Effects of Growth Solutions Ageing Time to the Formation of Gold Nanorods via Two-Step Approach for Plasmonic Applications

Plasmonics - We demonstrate the structural reorganization of gold nanorods (GNRs) that could fine-tune localized surface plasmon resonance (LSPR) by using modified wet chemical synthesis on the...     

Aphid population abundance and pestiferous effect on various bean plant species

The population abundance, infestation, and harmful effects of the aphid Aphis craccivora Koch (Hemiptera: Aphididae) were studied on four bean plant species, namely the country bean (Lablab purpureus var. BARI Seem 1), the yard‐long bean (Vigna sesquipedalis var. BARI Borboti 1), the hyacinth bean (Dolichos lablab var. BARI Seem 6), and the bush bean (Phaseolus vulgaris var. BARI Jar Seem 3). Aphid abundance and infestation on the leaves, inflorescences, flowers, and pods differed significantly among the bean plant species, with P. vulgaris and V. sesquipedalis having the lowest and highest results, respectively. Aphid severity grade and the number of trichomes of the bean plant species were negatively correlated. The duration of the growth stages among the bean plant species were significantly different, with V. sesquipedalis having the shortest durations. Aphid abundance and infestation significantly affected the physical and phytochemical characteristics of the bean plant species. The highest reduction of number of leaves, flower inflorescences, and pod inflorescences per plant, and moisture and chlorophyll content in the leaves was found in L. purpureus. The results for V. sesquipedalis revealed the highest reduction in plant height, seed weight, and pH, while those of D. lablab showed the highest reduction in leaf area.     

Mutation rate dynamics reflect ecological change in an emerging zoonotic pathogen

Mutation rates vary both within and between bacterial species, and understanding what drives this variation is essential for understanding the evolutionary dynamics of bacterial populations. In this study, we investigate two factors that are predicted to influence the mutation rate: ecology and genome size. We conducted mutation accumulation experiments on eight strains of the emerging zoonotic pathogen Streptococcus suis. Natural variation within this species allows us to compare tonsil carriage and invasive disease isolates, from both more and less pathogenic populations, with a wide range of genome sizes. We find that invasive disease isolates have repeatedly evolved mutation rates that are higher than those of closely related carriage isolates, regardless of variation in genome size. Independent of this variation in overall rate, we also observe a stronger bias towards G/C to A/T mutations in isolates from more pathogenic populations, whose genomes tend to be smaller and more AT-rich. Our results suggest that ecology is a stronger correlate of mutation rate than genome size over these timescales, and that transitions to invasive disease are consistently accompanied by rapid increases in mutation rate. These results shed light on the impact that ecology can have on the adaptive potential of bacterial pathogens.     

Ovariectomy augments pressure overload-induced hypertrophy associated with changes in Akt and nitric oxide synthase signaling pathways in female rats

To elucidate the molecular mechanism underlying estrogen-mediated cardioprotection in left ventricular (LV) hypertrophy and remodeling, we analyzed myocardial hypertrophy as well as cardiac function and hypertrophy-related protein expression in ovariectomized, aortic-banded rats. Wistar rats subjected to bilateral ovariectomy (OVX) were further treated with abdominal aortic stenosis. Effects on LV morphology and function were assessed using echocardiography, and expression of protein levels was determined by Western blot analysis. The heart-to-body weight ratio was most significantly increased in the OVX-pressure overload (PO) group compared with the OVX group and in the PO group compared with sham. The LV weight-to-body weight ratio was also significantly increased in the OVX-PO group compared with the OVX group and in the PO group compared with sham. The most significant increases in LV end diastolic pressure, LV developed pressure, and +/-dp/dt(max) were observed in the OVX-PO group compared with the OVX group and represent compensatory phenotypes against hypertrophy. Both endothelial nitric oxide (eNOS) synthase expression and activity was markedly reduced in the OVX-PO group, and protein kinase B (Akt) activity was largely attenuated. Marked breakdown of dystrophin was also seen in hearts of OVX-PO groups. Finally, significantly increased mortality was observed in the OVX-PO group following chronic isoproterenol administration. Our results demonstrate that rats subjected to ovariectomy are unable to compensate for hypertrophy, showed deteriorated heart function, and demonstrated increased mortality. Simultaneous impairment of eNOS and Akt activities and reduced dystrophin by ovariectomy likely contribute to cardiac decompensation during PO-induced hypertrophy in ovariectomized rats.     

La(3+) and Gd(3+) induce shape change of giant unilamellar vesicles of phosphatidylcholine

Lanthanides such as La(3+) and Gd(3+) are well known to have large effects on the function of membrane proteins such as mechanosensitive ionic channels and voltage-gated sodium channels, and also on the structure of phospholipid membranes. In this report, we have investigated effects of La(3+) and Gd(3+) on the shape of giant unilamellar vesicle (GUV) of dioleoylphosphatidylcholine (DOPC-GUV) and GUV of DOPC/cholesterol by the phase-contrast microscopy. The addition of 10-100 microM La(3+) (or Gd(3+)) through a 10-microm diameter micropipette near the DOPC-GUV (or DOPC/cholesterol-GUV) triggered several kinds of shape changes. We have found that a very low concentration (10 microM) of La(3+) (or Gd(3+)) induced a shape change of GUV such as the discocyte via stomatocyte to inside budded shape transformation, the two-spheres connected by a neck to prolate transformation, and the pearl on a string to cylinder (or tube) transformation. To understand the effect of these lanthanides on the shape of the GUV, we have also investigated phase transitions of 30 microM dipalmitoylphosphatidylcholine-multilamellar vesicle (DPPC-MLV) by the ultra-sensitive differential scanning calorimetry (DSC). The chain-melting phase transition temperature and the L(beta') to P(beta') phase transition temperature of DPPC-MLV increased with an increase in La(3+) concentration. This result indicates that the lateral compression pressure of the membrane increases with an increase in La(3+) concentration. Thereby, the interaction of La(3+) (or Gd(3+)) on the external monolayer membrane of the GUV induces a decrease in its area (A(ex)), whereas the area of the internal monolayer membrane (A(in)) keeps constant. Therefore, the shape changes of the GUV induced by these lanthanides can be explained reasonably by the decrease in the area difference between two monolayers (DeltaA=A(ex)-A(in)).     

Structural Characteristic of the Initial Unfolded State on Refolding Determines Catalytic Efficiency of the Folded Protein in Presence of Osmolytes

Osmolytes are low molecular weight organic molecules accumulated by organisms to assist proper protein folding, and to provide protection to the structural integrity of proteins under denaturing stress conditions. It is known that osmolyte-induced protein folding is brought by unfavorable interaction of osmolytes with the denatured/unfolded states. The interaction of osmolyte with the native state does not significantly contribute to the osmolyte-induced protein folding. We have therefore investigated if different denatured states of a protein (generated by different denaturing agents) interact differently with the osmolytes to induce protein folding. We observed that osmolyte-assisted refolding of protein obtained from heat-induced denatured state produces native molecules with higher enzyme activity than those initiated from GdmCl- or urea-induced denatured state indicating that the structural property of the initial denatured state during refolding by osmolytes determines the catalytic efficiency of the folded protein molecule. These conclusions have been reached from the systematic measurements of enzymatic kinetic parameters (K _m and k _cat), thermodynamic stability (T _m and ΔH _m) and secondary and tertiary structures of the folded native proteins obtained from refolding of various denatured states (due to heat-, urea- and GdmCl-induced denaturation) of RNase-A in the presence of various osmolytes.     

Determination of Heavy Metals in Fish and Vegetables in Bangladesh and Health Implications

Concentrations of six heavy metals (chromium, nickel, copper, arsenic, cadmium, and lead) in fish and vegetables were estimated to evaluate contamination levels and health risks for Bangladeshi adults. The analyzed metals varied between different species of fish and vegetables. Metals like Ni, Cd, and Pb in fish species were higher than the respective maximum allowable concentrations (MAC), whereas As, Cd, and Pb in some species of vegetables exceeded the MAC. Health risks associated with these metal intakes were evaluated in terms of dietary intake and target hazard quotients (THQs). The THQ values for individual metals were below 1 (except As for some species), suggesting that people would not experience significant health hazards if they ingest a single metal from one species of fish and/or vegetable. However, total metal THQ (TTHQ) signifies the potential non-carcinogenic health hazard to the highly exposed consumers in Bangladesh. Also, the estimation showed that the carcinogenic risk (TR) of arsenic and lead were within the acceptable range for fish but exceeded the accepted risk level for vegetables. From the health point of view, this study showed that the inhabitants who consume contaminated fish and vegetables are exposed chronically to metal pollution with carcinogenic and non-carcinogenic consequences.     

Comparative Analysis of the glg Operons of Pectobacterium chrysanthemi PY35 and Other Prokaryotes

A chromosomal region of Pectobacterium chrysanthemi PY35 that contains of genes for glycogen synthesis was isolated from a cosmid library. The operon consists of glycogen branching enzyme (glgB), glycogen debranching enzyme (glgX), ADP-glucose pyrophosphorylase (glgC), glycogen synthase (glgA), and glycogen phosphorylase (glgP) genes. Gene organization is similar to that of Escherichia coli. The purified ADP-glucose pyrophosphorylase (GlgC) was activated by fructose 1,6-bisphosphate and inhibited by AMP. The constructed glgX::Omega mutant failed to integrate into the chromosome of P. chrysanthemi by marker exchange. Phylogenetic analysis based on the 16S rDNA and the amino acid sequence of Glg enzymes showed correlation with other bacteria. gamma-Proteobacteria have the glgX gene instead of the bacilli glgD gene in the glg operon. The possible evolutionary implications of the results among the prokaryotes are discussed.     

The relationship between homozygosity and the frequency of the most frequent allele

Homozygosity is a commonly used summary of allele-frequency distributions at polymorphic loci. Because high-frequency alleles contribute disproportionately to the homozygosity of a locus, it often occurs that most homozygotes are homozygous for the most frequent allele. To assess the relationship between homozygosity and the highest allele frequency at a locus, for a given homozygosity value, we determine the lower and upper bounds on the frequency of the most frequent allele. These bounds suggest tight constraints on the frequency of the most frequent allele as a function of homozygosity, differing by at most 14 and having an average difference of 23 - pi(2)/18 approximately 0.1184. The close connection between homozygosity and the frequency of the most frequent allele-which we illustrate using allele frequencies from human populations-has the consequence that when one of these two quantities is known, considerable information is available about the other quantity. This relationship also explains the similar performance of statistical tests of population-genetic models that rely on homozygosity and those that rely on the frequency of the most frequent allele, and it provides a basis for understanding the utility of extended homozygosity statistics in identifying haplotypes that have been elevated to high frequency as a result of positive selection.