Direct isolation in cell-free medium of a spiroplasma fromHaemaphysalis leporispalustris (Acari: Ixodidae) in Maryland

A spiroplasma isolate, was obtained from rabbit ticks (Haemaphysalis leporispalustris) taken from cottontail rabbits in Maryland by inoculation of tick suspensions into SP-4 medium. The isolate was indistinguishable from an experimental vertebrate pathogen (suckling mouse cataract agent spiroplasma) when tested with other plant and tick spiroplasmas in growth inhibition, deformation, and metabolism inhibition tests. The isolated organism had a pathogenic profile for suckling rats and embryonated chicken eggs that differed significantly from that of other suckling mouse cataract agent strains. This is the first report of a direct spiroplasma isolation from ticks in cell-free medium, and confirms the specific association of spiroplasmas of the suckling mouse cataract agent serogroup with rabbit ticks.     

Cerebral energy metabolism during the onset and recovery from halothane anesthesia

Halothane (1%) was administered to twenty-two gram female Swiss-Albino mice which were sacrificed at times of 15 seconds, 45 seconds, 79 seconds and 5 minutes. Additional animals were exposed for 5 minutes and sacrificed 10 minutes after removal from halothane (recovery). Selected energy metabolites were measured in 100–500 nanogram samples from the inferior colliculus and the ascending reticular activating system.Results from this study showed an increase in glucose levels at 79 seconds, when the animals first lost their righting response. The glucose increase was similar in the inferior colliculus and reticular formation. ATP and phosphocreatine were increased at 45 seconds, and during the sleep period in the ascending reticular activiting system, and returned to normal during the recovery period. In the inferior colliculus, ATP was similarly increased from 45 seconds throughout the time course, whereas phosphocreatine was elevated at 79 seconds, and during recovery only. These data suggest a decrease in utilization of energy metabolities during halothane anesthesia, both in cells of the inferior colliculus and ascending reticular activating system.     

Incorporation of fucose and leucine into PNS myelin proteins in nerves undergoing early Wallerian degeneration

The simultaneous incorporation of [³H]fucose and [1-¹⁴C]leucine into normal rat sciatic nerve was examined using an in vitro incubation model. A linear rate of protein precursor uptake was found in purified myelin protein over 1/2–6 hr of incubation utilizing a supplemented medium containing amino acids. This model was then used to examine myelin protein synthesis in nerves undergoing degeneration at 1–4 days following a crush injury. Data showed a statistically significant decrease in the ratio of fucose to leucine at 2, 3, and 4 days of degeneration, which was the consequence of a significant increase in leucine uptake. These results, plus substantial protein recovery in axotomized nerves, are indicative of active synthesis of proteins that purify with myelin during early Wallerian degeneration.     

Factors influencing the growth and respiration of rat cerebral astrocytes in primary culture

Cell densities and respiratory rates of astrocytes from neonatal rat brain grown in primary culture were determined after 20–30 days in vitro. Cells grown in flasks reached lower densities (g DNA/cm²) and higher protein: DNA ratios than cells grown in petri dishes. Respiratory rates were lower for cells grown in flasks compared to cells grown in dishes. The pH of the medium in flasks fell below 6.9 between feedings while the pH of the medium in dishes remained at about 7.2. Cells grown in dishes with the medium pH adjusted to 6.8 also showed lower final cell densities, higher protein: DNA ratios, and lower respiratory rates, compared to cells grown under similar conditions at pH 7.5. Intermediate values of each parameter were found in cells grown at pH 7.5 for one week and then at 6.8 for 20 days. We conclude that the effects of ambient pH account for the differences in growth characteristics and respiratory rates of astrocytes grown in dishes versus those grown in flasks.