {Ê¨, tÊ‚+}, {Ê£, dÊ+ }, and {Ê¥, dÊ+ } embedded in Polish carrier words. In order to detect substitutions in the recognized words, recently proposed human factor cepstral coefficients (HFCC) have been implemented. Efficiency of the HFCC approach was compared to the application of standard mel-frequency cepstral coefficients (MFCC) as a feature vector. Both dynamic time warping (DTW), working on whole words or embedded phoneme patterns, and hidden Markov models (HMM) were used as classifiers. The HMM classifier was based on whole-word models as well as phoneme models. Results present a comparative analysis of DTW and HMM methods. Conclusions: The superiority of HFCC features over those of MFCC was demonstrated. Results obtained by DTW methods, mainly by modified phoneme-based DTW classifier, were slightly better in comparison with the HMM classifier. Results obtained for the detection of substitution in pairs {s, Ê‚}, {Ê¦, tÊ‚+}, {Ê£, Ê£+ } are very promising. The methods developed for these cases can be integrated into computer systems for speech therapy. For substitutions in pairs {É•, Ê‚}, {Ê¨, tÊ‚+}, {Ê¥, dÊ+ } further research is necessary.
International Differences in Asthma Guidelines for Children
Authors: Cope Shannon F. , Ungar Wendy J. , Glazier Richard H.
Published: November 2008

Background: Over the last decade, a number of clinical practice guidelines that include guidance for the management of pediatric asthma have been introduced. The consistency across pediatric asthma guidelines is unknown and the emphasis on establishing asthma control may vary. The objective of this paper was to depict the evolution of guidelines for pediatric asthma and to compare current international guidelines in terms of their organization, presentation of evidence and consideration of children, with special emphasis on definitions of asthma control and severity. Methods: A systematic search to identify asthma guidelines was conducted, and guidelines were searched for pediatric terms. The approaches used by guidelines to define assessments of asthma severity and control were compared between the United States, the Global Initiative for Asthma, Canada, the United Kingdom and Australia. Results: Pediatric considerations in the management of asthma have been integrated into the various guidelines to different degrees and through varied strategies. There were differences in the conceptual and operational approach used to assess asthma which emphasized either asthma severity or control. Conclusions: It will be important for future guidelines to clearly define whether the primary assessment parameter is asthma severity or control. Delineating the guideline development process and supporting evidence may improve transparency, consistency and guideline adherence.
Asthmatic Response Induced by Nasal Challenge with Allergen
Authors: Pelikan Zdenek
Published: November 2008

Background: There is a link between the upper and lower airways. Allergic rhinitis and bronchial asthma may coexist, but they can also affect each other. Objective: To investigate the possibility of nasal allergy being able to induce a secondary asthmatic response (AR). Methods: In 82 asthmatics responding insufficiently to standard antiasthmatic therapy and demonstrating negative ARs to bronchial challenge with allergen, 82 nasal challenges with various inhalant allergens were performed by means of rhinomanometry in combination with spirometry (vital capacity and forced expiratory volume in 1 s). In 33 control subjects suffering from allergic rhinitis (n = 18) or bronchial asthma (n = 15) only, 33 nasal challenges with inhalant allergens were performed by rhinomanometry and supplemented with spirometry. Results: Of the 82 nasal challenges, 69 produced a positive nasal response (p < 0.01) and 13 were negative (p > 0.05). In 58 cases with a positive nasal challenge, a secondarily induced AR was recorded (p < 0.01). The following types of ARs were documented: 17 isolated immediate ARs (p < 0.01), 24 isolated late ARs (p < 0.01), 12 dual late ARs (immediate + late, p < 0.05 and p < 0.01, respectively) and 5 isolated delayed ARs (p < 0.05). Conclusions: (1) An allergic reaction occurring initially in the nasal mucosa can play an important role in bronchial asthma by inducing a secondary AR, and (2) nasal challenge with allergen performed by rhinomanometry in combination with lung function recording (e.g. spirometry) may then determine the possible need for additional intranasal antiallergic treatment and sparing of antiasthmatic drugs.
Botulinum Toxin Type A – Treatment of a Patient with Multiple Cutaneous Piloleiomyomas
Authors: Sifaki Maria K. , Krueger-Krasagakis Sabine , Koutsopoulos Anastasios , Evangelou Georgios I. , Tosca Androniki D.
Published: November 2008

Background: Treatment of multiple cutaneous piloleiomyomas which are rare, frequently painful, benign tumors originating from the arrector pilorum muscle of hair follicles is difficult. Objective: To determine the efficiency of botulinum toxin type A (BT-A) treatment for pain relief of cutaneous piloleiomyomas. Methods: A patient with multiple painful piloleiomyomas was treated with local injections of 200 units of BT-A. Results: There was a rapid and sustained decrease in pain. Treatment was repeated every 3 months for 2 years with the same efficacy. Conclusion: BT-A may be a promising new treatment option for multiple painful cutaneous piloleiomyomas.
Porphyria Cutanea Tarda, Hepatitis C, Uroporphyrinogen Decarboxylase and Mutations of HFE Gene
Authors: Cribier Bernard , Chiaverini Christine , Dali-Youcef Nassim , Schmitt Michèle , Grima Michèle , Hirth Christine , Lacour Jean-Philippe , Chosidow Olivier
Published: November 2008

Background: Hemochromatosis gene (HFE) mutations and the hepatitis C virus (HCV) are known risk factors for porphyria cutanea tarda (PCT), but interactions with erythrocytic uroporphyrinogen decarboxylase (UROD) have seldom been addressed. Objective: In order toexamine the links between these factors, we conducted a multicentre prospective case-control study. Methods: PCT patients with (n = 32) or without HCV (n = 28) were matched to HCV+ (n = 32) and HCV– controls (n = 28). HFE mutations (C282Y and H63D) were analyzed by PCR. Results: PCT+/HCV+ patients were younger than PCT+/HCV– patients (46.9 vs. 58.2 years, p < 0.001). UROD values were not significantly different in HCV+ and HCV– patients. Both C282Y and H63D were more frequent in PCT+ patients than in controls, but there was no difference in HFE genotype according to HCV seropositivity. Mean UROD was lower in case of HFE mutations in both PCT patients and controls. Conclusion: In French patients, HCV infection is probably the major causal factor of PCT. It is not linked with HFE mutations, although they are significantly associated with PCT. A low erythrocytic UROD might be a predisposing factor. The UROD value was lower in patients with HFE mutations, suggesting a possible interaction between HFE genotype and UROD levels.
Co-Expression of KIT Receptor and Its Ligand Stem Cell Factor in Merkel Cell Carcinoma
Authors: Krasagakis Konstantin , Krüger-Krasagakis Sabine , Eberle Jürgen , Tsatsakis Aristidis , Tosca Androniki D. , Stathopoulos Efstathios N.
Published: November 2008

Background/Aims: KIT receptor has been implicated in the pathogenesis of cancer, either by mutation or autocrine activation. Merkel cell carcinoma (MCC) is a rare KIT-positive cutaneous tumor. We investigated the co-expression of KIT and its ligand stem cell factor (SCF) in MCC. Methods: Sixteen specimens from 13 MCC patients of various tumor stages were examined by immunohistochemistry for SCF, KIT, Ki67/MIB-1 and cleaved caspase 3 expression, and for apoptosis by TUNEL. Results: KIT was expressed in 13 of 16 tumors, and SCF in 15 of 16 specimens. Co-expression of KIT and SCF was detected in 12 of 16 tumors. KIT and SCF immunoreactivity scores were independent of tumor stage. Ki67/MIB-1 proliferation rates were high, whereas apoptosis rates were low, and did not depend on KIT or SCF expression. Conclusion: Co-expression of KIT and SCF in a high percentage of MCC tumors hints to an autocrine mechanism. KIT and SCF expression in primary tumors and in metastases suggests an early event in Merkel cell transformation.
Chloride Conductance of Mesangial Cells
Authors: Kurokawa Kiyoshi
Published: November 2008

In each nephron, a change in Cl delivered to the macula densa affects afferent arteriolar tone, and thus SNGFR. This phenomenon, called tubuloglomerular feedback (TGF), is the main function of the juxtaglomerular apparatus (JGA) and serves as the fine regulator of SNGFR. The phylogeny of the JGA strongly suggests that its physiological significance may be closely related to autoregulation of RPF and GFR and that JGA and TGF will allow maintenance of SNGFR in the face of low sodium intake. We propose that JGA, which appeared from amphibia, was a prerequisite, during evolution, for transition to terrestrial life style where abundant sodium intake was not guaranteed. In other words, our nephron is in essence a salt-conserving machinery to maintain SNGFR. Further, resetting of TGF or maladaptation of TGF in the presence of abundant salt intake may underlie the pathogenesis of essential hypertension.
Towards a Molecular View of Renal Proximal Tubular Reabsorption of Phosphate
Authors: Biber J. , Murer H.
Published: November 2008

Apical sodium-dependent transport of inorganic phosphate (Pi) in the proximal tubule plays a crucial role in renal Pi reabsorption and consequently in the maintenance of Pi homeostasis. This transport system represents a main target for acute and long-term regulation such as by parathyroid hormone, by growth factors and dietary intake of phosphate. In this short review we briefly describe the currently established cellular mechanism of proximal tubular Pi reabsorption and its regulation via the apical Na/Pi cotransport system. In a second part we will outline recent progress made with respect to the molecular cloning of renal Na/Pi cotransport systems. Knowledge about the molecular identity of these transport systems will make it possible to resolve yet unanswered questions about the molecular mechanisms involved in the physiology of the regulation of renal Pi reabsorption.
Hypotonicity-Evoked Release of Organic Osmolytes from Distal Renal Cells: Systems, Signals, and Sidedness
Authors: Kinne Rolf K.H. , Czekay Ralf-Peter , Grunewald Julia M. , Mooren Frank C. , Kinne-Saffran Evamaria
Published: November 2008

After a detailed description of early cellular, membrane and intracellular events in rat renal medullary collecting duct cells when exposed to hypotonicity, a synopsis on organic osmolyte transport properties possible trigger mechanisms and the cellular location of transport pathways is given. From the data currently available on renal and nonrenal cells, it is concluded that hypotonicity-evoked efflux of all organic osmolytes appears to be mediated by transport proteins which share a variety of properties more typical for channels than for carriers. A large diversity seems to exist, however, for the signalling mechanisms. Such diversity allows the cells to regulate the intracellular concentration of different organic osmolytes independently of each other, giving flexibility to the spectrum of osmotic responses. The site of release also varies from cell to cell; here conservation of organic osmolytes for future reuptake or further metabolism appears to be the major determinant.
Urinary Dopamine Excretion in Conscious Rats: Effect of Carbidopa in Different States of Sodium Balance
Authors: Mühlbauer Bernd , Osswald Hartmut
Published: November 2008

Urinary dopamine excretion was studied in seven different groups of rats (n = 6-12) with the following treatment regimens: normal chow and tap water (controls, CON), single administration of furosemide 20 mg/kg i.p. on day 1 and subsequent feeding of low sodium chow (low salt, LS), normal chow and 1 % NaCl as drinking water (high salt HS) normal chow and 1% NaCl plus deoxycorticosterone acetate 1 mg/kg/day i.p. (high salt plus DOCA, HS+DOCA); carbidopa 20 mg/kg/day p.o. (CDP) was administered in animals on normal chow (CON+CDP), in high salt rats (HS+ CDP), andinratsonhighsaltplusDOCA(HS+DOCA+CDP).Onday5, rats were placed in metabolic cages with free access to their respective drinking solution; chow was withheld. Urine was collected for 24 h and analyzed for sodium, creatinine, and dopamine. Urinary dopamine excretion rates did not change in proportion to large differences in sodium excretion in LS, HS, and HS+DOCA animals compared to CON. Only when urinary dopamine excretion of HS rats was compared to the LS group there was a moderate but significant increase of 27%. In the groups treated with CDP renal dopamine excretion was decreased by approximately 60% in comparison to the groups with the respective treatment condition but without CDP. Urinary sodium output was unchanged by CDP in CON+ CDP animals compared to CON. In HS+CDP and HS+DOCA+CDP groups renal sodium excretion was reduced by half compared to the HS and HS+DOCA groups, respectively. However, this effect was accompanied by a similar, approximately 55% reduction of oral volume and sodium intake. Renal sodium excretory capacity was unchanged by CDP treatment. Daily sodium balance (intake minus output) was similar in all experimental groups. We conclude that (1) changes in urinary sodium output during CDP treatment could be caused by extrarenal factors, and (2) sodium balance should be controlled in experiments on renal dopamine production in conscious animals. The results do not support the concept that endogenous dopamine is a crucial factor in the renal response to oral sodium load in conscious rats.
Regulation of Renal rK1-Kallikrein in Spontaneously Hypertensive Rats
Authors: Goud Danana , Oza Narendra B. , Mitsialis Alex , Levinsky Norman G.
Published: November 2008

Urinary and renal rK1-kallikrein was studied in spontaneously hypertensive rats (SHR) and their normotensive controls (WKY). It was demonstrated that the antiserum used for kallikrein radioimmunoassay (RIA) reacts with rK1- but not with rK7-protein. The specificity of the kininogenase assay was tested: rK7 had only 8% of the activity of rK1. Urinary kallikrein excretion by RIA was reduced by about two thirds in 5-week-old SHR compared WKY (11.5 versus 37.1µg/24h). On the contrary, the kidney content of rK1-kallikrein by RIA was increased by 40% in these rats (11.6 versus 8.4 ng/mg protein). The increase in kidney rK1 was confirmed by kininogenase assays. The same pattern of reduced urinary and increased renal rK1-kallikrein was observed in 8-week-old SHR rats. Kidney rK1-kallikrein mRNA tended to be lower (0.10 > p > 0.05) in SHR compared to WKY rats, suggesting that the increased kidney rK1 content is not due to increased rK1 synthesis. We hypothesize that the combination of high kidney content and low urinary excretion may be due to a defective mechanism for secretion of rK1 into the urine by tubular epithelial cells.
Cisplatin Nephrotoxicity: Site of Functional Disturbance and Correlation to Loss of Body Weight
Authors: Ammer U. , Natochin Yu. , David C. , Rumrich G. , Ullrich K.J.
Published: November 2008

We have investigated the effect of an intraperitoneal cisplatin injection (5 mg/kg body weight) into male Wistar rats on: (1) body weight; (2) proximal tubular transport of D-glucose and sulfate across the luminal membrane; (3) transport of ρ-aminohippuric acid (PAH) and sulfate across the contraluminal membrane; (4) urinary excretion of inulin; (5) urinary excretion and tissue accumulation of sulfofluorescein and (6) effect of the ‘protecting substances’, N-Methyl-D-glucamine-dithiocarbamate (NaG), diethyldithiocarbamate, mercaptosuccinate (MS), probenecid, and glycine on parameters 1 4 and 5. Five days after intraperitoneal application of cisplatin the following effects were observed: (1) body weight was reduced on average by 11% as compared to a 12% increase in control animals; (2) luminal sulfate and D-glucose transport was inhibited correlating with the degree of weight loss; (3) contraluminal PAH transport was also decreased in correlation to the loss of body weight, while contraluminal sulfate transport was not inhibited by cisplatin; (4) inulin excretion was reduced by 45%, the pattern for protection was the same as for the prevention of weight loss; (5) sulfofluorescein (SF) excretion in the urine was reduced by 43%, and (6) accumulation of SF into cortical tissue was augmented. Protecting substances prevented or mitigated weight loss, fall of urinary inulin and SF excretion as well as SF accumulation in cortical tissue with a similar pattern: N-glucamine-dithiocarbamate > mercaptosuccinate ≈ probenecid ≈ glycine. The data indicate: (1) that luminal (glucose and sulfate) and contraluminal (PAH) transport processes are affected by cisplatin; (2) that contraluminal transport (sulfate) can be unaffected or less affected than luminal transport processes (SF); (3) our method (SF) gives the possibility to monitor the balance between luminal and contraluminal transport steps in vivo; and (4) the correlation of body weight loss with decay of certain renal transport functions and their prevention with similar protecting patterns indicates that a simple index might be useful to monitor the cytotoxic status of an individual.
Transepithelial Ca2+ and Mg2+ Transport in the Cortical Thick Ascending Limb of Henle’s Loop of the Mouse Is a Voltage-Dependent Process
Authors: Di Stefano A. , Roinel N. , de Rouffignac C. , Wittner M.
Published: November 2008

The mechanisms responsible for transepithelial Ca2+ and Mg2+ transport in the isolated perfused cortical thick ascending limb (cTAL) of Henle’s loop of the mouse nephron were investigated by measuring transepithelial voltages (PDte) and transepithelial ion net fluxes (JNa, Jc1, Jĸ, Jca, JMg) by electron microprobe analysis. In the presence of furosemide (10-4 mol·l-1, lumen) and diphenylamine-2-carboxylate (DPC, 10-4 mol·l-1, bath), known inhibitors of NaCl reabsorption in the TAL, Ca2+ and Mg2+ reabsorption was completely inhibited. In the presence of furosemide, JCa fell from 0.75 ± 0.07 to -0.08 ± 0.09 pmol·min-1.mm-1 (n = 5) and JMg from 0.47 ± 0.04 to -0.01 ± 0.11 pmol·min-1.mm-1 (n = 5). In the presence of DPC, JCa fell from 0.57 ± 0.08 to -0.07 ± 0.11 pmol·min-1.mm-1 (n = 5), and JMg from 0.16 ± 0.02 to-0.11 ± 0.07pmol·min-1·mm-1(n = 5). With furosemide, inhibition of Ca2+ and Mg2+ transport was paralleled by a 93% inhibition of NaCl reabsorption, while in the presence of DPC there was a 60% reduction of NaCl reabsorption. These effects were fully reversed after removal of the inhibitors from the lumen or bath solutions. In the absence of active NaCl transport, a lumen-to-bath directed-NaCl gradient (lumen: 150 mM NaCl + furosemide, bath: 50 mM NaCl + 200 mM mannitol) generated a negative transepithelial dilution potential of-13.8 ± 1.1 mV (n = 8) which induced a significant Ca2+ and Mg2+ secretion into the tubular lumen of -0.59 ± 0.06 and 0.43 ± 0.05pmol·min-1·mm-1 (n = 8), respectively. Abath-to-lumen-directed NaCl gradient on the other hand (lumen: 50 mM NaCl + furosemide, bath: 150mM NaCl) generated a positive transepithelial dilution potential of +15.9 ± 0.6 mV (n = 7), inducing a significant Ca2+ and Mg2+ reabsorption of 0.62 ± 0.08 and 0.38 ± 0.07 pmol·min-1 mm-1(n = 7), respectively. Linear regression analysis of individual Ca2+ and Mg2+ net flux data versus voltage indicated that JCa and JMg were highly correlated to PDte. In conclusion, these data indicate that transepithelial Ca2+ and Mg2+ reabsorption in the mouse cTAL is predominantly a passive process, driven by the lumen-positive PDte.
Heterogeneous Metabolism and Toxicity of 4-Pentenoate along the Dog Nephron
Authors: Boulanger Yvan , Wong Hong , Noël Josette , Sénécal Jacques , Fleser Angelica , Gougoux André , Vinay Patrick
Published: November 2008

4-Pentenoate (4P) is a short-chain fatty acid which causes a complete renal Fanconi syndrome. We have examined the mechanism of 4P toxicity along the nephron after a prolonged (30 min) exposition of isolated renal tubular segments to this agent. In proximal tubules, 4P inhibited the activity of α-ketoglutarate dehydrogenase, pyruvate dehydrogenase, and β-oxidation, but not in thick ascending limb or inner medullary collecting duct tubules in suspension. These proximal effects were accompanied by a marked oxidation of the proximal redox state, with a fall in the tissue respiration and a low content of ATP. The acetyl-CoA content of proximal tubules was simultaneously reduced. Butyrate, acetate, hexanoate or octanoate did not exert these effects. In proximal tubules the metabolism of 4P led to the tissue accumulation of 3-keto-4-pentenoyl-CoA, a known unspecific inhibitor of metabolic oxidation. This metabolite was not detectable in thick ascending limbs which metabolized 4P rapidly. No metabolism of 4P was noted in collecting ducts. We conclude that β-oxidation probably differs in proximal and thick ascending limb tubules, allowing 4P metabolism to exert a specific toxicity in proximal tubules. A selective proximal defect in energy metabolism probably explains the Fanconi syndrome observed with exposition to 4P.
Insulin and Glucose Impact on Functional and Morphological Differentiation of Rabbit Proximal Tubule Cells in Primary Culture
Authors: Monteil Christelle , Leclere Caroline , Fillastre Jean Paul , Morin Jean Paul
Published: November 2008

Glucose and insulin impact on cellular phenotype expression was assessed on rabbit proximal tubule cells in primary culture. Glycolysis, gluconeogenesis pathways and lysosomal, mitochondrial, detoxication system, apical and basolateral membrane marker enzyme activities were assessed. Both insulin and glucose deprivation partially prevented the rise in glycolysis and delayed the drop of gluconeogenesis pathways. Scanning electron microscopy analysis of the apical surface of the monolayer revealed a much higher density of microvilli in glucose-free cultures compared to cultures developed with glucose. In conclusion, culture medium deprivation in both glucose and insulin allowed closer functional, biochemical and morphological properties to those which exist in the in vivo situation for proximal tubule cells.
Nephrotoxicity of Cyclosporine A in the Rat
Authors: Schmid Heide , Lindmeier Ismene , Schmitt Hans , Eissele Rolf , Neuhaus Gisela , Wehrmann Manfred
Published: November 2008

Cyclosporine A (15,30 or 50 mg/kg day) or olive oil (30 mg/kg day) were administered orally to 32 male Sprague-Dawley rats for 12 or 24 days, or withdrawn for 24 days following 24 days of treatment. The specific activity of a lysosomal marker enzyme N-acetyl-β-D-glucosaminidase was determined fluorometrically in single nephron segments microdissected from lyophilized kidney sections of these animals and of an additional 2 normal rats. The segments were classified according to their normal or reduced succinate dehydrogenase activity as detected in stained adjacent sections. In addition, urine specimens collected after 12, 24, 36, and 48 days of the experiment were tested for N-acetyl-β-D-glucosaminidase activity. After treatment with cyclosporine A, changes in the activities of N-acetyl-β-D-glucosaminidase were found only in the proximal tubules. In the convoluted segments with normal succinate dehydrogenase activity, the activity of N-acetyl-β-D-glucosaminidase was 138-163%, and in those with reduced succinate dehydrogenase activity, it was unchanged or 66-83% of the control values. In the straight segments with reduced succinate dehydrogenase activity, the activity of N-acetyl-β-D-glucosaminidase increased gradually along the medullary rays (122-214%) to the outer stripe of the outer medulla (178-263%) in comparison to the control values. In the urine specimens, the activity of N-acetyl-β-D-glucosaminidase was increased to 148-152%. These tubular and urinary changes were similar for each dosage and treatment period. After withdrawal of cyclosporine A they were not present. The variety of alterations occurring within the lysosomes along the proximal tubules of cyclosporine-A-treated rats implies the convoluted part as the site of increased release of N-acetyl-β-D-glucosaminidase into the urine.
Filtration Characteristics of the Single Isolated Perfused Glomerulus of Myxine glutinosa
Authors: Fels Lüder M. , Sanz-Altamira Pedro M. , Decker Brigitte , Elger Bernd , Stolte Hilmar
Published: November 2008

Using an in vitro microperfusion technique the filtration characteristics of single isolated glomeruli of the Atlantic hagfish (Myxine glutinosa) were investigated. The suitability of the method as a model to study glomerular function was evaluated. Experiments with a protein-free perfusate led to a filtration coefficient Kf (0.189 ± 0.181 nl × s-1 × mmHg-1) that was in the same order of magnitude as determined in vitro for other vertebrates. Morphometric analysis on serial thin sections (1 µm) revealed a glomerular capillary surface (A) of 1.84 ± 0.72 mm2. A linear relationship between glomerular diameter and A allowed the calculation of the hydraulic conductivity Lp (0.618 ± 0.384 µl × s-1 × mmHg-1 × cm-2). The data indicate that the isolated perfused glomerulus of M. glutinosa has filtration characteristics similar to higher vertebrates. The glomeruli of M. glutinosa, which in contrast to glomeruli of other animals are easy to dissect, are a suitable model for the study of glomerular filtration and permeability characteristics of vertebrates. An example of a possible application of the model is a study into the effects of adrenaline on glomerular filtration characteristics. Adrenaline led to increases in ultrafiltration pressure (PUF) > single nephron glomerular filtration rate (SNGFR) and filtration fraction (FF); Kf remained unaffected.
Effect of Ifosfamide Metabolites on Sodium-Dependent Phosphate Transport in a Model of Proximal Tubular Cells (LLC-PK1) in Culture
Authors: Mohrmann M. , Pauli A. , Walkenhorst H. , Schönfeld B. , Brandis M.
Published: November 2008

Ifosfamide (IF) is an alkylating cytostatic drug with urotoxic (hemorrhagic cystitis) and nephrotoxic side effects. Several cases of Fanconi syndrome in children following therapy with IF were reported. Little information is available concerning the pathomechanisms of transport inhibition by IF. We used a permanent renal epithelial cell line with proximal tubular characteristics (LLC-PK1) in order to investigate the effects of IF and some of its major metabolites (4-OH-IF, chloracetaldehyde, and acrolein). LLC-PK1 cells were used in a confluent state. Sodium-dependent and sodium-independent fluxes of 32PO4 were determined by standard techniques. Activities of marker enzymes of apical and basolateral membranes, of mitochondria, and of endoplasmic reticulum were determined in cell homogenates. IF induces a moderate stimulation of PO4 transport. 4-OH-IF also has a stimulatory effect on transport at low concentrations (up to 200 µmol/ l) and with short incubation (2h), while a 24-hour exposure of cells to 100 µmol/l of 4-OH-IF has an inhibitory effect of PO4 transport. Concentrations of 4-OH-IF which inhibit transport also reduce the activity of Na+-K+-ATPase. Chloracetaldehyde, like 4-OH-IF, induces a biphasic response of PO4 transport with stimulation in the low concentration range (up to 75 µmol/l) and inhibition at higher concentrations. Chloracetaldehyde reduces the activity of succinate-cytochrome coxidoreductase, suggesting that a defect in ATP generation might play a role in the pathogenesis of Fanconi syndrome induced by IF. Acrolein strongly damages monolayers and reduces sodium-dependent transport of P04 to very low levels at 150 µmol/l. It reduces the activities of both Na+-K+ ATPase and succinate-cytochrome c oxidoreductase. Acrolein also is the only metabolite with a moderate effect on alkaline phosphatase. We conclude that sodium-dependent transport of PO4 is highly sensitive to IF metabolites. In addition to direct toxic effects of IF metabolites on transport proteins within the apical plasma membrane, damage to mitochondrial enzymes and to Na+-K+ ATPase which generates the electrochemical gradients for secondary active PO4 transport may play an important role in the pathogenesis of Fanconi syndrome induced by IF.
Substrate Uptake and Utilization by the Kidney of Fed and Starved Rats in vivo
Authors: Elhamri Mohamed , Martin Mireille , Ferrier Bernard , Baverel Gabriel
Published: November 2008

In order to obtain information (1) on the quantitative contribution of various circulating substrates to renal metabolism and (2) on the relative importance of net luminal and basolateral transport for substrate uptake, we have precisely quantified the renal blood flow, the urinary flow, and the rates of substrate handling by the kidney of anesthetized fed and 72-hour-starved rats. For this, the concentration of twelve metabolites were simultaneously measured in arterial and venous whole blood and plasma as well as in urine of each rat thanks to the use of microassays based on enzymatic cycling. In fed rats, the main potential energy sources were glucose and lactate followed by fatty acids, ketone bodies, citrate and glycerol. Starvation caused a large increase in renal uptake and metabolism of fatty acids, ketone bodies, glutamine and glycerol, and a large inhibition of lactate utilization. The net peritubular uptake of acetoacetate, citrate, glycerol and free fatty acids demonstrated in both nutritional states was increased by starvation only for glycerol and free fatty acids; net peritubular efflux of both β-hydroxybutyrate and ammonium ions was stimulated whereas that of glutamine was converted into net peritubular uptake by starvation.
Effect of Low and High Potassium Diets on H+-K+-ATPase and Na+-K+-ATPase Activities in the Rat Inner Medullary Collecting Duct Cells
Authors: de B.Helou Claudia M. , de Araujo Magali , Seguro Antonio Carlos
Published: November 2008

This study was designed to measure H-K-ATPase and Na-K-ATPase activities in rat inner medullary collecting duct (IMCD) cells during potassium depletion and loading. Both enzyme activities were similarly distributed from the proximal to the distal portion of this nephron segment. One week K depletion did not stimulate H-K-ATPase activity but reduced Na-K-ATPase activity. Within 2 weeks after the onset of potassium depletion, the rats developed metabolic alkalosis, and H-K-ATPase activity was suppressed while Na-K-ATPase activity had returned to control values. H-K-ATPase activity was suppressed following potassium loading whereas Na-K-ATPase activity was unchanged. The results are consistent with the presence of H-K-ATPase in IMCD and indicate that H-K-ATPase and Na-K-ATPase activities are modulated by potassium intake.
The Role of the Proximal Tubule in Ochratoxin A Nephrotoxicity in vivo: Toxodynamic and Toxokinetic Aspects
Authors: Gekle Michael , Silbernagl Stefan
Published: November 2008

The proximal tubule of the kidney is regarded the main intrarenal target of the nephrotoxin Ochratoxin A (OTA). To gain further insight into the importance of the proximal tubule we investigated renal p-aminohippurate (PAH), inorganic phosphate (P), amino acid (AA) and OTA handling in male Wistar rats. The acute application of OTA (1.2 mg/kg) did not affect the renal handling of any of the substances investigated in contrast to the acute effect of OTA on ‘postproximal parts of the nephron. Application of OTA (0.5 mg/(kg·day)) over 6 days resulted in a dramatic decrease of the transport maximum of PAH (reduction to 15% of control) and to an increase of the apparent affinity of PAH to the organic anion transporter. Absolute excretion of P was not increased, whereas - due to the reduced GFR - the fractional excretion (FE) increased (to 180% of control). FE of the AA was not affected by OTA. Free-flow micropuncture experiments performed in L-homoarginine-loaded rats - to unmask possible small alterations of the amino acid transport kinetics - revealed that the proximal tubular transport of amino acids is not impaired by OTA. Subchronic exposure of the animals to OTA reduced the excretion of the mycotoxin itself to about 15% of controls. We conclude that the proximal tubule is not the main but one important intrarenal target of subchronically applied OTA. Furthermore, the action of OTA on the proximal tubule leads to decreased capacity to eliminate OTA possibly resulting in a self-enhancing effect
Simple Device for Continuous Measurement of Fluorescent Anions and Cations in the Rat Kidney in situ
Authors: Rohlicek V. , Ullrich K.J.
Published: November 2008

A simple device for fluorescence measurements on kidney surface in situ (FKS) is described. The device consists of (1) an illuminating unit, (2) a detector, (3) an evaluation unit. The device was developed for measurement of tissue content of anionic sulfofluorescein and cationic 4(4-dimethylaminostyryl)-N-methylpyridinium (ASP) during its secretion by proximal renal tubular cells.
Influence of Cell Culture Conditions and Passage Number on the Response of Membrane Voltage to ATP and Angiotensin II in Rat Mesangial Cells
Authors: Gloy Joachim , Greger Rainer , Schollmeyer Peter , Huber Markus , Pavenstädt Hermann
Published: November 2008

The influence of passage number and different culture conditions on the effect of ATP and angiotensin II (A II) on membrane voltage (Vm) of rat mesangial cells (MC) was examined with the patch clamp technique in slow and fast whole cell recordings. MC were characterized immunologically and grown in standard medium in primary culture (PC) and long-term culture up to passage 21 in the presence of 90 g/l fetal calf serum (LTC/ +FCS) or without or with 5 g/l FCS for 1-3 days (LTC/-FCS). In all three series the studies were performed in a FCS-free Ringer-like solution. Vm of MC did not differ in the series (PC: -49 ± lmV, n = 151; LTC/+FCS: -52 ± 1 mV, n = 49; LTC/-FCS: -51 ± 1 mV, n = 44). In primary culture and long-term cultured MC up to passage 8, FCS (ED50≈5 g/l), ATP (ED50 ≈ 2 × 10-6 mol/l) and AII (ED50 ≈ 5 × 10-10 mol/l) induced a depolarization of Vm. Reduction of extracellular Cl- concentration (from 145 to 32 mmol/l) had no effect on Vm but led to an increased depolarization of Vm by FCS, ATP and A II. In long-term cultured MC above passage 8 grown with 90 g/l FCS both ATP and AII induced a concentration-dependent hyperpolarization of Vm, which was attenuated in increased extracellular K+ concentration (from 3.6 to 33.6 mmol/l). In long-term cultured MC beyond passage 8, grown without or with a reduced FCS concentration of 5 g/l, ATP and A II led to a transient depolarization of Vm, which was increased in the presence of 32 mmol/l extracellular Cl-. The depolarization was followed by a hyperpolarization, which was attenuated in the presence of increased extracellular K+. The data indicate that vasoactive agents depolarize Vm of MC in primary culture by activating a Cl- conductance whereas they hyperpolarize Vm by activation of a K+ conductance in long-term cultured MC grown with FCS. The latter effect was partially reversed when FCS was omitted.
Relationship between Renal Mass and Atrial Natriuretic Peptide Release
Authors: Averbukh Z. , Berman S. , Weissgarten J. , Cohn M. , Golik A. , Cohen N. , Shaked U. , Modai D.
Published: November 2008

Serial serum atrial natriuretic peptide (ANP) determinations were performed in 15 uninephrectomized Charles River rats and in 15 sham-operated control animals during the 60 days following surgery. In a second group of 7 control and 7 uninephrectomized animals housed in metabolism cages, serum ANP, body weight, 24-hour urine volume, osmolality and sodium excretion were serially measured. In a third group of uninephrectomized and control rats the effect of acute salt loading 24 h, 6 and 60 days after surgery on serum ANP was studied. No significant changes in ANP levels were observed during the 60 days following surgery in control animals. In the uninephrectomized animals a sharp drop in basal ANP levels was evident 24 and 48 h after surgery, but increased levels of serum ANP were seen from day 6 to 28. Thereafter ANP returned to baseline levels for the rest of the study period. Urinary sodium excretion decreased in the nephrectomized animals on days 1 and 2 following surgery. No such change was seen in the control animals during the same period. Body weight, 24-hour urine volume and urine osmolality were not statistically different in the nephrectomized vs. control rats at any time and remained constant in each group throughout the experimental period. Central venous pressure (CVP) did not change significantly in both groups 24 h and 6 days following surgery. CVP rose similarly in both groups immediately following saline loading and returned to preload levels 1 h later. Nephrectomized animals showed no change in serum ANP 1 h after saline loading performed 24 h after surgery, while in control animals acute saline load resulted, as expected, in a significant rise in serum ANP. 6 and 60 days following surgery, augmented ANP release 1 h after acute salt loading was evident in both the nephrectomized and control groups. We suggest that some as yet unknown mechanism exists through which the renal mass contributes to the control of ANP secretion by the cardiac atria.
Relationship between Renal Mass and Atrial Natriuretic Peptide Release
Authors: Averbukh Z. , Berman S. , Weissgarten J. , Cohn M. , Golik A. , Cohen N. , Modai D.
Published: November 2008

We studied basal serum atrial natriuretic peptide (ANP) levels and the response to acute salt loading in rats with different grades of functional renal mass reduction. The six groups of rats studied included 2 controls, i.e. unoperated (n = 12) and sham-operated (n = 24) groups. Each of the 4 experimental groups (n = 24 in each) underwent one of the following procedures: bilateral nephrectomy; unilateral nephrectomy; bilateral ureteral ligation; unilateral ureteral ligation. Basal ANP was assessed in the intact controls and operated groups 4, 8,16 and 24 h after surgery. In addition, ANP was determined in the sham-operated controls and in the experimental groups 1 h following acute intravenous saline loading performed 4 h after surgery with central venous pressure monitoring. Basal ANP dropped significantly following bilateral nephrectomy but was not significantly altered after unilateral nephrectomy or the two modalities of ureteral ligation . In all 4 experimental groups ANP failed to rise after saline loading. We conclude that substantial renal damage results in early impairment in ANP secretion suggesting the existence of a renal physiological stimulus controlling ANP release by cardiac atria.
In vivo Hydrogen Peroxide Production in Rat Remnant Kidney
Authors: Van den Branden Christiane , Vamecq Joseph , Verbeelen Dierik , Roels Frank
Published: November 2008

In the rat remnant kidney hydrogen peroxide (H2O2) production is increased when compared to the normal kidney. The activities of the peroxisomal H2O2-producing oxidases, D-amino acid oxidase and acylcoenzyme A oxidase, and of the extraperoxisomal superoxide dismutase are decreased in renal homogenate. The peroxisomal L-α-hydroxyacid oxidase and L-lactate oxidase as well as the peroxisomal H2O2 scavenger catalase preserve their activity. The activity of the cytosolic scavenging system, glutathione peroxidase, is decreased by 40%. A starvation period of 48 h does not produce a measurable increase in H2O2 production in the normal nor in the remnant kidney. On visual inspection, peroxisomal morphology and distribution in the renal tubules are similar in the normal and remnant kidney tissue.
Glucose Metabolism in Dog Inner Medullary Collecting Ducts
Authors: Meury L. , Noël J. , Tejedor A. , Sénécal J. , Gougoux A. , Vinay P.
Published: November 2008

The adenosine triphosphate (ATP) generating pathways of dog inner medullary collecting ducts (IMCD) were examined in vitro using suspensions of dog IMCD tubules incubated under aerobic and anaerobic conditions. Glucose is always the preferred substrate for this tissue, even if lactate can be oxidized under aerobic conditions. The metabolism of glucose proceeds largely towards lactate accumulation in the presence or absence of oxygen. Glycogen is also consumed and more markedly so during anoxia. The pentose shunt represents a minor pathway for glucose metabolism in this tissue. Under aerobic conditions, the net oxidation of glucose to CO2 contributes significantly to the cell energetics, mitochondrial and cytoplasmic mechanisms sharing equally the ATP synthesis. In the absence of oxygen, only the cytoplasmic routes of ATP synthesis are used, but the apparent ATP turnover is markedly reduced. A marked inhibition of the activity of the Na-K-ATPase during anoxia explains this observation. The utilization of glucose for osmolyte synthesis is a minor process and appears to be suppressed under anaerobic conditions. It is concluded that the ATP turnover is low in dog IMCD cells as compared with that of other nephron segments and is largely dependent upon glucose availability under aerobic or anaerobic conditions.
Intracellular Ca2+-Mg2+ Interactions
Authors: Günther Theodor , Vormann Jürgen
Published: November 2008

To ascertain possible interactions of intracellular Mg2+ and Ca2+, the concentration of intracellular free Ca2+ ([Ca2+]i) and intracellular free Mg2+ ([Mg2+]i) were experimentally increased within physiological ranges and it was measured by means of fura-2 and mag-fura-2 whether the increased concentration of one divalent cation affected the concentration of the other. A four-fold increase of [Ca2+]i in rat thymocytes by concanavalin A or thapsigargin had no significant effect on [Mg2+]i. Incubation of rat thymocytes in Na+-free medium increased [Mg2+]i from 0.35 to 0.7 mM. This increase in [Mg2+]i did not affect [Ca2+]i or the action of thapsigargin on [Ca2+]i.
Low-Molecular-Weight Protein Competition for Binding Sites on Renal Brush Border Membranes
Authors: Dreisbach Albert W. , Batuman Vecihi
Published: November 2008

Immunoglobulin light chains, β2-microglobulin, insulin, and lysozyme are low-molecular-weight proteins (LMWP) shown to bind to renal brush border membranes. Competition among these proteins and the role of electrical charge in binding to brush border membranes have not been resolved. To investigate these factors, we performed displacement experiments with [125I]-labeled β2-microglobulin (pI - 5.6) using six species of LMWP over a pi range of 4.4-11.0. The inhibition constants, Ki, of these six competing ligands, χ- and λ-light chains, lysozyme, insulin, cytochrome c, and myoglobin, determined from the log displacement curves, ranged from 4×10-5 to 8×10-4M. These experiments show marked cross-competition among LMWP for binding to brush border membranes. There was no correlation between Ki and pI indicating that the molecular structure is a more important determinant of LMWP binding to brush border membranes than net electrical charge.
Effect of Myeloma Light Chains on Phosphate and Glucose Transport in Renal Proximal Tubule Cells
Authors: Batuman Vecihi , Guan Shangbo , O’Donovan Richard , Puschett Jules B.
Published: November 2008

Primary cultures of cells derived from the rat proximal tubule were exposed to up to 200 µM λ- or χ-light chain obtained from myeloma patients. Light chains inhibited the uptake of both phosphate and glucose by the cells while albumin had no effect. The half-maximal inhibitory concentration (IC50) of both the λ-and ĸ-light chains on phosphate transport were similar, 34 and 35 µM respectively. The IC50 of the ĸ-light chain on glucose transport was 360 µM. The inhibitory effect of light chains was dose-dependent (r = 0.90, p < 0.0l for the λ-light chain and r = 0.93, p < 0.001 for the χ-light chain, on phosphate transport; and r = 0.93, p < 0.00l for glucose transport). Dixon and Line-weaver-Burk plot analyses were characteristic for noncompet-itive inhibition. The inhibition constant 89 µMfor phosphate uptake derived from the Dixon plot was similar to the IC50 calculated from the dose-response curves. These findings indicate that light chains, at concentrations found in the tubule fluid of a typical myeloma patient, are potent inhibitors of phosphate and glucose transport in proximal tubular cells, and that direct cell toxicity is a major mechanism of light chain nephrotoxicity.
Ammonia Production from Hippurate by the Rat Kidney in vitro
Authors: Mályusz M. , Hackl A. , Wrigge P. , Lange M. , Mályusz T. , Sick H. , Gronow G.
Published: November 2008

Hippurate is known to be synthesized from benzoate and glycine in the liver and kidney. It takes part in renal ammoniagenesis by modulating the activity of γ-glutamyl transpeptidase (γGT). Due to its chemical structure, however, hippurate might also serve as a substrate of renal ammoniagenesis. Hippurate may yield ammonia either having been cleaved by hippuricase or by Erlenmeyer’s reaction after condensation with an aldehyde. In order to elucidate the possibility of hippurate being a substrate of renal ammoniagenesis, experiments were carried out on cortical kidney slices and on isolated tubular segments of the rat. The incubation medium (pH 7.1) was enriched with 10 mmol/l hippurate spiked with l5N-hippurate, some of the known competitive inhibitors of hippuricase, acivicin and different aldehydes. Factors known to affect hippuricase or γGT did not interfere with renal ammonia production. Glyceraldehyde (up to 1.0 mmol/l) but not glycerate had a stimulating effect, especially on the ammoniagenesis from hippurate. In normal rats fed a vegetarian diet, 1% of the added 15N moiety was found to be 15NH3. Renal l5NH3 production was significantly greater if, prior to the experiments, the animals were either acidotic or had a reduced renal mass or were fed animal proteins. These results indicate that hippurate may, to a certain extent, serve as substrate for ammoniagenesis.