Glucose and amino acid metabolism in chick telencephalon slices: Changes with incubation conditions and animals' development

Glucose and amino acid metabolism in 1- and 30-day-old chick telencephalon slices was studied in two incubation media in the presence or in the absence of a continuous oxygenation. Medium 1 has a composition and a tonicity similar to cerebrospinal fluid, medium 2 is hypertonic and does not contain any K⁺ ions. The incorporation of glucose carbon into amino acids and the distribution of radioactivity between the different amino acids are close to the ones observed in the chick brain in vivo only when the slices are incubated in medium 1, with oxygen at 30 days and without oxygen for the 1-day-old chick. It also appears that if oxygenation is necessary for incubation of mature brain tissue in vitro, the absence of the medium oxygenation is more suitable for the study of glucose metabolism in 1-day-old chick brain slices.     

Trabecular architecture and joint loading of the proximal humerus in extant hominoids,Ateles, and Australopithecus africanus

Objectives

Several studies have investigated potential functional signals in the trabecular structure of the primate proximal humerus but with varied success. Here, we apply for the first time a “whole‐epiphyses” approach to analysing trabecular bone in the humeral head with the aim of providing a more holistic interpretation of trabecular variation in relation to habitual locomotor or manipulative behaviors in several extant primates and Australopithecus africanus.

Materials and methods

We use a “whole‐epiphysis” methodology in comparison to the traditional volume of interest (VOI) approach to investigate variation in trabecular structure and joint loading in the proximal humerus of extant hominoids, Ateles and A. africanus (StW 328).

Results

There are important differences in the quantification of trabecular parameters using a “whole‐epiphysis” versus a VOI‐based approach. Variation in trabecular structure across knuckle‐walking African apes, suspensory taxa, and modern humans was generally consistent with predictions of load magnitude and inferred joint posture during habitual behaviors. Higher relative trabecular bone volume and more isotropic trabeculae in StW 328 suggest A. africanus may have still used its forelimbs for arboreal locomotion.

Discussion

A whole‐epiphysis approach to analysing trabecular structure of the proximal humerus can help distinguish functional signals of joint loading across extant primates and can provide novel insight into habitual behaviors of fossil hominins.

     

Possible role of a short extra loop of the long-chain flavodoxin from Azotobacter chroococcum in electron transfer to nitrogenase: Complete 1H, 15N and 13C backbone assignments and secondary solution structure of the flavodoxin

Summary The ¹H, ¹⁵N and ¹³C backbone and ¹H and ¹³C beta resonance assignments of the long-chain flavodoxin from Azotobacter chroococcum (the 20-kDa nifF product, flavodoxin-2) in its oxidized form were made at pH 6.5 and 30°C using heteronuclear multidimensional NMR spectroscopy. Analysis of the NOE connectivities, together with amide exchange rates, ³J_Hn_H coupling constants and secondary chemical shifts, provided extensive solution secondary structure information. The secondary structure consists of a five-stranded parallel -sheet and five -helices. One of the outer regions of the -sheet shows no regular extended conformation, whereas the outer strand 4/6 is interrupted by a loop, which is typically observed in long-chain flavodoxins. Two of the five -helices are nonregular at the N-terminus of the helix. Loop regions close to the FMN are identified. Negatively charged amino acid residues are found to be mainly clustered around the FMN, whereas a cluster of positively charged residues is located in one of the -helices. Titration of the flavodoxin with the Fe protein of the A. chroococcum nitrogenase enzyme complex revealed that residues Asn¹¹, Ser⁶⁸ and Asn⁷² are involved in complex formation between the flavodoxin and Fe protein. The interaction between the flavodoxin and the Fe protein is influenced by MgADP and is of electrostatic nature.Abbreviations SQ semiquinone - FMN riboflavin 5-monophosphate; nif, nitrogen fixation - TSP 3-(trimethylsilyl)propionate sodium salt - DSS 2,2-dimethyl-2-silapentane-5-sulfonate sodium salt Supplementary Material is available on request, comprising a Materials and Methods section for the expression and purification of the A. chroococcum flavodoxin, a Table S1 containing the parameters of the titration of A. chroococcum flavodoxin with the Fe protein, and a Table S2 containing the ¹⁵N, H^N, ¹³C, ¹H, ¹³C, ¹H and ¹³CO chemical shifts.To whom correspondence should be addressed.     

Building an HIV data mashup using Bio2RDF

We present an update to the Bio2RDF Linked Data Network, which now comprises ～30 billion statements across 30 data sets. Significant changes to the framework include the accommodation of global mirrors, offline data processing and new search and integration services. The utility of this new network of knowledge is illustrated through a Bio2RDF-based mashup with microarray gene expression results and interaction data obtained from the HIV-1, Human Protein Interaction Database (HHPID) with respect to the infection of human macrophages with the human immunodeficiency virus type 1 (HIV-1).     

Angiotensin-converting enzyme inhibitor captopril prevents volume overload cardiomyopathy in experimental chronic aortic valve regurgitation

The efficacy of angiotensin-converting enzyme inhibitors (ACEIs) in the treatment of chronic aortic regurgitation (AR) is not well established and remains controversial. The mechanisms by which ACEIs may protect against left-ventricular (LV) volume overload are not well understood, and clinical trials performed until now have yielded conflicting results. This study was therefore performed to assess the effectiveness of two different doses of the ACEI captopril in a rat model of chronic AR. We compared the effects of a 6-month low-dose (LD) (25 mg/kg) or higher dose (HD) (75 mg/kg) treatment with captopril on LV function and hypertrophy in Wistar rats with severe AR. Untreated animals developed LV eccentric hypertrophy and systolic dysfunction. LD treatment did not prevent hypertrophy and provided modest protection against systolic dysfunction. HD treatment preserved LV systolic function and dimensions and tended to slow hypertrophy. The cardiac index remained high and similar among all AR groups, treated or not. Tissue renin-angiotensin system (RAS) analysis revealed that ACE activity was increased in the LVs of AR animals and that only HD treatment significantly decreased angiotensin II receptor mRNA levels. Fibronectin expression was increased in the LV or AR animals, but HD treatment almost completely reversed this increase. The ACE inhibitor captopril was effective at high doses in this model of severe AR. These effects might be related to the modulation of tissue RAS and the control of fibrosis.     

Effect of obesity on high-density lipoprotein metabolism

Reduced levels of high-density lipoproteins (HDL) in non-obese and obese states are associated with increased risk for the development of coronary artery disease. Therefore, it is imperative to determine the mechanisms responsible for reduced HDL in obese states and, conversely, to examine therapies aimed at increasing HDL levels in these individuals. This paper examines the multiple causes for reduced HDL in obese states and the effect of exercise and diet--two non-pharmacologic therapies--on HDL metabolism in humans. In general, the concentration of HDL-cholesterol is adversely altered in obesity, with HDL-cholesterol levels associated with both the degree and distribution of obesity. More specifically, intra-abdominal visceral fat deposition is an important negative correlate of HDL-cholesterol. The specific subfractions of HDL that are altered in obese states include the HDL2, apolipoprotein A-I, and pre-beta1 subfractions. Decreased HDL levels in obesity have been attributed to both an enhancement in the uptake of HDL2 by adipocytes and an increase in the catabolism of apolipoprotein A-I on HDL particles. In addition, there is a decrease in the conversion of the pre-beta1 subfraction, the initial acceptor of cholesterol from peripheral cells, to pre-beta2 particles. Conversely, as a means of reversing the decrease in HDL levels in obesity, sustained weight loss is an effective method. More specifically, weight loss achieved through exercise is more effective at raising HDL levels than dieting. Exercise mediates positive effects on HDL levels at least partly through changes in enzymes of HDL metabolism. Increased lipid transfer to HDL by lipoprotein lipase and reduced HDL clearance by hepatic triglyceride lipase as a result of endurance training are two important mechanisms for increases in HDL observed from exercise.     

Sterols have higher affinity for sphingomyelin than for phosphatidylcholine bilayers even at equal acyl-chain order

The interaction between cholesterol and phospholipids in bilayer membranes is important for the formation and maintenance of membrane structure and function. However, cholesterol does not interact favorably with all types of phospholipids and, for example, prefers more ordered sphingomyelins (SMs) over phosphatidylcholines (PCs). The reason for this preference is not clear. Here we have studied whether acyl-chain order could be responsible for the preferred sterol interaction with SMs. Acyl-chain order was deduced from diphenylhexatriene anisotropy and from the deuterium order parameter obtained by ²H-NMR on bilayers made from either 14:0/14:0_(d27)-PC, or 14:0_(d27)-SM. Sterol/phospholipid interaction was determined from sterol bilayer partitioning. Cholestatrienol (CTL) was used as a fluorescence probe for cholesterol, because its relative membrane partitioning is similar to cholesterol. When CTL was allowed to reach equilibrium partitioning between cyclodextrins and unilamellar vesicles made from either 14:0/14:0-PC or 14:0-SM, the molar-fraction partitioning coefficient (K_x) was approximately twofold higher for SM bilayers than for PC bilayers. This was even the case when the temperature in the SM samples was raised to achieve equal acyl-chain order, as determined from 1,6-diphenyl-1,3,5-hexatriene (DPH) anisotropy and the deuterium order parameter. Although the K_x did increase with acyl-chain order, the higher K_x for SM bilayers was always evident. At equal acyl-chain order parameter (DPH anisotropy), the K_x was also higher for 14:0-SM bilayers than for bilayers made from either 14:0/15:0-PC or 15:0-/14:0-PC, suggesting that minor differences in chain length or molecular asymmetry are not responsible for the difference in K_x. We conclude that acyl-chain order affects the bilayer affinity of CTL (and thus cholesterol), but that it is not the cause for the preferred affinity of sterols for SMs over matched PCs. Instead, it is likely that the interfacial properties of SMs influence and stabilize interactions with sterols in bilayer membranes.     

Influence of RT-qPCR primer position on EGFR interference efficacy in lung cancer cells

Background  

Real-time quantitative RT-PCR (RT-qPCR) is a "gold" standard for measuring steady state mRNA levels in RNA interference assays. The knockdown of the epidermal growth factor receptor (EGFR) gene with eight individual EGFR small interfering RNAs (siRNAs) was estimated by RT-qPCR using three different RT-qPCR primer sets.