pH as an indicator of free fatty acid release from adipocytes.

A convenient method of measuring initial rates of free fatty acid efflux from isolated adipocytes during triglyceride breakdown by hormone-sensitive lipase is described. The procedure is based on the dissociation of protons from carboxyl groups of free fatty acids. A recording pH meter is used to monitor H+ concentration in the medium continuously as an index of free fatty acid release. A stoichiometric relationship was demonstrated between proton release and extracellular free fatty acid concentration as determined by the 63Ni radioassay method of Ho (1970. Anal. Biochem. 36: 105-113). An acid pH (6.8) caused a reduction in proton release, which was immediately and completely reversed by raising the pH to 7.4.     

Immaculate tits: head plumage pattern as an indicator of quality in birds

Great tits, Parus major, display their white cheek patches to one another during intraspecific encounters. We measured the size of these patches and the regularity of their borders (immaculateness) as part of an investigation into their function as signals. Patch size was not significantly related to any of our measures of fitness, but male great tits with more immaculate cheek patches had significantly greater access to a safer feeding site in winter and produced heavier chicks in small woods. Females with more immaculate patches bred significantly earlier in 2 of the 3 years of the study in both large and small woods. We decreased the immaculateness of both sexes with dye and found that competition with other tits significantly increased their exposure to danger when feeding. Factors resulting in reduced immaculateness included ectoparasites, fighting with conspecifics, faster feather wear in young birds and the timing of the autumn moult. Selection for immaculateness by conspecifics may be one mechanism responsible for the evolution of regular head and body patterns in several species of birds and in other animals.     

Mg2+ as an indicator of nutritional status in marine bacteria

Cells maintain an osmotic pressure essential for growth and division, using organic compatible solutes and inorganic ions. Mg²⁺, which is the most abundant divalent cation in living cells, has not been considered an osmotically important solute. Here we show that under carbon limitation or dormancy native marine bacterial communities have a high cellular concentration of Mg²⁺ (370–940 m) and a low cellular concentration of Na⁺ (50–170 m). With input of organic carbon, the average cellular concentration of Mg²⁺ decreased 6–12-fold, whereas that of Na⁺ increased ca 3–4-fold. The concentration of chlorine, which was in the range of 330–1200 m and was the only inorganic counterion of quantitative significance, balanced and followed changes in the concentration of Mg²⁺+Na⁺. In an osmotically stable environment, like seawater, any major shift in bacterial osmolyte composition should be related to shifts in growth conditions, and replacing organic compatible solutes with inorganic solutes is presumably a favorable strategy when growing in carbon-limited condition. A high concentration of Mg²⁺ in cells may also serve to protect and stabilize macromolecules during periods of non-growth and dormancy. Our results suggest that Mg²⁺ has a major role as osmolyte in marine bacteria, and that the [Mg²⁺]/[Na⁺] ratio is related to its physiological condition and nutritional status. Bacterial degradation is a main sink for dissolved organic carbon in the ocean, and understanding the mechanisms limiting bacterial activity is therefore essential for understanding the oceanic C-cycle. The [Mg²⁺]/[Na⁺]-ratio in cells may provide a physiological proxy for the transitions between C-limited and mineral nutrient-limited bacterial growth in the ocean''s surface layer.     

Serum extracellular superoxide dismutase activity as an indicator of zinc status in humans

The present study focused on whether serum extracellular superoxide dimutase (EC-SOD) activity can be used as a functional indicator of marginal zinc deficiency in humans. Subjects in this study were 444 healthy adults over 30 yr of age living a normal rural life in Kyunggi province, Korea. The mean dietary zinc intake of subjects obtained from one 24-h recall was 6.41 ± 4.35 mg and the average serum zinc concentration of the subjects was 11.06 ± 2.44 (μmol/L. Subjects were divided into three groups by serum zinc concentrations: adequate (serum zinc >10.7 (μmol/L), low (serum zinc 9.0–10.7 μmol/L), and very low (serum zinc <9.0 μmol/L) groups. A total of 50 subjects were selected from the three groups for analysis of EC-SOD activities. The EC-SOD activity of subjects increased with increasing serum zinc concentrations, and the activities of the three groups were significantly different as indicated by the Kruskal-Wallis test (p = 0.0239). Also, serum EC-SOD activities were significantly correlated with serum zinc concentrations (r = 0.289,p = 0.04). Serum EC-SOD activities, however, were not significantly correlated to the dietary zinc intakes. In conclusion, these results show that EC-SOD activities are decreased in subjects with low serum zinc concentrations and suggest that EC-SOD activity may be a functional indicator of zinc nutritional status in humans.     

Urea concentration in collared peccary milk as an indicator of protein nutritional status

Milk urea nitrogen (UN) concentration was examined as a possible index to protein-energy intake in female collared peccaries (Tayassu tajacu). Captive adults were bred and assigned to one of four experimental diets through gestation and lactation. Females fed a high protein diet produced milk with UN concentrations exceeding those of low-protein-fed females. A low energy intake tended to elevate UN concentrations in milk.     

Iron:phosphorus ratio in surface sediment as an indicator of phosphate release from aerobic sediments in shallow lakes

Analysis of Danish lakes showed that both mean winter and mean summer concentrations of lake water total phosphorus in the trophogenic zone correlated negatively with the total iron to total phosphorus ratio (Fe:P) in surface sediments. No correlation was found between the water total phosphorus concentration and either the sediment phosphorus concentration alone or with sediment calcium concentration. The increase in total phosphorus from winter to summer, which is partly a function of net internal P-loading, was lowest in lakes with high Fe:P ratios in the surface sediment.A study of aerobic sediments from fifteen lakes, selected as representative of Danish lakes with respect to the sediment Fe and phosphorus content, showed that the release of soluble reactive phosphorus was negatively correlated with the surface sediment Fe:P ratio. Analysis of phosphate adsorption properties of surface sediment from 12 lakes revealed that the capability of aerobic sediments to buffer phosphate concentration correlated with the Fe:P ratio while the maximum adsorption capacity correlated with total iron. Thus, the Fe:P ratio may provide a measure of free sorption sites for orthophosphate ions on iron hydroxyoxide surfaces.The results indicate that provided the Fe:P ratio is above 15 (by weight) it may be possible to control internal P-loading by keeping the surface sediment oxidized. Since the Fe:P ratio is easy to measure, it may be a useful tool in the management of shallow lakes.     

Sap flow as an indicator of transpiration and the water status of young apricot trees

The relationship between water loss via transpiration and stem sap flow in young apricot trees was studied under different environmental conditions and different levels of soil water status. The experiment was carried out in a greenhouse over a 2-week period (November 2–14, 1997) using three-year-old apricot trees (Prunus armeniaca cv. Búlida) growing in pots. Diurnal courses of leaf water potential, leaf conductance and leaf turgor potential also were recorded throughout the experiment. Data from four days of different enviromental conditions and soil water availability have been selected for analysis. On each of the selected days the leaf water potential and the mean transpiration rates were well correlated. The slope of the linear regression of this correlation, taken to indicate the total hydraulic resistance of the tree, confirmed an increasing hydraulic resistance under drought conditions. When the trees were not drought stressed the diurnal courses of sap flow and transpiration were very similar. However, when the trees were droughted, measured of sap flow slightly underestimated actual transpiration. Our heat-pulse measurements suggest the amount of readily available water stored in the stem and leaf tissues of young apricot trees is sufficient to sustain the peak transpiration rates for about 1 hour. This revised version was published online in June 2006 with corrections to the Cover Date.     

A re-valuation of the Araphidineae/Centrales index as an indicator of lake trophic status

SUMMARY. Comparisons of pre- and post-settlement diatom assemblages from the sediment of twenty-five Minnesota lakes reveals that Stephanodiscus hantzschii percentages are more consistent indicators of human disturbance than the Araphidineae/Centrales (A/C) index. In a set of eighty surface sediment samples from lakes whose water chemistry is known, S. hantzschii , a centric diatom, is abundant as a microfossil in lakes with total phosphorus > 15 μg I⁻¹ and alkalinity > 1.5 m-equiv. I⁻¹. High Araphidineae/Centrales indices are characteristic of lakes with only moderate total phosphorus levels and very low alkalinities.     

Variability of the level of thermoresistance as an indicator of the functional status of a cell

Effect of acclimating temperature on the thermoresistance of isolated ciliated gill epithelium of Anodonta anatina was studied. One strip of gills from each mussel was used to determine the initial level of thermoresistance (survival time at 40 degrees C). Other strips were kept at 24 degrees C until their death, and their thermoresistance and fluorescence after Ethidium bromide staining were determined at different time intervals. After a short exposure at 24 degrees C the mean level of thermoresistance of the epithelium increased. The individual shift in the value and direction of cell thermoresistance in different mussels negatively correlated with its initial level. It resulted in narrowing the extent of individual variability of the level of thermoresistance. The prolongation of exposure at 24 degrees C decreased the mean level of thermoresistance, disturbed the negative correlation, and increased the variability of thermoresistance level. The value of cell fluorescence remained constant within 48 h. The increase in fluorescence was observed 12 h after reducing the mean thermoresistance level. Hence, the dynamics of variability in the thermoresistance level is a most sensitive indication of the cell functional state.     

Lacustrine profundal meiobenthos as an environmental indicator

Organic loading and eutrophy is indicated at profundal depths by large numbers of resting copepodid stages of cyclopoid copepods, by the occurrence of the naidid oligochaete species, Amphichaeta leydigii and Specaria josinae, and the harpacticoid species Canthocamptus staphylinus, and by a low meiobenthos/macrobenthos biomass ratio. An oligotrophic environment is indicated by the occurrence of the aeolosomatid oligochaetes Aeolosoma quaternarium, A. hemprichi and Rheomorpha neiswestnovae, the naidid oligochaete Chaetogaster langi and the harpacticoid species Attheyella crassa and a high meiobenthos/macrobenthos biomass ratio.     

Progesterone receptor as an indicator of sperm function

Expression of progesterone receptor (PR) localization on spermatozoa was determined in men with normal and abnormal spermiograms. Studies were also carried out to evaluate the potential of PR as a marker of sperm function. Progesterone receptor expression on spermatozoa from men with normozoospermia (n = 8), oligozoospermia (n = 7), asthenozoospermia (n = 8), oligoasthenozoospermia (n = 7), and teratozoospermia (n = 11) was analyzed using an immunocytochemical method with monoclonal antibodies against PR, and flow cytometry using a cell-impermeable fluorescein-tagged progesterone coupled to BSA complex (P-FITC-BSA). Both methods revealed significantly fewer (P < 0.05) PR-positive spermatozoa in men with oligozoospermia, asthenozoospermia, oligoasthenozoospermia, and teratozoospermia compared with men with normozoospermia, thereby suggesting that down-regulation of PR expression in spermatozoa may be one of the causes of male infertility. Spermatozoa from men with normozoospermia (n = 12), oligozoospermia (n = 12), asthenozoospermia (n = 12), oligoasthenozoospermia (n = 9), and teratozoospermia (n = 10) were exposed to low osmotic conditions in the hypoosmotic swelling (HOS) test and then analyzed for PR expression using P-FITC-BSA complex. A significantly higher percentage (P < 0.05) of spermatozoa with physiologically active plasma membrane (HOS+) lacked PR expression (HOS+PR-) in all categories of men with infertility, thereby suggesting that compared to the HOS test, PR expression is a better indicator of sperm function. Furthermore, PR expression in spermatozoa showed a strong (P < 0.05) positive correlation with their ability to undergo an in vitro acrosome reaction. This was observed in all study groups (i.e., normozoospermia, r = 0.8545; oligozoospermia, r = 0.8711; asthenozoospermia, r = 0.7645; oligoasthenozoospermia, r = 0.9003; and teratozoospermia, r = 0.8676). This suggests a potential role for PR in the events leading to the acrosome reaction in sperm.     

Nutrition and immune system: the size of the thymus as an indicator of the newborn's nutrition status

Summary: The thymus is a central lymphatic organ reaching its largest size after the delivery. Its size is significantly affected by endogenous and exogenous negative factors. In our research, we investigated the relationship between the size of the thymus determined by sonography and anthropometric parameters as well as indexes demonstrating the nutritional status. The examined group consisted of 212 full-term newborns, all of which passed an anthropometric examination during the first five days after delivery (birth weight and length, mid-arm and head circumference). The following nutritional status indexes were calculated from estimated anthropometric dimensions: Quételet's index, Rohrer's index, birth weight-to-length ratio and mid-arm-to-head circumference ratio. The size of the thymus was assessed by sonography and expressed as the multiple of transversal width of the cranial thymus part and sagittal area of the major thymus lobe (so-called 'Thymic Index'). The Thymic Index showed a positive correlation with the majority of indicators of the newborn's nutritional status, but all of these correlations are low (Spearman correlation coefficients 0.228-0.409). The correlation of the size of thymus with the birth weight or birth weight-to-length ratio was stronger than the correlation with the Quételet's index or mid-arm circumference. The size of the thymus reflects the newborn's nutritional status assumed by anthropometry and can represent one of the "barometers of nutrition". Normal nutrition in the prenatal period plays a relatively critical role in the development of the immune system.     

Dietary selenium in humans toenails as an indicator

Mounting laboratory and epidemiologic evidence suggests that selenium may be important in the etiology of both cancer and heart disease. We explored the use of hair and nails as indicators of selenium intake by measuring their selenium levels using neutron activation analysis, a highly sensitive and precise nondestructive technique. Levels in duplicate samples of nails, hair, and blood were all reasonably reproducible. However, selenium-containing shampoos severely contaminated some of the hair specimens, suggesting that use of hair in epidemiologic studies could be misleading. The mean selenium level in toenails from South Dakota (a known high selenium area) was 1.17 ppm (1SE = 0.09). This was significantly higher than mean levels from Boston and Georgia (medium selenium intake area) of 0.74 ppm (0.04) and 0.81 (0.03), respectively. The mean selenium level in toenails from New Zealand (low selenium area) was 0.26 (0.02) and these levels did not overlap those of other areas. The South Dakota specimens showed marked familial aggregation, probably reflecting dietary differences. Since toenails vary in length, clippings from different toes represent different time periods of formation; clippings from all ten toes reflect selenium levels integrated over an extended period. As toenails are easily collected, transported, and stored, and reflect longterm intake, they can be useful in epidemiologic studies of selenium and chronic disease.     

Carbon as an indicator of Daphnia condition in an alpine lake

Carbon–length relationships can be used to indicate the condition of daphnids in natural situations. We examined the Daphnia galeata population of an alpine lake (Oberer, Arosasee, Switzerland), where most individuals display diel vertical migration behaviour (DVM). Normally, migrating daphnids face a trade-off between `predator safe areas' in the hypolimnion and `food rich areas' with high predation risk. However, in alpine lakes, with chlorophyll a and POC maxima typically in deeper layers and weak temperature gradients, migrating species are confronted less with this trade-off. We investigated the seasonal changes in carbon content of D. galeata in different depth strata in relation to environmental parameters of the lake. The carbon content of D. galeata was high in spring, but declined considerably in summer and increased slightly in autumn. The low values indicate that D. galeata are food limited for much of the year. The slopes of the regression lines between carbon content and body length varied seasonally, but were not significantly different among depths on a given date. In summer, D. galeata individuals residing in the deep layers during the day had a significantly higher carbon content than individuals in the surface layers. During the rest of the year, the carbon content of individuals was similar among all depth strata. We conclude that migrating D. galeata and individuals remaining in deep layer had better body conditions compared to non-migrating D. galeata in this alpine lake during summer, when migration amplitudes were highest.     

Periphyton growth as an indicator of eutrophication; an experimental approach

Growth of periphyton was studied in the Archipelago Sea (Finland) during summer 1994 as a part of the annual monitoring control of fish farms. Experimental growth plates (Whatman GF/C filters) were incubated (two weeks) at 213 sites in different parts of the Archipelago Sea and in the coastal area north of the Archipelago Sea. At each site incubations were repeated two or three times during the summer (July 4- -September 1). The growth of periphyton was measured as the amount of chlorophyll a (mg m-2) extracted from the incubation plates. The growth varied significantly among different parts of the study area. The strongest growth was observed in the inner archipelago and in areas with high fish production and relatively slow water exchange. In the outer archipelago, rapid water exchange ensured good mixing of nutrients from fish farms and other sources into relatively large water volumes. The local impacts of nutrient loading thus remained too low to be detected by measuring nutrient concentrations or periphyton growth. Periphyton growth was positively correlated with concentrations of total nitrogen, total phosphorus and chlorophyll a in the productivity layer (approximately 2 × Secchi depth). A significant inverse correlation was also shown between periphyton growth and Secchi depth. Archipelago areas with different levels of eutrophication could satisfactorily be distinguished in this study. The results were consequent with previous classifications of the eutrophication levels in the Archipelago Sea. Periphyton studies thus are a useful addition to conventional monitoring programs. This revised version was published online in July 2006 with corrections to the Cover Date.