On the lack of formation of l-(+)-3-hydroxybutyrate by liver

The terminal carbon of palmitic acid, traced with ¹⁴C, is preferentially incorporated into carbon 4 of hydroxybutyrate formed by hepatocytes and perfused livers from 18- to 19-day-old rats and perfused livers from fasted adult rats. However, ¹⁴C from [13-¹⁴C]palmitic acid is incorporated into carbon 1 of the hydroxybutyrate to the same extent as any one of the first 12 carbons of palmitic acid as assessed with [1-¹⁴C]palmitic acid and [6-¹⁴C]palmitic acid. Therefore, the hydroxybutyrate is formed via hydroxymethylglutaryl-CoA, i.e., it is in the d configuration, and hydrolysis of l-hydroxybutyryl-CoA, the intermediate in the β oxidation of the palmitate, does not occur. Further, a negligible amount of ¹⁴C remains in hydroxybutyrate formed from ¹⁴C-labeled palmitic acid by isolated hepatocytes and perfused livers from the young rats, when the hydroxybutyrate is treated with d-(?)-3-hydroxybutyrate dehydrogenase to convert the d isomer to acetoacetate. Thus, l-(+)-3-hydroxybutyrate is not produced by rat liver as assessed using these preparations.     

Effect of losartan and enalapril on cognitive deficit caused by Goldblatt induced hypertension

The present study was designed to evaluate the learning and memory, in an altered physiological state associated with increased blood pressure and activated renin angiotensin system in Wistar rats. The role of angiotensin in cognitive function was assessed by treatment with angiotensin converting enzyme (ACE) inhibitor enalapril (2 mg/kg), angiotensin 1 receptor (AT(1)) antagonist losartan (5 mg/kg) and their combination. The experimental renal hypertension was induced by the method of Goldblatt. Learning and memory was assessed using the radial arm maze test. Acetylcholine esterase (AChE) levels in the pons medulla, hippocampus, striatum and frontal cortex were measured as a cholinergic marker of learning and memory. Results indicate that in comparison to normotensive rats, renal hypertensive rats committed significantly higher number of errors and took more trials and days to learn the radial arm maze learning and exhibited memory deficit in the radial arm maze retrieval after two weeks of retention interval, indicating impaired acquisition and memory. Treatment with enalapril, losartan and their combination attenuated the observed memory deficits indicating a possible role of renin angiotensin system in cognitive function. AChE level was reduced in hippocampus and frontal cortex of renal hypertensive rats which could be attributed to the observed memory deficit in hypertensive rats. It can be concluded that, renal hypertensive rats had a poor acquisition, retrieval of the learned behavior, perhaps a possible disturbance in memory consolidation process and that this state was reversed with ACE inhibitor enalapril and AT 1 receptor antagonist losartan.     

Macromolecules that prefer their membranes curvy

Understanding the mechanisms that underlie the organization of bacterial cells has become a significant challenge in the field of bacterial cytology. Of specific interest are early macromolecular sorting events that establish cellular non‐uniformity and provide chemical landmarks for later localization events. In this review, we will examine specific examples of lipids and proteins that appear to exploit differences in membrane curvature to drive their localization to particular regions of a bacterial cell. We will also discuss the physical limits of curvature‐mediated localization within bacteria, and the use of modelling to infer biophysical properties of curvature‐sensing macromolecules.     

A quantitative structure–activity relationship study on some aromatic/heterocyclic sulfonamides and their charged derivatives acting as carbonic anhydrase inhibitors

A quantitative structure–activity relationship (QSAR) study is made on a series of aromatic/heterocyclic sulfonamides and their charged derivatives acting as carbonic anhydrase (CA) inhibitors. These compounds were studied by Scozzafava et al. (J. Med. Chem. 2000; 43: 292) for the selective inhibition of CAs—sulfonamides generally do not discriminate between different CA isozymes and hence exhibit many undesirable side effects when used as drugs against a particular disease. In this communication, an attempt has been made to investigate the physicochemical and structural properties that can make them selective for a given CA isozyme. Based on in vitro data reported by Scozzafava et al. against two cytosolic isozymes and one membrane-bound isozyme, the QSAR study has shown that uncharged compounds cannot be made selective for cytosolic or membrane-bound isozyme since in both the cases the compounds appear to follow the same mechanism of inhibition. However, for the charged compounds the polarizability of the molecule seems to greatly favor the inhibition of the membrane-bound enzyme, and hence they can be made selective for this enzyme by enhancing their polarizability, which is found to play no role in the inhibition of cytosolic enzymes.     

The interactome of a PTB domain-containing adapter protein, Odin, revealed by SILAC

Signal transduction pathways are tightly controlled by positive and negative regulators. We have previously identified Odin (also known as ankyrin repeat and sterile alpha motif domain-containing 1A; gene symbol ANKS1A) as a negative regulator of growth factor signaling; however, the mechanisms through which Odin regulates these pathways remain to be elucidated. To determine how Odin negatively regulates growth factor signaling, we undertook a proteomic approach to systematically identify proteins that interact with Odin using the SILAC strategy. In this study, we identified 18 molecules that were specifically associated in a protein complex with Odin. Our study established that the complete family of 14-3-3 proteins occur in a protein complex with Odin, which is also supported by earlier reports that identified a few members of the 14-3-3 family as Odin interactors. Among the novel protein interactors of Odin were CD2-associated protein, SH3 domain kinase binding protein 1 and DAB2 interacting protein. We confirmed 8 of the eighteen interactions identified in the Odin protein complex by co-immunoprecipitation experiments. Finally, a literature-based network analysis revealed that Odin interacting partners are involved in various cellular processes, some of which are key molecules in regulating receptor endocytosis.     

Role of heterozygous APC mutation in niche succession and initiation of colorectal cancer--a computational study

Mutations in the adenomatous polyposis coli (APC) gene are found in most colorectal cancers. They cause constitutive activation of proliferative pathways when both alleles of the gene are mutated. However studies on individuals with familial adenomatous polyposis (FAP) have shown that a single mutated APC allele can also create changes in the precancerous colon crypt, like increased number of stem cells, increased crypt fission, greater variability of DNA methylation patterns, and higher somatic mutation rates. In this paper, using a computational model of colon crypt dynamics, we evolve and investigate a hypothesis on the effect of heterozygous APC mutation that explains these different observations. Based on previous reports and the results from the computational model we propose the hypothesis that heterozygous APC mutation has the effect of increasing the chances for a stem cell to divide symmetrically, producing two stem cell daughters. We incorporate this hypothesis into the model and perform simulation experiments to investigate the consequences of the hypothesis. Simulations show that this hypothesis links together the changes in FAP crypts observed in previous studies. The simulations also show that an APC(+/-) stem cell gets selective advantages for dominating the crypt and progressing to cancer. This explains why most colon cancers are initiated by APC mutation. The results could have implications for preventing or retarding the onset of colon cancer in people with inherited or acquired mutation of one APC allele. Experimental validation of the hypothesis as well as investigation into the molecular mechanisms of this effect may therefore be worth undertaking.     

Differential Targeting of Viral Components by CD4+ versus CD8+ T Lymphocytes in Dengue Virus Infection

Dengue virus (DENV) is the principal arthropod-borne viral pathogen afflicting human populations. While repertoires of antibodies to DENV have been linked to protection or enhanced infection, the role of T lymphocytes in these processes remains poorly defined. This study provides a comprehensive overview of CD4⁺ and CD8⁺ T cell epitope reactivities against the DENV 2 proteome in adult patients experiencing secondary DENV infection. Dengue virus-specific T cell responses directed against an overlapping 15mer peptide library spanning the DENV 2 proteome were analyzed ex vivo by enzyme-linked immunosorbent spot assay, and recognition of individual peptides was further characterized in specific T cell lines. Thirty novel T cell epitopes were identified, 9 of which are CD4⁺ and 21 are CD8⁺ T cell epitopes. We observe that whereas CD8⁺ T cell epitopes preferentially target nonstructural proteins (NS3 and NS5), CD4⁺ epitopes are skewed toward recognition of viral components that are also targeted by B lymphocytes (envelope, capsid, and NS1). Consistently, a large proportion of dengue virus-specific CD4⁺ T cells have phenotypic characteristics of circulating follicular helper T cells (CXCR5 expression and production of interleukin-21 or gamma interferon), suggesting that they are interacting with B cells in vivo. This study shows that during a dengue virus infection, the protein targets of human CD4⁺ and CD8⁺ T cells are largely distinct, thus highlighting key differences in the immunodominance of DENV proteins for these two cell types. This has important implications for our understanding of how the two arms of the human adaptive immune system are differentially targeted and employed as part of our response to DENV infection.