Distribution and importance of Ethiopian vertisols and location of study sites

This chapter describes the distribution, use and importance of Vertisols in Ethiopia and indicates the study sites of the Joint Vertisol Project. Land and soil features are examined with particular reference to parent materials and landscape features, soil characterisation (colour, texture and depth-to-root-restricting layer). Distribution of Vertisols along the 12 physiographic regions of Ethiopia is described, the major agro-ecological zones of Ethiopia is listed, and distribution of Vertisols and their associations in Ethiopia is shown. Also grain yields some food crops on Vertisols under traditional management in the central Ethiopian highlands and potential arable areas of Vertisols in the different thermal and growing period zones

Conformational landscapes of DNA polymerase I and mutator derivatives establish fidelity checkpoints for nucleotide insertion

The fidelity of DNA polymerases depends on conformational changes that promote the rejection of incorrect nucleotides before phosphoryl transfer. Here, we combine single-molecule FRET with the use of DNA polymerase I and various fidelity mutants to highlight mechanisms by which active-site side chains influence the conformational transitions and free-energy landscape that underlie fidelity decisions in DNA synthesis. Ternary complexes of high fidelity derivatives with complementary dNTPs adopt mainly a fully closed conformation, whereas a conformation with a FRET value between those of open and closed is sparsely populated. This intermediate-FRET state, which we attribute to a partially closed conformation, is also predominant in ternary complexes with incorrect nucleotides and, strikingly, in most ternary complexes of low-fidelity derivatives for both correct and incorrect nucleotides. The mutator phenotype of the low-fidelity derivatives correlates well with reduced affinity for complementary dNTPs and highlights the partially closed conformation as a primary checkpoint for nucleotide selection

Low-fidelity DNA synthesis by human DNA polymerase theta

Human DNA polymerase theta (pol θ or POLQ) is a proofreading-deficient family A enzyme implicated in translesion synthesis (TLS) and perhaps in somatic hypermutation (SHM) of immunoglobulin genes. These proposed functions and kinetic studies imply that pol θ may synthesize DNA with low fidelity. Here, we show that when copying undamaged DNA, pol θ generates single base errors at rates 10- to more than 100-fold higher than for other family A members. Pol θ adds single nucleotides to homopolymeric runs at particularly high rates, exceeding 1% in certain sequence contexts, and generates single base substitutions at an average rate of 2.4 × 10−3, comparable to inaccurate family Y human pol κ (5.8 × 10−3) also implicated in TLS. Like pol κ, pol θ is processive, implying that it may be tightly regulated to avoid deleterious mutagenesis. Pol θ also generates certain base substitutions at high rates within sequence contexts similar to those inferred to be copied by pol θ during SHM of immunoglobulin genes in mice. Thus, pol θ is an exception among family A polymerases, and its low fidelity is consistent with its proposed roles in TLS and SHM

Traditional values of virginity and sexual behaviour in rural Ethiopian youth: results from a cross-sectional study

<p>Abstract</p> <p>Background</p> <p>Delaying sexual initiation has been promoted as one of the methods of decreasing risks of HIV among young people. In traditional countries, such as Ethiopia, retaining virginity until marriage is the norm. However, no one has examined the impact of this traditional norm on sexual behaviour and risk of HIV in marriage. This study examined the effect of virginity norm on having sex before marriage and sexual behaviour after marriage among rural Ethiopian youth.</p> <p>Methods</p> <p>We did a cross-sectional survey in 9 rural and 1 urban area using a probabilistic sample of 3,743 youth, 15–24 years of age. Univariate analysis was used to assess associations between virginity norm and gender stratified by area, and between sexual behaviour and marital status. We applied Kaplan-Meier and Cox regression analysis to estimate age at sexual debut and assessed the predictors of premarital sex among the never-married using SPSS.</p> <p>Results</p> <p>We found that maintaining virginity is still a way of securing marriage for girls, especially in rural areas; the odds of belief and intention to marry a virgin among boys was 3–4 times higher among rural young males. As age increased, the likelihood of remaining a virgin decreased. There was no significant difference between married and unmarried young people in terms of number of partners and visiting commercial sex workers. Married men were twice more likely to have multiple sexual partners than their female counterparts. A Cox regression show that those who did not believe in traditional values of preserving virginity (adjusted hazard ratio [AHR] = 2.91 [1.92–4.40]), alcohol drinkers (AHR = 2.91 [1.97–4.29]), Khat chewers (AHR = 2.36 [1.45–3.85]), literates (AHR = 18.01 [4.34–74.42]), and the older age group (AHR = 1.85 [1.19–2.91]) were more likely to have premarital sex than their counterparts.</p> <p>Conclusion</p> <p>Although virginity norms help delay age at sexual debut among rural Ethiopian youth, and thus reduces vulnerability to sexually transmitted infections and HIV infection, vulnerability among females may increase after marriage due to unprotected multiple risky sexual behaviours by spouses. The use of preventive services, such as VCT before marriage and condom use in marriage should be part of the HIV/AIDS prevention and control strategies.</p

Alternative application of oxen power for its optimal use

Draught animals have been used in Ethiopia since the third millennium B.C. It has been confined to land preparation and seed covering using the traditional implement 'maresha', pulled mainly by a pair of oxen under a ridged neck yoke. Even though research to replace the 'maresha' and to develop multi purpose use of animal power have been carried in different parts of the country, adoption has been slow until recent years where changes in tillage practices/ implements are becoming visible in some areas of the country. Employing draught animals for alternative animal powered technologies is not yet practiced by Ethiopian farmers at large. The diversified use of draught animals offers an opportunity for optimising the large energy source at hand, especially during the off season period

Re-engineering the polymerase domain of Klenow fragment and evaluation of overproduction and purification strategies.

We describe experiments to produce large quantities of the polymerase domain of E. coli DNA polymerase I for biochemical and biophysical studies. The polymerase domain derivative used in previous studies was insoluble when overproduced and tended to aggregate during purification. These problems were solved by a combination of two distinct strategies. By changing the expression system, we were able to obtain the overproduced protein in a soluble form, a necessary first step since attempts to purify the polymerase domain from the insoluble pellet were unsuccessful. The tendency of the polymerase domain to aggregate was eliminated by re-engineering the protein so as to remove both a solvent-exposed hydrophobic patch and a potentially unstructured region at the extreme N-terminus. Unlike the original construct, the re-engineered derivatives chromatographed as a single species and could be purified to homogeneity in good yield. Our experience in this study emphasizes the level of ignorance of the factors that influence protein overproduction and the need, in difficult cases, to evaluate many strategies in a semi-empirical manner

Vertisol surface drainage and effects on soil and nutrient conservation, excess water disposal and wheat growth at Debre Zeit

Gives results of the 1987 main rainy season results of the trials conducted to determine the effects of vertisol surface drainage on soil and nutrient conservation, excess water disposal and wheat growth at the Debre Zeit ILCA station and at Hidi