Do spermatogonial stem cells have a circadian rhythm?

Mitotic index was determined in whole mounts of segments of seminiferous tubules of (101 X C3Hf)F1 male mice at 3 hr intervals from 18.00 to 06.00 hours, and at hourly intervals from 08.

Patterns of cell proliferation during recovery from oxygen injury. Species differences.

Do rats, mice, hamsters, and marmosets respond differently to acute lung injury? Animals of each species were exposed to 100% oxygen for 48 h, then osmotic pumps, which released 3H-thymidine for a 1-wk period, were implanted. The labeling index (LI) (cells labeled/total cells counted) was increased in all 4 species. Repair in rats was manifested by a high LI, dominated by endothelial cell proliferation.

Ethylene oxide dose and dose-rate effects in the mouse dominant-lethal test.

In the dose-response study, male mice were exposed by inhalation to ethylene oxide (EtO) for 4 consecutive days. Mice were exposed for 6 hr per day to 300 ppm, 400 ppm, or 500 ppm EtO for a daily total of 1,800, 2,400, or 3,000 ppm X hr (total exposures of 7,200, 9,600 and 12,000 ppm X hr), respectively. In the dose-rate study, mice were given a total exposure of 1,800 ppm X hr per day, also for 4 consecutive days, delivered either at 300 ppm in 6 hr, 600 ppm in 3 hr, or 1,200 ppm in 1.

Difference in the response of two hybrid stocks of mice to X-ray induction of chromosome aberrations in spermatogonial stem cells.

Ionizing radiation induces balanced reciprocal translocations in spermatogonial stem cells of mice. From cells carrying these rearrangements, which can be scored cytologically in the diakinesis-metaphase I stage, balanced normal, balanced translocated and unbalanced (duplication/deficiency) sperm can be produced. The relationship between expected (calculated from cytological data) and observed frequencies of embryonic lethality (presumably as a result of unbalanced sperm fertilizing the egg) following exposure of spermatogonial stem cells to X-rays was studied in two hybrid stocks.

Quantitative aspects of metal ion content and toxicity in Drosophila.

As a basis for both a genetic and a biochemical approach to a study of metal ion effects, a method for quantitating the toxic response of Drosophila to metal ions was developed. The response to 13 metal ions has been examined, including several chemical groups from the periodic table: the IIb ions Zn2+, Cd2+, and Hg2+; the IIa ions, Be2+, Mg2+, Sr2+, and Ba2+; the transition elements, Ni2+, Cu2+, Co2+, and Mn2+: and trivalent ions, Y3+ and Cr3+. The standard test procedure provides estimates of the median lethal concentration (LC50) and the range of the tolerance distribution both of which are obtained by the method of probit transformation.

Heritable translocation test in mice.

The status of the heritable-translocation test in mice with respect to its usefulness in practical testing was evaluated by using information available in the open literature. A total of 47 reports were evaluated; 29 were judged to contain adequate information to classify whether or not a given chemical induced heritable translocations. Heritable-translocation data were available for 32 compounds; data were not adequate for 15 compounds.

The dose-response relationship for ultraviolet-light-induced mutations at the hypoxanthine-guanine phosphoribosyltransferase locus in Chinese hamster ovary cells.

Exposure of Chinese hamster ovary (CHO) cells clone K1BH4 to ultraviolet (UV) light at doses up to 86 ergs/mm2 did not significantly reduce cell survival, but UV doses of 86-648 ergs/mm2 produced an exponential cell killing. Observed mutation frequency ro 6-thioguannine resistance induced by UV increases approximately in proportion to increasing doses up to 260 ergs/mm2 in a range of 5-648 ergs/mm2 examined. The pooled data of mutation frequency f(X) as a function of dose X from 0-260 ergs/mm2 is adequately described by f(X)=10(-6) (13.

The dose-response relationship for ethyl methanesulfonate-induced mutations at the hypoxanthine-guanine phosphoribosyl transferase locus in Chinese hamster ovary cells.

The frequency of ethyl methanesulfonate (EMS)-induced mutations to 6-thioguanine resistance in a Chinese hamster ovary cells clone K1-BH4 was studied at many EMS doses including the minimally lethal range (0-100 microng/ml) as well as the exponential killing portion (100-800 microng/ml) of the survival curve. The mutation frequency increases approximately in proportion with increasing EMS concentration at a fixed treatment time. The pooled data for the observed mutation frequency, f(X), as a function of EMS dose X, is adequately described by a linear function f(X)=10(-6)(8.

Effects of dose on the induction of dominant-lethal mutations and heritable translocations with ethyl methanesulfonate in male mice.

Genetic damage by ethyl methanesulfonate (EMS) in male mice was measured at doses ranging from 50 to 300 mg/kg with dominant-lethal mutations and reciprocal translocations as endpoints. No appreciable increase in dominant-lethal mutations was detected following a dose of 100 mg/kg. Dominant lethals induced by EMS were convincingly detected only after a dose of 150 mg/kg, but in the translocation experiment an increase in the genetic effect was detectable at the 50 mg/kg dose.