Cell survival and DNA double-strand break repair following X-ray or neutron irradiation of V79 cells

We have investigated the effects of 250kVp X-rays and 2.3 MeV (mean energy) neutrons on the cell survival, DNA double-strand break (dsb) induction and repair (using the Kohn neutral elution technique) in V79 cells. The lethal effects of neutrons were shown to be significantly greater than for a similar dose of X-rays (RBE = 3.55 at 10 per cent survival). However, the RBE for dsb induction, in a dose range of 10-50 Gy, was 1. On investigating the repair of DNA dsb induced by either X-ray or neutron irradiation, clear differences in the pattern of repair were found. Both a fast and a slow component of repair were seen in both cases; the former, however, was reduced following neutron irradiation and, since the amount of slow repair was similar in both cases, this resulted in proportionally more unrejoined breaks after neutrons. These experiments were carried out with elution buffer at pH 9.6; however, when similar experiments were performed at pH 7.2 the results obtained support our earlier findings. We suggest that these differences in DNA dsb repair reflect basic differences in the nature of the lesions induced by high- and low-LET ionizing radiations.     

Socio-economic differences in mortality and morbidity

In England and Wales interest in differences in health between different sectors of the community can be traced back to analyses of vital registration records in the 1840s. Increased attention in recent years to differences between socio-economic groups, in part in response to initiatives by the World Health Organisation, has again exposed the limitations of traditional data. National data on this topic are now based on the OPCS Longitudinal Study, a record linkage study as used in a number of countries. Such studies provide more reliable measures of differences, cover a wider range of social dimensions, and also allow different explanations of differences to be investigated. Analyses of differences in mortality are complemented by longitudinal analyses of differences in health and morbidity now deriving from other studies such as the birth cohort studies which provide a basis for investigating processes. The time is ripe for more effort to be put into international comparisons of differences.     

Effect of a glutamine-supplemented enteral diet on methotrexate-induced enterocolitis

Administration of an elemental diet to rats given methotrexate (MTX), 20 mg/kg intraperitoneally (ip), results in 100% mortality from severe enterocolitis. Previous studies indicate that glutamine (GLN), which is not present in elemental diets, is the preferred oxidative substrate for the gut and may facilitate intestinal recovery after injury. This study investigated the effects of a glutamine-supplemented elemental diet (GLN-ED) on nutritional status, intestinal morphometry, bacterial translocation and survival in this lethal model of intestinal injury. Three experiments were performed. In the first experiment, rats received an intragastric elemental diet supplemented with either 2% GLN or an equivalent amount of glycine (Control). After 4 days animals received either MTX, 20 mg/kg ip, or saline ip and were killed 3 days later. The GLN-ED resulted in significantly decreased weight loss, improved nitrogen retention, and increased mucosal weight, protein, and DNA content of the jejunum and colon. In the second experiment rats were assigned to diet as in the first experiment, but all animals received MTX. Control diet animals died within 120 hrs of MTX administration. The GLN-ED group had significantly longer survival time and decreased mortality. In the third experiment animals were assigned to diet and MTX as in the first experiment. Ninety-six hrs later aortic blood cultures revealed enteric bacteremia in animals administered MTX. GLN-ED resulted in a significant reduction in the incidence of bacteremia. These experiments showed that a GLN-ED significantly improved nutritional status, decreased intestinal injury, decreased bacterial translocation, and resulted in improved survival in a lethal model of enterocolitis.     

Conjunctival flaps in the treatment of refractory pseudomonas corneal abscess

Pseudomonas corneal abscess can result in a rapid downhill clinical course despite institution of appropriate medical measures. In this situation the clinician is faced with surgical intervention. A series of patients treated and stabilized through conjunctival flap therapy are presented. The role of conjunctival flap therapy in halting the progression of this entity is described.