The effect of sodium chloride on phage formation by staphylococci at elevated temperatures

In experiments with the K strain of Staphylococcus aureus and the K race of bacteriophage suspended in tryptose phosphate broth and maintained at 42 degrees C. it was found that the presence of 1 M NaCl produced certain drastic changes in the relationship between the host cells and the infecting virus: 1. Staphylococci grown at 42 degrees C. in plain broth or in NaCl-broth are "activated," i.e. when growth is stopped by lowering the temperature to 5 degrees C. and phage is added, the activity titre immediately displays a rise of 15- to 16-fold. 2. 1 M NaCl tends to prevent the sorption of phage by cocci and this effect is more pronounced at 42 degrees C. than at 5 degrees C. When the activation test is conducted at 5 degrees C. (the usual temperature) most of the phage is picked up by the cells and the described increase in activity titre follows. If the test takes place at 42 degrees C. there is little sorption and correspondingly little rise in phage titre. 3. Mixtures of staphylococci and phage incubated at 42 degrees C. in NaCl-broth fail to produce phage; the final plaque and activity titres are identical with the initial titres. Here, also, the influence of 1 M NaCl in preventing contact of phage with cocci appears to account for the results. 4. Similar mixtures held at 42 degrees C. in plain broth exhibit a drop of about 60 per cent in activity and plaque titres. The loss of phage may be due to adsorption on dead cells accumulating in the suspension or to the thermolability of the bacterium-phage complex, or to both.     

A novel redox system for CNS-directed delivery of estradiol causes sustained LH suppression in castrate rats

A series of 4 studies was conducted to examine the estrogen-like activity of a chemical delivery system (CDS) coupled to estradiol (E2). The CDS is based on a redox system, analogous to the NAD+ in equilibrium NADH coenzyme system and has previously been shown capable of sustained and site specific drug delivery to the central nervous system. The ability of CDS-E2 to suppress luteinizing hormone (LH) in gonadectomized rats was examined as an index of sustained estrogen action. A single dose of CDS-E2 resulted in significantly decreased LH serum levels in castrate rats through at least 24 days while an equimolar dose of E2 resulted in only transient LH decrease. Serum E2 levels were not different between the treatment groups, indicating that peripheral estrogen could not readily explain sustained hormone activity. A dose-response relationship was observed 12 days post-drug treatment in all monitored estrogen activities which showed CDS-E2 is more potent compared to equimolar E2. Further, LH suppression was significantly greater compared to ovariectomized rats treated with equimolar estradiol valerate, while anterior pituitary weights were not different between groups. Together with our previous data, these studies show that CDS-E2 exerts sustained estrogen-like activity which cannot be readily attributed to circulating E2 levels. These findings are consistent with a sustained, brain directed delivery of estrogen.     

Development of a peptide-containing chewing gum as a sustained release antiplaque antimicrobial delivery system

The objective of this study was to characterize the stability of KSL-W, an antimicrobial decapeptide shown to inhibit the growth of oral bacterial strains associated with caries development and plaque formation, and its potential as an antiplaque agent in a chewing gum formulation. KSL-W formulations with or without the commercial antibacterial agent cetylpyridinium chloride (CPC) were prepared. The release of KSL-W from the gums was assessed in vitro using a chewing gum apparatus and in vivo by a chew-out method. A reverse-phase high-performance liquid chromatography method was developed for assaying KSL-W. Raw material stability and temperature and pH effects on the stability of KSL-W solutions and interactions of KSL-W with tooth-like material, hydroxyapatite discs, were investigated. KSL-W was most stable in acidic aqueous solutions and underwent rapid hydrolysis in base. It was stable to enzymatic degradation in human saliva for 1 hour but was degraded by pancreatic serine proteases. KSL-W readily adsorbed to hydroxyapatite, suggesting that it will also adsorb to the teeth when delivered to the oral cavity. The inclusion of CPC caused a large increase in the rate and extent of KSL-W released from the gums. The gum formulations displayed promising in vitro/ in vivo release profiles, wherein as much as 90% of the KSL-W was released in a sustained manner within 30 minutes in vivo. These results suggest that KSL-W possesses the stability, adsorption, and release characteristics necessary for local delivery to the oral cavity in a chewing gum formulation, there-by serving as a novel antiplaque agent. Published: March 30, 2007     

Microscopic evaluation of vesicles shed by rat erythrocytes at elevated temperatures

It is hypothesized that the elevation of the temperature of the blood during heat stress may cause an increase of the shedding of erythrocyte membrane vesicles. Therefore, the increase of vesicle numbers following heat stress may be indicative of and proportional to the level heat stress. In order to test this hypothesis, erythrocytes and the vesicles shed by erythrocytes were collected from rat blood and analyzed after the elevation of body temperature by exposure to external heat. The images of erythrocytes and vesicles were analyzed by a custom light microscopy system with spatial resolution of better than 90 nm. The samples were observed in an aqueous environment and required no freezing, dehydration, staining, shadowing, marking or any other manipulation. The elevation of temperature from 36.7±0.3 to 40.3±0.4 °C resulted in significant increase of the concentration of vesicles in blood. At a temperature of 37 °C, mean vesicle concentrations and diameters found in rat blood were (1.4±0.2)×10⁶ vesicles/μL and 0.436±0.03 μm, respectively. The concentration of free vesicles increased after exposure to heat to (3.8±0.3)×10⁶ vesicles/μL. It was estimated that 80% of all vesicles found in rat blood are smaller than 0.45 μm. The increase in the number of vesicle associated with elevated temperatures may be indicative of the heat stress level and serve as diagnostic test of erythrocyte stability and heat resistance.     

A novel synergistic galactomannan-based unit dosage form for sustained release of acarbose

In the current study, the potential of a novel combination of a galactomannan with acarbose (100 mg) was evaluated for attaining a desired hypoglycaemic effect over a prolonged period of time. Three major antidiabetic galactomannans viz., fenugreek gum, boswellia gum, and locust bean gum were selected in order to achieve a synergistic effect in the treatment alongwith retardation in drug release. In vitro studies indicated that batches containing various proportions of fenugreek gum (AF40-60) were able to control drug release for a longer duration of approximately 10–12 h. In contrast, the matrices prepared using boswellia and locust bean gum were able to sustain the release for relatively shorter durations. Drug release mainly followed first-order release kinetics owing to the highly soluble nature of the drug. In vivo study depicted a significant reduction (p < 0.001) in the postprandial blood glucose and triglyceride levels in the diabetic rats on treatment with formulation AF40. Thus, the developed system provides a better control of the postprandial glycaemic levels and it also obviates the need of conventional multiple dosing of acarbose. Furthermore, it also reduces the occurrence of side effects like diarrhea and loss of appetite.     

Facile preparation of well-defined near-monodisperse chitosan/sodium alginate polyelectrolyte complex nanoparticles (CS/SAL NPs) via ionotropic gelification: A suitable technique for drug delivery systems

Polymeric nanoparticles have emerged as a promising approach for drug delivery systems. We prepared chitosan (CS)/sodium alginate (SAL) polyelectrolyte complex nanoparticles (CS/SAL NPs) via a simple and mild ionic gelation method by adding a CS solution to a SAL solution, and investigated the effects of molecular weight of the added CS, and the SAL:CS mass ratio on the formation of the polyelectrolyte complex nanoparticles. The well-defined CS/SAL NPs with near-monodisperse particle size of about 160 nm exhibited a pH stable structure, and pH responsive properties with a negatively or positively charged surface. The so-called “electrostatic sponge” structure of the polyelectrolyte complex nanoparticles enhanced their drug-loading capacity towards the differently charged model drug molecules, and favored controlled release. We also found that the drug-loading capacity was influenced by the nature of the drugs and the drug-loading media, while drug release was affected by the solubility of the drugs in the drug-releasing media. The biocompatibility and biodegradability of the polyelectrolytes in the polyelectrolyte complex nanoparticles were maintained by ionic interactions. These results indicate that CS/SAL NPs can represent a useful technique for pH-responsive drug delivery systems.     

Growth rate of Enterobacteriaceae at elevated temperatures: limitation by methionine.

The effect of elevated temperatures on growth rate was studied in five strains of Enterobacteriaceae. In all the strains tested a shift to the elevated temperature resulted in an immediate decrease in growth rate which was due to limitation in the availability of endogenous methionine. The first biosynthetic enzyme of the methionine pathway-homoserine transsuccinylase-was studied in extracts of Aerobacter aerogenes, Salmonella typhimurium, and Escherichia coli and was shown to be temperature sensitive in all of them.     

Reduction of ribonuclease by glutathione at elevated temperatures: the molecular mechanism

1. The mechanism of the reaction between ribonuclease and GSH at elevated temperatures has been studied by using N-(4-dimethylamino-3,5-dinitrophenyl)-maleimide to label the reduced ribonuclease. 2. After incubation for 2hr. at 35 degrees , enzymically active ribonuclease was recovered; at 50.8 degrees half of the initial ribonuclease was recovered as enzymically active ribonuclease and half as reduced labelled ribonuclease; at 55 degrees all of the initial ribonuclease was recovered in the labelled form. 3. It was inferred that the rate-limiting step was the reduction of the first disulphide bond in any one molecule. This was followed by rapid reduction of the other bonds in the same molecule.     

Injectable biodegradable starch/chitosan delivery system for the sustained release of gentamicin to treat bone infections

Starch-conjugated chitosan microparticles were produced aimed to be used as a carrier for the long term sustained/controlled release of antibiotic drugs to control bone infection. The microparticles were prepared by a reductive alkylation crosslinking method. The obtained microparticles showed a spherical shape, with a slightly rough and porous surface, and a size range of 80-150 μm. Gentamicin was entrapped into the starch-conjugated chitosan microparticles and its release profile was studied in vitro. Increasing concentrations of gentamicin (from 50 to 150 mg/mL) led to a decrease in the encapsulation efficiency (from 67 to 55%), while drug loading increased from 4 to 27%. A sustained release of gentamicin was observed over a period of 30 days. The release kinetics could be controlled using an ionic crosslinker agent. In addition, a bacterial inhibition test on Staphylococcus aureus shows a diameter of the sample inhibition zone ranging from 12 to 17 mm (70-100% of relative activity).     

不同炭化温度制备的蚕丝被废弃物生物炭对重金属Cd2+的吸附性能

以蚕丝被废弃物为原料,在300、500和700 ℃高温缺氧条件下热解炭化制备成3种生物炭(BC300、BC500和BC700).利用扫描电镜(SEM)、傅里叶红外光谱仪(FT-IR)、X-射线衍射仪(XRD)、比表面积分析仪等对其理化性质进行表征,并研究了不同温度下制备的生物炭对溶液中Cd²⁺的吸附特性.结果表明: 随着炭化温度上升,BET比表面积、pH、灰分均增大,生物炭表面形态结构越来越不规则.XRD结果显示:不同温度下获得的生物炭中均含有一定量的方解石,FT-IR光谱图上的峰主要为-OH和方解石典型的吸收峰;pH对生物炭吸附Cd²⁺的影响不大;Langmuir方程能更好地拟合3种生物炭对Cd²⁺的吸附等温过程,其最大吸附量分别为25.61、52.41和91.07 mg·g^-1.3种生物炭对Cd²⁺吸附过程均更符合准二级动力学方程,且BC700对Cd²⁺的吸附效果最佳.进一步研究离子浓度及阳离子共存对BC700吸附Cd²⁺的影响,结果显示: NaCl浓度越高,对Cd²⁺的吸附抑制越明显;共存阳离子中,Ca²⁺和Mg²⁺对Cd²⁺的吸附抑制更明显,而K⁺几乎无影响.因此,以蚕丝被废弃物制备的生物炭作为去除水体中Cd²⁺的吸附剂具有较强的应用潜力.     

A hydrodynamic study of the depolymerisation of a high methoxy pectin at elevated temperatures

The hydrodynamic properties (intrinsic viscosity, [η]; infinite dilution sedimentation coefficient, s_20,w⁰; weight average molecular weight, M_w and translational frictional ratio, f/f₀) of a high methoxy pectin have been evaluated at various temperatures (20–60°C). A reduction in the value of all four hydrodynamic parameters is indicative of depolymerisation and is in agreement with an earlier study using viscometry [Axelos, M.A.V., & Branger, M., (1993). Food Hydrocolloids, 7, 91–102]. The apparent linearity of the Mark – Houwink plot of log[η] vs log M_w suggests that the conformation of the pectin molecule does not change significantly over the temperature range studied. The evaluation of the Mark–Houwink viscosity exponent (a=0.84) indicates a moderately extended structure. This then allows the calculation of the number of Kuhn statistical lengths per chain from the adapted ‘blob’ theory of Dondos [Dondos A. (2001). Polymer, 42, 897–901]. The weight average number of Kuhn statistical lengths per chain is reduced from (170±10) to (125±10) when the temperature is increased from 20–60°C. This may be of significance as many high methoxy pectins are exposed to high temperatures during processing in both the food and pharmaceutical industries.     

Pressure assisted stabilization of biocatalysts at elevated temperatures: Characterization by dynamic light scattering

The effect of pressure, at elevated temperatures, is reported on the activity and stability of a thermophilic endo‐β‐glucanase from the filamentous fungus Talaromyces emersonii. The production of reduced sugars after treatment at different temperatures and pressures is used as a measure of the activity and stability of the enzyme. The activity of the enzyme is maintained to higher temperatures with increasing pressure. For example, the relative activity of endo‐β‐glucanase decreases to 30% after 4 h at 75°C and 1 bar, whereas it is preserved at 100% after 6 h at 75°C and 230 bar. High‐pressure dynamic light scattering is used to characterize the hydrodynamic radius of the enzyme as a function of pressure, temperature, and time. At higher temperature the hydrodynamic radius increases with time, whereas increasing pressure suppresses this effect. Changes in the hydrodynamic radius are correlated with the activity measurements obtained at elevated pressures, since the changes in the hydrodynamic radius indicate structural changes of the enzyme, which cause the deactivation. Biotechnol. Bioeng. 2013; 110: 1674–1680. © 2012 Wiley Periodicals, Inc.     

Inhibition of host DNA synthesis by adenovirus infection is reversed at elevated temperatures.

Infection of KB cells by adenovirus normally results in a drastic reduction of host DNA synthesis at 33 to 37 degrees C. This inhibition was largely reversed by raising the temperature to 41 degrees C. Inhibition was reinstated if the temperature is lowered.     

Enhanced leaching of product at elevated temperatures: alpha-amylase produced by Bacillus licheniformis M27 in solid state fermentation system

Leaching of alpha-amylase from bacterial bran, produced by Bacillus licheniformis M27 in solid state fermentation was about 2.2 times higher at 50°C as compared to that at 30°C. Further increase by about 19% in leaching efficiency was observed when contact time was extended from 60 to 120 min. The overall increase of 2.54 times under these strategies is of economic importance and no information was available earlier on enhanced leaching of enzyme from fermented bran at elevated temperatures.     

Preparation and characterization of a novel pH-sensitive chitosan-g-poly (acrylic acid)/attapulgite/sodium alginate composite hydrogel bead for controlled release of diclofenac sodium

A series of pH-sensitive composite hydrogel beads composed of chitosan-g-poly (acrylic acid)/attapulgite/sodium alginate (CTS-g-PAA/APT/SA) was prepared as drug delivery matrices crosslinked by Ca²⁺ owing to the ionic gelation of SA. The structure and surface morphology of the composite hydrogel beads were characterized by FTIR and SEM, respectively. pH-sensitivity of these composite hydrogels beads and the release behaviors of drug from them were investigated. The results showed that the composite hydrogel beads had good pH-sensitivity. The cumulative release ratios of diclofenac sodium (DS) from the composite hydrogel beads were 3.76% in pH 2.1 solution and 100% in pH 6.8 solutions within 24 h, respectively. However, the cumulative release ratio of DS in pH 7.4 solution reached 100% within 2 h. The DS cumulative release ratio reduced with increasing APT content from 0 to 50 wt%. The drug release was swelling-controlled at pH 6.8.     

一种新型蛋白类药物口服载体的海藻酸钠/巯基化果糖-壳聚糖复合水凝胶

壳聚糖经果糖修饰以改善其水溶性,再经半胱氨酸修饰得到巯基化果糖-壳聚糖。海藻酸钠与巯基化果糖-壳聚糖混合溶液经氯化钙及硫酸钠双重交联制得复合水凝胶珠。溶胀试验结果表明:该凝胶珠在pH值6.8及7.4时的溶胀率分别是pH值1.2时的7倍和10倍左右。牛血清白蛋白(BSA)包载试验结果表明:BSA重量为凝胶珠质量的20%时,包载率可达94%以上,随着巯基化果糖-壳聚糖在凝胶珠中比例增加,BSA包载率上升。BSA释放试验表明:pH值1.2时BSA的释放率很低,只有6%～10%的BSA从凝胶珠中释放出来,随后累积释放量基本不变;pH值6.8和pH值7.4时BSA的释放率迅速提高,因此这种复合水凝胶珠可作为一种潜在的口服蛋白类药物载体。     

A study of the thermal unfolding of Escherichia coli phenylalanine transfer RNA by chemical modification at elevated temperatures.

Escherichia coli tRNAPhe was modified by 3 M sodium bisulphite pH 6.0 for 24 h in the temperature range 25 degrees C (x 5 degrees C) to 55 degrees C and in the absence of added magnesium ions. The sites and extents of conversion of cytidines to uridine occurring at each temperature were determined by fingerprinting. The new sites of cytidine modification found at higher reaction temperatures were assumed to arise from breakage of secondary and tertiary structure hydrogen bonds involving cytidine residues. From these data, we conclude that hydrogen bonds within the 'complex core' of the tRNA (including the base pairs G-10 . C-25, C-11 . G-24 and C-13 . G-21 within the dihydrouridine stem and the tertiary structure base pair G-15 . C-48 melt at a lower temperature than the tertiary structure hydrogen bonds between G-19 in the dihydrouridine loop and C-56 in the TpsiC loop.