N,N′-Olefin Functionalized Bis-Imidazolium Gold(I) Salt Is an Efficient Candidate to Control Keratitis-Associated Eye Infection

Keratitis treatment has become more complicated due to the emergence of bacterial or fungal pathogens with enhanced antibiotic resistance. The pharmaceutical applications of N-heterocyclic carbene complexes have received remarkable attention due to their antimicrobial properties. In this paper, the new precursor, 3,3′-(p-phenylenedimethylene) bis{1-(2- methyl-allyl)imidazolium} bromide (1a) and its analogous PF₆ salt (1b) were synthesized. Furthermore, silver(I) and gold(I) -N-heterocyclic carbene (NHC) complexes [Ag₂LBr₂/Au₂LBr₂; 2a/3a], [(Ag₂L₂)(PF₆)₂/(Au₂L₂)(PF₆)₂; 2b/3b] were developed from their corresponding ligands. All compounds were screened for their antimicrobial activities against multiple keratitis-associated human eye pathogens, including bacteria and fungi. Complexes 2a and 3a showed highest activity, and the effectiveness of 3a was also studied, focusing eradication of pathogen biofilm. Furthermore, the structures of 1a, 2a and 3b were determined using single crystal X-ray analysis, 2b and 3a were optimized theoretically. The mechanism of action of 3a was evaluated by scanning electron microscopy and docking experiments, suggesting that its target is the cell membrane. In summary, 3a may be helpful in developing antimicrobial therapies in patients suffering from keratitis-associated eye infections caused by multidrug-resistant pathogens.     

Diurnal Profiles of Blood Glucose in Relation to Time of Administration of Melatonin in Male Spotted Munia (Lonchura punctulata)

The study was aimed at demonstration of the effect of a single acute dose of melatonin (0.5 mg/ 100 g body wt.) on the diurnal profile of blood glucose in male spotted munia in relation to the administration of hormone at the onset of light (i.e., at 06.00 h) or at the onset of darkness (i.e., at 18.00 h) under natural photoperiodic (~12L : 12D) conditions. Blood samples from all birds belonging to the control, sham-control (administered only with the vehicle of hormone, i.e., ethanol-saline 1:9 v/v), and melatonin treated groups were collected at four time points, i.e. 06.00 h, 12.00 h, 18.00 h, and 24.00 h, in a 24 hour cycle. The blood glucose levels in control and sham-control birds showed marked variation with regard to the time of sampling, with a mid-day peak and morning nadir. Exogenous melatonin induced a significant alteration in this diurnal pattern of blood glucose with a marked variation in relation to the time of administration of melatonin. While morning administration of melatonin resulted in hypoglycemia at 12.00 h and 24.00 h and hyperglycemia at 18.00 h, the response to evening injection of melatonin was only hypoglycemic at 24.00 h leaving the glycemic values at other time-points almost unaltered compared to the blood glucose levels in control and sham-control munias. The results of this investigation demonstrate for the first time that a schedule of morning administration of melatonin induces a more broad range of variations in the blood glucose levels than a schedule of evening administration does.     

The molecular basis for antimicrobial activity of pore-forming cyclic peptides

The mechanism of action of antimicrobial peptides is, to our knowledge, still poorly understood. To probe the biophysical characteristics that confer activity, we present here a molecular-dynamics and biophysical study of a cyclic antimicrobial peptide and its inactive linear analog. In the simulations, the cyclic peptide caused large perturbations in the bilayer and cooperatively opened a disordered toroidal pore, 1–2 nm in diameter. Electrophysiology measurements confirm discrete poration events of comparable size. We also show that lysine residues aligning parallel to each other in the cyclic but not linear peptide are crucial for function. By employing dual-color fluorescence burst analysis, we show that both peptides are able to fuse/aggregate liposomes but only the cyclic peptide is able to porate them. The results provide detailed insight on the molecular basis of activity of cyclic antimicrobial peptides.     

Viscoelastic Behavior of Human Lamin A Proteins in the Context of Dilated Cardiomyopathy

Lamins are intermediate filament proteins of type V constituting a nuclear lamina or filamentous meshwork which lines the nucleoplasmic side of the inner nuclear membrane. This protein mesh provides a supporting scaffold for the nuclear envelope and tethers interphase chromosome to the nuclear periphery. Mutations of mainly A-type lamins are found to be causative for at least 11 human diseases collectively termed as laminopathies majority of which are characterised by aberrant nuclei with altered structural rigidity, deformability and poor mechanotransduction behaviour. But the investigation of viscoelastic behavior of lamin A continues to elude the field. In order to address this problem, we hereby present the very first report on viscoelastic properties of wild type human lamin A and some of its mutants linked with Dilated cardiomyopathy (DCM) using quantitative rheological measurements. We observed a dramatic strain-softening effect on lamin A network as an outcome of the strain amplitude sweep measurements which could arise from the large compliance of the quasi-cross-links in the network or that of the lamin A rods. In addition, the drastic stiffening of the differential elastic moduli on superposition of rotational and oscillatory shear stress reflect the increase in the stiffness of the laterally associated lamin A rods. These findings present a preliminary insight into distinct biomechanical properties of wild type lamin A protein and its mutants which in turn revealed interesting differences.     

Options for Optimal Coverage of Free C-Section Services for Poor Mothers in Indian State of Gujarat: Location Allocation Analysis Using GIS

Background

Gujarat, a western state of India, has seen a steep rise in the proportion of institutional deliveries over the last decade. However, there has been a limited access to cesarean section (C-Section) deliveries for complicated obstetric cases especially for poor rural women. C-section is a lifesaving intervention that can prevent both maternal and perinatal mortality. Poor women bear a disproportionate burden of maternal mortality, and lack of access to C-section, especially for these women, is an important contributor for high maternal and perinatal mortality in resource limited settings. To improve access for this underserved population in the context of inadequate public provision of emergency obstetric services, the state government of Gujarat initiated a public private partnership program called “Chiranjeevi Yojana” (CY) in 2005 to increase the number of facilities providing free C-section services. This study aimed to analyze the current availability of these services in three districts of Gujarat and to identify the best locations for additional service centres to optimize access to free C-section services using Geographic Information System technology.

Methodology

Supply and demand for obstetric care were calculated using secondary data from sources such as Census and primary data from cross-sectional facility survey. The study is unique in using primary data from facilities, which was collected in 2012–13. Information on obstetric beds and functionality of facilities to calculate supply was collected using pretested questionnaire by trained researchers after obtaining written consent from the participating facilities. Census data of population and birth rates for the study districts was used for demand calculations. Location-allocation model of ArcGIS 10 was used for analyses.

Results

Currently, about 50 to 84% of populations in all three study districts have access to free C-section facilities within a 20km radius. The model suggests that about 80–96% of the population can be covered for free C-section services with addition of 4–6 centres in critical but underserved regions. It was also suggested that upgrading of public sector facilities with minimal investment can improve the services.

Conclusion

This study highlights utility of Geographic Information System technology for planning service centres to optimize access to vital lifesaving procedure such as C-section. Although the location allocation methodology has been available for decades, it has been used sparsely by public health professionals. This paper makes an important contribution to the literature for use of the method for planning in resource limited settings.     

Mechanisms underlying the micron‐scale segregation of sterols and GM1 in live mammalian sperm

We demonstrate for the first time that a stable, micron‐scale segregation of focal enrichments of sterols exists at physiological temperature in the plasma membrane of live murine and human sperm. These enrichments of sterols represent microheterogeneities within this membrane domain overlying the acrosome. Previously, we showed that cholera toxin subunit B (CTB), which binds the glycosphingolipid, G_M1, localizes to this same domain in live sperm. Interestingly, the G_M1 undergoes an unexplained redistribution upon cell death. We now demonstrate that G_M1 is also enriched in the acrosome, an exocytotic vesicle. Transfer of lipids between this and the plasma membrane occurs at cell death, increasing G_M1 in the plasma membrane without apparent release of acrosomal contents. This finding provides corroborative support for an emerging model of regulated exocytosis in which membrane communications might occur without triggering the “acrosome reaction.” Comparison of the dynamics of CTB‐bound endogenous G_M1 and exogenous BODIPY–G_M1 in live murine sperm demonstrate that the sub‐acrosomal ring (SAR) functions as a specialized diffusion barrier segregating specific lipids within the sperm head plasma membrane. Our data show significant differences between endogenous lipids and exogenous lipid probes in terms of lateral diffusion. Based on these studies, we propose a hierarchical model to explain the segregation of this sterol‐ and G_M1‐enriched domain in live sperm, which is positioned to regulate sperm fertilization competence and mediate interactions with the oocyte. Moreover, our data suggest potential origins of subtypes of membrane raft microdomains enriched in sterols and/or G_M1 that can be separated biochemically. J. Cell. Physiol. 218: 522–536, 2009. © 2008 Wiley‐Liss, Inc.