Identification of a region in G protein γ subunits conserved across species but hypervariable among subunit isoforms

The heterotrimeric GTP binding proteins, G proteins, consist of three distinct subunits: alpha, beta, and gamma. There are 12 known mammalian gamma subunit genes whose products are the smallest and most variable of the G protein subunits. Sequencing of the bovine brain gamma(10) protein by electrospray mass spectrometry revealed that it differs from the human protein by an Ala to Val substitution near the N-terminus. Comparison of gamma isoform subunit sequences indicated that they vary substantially more at the N-terminus than at other parts of the protein. Thus, species variation of this region might reflect the lack of conservation of a functionally unimportant part of the protein. Analysis of 38 gamma subunit sequences from four different species shows that the N-terminus of a given gamma subunit isoform is as conserved between different species as any other part of the protein, including highly conserved regions. These data suggest that the N-terminus of gamma is a functionally important part of the protein exhibiting substantial isoform-specific variation.     

Clonal analysis of the undifferentiated wing disk of Drosophila

Using a new cell marker, we have examined the early clonal restrictions in wing imaginal disks from late third instar larvae of Drosophila. Large clones do not significantly alter the gross structure of the disks, allowing us to map the clones relative to morphological landmarks. Clones in the posterior region of the disks behave in a similar way to clones in the adult cuticle; that is, they appear to be restricted to a defined compartment, and the presumptive anterior/posterior compartment border defined by these clones is located in a similar place in every disk. In contrast, clones in the anterior region of the wing disks often cross into the region normally occupied by the posterior compartment and, especially near the margins of the disk, show no common posterior boundary. We believe that the anterior clones are “pushing” the anterior/posterior compartment border, and that this pushing is related to the growth advantage of the marked cells, which are Minute⁺ in a Minute background. Finally, we find that clones do not cross between the adepithelial cells, which contribute to the adult musculature, and the disk epithelium.     

Growth of Aeromonas spp. at 4°C and related toxin production

Over the last few years Aeromonas spp. have been considered to be potential intestinal pathogens (Altwegg & Geiss 1989). Recently, detailed evidence has linked a strain from contaminated shrimp with a clinical isolate from a patient with diarrhoea and found them to be the same (Altwegg et al. 1991). It is now known that Aeromonas spp. are present in many foods, especially those of animal origin (Palumbo et al. 1989). Furthermore, previous studies have shown that these organisms are quite capable of growing at refrigeration temperatures. For example, Palumbo et al. (1985) found that seven out of 14 strains showed significant growth within 14 d at 5°C. However, most studies have only examined a relatively small number of strains, which were not speciated and were simply called A. hydrophila.
In this paper we examine the growth of 36 strains of aeromonas (divided into A. hydrophila, A. sobria and A. caviae ) at 4°C, and their ability to produce cyotoxins at 4°C, 30°C and 37°C.     

A Note on Testing Hypotheses about Trimmed Means

A well known result is that skewness can cause problems when testing hypotheses about measures of location, particulary when a one-sided test is of interest. Wilcox (1994) reports both theoretical and simulation results showing that when testing hypotheses about trimmed means, control over Type I error probabilities can be substantially better than methods for means. However, at least in some situations, control over the probability of a Type I error might still be judged to be inadequate. One way of adressing this concern is to combine trimmed means with the bootsrap method advocated by Westfall and Yuong (1993). This note reports simulation results indicating that there are situations where substantial improvements over Type I error probabilities are indeed obtained.     

Application of glucose at low concentrations to grass swards in waste-derived compost can significantly increase long-term yields

Carbohydrates have a range of effects on soil, dependent on the frequency and concentration of the application. Small quantities of glucose have the effect of accelerating the removal of available N (NH₄ ⁺, NO₃ ^–) through incorporation into the bodies of microorganisms. This reduces plant growth (Jenkinson, 1985), the rate of which depends largely on the presence of available N (Addiscott et al., 1991). However, in theory, if appropriate soil glucose concentrations are maintained, asymbiotic N₂-fixation will occur, supplying extra nitrogen nutrition to plants over an extended period. Here, it is demonstrated that the use of 0.028 M glucose and an appropriate source of N₂-fixing bacteria (green waste-derived compost) can result in increased grass dry matter yields of over 50% in a glasshouse experiment.