RADIATION FACTS FOR PUBLIC HEALTH OFFICERS

In the medical use of x-rays a few kinds of examinations contribute a large percentage of the gonadal exposure. Dose reduction to a population need not require total reduction nor restriction of the medical use, but study and attention to a few examinations in the pelvic region may satisfy the most skeptical that the use is justified or indicate the need for modification of our present indications for taking x-rays in this area.The potential dangers of ionizing radiation have long been respected and responsible organizations are constantly studying new developments that might add to the dangers and new knowledge that might affect conclusions.     

THE ORIGIN,FERTILITY AND TRANSMISSION OF MONOSOMICS IN GOSSYPIUM

The origin of 51 monosomic plants in Gossypium hirsutum is described, and the great majority are shown to be fertile and transmissible. Both fertility and transmission rate can be increased by outcrossing and selection. Monosomics which have been isolated in a standard hirsutum background can be recognized by distinct morphological characteristics, including modifications of both vegetative and reproductive structures such as smaller or narrower leaves, smaller flowers or flower parts, and smaller, longer, or partially collapsed bolls. Monosomics involving the large chromosomes, i.e., the A genome, are recovered more frequently than are monosomics of the D (small chromosomes) genome. Furthermore, monosomics of certain of the A chromosomes are recovered more frequently than others. Of 20 identified hirsutum monosomics, 7 are chromosome A-2, 7 are A-4, 3 are A-6, and 1 each is A-1, D-17 and D-18.     

Differential effects of prostaglandin E2 on contractions of airway smooth muscle

In an in vitro muscle bath, the active tension generated by strips of canine tracheal smooth muscle responding to cumulative additions of either histamine (10(-8) to 10(-3) M) or acetylcholine (10(-9) to 10(-3) M) was measured in the absence and presence of prostaglandin E2 (PGE2) (10(-6) to 10(-5) M). When contractile responses of equal magnitude were compared, the contractions elicited by acetylcholine were resistant to the inhibitory effects of PGE2, relative to comparable contractions elicited by histamine. To assess the role of adenylate cyclase in determining the different responses to histamine and acetylcholine in the presence of PGE2, we assayed adenylate cyclase activity in membranes prepared from canine tracheal smooth muscle and found that acetylcholine, but not histamine, decreased PGE2-stimulated adenylate cyclase activity by 48 +/- 2% (mean +/- SE; n = 5). However, in other experiments, we found that even large pharmacological increases in tissue adenosine 3',5'-cyclic monophosphate (cAMP) content only partially inhibited muscarinic tone. Also, exogenously applied analogues of cyclic AMP inhibited contractions induced by histamine more effectively than comparable contractions induced by acetylcholine. We concluded that acetylcholine decreased adenylate cyclase activity in membranes prepared from canine tracheal smooth muscle and that this effect may have contributed to, but did not completely account for, the relative resistance of muscarinic contractions to the inhibitory effects of PGE2.