Restoring adenine nucleotides in a brain slice model of cerebral reperfusion.

Tissue adenine nucleotides are depleted during cerebral ischemia, impeding recovery after reperfusion. Although prior studies have attempted to prevent the initial loss of adenylates, the present study tests the hypothesis that stimulating synthesis of adenine nucleotides, through either adenosine kinase or adenine phosphoribosyltransferase, would result in significant cerebroprotection. To study the effects on neurons and glia directly while avoiding the influence of the cerebral vasculature, hippocampal brain slices were used for the model of transient ischemia with reperfusion. The standard brain slice insult of brief exposure to anoxia with aglycemia was modified based on studies which showed that a 30-minute exposure to air with 1 mmol/L glucose produced a stable, moderate reduction in ATP during the insult and that, 2 hours after return to normal conditions, there was moderate depletion of tissue adenine nucleotides and histologic injury. Treatments with 1 mmol/L adenosine, AMP, or adenine were equivalent in partially restoring adenine nucleotides. Despite this, only adenosine afforded histologic protection, suggesting a protective role for adenosine receptors. There also was evidence for metabolic cycling among adenine nucleotides, nucleosides, and purines. Adenosine may exert direct cerebroprotective effects on neural tissue as well as indirect effects through the cerebral vasculature.

Retinoblastoma: problems and perspectives from India.

This study examined the salient clinical and epidemiological characteristics of retinoblastoma (RB) in India, thereby highlighting the problems encountered there. The epidemiological characteristics of 296 patients with RB over 8 years were evaluated using hospital records and postal follow-ups. Unilateral disease was seen in 61.8% of patients. The overall median age at presentation was 3.5 years (3.5 years for unilateral RB and 1.0 years for bilateral RB). The male/female ratio was 1.4:1. The median duration of symptomatic disease was 8 months. Consanguineous marriage was seen in 17% and family history of RB was noted in 1.7% cases. Also, 2% had a history of other malignancy in the family. Associated congenital malformation was seen in 10.5% of cases. A second malignancy was seen in 0.67% of cases at a mean duration of 4.5 years after completion of therapy. A predominance of advanced-stage disease (74.5% had Reese-Ellsworth group IV and V disease) was seen in our series. Only 43.6% of patients had disease localized to the globe without any infiltration/invasion. The majority of cases had advanced-stage disease at presentation and came from the underprivileged class of society. Patients with bilateral RB presented much earlier than those with unilateral disease. In patients with unilateral RB, higher age at presentation as well as advanced disease may be related to much delay in seeking medical attention. In view of the advanced stage at presentation, there also exist a possibility of difference in the biology of the tumor seen in these patients.