Bacteriophage T4 Gene 32 Participates in Excision Repair as Well as Recombinational Repair of Uv Damages

Gene 32 of phage T4 has been shown previously to be involved in recombinational repair of UV damages but, based on a mutant study, was thought not to be required for excision repair. However, a comparison of UV-inactivation curves of several gene 32 mutants grown under conditions permissive for progeny production in wild-type or polA- hosts demonstrates that gene 32 participates in both kinds of repair. Different gene 32 mutations differentially inactivate these repair functions. Under conditions permissive for DNA replication and progeny production, all gene 32 mutants investigated here are partially defective in recombinational repair, whereas only two of them, P7 and P401, are also defective in excision repair. P401 is the only mutant whose final slope of the inactivation curve is significantly steeper than that of wild-type T4. These results are discussed in terms of interactions of gp32, a single-stranded DNA-binding protein, with DNA and with other proteins.     

Evaporation process in histological tissue sections for neutron autoradiography

The analysis of the distribution and density of nuclear tracks forming an autoradiography in a nuclear track detector (NTD) allows the determination of ¹⁰B atoms concentration and location in tissue samples from Boron Neutron Capture Therapy (BNCT) protocols. This knowledge is of great importance for BNCT dosimetry and treatment planning. Tissue sections studied with this technique are obtained by cryosectioning frozen tissue specimens. After the slicing procedure, the tissue section is put on the NTD and the sample starts drying. The thickness varies from its original value allowing more particles to reach the detector and, as the mass of the sample decreases, the boron concentration in the sample increases. So in order to determine the concentration present in the hydrated tissue, the application of corrective coefficients is required. Evaporation mechanisms as well as various factors that could affect the process of mass variation are outlined in this work. Mass evolution for tissue samples coming from BDIX rats was registered with a semimicro analytical scale and measurements were analyzed with software developed to that end. Ambient conditions were simultaneously recorded, obtaining reproducible evaporation curves. Mathematical models found in the literature were applied for the first time to this type of samples and the best fit of the experimental data was determined. The correlation coefficients and the variability of the parameters were evaluated, pointing to Page’s model as the one that best represented the evaporation curves. These studies will contribute to a more precise assessment of boron concentration in tissue samples by the Neutron Autoradiography technique.     

Nudibranchs out of water: long-term temporal variations in the abundance of two <Emphasis Type="Italic">Dendrodoris</Emphasis> species under emersion

The sudden appearance and disappearance of nudibranchs in intertidal areas have puzzled researchers all over the world, giving rise to a great diversity of theories to explain it. Here we conducted a five-year survey to evaluate seasonal changes in the abundance of Dendrodoris herytra and D. grandiflora in the Sado estuary (Portugal) and to explore a possible relationship with environmental factors such as temperature, salinity, turbidity and dissolved oxygen. Moreover, we report, for the first time, the capacity of Dendrodoris nudibranchs to tolerate emersion (unhidden and completely exposed to sun exposure) during low tides. Our results showed that both species consistently started to appear emerged in March, reaching a peak abundance between April and May, and completely disappearing in July. In both species, this temporal trend was significantly associated with water temperature, turbidity, and dissolved oxygen, but not with salinity. We argue that the sudden appearance and disappearance of these nudibranchs in intertidal areas may result from a seasonal horizontal movement of adult nudibranchs from subtidal areas to mate in intertidal areas during spring, when phytoplankton production is enhanced and planktotrophic larvae may benefit from greater food availability.     

Changes in UV-B radiation screening effectiveness with leaf age in Rhododendron maximum

We examined how ultraviolet-B radiation (UV-B; 300 nm) screening effectiveness changes with leaf age in Rhododendron maximum growing in a shaded understory by measuring depth of penetration and epidermal transmittance with a fibre-optic microprobe. Depth of penetration (and epidermal transmittance) of UV-B decreased with leaf age in 1- to 4-year-old leaves, averaging 62 (32), 52 (22), 45 (16) and 48 μm (13%), respectively. Epidermal thickness increased with age in 1- to 4-year-old leaves due to a thickening of the cuticle from an average of 20 to 29μm. Ultraviolet-B-absorbing compound concentrations increased with age from 1–3 to 1–5 A₃₀₀ cm^?2 leaf area. Concentrations of UV-B-absorbing compounds (area basis) were a strong predictor of depth of penetration (r²= 0.82) and epidermal transmittance (r²= 0.95) of UV-B in mature (1–4 year-old) foliage. Chlorophyll concentrations (area basis) increased in leaves up to 3 years of age. Current-year leaves (30 d old) were exceptional in that while they were particularly effective at screening UV-B (depth of penetration and epidermal transmittance averaged 39μm and 5%, respectively) they had relatively low concentrations of UV-B-absorbing compounds (1.3 A₃₀₀ cm^?2). Our findings show that UV-B-screening effectiveness is not necessarily related to absorbing compound concentrations on a whole-leaf basis, possibly due to anatomical changes within the epidermis that occur with leaf age.     

Ac/Ds transposon mutagenesis in Arabidopsis thaliana: mutant spectrum and frequency of Ds insertion mutants

Using a two-component Ac/Ds system consisting of a stabilized Ac element (Ac_c1) and a non-autonomous element (Ds_A), 650 families of plants carrying independent germinal Ds_A excisions/transpositions were isolated. Progenies of 559 of these Ac_c1/Ds_A families, together with 43 families of plants selected for excision/transposition of wild-type (wt)Ac, were subjected to a broad screening program for mutants exhibiting visible alterations. This resulted in the identification of 48 mutants showing a wide variety of mutant phenotypes, including embryo lethality (24 mutants), chlorophyll defects (5 mutants), defective seedlings (2 mutants), reduced fertility (5 mutants), reduced size (3 mutants), altered leaf morphology (2 mutants), dark green, unexpanded rosette leaves (3 mutants), and aberrant flower or shoot morphology (4 mutants). To test whether these mutants were due to transposon insertions, a series of Southern blot experiments was performed on 28 families, comparing in each case several mutant plants with others showing the wild-type phenotype. A preliminary analysis revealed in 4 of the 28 families analyzed a common, novel Ds_A fragment in all mutant plants, which was present only in heterozygous plants with wt phenotype, as expected for Ds_A insertion mutations. These four mutants included two showing embryo lethality, one with dark green, unexpanded rosette leaves and stunted inflorescences, and one with curly growth of stems, leaves and siliques. Further evidence for Ds_A insertion mutations was obtained for one embryo lethal mutant and for the stunted mutant, while in case of the second embryo lethal mutant, the Ds_A insertion could be separated from the mutant locus by genetic recombination.     

Obesity and Malnutrition in a Shantytown Population in the City of São Paulo,Brazil

To investigate the prevalence of obesity and malnutrition in the poor Brazilian population we conducted a survey on the socioeconomic and nutritional status of 535 families (comprising 2 411 individuals) living in shanty towns in the city of São Paulo. There was a 30% prevalence of malnutrition in the children, with chronic malnutrition as the most predominant problem. The prevalence of obesity was 6.4% in boys and 8.7% in girls. Overweight and obesity associated with stunting was found in 5.8% of boys and 6.8% girls. Adolescents showed a higher prevalence of malnutrition when weight-for-age distribution was used (boys 46.4%, girls 40.2%), but a right deviation in the distribution was observed with an increase in obesity and a decrease of malnutrition was observed (obesity was 21% in girls and 8.8% in boys; malnutrition was 15.5% in boys and 12.6% in girls) when the weight-for-height adjustment was made. Stunting was the most predominant type of malnutrition in both sexes. Obesity associated with stunting was more common than obesity without stunting, both in younger children and adolescents. Adults had a higher prevalence of obesity than malnutrition according to both the Metropolitan Life Insurance tables (1.7% of undernutrition, 16.7% of overweight, and 14.1% of obesity) and Body Mass Index (8.5% of undernutrition, 21.9% of overweight, and 14.6% of obesity). There was an increase in the percentage of obese children when at least one adult in the family was obese and an increased percentage of malnourished children when undernourished adults were present in the family. Obesity among the adults of the family decreased the occurrence of malnutrition among the children. In 9% of families there was a coexistence of obesity in the adults and malnutrition in the children. These results demonstrate a coexistence of malnutrition and obesity in poor urban Brazilian communities.     

Cytosolic and chloroplastic glutamine synthetase of sugarbeet (Beta vulgaris) respond differently to organ ontogeny and nitrogen source

Changes in the activity and subunit composition of cytosolic glutamine synthetase (GS 1; EC 6.3.1.2) and chloroplastic GS (GS 2) were studied in response to an internal (organ ontogeny) and external signal (N source: NO₃⁻ or NH₄⁺). Maximum GS 1 activity of all organs examined was measured in the fibre roots, irrespective of the N source. The response of GS 1 to the N source was, however, organ specific. In the fibre roots, NH₄⁺ nutrition resulted in a 2- to 7-fold (based on protein or freshweight, respectively) increase of GS 1 activity compared to NO₃⁻-grown plants. In contrast to the roots, GS 1 activity in the leaf blades was 2-fold lower with NH₄⁺ nutrition, whereas only minor changes occurred in the petioles. GS 2 activity was highest in the mature and senescing leaf blade; activity was 2-fold higher with NH₄⁺ than with NO₃⁻ nutrition. Not only activity, but also subunit composition of GS 1 changed during organ ontogeny as well as in response to the N source. In contrast to GS 1, only minor changes were evident in GS 2 subunit composition, despite significant changes in GS 2 activity. Up to 5 different GS 1 subunits of ≈41–43 kDa were separated; they were identical in all organs examined. GS 2 was composed of 4 different subunits of ≈48 kDa.     

Is the root-colonizing endophyte <Emphasis Type="Italic">Acremonium strictum</Emphasis> an ericoid mycorrhizal fungus?

In previous investigations, we found that Acremonium strictum (strain DSM 100709) developed intracellular structures with similarity to mycelia of ericoid mycorrhizal fungi in the rhizodermal cells of flax plants and in hair roots of Rhododendron plantlets. A. strictum had also been isolated from roots of ericaceous salal plants and was described as an unusual ericoid mycorrhizal fungus (ERMF). As its mycorrhizal traits were doubted, we revised the hypothesis of a mycorrhizal nature of A. strictum. A successful synthesis of mycorrhiza in hair roots of inoculated ericaceous plants was a first step of evidence, followed by fluorescence microscopy with FUN^®1 cell stain to observe the vitality of the host cells at the early infection stage. In inoculation trials with in vitro-raised mycorrhiza-free Rhododendron plants in axenic liquid culture and in greenhouse substrate culture, A. strictum was never observed in living hair root cells. As compared to the ERMF Oidiodendron maius and Rhizoscyphus ericae that invaded metabolically active host cells and established a symbiotic unit, A. strictum was only found in cells that were dead or in the process of dying and in the apoplast. In conclusion, A. strictum does not behave like a common ERMF—if it is one at all. A comparison of A. strictum isolates from ericaceous and non-ericaceous hosts could reveal further identity details to generalize or specify our findings on the symbiotic nature of A. strictum. At least, the staining method enables to discern between true mycorrhizal and other root endophytes—a tool for further studies.