RESUMEN

An isotope dilution congener-specific method for the determination of the most abundant and most toxic polychlorinated naphthalenes (PCNs) was developed using gas chromatography with high resolution mass spectrometry (GC-HRMS). The method was used to determine the concentration of 24 target congeners and total PCN concentrations in fish and sediment samples. Tissue samples were extracted using pressurized liquid extraction (PLE) and sediment samples were extracted using Soxhlet extraction. Sample extracts were cleaned up using either a manual two-stage open column procedure or an automated FMS Power Prep System with multi-analyte and multi-sample capability using a three-column cleanup procedure. Sediment extracts were cleaned up with a dual open column cleanup technique involving the use of both a multi-layered silica (silver nitrate/acid/base/neutral silica) column followed by column containing carbon-activated silica. Fish tissue extracts were cleaned up on the automated system involving the use of a high capacity ABN (acid/base/neutral column), carbon celite column, and a basic alumina column. The method is capable of producing instrument detection limits (IDLs) between 0.06 and 0.13pg for each PCN (on column), with method detection limits (MDLs) for the fish extracts ranging from 1.3 to 3.4pg/g (wet weight) and 0.46 to 1.2pg/g (dry weight) for sediments. The average accuracy of 34 spiked fish samples analysed over a period of several months was 100% with a precision (%RSD) of 12%. Similarly, the average accuracy for 28 spiked sediment samples was 104% with a precision (%RSD) of 12%. The application of the method to environmental samples was demonstrated through the analysis of sediment and fish samples obtained from Lake Ontario, Canada. The method is used both for the determination of 24 PCNs and to perform non-targeted screening for the remaining 51 PCN congeners, which are included in the total PCN quantification result. It is currently one of the most comprehensive and accurate congener-specific methods available and was developed from the existing techniques used for the determination of polychlorinated dioxins and furans to produce high quality data with only minor modifications in the clean-up procedure. It can therefore be readily adopted by other laboratories performing dioxin and POP analyses.

Asunto(s)

RESUMEN

AIM: To determine the effect of two physiologically important temperatures on growth and chemotaxis in Campylobacter jejuni. METHODS AND RESULTS: Growth curves of Camp. jejuni were compared at 37 degrees C and 42 degrees C. Chemotaxis was compared at 37 degrees C and 42 degrees C by the disc and capillary assays. Student's t-test was applied to the results of the capillary assay to assess the significance in the difference between chemotaxis at the two temperatures. Both, the growth rate and chemotactic ability of the isolate, were found to be greater at 37 degrees C. CONCLUSIONS: Quorum sensing (related to population density), a regulation mechanism of virulence in micro-organisms, has been reported in Campylobacter. Chemotaxis is also a known virulence factor of Campylobacter. Both, growth (in terms of population density) and chemotaxis, being greater at 37 degrees C than at 42 degrees C, suggests that the physiological temperature of humans (37 degrees C) might be more favourable for the expression of virulence in Campylobacter than that of birds (42 degrees C). SIGNIFICANCE AND IMPACT OF THE STUDY: It is as yet not known why Campylobacter causes disease in humans but is avirulent in birds. This study suggests that the human body temperature is optimum for growth and chemotaxis in Campylobacter. There is scope for the study of temperature regulation of other virulence determinants of Campylobacter.

Asunto(s)

RESUMEN

In all 312 actinomycete strains were isolated from water and soil samples from different regions. All these isolates were purified and screened for their antifungal activity against pathogenic fungi. Out of these, 22% of the isolates exhibited activity against fungi. One promising strain, Streptomyces albidoflavus PU 23 with strong antifungal activity against pathogenic fungi was selected for further studies. Antibiotic was extracted and purified from the isolate. Aspergillus spp. was most sensitive to the antibiotic followed by other molds and yeasts. The antibiotic was stable at different temperatures and pH tested and there was no significant loss of the antifungal activity after treatment with various detergents and enzymes. Synergistic effect was observed when the antibiotic was used in combination with hamycin. The antibiotic was fairly stable for a period of 12 months at 4 degree C. The mode of action of the antibiotic seems to be by binding to the ergosterol present in the fungal cell membrane resulting in the leakage of intracellular material and eventually death of the cell. The structure of the antibiotic was determined by elemental analysis and by ultraviolet (UV), Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) and liquid chromatography mass spectra (LCMS). The antibiotic was found to be a straight chain polyhydroxy, polyether, non-proteinic compound with a single double bond, indicating a nonpolyene antifungal antibiotic.

Asunto(s)

RESUMEN

BACKGROUND & OBJECTIVE: Dermatophytes responsible for causing dermatophytoses in humans have acquired resistance to certain antimycotic drugs. We isolated naturally occurring actinomycetes with an ability to produce metabolites having antimycotic property. The timecourse of antifungal metabolite production in terms of arbitrary units (AU) under optimum conditions was studied. METHODS: Water and soil samples were collected from various locations. The actinomycetes were isolated on starch casein medium and screened for their antifungal activity against yeasts and molds including dermatophytes. One promising isolate which showed a unique, stable and interesting property of inhibiting only dermatophytes was selected and characterized. Optimization of antifungal metabolite production in terms of AU using Trichphyton rubrum as target was done. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values of the culture supernatant from the isolate and that of griseofulvin were determined for all dermatophytes. RESULTS: Of the 218 actinomycete isolates, 14 per cent produced the metabolites having antifungal activity. The selected actinomycete, identified as Streptomyces rochei AK 39 produced metabolite, which was active against only dermatophytes whereas yeasts and other molds were resistant to it. Starch casein medium was found to be good for inducing antifungal activity in the isolate. The maximum antifungal metabolite production (400 AU/ml) was achieved in the late log phase, which remained constant during the stationery phase, and it was extracellular in nature. The MIC and MFC values of the culture supernatant from the isolate against the dermatophytes were within the range 1.25 to 5 and 1.25 to 10 AU/ml respectively. INTERPRETATION & CONCLUSION: The metabolite from Streptomyces rochei AK 39 was produced during late log phase and was active against only dermatophytes with a greater potency than griseofulvin. However, this needs further investigation using purified powdered form of the active component.

Asunto(s)

RESUMEN

About 312 actinomycetes were isolated from soil samples on chitin agar. All these isolates were purified and screened for their antifungal activity against pathogenic fungi. Out of these, 22% of the isolates exhibited activity against fungi. One promising isolate with strong antifungal activity against pathogenic fungi was selected for further studies. This isolate was from Pune, and was active against both yeasts and molds. Various fermentation parameters were optimized. Based on morphological and biochemical parameters, the isolate was identified as Streptomyces. The correlation of antifungal activity with growth indicated growth dependent production of antimetabolite. Maximum antifungal metabolite production (600 units/ml) was achieved in the late log phase, which remained constant during stationery phase, and it was extracellular in nature.

Asunto(s)

RESUMEN

BACKGROUND: Peptide YY (PYY) is a 36 amino-acid peptide secreted from ileal L cells following meals. The cleaved subpeptide PYY[3-36] is biologically active and may constitute the majority of circulating PYY-like immunoreactivity. The peptide family that includes PYY, pancreatic peptide and neuropeptide Y is noted for its orexigenic effect following intracerebroventricular administration. OBJECTIVE: To investigate the effects of peripheral (intraperitoneal and chronic subcutaneous) infusions of PYY[3-36] on food intake, body weight and glycemic indices. DESIGN/RESULTS: Food intake was measured in normal mice and in several rodent models of obesity and type II diabetes. In marked contrast to the reported central orexigenic effects, in the present study, PYY[3-36] acutely inhibited food intake by up to 45%, with an ED(50) of 12.5 microg/kg in fasted female NIH/Swiss mice. A 4-week infusion reduced weight gain in female ob/ob mice, without affecting the cumulative food intake. In diet-induced obese male mice, PYY[3-36] infusion reduced cumulative food intake, weight gain and epididymal fat weight (as a fraction of carcass) with similar ED(50)'s (466, 297 and 201 microg/kg/day, respectively) and prevented a diet-induced increase in HbA1c. Infusion at 100 microg/kg/day for 8 weeks in male fa/fa rats reduced the weight gain (288+/-11 vs 326+/-12 g in saline-infused controls; P<0.05), similar to effects in a pair-fed group. In female ob/ob and db/db mice, there was no acute effect of PYY[3-36] on plasma glucose concentrations. In male diabetic fatty Zucker rats, PYY[3-36] infused for 4 weeks reduced HbA1c and fructosamine (ED(50)'s 30 and 44 microg/kg/day). CONCLUSION: Peripheral PYY[3-36] administration reduced the food intake, body weight gain and glycemic indices in diverse rodent models of metabolic disease of both sexes. These findings justify further exploration of the potential physiologic and therapeutic roles of PYY[3-36].

Asunto(s)

RESUMEN

PURPOSE: Campylobacter spp. is a major food borne pathogen and shows resistance towards gamma radiation. In the present study, effect of gamma radiation was assessed on the indigenous strains of Campylobacter spp. inoculated in food and water samples. METHODS: Campylobacter spp. were isolated from river water and faeces of various birds and animals. The growth rate was studied for these isolates by propagating them in Kapadnis-Baseri medium. The survival of Campylobacter spp. inoculated in food and water samples was tested after exposing them to gamma radiation. RESULTS: The isolates survived well in meat and milk samples and were sensitive to 1.8 KGy dose of gamma radiation, which lies with in the FDA limit. The effect of radiation on Campylobacter spp. varied with the species and the type of food. CONCLUSIONS: The results obtained suggest that the dose of gamma radiation should be standardized depending on the Campylobacter spp. and the type of food that is being processed.