Coexisting role of fasting or feeding and dietary lipids in the control of gene expression of enzymes involved in the synthesis of saturated, monounsaturated and polyunsaturated fatty acids

In the liver, maintaining lipid homeostasis is regulated by physiological and exogenous factors. These lipids are synthesized by Fasn, elongases and desaturases. Interactions in an organism among these factors are quite complex and, to date, relatively little is known about them. The aim of this study was to evaluate the coexisting role of physiological (insulin, fasting and feeding) and exogenous (dietary lipids) factors in the control of gene expression of Fasn, elongases and desaturases via Srebf-1c in liver from rats. Gene expression of encoding enzymes for fatty acid synthesis and fatty acid composition was evaluated in liver from rats in fasting and feeding (at 30, 60, 90 and 120 min after feeding) when food intake (adequate or high-lipid diet) was synchronized to a restricted period of 7h. Fasn, Scd and Fads2 were induced during 120 min after initial feeding in both dietary groups. This induction may be activated in part by insulin via Srebf-1c. Also, we showed for the first time that Elovl7 may be regulated by insulin and dietary lipids. The failure to synthesize saturated and monounsaturated fatty acids is consistent with a downregulation of Fasn and Scd, respectively, by dietary lipids. A higher content of LC-PUFAs was observed due to a high expression of Elovl2 and Elovl5, although Fads2 was suppressed by dietary lipids. Therefore, elongases may have a mechanism that is Srebf-1c-independent. This study suggests that a high-lipid diet triggers, during 120 min after initial feeding, a tight coordination among de novo lipogenesis, elongation, and desaturation and may not always be regulated by Srebf-1c. Finally, upregulation by feeding (insulin) of Fasn, Scd, Fads2 and Srebf-1c is insufficient to compensate for the inhibitory effect of dietary lipids.     

Dental microwear and stable isotopes inform the paleoecology of extinct hominins

Determining the diet of an extinct species is paramount in any attempt to reconstruct its paleoecology. Because the distribution and mechanical properties of food items may impact postcranial, cranial, mandibular, and dental morphologies related to their procurement, ingestion, and mastication, these anatomical attributes have been studied intensively. However, while mechanical environments influence skeletal and dental features, it is not clear to what extent they dictate particular morphologies. Although biomechanical explanations have been widely applied to extinct hominins in attempts to retrodict dietary proclivities, morphology may say as much about what they were capable of eating, and perhaps more about phylogenetic history, than about the nature of the diet. Anatomical attributes may establish boundary limits, but direct evidence left by the foods that were actually (rather than hypothetically) consumed is required to reconstruct diet. Dental microwear and the stable light isotope chemistry of tooth enamel provide such evidence, and are especially powerful when used in tandem. We review the foundations for microwear and biogeochemistry in diet reconstruction, and discuss this evidence for six early hominin species (Ardipithecus ramidus, Australopithecus anamensis, Au. afarensis, Au. africanus, Paranthropus robustus, and P. boisei). The dietary signals derived from microwear and isotope chemistry are sometimes at odds with inferences from biomechanical approaches, a potentially disquieting conundrum that is particularly evident for several species.     

A profile of native integration sites used by φC31 integrase in the bovine genome

The Streptomyces phage φC31 integrase can efficiently target attB-bearing transgenes to endogenous pseudo attP sites within mammalian genomes.To better understand the activity ofφC31 integrase in the bovine genome,DNA sequences of 44 integration events were analyzed,and 32 pseudo attP sites were identified.The majority of these sites share a sequence motif that contains inverted repeats and has similarities to wild-type attP site.Genomic DNA flanking these sites typically contained repetitive sequence elements,such as short and long interspersed repetitive elements.These sequence features indicate that DNA sequence recognition plays an important role in guidingφC31-mediated site-specific integration.In addition,BF27 integration hotspot sites were identified in the bovine genome, which accounted for 13.6%of all isolated integration events and mapped to an intron of the deleted in liver cancer 1(DLC1) gene.Also we found that the pseudo attP sites in the bovine genome had other features in common with those in the human genome.This study represents the first time that the sequence features of pseudo attP sites in the bovine genome were analyzed.We conclude that this site-specific integrase system has great potential for applied modifications of the bovine genome.     

Biogeochemical and craniometric investigation of dietary ecology, niche separation, and taxonomy of Plio-Pleistocene cercopithecoids from the Makapansgat Limeworks

Three sympatric fossil cercopithecoid genera (Cercopithecoides, Parapapio, and Theropithecus) occur in Members 3 and 4 at the Makapansgat Limeworks hominin locality, South Africa, and their presence in a single ecosystem suggest a certain degree of ecological and/or dietary differentiation between taxa. Here, we explore the extent of dietary niche separation amongst these taxa using stable isotope (13C/12C, 18O/16O) and trace-element (Sr, Ba, Ca) analyses of fossil tooth enamel. In particular we searched for evidence of subtle niche separation between the more closely related, morphologically similar taxa of the genus Parapapio, as uncertainties exist around their taxonomy and taxonomic identification. Given these uncertainties, craniometric analyses were also performed to ground the dietary interpretations in a morphological context. The results found no clear taxonomic signal in the craniometric data for the Parapapio sample, and further indicate that this sample was no more variable morphologically than a single, geographically circumscribed, extant chacma baboon sample. In contrast, two overlapping dietary ecologies were found within this same Makapansgat Parapapio sample. Additionally, two widely differing dietary ecologies were found within the Cercopithecoides williamsi sample, while results for Theropithecus darti indicate a predominantly C4 diet. Hence, although biogeochemical dietary indicators point towards distinct dietary ecologies within and between fossil genera at Makapansgat, within the genus Parapapio disjunctions exist between the dietary categories and the taxonomic assignment of specimens.     

Ligand and metal X-ray absorption in transition metal complexes

The ligand K edges and metal L edges of transition metal complexes are discussed within the perspective of recent progress in calculations on bulk transition metal oxides. Similarities and differences between bulk transition metal systems and coordination complexes are discussed. It is argued that the core hole effect reduces the amount of ligand p-states in the 3d-band (the β² value) by approximately 10-20%. It is suggested that matrix elements do not have to be included in XAS calculations if one calculates the projected DOS in the area of the core state radius. In case of metal L edge spectra, the additional effects of multiplets and charge transfer are discussed and compared with DFT calculations.     

<Emphasis Type="Italic">Helitron</Emphasis> mediated amplification of cytochrome P450 monooxygenase gene in maize

The mass movement of gene sequences by Helitrons has significantly contributed to the lack of gene collinearity reported between different maize inbred lines. However, Helitron captured-genes reported to date represent truncated versions of their progenitor genes. In this report, we provide evidence that maize CYP72A27-Zm gene represents a cytochrome P450 monooxygenase (P450) gene recently captured by a Helitron and transposed into an Opie-2 retroposon. The four exons of the CYP72A27 gene contained within the element contain a putative open reading frame (ORF) for 428 amino acid residues. We provide evidence that Helitron captured CYP72A27-Zm is transcribed. To identify the progenitor gene and the evolutionary time of capture, we searched the plant genome database and discovered other closely related CYP72A27-Zm genes in maize and grasses. Our analysis indicates that CYP72A27-Zm represents an almost complete copy of maize CYP72A26-Zm gene captured by a Helitron about 3.1 million years ago (mya). The Helitron-captured gene then duplicated twice, approximately 1.5-1.6 mya giving rise to CYP72A36-Zm and CYP72A37-Zm. These data provide evidence that Helitrons can capture and mobilize intact genes that are transcribed and potentially encode biologically relevant proteins.     

Patchy distribution of flexible genetic elements in bacterial populations mediates robustness to environmental uncertainty

The generation and maintenance of genetic variation seems to be a general ecological strategy of bacterial populations. Thereby they gain robustness to irregular environmental change, which is primarily the result of the dynamic evolution of biotic interactions. A benefit of maintaining population heterogeneity is that only a fraction of the population has to bear the cost of not (yet) beneficial deviation. On evolutionary time frames, an added value of the underlying mechanisms is evolvability, i.e. the heritable ability of an evolutionary lineage to generate and maintain genetic variants that are potentially adaptive in the course of evolution. Horizontal gene transfer is an important mechanism that can lead to differences between individuals within bacterial populations. Broad host-range plasmids foster this heterogeneity because they are typically present in only a fraction of the population and provide individual cells with genetic modules newly acquired from other populations or species. We postulate that the benefit of robustness on population level could balance the cost of transfer and replication functions that plasmids impose on their hosts. Consequently, mechanisms that make a subpopulation conducive to specific conjugative plasmids may have evolved, which could explain the persistence of even cryptic plasmids that do not encode any traits.