Double-strand break repair by Ku70 requires heterodimerization with Ku80 and DNA binding functions

Heterodimers of the 70 and 80 kDa Ku autoantigens (Ku70 and Ku80) activate the DNA-dependent protein kinase (DNA-PK). Mutations in any of the three subunits of this protein kinase (Ku70, Ku80 and DNA-PKcs) lead to sensitivity to ionizing radiation (IR) and to DNA double-strand breaks, and V(D)J recombination product formation defects. Here we show that the IR repair, DNA end binding and DNA-PK defects in Ku70-/- embryonic stem cells can be counteracted by introducing epitope-tagged wild-type Ku70 cDNA. Truncations and chimeras of Ku70 were used to identify the regions necessary for DNA end binding and IR repair. Site-specific mutational analysis revealed a core region of Ku70 responsible for DNA end binding and heterodimerization. The propensity for Ku70 to associate with Ku80 and to bind DNA correlates with the ability to activate DNA-PK, although two mutants showed that the roles of Ku70 in DNA-PK activation and IR repair are separate. Mutation of DNA-PK autophosphorylation sites and other structural motifs in Ku70 showed that these sites are not necessary for IR repair in vivo. These studies reveal Ku70 features required for double-strand break repair.     

A prospective evaluation of a diffractive versus a refractive designed multifocal intraocular lens

OBJECTIVE: To evaluate prospectively a diffractive (811E, Pharmacia; power add +4.0 D) versus a refractive (PA154N, Allergan; power add +3.5 D) designed multifocal lens. PARTICIPANTS: Eighty patients planned for cataract surgery without additional ocular pathologies were randomized into the diffractive or refractive group, respectively. INTERVENTION: A standardized no-stitch phacoemulsification with implantation of one of the two multifocal lenses was performed in each patient. MAIN OUTCOME MEASURES: Distance and near-visual acuity, contrast sensitivity, low contrast visual acuity, glare visual acuity, and depth of focus were measured after surgery. RESULTS: All treated patients had best-corrected visual acuities of 20/30 or better. Near-uncorrected vision was significantly better (P < 0.0001) with the diffractive lens (mean, J1) than with the refractive lens (mean, J4). Low contrast visual acuity (61 +/- 12% versus 59 +/- 9%), glare visual acuity (39 +/- 19% versus 38 +/- 14%), and contrast sensitivity (1.48 +/- 0.08 versus 1.50 +/- 0.12) were not significantly different between the groups. CONCLUSIONS: Both lens designs showed satisfactory functional results with advantages for the diffractive lens design.     

Adipose tissue development during early postnatal life in ewe-reared lambs

This study examines the precise time course that brown adipose tissue (BAT) takes to adopt the characteristics of white adipose tissue in postnatal lambs. Perirenal adipose tissue was sampled from ewe-reared lambs within 1 h of birth and at 1, 2, 4, 7, 14, 21 and 30 days of age and analysed for the amount of mRNA for uncoupling protein (UCP), the amount and activity of UCP, and protein, mitochondrial protein and lipid content. This was combined with measurements of colonic temperature and jugular venous plasma concentrations of thyroid hormones and insulin-like growth factor-1 (IGF-1). Over the first 4-7 days of age, large quantities of UCP mRNA were associated with a peak in plasma triiodothyronine concentration at 2 days of age followed by a maximal amount and activity of UCP at 4 days and a basal colonic temperature of 39.3 degrees C. Between 7 and 30 days there was a large increase in lipid deposition as the amount and activity of UCP and the amount of UCP mRNA declined to basal values and colonic temperature was maintained at 40 degrees C. A significant positive relationship between perirenal adipose tissue lipid content and plasma IGF-1 concentration was observed throughout the study period. It is concluded that ovine adipose tissue maturation occurs in two distinct phases over the first month of life. The precise time scale of this process could be regulated in part by the lamb's body temperature which determines whether adipose tissue is required for heat production (i.e. BAT) or as an endogenous energy source (i.e. white adipose tissue).     

Artefacts in MR images of electrical current distribution

Artefacts in images of electrical current distribution measured by magnetic resonance imaging (MRI) are presented. These artefacts, caused by the effects of the connecting cables used to apply the electrical current to the object during the MRI scan, can lead to an underestimation of the magnitude of the electrical current measured in the experiment. The size of this underestimate depends upon the experimental geometry, but in the experiments and simulations described here, performed with a cylindrical phantom approximately 8 cm long and 8 cm in diameter, the difference can be 27%. These artefacts are reduced if the connecting cables are rigidly fixed to the object so that the induced magnetic field is correctly measured during the MRI experiment.     

Nonsecretory IgA1 autoantibodies targeting desmosomal component desmoglein 3 in intraepidermal neutrophilic IgA dermatosis

Intraepidermal neutrophilic IgA dermatosis, a rare skin disease entity manifested with blisters and pustules clinically and lower epidermal blister, acantholysis, and neutrophilic infiltration pathologically, was first reported in 1985. Although the disease is characterized by IgA autoantibodies targeting the epithelial cell surface component, the target antigen has not been determined. We investigated a patient with this disease by histopathology, direct and indirect immunofluorescence, immunoblotting, and immunoadsorption studies. The pustular lesion was characterized by blister at the lower epidermis, acantholysis, and neutrophilic infiltration. Nonsecretory IgA1 subclass autoantibodies targeting the lower epithelial cell surfaces were detected in the patient's skin and serum. The patient's IgA autoantibodies labeled a recombinant desmosomal protein desmoglein 3 on immunoblotting and the immunolabeling of epithelial cell surfaces was eliminated by preadsorption with desmoglein 3. Thus, desmoglein 3 is identified as a target antigen in intraepidermal neutrophilic IgA dermatosis. The ability of IgA1 autoantibodies to bind neutrophils may be responsible for the prominent neutrophilic infiltration observed histopathologically and for the pustular lesions observed clinically.     

Direct nn-Scattering Measurement With the Pulsed Reactor YAGUAR

Although crucial for resolving the issue of charge symmetry in the nuclear force, direct measurement of nn-scattering by colliding free neutrons has never been performed. At present the Russian pulsed reactor YAGUAR is the best neutron source for performing such a measurement. It has a through channel where the neutron moderator is installed. The neutrons are counted by a neutron detector located 12 m from the reactor. In preliminary experiments an instantaneous value of 1.1 × 10¹⁸/cm²s was obtained for the thermal neutron flux density. The experiment will be performed by the DIANNA Collaboration as International Science & Technology Center (ISTC) project No. 2286.