Swelling and de-swelling kinetics of gelatin hydrogels in ethanol-water marginal solvent

Controlled osmotic swelling and de-swelling measurements have been performed on gelatin, a polyampholyte, hydrogels suspended in water-ethanol marginal solvent at room temperature (20 degrees C) where the alcohol concentration was changed from 0 to 100% (v/v). The change in gel mass was monitored as function of time until osmotic equilibrium was established with the surrounding solvent. It was observed that osmotic pressure of polymer-solvent mixing, pi(m)相似文献   

An Opportunistic Bacterial Pathogen, Pseudomonas alcaligenes , May Limit the Perpetuation of Oryctes Virus, a Biocontrol Agent of Oryctes rhinoceros L.

Pseudomonas alcaligenes was detected at a high concentration (10 9 -10 10 cells mL -1 ) in the haemolymph of some dead Oryctes rhinoceros grubs collected from its breeding sites in the three southern districts, viz. Alleppey, Quilon and Kottayam of Kerala State, India. In a laboratory colony maintained for production of Oryctes virus, an important biocontrol agent of this major coconut pest, approximately 52% of the grubs succumbed to septicaemia with similar symptoms. The bacterium was found to be a component of the gut microflora of healthy grubs. Occurrence of the viral infection naturally or when induced in the laboratory in the O. rhinoceros grubs, appeared to be one of the biotic stress factors for P.alcaligenes to become an opportunistic pathogen. A preponderance of this bacterial infection in field populations during the periods when natural viral infection in grubs was above average, agrees with this observation. This finding becomes significant as infection by the opportunistic bacterial pathogen, P. alcaligenes , reduces the production of Oryctes virus inoculum in nature and limits the field-perpetuation of this viral biocontrol agent.     

A novel Delta9 acyl-lipid desaturase, DesC2, from cyanobacteria acts on fatty acids esterified to the sn-2 position of glycerolipids

Acyl-lipid desaturases are enzymes that convert a C-C single bond into a C=C double bond in fatty acids that are esterified to membrane-bound glycerolipids. Four types of acyl-lipid desaturase, namely DesA, DesB, DesC, and DesD, acting at the Delta12, Delta15, Delta9, and Delta6 positions of fatty acids respectively, have been characterized in cyanobacteria. These enzymes are specific for fatty acids bound to the sn-1 position of glycerolipids. In the present study, we have cloned two putative genes for a Delta9 desaturase, designated desC1 and desC2, from Nostoc species. The desC1 gene is highly similar to the desC gene that encodes a Delta9 desaturase that acts on C18 fatty acids at the sn-1 position. Homologues of desC2 are found in genomes of cyanobacterial species in which Delta9-desaturated fatty acids are esterified to the sn-2 position. Heterologous expression of the desC2 gene in Synechocystis sp. PCC 6803, in which a saturated fatty acid is found at the sn-2 position, revealed that DesC2 could desaturate this fatty acid at the sn-2 position. These results suggest that the desC2 gene is a novel gene for a Delta9 acyl-lipid desaturase that acts on fatty acids esterified to the sn-2 position of glycerolipids.     

Optimizing recombinant protein expression in the T7 system under the control of the proUp promoter

-Galactosidase and streptokinase expression was tested under the control of the T7 promoter in batch and fed-batch cultures. An Escherichia coli host GJ1158, which contained the T7 RNA polymerase gene under the osmo-responsive proUp promoter, was used for expression studies. -Galactosidase expression was enhanced from 26 mg l^–1 to 127 mg l^–1 in batch culture when a combination of sucrose and sorbitol was used instead of salt as an inducer. Similarly in fed-batch cultures 140 mg streptokinase l^–1 was formed with sucrose and sorbitol induction which was higher than that achieved with IPTG induced cultures.     

Functional conservation of MBD proteins: MeCP2 and Drosophila MBD proteins alter sleep

Proteins containing a methyl‐CpG‐binding domain (MBD) bind 5mC and convert the methylation pattern information into appropriate functional cellular states. The correct readout of epigenetic marks is of particular importance in the nervous system where abnormal expression or compromised MBD protein function, can lead to disease and developmental disorders. Recent evidence indicates that the genome of Drosophila melanogaster is methylated and two MBD proteins, dMBD2/3 and dMBD‐R2, are present. Are Drosophila MBD proteins required for neuronal function, and as MBD‐containing proteins have diverged and evolved, does the MBD domain retain the molecular properties required for conserved cellular function across species? To address these questions, we expressed the human MBD‐containing protein, hMeCP2, in distinct amine neurons and quantified functional changes in sleep circuitry output using a high throughput assay in Drosophila. hMeCP2 expression resulted in phase‐specific sleep loss and sleep fragmentation with the hMeCP2‐mediated sleep deficits requiring an intact MBD domain. Reducing endogenous dMBD2/3 and dMBD‐R2 levels also generated sleep fragmentation, with an increase in sleep occurring upon dMBD‐R2 reduction. To examine if hMeCP2 and dMBD‐R2 are targeting common neuronal functions, we reduced dMBD‐R2 levels in combination with hMeCP2 expression and observed a complete rescue of sleep deficits. Furthermore, chromosomal binding experiments indicate MBD‐R2 and MeCP2 associate on shared genomic loci. Our results provide the first demonstration that Drosophila MBD‐containing family members are required for neuronal function and suggest that the MBD domain retains considerable functional conservation at the whole organism level across species.     

Biochemical evidence for PGI2 and PGE2 receptors in the rabbit renal preglomerular microvasculature

It has been proposed that a portion of the biologic actions of vasodilator prostaglandins occurs via an interaction with specific adenylate cyclase-linked receptors. This hypothesis was explored further in the renal microvasculature by examining the effects of PGI2, PGE1, and PGE2 on rabbit preglomerular microvascular adenylate cyclase. A membrane preparation derived from freshly isolated rabbit renal preglomerular microvessels was used in these studies. NaF, forskolin, or 5'-guanylyl imidodiphosphate were found to be effective in increasing adenylate cyclase activity in the absence of exogenous guanosine-5'-triphosphate. A dose-dependent stimulation of adenylate cyclase was also observed with guanosine-5'-triphosphate. PGE1, PGE2, and PGI2 produced a dose-dependent stimulation of adenylate cyclase activity only in the presence of guanosine-5'-triphosphate suggesting that this nucleotide is essential for prostaglandin-induced stimulation of the enzyme. PGI2 exhibited a time-dependent increase in adenylate cyclase activity and this increased activity reached a plateau at 20-25 min. When PGE1 and PGE2 were added together, no additive effect on adenylate cyclase stimulation was noted whereas PGI2 and PGE2 when added together produced an additive stimulatory effect. When viewed together, these data suggest the presence of separate PGI2 and PGE adenylate cyclase-linked receptors in rabbit renal preglomerular microvessels. These findings also suggest that in the renal microvasculature, cyclic AMP may be a second messenger mediating the vasodilatory effects of both PGI2 and PGE2.     

Putative Virulence Traits and Pathogenicity of Vibrio cholerae Non-O1, Non-O139 Isolates from Surface Waters in Kolkata, India

Vibrio cholerae non-O1, non-O139 was isolated from natural surface waters from different sites sampled in diarrhea endemic zones in Kolkata, India. Twenty-one of these isolates were randomly selected and included in the characterization. The multiserogroup isolates were compared by their virulence traits with a group of clinical non-O1, non-O139 isolates from the same geographic area. Of the 21 environmental isolates, 6 and 14 strains belonged to Heiberg groups I and II, respectively. Three of the environmental isolates showed resistance to 2,2-diamine-6,7-diisopropylpteridine phosphate. All of the non-O1, non-O139 strains were positive for toxR, and except for one environmental isolate, none of them were positive for tcpA in the PCR assay. None of the isolates were positive for genes encoding cholera toxin (ctxA), heat-stable toxin (est), heat-labile toxin (elt), and Shiga toxin variants (stx) of Escherichia coli. Additionally, except for one environmental isolate (PC32), all were positive for the gene encoding El Tor hemolysin (hly). The culture supernatants of 86% (18 of 21) of the environmental isolates showed a distinct cytotoxic effect on HeLa cells, and some of these strains also produced cell-rounding factor. The lipase, protease, and cell-associated hemagglutination activities and serum resistance properties of the environmental and clinical isolates did not differ much. However, seven environmental isolates exhibited very high hemolytic activities (80 to 100%), while none of the clinical strains belonged to this group. The environmental isolates manifested three adherence patterns, namely, carpet-like, diffuse, and aggregative adherence, and the clinical isolates showed diffuse adherence on HeLa cells. Of the 11 environmental isolates tested for enteropathogenic potential, 8 (73%) induced positive fluid accumulation (≥100) in a mouse model, and the reactivities of these isolates were comparable to those of clinical strains of non-O1, non-O139 and toxigenic O139 V. cholerae. Comparison of the counts of the colonized environmental and clinical strains in the mouse intestine showed that the organisms of both groups had similar colonizing efficiencies. These findings indicate the presence of potentially pathogenic V. cholerae non-O1, non-O139 strains in surface waters of the studied sites in Kolkata.     

Analysis of γ-Aminobutyric AcidA Receptor Subunits in the Mouse Cochlea by Means of the Polymerase Chain Reaction

Abstract: Unlike 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), which produces consistent decreases in levels of striatal dopamine (DA) with considerably smaller and more variable effects on mouse brain levels of serotonin (5-HT) and norepinephrine (NE), a novel amine-substituted MPTP analogue, 1-methyl-4-(2'-aminophenyl)-1,2,3,6-tetrahydropyridine (2'-NH₂-MPTP), administered in a standard mouse dosing paradigm for MPTP (20 mg/kg X 4) did not affect striatal DA but led to marked reductions (60–70%) in levels of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), and NE measured in frontal cortex and hippocampus 1 week after treatment. Another 2'-substituted MPTP analogue, 1-methyl-4-(2'-methylphenyl)-1,2,3,6-tetrahydropyridine, affected cortical and hippocampal 5-HT, 5-HIAA, and NE only minimally, while markedly reducing the DA content in striatum (90%), thus indicating that the substituent (-NH₂ versus -CH₃) at the 2'position is important for the differential effects of these MPTP analogues. In a replication study with a 3-week end point, hippocampal and cortical 5-HT, 5-HIAA, and NE levels remained depressed with no indication of recovery. These results suggest that 2'-NH₂-MPTP may be a novel, regionally selective neurotoxin for serotonergic and norad-renergic nerve terminals.     

Gluconobacter oxydans: its biotechnological applications

Gluconobacter oxydans is a gram-negative bacterium belonging to the family Acetobacteraceae. G. oxydans is an obligate aerobe, having a respiratory type of metabolism using oxygen as the terminal electron acceptor. Gluconobacter strains flourish in sugary niches e.g. ripe grapes, apples, dates, garden soil, baker's soil, honeybees, fruit, cider, beer, wine. Gluconobacter strains are non-pathogenic towards man and other animals but are capable of causing bacterial rot of apples and pears accompanied by various shades of browning. Several soluble and particulate polyol dehydrogenases have been described. The organism brings about the incomplete oxidation of sugars, alcohols and acids. Incomplete oxidation leads to nearly quantitative yields of the oxidation products making G. oxydans important for industrial use. Gluconobacter strains can be used industrially to produce L-sorbose from D-sorbitol; D-gluconic acid, 5-keto- and 2-ketogluconic acids from D-glucose; and dihydroxyacetone from glycerol. It is primarily known as a ketogenic bacterium due to 2,5-diketogluconic acid formation from D-glucose. Extensive fermentation studies have been performed to characterize its direct glucose oxidation, sorbitol oxidation, and glycerol oxidation. The enzymes involved have been purified and characterized, and molecular studies have been performed to understand these processes at the molecular level. Its possible application in biosensor technology has also been worked out. Several workers have explained its basic and applied aspects. In the present paper, its different biotechnological applications, basic biochemistry and molecular biology studies are reviewed.     

Assessment of genetic diversity in 31 species of mangroves and their associates through RAPD and AFLP markers

Random amplified polymorphic DNA (RAPD) and amplified fragment length polymorphism (AFLP) markers were used to assess the genetic diversity in 31 species of mangroves and mangrove associates. Four AFLP primer combinations resulted in the amplification of 840 bands with an average of 210 bands per primer combination and 11 RAPD primers yielded 319 bands with an average of 29 bands per primer. The percentage of polymorphism detected was too high indicating the high degree of genetic variability in mangrove taxa both at inter- and intra-generic levels. In the dendrogram, species belonging to a particular family/ genus, taxa inhabiting similar habitats or having similar adaptations tended to be together. There were exceptions too; as many unrelated species of mangroves form clusters. The intrafamilial classification and inter-relationships of genera in the family Rhizophoraceae could be confirmed by molecular analysis. Both the markers RAPD and AFLP were found equally informative and useful for a better understanding of the genetic variability and genome relationships among mangroves and their associated species.