Why Doesn't the Creed Read "Always Be Critical"? An Examination of a Liberal Curriculum

Using ethnographic data collected in a second grade classroom over the course of a school year, this paper describes the ways in which one school's discourse of liberalism is deleteriously deployed. We view the school's discipline creed as emblematic of the school's liberal curriculum, and interrogate the effects on four African American boys in the classroom when the school enacts this creed. Despite the agency that these boys obviously had, they were unable to control the ways in which they were placed at a structural disadvantage and manipulated by a system far more powerful than they were. The results were that these four boys suffered. Not only did the intended liberal curriculum fail to be translated fully into the enacted curriculum, the liberal underpinnings of this curriculum precluded teachers and students from taking any critical stance.     

GROWTH AND DEVELOPMENT OF THE MALE GAMETOPHYTE OF GINKGO BILOBA WITHIN THE OVULE (IN VIVO)

The mature male gametophyte of Ginkgo biloba can be divided into two regions: a large saccate structure that is suspended within the fertilization chamber above the archegonia, and a pervasive, highly branched haustorial system that ramifies through the intercellular air spaces of the apex of the nucellus. This morphology appears to differ in many ways from the simpler more typical male gametophytes of most other groups of seed plants. Growth and development of the male gametophyte of Ginkgo biloba were studied using computer reconstruction techniques to generate images of the gametophyte from data derived from serial sections through the ovule. These investigations reveal that morphological development of the male gametophyte of Ginkgo biloba is divided into three distinct phases: 1) Germination, characterized by an initial brief period of diffuse growth. This phenomenon has not been described for any other seed plant male gametophyte; 2) Initiation of tip growth and the formation of a tubular body, as typifies all seed plant male gametophytes. In Ginkgo, this is accompanied by a high degree of branching, giving rise to an extensively branched haustorial system; 3) Late swelling of the proximal unbranched portion of the gametophyte resulting in formation of the saccate structure that is characteristic of the mature gametophyte. This process appears to be very similar to late development in cycad male gametophytes. Thus, despite the seemingly anomalous morphology of the mature male gametophyte of Ginkgo biloba, specific patterns of growth and development are in many ways similar to growth processes expressed by the male gametophytes of some or all major groups of seed plants.     

Parasitoid behaviour: predicting field from laboratory

Abstract.  1. Most of what is known about parasitoid behaviour comes from laboratory observations: field quantitative observations on searching parasitoids are extremely difficult to do and are rare. The basic components of Aphytis melinus 's response to California red scale ( Aonidiella aurantii ) were studied in the laboratory: encounter, rejection, drumming, probing, oviposition, and host-feeding. It was then asked whether these observations provided a reliable guide to behaviour in the field in a situation that was very different from the laboratory.
2. Field observations were carried out on bark on the trunk and interior branches of trees where live scale density is extremely high in patches, dead scale make up 90% of all scale, and could be expected to interfere with Aphytis search.
3. The laboratory observations predicted well the time taken in the field for each basic event (drumming or probing) and average times spent on a scale. Also well predicted were the distributions of times spent on drumming, probing, and total time on a scale. Rejection rates were much higher in the field. Thus, the laboratory studies predicted foraging behaviour in the field with variable success; potential explanations for observed mismatch between laboratory and field and its possible larger implications are discussed.     

Polymorphisms of DQ β genes in HLA-DR4 haplotypes from healthy and diabetic individuals

The restriction fragment length polymorphism (RFLP) of DQ was assessed in a panel of control and insulin-dependent diabetes (IDD) patients who were serologically typed as HLA-DR4 homozygotes or HLA-DR3, DR4 heterozygotes. Digestions of genomic DNA with Barn HI, Bg1 II, Pst I, Xba I, and Hind III revealed a total of 15 RFLPs in the panel of 71 HLA-DR4 chromosomes. These RFLPs were organized into six allelic groups on the basis of segregation analysis in families. Complete RFLP haplotypes for the 5 restriction enzymes could be constructed for 42 of the HLA-DR4 chromosomes. This analysis revealed 18 RFLP haplotypes of DQ associated with the DR4 chromosomes tested. Two of these haplotypes, designated DQ3.DR4.a and DQ3.DR4.b, accounted for over 50 % of the DR4 chromosomes analyzed. These two haplotypes were antithetical for the RFLPs detected by all five enzymes, indicating that they represent very distinct forms of DQ . The remaining 16 haplotypes were infrequent or unique and were closely related to either a DQ3.DR4.a or DQ3.DR4.b. Two of the RFLPs detected, a 5.8 kb Bg1 II fragment and a 10.5 kb Barn HI fragment, had increased frequencies in disease-associated chromosomes. However, none of the RFLPs we detected exhibited a statistically significant increase in IDD or control populations. In contrast, the DQ3.DR4.b DQ haplotype was significantly decreased in IDD-associated DR4 chromosomes. (P=0.04). These results suggest that the DQ3.DR4.b DQ allele may be protective for the development of IDD.     

Chloroplast photooxidation inhibits the expression of a set of nuclear genes

Summary Mutations or herbicides which inhibit the accumulation of carotenoid pigments in higher plants also result in the arrest of chloroplast development at a very early stage. The cause is extensive photooxidative damage within the chloroplast in the absence of protective carotenoids. Because the extent of photooxidation is dependent upon light intensity, normal chloroplast development can occur when carotenoid-deficient seedlings are grown in very dim light. Normal accumulation of chloroplastic and cytosolic mRNAs encoding chloroplast proteins proceeds only under permissive dim light conditions. Illumination with higher intensity light causes rapid chlorophyll photooxidation and the loss of two cytosolic mRNAs coding for proteins destined for the chloroplast, but does not affect another light-regulated cytosolic mRNA encoding a cytosolic protein. This experimental system may have uncovered a mechanism which coordinates the expression of genes in different cellular compartments.Abbreviations LHCP light-harvesting chlorophyll a/b protein - SSu small subunit - RuBP fibulose 1,5-bisphoshate - PEP phosphoenolpyruvate     

Genetic research with nonhuman primates: serving the needs of mankind Symposium summary and future prospects

The wide array of papers delivered at this symposium, ranging from population genetics to molecular genetics, is convincing evidence that genetic research with nonhuman primates is in full bloom. In fact, progress has been quite remarkable considering that a significant number of pedigreed colonies of nonhuman primates have been available for less than 25 years, which is hardly enough time to raise 3 generations of chimpanzees, 5 generations of baboons or 6 generations of rhesus monkeys. Were it not for these pedigreed colonies, we would not have been privileged to have this assemblage of papers on behavior, social structure, predisposition to disease and management of breeding colonies. It is indeed exciting that preliminary evidence has been obtained for major genes that play a role in susceptibility to dyslipoproteinemias in baboons, and that monoclonal antibodies and DNA markers are helping us to understand cholesterol metabolism. And thanks to computers, we can now rank animals in a colony in terms of their useful genotypes as well as their productivity. One can not help but be impressed with the commonality of humans and nonhuman primates at the structural and functional levels. For example, the major histocompatibility systems and the maternal-fetal relationships are very similar. We heard that this similarity is even more striking at the chromosomal, biochemical and DNA levels. A provocative question yet to be answered is, “what accounts for the obvious differences between humans and nonhuman primates in view of these incredible similarities?” In light of these advances, this symposium was at the cutting edge of primate genetics and the papers published in this issue of Genetica are certain to be hallmarks in the literature.     

Endosymbiotic origin and codon bias of the nuclear gene for chloroplast glyceraldehyde-3-phosphate dehydrogenase from maize

Summary The nuclei of plant cells harbor genes for two types of glyceraldehyde-3-phosphate dehydrogenases (GAPDH) displaying a sequence divergence corresponding to the prokaryote/eukaryote separation. This strongly supports the endosymbiotic theory of chloroplast evolution and in particular the gene transfer hypothesis suggesting that the gene for the chloroplast enzyme, initially located in the genome of the endosymbiotic chloroplast progenitor, was transferred during the course of evolution into the nuclear genome of the endosymbiotic host. Codon usage in the gene for chloroplast GAPDH of maize is radically different from that employed by present-day chloroplasts and from that of the cytosolic (glycolytic) enzyme from the same cell. This reveals the presence of subcellular selective pressures which appear to be involved in the optimization of gene expression in the economically important graminaceous monocots.