Molecular analysis of large transposable elements carrying the white locus of Drosophila melanogaster

A large transposable element (TE) comprising the white-apricot and roughest genes has been found to transpose to well over a hundred sites scattered over the Drosophila genome. We report the cloning of the essential parts of several TEs. TE98 and TE28 sequences were cloned by `walking' along the chromosome from the previously cloned heatshock genes. The ends of the TEs are characterized by dispersed repetitive elements belonging to the foldback (FB) family. FB elements are also associated with two independently isolated transposable elements originating from the white locus, Tp w^c-1 and Tp w^+IV. The strong correlation between FB elements and large composite transposons suggests that a pair of these elements can mobilize large intermediary DNA segments. One particular FB family member, FB-NOF, is associated with TE28, the white-crimson (w^c) mutant, the w^c-derived Tp w^c-1 and probably also with Tp w^+IV. A unique sequence located close to the white end of TE28 was used to clone the borders of TE77 and the surrounding sequences in the bithorax region, indicating that the TE can be used as a probe for gene isolation. Some evolutionary implications of the large composite transposons are discussed.     

Recognition of bulged DNA by a neocarzinostatin product via an induced fit mechanism

The binding of the wedge-shaped isostructural analogue of the biradical species of the chromphore of antitumor antibiotic neocarzinostatin to sequence-specific bulged DNAs results in alterations in ellipticity of the DNAs. Circular dichroism (CD) spectroscopic results suggest that the drug specifically recognizes bulges of DNA via a combination of conformational selection and induced fit, not by binding to a preorganized site. Analysis of circular dichroism spectra indicates that the degree of induced fit observed is primarily a consequence of optimising van der Waals contacts with the walls of the bulge cavity. The effective recognition of the bulge site on duplex DNA appears to depend to a significant extent on the bent groove space being flexible enough to be able to adopt the geometrically optimal conformation compatible with the wedge-shaped drug molecule, rather than involving 'lock and key' recognition. The spectroscopic results indicate a change of DNA conformation, consistent with an allosteric binding model. Spectroscopic studies with various bulged DNAs also reveal that the binding strength directly correlates with the stability of the bulge structures.     

A new species of Cosmocercidae (Ascaridida) in the worm lizard, Amphisbaena bolivica (Squamata: Amphisbaenidae), from Argentina

Aplectana tucumanensis n. sp., from the large intestine of Amphisbaena bolivica, is described and illustrated. Of the 43 nominal species of Aplectana, A. tucumanensis n. sp. represents the fourth species reported in Amphisbaena spp. These 4 species are separated on the basis of male characters: spicules of Aplectana alba approximately 60 micro in length, Aplectana pusilla and A. tucumanensis approximately 100 micro, Aplectana raillieti greater than 230 micro; papillae pattern of A. pusilla with 3 preanal pairs, 2 adanal pairs, 6 postanal pairs, and 1 median papilla compared to 9 preanal pairs, 1 adanal pair, 6 postanal, and no median papilla for A. tucumanensis.     

Efficiency of autoregulatory homeostatic responses to imposed caloric excess in lean men

Obesity implies a failure of autoregulatory homeostatic responses to caloric excess. We studied the mechanisms, effectiveness, and limits of such responses in six lean (21.9 +/- 1.3 kg/m(2)), healthy men based in a metabolic suite for 17 wk of progressive intermittent overfeeding (OF) (3 wk, baseline; 3 wk, 20% OF; 1 wk, ad libitum; 3 wk, 40% OF; 1 wk, ad libitum; 3 wk, 60% OF; 3 wk, ad libitum). Body composition was assessed by a four-compartment model using dual X-ray absorptiometry, deuterium dilution, and plethysmography. Magnetic resonance imaging assessed subcutaneous/visceral fat at abdominal level at baseline and at the end of 60% OF. Energy intake was assessed throughout, energy expenditure (EE) and substrate oxidation rates were measured repeatedly by whole body calorimetry (calEE), and free-living EE (TEE) was measured by doubly labeled water at baseline and after 60% OF. At the end of 60% OF, calEE and TEE had increased by just 11.4% (P = 0.001) and 16.2% (P = 0.001), respectively. Weight and body fat (fat mass) had increased by 5.98 kg (8.8%, P = 0.001) and 3.31 kg (22.6%, P = 0.01), respectively. The relative increase in visceral fat (32.6%, P = 0.02) exceeded that of subcutaneous fat (13.3%, P = 0.002) in the abdominal region. The computed energy cost of tissue accretion differed from the excess ingested by only 13.1% (using calEE) and 11.6% (using TEE), indicating an absence of effective dissipative mechanisms. We conclude that elevations in EE provide very limited autoregulatory capacity in body weight regulation, and that regulation must be dominated by hypothalamic modulation of energy intake. This result supports present conclusions from genetic studies in which all known causes of human obesity are related to defects in the regulation of appetite.     

Measuring physical traits of primates remotely: the use of parallel lasers

Physical traits, such as body size, and processes like growth can be used as indices of primate health and can add to our understanding of life history and behavior. Accurately measuring physical traits in the wild can be challenging because capture is difficult, disrupts animals, and may cause injury. To measure physical traits of arboreal primates remotely, we adapted a parallel laser technique that has been used with terrestrial and marine mammals. Two parallel lasers separated by a known distance (4 cm) and mounted onto a digital camera are projected onto an animal. When a photograph is taken, the laser projections on the target provide a scale bar. We validated the technique for measuring the physical traits of identifiable red colobus monkeys (Procolobus rufomitratus) in Kibale National Park, Uganda. First, we photographed the tails of monkeys with laser projections and compared these with measurements previously obtained when the animals were captured. Second, we manually measured the distance between two markers placed on tree branches at similar heights to those used by monkeys, and compared them with the measurements obtained through digital photographs of the markers with parallel laser projections. The mean tail length of the monkeys via manual measurements was 63.3+/-4.4 cm, and via remote measurements was 63.0+/-4.1 cm. The mean distance between the markers on tree branches via manual measurements was 13.8+/-3.59 cm, and via remote measurements was 13.9+/-3.58 cm. The mean error using parallel lasers was 1.7% in both cases. Although the needed precision will depend on the question asked, our results suggest that sufficiently precise measurements of physical traits or substrates of arboreal primates can be obtained remotely using parallel lasers.     

PfeIK1, a eukaryotic initiation factor 2α kinase of the human malaria parasite Plasmodium falciparum, regulates stress-response to amino-acid starvation

Background

Plasmodium falciparum -parasitized red blood cells (RBCs) are equipped with protective antioxidant enzymes and heat shock proteins (HSPs). The latter are only considered to protect against thermal stress. Important issues are poorly explored: first, it is insufficiently known how both systems are expressed in relation to the parasite developmental stage; secondly, it is unknown whether P. falciparum HSPs are redox-responsive, in view of redox sensitivity of HSP in eukaryotic cells; thirdly, it is poorly known how the antioxidant defense machinery would respond to increased oxidative stress or inhibited antioxidant defense. Those issues are interesting as several antimalarials increase the oxidative stress or block antioxidant defense in the parasitized RBC. In addition, numerous inhibitors of HSPs are currently developed for cancer therapy and might be tested as anti-malarials. Thus, the joint disruption of the parasite antioxidant enzymes/HSP system would interfere with parasite growth and open new perspectives for anti-malaria therapy.

Methods

Stage-dependent mRNA expression of ten representative P. falciparum antioxidant enzymes and hsp 60/70–2/70–3/75/90 was studied by quantitative real-time RT-PCR in parasites growing in normal RBCs, in RBCs oxidatively-stressed by moderate H2O2 generation and in G6PD-deficient RBCs. Protein expression of antioxidant enzymes was assayed by Western blotting. The pentosephosphate-pathway flux was measured in isolated parasites after Sendai-virus lysis of RBC membrane.

Results

In parasites growing in normal RBCs, mRNA expression of antioxidant enzymes and HSPs displayed co-ordinated stage-dependent modulation, being low at ring, highest at early trophozoite and again very low at schizont stage. Additional exogenous oxidative stress or growth in antioxidant blunted G6PD-deficient RBCs indicated remarkable flexibility of both systems, manifested by enhanced, co-ordinated mRNA expression of antioxidant enzymes and HSPs. Protein expression of antioxidant enzymes was also increased in oxidatively-stressed trophozoites.

Conclusion

Results indicated that mRNA expression of parasite antioxidant enzymes and HSPs was co-ordinated and stage-dependent. Secondly, both systems were redox-responsive and showed remarkably increased and co-ordinated expression in oxidatively-stressed parasites and in parasites growing in antioxidant blunted G6PD-deficient RBCs. Lastly, as important anti-malarials either increase oxidant stress or impair antioxidant defense, results may encourage the inclusion of anti-HSP molecules in anti-malarial combined drugs.     

GSTM1 and GSTT1 polymorphisms as modifiers of age at diagnosis of hereditary nonpolyposis colorectal cancer (HNPCC) in a homogeneous cohort of individuals carrying a single predisposing mutation

The variability in phenotype that occurs for so-called ‘single-gene disorders’ may be because of germline alterations in numerous primary and “modifier” genes. Within HNPCC families harbouring the same primary predisposing mutation, differences exist in the site of cancer, age of onset of disease symptoms and, consequently, survival until diagnosis of disease. The current study investigated a cohort of 129 individuals, from 13 different families, who harbour the identical nonsense mutation (C1528T) in the hMLH1 gene, predisposing them primarily to Lynch I syndrome. This cohort was screened for previously described polymorphisms in the glutathione-S-transferase genes, viz. GSTT1 and GSTM1. Male null carriers for both GSTT1 and GSTM1 were approximately three times more at risk of developing cancer at an earlier age when compared to non-null males. This work, particularly because of the relatively large “homogeneous” primary mutation cohort, provides evidence that genotypic changes distinct from the primary ‘HNPCC-causing’ mutation, influence the survival period until diagnosis of disease. It provides an impetus for expanding the study to include a wider range of candidate modifier genes. Such work may potentially lead to the development of individualised interval screening regimens for individuals with varying modifier genotypes—an attractive option in a resource-poor country.