In 134 males and 242 females, aged 20-70 years, most of them randomly selected from population studies, the body composition was estimated from the measurements of body height (BH), body weight (BW), total body potassium (TBK) and total body water (TBW). TBK was measured with isotope dilution technique using 42K or determined as 40K in a whole body counter. TBW was determined with an isotope dilution technique using tritiated water, assayed in urine or plasma. From these data, body cell mass (BCM), intra- and extra-cellular water (ICW and ECW, resp.) and body fat (BF) were calculated for each individual. Significant correlations were found between age versus TBK, ECW, BF and ECW/ICW; between BW versus TBK, TBW, ECW, BF and ECW/ICW; (females only) and between BH versus TBK, TBW, ECW (females only) and ECW/ICW. For the prediction of TBK, TBW and BF, multiple regression equations based on BW, BH and age are given. These equations are also presented diagrammatically. The problems with the methods used are considered as well as the applicability of the formulas for the calculation of BCM etc. The predictive value of the results when both TBW and TBK are used for the calculation of body composition data is discussed and compared with similar results, based on TBW or TBK only. It is concluded, that the most reliable method for calculation of BF is to estimate both TBW and TBK.

Summary1. Habitat degradation is a major reason for species extinctions. For parasite-host interactions, the decline of a parasite may not only be related to the parasite's tolerance to habitat degradation but also indirectly through the host's tolerance to the same disturbance. 2. Our objective was to explore the cause of population declines of the freshwater pearl mussel Margaritifera margaritifera by relating the age distribution, density and growth of the mussels with turbidity, sedimentation rates and density of the mussel's host, trout Salmo trutta, in 26 Swedish streams.3. An analysis of the age structure of nine mussel populations showed that maximum age differed by 60 years, with five populations having low proportions of juvenile mussels. Adult mussel density was higher at sites where juvenile mussels occurred than at sites lacking juvenile mussels. 4. Growth of adult mussels during the past 10 years was lower in the five streams lacking recent recruitment than in the four streams with recent recruitment, indicating that some environmental factor may be negatively impacting these populations. 5. A comparison among 24 populations indicated that turbidity and sedimentation may be responsible for recruitment failure in 58% of the populations. The age of the youngest mussel was positively related to turbidity and sedimentation, and juvenile mussel density was negatively related to turbidity and sedimentation. In contrast, trout density was not related to recruitment of mussels or sedimentation, but was positively related to turbidity in all streams, both with and without recent mussel recruitment. 6. Synthesis and applications. Recruitment failure of M. margaritifera appears to be related to its own vulnerability to turbidity and sedimentation rather than to its host's response to this type of habitat degradation. The results from our study suggest that managers might be able to evaluate the potential viability of mussel populations by measuring stream turbidity. Restoration activities to improve the mussels' environment should focus on reducing fine material transport into streams.

The absorption of zinc in man from composite meals based on bread was measured with a radionuclide technique using 65Zn and whole-body counting. Bread was made up from wheat flour of 100 and 72% extraction rate. A lower absolute amount of zinc was absorbed from the white bread compared to the absorption from the same amount of wholemeal bread. When the two types of bread were enriched with zinc chloride the absorption was higher from the white bread than from the wholemeal bread. Addition of calcium in the form of milk products improved the absorption of zinc from a meal with wholemeal bread. A significant positive correlation was found between zinc absorption and the protein content in meals containing milk, cheese, beef, and egg in various combinations with the wholemeal bread.

1. In the present study we tested the hypothesis that birds suppress their adrenocortical response to stress when breeding in a severe environment. 2. We measured increases in circulating levels of corticosterone following capture and handling in populations of Willow Warblers, Phylloscopus trochilus, breeding in a rich deciduous forest in southern Sweden and in Willow Warblers breeding in a subarctic environment in Swedish Lapland. Data from an 8‐year study on survival rates and nest predation in southern and northern Sweden are also included. 3. By comparing the changes in corticosterone levels immediately following capture, handling and restraint, and then up to 1‐h post‐capture across gender and latitude, we were able to assess possible ecological influences. 4. Willow Warblers had about the same survival rates in northern and southern Sweden (0·27 and 0·30, respectively). Depredated clutches were normally replaced in southern Sweden (72%), but not in northern Sweden (1%). 5. A reduced adrenocortical response to stress was found in Willow Warblers of both sexes breeding in northern Sweden where conditions were more severe and the nesting season shorter than in southern Sweden. At the southern site, males had a significantly more robust adrenocortical response to stress than females, whereas at the northern site changes in corticosterone following capture were identical in males and females. Maximum corticosterone levels generated by the capture stress protocol were significantly higher in males at the southern site than in all other groups. 6. There were marked individual variations in the patterns of corticosterone changes following capture in all groups, but there were no significant relationships of dynamics of corticosterone changes to body mass or fat score in males. However, in females at the southern site, the maximum corticosterone level and the rate of corticosterone increase during the capture stress protocol were positively correlated with body mass. In contrast, at the northern site females showed negative correlations of body mass with maximum corticosterone and rate of corticosterone increase. These differences may reflect different ecological bases for modulation of the adrenocortical response to stress with latitude, and with gender.

ABS TRA CT A new radioisotope method to measure iron absorption from the whole diet was used in this study. The method is based on the concept that food iron is absorbed from two pools, the heme iron pool and the nonheme iron pool, which can be especially labeled with two radioiron isotopes given as hemoglobin and as an iron salt. The purpose of this study was to test the accuracy of this two-pool extrinsic tag method.The meals served were composed as an average of 6 wk consumption in the present material of 32 young enlisted men. The mean and total heme and nonheme iron absorption in all the 32 young men was 1.01±0.11. This figure agrees well with the mean daily losses expected for this group of subjects (1.0 mg). The conclusion can therefore be made that there are no major systematic errors of the present method to measure the total iron absorption from a mixed diet.In one series a comparison was made of the absorption of heme and nonheme iron from the meals. A significant correlation between the absorption of the two kinds of iron was found. However, a much greater fraction of the heme iron was absorbed (37%) than of the nonheme iron (5%).The absorption both from breakfast and lunch was in two series found to give a good prediction of the total daily nonheme iron absorption. One series was designed to compare the effect of two levels of iron fortification. There was a significant increase in iron absorption when the level of iron fortification of the meals was increased.

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Abstract. Iron absorption, bone‐marrow smears and haematological parameters were repeatedly studied during pregnancy in 50 women. The same studies were repeated two months after delivery. The material was randomly divided into two groups. Twenty‐four women were treated with 200 mg of ferrous iron daily while 26 were given placebo. The iron absorption was measured from radioiron‐labelled test doses of 100 mg ferrous iron in a whole‐body counter with high sensitivity.In the placebo group the iron absorption increased throughout pregnancy from an average of 6.5 % at the 12th week to 14.3 % at the 35th week of gestation. Two months after delivery the absorption was higher than initially. In the iron‐treated group the absorption increased between the 24th and 35th week of gestation from 6.0 to 8.6 %. After delivery 5.5 % of the test dose was absorbed.The haemosiderin iron in the bone‐marrow was mobilized during pregnancy. In the placebo group no woman had more than trace of haemosiderin in the bone‐marrow smears at the 35th week of gestation. In the iron‐treated group 65 % had the same bone‐marrow findings. The amount of bone‐marrow haemosiderin at term seems not to have the same significance for the diagnosis of iron deficiency in pregnancy as in non‐pregnant subjects. Two months after delivery about 50 % of the women in the placebo group had restored their iron depots. In the iron‐group the haemosiderin content in the bone‐marrow smears was enhanced in most women compared to early pregnancy. In the placebo group haematoLogical data indicated a high frequency of iron deficiency in late pregnancy while in the iron‐treated group iron deficiency was prevented.

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