Hardening by abscisic acid of tobacco plantlets grownin vitro

Tobacco plantlets were grownin vitro on Murashige and Skoog’s medium with2 % of saccharose. Addition of 0.01 mM abscisic acid (ABA) into the medium decreased stomatal conductance of the adaxial epidermis and especially the abaxial epidermis without negative effects on growth parameters. As a result the rate of water loss from ABA-treated plantlets taken out of cultivation vessels was slower than that of control plantlets. This could help their acclimation after transplantation toex vitro conditions.     

Nucleolar Organizer ultrastructure in Allium cepa

The Nuoleolar Organizer Region (NOR) was studied in Allium cepa. The cells analyzed were: meristematic root tip cells, cells from the layers of the anther (exothecium, intermediate layer cells, endothecium and tapetum) and meiocytes from preleptotene to diptotene. Conventional electron microscope techniques and serial section were used in the study. Ultracytochemical tests, using preferential techniques for nucleic acids were also applied. The results show that: a) Although the NOR may have a very variable form in the different cells analyzed, in each case its fine structure is similar, being constituted of chromatin differentiated in high and low density zones. b) In each case, its cytochemical characteristics are similar; highly positively to EDTA (preferential stain for RNP) being observed in the low density zones. As scattered chromatin these would constitute the active regions of the NOR. c) In certain cases a clear relationship is seen between NOR volume and the size of the nucleolus. d) The chromatin associated to the NOR always appears as very dense zones. e) The NOR-Nucleolus relationships are established exclusively with the latter's fibrillar pars. f) The nucleolar segregation phenomenon takes place sometimes as a result of a NOR contraction and in other cases depends on the position of the NOR in relation to the nucleolus. g) In preleptotene, the NOR shows its characteristic morphology and is positive to EDTA, while from zygotene to diplotene the structure of the NOR presents no differences from the rest of the chromatin and only the lateral elements of the synaptonemal complex or its remnants are positive to EDTA. h) The synaptonemal complex runs through the NOR with no differentiation and on occasions its lateral elements show associations with the nucleolus.     

Elevated atmospheric CO2 modifies responses to water-stress and flowering of Mediterranean desert truffle mycorrhizal shrubs

Predicted increases in atmospheric concentration of carbon dioxide (CO₂) coupled with increased temperatures and drought are expected to strongly influence the development of most of the plant species in the world, especially in areas with high risk of desertification like the Mediterranean basin. Helianthemum almeriense is an ecologically important Mediterranean shrub with an added interest because it serves as the host for the Terfezia claveryi mycorrhizal fungus, which is a desert truffle with increasingly commercial interest. Although both plant and fungi are known to be well adapted to dry conditions, it is still uncertain how the increase in atmospheric CO₂ will influence them. In this article we have addressed the physiological responses of H. almeriense × T. claveryi mycorrhizal plants to increases in atmospheric CO₂ coupled with drought and high vapor pressure deficit. This work reports one of the few estimations of mesophyll conductance in a drought deciduous Mediterranean shrub and evaluates its role in photosynthesis limitation. High atmospheric CO₂ concentrations help desert truffle mycorrhizal plants to cope with the adverse effects of progressive drought during Mediterranean springs by improving carbon net assimilation, intrinsic water use efficiency and dispersal of the species through increased flowering events.     

Severe acute respiratory syndrome coronavirus fails to activate cytokine-mediated innate immune responses in cultured human monocyte-derived dendritic cells

Activation of host innate immune responses was studied in severe acute respiratory syndrome coronavirus (SCV)-infected human A549 lung epithelial cells, macrophages, and dendritic cells (DCs). In all cell types, SCV-specific subgenomic mRNAs were seen, whereas no expression of SCV proteins was found. No induction of cytokine genes (alpha interferon [IFN-alpha], IFN-beta, interleukin-28A/B [IL-28A/B], IL-29, tumor necrosis factor alpha, CCL5, or CXCL10) or IFN-alpha/beta-induced MxA gene was seen in SCV-infected A549 cells, macrophages, or DCs. SCV also failed to induce DC maturation (CD86 expression) or enhance major histocompatibility complex class II expression. Our data strongly suggest that SCV fails to activate host cell cytokine gene expression in human macrophages and DCs.     

Kinase-mediated trapping of bi-functional conjugates of paclitaxel or vinblastine with thymidine in cancer cells

In the present work, we explore the possibility of introducing selectivity to existing chemotherapeutics via the design of non-pro-drug, bi-functional molecules comprising a microtubule-binding agent and a substrate for a disease-associated kinase. The design, synthesis, and in vitro biological evaluation of paclitaxel-thymidine and vinblastine-thymidine bi-functional conjugates are reported here. This work provides the first account of 'kinase-mediated trapping' of cancer therapeutics.     

Immunological evaluation of Escherichia coli-derived hepatitis C virus second envelope protein (E2) variants.

Two variants of the hepatitis C virus (HCV) E2 envelope protein, lacking the C-terminal domain and comprising amino acids 458-650 (E2A) and 382-605 (E2C), respectively, were efficiently produced in BL21 (DE3) Escherichia coli cells. E2A and E2C were used to immunize mice. The E2C variant induced the maximal mean antibody titer. Anti-E2C mouse sera reacted mainly with E2 synthetic peptides covering the 70 amino acid N-terminal region of the E2 protein. Moreover, a panel of anti-HCV positive human sera recognized only the E2C protein (28.2%) and the synthetic peptide covering the HVR-1 of the E2 protein (23.1%). These data indicate the existence of an immunologically relevant region in the HVR-1 of the HCV E2 protein.     

In vitro culture and biochemical characterization of six trypanosome isolates from Peru and Brazil

Six trypanosomatids isolated from different geographical areas from South America (Peru and Brazil) and different vectors and reservoir hosts (the triatomine Panstrongylus chinai [TP1], Triatoma infestans [TP2], Rhodnius ecuadorensis [TP3], R. prolixus [TB1], Didelphys marsupialis [TB2]), and one from a human asymptomatic patient [TB3], were characterized using lectin agglutination, isoenzyme profile, in vitro culture final metabolite patterns, and compared with a reference strain (Trypanosoma cruzi, Maracay strain [TC]). The different isolates were cultured in vitro in Grace's medium supplemented with 10% inactivated bovine foetal serum. According to our results and the statistical study, the isolate obtained from R. ecuadorensis should be designed as a Trypanosoma rangeli sp., showing all other isolates strong similarities to T. cruzi. Between them, two clusters could be identified, strongly correlating with the geographical origin. Cluster I grouped isolates from Peru and T. cruzi reference strain, and cluster II grouped the three Brazilian isolates.