Genetic and genomic approaches for the discovery of parasite genes involved in antimalarial drug resistance

The biggest threat to the war on malaria is the continued evolution of drug resistance by the parasite. Resistance to almost all currently available antimalarials now exists in Plasmodium falciparum which causes the most suffering among all human malaria parasites. Monitoring of antimalarial efficacy and the development and subsequent spread of resistance has become an important part in the treatment and control of malaria. With recent reports of reduced efficacy of artemisinin, the current recommended treatment for uncomplicated malaria, there is urgent need for better methods to recognize and monitor drug resistance for effective treatment. Molecular markers have become a welcome addition to complement the more laborious and costly in vitro and in vivo methods that have traditionally been used to monitor drug resistance. However, there are currently no molecular markers for resistance to some antimalarials. This review highlights the role of the various genetic and genomic approaches that have been used in identifying the molecular markers that underlie drug resistance in P. falciparum. These approaches include; candidate genes, genetic linkage and genome-wide association studies. We discuss the requirements and limitations of each approach and use various examples to illustrate their contributions in identifying genomic regions of the parasite associated with antimalarial drug responses

Reproductive traits in Ethiopian male goats

This thesis characterizes reproductive traits of Ethiopian male goats raised under extensive husbandry and subjected to differential nutritional management. A total of 177 extensively-managed indigenous bucks of 5 breeds (i.e., Arsi–Bale [AB], Central Highlands [CH], Afar, Boran and Woito-Guji [WG]) were selected following stratified random sampling.The bucks were compared according to three age classes (<14 mo [young], 14–19.5 mo [intermediate] and 19.6–24 mo [old]) to determine whether breed and age influenced body size, testicular traits and epididymal sperm morphology. Bucks of a single goat breed (Ogaden; n= 35), selected by simple random sampling, were used to determine responses to differential nutritional treatments. Dietary treatments consisted of native hay fed ad libitum (control, C), native hay supplemented with 1% of body weight (BW) of agro–industrial by-products (Treatment 1, T1), native hay supplemented with 1% of BW of khat (Catha edulis) leftovers (Treatment 2, T2) and khat leftovers fed ad libitum (Treatment 3, T3). Breed, age and their interaction affected (P<0.05 to P<0.001) BW, body condition score (BCS), scrotal circumference (SC) and testicular weight (TW). Comparing all age classes, Boran displayed the highest (P<0.05) BW, greatest SC and heaviest TW, while Afar displayed the lowest values for these characteristics. Expressed as percentage of BW, Afar bucks had the highest TW. Regarding epididymal sperm morphology, most acrosome defects were displayed by CH (P<0.05) while AB mainly showed loose sperm heads (P<0.05). Bucks from a lowland agroclimate (i.e., Afar, Boran and WG) displayed more total sperm-head abnormalities (P<0.05) than did bucks of highland breeds (i.e., AB and CH). Younger bucks showed more (P<0.05) loose sperm heads, while older bucks had more (P<0.05) acrosome defects. Bucks fed according to the T1–T3 treatments improved (P<0.05) their BW, BCS, testicular size and testicular weight compared to controls. Goats in treatment groups T1–T3 showed higher (P<0.05) sperm motility, sperm concentration per mL and total number of spermatozoa per ejaculate compared to controls. Of groups T1–T3, bucks in T3 had the highest BW and testicular size. Feeding goats according to the T1–T3 regimes improved (P<0.001) feed dry matter (DM) and nutrient intake, and the occurrence of morphologically normal spermatozoa, compared to controls. Of the T1–T3 treatments, feeding according to T3 and T2 resulted in higher (P<0.05) DM, organic matter and gross energy intakes, while T1 followed by T3 resulted in the highest (P<0.05) crude protein intake, and T3 the highest occurrence of morphologically normal spermatozoa. In conclusion, body size, testicular traits and sperm morphology of Ethiopian bucks raised under extensive management were influenced by breed and age. Nutritional supplementation with khat leftovers and an agro–industrial by-product mix improved feed intake, growth and semen characteristics; these feedstuffs could be considered alternative feed resources to enhance goat production under smallholder farming systems in Ethiopia

Riboflavin-sensitized photooxidation of Ceftriaxone and Cefotaxime: kinetic study and effect on Staphylococcus aureus

Trace amounts of the widely used β-lactam antibiotics (Atbs) in waste water may cause adverse effects on the ecosystems and contribute to the proliferation of antibiotic-resistant bacteria. On these grounds, kinetic and mechanistic aspects of photosensitized degradation of Ceftriaxone (Cft) and Cefotaxime (Ctx), have been studied in pure water by stationary and time-resolved techniques. Additionally, possible implications of these photoprocesses on the antimicrobial activity of the Atbs have also been investigated. Photoirradiation of aqueous solutions of Cft and Ctx produces the degradation of both Atbs in the presence of Riboflavin (vitamin B2), a well known pigment dissolved in natural aquatic systems. The process occurs through Type I and Type II mechanisms, with effective prevalence of the former. The participation of O2−, OH and O2(1Δg) is supported by experiments of oxygen consumption carried out in the presence of specific scavengers for such reactive oxygen species. Microbiological assays exhibit a parallelism between the rate of Cft and Ctx photodegradation and the loss of their bactericidal capacity on Staphylococcus aureus strains. Results contribute to both understanding kinetic and mechanism aspects of the degradation and predicting on natural decay of Atbs waste water-contaminants.Fil: Reynoso, Eugenia. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Spesia, Mariana Belen. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Garcia, Norman Andino. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Biasutti, Maria Alicia. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Criado, Susana Noemi. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Using abundance data to assess the relative role of sampling biases and evolutionary radiations in Upper Muschelkalk ammonoids

The Middle Triassic ammonoid genus Ceratites diversified spectacularly within the Germanic Muschelkalk Basin during the Anisian/Ladian (244–232 Mya). Previous studies have interpreted this diversification as a sequence of rapid, endemic radiations from a few immigrant taxa. Here we investigate the possibility that geological and sampling biases, rather than ecological and evolutionary processes, are responsible for this pattern. A new specimen based dataset of Ceratites species-richness and abundance was assembled. This dataset was combined with 1:200000 geological maps in a geodatabase to facilitate geospatial analyses. One set of analyses compared species richness per geological map with the number of occurrences and localities per map. Per-map change in the amount of rock available to sample for fossils was also included as a variable. Of these three variables, number of occurrences is the most strongly correlated with richness. Variation in the amount of rock is not a strong determinant of species-richness. However, rarefaction of basin-wide species/abundance data demonstrates that differences in species-richness through time are not attributable to sample size differences. The average percent similarity among sites remained close to 50% throughout the Upper Muschelkalk. The rank abundance distribution (RAD) of species from the first interval of the Upper Muschelkalk is consistent with colonization of a disturbed environment, while the other two intervals have RADs consistent with more stable ecosystems. These results indicate that genuine ecological and evolutionary events are partly responsible for the observed differences in richness and abundance. Although changes in the RADs through time support changes in the ammonoid assemblage structure, the processes underlying increasing richness and change in RADS cannot be explained by increasing geographic distinctiveness or isolation among the ammonoid assemblages present at different localities

Measuring telomere length and telomere dynamics in evolutionary biology and ecology

Telomeres play a fundamental role in the protection of chromosomal DNA and in the regulation of cellular senescence. Recent work in human epidemiology and evolutionary ecology suggests adult telomere length (TL) may reflect past physiological stress and predict subsequent morbidity and mortality, independent of chronological age. Several different methods have been developed to measure TL, each offering its own technical challenges. The aim of this review is to provide an overview of the advantages and drawbacks of each method for researchers, with a particular focus on issues that are likely to face ecologists and evolutionary biologists collecting samples in the field or in organisms that may never have been studied in this context before. We discuss the key issues to consider and wherever possible try to provide current consensus view regarding best practice with regard to sample collection and storage, DNA extraction and storage, and the five main methods currently available to measure TL. Decisions regarding which tissues to sample, how to store them, how to extract DNA, and which TL measurement method to use cannot be prescribed, and are dependent on the biological question addressed and the constraints imposed by the study system. What is essential for future studies of telomere dynamics in evolution and ecology is that researchers publish full details of their methods and the quality control thresholds they employ

Assessing the effects of repeated handling on physiology and condition of semi-precocial nestlings

Repeated exposure to elevated levels of glucocorticoids during development can have long-term detrimental effects on survival and fitness, potentially associated with increased telomere attrition. Nestling birds are regularly handled for ecological research, yet few authors have considered the potential for handling-induced stress to influence hormonally-mediated phenotypic development or bias interpretations of subsequent focal measurements. We experimentally manipulated the handling experience of the semi-precocial nestlings of European Storm Petrel Hydrobates pelagicus to simulate handling in a typical field study and examined cumulative effects on physiology and condition in late postnatal development. Neither baseline corticosterone (the primary glucocorticoid in birds), telomere length nor body condition varied with the number of handling episodes. The absence of a response could be explained if Storm Petrels did not perceive handling to be stressful or if there is dissociation of the hypothalamic-pituitary-adrenal axis from stressful stimuli in early life. Eliciting a response to a stressor may be maladaptive for cavity-dwelling young that are unable to escape or defend themselves. Furthermore, avoiding elevated overall glucocorticoid exposure may be particularly important in a long-lived species, in which accelerated early-life telomere erosion could impact negatively upon longevity. We propose that the level of colony-wide disturbance induced by investigator handling of young could be important in underlining species-specific responses. Storm Petrel nestlings appear unresponsive to investigator handling within the limits of handling in a typical field study and handling at this level should not bias physiological and morphological measurements

Acoustic portrait of herring in Vestfjord, january 1996, with geostatistical analysis

In January 1996 the stock of Norwegian spring-spawning herring (Clupea harengus) was acoustically surveyed in the wintering area. Both immature and mature fish were present. Because of the comparative lateness of the survey, the spawning migration had already begun, and the total survey area extended from the inner reaches of Ofotfjord and Tysfjord to the sea area southwest of Vestfjord, well over 200 nautical miles from end to end. Coverage of the Vestfjord area alone occupied three days, thus also including diurnal vertical migration. The evident complex of dynamics is described in two ways: (1) by acoustic images of herring distribution in vertical sections of Vestfjord, and (2) through variograms computed for strata identified by the visual presentation. Speculation is offered on the use of such an analysis in stratification

Dynamics of wintering Norwegian spring-spawning herring at the entrance to Tysfjorden, December 1996

The entrance region to Tysfjorden was acoustically surveyed a total of eleven times during the December 1996 abundance survey of the spawning stock of Norwegian spring-spawning herring (Clupea harengus). The observations are summarized through maps of the distribution, vertical sections, and statistical measures of acoustic density in each of two strata. Experimental variograms are modeled, yielding parameter values that summarize the major properties of aggregation. The collective measures of density and aggregation portray a highly dynamic situation with strong diel variation but a general persistence of the fish distribution over the eleven days of its repeated observation