bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Endocannabinoids in 5-HT2 Receptor-Mediated Effects
Authors: Connelly William M. , Baggott Matthew J.
Published: November 2008

Endocannabinoids are lipid retrograde messengers that can be released by postsynaptic depolarization and/or activation of certain metabotropic receptors. We review a recent report that activation of metabotropic 5-HT2 receptors by endogenous serotonin induces the release of endocannabinoids in the olivary nucleus and suppresses glutamatergic input through a presynaptic action. This serotonin–endocannabinoid interaction has implications in the pathophysiology of pain and mental illness and raises the possibility that drugs targeting the 5-HT2 receptor may act by modulating endocannabinoid release.
Effects of Sodium Vanadate on Various Types of Vascular Smooth Muscles
Authors: Shimada Tomoko , Shimamura Keiichi , Sunano Satoru
Published: November 2008

Effects of sodium vanadate on various vascular smooth muscles of guinea pigs, rabbits, and Wistar Kyoto rats (WKY) were studied. Sodium vanadate of concentrations higher than 10-5 M induced contractions in the aortae of all animals. The contractile effects varied among vascular smooth muscles, and mesenteric arteries showed no or only weak contractile response to the drug, while aortae showed higher contractile responses. In the portal veins, potentiation of spontaneous contractions was observed by the application of sodium vanadate. These responses were not blocked by treatments with adrenergic blocking agents or indomethacin, indicating the direct action of the drug on vascular smooth muscles. Treatment with 4,4’-diisothiocyanostilbene-2,2’-disulfonic acid (DIDS) blocked completely the contractile effects of sodium vanadate, whereas it showed no effect on K-contractures. Partial depolarization of the membrane by elevations of K concentration potentiated sodium vanadate-induced contractions and minimized the variations of responses among preparations. In K-depolarized preparations, sodium vanadate often induced relaxation of preparations. The contractile effects of sodium vanadate were not blocked by treatment with ouabain, though ouabain also showed contractile actions in a number of preparations. It was suggested that vanadate acts directly on vascular smooth muscles and causes contractions without relation to the inhibition of NaK-ATPase. It may cause contractions inhibiting Ca-ATPase of sarcoplasmic reticulum and/or of cell membrane, and cause relaxation by inhibiting ATPase of contractile proteins. The variations of the responses may be explained by differences of membrane permeability to vanadate.
Histamine-Induced Constriction and Dilatation of Rabbit Middle Cerebral Arteries in vitro: Role of the Endothelium
Authors: Sercombe R. , Verrecchia C. , Philipson V. , Oudart N. , Dimitriadou V. , Bouchaud C. , Seylaz J.
Published: November 2008

We studied the effects of histamine on perfused rabbit middle cerebral arteries in vitro. Intact and endothelium-denuded preparations were compared. Histamine caused concentration-dependent constrictions in intact vessels which were competitively inhibited by an H1 receptor antagonist. This constriction was potentiated by either H2-receptor blockade or endothelium denudation. The greatest potentiation was observed with intraluminal as opposed to extraluminal administration. The H1 receptor agonist pyridylethylamine induced similar concentration-dependent constriction in intact and denuded preparations. After pre-constriction, histamine, in the presence of an H1 receptor antagonist, dilated intact vessels to a maximum of 45.1 %, and endothelium-denuded vessels to a maximum of 22% (p < 0.02). We conclude that rabbit middle cerebral arteries possess H1 constrictory and H2 dilatory receptors, and that many of the H2 dilatory receptors are situated on the endothelial cells.
Development of Phonemic Distinction in Japanese Preschool Children
Authors: Tamashige Eiko , Nishizawa Noriko , Itoda Hisashi , Kasai Satoko , Igawa Hiroharu H. , Fukuda Satoshi
Published: November 2008

The literature suggests that, within several months of birth, infants develop the ability to distinguish between different speech sounds. However, the time frame for discrimination of a specific phonological system remains unclear. In order to clarify this, the discrimination responses of 211 preschool children were examined. The test battery consisted of 16 pairs of Japanese words, of which each pair contained distinctive phonemes in the initial syllables only. Test stimuli were presented in 2 ways: one as a whole test word and the other as only the initial syllable, which contained the target phoneme. When the test stimuli were whole words, correct discrimination exceeded 60% for test pairs in age groups older than 2:06–2:11 chronological age (years:months). However, when initial syllables were used, correct discrimination only exceeded 60% in age groups older than 3:06–3:11. Phonemic distinction within syllables seems to be established during early preschool age in Japanese children.
Effect of Peroxisome Proliferator-Activated Receptor-Gamma on Airway Smooth Muscle Thickening in a Murine Model of Chronic Asthma
Authors: Rhee Chin Kook , Lee Sook Young , Kang Ji Young , Kim Seung Joon , Kwon Soon Suk , Kim Young Kyoon , Park Sung Hak
Published: November 2008

Background: Asthma is characterized by airway hyperresponsiveness (AHR), inflammation and remodeling. Peroxisome proliferator-activated receptors (PPARs) were reported to regulate inflammatory responses in many cells. In this study we examined the effect of a PPAR-γ agonist on the airway smooth muscle and the production of transforming growth factor (TGF)-β1 and vascular endothelial growth factor (VEGF). Methods: We developed a mouse model of airway remodeling including smooth muscle thickening in which ovalbumin (OVA)-sensitized mice were repeatedly exposed to intranasal OVA administration twice a week for 3 months. Mice were treated intranasally with ciglitazone during OVA challenge. Results: Mice chronically exposed to OVA developed sustained eosinophilic airway inflammation and AHR to methacholine compared with control mice. In addition, the mice chronically exposed to OVA developed features of airway remodeling, including thickening of the peribronchial smooth muscle layer. Administration of ciglitazone intranasally significantly inhibited the development of AHR, eosinophilic inflammation, and importantly, airway smooth muscle remodeling in mice chronically exposed to OVA. However, intranasal ciglitazone treatment did not reduce the level of TGF-β1 and VEGF in bronchoalveolar lavage fluid. Conclusions: These results suggest that intranasal administration of ciglitazone can prevent not only airway inflammation, but also airway remodeling associated with chronic allergen challenge. The mechanism might not be related to VEGF and TGF production. Further study is needed.
The Effects of Heat-Killed Wild-Type Lactobacillus casei Shirota on Allergic Immune Responses in an Allergy Mouse Model
Authors: Lim Lay Hong , Li Hai Yan , Huang Chiung Hui , Lee Bee Wah , Lee Yuan Kun , Chua Kaw Yan
Published: November 2008

Background: Probiotics are used as a management strategy for allergic diseases, but their effects on allergic responses in sensitized allergic individuals remain unclear. This study explored the immunomodulatory effects of probiotics on allergen-specific allergic reactions in an allergy mouse model. Methods: C57BL/6 mice were presensitized by epicutaneous patching with recombinant Der p 2, and were subsequently administered orally with either heat-killed wild-type Lactobacillus casei or NaHCO3 buffer for 5 weeks (n = 6 per group). All mice then received 2 subcutaneous immunizations of Der p 2 to mimic allergen immunotherapy, followed by aerosol challenge with Der p 2 a week later. Results: The Der p 2-sensitized mice fed L. casei showed significantly lower Der p 2-specific IgE and IgG1 after subcutaneous immunizations and airway challenge with Der p 2 compared to the control, unfed group. Splenic T cells of mice fed L. casei showed suppression of Th-2 (IL-5, IL-13, IL-10 and IL-4) and proinflammatory (TNF-α, IFN-γ) cytokines. Following airway allergen challenge, the mice fed L. casei showed histological evidence of attenuation of lung inflammation, as well as reductions in the total cell count and Th2 and proinflammatory cytokines in bronchoalveolar lavage fluid, compared to controls. Taken together, these results suggest that the oral administration of heat-killed L. casei could effectively downregulate the pre-existing Th-2 allergic responses and pulmonary inflammatory responses upon subcutaneous and airway allergen challenge. Conclusions:L. casei has intrinsic adjuvant and immunomodulatory properties that could potentially be exploited for secondary prevention or treatment of allergic respiratory diseases.
Phosphate Binder Impact on Bone Remodeling and Coronary Calcification – Results from the BRiC Study
Authors: Barreto Daniela Veit , Barreto Fellype de Carvalho , de Carvalho Aluízio Barbosa , Cuppari Lilian , Draibe Sérgio Antonio , Dalboni Maria Aparecida , Moyses Rosa Maria Affonso , Neves Kátia Rodrigues , Jorgetti Vanda , Miname Marcio , Santos Raul D. , Canziani Maria Eugênia Fernandes
Published: November 2008

Backgroundand Aims: Calcium-containing phosphate binders have been shown to increase the progression of vascular calcification in hemodialysis patients. This is a prospective study that compares the effects of calcium acetate and sevelamer on coronary calcification (CAC) and bone histology. Methods: 101 hemodialysis patients were randomized for each phosphate binder and submitted to multislice coronary tomographies and bone biopsies at entry and 12 months. Results: The 71 patients who concluded the study had similar baseline characteristics. On follow-up, the sevelamer group had higher levels of intact parathyroid hormone (498 ± 352 vs. 326 ± 236 pg/ml, p = 0.017), bone alkaline phosphatase (38 ± 24 vs. 28 ± 15 U/l, p = 0.03) and deoxypyridinoline (135 ± 107 vs. 89 ± 71 nmol/l, p = 0.03) and lower LDL cholesterol (74 ± 21 vs. 91 ± 28 mg/dl, p = 0.015). Phosphorus (5.8 ± 1.0 vs. 6 ± 1.0 mg/dl, p = 0.47) and calcium (1.27 ± 0.07 vs. 1.23 ± 0.08 mmol/l, p = 0.68) levels did not differ between groups. CAC progression (35 vs. 24%, p = 0.94) and bone histological diagnosis at baseline and 12 months were similar in both groups. Patients of the sevelamer group with a high turnover at baseline had an increase in bone resorption (eroded surface, ES/BS = 9.0 ± 5.9 vs. 13.1 ± 9.5%, p = 0.05), whereas patients of both groups with low turnover at baseline had an improvement in bone formation rate (BFR/BS = 0.015 ± 0.016 vs. 0.062 ± 0.078, p = 0.003 for calcium and 0.017 ± 0.016 vs. 0.071 ± 0.084 μm3/μm2/day, p = 0.010 for sevelamer). Conclusions: There was no difference in CAC progression or changes in bone remodeling between the calcium and the sevelamer groups.
Turning Loss Into Opportunity: The Key Deletion of an Escape Circuit in Decapod Crustaceans
Authors: Faulkes Zen
Published: November 2008

Decapod crustacean escape responses are adaptive behaviors whose neural bases are well understood. The escape circuit is composed of giant neurons. Lateral giant interneurons (LGs) respond to posterior stimuli by generating a somersaulting tailflip; medial giant interneurons (MGs) respond to anterior stimuli with a backwards tailflip. Both sets of interneurons connect to giant fast flexor motor neurons (MoGs). Most features of the escape circuit are thought to result from strong selective pressure to respond to stimuli in the shortest possible time. Despite the apparent advantages of the escape circuit, it has been lost in multiple taxa independently. Some losses of the escape circuit may be rare cases of disaptation, where organisms are less well adapted than related species (i.e., those with the escape circuit). The losses of the escape circuit might be key deletions that promoted the radiation of decapod crustaceans by increasing selection pressure for species to evolve new anti-predator strategies and removing constraints against change.
Variation in Brain Organization and Cerebellar Foliation in Chondrichthyans: Batoids
Authors: Lisney Thomas J. , Yopak Kara E. , Montgomery John C. , Collin Shaun P.
Published: November 2008

Interspecific variation in relative brain size (encephalization), the relative size of the five major brain areas (the telencephalon, diencephalon, mesencephalon, cerebellum, and medulla) and the level of cerebellar foliation was assessed in over 20 representative species of batoid (skates and rays), from eight families. Using species as independent data points and phylogenetically independent contrasts, relationships among each of the neuroanatomical variables and two ecological variables, habitat and lifestyle, were assessed. Variation in relative brain size and brain organization appears to be strongly correlated with phylogeny. Members of the basal orders Rajiformes and Torpediniformes tend to have relatively small brains, with relatively small telencephalons, large medullas, and smooth, unfoliated cerebellums. More advanced Myliobatiformes possess relatively large brains, with relatively large telencephalons, small medullas, and complex, heavily foliated cerebellums. Increased brain size, telencephalon size, and cerebellar foliation also correlate with living in a complex habitat (such as in association with coral reefs) and an active, benthopelagic lifestyle, but as primary habitat and lifestyle also closely match phylogenetic relationships in batoids, it is difficult to separate the influence of phylogeny and ecological factors on brain organization in these animals. However, the results of two forms of multivariate analysis (principal component analysis and cluster analysis) reveal that certain species are clustered with others that share ecological traits, rather than with more closely related species from the same order. This suggests that ecological factors do play a role in defining patterns of brain organization and there is some evidence for ‘cerebrotypes’ in batoids.
Dietary Intake of Natural Sources of Docosahexaenoic Acid and Folate in Pregnant Women of Three European Cohorts
Authors: Franke C. , Verwied-Jorky S. , Campoy C. , Trak-Fellermeier M. , Decsi T. , Dolz V. , Koletzko B.
Published: November 2008

Background: Folic acid plays a fundamental role in cell division and differentiation. Docosahexaenoic acid (DHA) has been associated with infantile neurological and cognitive development. Thus, optimal intrauterine development and growth requires adequate supply of these nutrients during pregnancy. Methods: Healthy pregnant women, aged 18–41 years, were recruited in Granada (Spain; n = 62), Munich (Germany; n = 97) and Pécs (Hungary; n = 152). We estimated dietary DHA and folate intake in weeks 20 (w20) and 30 of gestation (w30) using a food frequency questionnaire with specific focus on the dietary sources of folate and DHA. Results: Both w20 and w30 Spanish participants had significantly higher daily DHA intakes (155 ± 13 and 161 ± 9 mg/1,000 kcal) than the German (119 ± 9 and 124 ± 12 mg/1,000 kcal; p = 0.002) and Hungarian participants (122 ± 8 and 125 ± 10 mg/1,000 kcal; p = 0.005). Hungarian women had higher folate intakes in w20 and w30 (149 ± 5 and 147 ± 6 μg/1,000 kcal) than Spanish (112 ± 2 and 110 ± 2 μg/1,000 kcal; p < 0.001) and German participants (126 ± 4 and 120 ± 6 μg/1,000 kcal; p < 0.001), respectively. Conclusion: Dietary DHA and folate intake of pregnant women differs significantly across the three European cohorts. Only 7% of the participants reached the recommended folate intake during pregnancy, whereas nearly 90% reached the DHA recommended intake of 200 mg per day.
Lifestyle Drugs in Old Age – A Mini-Review
Authors: Harth W. , Seikowski K. , Hermes B.
Published: November 2008

Normal aging is no disease. The individual lifestyle may be responsible for a large fraction of the so-called ‘age-related’ changes. An increasing number of healthy individuals make use of ‘lifestyle’ drugs, such as nootropics, psychopharmaca, hormones and ecodrugs. In this respect, the fact that many people try to improve their outer appearance, to solve their ‘cosmetic problems’, to influence their rate of hair growth and to altogether delay, halt or even reverse the natural aging process has become a relevant matter for the practising doctor. Lifestyle drugs are taken in an attempt to increase personal life quality by means of attaining a certain psychosocially defined medical or beauty ideal, rather than to manage a medically identifiable, well-defined disease. Often, patients suffering from somatoform disorders such as hypochondriac disorders, body dysmorphic disorders, somatization disorders or persistent somatoform pain disorders may spontaneously ask physicians to prescribe them lifestyle drugs. Also, when ‘healthy’ people demand a lifestyle drug, possible side effects and contraindications must be taken into consideration and ruled out.
Cytoskeleton and Epithelial Polarity
Authors: Drenckhahn Detlev , Jöns Thomas , Kollert-Jöns Alice , Koob Rainer , Kraemer Doris , Wagner Susanne
Published: November 2008

The membrane surface of polarized epithelial cells can be divided in apical and basolateral domains that differ in molecular composition and function. Components of the cytoskeleton are involved in critical steps of both generation and maintenance of cell polarity. Generation of polarity is controlled by microtubules that serve as uniformly aligned and polarized cytoplasmic guiding structures for the vectorial and selective transport of Golgi-derived carrier vesicles to the apical cell surface. Targeting of membrane proteins to the basolateral cell surface does not depend on microtubules but follows the constitutive bulk flow of membranes. Once inserted into the lipid bilayer several membrane proteins such as the kidney anion exchanger 1 (AE1) and the sodium pump become immobilized at specialized microdomains of the lateral cell surface. Evidence is provided that both membrane proteins are linked via ankyrin to the spectrin-based membrane cytoskeleton that underlies the basolateral membrane domain. Linkage of these and other integral membrane proteins to the cytoskeleton may not only place them to specialized sites of the plasma membrane but may also prevent these transporters from clustering and endocytosis, thus helping them to stay at the cell surface. In search of sequence motifs involved in binding of integral membrane proteins to components of the cytoskeleton we found that the binding interface of AE1 to protein 4.1 (an actin and spectrin cross-linking protein) consists of a cluster of five amino acid residues, namely IRRRY in AE1 and LEEDY on protein 4.1. This motif may play a more general role in cytoskeleton membrane linkages.
The Biological Significance of Cell Volume
Authors: Lang F. , Ritter M. , Völkl H. , Häussinger D.
Published: November 2008

To survive, cells have to avoid excessive alterations of their volume. To this end, cells have developed a complex machinery of cell volume regulatory mechanisms comprising transport across the cell membrane and metabolism. Upon cell swelling, they loose electrolytes mainly via selective K+ channels and unselective ion channels and/or KCl symport, upon cell shrinkage they accumulate ions by Na+, K+,2Cl- cotransport and parallel operation of Na+/H+ exchange and Cl-/ HC03- exchange. In addition, cell shrinkage stimulates glycogenolysis, proteolysis and formation of organic osmolytes such as amino acids, methylamines and polyols. Cell swelling stimulates formation of glycogen and proteins and cellular release of organic osmolytes. Alterations of cell volume do play a crucial role in the regulation of cell function, as illustrated by four examples: 1. Epithelial transport may lead to cell swelling, which then triggers volume regulatory mechanisms modifying transcellular transport.2. Insulin swells hepatocytes by activation of Na+, K+,2Cl- cotransport and Na+/H+ exchange, glucagon shrinks those cells by activation of ion channels. The respective volume changes participate in the regulation of cellular protein and glycogen metabolism by these hormones.3. Growth factors and expression of ras oncogene activate Na+ , K+ ,2Cl- cotransport and Na+/H+ exchange leading to the respective cell swelling.4. Hepatocyte swelling triggers a hepatorenal reflex decreasing renal blood flow.
Metabolism of Dexamethasone: Sites and Activity in Mammalian Tissues
Authors: Siebe H. , Baude G. , Lichtenstein I. , Wang D. , Bühler H. , Hoyer G.-A. , Hierholzer K.
Published: November 2008

We have used in vitro techniques to study the metabolism of dexamethasone. Tissue slices, homogenates and microsomal fractions of various mammalian organs from rats and humans have been used. We focused particularly on the question of whether or not dexamethasone (Dexa) is oxidized at the C11-OH group by 11β-hydroxysteroid-dehydrogenase. High activities of this enzyme system for Dexa were localized in renal cortex and rectum. Material from both human and murine liver was ineffective. The main metabolite formed from Dexa in renal and intestinal systems was identified by different mass-spectrometric techniques including on line HPLC mass spectrometry as 11-dehydro-dexamethasone. This finding was corroborated by the observation that both corticosterone and glycyrrhetinic acid block the metabolic transformation of Dexa.
lnterleukin-1 and Glomerular Mesangial Cells
Authors: Zoja Carla , Rambaldi Alessandro , Remuzzi Giuseppe
Published: November 2008

Our previous in vitro study demonstrated that interleukin-1 (IL-1) stimulates gene expression and production of leukocyte chemotactic factors, colony-stimulating factors and interleukin-6 in human mesangial cells in culture. Here we investigated whether IL-1 regulates its own gene expression in human mesangial cells. Northern blot experiments showed that IL-1 induced IL-1 mRNA expression in a dose-dependent manner. The action of IL-1 on mesangial cells was mediated through the IL-1 receptor type I, which is constitutively expressed by mesangial cells. Recombinant IL-1 receptor antagonist blocked the IL-1 mRNA as well as interleukin-6 and interleukin-8 gene expression induced by IL-1. These data support the crucial role played by IL-1 in regulating mesangial cell cytokine genes within the glomerulus during immunological or inflammatory processes.
Characteristics and Regulation of Na/Pi Cotransport in a SV-40-Transformed Rabbit Proximal Tubular Cell Line
Authors: Mütter Daniel , Forgo Jutka , Murer Heini , Biber Jürg
Published: November 2008

An SV-40-transformed cell line of rabbit S2 proximal tubular origin (RKPC-2 cells) was used to characterize Na/Pi cotransport. Pi saturation experiments showed simple Michaelis-Menten behaviour and an apparent Km of 106 µM; Hill analysis of Na+ concentration dependence results in an apparent Km for Na+ of about 130 mM and suggests a stoichiometry exceeding unity. Exposure of confluent monolayers to low Pi medium induced an increase in Na/Pi cotransport. Incubation with 10-9 M parathyroid hormone produced a ‘paradoxical’ stimulation of Na/Pi cotransport, mimicked by pharmacological activation of protein kinase A or protein kinase C. The above regulatory events, observed on Na/Pi cotransport, were not observed for Na+-dependent amino acid transport (L-proline and/or L-glutamic acid).
Effect of Methylprednisolone on Transforming Growth Factor-Beta, Insulin-Like Growth Factor-I, and Basic Fibroblast Growth Factor Gene Expression in the Kidneys of NZB/W F1 Mice
Authors: Nakamura Tsukasa , Ebihara Isao , Nagaoka Isao , Osada Shiori , Tomino Yasuhiko , Koide Hikaru
Published: November 2008

The present study was carried out to determine whether transforming growth factor-β, insulin-like growth factor-I and basic fibroblast growth factor mRNA levels were correlated with disease activity in NZB/W F1 mice, an animal model of systemic lupus erythematosus. Levels of mRNA for these three growth factors increased significantly as nephritis progressed in these mice. At 48 weeks of age, transforming growth factor-β, insulin-like growth factor-I, and basic fibroblast growth factor mRNA levels showed a 11- (p < 0.001), 10- (p < 0.001), and 8-fold (p < 0.001) increase, respectively, in the renal cortex of NZB/W F1 mice when compared with NZW control mice. In NZW kidneys, these mRNA levels showed little change throughout the study period. At 24 weeks of age, NZB/W F1 mice were divided in 2 groups that received either methylprednisolone or saline injections for 24 weeks. The development of histological lesions and the increase in these growth factor mRNA levels in the kidneys of NZB/W F1 mice were both suppressed by methylprednisolone. These results indicate that the transforming growth factor-β, insulin-like growth factor and basic fibroblast growth factor may play a role in the progression of murine lupus nephritis and that methylprednisolone may be an effective treatment at the transcription level of these growth factor genes for this type of nephritis.
Localization and Degradation of Calcitonin in Renal Proximal Tubule of Rat Visualized by Immunocytochemistry
Authors: Birn Henrik , Christensen Erik Ilsø
Published: November 2008

Immunocytochemical and cryoultramicrotomy techniques were applied to label endogenous as well as intravenously injected calcitonin (CT) in rat kidney. Endogenous CT was located to the membranes of the brush border, endocytotic invaginations and vacuoles and dense apical tubules suggesting degradation at the brush border and/or within endocytotic vacuoles after glomerular filtration of endogeneous CT There was no labeling at the basolateral membranes indicating that possible basolateral binding sites are of minor quantitative importance in degradation. After injection of human CT there was an additional labeling of lysosomes whereas injection of insulin did not change the labeling pattern for endogenous CT indicating that the uptake of CT involves specific binding sites. Quantitative immunocytochemistry after injection of h-CT applying monoclonal antibodies against two different fragments of CT showed that the relative amounts of these fragments differed in vacuoles and lysosomes from that observed in the brush border, but no difference was seen in dense apical tubules. This suggests that injected CT may be degraded both at the brush border, within endocytotic vacuoles and lysosomes and that some fragments are more sensitive to hydrolysis in lysosomes than others. Furthermore, it indicates an early formation of dense apical tubules before detectable degradation of CT occurs in endocytotic vacuoles.
Renal Expression of mRNAs for Endothelin-1, Endothelin-3 and Endothelin Receptors in NZB/W F1 Mice
Authors: Nakamura Tsukasa , Ebihara Isao , Fukui Mitsumine , Osada Shiori , Tomino Yasuhiko , Masaki Tomoh , Goto Katsutoshi , Furuichi Yasuhiro , Koide Hikaru
Published: November 2008

Endothelin (ET)-1 ET-3, and ET receptors are widely distributed in the vascular system and the kidney. The present study was designed to measure the renal concentrations of ET-1, ET-3, and ET receptor mRNAs in NZB/W Fl mice at 8,24, and 48 weeks of age. The renal concentration of ET-1 mRNA increased significantly in NZB/W F1 mice as their nephritis progressed, reaching, by 48 weeks, a 10-fold higher concentration than in control NZW mice. Renal ET-3 mRNA concentrations, however, remained unchanged. The renal concentrations of ET receptor A and B mRNAs in NZB/W F1 mice increased gradually with the progression of nephritis, reaching 5- and 3-fold higher concentrations, respectively, at 48 weeks of age than found in control mice. Transforming growth factor-β (TGF-β) and tumor necrosis factor-α (TNF-α) have been shown to stimulate ET-1 mRNA expression in cultured mesangial cells. We therefore also examined the concentrations of TGF-β and TNF-α mRNAs in the renal tissues of NZB/W F1 mice and found that at 48 weeks of age they were 10-and 8-fold higher, respectively, than in control NZW mice. At 24 weeks, NZB/W F1 mice were divided into two groups receiving either methylprednisolone (MPSL) or saline injections for the following 24 weeks. The development of the histologic lesions characteristic of lupus nephritis and the increased renal concentrations of ET-1, ET receptors, TGF-β and TNF-α mRNAs were suppressed by MPSL treatment. These data suggest that ET and ET receptor gene transcription is upregulated in the renal tissues of NZB/W F1 mice and that the beneficial treatment of lupus nephritis with MPSL is accompanied by a reduction in the elevated concentrations of ET-1, ET receptors, TGF-β and TNF-α mRNAs.
Identification of an External NADH Oxidase in Rat Kidney Cortex Mitochondria
Authors: Linke Burkhard , Henke Wolfgang , Gerber Gerhard
Published: November 2008

Intact rat kidney cortex mitochondria oxidize external NADH and NADPH. Basal NADH oxidation of mitochondria, but not basal NADPH oxidation, is stimulated by hexammineruthenium (HR). 10.7 µmol/l HR induce 50% of the maximal NADH-oxidizing activity and amounted to 169 nmol NADH/ min/mg of mitochondrial protein. The HR-stimulated NADH oxidation involves a stoichiometric 1:1 oxygen consumption. The electron transfer from NADH to oxygen does not occur via the respiratory chain complex I, but is connected with a superoxide anion radical formation. Experiments with intact mitochondria, submitochondrial particles and inner mitochondrial membranes show that rat kidney cortex mitochondria possess a NADH oxidase localized on the outer surface of the inner mitochondrial membrane.
Effect of Glucocorticoids on Mitochondrial Oxidative Enzyme and Na-K-ATPase Activities in the Rat Proximal Tubule and Thick Ascending Limb of Henle
Authors: Djouadi F. , Wijkhuisen A. , Bastin J. , Vilar J. , Merlet-Bénichou C.
Published: November 2008

The activities of three mitochondrial oxidative enzymes (citrate synthase, 3-ketoacid-CoA transferase, β-hydroxyacyl-CoA dehydrogenase) and Na-K-ATPase were microassayed in isolated segments of the rat proximal convoluted tubule (PCT) and medullary thick ascending limb of the loop of Henle (mTAL). The effects of adrenalectomy (ADX) and ADX plus exogenous glucocorticoids were analyzed. The hormonal replacement was daily injections of dexamethasone (10 µg/l00 g body weight/24 h) for 5 days. ADX lowered the activity of all oxidative enzymes studies in the mTAL, but not in the PCT and led to a decrease in Na-K-ATPase in both nephron segments. Dexamethasone restored the normal level of oxidative enzymes and Na-K-ATPase in the mTAL and of Na-K-ATPase in the PCT. We conclude that the activities of citrate synthase, 3-ketoacid-CoA transferase and β-hydroxyacyl-CoA dehydrogenase and of Na-K-ATPase are coordinately regulated in the mTAL and that glucocorticoids are essential for the long-term regulation of these enzyme activities in this nephron segment. In contrast, the activities of mitochondrial oxidative enzymes are not influenced by glucocorticoids in the PCT. This study presents the first evidence for a cell-specific regulation by glucocorticoids of oxidative metabolism in the nephron of adult rat kidney.
Omeprazole and SCH 28080 Inhibit Acid Secretion by the Turtle Urinary Bladder
Authors: Graber Mark L. , Devine Philip
Published: November 2008

There is now convincing evidence that in addition to the vacuolar-type H+-ATPase, a gastric-type H+/K+-ATPase participates in acidification by the distal nephron. To determine whether a similar pump exists in the turtle bladder, we examined the dependence of acid secretion on mucosal K+ and the effects of supposedly specific inhibitors of the gastric H+/K+-ATPase, omeprazole and SCH 28080. In CO2-stimulated bladders both drugs produced dose-dependent inhibition of electrogenic H+ secretion measured as the reverse short-circuit current (RSCC). At the highest concentrations tested, H+ secretion decreased 45 ± 16% with mucosal and 20 ± 7% with serosal omeprazole (p < 0.01). SCH 28080 at 400 µM produced essentially complete inhibition of H+ secretion with either mucosal or serosal application. When H+ secretion was purposefully inhibited by DIDS or an adverse mucosal pH gradient, SCH 28080 had no effect on RSCC. Removing mucosal K+ (measured K+ < 50 µM)  with or without mucosal barium, had no effect on RSCC. The inhibition of RSCC by omeprazole was reversed by mercaptoethanol. Finally, HCO3 secretion, as measured by either RSCC or pH-stat titration, increased significantly in response to 400 µM SCH 28080. The results demonstrate that these compounds inhibit acid secretion by the turtle bladder but stimulate the secretion of base. In view of the total independence of acid secretion on potassium, it is unlikely that any of the bladder’s acid secretion is mediated by an H+/K+-ATPase. The most reasonable interpretation of the data is that omeprazole and SCH 28080, previously thought to be specific inhibitors of the H+/K+-ATPase, also inhibit the vacuolar H+-ATPase of the turtle bladder. The results also indicate that HCO3 secretion by the bladder employ a different mechanism of H+ transport than is used for acid secretion; there is no simple reversal of polarity in the acid- versus base-secreting cells.
Influence of Renal Functional Mass on the Catabolism of Endogenous Gastrin in Humans
Authors: Kes Petar , Reiner Željko , Filjak Katarina
Published: November 2008

The influences of renal function and mass on the catabolism of serum gastrin were studied in 27 patients with hypertension caused by unilateral parenchymal renal disease (77.8%), renal artery stenosis (11.1%) and essential hypertension (11.1%). Blood for gastrin analysis was taken by catheterization from the aorta, inferior vena cava, renal veins and cubital vein. Separate renal functions were measured using radioisotope methods and the renal mass was also calculated. Significant differences (p < 0.001) in serum gastrin concentration between the aorta (29.5 ± 6.7pmol/l), inferior vena cava (23.4 ± 5.8 pmol/l) and cubital vein (19.4 ± 4.5 pmol/l) were found. Extrarenal gastrin extraction amounted to 12.5% and was considerably lower than renal gastrin extraction (20.5%). There was a significant positive correlation between renal gastrin extraction and renal blood flow or renal functional mass. Kidneys have an important, but not exclusive, role in the catabolism of endogenous gastrin in humans. In the catabolism of some, or at least some molecular forms of, gastrin, the capillary systems of extrarenal tissues have an important role.
Selective Release of Apical Membrane Enzymes from Cultured Renal Epithelia by Phosphatidylinositol-Specific Phospholipase C
Authors: Netzer Alexandra , Gstraunthaler Gerhard
Published: November 2008

Membrane proteins can be attached to the plasma membrane in several ways. Recently, a mechanism has been described by which a number of cell surface proteins are anchored to the exoplasmic side of the plasma membrane by covalent linkage to glycosyl-phosphatidylinositol (GPI). The growth properties of renal epithelial cells in tissue culture enable free access to apical cell surface and brush border membrane proteins. To study the nature of membrane anchoring of apical plasma membrane enzymes in cultured renal epithelial cells, confluent LLC-PK1, OK, NRK, and MDCK epithelia were treated in tissue culture dishes with bacterial phosphatidylinositol-specific phospholipase C (PI-PLC), and the PI-PLC-specific release into the tissue culture medium of the apical membrane enzymes alkaline phosphatase (AP) γ-glutamyl transpeptidase, leucine aminopeptidase trehalase and maltase was determined. Of the five enzymes tested AP and trehalase, already described as GPI-anchored membrane proteins, were specifically released by PI-PLC from intact cell monolayers. Of the four cell lines investigated, LLC-PK1 cells express AP and trehalase which were released by PI-PLC. In OK cells, which lack AP activity, only trehalase was found to have PI-PLC-releaseable enzyme activity. MDCK cells, on the other hand, express AP activity, releaseable by PI-PLC, but no trehalase activity. In studies on the time course of synthesis and reinsertion of AP into the apical membrane of LLC-PK1 cells after removal by PI-PLC, a 60% recovery of AP activity was obtained only after 7 days. Analysis of protein release by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of culture supernatants after surface labeling with biotin and subsequent Western blotting with streptavidin revealed four protein bands at approximately 130, 90, 30, and 20 kD in LLC-PK1 cells and five GPI-anchored proteins at 110 85 65 40 and 26 kD in OK cultures. The finding of a PI-PLC-specific release of apical membrane enzymes from renal tubular cell lines of different species (pig, opossum, rat, and dog) and of different nephron origin indicates a high conservation of the GPI anchor of renal brush border membrane proteins and further proves the high degree of differentiation retained by the cell lines in tissue culture. In addition, this method may provide a possible tool for isolating GPI-anchored apical membrane proteins from intact epithelial monolayer cultures.
The Direct Renal Tubular Effect of Angiotensin II in Chicken
Authors: Cuypers Yves , McConaghey Paddy , Steels Paul
Published: November 2008

Taking advantage of the particular renal vascular arrangement in cocks, angiotensin II was injected (0.12-0.96 µg/min) into the portal system of one kidney in order to increase the angiotensin II concentration in the physiological nanomolar range at the level of the renal tubules. Angiotensin II induced an increase in blood pressure of 5% and a bilateral rise in glomerular filtration rate and effective renal plasma flow of 28 and 22%, respectively. The urine volume increased five times on the infused side and three times on the control side. The Na+ excretion increased 14 times on the infused side and only seven times on the control side. During angiotensin infusion, the fractional water excretion was 4.9% on the infused side and 2.9% on the control side versus 1.1 and 1.2% during the control period. For the fractional Na+ excretion, the respective values were 2 and 1.2% versus 0.2 and 0.2% during the control period. The differences between the two kidneys demonstrate the direct tubular action of angiotensin II, inhibiting the tubular Na+ and water reabsorption at physiological nanomolar concentrations. Angiotensin seems thus to play an important intrarenal role.
Effects of Luminal Vasopressin on Intracellular Calcium in Microperfused Rat Medullary Thick Ascending Limb
Authors: Burgess W.J. , Balment R.J. , Beck J.S.
Published: November 2008

Recent evidence suggests that vasopressin exerts a regulatory influence on transport processes in the rabbit cortical collecting duct via both the baso-lateral and luminal membranes. The present study was undertaken to examine whether luminal vasopressin receptors, coupled to changes in intracellular calcium, were also present in microperfused rat medullary thick ascending limb (mTAL), a key element of the urine concentrating mechanism. Addition of 1 nM vasopressin to the luminal microperfusate elicited a small but significant and sustained rise in intracellular calcium, from basal values of 100.1 ± 20.1 to 169.6 ± 24.1 nM after 250 s. The effect observed following luminal addition of vasopressin was dose-dependent, with a larger increment of 190.2 ± 32.2nM evoked by addition of 1 µM vasopressin. Addition of 1 µM oxytocin to the lumen did not cause a significant increase in intracellular calcium concentration, consistent with the response to vasopressin being mediated by specific luminal vasopressin receptors. In the absence of calcium in the bath and lumen together or in the bath alone, a residual response to 1 µM luminal vasopressin was still evident, suggestive of a small component of release of calcium from intracellular stores. Selective calcium removal from the luminal microperfusate alone left the response intact. These data are congruous with a model of vasopressin-induced entry of calcium which occurs via the basolateral membrane following ligand binding to the apical membrane. These findings, coupled with earlier observations in the collecting duct, suggest that a fundamental re-assessment of where and how vasopressin, and perhaps other hormones, acts in the kidney may be required. Hormonal regulation of distal tubular function may not therefore be determined only by blood-borne delivery of hormone, but may also involve tubular fluid delivery to apical receptors in distal nephron sites.
Diminished Diuretic and Natriuretic Response to Furosemide in Potassium-Depleted Rats
Authors: Hropot M. , Klaus E. , Unwin R. , Giebisch G.
Published: November 2008

Renal clearance and tubule microperfusion experiments were carried out to investigate the effects of chronic potassium depletion upon the renal response to furosemide. Rats kept on a potassium-deficient diet for 3 weeks developed hypokalemia, metabolic alkalosis, and decreased aldosterone levels. These rats responded to an oral administration of furosemide (32 mg/ kg) with a blunted excretion rate of urine and sodium. Whereas furosemide increased fractional urine sodium excretion to 5.2% in control rats, the corresponding rate in potassium-depleted rats was 2.8%. The urinary excretion of furosemide was also significantly reduced during potassium depletion from 3.06 mg/kg in control rats to 0.97 mg/kg in potassium-depleted rats. In separate experiments, loops of Henle were pump-perfused with furosemide-containing solutions in control and potassium-depleted rats. No major modification of the inhibitory effects of furosemide on sodium transport was observed when the potassium concentration of the perfusion fluid was kept at the low levels expected in hypokalemic rats. Metabolic alkalosis unaccompanied by potassium deprivation did not decrease the diuretic response to furosemide. These experiments indicate that potassium deprivation reduces the diuretic effects of furosemide by mechanisms including diminished furosemide delivery to its tubule site of action.
Protective Effect of Anti-Inflammatory Corticosteroid Triamcinolone in Cisplatin Nephrotoxicity
Authors: Reznik Lev V. , Gambaryan Stepan P.
Published: November 2008

The corticosteroid, triamcinolone, was examined as a potential antagonist for the nephrotoxicity of cisplatin in female Wistar rats. The changes in renal function and renal morphology were assessed on the 3rd day after administration of cisplatin (7.5 mg/kg BW) and in animals given triamcinolone retard (4 mg/kg BW) 6 h before administration of cisplatin. Pretreatment with triamcinolone resulted in much less severe changes in renal function after cisplatin administration (serum urea: triamcinolone plus cisplatin 14.29 ± 1.90 mg/l, cisplatin alone 21.60+2.34 mg/l, p < 0.05, control 2.78 ± 0.19 mg/l, serum creatinine: triamcinolone plus cisplatin 0.21 ± 0.02 mg/l, cisplatin alone 0.30 ± 0.02 mg/l, p < 0.05, control 0.06 ± 0.01 mg/l). In contrast to cisplatin-treated animals in triamcinolone-pretreated rats alterations of water content were found neither in renal cortex (triamcinolone plus cisplatin 3.39 ± 0.16g/g dry weight, cisplatin alone 4.07 ± 0.07g/g dry weight, control 3.07 ± 0.07 g/g dry weight) nor in outer medulla (triamcinolone plus cisplatin 4.20 ± 0.22 g/g dry weight, cisplatin alone 4.98 ± 0.21 g/g dry weight, control 3.84 ± 0.11 g/g dry weight) compared to control. The structure of the kidney following cisplatin administration demonstrated extensive lesions of S3 segments of the proximal tubule. The changes in proximal convoluted tubules were widespread and ranged from the decrease of the amount of microvilli to loss of brush border or even to cell death. In triamcinolone-pretreated rats the structure of the cortex appeared to be virtually normal and tissue of medulla was only slightly damaged
Isolation of Single Mammalian Proximal Tubule Cells: Effects of Hypotonic Shocks on Cell Yield and Function
Authors: Lapointe Jean-Yves , Garneau Line , Wallendorff Bernadette , Marsolais Mireille
Published: November 2008

Nord et al. [Am J Physiol 1986;250:F539-F550] proposed a method to give a high yield of proximal tubule cells by exposing a suspension of rabbit cortical tubules to a hypotonic shock in calcium-free media. The present study desribes the effects of both amplitude and duration of the hypotonic treatment on some transport-related characteristics of individual cells as compared to the starting tubule suspension. The averaged cell yield increased by an order of magnitude when the osmolality of the hypotonic solution was varied in four steps from 200 (C200 cells) to 70 mosm/kg H2O (C70 cells) while the proportion of trypan blue-positive cells progressively decreased from 33% for C200 cells to 9.5% for C70 cells. An increase in duration of the hypotonic shock from 0.5 to 6 min did not change the cell yield of C200 cells while it significantly increased that of C70 cells by 61%. Basal and ouabain-sensitive oxygen consumption (QO2) increased by 57 and 155%, respectively, from C70 to C200 cells but was approximately one order of magnitude smaller than the QO2 measured for tubule suspension. Intracellular ATP content averaged 5.5 ± 0.8 nmol/mg for the starting tubule suspension, 4.6 ± 0.8 nmol/mg for C70 cells but only 1.3 ± 0.1 nmol/mg for C200 cells. The maximal velocity for phloridzin-sensitive α-methyl glucose transport averaged 13.7 ± 1.7 nmol min-1 mg-1 for C70 cells and only 6.3 ± 1.3 nmol min-1 mg-1 for C200 cells which is approximately one order of magnitude smaller than what can be expected from a tubule presenting a good access to luminal membrane. We conclude from these results that, in the process of isolating individual cells from a polarized epithelium, membrane transport rates have decreased by one order of magnitude and this reduction is intensified by a large hypotonic shock. In comparison with C200 cells, the cells obtained with a large hypotonic shock give a high yield, a larger proportion of trypan blue-negative cells and their lower overall transport rate allows the cells to maintain a better electrochemical gradient for Na and a higher intracellular ATP level.
Characterization of the Synthesis and Release of Dopamine in LLC-PK1 Cells
Authors: Dawson Jr. Ralph , Felheim Rhonda , Phillips Ian
Published: November 2008

The ability of a renal epithelial cell line of porcine origin (LLC-PK1) to synthesize dopamine (DA) from L-dopa and release DA into the culture media was studied. L-Dopa was rapidly taken up by LLC-PK1 cells and converted to DA which was then released into the media. L-Dopa uptake and conversion to DA was competitively inhibited by other aromatic amino acids (Tyr and Phe). Studies were conducted to assess L-dopa uptake, DA synthesis and DA release in LLC-PK1 cells in response to changes in the ionic composition of the Krebs-Ringer bicarbonate (KRB) buffer media and to various drugs known to alter renal transport function. Sodium chloride addition to KRB media resulted in enhanced DA release into the media that was significantly attenuated by both quinine (1 mM) and benzamil (0.1 mM). Other sodium salts (sodium acetate and sodium phosphate) also enhanced DA release from LLC-PK1 cells. Salts containing chloride (LiCl, NH4Cl, choline chloride) stimulated a greater efflux of DA from LLC-PK1 cells than sodium salts at equimolar concentrations. Osmotic stimuli (sucrose, mannitol and dextran, 50-200 mM) also elicited increased DA release from LLC-PK1cells into the media but not to the same extent as inorganic salts. DA release (secretion) from LLC-PK1 cells was strongly inhibited (25-50%) by drugs known to be substrates for the renal cation transport system. These studies have characterized extensively the factors that govern and regulate the synthesis of DA from L-dopa and the transport system responsible for the secretion (release) of intracellular DA into the media.