Allometric growth and adaptive value of exaggerated body parts in the larvae of Gratiana spadicea (Klug) (Coleoptera: Chrysomelidae)

1. Larvae of tortoise beetles present exaggerated body parts in association with an abdominal shield, which is made of faeces and exuviae that are deposited on the urogomphi throughout ontogeny. Growth trajectories and scaling relationships of these functional structures associated with the shield, if any, are unknown. 2. This study of Gratiana spadicea first tested, under field conditions, whether there is adaptive value associated with the shield regarding protection against predation and sunlight. Then, under laboratory conditions, the growth trajectory and allometric relationships among body parts were investigated, including scoli, individual and apparent furcae, and shield. The influence of food deprivation on the development of these structures was also determined. 3. Findings from previous studies were confirmed, suggesting that the adaptive value assigned to the shield is related to protection against predators. The present study demonstrated for the first time that the shield acts as a parasol in cassidines, decreasing the exposure of their larval body to sunlight. The scoli and apparent furca are exaggerated structures of G. spadicea, the development of which involves allometric growth and greater energetic investment (positive allometry) during ontogeny. There was proportionally less energetic investment for somatic construction of individual furca (negative allometry) due to the accumulation of the exuviae. 4. The possible consequences, in terms of developmental costs and survivorship benefits associated with the evolution of such exaggerated structures, are discussed.     

Chromosome evolution and phylogeny in Ronderosia (Orthoptera,Acrididae, Melanoplinae): clues of survivors to the challenge of sympatry?

In an attempt to unveil the origin of neo‐sex chromosomes in Ronderosia Cigliano grasshoppers, we performed a combined phylogenetic analysis based on morphological (external morphology and male genitalia) and molecular data (COI, COII, 16S and ITS2) to explore the chromosome evolution within the genus. We also analysed the distributional patterns of the various Ronderosia species and considered the possible role of chromosome rearrangements (CRs) in speciation processes within the genus in the light of ‘suppressed‐recombination’ models. We mapped the states of three chromosomal characters on the combined tree topology. The combined evidence supported Ronderosia as a monophyletic group. The cytogenetic analyses of the genus demonstrated the importance of rearranged karyotypes with single, complex and multiples neo‐sex chromosome determination systems in all species. The chromosome character optimisation suggests X‐autosome centric fusion as the mechanism responsible for neo‐sex chromosome formation in most Ronderosia species, except in R. dubia and R. bergii. Similar autosomes were involved in fusions with the ancestral X chromosome in Ronderosia, supporting previous hypotheses on the unique origin of X‐autosome fusion for the sex chromosome in the genus. As a source of chromosome variation, autosome‐autosome centric fusion played a secondary role in Ronderosia compared with other Dichroplini. Given the homogeneity in the morphological features, the sympatric distribution of closely related species and the intrinsic property of centric fusion as suppressors of the crossing over, we suggest that CRs may have played a key role during the speciation process within Ronderosia.     

O2-triggered changes of membrane fatty acid composition have no effect on Arrhenius discontinuities of respiration in sycamore (Acer pseudoplatanus L.) cells

Sycamore cells (Acer pseudoplatanus L.) in suspension culture were grown at 25 degrees C in culture medium containing two oxygen concentrations: 250 microM O2 (standard conditions) and 10 microM O2 (O2-limiting conditions). The decrease of O2 concentration in the culture medium did not modify significantly the relative proportion of each phospholipid. In contrast, the molar proportion of fatty acids was dramatically changed in all lipid classes of the cell membranes; the average percentage of oleate increased from 3 to 45% whereas that of linoleate decreased from 49 to 22%. When normal culture conditions were restored (250 microM O2), oleate underwent a rapid desaturation process; the loss of oleic acid was associated with a stoichiometric appearance of linoleic acid at a rate of about 4 nmol of oleate desaturated/h/10(6) cells. Under these conditions, no change in the Arrhenius-type plots of the rate of sycamore cell respiration was observed; the values of the transition temperature and of the Arrhenius activation energy (Ea) associated with the cell respiration as well as with the respiration-associated enzymes remained unchanged. Thus it was concluded that the fact that a strong decrease in the fraction of unsaturated fatty acid residues present in the mitochondria had no effect on electron transport rates and Arrhenius plot discontinuities casts doubt on the significance of such changes in terms of chilling injury. Finally it is suggested that some of the Arrhenius discontinuities observed at the level of membrane enzyme could be the consequence of intrinsic thermotropic changes in protein arrangement independent of lipid fluidity.     

Prevalence of diabetes in glaucoma.

Oral glucose 75 g was given to 352 patients with chronic glaucoma, acute glaucoma, or ocular hypertension and 73 patients without glaucoma. The proportion of patients with shallow anterior chambers who showed an abnormal response was significantly greater than that in patients with deep anterior chambers and in the control group (p less than 0.005). The probability of developing an abnormal response to oral glucose tests increased as the depth of the anterior chamber decreased; these two variables showed a significant negative linear correlation (r = -0.79, p less than 0.001). The high prevalence of autonomic dysfunction in patients with shallow anterior chambers and glaucoma may explain this association. Because of this, acute glaucoma should be regarded as a symptom of diabetes.     

Prostaglandin E2 inhibits the activation of cloned T cell hybridomas

To minimize complicating interactions inherent in heterogeneous cell populations, we used a panel of cloned murine autoreactive (E8.A1) and antigen-specific (HEL.C10, HEL.B14) T cell hybridomas to examine the effect of prostaglandin E2 (PGE2) on T cell activation. These T cells secrete interleukin 2 (IL 2) when co-cultured with a cloned population of I region-matched stimulator cells (TA3), or with mitogenic signals in the absence of TA3 stimulator cells. Physiologic concentrations of PGE2 inhibited the induction of IL 2 secretion by the T cell hybridomas tested, when they were activated either by TA3 cells or by mitogenic signals. IL 2 production was inhibited in a dose-dependent manner by concentrations of PGE2 between 10(-7) and 10(-11) M, with 50% inhibition occurring at 10(-10) M. Pretreatment of the T hybridoma cells with 10(-7) M PGE2 for 1 hr before culture also resulted in marked inhibition of IL 2 secretion. Similar pretreatment of the TA3 cells did not affect their ability to activate the T cell hybridomas. PGE2 at 10(-8) M induced a 30-fold increase in cAMP levels within 25 min of addition to culture of the E8.A1 T cell hybridoma, but caused no significant elevation of cAMP levels in TA3 cells. The direct addition of dibutyryl cAMP (dcAMP) to cultures of E8.A1 cells resulted in marked inhibition of IL 2 secretion when stimulated by TA3 or by mitogenic signals, with an average of 80% inhibition occurring at 10(-4) M dcAMP. PGE2 and dcAMP also inhibited the growth of E8.A1 cells. Initially, cell growth was virtually halted, but began to recover between 24 and 48 hr after the addition of either PGE2 or dcAMP. Neither PGE2 nor dcAMP inhibited the division of TA3 cells. High affinity binding sites for PGE2 were detected in the E8.A1 T cell hybridomas with an apparent Kd of 7.6 X 10(-10) M, which is consistent with the functional data. No specific binding was detected in the TA3 stimulator cells. These findings suggest that the immunosuppressive effects of PGE2 are localized to the T cell, are receptor regulated, and may be mediated by the associated increase of cAMP levels in the T cell hybridomas.     

Evidence Inconsistent with the Blaauw Model of Phototropism

The Blaauw model of phototropism equates the inhibition of growthat the illuminated side of a unilaterally illuminated organwith the blue light inhibition of overall organ extension evidentwhen some shoots are exposed to uniform blue light However,a study of the growth responses of Avena coleoptiles exposedto omnilateral, equal bilateral, unequal bilateral and unilateralblue light has revealed some light induced growth rate changeswhich cannot be explained by the Blaauw model. The growth responsesof cells at the illuminated and shaded sides of phototropicallystimulated coleoptiles seem to depend on the existence of alight gradient across the whole organ rather than the absolutelevels of light at either side. Key words: Phototropism, Avena coleoptile, Blaauw hypothesis, Blue light, Growth inhibition     

Mechanism of the cerebrovascular effect of piracetam

Piracetam produces a more pronounced effect on cerebral circulation disturbed by hemorrhagic shock as compared with intact animals. Piracetam has a depressant effect on the nervous regulation of cerebral circulation by suppressing the reflex constriction of the vessels in both arterial systems of the brain. The cerebrovascular effects of piracetam are not mediated through the GABAergic bicuculline-sensitive mechanisms, which is supported by experiments where the drug exhibits its effects under the blockade of GABA receptors.