Microhabitat choice and diet of rodents in Maynugus irrigation field, northern Ethiopia

An ecological study on the choice of microhabitat and diet of small mammals was carried out in Maynugus irrigation field of the Tigray region in northern Ethiopia. Abundance of rodents was high during the reproductive phase of the agricultural plants. Mastomys erythroleucus occurred more frequently in vegetable fields, whereas Arvicanthis dembeensis was more frequent in habitats with monocot plants. Scrotal males and reproductive females consumed more food by weight than abdominal males and quiescent females. Arvicanthis dembeensis consumed more food than M. erythroleucus. Both the species consumed more food during the main rainy season. All the cultivated plants were attacked by these rodents with a degree of difference in relation to season, species, sex, age and sexual condition. As rodent attack was more intense during the fruiting phase of the plants, rodent control management should be carried out during the flowering phase.     

Evaluation of the Influence of thiosemicarbazone–triazole hybrids on genes implicated in lipid oxidation and accumulation as potential anti-obesity agents

A series of thiosemicarbazone–triazole hybrids 1a–h are efficiently synthesised and evaluated for their influence on the expression of genes, cpt-1, acc-1 and pgc-1, which are essential in lipid metabolism. The test results show that hybrids 1c and 1g exhibited relatively high influence on the expression of cpt-1 and pgc-1 and suppression of acc-1 as desired.     

Effects of alkyltin compounds on hydrogen-oxidizing anaerobic bacteria

Methyl and butyltin compounds were inhibitory to all anaerobes examined, but there were great variations, depending on the specific alkyltin and bacterium. The methanogens were inhibited more strongly by methyl than by butyl derivatives; more than 50% inhibition occurred with 0.025–0.5 mM of the methyltins, whereas 0.16–1.8 mM butyltins were needed for the same level of inhibition; tri-butyltin was the least toxic.Methanosarcina barkeri was, in general, more resistant than theMethanococcus sp. andMethanobacterium bryantii. TheDesulfovibrio were more strongly inhibited by mono-methyltin than by di- and tri-methyl derivatives; butyltins were, in general, not so toxic. Mono-methyltin at 0.15 mM almost completely inhibited three of the sulfate reducers, butDesulfovibrio thermophilus required 0.7 mM for this level of inhibition. Tri-butyltin at 1.8 mM did not cause major inhibition, whereas mono- and di-butyltins were more inhibitory.Acetobacterium woodii was most affected by mono- and dimethyltins, and least by tri-methyltin and mono-butyltin. In contrast,Wollinella succinogenes was most affected by tri-methyltin. This study suggests several major groups of anaerobes thought to be involved in metal biocorrosion vary greatly in their response to alkyltins; most interesting is the relative insensitivity by methanogens and sulfate reducers to tri-butyltin, which is a major component in commercial antifouling paints. Our results differ considerably from those reported for aerobic microorganisms, which were found to be most affected by tributyltin.     

Nitrate as a sole nitrogen source forMethanococcus thermolithotrophicus and its effect on growth of several methanogenic bacteria

Methanococcus (Mc.) thermolithotrophicus can use nitrate as the sole source of nitrogen, but four other species of methanogens cannot. The growth rate was similar on both nitrate and ammonium, but yields were 20–25% lower on nitrate.Mc. thermolithotrophicus, Methanobacterium thermoautotrophicum, andMethanobrevibacterium smithii were not inhibited by 20 mM nitrate, butMethanospirillum hungatei was inhibited 35%, andMethanosarcina barkeri was completely inhibited by 20 mM nitrate. WhenMc. thermolithotrophicus was growing with nitrate as the sole source of nitrogen, growth was dependent on either molybdenum or tungsten, and the presence of both gave the best growth response; vanadium or chromium did not replace the requirement for these metals. Growth on ammonium could not be strictly demonstrated to require either of these metals, but both molybdenum and tungsten stimulated growth.     

Active hexose correlated compound enhances the immune function of mice in the hindlimb-unloading model of spaceflight conditions.

Hindlimb unloading is a ground-based model that simulates some of the aspects of spaceflight conditions, including lack of load bearing on hindlimbs and a fluid shift to the head. It has been shown that treatment with active hexose correlated compound (AHCC) restores resistance to infection in mice maintained under hindlimb-unloading conditions. The present study was designed to clarify the mechanisms by which AHCC enhances resistance to infection in this model. We hypothesized that oral administration of AHCC will enhance the function of the immune system, which could lead to the increased resistance to infection observed in this model. AHCC or the excipient was orally administered to mice, and the function of the immune system was assessed in spleen and peritoneal cells isolated from those groups. The results of the present study showed that administration of AHCC for 1 wk before and throughout the second day of the hindlimb-unloading period enhanced the function of the immune system assessed by spleen cell proliferation and cytokine production in spleens and nitric oxide and cytokine production in peritoneal cells. These findings suggest that AHCC can be used as a potent immunoenhancer, especially in cases in which the immune system is suppressed by any condition, including diseases such as human immunodeficiency virus infection and cancer.     

Accounting for the decrease of photosystem photochemical efficiency with increasing irradiance to estimate quantum yield of leaf photosynthesis

Maximum quantum yield for leaf CO₂ assimilation under limiting light conditions (Φ _CO2LL) is commonly estimated as the slope of the linear regression of net photosynthetic rate against absorbed irradiance over a range of low-irradiance conditions. Methodological errors associated with this estimation have often been attributed either to light absorptance by non-photosynthetic pigments or to some data points being beyond the linear range of the irradiance response, both causing an underestimation of Φ _CO2LL. We demonstrate here that a decrease in photosystem (PS) photochemical efficiency with increasing irradiance, even at very low levels, is another source of error that causes a systematic underestimation of Φ _CO2LL. A model method accounting for this error was developed, and was used to estimate Φ _CO2LL from simultaneous measurements of gas exchange and chlorophyll fluorescence on leaves using various combinations of species, CO₂, O_2, or leaf temperature levels. The conventional linear regression method under-estimated Φ _CO2LL by ca. 10–15 %. Differences in the estimated Φ _CO2LL among measurement conditions were generally accounted for by different levels of photorespiration as described by the Farquhar-von Caemmerer–Berry model. However, our data revealed that the temperature dependence of PSII photochemical efficiency under low light was an additional factor that should be accounted for in the model.     

Awash National Park,Ethiopia: use policy,ethnic conflict and sustainable resources conservation in the context of decentralization

In response to recent decentralization in Ethiopia, we investigated pressure exerted on Awash National Park (ANP), vis‐a‐vis park resources; causes of park‐related conflicts and the impact of policy on sustainable resources conservation before decentralization (pre‐1995) and after decentralization (post‐1995). The study's aim was to assess the implementation of sustainable resources conservation in terms of use policy and conflicts in protected areas. We sampled a total of 210 respondents by stratified random sampling and group discussion participants and key informants using purposive sampling technique. Our results show that while policy problems were perceived to be the main threats to the park pre‐1995, demand for pasture land and water, resource‐caused conflicts, expansion of private and state farms were identified as main threats to the park post‐1995. Before decentralization (pre‐1995), inequitable resource sharing and poor organizational structures were the main causes of ethnic conflicts, whereas after decentralization, increasing demand for various resources were the main causes of conflict. We recommend experiences from the Simen National Park be tested to the benefit of improving the state of ANP.