ABSTRACT
Understanding the mechanisms of X-ray radiation damage in biological systems is of prime interest in medicine (radioprotection, X-ray therapy ). Study of low-energy rays, such as soft-X rays and light ions, points to attribute their lethal effect to clusters of energy deposition by low-energy electrons. The first step, at the atomic or molecular level, is often the ionization of inner-shell electrons followed by Auger decay in an aqueous environment. We have developed an experimental set-up to perform electron coincidence spectroscopy on molecules in a water micro-jet. We present here the first results obtained on sodium benzoate solutions, irradiated at the oxygen and carbon K-edges.
ABSTRACT
In light of different recent results suggesting that the adult mammalian central nervous system can produce new neurons, possibly as an endogenous repair mechanism, we investigated whether neurogenesis occurs in response to photoreceptor degeneration in the rd1 mouse, a model of human-inherited retinal dystrophy. Bromodeoxy-Uridine (BrdU) incorporation and proliferating cell nuclear antigen (PCNA) expression experiments detected cell proliferation in the extreme peripheral retina, in both wt and rd1 retina, independent of degeneration. BrdU incorporation and PCNA expression also occurred in rd1 photoreceptors. Our results strongly suggest that these photoreceptors undergo DNA repair: p53, PCNA, and DNA ligase IV are expressed before photoreceptor death, consistent with a model where photoreceptors expressing the rd1 mutation activate a process of DNA repair but which is overwhelmed by the disease mutation leading to apoptotic death. The existence of such a balance offers potential new targets for neuroprotective approaches.
Subject(s)
DNA Repair , Retina/metabolism , Retinal Degeneration/genetics , Retinal Degeneration/physiopathology , Animals , Cell Division/drug effects , Cell Division/physiology , Mice , Mice, Inbred C3H , Mice, Inbred C57BL , Mice, Mutant Strains , Photoreceptor Cells, Vertebrate/metabolism , Rats , Retina/cytology , Retinal Degeneration/pathologyABSTRACT
STUDY OBJECTIVE: The objective of this retrospective study was to report the results of a series of 81 cases of perineal gangrene treated in the same center. PATIENTS AND METHODS: From 1988 to 1998, 81 patients (64 males, 17 females, mean age: 58 years) with perineal gangrene were treated by a medico-surgical team, by means of a protocol combining appropriate intensive care measures based on a new bacteriologic concept of infectious agents, extensive excisions and drainage of the infraperitoneal region and hyperbaric oxygen therapy. RESULTS: The mortality rate was 24.7%. Mean duration of intensive care stay was 19 days, mean duration of hospital stay was 31 +/- 4 days (range: 6 to 60 days). Risk factors were: age > 68 years (p = 0.001), shock (p = 0.83), subcutaneous crepitation (p = 0.25) and severity index > 10 (p = 0.003). Sequelae were anal incontinence (n = 3) and permanent colostomy (n = 5). Secondary plastic reconstruction was necessary in four patients. There were no urologic or genital sequelae. CONCLUSION: Perineal gangrene is still a very serious disease. The time to treatment, the simplified severity index and consideration of bacteriologic combinations are the main prognostic factors.
