Body fluid volumes and their relation to mean arterial pressure and plasma renin activity (PRA) were examined in heminephrectomized rats after 4 wk of treatment with deoxy-corticosterone acetate (DOCA) and placed on one of three levels of salt intake, either high (D-HS), normal (D-NS), or low (D-LS); sham-operated rats, which received heminephrectomy and no DOCA treatment, also received high (S-HS), normal (S-NS), or low (S-LS) intakes of salt. Body fluid volumes were measured as the distribution volumes of radioiodinated serum albumin, 35SO4, and tritiated water for plasma volume (PV), extracellular fluid volume (EFV), and total body water (TBW), respectively. Approximately the same degrees of hypertension occurred in the D-HS and D-NS rats, but the D-LS rats were normotensive. PV and EFV were increased only in the D-HS rats, with no prominent changes occurring in the D-NS rats. Intracellular fluid volume (ICF) was not changed in the D-NS rats when compared with the S-NS rats. The ratios of PV/EFV and EFV/TBW in the DOCA-treated groups on high or normal salt were not different from their controls. PRA was greatly suppressed in the D-HS and D-NS rats when compared with all other groups. In another group of D-HS rats, sodium was restricted for 2 wk; in this group the mean arterial pressure fell to control levels without significant changes in PV, but interstitial fluid volume was reduced to normal levels. These results demonstrated that 1) in DOCA-salt hypertensive rats there is expansion of body fluid volumes that are proportionally distributed among the PV, EFV, and ICF; 2) increases in body fluid volumes are not necessary for DOCA to maintain hypertension; 3) a certain minimal amount of dietary sodium is necessary for the development and maintenance of hypertension; and 4) following DOCA treatment the suppression of PRA is not due solely to expansion of body fluid volumes.
To explore which lifestages affect the stock size of young-of-the-year mantis shrimp Oratosquilla oratoria in Tokyo Bay, Japan, we investigated interannual variations in the quantitative relationships among egg production, larval density, and juvenile density. We collected adult females, larvae, and juveniles during monthly field surveys from 2004 to 2007. The interannual trend for the juvenile density index differed from those for egg production and larval density; although indices of both egg production and larval density were high in 2004 and 2007, the juvenile density index was high only in 2007, suggesting high mortality during the pelagic larval stage or the early phase of the postsettlement juvenile stage in 2004. We found that larval settlement started at the end of August and peaked in October, although larvae from the early spawning season (May-June) should have settled in August or earlier. Juveniles were found throughout the bay except in areas where bottom hypoxia occurred, suggesting that hypoxia restricts the spatial distribution of juveniles. Our results suggest that mortality during the early life history fluctuates among years, probably because of changes in environmental conditions in the bay, resulting in interannual variation in the stock size of youngof-the-year juvenile O. oratoria.
Time-related alterations in a digitalis-like factor in urine were examined by means of cross-reactivity with an anti-digoxin antibody during the development of hypertension in DOCA-salt rats. Daily urinary sodium excretion was also measured. After hypertension had developed, plasma levels of the digitalis-like factor were determined by two methods: radioimmunoassay for digoxin and a receptor binding assay using 3H-ouabain and a rat brain synaptosomal protein. Urinary digoxin-like immunoreactivity increased gradually and significantly in the DOCA-salt rats as compared with that of sham-operated high-salt rats and normal-salt rats. Urinary sodium excretion was significantly higher in the DOCA-salt rats, and a significant correlation (r = 0.56, p less than 0.001) was observed between the daily urinary digoxin-like immunoreactivity and daily sodium excretion. In plasma, both digoxin-like immunoreactivity and ouabain-like binding activity were significantly higher in the DOCA-salt rats than in the other 2 groups. These results suggest that digitalis-like factor plays an important role in the development of hypertension in DOCA-salt rats.
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