Biomedical subjects

Li-Yih Lin

Publications and source records attributed to Li-Yih Lin.

5 recordsLinked to original sources

PubMed2005

Proton pump-rich cell secretes acid in skin of zebrafish larvae.

The mammalian kidney excretes its metabolic acid load through the proton-transporting cells, intercalated cells, in the distal nephron and collecting duct. Fish excrete acid through external organs, gill, or skin; however, the cellular function is still controversial. In this study, molecular and electrophysiological approaches were used to identify a novel cell type secreting acid in skin of zebrafish (Danio rerio) larvae. Among keratinocytes covering the larval surface, novel proton-secreting ionocytes, proton pump (H(+)-ATPase)-rich cells, were identified to generate strong outward H(+) flux. The present work demonstrates for the first time, with a noninvasive technique, H(+)-secreting cells in an intact animal model, the zebrafish, showing it to be a suitable model in which to study the functions of vertebrate transporting epithelia in vivo.

Acids↗

PubMed2005

How can teleostean inner ear hair cells maintain the proper association with the accreting otolith?

The perception of equilibrium and sound in fish depends on the deflection of hair bundles of hair cell by the otolith. However, the accreting nature of teleostean otoliths poses a problem for maintenance of proper contact between the hair bundle and the otolith surface. Immunocytochemical staining localizes abundant proton-secreting H(+)-ATPase in the apical membrane of the hair cells. The H(+)-ATPase-mediated proton secretion into the endolymph causes an approximately 0.4-unit pH decrease, which was quantified by an H(+)-selective microelectrode. Thus, the hair cells maintain the proper distance from the otolith by neutralizing the alkaline endolymph to retard CaCO(3) deposition on the otolith opposite the sensory macula. Carbonic anhydrase, which hydrolyses CO(2) and produces HCO(3) (-) and H(+), was also localized in the hair cells. Ionocytes showed prominent immunostaining of carbonic anhydrase and Na(+)-K(+)-ATPase, indicating its role in transepithelial transport of HCO(3) (-) across the membranous labyrinth into the endolymph. Ionocytes form a ring closely surrounding the sensory macula. HCO(3) (-) secreted from the ionocytes may serve as a barrier to neutralize H(+) diffused from the sensory macula while keeping the endolymph alkaline outside the sensory macula. The ingenious arrangement of ionocytes and hair cells results in a unique sculptured groove, which is a common feature on the proximal surface of all teleostean otoliths.

Animals↗

PubMed2005

Epithelial Ca(2+) channel expression and Ca(2+) uptake in developing zebrafish.

The purpose of the present work was to study the possible role of the epithelial Ca(2+) channel (ECaC) in the Ca(2+) uptake mechanism in developing zebrafish (Danio rerio). With rapid amplification of cDNA ends, full-length cDNA encoding the ECaC of zebrafish (zECaC) was cloned and sequenced. The cloned zECaC was 2,578 bp in length and encoded a protein of 709 amino acids that showed up to 73% identity with previously described vertebrate ECaCs. The zECaC was found to be expressed in all tissues examined and began to be expressed in the skin covering the yolk sac of embryos at 24 h postfertilization (hpf). zECaC-expressing cells expanded to cover the skin of the entire yolk sac after embryonic development and began to occur in the gill filaments at 96 hpf, and thereafter zECaC-expressing cells rapidly increased in both gills and yolk sac skin. Corresponding to ECaC expression profile, the Ca(2+) influx and content began to increase at 36-72 hpf. Incubating zebrafish embryos in low-Ca(2+) (0.02 mM) freshwater caused upregulation of the whole body Ca(2+) influx and zECaC expression in both gills and skin. Colocalization of zECaC mRNA and the Na(+)-K(+)-ATPase alpha-subunit (a marker for mitochondria-rich cells) indicated that only a portion of the mitochondria-rich cells expressed zECaC mRNA. These results suggest that the zECaC plays a key role in Ca(2+) absorption in developing zebrafish.

Amino Acid Sequence↗

PubMed2004

Mitochondria-rich cell activity in the yolk-sac membrane of tilapia (Oreochromis mossambicus) larvae acclimatized to different ambient chloride levels.

Mitochondria-rich cells (MRCs) in the yolk-sac membrane of tilapia (Oreochromis mossambicus) larvae were examined by Na+/K(+)-ATPase immunocytochemistry and vital staining for glycoproteins following acclimation to high (7.5-7.9 mmol l(-1)), normal (0.48-0.52 mmol l(-1)) or low (0.002-0.007 mmol l(-1)) ambient Cl- levels. With a combination of concanavalin-A (Con-A)-Texas-Red conjugate staining (larvae exposed to the dye in vivo in the water) and a monoclonal antibody raised against Na+/K(+)-ATPase, MRCs were easily recognized and presumed to be active when Con-A-positive (i.e. with their apical membrane in contact with the water) or inactive when Con-A-negative. The proportion of active cells gradually increased during a 48-h acclimation to low-Cl- medium but decreased during acclimation to high-Cl- medium. Total densities of MRCs did not change when ambient chloride levels were altered. Furthermore, in live larvae exposed to changes in ambient Cl-, yolk-sac MRCs, vitally stained with DASPEI and subsequently traced in time, did not significantly alter turnover. The polymorphism of the apical membrane compartment of the MRCs represents structural modification of the active MRCs. Yolk-sac pavement cells labeled with the membrane marker FM1-43 (fluorescent lipophilic tracer) were shown to cover active MRCs in larvae transferred from normal to high ambient Cl- levels, thereby inactivating the MRCs.

Acclimatization↗

PubMed2002

Cellular distributions of creatine kinase in branchia of euryhaline tilapia (Oreochromis mossambicus).

Although euryhaline teleosts can adapt to environmental fluctuation of salinity, their energy source for responding to changes in salinity and osmolarity remains unclear. This study examines the cellular localization of creatine kinase (CK) expression in branchia of tilapia (Oreochromis mossambicus). Western blot analysis of muscle-type CK (MM form) revealed a high association with salinity changes, but BB and MB forms of CK in the gills of fish adapted to seawater did not change. With the use of immunocytochemistry, three CK isoforms (MM, MB, and BB) were localized in mitochondria-rich (MR) cells and other epithelial cells of tilapia gills. In addition, staining intensity of MM-form CK in MR cells increased after seawater transfer, whereas BB and MB forms did not significantly change. To our knowledge, this work presents the first evidence of CK expression in MR cells of tilapia gills, highlighting the potential role of CK in providing energy for ion transport.

Animals↗