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Biomedical subjects

T Demeke

Publications and source records attributed to T Demeke.

10 recordsLinked to original sources
PubMed2000

Development of a PCR marker for rapid identification of the Bt-10 gene for common bunt resistance in wheat.

In western Canada, the Bt-10 resistance gene in wheat (Triticum aestivum) is effective against all the known races of common bunt caused by Tilletia tritici and T laevis. The genotypes of 199 F2 plants, originated from a cross between BW553 containing Bt-10 and the susceptible spring wheat cultivar 'Neepawa,' were established in greenhouse and field inoculation studies. A ratio of 1:2:1 resistant : heterozygous : susceptible was observed for bunt reaction, indicating that Bt-10 was expressed in a partially dominant fashion. A polymorphic DNA fragment, amplified using RAPD, and previously shown to be linked to Bt-10 was sequenced and SCAR (sequence characterized amplified region) primers devised. However, SCAR primers failed to amplify the polymorphic fragment. Restriction of PCR products with DraI revealed a polymorphic fragment of 490 bp resulting from a single base pair difference between lines possessing Bt-10 and those lacking the gene. As per the base pair difference, FSD and RSA primers were designed to generate a 275-bp polymorphic DNA fragment. Both 275- and 490-bp polymorphic fragments were present in all of the 22 cultivars known to carry Bt-10, and absent in all 16 cultivars lacking Bt-10. A 3:1 ratio was observed for presence: absence of the 275-bp marker in the F2 population. Using Southern analysis, the 490-bp fragment was effective in differentiating homozygous resistant plants from those heterozygous for Bt-10, based on its presence and the hybridization signal strength. A 1:2:1 resistant : heterozygous : susceptible ratio was also observed for the molecular marker and corresponded to 88% of the phenotypes deduced from the original F2 population. The molecular marker was estimated to be between 1.1 cM and 6.5 cM away from the Bt-10 resistance gene, based on the segregation analysis. Segregation analyses of Bt-10 and the 275-bp marker, evaluated in three different Canada Prairie Spring (CPS) wheat populations, demonstrated a segregation ratio of 3:1 for the molecular marker in two of the populations. These results demonstrated that the PCR marker system using the FSD and RSA primer pair permitted a rapid and reliable identification of individual lines carrying the Bt-10 gene for resistance to common bunt.

Blotting, Southern↗
PubMed1996

A DNA marker for the Bt-10 common bunt resistance gene in wheat.

The Bt-10 bunt gene confers resistance to most races of the common bunt fungi, Tilletia tritici and T. laevis. The RAPD technique, employing a total of 965 decamer primers, was used to identify polymorphic markers between resistant (BW553) and susceptible ('Neepawa") near-isogenic lines. Primer 196 (5' CTC CTC CCC C 3') produced a 590 base pair (bp) reproducible fragment only in the resistant near-isogenic line. The 590-bp DNA fragment was present in all the 22 wheat cultivars known to carry the Bt-10 resistance gene and also in 15 resistant F2 lines obtained from a cross between the resistant parent, BW553, and the susceptible parent, 'Neepawa'. The 590-bp fragment was absent in 16 susceptible cultivars tested and in 15 susceptible F2 lines obtained from the cross described above. These results suggest a close linkage between the presence of the 590-bp fragment and the Bt-10 resistance gene. Primer 372 (5' CCC ACT GAC G 3') amplified a 1.0-kilobase (kb) fragment that was present only in the susceptible near-isogenic line. This 1.0-kb fragment was present in 13 of the 16 susceptible cultivars and in 13 of the 15 susceptible F2 lines. However, the primer also amplified the 1.0-kb fragment in some resistant cultivars and resistant F2 lines, suggesting a looser linkage between the occurrence of the fragment and the susceptible allele.

Base Sequence↗
PubMed1993

Goitre in Ethiopia.

A stratified goitre survey was conducted on 35,635 schoolchildren and 19,158 household members in all Regions of Ethiopia except Eritrea and Tigrai. The gross goitre prevalence (mean of male and female values) among schoolchildren and household members was 30.6 and 18.7% respectively, while that of visible goitre was 1.6 and 3.2% respectively. Prevalence was higher in females (27.3% in household members and 36.1% in schoolchildren) than in males (10.1% in household members and 25.1% in schoolchildren) and increased with age more in females than in males. The prevalence rates at higher altitudes were higher than those at lower altitudes in both schoolchildren and household members. Using an epidemiological model the consequences of iodine deficiency, including cretinism and maternal wastage, have been estimated.

Adolescent↗
PubMed1992

The effects of plant polysaccharides and buffer additives on PCR.

A survey of the inhibitory effects of various plant polysaccharides on PCR amplification of a 974-bp section of rbcL in spinach revealed that most of the polysaccharides tested (arabinogalactan, carrageenan, dextran, gum guar, gum karaya, gum locust bean, inulin, mannan, pectin, starch and xylan) were not inhibitory. In contrast, two of the acidic polysaccharides (dextran sulfate and gum ghatti) were inhibitory. The addition of 0.5% Tween 20 reversed the inhibitory effects of gum ghatti (polysaccharide:DNA ratio of 500:1). The inhibitory effect of dextran sulfate (50:1) could be reversed by the addition of Tween 20 (0.25% or 0.5%), DMSO (5%) or polyethylene glycol 400 (5%), but none of these three additives were effective at a 100:1 ratio of dextran sulfate/DNA.

Biotechnology↗
PubMed1991

Xerophthalmia in Ethiopia: a nationwide ophthalmological, biochemical and anthropometric survey.

A total of 6636 children, aged from 6 months to 6 years and selected throughout the country using a multi-staged stratified sample design, were examined for signs of xerophthalmia. The concentrations of retinol and of beta-carotene were measured in 742 children, including those with xerophthalmia and every twentieth of the remaining children. Anthropometric measurements were made on 2909 of the children. Bitot's spots were seen in 1.0% of all children, with a higher prevalence in the pastoral (1.6%) and cropping (1.1%) agro-ecological zones than in the zones characterized by cash crops (0.4%) and 'ensete' (false banana, Ensete ventricosum) (0.0%). One case of corneal xerosis and 2 cases of corneal scar were also seen. Serum retinol levels were in the 'deficient' range (less than 0.35 mumol l-1) in 16% and 'low' (0.35-0.69 mumol l-1) in 44% of children. Serum retinol and clinical signs did not show any correlation with occupation and education of head of household, household size or anthropometric measurements. More stunting than wasting was observed, with peak prevalence of these signs of malnutrition being observed in the second year of life.

Agriculture↗
PubMed1990

Seasonal energy deficiency in Ethiopian rural women.

The purpose of the study was to establish the existence of seasonal exposure to energy deficiency in rural areas of developing countries and to investigate the sequence of appearance and the nature of energy-sparing mechanisms utilized under real life conditions. The body weight of a group of 226 rural Ethiopian women was measured repeatedly over a one year period, at 45 day intervals. On a sub-group of 22 non-pregnant women total energy intake, TEI, total energy expenditure, TEE, and basal metabolic rate, BMR were also measured by the precise weighing method and by indirect calorimetry (Kofranyi-Michaelis respirometer or Douglas bag) and activity diaries. Body weight was found to have a moderate but statistically significant seasonal trend, with an overall loss of 1.6 kg. Women with higher BMI had larger seasonal swings of their body weight. Seasonal fluctuations were also found for TEI (maximum difference 420 kcal/d, not significant), and for BMR (maximum difference 200 kcal/day, P less than 0.000). TEE (mean yearly value of 1909 kcal/d, 42 kcal/kg) was very stable over the year and did not show any seasonal fluctuation. The present findings suggest that, under the study circumstances, seasonal exposure to fluctuation in food availability caused a moderate weight loss which was sufficient to induce metabolic adaptations, but not to cause any detectable change in physical activity.

Adaptation, Physiological↗