Effects of diet on rumen proliferation and fecal shedding of Escherichia coil O157:H7 in calves

Calves inoculated with Escherichia coli O157:H7 and fed either a high-roughage or high-concentrate diet were evaluated for rumen proliferation and fecal shedding of E. coli O157:H7. Calves fed the high-roughage diet had lower mean rumen volatile fatty acid concentrations and higher rumen pH values than did calves fed the high-concentrate diet. Despite these differences in rumen conditions, the calves fed the high-roughage diet did not have greater rumen populations of E. coli O157: H7 and did not exhibit increased or longer fecal shedding compared with the calves fed the high-concentrate diet. Two calves shedding the highest mean concentrations of E. coli O157:H7 were both fed the high-concentrate diet. There was a significant (P < 0.05) positive correlation between fecal shedding and rumen volatile fatty acid concentration in calves fed a high-concentrate diet. The effects of diet on E. coli O157:H7 proliferation and acid resistance were investigated using an in vitro rumen fermentation system. Rumen fluid collected from steers fed a high-roughage diet, but not from steers fed a high-concentrate diet, supported the proliferation of E. coli O157:H7. Rumen fluid from steers fed a high-concentrate diet rapidly induced acid resistance in E. coli O157:H7. The impact of diet on fecal shedding of E. coli O157:H7 is still unclear and may depend on dietary effects on fermentation in the colon and on diet-induced changes in the resident microflora. However, rapid development of acid tolerance by E. coli O157:H7 in the rumens of calves fed high-concentrate diets, allowing larger populations to survive passage through the acidic abomasum to proliferate in the colon, may be one factor that influences fecal shedding in cattle on feed.     

Inactivation of Escherichia coli O157:H7 and Listeria monocytogenes on plastic kitchen cutting boards by electrolyzed oxidizing water.

One milliliter of culture containing a five-strain mixture of Escherichia coli O157:H7 (approximately 10(10) CFU) was inoculated on a 100-cm2 area marked on unscarred cutting boards. Following inoculation, the boards were air-dried under a laminar flow hood for 1 h, immersed in 2 liters of electrolyzed oxidizing water or sterile deionized water at 23 degrees C or 35 degrees C for 10 or 20 min; 45 degrees C for 5 or 10 min; or 55 degrees C for 5 min. After each temperature-time combination, the surviving population of the pathogen on cutting boards and in soaking water was determined. Soaking of inoculated cutting boards in electrolyzed oxidizing water reduced E. coli O157:H7 populations by > or = 5.0 log CFU/100 cm2 on cutting boards. However, immersion of cutting boards in deionized water decreased the pathogen count only by 1.0 to 1.5 log CFU/100 cm2. Treatment of cutting boards inoculated with Listeria monocytogenes in electrolyzed oxidizing water at selected temperature-time combinations (23 degrees C for 20 min, 35 degrees C for 10 min, and 45 degrees C for 10 min) substantially reduced the populations of L. monocytogenes in comparison to the counts recovered from the boards immersed in deionized water. E. coli O157:H7 and L. monocytogenes were not detected in electrolyzed oxidizing water after soaking treatment, whereas the pathogens survived in the deionized water used for soaking the cutting boards. This study revealed that immersion of kitchen cutting boards in electrolyzed oxidizing water could be used as an effective method for inactivating foodborne pathogens on smooth, plastic cutting boards.     

Female-to-male sex pheromones of low volatility in the Asian elephant,Elephas maximus

In their natural ecosystems, the sexes of Asian elephants,Elephas maximus, live separately. For several weeks prior to ovulation, the urine and cervical mucus of female Asian elephants contain extractable chemical agents of low volatility that elicit a high frequency of flehmen responses from bull elephants as an integral part of mating. Subsequent to flehmen responses, male sexual arousal occurs and, if the female is available, mating results. During the course of our project to determine the agent(s) and describe the responses associated with female to male sexual communication, we have identified an unusual compound. This compound, apparently the sole component of the active fraction, was identified by mass, proton nuclear magnetic resonance, ultraviolet/visible, and infrared spectrometries as indolo-[2,1-b] quinazoline-6,12-dione (tryptanthrine). Exhaustive and repetitive bioassays established that pure authentic (synthetic) tryptanthrine was not the compound responsible for the bioresponse. Rather a coeluting minor component, also of low volatility, elicited the male bioresponse.     

Structural modeling of the pro-ocytocin-neurophysin precursor

The hormonal precursor pro-ocytocin-neurophysin is activated by selectivecleavage at Arg2-Ala13, producing mature ocytocin and neurophysin. Tounderstand the cleavage mechanism better, and in particular the recognitionof the cleavage site, it is necessary to characterize the three-dimensionalstructure of the precursor molecule. Here we combine a variety ofexperimental data with molecular modeling and dynamics calculations toderive possible precursor conformations. In the models obtained, theN-terminus of the precursor, corresponding to the ocytocin segment, ishydrogen bonded in a pocket of the neurophysin moiety in a similar mannerto a crystallographically obtained non-covalent complex between the twomolecules. The calculations suggest that although the ocytocin segment isrelatively flexible, it adopts a stable, broad loop structure in thevicinity of the cleavage region, which may constitute the structuralelement recognized by the cleaving enzyme. The calculations also suggest apossible widening of the distance between the two neurophysin domains inthe precursor relative to that in the non-covalent neurophysin- ocytocincomplex.     

Solution Structure and Constrained Molecular Dynamics Study of Vitamin B12 Conjugates of the Anorectic Peptide PYY(3–36)

Vitamin B₁₂–peptide conjugates have considerable therapeutic potential through improved pharmacokinetic and/or pharmacodynamic properties imparted on the peptide upon covalent attachment to vitamin B₁₂ (B₁₂). There remains a lack of structural studies investigating the effects of B₁₂ conjugation on peptide secondary structure. Determining the solution structure of a B₁₂–peptide conjugate or conjugates and measuring functions of the conjugate(s) at the target peptide receptor may offer considerable insight concerning the future design of fully optimized conjugates. This methodology is especially useful in tandem with constrained molecular dynamics (MD) studies, such that predictions may be made about conjugates not yet synthesized. Focusing on two B₁₂ conjugates of the anorectic peptide PYY(3–36), one of which was previously demonstrated to have improved food intake reduction compared with PYY(3–36), we performed NMR structural analyses and used the information to conduct MD simulations. The study provides rare structural insight into vitamin B₁₂ conjugates and validates the fact that B₁₂ can be conjugated to a peptide without markedly affecting peptide secondary structure.     

Effects of triparanol and AY-9944 upon sterol biosynthesis inChlorella

The growth rates of three species ofChlorella were inhibited by triparanol and AY-9944.Chlorella emersonii was noticeably more resistant to both inhibitors than the other species. A large number of sterols were isolated and identified in inhibited cultures. Ca. 18 of these were identified from nature for the first time. Triparanol resulted in inhibition of the removal of the 14α methyl group. It also inhibited the second alkylation of the side chain and, in one species, strongly inhibited the Δ⁸ → Δ⁷ isomerase reaction. InC. ellipsoidea, triparanol also inhibited Δ¹⁴-reductase and Δ⁷-reductase. The introduction of the Δ²² double bond was inhibited by both drugs. The effect of AY-9944 was similar to that of triparanol inC. emersonii, but it was an extremely effective Δ¹⁴-reductase inhibitor inC. ellipsoidea. These various types of inhibition of sterol synthesis indicate a lack of specificity of both drugs inChlorella and suggest that primitive plants such as these may be valuable as test organisms in an evaluation of the activity of potential inhibitors of sterol biosynthesis.