Activation of OR1A1 suppresses PPAR-γ expression by inducing HES-1 in cultured hepatocytes

Olfactory receptors (ORs) comprise the largest G protein-coupled receptor gene superfamily. Recent studies indicate that ORs are also expressed in non-olfactory organs, including metabolically active tissues, although their biological functions in these tissues are largely unknown. In this study, OR1A1 expression was detected in HepG2 liver cells. OR1A1 activation by (−)-carvone, a known OR1A1 ligand, increased the cyclic adenosine monophosphate (cAMP), but not intracellular Ca²⁺ concentration, thereby inducing protein kinase A (PKA) activity with subsequent phosphorylation of cAMP response element-binding protein (CREB) and upregulation of the CREB-responsive gene hairy and enhancer of split (HES)-1, a corepressor of peroxisome proliferator-activated receptor-γ (PPAR-γ) in hepatocytes. In (−)-carvone-stimulated cells, the repression of PPAR-γ reduced the expression of the target gene, mitochondrial glycerol-3-phosphate acyltransferase, which encodes a key enzyme involved in triglyceride synthesis. Intracellular triglyceride level and lipid accumulation were reduced in cells stimulated with (−)-carvone, effects that were diminished following the loss of OR1A1 function. These results indicate that OR1A1 may function as a non-redundant receptor in hepatocytes that regulates the PKA-CREB-HES-1 signaling axis and thereby modulates hepatic triglyceride metabolism.     

Intermittent cold-induced hippocampal oxidative stress is associated with changes in the plasma lipid composition and is modifiable by vitamins C and E in old rats

This study primarily investigated the effects of intermittent cold exposure (ICE) on oxidative stress (OS) in the hippocampus(HC) and plasma lipid profile of old male rats. Secondly, it evaluated structural changes in the hippocampus region of the rat’s brain. Thirdly, it attempted an evaluation of the effectiveness of the combined supplement of vitamins C and E in alleviating cold stress in terms of these biochemical parameters. Thirty male rats aged 24 months were divided into groups of five each: control (CON), cold-exposed at 10 °C (C10), cold-exposed at 5 °C (C5), supplemented control (CON+S), and supplemented cold-exposed at either 5 °C (C5+S) or 10 °C (C10+S). The rats were on a daily supplement of vitamin C and vitamin E. Cold exposure lasted 2 h/day for 4 weeks. Rats showed increased levels of hydrogen peroxide (H₂O₂), and thiobarbituric acid reactive substances (TBARS) in the HC at 10 °C with further increase at 5 °C. Cold also induced neuronal loss in the hippocampus with concomitant elevations in total cholesterol (TCH), triglycerides (TG) and low-density lipoproteins (LDL-C) levels, and a depletion in high-density lipoprotein (HDL-C). A notable feature was the hyperglycaemic effects of ICE and depleted levels of vitamins C and E in the hippocampus and plasma while supplementation increased their levels. More importantly, a positive correlation was observed between plasmatic LDL-C, TCH and TG and hippocampal TBARS and H₂O₂ levels. Further, intensity of cold emerged as a significant factor impacting the responses to vitamin C and E supplementation. These results suggest that cold-induced changes in the plasma lipid profile correlate with OS in the hippocampus, and that vitamin C and E together are effective in protecting from metabolic and possible cognitive consequences in the old under cold exposures.     

Spontaneous curvature of fluid vesicles induced by trans-bilayer sugar asymmetry

We present measurements of the effective spontaneous curvature of fluid lipid bilayers as a function of trans-bilayer asymmetry. Experiments are performed on micrometer-scale vesicles in sugar solutions with varying species across the membrane. There are two effects leading to a preferred curvature of such a vesicle. The spontaneous curvatures of the two monolayers as well as their area difference combine into an effective spontaneous curvature of the membrane. Our technique for measuring this parameter allows us to use vesicle morphology as a probe for general membrane-solute interactions affecting elasticity. Received: 3 June 1998 / Revised version: 18 August 1998 / Accepted: 21 August 1998     

The use of energy stores in the puerulus of the spiny lobster Jasus edwardsii across the continental shelf of New Zealand

Nektonic pueruli of the spiny lobster, Jasus edwardsii, were caught from two locations about 20 km apart across the continental shelf on the south east of the North Island, New Zealand. The pueruli were assayed for total protein, glucose, glycogen, and lipid content. Only the lipid content differed between pueruli caught onshore and offshore (mean difference=3.1 mg or 3.4% of dry mass). The average difference in lipid content measured over this distance was used to calculate the rate of energy consumption and timing for pueruli to actively swim from the continental shelf to shore. These results confirmed previous theoretical estimates and indirect measures. Furthermore, the rate of energy consumption would allow all of the pueruli caught offshore to swim to shore based on their total measured lipids. However, some individuals with low energy stores may be energetically compromised at arrival which may affect their subsequent moulting and survival. The results of this study indicate that lipid is the primary format for energy storage of the nektonic puerulus of the spiny lobster and that these lipid reserves have sufficient energetic capacity to allow the puerulus to actively swim the distance across the shelf to settle on the coast.     

Developmental costs of rapid growth in a damselfly

Abstract.  1. Developmental costs of rapid growth in terms of increased fluctuating asymmetry are expected to contribute to the widespread occurrence of growth rates below the physiological maximum, but have rarely been demonstrated. Here, these costs are studied for the first time in an invertebrate, the damselfly Lestes viridis , using a rearing experiment where early- and late-hatched larvae of both sexes were reared at decreasing or permanent water levels.
2. Late-hatched animals were more asymmetrical than early-hatched animals except for males in the drying treatment. Also, females were more asymmetrical than males except in early-hatched animals in the drying treatment.
3. The data presented suggest that in females but not in males treatment groups with higher growth rates have more asymmetrical wings. However, at the individual level no relationship between growth rate and asymmetry was present.
4. Possible reasons why the suggested trade-off between growth and developmental instability was not present at the individual level, and at the group level only in females, are discussed.     

The influence of Ca2+ on the lateral lipid distribution and phase transition in phosphatidylethanolamine/phosphatidylserine vesicles

The lateral lipid distribution within dipalmitoylphosphatidylethanolamine (DPPE)/dipalmitoylphosphatidylserine (DPPS) vesicle membranes was investigated under the influence of Ca²⁺ using a lipid cross-linking method. To characterize the phase transition in DPPE/DPPS vesicles and to correlate the different phase states of the membrane lipids with the obtained lipid distribution ESR measurements using a fatty acid spin label were carried out. It is shown that Ca²⁺ has a significant influence on the lateral lipid distribution within the fluid phase of the membrane lipids; instead of a slight alternating lipid arrangement in absence of Ca²⁺ due to the electrostatic interaction between the DPPS headgroups after addition of Ca²⁺ a lateral cluster structure is characteristic of the fluid phase.     

The evolutionary geometry of human anatomy: Discovering our inner fly

The human body is one still frame in a very long evolutionary movie. Anthropologists focus on the last few scenes, whereas geneticists try to trace the screenplay back as far as possible. Despite their divergent time scales (millions versus billions of years), both disciplines share a reliance on a third field of study whose scope spans only a matter of days to months, depending on the organism. Embryology is crucial for understanding both the pliability of anatomy and the modularity of gene circuitry. The relevance of human embryology to anthropology is obvious. What is not so obvious is the notion that equally useful clues about human anatomy can be gleaned by studying the development of the fruit fly, an animal as different from us structurally as it is distant from us evolutionarily. The underlying kinship between ourselves and flies has only become apparent recently, thanks to revelations from the nascent field of evolutionary developmental biology, or evo‐devo. All bilaterally symmetric animals, it turns out, share a common matrix of body axes, a common lexicon of intercellular signals, and a common arsenal of genetic gadgetry that evolution has tweaked in different ways in different lineages to produce a dazzling spectrum of shapes and patterns. Anthropologists can exploit this deep commonality to search our genome more profitably for the mutations that steered us so far astray from our fellow apes.     

Within-individual changes in developmental stability affect flight performance

Developmental stability, as measured by fluctuating asymmetry,has been purported to be an indicator of individual quality,and low asymmetry can be selected for by sexual selection processes.However, low asymmetry can also arise due to biomechanical constraintsoperating on trait design, as it is predicted that asymmetrywill decrease mechanical efficiency. Specifically, it has beenpredicted that wing length asymmetry will be negatively relatedto avian flight performance. To date, empirical investigationshave only studied the influence of increasing asymmetry beyondnaturally occurring average values. I examined the influenceof within-individual changes in primary feather developmentalstability on flight performance in European starlings by studyingasymmetry and flight before and after wing molt. Individualsthat exhibited a decrease in wing asymmetry through molt experiencedincreased aerodynamic performance in terms of both angle oftakeoff and level flapping-flight speed. Birds that increasedwing asymmetry suffered a decrease in flight performance. Takeoffspeed and the ability to negotiate an aerial obstacle coursewere unaffected by asymmetry. My data provide empirical supportfor the predicted influence of wing asymmetry on flight, eventhough the changes in asymmetry were very small (mean = 0.47%of trait size) and further indicate the importance of biomechanicalconsiderations in any study of developmental stability