Leptin, but not immune function, is linked to reproductive responsiveness to photoperiod

Energetic demands are high while energy availability is minimum during winter. To cope with this energetic bottleneck, animals exhibit numerous energy-conserving adaptations during winter, including changes in immune and reproductive functions. A majority of individual rodents within a population inhibits reproductive function (responders) as winter approaches. A substantial proportion of small rodents within a species, however, fails to inhibit reproduction (nonresponders) during winter in the field or in the laboratory when maintained in winter-simulated day lengths. In contrast, immune function is bolstered by short day lengths in some species. The specific mechanisms that link reproductive and immune functions remain unspecified. Leptin is a hormone produced by adipose tissue, and several studies suggest that leptin modulates reproductive and immune functions. The present study sought to determine if photoperiodic alterations in reproductive function and leptin concentrations are linked to photoperiod-modulated changes in immune function. Siberian hamsters (Phodopus sungorus) were housed in either long (LD 16:8) or short (LD 8:16) day lengths for 9 wk. After 9 wk, blood samples were collected during the middle of the light and dark phase to assess leptin concentrations. One week later, animals were injected with keyhole limpet hemocyanin to evaluate humoral immunity. Body mass, body fat content, and serum leptin concentrations were correlated with reproductive responsiveness to photoperiod; short-day animals with regressed gonads exhibited a reduction in these measures, whereas short-day nonresponders resembled long-day animals. In contrast, immune function was influenced by photoperiod but not reproductive status. Taken together, these data suggest that humoral immune function in Siberian hamsters is independent of photoperiod-mediated changes in leptin concentrations.     

Gamma-secretase activity is present in rafts but is not cholesterol-dependent

Cholesterol has been claimed to be involved in the generation and/or accumulation of amyloid beta protein (Abeta). However, the underlying molecular mechanisms have not been fully elucidated yet. Here, we have investigated the effect of membrane cholesterol content on gamma-secretase activity using Chinese hamster ovary cells stably expressing beta-amyloid precursor protein (APP) and either wild-type or N141I mutant-type presenilin 2. Cholesterol was acutely depleted from the isolated membrane by methyl-beta-cyclodextrin, and Abeta production was assessed in a cell-free assay system. Reduced cholesterol did not significantly alter the amounts of Abeta produced by either total cell membranes or cholesterol-rich low-density membrane domains. Even its extremely low levels in the latter domains did not affect Abeta production. This indicates that the membrane cholesterol content does not directly modulate the activity of gamma-secretase. To ascertain that gamma-secretase resides in cholesterol-rich membrane domains, low-density membrane domains were further fractionated with BCtheta (biotinylated theta-toxin nicked with subtilisin Carlsberg protease), which has recently been shown to bind selectively to rafts of intact cells. The membrane domains purified with BCtheta did indeed produce Abeta. These observations indicate that the gamma-cleavage required for generating Abeta occurs in rafts, but its activity is virtually cholesterol-independent.     

The rate of spontaneous epistaxis is not linked to the lunar cycle but shows seasonal variations

Since 50–60% of the human body consists of water, the physiology of blood circulation might be affected by a full moon differently than during other days of the month. This study analyzed a potential association among lunar phases, seasonal variations, and the rate of spontaneous epistaxis. Consecutive admissions solely for spontaneous epistaxis to an otolaryngology emergency room of a single medical center during 1 year were evaluated. The applied tests failed to show changes of admissions during different lunar phases. According to multiple comparisons, admissions were significantly less frequent during the summer months, similar to findings from other countries of the northern hemisphere with varying climates, suggesting an influence of circannual rhythms rather than of environmental conditions.     

MAP4 counteracts microtubule catastrophe promotion but not tubulin-sequestering activity in intact cells

Microtubules are polar polymers that continually switch between phases of elongation and shortening, a property referred to as dynamic instability. The ubiquitous microtubule associated protein 4 (MAP4) shows rescue-promoting activity during in vitro assembly of microtubules (i.e., promotes transitions from shortening to elongation), but its regulatory role in intact cells is poorly defined. Here, we demonstrate that ectopic MAP4 promotes outgrowth of extended MTs during beta1-integrin-induced cell spreading. An inducible cotransfection protocol was employed to further analyze the regulatory role of MAP4 in human leukemia cells with microtubules partially destabilized by either ectopic tubulin-sequestering proteins or proteins that promote catastrophes (i.e., transitions from elongation to shortening). Coexpression of proteins that sequester free tubulin heterodimers with different efficiencies was found to abolish microtubule stabilization by MAP4. In contrast, however, the microtubule-stabilizing activity of MAP4 was found to suppress the activities of two distinct and specific catastrophe promoters, namely, XKCM1 and a nonsequestering truncation derivative of Op18/stathmin. These observations reveal specificity in the microtubule-stabilizing activity of MAP4 that differentiates between two mechanistically distinct types of MT destabilization.     

Osmoregulatory fluid intake but not hypovolemic thirst is intact in mice lacking angiotensin

Water intakes in response to hypertonic, hypovolemic, and dehydrational stimuli were investigated in mice lacking angiotensin II as a result of deletion of the angiotensinogen gene (Agt-/- mice), and in C57BL6 wild-type (WT) mice. Baseline daily water intake in Agt-/- mice was approximately threefold that of WT mice because of a renal developmental disorder of the urinary concentrating mechanisms in Agt-/- mice. Intraperitoneal injection of hypertonic saline (0.4 and 0.8 mol/l NaCl) caused a similar dose-dependent increase in water intake in both Agt-/- and WT mice during the hour following injection. As well, Agt-/- mice drank appropriate volumes of water following water deprivation for 7 h. However, Agt-/- mice did not increase water or 0.3 mol/l NaCl intake in the 8 h following administration of a hypovolemic stimulus (30% polyethylene glycol sc), whereas WT mice increased intakes of both solutions during this time. Osmoregulatory regions of the brain [hypothalamic paraventricular and supraoptic nuclei, median preoptic nucleus, organum vasculosum of the lamina terminalis (OVLT), and subfornical organ] showed an increased number of neurons exhibiting Fos-immunoreactivity in response to intraperitoneal hypertonic NaCl in both Agt-/- mice and WT mice. Polyethylene glycol treatment increased Fos-immunoreactivity in the subfornical organ, OVLT, and supraoptic nuclei in WT mice but only increased Fos-immunoreactivity in the supraoptic nucleus in Agt-/- mice. These data show that brain angiotensin is not essential for the adequate functioning of neural pathways mediating osmoregulatory thirst. However, angiotensin II of either peripheral or central origin is probably necessary for thirst and salt appetite that results from hypovolemia.     

Selective enhancement of the activity of C-terminally truncated, but not intact, acetylcholinesterase

Acetylcholinesterase (AChE) is one of the fastest enzymes approaching the catalytic limit of enzyme activity. The enzyme is involved in the terminal breakdown of the neurotransmitter acetylcholine, but non-enzymatic roles have also been described for the entire AChE molecule and its isolated C-terminal sequences. These non-cholinergic functions have been attributed to both the developmental and degenerative situation: the major form of AChE present in these conditions is monomeric. Moreover, AChE has been shown to lose its typical characteristic of substrate inhibition in both development and degeneration. This study characterizes a form of AChE truncated after amino acid 548 (T548-AChE), whose truncation site is homologue to that of a physiological form of T-AChE detected in fetal bovine serum that has lost its C-terminal moiety supposedly due to proteolytic cleavage. Peptide sequences covered by this C-terminal sequence have been shown to be crucially involved in both developmental and degenerative mechanisms in vitro. Numerous studies have addressed the structure-function relationship of the AChE C-terminus with T548-AChE representing one of the most frequently studied forms of truncated AChE. In this study, we provide new insight into the understanding of the functional characteristics that T548-AChE acquires in solution: T548-AChE is incubated with agents of varying net charge and molecular weight. Together with kinetic studies and an analysis of different molecular forms and aggregation states of T548-AChE, we show that the enzymatic activity of T548-AChE, an enzyme verging at its catalytic limit is, nonetheless, apparently enhanced by up to 800%. We demonstrate, first, how the activity of T548-AChE can be enhanced through agents that contain highly positive charged moieties. Moreover, the un-competitive mechanism of activity enhancement most likely involves the peripheral anionic site of AChE that is reflected in delayed substrate inhibition being observed for activity enhanced T548-AChE. The data provides evidence towards a mechanistic and functional link between the form of AChE unique to both development and degeneration and a C-terminal peptide of T-AChE acting under those conditions.     

Inbreeding linked to amphibian survival in the wild but not in the laboratory

We examined the effects of inbreeding on the performance of wood frog (Rana sylvatica) larvae in the field and in the laboratory. We used microsatellite analysis to establish the parentage and degree of inbreeding of the larvae. Two different estimators of inbreeding were used. The first was based on average multilocus heterozygosity, and the second was based on a molecular relatedness estimator. The estimators were highly correlated, and both showed a significant negative relationship between inbreeding and survival in the wild. However, there was no evidence that inbreeding influenced growth or development in the wild. Neither was there any evidence that inbreeding affected survival, growth, or development in the laboratory. These results suggest that, for wood frogs, inbreeding has a bigger effect on fitness in the wild than in captivity and that measurements of survival are more sensitive than measures of growth or development.     

Metabolic rate is negatively linked to adult survival but does not explain latitudinal differences in songbirds

Survival rates vary dramatically among species and predictably across latitudes, but causes of this variation are unclear. The rate‐of‐living hypothesis posits that physiological damage from metabolism causes species with faster metabolic rates to exhibit lower survival rates. However, whether increased survival commonly observed in tropical and south temperate latitudes is associated with slower metabolic rate remains unclear. We compared metabolic rates and annual survival rates that we measured across 46 species, and from literature data across 147 species of birds in northern, southern and tropical latitudes. High metabolic rates were associated with lower survival but survival varied substantially among latitudinal regions independent of metabolism. The inability of metabolic rate to explain latitudinal variation in survival suggests (1) species may evolve physiological mechanisms that mitigate physiological damage from cellular metabolism and (2) extrinsic rather than intrinsic sources of mortality are the primary causes of latitudinal differences in survival.     

Coevolution is linked with phenotypic diversification but not speciation in avian brood parasites

Coevolution is often invoked as an engine of biological diversity. Avian brood parasites and their hosts provide one of the best-known examples of coevolution. Brood parasites lay their eggs in the nests of other species, selecting for host defences and reciprocal counteradaptations in parasites. In theory, this arms race should promote increased rates of speciation and phenotypic evolution. Here, we use recently developed methods to test whether the three largest avian brood parasitic lineages show changes in rates of phenotypic diversity and speciation relative to non-parasitic lineages. Our results challenge the accepted paradigm, and show that there is little consistent evidence that lineages of brood parasites have higher speciation or extinction rates than non-parasitic species. However, we provide the first evidence that the evolution of brood parasitic behaviour may affect rates of evolution in morphological traits associated with parasitism. Specifically, egg size and the colour and pattern of plumage have evolved up to nine times faster in parasitic than in non-parasitic cuckoos. Moreover, cuckoo clades of parasitic species that are sympatric (and share similar host genera) exhibit higher rates of phenotypic evolution. This supports the idea that competition for hosts may be linked to the high phenotypic diversity found in parasitic cuckoos.     

Cell membrane, but not circulating, carcinoembryonic antigen is linked to a phosphatidylinositol-containing hydrophobic domain

Carcinoembryonic antigen is present in the cell membrane of most tumors of colorectal origin and in the plasma of patients with colorectal cancer and other malignancies. In this paper we demonstrate that carcinoembryonic antigen can be released from HT-29 cells by phosphatidylinositol specific phospholipase C. Triton X-114 phase separation shows that phospholipase C converts the antigen into a water soluble protein. In addition, plasma carcinoembryonic antigen behaves as the cleaved antigen in phase separation experiments. This strongly suggests that carcinoembryonic antigen is attached to cell membranes by a glycosyl-phosphatidylinositol anchor and that it can be released in vivo by enzymatic cleavage of the hydrophobic tail.     

Arabidopsis TRAPPII is functionally linked to Rab-A,but not Rab-D in polar protein trafficking in trans-Golgi network

The trans-Golgi network (TGN) in plant cells is an independent organelle, displaying rapid association and dissociation with Golgi bodies. In plant cells, the TGN is the site where secretory and endocytic membrane trafficking meet. Cell wall components, signaling molecules and auxin transporters have been found to undergo intracellular trafficking around the TGN. However, how different trafficking pathways are regulated and how different cargoes are sorted in the TGN is poorly defined in plant cells. Using a combined approach of genetic and in vivo imaging, we recently demonstrated that Arabidopsis TRAPPII acts in the TGN and is required for polar targeting of PIN2, but not PIN1, auxin efflux carrier in root tip cells. Here, we report that, TRAPPII in Arabidopsis is required for polar distribution of AUX1, an auxin influx carrier in protophloem cells and epidermal cells of Arabidopsis root tips. In yeast cells, TRAPPII serves as a guanine-nucleotide exchange factor (GEF) for Ypt1 and Ypt31/32 in late Golgi trafficking, while in mammalian cells, TRAPPII acts as a GEF for Rab1 (homolog of yeast Ypt1) in early Golgi trafficking. We show here that TRAPPII in Arabidopsis is functionally linked to Rab-A proteins, homologs of yeast Ypt31/32, but not Rab-D proteins, homologs of yeast Ypt1 and animal Rab1 proteins.     

Evolution of nerve fiber degeneration in the striatum in the MPTP-treated squirrel monkey

We have examined the ultrastructure of the striatum in squirrel monkeys 1–5 d after a single sc injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) 2.5 mg/kg. One untreated monkey served as control. We expected to find a dense degeneration of the dopamine terminals, but found instead that the main abnormality consisted of a focal vacuolation of the tissue, perhaps related to the striosome/matrix mosaic of the neostriatum. The vacuolation involved not only terminals, but also other parts of the neuropil. The severity of the destructive process increased from d 1–5. We conclude that MPP⁺, the toxic metabolite of MPTP, may gain access to the neuropil, either before or after its active uptake into and subsequent destruction of the dopamine terminals. p In the present study, abnormalities were observed simultaneously in the striatum and substantia nigra as early as 24 h after MPTP administration. It is, however, possible that the time-course might differ between the two locations with even shorter time intervals or changes in dosage of MPTP.     

Acorn production is linked to secondary growth but not to declining carbohydrate concentrations in current-year shoots of two oak species

In trees, reproduction constitutes an important resource investment which may compete with growth for resources. However, detailed analyses on how growth and fruit production interact at the shoot level are scarce. Primary canopy growth depends on the development of current-year shoots and their secondary growth might also influence the number and size of fruits supported by them. We hypothesise that an enhanced thickening of current-year shoots is linked positively to acorn production in oaks. We analysed the effect of acorn production on shoot growth of two co-occurring Mediterranean oak species with contrasting leaf habit (Quercus ilex, Quercus faginea). Length and cross-sectional area of current-year shoots, apical bud mass, number of leaves and acorns, xylem and conductive area, number of vessels of acorn-bearing and non-bearing shoots were measured in summer and autumn. Nitrogen and carbohydrates analyses were also performed in stems and leaves of both shoot types. Stem cross-sectional area increased in acorn-bearing shoots when compared with non-bearing shoots for both species and such surplus secondary growth was observed since summer. In bearing shoots, the total transversal area occupied by vessels decreased significantly from basal to apical positions along the stem as did the xylem area and the number of vessels. Leaves of bearing shoots showed lower nitrogen concentration than those of non-bearing shoots. Carbohydrate concentrations did not differ in stems and leaves as a function of the presence of acorns. Such results suggest that carbohydrates may preferentially be allocated towards reproductive shoots, possibly through enhanced secondary growth, satisfying all their carbon demands for growth and reproduction. Our findings indicate that acorn production in the two studied oaks depends on shoot secondary growth.     

Genome size is not related to life-history traits in primates.

Genome size (C value, the haploid DNA content of the nucleus) varies widely among eukaryotes, increasing through duplication or insertion of transposable elements and decreasing through deletions. Here, we investigate relationships between genome size and life-history attributes potentially related to fitness, including body mass, brain mass, gestation time, age at sexual maturity, and longevity, in 42 species of primates. Using multivariate and phylogenetically informed analyses, we show that genome size is unrelated to any of these traits. Genome size exhibits little variation within primates and its evolution does not appear to be correlated with changes in life-history traits. This further indicates that the phenotypic consequences of variation in genome size are dependent on the particular biology of the group in question.     

Ketocarotenoid circulation,but not retinal carotenoid accumulation,is linked to eye disease status in a wild songbird

Pathogenic or parasitic infections pose numerous physiological challenges to organisms. Carotenoid pigments have often been used as biomarkers of disease state and impact because they integrate multiple aspects of an individual’s condition and nutritional and health state. Some diseases are known to influence carotenoid uptake from food (e.g. coccidiosis) and carotenoid use (e.g. as antioxidants/immunostimulants in the body, or for sexually attractive coloration), but there is relatively little information in animals about how different types of carotenoids from different tissue sources may be affected by disease. Here we tracked carotenoid accumulation in two body pools (retina and plasma) as a function of disease state in free-ranging house finches (Haemorhous mexicanus). House finches in eastern North America can contract mycoplasmal conjunctivitis (Mycoplasma gallisepticum, or MG), which can progress from eye swelling to eye closure and death. Previous work showed that systemic immune challenges in house finches lower carotenoid levels in retina, where they act as photoprotectors and visual filters. We assessed carotenoid levels during the molt period, a time of year when finches uniquely metabolize ketocarotenoids (e.g. 3-hydroxy-echinenone) for acquisition of sexually selected red plumage coloration, and found that males infected with MG circulated significantly lower levels of 3-hydroxy-echinenone, but no other plasma carotenoid types, than birds exhibiting no MG symptoms. This result uncovers a key biochemical mechanism for the documented detrimental effect of MG on plumage redness in H. mexicanus. In contrast, we failed to find a relationship between MG infection status and retinal carotenoid concentrations. Thus, we reveal differential effects of an infectious eye disease on carotenoid types and tissue pools in a wild songbird. At least compared to retinal sources (which appear somewhat more temporally stable than other body carotenoid pools, even to diseases of the eye evidently), our results point to either a high physiological cost of ketocarotenoid synthesis (as is argued in models of sexually selected carotenoid coloration) or high benefit of using this ketocarotenoid to combat infection.     

Positive selection in ASPM is correlated with cerebral cortex evolution across primates but not with whole-brain size

The rapid increase of brain size is a key event in human evolution. Abnormal spindle-like microcephaly associated (ASPM) is discussed as a major candidate gene for explaining the exceptionally large brain in humans but ASPM's role remains controversial. Here we use codon-specific models and a comparative approach to test this candidate gene that was initially identified in Homo-chimp comparisons. We demonstrate that accelerated evolution of ASPM (omega = 4.7) at 16 amino acid sites occurred in 9 primate lineages with major changes in relative cerebral cortex size. However, ASPM's evolution is not correlated with major changes in relative whole-brain or cerebellum sizes. Our results suggest that a single candidate gene such as ASPM can influence a specific component of the brain across large clades through changes in a few amino acid sites. We furthermore illustrate the power of using continuous phenotypic variability across primates to rigorously test candidate genes that have been implicated in the evolution of key human traits.     

Global analysis reveals that cryptic diversity is linked with habitat but not mode of life

The ubiquity of genetically distinct, cryptic species is limiting any attempt to estimate local or global biodiversity as well as impeding efforts to conserve species or control pests and diseases. Environmental factors or biological traits promoting rapid diversification into morphologically similar species remain unclear. Here, using a meta‐analysis of 1230 studies using DNA sequences to search for cryptic diversity in metazoan taxa, we test two hypotheses regarding the frequency of cryptic taxa based on mode of life and habitat. First, after correcting for study effort and accounting for higher taxonomic affinities and biogeographical region of origins, our results do not support the hypothesis that cryptic taxa are more frequent among parasitic than free‐living taxa. Second, in contrast, the results support the hypothesis that cryptic taxa are more common in certain habitats than others: for a given study effort, more cryptic taxa are found in freshwater than in terrestrial or marine taxa. These findings suggest that the greater heterogeneity and fragmentation of freshwater habitats may promote higher rates of genetic differentiation among its inhabitants, a general pattern with serious implications for freshwater conservation biology.     

Cannabidiol increases Fos expression in the nucleus accumbens but not in the dorsal striatum

Preclinical and clinical studies suggest that cannabidiol (CBD), a major component of Cannabis sativa, could produce antipsychotic effects without causing extra-pyramidal side-effects. In the present paper we employed the detection of Fos protein to investigate neuronal activation in the dorsal striatum and nucleus accumbens of male Wistar rats after systemic administration of CBD (120 mg/kg), haloperidol (1 mg/kg) or clozapine (20 mg/kg). Only haloperidol was able to increase the number of Fos immunoreactive neurons (FIr) in the dorsal striatum (vehicle: 0.07 +/- 0.07/0.1 mm(2), haloperidol: 28.3 +/- 8.9/0.1 mm(2), p < 0.01). In contrast, both haloperidol and CBD significantly increased FIr in the nucleus accumbens (Vehicle: 0 +/- 0/0.1 mm(2), haloperidol: 7.2 +/- 2.7/0.1 mm(2), CBD: 4.0 +/- 1.9/0.1 mm(2), p < 0.05). Clozapine also produced a barely significant increase in FIr (3.0 +/- 1.7/0.1 mm(2), p = 0.062). These results show that CBD is able to induce FIr in a limbic- but not in a motor-related area.     

Mitochondrial function declines with age within individuals but is not linked to the pattern of growth or mortality risk in zebra finch

Mitochondrial dysfunction is considered a highly conserved hallmark of ageing. However, most of the studies in both model and non-model organisms are cross-sectional in design; therefore, little is known, at the individual level, on how mitochondrial function changes with age, its link to early developmental conditions or its relationship with survival. Here we manipulated the postnatal growth in zebra finches (Taeniopygia guttata) via dietary modification that induced accelerated growth without changing adult body size. In the same individuals, we examined blood cells mitochondrial functioning (mainly erythrocytes) when they were young (ca. 36 weeks) and again in mid-aged (ca. 91 weeks) adulthood. Mitochondrial function was strongly influenced by age but not by postnatal growth conditions. Across all groups, within individual ROUTINE respiration, OXPHOS and OXPHOS coupling efficiency significantly declined with age, while LEAK respiration increased. However, we found no link between mitochondrial function and the probability of survival into relatively old age (ca. 4 years). Our results suggest that the association between accelerated growth and reduced longevity, evident in this as in other species, is not attributable to age-related changes in any of the measured mitochondrial function traits.