Stenocereus zopilotensis Arreola-Nava and Terrazas (Cactaceae), a new species from Mexico

Stenocereus zopilotensis Arreola-Nava and Terrazas, a new species from the Zopilote Canyon, municipality of Zumpango del Rio in the center of the state of Guerrero (Mexico), is described and illustrated. This new species is compared toStenocereus quevedonis J. G. Ortega,S. fricii Sánchez-Mej., andS. pruinosus (Otto) Buxb. based on morphological similarity. Moreover, the new species grows sympatrically withS. pruinosus.     

Molecular characterization of a novel lipase-like pathogen-inducible gene family of Arabidopsis

In a differential screening between Arabidopsis plants pretreated with the resistance-inducer beta-aminobutyric acid and untreated control plants, we have identified a gene encoding a novel lipase-like protein, PRLIP1. The abundance of PRLIP1 mRNAs in Arabidopsis leaves was up-regulated by application of beta-aminobutyric acid, salicylic acid (SA), and ethylene as well as by various pathogens. Induction of PRLIP1 depended on a functioning SA and ethylene signal transduction pathway but was independent of jasmonate signaling. This novel pathogenesis-related (PR) gene of Arabidopsis belongs to a gene family consisting of six (PRLIP1, PRLIP2, PRLIP4, PRLIP5, PRLIP6, and PRLIP7) closely related members in tandem position on chromosome 5. Among these genes, PRLIP2 also was induced in leaves by SA and infections by pathogens but on a much lower level than PRLIP1. The PRLIP1 family showed a tissue-specific expression pattern. Both PRLIP1 and PRLIP2 were specifically expressed in leaves and siliques, PRLIP1 additionally in stems and flowers. The expression of PRLIP6 and PRLIP4 was root specific, whereas mRNA of PRLIP5 and PRLIP7 were not detected in any of these tissues. The more distantly related genes PRLIP3, PRLIP9, and PRLIP8 were found on chromosomes 2, 4, and 5, respectively. The expression level of PRLIP3 was checked and found constitutive during the different stress conditions tested. The PRLIP1 gene was overexpressed in Escherichia coli, and the resulting PRLIP1 protein showed esterase activity on p-nitrophenyl-butyrate and allowed the growth of the bacteria on lipidic substrates such as Tween20 or Tween80.     

Comparative study of three methods for non-radioactive in vivo DNA labeling in Escherichia coli using nucleoside analogs

In the present work, a comparative study of 5-FdUrd, thy-, and metabolic in vivo labeling methods for plasmid and chromosomal DNA in E. coli DH5alpha cells was performed in order to achieve the best thymidine substitution method by 5-BrdUrd. According to the colorimetric immunoenzymatic results, we found that the minimal detectable labeled DNA (MDLD) was 312pg with the 5-FdUrd and thy- methods for 5-BrdUrd labeled plasmid DNA. 5-BrdUrd replaced about 96% of the total thymidine by 5-FdUrd methods; for the thy- and metabolic labeling methods, the MDLD value was 1,25 ng for denatured 5-BrdUrd chromosomal DNA. Pyrimidine nucleoside analogues were also evaluated as immunochemical markers for their in vivo introduction into DNA.     

Feeding is not necessary for triggering plasticization of the abdominal cuticle in haematophagous bugs

A simple device was used to quantify changes in the mechanical properties of the cuticle of Rhodnius prolixus and Triatoma infestans that take place when these insects feed, i.e., plasticization. Different stimuli were presented for 1min to test for their ability to trigger plasticization. These were: a blood meal, a Ringer solution meal, contact with a warm surface and thermal stimulation without such contact. Our results supplant any previous hypotheses that have supposed that the presence of food in the alimentary tract is necessary to evoke plasticization. We find that mere contact of the proboscis with a warm surface (without any food intake) is sufficient to trigger plasticization indistinguishable from that produced by a blood meal. Thermal stimulation alone, i.e., without physical contact, was not effective.     

A new technique for desorbing substances tightly bound to affinity gels: flat-bed electrophoretic desorption in Sephadex via isoelectric focusing (FEDS-IEF)

In some cases, proteins and other molecules which are tightly bound to affinity gels can be recovered under mild conditions by electrophoresis. We have extended this technique by running electrophoretic desorption in flat-beds of Sephadex in the presence of ampholytes (FEDS-IEF). A number of advantages of this technique are noted: due to the geometry of the apparatus, high voltages can be used which result in short running times; there are no physical barriers to the migration of the protein and no abrupt conductivity drops; desorbed samples are easily located and recovered; and relatively large sample loads can be readily accommodated. Running times are very sensitive to the experimental conditions. Affinity gels should be applied as a narrow zone, distant from the anticipated banding position of the desorbed species. A wide ampholyte interval is generally recommended. The system appears to be gentle and flexible enough to allow investigators to optimize the conditions for desorption of various affinity gel systems.     

Cryptococcus neoformans varieties as agents of cryptococcosis in Brazil

The study of the clinical isolates of Cryptococcus neoformans from 83 Brazilian patients with disseminated cryptococcosis showed that 75 were C. neoformans var. neoformans and 8 were var. gattii. Twenty-seven isolates were serotyped; all 19 var. neoformans were serotype A and all 8 var. gattii were serotype B. The correlation of the varieties of C. neoformans with the presence or not of hosts predisposing conditions to the mycosis showed that: (1) cryptococcosis caused by gattii variety occurred in 7 (58.3%) of the 12 nonimmunosuppressed patients, and (2) cryptococcosis caused by neoformans variety occurred in 65 (98.5%) of the 66 AIDS patients and in all 5 patients with other immunosuppressive conditions. The comparison of the distribution of the gattii and neoformans varieties between the nonimmunosup-pressed and immunosuppressed patients showed a significant statistical difference (p < 0.01).     

Universal foliage-stem scaling across environments and species in dicot trees: plasticity, biomechanics and Corner's Rules

Trees range from small-leaved, intricately branched species with slender stems to large-leaved, coarsely branched ones with thick stems. We suggest a mechanism for this pattern, known as Corner's Rules, based on universal scaling. We show similar crown area–stem diameter scaling between trunks and branches, environments, and species spanning a wide range of leaf size and stem biomechanics. If crown and stem maintain metabolically driven proportionality, but similar amounts of photosynthates are produced per unit crown area, then the greater leaf spacing in large-leaved species requires lower density stem tissue and, meeting mechanical needs, thicker stems. Congruent with this scenario, we show a negative relationship between leaf size and stem Young's modulus. Corner's Rules emerge from these mutual adjustments, which suggest that adaptive studies cannot consider any of these features independently. The constancy of scaling despite environmental challenges identifies this trait constellation as a crucial axis of plant diversification.     

Acidosis improves uptake of antigens and MHC class I-restricted presentation by dendritic cells

It is widely appreciated that inflammatory responses in peripheral tissues are usually associated to the development of acidic microenvironments. Despite this, there are few studies aimed to analyze the effect of extracellular pH on immune cell functions. We analyzed the impact of acidosis on the behavior of dendritic cells (DCs) derived from murine bone marrow. We found that extracellular acidosis (pH 6.5) markedly stimulated the uptake of FITC-OVA, FITC-dextran, and HRP by DCs. In fact, to reach similar levels of endocytosis, DCs cultured at pH 7.3 required concentrations of Ag in the extracellular medium almost 10-fold higher compared with DCs cultured at pH 6.5. Not only the endocytic capacity of DCs was up-regulated by extracellular acidosis, but also the expression of CD11c, MHC class II, CD40, and CD86 as well as the acquisition of extracellular Ags by DCs for MHC class I-restricted presentation. Importantly, DCs pulsed with Ag under acidosis showed an improved efficacy to induce both specific CD8(+) CTLs and specific Ab responses in vivo. Our results suggest that extracellular acidosis improves the Ag-presenting capacity of DCs.     

Repeated plasticization and recovery of cuticular stiffness in the blood-sucking bug Triatoma infestans in the feeding context

Triatominae bugs experience changes in the mechanical properties of their cuticle prior to feeding. This process-plasticization-allows a rapid stretching of the unsclerotized abdominal cuticle of triatominae larvae and it is evoked by sensory inputs related to feeding. We tested: (a) whether the cuticle recovers its original mechanical properties after plasticization, (b) whether repeated stimulation would be able to evoke recurrent plasticization along the same larval instar, (c) the temporal course of recovering cuticular stiffness. We injected Ringer solution into the body cavity of the bugs at constant pressure, using the injection rate (ml/min) as a measure of the cuticle extensibility. To trigger plasticization, individuals were allowed to feed on blood from an artificial feeder at 32+/-2 degrees C. After plasticization occurred, the abdominal cuticle gradually recovered its original mechanical properties. Bugs were capable of plasticizing for a second time when repeatedly stimulated. The effects of plasticization vanished between 1 and 2 h after stimulation. Although one full meal could suffice to accomplish moult in other Triatomine species, Triatoma infestans is able to feed repeatedly during a single larval instar. Accordingly to this, their cuticle recovers stiffness in some hours and becomes able to respond repeatedly to sensory inputs associated with feeding.