A Design Pattern for Decentralised Decision Making

The engineering of large-scale decentralised systems requires sound methodologies to guarantee the attainment of the desired macroscopic system-level behaviour given the microscopic individual-level implementation. While a general-purpose methodology is currently out of reach, specific solutions can be given to broad classes of problems by means of well-conceived design patterns. We propose a design pattern for collective decision making grounded on experimental/theoretical studies of the nest-site selection behaviour observed in honeybee swarms (Apis mellifera). The way in which honeybee swarms arrive at consensus is fairly well-understood at the macroscopic level. We provide formal guidelines for the microscopic implementation of collective decisions to quantitatively match the macroscopic predictions. We discuss implementation strategies based on both homogeneous and heterogeneous multiagent systems, and we provide means to deal with spatial and topological factors that have a bearing on the micro-macro link. Finally, we exploit the design pattern in two case studies that showcase the viability of the approach. Besides engineering, such a design pattern can prove useful for a deeper understanding of decision making in natural systems thanks to the inclusion of individual heterogeneities and spatial factors, which are often disregarded in theoretical modelling.     

Chromosome studies in the red howler monkey, Alouatta seniculus stramineus (Platyrrhini, Primates): description of an X1X2Y1Y2/X1X1X2X2 sex-chromosome system and karyological comparisons with other subspecies

In the red howler monkey, Alouatta seniculus stramineus (2n = 47, 48, or 49), variations in diploid chromosome number are due to different numbers of microchromosomes. Males exhibit a Y;autosome translocation involving the short arm of an individual biarmed autosome. Consequently, the sex-chromosome constitution in the male is X1X2Y1Y2, with X1 representing the original X chromosome, X2 the biarmed autosome (No. 7), Y1 the Y;7p translocation product, and Y2 the acrocentric homolog of 7q. In the first meiotic division, a quadrivalent with a chain configuration can be observed in spermatocytes. Females have an X1X1X2X2 sex-chromosome constitution. Chromosome heteromorphisms were observed in pair 13, due to a pericentric inversion, and pair 19, due to the presence of constitutive heterochromatin. Microchromosomes, which varied in number between individuals, were also heterochromatic. NOR-staining was observed at two separate sites on a single chromosome pair (No. 10). A comparison of A.s. stramineus with A.s. macconnelli shows that these two subspecies have identical diploid chromosome numbers (47, 48, or 49), again due to a varying number of microchromosomes, and that they share a similar sex-chromosome constitution. Their karyotypes, however, are not identical, but can be derived from each other by a reciprocal translocation. Further comparisons with other A. seniculus subspecies reported in the literature indicate that this taxon is not karyologically uniform and that substantial chromosome shuffling has occurred between populations that have been considered to be subspecies by taxonomic criteria based on their morphometric attributes.     

A gene for familial paroxysmal dyskinesia (FPD1) maps to chromosome 2q.

Dyskinesias are hyperkinetic and involuntary movements that may result from any of a number of different genetic, infectious, and drug-induced causes. Some of the hereditary dyskinetic syndromes are characterized by paroxysmal onset of the abnormal movements. The classification of the familial paroxysmal dyskinesias (FPD) recognizes several distinct, although overlapping, phenotypes. Different forms of the disorder include attacks that are (1) induced by sudden movement (kinesiogenic); (2) spontaneous (non-kinesiogenic); and (3) induced by prolonged periods of exertion. Linkage analysis was pursued in a family segregating an autosomal dominant allele for non-kinesiogenic FPD. The disease allele was mapped to a locus on chromosome 2q31-36 (LOD score 4.64, theta = 0). Identification of distinct genetic loci for the paroxysmal dyskinesias will lead to a new genetic classification and to better understanding of these disorders.     

Studies on the N-acetyl-beta-D-hexosaminidase B from germinating Lupinus luteus L. seeds. I. Purification and characterization

The N-acetyl-beta-D-hexosaminidase B of germinating Lupinus luteus L. seeds (McFarlane et al. (1984) Phytochemistry 23, 2431-2433) was partially purified with a six-step purification procedure following extraction. This enzyme consists of one protein chain (Mr 69,000, as determined by SDS-PAGE and 62,500, as obtained by gel filtration on Bio-Gel P-60 Gel) and has a neutral isoelectric point (pI = 7.05, as determined by chromatofocusing). Moreover, it was found to be very sensitive to low ionic strength, especially in the presence of different gels based on Sephadex. Considering the substrate specificity, the enzyme splits both p-nitrophenyl-2-acetamido-2-deoxy-beta-D-glucosaminide and -galactosaminide substrates, but lacks N,N'-diacetylchitobiase activity. A new mixed-substrate procedure was developed and is presented here to demonstrate that a common active site is responsible for the splitting of both synthetic substrates.     

Evolution of Helix Formation in the Ribosomal Internal Transcribed Spacer 2 (ITS2) and Its Significance for RNA Secondary Structures

Helices are the most common elements of RNA secondary structure. Despite intensive investigations of various types of RNAs, the evolutionary history of the formation of new helices (novel helical structures) remains largely elusive. Here, by studying the nuclear ribosomal Internal Transcribed Spacer 2 (ITS2), a fast-evolving part of the eukaryotic nuclear ribosomal operon, we identify two possible types of helix formation: one type is “dichotomous helix formation”—transition from one large helix to two smaller helices by invagination of the apical part of a helix, which significantly changes the shape of the original secondary structure but does not increase its complexity (i.e., the total length of the RNA). An alternative type is “lateral helix formation”—origin of an extra helical region by the extension of a bulge loop or a spacer in a multi-helix loop of the original helix, which does not disrupt the pre-existing structure but increases RNA size. Moreover, we present examples from the RNA sequence literature indicating that both types of helix formation may have implications for RNA evolution beyond ITS2.