Characteristics of Symmetric Surface Plasmon Polariton Mode in Glass–Metal–Glass Waveguide

The propagation characteristics of symmetric surface plasmon polariton mode in a glass–metal–glass waveguide are presented. Gallium lanthanum sulfide has been taken as the glass and silver (Ag) has been used as the metal. The analysis has been done both numerically and analytically. A two-dimensional finite-difference time-domain-based simulation model has been developed in order to analyze the propagation characteristics numerically. The obtained results using numerical and analytical methods have been compared and a very good agreement has been found.     

pH-sensitive hydrogel based on a novel photocross-linkable copolymer

A pH sensitive hydrogel has been prepared by a UV irradiation technique. Starting polymer was the PHM (poly hydroxyethylaspartamide methacrylated) obtained from polyaspartamide (PHEA) partially derivatized with methacrylic anhydride (MA). This new copolymer has been further derivatized with succinic anhydride (SA) to obtain PHM-SA that has been cross-linked by UV irradiation to form a pH sensitive hydrogel. The network, recovered after washing as a powder, has been been characterized by FT-IR spectrophotometry and particle size distribution analysis. Moreover, to have information about water affinity of the prepared sample, swelling measurements have been carried out in aqueous media mimicking biological fluids. The possibility to employ the prepared hydrogel as a pH-sensitive drug delivery system (DDS) has been investigated. In particular, ibuprofen ((S)(+)4-isobutyl-alpha-methylphenyl-acetic acid), chosen as a model drug, has been entrapped into the PHM-SA hydrogel, and in vitro release studies have showed that its release rate depends on different swelling of the network as a function of the environmental pH.     

Study of a comparative statistical analytical model for nucleotide sequences in the genome of viruses of the Papovaviridae family

In the present study a model for comparative analysis of nucleotide sequences has been developed, in order to evaluate statistical features of nucleotide distribution in DNA strands without any genetic relationship. Every DNA strand has been considered as a finite Markov chain; a matrix, whose elements represent the number of couplings between a nucleotide and the following one in 5'-3' direction, has been used for every DNA strand, and the statistical relationship has been detected by using Kendall's test. The genomes of Polyomavirus (strain A2) and DPV have been analysed by the proposed model; a substantial likeness between the behaviour of nucleotide distribution on all four DNA strands analysed has been shown; the strongest likeness concerned the complementary strands of Polyomavirus as well as the homologous sense strands of both viruses.     

Radioimmunoassay of polypeptide hormones using immunochemically coated plastic tubes

A method has been developed for immobilisation of antisera on fresh plastic tubes through an immunochemical bridge. This type of immobilisation has been shown to be more consistent than direct adsorption on plastic. Such immunochemically coated antisera on plastic tube has been used in the development of a noncentrifugation radioimmunoassay. This assay system has been found to be technically as sound as the conventional method.     

Ancient lakes as evolutionary reservoirs: evidence from the thalassoid gastropods of Lake Tanganyika

Ancient lakes are often collectively viewed as evolutionary hot spots of diversification. East Africa's Lake Tanganyika has long been the subject of scientific interest owing to dramatic levels of endemism in species as diverse as cichlid fishes, paludomid gastropods, decapod and ostracod crustaceans and poriferans. It is the largest and deepest of the African rift lakes, and its endemic fauna has been presented with a stable inland environment for over 10 Myr, offering unique opportunities for within-lake diversification. Although astonishing diversification has been documented in the endemic cichlid fauna of the lake, similar patterns of rapid diversification have long been assumed for other groups. In contrast to this hypothesis of rapid speciation, we show here that there has been no acceleration in the rate of speciation in the thalassoid gastropods of the lake following lake colonization. While limited within-lake speciation has occurred, the dramatic conchological diversity of gastropods presently found within the lake has evolved from at least four major lineages that pre-date its formation by as much as 40 Myr. At the same time, a widespread group of African gastropods appears to have evolved from taxa presently found in the lake. While Lake Tanganyika has been a cradle of speciation for cichlid fishes, it has also been an important evolutionary reservoir of gastropod lineages that have been extirpated outside the basin.     

A novel property of DNA - as a bioflotation reagent in mineral processing

Environmental concerns regarding the use of certain chemicals in the froth flotation of minerals have led investigators to explore biological entities as potential substitutes for the reagents in vogue. Despite the fact that several microorganisms have been used for the separation of a variety of mineral systems, a detailed characterization of the biochemical molecules involved therein has not been reported so far. In this investigation, the selective flotation of sphalerite from a sphalerite-galena mineral mixture has been achieved using the cellular components of Bacillus species. The key constituent primarily responsible for the flotation of sphalerite has been identified as DNA, which functions as a bio-collector. Furthermore, using reconstitution studies, the obligatory need for the presence of non-DNA components as bio-depressants for galena has been demonstrated. A probable model involving these entities in the selective flotation of sphalerite from the mineral mixture has been discussed.     

Persistence of bacterial pathogens as a physiological phenomenon

The complex ecosystem of humans and microbes has been presented as an associative symbiosis based on a mutual support of symbionts with different consequences for them. Conditions for the persistence of bacteria have been defined: their resistance to environmental factors, antagonism in biocenosis, and stability to withstand host defense mechanisms. The key role of bacterial peptidoglycan has been defined for their survival in an infected organism, and the classification for persistent mechanisms of pathogens has been given. The group of bacterial secreted protease providing microbial resistance to defense factors of the organism has been described. Host colonizing resistance has been presented as a physiological regulatory system controlling bacterial penetration into an organism. Regulatory mechanisms for bacterial persistence have been discussed.     

Socioeconomic covariates and their impact on the opportunity for natural selection in a riparian tribe of Northeast India

The intensity of natural selection correlates with various bio-social variables which influence the genetic structure of a population. In this paper it has been sought to find out the influence of variable environmental setting and economic condition on selection intensity among the Mising tribal population of Assam, Northeast India. Detailed reproductive pattern of 309 post menopausal women is obtained and a comparison has been made between different environmental as well as economic backgrounds. The impact of secular change on selection intensity has been assessed. For this study I have proposed a modified formula of Johnston & Kensinger's (1971) index for selection intensity. Crow's index of selection intensity has also been used for comparative analyses. After considering standard statistical procedure, a clear disparity of selection intensity has been noticed in terms of varying socioeconomic condition as well as habitational background. It can be concluded from the study that environmental factors act more in terms of selection pressure on infants rather than the other post natal stages.     

A 3D model of the peripheral benzodiazepine receptor and its implication in intra mitochondrial cholesterol transport

A three-dimensional (3D) model of the peripheral benzodiazepine receptor (PBR) has been built using molecular dynamics simulations.The transmembrane domain of the receptor has been modeled as five alpha-helices, which are not long enough to cross the entire bilaver membrane hut correspond approximately to only one phospholipid layer. The receptor model has also been tested as a cholesterol carrier, and molecular dynamics simulations have shown that it could indeed accommodate a cholesterol molecule within the five helices. All three known PBR sequences have been modeled, and no significant difference has been found between them.     

THE ACCUMULATION OF ELECTROLYTES : VII. ORGANIC ELECTROLYTES PART 2

Analyses have been made of the inorganic constituents of the juices expressed from the leaves of Rheum, Rumex, and Oxalis. It has been shown that in all cases there is a large excess of inorganic cations over anions in the sap, the average ratio of cations to anions being 3.8 (Part 1, p. 239). The ash analyses of plant tissues (chiefly leaves) reported in the literature have been examined critically, and it has been shown that the preponderance of inorganic cations over inorganic anions in the ash and in the sap is general. It has been concluded that the excess of inorganic cations is consistent with the view that cations pass into the protoplasm chiefly in the form of hydroxides, and are accumulated either in the form of organic salts (such as the oxalates) or in non-polar linkage. It has been concluded that practically all the potassium and sodium found in plant ash must have been present originally in the form of soluble ionogenic compounds, but that a considerable part of the calcium and magnesium may have been present originally in the form of insoluble salts or as components of non-polar compounds. The methods whereby the cations, particularly potassium, may have been accumulated have been discussed, and it has been concluded that as it does not seem very probable that they enter chiefly as nitrates or bicarbonates we may suppose that they go in to a large extent as hydrates: this is highly probable in the case which has been most carefully investigated (Valonia).     

LTP, post or pre? A look at the evidence for the locus of long-term potentiation.

It seems self-evident that changes in the cellular synaptic function of the brain must underlie the formation and storage of cognitive memories. Because it has been identified as a brain area important in the formation of memory, the hippocampus has been a focus in the study of such synaptic changes. An activity-induced increase in hippocampal synaptic efficacy, known as long-term potentiation (LTP), has been widely studied as a potential substrate for memory. This paper briefly reviews some of the significant progress that has been made in understanding the cellular mechanisms that underlie LTP, including recent experiments dealing with its synaptic locus, or the question of whether the mechanism regulating LTP is pre- or postsynaptic.     

Mathematical model study of megakaryocytopoiesis. 1. The simulation model, cell steady-state distribution and the number of divisions in a proliferating population

A method of simulation has been proposed for studying megakaryocytopoiesis. A model has been developed which takes into account the age structure of cell population, the stochasticity of their maturation, and the principles of megakaryocytopoiesis regulation (known from the experiments). The mean number of divisions in a proliferating pool has been determined, as well as the duration of development of the cells with a positive acetylcholine esterase reaction.     

Construction, assembling and application of a trehalase-GOD enzyme electrode system

Trehalose is a disaccharide important in foods, serving as a glucose source in many and also as an additive in the food preparation. Because of its peculiar physico-chemical properties it plays an important role as preservative in drying and deep-freezing treatments. A new biosensor for trehalose determination has been realized by means of a flow system, based on a reactor in which the trehalase enzyme catalyses its hydrolysis into two alpha,d-glucose molecules, and a GOD (glucose oxidase) amperometric biosensor is employed for the glucose determination. The optimum operative conditions have been laid out and a particular attention has been paid to the immobilization procedure of the two enzymes. The electrode used is of the SPE (screen-printed electrode) type and has been activated with the Prussian Blue (PB) and then assembled using GOD immobilized with Nafion. The reactor has been prepared with the trehalase enzyme chemically immobilized on an Immunodyne ABC membrane. As demonstration of its utility, the biosensor has been tested on a real sample of Boletus edulis mushroom.     

Familial juvenile hyperuricaemic nephropathy is not such a rare genetic metabolic purine disease in Britain

Renal disease is rare today in classic adult gout, and gout is rare in renal disease--especially in the young. Here we summarise studies in 158 patients from 31 kindreds diagnosed with familial juvenile hyperuricaemic nephropathy FJHN from a total of 230 kindred members studied in Great Britain. Some patients have been followed for up to 30 years, and allopurinol has ameliorated the progression of the renal disease in all 113 surviving members provided: They have been diagnosed and treated sufficiently early. Compliance with allopurinol treatment and diet has been as important as early recognition. Hypertension has been rigorously controlled. The use of oral contraceptives has been avoided, as has pregnancy in any female with a Glomelar Filtration Rate GFR <70 ml/min. The question arising is: Why is FJHN the most prevalent genetic purine disorder diagnosed in Britain? Is it a lack of awareness which needs to be improved Europe-wide?     

Chemotaxis of Ralstonia sp. SJ98 towards p-nitrophenol in soil

Bioremediation of contaminated sites has been accepted as an efficient and cheaper alternative to physicochemical means of remediation in several cases. Although chemotactic behaviour of many bacteria has been studied earlier and assays have been developed to study bacterial chemotaxis in semi-solid media, this phenomenon has never been demonstrated in soil. For bioremediation application it is important to know whether bacteria actually migrate through the heterogenous soil medium towards a gradient of a particular chemoattractant. In the present study we have successfully demonstrated bacterial chemotaxis of a Ralstonia sp. SJ98 in soil microcosm using qualitative and quantitative plate and tray assays. The migration of bacteria has been established using several methods such as plate counting, vital staining and flow cytometry and slot blot hybridization. A non-chemotactic p-nitrophenol utilizing strain Burkholderia cepacia RKJ200 has been used as negative control. Our work clearly substantiates the hypothesis that chemotactic bacteria may enhance in situ bioremediation of toxic pollutants from soils and sediments.     

Prolactin receptors and breast cancer

A study has been carried out on 116 mammary neoplasias in which the prolactin receptors together with other clinical and hormonal parameters have been determined. A 46.3% frequency of PRLR+ has been obtained as well as a statistically significant correlation between these and blood estradiol (p less than 0.05). PRLR- have greater survival and PRLR may act as a growth factor.     

Mechanism of sulfide-quinone reductase investigated using site-directed mutagenesis and sulfur analysis

Biological sulfide oxidation is a reaction occurring in all three domains of life. One enzyme responsible for this reaction in many bacteria has been identified as sulfide:quinone oxidoreductase (SQR). The enzyme from Rhodobacter capsulatus is a peripherally membrane-bound flavoprotein with a molecular mass of approximately 48 kDa, presumably acting as a homodimer. In this work, SQR from Rb. capsulatus has been modified with an N-terminal His tag and heterologously expressed in and purified from Escherichia coli. Three cysteine residues have been shown to be essential for the reductive half-reaction by site-directed mutagenesis. The catalytic activity has been nearly completely abolished after mutation of each of the cysteines to serine. A decrease in fluorescence on reduction by sulfide as observed for the wild-type enzyme has not been observed for any of the mutated enzymes. Mutation of a conserved valine residue to aspartate within the third flavin-binding domain led to a drastically reduced substrate affinity, for both sulfide and quinone. Two conserved histidine residues have been mutated individually to alanine. Both of the resulting enzymes exhibited a shift in the pH dependence of the SQR reaction. Polysulfide has been identified as a primary reaction product using spectroscopic and chromatographic methods. On the basis of these data, reaction mechanisms for sulfide-dependent reduction and quinone-dependent oxidation of the enzyme and for the formation of polysulfide are proposed.     

Melanocyte-directed enzyme prodrug therapy (MDEPT): development of a targeted treatment for malignant melanoma.

A novel prodrug rationally designed to function as a tyrosinase substrate has been synthesised to allow targeted treatment of malignant melanoma. This agent has been evaluated for tyrosinase-mediated drug release, and has been shown to act in the desired manner. Furthermore, differential cytotoxicity has been demonstrated in cell lines which express tyrosinase and those which do not.     

Chemical synthesis of cellulose and cello-oligomers using a hydrolysis enzyme as a catalyst

Regio- and stereo-selective synthesis of polysaccharides and oligosaccharides has been achieved by using glycosyl fluorides as substrates for cellulases. This methodology has successfully been applied to the first synthesis of cellulose via a non-biosynthetic pathway as well as to a selective preparation of cello-oligosaccharides and unnatural oligosaccharides. Using the enzymatic polymerization, it is possible to control the relative direction (parallel or anti-parallel) of each glucan chain in the synthetic cellulose in vitro. Based on these results, a new concept of ‘allos-selectivity’ in polymer synthesis has been proposed.