Identity of the antibiotic ramihyphin A and cyclosporin A

The antifungal antibiotic ramihyphin A, isolated fromFusarium solani strain S-435 in 1974, was shown to be identical with cyclosporin A.     

Comparison of the catalytic properties of the botulinum neurotoxin subtypes A1 and A5

Clostridium botulinum neurotoxins (BoNTs) cause the life-threatening disease botulism through the inhibition of neurotransmitter release by cleaving essential SNARE proteins. There are seven serologically distinctive types of BoNTs and many subtypes within a serotype have been identified. BoNT/A5 is a recently discovered subtype of type A botulinum neurotoxin which possesses a very high degree of sequence similarity and identity to the well-studied A1 subtype. In the present study, we examined the endopeptidase activity of these two BoNT/A subtypes and our results revealed significant differences in substrate binding and cleavage efficiency between subtype A5 and A1. Distinctive hydrolysis efficiency was observed between the two toxins during cleavage of the native substrate SNAP-25 versus a shortened peptide mimic. N-terminal truncation studies demonstrated that a key region of the SNAP-25, including the amino acid residues at 151 through 154 located in the remote binding region of the substrate, contributed to the differential catalytic properties between A1 and A5. Elevated binding affinity of the peptide substrate resulted from including these important residues and enhanced BoNT/A5's hydrolysis efficiency. In addition, mutations of these amino acid residues affect the proteolytic performance of the two toxins in different ways. This study provides a better understanding of the biological activity of these toxins, their performance characteristics in the Endopep-MS assay to detect BoNT in clinical samples and foods, and is useful for the development of peptide substrates.     

A comparison of the nucleotide sequence of the A subunit of heat-labile enterotoxin and cholera toxin

Abstract The heat-labile enterotoxin genes from plasmid P307 have been cloned into pAT153. A comparison of the sequence of the LT-A gene with that of the A subunit of cholera toxin shows extensive homology. There are a number of significant differences between the sequence of the LT-A gene reported here and that published previously.     

A History and Ethnography of the Beothuk

History and Ethnography of the Beothuk. Ingeborg Marshall. Montreal: McGill-Queen's University Press, 1996. 640 pp.     

A Hierarchy of Time-Scales and the Brain

In this paper, we suggest that cortical anatomy recapitulates the temporal hierarchy that is inherent in the dynamics of environmental states. Many aspects of brain function can be understood in terms of a hierarchy of temporal scales at which representations of the environment evolve. The lowest level of this hierarchy corresponds to fast fluctuations associated with sensory processing, whereas the highest levels encode slow contextual changes in the environment, under which faster representations unfold. First, we describe a mathematical model that exploits the temporal structure of fast sensory input to track the slower trajectories of their underlying causes. This model of sensory encoding or perceptual inference establishes a proof of concept that slowly changing neuronal states can encode the paths or trajectories of faster sensory states. We then review empirical evidence that suggests that a temporal hierarchy is recapitulated in the macroscopic organization of the cortex. This anatomic-temporal hierarchy provides a comprehensive framework for understanding cortical function: the specific time-scale that engages a cortical area can be inferred by its location along a rostro-caudal gradient, which reflects the anatomical distance from primary sensory areas. This is most evident in the prefrontal cortex, where complex functions can be explained as operations on representations of the environment that change slowly. The framework provides predictions about, and principled constraints on, cortical structure–function relationships, which can be tested by manipulating the time-scales of sensory input.     

Expression and function of the Eph A receptors and their ligands ephrins A in the rat thymus

Thymus development and function are dependent on the definition of different and graded microenvironments that provide the maturing T cell with the different signals that drive its maturation to a functional T lymphocyte. In these processes, cell-cell interactions, cell migration, and positioning are clues for the correct functioning of the organ. The Eph family of receptor tyrosine kinases and their ligands, the ephrins, has been implicated in all these processes by regulating cytoskeleton and adhesion functioning, but a systemic analysis of their presence and possible functional role in thymus has not yet been conducted. In this regard, the current study combines different experimental approaches for analyzing the expression of four members of the Eph A family and their ligands, ephrins A, in the embryonic and adult rat thymus. The patterns of Eph and ephrin expression in the distinct thymic regions were different but overlapping. In general, the studied Eph A were expressed on thymic epithelial cells, whereas ephrins A seem to be more restricted to thymocytes, although Eph A1 and ephrin A1 are expressed on both cell types. Furthermore, the supply of either Eph A-Fc or ephrin A-Fc fusion proteins to fetal thymus organ cultures interferes with T cell development, suggesting an important role for this family of proteins in the cell mechanisms that drive intrathymic T cell development.     

A review of the phylogeny and biology of the Diaporthales

The ascomycete order Diaporthales is reviewed based on recent phylogenetic data that outline the families and integrate related asexual fungi. The order now consists of nine families, one of which is newly recognized as Schizoparmeaceae fam. nov., and two families are recircumscribed. Schizoparmeaceae fam. nov., based on the genus Schizoparme with its anamorphic state Pilidella and including the related Coniella, is distinguished by the three-layered ascomatal wall and the basal pad from which the conidiogenous cells originate. Pseudovalsaceae is recognized in a restricted sense, and Sydowiellaceae is circumscribed more broadly than originally conceived. Many species in the Diaporthales are saprobes, although some are pathogenic on woody plants such as Cryphonectria parasitica, the cause of chestnut blight, and agricultural crops such as canker diseases of soybean and sunflower caused by species of Diaporthe-Phomopsis in both temperate and tropical regions. Members of the Diaporthales such as Apiognomonia-Discula and Diaporthe-Phomopsis are commonly encountered as endophytes of woody plants.     

Identification of gibberellin A4 in Pisum sativum L. and the effects of applied gibberellins A9, A4, A5 and A3 on the le mutant

Gibberellin A₄ (GA₄) was identified for the first time in the garden pea (Pisum sativum) L.), by gas chromatography-mass spectrometry. However, in wild-type shoots the level of GA₄ was only about 6% of the level of GA₁, and it is therefore unlikely that GA₄ plays a major role per se in the control of pea stem elongation. In shoots of the le mutant, GA₄ was not detected, while the level of GA₉ was approximately twice that found in the wild-type. The le mutation also markedly reduced the elongation response to applied GA₉. It appears, therefore, that in Pisum the le mutation blocks the 3-hydroxylation of GA₉ to GA₄, in addition to the 3-hydroxylation of GA₂₀ to GA₁. In contrast, the le mutation did not reduce the response to applied GA₅, suggesting the step GA₅ to GA₃ is not catalysed by the enzyme controlled by the Le gene. The step GA₅ to GA₃ was confirmed in peas by metabolite analysis after treatment with deuterated GA₅.