Safety evaluation of nuclear polyhedrosis virus replication in pigs

To evaluate the hygienic risk involved in using baculoviruses for insect pest control, safety studies are required. Pigs were chosen as representative test animals of commercial and agricultural importance. The tests were aimed at detecting virus propagation, immune reactions, and signs of acute infection (changes in body temperature and hematology profile, swelling of lymph nodes). Four of five animals inoculated with nuclear polyhedrosis virus showed a slight temperature rise at day 2 postinfection. After day 4 postinfection, no differences between infected animals and controls were observed. In the bioassay, virus activity could be recovered from fecal samples; however, no activity was found in organ extracts. The data did not indicate hygienic risks involved in the application of nuclear polyhedrosis virus, especially that from Mamestra brassicae, in biological pest control.     

Inactivation of coliphage MS-2 and poliovirus by copper, silver, and chlorine.

The efficacy of electrolytically generated copper and silver ions (400 and 40 micrograms/L, respectively) was evaluated separately and in combination with free chlorine (0.2 and 0.3 mg/L) for the inactivation of coliphage MS-2 and poliovirus type 1 in water at pH 7.3. The inactivation rate was calculated as log10 reduction/min: k = -(log10 Ct/C0)/t. The inactivation of both viruses was at least 100 times slower in water containing 400 and 40 micrograms/L copper and silver, respectively (k = 0.023 and 0.0006 for MS-2 and poliovirus, respectively), compared with water containing 0.3 mg/L free chlorine (k = 4.88 and 0.036). Significant increases in the inactivation rates of both viruses were observed in test systems containing 400 and 40 micrograms/L copper and silver, respectively, with 0.3 mg/L free chlorine when compared with the water systems containing either metals or free chlorine alone. Poliovirus was approximately 10 times more resistant to the disinfectants than coliphage MS-2. This observation suggests either a synergistic or an additive effect between the metals and chlorine for inactivation of enteric viruses. Use of copper and silver ions in water systems currently used in swimming pools and spas may provide an alternative to high levels of chlorination.     

A new concept of fibrin formation based upon the linear growth of interlacing and branching polymers and molecular alignment into interlocked single-stranded segments

In a previous electron microscopic study of early fibrin polymers processed by freeze drying and rotatory shadowing, a large proportion of loosely constructed, frequently branching linear molecular chains was observed; their structural organization was inconsistent with a half-staggered double-stranded model for fibrin polymerization. These conflicting results prompted us to investigate the structure of early fibrin polymers prepared according to a large variety of methods currently used for electron microscopy of macromolecules. By use of a systematic random sampling procedure, fibrin polymers were photographically recorded. They were classified according to their morphological form, and the frequency of occurrence of each configuration was determined. Half-staggered double-stranded forms accounted for less than 1% of all types encountered. Interpretation of the structural organization manifested in the diverse polymer forms observed necessitated the construction of a new interlocked single-strand model for fibrin polymerization. The fibrin polymerization process combines simultaneous propagation of linear growth, branching, and lateral interlocking (leading to lateral association), resulting in the rapid formation of a fibrin network. The structural pattern developing during growth of fibrin polymers appears to be determined principally by the enzymatic mechanism and not solely by the intrinsic molecular structure of fibrinogen. The validity of the interlocked single-strand model was tested by selective fibrinopeptide-B-releasing experiments. Under such activation conditions, the polymer forms predicted according to this and the half-staggered double-strand models should differ; the structures observed were indeed consistent with the interlocked single-strand hypothesis. The compatibility of existing data with this model is discussed.     

The methylenetetrahydrofolate-mediated biosynthesis of ribothymidine in the transfer-RNA of Streptococcus faecalis: incorporation of hydrogen from solvent into the methyl moiety.

The methyl carbon of ribothymidine in the tRNA of Streptococcus faecalis is derived from 5,10-methylenetetrahydrofolate, not S-adenosylmethionine. Isotope labeling experiments have shown that the reduction of the methylene carbon of the folate cofactor to the methyl carbon of the modified residue involves a mechanism in which hydrogen from solvent is incorporated into the methyl moiety. Although the identity of the reducing agent involved directly in this novel methylation remains to be established, data suggest that reduced flavin serves this function in vitro.     

The VMO:VL activation ratio while squatting with hip adduction is influenced by the choice of recording electrode

Concomitant hip adduction during squatting has long been advocated as a rehabilitative method to preferentially activate the VMO in persons with patellofemoral pain. This practice however has been based on research using surface electrodes which are prone to crosstalk from neighboring muscles (i.e., adductor magnus). This study sought to determine whether activation levels of the VMO relative to the VL while squatting with hip adduction would differ based on the choice of recording electrode. Ten healthy subjects performed a maneuver with hip adduction and without hip adduction. The mean VMO and VL activation levels were recorded simultaneously with surface and indwelling fine-wire electrodes. For both recording electrodes, the VMO and VL activity increased significantly with the addition of hip adduction (p < 0.05). However, the increase in VMO activation was more pronounced with surface electrodes, resulting in a significantly higher VMO:VL ratio with the incorporation of hip adduction compared to without hip adduction (p < 0.05). No difference in the VMO:VL ratio was observed between the two squat conditions for the fine-wire electrodes (p > 0.05). Our findings suggest that the VMO:VL activation ratio when squatting with hip adduction is influenced by electrode choice.     

Performance of a new dynamic model for predicting diurnal time courses of stomatal conductance at the leaf level

Under natural conditions, plants are subjected to continuous changes of irradiance that drive variations of stomatal conductance to water vapour (g_s). We propose a dynamic model to predict the temporal response of g_s at the leaf level using an asymmetric sigmoid function with a unique parameter describing time constants for increasing and decreasing g_s. The model parameters were adjusted to observed data using Approximate Bayesian Computation. We tested the model performance for (1) instant changes of irradiance; or (2) continuous and controlled variations of irradiance simulating diurnal time courses. Compared with the two mostly used steady‐state models, our dynamic model described daily time courses of g_s with a higher accuracy. In particular, it was able to describe the hysteresis of g_s responses to increasing/decreasing irradiance and the resulting rapid variations of intrinsic water‐use efficiency. Compared to the mechanistic model of temporal responses of g_s by Kirschbaum, Gross & Pearcy, for which time constants were estimated with a large variance, our model estimated time constants with a higher precision. It is expected to improve predictions of water loss and water‐use efficiency in higher scale models by using a small number of parameters.     

Diversity of Ferrous Iron-Oxidizing,Nitrate-Reducing Bacteria and their Involvement in Oxygen-Independent Iron Cycling

In previous studies, three different strains (BrG1, BrG2, and BrG3) of ferrous iron-oxidizing, nitrate-reducing bacteria were obtained from freshwater sediments. All three strains were facultative anaerobes and utilized a variety of organic substrates and molecular hydrogen with nitrate as electron acceptor. In this study, analyses of 16S rDNA sequences showed that strain BrG1 was affiliated with the genus Acidovorax, strain BrG2 with the genus Aquabacterium, and strain BrG3 with the genus Thermomonas. Previously, bacteria similar to these three strains were detected with molecular techniques in MPN dilution series for ferrous iron-oxidizing, nitrate-reducing bacteria inoculated with different freshwater sediment samples. In the present study, further molecular analyses of these MPN cultures indicated that the ability to oxidize ferrous iron with nitrate is widespread amongst the Proteobacteria and may also be found among the Gram-positive bacteria with high GC content of DNA. Nitrate-reducing bacteria oxidized ferrous iron to poorly crystallized ferrihydrite that was suitable as an electron acceptor for ferric iron-reducing bacteria. Biologically produced ferrihydrite and synthetically produced ferrihydrite were both well suited as electron acceptors in MPN dilution cultures. Repeated anaerobic cycling of iron was shown in a coculture of ferrous iron-oxidizing bacteria and the ferric iron-reducing bacterium Geobacter bremensis. The results indicate that iron can be cycled between its oxidation states +II and +III by microbial activities in anoxic sediments.