The characteristics of B-lymphoblastoid cell strains transformed by Epstein ± Barr virus (EBV) from normal individuals and Werner's syndrome (WRN) patients were compared. We continuously passaged cell strains from 28 WRN patients and 20 normal individuals for about 2 years corresponding to over 160 population doubling levels (PDLs). First, the WRN mutation signi®cantly suppressed the immortalization: all the 28 cell strains from WRN patients, as well as 15 out of 20 cell strains from normal individuals, died out before 160 PDLs mostly without developing a signi®cant telomerase activity. The remaining ®ve cell strains from normal individuals became moderately/strongly telomerase-positive and, three of them were apparently immortalized with an in®nitively proliferating activity. Second, the monitoring of the telomere length of both normal and WRN cell strains during the culture period suggests that the WRN gene mutation causes abnormal dynamics of the telomere: (1) a signi®cant proportion of WRN cell strains showed drastic shortening or lengthening of telomere lengths during cell passages compared with normal cell strains, and (2) WRN cell strains terminated their life-span at a wide range of telomere length (between 3.5 and 18.5 Kbp), whereas normal cell strains terminated within a narrow telomere length range (between 5.5 and 9 Kbp). The chromosomal aberration characteristic of WRN cells, including translocation was con®rmed in our experiment. We discussed the correlation between the chromosomal instability, abnormal telomere dynamics and inability of immortalization of the WRN B-lymphobloastoid cell strains.

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SUMMARY Marine teleosts actively excrete SO 42-and keep the plasma concentration of this ion much lower than that of environmental seawater (SW). We used the eel as a model to study the excretory mechanism of SO 4 2-because this euryhaline species changes SO 4 2-regulation drastically after transfer from freshwater (FW) to SW. Time-course studies showed that plasma SO 4 2-concentration decreased 3days after transfer of eels from FW to SW, while urine SO 4 2-concentration increased on 1day. Detailed analyses showed that urine SO 4 2-concentration increased linearly from 6h after SW transfer; however, this did not immediately translate to increased SO 4 2-excretion because the volume of urine was decreased. We identified five SO 4 2-transporters in the eel kidney. Three of these (Slc26a1, Slc26a6b and Slc26a6c) are expressed in both SW-and FW-acclimated eels while Slc26a6a and Slc13a1 are expressed in SW-acclimated eels and FW-acclimated eels, respectively. We showed that changes in Slc26a6a and Slc13a1 gene expression occurred 1-3days after SW transfer. In SW eel kidneys, immunohistochemistry using specific antisera against each transporter protein showed that Slc26a6a and Slc26a6c are localized on the apical membrane of the P1 segment of the proximal tubule, while Slc26a6b is localized on the apical membrane and Slc26a1 on the basolateral membrane of the P2 segment. The current study revealed complex molecular mechanisms of SO 4 2-excretion in the SW eel kidney that involve segment-specific localization of multiple Slc transporters in proximal tubules and modulation of their expression in different SO 4 2-environments. This precise regulatory mechanism may endow the eel with euryhalinity.

Thirst aroused in the forebrain by angiotensin II (AngII) or buccal drying motivates terrestrial vertebrates to search for water, whereas aquatic fish can drink surrounding water only by reflex swallowing generated in the hindbrain. Indeed, AngII induces drinking through the hindbrain even after removal of the whole forebrain in aquatic fish. Here we show that AngII induces thirst also in the amphibious mudskipper goby without direct action on the forebrain, but through buccal drying. Intracerebroventricular injection of AngII motivated mudskippers to move into water and drink as with tetrapods. However, AngII primarily increased immunoreactive c-Fos at the hindbrain swallowing center where AngII receptors were expressed, as in other ray-finned fish, and such direct action on the forebrain was not found. Behavioural analyses showed that loss of buccal water on land by AngII-induced swallowing, by piercing holes in the opercula, or by water-absorptive gel placed in the cavity motivated mudskippers to move to water for refilling. Since sensory detection of water at the bucco-pharyngeal cavity like ‘dry mouth’ has recently been noted to regulate thirst in mammals, similar mechanisms seem to have evolved in distantly related species in order to solve osmoregulatory problems during terrestrialization.

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