Opa-like repeats in the genome of the Medfly Ceratitis capitata

The sequence determination of several genomic clones isolated from the Mediterranean fruitfly Ceratitis capitata identified the existence of opa-like repeats, often more than one being clustered in small chromosomal segments. These repeats have previously been shown to consist of stretches of tandemly reiterated glutamine-encoding residues, and they are found in multiple genes of several organisms. Most of the repeats described here are flanked or interrupted by stop codons in all reading frames and, thus, could not possibly be part of protein-coding sequences. Furthermore, these repeats, of which there are several hundred in the genome of the Medfly, can be used effectively for the determination of sequence polymorphisms, providing a convenient approach to obtain additional landmarks for the construction of genomic maps of this economically important insect.This paper is dedicated to the memory of our colleague and friend Dr. Jim Flach who took part in the initial phase of this work and died during the course of the investigation.     

Comparative efficacy of amphotericin B,clotrimazole and itraconazole againstAspergillus spp.

The susceptibilities of two isolates ofAspergillus flavus, one from a human case of recalcitrant mycotic keratitis, and an environmental isolate ofA. fumigatus, to itraconazole, clotrimazole and amphotericin B were measured. Observations of macroscopic growth and microscopic evaluations of conidia germination both indicated that the two isolates ofA. flavus were markedly more resistant to amphotericin B than to itraconazole and clotrimazole. Itraconazole was more effective than clotrimazole for all isolates. Ourin vitro susceptibility results suggest the use of itraconazole should be a primary consideration in the treatment ofAspergillus keratitis.     

Stable chromosome aberrations 25 years after severe accidental radiation exposure

A thorough cytogenetic analysis using G-banding was performed on 100 peripheral blood lymphocytes from an individual who had been accidentally exposed to radiation more than 25 years previously. More than 60% of the analysed cells were found to possess one or more stable chromosome aberrations (e.g. reciprocal translocations). Chromosomes 1 and 11 were more involved in these aberrations than would be expected from the relative chromosome lengths. No identical stable aberrations were found, suggesting that, 25 years after nearlethal exposure, haemopoietic stem cells display substantial diversity.     

Spatial scale impacts microbial community composition and distribution within and across stream ecosystems in North and Central America

A mechanistic understanding of factors that structure spatiotemporal community composition is a major challenge in microbial ecology. Our study of microbial communities in the headwaters of three freshwater stream networks showed significant community changes at the small spatial scale of benthic habitats when compared to changes at mid- and large-spatial scales associated with stream order and catchment. Catchment (which included temperate and tropical catchments) had the strongest influence on community composition followed by habitat type (epipsammon or epilithon) and stream orders. Alpha diversity of benthic microbiomes resulted from interactions between catchment, habitat, and canopy. Epilithon contained relatively more Cyanobacteria and algae while Acidobacteria and Actinobacteria proportions were higher in epipsammic habitats. Turnover from replacement created ~60%–95% of beta diversity differences among habitats, stream orders, and catchments. Turnover within a habitat type generally decreased downstream indicating longitudinal linkages in stream networks while between habitat turnover also shaped benthic microbial community assembly. Our study suggests that factors influencing microbial community composition shift in dominance across spatial scales, with habitat dominating locally and catchment dominating globally.     

Parasitism and decreased response to sex pheromones in malePeriplaneta americana (Dictyoptera: Blattidae)

Parasites are known to alter the behavior of their hosts, but little is known about their effects on responses to sexual stimuli. Periplaneta americanainfected with the acanthocephalan Moniliformis moniliformiswere compared to uninfected animals in their behavioral and electroantennogram responses to a synthetic P. americanapheromone component, periplanone-B, and a pheromone mimic, bornyl acetate. In a t-maze there was no significant difference between infected animals' responses to periplanone-B and a random binomial distribution; the responses of uninfected animals were significantly nonrandom. The electroan-tennogram responses of infected and uninfected animals to bornyl acetate or periplanone-B did not differ significantly, however, indicating that the alteration probably does not occur at the peripheral level but at a central nervous system level.     

Distribution of NO3− reduction between roots and shoots of peachtree seedlings as affected by NO3− uptake rate

The distribution of NO₃^? reduction between roots and shoots was studied in hydro-ponically-grown peach-tree seedlings (Prunus persica L.) during recovery from N starvation. Uptake, translocation and reduction of NO₃^?, together with transport through xylem and phloem of the newly reduced N were estimated, using ¹⁵N labellings, in intact plants supplied for 90 h with 0.5 mM NH₄⁺ and 0.5, 1.5 or 10 mM NO₃^?. Xylem transport of NO₃^? was further investigated by xylem sap analysis in a similar experiment. The roots were the main site of NO₃^? reduction at all 3 levels of NO₃^? nutrition. However, the contribution of the shoots to the whole plant NO₃^? reduction increased with increasing external NO₃^? availability. This contribution was estimated to be 20, 23 and 42% of the total assimilation at 0.5, 1.5 and 10 mM NO₃^?, respectively. Both ¹⁵N results and xylem sap analysis confirmed that this trend was due to an enhancement of NO₃^? translocation from roots to shoots. It is proposed that the lack of NO₃^? export to the shoots at low NO₃^? uptake rate resulted from a competition between NO₃^? reduction in the root epidermis/cortex and NO₃^? diffusion to the stele. On the other hand, net xylem transport of newly reduced N was very efficient since ca 70% of the amino acids synthesized in the roots were translocated to the shoots, regardless of the level of NO₃^? nutrition. This net xylem transport by far exceeded the net downward phloem transport of the reduced N assimilated in shoots. As a consequence, the reduced N resulting from NO₃^? assimilation, principally occurring in the roots, was mainly incorporated in the shoots.     

PHYCOGENETIC COMPARISON OF THE SMALL-SUBUNIT RIBOSOMAL DNA SEQUENCE OF COSTARIA COSTATA (PHAEOPHYTA) WITH THOSE OF OTHER ALGAE,VASCULAR PLANTS AND OOMYCETES1

The small-subunit ribosomal DNA (rDNA) coding sequence was determined for the help Costaris Costata (Phaeophyta) and compared to those of chlorophyll a + b- and chlorophyll a + c-containing vascular and nonvascular plants. Phylogenetic comparison of all sequences indicated a common ancestor for phaeophytes, chrysophytes and oomycetes. Phylogenies based on rDNA sequence data and those based on plastid characteristics were compared. Relative evolutionary distances between some taxa, derived from rDNA sequence data, conflicted with findings of plastid-based phylogenies.     

Leptin and OB-R: Body weight regulation by a cytokine receptor

There has been intense recent interest in the molecules and pathways governing mammalian body weight regulation. Leptin (OB), an ancestral member of the cytokine family, is an adipocyte-secreted circulating hormone exhibiting weight regulatory properties. Recently, the leptin receptor (OB-R) was identified and shown to exhibit sequence homology and functional similarity to members of the class I cytokine receptor family. The mechanisms governing OB-R triggering and signal transduction have begun to be elucidated, providing new insight into the pathways controlling mammalian body weight homeostasis.     

A Major Gene for Resting Metabolic Rate Unassociated with Body Composition: Results from the Québec Family Study

A major gene hypothesis for resting metabolic rate (RMR) was investigated using segregation analysis (POINTER) of data on families participating in Phase 2 of the Québec Family Study. Complete analyses were conducted on RMR adjusted for age, and also on RMR adjusted for age and other covariates, primarily fat mass (FM) and fat-free mass (FFM). Prior to adjustment for covariates, support for a major gene hypothesis was equivocal — i.e., there was evidence for either a major gene or a multifactorial component (i.e., polygenic and/or familial environment). The multifactorial model was preferred over the major gene model, although the latter did segregate according to Mendelian expectations. However, after the effects of FM and FFM were accounted for, a major gene effect was unambiguous and compelling. The putative locus accounted for 57% of the variance, affected 7% of the sample, and led to high values of RMR. The lack of a significant multifactorial effect suggested that the familial etiology of RMR adjusted for FM and FFM was likely to be entirely a function of the major locus. Comparing the RMR results from pre- and post-adjustment for FM and FFM suggests a plausible hypothesis. We know from earlier studies in this sample that there is a putative major gene for FM and a major non-Mendelian effect for FFM. The current study leads us to speculate that: (1) the gene(s) affecting body size and body composition also may have an effect on RMR, and further (2) removal of the effect of the major gene(s) for body size and composition allowed for detection of an additional major gene affecting only the RMR. Thus, RMR appears to be an oligogenic trait.