Permeabilization and lysis induced by bacteriocins and its effect on aldehyde formation by Lactococcus lactis

Permeabilization induced by lacticin 3147, lactococcins A, B and M, enterocin AS-48 and nisin, bacteriocins described as cell membrane-pore forming and lytic agents, enhanced in all cases aldehyde formation by Lactococcus lactis IFPL730. Nevertheless, the conversion of isoleucine into 2-methylbutyraldehyde depended not only on the degree of permeabilization but also on the bacteriocin that caused the cell membrane damage. The highest values of 2-methylbutyraldehyde corresponded to cell suspensions containing lacticin 3147 and lactococcins, treatments that provoked further lysis in addition to induced permeabilization.     

Changes in the Chlorophyll Content and Cytokinin Levels in the Top Three Leaves of New Plant Type Rice During Grain Filling

This paper reports the ways that the differences in leaf senescence are related to grain filling, grain yield, and the dynamics of cytokinins (CKs) in the top three leaves of four field-grown new plant type (NPT) rice, a tropical japonica developed at the International Rice Research Institute, Philippines, to increase the yield potential of rice. The chlorophyll content in leaves decreased from flowering to maturity in all the NPT lines, whereas the grain filling percentage was higher in the fast-senescing NPT line than in slow-senescing NPT line. Grain yield was positively correlated with senescence in the flag leaf. Rapid changes in the CK levels were recorded in the leaves of the fast-senescing line, whereas the CK levels were relatively stable in leaves of the slow-senescing line, suggesting that the dynamics of CKs in the fast-senescing line are vital for fast senescence. There were no significant changes in bioactive CKs, CK O-glucosides (storage CKs), and cis-zeatin derivatives in different leaves of the slow-senescing NPT line between 0 and 3 weeks after flowering, suggesting that the content of these CKs is relatively stable during grain filling. A progressive increase in levels of bioactive CKs was positively correlated with gradual accumulation of CK N-glucosides (inactive CKs) in the top three leaves of the slow-senescing NPT line, whereas the decrease of bioactive CKs in the flag leaf of the fast-senescing line was accompanied by accumulation of CK O-glucosides. These results suggest that there is a higher rate of biosynthesis and/or import of bioactive CKs as well as their turnover which may favor delay of leaf senescence in the slow-senescing NPT line.     

The status of dwarf carnivores on Cozumel Island, Mexico

Cozumel Island in the Mexican Caribbean is inhabited by four carnivores, of which two, the Cozumel coati Nasua nelsoni and pygmy raccoon Procyon pygmaeus, are endemic species. The taxonomic status of a third carnivore, a dwarf gray fox Urocyon cinereoargenteus, is undetermined, but may deserve subspecific or species-level recognition. The fourth species, the kinkajou (Potos flavus), may be a recent introduction. We review the status of these carnivores, report our field observations and results of line transect and trapping efforts, discuss current threats to these taxa, and make recommendations for their conservation. A population density of 0.43 ± 0.27 coatis/km², and a total island population size of 150 ± 95 individuals, was estimated from 386 km of line transects in 1994–1995. Intensive trapping efforts (1479 trap-nights) in 2001 at multiple localities were unsuccessful. Pygmy raccoons were observed in the mangrove and coastal wetland areas of the island and in 2001 we captured 11 individuals with the same sampling efforts as for coatis (8.8 raccoons/1000 trap-nights). The gray fox is also apparently very rare on the island. While a few observations of the animals have been made (1984, 1994 and 2001), no animals were seen along transects and none were trapped. The primary threats to the persistence of these taxa include introduced congeners, introduced predators, parasite and disease spill-over from exotic animals, habitat fragmentation, hunting and collection as pets, and hurricanes. We suggest that the Cozumel coati, pygmy raccoon, and the Cozumel population of the gray fox be considered as Critically Endangered according to the IUCN classification system. Current conservation actions focusing on Cozumel carnivores are extremely limited. We recommend eradication of introduced species, maintenance of habitat connectivity, ex situ conservation programs, explicit public policies on land-use and sustainable development, public awareness campaigns, and continuous scientific research and monitoring.     

Limited degradation of industrial,synthetic and natural lignins by Serratia marcescens

Summary Serratia marcescens was found to degrade kraft lignin by only 15%. When ¹⁴C-radiolabelled lignocelluloses and DHP lignins were used as substrates the bacterium mineralized to ¹⁴CO₂ only 1.1–1.9% and 0.4–0.8% of the lignins respectively. However, some 44.4% of the ¹⁴C--DHP lignin was recovered as soluble radiolabelled products.     

Substrate and positional specificity of feruloyl esterases for monoferuloylated and monoacetylated 4-nitrophenyl glycosides

4-Nitrophenyl glycosides of 2-, 3-, and 5-O-(E)-feruloyl- and 2- and 5-O-acetyl-alpha-L-arabinofuranosides and of 2-, 3-, and 4-O-(E)-feruloyl- and 2-, 3- and 4-O-acetyl-beta-D-xylopyranosides, compounds mimicking natural substrates, were used to investigate substrate and positional specificity of type-A, -B, and -C feruloyl esterases. All the feruloyl esterases behave as true feruloyl esterases showing negligible activity on sugar acetates. Type-A enzymes, represented by AnFaeA from Aspergillus niger and FoFaeII from Fusarium oxysporum, are specialized for deferuloylation of primary hydroxyl groups, with a very strong preference for hydrolyzing 5-O-feruloyl-alpha-L-arabinofuranoside. On the contrary, type-B and -C feruloyl esterases, represented by FoFaeI from F. oxysporum and TsFaeC from Talaromyces stipitatus, acted on almost all ferulates with exception of 4- and 3-O-feruloyl-beta-D-xylopyranoside. 5-O-Feruloyl-alpha-L-arabinofuranoside was the best substrate for both TsFaeC and FoFaeI, although catalytic efficiency of the latter enzyme toward 2-O-feruloyl-alpha-L-arabinofuranoside was comparable. In comparison with acetates, the corresponding ferulates served as poor substrates for the carbohydrate esterase family 1 feruloyl esterase from Aspergillus oryzae. The enzyme hydrolyzed all alpha-L-arabinofuranoside and beta-D-xylopyranoside acetates. It behaved as a non-specific acetyl esterase rather than a feruloyl esterase, with a preference for 2-O-acetyl-beta-D-xylopyranoside.     

Neuronal and mixed neuronal glial tumors associated to epilepsy. A heterogeneous and related group of tumours

The group of brain tumors with mature components encompasses several pathological entities including: the ganglioneuroma; the gangliocytoma; the ganglioglioma; the desmoplastic ganglioglioma; the neurocitoma and a group of glioneuronal hamartomatous tumorous lesions, such as meningoangiomatosis. The dysembryoplastic neuroepithelial tumor is characterized by the presence of multiple cortical nodules made up of small, oligo-like cells and a myxoid pattern rich in mucopolysaccharides. Mature neuronal cells are frequently detected throughout the tumor. Most of them are associated with microhamartias in the adjacent brain and pharmacoresistant epilepsy. The excellent prognosis of the majority of these tumors and the potential for malignant transformation of the glial component in the ganglioglioma are the two most remarkable findings. Histological signs of anaplasia and greater mitotic and proliferative activities are associated with local recurrences. Atypical neurocytomas occur only exceptionally. Treatment choices are surgical resectioning and, in those cases presenting greater proliferative activity and cytological atypia, postoperative radiotherapy may be recommended. This paper reviews this heterogeneous group of neoplasms and hamartomatous lesions, pointing out presumable transitions among the different types of mixed neuronal and glial brain tumors. A single term of "mixed neuronal-glial tumors" is defended, distinguishing different subgroups of tumors, depending on the predominant cellular component.     

Large-Scale Patterns of Quercus ilex, Quercus suber, and Quercus pyrenaica Regeneration in Central-Western Spain

In Central-Western Spain, forests and woodlands composed of Quercus sp. support outstanding levels of biodiversity, but there is increasing concern about their long-term persistence due to a lack of regeneration. We hypothesize that this regenerative lack is operating on a large geographic scale; that there are differences in the abundance of regeneration between three oak species; that oak regeneration is governed mainly by forest management and structure; and that shrubs act as important physical protectors of seedlings and saplings. We analyzed whether densities of oak seedlings and saplings in several size classes were related to stand-structure, understory, and physiographic variables potentially affecting regeneration. Data collected at a regional level (1 km × 1 km grid) by the Spanish Forest Inventory were evaluated from 2,816 plots. Results revealed that regeneration failure was common for all size categories, from small seedlings to large saplings, and for the three oak species studied, especially the evergreens. Of the Quercus ilex, Q. suber, and Q. pyrenaica plots studied, 49%, 62%, and 20% were lacking any small seedlings, and 82%, 96%, and 56% did not have any large saplings, respectively. Regeneration was positively correlated with tree cover and density, especially of small and medium-sized trees, and negatively correlated with the presence of large trees, indicating that regeneration failure is mostly associated with more open, uniform, and/or aged woodlands. Regeneration densities of Q. ilex and Q. suber were positively correlated with all understory variables, suggesting that the presence of pioneer shrubs represent a major safe site for early tree recruitment, independent from specific shrub species.     

Limited overlapping roles of P15(INK4b) and P18(INK4c) cell cycle inhibitors in proliferation and tumorigenesis

Entry of quiescent cells into the cell cycle is driven by the cyclin D-dependent kinases Cdk4 and Cdk6. These kinases are negatively regulated by the INK4 cell cycle inhibitors. We report the generation of mice defective in P15(INK4b) and P18(INK4c). Ablation of these genes, either alone or in combination, does not abrogate cell contact inhibition or senescence of mouse embryo fibroblasts in culture. However, loss of P15(INK4b), but not of P18(INK4c), confers proliferative advantage to these cells and makes them more sensitive to transformation by H-ras oncogenes. In vivo, ablation of P15(INK4b) and P18(INK4c) genes results in lymphoproliferative disorders and tumor formation. Mice lacking P18(INK4c) have deregulated epithelial cell growth leading to the formation of cysts, mostly in the cortical region of the kidneys and the mammary epithelium. Loss of both P15(INK4b) and P18(INK4c) does not result in significantly distinct phenotypic manifestations except for the appearance of cysts in additional tissues. These results indicate that P15(INK4b) and P18(IKN4c) are tumor suppressor proteins that act in different cellular lineages and/or pathways with limited compensatory roles.