Dormancy as exaptation to protect mimetic seeds against deterioration before dispersal

Mimetic seeds simulate the appearance of fleshy fruits and arilled seeds without producing nutritive tissues as a reward for seed dispersers. In this strategy of seed dispersal, seeds may remain attached to the mother plant for long periods after maturity, increasing their availability to naive seed dispersers. The hypothesis that seed coat impermeability in many tropical Fabaceae with mimetic seeds serves as an exaptation to protect the seeds from deterioration and rotting while awaiting dispersal was investigated. Seed coat impermeability was evaluated in five mimetic-seeded species of tropical Fabaceae in south-eastern Brazil (Abarema langsdorffii, Abrus precatorius, Adenanthera pavonina, Erythrina velutina and Ormosia arborea) and in Erythrina speciosa, a `basal` species in its genus, which has monochromatic brown seeds and no mimetic displays. Seed hardness was evaluated as a defence against accelerated ageing (humid chamber at 41 degrees C for 144 h). Seed development and physiological potential of O. arborea was evaluated and the effect of holding mature seeds in pods on the mother plant in the field for a period of 1 year under humid tropical conditions was compared with seeds stored under controlled conditions (15 degrees C and 40 % relative air humidity). All five mimetic-seeded species, and E. speciosa, showed strong coat impermeability, which protected the seeds against deterioration in accelerated ageing. Most O. arborea seeds only became dormant 2 months after pod dehiscence. Germination of seeds after 1 year on the plant in a humid tropical climate was 56 %, compared with 80 % for seeds stored in controlled conditions (15 degrees C, 45 % relative humidity). Seedling shoot length after 1 year did not differ between seed sources. Dormancy acts in mimetic-seeded species as an exaptation to reduce seed deterioration, allowing an increase in their effective dispersal period and mitigating the losses incurred by low removal rates by naive avian frugivores.

Silicon distribution and accumulation in shoot tissue of the tropical forage grass Brachiaria brizantha

Silicon (Si) accumulation in organs and cells is one of the most prominent characteristics of plants of the family Poaceae. Many species from this family are used as forage plants for animal feeding. The present study investigates in Brachiaria brizantha (Hochst. ex A. Rich.) Stapf. cv. Marandu: (1) the dry matter production and Si content in shoot due to soil Si fertilizations; (2) the Si distribution among shoot parts; and (3) the silica deposition and localization in leaves. Plants of B. brizantha cv. Marandu were grown under contrasting Si supplies in soil and nutrient solution. Silica deposition and distribution in grass leaf blades were observed using light microscope and scanning electron microscope equipped with an energy dispersive X-ray spectrometer (SEM-EDXS). Silicon concentration in the B. brizantha shoot increased according to the Si supply. Silicon in grass leaves decreased following the order: mature leaf blades > recently expanded leaf blades > non-expanded leaf blades. Silicon accumulates mainly on the upper (adaxial) epidermis of the grass leaf blades and, especially, on the bulliform cells. The Si distribution on adaxial leaf blade surface is non uniform and reflects a silica deposition exclusively on the cell wall of bulliform cells.

Growth-active gibberellins overcome the very slow shoot growth of Hancornia speciosa, an important fruit tree from the Brazilian ""Cerrado""

Shoot elongation of Hancornia speciosa, an endangered tree from the Brazilian savannah ""Cerrado"", is very slow, thus limiting nursery production of plants. Gibberellins (GAs) A(1), A(3), and A(5), and two inhibitors of GA biosynthesis, trinexapac-ethyl and ancymidol were applied to shoots of Hancornia seedlings. GA(1) and GA(3) significantly stimulated shoot elongation, while GA(5) had no significant effect. Trinexapac-ethyl and ancymidol, both at 100 A mu g per seedling, inhibited shoot elongation up to 45 days after treatment, though the effect was statistically significant only for ancymidol. Somewhat surprisingly, exogenous GA(3) more effectively stimulated shoot elongation in SD-grown plants, than in LD-grown plants. The results from exogenous application of GAs and inhibitors of GA biosynthesis imply that Hancornia shoot growth is controlled by GAs, and that level of endogenous growth-active GAs is likely to be the limiting factor for shoot elongation in Hancornia. Application of GAs thus offer a practical method for nursery production of Hancornia seedlings for outplanting into the field.

Redefining functional models of basal ganglia organisation: Role for the posteroventral pallidum in linguistic processing?

Traditionally the basal ganglia have been implicated in motor behavior, as they are involved in both the execution of automatic actions and the modification of ongoing actions in novel contexts. Corresponding to cognition, the role of the basal ganglia has not been defined as explicitly. Relative to linguistic processes, contemporary theories of subcortical participation in language have endorsed a role for the globus pallidus internus (GPi) in the control of lexical-semantic operations. However, attempts to empirically validate these postulates have been largely limited to neuropsychological investigations of verbal fluency abilities subsequent to pallidotomy. We evaluated the impact of bilateral posteroventral pallidotomy (BPVP) on language function across a range of general and high-level linguistic abilities, and validated/extended working theories of pallidal participation in language. Comprehensive linguistic profiles were compiled up to 1 month before and 3 months after BPVP in 6 subjects with Parkinson's disease (PD). Commensurate linguistic profiles were also gathered over a 3-month period for a nonsurgical control cohort of 16 subjects with PD and a group of 16 non-neurologically impaired controls (NC). Nonparametric between-groups comparisons were conducted and reliable change indices calculated, relative to baseline/3-month follow-up difference scores. Group-wise statistical comparisons between the three groups failed to reveal significant postoperative changes in language performance. Case-by-case data analysis relative to clinically consequential change indices revealed reliable alterations in performance across several language variables as a consequence of BPVP. These findings lend support to models of subcortical participation in language, which promote a role for the GPi in lexical-semantic manipulation mechanisms. Concomitant improvements and decrements in postoperative performance were interpreted within the context of additive and subtractive postlesional effects. Relative to parkinsonian cohorts, clinically reliable versus statistically significant changes on a case by case basis may provide the most accurate method of characterizing the way in which pathophysiologically divergent basal ganglia linguistic circuits respond to BPVP.

PACAP stimulates dopamine neuronal activity in the medial basal hypothalamus and inhibits prolactin

In sheep intracerebroventricular injection of PACAP (10 nmol) significantly (P < 0.01) stimulated the levels of the dopamine metabolite DOPAC within the medial basal hypothalamus las measured by in vivo microdialysis) and this effect was temporally correlated with a significant (P < 0.05) suppression in peripheral prolactin concentrations. This result is in accord with the hypothesis that PACAP suppresses prolactin secretion from the anterior pituitary gland by stimulating dopamine release from tuberoinfundibular dopaminergic neurons. (C) 1998 Elsevier Science B.V.

Long-distance signalling and a mutational analysis of branching in pea

Four ramosus mutants with increased branching at basal and aerial nodes have been used to investigate the genetic regulation of bud outgrowth in Pisum sativum L. (garden pea). Studies of long-distance signalling, xylem sap cytokinin concentrations, shoot auxin level, auxin transport and auxin response are discussed. A model of branching control is presented that encompasses two graft-transmissible signals in addition to auxin and cytokinin. Mutants rms1 through rms4 are not deficient in indole-3-acetic acid (IAA) or in the basipetal transport of this hormone. Three of the four mutants, rms1, rms3 and rms4, have very reduced cytokinin concentrations in xylem sap from roots. This reduction in xylem sap cytokinin concentration appears to be caused by a property of the shoot and may be part of a feedback mechanism induced by an aspect of bud outgrowth. The shoot-to-root feedback signal is unlikely to be auxin itself, as auxin levels and transport are not correlated with xylem sap cytokinin concentrations in various intact and grafted mutant and wild-type plants. Rms1 and Rms2 act in shoot and rootstock to regulate the level or transport of graft-transmissible signals. Various grafting studies and double mutant analyses have associated Rms2 with the regulation of the shoot-to-root feedback signal. Rms1 is associated with a second unknown graft-transmissible signal that is postulated to move in the direction of root-to-shoot. Exogenous auxin appears to interact with both of the signals regulated by Rms1 and Rms2 in the inhibition of branching after decapitation. The action of Rms3 and Rms4 is less apparent at this stage, although both appear to act largely in the shoot.

Anthropometric measures in relation to Basal Cell Carcinoma: a longitudinal study

Background: The relationship between anthropometric indices and risk of basal cell carcinoma ( BCC) is largely unknown. We aimed to examine the association between anthropometric measures and development of BCC and to demonstrate whether adherence to World Health Organisation guidelines for body mass index, waist circumference, and waist/ hip ratio was associated with risk of BCC, independent of sun exposure. Methods: Study participants were participants in a community- based skin cancer prevention trial in Nambour, a town in southeast Queensland ( latitude 26 degrees S). In 1992, height, weight, and waist and hip circumferences were measured for all 1621 participants and weight was remeasured at the end of the trial in 1996. Prevalence proportion ratios were calculated using a log- binomial model to estimate the risk of BCC prior to or prevalent in 1992, while Poisson regression with robust error variances was used to estimate the relative risk of BCC during the follow- up period. Results: At baseline, 94 participants had a current BCC, and 202 had a history of BCC. During the 5- year follow- up period, 179 participants developed one or more new BCCs. We found no significant association between any of the anthropometric measures or indices and risk of BCC after controlling for potential confounding factors including sun exposure. There was a suggestion that short- term weight gain may increase the risk of developing BCC for women only. Conclusion: Adherence to World Health Organisation guidelines for body mass index, waist circumference and waist/ hip ratio is not significantly associated with occurrence of basal cell carcinomas of the skin.

The shoot controls zeatin riboside export from pea roots. Evidence from the branching mutant rms4

The rms4 mutant of pea (Pisum sativum L.) was used in grafting studies and cytokinin analyses of the root xylem sap to provide evidence that, at least for pea, the shoot can modify the import of cytokinins from the root. The rms4 mutation, which confers a phenotype with increased branching in the shoot, causes a very substantial decrease (down to 40-fold less) in the concentration of zeatin riboside (ZR) in the xylem sap of the roots. Results from grafts between wild-type (WT) and rms4 plants indicate that the concentration of cytokinins in the xylem sap of the roots is determined almost entirely by the genotype of the shoot. WT scions normalize the cytokinin concentration in the sap of rms4 mutant roots, whereas mutant scions cause WT roots to behave like those of self-grafted mutant plants. The mechanism whereby rms4 shoots of pea cause a down-regulation in the export of cytokinins from the roots is unknown at this time. However, our data provide evidence that the shoot transmits a signal to the roots and thereby controls processes involved in the regulation of cytokinin biosynthesis in the root.

Intracellular free Ca2+ and basal Mn2+ influx in cultured aortic smooth muscle cells from spontaneously hypertensive and normotensive Wistar-Kyoto rats.

Numerous studies investigating the possible role of altered Ca2+ homeostasis in hypertension have compared resting and agonist-stimulated intracellular free Ca2+ ([Ca2+](i)) in cultured aortic smooth muscle cells from spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. However, such studies have not given consistent results. Differences in the method used to load cells with the Ca2+-sensitive indicator fura-2 have been investigated here as a possible source of variability between studies. We also describe the adaptation of a fluorescence technique for the assessment of basal Ca2+ permeability in SHR and WKY through the measurement of Mn2+ influx. The results are consistent with the hypothesis that basal Ca2+ influx is elevated in cultured aortic smooth muscle cells from SHR compared to those from WKY. However, this was not reflected as a significant difference between the two strains in basal or angiotensin II (200 nmol/L)stimulated [Ca2+](i). Furthermore, this result was not dependent on the protocol used to load cells with fura-2. Hence, measurement of bulk [Ca2+](i) does not appear to be the most sensitive parameter for altered Ca2+ homeostasis in SHR. Other compartments of the cell may better reflect altered Ca2+ fluxes in hypertension and are discussed in this work.

PTCH1 gene mutations in exon 17 and loss of heterozygosity on D9S180 microsatellite in sporadic and inherited human basal cell carcinomas

Background Basal cell carcinomas (BCCs) are the most frequent human cancer that results from malignant transformation of basal cells in the epidermis. Gorlin syndrome is a rare inherited autosomal dominant disease that predisposes with multiple BCCs and other birth defects. Both sporadic and inherited BCCs are associated with mutations in the tumor suppressor gene PTCH1, but there is still uncertainty on the role of its homolog PTCH2. Objectives To search for mutations and genomic instability in sporadic and inherited BCCs. Methods DNA obtained from leukocytes and tumor cells was amplified by polymerase chain reaction regarding five exons of PTCH1 and PTCH2 and neighboring microsatellites. Exons were sequenced and compared with the GenBank database. Results Only D9S180, of six microsatellites, showed loss of heterozygosity in three BCCs (two sporadic and one inherited). One sporadic BCC presented the mutation g. 2885G>C in exon 17 of PTCH1, which predicts the substitution p.R962T in an external domain of the protein. In addition, the leukocytes and tumor cells of one patient with Gorlin syndrome showed the mutation g. 2839T>G in the same exon and gene, which predicts a p.E947stop and truncated protein. All control and tumor samples presented IVS9 + 217T in intron 9 of PTCH1. Conclusion Mutations found in the PTCH1 gene and neighboring repetitive sequences may have contributed to the development of the studied BCCs.

The rms1 mutant of pea has elevated indole-3-acetic acid levels and reduced root-sap zeatin riboside content but increased branching controlled by graft-transmissible signal(s)

Rms1 is one of the series of five ramosus loci in pea (Pisum sativum L.) in which recessive mutant alleles confer increased branching at basal and aerial vegetative nodes. Shoots of the nonallelic rms1 and rms2 mutants are phenotypically similar in most respects. However, we found an up to 40-fold difference in root-sap zeatin riboside ([9R]Z) concentration between rms1 and rms2 plants. Compared with wild-type (WT) plants, the concentration of [9R]Z in rms1 root sap was very low and the concentration in rms2 root sap was slightly elevated. To our knowledge, the rms1 mutant is therefore the second ramosus mutant (rms4 being the first) to be characterized with low root-sap [9R]Z content. Like rms2, the apical bud and upper nodes of rms1 plants contain elevated indole-3-acetic acid levels compared with WT shoots. Therefore, the rms1 mutant demonstrates that high shoot auxin levels and low root-sap cytokinin levels are not necessarily correlated with increased apical dominance in pea. A graft-transmissible basis of action has been demonstrated for both mutants from reciprocal grafts between mutant and WT plants. Branching was also largely inhibited in rms1 shoots when grafted to rms2 rootstocks, but was not inhibited in rms2 shoots grafted to rms1 rootstocks. These grafting results are discussed, along with the conclusion that hormone-like signals other than auxin and cytokinin are also involved.

De novo mutations of the Patched gene in nevoid basal cell carcinoma syndrome help to define the clinical phenotype

The demonstration that mutations in the Patched (PTCH) gene cause nevoid basal cell carcinoma syndrome (NBCCS) has led to the identification of the exact molecular lesion in a percentage of individuals with the syndrome, In addition, it has been possible to determine, through molecular analysis of parents and other relatives of these individuals, if the mutation is inherited or has arisen de novo, We have previously reported 28 mutations in individuals with NBCCS, and here we present an additional 4 novel mutations, We have also analyzed relatives of a number of the individuals in whom we have found mutations, In total we have identified 8 individuals who carry a de novo mutation in the PTCH gene, In 5 of these cases, clinical and radiological examination had not unequivocally ruled out a diagnosis in one of the parents, This helps to define the clinical phenotype and suggests that diagnostic criteria in this complex syndrome may require review. (C) 1997 Wiley-Liss, Inc.