Cooperative control of translational fidelity by ribosomal proteins in Escherichia coli

Summary Two spontaneous mutants of Escherichia coli strain KMBL-146 selected for resistance to the aminoglycoside antibiotic neamine show severe restriction of amber suppressors in vivo. Purified ribosomes from the mutant strains exhibit low neamine-induced misreading in vitro and a decreased affinity for the related antibiotic streptomycin.Biochemical analysis shows that the mutants each have two modified 30S ribosomal proteins, S12 and S5. In agreement with these results, genetic analysis shows that two mutations are present, neither of which confers resistance to neamine by itself; the mutation located in gene rpxL (the structural gene for protein S12) confers streptomycin dependence but this dependence is suppressed in the presence of the second mutation, located in gene rpxE (the structural gene for protein S5).     

Acetyl groups in cell-wall preparations from higher plants

O-Acetyl groups were detected by i.r. spectroscopy in cell-wall preparations from grasses and other higher plants and their presence was confirmed chemically. The amounts present are likely to influence both the physical state of the cell-wall polysaccharides and also their digestion by enzymes.     

Phylogenetic incongruence in the Drosophila melanogaster species group

Drosophila melanogaster and its close relatives are used extensively in comparative biology. Despite the importance of phylogenetic information for such studies, relationships between some melanogaster species group members are unclear due to conflicting phylogenetic signals at different loci. In this study, we use twelve nuclear loci (eleven coding and one non-coding) to assess the degree of phylogenetic incongruence in this model system. We focus on two nodes: (1) the node joining the Drosophila erecta-Drosophila orena, Drosophila melanogaster-Drosophila simulans, and Drosophila yakuba-Drosophila teissieri lineages, and (2) the node joining the lineages leading to the melanogaster, takahashii, and eugracilis subgroups. We find limited evidence for incongruence at the first node; our data, as well as those of several previous studies, strongly support monophyly of a clade consisting of D. erecta-D. orena and D. yakuba-D. teissieri. By contrast, using likelihood based tests of congruence, we find robust evidence for topological incongruence at the second node. Different loci support different relationships among the melanogaster, takahashii, and eugracilis subgroups, and the observed incongruence is not easily attributable to homoplasy, non-equilibrium base composition, or positive selection on a subset of loci. We argue that lineage sorting in the common ancestor of these three subgroups is the most plausible explanation for our observations. Such lineage sorting may lead to biased estimation of tree topology and evolutionary rates, and may confound inferences of positive selection.     

Defining the roles of T cell membrane proteinase and CD44 in type 1 diabetes

Membrane type-1 matrix metalloproteinase (MT1-MMP) shedding of the signaling and adhesion CD44 receptor plays a significant role in stimulating cancer cells locomotion. Similarly, and unexpectedly, MT1-MMP-dependent shedding of CD44 plays an equally significant role in regulating the adhesion to the pancreatic vasculature and also in the concomitant transendothelial migration and intra-islet homing of the diabetogenic, cytotoxic, T cells. Inactivation of the T cell MT1-MMP functionality by clinically tested, synthetic inhibitors leads to an extended immobilization of the T killer cells on the pancreatic vasculature and, subsequently, to immunosuppression because of the cessation of the T cell transmigration and homing. Injections of insulin jointly with an MT1-MMP inhibitor stimulated the regeneration of functional, insulin-producing, beta-cells in acutely diseased non-obese diabetic (NOD) mice. After insulin injections were suspended and inhibitor injections continued, diabetic NOD mice maintained mild hyperglycemia and did not require further insulin injections for survival. Overall, these data provide a substantive mechanistic rationale for clinical trials of the inhibitors of MT1-MMP in human type 1 diabetes.     

Alzheimer's disease and non-demented high pathology control nonagenarians: comparing and contrasting the biochemistry of cognitively successful aging

The amyloid cascade hypothesis provides an economical mechanistic explanation for Alzheimer's disease (AD) dementia and correlated neuropathology. However, some nonagenarian individuals (high pathology controls, HPC) remain cognitively intact while enduring high amyloid plaque loads for decades. If amyloid accumulation is the prime instigator of neurotoxicity and dementia, specific protective mechanisms must enable these HPC to evade cognitive decline. We evaluated the neuropathological and biochemical differences existing between non-demented (ND)-HPC and an age-matched cohort with AD dementia. The ND-HPC selected for our study were clinically assessed as ND and possessed high amyloid plaque burdens. ELISA and Western blot analyses were used to quantify a group of proteins related to APP/Aβ/tau metabolism and other neurotrophic and inflammation-related molecules that have been found to be altered in neurodegenerative disorders and are pivotal to brain homeostasis and mental health. The molecules assumed to be critical in AD dementia, such as soluble or insoluble Aβ40, Aβ42 and tau were quantified by ELISA. Interestingly, only Aβ42 demonstrated a significant increase in ND-HPC when compared to the AD group. The vascular amyloid load which was not used in the selection of cases, was on the average almost 2-fold greater in AD than the ND-HPC, suggesting that a higher degree of microvascular dysfunction and perfusion compromise was present in the demented cohort. Neurofibrillary tangles were less frequent in the frontal cortices of ND-HPC. Biochemical findings included elevated vascular endothelial growth factor, apolipoprotein E and the neuroprotective factor S100B in ND-HPC, while anti-angiogenic pigment epithelium derived factor levels were lower. The lack of clear Aβ-related pathological/biochemical demarcation between AD and ND-HPC suggests that in addition to amyloid plaques other factors, such as neurofibrillary tangle density and vascular integrity, must play important roles in cognitive failure.     

Repellent plants provide affordable natural screening to prevent mosquito house entry in tropical rural settings--results from a pilot efficacy study

Sustained malaria control is underway using a combination of vector control, prompt diagnosis and treatment of malaria cases. Progress is excellent, but for long-term control, low-cost, sustainable tools that supplement existing control programs are needed. Conventional vector control tools such as indoor residual spraying and house screening are highly effective, but difficult to deliver in rural areas. Therefore, an additional means of reducing mosquito house entry was evaluated: the screening of mosquito house entry points by planting the tall and densely foliated repellent plant Lantana camara L. around houses. A pilot efficacy study was performed in Kagera Region, Tanzania in an area of high seasonal malaria transmission, where consenting families within the study village planted L. camara (Lantana) around their homes and were responsible for maintaining the plants. Questionnaire data on house design, socioeconomic status, malaria prevention knowledge, attitude and practices was collected from 231 houses with Lantana planted around them 90 houses without repellent plants. Mosquitoes were collected using CDC Light Traps between September 2008 and July 2009. Data were analysed with generalised negative binomial regression, controlling for the effect of sampling period. Indoor catches of mosquitoes in houses with Lantana were compared using the Incidence Rate Ratio (IRR) relative to houses without plants in an adjusted analysis. There were 56% fewer Anopheles gambiae s.s. (IRR 0.44, 95% CI 0.28-0.68, p<0.0001); 83% fewer Anopheles funestus s.s. (IRR 0.17, 95% CI 0.09-0.32, p<0.0001), and 50% fewer mosquitoes of any kind (IRR 0.50, 95% CI 0.38-0.67, p<0.0001) in houses with Lantana relative to controls. House screening using Lantana reduced indoor densities of malaria vectors and nuisance mosquitoes with broad community acceptance. Providing sufficient plants for one home costs US $1.50 including maintenance and labour costs, (30 cents per person). L. camara mode of action and suitability for mosquito control is discussed.     

Synthesis and evaluation of potent and selective MGL inhibitors as a glaucoma treatment

Monoacylglycerol lipase (MGL) inhibition provides a potential treatment approach to glaucoma through the regulation of ocular 2-arachidonoylglycerol (2-AG) levels and the activation of CB1 receptors. Herein, we report the discovery of new series of carbamates as highly potent and selective MGL inhibitors. The new inhibitors showed potent nanomolar inhibitory activity against recombinant human and purified rat MGL, were selective (>1000-fold) against serine hydrolases FAAH and ABHD6 and lacked any affinity for the cannabinoid receptors CB1 and CB2. Protein-based ¹H NMR experiments indicated that inhibitor 2 rapidly formed a covalent adduct with MGL with a residence time of about 6?h. This interconversion process “intrinsic reversibility” was exploited by modifications of the ligand’s size (length and bulkiness) to generate analogs with “tunable’ adduct residence time (τ). Inhibitor 2 was evaluated in a normotensive murine model for assessing intraocular pressure (IOP), which could lead to glaucoma, a major cause of blindness. Inhibitor 2 was found to decrease ocular pressure by ～4.5?mmHg in a sustained manner for at least 12?h after a single ocular application, underscoring the potential for topically-administered MGL inhibitors as a novel therapeutic target for the treatment of glaucoma.