Pollen-Derived Haploids of Nicotiana Knightiana, N. raimondii, and N. attenuata

Haploid plantlets were obtained in large numbers in three diploid,24-chromosome species of Nicotiana by culture of anthers ator just past the first pollen mitosis. The three species wereN. Knightiana, N. raimondii, and N. attentiata. Efficiency ofhaploid production varied from about 10 per cent in N. attenuatacultures to 30 and 38 per cent respectively in cultures of N.raimondii and N. Knightiana. H-medium without hormones and standardcultural conditions were used. N. Knightiana appeared to beespecially suitable for haploid studies on account of its highplantlet productivity, low chromosome number, and distinctivekaryotype.     

Interpretation of territorial behaviour in terms of a critical disability hypothesis

The hypothesis is that the great majority of behaviour relating to territorial defence presents difficult anomalies in terms of the normal explanatory mechanism of individual selection. Many, if not all, of the difficulties involved can be solved by using a critical disability hypothesis based upon the principle of "group selection". Given this latter model, it is possible to predict the development of (1) highly variable territories, (2) microterritories and (3) macroterritories.     

Ultrastructure of the Erythrocytic Stages of Plasmodium malariae1

This report describes the fine structure of the erythrocytic stages of Plasmodium malariae. Erythrocytic parasites from a naturally acquired human infection and an experimentally infected chimpanzee were morphologically indistinguishable and structurally similar to other primate malarias. New findings included observations of highly structured arrays of merozoite surface coat proteins in the cytoplasm of early schizonts and on the surface of budding merozoites and the presence of knobs in the membranes of Maurer's clefts. Morphological evidence is presented suggesting that proteins are transported between the erythrocyte surface and intracellular parasites via two routes: one associated with Maurer's clefts for transport of membrane-associated knob material and a second associated with caveolae in the host cell membrane for the import or export of host- or parasite-derived substances through the erythrocyte cytoplasm.     

Physiological Predetermination of the Order of Hardseededness Breakdown in Subterranean Clover (Trifolium subterraneum L.)

Hardseededness breakdown in the burr of subterranean clover(Trifolium subterraneum L.) was found to be non-random in occurrencewith respect to the relative position of seed in the burr. Thissuggests the presence of a predeterminative mechanism of theorder of hardseededness breakdown. While seed moisture content did not exhibit a pattern of variationconsistent with that for hardseededness breakdown, seed weightvariation appeared to conform closely with the pattern of breakdown. It is postulated that, either differences in seed size per sewithin the burr may determine the order of hardseededness breakdown,or that such differences may reflect a disproportionate supplyof translocate, and hence promotors or inhibitors, of hardseedednessbreakdown to the seeds of the burr. The implications of this finding to the assessment of genotypesfor differences in level of hardseededness level have been outlined.     

The Exudation from Excised Maize Roots Bathed in Sulphate Media

The fluid exudation fluxes of excised maize roots bathed ina variety of K₂SO₄ solutions have been measured, along withthe ionic concentrations and osmolalities of the exudates. Anapparent imbalance of inorganic ionic charge in the exudate,and a discrepancy in the total salt concentrations comparedwith the measured osmolalities, suggest the presence of significantamounts of organic anions in the exuded fluid. Thin-layer chromatographicmethods indicate these to be mainly amino-acids and organicacids of the Kreb's cycle. Linear regression analysis showsthat the exudation flux is satisfactorily described by a simpleosmotic process together with a constant non-osmotic water fluxof 0.43 µ1 cm^-2 h^-1. The osmotic permeability for theroot is found to be 0.18 x 10^-6 cm sec^-1 atm^-1. The exudationfrom sulphate media is contrasted with that from chloride media.     

The shape of things to come: linking developmental plasticity to post‐metamorphic morphology in anurans

Development consists of growth and differentiation, which can be partially decoupled and can be affected by environmental factors to different extents. In amphibians, variation in the larval environment influences development and causes changes in post‐metamorphic shape. We examined post‐metamorphic consequences, both morphological and locomotory, of alterations in growth and development. We reared tadpoles of two phylogenetically and ecologically distant frog species (the red‐eyed treefrog Agalychnis callidryas and the African clawed frog Xenopus laevis) under different temperatures with ad libitum food supply and under different food levels at a constant temperature. Low temperature and low food levels both resulted in similarly extended larval periods. However, low temperature yielded relatively long‐legged frogs with a lower degree of ossification than warm temperature, whereas low food yielded relatively short‐legged frogs with a higher degree of ossification than high food levels. Such allometric differences had no effect on locomotor performance of juveniles. Our results provide a basis for understanding the relationship between growth, differentiation and post‐metamorphic shape in anurans and help explain many of the discrepancies reported in previous studies.     

Functional characterisation of the regulation of CAAT enhancer binding protein alpha by GSK-3 phosphorylation of Threonines 222/226

Background  

Glycogen Synthase Kinase-3 (GSK3) activity is repressed following insulin treatment of cells. Pharmacological inhibition of GSK3 mimics the effect of insulin on Phosphoenolpyruvate Carboxykinase (PEPCK), Glucose-6 Phosphatase (G6Pase) and IGF binding protein-1 (IGFBP1) gene expression. CAAT/enhancer binding protein alpha (C/EBPα) regulates these gene promoters in liver and is phosphorylated on two residues (T222/T226) by GSK3, although the functional outcome of the phosphorylation has not been established. We aimed to establish whether CEBPα is a link between GSK3 and these gene promoters.