6 results on '"Keigo Kakumura"'
Search Results
2. Comprehensive analysis of genes contributing to euryhalinity in the bull shark, Carcharhinus leucas; Na+-Cl− co-transporter is one of the key renal factors up-regulated in acclimation to low-salinity environment in bull sharks, but not in houndsharks, Triakis scyllium
- Author
-
Souichirou Takabe, Yosuke Matsumoto, Masaru Nakamura, Itaru Imaseki, Wataru Takagi, Rui Matsumoto, Yuichiro Hara, Yuki Honda, Taro Watanabe, Kiyomi Murakumo, Keiichi Ueda, Midori Wakabayashi, Shigehiro Kuraku, Susumu Hyodo, and Keigo Kakumura
- Subjects
0106 biological sciences ,0303 health sciences ,biology ,urogenital system ,Physiology ,Reabsorption ,030310 physiology ,Zoology ,Euryhaline ,Aquatic Science ,Bull shark ,biology.organism_classification ,010603 evolutionary biology ,01 natural sciences ,Acclimatization ,03 medical and health sciences ,Triakis scyllium ,Houndshark ,Insect Science ,Carcharhinus ,Osmoregulation ,Animal Science and Zoology ,Molecular Biology ,Ecology, Evolution, Behavior and Systematics - Abstract
Most of the cartilaginous fishes live principally in seawater (SW) environments, while a limited number of species including the bull shark, Carcharhinus leucas, inhabit both SW and freshwater (FW) environments during their life cycle. Euryhaline elasmobranchs maintain high internal urea and ion levels even in FW environments, but little is known about the osmoregulatory mechanisms that enable them to maintain internal homeostasis in hypoosmotic environments. In the present study, we focused on the kidney because this is the only organ that can excrete excess water from the body in a hypoosmotic environment. We conducted a transfer experiment of bull sharks from SW to FW and performed differential gene expression analysis between the two conditions using RNA-seq. A search for genes up-regulated in the FW-acclimated bull shark kidney indicated that the expression of the Na+-Cl− cotransporter (NCC; Slc12a3) was ten times higher in the FW-acclimated fish compared to that in SW fish. In the kidney, apically-located NCC was observed in the late distal tubule and in the anterior half of collecting tubule where basolateral Na+/K+-ATPase was also expressed, implying that these segments contribute to NaCl reabsorption from the filtrate for diluting the urine. This expression pattern was not observed in the houndshark, Triakis scyllium, that had been transferred to 30% SW; this species cannot survive in FW environment. The salinity transfer experiment combined with a comprehensive gene screening approach demonstrates that NCC is a key renal protein that contributes to the remarkable euryhaline ability of the bull shark.
- Published
- 2019
3. Gene expression and cellular localization of ROMKs in the gills and kidney of Mozambique tilapia acclimated to fresh water with high potassium concentration
- Author
-
Junya Hiroi, Soichi Watanabe, Fumiya Furukawa, Toyoji Kaneko, and Keigo Kakumura
- Subjects
Gills ,Gill ,medicine.medical_specialty ,Oreochromis mossambicus ,food.ingredient ,Physiology ,Acclimatization ,Gene Expression ,Fresh Water ,Kidney ,food ,Physiology (medical) ,Internal medicine ,medicine ,Animals ,Solute Carrier Family 12, Member 4 ,Potassium Channels, Inwardly Rectifying ,Cellular localization ,biology ,Osmolar Concentration ,Tilapia ,Water-Electrolyte Balance ,Apical membrane ,biology.organism_classification ,Endocrinology ,medicine.anatomical_structure ,Potassium ,ROMK ,Osmoregulation - Abstract
Regulation of plasma K+levels in narrow ranges is vital to vertebrate animals. Since seawater (SW) teleosts are loaded with excess K+, they constantly excrete K+from the gills. However, the K+regulatory mechanisms in freshwater (FW)-acclimated teleosts are still unclear. We aimed to identify the possible K+regulatory mechanisms in the gills and kidney, the two major osmoregulatory organs, of FW-acclimated Mozambique tilapia ( Oreochromis mossambicus). As a potential molecular candidate for renal K+handling, a putative renal outer medullary K+channel (ROMK) was cloned from the tilapia kidney and tentatively named “ROMKb”; another ROMK previously cloned from the tilapia gills was thus renamed “ROMKa”. The fish were acclimated to control FW or to high-K+(H-K) FW for 1 wk, and we assessed physiological responses of tilapia to H-K treatment. As a result, urinary K+levels were slightly higher in H-K fish, implying a role of the kidney in K+excretion. However, the mRNA expression levels of both ROMKa and ROMKb were very low in the kidney, while that of K+/Cl−cotransporter 1 (KCC1) was robust. In the gills, ROMKa mRNA was markedly upregulated in H-K fish. Immunofluorescence staining showed that branchial ROMKa was expressed at the apical membrane of type I and type III ionocytes, and the ROMKa immunosignals were more intense in H-K fish than in control fish. The present study suggests that branchial ROMKa takes a central role for K+regulation in FW conditions and that K+excretion via the gills is activated irrespective of environmental salinity.
- Published
- 2014
4. Multiple urea transporter proteins in the kidney of holocephalan elephant fish (Callorhinchus milii)
- Author
-
Soichi Watanabe, Toyoji Kaneko, John A. Donald, Susumu Hyodo, Justin D. Bell, Keigo Kakumura, and Tes Toop
- Subjects
Physiology ,Phloretin ,Urea transporter ,Molecular Sequence Data ,Renal urea handling ,Xenopus ,Kidney ,Biochemistry ,Evolution, Molecular ,Mice ,chemistry.chemical_compound ,Molecular evolution ,medicine ,Animals ,Humans ,Urea ,Amino Acid Sequence ,Cloning, Molecular ,Molecular Biology ,Phylogeny ,biology ,Reabsorption ,Fishes ,Membrane Transport Proteins ,biology.organism_classification ,medicine.anatomical_structure ,chemistry ,biology.protein - Abstract
Reabsorption of filtered urea by the kidney is essential for retaining high levels of urea in marine cartilaginous fish. Our previous studies on the shark facilitative urea transporter (UT) suggest that additional UT(s) comprising the urea reabsorption system could exist in the cartilaginous fish kidney. Here, we isolated three cDNAs encoding UTs from the kidney of elephant fish, Callorhinchus milii, and termed them efUT-1, efUT-2 and efUT-3. efUT-1 is orthologous to known elasmobranch UTs, while efUT-2 and efUT-3 are novel UTs in cartilaginous fish. Two variants were found for efUT-1 and efUT-2, in which the NH(2)-terminal intracellular domain was distinct between the variants. Differences in potential phosphorylation sites were found in the variant-specific NH(2)-terminal domains. When expressed in Xenopus oocytes, all five UT transcripts including the efUT-1 and efUT-2 variants induced more than a 10-fold increase in [(14)C] urea uptake. Phloretin inhibited dose-dependently the increase of urea uptake, suggesting that the identified UTs are facilitative UTs. Molecular phylogenetic analysis revealed that efUT-1 and efUT-2 had diverged in the cartilaginous fish lineage, while efUT-3 is distinct from efUT-1 and efUT-2. The present finding of multiple UTs in elephant fish provides a key to understanding the molecular mechanisms of urea reabsorption system in the cartilaginous fish kidney.
- Published
- 2009
5. Morphological and molecular investigations of the holocephalan elephant fish nephron: the existence of a countercurrent-like configuration and two separate diluting segments in the distal tubule
- Author
-
Toyoji Kaneko, John A. Donald, Keigo Kakumura, Justin D. Bell, Susumu Hyodo, Wataru Takagi, Souichirou Takabe, Tes Toop, Norifumi Konno, and Kumi Hasegawa
- Subjects
Fish Proteins ,Histology ,Renal urea handling ,Nephron ,Biology ,Models, Biological ,Pathology and Forensic Medicine ,chemistry.chemical_compound ,medicine ,Animals ,RNA, Messenger ,Cloning, Molecular ,Kidney Tubules, Collecting ,In Situ Hybridization ,Phylogeny ,Kidney ,Reabsorption ,Cell Biology ,Anatomy ,Renal corpuscle ,Immunohistochemistry ,Protein Subunits ,medicine.anatomical_structure ,Tubule ,chemistry ,Biophysics ,Urea ,Cotransporter ,Electric Fish - Abstract
In marine cartilaginous fish, reabsorption of filtered urea by the kidney is essential for retaining a large amount of urea in their body. However, the mechanism for urea reabsorption is poorly understood due to the complexity of the kidney. To address this problem, we focused on elephant fish (Callorhinchus milii) for which a genome database is available, and conducted molecular mapping of membrane transporters along the different segments of the nephron. Basically, the nephron architecture of elephant fish was similar to that described for elasmobranch nephrons, but some unique features were observed. The late distal tubule (LDT), which corresponded to the fourth loop of the nephron, ran straight near the renal corpuscle, while it was convoluted around the tip of the loop. The ascending and descending limbs of the straight portion were closely apposed to each other and were arranged in a countercurrent fashion. The convoluted portion of LDT was tightly packed and enveloped by the larger convolution of the second loop that originated from the same renal corpuscle. In situ hybridization analysis demonstrated that co-localization of Na(+),K(+),2Cl(-) cotransporter 2 and Na(+)/K(+)-ATPase α1 subunit was observed in the early distal tubule and the posterior part of LDT, indicating the existence of two separate diluting segments. The diluting segments most likely facilitate NaCl absorption and thereby water reabsorption to elevate urea concentration in the filtrate, and subsequently contribute to efficient urea reabsorption in the final segment of the nephron, the collecting tubule, where urea transporter-1 was intensely localized.
- Published
- 2015
6. Morphological and functional characteristics of the kidney of cartilaginous fishes: with special reference to urea reabsorption
- Author
-
Susumu Hyodo, Keigo Kakumura, Kumi Hasegawa, Wataru Takagi, and Yoko Yamaguchi
- Subjects
Fish Proteins ,Salinity ,Physiology ,Renal urea handling ,Cartilaginous fish ,Biology ,chemistry.chemical_compound ,Osmoregulation ,Species Specificity ,Physiology (medical) ,medicine ,Animals ,Urea ,Seawater ,Kidney ,urogenital system ,Fishes ,Membrane Transport Proteins ,Nephrons ,Adaptation, Physiological ,Renal Reabsorption ,medicine.anatomical_structure ,chemistry ,Biochemistry ,Adaptation - Abstract
For adaptation to high-salinity marine environments, cartilaginous fishes (sharks, skates, rays, and chimaeras) adopt a unique urea-based osmoregulation strategy. Their kidneys reabsorb nearly all filtered urea from the primary urine, and this is an essential component of urea retention in their body fluid. Anatomical investigations have revealed the extraordinarily elaborate nephron system in the kidney of cartilaginous fishes, e.g., the four-loop configuration of each nephron, the occurrence of distinct sinus and bundle zones, and the sac-like peritubular sheath in the bundle zone, in which the nephron segments are arranged in a countercurrent fashion. These anatomical and morphological characteristics have been considered to be important for urea reabsorption; however, a mechanism for urea reabsorption is still largely unknown. This review focuses on recent progress in the identification and mapping of various pumps, channels, and transporters on the nephron segments in the kidney of cartilaginous fishes. The molecules include urea transporters, Na+/K+-ATPase, Na+-K+-Cl−cotransporters, and aquaporins, which most probably all contribute to the urea reabsorption process. Although research is still in progress, a possible model for urea reabsorption in the kidney of cartilaginous fishes is discussed based on the anatomical features of nephron segments and vascular systems and on the results of molecular mapping. The molecular anatomical approach thus provides a powerful tool for understanding the physiological processes that take place in the highly elaborate kidney of cartilaginous fishes.
- Published
- 2014
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.