Detection of Salmonella spp. in oysters by PCR.

PCR DNA amplification of a region of the himA gene of Salmonella typhimurium specifically detected Salmonella spp. In oysters, 1 to 10 cells of Salmonella spp. were rapidly detected by the PCR following a pre-enrichment step to increase sensitivity and to ensure that detection was based on the presence of viable Salmonella spp.     

Antimicrobial resistance including Extended Spectrum Beta Lactamases (ESBL) among E. coli isolated from kenyan children at hospital discharge

BackgroundChildren who have been discharged from hospital in sub-Saharan Africa remain at substantial risk of mortality in the post-discharge period. Antimicrobial resistance (AMR) may be an important factor. We sought to determine the prevalence and risk factors associated with AMR in commensal Escherichia coli (E. coli) from Kenyan children at the time of discharge.Methodology/Principle findingsFecal samples were collected from 406 children aged 1–59 months in western Kenya at the time of discharge from hospital and cultured for E. coli. Susceptibility to ampicillin, ceftriaxone, cefotaxime, ceftazidime, cefoxitin, imipenem, ciprofloxacin, gentamicin, combined amoxicillin/clavulanic acid, trimethoprim-sulfamethoxazole, azithromycin, and chloramphenicol was determined by disc diffusion according to guidelines from the Clinical and Laboratory Standards Institute (CLSI). Poisson regression was used to determine associations between participant characteristics and the presence of extended-spectrum beta-lactamases (ESBL) producing E. coli. Non-susceptibility to ampicillin (95%), gentamicin (44%), ceftriaxone (46%), and the presence of ESBL (44%) was high. Receipt of antibiotics during the hospitalization was associated with the presence of ESBL (aPR = 2.23; 95% CI: 1.29–3.83) as was being hospitalized within the prior year (aPR = 1.32 [1.07–1.69]). Open defecation (aPR = 2.02; 95% CI: 1.39–2.94), having a toilet shared with other households (aPR = 1.49; 95% CI: 1.17–1.89), and being female (aPR = 1.42; 95% CI: 1.15–1.76) were associated with carriage of ESBL E. coliConclusions/SignificanceAMR is common among isolates of E. coli from children at hospital discharge in Kenya, including nearly half having detectable ESBL.     

Characterization of benextramine as an irreversible alpha-adrenergic blocker and as a blocker of potassium-activated calcium channels

An irreversible alpha-adrenergic blocker, benextramine [N,N'-bis(o-methoxybenzylamine-n-hexyl)-cysteamine] was used as a probe to study the possible interrelationship between alpha-adrenoceptors and the K+-activated Ca2+-channels. Benextramine, a tetraamine disulfide, acts irreversibly both on the alpha 1-adrenoceptor (t 1/2 = 3 min) and the alpha 2-adrenoceptors. These studies were carried out on rat brain synaptosomes, [3H]prazosin and [3H]clonidine binding. Benextramine blocked Ca2+ influx in rat brain synaptosomes under both depolarizing (75 mM KCl) and normal conditions (5 mM KCl). Its action at the channel is reversible with IC50 = 10 +/- 5 microM of the net Ca2+ influx. This makes benextramine a most potent Ca2+ blocker compared to verapamil or nicardipine (IC50 = 200 microM and 170 microM, respectively). Pretreatment of rat brain slices with benextramine gave a synaptosomal preparation which was devoid of either alpha 1-adrenergic or alpha 2-adrenergic binding capacity due to the irreversible binding of benextramine, but with an undisturbed Ca2+ influx. Thus, these results suggest that the alpha-adrenoceptors and the Ca2+-channels are independent of each other, and that full occupancy of the alpha-receptors does not affect the net calcium flux.     

Detection of early pregnancy factor (EPF) using the rabbit ovary and oviduct perfused in vitro

Two peaks of rabbit serum EPF activity were seen over the course of pregnancy. Rabbit ovaries with or without attached oviducts were perfused in vitro for 5 h beginning 12, 16, 24, 48, 72 and 120 h after mating. Perfused isolated ovaries did not produce EPF in vitro, but significant EPF activity was detected in the perfusate of the ovary together with oviduct. Pseudopregnant animals and those rabbits that did not ovulate exhibited no perfusate EPF activity. Perfusate EPF activity was highest at the time embryos were at the pronuclear stage and continued through the morula stage. Although the location of embryos at 72 h after mating varied between oviduct and uterus, EPF activity was maintained over the perfusion period. The results suggest that EPF release occurs within 3 h of fertilization and that the presence of the preblastocyst embryo is crucial for EPF release.     

Measurement of the effects of cadmium stress on protozoan grazing of bacteria (bacterivory) in activated sludge by fluorescence microscopy

The effect of cadmium stress on protozoan bacterivory in sewage sludge was measured by experimentally exposing sludge communities to 0 to 150 mg of Cd per liter for up to 6 h and then determining the rates of protozoan grazing on bacteria, using a double-staining technique and epifluorescence microscopy. Bacterivory was measured by incubating the sludge with fluorescently labeled bacterium-sized latex beads and directly observing ingestion of the beads and bacterial cells in the sludge by epifluorescence microscopy of preserved samples. Staining with 4',6-diamidino-2-phenylindole and acridine orange permitted the simultaneous determination of protozoan numbers and bacterivory activity as estimated by the number of bacterial cells and bacterium-sized latex beads ingested by the representative ciliate Aspidisca costata. Enumeration with latex beads proved to be an effective way of estimating bacterivory in sludges subjected to heavy-metal stress. This technique should prove useful for determining the effects of other chemical stresses on protozoan numbers and bacterivory in organic-rich environments. Although the number of protozoa declined significantly only after exposure to 100 mg of Cd per liter for 4 h, grazing, as indicated by bead ingestion, was significantly inhibited by Cd concentrations of greater than 25 mg/liter in less than 1 h, and exposure to 100 mg of Cd per liter effectively stopped protozoan grazing within 1 h of exposure. Protozoan ingestion of latex beads and bacteria was inversely correlated to Cd concentration and exposure time. The reduction of protozoan bacterivory by Cd provides a possible explanation for the increase in suspended bacteria in the effluents of metal-stressed treatment facilities.     

Quantitative light microscopic analysis of corpus luteum growth during pseudopregnancy in the rabbit

We employed stereological methods at the light-microscope level to examine the mechanism by which corpora lutea (CL) grow during the course of pseudopregnancy in the rabbit. Corpus luteum volume per ovary, the absolute volume of luteal cells per CL, individual luteal cell volume, the number of luteal and endothelial cells per CL, and capillary surface area per CL were examined in rabbits at Days 1, 4, 7, 11, and 18 of pseudopregnancy. Total CL volume increased from 3.7 +/- 0.1 microliter to 30.3 +/- 0.5 microliter over Days 1 to 11 and thereafter decreased to 15.2 +/- 1.1 microliter by Day 18. Stereological analyses showed that the increases in CL volume from Day 1 to Day 11 were due primarily to increases in the volume of individual luteal cells (from 2.6 +/- 0.2 pl on Day 1 to 23.5 +/- 1.7 pl on Day 11, 1 pl = (10 mu)3; r = 0.96), and that the decrease in CL volume after Day 11 resulted largely from a decrease in luteal cell volume (to 12.8 +/- 1.5 pl). In contrast, no change was seen in the number of luteal cells per CL (range 9.1 x 10(5)-12.5 x 10(5)). These data show that CL growth and subsequent regression during pseudopregnancy result primarily from changes in the volume of individual luteal cells, and not from changes in the number of luteal cells. These data support the hypothesis that modulation of progesterone production during pseudopregnancy is due to changes in individual luteal cell volume and not to changes in cell number.     

Biosynthesis of chlorophyll P-680 of photosystem II in greening leaves of plants adapted to heat shock

In etiolated pea and maize leaves illuminated after incubation at 38 degreesC, a new dark reaction was shown manifested in the bathochromic shift of spectral bands and accompanied by esterification of the product of protochlorophyllide photochemical reduction--Chld 684/676: Chld 684/676 --> Chl 688/680. After completion of the reaction a rapid (20-30 sec) quenching of the fluorescence of the reaction product (Chl 688/680) was observed. The reaction Chld 684/676 --> Chl 688/680 is inhibited under anaerobic conditions and in the presence of cyanide; the reaction accompanied by Chl 688/680 fluorescence quenching is not observed in pea mutants with impaired function of photosystem II reaction centers. The spectral properties of the formed Chl form with the absorption maximum at 680 nm, fluorescence quenching, and simultaneous synthesis of pheophytin suggest that the reaction is connected with the chlorophyll of photosystem II reaction center--P-680.