Disruption of the developmental programme of Trypanosoma brucei by genetic ablation of TbZFP1, a differentiation-enriched CCCH protein

The regulation of differentiation is particularly important in microbial eukaryotes that inhabit multiple environments. The parasite Trypanosoma brucei is an extreme example of this, requiring exquisite gene regulation during transmission from mammals to the tsetse fly vector. Unusually, trypanosomes rely almost exclusively on post-transcriptional mechanisms for regulated gene expression. Hence, RNA binding proteins are potentially of great significance in controlling stage-regulated processes. We have previously identified TbZFP1 as a trypanosome molecule transiently enriched during differentiation to tsetse midgut procyclic forms. This small protein (101 amino acids) contains the unusual CCCH zinc finger, an RNA binding motif. Here, we show that genetic ablation of TbZFP1 compromises repositioning of the mitochondrial genome, a specific event in the strictly regulated differentiation programme. Despite this, other events that occur both before and after this remain intact. Significantly, this phenotype correlates with the TbZFP1 expression profile during differentiation. This is the first genetic disruption of a developmental regulator in T. brucei. It demonstrates that programmed events in parasite development can be uncoupled at the molecular level. It also further supports the importance of CCCH proteins in key aspects of trypanosome cell function

Generating ellipsis using discourse structures

This article describes an effort to generate elliptic sentences, using Dependency Trees connected by Discourse Relations as input. We contend that the process of syntactic aggregation should be performed in the Surface Realization stage of the language generation process, and that Dependency Trees with Rhetorical Relations are excellent input for a generation system that has to generate ellipsis. We also propose a taxonomy of the most common Dutch cue words, grouped according to the kind of discourse relations they signal

Quantification of carboxyl groups in carbodiimide cross-linked collagen sponges

Glutaraldehyde (GA) fixation of bioprosthetic tissue is a well adapted technique, with commercial products on the market for almost 40 years. Amine groups present in tissue react with GA to form different types of cross-links. An estimation of the degree of cross-linking of the tissue can be obtained by measuring the concentration of residual amine groups, which is frequently carried out with the 2,4,6 trinitrobenzene sulphonic acid (TNBS) assay. Cross-linked tissue and collagen matrices are usually further characterized by determining their physical properties (such as the shrinkage temperature), biological properties (such as resistance to enzymatic degradation), and mechanical properties before in vivo evaluation takes place. In an effort to improve the properties of cross-linked tissue and collagen, alternative cross-linking methods have been developed. One of these methods is based on the use of water soluble carbodiimides (CDI). It is generally accepted that this cross-linking method leads only to the formation of amide linkages between tissue carboxyl and amine groups. Therefore, until recently the TNBS assay was also used to determine the degree of cross-linking of CDI cross-linked tissue and collagen. However, it cannot be excluded that after activation of carboxyl groups of tissue and collagen by CDI, these groups can react with other nucleophiles (like hydroxyl groups) present in the matrix. To obtain a better insight in the degree of cross-linking of CDI cross-linked matrices a reliable assay for quantification of residual carboxyl groups is required. Up to now such an assay was not available. In this study a new assay to determine residual carboxyl groups in CDI cross-linked collagen matrices is presented. Reconstituted dermal bovine collagen matrices (RDBC) were cross-linked with a water soluble CDI and N-hydroxysuccinimide (NHS) and residual carboxyl groups were labeled using 5-bromomethyl fluorescein. Subsequently, the fluorescent label was released by mild hydrolysis and quantified with capillary zone electrophoresis. A calibration curve relating the concentration of carboxyl groups with peak intensities was obtained using SephadexTM standards with known concentrations of carboxyl groups. The concentration of carboxyl groups in unprocessed RDBC as determined with this new technique was equal to the concentration of carboxyl groups measured by amino acid analysis. On the basis of the concentration of residual carboxyl groups determined for CDI/NHS cross-linked RDBC and RDBC, in which the amine groups were blocked with propionaldehyde before CDI/NHS cross-linking, it was concluded that activated carboxyl groups can also react with other groups (such as hydroxyl groups) present in the matrix. This implies that the crosslink density of RDBC matrices after treatment with CDI/NHS is higher than expected on the basis of amide bond formation only, as determined by the TNBS assay

Expenditure elasticities for rural households in the Embo ward, Umbumbulu, KwaZulu-Natal

Household consumption patterns were investigated to determine the impact of an income shock on household expenditure and to establish the potential for demand-led growth in a rural area of KwaZulu-Natal. Household consumption data were collected from sample households in the Embo ward of Umbumbulu, KwaZulu-Natal during October 2004 and March 2005. Budget shares and expenditure elasticities were estimated for household consumption categories for the two study periods, allowing for a comparison of expenditure elasticities between the two seasons. Results suggest that expenditure elasticities for consumer expendables, durables and transport were highly elastic, while expenditure elasticities for the aggregate food category were negative (October) and highly inelastic (March). Analysis of the expenditure categories of tradable and non-tradable goods and services showed expenditure on tradable non-farm goods and services to have the greatest potential for demand-led growth with expenditure elasticities of 2.88 and 2.91, respectively. The category of non-tradable non-farm goods and services was not statistically significant for both periods and the category non-tradable farm goods and services was not statistically significant for October. A seasonal difference in expenditure patterns was apparent, suggesting that responses to income changes vary at different times of the year.Expenditure elasticities, demand-led growth, Umbumbulu region, KwaZulu-Natal, Consumer/Household Economics,

Food security policy choices: A review of the usefulness of public policy taxonomies

This paper addresses the "dependent variable" problem in food security policies, namely the difficulty in classifying food security  policies that limits comparative policy studies. Policy comparisons require criteria that are general enough for broad application butsensitive to the context. A rigorous and objective basis for comparisons would allow for studying how policies, and food security policies in particular, emerge. This is important in Africa as, in the past, food security and nutrition crises have been attributed to thefailure of government policies. This paper reviews the main key available public policy classifications based on their predictability, mutual-exclusivity and relevance. These include Lowi's and Wilson's typologies, the agricultural policies' classification by Norton and the FAO-FAPDA classification. The review found that available typologies do not accommodate multi-sectoral actions and are not entirely applicable to food security public policy classification. The domain shift from food policy to food security, and more recently to food systems demands that all elements in the food system to be taken into consideration in the policy process. This limits the use of policies as "dependent variables" and hence the study of how they emerge, particularly in Africa. A critique of available policy classes shows that these cannot be treated as "dependent variables". It is argued that a potential solution to the "dependent variable" problem of food security policies lies in the development of a taxonomy, simplifying their complexity with analytical shortcuts. Having reviewed Candel and Daugbjergs’ recent taxonomy, refinements are proposed to be applied in the African context. The proposed taxonomy represents an alternative to classify food security policies in Africa along four core dimensions. This classification offers prospects for researchers to study what factors drives policy-classes in one direction or the other, along the four dimensions. Althoughthe scales and calibration of the four dimensions will need to be developed and tested, the proposed typology offers a way to treat the dimensions as “dependent variables”. Key words: policy-classification, food-security policy, food systems s, policy-taxonomy, Lowi, Wilson, dependent variable problem, Afric

Transcription analysis of apple fruit development using cDNA microarrays

The knowledge of the molecular mechanisms underlying fruit quality traits is fundamental to devise efficient marker-assisted selection strategies and to improve apple breeding. In this study, cDNA microarray technology was used to identify genes whose expression changes during fruit development and maturation thus potentially involved in fruit quality traits. The expression profile of 1,536 transcripts was analysed by microarray hybridisation. A total of 177 genes resulted to be differentially expressed in at least one of the developmental stages considered. Gene ontology annotation was employed to univocally describe gene function, while cluster analysis allowed grouping genes according to their expression profile. An overview of the transcriptional changes and of the metabolic pathways involved in fruit development was obtained. As expected, August and September are the two months where the largest number of differentially expressed genes was observed. In particular, 85 genes resulted to be up-regulated in September. Even though most of the differentially expressed genes are involved in primary metabolism, several other interesting functions were detected and will be presented

Role of Bruton's tyrosine kinase in B cells and malignancies

Bruton's tyrosine kinase (BTK) is a non-receptor kinase that plays a crucial role in oncogenic signaling that is critical for proliferation and survival of leukemic cells in many B cell malignancies. BTK was initially shown to be defective in the primary immunodeficiency X-