Book Reviews

Systemic Practice and Action Research -     

New records for Monotropa hypopithys (Ericaceae) from Colorado

Monotropa hypopithys L., rarely collected in Colorado, was taken five times during 1984. Coupled with previous collections, it is now known from 10 Colorado counties. The cool, moist August of 1984 may have contributed to its apparent ubiquity.     

Platelets as a model for neurones?

The multiple biochemical and pharmacological similarities existing between blood platelets and 5-hydroxytryptamine (5-HT)-containing neurones of the CNS point to the platelets as a reliable model for the biochemical characterization of 5-HT releasers and uptake blockers which interfere with the storage and the active carrier mechanism of 5-HT in the neurones, respectively. In addition, the affinity displayed by dopamine and by dopaminergic neurotoxin MPP⁺ for the platelet 5-HT transport and storage indicates also some similarities between platelets and the dopaminergic system of the CNS. Since human platelets contain almost exclusively monoamine oxidase type B (MAO-B), they can be used as a source for the purification and characterization of this human enzyme. Human platelets thus offer an excellent peripheral model to indirectly assess the degree and duration of MAO-B inhibition occurring in the CNS. To date, knowledge of the many biochemical mechanisms underlying platelet physiology is still fragmentary. In fact, the functional role of binding sites located on the platelet cytoplasmic membrane, i.e. their coupling to a specific transmembrane signalling mechanism, is still in need of a precise biochemical and physiological characterization.     

Unusual sequences in the murine immunoglobulin mu-delta heavy-chain region

The delta heavy (H) chain of mouse immunoglobulin D (IgD) is unusual both in its structure and in its differential expression relative to immunoglobulin M (IgM; reviewed in ref. 1). The region of DNA between IgM and IgD H-chain constant-region genes is probably implicated in this control. So far only fragments of the area have been sequenced. Now, however, we present the complete sequence as well as the sequence of the introns of the C delta gene. We have found several interesting features (Fig. 1), including an open reading frame (ORF) between Cmu and C delta which encodes 146 amino acids that might represent a previously unsuspected domain-like protein; three blocks of simple repetitive sequences; a 162-base pair (bp) unique-sequence inverted repeat; and a domain-like pseudogene in the large intron of C delta. We have not found, however, any sequence 5' of C delta resembling the switch (S) recombination sequences associated with class switching in other heavy chains. Moreover, we have determined the 3' deletion end point of an IgD-producing myeloma and find no sequences reminiscent of switch sites nearby.     

The Drosophila melanogaster Genetic Reference Panel

A major challenge of biology is understanding the relationship between molecular genetic variation and variation in quantitative traits, including fitness. This relationship determines our ability to predict phenotypes from genotypes and to understand how evolutionary forces shape variation within and between species. Previous efforts to dissect the genotype-phenotype map were based on incomplete genotypic information. Here, we describe the Drosophila melanogaster Genetic Reference Panel (DGRP), a community resource for analysis of population genomics and quantitative traits. The DGRP consists of fully sequenced inbred lines derived from a natural population. Population genomic analyses reveal reduced polymorphism in centromeric autosomal regions and the X chromosome, evidence for positive and negative selection, and rapid evolution of the X chromosome. Many variants in novel genes, most at low frequency, are associated with quantitative traits and explain a large fraction of the phenotypic variance. The DGRP facilitates genotype-phenotype mapping using the power of Drosophila genetics.