Contraception in mares heteroimmunized with pig zonae pellucidae

Ten fertile feral mares and 6 domestic horses (4 fertile mares, 1 infertile mare, 1 gelding) were immunized with heat-solubilized pig zonae pellucidae by 4 injections equivalent to 2000 or 5000 zonae each at 2-4-week intervals and a booster injection of 20,000 zonae 6-10 months after the last of the initial inoculations. The immune response was reflected by high antibody levels as measured by an enzyme-linked immunosorbent assay (ELISA) using immobilized pig zona antigen. In-vivo inhibition of fertility occurred in 12 (86%) of the 14 fertile mares studied and persisted for a minimum of 7 months. Repeated mating of the fertile domestic mares resulted in conception when anti-pig zona antibody concentrations had decreased from initial peak absorbance ratios (greater than 1.0) to relatively lower levels (0.64 or less with one exception). An indirect immunofluorescence assay, revealed a considerably lower cross-reactive antibody titre with horse oocytes as compared to pig oocytes. Clinical, endocrinological and histological analyses of the ovaries and their function following regained fertility after immunization revealed no abnormalities. One mare remained infertile.     

Gene-culture coevolutionary theory

Gene-culture coevolutionary theory is a branch of theoretical population genetics that models the transmission of genes and cultural traits from one generation to the next, exploring how they interact. These models have been employed to examine the adaptive advantages of learning and culture, to investigate the forces of cultural change, to partition the variance in complex human behavioral and personality traits, and to address specific cases in human evolution in which there is an interaction between genes and culture.     

Characterization of a calcium/calmodulin-dependent protein kinase homolog from maize roots showing light-regulated gravitropism

Roots of many species respond to gravity (gravitropism) and grow downward only if illuminated. This light-regulated root gravitropism is phytochrome-dependent, mediated by calcium, and inhibited by KN-93, a specific inhibitor of calcium/calmodulin-dependent protein kinase II (CaMK II). A cDNA encoding MCK1, a maize homolog of mammalian CaMK, has been isolated from roots of maize (Zea mays L.). The MCK1 gene is expressed in root tips, the site of perception for both light and gravity. Using the [³⁵S]CaM gel-overlay assay we showed that calmodulin-binding activity of the MCK1 is abolished by 50 M KN-93, but binding is not affected by 5 M KN-93, paralleling physiological findings that light-regulated root gravitropism is inhibited by 50 M KN-93, but not by 5 M KN-93. KN-93 inhibits light-regulated gravitropism by interrupting transduction of the light signal, not light perception, suggesting that MCK1 may play a role in transducing light. This is the first report suggesting a physiological function for a CaMK homolog in light signal transduction.Abbreviations CaM calmodulin - CaMK (II) Ca²⁺/calmodulin-dependent protein kinase (II) - CBP CaM-binding protein - CDPK Ca²⁺-dependent protein kinase - MCK1 maize homolog of mamalian CaMK This work is supported by the National Aeronautics and Space Administration grant No: NAGW 238.     

Xerxes, a new name to replace Alcantara (Asteraceae: Vernoniae)

Xerxes is proposed as a new name to replace Alcantara Glaziou ex G. M Barroso (Asteraceae) (1969), not Alcantarea (Morren ex Mez) Harms (Bromeliaceae) (1929). The genus is monotypic, represented by Xerxes ekmanianum , comb. nov.     

Bi-directional inflorescence development inArabidopsis thaliana: Acropetal initiation of flowers and basipetal initiation of paraclades

In this study we investigated Arabidopsis thaliana (L.) Heynh. inflorescence development by characterizing morphological changes at the shoot apex during the transition to flowering. Sixteen-hour photoperiods were used to synchronously induce flowering in vegetative plants grown for 30 d in non-inductive 8-h photoperiods. During the first inductive cycle, the shoot apical meristem ceased producing leaf primordia and began to produce flower primordia. The differentiation of paraclades (axillary flowering shoots), however, did not occur until after the initiation of multiple flower primordia from the shoot apical meristem. Paraclades were produced by the basipetal activation of buds from the axils of leaf primordia which had been initiated prior to photoperiodic induction. Concurrent with the activation of paraclades was the partial suppression of paraclade-associated leaf primordia, which became bract leaves. The suppression of bract-leaf primordia and the abrupt initiation of flower primordia during the first inductive photoperiod is indicative of a single phase change during the transition to flowering in photoperiodically induced Arabidopsis. Morphogenetic changes characteristic of the transition to flowering in plants grown continuously in 16-h photoperiods were qualitatively equivalent to the changes observed in plants which were photoperiodically induced after 30 d. These results suggest that Arabidopsis has only two phases of development, a vegetative phase and a reproductive phase; and that the production of flower primordia, the differentiation of paraclades from the axils of pre-existing leaf primordia and the elongation of internodes all occur during the reproductive phase.     

Effects of Motility and Adsorption Rate Coefficient on Transport of Bacteria through Saturated Porous Media

Three strains of Pseudomonas fluorescens with different motility rates and adsorption rate coefficients were injected into porous-medium reactors packed with l-mm-diameter glass spheres. Cell breakthrough, time to peak concentration, tailing, and cell recovery were measured at three interstitial pore velocities (higher than, lower than, and much lower than the maximal bacterial motility rate). All experiments were done with distilled water to reduce the effects of growth and chemotaxis. Contrary to expectations, motility did not result in either early breakthrough or early time to peak concentration at flow velocities below the motility rate. Bacterial size exclusion effects were shown to affect breakthrough curve shape at the very low flow velocity, but no such effect was seen at the higher flow velocity. The tendency of bacteria to adsorb to porous-medium surfaces, as measured by adsorption rate coefficients, profoundly influenced transport characteristics. Cell recoveries were shown to be correlated with the ratio of advective to adsorptive transport in the reactors. Adsorption rate coefficients were found to be better predictors of microbial transport phenomena than individual characteristics, such as size, motility, or porous-medium hydrodynamics.     

On the probability of loss of new mutations in the presence of linkage disequilibrium

A new selectively neutral mutation occurs in a multilocus genetic background that has achieved a stable equilibrium at which there is a linkage disequilibrium. Perturbation techniques are applied to an extension of the branching process formulation of Fisher in order to address the question of extinction probabilities. We show that under appropriate conditions the probability of extinction of the new mutant is increased by the existence of linkage disequilibrium in the genetic background.Research supported in part by NIH grant GM 28016     

Novel Miscanthus hybrids: Modelling productivity on marginal land in Europe using dynamics of canopy development determined by light interception

New biomass crop hybrids for bioeconomic expansion require yield projections to determine their potential for strategic land use planning in the face of global challenges. Our biomass growth simulation incorporates radiation interception and conversion efficiency. Models often use leaf area to predict interception which is demanding to determine accurately, so instead we use low-cost rapid light interception measurements using a simple laboratory-made line ceptometer and relate the dynamics of canopy closure to thermal time, and to measurements of biomass. We apply the model to project the European biomass potentials of new market-ready hybrids for 2020–2030. Field measurements are easier to collect, the calibration is seasonally dynamic and reduces influence of weather variation between field sites. The model obtained is conservative, being calibrated by crops of varying establishment and varying maturity on less productive (marginal) land. This results in conservative projections of miscanthus hybrids for 2020–2030 based on 10% land use conversion of the least (productive) grassland and arable for farm diversification, which show a European potential of 80.7–89.7 Mt year⁻¹ biomass, with potential for 1.2–1.3 EJ year⁻¹ energy and 36.3–40.3 Mt year⁻¹ carbon capture, with seeded Miscanthus sacchariflorus × sinensis displaying highest yield potential. Simulated biomass projections must be viewed in light of the field measurements on less productive land with high soil water deficits. We are attempting to model the results from an ambitious and novel project combining new hybrids across Europe with agronomy which has not been perfected on less productive sites. Nevertheless, at the time of energy sourcing issues, seed-propagated miscanthus hybrids for the upscaled provision of bioenergy offer an alternative source of renewable energy. If European countries provide incentives for growers to invest, seeded hybrids can improve product availability and biomass yields over the current commercial miscanthus variety.     

Vasoconstriction in active skeletal muscles: a potential role for P2X purinergic receptors?

There is evidence that ATP acts as a neurotransmitter in vascular smooth muscle and is coreleased with norepinephrine from sympathetic nerves. We hypothesized that P2X-receptor stimulation with the selective P2X-receptor agonist alpha,beta-methylene ATP would produce vasoconstriction in resting and exercising skeletal muscle. Six mongrel dogs were instrumented chronically with flow probes on the external iliac arteries of both hindlimbs and a catheter in one femoral artery. The selective P2X agonist alpha,beta-methylene ATP was infused as a bolus into the femoral artery catheter at rest and during mild, moderate, and heavy exercise. Intra-arterial infusions of alpha,beta-methylene ATP elicited reductions in vascular conductance of 54 +/- 5, 49 +/- 8, 39 +/- 8, and 30 +/- 6% at rest, 3 miles/h, 6 miles/h, and 6 miles/h at a 10% grade, respectively. The agonist infusions did not affect blood flow in the contralateral iliac artery. To examine whether nitric oxide is responsible for the attenuated vasoconstrictor response to P2X stimulation, the infusions were repeated in the presence of NG-nitro-l-arginine methyl ester. After nitric oxide synthase blockade, intra-arterial infusions of alpha,beta-methylene ATP elicited reductions in vascular conductance of 56 +/- 7, 61 +/- 8, 52 +/- 9, and 40 +/- 7% at rest, 3 miles/h, 6 miles/h, and 6 miles/h at a 10% grade, respectively. P2X-receptor responsiveness was attenuated during exercise compared with rest. Blockade of nitric oxide production did not affect the attenuation of P2X-receptor responsiveness during exercise. These data support the hypothesis that P2X purinergic receptors can produce vasoconstriction in exercising skeletal muscle.