Modifications of benzene myelotoxicity and metabolism by phenobarbital, SKF-525A and 3-methylcholanthrene

It has recently been suggested that the primary myelotoxic species generated from benzene is not produced directly from the parent compound, but from phenol or an even later metabolite (11). Several compounds that alter the activities of microsomal oxidative and conjugating enzymes were studied for their effects on benzene's myelotoxicity and metabolism. Phenobarbital (PB) protected animals from leucopenia and increased both to total amount of phenol as well as the amount of unconjugated phenol excreted in the urine. SKF-525A had no effect on the leucopenia, whereas it reduced the conversion of benzene to phenol without changing the excretion of unconjugated phenol. 3-Methylcholanthrene also did not prevent the leucopenia, but it did increase the conversion of benzene to phenol and the amount of unconjugated phenol excreted during the first days of the experiment. These data indicate that the early phases of benzene's metabolism may be modulated by the drug pretreatments employed, but myelotoxicity was abated only by PB. We conclude that the marrow effect of benzene is due to a metabolic product other than phenol and, furthermore that the formation of this toxic principle is not strictly dependent on the rate of phenol production.     

A thin-layer optical cell for spectroscopic studies of oxygen binding to hemoglobin

A thin-layer sample cell for examination of the spectra of hemoglobin at various degrees of gaseous-ligand saturation has been constructed to fit into a Cary 17 spectrophotometer. Small sample volumes of 50 μl are used. Equilibration times of only a few minutes are required between taking spectra at different degrees of saturation. Apparatus stability is high as revealed by reproducibility and isosbestic point behavior. Incorporation of an oxygen electrode enables simultaneous measurement of oxygen partial pressure for intermediate spectra.     

Prospective Memory Function in Late Adulthood: Affect at Encoding and Resource Allocation Costs

Some studies have found that prospective memory (PM) cues which are emotionally valenced influence age effects in prospective remembering, but it remains unclear whether this effect reflects the operation of processes implemented at encoding or retrieval. In addition, none of the prior ageing studies of valence on PM function have examined potential costs of engaging in different valence conditions, or resource allocation trade-offs between the PM and the ongoing task. In the present study, younger, young-old and old-old adults completed a PM task in which the valence of the cues varied systematically (positive, negative or neutral) at encoding, but was kept constant (neutral) at retrieval. The results indicated that PM accuracy did not vary as a function of affect at encoding, and that this effect did not interact with age group. There was also no main or interaction effect of valence on PM reaction time in PM cue trials, indicating that valence costs across the three encoding conditions were equivalent. Old-old adults’ PM accuracy was reduced relative to both young-old and younger adults. Prospective remembering incurred dual-task costs for all three groups. Analyses of reaction time data suggested that for both young-old and old-old, these costs were greater, implying differential resource allocation cost trade-offs. However, when reaction time data were expressed as a proportional change that adjusted for the general slowing of the older adults, costs did not differ as a function of group.