@article{kiilerich_tipsmark_borski_madsen_2011, title={Differential effects of cortisol and 11-deoxycorticosterone on ion transport protein mRNA levels in gills of two euryhaline teleosts, Mozambique tilapia (Oreochromis mossambicus) and striped bass (Morone saxatilis)}, volume={209}, ISSN={["0022-0795"]}, DOI={10.1530/joe-10-0326}, abstractNote={The role of cortisol as the only corticosteroid in fish osmoregulation has recently been challenged with the discovery of a mineralocorticoid-like hormone, 11-deoxycorticosterone (DOC), and necessitates new studies of the endocrinology of osmoregulation in fish. Using an in vitro gill explant incubation approach, DOC-mediated regulation of selected osmoregulatory target genes in the gill was investigated and compared with that of cortisol in two euryhaline teleosts, Mozambique tilapia (Oreochromis mossambicus) and striped bass (Morone saxatilis). The effects were tested in gills from both fresh water (FW)- and seawater (SW)-acclimated fish. Both cortisol and DOC caused an up-regulation of the Na+,K+-ATPase α1 subunit in SW-acclimated tilapia but had no effect in FW-acclimated fish. Cortisol conferred an increase in Na+,K+,2Cl− cotransporter (NKCC) isoform 1a transcript levels in FW- and SW-acclimated tilapia, whereas DOC had a stimulatory effect only in SW-acclimated fish. Cortisol had no effect on NKCC isoform 1b mRNA levels at both salinities, while DOC stimulated this isoform in SW-acclimated fish. In striped bass, cortisol conferred an up-regulation of Na+,K+-ATPase α1 and NKCC transcript levels in FW- and SW-acclimated fish, whereas DOC resulted in down-regulation of these transcripts in FW-acclimated fish. It was also found that both corticosteroids may rapidly (30 min) alter the mitogen-activated protein kinase signalling pathway in gill, inducing phosphorylation of extracellular signal-regulated kinase 1 (ERK1) and ERK2 in a salinity-dependent manner. The study shows a disparate organisation of corticosteroid signalling mechanisms involved in ion regulation in the two species and adds new evidence to a role of DOC as a mineralocorticoid hormone in teleosts.}, number={1}, journal={JOURNAL OF ENDOCRINOLOGY}, author={Kiilerich, Pia and Tipsmark, Christian K. and Borski, Russell J. and Madsen, Steffen S.}, year={2011}, month={Apr}, pages={115–126} }
 @article{tipsmark_strom_bailey_borski_2008, title={Leptin stimulates pituitary prolactin release through an extracellular signal-regulated kinase-dependent pathway}, volume={196}, ISSN={["1479-6805"]}, DOI={10.1677/JOE-07-0540}, abstractNote={Leptin was initially identified as a regulator of appetite and weight control centers in the hypothalamus, but appears to be involved in a number of physiological processes. This study was carried out to examine the possible role of leptin in regulating prolactin (PRL) release using the teleost pituitary model system. This advantageous system allows isolation of a nearly pure population of lactotropes in their natural, in situ aggregated state. The rostral pars distalis were dissected from tilapia pituitaries and exposed to varying concentrations of leptin (0, 1, 10, 100 nM) for 1 h. Release of PRL was stimulated by leptin in a potent and concentration-dependent manner. A time-course experiment showed that the strongest response in PRL release with leptin occurs within the first hour (approximately sixfold), and stimulation was sustained after 16 h (approximately twofold). Many of the actions of leptin are mediated by the activation of extracellular signal-regulated kinase (ERK1/2) but nothing is known about the cellular mechanisms by which leptin might regulate PRL secretion in vertebrates. We therefore tested whether ERK1/2 might be involved in the leptin PRL response and found that the ERK inhibitor, PD98059, hindered leptin-induced PRL release. We further analyzed leptin response by quantifying tyrosine and threonine phosphorylation of ERK1/2 using western blots. One hour incubation with leptin induced a concentration-dependent increase in phosphorylated, and thus active, ERK1/2. Our data show that leptin is a powerful stimulator of in vitro PRL release and that its actions occur in part through stimulation of ERK1/2.}, number={2}, journal={JOURNAL OF ENDOCRINOLOGY}, author={Tipsmark, Christian K. and Strom, Christina N. and Bailey, Sean T. and Borski, Russell J.}, year={2008}, month={Feb}, pages={275–281} }
 @article{tipsmark_luckenbach_madsen_kiilerich_borski_2008, title={Osmoregulation and expression of ion transport proteins and putative claudins in the gill of Southern Flounder (Paralichthys lethostigma)}, volume={150}, ISSN={["1531-4332"]}, DOI={10.1016/j.cbpa.2008.03.006}, abstractNote={The southern flounder is a euryhaline teleost that inhabits ocean, estuarine, and riverine environments. We investigated the osmoregulatory strategy of juvenile flounder by examining the time-course of homeostatic responses, hormone levels, and gill Na(+),K(+)-ATPase and Na(+),K(+),2Cl(-) cotransporter protein expression after salinity challenge. Transfer of freshwater (FW)-acclimated flounder to sea water (SW) induced an increase in plasma osmolality and cortisol and a decrease in muscle water content, plasma insulin-like growth factor I (IGF-I) and hepatic IGF-I mRNA, all returning to control levels after 4 days. Gill Na(+),K(+)-ATPase and Na(+),K(+),2Cl(-) cotransporter protein levels were elevated in response to SW after 4 days. Transfer of SW-acclimated flounder to FW reduced gill Na(+),K(+)-ATPase and Na(+),K(+),2Cl(-) cotransporter protein, increased plasma IGF-I, but did not alter hepatic IGF-I mRNA or plasma cortisol levels. Gill claudin-3 and claudin-4 immunoreactive proteins were elevated in FW versus SW acclimated flounder. The study demonstrates that successful acclimation of southern flounder to SW or FW occurs after an initial crisis period and that the salinity adaptation process is associated with changes in branchial expression of ion transport and putative tight junction claudin proteins known to regulate epithelial permeability in mammalian vertebrates.}, number={3}, journal={COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY A-MOLECULAR & INTEGRATIVE PHYSIOLOGY}, author={Tipsmark, Christian K. and Luckenbach, J. Adam and Madsen, Steffen S. and Kiilerich, Pia and Borski, Russell J.}, year={2008}, month={Jul}, pages={265–273} }
 @article{picha_turano_tipsmark_borski_2008, title={Regulation of endocrine and paracrine sources of Igfs and Gh receptor during compensatory growth in hybrid striped bass (Morone chrysops X Morone saxatilis)}, volume={199}, ISSN={["1479-6805"]}, DOI={10.1677/JOE-07-0649}, abstractNote={Compensatory growth (CG) is a period of growth acceleration that exceeds normal rates after animals are alleviated of certain growth-stunting conditions. In hybrid striped bass (HSB, Morone chrysops×Morone saxatilis), 3 weeks of complete feed restriction results in a catabolic state that, when relieved, renders a subsequent phase of CG. The catabolic state was characterized by depressed levels of hepatic Type I and II GH receptor (ghr1, ghr2) and igf1 mRNA, along with considerable decreases in plasma Igf1. The state of catabolism also resulted in significant declines in hepatic igf2 mRNA and in circulating 40 kDa Igf-binding protein (Igfbp). Skeletal muscle expression of ghr2 mRNA was significantly increased. Upon realimentation, specific growth rates (SGRs) were significantly higher than sized-matched controls, indicating a period of CG. Hepatic ghr1, ghr2, igf1 and igf2 mRNA levels along with plasma Igf1 and 40 kDa Igfbp increased rapidly during realimentation. Plasma Igf1 and total hepatic igf2 mRNA were significantly correlated to SGR throughout the study. Skeletal muscle igf1 mRNA also increased tenfold during CG. These data suggest that endocrine and paracrine/autocrine components of the GH–Igf axis, namely igf1, igf2, and ghr1 and ghr2, may be involved in CG responses in HSB, with several of the gene expression variables exceeding normal levels during CG. We also demonstrate that normalization of hepatic mRNA as a function of total liver production, rather than as a fraction of total RNA, may be a more biologically appropriate method of quantifying hepatic gene expression when using real-time PCR.}, number={1}, journal={JOURNAL OF ENDOCRINOLOGY}, author={Picha, Matthew E. and Turano, Marc J. and Tipsmark, Christian K. and Borski, Russell J.}, year={2008}, month={Oct}, pages={81–94} }
 @article{tipsmark_baltzegar_ozden_grubb_borski_2008, title={Salinity regulates claudin mRNA and protein expression in the teleost gill}, volume={294}, ISSN={["1522-1490"]}, DOI={10.1152/ajpregu.00112.2007}, abstractNote={The teleost gill carries out NaCl uptake in freshwater (FW) and NaCl excretion in seawater (SW). This transformation with salinity requires close regulation of ion transporter capacity and epithelial permeability. This study investigates the regulation of tight-junctional claudins during salinity acclimation in fish. We identified claudin 3- and claudin 4-like immunoreactive proteins and examined their expression and that of select ion transporters by performing Western blot in tilapia ( Oreochromis mossambicus) gill during FW and SW acclimation. Transfer of FW tilapia to SW increased plasma osmolality, which was corrected after 4 days, coinciding with increased gill Na+-K+-ATPase and Na+-K+-2Cl−cotransporter expression. Gill claudin 3- and claudin 4-like proteins were reduced with exposure to SW. Transfer to FW increased both claudin-like proteins. Immunohistochemistry shows that claudin 3-like protein was localized deep in the FW gill filament, whereas staining was found apically in SW gill. Claudin 4-like proteins are localized predominantly in the filament outer epithelial layer, and staining appears more intense in the gill of FW versus SW fish. In addition, tilapia claudin 28a and 30 genes were characterized, and mRNA expression was found to increase during FW acclimation. These studies are the first to detect putative claudin proteins in teleosts and show their localization and regulation with salinity in gill epithelium. The data indicate that claudins may be important in permeability changes associated with salinity acclimation and possibly the formation of deeper tight junctions in FW gill. This may reduce ion permeability, which is a critical facet of FW osmoregulation.}, number={3}, journal={AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY}, author={Tipsmark, Christian K. and Baltzegar, David A. and Ozden, Ozkan and Grubb, Brenda J. and Borski, Russell J.}, year={2008}, month={Mar}, pages={R1004–R1014} }
 @article{sondergaard madsen_norholm jensen_kolbaek tipsmark_kiilerich_borski_2007, title={Differential regulation of cystic fibrosis transmembrane conductance regulator and Na+ ,K+-ATPase in gills of striped bass, Morone saxatilis: effect of salinity and hormones}, volume={192}, ISSN={["1479-6805"]}, DOI={10.1677/JOE-06-0016}, abstractNote={Effects of salinity and hormones on cystic fibrosis transmembrane conductance regulator (CFTR) and α-subunit Na+,K+-ATPase (α-NKA) mRNA (analysed by semi-quantitative PCR) and protein expression (analysed by western blotting and immunocytochemistry) were investigated in gills of striped bass. Freshwater (FW) to seawater (SW) transfer induced a disturbance in serum [Na+]. Gill CFTR protein, mRNA level and Na+,K+-ATPase activity were unaffected by SW transfer, whereas α-NKA mRNA increased after transfer. CFTR immunoreactivity was observed in large cells in FW and SW gill filaments at equal intensity. Cortisol decreased serum [Na+] in FW fish, but had no effect on gill Na+,K+-ATPase activity, α-NKA and CFTR mRNA levels. Incubation of gill tissue with cortisol (24 h, >0.01 μg/ml) and epidermal growth factor (EGF 10 μg/ml) decreased CFTR mRNA levels relative to pre-incubation and control levels. CFTR expression was unaffected by IGF-I (10 μg/ml). α-NKA mRNA levels decreased by 50% after 24 h control incubation; it was slightly stimulated by cortisol and unaffected by IGF-I and EGF. In isolated gill cells, phosphorylation of extracellular-regulated kinase (ERK) 1/2 was stimulated by EGF but not affected by IGF-I. This study is the first to report a branchial EGF response and to demonstrate a functional ERK 1/2 pathway in the teleost gill. In conclusion, CFTR and Na+,K+-ATPase are differentially regulated by salinity and hormones in gills of striped bass, despite the putative involvement of both in salt excretion.}, number={1}, journal={JOURNAL OF ENDOCRINOLOGY}, author={Sondergaard Madsen, Steffen and Norholm Jensen, Lars and Kolbaek Tipsmark, Christian and Kiilerich, Pia and Borski, Russell John}, year={2007}, month={Jan}, pages={249–260} }
 @article{tipsmark_luckenbach_madsen_borski_2007, title={IGF-I and branchial IGF receptor expression and localization during salinity acclimation in striped bass}, volume={292}, ISSN={["1522-1490"]}, DOI={10.1152/ajpregu.00915.2005}, abstractNote={The initial response of the IGF-I system and the expression and cellular localization of IGF type-I receptor (IGF-IR) were studied in the gill of a euryhaline teleost during salinity acclimation. Exposure of striped bass ( Morone saxatilis) to hyperosmotic and hypoosmotic challenges induced small, transitory (<24 h) deflections in hydromineral balance. Transfer from freshwater (FW) to seawater (SW) induced an initial decrease in plasma IGF-I levels after 24 h in both fed and fasted fish. There was an overall decrease in liver IGF-I mRNA levels after SW transfer, suggesting that decreased plasma levels may be due to a decline in hepatic IGF-I synthesis. No changes were observed in gill IGF-I mRNA, but SW transfer induced an increase in gill IGF-IR mRNA after 24 h. Transfer from SW to FW induced an increase in plasma IGF-I levels in fasted fish. In fed fish, no significant changes were observed in either plasma IGF-I, liver, or gill IGF-I mRNA, or gill IGF-IR mRNA levels. In a separate experiment, FW-acclimated fish were injected with saline or IGF-I prior to a 24-h SW challenge. Rapid regain of osmotic balance following SW transfer was hindered by IGF-I. Immunohistochemistry revealed for the first time in teleosts that IGF-IR and Na+-K+-ATPase are localized in putative chloride cells at the base of the lamellae, identifying these cells in the gill as a target for IGF-I and IGF-II. Overall the data suggest a hyperosmoregulatory role of IGF-I in this species.}, number={1}, journal={AMERICAN JOURNAL OF PHYSIOLOGY-REGULATORY INTEGRATIVE AND COMPARATIVE PHYSIOLOGY}, author={Tipsmark, Christian Kolbaek and Luckenbach, John Adam and Madsen, Steffen Sondergaard and Borski, Russell John}, year={2007}, month={Jan}, pages={R535–R543} }
 @article{tipsmark_weber_strom_grau_hirano_borski_2005, title={Involvement of phospholipase C and intracellular calcium signaling in the gonadotropin-releasing hormone regulation of prolactin release from lactotrophs of tilapia (Oreochromis mossambicus)}, volume={142}, ISSN={["1095-6840"]}, DOI={10.1016/j.ygcen.2004.11.009}, abstractNote={Gonadotropin-releasing hormone (GnRH) is a potent stimulator of prolactin (PRL) secretion in various vertebrates including the tilapia, Oreochromis mossambicus. The mechanism by which GnRH regulates lactotroph cell function is poorly understood. Using the advantageous characteristics of the teleost pituitary gland from which a nearly pure population of PRL cells can be isolated, we examined whether GnRH might stimulate PRL release through an increase in phospholipase C (PLC), inositol triphosphate (IP3), and intracellular calcium (Ca(i)2+) signaling. Using Ca(i)2+ imaging and the calcium-sensitive dye fura-2, we found that chicken GnRH-II (cGnRH-II) induced a rapid dose-dependent increase in Ca(i)2+ in dispersed tilapia lactotrophs. The Ca(i)2+ signal was abolished by U-73122, an inhibitor of PLC-dependent phosphoinositide hydrolysis. Correspondingly, cGnRH-II-induced tPRL188 secretion was inhibited by U-73122, suggesting that activation of PLC mediates cGnRH-II's stimulatory effect on PRL secretion. Pretreatment with 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8), an inhibitor of Ca2+ release from intracellular stores, impeded the effect of cGnRH-II on Ca(i)2+. To further address the possible involvement of intracellular Ca2+ stores, IP3 concentrations in the tilapia rostral pars distalis (RPD containing 95-99% PRL cells) was determined by a radioreceptor assay. We found that GnRH-II induces a rapid (<5min) and sustained increase in IP3 concentration in the RPD. Secretion of tPRL(188) in response to cGnRH-II was suppressed by Ca2+ antagonists (TMB-8 and nifedipine). These data, along with our previous findings that show PRL release increases with a rise in Ca(i)2+, suggest that GnRH may elicit its PRL releasing effect by increasing Ca(i)2+. Furthermore, the rise in Ca(i)2+ may be derived from PLC/IP3-induced mobilization of Ca2+ from intracellular stores along with influx through L-type voltage-gated Ca2+ channels.}, number={1-2}, journal={GENERAL AND COMPARATIVE ENDOCRINOLOGY}, author={Tipsmark, CK and Weber, GM and Strom, CN and Grau, EG and Hirano, T and Borski, RJ}, year={2005}, month={May}, pages={227–233} }
 @article{tipsmark_madsen_borski_2004, title={Effect of salinity on expression of branchial ion transporters in striped bass (Morone saxatilis)}, volume={301A}, ISSN={["0022-104X"]}, DOI={10.1002/jez.a.119}, abstractNote={Abstract}, number={12}, journal={JOURNAL OF EXPERIMENTAL ZOOLOGY PART A-COMPARATIVE EXPERIMENTAL BIOLOGY}, author={Tipsmark, CK and Madsen, SS and Borski, RJ}, year={2004}, month={Dec}, pages={979–991} }