Chronic and cyclical neuronal loss in hippocampal slice cultures following transient inhibition of the type 1 isoform of superoxide dismutase.

Increased oxidative stress contributes to chronic neurodegenerative diseases, yet the underlying mechanisms are poorly understood. Hippocampal slice cultures prepared from 20-30-day-old mice or rats were used to model chronic neuronal loss following oxidative stress. Neuronal loss was initiated by inhibition of the antioxidant enzyme, superoxide dismutase type 1 (SOD1), using the copper chelator diethyldithiocarbamate (DDC). Continuous DDC treatment of slice cultures induced delayed neuronal loss beginning at 9 days of treatment that lasted for over 4 weeks. Neuronal loss was not uniform, rather it was cyclic: peaking at days 9-13 and at days 19-21 after DDC exposure. Neuronal loss was significantly attenuated in slice cultures that overexpress SOD1, suggesting that SOD1 inhibition was responsible. Inhibitors of nitric oxide synthase also attenuated DDC-induced neuronal loss. Chronic neuronal loss, however, did not require continuous SOD1 inhibition. Application of DDC for 13 days resulted in loss of SOD1 activity. Removal of DDC restored SOD1 activity, yet the cycles of cell loss continued until no neurons remained. Astrocyte activation was observed following the second peak of neuronal loss. Media conditioned by cultures following DDC removal induced neuronal loss and microglial activation in recipient cultures. These data suggest that slice cultures released soluble neurotoxic factor(s) following DDC removal. These data also suggest that a transient reduction of SOD1 activity leads to chronic loss of hippocampal neurons. This neuronal loss may be mediated by soluble neurotoxic factor(s) and microglial activation. Cyclical neuronal loss may also underlie chronic neurodegeneration in vivo.

Treatment of recurrent attacks of supraventricular tachycardia during pregnancy causing complications in both mother and fetus.

Cardiac arrhythmias including supraventricular tachycardia are commonly encountered during pregnancy. The case of a young Indian woman with recurrent attacks of supraventricular tachycardia during pregnancy which was managed with adenosine and verapamil is reported. The possible mechanisms of maternal and fetal complications are discussed.

Partial CviJI digestion as an alternative approach to generate cosmid sublibraries for large-scale sequencing projects.

We demonstrate an alternative method for the generation of random subclones for large-scale shotgun human DNA sequencing projects. Miniprep DNA from a human cosmid clone was partially digested with CviJI, size-fractionated by agarose gel electrophoresis and cloned into bacteriophage M13. A library consisting of 10(5) subclones of 1.1 kb average size was recovered from one gel fraction containing approximately 300 ng of partially digested DNA. DNA sequences from an initial 103 subclones demonstrate that 100 of the subclones cover 90% of the cosmid, which is close to the 92% expected if the subclones were generated at random. DNA sequences from three of the subclones did not match the cosmid sequences, establishing that miniprep DNA can be used for library construction with little concern for contamination with genomic E. coli DNA. The use of CviJI to generate random DNA fragments thus offers a simple alternative to other commonly used fragmentation methods, such as shearing or sonication, for the generation of random sublibraries for large-scale human shotgun DNA sequencing projects.