RESUMEN

Water conservation is one of the most challenging processes for terrestrial vertebrates and is necessary for their survival. Birds are the only vertebrate animals other than mammals that have the ability to concentrate their urine. Previously, we identified and characterized aquaporins (AQP)1-4 responsible for urine concentration in Japanese quail kidneys. Today, a total of 13 orthologs for these genes have been reported in birds. Bird AQPs can be classified into four subfamilies: 1) Classical AQPs (AQP0-5 and novel member, AQP4-like) that conserve the selectivity filter; 2) aquaglyceroporins (AQP3, 7, 9 and 10) that retain an aspartic acid residue in the second NPA box and expand the pore to accept larger molecules; 3) unorthodox AQPs (AQP11-12) which structurally resemble their mammalian counterparts; 4) AQP8-type, a subfamily that differs from mammalian AQP8. Interestingly, over the course of time, birds lost their mammalian counterpart AQP6 but obtained a novel AQP4-like aquaporin member. In quail and/or chicken kidneys, at least six AQPs are expressed. Quail AQP1 (qAQP1) is expressed in both cortical and medullary proximal tubules but is absent in the descending limb (DL) and the thick ascending limb (TAL), supporting our previous finding that the DL and TAL are water impermeable. AQP2, an arginine vasotocin (AVT)-sensitive water channel, is exclusively expressed in the principal cells of the collecting duct (CD). AQP4 is unlikely to participate in free water resorption from the collecting duct (CD), and only AQP3 may represent an exit pathway for water reabsorbed apically via AQP2. While AQP9 is not expressed in mammalian kidneys, AQP9 was recently found in chicken kidneys. This review summarizes the current knowledge of the structure, function and expression of bird AQPs.

Asunto(s)

Acuaporinas/fisiología , Capacidad de Concentración Renal , Animales , Aves , Túbulos Renales Colectores/metabolismo , Especificidad de la Especie

RESUMEN

The renin-angiotensin system (RAS) evolved early among vertebrates and remains functioning throughout the vertebrate phylogeny and has adapted to various environments. The RAS is crucial for the regulation of blood pressure, fluid-electrolyte balance and tissue homeostasis. The RAS is also expressed during early ontogeny in renal and extra-renal tissues, and exerts unique vascular growth and differentiation functions. In this brief review, we describe advances from molecular-genetic and whole animal approaches and discuss similarities and unique aspects of the RAS in the context of embryonic development and vertebrates' phylogeny.

Asunto(s)

Endotelio Vascular/metabolismo , Sistema Renina-Angiotensina/fisiología , Renina/metabolismo , Animales , Arterias/metabolismo , Arteriolas/metabolismo , Presión Sanguínea , Diferenciación Celular , Pollos , Homeostasis , Humanos , Riñón/metabolismo , Filogenia , ARN Mensajero/metabolismo , Equilibrio Hidroelectrolítico

RESUMEN

Renin or a renin-like enzyme evolved in ancestral vertebrates and is conserved along the vertebrate phylogeny. The ontogenic development of renin, however, is not well understood in nonmammalian vertebrates. We aimed to determine the expression patterns and relative abundance of renin mRNA in pre- and postnatal chickens (Gallus gallus, White Leghorn breed). Embryonic day 13 (E13) embryos show renal tubules, undifferentiated mesenchymal structures, and a small number of developing glomeruli. Maturing glomeruli are seen in post-hatch day 4 (D4) and day 30 (D30) kidneys, indicating that nephrogenic activity still exists in kidneys of 4-week-old chickens. In E13 embryos, renin mRNA measured by quantitative polymerase chain reaction in the adrenal glands is equivalent to the expression in the kidneys, whereas in post-hatch D4 and D30 maturing chicks, renal renin expressions increased 2-fold and 11-fold, respectively. In contrast, relative renin expression in the adrenals became lower than in the kidneys. Furthermore, renin expression is clearly visible by in situ hybridization in the juxtaglomerular (JG) area in D4 and D30 chicks, but not in E13 embryos. The results suggest that in chickens, renin evolved in both renal and extrarenal organs at an early stage of ontogeny and, with maturation, became localized to the JG area. Clear JG structures are not morphologically detectable in E13 embryos, but are visible in 30-day-old chicks, supporting this concept.

Asunto(s)

Pollos/genética , Regulación de la Expresión Génica , Renina/genética , Animales , Embrión de Pollo , Aparato Yuxtaglomerular/citología , Aparato Yuxtaglomerular/metabolismo , Organogénesis , ARN Mensajero/genética , ARN Mensajero/metabolismo , Renina/metabolismo , Sistema Renina-Angiotensina

RESUMEN

Renin substrate, biological renin activity, and/or renin-secreting cells in kidneys evolved at an early stage of vertebrate phylogeny. Angiotensin (Ang) I and II molecules have been identified biochemically in representative species of all vertebrate classes, although variation occurs in amino acids at positions 1, 5, and 9 of Ang I. Variations have also evolved in amino acid positions 3 and 4 in some cartilaginous fish. Angiotensin receptors, AT1 and AT2 homologues, have been identified molecularly or characterized pharmacologically in nonmammalian vertebrates. Also, various forms of angiotensins that bypass the traditional renin-angiotensin system (RAS) cascades or those from large peptide substrates, particularly in tissues, are present. Nonetheless, the phylogenetically important functions of RAS are to maintain blood pressure/blood volume homeostasis and ion-fluid balance via the kidney and central mechanisms. Stimulation of cell growth and vascularization, possibly via paracrine action of angiotensins, and the molecular biology of RAS and its receptors have been intensive research foci. This review provides an overview of: (1) the phylogenetic appearance, structure, and biochemistry of the RAS cascade; (2) the properties of angiotensin receptors from comparative viewpoints; and (3) the functions and regulation of the RAS in nonmammalian vertebrates. Discussions focus on the most fundamental functions of the RAS that have been conserved throughout phylogenetic advancement, as well as on their physiological implications and significance. Examining the biological history of RAS will help us analyze the complex RAS systems of mammals. Furthermore, suitable models for answering specific questions are often found in more primitive animals.

Asunto(s)

Riñón/anatomía & histología , Riñón/fisiología , Sistema Renina-Angiotensina/fisiología , Angiotensinas/fisiología , Animales , Humanos , Filogenia , Renina/fisiología , Vertebrados

RESUMEN

Nephrin, a major intercellular junction (ICJ) molecule of mammalian podocytes in the renal glomerulus, is absent in the avian genome. We hypothesized that birds use ICJ molecules other than nephrin in their podocytes. Therefore, in the present study, we examined the possible involvement of adherens junction (AJ) proteins in the ICJs of avian podocytes. We found the AJ proteins N-cadherin and α- and ß-catenins in podocytes of quail and chickens but not in those of rats, pigs or humans. The AJ proteins were prominent in avian glomerulus-rich fractions in immunoblot analyses, and in immunofluorescence microscopy analyses, they were localized along glomerular capillary walls appearing in at least two staining patterns: weakly diffuse and distinctly granular. Immunoelectron microscopy demonstrated that the significant accumulation of immunogold particles for the AJ proteins were especially evident in avian slit diaphragms and AJs. Furthermore, N-cadherin was found to be expressed in all nephron cells in the early developmental stage but became confined to podocytes during maturation. These results indicate that avian slit diaphragms clearly express AJ proteins as compared with that in the mammal-where AJ proteins are suppressed to an extremely low level-and that avian podocytes are interconnected by AJs per se in addition to slit diaphragms.

Asunto(s)

Uniones Adherentes/química , Uniones Adherentes/metabolismo , Proteínas de la Membrana/deficiencia , Podocitos/química , Podocitos/metabolismo , Animales , Cadherinas/metabolismo , Cateninas/metabolismo , Pollos , Coturnix , Femenino , Humanos , Ratas , Ratas Wistar , Porcinos

RESUMEN

For terrestrial vertebrates, water economy is a prerequisite for survival, and the kidney is their major osmoregulatory organ. Birds are the only vertebrates other than mammals that can concentrate urine in adaptation to terrestrial environments. Aquaporin (AQP) and glyceroporin (GLP) are phylogenetically old molecules and have been found in plants, microbial organisms, invertebrates, and vertebrates. Currently, 13 AQPs/aquaGLPs and isoforms are known to be present in mammals. AQPs 1, 2, 3, 4, 6, 7, 8, and 11 are expressed in the kidney; of these, AQPs 1, 2, 3, 4, and 7 are shown to be involved in fluid homeostasis. In avian kidneys, AQPs 1, 2, 3, and 4 have been identified and characterized. Also, gene and/or amino acid sequences of AQP5, AQP7, AQP8, AQP9, AQP11, and AQP12 have been reported in birds. AQPs 2 and 3 are expressed along cortical and medullary collecting ducts (CDs) and are responsible, respectively, for the water inflow and outflow of CD epithelial cells. While AQP4 plays an important role in water exit in the CD of mammalian kidneys, it is unlikely to participate in water outflow in avian CDs. This review summarizes current knowledge on structure and function of avian AQPs and compares them to those in mammalian and nonmammalian vertebrates. Also, we aim to provide input into, and perspectives on, the role of renal AQPs in body water homeostasis during ontogenic and phylogenetic advancement.

Asunto(s)

Acuaporinas/metabolismo , Aves/metabolismo , Riñón/metabolismo , Animales , Acuaporinas/genética , Aves/genética , Células Epiteliales/metabolismo , Homeostasis/genética , Humanos , Riñón/patología , Agua/metabolismo

RESUMEN

BACKGROUND: Recent reports suggest that low birthweight (LBW) is a risk factor for kidney diseases, including focal segmental glomerulosclerosis (FSGS), although the underlying pathological mechanism remains unknown. Podocyte loss triggers glomerulosclerosis; however, whether FSGS in LBW children is associated with podocytopenia is unclear. METHODS: We reviewed the birthweights and gestational age of all patients who underwent renal biopsies from 1995 to 2011 at our Institute. Sixteen patients had FSGS, of which 6 (37.5%) had LBW; this LBW rate was significantly higher than the overall LBW rate in Japan (9.7%). The incidence of LBW was also high in patients with minimal change nephrotic syndrome (MCNS; 12.5%). The glomerular cell numbers in biopsy sections were calculated using computer image analysis and compared with FSGS of normal birthweight (NBW-FSGS). Biopsy specimens from age-matched patients with MCNS were also compared. Wilms' tumor-1 (WT1) immunohistochemistry was performed to enumerate the podocytes. RESULTS: All patients in the LBW-FSGS group were also preterm, with an average gestational age of 25.8 weeks. The number of podocytes per glomerulus in the LBW-FSGS patients was 34 and 24% lower as compared to that in the MCNS patients (p < 0.01) and the NBW-FSGS patients (p < 0.05), respectively. Similar results were observed for the WT1-positive glomerular cell number. CONCLUSION: LBW and premature birth were associated with FSGS development. The possibility that LBW and premature birth may be predisposing factors for severe podocytopenia in children with FSGS warrants further investigation.

Asunto(s)

Peso al Nacer , Edad Gestacional , Glomeruloesclerosis Focal y Segmentaria/diagnóstico , Podocitos/patología , Adolescente , Biopsia , Niño , Femenino , Humanos , Inmunohistoquímica , Incidencia , Recién Nacido de Bajo Peso , Recién Nacido , Recien Nacido Prematuro , Japón , Riñón/patología , Enfermedades Renales/epidemiología , Masculino , Nefrosis Lipoidea/diagnóstico , Estudios Retrospectivos , Factores de Riesgo , Proteínas WT1/metabolismo

RESUMEN

Before sexual maturation, chickens (Gallus gallus) show high blood pressure (BP) and neointimal plaques in the lower abdominal aortae (AbA). We investigated age/sex-related changes in pulse wave velocity (PWV), elastin, collagen, and protein levels in AbA, and cardiac morphology to determine whether PWV increases during incremental increases in BP of maturing fowl, while arterial stiffness becomes dominant with aging. PWV (m/s) was significantly greater in male chicks (6-7 weeks, 9.3+/-0.8; females, 6.1+/-0.5) and remained high in cockerels (13 weeks), young (27-28 weeks), and adults (44-66 weeks). PWV increased in prepubertal pullets (10.0+/-0.9), dropped significantly in young hens, and remained low in adults. In contrast, medial thickness, protein levels, and collagen levels increased, while elastin/collagen ratios decreased, with maturation/aging. Males had heavier ventricular mass and thicker ventricular walls than females at all ages; left ventricular thickness decreased with maturation/aging. Thus, sustained high BP may have caused progressive medial hypertrophy, increased aortic rigidity, and enlarged hearts with left ventricular dilation. PWV of AbA was already greater in male chicks at an age when both sexes have similar collagen levels and low protein levels, suggesting that a factor other than structural stiffness may be an important determinant of PWV.

Asunto(s)

Envejecimiento/fisiología , Aorta/patología , Presión Sanguínea , Pollos/fisiología , Factores Sexuales , Animales , Aorta/fisiología , Peso Corporal , Femenino , Masculino

RESUMEN

Birds and mammals are the only vertebrates that can concentrate urine. Avian kidneys contain structurally primitive loopless nephrons and also more advanced looped nephrons, in the cortical and medullary regions, respectively. We have identified the gene sequence of an aquaporin 2 (AQP2)-homologue water channel in collecting ducts of kidneys from adult quail, Coturnix japonica. Although immunoreactive quail AQP2 (qAQP2) was found in both types of nephrons, the expression is enhanced more clearly in the medullary regions after water deprivation. We therefore hypothesized that regulation of qAQP2 expression in quail kidneys via antidiuretic hormone (ADH) may require more advanced nephron structure. In this study, we determined the expression of qAQP2 mRNA in tissues isolated from the cortical and medullary regions before and after water deprivation, by conventional reverse transcriptase-polymerase chain reaction (RT-PCR) and quantitative real-time PCR. In both normally hydrated and water-deprived groups, qAQP2 mRNA levels in the medullary regions were significantly higher (P<0.01) than in the cortical regions. In medullary areas, qAQP2 mRNA levels (real-time PCR normalized with 18S) were significantly higher (P<0.01, ANOVA) after water deprivation (1.09+/-0.10) than in normally hydrated controls (0.46+/-0.08). In cortical areas, qAQP2 mRNA levels were also higher after water deprivation (0.37+/-0.05) than in controls (0.11+/-0.02). qAQP2 mRNA signals determined by in situ hybridization of digoxigenin-labeled riboprobe were also enhanced after water deprivation in both cortical and medullary collecting ducts. The results suggest that, contrary to our hypothesis, the endogenous production of ADH by water deprivation stimulates qAQP2 mRNA in both loopless and looped nephrons.

Asunto(s)

Acuaporina 2/genética , Proteínas Aviares/genética , Coturnix , Regulación de la Expresión Génica , Túbulos Renales Colectores/metabolismo , Codorniz/genética , Animales , Acuaporina 2/metabolismo , Proteínas Aviares/metabolismo , Peso Corporal , Hibridación in Situ , Codorniz/anatomía & histología , Codorniz/metabolismo , ARN Mensajero/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Privación de Agua

RESUMEN

Although birds and mammals have evolved from primitive tetrapods and advanced divergently, both can conserve water by producing hyperosmotic urine. Unique aspects in the avian system include the presence of loopless and looped nephrons, lack of the thin ascending limb of Henle's loop, a corticomedullary osmotic gradient primarily consisting of NaCl without contribution of urea, and significant postrenal modification of final urine. The countercurrent multiplier mechanism operates between the descending and ascending limbs of Henle via recycling of a single solute (NaCl) with no water accompaniment, forming an osmotic gradient along the medullary cone. Bird kidneys and developing rat kidneys share morphological and functional characteristics. Avian kidneys express aquaporin (AQP) 1, 2, and 4 homologues that share considerable homology with mammalian counterparts, but their distribution and function may not be the same. AQP2 expression in Japanese quail (q) evolves in the collecting duct of early metanephric kidneys and continues to increase in intensity and distribution during nephrogenesis and maturation. qAQP2 mRNA and protein are increased by arginine vasotocin (avian ADH), but vasotocin-induced enhancement of cAMP production and water permeability are less marked than in mammalian kidneys. Nephrogenesis is delayed by insufficient nutrition in avian embryos and newborns and results in fewer nephrons and an impaired water balance in adults. Diabetes insipidus quail with homozygous autosomal recessive mutation and an unaffected vasotocin system have low AQP2 expression, underdeveloped medullary cones. Comparative studies will provide important insight into integrative, cellular, and molecular mechanisms of epithelial water transport and its control by humoral, neural, and hemodynamic mechanisms.

Asunto(s)

Acuaporinas/metabolismo , Acuaporinas/orina , Aves/fisiología , Animales , Evolución Biológica , Humanos , Riñón/metabolismo , Ósmosis/fisiología

RESUMEN

Avian kidneys have loopless and looped nephrons; a countercurrent multiplier mechanism operates in the latter by NaCl recycling. We identified an aquaporin-2 (AQP2) homolog in apical/subapical regions of cortical and medullary collecting duct (CD) cells in kidneys of Japanese quail (q), Coturnix japonica. We investigated whether undernutrition during the embryonic/maturation period retards kidney and AQP2 development in quail and programs impaired volume regulation in adults. Protocols included 1) time course and 2) effects of 5-10% egg white withdrawal (EwW) or 48-h post-hatch food deprivation (FD) on nephron growth and qAQP2 mRNA expression, and 3) effects of EwW and FD on qAQP2 mRNA responses to 72-h water deprivation in adults. In metanephric kidneys, qAQP2 mRNA is expressed in medullary CDs at embryonic day 10; distribution and intensity increase during maturation. The number and size of glomeruli continue to increase after birth, whereas nephrogenic zones decrease. In EwW embryos, qAQP2 mRNA expression is initially delayed, then restored; birth weight and hatching rate are lower than in controls. Adults from EwW embryos and FD chicks have fewer (P < 0.01) glomeruli. Water deprivation reduces body weight more in EwW birds than in controls. The results suggest that qAQP2 evolved in metanephric kidneys and that undernutrition may retard nephrogenesis, leading to impaired adult water homeostasis.

Asunto(s)

Acuaporina 2/fisiología , Coturnix/fisiología , Homeostasis/fisiología , Riñón/fisiología , Equilibrio Hidroelectrolítico/fisiología , Animales , Animales Recién Nacidos , Acuaporina 2/genética , Peso Corporal/fisiología , Cateterismo , Electrólitos/sangre , Embrión no Mamífero/metabolismo , Homeostasis/genética , Hibridación in Situ , Riñón/embriología , Riñón/crecimiento & desarrollo , Desnutrición/fisiopatología , Nefronas/embriología , Nefronas/crecimiento & desarrollo , Nefronas/fisiología , Concentración Osmolar , ARN Mensajero/biosíntesis , ARN Mensajero/genética , Equilibrio Hidroelectrolítico/genética

RESUMEN

Water deprivation or arginine vasotocin upregulates aquaporin-2 (AQP2) expression in apical and subapical regions of medullary collecting duct (CD) cells of Coturnix coturnix quail (q) kidneys. We therefore aimed to determine whether the CD has AQPs mediating water exit from the intracellular to the extracellular (interstitial) space. Using a homologue cloning technique, we isolated two distinct qAQP4 cDNAs from quail medullary cones; long (L, open reading frames) and short (S) cDNA encoded 335 (qAQP4-L) and 301 (qAQP4-S) amino acids with, respectively, 80% and 87% identity to human long- and short-form AQP4. qAQP4-S is identical to qAQP4-L from the second initiation site. Both isoforms have two NPA motifs, but lack cysteine at the known mercury-sensitive site. qAQP4-L and qAQP4-S are expressed in membranes of Xenopus laevis oocytes, but both failed to increase the water permeability (P(f)) of oocytes exposed to a hypotonic solution. Glutamate (Q242) replacement with histidine did not increase P(f). With conventional RT-PCR and real-time PCR, qAQP4-L/S mRNA signals were detected in the brain, lung, heart, intestine, adrenal gland, skeletal muscle, liver, and kidney (higher in medulla than in cortical region). qAQP4-L mRNA was detected only in the brain and adrenal gland. Orthogonal arrays of intramembranous particles were not detected in quail CDs. The results suggest that although qAQP4-L and qAQP4-S have high homology to mammalian AQP4, their physiological function may be different.

Asunto(s)

Acuaporina 4/genética , Coturnix , ADN Complementario/genética , Riñón/anatomía & histología , Riñón/metabolismo , Codorniz/genética , Secuencia de Aminoácidos , Animales , Acuaporina 4/química , Acuaporina 4/metabolismo , Permeabilidad de la Membrana Celular , Clonación Molecular , ADN Complementario/aislamiento & purificación , Femenino , Perfilación de la Expresión Génica , Regulación de la Expresión Génica , Humanos , Túbulos Renales Colectores/ultraestructura , Masculino , Ratones , Datos de Secuencia Molecular , Oocitos/citología , Ósmosis , Filogenia , ARN Complementario , Análisis de Secuencia de ADN , Agua/metabolismo , Xenopus

RESUMEN

Fowl (males more than females) show maturation-dependent rises in blood pressure (BP) and formation of neointimal plaques (NPs), resembling balloon catheter injury-induced neointima, in the abdominal aorta (AbA) just above the bifurcation. The plaque comprises neointimal cells containing abundant endoplasmic reticulum and extracellular matrix. Hence, we investigated whether rapid incremental BP increases in male chicks trigger NP formation, possibly via endothelial injury in hemodynamically selective areas. In 6-wk-old chicks (n = 8) treated 4 wk with solvent (Sv; minipump) or arginine supplement (Arg; 0.3% in drinking water), BP increased from 140 +/- 5 to 159 +/- 4 (Sv) and from 138 +/- 4 to 157 +/- 3 (Arg) mmHg, whereas propranolol treatment (Prop, 8 mg.kg(-1).day(-1); minipump) prevented the rise. Arg and Prop groups had, respectively, 73% and 77% smaller (P < 0.05) NP areas and 19% and 25% less (P < 0.01) AbA medial thickness than Sv controls. In 16-wk-old cockerels, established BP remained high after Sv and Arg treatments. In the Prop group, BP decreased, but neither NP area nor medial thickness was lower than in the Sv group, whereas the Arg group showed greater NP area and medial thickness. Pulse pressure, determined by intravascular transducer, increased as the pulse wave descended the aorta. The results suggest that maturation-dependent rises in BP in chicks may trigger NP formation in the lower segment of the AbA, which was prevented by inhibition of BP increase, or via a possible increase in nitric oxide availability. BP reduction exerts no effect once BP reaches a plateau. Involvement of endothelial injury leading to NP formation and hemodynamic forces selective for the lesion-prone area remain to be determined.

Asunto(s)

Presión Sanguínea/fisiología , Endotelio Vascular/patología , Hipertensión/patología , Túnica Íntima/patología , Envejecimiento/fisiología , Animales , Aorta Abdominal/efectos de los fármacos , Aorta Abdominal/patología , Arginina/farmacología , Presión Sanguínea/efectos de los fármacos , Pollos , Modelos Animales de Enfermedad , Hemodinámica , Masculino , Propranolol/farmacología , Solventes

RESUMEN

Chickens (males more than females) have higher blood pressure (BP) than most mammals and spontaneously develop vascular neointimal plaques (NP) and diffuse subendothelial thickening in the lower segment of the abdominal aorta (AbA, referred to as 'NP-prone area') that partly resemble atherosclerotic lesions in mammals. NP areas, which are larger in males, have a causal relationship with incremental increases in BP during maturation. We hypothesize that decreased wall distensibility and altered hemodynamic forces at the NP-prone area may contribute to the NP formation. We measured pressure pulse wave (PW) and systolic and diastolic BP along the descending aorta in anesthetized chickens at different ages using an intravascular microtip transducer and calculated pulse pressure (PP) as an indicator for artery distensibility. At all ages examined and in both sexes, the PW showed a sharper peak at the more peripheral locations and the amplitude of the PW increased as it descended the aorta. PP, expressed as relative increases from the PP in the aortic arch (%), was 40.4+/-12.6 and 71.4+/-18.6 at the AbA and ischiadic artery, respectively, in young males (24-27 weeks); 23.5+/-8.6 and 43.8+/-16.2 in adults (72-75 weeks); and 5.4+/-3.4 and 9.1+/-4.9 in chicks (5-7 weeks). Location-dependent increases in PP were significantly higher in young males (P<0.05). The PP increases in females were not different among the three age groups. The contour of the PW in the proximal aorta changes in older birds, exhibiting steeper increases in the ascending and descending limbs, suggesting that faster wave reflection from the periphery augments peak systolic pressure. NP was most frequently seen in the lower segment of the abdominal aorta in older males. These results suggest that: (1) site-dependent increases in PP amplitude are marked in young males, possibly reflecting a reduction in arterial wall elasticity enhanced by incremental rises in BP, and (2) NP formation may contribute to the stiffness of aortic walls in the NP-prone area.

Asunto(s)

Aorta/fisiología , Presión Sanguínea/fisiología , Pollos/fisiología , Factores de Edad , Anestesia , Animales , Aorta/citología , Aorta Abdominal/citología , Femenino , Frecuencia Cardíaca , Masculino , Factores Sexuales

RESUMEN

Kidneys play an essential role in fluid-ion balance, but the mechanisms of renal handling of water vary depending on structural organization of kidneys and the environment. Fishes and amphibians in a hypoosmotic environment excrete excess water by forming dilute urine, whereas terrestrial tetrapods require water conservation by the kidney for survival. Diluting segments operated by a luminal Na(+)-K(+)-2Cl(-) cotransporter coupled with a basolateral Na(+)-K(+) pump are essential in forming dilute urine. In birds and mammals, the diluting segment that has the same transport characteristics now serves, with the development of additional architectural organization, for countercurrent urine concentration and water conservation. Recently, a number of aquaporin (AQP) water channels have been identified in various transporting epithelia. AQPs conserve the NPA (asparagine-proline-alanine) motif, forming pores selective to water. Although all vertebrate kidneys presumably possess AQP water channels, AQP homologues have been cloned only from amphibian, avian and mammalian renal systems. Studies on expression sites, function and regulation of AQPs will provide important insight into cellular and molecular mechanisms of epithelial water transport and its control by humoral, neural and hemodynamic mechanisms.

Asunto(s)

Túbulos Renales/fisiología , Vertebrados/fisiología , Agua/metabolismo , Animales , Acuaporinas/metabolismo , Transporte Biológico , Hormonas/metabolismo

RESUMEN

We studied image quality (contrast) and patient dose reduction using heavy metal filters in lumbar spine and abdomen x-ray examination. Heavy metal filters used in this study are gadolinium, holmium and ytterbium and these combinations. These filters have k-absorption edge in the range from 50 to 70 keV. Image quality and patient dose in 70-90 kV tube voltage with heavy metal filters were compared with 80 kV tube voltage without filter. Image quality was improved in four percent and patient dose could be reduced by 30%. However, tube loading increased from 1.6 to 2.2 times. It was found that the best filter choices gave better image and reduced patient dose compared to without filter.

Asunto(s)

Filtración/métodos , Metales Pesados , Protección Radiológica/métodos , Intensificación de Imagen Radiográfica/métodos , Gadolinio , Holmio , Humanos , Vértebras Lumbares/diagnóstico por imagen , Dosis de Radiación , Radiografía Abdominal , Iterbio