Circadian Neuroendocrine Role in Age-Related Changes in Body Fat Stores and Insulin Sensitivity of the Male Sprague-Dawley Rat

A role for circadian neuroendocrine rhythms in the age-related development of obesity and insulin resistance was investigated in the male Sprague-Dawley rat. The phases and amplitudes of the plasma rhythms of several metabolic hormones (i.e. corticosterone, prolactin, insulin, and triiodothyronine) differed in lean, insulin-sensitive (3-week-old rats). insulin-resistant (8-week-old rats) and obese, insulin-resistant (44-week-old rats) animals. Simulation of the daily rhythms of endogenous corticosterone and prolactin by daily injections of the hormones at times corresponding to the peak levels found in 3-week-old rats reversed age-related increases in insulin resistance and body fat in older (5-6-month-old) rats. Ten such daily injections of corticosterone and prolactin in 12-14-week-old rats produced long-term reductions in body fat stores (30%). plasma insulin concentration (40%'). and insulin resistance (60%) (determined by a glucose tolerance test) measured 11-14 weeks after the treatment. Alterations in circadian neuroendocrine rhythms may account for age-related changes in carbohydrate and lipid metabolism in the male Sprague-Dawley rat, and resetting of these rhythms by appropriately timed daily injections of corticosterone and prolactin may help maintain metabolism characteristic of younger animals.     

First chromosome scale genomes of ithomiine butterflies (Nymphalidae: Ithomiini): Comparative models for mimicry genetic studies

The ithomiine butterflies (Nymphalidae: Danainae) represent the largest known radiation of Müllerian mimetic butterflies. They dominate by number the mimetic butterfly communities, which include species such as the iconic neotropical Heliconius genus. Recent studies on the ecology and genetics of speciation in Ithomiini have suggested that sexual pheromones, colour pattern and perhaps hostplant could drive reproductive isolation. However, no reference genome was available for Ithomiini, which has hindered further exploration on the genetic architecture of these candidate traits, and more generally on the genomic patterns of divergence. Here, we generated high-quality, chromosome-scale genome assemblies for two Melinaea species, M. marsaeus and M. menophilus, and a draft genome of the species Ithomia salapia. We obtained genomes with a size ranging from 396 to 503 Mb across the three species and scaffold N50 of 40.5 and 23.2 Mb for the two chromosome-scale assemblies. Using collinearity analyses we identified massive rearrangements between the two closely related Melinaea species. An annotation of transposable elements and gene content was performed, as well as a specialist annotation to target chemosensory genes, which is crucial for host plant detection and mate recognition in mimetic species. A comparative genomic approach revealed independent gene expansions in ithomiines and particularly in gustatory receptor genes. These first three genomes of ithomiine mimetic butterflies constitute a valuable addition and a welcome comparison to existing biological models such as Heliconius, and will enable further understanding of the mechanisms of adaptation in butterflies.     

SEM localization of laminin on the basement membrane of the chick corneal epithelium with immunolatex microspheres

Embryonic chick corneal explants were soaked in mild detergent and the anterior corneal epithelium was peeled from its basement membrane, leaving the lamina lucida surface exposed and supported on the subjacent primary stroma. Explants were treated with rabbit anti-laminin IgG, followed by sheep anti-rabbit IgG linked microspheres, and processed for SEM. The lucida surface was heavily decorated with microspheres, whereas controls treated with preimmune rabbit IgG were essentially beadless. Laminin distribution was not regular, appearing denser in some regions than others. However, the connective tissue surface of the basement membrane was never laminin-positive, even after treatment with hyaluronidase. These results suggest the basal lamina of the corneal epithelium is asymmetric, with preferential location of laminin to the lucida surface of the basement membrane.     

Genetic studies of the Fv-1 locus of mice: linkage with Gpd-1 in recombinant inbred lines.

Multiple recombinant inbred lines, derived from crosses between strains permissive to N-tropic murine leukemia viruses (Fv-1n) and strains permissive to B-tropic murine leukemia viruses (Fv-1b), have been characterized as to Fv-1 genotype and other chromosome 4 markers, including the closely linked hexose-6-phosphate dehydrogenase isozyme locus (Gpd-1). Only one recombinant between Fv-1 and Gpd-1 was found among 45 lines tested. On this basis, the distance between Fv-1 and Gpd-1 is estimated to be 0.6 centimorgans. None of the lines was either resistant or susceptible to both N- and B-tropic viruses. Nineteen other inbred strains, previously untested, were characterized as either Fv-1n or Fv-1b.     

Glucan synthesis by intact cotton fibres fed with different precursors at the stages of primary and secondary wall formation

Seed clusters of individual locules from fruit capsules of Gossypium arboreum L. with adhering intact fibres were fed with radioactive uridinediphosphoglucose (UDPG), guanosinediphosphoglucose (GDPG), glucose and sucrose. The incorporation into high molecular weight glucans of the fibres was studied. For primary wall fibres, UDPG at 1 mM was by far the best precursor, whereas sucrose was the best precursor for secondary wall fibres. No competition was observed between the incorporation of glucose from UDPG and from sucrose when the two were fed simultaneously to secondary wall fibres, indicating that their metabolic pathways are well separated when they are fed from the apoplast. Inhibitors of respiratory ATP-formation strongly inhibited incorporation of sucrose but not that of UDPG. Sucrose incorporation was studied at five different stages of development of the cotton fibres. At the stage of most intense secondary wall formation the incorporation rate was about 300 times that during primary wall formation (24 days post anthesis (DPA)). Incorporation from 1 mM UDPG or GDPG by secondary wall fibres (35 DPA) was less than twice that of primary wall fibres (22 DPA), indicating that the two sugar nucleotides are not readily used as precursors for secondary wall cellulose when they are fed to the exterior of intact cells. The high molecular weight non-cellulosic glucans formed from UDPG and sucrose at 5 and 1,000 M were solubilized in strongly alkaline solutions or dimethyl-sulfoxide (DMSO) and were partially characterized by degradation with an exo--1,3-glucanase. After feeding for one hour, at most 1/3 of the radioactivity in high molecular weight material was found in cellulose and at least 2/3 in -1,3-glucan. The proportions varied little for fibres in the age range of 30 to 48 DPA when sucrose was the precursor although the total incorporation varied by a factor of about four. The fact that at all stages of secondary wall formation -1,3-glucan is synthesized at a very high rate, but that the total amount in the cell wall does not exceed 2% in the later stages of wall formation, can be interpreted in terms of a high turnover of this polysaccharide if it is assumed that wound effects are negligible in the system under study.Abbreviations UDPG uridinediphosphoglucose - GDPG guanosinediphosphoglucose - HEPES N-2-hydroxyethylpiperazine-N-2-ethansulphonic acid - DMSO dimethyl-sulfoxide - DNP 2,4-dinitrophenol - DPA days post anthesis     

A Lipoxygenase from Leaves of Tomato (Lycopersicon esculentum Mill.) Is Induced in Response to Plant Pathogenic Pseudomonads

Lipoxygenase (LOX) mRNA, enzyme protein, and enzyme activity were found to be induced in leaves of tomato (Lycopersicon esculentum Mill. cv Moneymaker) on inoculation with plant pathogenic bacteria. The rate of enzyme activity with linoleic or linolenic acid as substrate was approximately 10 times greater than that with arachidonic acid. Optimum activity was at pH 7.0. In the incompatible interaction, which was associated with a hypersensitive reaction (HR), a single band with relative molecular weight approximately 100,000 was revealed by probing western blots of enzyme extracts with antiserum raised against a pea lipoxygenase. Changes in the intensity of this band reflected the changes observed in LOX enzyme activity after bacterial inoculations. In the hypersensitive reaction, i.e. after inoculation with Pseudomonas syringae pv syringae, LOX mRNA was induced by 3 hours and enzyme activity began to increase between 6 and 12 hours and had reached maximum levels by 24 to 48 hours. In tomato leaves inoculated with P. syringae pv tomato (compatible interaction), LOX mRNA was induced later and enzyme activity changed only marginally in the first 24 hours, then increased steadily up to 72 hours, reaching the levels seen in the HR.     

Divergence between GLUT4 mRNA and protein abundance in skeletal muscle of insulin resistant rats

Hyperglycemia and skeletal muscle insulin resistance coexist in uncontrolled type 2 diabetes mellitus. Similar defects in insulin action were observed in glucose-infused, normal rats, a model of glucose toxicity. In these rats insulin-stimulated glucose uptake by skeletal muscle was decreased due to a post-receptor defect. We investigated whether the impaired glucose uptake resulted from a decrease in the abundance of the predominant muscle glucose transporter (GLUT4) mRNA and/or protein. GLUT4 protein abundance in the hyperglycemic rats was not different from the control group despite a 50% decrease in muscle glucose uptake. GLUT4 mRNA abundance was 2.5-fold greater in the hyperglycemic rats as compared to the control animals. We conclude that the coexistence of hyperglycemia and hyperinsulinemia results in (1) a defect in GLUT4 compartmentalization and/or functional activity and (2) a divergence between GLUT4 mRNA levels and translation.