RESUMEN
To examine possible roles of vasotocin (VT), isotocin (IT), prolactin (PRL) and growth hormone (GH) in osmoregulation of a stenohaline marine teleost, tiger puffer (Takifugu rubripes), changes in expression levels of these genes following hypoosmotic challenge, were examined in two experiments. Fish were transferred from 100% seawater (SW) to 33% SW, 10% SW and fresh water (FW), and left for 3days in experiment I. In experiment II, fish were transferred to FW, and left for 1day. Changes in plasma osmolality, concentrations of Na(+) and Cl(-), and Na(+)/K(+)-ATPase activity in the gills and kidney were examined. Changes in the absolute amounts of VT, IT, PRL and GH mRNAs were determined by real-time PCR. In experiment I, almost all fish survived over 3days of acclimation. The plasma parameters decreased on day 1, and remained at similar levels until day 3. The renal Na(+)/K(+)-ATPase activity significantly increased in 10% SW and FW on day 1. The amounts of VT and IT mRNAs tended to decrease in the hypoosmotic conditions on day 1. The amounts of PRL mRNA significantly increased in the hypoosmotic conditions, whereas those of GH mRNA decreased in FW. In experiment II, the amount of VT mRNA significantly decreased in FW concomitantly with the changes in PRL and GH mRNAs. The present results suggest that the hyperosmotic responses may be regulated by neuroendocrine factors such as VT, PRL and GH in tiger puffer, as in case of euryhaline teleosts. Particularly, the present study first shows that the expression of VT gene may be down-regulated following hypoosmotic challenge in the stenohaline marine fish.
Asunto(s)
Hormona del Crecimiento/biosíntesis , Oxitocina/análogos & derivados , Prolactina/biosíntesis , Takifugu/metabolismo , Vasotocina/biosíntesis , Equilibrio Hidroelectrolítico/fisiología , Animales , Expresión Génica , Branquias/enzimología , Hormona del Crecimiento/genética , Oxitocina/biosíntesis , Oxitocina/genética , Prolactina/genética , ARN Mensajero/metabolismo , ATPasa Intercambiadora de Sodio-Potasio/metabolismo , Takifugu/genética , Vasotocina/genéticaRESUMEN
Microglia participate in immune responses in the brain. However, little is known about the contact-mediated interaction between microglia and neurons. We report here that the cell-to-cell contacts between microglial processes and dendrites of hippocampal CA1 neurons were dramatically increased in density and area following local injection of kainic acid (KA). A similar KA-induced increase in the degree of intercellular contacts was observed in mice lacking telencephalin (TLCN), a neuronal dendritic adhesion molecule of ICAM family. The results suggest that adhesive contacts independent of TLCN and contact-mediated interactions between microglia and dendrites were promoted by excitotoxic brain injury.
Asunto(s)
Comunicación Celular/efectos de los fármacos , Dendritas/efectos de los fármacos , Hipocampo/citología , Ácido Kaínico/farmacología , Microglía/efectos de los fármacos , Neurotoxinas/farmacología , Células Piramidales/citología , Animales , Proteínas de Unión al Calcio/metabolismo , Recuento de Células/métodos , Galectina 3/metabolismo , Hipocampo/efectos de los fármacos , Masculino , Ratones , Ratones Endogámicos C57BL , Proteínas de Microfilamentos , Microglía/fisiología , Modelos Neurológicos , Factores de TiempoRESUMEN
Osmoregulatory mechanisms in holocephalan fishes are poorly understood except that these fish are known to conduct urea-based osmoregulation as in elasmobranchs. We, therefore, examined changes in plasma parameters of elephant fish Callorhinchus milii, after gradual transfer to concentrated (120%) or diluted (80%) seawater (SW). In control fish, plasma Na and urea concentrations were about 300 mmol l(-1) and 450 mmol l(-1), respectively. These values were equivalent to those of sharks and rays, but the plasma urea concentration of elephant fish was considerably higher than that reported for chimaeras, another holocephalan. After transfer to 120% SW, plasma osmolality, urea and ion concentrations were increased, whereas transfer to 80% SW resulted in a fall in these parameters. The rises in ion concentrations were notable after transfer to 120% SW, whereas urea concentration decreased predominantly following transfer to 80% SW. In elephant fish, we could not find a discrete rectal gland. Instead, approximately 10 tubular structures were located in the wall of post-valvular intestine. Each tubular structure was composed of a putative salt-secreting component consisting of a single-layered columnar epithelium, which was stained with an anti-Na(+),K(+)-ATPase serum. Furthermore, Na(+),K(+)-ATPase activity in the tubular structures was significantly increased after acute transfer of fish to concentrated SW (115%). These results suggest that the tubular structures are a rectal gland equivalent, functioning as a salt-secreting organ. Since the rectal gland of elephant fish is well developed compared to that of Southern chimaera, the salt-secreting ability may be higher in elephant fish than chimaeras, which may account for the lower plasma NaCl concentration in elephant fish compared to other chimaeras. Since elephant fish have also attracted attention from a viewpoint of genome science, the availability of fish for physiological studies will make this species an excellent model in holocephalan fish group.
Asunto(s)
Peces/fisiología , Glándula de Sal/fisiología , ATPasa Intercambiadora de Sodio-Potasio/metabolismo , Equilibrio Hidroelectrolítico/fisiología , Análisis de Varianza , Animales , Pesos y Medidas Corporales , Histocitoquímica , Glándula de Sal/anatomía & histología , Agua de Mar/química , Sodio/sangre , Urea/sangre , VictoriaRESUMEN
To examine the manner of interactions between immune cells and central nervous system (CNS) neurons, mouse hippocampal neurons were co-cultured with lymphokine (IL-2)-activated killer (LAK) cells. Immunocytochemical and time-lapse observations indicated that LAK cells migrated along neuronal processes and made adhesive contacts with them. In addition to the direct physical effects, LAK cells released glutamate, induced the formation of beads-like structure in the dendrites of about 14% of hippocampal neurons and caused the reduction of dendritic protrusions. These results suggest that infiltrating immune cells can form direct adhesive connections with CNS neurons and affect their dendritic morphology.
Asunto(s)
Dendritas/inmunología , Hipocampo/fisiología , Células Asesinas Activadas por Linfocinas/inmunología , Activación de Linfocitos/inmunología , Subgrupos Linfocitarios/inmunología , Animales , Adhesión Celular/inmunología , Comunicación Celular/inmunología , Movimiento Celular/inmunología , Células Cultivadas , Técnicas de Cocultivo , Citotoxicidad Inmunológica , Inmunohistoquímica , Interleucina-2/inmunología , Ratones , Neuronas/fisiologíaRESUMEN
To elucidate the mechanisms associated with water absorption in the intestine, we compared drinking and intestinal water absorption in freshwater- and seawater-adapted Japanese eels, and investigated a possible involvement of aquaporin (AQP) in the absorption of water in the intestine. Seawater eels ingested more water than freshwater eels, the drinking rate being 0.02 ml kg(-1) h(-1) in fresh water and 0.82 ml kg(-1) h(-1) in sea water. In intestinal sacs prepared from freshwater and seawater eels, water absorption increased in time- and hydrostatic pressure-dependent manners. The water absorption rates were greater in seawater sacs than in freshwater sacs, and also greater in the posterior intestine than in the anterior. In view of the enhanced water permeability in the intestine of seawater eel, we cloned two cDNAs encoding AQP from the seawater eel intestine, and identified two eel homologues (S-AQP and L-AQP) of mammalian AQP1. S-AQP and L-AQP possessed the same amino acid sequence, except that one amino acid was lacking in S-AQP and two amino acids were substituted. Eel AQP1 was expressed predominantly in the intestine, and the expression levels were higher in seawater eel than in freshwater eel. Immunocytochemical studies revealed intense AQP1 immunoreaction in the apical surface of columnar epithelial cells in seawater eel, in which the immunoreaction was stronger in the posterior intestine than in the anterior. In contrast, the immunoreaction was faint in the freshwater eel intestine. Preferential localization of AQP1 in the apical membrane of epithelial cells in the posterior intestine of seawater eel indicates that this region of the intestine is responsible for water absorption, and that AQP1 may act as a water entry site in the epithelial cells.
Asunto(s)
Anguilla/fisiología , Acuaporinas/metabolismo , Células Epiteliales/metabolismo , Absorción Intestinal/fisiología , Mucosa Intestinal/fisiología , Agua/metabolismo , Secuencia de Aminoácidos , Análisis de Varianza , Animales , Acuaporina 1 , Acuaporinas/genética , Northern Blotting , Western Blotting , ADN Complementario/genética , Ingestión de Líquidos/fisiología , Células Epiteliales/fisiología , Agua Dulce , Inmunohistoquímica , Mucosa Intestinal/metabolismo , Japón , Datos de Secuencia Molecular , Agua de Mar , Análisis de Secuencia de ADNRESUMEN
Despite unfavorable conditions, a single species of fish, Osorezan dace, lives in an extremely acidic lake (pH 3.5) in Osorezan, Aomori, Japan. Physiological studies have established that this fish is able to prevent acidification of its plasma and loss of Na(+). Here we show that these abilities are mainly attributable to the chloride cells of the gill, which are arranged in a follicular structure and contain high concentrations of Na(+)-K(+)-ATPase, carbonic anhydrase II, type 3 Na(+)/H(+) exchanger (NHE3), type 1 Na(+)-HCO(3)(-) cotransporter, and aquaporin-3, all of which are upregulated on acidification. Immunohistochemistry established their chloride cell localization, with NHE3 at the apical surface and the others localized to the basolateral membrane. These results suggest a mechanism by which Osorezan dace adapts to its acidic environment. Most likely, NHE3 on the apical side excretes H(+) in exchange for Na(+), whereas the electrogenic type 1 Na(+)-HCO(3)(-) cotransporter in the basolateral membrane provides HCO(3)(-) for neutralization of plasma using the driving force generated by Na(+)-K(+)-ATPase and carbonic anhydrase II. Increased expression of glutamate dehydrogenase was also observed in various tissues of acid-adapted dace, suggesting a significant role of ammonia and bicarbonate generated by glutamine catabolism.
Asunto(s)
Adaptación Fisiológica , Peces/fisiología , Agua Dulce/química , Animales , Acuaporina 3 , Acuaporinas/metabolismo , Anhidrasa Carbónica II/genética , Clonación Molecular , Inducción Enzimática , Branquias/enzimología , Concentración de Iones de Hidrógeno , Japón , Riñón/enzimología , Oocitos , ARN Mensajero/genética , ARN Mensajero/metabolismo , Sodio/metabolismo , Simportadores de Sodio-Bicarbonato/genética , Simportadores de Sodio-Bicarbonato/metabolismo , Intercambiadores de Sodio-Hidrógeno/genética , Intercambiadores de Sodio-Hidrógeno/metabolismo , ATPasa Intercambiadora de Sodio-Potasio/genética , Regulación hacia Arriba , Xenopus laevisRESUMEN
An RBCC (RING finger, B-box, and coiled-coil) protein was identified that belongs to the superfamily of zinc-binding proteins and is specifically expressed in the gill of eel, Anguilla japonica. Euryhaline fishes such as eels can migrate between freshwater and seawater, which is considered to be accomplished by efficient remodeling of the architecture and function of the gill, a major osmoregulatory organ. To identify molecules involved in such adaptive changes, we performed differential display using mRNA preparations from freshwater and seawater eel gills and obtained an RBCC clone among several differentially expressed clones. The clone encoded a protein of 514 amino acid residues with structural features characteristic of the RBCC protein; we therefore named it eRBCC (e for eel). eRBCC mRNA was specifically expressed in the gills with a greater extent in the gills of freshwater eels. Immunohistochemistry revealed that the expression of eRBCC is confined to particular epithelial cells of the gills including freshwater-specific lamellar chloride cells. The RING finger of eRBCC was found to have a ubiquitin ligase activity, suggesting an important regulatory role of eRBCC in the remodeling of branchial cells.
Asunto(s)
Anguilas/genética , Ligasas/biosíntesis , Ligasas/química , Dedos de Zinc , Secuencia de Aminoácidos , Animales , Secuencia de Bases , Northern Blotting , Western Blotting , Células COS , Clonación Molecular , ADN Complementario/metabolismo , Anguilas/metabolismo , Células Epiteliales , Perfilación de la Expresión Génica , Branquias/metabolismo , Inmunohistoquímica , Ligasas/metabolismo , Microscopía Fluorescente , Datos de Secuencia Molecular , Unión Proteica , Estructura Terciaria de Proteína , ARN Mensajero/metabolismo , Ribonucleasas/metabolismo , Homología de Secuencia de Aminoácido , Factores de Tiempo , Distribución Tisular , Ubiquitina/metabolismoRESUMEN
In eels, a CaCl(2) solution was infused into the pneumatic duct vein. Plasma Ca levels were significantly increased during 3 hr and were followed by significant raises in plasma calcitonin levels. These results strongly suggest that, in eels, direct raises in blood Ca levels by infusion of a high-Ca solution via blood vessels can accelerate the secretion of calcitonin from the ultimobranchial gland.