A reassessment of the binding of napthaleneacetic acid by membrane preparations from maize

Naphthalene-1-acetic acid (NAA) binding by membrane fractions derived from maize has been re-evaluated. Using a computer curve-fitting procedure only one major type of NAA binding, in terms of binding affinity, could be identified. Auxins, antiauxins and structurally related compounds have been tested for their competitive effect on NAA binding and the inhibitor constants for a number of these have been determined. Extracts from various plant species have been examined for their NAA binding ability, but all showed much less binding than maize leaf or coleoptile preparations. The possibility of the NAA binding by maize extracts being due to a true hormone receptor is discussed.Abbreviations BA benzoic acid - CPIB p-chlorophenoxyisobutyric acid - 2,4-D 2,4-dichlorophenoxyacetic acid - DCB 2,4-dichlorobenzoic acid - IAA indolyl-3-acetic acid - NAA napthalene-1-acetic acid - 2-NAA napthalene-2-acetic acid - NAOA napthalene-2-oxyacetic acid - PA phenylacetic acid - PU phenylurea - 2,4,5-T 2,4,5-trichlorophenoxyacetic acid - TIBA 2,3,5-triiodobenzoic acid     

Adult emergence phenology in checkerspot butterflies: the effects of macroclimate,topoclimate, and population history

The prediction of adult emergence times in insect populations can be greatly complicated by microclimatic gradients, especially in circumstances where distributions of juveniles along those gradients vary from year to year. To investigate adult emergence patterns in topographically heterogeneous habitats, we built a model of postdiapause development of the Bay checkerspot butterfly, Euphydryas editha bayensis. The model uses slope-specific insolation as the rate-controlling variable, and accounts for both solar exposure of the habitat and cloud cover. Instar-specific larval mass gains per unit of insolation were determined from mark-recapture experiments. A small correction for daily low temperatures was used to calibrate the model to five years of field data on larval mass. The model predicted mean mass of 90% of larval samples within 4 clear days over a 70–120 day growing season. The magnitude of spatial variation in emergence times across habitat slopes is greater than annual variation in emergence times due to yearly weather conditions. Historical variation (yearly shifts in larval distributions across slopes) is an important determinant of mean population emergence dates. All of these factors need to be considered in understanding adult emergence phenology in this butterfly and in other insects inhabiting heterogeneous thermal environments. Such an understanding can be useful in managing insect populations for both pest control and conservation.     

The properties of transketolase from photosynthetic tissue

Transketolase (E.C. 2.2.1.1.) has been partially purified from wheat (Triticum aestivum, cv. Sappo) and spinach (Spinacia oleracea) leaves. The fully-active enzyme is a tetramer of relative molecular mass (M_r) of 150 kM_r requiring thiamin pyrophosphate for maximal activity, and dissociating into a 74 kM_r dimer in its absence or in dilute solution. The chloroplastic transketolase (over 75% of the cellular total) is magnesium-stimulated but the cytosolic form is magnesium-insensitive. Both chloroplastic and cytosolic transketolase showed similar broad specificities towards several ketose phosphate substrates including fructose 6-phosphate and sedoheptulose 7-phosphate. Wheat and spinach leaf transketolases are not light-activated and closely resemble the yeast enzyme in many of their properties.Abbreviations Mr relative molecular mass - TPP thiamin pyrophosphate - Tris 2-amino-2-(hydroxymethyl)-1,3-propandiol     

Allozyme Variation Patterns and Multiple Hybridization Origins: Clonal Variation Among Four Sibling Parthenogenetic Caucasian Rock Lizards

Allozyme electrophoresis of four sibling parthenogenetic Caucasian rock lizards Darevskia unisexualis, D.uzzelli, D.sapphirina, and D.bendimahiensis found seven clones and five variable loci. The data supported the hypothesis that D.raddei and D.valentini are the parental species of all four parthenogens. Variation patterns in Darevskia were summarized. Species that originated from a single F₁ typically consisted of one widespread clone with a few rare clones. Species with multiple origins displayed variation only slightly higher than species with a single origin. This is contrary to other genera of parthenogenetic lizards, in which cases massive clonal variations were observed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Sequence of an oleocin cDNA from Brassica napus

Antibodies raised against purified rapeseed 19 kDa oleosin protein were used to screen an embryo-derived gt11 expression library from Brassica napus. A near full-length cDNA clone, BnV, was isolated. The 781 bp cDNA contained an open reading frame of 549 bp followed by an untranslated region of 222 pb and a poly(A) region of 10 bp. Comparisons between this cDNA and a different oleosin cDNA previously isolated from the same library showed high degrees of sequence similarity in the central domain region and in the 3 untranslated region. Sequence similarities between the derived protein sequence of this cDNA and all other known oleosin protein sequences are discussed.     

Nitric oxide production by cultured aortic endothelial cells in response to thiol depletion and replenishment

The requirements and influence of thiols on the production of nitric oxide (NO) were examined in cultured porcine aortic endothelial cells. NO production was diminished when cells were pretreated with thiol-depleting agents (IC50: N-ethylmaleimide, 30 microM; 1-chloro-2,4-dinitrobenzene, 200 microM; diamide, 1.5 mM; diethyl maleate, 20 mM). The depletion of glutathione (45-99% loss at the various IC50 values) and protein thiols (3-25% loss at IC50) showed no consistent relationship to decreased NO production. The effects of the agents on NO production were not linked to altered sensitivity to the stimulant (calcium ionophore A23187; maximal effect at 10 microM), but roughly paralleled the appearance of cell damage (17-44% lactate dehydrogenase release at IC50). The decrease in NO production due to 1-chloro-2,4-dinitrobenzene was partially reversed by cysteine, dithioerythritol, and dihydrolipoate, whereas cystine partially reversed the decrease due to diamide or diethyl maleate. On the other hand, several thiols diminished NO production in control cells. Overall, alterations of NO production did not parallel the depletion or replenishment of either glutathione, protein thiol, or soluble thiol pools, and so the results argue against hypotheses that cellular thiols are either substrates or necessary cofactors in the pathway of NO synthesis in endothelial cells.     

Macrophage colony stimulating factor prevents NMDA-induced neuronal death in hippocampal organotypic cultures

Macrophage colony stimulating factor (M-CSF) and its receptor are up-regulated in the brain in Alzheimer's disease (AD), in transgenic mouse models for AD, and experimental models for traumatic and ischemic brain injury. M-CSF induces activation and proliferation of microglial cells and expression of proinflammatory cytokines. We examined the role of M-CSF in excitotoxic neuronal cell death in organotypic hippocampal cultures. NMDA treatment induced neuronal apoptosis and caspase-3 activation in organotypic hippocampal cultures, whereas treatment with M-CSF protected hippocampal neurons from NMDA-induced apoptosis. Caspase-3 activation was inhibited by M-CSF treatment to the same degree as with the caspase inhibitor Z-VAD-FMK. These results suggest that M-CSF has neuroprotective properties through inhibition of caspase-3 that could promote neuronal survival after excitotoxic insult. The role of M-CSF in neurological disease should be reevaluated as a microglial activator with potentially neuroprotective effects.     

Primary cilia and forebrain development

With a microtubule-based axoneme supporting its plasma membrane-ensheathed projection from the basal body of almost all cell types in the human body, and present in only one copy per cell, the primary cilium can be considered an organelle sui generis. Although it was first observed and recorded in histological studies from the late 19th century, the tiny structure was essentially forgotten for many decades. In the past ten years, however, scientists have turned their eyes once again upon primary cilia and realized that they are very important for the development of almost all organs in the mammalian body, especially those dependent upon the signaling from members Hedgehog family, such as Indian and Sonic hedgehog. In this review, we outline the roles that primary cilia play in forebrain development, not just in the crucial transduction of Sonic hedgehog signaling, but also new results showing that cilia are important for cell cycle progression in proliferating neural precursors. We will focus upon cerebral cortex development but will also discuss the importance of cilia for the embryonic hippocampus, olfactory bulb, and diencephalon.     

The BMP signaling gradient patterns dorsoventral tissues in a temporally progressive manner along the anteroposterior axis

Patterning of the vertebrate anteroposterior (AP) axis proceeds temporally from anterior to posterior. How dorsoventral (DV) axial patterning relates to AP temporal patterning is unknown. We examined the temporal activity of BMP signaling in patterning ventrolateral cell fates along the AP axis, using transgenes that rapidly turn "off" or "on" BMP signaling. We show that BMP signaling patterns rostral DV cell fates at the onset of gastrulation, whereas progressively more caudal DV cell fates are patterned at progressively later intervals during gastrulation. Increased BMP signal duration is not required to pattern more caudal DV cell fates; rather, distinct temporal intervals of signaling are required. This progressive action is regulated downstream of, or in parallel to, BMP signal transduction at the level of Smad1/5 phosphorylation. We propose that a temporal cue regulates a cell's competence to respond to BMP signaling, allowing the acquisition of a cell's DV and AP identity simultaneously.     

Production of a recombinant form of early pregnancy factor that can prolong allogeneic skin graft survival time in rats

Early pregnancy factor (EPF), an extracellular chaperonin 10 homologue, has immunosuppressive and growth factor properties. In order to carry out more extensive studies on the in vivo characteristics of EPF, a recombinant form of the molecule has been prepared. Recombinant human EPF (rEPF) was expressed in Escherichia coli using the plasmid pGEX-2T expression system. Potency of rEPF in vitro in the rosette inhibition test, the bioassay for EPF, was equivalent to that of native EPF (nEPF), purified from human platelets, and synthetic EPF (sEPF). However, the half-life of activity (50% decrease in the log value) in serum, following i.p. injection, was significantly decreased (3.2 h, compared with nEPF 6.2 days, sEPF 5.8 days). This was thought to be due to modification of the N-terminus of the recombinant molecule inhibiting binding to serum carrier proteins. Because EPF can modify Th1 responses, the ability of the recombinant molecule to suppress allogeneic graft rejection was investigated. Following skin grafts from Lewis rats to DA rats and vice versa, rEPF was delivered locally at the graft site and the effect on survival time of the allografts noted. Results demonstrated that rEPF treatment significantly prolonged skin graft survival time by as much as 55% in stringent models of transplantation across major histocompatibility barriers.