SUMMARY
Adult male mice were treated with oestradiol for 10 weeks and for the last half of this period they were given relatively large daily doses of testosterone and highly purified human pituitary follicle-stimulating hormone (FSH), singly and in combination.
Oestradiol treatment reduced and testosterone restored the yields of mature (step 16) spermatids from round (step 7) spermatids, round spermatids from pachytene primary spermatocytes and pachytene from preleptotene spermatocytes. At the dose level used FSH was not effective alone but appeared to augment the effect of testosterone on the yield of round spermatids from preleptotene spermatocytes.
SUMMARYA single dose of y-radiation to Escherichia coli B gave a semi-logarithmic dose-response curve. A second irradiation 3, 6, or 18 hr after a priming dose of 8 h a d showed that the cells had become more radio-sensitive during the incubation between irradiations.When mercaptoethylamine was present during irradiation, protection against the lethal effects of the y-radiation occurred. After a priming dose to the bacteria in the presence of the radio-protective chemical, and incubations for 3,6, or I 8 hrinits absence, asecond irradiation in the absence of the chemical showed them to be much more radio-resistant than the normal unprotected Escherichia coli B. This indicates that the presence of the protector during irradiation alters the type of damage induced or the development and repair of that damage.
A chemical method for the separation of heme and nonheme iron-containing fractions in mouse tissues has been used to study the uptake of 59Fe into both the heme and nonheme iron fractions in spleen and femoral bone marrow, in order to investigate the possible relationships between the total uptake into spleen tissue and the rate of uptake into the heme fractions. In control mice, only about one third of the 59Fe is directly associated with heme during the first day after administration, and this fraction decreases as radioactive red cells are released from the spleen into blood. Ten days after X-irradiation of mice, the proportion of 59Fe in the spleen heme fraction 6 hr after intraperitoneal administration decreased from about 30 to 10% of the total splenic activity as the radiation dose was increased from 500 to 750 rads. A similar alteration in the proportion of 59 Fe in the spleen haem fraction occurred in mouse radiation chimeras as the dose of injected syngeneic bonemarrow cells was reduced from 5 x 105 to zero. Similar results were found in femoral bone marrow. These results indicate that in this system the rate of uptake into whole tissue is not a measure of the uptake into heme; it is necessary, therefore, to use the method involving the measurement of iron uptake into heme, rather than the total tissue uptake, when estimating hemoglobin synthesis or erythropoiesis.
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