The presence of the past: youth,memory making and the politics of self-determination in southeastern Nigeria

This article focuses on recent reconstructions of Igbo ‘memory’ by the Movement for the Actualization of the Sovereign state of Biafra (MASSOB). MASSOB is a second-generation Igbo separatist movement that draws on a collection of ‘memory repertoires’ to agitate for the self-determination and exit of the Igbo ethnic group from the Nigerian state into an alternative political and administrative arrangement known as the Republic of Biafra. The core issues relate to dual narratives generated by the Nigerian–Biafran War. While the state shapes the official history, memories and narratives of the war to suit its own vision, interests and politics, MASSOB contests these official views as the sole legitimate framework for remembering and interpreting the war, but still connects to the war as a war of Igbo national liberation. These contestations provide the context for the enactment of memory claims and counterclaims, and their association with political violence in contemporary Nigeria.     

Disabled-2 mediates c-Fos suppression and the cell growth regulatory activity of retinoic acid in embryonic carcinoma cells

F9 embryonic stem cell-like teratocarcinoma cells are widely used to study early embryonic development and cell differentiation. The cells can be induced by retinoic acid to undergo endodermal differentiation. The retinoic acid-induced differentiation accompanies cell growth suppression, and thus, F9 cells are also often used as a model for analysis of retinoic acid biological activity. We have recently shown that MAPK activation and c-Fos expression are uncoupled in F9 cells upon retinoic acid-induced endodermal differentiation. The expression of the candidate tumor suppressor Disabled-2 is induced and correlates with cell growth suppression in F9 cells. We were not able to establish stable Disabled-2 expression by cDNA transfection in F9 cells without induction of spontaneous cell differentiation. Transient transfection of Dab2 by adenoviral vector nevertheless suppresses Elk-1 phosphorylation, c-Fos expression, and cell growth. In PA-1, another teratocarcinoma cell line of human origin that has no or very low levels of Disabled-2, retinoic acid fails to induce Disabled-2, correlating with a lack of growth suppression, although PA-1 is responsive to retinoic acid in morphological change. Transfection and expression of Disabled-2 in PA-1 cells mimic the effects of retinoic acid on growth suppression; the Disabled-2-expressing cells reach a much lower saturation density, and serum-stimulated c-Fos expression is greatly suppressed and disassociated from MAPK activation. Thus, Dab2 is one of the principal genes induced by retinoic acid involved in cell growth suppression, and expression of Dab2 alone is sufficient for uncoupling of MAPK activation and c-Fos expression. Resistance to retinoic acid regulation in PA-1 cells likely results from defects in retinoic acid up-regulation of Dab2 expression.     

Predators,parasitoids and pathogens of ticks: A review

Research conducted on natural enemies of ticks, namely predators, parasitoids and pathogens, is reviewed. Predators include ants, birds, rodents, lizards, shrews, spiders and domestic chickens. All the known parasitoids are hymenopteran wasps belonging to the genera Ixodiphagus and Hunterellus. The work so far done on bacteria, fungi, viruses and rickettsiae which are pathogenic to ticks is reviewed, both with regard to experimental infections and natural infections. The possibilities of using natural enemies as biological control agents of ticks are discussed.     

Manipulating assimilate availability provides insight into the genes controlling grain size in sorghum

Variation in grain size, a major determinant of grain yield and quality in cereal crops, is determined by both the plant’s genetic potential and the available assimilate to fill the grain in the absence of stress. This study investigated grain size variation in response to variation in assimilate supply in sorghum using a diversity panel (n = 837) and a backcross-nested association mapping population (n = 1421) across four experiments. To explore the effects of genetic potential and assimilate availability on grain size, the top half of selected panicles was removed at anthesis. Results showed substantial variation in five grain size parameters with high heritability. Artificial reduction in grain number resulted in a general increase in grain weight, with the extent of the increase varying across genotypes. Genome-wide association studies identified 44 grain size quantitative trait locus (QTL) that were likely to act on assimilate availability and 50 QTL that were likely to act on genetic potential. This finding was further supported by functional enrichment analysis and co-location analysis with known grain number QTL and candidate genes. RNA interference and overexpression experiments were conducted to validate the function of one of the identified gene, SbDEP1, showing that SbDEP1 positively regulates grain number and negatively regulates grain size by controlling primary branching in sorghum. Haplotype analysis of SbDEP1 suggested a possible role in racial differentiation. The enhanced understanding of grain size variation in relation to assimilate availability presented in this study will benefit sorghum improvement and have implications for other cereal crops.     

Investigation into the possible cause of subjective decreased sensory perception in the nipple-areola complex of women with macromastia

Patients with macromastia often comment on a lack of sensation in their nipple-areola complex. A study was designed to investigate the cause of this decreased sensation. Two hypotheses were proposed. First, the decreased sensation could result from neuropraxia of the sensory nerve fibers secondary to traction caused by the heavy breast parenchyma. The second hypothesis proposed that tissue expansion of the nipple and areola by the voluminous breast parenchyma caused a decrease in nerve fibers per surface area and hence decreased sensory perception. Sixty-one patients were assessed in the study. All patients underwent surgery in which histological biopsy of either the areola alone (31 reduction mammaplasty patients) or the nipple and areola (30 mastectomy patients) was possible. Before surgery, each nipple-areola complex was tested with Weinstein Enhanced Sensory Test monofilaments as a quantitative test of tactile sensation. Breast cup size, ptosis, and weight of tissue excised were recorded to allow general assessment of the breast size. The nipple and areola biopsy specimens were assessed using immunohistochemistry (S-100 polyclonal antibody, Dako Z311) to measure nerve fiber count per unit area. Statistical analysis was undertaken to find any association among sensitivity, breast cup size, ptosis, weight of tissue resected, and nerve fiber density in the nipple and areola biopsy specimens. Sensitivity at the areola decreased with increasing breast cup size (r = 0.47, p < 0.001) and ptosis (r = 0.42, p = 0.002 for increasing distance between inframammary crease and nipple; r = 0.49, p < 0.001 for increasing manubrium to nipple distance). There was a weak correlation between nerve fiber density at the areola and breast cup size (r = -0.22, p = 0.1). Sensitivity at the nipple was higher than at the areola. Nerve fiber density count at the nipple was higher than at the areola, but there was no statistically significant correlation between nipple sensitivity and breast cup size, ptosis, or weight of tissue resected. The results suggest that the areola and nipple are different in their neuroanatomy. The areola is a thin, pliable structure that is predisposed to stretch as the breast enlarges and therefore experience a decrease in nerve fiber density. The nipple is a compact structure that is less likely to stretch with breast enlargement. In the nipple, neither sensory perception nor nerve fiber density varied with size or breast ptosis. The perceived lack of sensation in the nipple-areola complex is multifactorial. This study shows that neither traction injury to the sensory nerves nor decreased nerve density alone can explain the subjective numbness reported by patients with macromastia. Psychological factors, such as dissatisfaction with body form or interpretation of lack of sensation in the areola as also affecting the nipple, may influence the patient's assessment of the nipple-areola sensitivity.