Isethionate may not be an inert substitute for extracellular chloride in the central nervous system

Summary Replacement of extracellular chloride with isethionate or methylsulphate causes an increased efflux of 1-[¹⁴C]-GABA from the in vivo superfused rat cuneate nucleus. This raises the question of the suitability of these anions as inert substitutes for chloride in studies on the ionic dependency of membrane phenomena in the central nervous system.Supported in part by a grant from the Medical Endowment Funds of the University of Aberdeen.N. B. supported by grants from CAPES and FAPESP, Brazil, J. A. A. supported by grants from CNPq and FAPESP, Brazil.     

Observations of a certain arrangement in the nucleolar chromatin after continuous ethidium bromide treatment

Summary This work is an ultrastructural and cytochemical study of a structure observed in the nucleolus of Allium cepa meristematic cells after nucleolar disgregation, by a continuous treatment of 12 h with ethidium bromide. The ultrastructural and cytochemical data allow us to consider this structure as the intranucleolar chromatin collapsed by the effect of the drug.     

Autophagy: molecular mechanisms,physiological functions and relevance in human pathology

Autophagy is a degradative mechanism mainly involved in the recycling and turnover of cytoplasmic constituents from eukaryotic cells. Over the last years, yeast genetic screens have considerably increased our knowledge about the molecular mechanisms of autophagy, and a number of genes involved in fundamental steps of the autophagic pathway have been identified. Most of these autophagy genes are present in higher eukaryotes indicating that this process has been evolutionarily conserved. In yeast, autophagy is mainly involved in adaptation to starvation, but in multicellular organisms this route has emerged as a multifunctional pathway involved in a variety of additional processes such as programmed cell death, removal of damaged organelles and development of different tissue-specific functions. Furthermore, autophagy is associated with a growing number of pathological conditions, including cancer, myopathies and neurodegenerative disorders. The physiological and pathological roles of autophagy, as well as the molecular mechanisms underlying this multifunctional pathway, are discussed in this review.Received 12 January 2004; received after revision 29 January 2004; accepted 4 February 2004     

Senataxin, the ortholog of a yeast RNA helicase, is mutant in ataxia-ocular apraxia 2

Ataxia-ocular apraxia 2 (AOA2) was recently identified as a new autosomal recessive ataxia. We have now identified causative mutations in 15 families, which allows us to clinically define this entity by onset between 10 and 22 years, cerebellar atrophy, axonal sensorimotor neuropathy, oculomotor apraxia and elevated alpha-fetoprotein (AFP). Ten of the fifteen mutations cause premature termination of a large DEAxQ-box helicase, the human ortholog of yeast Sen1p, involved in RNA maturation and termination.     

Litter production and decomposition in a terra-firme forest of Central Amazonia

Summary Chemical and biological aspects of litter production and decomposition were studied in three distinct areas of the Central Amazon. Litter production was measured during three years, employing the litter trap technique, with adapted conical collectors. Leaf litter decomposition was studied in experiments, over five-month-periods with repetitions for the dry and wet seasons, using the nylon-mesh bag technique. The greatest litter production took place during the drier period of the year, mainly from June to October, while decomposition processes were more accentuated in the wet season: in the plateau site, one-half, of the litter disappears, according to a mathematical model, in about, 218 days under dry season conditions as against 32 days in the wet season. In the rainy season, weight reduction and mineral losses from decomposing leaves occurred more rapidly, owing to the intense biological activity on the material during this period. Particularly noticeable was the intense activity of termites in organic matter breakdown and mineral removal, and the extensive root penetration in the decomposing leaves, which removed some minerals but increased the amounts of other. Leaching effects were also quite noticeable in this period. During the rainy season, in the latosol sites, termites were responsible for more than 40% of the removal of decomposing leaves. While intense biological activity appears to be the major factor responsible for weight reduction and loss of many minerals, as well as for the accumulation of some other minerals (mainly zinc iron and aluminium) in the decomposing material, leaching seems to be the major factor responsible for the loss of certain minerals such as potassium, boron and copper.