Showing papers in "Comparative Biochemistry and Physiology A-molecular & Integrative Physiology in 2003"

Nitrite disrupts multiple physiological functions in aquatic animals.

Abstract: Nitrite is a potential problem in aquatic environments. Freshwater fish actively take up nitrite across the gills, leading to high internal concentrations. Seawater fish are less susceptible but do take up nitrite across intestine and gills. Nitrite has multiple physiological effects. Its uptake is at the expense of chloride, leading to chloride depletion. Nitrite also activates efflux of potassium from skeletal muscle and erythrocytes, disturbing intracellular and extracellular K(+) levels. Nitrite transfer across the erythrocytic membrane leads to oxidation of haemoglobin to methaemoglobin (metHb), compromising blood O(2) transport. Other haem proteins are also oxidised. Hyperventilation is observed, and eventually tissue O(2) shortage becomes reflected in elevated lactate concentrations. Heart rate increases rapidly, before any significant elevations in metHb or extracellular potassium occur. This suggests nitrite-induced vasodilation (possibly via nitric oxide generated from nitrite) that is countered by increased cardiac pumping to re-establish blood pressure. Nitrite can form and/or mimic nitric oxide and thereby interfere with processes regulated by this local hormone. Steroid hormone synthesis may be inhibited, while changes in ammonia and urea levels and excretion rates reflect an influence of nitrite on nitrogen metabolism. Detoxification of nitrite occurs via endogenous oxidation to nitrate, and elimination of nitrite takes place both via gills and urine. The susceptibility to nitrite varies between species and in some cases also within species. Rainbow trout fall into two groups with regard to susceptibility and physiological response. These two groups are not related to sex but show significant different nitrite uptake rates.

Oxidative stress in streptozotocin-induced diabetic rats: effects of garlic oil and melatonin.

Abstract: In the present study, oxidative stress in diabetic model and the effect of garlic oil or melatonin treatment were examined. Streptozotocin (60 mg/kg body weight, i.p.)-induced diabetic rats, showed a significant increase of plasma glucose, total lipids, triglyceride, cholesterol, lipid peroxides, nitric oxide and uric acid. Concomitantly, significant decreases in the levels of antioxidants ceruloplasmin, albumin and total thiols were found in the plasma of diabetic rats. Lipid peroxide levels were significantly increased in erythrocyte lysate and in homogenates of liver and kidney, while superoxide dismutase (SOD) activities were decreased in tissue homogenates of liver and kidney. Treatment of diabetic rats with garlic oil (10 mg/kg i.p.) or melatonin (200 μg/kg i.p.) for 15 days significantly increased plasma levels of total thiol, ceruloplasmin activities, albumin. Lipid peroxides, uric acid, blood glucose, total lipid, triglyceride and cholesterol were decreased significantly after treatment with garlic oil or melatonin. Nitric oxide levels were decreased significantly in rats treated with melatonin only. In erythrocytes lysate, glutathione S-transferase (GST) activities were increased significantly in rats treated with garlic oil or melatonin, while lipid peroxides decreased significantly and total thiol increased significantly in melatonin or garlic oil treatment, respectively. In liver homogenates of rats treated with garlic or melatonin, lipid peroxides were decreased significantly, and GST activities increased significantly, while SOD activities were increased significantly in liver and kidney after garlic or melatonin treatment. The results suggest that garlic oil or melatonin may effectively normalize the impaired antioxidants status in streptozotocin induced-diabetes. The effects of these antioxidants of both agents may be useful in delaying the complicated effects of diabetes as retinopathy, nephropathy and neuropathy due to imbalance between free radicals and antioxidant systems. Moreover, melatonin may be more powerful free radical scavenger than garlic oil.

Na+ +K+-ATPase in gills of aquatic crustacea

Abstract: The sodium pump, or Na(+)+K(+)-ATPase, provides at least part of the driving force for transepithelial movement of monovalent ions across the gills and other transporting tissues in many aquatic animals including the Crustacea. The crustacean Na(+)+K(+)-ATPase, like that in all animal cells, is composed of a catalytic alpha-subunit and an accompanying beta-subunit. The amino acid sequence of the crustacean alpha-subunit is 71-74% identical to vertebrate alpha-subunit sequences. In brachyuran Crustacea, the Na(+)+K(+)-ATPase is more highly expressed in posterior gills compared with anterior and is found predominantly in mitochondria-rich cells that are morphologically and biochemically specialized to mediate NaCl uptake from the medium. When the external salinity is lowered from that of normal seawater, producing conditions in which many euryhaline Crustacea hyperosmo regulate their hemolymph, both the enzymatic activity of the Na(+)+K(+)-ATPase and the gene expression of the alpha-subunit are increased in these tissues. Although the precise regulatory mechanism is not known, evidence suggests that crustacean hyperglycemic hormone may be responsible for the induction of Na(+)+K(+)-ATPase activity. Whether it also plays a role in activation of gene transcription is not known. A comparison of a range of aquatic Crustacea suggests that the level of Na(+)+K(+)-ATPase function in transporting tissues may be correlated with their ability to invade estuarine habitats.

Cooking as a biological trait

Abstract: No human foragers have been recorded as living without cooking, and people who choose a 'raw-foodist' life-style experience low energy and impaired reproductive function. This suggests that cooking may be obligatory for humans. The possibility that cooking is obligatory is supported by calculations suggesting that a diet of raw food could not supply sufficient calories for a normal hunter-gatherer lifestyle. In particular, many plant foods are too fiber-rich when raw, while most raw meat appears too tough to allow easy chewing. If cooking is indeed obligatory for humans but not for other apes, this means that human biology must have adapted to the ingestion of cooked food (i.e. food that is tender and low in fiber) in ways that no longer allow efficient processing of raw foods. Cooking has been practiced for ample time to allow the evolution of such adaptations. Digestive adaptations have not been investigated in detail but may include small teeth, small hind-guts, large small intestines, a fast gut passage rate, and possibly reduced ability to detoxify. The adoption of cooking can also be expected to have had far-reaching effects on such aspects of human biology as life-history, social behavior, and evolutionary psychology. Since dietary adaptations are central to understanding species evolution, cooking appears to have been a key feature of the environment of human evolutionary adaptedness. Further investigation is therefore needed of the ways in which human digestive physiology is constrained by the need for food of relatively high caloric density compared to other great apes.

Kenyan dominance in distance running

Abstract: Critical physiological factors for performance in running are maximal oxygen consumption (VO(2max)), fractional VO(2max) utilization and running economy. While Kenyan and Caucasian elite runners are able to reach very high, but similar maximal oxygen uptake levels, the VO(2max) of black South African elite runners seems to be slightly lower. Moreover, the studies of black and white South African runners indicate that the former are able to sustain the highest fraction of VO(2max) during long distance running. Results on adolescent Kenyan and Caucasian boys show that these boys are running at a similar percentage of VO(2max) during competition. Kenyan elite runners, however, appear to be able to run at a high % of VO(2max) which must then have been achieved by training. A lower energy cost of running has been demonstrated in Kenyan elite runners and in untrained adolescent Kenyan boys compared to their Caucasian counterparts. In agreement with this are the results from studies on black South African elite runners who have shown similar low energy costs during running as the Kenyan elite runners. The good running economy cannot be explained by differences in muscle fibre type as they are the same in Kenyan and Caucasian runners. The same is true when comparing untrained adolescent Kenyan boys with their Caucasian counterparts. A difference exists in BMI and body shape, and the Kenyans long, slender legs could be advantageous when running as the energy cost when running is a function of leg mass. Studies comparing the response to training of Kenyans and Caucasians have shown similar trainability with respect to VO(2max), running economy and oxidative enzymes. Taken all these data together it appears that running at a high fractional VO(2max) and having a good running economy may be the primary factors favouring the good performance of endurance athletes rather than them having a higher VO(2max) than other elite runners. In addition to having the proper genes to shape their bodies and thereby contributing to a good running economy, the Kenyan elite runners have trained effectively and used their potential to be in the upper range both in regard to VO(2max) and to a high utilization of this capacity during endurance running.

Evolution of dietary antioxidants

Abstract: Oxygen is vital for most organisms but, paradoxically, damages key biological sites. Oxygenic threat is met by antioxidants that evolved in parallel with our oxygenic atmosphere. Plants employ antioxidants to defend their structures against reactive oxygen species (ROS; oxidants) produced during photosynthesis. The human body is exposed to these same oxidants, and we have also evolved an effective antioxidant system. However, this is not infallible. ROS breach defences, oxidative damage ensues, accumulates with age, and causes a variety of pathological changes. Plant-based, antioxidant-rich foods traditionally formed the major part of the human diet, and plant-based dietary antioxidants are hypothesized to have an important role in maintaining human health. This hypothesis is logical in evolutionary terms, especially when we consider the relatively hypoxic environment in which humans may have evolved. In this paper, the human diet is discussed briefly in terms of its evolutionary development, different strategies of antioxidant defence are outlined, and evolution of dietary antioxidants is discussed from the perspectives of plant need and our current dietary requirements. Finally, possibilities in regard to dietary antioxidants, evolution, and human health are presented, and an evolutionary cost-benefit analysis is presented in relation to why we lost the ability to make ascorbic acid (vitamin C) although we retained an absolute requirement for it.

Metabolic correlates of hominid brain evolution.

Abstract: Large brain sizes in humans have important metabolic consequences as humans expend a relatively larger proportion of their resting energy budget on brain metabolism than other primates or non-primate mammals. The high costs of large human brains are supported, in part, by diets that are relatively rich in energy and other nutrients. Among living primates, the relative proportion of metabolic energy allocated to the brain is positively correlated with dietary quality. Humans fall at the positive end of this relationship, having both a very high quality diet and a large brain size. Greater encephalization also appears to have consequences for aspects of body composition. Comparative primate data indicate that humans are 'under-muscled', having relatively lower levels of skeletal muscle than other primate species of similar size. Conversely, levels of body fatness are relatively high in humans, particularly in infancy. These greater levels of body fatness and reduced levels of muscle mass allow human infants to accommodate the growth of their large brains in two important ways: (1) by having a ready supply of stored energy to 'feed the brain', when intake is limited and (2) by reducing the total energy costs of the rest of the body. Paleontological evidence indicates that the rapid brain evolution observed with the emergence of Homo erectus at approximately 1.8 million years ago was likely associated with important changes in diet and body composition.

Hyperinsulinemic diseases of civilization: more than just Syndrome X

Abstract: Compensatory hyperinsulinemia stemming from peripheral insulin resistance is a well-recognized metabolic disturbance that is at the root cause of diseases and maladies of Syndrome X (hypertension, type 2 diabetes, dyslipidemia, coronary artery disease, obesity, abnormal glucose tolerance). Abnormalities of fibrinolysis and hyperuricemia also appear to be members of the cluster of illnesses comprising Syndrome X. Insulin is a well-established growth-promoting hormone, and recent evidence indicates that hyperinsulinemia causes a shift in a number of endocrine pathways that may favor unregulated tissue growth leading to additional illnesses. Specifically, hyperinsulinemia elevates serum concentrations of free insulin-like growth factor-1 (IGF-1) and androgens, while simultaneously reducing insulin-like growth factor-binding protein 3 (IGFBP-3) and sex hormone-binding globulin (SHBG). Since IGFBP-3 is a ligand for the nuclear retinoid X receptor a, insulin-mediated reductions in IGFBP-3 may also influence transcription of anti-proliferative genes normally activated by the body’s endogenous retinoids. These endocrine shifts alter cellular proliferation and growth in a variety of tissues, the clinical course of which may promote acne, early menarche, certain epithelial cell carcinomas, increased stature, myopia, cutaneous papillomas (skin tags), acanthosis nigricans, polycystic ovary syndrome (PCOS) and male vertex balding. Consequently, these illnesses and conditions may, in part, have hyperinsulinemia at their root cause and therefore should be classified among the diseases of Syndrome X. 2003 Elsevier Science Inc. All rights reserved.

Chronic effects of copper exposure versus endocrine toxicity: two sides of the same toxicological process?

Abstract: Chronic sub-lethal exposure to copper (Cu) causes a series of cellular and physiological changes in fish that enable the animal to survive. Copper is also an endocrine disrupting metal in the aquatic environment, and has a number of normal neuro-endocrine roles in vertebrates. This paper explores whether the chronic effects of Cu exposure can be explained by the effects of Cu on neuro-endocrine functions in fish. Chronic Cu exposure involves complex physiological adjustments in many body systems, including increased oxygen consumption, reduced mean swimming speed, up-regulation of ionic regulation, decreasing lymphocyte levels and increasing neutrophils, altered immunity, modulation of Cu-dependent and independent enzyme activities, and proliferation of epithelial cells in gills or intestine. These responses can occur with exposure via the food or the water and can be rationalised into three major categories: (1) up-regulation of enzymes/metabolism (2) altered haematopoietic responses and (3) altered cellularity (cell type, turnover or size) in tissues. Some of these responses can be explained by stimulation of general stress responses, including the adrenergic response and stimulated cortisol release via the hypothalamic-pituitary-interrenal axis. This can occur despite evidence of vacuolation and foci of necrosis in the brain, and increased macrophage activity, in the kidney of fish exposed to dietary Cu. In addition to generic stress responses, Cu regulates specific neuro-endocrine functions, including the loss of circadian rhythm during dietary Cu exposure that involves the failure to respond to circulating melatonin and a loss of circulating serotonin. We conclude that the chronic physiological effects of Cu and apparent endocrine disrupting effects of Cu are two sides of the same toxicological process.

An evolutionary perspective on human physical activity: implications for health.

Abstract: At present, human genes and human lives are incongruent, especially in affluent Western nations. When our current genome was originally selected, daily physical exertion was obligatory; our biochemistry and physiology are designed to function optimally in such circumstances. However, today's mechanized, technologically oriented conditions allow and even promote an unprecedentedly sedentary lifestyle. Many important health problems are affected by this imbalance, including atherosclerosis, obesity, age-related fractures and diabetes, among others. Most physicians recognize that regular exercise is a critical component of effective health promotion regimens, but there is substantial disagreement about details, most importantly volume: how much daily caloric expenditure, as physical activity, is desirable. Because epidemiology-based recommendations vary, often confusing and alienating the health-conscious public, an independent estimate, arising from a separate scientific discipline, is desirable, at least for purposes of triangulation. The retrojected level of ancestral physical activity might meet this need. The best available such reconstruction suggests that the World Health Organization's recommendation, a physical activity level of 1.75 ( approximately 2.1 MJ (490 kcal)/d), most closely approximates the Paleolithic standard, that for which our genetic makeup was originally selected.

Survival of the fattest: fat babies were the key to evolution of the large human brain.

Abstract: a Abstract In the past 2 million years, the hominid lineage leading to modern humans evolved significantly larger and more sophisticated brains than other primates. We propose that the modern human brain was a product of having first evolved fat babies. Hence, the fattest (infants) became, mentally, the fittest adults. Human babies have brains and body fat each contributing to 11-14% of body weight, a situation which appears to be unique amongst terrestrial animals. Body fat in human babies provides three forms of insurance for brain development that are not available to other land-based species: (1) a large fuel store in the form of fatty acids in triglycerides; (2) the fatty acid precursors to ketone bodies which are key substrates for brain lipid synthesis; and (3) a store of long chain polyunsaturated fatty acids, particularly docosahexaenoic acid, needed for normal brain development. The triple combination of high fuel demands, inability to import cholesterol or saturated fatty acids, and dependence on docosahexaenoic acid puts the mammalian brain in a uniquely difficult situation compared with other organs and makes its expansion in early humans all the more remarkable. We believe that fresh- and salt-water shorelines provided a uniquely rich, abundant and accessible food supply, and the only viable environment for evolving both body fat and larger brains in human infants. 2003 Elsevier Science Inc. All rights reserved.

Effects of fasting on growth hormone/insulin-like growth factor I axis in the tilapia, Oreochromis mossambicus.

Abstract: Effects of fasting on the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis were examined in the tilapia ( Oreochromis mossambicus ) acclimated to fresh water. Fasting for 2 weeks resulted in significant reductions in body weight, specific growth rate and hepatosomatic index in both males and females. Significant reductions in specific growth rates were observed after 1 and 2 weeks in both sexes, although the decrease in body weight was not significant in the female. A significant reduction was also seen in the condition factor of females after 2 weeks. No change was seen in the gonadosomatic index in either sex. Two weeks of fasting also produced a significant reduction in plasma IGF-I but not in plasma GH, prolactin (PRL 188 ) or cortisol. Significant reductions in the hepatic IGF-I mRNA were seen in both sexes. On the other hand, a significant increase was observed in cortisol receptor mRNA in the female liver. Plasma IGF-I levels were correlated significantly with specific growth rate, condition factor and hepatosomatic index, indicating that plasma IGF-I is a good indicator of growth in the tilapia. No change was seen in plasma glucose or osmolality after 2 weeks of fasting. During fasting, tilapia appears to convert metabolic energy from growth to basal metabolism including maintenance of ion and water balance.

Gonadal development and associated changes in liver size and sexual steroids during the reproductive cycle of captive male and female Atlantic cod (Gadus morhua L.).

Abstract: Gametogenesis in female and male Atlantic cod ( Gadus morhua L.) was investigated by sampling blood plasma and gonadal tissue from 19 to 33-month-old fish. The reproductive cycles of both female and male Atlantic cod are characterized by distinct annual variations in gonadal size and developmental stage and these are associated with changes in sex steroids and liver size. I H did not change during early gonadal development, but both spent females and males had lower I H than late maturing females and spermiating males, respectively. In females I G was correlated to plasma E2 levels and they were highest in spawning females. The lowest levels during the reproductive cycle were observed in spent females. Plasma T levels were low throughout ovarian development, and were at a minimum in spent females. 11-ketotestosterone in plasma of males increased rapidly during spermiation, while T increased at earlier testicular stages and reached maximum during spermiation. High plasma levels of steroids in male and female cod during spawning serve to promote further development and growth of less advanced stages of germ cells.

The expression of gill Na, K-ATPase in milkfish, Chanos chanos, acclimated to seawater, brackish water and fresh water

Abstract: Juvenile milkfish Chanos chanos (Forsskal, 1775) were transferred from a local fish farm to fresh water (FW; 0 per thousand ), brackish water (BW; 10 per thousand, 20 per thousand ) and seawater (SW; 35 per thousand ) conditions in the laboratory and reared for at least two weeks. The blood and gill of the fish adapted to various salinities were analyzed to determine the osmoregulatory ability of this euryhaline species. No significant difference was found in plasma osmolality, sodium or chloride concentrations of milkfish adapted to various salinities. In FW, the fish exhibited the highest specific activity of Na, K-ATPase (NKA) in gills, while the SW group was found to have the lowest. Relative abundance of branchial NKA alpha-subunit revealed similar profiles. However, in contrary to other euryhaline teleosts, i.e. tilapia, salmon and eel, the naturally SW-dwelling milkfish expresses higher activity of NKA in BW and FW. Immunocytochemical staining has shown that most Na, K-ATPase immunoreactive (NKIR) cells in fish adapted to BW and SW were localized to the filaments with very few on the lamellae. Moreover, in FW-adapted milkfish, the number of NKIR cells found on the lamellae increased significantly. Such responses as elevated NKIR cell number and NKA activity are thought to improve the osmoregulatory capacity of the milkfish in hyposaline environments.

Metabolic priorities during starvation: enzyme sparing in liver and white muscle of Atlantic cod, Gadus morhua L.

Abstract: Atlantic cod, Gadus morhua, respond to starvation first by mobilising hepatic lipids, then muscle and hepatic glycogen and finally muscle proteins. The dual role of proteins as functional elements and energetic reserves should lead to a temporal hierarchy of mobilisation where the nature of a function dictates its conservation during starvation. We examined (1) whether lysosomal and anti-oxidant enzymes in liver and white muscle are spared during prolonged starvation, (2) whether the responses of these enzymes in muscle vary longitudinally. Hepatic contents of lysosomal proteases decreased with starvation, whereas those of catalase (CAT) increased and lysosomal enzymes of carbohydrate metabolism and glutathione S-transferase (GST) did not change. In white muscle, starvation decreased the specific activity of lysosomal enzymes of carbohydrate degradation and doubled that of cathepsin D (CaD). The activity of anti-oxidant enzymes and acid phosphatase in muscle was unchanged with starvation. In white muscle neither lysosomal enzymes nor anti-oxidant enzymes varied significantly with sampling position. In cod muscle, antioxidant enzymes, CaD and acid phosphatase are spared during a period of starvation that decreases lysosomal enzymes of carbohydrate metabolism and decreases glycolytic enzyme activities. In cod liver, the anti-oxidant enzymes, CAT and GST, were also spared during starvation.

Time of day and water temperature modify the physiological stress response in green sturgeon, Acipenser medirostris.

Abstract: The effects of time of day and water temperature on the acute physiological stress response were investigated in young-of-the-year green sturgeon ( Acipenser medirostris ). The response to a 1-min air-emersion stressor was assessed during the day (08.00 h) and at night (20.00 h), as well as after acclimation to either 11 °C or 19 °C. Blood samples were collected prior to stress and at several times after exposure to the stressor, and plasma concentrations of cortisol, lactate, and glucose were determined. The magnitudes of cortisol (19.1 ng ml −1 vs. 4.9 ng ml −1 ) and lactate (190.6 mg l −1 vs. 166.7 mg l −1 ) were significantly higher in fish stressed at night when compared with the day. There were no significant differences in glucose levels between time periods. Although, acclimation temperature did not affect peak cortisol concentrations (56.7 and 50.3 ng ml −1 at 11 °C and 19 °C, respectively), the duration of the response was significantly extended at 11 °C. Post-stressor lactate increases were similar between temperature groups, but at 11 °C post-stressor glucose levels were significantly increased through 6 h, suggesting stressor-induced glycogenolysis and gluconeogenesis or decreased glucose utilization. These data demonstrate that the physiological stress response in green sturgeon is modified by both time of day and temperature.

Salinity-mediated carbonic anhydrase induction in the gills of the euryhaline green crab, Carcinus maenas

Abstract: The euryhaline green crab, Carcinus maenas, is a relatively strong osmotic and ionic regulator, being able to maintain its hemolymph osmolality as much as 300 mOsm higher than that in the medium when the crab is acclimated to low salinity. It makes the transition from osmoconformity to osmoregulation at a critical salinity of 26 ppt, and new acclimated concentrations of hemolymph osmotic and ionic constituents are reached within 12 h after transfer to low salinity. One of the central features of this transition is an 8-fold induction of the enzyme carbonic anhydrase (CA) in the gills. This induction occurs primarily in the cytoplasmic pool of CA in the posterior, ion-transporting gills, although the membrane-associated fraction of CA also shows some induction in response to low salinity. Inhibition of branchial CA activity with acetazolamide (Az) has no effect in crabs acclimated to 32 ppt but causes a depression in hemolymph osmotic and ionic concentrations in crabs acclimated to 10 ppt. The salinity-sensitive nature of the cytoplasmic CA pool and the sensitivity of hemolymph osmotic/ionic regulation to Az confirm the enzyme's role in ion transport and regulation in this species. CA induction is a result of gene activation, as evidenced by an increase in CA mRNA at 24 h after transfer to low salinity and an increase in protein-specific CA activity immediately following at 48 h post-transfer. CA gene expression appears to be under inhibitory control by an as-yet unidentified repressor substance found in the major endocrine complex of the crab, the eyestalk.

Rapid morphological change in living humans: implications for modern human origins.

Abstract: Human body size and body proportions are interpreted as markers of ethnicity, 'race,' adaptation to temperature, nutritional history and socioeconomic status. Some studies emphasize only one of these indicators and other studies consider combinations of indicators. To better understand the biocultural nature of human size and proportions a new study of the growth of Maya-American youngsters was undertaken in 1999 and 2000. One purpose of this research is to assess changes in body proportion between Maya growing up in the US and Maya growing up in Guatemala. Height and sitting height of 6-12-year-old boys and girls (n=360) were measured and the sitting height ratio [sitting height/height]x100, a measure of proportion, was calculated. These data are compared with a sample of Maya of the same ages living in Guatemala and measured in 1998 (n=1297). Maya-American children are currently 10.24 cm taller, on average, and have a significantly lower sitting height ratio, (i.e. relatively longer legs, averaging 7.02 cm longer) than the Guatemala Maya. Maya-American children have body proportions more like those of white children in the US than like Maya children in Guatemala. Improvements in the environment for growth, in terms of nutrition and health, seem to explain both the trends in greater stature and relatively longer legs for the Maya-Americans. These findings are applied to the problem of modern human origins as assessed from fossil skeletons. It has been proposed that heat adapted, relatively long-legged Homo sapiens from Africa replaced the cold adapted, relatively short-legged Homo neandertalensis of the Levant and Europe [J Hum Evol 32 (1997a) 423]. Skeletal samples of Maya adults from rural Guatemala have body proportions similar to adult Neandertals and to skeletal samples from Europe with evidence of nutritional and disease stress. Just as nutrition and health status explains the differences in the body proportions of living Maya children, these factors, along with adaptation to climate, may also explain much of the differences between the Neandertal and African hominid samples.

Allometric cascade: a model for resolving body mass effects on metabolism.

Abstract: Expanding upon a preliminary communication (Nature 417 (2002) 166), we here further develop a ‘multiple-causes model’ of allometry, where the exponent b is the sum of the influences of multiple contributors to control. The relative strength of each contributor, with its own characteristic value of b i , is determined by c i , the control contribution or control coefficient. A more realistic equation for the scaling of metabolism with body size thus can be written as BMR= MR 0 Σ c i ( M / M 0 ) bi , where MR 0 is the ‘characteristic metabolic rate’ of an animal with a ‘characteristic body mass’, M 0 . With M 0 of 1 unit mass (usually kg), MR 0 takes the place of the value a , found in the standard scaling equation, b i is the scaling exponent of the process i , and c i is its control contribution to overall flux, or the control coefficient of the process i . One can think of this as an allometric cascade, with the b exponent for overall energy metabolism being determined by the b i and c i values for key steps in the complex pathways of energy demand and energy supply. Key intrinsic factors (such as neural and endocrine processes) or ecological extrinsic factors are considered to act through this system in affecting allometric scaling of energy turnover. Applying this model to maximum vs. BMR data for the first time explains the differing scaling behaviour of these two biological states in mammals, both in the absence and presence of intrinsic regulators such as thyroid hormones (for BMR) and catecholamines (for maximum metabolic rate).

Standard energetics of phyllostomid bats: the inadequacies of phylogenetic-contrast analyses.

Abstract: The basal rates of metabolism (BMR) of bats belonging to the family Phyllostomidae are re-examined after an earlier correlation with food habits was rejected because it did not take phylogeny into consideration. This rejection was based on an erroneous attribution of food habits and on an analytical method, phylogenetic contrasts, that ignores interactions that occur among character states and preferentially attributes responsibility for character states to phylogeny. The re-examination made here was based on analysis of covariance, which makes no a priori assumptions on the relative impact of factors that influence character states and permits factor interactions to be identified. A resulting model, based on variation in body mass, food habits, occurrence with respect to elevation, and residence on islands or continents, accounts for 99.4% of the variation in the BMR of 30 species of phyllostomids. Basal rate is also correlated with subfamily, but only if food habits are excluded because they are correlated with subfamily affiliation, as is residence on islands and continents, two examples of factor interaction. The preference to assign the effects of food habits and island residence on basal rate to subfamily affiliation (and phylogeny) is not justified. The concept that quantitative physiological characters can be transmitted via phylogeny without regard to the habits of animals and the characteristics of their environments cannot be defended. Phylogeny is the historical context in which the evolution of character states occurs, not the ‘cause’ of their evolution.

Adaptive patterns of osmotic and ionic regulation, and the invasion of fresh water by the palaemonid shrimps.

Abstract: To evaluate trends in the osmoregulatory behavior of neotropical, palaemonid shrimps, we investigated osmotic and ionic regulatory patterns in five species of Palaemon or Macrobrachium. The species’ life histories depend on saline water to differing degrees, their habitats ranging from the marine/intertidal (P. northropi), through estuaries (P. pandaliformis) to coastal, freshwater streams (M. olfersii, M. potiuna) and inland, continental river systems (M. brasiliense). Hemolymph osmolality, chloride, sodium and magnesium concentrations were measured in shrimps exposed to experimental media ranging from fresh water (<0.5‰) to concentrated seawater (42‰) for up to 10 days. The marine and estuarine Palaemon species exhibit well-developed hyper/hypo-osmotic, sodium and chloride regulatory capabilities in mid-range salinities, tending to hyperconform in low salinities. The freshwater Macrobrachium species show variable hyperosmotic, sodium and chloride regulatory capacities, tending to hypoconform or unable to survive at higher salinities. All species hyper-regulate magnesium in fresh water, but hyporegulate strongly in saline media. Palaemonids from the saline habitats show the strongest osmoregulatory capabilities, and fresh water may have been gradually invaded by ancestral species with similar regulatory capacity. However, this regulatory plasticity has been lost to varying degrees in extant freshwater species.

Dietary diversity, child nutrition and health in contemporary African communities.

Abstract: Many infants in sub-Saharan Africa (SSA) begin to receive cereal-based supplemental feeds well before the age (6 months) recommended for the introduction of 'safe and nutritionally adequate' complementary foods, or in rarer instances, do not receive these until the second year. The diets offered are monotonous and bulky, and rarely cover the shortfall left by breast milk in providing the energy and nutrients required to support rapid growth, build nutrient stores and assure resistance to infection. The pattern of growth and prevalence of malnutrition observed from birth through the first 5 years in SSA are suggestive of the nutrient inadequacies of the diet and the experience of infection. However, it is difficult to link poor growth and specific nutrient deficiencies in epidemiological studies because multiple nutrients are required for growth and deficiencies usually involve several nutrients. Moreover, accurate measurement of nutrient intakes is no small challenge. In this regard, qualitative and easier-to-measure characteristics of diet which are associated with nutrient adequacy could serve as alternative determinant factors in studies looking at causes of malnutrition. Dietary diversity is proposed as a candidate indicator of food security and predictor of nutritional status, but there is need for further research to standardize definitions and methodology before it can be applied widely.

Biochemical composition during growth and starvation of early larval stages of cultured spiny lobster (Jasus edwardsii) phyllosoma.

Abstract: We examined biochemical changes accompanying feeding and starvation from hatch to Stage VI (day 74 after hatch) in spiny lobster, Jasus edwardsii, phyllosoma larvae. Larval dry weights (dw) increased 17-fold from hatch (80+/-1 microg) to Stage VI (1415+/-44 microg). Larvae starved for 6-11 days at Stages II, IV and VI were 14-40% lighter than their fed counterparts fed enriched Artemia. The increases and losses in total dry weight during feeding and starvation were associated with changes in the content of protein (constituting 31.4-41.7% of dw) and carbohydrate (constituting 2.6-5.3% of dw), while larger changes in lipid content indicated its greater importance as an energy substrate. Lipid content increased from 7.9% of dw at hatch to its highest of 12.5% at Stage IV, but declined by 50% or more during starvation. This suggests that protein, carbohydrate and lipid are all important energy stores, although lipids are catabolized at a greater rate during food deprivation. The principal lipid class was polar lipid (PL; 79-92% of total lipid), followed by sterol (ST; 6-20%), with triacylglycerol and other lipid classes at <2%. PL were catabolized and ST were conserved during starvation. Changes in the fatty acid (FA) profile had mostly occurred before the first moult at day 8 after hatch, with gradual changes thereafter to Stage VI, reflecting their abundance in the Artemia diet. There was some conservation of the major essential FAs, 20:4n-6, 20:5n-3, 22:6n-3, and the FA profile showed large gains in the C(18) polyunsaturated FA, 18:1n-9, 18:2n-6. Ascorbic acid content increased 10-fold from hatch to the end of Stage I (36 and 333 microgg(-1) dw, respectively), while the content at the end of Stage II was higher in fed than that in starved larvae (439 and 174 microgg(-1) dw, respectively). Our study will assist in the development of alternatives to nutritionally incomplete diets, such as live ongrown Artemia, to meet the requirements of phyllosoma in culture.

Environmental endocrine disrupters dysregulate estrogen metabolism and Ca2+ homeostasis in fish and mammals via receptor-independent mechanisms.

Abstract: Xenoestrogen endocrine disrupters (EDs) in the environment are thought to be responsible for a number of examples of sexual dysfunction that have recently been reported in several species. There is growing concern that these compounds may also cause abnormalities of the male reproductive tract and reduced spermatogenesis in man. Whilst some effects of EDs may be receptor-mediated, there is growing evidence that these compounds can exert potent effects in vivo by directly interacting with cellular enzyme targets. Here we report on, and review, the effects of alkylphenols and other EDs on two such enzymes: (1) sulfotransferases, which convert active estrogenic steroids to inactive steroid sulfates; and (2) Ca 2+ -ATPases, which are responsible for maintaining low, physiological, intracellular Ca 2+ concentrations. These enzymes are potently inhibited by EDs in both fish and mammalian species. The increased concentrations of active estrogens and the likely cytotoxic effects of elevated concentrations of intracellular Ca 2+ arising from these effects may underlie some of the endocrine disrupting potential of these widespread industrial pollutants.

Effect of temperature on lipids, proteins, and carbohydrates levels during development from egg extrusion to juvenile stage of Cherax quadricarinatus (Decapoda: Parastacidae)

Abstract: The influence of temperature on biochemical composition, survival and duration of development of Cherax quadricarinatus from egg extrusion to juvenile was analyzed. Berried females were individually subjected to each of 22, 25, 28 and 31 degrees C (n=5 per temperature). Egg samples were obtained every 3 days from egg extrusion to juvenile stage for biochemical analysis. Duration of development and survival decreased with increasing temperature. At 22 and 25 degrees C half of the initial lipid content was consumed during development. At 28 and 31 degrees C, 80% of the initial amount of lipids was consumed. For proteins, depletion rate was significantly lower at 25 degrees C (36% of the initial amount) than at 22, 28 and 31 degrees C (61-65% of the initial amount). For carbohydrates, a significant consumption was observed only at 22 degrees C. Total energy consumption was lower at 22 and 25 degrees C than at 28 and 31 degrees C. We conclude that 22-25 degrees C is the optimal temperature range for C. quadricarinatus egg incubation, although 25 degrees C might be better in terms of development duration in terms of survival, energy cost and protein consumption.

Comparative ionic flux and gill mucous cell histochemistry: effects of salinity and disease status in Atlantic salmon (Salmo salar L.).

Abstract: Two experiments were conducted to assess the physiological effects of freshwater exposure and amoebic gill disease (AGD) in marine Atlantic salmon ( Salmo salar L.). The first experiment monitored marine salmon during a 3 h freshwater exposure, the standard treatment for AGD in Tasmania. The second experiment described the gill mucous cell histochemistry for freshwater adapted and seawater acclimated fish (AGD affected and unaffected) for possible correlations to ionoregulation. When exposed to freshwater, marine Atlantic salmon experienced a minor ionoregulatory dysfunction represented by a net efflux of Cl − ions at 3 h. AGD affected fish experienced the net efflux of Cl − ions 1 h sooner, and had a significantly greater net efflux of total ammonia. Changes to gill mucous cell populations corresponded to differing salinity and the presence of AGD. In AGD affected fish, these populations significantly differed between lesion and non-lesion associated areas of the gill filament. Our results have shown changes in the ionoregulatory capacity of Atlantic salmon due to freshwater exposure and AGD. Gill mucous cell histochemistry indicates the potential importance of the mucous layer in ionoregulation and disease. In comparison to previous studies on rainbow trout, these results suggest that Atlantic salmon have a greater short-term ionoregulatory capacity.

Review of the monotreme fossil record and comparison of palaeontological and molecular data.

Abstract: Monotremes have traditionally been considered a remnant group of mammals descended from archaic Mesozoic stock, surviving to the present day on the relatively isolated Australian continent. Challenges to this orthodoxy have been spurred by discoveries of ‘advanced’ Cretaceous monotremes ( Steropodon galmani , Archer, M., et al., 1985. First Mesozoic mammal from Australia—an Early Cretaceous monotreme, Nature. 318, 363–366) as well as by results from molecular data linking monotremes to therian mammals (specifically to marsupials in some studies). This paper reviews the monotreme fossil record and briefly discusses significant new information from additional Cretaceous Australian material. Mesozoic monotremes (including S. galmani ) were a diverse group as evidenced by new material from the Early Cretaceous of New South Wales and Victoria currently under study. Although most of these new finds are edentulous jaws (limiting dental comparisons and determination of dietary niches), a range of sizes and forms has been determined. Some of these Cretaceous jaws exhibit archaic features—in particular evidence for the presence of a splenial bone in S. galmani —not seen in therian mammals or in post-Mesozoic (Tertiary and Quaternary) monotreme taxa. Tertiary monotremes were either archaic ornithorhynchids (toothed platypuses in the genera Monotrematum and Obdurodon ) or tachyglossids (large echidnas in the genera Megalibgwilia and Zaglossus ). Quaternary ornithorhynchid material is referable to the sole living platypus species Ornithorhynchus anatinus . Quaternary echidnas, however, were moderately diverse and several forms are known ( Megalibgwilia species; ‘ Zaglossus’ hacketti ; Zaglossus species and Tachyglossus aculeatus ).

The effect of copper on osmoregulation in the freshwater amphipod Gammarus pulex.

Abstract: The influence of copper on osmoregulation in the freshwater amphipod Gammarus pulex was determined from the analysis of water permeability, haemolymph sodium concentration, sodium influx and gill Na(+)/K(+) ATPase and Mg(2+) ATPase activity. Exposure to nominal copper concentrations of 100 microg l(-1) or greater caused a significant reduction in both haemolymph sodium concentration and sodium influx within 4 h. Measurements of water permeability, expressed as the half-time of exchange of body water (t(1/2)), excluded structural gill damage as the cause of this fall in haemolymph sodium. Copper at 10 microg l(-1) or above in the assay solution significantly reduced gill Na(+)/K(+) ATPase activity. In contrast gill Mg(2+) ATPase activity was markedly less affected by copper. These differences in enzyme sensitivity were considered with respect to the potential mechanisms of copper toxicity.

Glycolysis and pyruvate oxidation in cardiac hypertrophy--why so unbalanced?

Abstract: Cardiac hypertrophy, induced by chronic pressure or volume overload, is associated with abnormalities in energy metabolism as well as characteristic increases in muscle mass and alterations in the structure of the heart. Hypertrophied hearts display increased rates of glycolysis and overall glucose utilization, but rates of pyruvate oxidation do not rise in step with rates of pyruvate generation. Glycolysis and glucose oxidation, therefore, become markedly less 'coupled' in hypertrophied hearts than in non-hypertrophied hearts. Because the pyruvate dehydrogenase complex (PDC) contributes so powerfully to the control of glucose oxidation, we set out to test the hypothesis that the function of PDC is impaired in cardiac hypertrophy. In this review we describe evidence indicating that the alterations in glucose metabolism in hypertrophied hearts cannot be explained simply by changes in PDC expression or control. Additional mechanisms that may lead to an altered balance of pyruvate metabolism in cardiac hypertrophy are discussed, with commentaries on possible changes in pyruvate transport, NADH shuttles, lactate dehydrogenase, and amino acid metabolism.

Regulation of renal proximal and distal tubule transport: sodium, chloride and organic anions

Abstract: Renal tubular transport and its regulation are reviewed for Na(+) (and Cl(-)), and for fluid and organic anions (including urate). Filtered Na(+) (and Cl(-)) is reabsorbed along the tubules but only in mammals and birds does most reabsorption occur in the proximal tubules. Reabsorption involves active transport of Na(+) and passive reabsorption of Cl(-). The active Na(+) step always involves Na-K-ATPase at the basolateral membrane, but the entry step at luminal membrane varies among tubule segments and among vertebrate classes (except for Na(+)-2Cl(-)-K(+) cotransporter in diluting segment). Regulation can involve intrinsic, neural and endocrine factors. Proximal tubule fluid reabsorption is dependent on Na(+) reabsorption in all vertebrates studied, except ophidian reptiles. Fluid secretion occurs in glomerular and aglomerular fishes, reptiles and even mammals, but its significance is not always clear. A non-specific transport system for net secretion of organic anions (OAs) exists in the proximal renal tubules of almost all vertebrates. Net transepithelial secretion involves: (1) transport into the cells at the basolateral side against an electrochemical gradient by a tertiary active transport process, in which the final step involves OA/alpha-ketoglutarate exchange and (2) movement out of the cells across the luminal membrane down an electrochemical gradient by unknown carrier-mediated process(es). Regulation may involve protein kinase C and mitogen-activated protein kinase. Urate is net secreted in the proximal tubules of birds and reptiles. This process is urate-specific in reptiles but in birds, it may involve both a urate-specific system and the general OA system.