Genetic, Structural, and Two-Dimensional Protein Electrophoretic Characterization of Normal and dek23 Mutant Embryogenesis in Maize (Zea mays L.)

Embryogenesis in maize (Zea mays L.) is a genetically regulated process that gives rise to a large embryo with shoot and root apical meristems, a large scutellum, and five or six leaf primordia. An embryo-lethal defective kernel mutation dek23, located on chromosome arm 2L, affects the formation of the shoot apical meristem, coleoptilar ring, and leaf primordia in mutant embryos. Comparison of mutant and normal embryo development at the structural and biochemical levels should give insight into the role of the dek23 normal gene product in normal development. Fresh dissection, light microscopy, and transmission electron microscopy of normal and mutant embryos at different developmental stages reveal a divergence between mutant and normal embryo morphology at nine days after pollination (dap). Mutant embryos are developmentally delayed and the cells of the shoot apical meristem region contain enlarged vacuoles and abnormal nuclei and subsequently become necrotic. Two-dimensional polyacrylamide gel protein profiles of normal embryos from the transition stage (nine dap) through stage 5/6 (40 dap) were obtained and used as standards for comparison to mutant embryo protein profiles at five different developmental stages. Normal embryo protein profiles exhibited a set of 16 landmark spots found at all stages. Two early embryonic proteins were found in embryos up to stage 1. Three stage specific proteins were observed at the coleoptilar stage, as well as a set of spots that increased in intensity until stage 3 and then decreased. Accumulation of globulin storage proteins was clearly evident. Mutant embryo profiles were generally similar to normal profiles of an earlier chronological age. Two landmark spots found in normal profiles were absent or diminished in mutant profiles. One early embryonic protein identified in normal profiles was also absent from mutant profiles, and may provide a marker for identifying mutant embryos before morphological differences are evident. Mutant embryos failed to accumulate any globulins. The dek23 locus was mapped 22 centimorgans distal to w3. Reduced sexual transmission of the mutant allele through the pollen and unequal distribution of mutant kernels on a self pollinated ear indicate that the dek23 gene is active in the male gametophyte

Minimally invasive biomarkers to detect maternal physiological status in sow saliva and milk

In this study, we aimed to validate existing plasma assays to measure biomarkers for maternal signalling in milk and saliva of lactating sows. These biological samples are minimally invasive to the animal and could give a physiological profile of maternal qualities available to their piglets. Sows were farrowed in a zero-confinement system, and their colostrum and milk samples were manually collected during naturally occurring let-downs (i.e. not induced) over the lactation period. Saliva sampling involved sows voluntarily accepting cotton buds to chew without restraint. Commercial kits designed for blood plasma were tested, and any modifications and results are given. We successfully measured total protein, cortisol, tumour necrosis factor-α (TNF-α) and oxytocin in pig milk and saliva and immunoglobulin G (IgG) in pig milk samples. We were unsuccessful at measuring relaxin and serotonin in these biological samples. We observed higher levels of biomarkers in milk than in saliva. The measurement of TNF-α in pig milk for the first time revealed increased levels with larger litters. This development will allow more detailed understanding of biomarkers in milk. There was also evidence that the minimally invasive technique of using saliva sampling did not interrupt natural oxytocin production around parturition

Toward a geography of black internationalism: Bayard Rustin, nonviolence and the promise of Africa

This article charts the trip made by civil rights leader Bayard Rustin to West Africa in 1952, and examines the unpublished ‘Africa Program’ which he subsequently presented to leading American pacifists. I situate Rustin’s writings within the burgeoning literature on black internationalism which, despite its clear geographical registers, geographers themselves have as yet made only a modest contribution towards. The article argues that within this literature there remains a tendency to romanticize cross-cultural connections in lieu of critically interrogating their basic, and often competing, claims. I argue that closer attention to the geographies of black internationalism, however, allows us to shape a more diverse and practiced sense of internationalist encounter and exchange. The article reconstructs the multiplicity of Rustin’s black internationalist geographies which drew eclectically from a range of Pan-African, American and pacifist traditions. Though each of these was profoundly racialized, they conceptualized race in distinctive ways and thereby had differing understandings of what constituted the international as a geographical arena. By blending these forms of internationalism Rustin was able to promote a particular model of civil rights which was characteristically internationalist in outlook, nonviolent in principle and institutional in composition; a model which in selective and uneven ways continues to shape our understanding of the period