Retrospective observations on the transmission of East Coast fever in Zimbabwe

Summary Records of 283 outbreaks of East Coast fever in Zimbabwe in the period 1914 to 1946 reveal that transmission of infection occurred throughout the year with peaks in January to March and May to July. The high level of transmission in January to March coincides with the known seasonal occurrence of adultRhipicephalus appendiculatus. It is suggested that transmission at other times of the year may have been effected by a population ofR. appendiculatus which did not exhibit a strictly seasonal life-cycle and has since been eradicated.

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Observaciones retrospectivas sobre la transmision de fiebre de la costa este en zimbabwe

Resumen Los registros de 283 brotes de Fiebre de la Costa Este en Zimbabwe en el periodo 1914–1946 revelaron, que la transmisión de la enfermedad ocurrió durante todo el a?o, con aumentos en enero-marzo y mayo–julio. El nivel alto de transmisión enenero-marzo coincide con la conocida ocurrencia estacional deRhipicephalus appendiculatus adultos. Se sugiere que la transmisión en otras épocas del a?o, podrían haber sido afectadas por poblaciones deR. appendiculatus el cual no exhibe cidos de vida estrictos y que ha sido erradicado.

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Observation a posteriori sur la transmission au zimbabwe de la theileriose

Résumé Les relevés de 283 foyers de la theileriose au Zimbawe durant la période 1914–1946 ont révélé que la transmission de l'infection s'effectue tout au long de l'année avec des pointes en janvier–mars et mai–juillet. Le haut degré de transmission de l'infection en janvier–mars co?ncide avec la fréquence saisonnière connue desRhipicephalus appendiculatus adultes. Ce fait suggère que la transmission pendant les autres époques de l'année pouvait avoir été réalisée par une population deR. appendiculatus qui ne possédait pas un cycle strictement saisonnier et qui a été éliminée depuis lors.

     

Genetic control over grain damage in a spring barley mapping population

A genetic map was constructed using DNA‐based markers in a barley mapping population derived from the cross ‘Tankard’בLivet’, that was developed to explore the genetic control over grain damage in spring barley cultivars. Quantitative trait loci (QTL) were located for husk skinning, gape between the lemma and palea and splitting of the fused pericarp/testa/aleurone tissues. The QTL accounted for 70% of the genetic variation in Split and 60% of the genetic variation in Gape and Skinning. The QTL were clustered on chromosomes 1H, 4H, 5H, 6H and 7H. QTL analysis indicates the possibility of transgressive segregation for grain splitting and so the breeding of lines with more extreme splitting. This is of concern to the malting industry as, without extensive phenotypic assessment, such lines could be commercialized, as was the case of Landlord, and put malting barley supplies at risk. These findings are discussed in relation to the genetic control over traits including grain length and width.     

New strategies for increasing heterozygosity in crops: Vicia faba mating system as a study case

Our research assesses the feasibility of using artificial selection on pre-mating floral traits to modify the mating system of faba bean (Vicia faba). This analysis considered two synthetic populations, which were derived from different genetic pools and had undergone five years of multiplication. For these populations, we identified floral and inflorescence traits that influence outcrossing per plant and examined the relative importance of these traits in governing yield. Codominant isozyme loci and the mixed-mating model were used to estimate the multilocus female outcrossing rate. A maternal half-sib design was used to evaluate the additive genetic component of floral and inflorescence traits, yield and yield components. Multiple regression was used to assess the effects of floral and inflorescence traits on outcrossing and yield and components of yield. The two populations exhibited mixing mating. Self-fertilization appears to result from the action of pollinating bees, so that its incidence could be modified by selection on floral and inflorescence traits that affect pollination. Floral and inflorescence traits affected individual differences in outcrossing unequally, with most variation being associated with the numbers of displayed flowers and inflorescences. Variation among plants in reward traits and in shape, although statistically significant, had limited and inconsistent influences on individual differences in outcrossing. Yield and its components varied strongly with aspects of floral display and, to a lesser extent, floral design, except for seed weight. Overall, our results imply that both outcrossing and yield could be enhanced by selection for plants that produce more inflorescences, each with relatively few flowers.     

Pressure-induced unfolding and aggregation of the proteins in whey protein concentrate solutions

Whey protein concentrate solutions (12% w/v, pH 6.65 +/- 0.05) were pressure treated at 800 MPa for 20-120 min and then examined using size exclusion chromatography (SEC), small deformation rheology, transmission electron microscopy, and various types of one-dimensional (1D) and two-dimensional (2D) polyacrylamide gel electrophoresis (PAGE). The pressure-treated samples showed a time-dependent loss of native whey proteins by SEC and 1D PAGE and a corresponding increase in non-native proteins and protein aggregates of different sizes. These aggregates altered the viscosity and opacity of the samples and were shown to be cross-linked by intermolecular disulfide bonds and by noncovalent interactions using 1D PAGE [alkaline (or native), sodium dodecyl sulfate (SDS), and SDS of reduced samples (SDS(R))] and 2D PAGE (native:SDS and SDS:SDS(R)). The sensitivity of the major whey proteins to pressure was in the order beta-lactoglobulin B (beta-LG B) > beta-LG A > bovine serum albumin (BSA) > alpha-lactalbumin (alpha-LA), and the large internal hydrophobic cavity of beta-LG may have been partially responsible for its sensitivity to high-pressure treatments. It seemed likely that, at 800 MPa, the formation of a beta-LG disulfide-bonded network preceded the formation of disulfide bonds between alpha-LA or BSA and beta-LG to form multiprotein aggregates, possibly because the disulfide bonds of alpha-LA and BSA are less exposed than those of beta-LG either during or after pressure treatment. It may be possible that intermolecular disulfide bond formation occurred at high pressure and that hydrophobic association became important after the high-pressure treatment.     

Field parameterization of an empirical sheetwash transport equation

Specially designed instruments were used to sample surface water and sediment discharge on a set of small hillslopes. The data set produced is unique as it includes simultaneous observations of surface water and sediment discharge, local surface declivity and drainage area at several points over the slope surface, and the precipitation intensity taken a number of times through natural storm events. The data are used to parameterize an empirical sediment transport law, expressing sediment transport as a power function of the local declivity and surface water discharge. A good fit to the observed data is achieved, suggesting that these field techniques may be used to parameterize the equation for different soils. A dynamic catena effect involving surface grain size, local declivity and the form of the sediment transport equation is recognized that may have significant implications for the form of sediment transport and long-term hillslope development.     

Identification of odorous gases originating from refuse waste

The complex mixture of gaseous compounds emitted from refuse wastes was scrubbed through an activated carbon column until odor breakthrough occurred. Refuse air samples were collected at the influent and effluent ports of the column for analysis on a gas chromatograph-mass spectrometer system. Sampling techniques involved the concentration of gaseous volatiles on Tenax GC adsorption tubes prior to thermal desorption onto a capillary fused-silica column for compound separation. Separated compounds were scanned by a quadrapole mass selective detector and compounds were matched against a library of mass spectra and available gas standards. Results indicated that the typical odorous gases emitted from refuse waste consisted mainly of carboxylic acids and some S compounds. Sensory tests revealed that a sweetish odor was associated with the carboxylic acids which eluted from the carbon column first.     

Investigation of ovicell hyperplasia in bryozoans chronically exposed to natural oil seepage

Systemic collection and examination of bryozoans from surface, subsurface and benthic kelp fronds in an area chronically exposed to natural oil seepage revealed no instances of ovicell hyperplasia. Reasons are presented to explain the contrast between these findings and reported ovicell hyperplasia in other species exposed to creosote and petroleum hydrocarbons.