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B M Cattanach

Publications and source records attributed to B M Cattanach.

At least 73 records · Page 4Linked to original sources
PubMed1980

Modified genetic response to X-irradiation of mouse spermatogonial stem cells surviving treatment with TEM.

Earlier studies have shown that the genetic response to X-irradiation of mouse spermatogonial stem-cell populations that are recovering from a previous radiation exposure may differ from that of a normal, unirradiated stem-cell population. Similar modified responses to X-irradiation have now been observed in stem spermatogonia that are recovering from treatment with the chemical mutagen, TEM. (1) In contrast to a normal response to 900 R, high translocation yields were obtained when this dose was administered 24 h after a TEM treatment. (2) A small but non-significant increase above a normal response to 500 R was obtained when this dose followed 24 h after TEM treatment and a normal response to 500 R was obtained from the reverse order treatment (500 R + TEM). (3) When given 4 days after a TEM treatment, the translocation yield from 500 R was only about half that normally obtained. Unexpectedly, a similar low response was obtained from the reverse order treatment which, if verified, would suggest selective cell killing by the TEM. THe chemical administered alone, was almost totally ineffective in producing recoverable translocations in stem spermatogonia. Since it is unlikely that TEM and X-rays should similarly synchronize the cell cycle of surviving stem spermatogonia it is concluded that the modified genetic responses obtained result from a different cause. Depletion of the stem-cell population is suggested as the common mediating factor. This may 'trigger' the radio-resistant, long cycling stem cells into a more active cycle such that, 24--48 h later, survivors may be highly 'synchronized' into either a sensitive cell-cycle stage or transient state preparatory to entering a shorter cell cycle to achieve repopulation. The low translocations yields obtained with longer intervals between treatments may typify the genetic response of the repopulating stem cells.

Animals↗
PubMed1979

Translocation yield from mouse spermatogonial stem cells following unequal-sized x-ray fractionations: evidence of radiation-induced loss of heterogeneity.

Previous work has shown that a high yield of genetic damage can be recovered from stem spermatogonia exposed to a high (900 R) X-ray dose, despite extensive cell killing, when this follows 24 h after a smaller (100 R) radiation exposure. This differs from the response of the normal stem-cell population and has been interpreted to mean that the more radio-resistant cells surviving the first exposure become sensitive both to radiation-induced killing and genetic damage after this time interval and, as a consequence, lose the heterogeneity in radio-sensitivity that typifies a normal stem-cell population. Similar results have now been obtained with doses of 600 and 800 R given in fractions of 100 + 500 R and 100 + 700 R 24 h apart. Yields of translocations among spermatocytes were higher than obtained with the single doses and responses consistent with the fractions acting additively were obtained when the fractions were given in reverse order. Further analyses of the data provided support for the concept that 24 h after a radiation exposure there is a loss of heterogeneity in radio-sensitivity in the surviving stem-cell population.

Animals↗
PubMed1979

Enzyme levels in testis and other tissues of genetically sex-reversed mice.

The specific activity of G6PD and PGK were measured in the testes, seminal vesicles, and livers of Sxr/+,XX mice, their Sxr/+,XY littermates and normal mice. While G6PD activity was high in the testes of young normal mice and declined as the testes matured, in the testes of Sxr/+,XX mice activity remained high, suggesting a failure of the Sertoli cells to mature normally. The activity of PGK was low in the testes of young normal mice, and increased as the testes matured. The testes of young Sxr/+,XX mice had high activity of this enzyme which remained high into adulthood. The high activity in young mice suggests an abnormality in the somatic cells. The seminal vesicle and liver measurements of G6PD and PGK confirmed that the Sxr/+,XX mice were phenotypically normal males except with respect to the testis. The developmental patterns of both enzymes in testes lacking germinal cells indicate that the maturation of the somatic cells of the normal testis is influenced by the presence of germinal cells.

Animals↗
PubMed1976

Translocation yield from the mouse spermatogonial stem cell following fractionated X-ray treatments: influence of unequal fraction size and of increasing fractionation interval.

(1) The genetic response of the mouse spermatogonial stem cell to a high dose of X-rays given in two unequal fractions 24 h apart can be dependent upon the order in which the two fractions are given. When 1000 R was administered as 100 R followed by 900 R the recovered translocation yield (22%) was similar to that which can be obtained by extrapolation from lower doses and also to that of a 500 + 500 R 24 h fractionation. By contrast, when the 900 R preceded the 100 R the response was much lower (7.4%), yet still greater than that produced by a single 1000 R treatment (4.5%). The same order of effectiveness was observed for length of sterile period. (2) The sub-additive translocation yields previously obtained with 800 R treatments given in fractions of 500 R and 300 R at intervals of 3-12 days were found to be maintained with intervals up to at least 15 days but additivity was regained by the end of the third week. Sterile period data indicated that with these intervals the germinal epithelium had recovered sufficiently from the first fraction for spermatogenesis to restart before the second fraction was given. (3) It is concluded from the two experiments that (a) 24 h after a radiation exposure the surviving stem cells are more sensitive than formerly both to killing and genetic damage, (b) at this time they are no longer heterogeneous in their radiosensitivities, so that increasing yields of genetic damage may be obtained with increasing dose i.e. there is no fall in yield at higher doses, (c) the change in sensitivity could be a consequence of a synchronization to a sensitive stage in a cell cycle, or to a transitional phase preparatory to entering a different cell cycle. (d) to achieve rapid repopulation of the germinal epithelium the surviving stem cells are stimulated to enter a shorter cell cycle and this is the cause of the sub-additive translocation yields with fractionation intervals of 3-15 days, (e) the recommencement of spermatogenesis is associated with the reestablishment of the heterogeneity in radiosensitivity among the stem cells. At this time additive translocation yields can again be recovered.

Animals↗