Phytogeography of the bryophyte floras of oak forests and páramo of the Cordillera de Talamanca, Costa Rica

Aim Central America is a biogeographically interesting area because of its location between the rich and very different biota of North and South America. We aim to assess phytogeographical patterns in the bryophyte floras of oak forests and páramo of the Cordillera de Talamanca, Costa Rica. Location Tropical America, in particular the montane area of Cordillera de Talamanca, Costa Rica. Methods The analysis is based on a new critical inventory of the montane bryophyte flora of Cordillera de Talamanca. All species were assigned to phytogeographical elements on the basis of their currently known distribution. Absolute and percentage similarities were employed to evaluate floristic affinities. Results A total of 401 species [191 hepatics (liverworts), one hornwort, 209 mosses] are recorded; of these, 251 species (128 hepatics, one hornwort, 122 mosses) occur in oak forests. Ninety‐three per cent of all oak forest species are tropical in distribution, the remaining 7% are temperate (4%) and cosmopolitan (3%) species. The neotropical element includes almost 74% of the species, the wide tropical element (pantropical, amphi‐atlantic, amphi‐pacific) only 19%. A significant part of the neotropical species from oak forests are species with tropical Andean‐centred ranges (27%). As compared with bryophyte species, vascular plant genera in the study region are represented by fewer neotropical, more temperate and more amphi‐pacific taxa. Bryophyte floras of different microhabitats within the oak forest and epiphytic bryophyte floras on Quercus copeyensis in primary, early secondary and late secondary oak forest show a similar phytogeographical make‐up to the total oak forest bryophyte flora. Comparison of oak forest and páramo reveals a greater affinity of the páramo bryophyte flora to temperate regions and the great importance of the páramo element in páramo. Surprisingly, oak forests have more Central American endemics than páramo. Main conclusions (1) Providing first insights into the phytogeographical patterns of the bryophyte flora of oak forests and páramo, we are able to confirm general phytogeographical trends recorded from vascular plant genera of the study area although the latter were more rich in temperate taxa. (2) Andean‐centred species are a conspicuous element in the bryophyte flora of Cordillera de Talamanca, reflecting the close historical connection between the montane bryophyte floras of Costa Rica and South America. (3) High percentages of Central American endemics in the bryophyte flora of the oak forests suggest the importance of climatic changes associated with Pleistocene glaciations for allopatric speciation.     

The effects of ketamine, phencyclidine and lidocaine on catecholamine secretion from cultured bovine adrenal chromaffin cells

The ability of ketamine, phencyclidine and analogues to alter catecholamine secretion from cultured bovine adrenal chromaffin cells was investigated. Both ketamine and phencyclidine specifically inhibited nicotinic agonist-induced secretion at concentrations which did not alter secretion induced by elevated K+ depolarization. The inhibition of nicotinic agonist-induced secretion was not overcome by increasing concentrations of nicotinic agonist. The effects of stereoisomer pairs of phencyclidine-like drugs - dexoxadrol, levoxadrol and (+)PCMP, (-)PCMP - did not reveal stereospecificity for the inhibition, in contrast to the stereospecific behavioral effects of the drugs. The local anesthetic lidocaine (0.3 mM) also noncompetitively inhibited nicotinic agonist-induced secretion without inhibiting elevated K+-induced secretion. The data indicate that ketamine and phencyclidine at clinically relevant concentrations specifically inhibit the adrenal chromaffin cell nicotinic receptor at a site similar to or identical with the site of action of local anesthetic. Although the nicotinic receptor inhibition is probably not related to the anesthetic and behavioral effects of ketamine and phencyclidine, it is likely that the centrally mediated increase in sympathetic nervous system activity which is characteristic of these drugs is moderated by the peripheral blocking effects on catecholamine secretion from the adrenal medulla.     

Fe2+-Induced Lysis and Lipid Peroxidation of Chromaffin Granules

Chromaffin granules, the catecholaminergic storage granules from adrenal chromaffin cells, lysed in 10(-9)-10(-7) M Fe2+. Lysis was accompanied by the production of malondialdehyde which results from lipid peroxidation. Both chromaffin granule lysis and malondialdehyde production were inhibited by the free radical trapping agent butylated hydroxytoluene but not by catalase and/or superoxide dismutase. The results suggest that lysis resulted from a direct transfer of electrons from Fe2+ to a component of the chromaffin granule membrane without the participation of either superoxide or hydrogen peroxide and may have resulted from lipid peroxidation. In some experiments, ascorbate alone induced chromaffin granule lysis which was inhibited by EDTA, EGTA, or deferoxamine. The lysis was probably caused by trace amounts of reducible polyvalent cation. Lysis sometimes occurred when Ca2+ was added with EGTA (10 microM free Ca2+ concentration) and was consistently observed together with malondialdehyde production in the presence of Ca2+, EGTA, and 10 microM Fe2+ (total concentration). The apparent Ca2+ dependency for chromaffin granule lysis and malondialdehyde production was probably caused by a trace reducible polyvalent ion displaced by Ca2+ from EGTA and not by a Ca2+-dependent reaction involving the chromaffin granule.     

Review of clinical studies on dendritic cell-based vaccination of patients with malignant melanoma: assessment of correlation between clinical response and vaccine parameters

During the past years numerous clinical trials have been carried out to assess the ability of dendritic cell (DC) based immunotherapy to induce clinically relevant immune responses in patients with malignant diseases. A broad range of cancer types have been targeted including malignant melanoma which in the disseminated stage have a very poor prognosis and only limited treatment options with moderate effectiveness. Herein we describe the results of a focused search of recently published clinical studies on dendritic cell vaccination in melanoma and review different vaccine parameters which are frequently claimed to have a possible influence on clinical response. These parameters include performance status, type of antigen, DC maturation status, route of vaccine administration, use of adjuvant, and vaccine induced immune response. In total, 38 articles found through Medline search, have been included for analysis covering a total of 626 patients with malignant melanoma treated with DC based therapy. Clinical response (CR, PR and SD) were found to be significantly correlated with the use of peptide antigens (p = 0.03), the use of any helper antigen/adjuvant (p = 0.002), and induction of antigen specific T cells (p = 0.0004). No significant correlations between objective response (CR and PR) and the tested parameters were found. However, a few non-significant trends were demonstrated; these included an association between objective response and use of immature DCs (p = 0.08), use of adjuvant (p = 0.09), and use of autologous antigen preparation (p = 0.12). The categorisation of SD in the response group is debatable. Nevertheless, when the SD group were analysed separately we found that SD was significantly associated with use of peptide antigens (p = 0.0004), use of adjuvant (p = 0.01), and induction of antigen specific T cells (p = 0.0003). No specific route of vaccine administration showed superiority. Important lessons can be learned from previous studies, interpretation of these findings should, however, be done with reservation for the many minor deviations in the different treatment schedules among the published studies, which were not considered in order to be able to process and group the data.     

Bovine chromaffin granule membranes undergo Ca(2+)-regulated exocytosis in frog oocytes

We have devised a new method that permits the investigation of exogenous secretory vesicle function using frog oocytes and bovine chromaffin granules, the secretory vesicles from adrenal chromaffin cells. Highly purified chromaffin granule membranes were injected into Xenopus laevis oocytes. Exocytosis was detected by the appearance of dopamine-beta-hydroxylase of the chromaffin granule membrane in the oocyte plasma membrane. The appearance of dopamine-beta-hydroxylase on the oocyte surface was strongly Ca(2+)-dependent and was stimulated by coinjection of the chromaffin granule membranes with InsP3 or Ca2+/EGTA buffer (18 microM free Ca2+) or by incubation of the injected oocytes in medium containing the Ca2+ ionophore ionomycin. Similar experiments were performed with a subcellular fraction from cultured chromaffin cells enriched with [3H]norepinephrine-containing chromaffin granules. Because the release of [3H]norepinephrine was strongly correlated with the appearance of dopamine-beta-hydroxylase on the oocyte surface, it is likely that intact chromaffin granules and chromaffin granule membranes undergo exocytosis in the oocyte. Thus, the secretory vesicle membrane without normal vesicle contents is competent to undergo the sequence of events leading to exocytosis. Furthermore, the interchangeability of mammalian and amphibian components suggests substantial biochemical conservation of the regulated exocytotic pathway during the evolutionary progression from amphibians to mammals.     

Blown fuse regulates stretching and outgrowth but not myoblast fusion of the circular visceral muscles in Drosophila

Circular visceral muscles of Drosophila are binuclear syncytia arising from fusion of two different kinds of myoblasts: a circular visceral founder cell and one visceral fusion-competent myoblast. In contrast to fusion leading to the somatic body-wall musculature, myoblast fusion for the circular visceral muscles does not result in massive syncytia but instead in syncytia interconnected with multiple cytoplasmic bridges, which differentiate into large web-shaped muscles. Here, we show that these syncytial circular visceral muscles build a gut-enclosing network with the interwoven longitudinal visceral muscles. At the ultrastructural level, during circular visceral myoblast fusion and the first step of somatic myoblast fusion prefusion complexes and electron-dense plaques were not detectable which was surprising as these structures are characteristic for the second step of somatic myoblast fusion. Moreover, we demonstrate that Blown fuse (Blow), a cytoplasmic protein essential for the second step of somatic myoblast fusion, plays a different role in circular visceral myogenesis. Blow is known to be essential for progression beyond the prefusion complex in the somatic mesoderm; however, analysis of blow mutants established that it has a restricted role in stretching and outgrowth of the syncytia in the circular visceral muscles. Furthermore, we also found that in the visceral mesoderm, Blow is expressed in both the fusion-competent myoblasts and circular visceral founders, while expression in the somatic mesoderm is initially restricted to fusion-competent myoblasts. We also demonstrate that different enhancer elements in the first intron of blow are responsible for this distinct expression pattern. Thus, we propose a model for Blow in which this protein is involved in at least two clearly differing processes during Drosophila muscle formation, namely somatic myoblast fusion on the one hand and stretching and outgrowth of circular visceral muscles on the other.     

mTOR and S6K1 mediate assembly of the translation preinitiation complex through dynamic protein interchange and ordered phosphorylation events

In response to nutrients, energy sufficiency, hormones, and mitogenic agents, S6K1 phosphorylates several targets linked to translation. However, the molecular mechanisms whereby S6K1 is activated, encounters substrate, and contributes to translation initiation are poorly understood. We show that mTOR and S6K1 maneuver on and off the eukaryotic initiation factor 3 (eIF3) translation initiation complex in a signal-dependent, choreographed fashion. When inactive, S6K1 associates with the eIF3 complex, while the S6K1 activator mTOR/raptor does not. Cell stimulation promotes mTOR/raptor binding to the eIF3 complex and phosphorylation of S6K1 at its hydrophobic motif. Phosphorylation results in S6K1 dissociation, activation, and subsequent phosphorylation of its translational targets, including eIF4B, which is then recruited into the complex in a phosphorylation-dependent manner. Thus, the eIF3 preinitiation complex acts as a scaffold to coordinate a dynamic sequence of events in response to stimuli that promote efficient protein synthesis.