SIRT1 is required for AMPK activation and the beneficial effects of resveratrol on mitochondrial function

Resveratrol induces mitochondrial biogenesis and protects against metabolic decline, but whether SIRT1 mediates these benefits is the subject of debate. To circumvent the developmental defects of germline SIRT1 knockouts, we have developed an inducible system that permits whole-body deletion of SIRT1 in adult mice. Mice treated with a moderate dose of resveratrol showed increased mitochondrial biogenesis and function, AMPK activation, and increased NAD(+) levels in skeletal muscle, whereas SIRT1 knockouts displayed none of these benefits. A mouse overexpressing SIRT1 mimicked these effects. A high dose of resveratrol activated AMPK in a SIRT1-independent manner, demonstrating that resveratrol dosage is a critical factor. Importantly, at both doses of resveratrol no improvements in mitochondrial function were observed in animals lacking SIRT1. Together these data indicate that SIRT1 plays an essential role in the ability of moderate doses of resveratrol to stimulate AMPK and improve mitochondrial function both in vitro and in vivo.     

The relative efficiency of the Hardy-Weinberg equilibrium-likelihood and the conditional on parental genotype-likelihood methods for candidate-gene association studies.

Selecting a control group that is perfectly matched for ethnic ancestry with a group of affected individuals is a major problem in studying the association of a candidate gene with a disease. This problem can be avoided by a design that uses parental data in place of nonrelated controls. Schaid and Sommer presented two new methods for the statistical analysis using this approach: (1) a likelihood method (Hardy-Weinberg equilibrium [HWE] method), which rests on the assumption that HWE holds, and (2) a conditional likelihood method (conditional on parental genotype [CPG] method) appropriate when HWE is absent. Schaid and Sommer claimed that the CPG method can be more efficient than the HWE method, even when equilibrium holds. It can be shown, however that in the equilibrium situation the HWE method is always more efficient than the CPG method. For a dominant disease, the differences are slim. But for a recessive disease, the CPG method requires a much larger sample size to achieve a prescribed power than the HWE method. Additionally, we show how the relative risks for the various candidate-gene genotypes can be estimated without relying on iterative methods. For the CPG method, we represent an asymptotic power approximation that is sufficiently precise for planning the sample size of an association study.     

Effects of Intermating Interval on Spermatophore Size and Sperm Number in the Simultaneously Hermaphroditic Land Snail Arianta arbustorum

We examined the effect of intermating interval on spermatophore size and number of sperm delivered in the simultaneously hermaphroditic land snail, Arianta arbustorum . Snails that remated after 6–7 d transferred smaller spermatophores which contained fewer sperm than snails that remated after eight and more days. This indicates that individuals of A. arbustorum need at least 8 d to completely replenish their sperm reserves after a successful copulation. We suggest that the interval between two copulations is also influenced by the energy costs of the long-lasting courtship behaviour with extensive mucus production.     

Effects of population subdivision and catastrophes on the persistence of a land snail metapopulation

We modeled the dynamics of a metapopulation of the land snail Arianta arbustorum in north-eastern Switzerland to investigate the effect of population subdivision on the persistence of a land snail metapopulation and to analyze the interaction between spatial factors, population subdivision, and catastrophes. We developed a spatially structured, stochastic, age-structured metapopulation model with field data from previous studies on the metapopulation in Switzerland and experimental and meteorological data. The model incorporated distance-dependent dispersal through stream banks, correlated environmental fluctuations, and catastrophes resulting from heavy rains. The results point to various complex interactions among factors involved in metapopulation dynamics and suggest that in some cases population subdivision may act to decrease threats from environmental fluctuations and catastrophes.     

Primary and quaternary structure of the catabolic ornithine carbamoyltransferase from Pseudomonas aeruginosa. Extensive sequence homology with the anabolic ornithine carbamoyltransferases of Escherichia coli

We have determined the complete nucleotide sequence of the arcB gene from Pseudomonas aeruginosa strain PAO and we have purified the arcB product, the catabolic ornithine carbamoyltransferase (EC 2.1.3.3), to apparent homogeneity from the same strain. The N-terminal amino acid sequence, the total amino acid composition and the subunit size of the purified enzyme were in agreement with nucleotide sequencing results, which predict a polypeptide of 336 amino acids (Mr 38,108). Crosslinking experiments suggest that the native enzyme (apparent Mr approx. 420,000) basically consists of a trimer aggregating to form nonamers or dodecamers. The arcB gene of P. aeruginosa had strong homology with the argF and argI genes which code for the anabolic ornithine carbamoyltransferase isoenzymes in Escherichia coli; 63% of the nucleotides and 57% of the amino acids were absolutely conserved in arcB and argF. This indicates a close evolutionary relationship between these genes although their products have different physiological functions in the cell. Under conditions of induction (energy depletion) the catabolic ornithine carbamoyltransferase represented greater than or equal to 10% of the total cellular protein. Like other highly expressed Pseudomonas genes, the arcB gene was found not to use seven codons which correspond to minor or weakly interacting tRNA species in E. coli.     

Exaggerated male forelegs are not more differentiated than wing morphology in two widespread sister species of black scavenger flies

Sexual selection represents a potent force that can drive rapid population differentiation in traits related to reproductive success. Hence, sexual traits are expected to show greater population divergence than non-sexual traits. We test this prediction by exploring patterns of morphological differentiation of the exaggerated fore femur (a male-specific sexual trait) and the wing (a non-sexual trait) among allopatric and sympatric populations of the widespread sister dung fly species Sepsis neocynipsea and Sepsis cynipsea (Diptera: Sepsidae). While both species occur in Eurasia, S. neocynipsea also abounds in North America, albeit previous studies suggest strong differentiation in morphology, behavior, and mating systems. To evaluate the degree of differentiation expected under neutrality between S. cynipsea, European S. neocynipsea, and North American S. neocynipsea, we genotyped 30 populations at nine microsatellite markers, revealing almost equal differentiation between and minor differentiation among geographic populations within the three lineages. Landmark-based analysis of 18 populations reared at constant 18 and 24°C in a laboratory common garden revealed moderate temperature-dependent phenotypic plasticity and significant heritable differentiation in size and shape of male forelegs and wings among iso-female lines of the three lineages. Following the biological species concept, there was weaker differentiation between cross-continental populations of S. neocynipsea relative to S. cynipsea, and more fore femur differentiation between the two species in sympatry versus allopatry (presumably due to character displacement). Contrary to expectation, wing morphology showed as much shape differentiation between evolutionary independent lineages as fore femora, providing no evidence for faster diversification of traits primarily engaged in mating.     

Experimental habitat fragmentation and invertebrate grazing in a herbaceous grassland species

A field experiment was conducted to examine the effects of habitat fragmentation on herbivore damage to individually tagged leaves of Betonica officinalis rosettes. Fragments of different size and corresponding control plots were established at three study sites in nutrient-poor calcareous grasslands in the northern Swiss Jura mountains. Leaf damage was recorded three times over the growing season (late spring, summer and early autumn). Five years after the initiation of the fragmentation, the density of rosettes did not differ between fragments and control plots. The number of leaves per rosette was higher in fragments than in control plots in summer but not in late spring and early autumn. The extent of leaf damage, expressed as proportion of leaf area removed by invertebrate herbivores, increased over the vegetation period. Leaf damage was greater in fragments than in control plots at two study sites, whereas the opposite (less strongly expressed) was found at the third site. Number of species and density (individuals per m²) of potential herbivores (gastropods and grasshoppers) were recorded in all fragments and control plots. Effects of fragmentation on the number of species and densities depended on plot size and differed between gastropods and grasshoppers. Leaf damage in fragments increased with increasing density of gastropods if the third site, which had lowest leaf damage, was excluded. Such a positive relationship was neither found in control plots nor for grasshopper densities. Thus, movement of gastropods in fragments was probably restricted which resulted in increased feeding pressure at least in two sites. However, even if our fragmentation experiment was well designed and replicated, the interpretation of these experimental results remains difficult because there was large site-to-site and seasonal variation.     

Hemoglobin tacoma — A β-chain variant

A hitherto unknown inherited hemoglobin variant, Hb Tacoma, was discovered in three healthy members of a family of European extraction.Hybridization experiments with canine hemoglobin indicated a structural abnormality in the -chain. The variant was therefore designated as Hb _{2 2} ^Tacoma. Separation of Hb Tacoma from Hb A could only be clearly achieved by starch grain electrophoresis in TEB buffer at pH 8.6–9.0, where Hb Tacoma moved more rapidly towards the anode than Hb A; gradient column chromatography on DEAE cellulose and CM-Sephadex achieved partial separation. The proportion of abnormal hemoglobin in the heterozygote amounted to 43 per cent of the total hemoglobin. Hb Tacoma was less heat resistant and became more rapidly denatured in 8 M urea solution than Hb A, Hb C, or Hb S.On thin-layer starch gel electrophoresis in TCB buffer at pH 8.6 Hb Tacoma was associated with an electrophoretically slow, benzidine-positive component, Hb Tacoma-slow. The exact biochemical nature of this minor component could not be determined, although a polymeric product of Hb Tacoma is suspected.Heterozygosity for Hb Tacoma is associated with a raised Hb A₂ level without evidence of -thalassemia.A preliminary report of Hb Tacoma was presented at the Annual Meeting of the American Society of Human Genetics, Boulder, Colorado, August, 1964, and at the Seventh Annual Meeting of the American Society of Hematology, November, 1964, Seattle, Washington (Blood, 24, 848 (1964)).     

Ultrastructure of Aplysia neurons having different degrees of light sensitivity.

The relationship between ultrastructure and photosensitivity of pigmented neurons of the abdominal ganglion of Aplysia californica was investigated using electron microscopy and electrophysiological methods. Four identified neurons of similar light microscopic appearance were examined; two are photoresponsive and two are not. Illumination hyperpolarizes both responsive neurons. One of them, R2, requires roughly 100 times greater light intensities than does the other, the ventral photoresponsive neuron (VPN), for similar responses. Two neurons lying adjacent to VPN and similar in appearance to VPN do not have measurable electrophysiological responses to even the highest light intensities. All four neurons contained lipochondria, pigmented organelles associated with the light response. Therefore the presence of these organelles is not the only requirement for light sensitivity in these neurons. Illumination appeared to increase the number of membranous lipochondria in both R2 and the ventral neurons, but only in R2 was this increase significant. Factors such as the concentration of lipochondria near the plasma membrane may affect quantitative aspects of the light response, but in the insensitive cells the lipochondria are apparently uncoupled from other factors required for the light response.