Injuries of the pelvis and hip in children

♦ Displaced cervical fractures must be reduced and then fixed with lag screws♦ Avascular necrosis remains a significant problem♦ Intertrochanteric fractures may be treated closed with traction if an adequate reduction can be obtained and held♦ Dislocated hips should be reduced as soon as possible, open if necessary♦ Pelvic fractures are associated with a high mortality not so much from bleeding from pelvic veins as from accompanying major trauma to the rest of the body♦ The elasticity of children’s bones allows for single breaks in the pelvic ring.

Change in DNA after Exposure to Hydrogen Atoms.

The action of hydrogen atoms — generated in an electrodeless high frequency gas discharge — on calf thymus DNA in aqueous solution was investigated. The loss of priming activity was compared with the appearance of single strand breaks in native and denatured DNA, double strand breaks, denatured zones, base damage and rupture of hydrogen bonds. The primary lesions after exposure to H atoms and gamma radiation, respectively, are single strand breaks and base damage. Double strand breaks originating from accumulation of single breaks, and rupture of hydrogen bonds caused by single breaks and base damage, were identified as secondary lesions. In relation to strand breaks arising from radical attack on the sugar-phosphate backbone of the DNA molecule, base damage is about 12.5 times more frequent after Η-exposure than after γ-irradiation. It is concluded from this observation, that single strand breaks are the predominant critical lesions responsible for the loss of the functional activity of DNA.

The action of γ -rays on sodium deoxyribonucleate in solution. - II. Degradation

Changes in the molecular weight and shape of herring sperm sodium deoxyribonucleate ( DNA ) which were effected by γ -irradiation in aqueous solution, without exclusion of oxygen, have been followed by means of the light scattering method. The molecular weights ( M L ) were proportional to the first power of the intrinsic viscosities of the irradiated solutions, and this confirmed the basis of previous deductions of the mechanism of degradation (Cox, Overend, Peacocke & Wilson 1955, 1958). This relation agrees with the model of a stiff, highly extended, coiled configuration for DNA in solution, which was also indicated by the proportionality of the radius of gyration of the degraded DNA to the square root of the molecular weight. The probability ( p ) of occurrence of a fragmentation of the molecule as represented by M L -1 , was a linear function of the square of the radiation dosage ( R ) over the dosage range of the experiments (⊁ 16 eV/P atom). From this it was deduced (i) that p ∝ R 2 , which confirmed the need for two independent, single breaks in the two chains of DNA to produce a double, fragmenting break, and (ii) that the molecular weight distribution was the same at all R , including R = 0, and this implies that the initial molecular weight distribution of the unirradiated DNA was also random. Heating of the irradiated samples caused a further reduction in M L which was greater the larger the previous radiation dosage, but this reduction was much smaller than would have been expected in the absence of any entanglement between the two disordered chains of the DNA . An attempt is made to estimate the extent to which there is a contribution to the process of degradation from single breaks which are not at opposite positions in the two polynucleotide chains.