Cytogenetic effects of benzene: dosimetric studies on rats exposed to benzene vapour

Rats were exposed to benzene vapour at nominal concentrations in air of 1, 10, 100 and 1000 ppm acutely for 6 h. Bone marrow cells from each animal were examined for chromosomal abnormalities 24 h after the end of the exposure period. This analysis was carried out on 250 metaphases per animal where possible and showed a significant increase in the percentage of cells with chromosomal abnormalities, excluding gaps, in the groups of animals exposed to 100 and 1000 ppm benzene. In the 10-ppm and 1-ppm exposure groups there were elevated levels of cells with abnormalities which showed evidence of being dose-related, although they were not statistically significant.     

ACTH secretion in mouse pituitary tumor cells in culture: Inhibition of CRF-stimulated hormone release by somatostatin

Synthetic corticotropin-releasing factor (CRF) stimulates ACTH secretion in the clonal mouse pituitary cell strain AtT20/D16v (D16) in a dose-dependent manner with a half-maximal effect at 2×10^?9M. A single dose of 5×10^?9M CRF maximally stimulates the rate of ACTH secretion during the initial two hrs of treatment. During the period of maximal CRF stimulation intracellular hormone concentration declines progressively to a nadir at 4 hrs. During the ensuing 24 hrs of incubation intracellular hormone levels in CRF-stimulated cells increase gradually toward control values. Somatostatin (SRIF) inhibits the secretory response to CRF. This action of SRIF is dose-dependent with a half-maximal effect at 1×10^?9M and results in decreased maximal ACTH secretion with little effect on the ED₅₀ for CRF.     

Release of protein from normal and mutant tomato cell walls

The nitrogen content of cell wall preparations from normal tomato (cv Ailsa Craig) fruit remained constant during ripening, whereas salt-soluble protein increased throughout this process. Tomato polygalacturonase released about twice as much protein from the preparations as salts did, with a maximum at the orange stage of development. Polygalacturonase-solubilized protein from the tomato mutant `ripening inhibitor' (rin) was less, and that from the mutant `Never ripe' (Nr) cell walls was more than that from normal wall preparations. Release of protein by fungal cellulase was limited, but was increased by the addition of polygalacturonase from the same source. Salt-solubilized protein contained a range of enzymic activities but these were distributed between fewer multimolecular forms than is the case for whole cell preparations. The results suggest that metabolically active protein, removable by strong salt solutions, cellulase, or polygalacturonase, remains attached to the cell walls of tomato fruit until late in ripening. The unusual amounts of protein attached to the cell walls of mutant fruit appear to be a reflection of the absence of some or all of the isoenzymes of polygalacturonase that are associated with normal ripening.     

SPRING MIGRATION OVER PUERTO RICO AND THE WESTERN ATLANTIC, A RADAR STUDY

Migration over Puerto Rico was recorded by time-lapse filming of the display of a long-range surveillance radar on 40 days and 37 nights in the period 2 March-29 May 1971. Moderate density movements occurred every night; low density movements occurred on most days. Many birds, primarily passerines, took off from Puerto Rico each evening at 20–45 minutes after sunset.
Almost all birds flew to the west, NW or north. Birds were seen approaching from the direction of the Windward Islands and Venezuela, over Puerto Rico, and departing towards the Bahamas and eastern coast of the U.S. Uni- and multivariate analyses showed that the number of birds departing W-N each evening was positively correlated with following winds.
There is less night-to-night variation in the amount of migration at Puerto Rico than in eastern North America. However, this is apparently the result of less variable weather in the tropics, not the result of any lesser degree of meteorological selectivity by the migrants.
The tracks of the birds were correlated with wind direction. Birds moved WNW-NW with NE side winds but NW-NNW with SE following winds. The tracks were rarely exactly downwind. The variance amongst the directions of individual birds at any given time was usually small and not correlated with cloud cover or magnetic disturbances. The estimated headings of the birds varied from day to day in a pattern suggesting adjustment of headings to compensate at least partially for lateral wind drift.
In autumn many birds approach Puerto Rico from the north or even east of north; in spring few birds moved in the opposite directions. This difference in routes takes advantage of prevailing wind patterns.