Our results show that as renal function deteriorates in glomerulopathy the nocturnal dip in blood pressure is lost, resulting in enhanced urinary sodium and protein excretions during night. These findings are compatible with our proposal that impaired natriuresis during daytime makes nocturnal blood pressure elevated to compensate for diminished natriuresis by pressure natriuresis. We speculate that nocturnal glomerular capillary hypertension contributes, at least in part, to enhanced urinary sodium and protein excretions during night.

A colony (ca. 2,000 birds) of the Great Cormorant (Phalacrocorax carbo) is present in Shinobazunoike Pond, Tokyo, Japan. The cormorants feed in rivers and in Tokyo Bay. The major direction of their daily flight in winter is to the rivers, and in summer to the Bay (Fukuda 1985). The relative importance of the two feeding sites in terms of dietary contribution is unknown. Dietary studies conventionally depend on stomach contents, cast pellets, and field observations. Although useful to reveal birds' choice of prey species, such details cannot determine the relative dependence of cormorants on the two feeding areas. Stable carbon isotope analysis of bird tissues is a convenient way to measure such dependence, as it tells if the organic carbon in the tissues is terrestrial or marine in origin. Compared with conventional dietary studies, isotope analysis is less susceptible to day-by-day variation of prey species and is in principle free of numerical bias for easily identifiable foods. The two stable isotopes of carbon are x2C and •3C. In various biogeochemical reactions, they react at different rates, and the ratio •3C/•2C of various carbon reservoirs becomes different (Mizutani and Wada

The use of stable isotopes of bioelements to analyze diets of animals in nature requires precise knowledge of any changes in the isotope ratios that take place after assimilation. Therefore, the influence of diet on the distribution of carbon and nitrogen isotopes in feathers of 11 species of birds on a constant diet was studied. The standard deviation in °13C and °15N in naturally obtained foods like fish during 6 yr was °1%. Factory—manufactured pellets generally gave lower deviations (0.2% for °13C and °0.6% for °15N). Feathers showed an enrichment relative to food in both 13C and 15N, although its extent varied among different bird species. Isotope ratios for 13C and 15N from diet to feathers converged. The nature of the enrichment factors is discussed in relation to the convergence and temporal window size. Neither enrichment showed an age dependency among adult birds, and neither depended on the nitrogen content in the bird's diet. These results show that the stable isotope approach can be applied not only to these 11 species but to birds whose isotope enrichment factors are so far unknown.

In healthy subjects, blood pressure (BP) drops by 10-20% during the night. Conversely, in patients with the salt-sensitive type of hypertension or chronic kidney disease, nighttime BP does not fall, resulting in an atypical pattern of circadian BP rhythm that does not dip. This pattern is referred to as the 'non-dipper' pattern. Loss of renal functional reserve, due to either reduced ultrafiltration capacity or enhanced tubular sodium reabsorption, induces the salt-sensitive type of hypertension. When salt intake is excessive in patients with salt-sensitive hypertension, the defect in sodium excretory capability becomes evident, resulting in elevated BP during the night. This nocturnal hypertension compensates for diminished natriuresis during the daytime and enhances pressure natriuresis during the night. Nocturnal hypertension and the non-dipper pattern of circadian BP rhythm cause cardiovascular events. When excess salt intake is loaded in patients who are in a salt-sensitive state, glomerular capillary pressure is also elevated, resulting in glomerular sclerosis and eventual renal failure. In this way, salt sensitivity and excess salt intake contribute to both cardiovascular and renal damage at the same time. We propose that salt sensitivity of BP and excess salt intake have important roles in the genesis of the cardiorenal connection. Salt sensitivity and circadian rhythm of BP are the keys to understanding the connections between cardiovascular and renal complications.

As renal function deteriorated, nocturnal polyuria was seen, being consistent with classical recognition. Furthermore, this increase in nocturnal urine volume seemed related to osmotic diuresis mainly by natriuresis rather than to water diuresis or urea excretion.