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J H Hendry

Publications and source records attributed to J H Hendry.

At least 163 records · Page 9Linked to original sources
PubMed1987

Deriving cell survival curves from the overall responses of irradiated tumours: analysis of published data for tumour spheroids.

Curves of growth delay (GD) or 'cure' after graded doses of radiation have been analysed for 16 lines of human and animal tumours grown as multicellular spheroids in vitro. Dose-survival curves were derived for those cellular units from which spheroids regrow after unsuccessful irradiation (spheroid-regenerating cellular units, SRU). For 10 sets of data from 6 spheroid lines, the Do's and extrapolation numbers of the SRU derived by GD could be compared with the response of the clonogenic cells of the spheroids. For Do, a good correlation (r = 0.910) was found between the two; this was true also for Do derived from curves of spheroid 'cure' (7 sets of data from 6 spheroid lines) and clonogenic cells (r = 0.986). Using GD, the correlation of extrapolation numbers was less good (r = 0.682), the values for SRU commonly being higher than those for clonogenic cells. This may reflect features of the growth curves of spheroids after the lower range of doses of radiation. For human and animal tumour spheroids of 250 microns or less, derived Do ranged from 0.5 to 2.5 Gy. For spheroids of 350 microns or more, derived Do for animal tumour lines ranged from 3.4 to 4.2 Gy, for human lines from 1.5 to 2.1 Gy.

Animals↗
PubMed1987

Standardization of procedures for ectopic marrow grafting. II. Influence on recipients of radiation dose and field size.

The ectopic implantation of mouse marrow to the kidney capsule offers considerable scope as an assay of the hemopoietic microenvironment. Our previous work has shown that whole-body irradiation of the graft recipient prior to implantation results in superior ossicle formation in the kidney of the host. Here we report that a range of irradiation doses over a 4-Gy threshold are equivalent with respect to conditioning the graft recipient. We also show that two distinct and separable influences affect graft growth in the irradiated recipient, namely, a local effect brought about in the irradiated kidney (and restricted to it) and secondly, a systemic effect resulting from irradiation of sites other than the kidney, which nevertheless affects ossicle growth in the shielded renal capsule.

Animals↗
PubMed1987

Sensitivity and recovery of stromal progenitor cells (CFU-F) in mouse bone marrow given gamma-irradiation at 0.65 Gy per day.

The sensitivity of stromal progenitor cells (CFU-F) in mouse marrow to whole-body 60Co gamma-irradiation delivered at 0.65 Gy per day, was characterised by a D0 value of about 2.5 Gy up to an accumulated dose of 5 Gy. The cells were less sensitive to higher doses. The rate of recovery following irradiation for 14 days (9.1 Gy) was less than the rate after 30 days irradiation (19.5 Gy). The latter rate of recovery approached that of the stem cells (CFU-S). At 9-10 months after either dose of irradiation, recovery of both CFU-F and CFU-S was incomplete at 30-70% of the aged control.

Animals↗
PubMed1986

Leydig cell function in the pubertal rat following local testicular irradiation.

Dose- and time-response relationships were measured after irradiation of the pubertal rat testis with between 1 and 20 Gy of 300 kVp X-rays. The threshold dose for Leydig cell dysfunction was about 5 Gy. Dysfunction after higher doses was observed by 2 weeks post-irradiation as a dose-dependent decrease in serum testosterone (T) concentrations, and the levels were undetectable after 15 or 20 Gy. Despite the recovery of serum T by 24 and 36 weeks, dysfunction of the Leydig cell population was still observed as an increase in luteinizing hormone (LH) secretion (1.5 to 2-fold increase after 15 or 20 Gy at 24 weeks; 2 to 3-fold increase after 10 or 20 Gy at 36 weeks). The endocrine changes were probably due to the observed loss of Leydig cells following irradiation. These results indicate that the Leydig cells of pubertal rats are more radioresponsive than those of the adult.

Animals↗
PubMed1986

Seminiferous epithelial function in the pubertal rat following local testicular irradiation.

The dose- and time-related responses of the irradiated seminiferous epithelium in the pubertal rat have been investigated. The threshold dose for Sertoli cell dysfunction, as assessed by serum androgen binding protein (ABP) concentrations, was estimated to be 5 Gy. A significant reduction (to less than 50% of control levels) in serum ABP was observed at 8 weeks post-irradiation, with further reductions at later times (24 and 36 weeks). Serum follicle-stimulating hormone (FSH) was elevated to between 130 and 175% of control at only 2 weeks post-irradiation, but recovered with time. Normal FSH levels seemed to be related to recovery of spermatogenesis, as assessed by counts of regenerating tubule cross-sections. The results indicate that the clonogenic spermatogonia and Sertoli cells of the pubertal rat testis are less sensitive to radiation than those of the adult.

Androgen-Binding Protein↗
PubMed1986

The radiosensitivity of microcolony- and macrocolony-forming cells in mouse tail epidermis.

A new microcolony technique is described for measuring the survival of colony-forming cells in mouse tail epidermis. The survival curve is characterised by D0 = 2.70 +/- 0.12 Gy. The number of microcolonies per cm2 is similar to the number of macrocolonies after high doses, which shows for the first time that all microcolonies (greater than or equal to 32 cells) in epidermis develop into macrocolonies. At low doses the number of macrocolonies underestimates the number of colony-forming cells because of coalescence of microcolonies to form macrocolonies. This results in a lower apparent sensitivity of macrocolony-forming cells by a factor of about 1.5. About 3% of basal cells in tail epidermis appear to be capable of colony formation.

Animals↗
PubMed1986

Residual deficiencies in hemopoietic precursor cell populations after repeated irradiation of mice with x-rays or neutrons: dose-response relationships.

Persistent reductions in the femoral content of hemopoietic colony-forming cells (CFU-S and GM-CFC) were observed after four doses of irradiation, delivered with three weeks between doses. In general, the reductions were dose dependent, and similar reductions were produced by single doses and repeated doses using the same total dose. After the lowest doses investigated, 4 X 0.75 Gy 300-kVp x-rays or 4 X 0.38 Gy 14.7-MeV neutrons, the recovered levels remained at 60%-80% of control for at least one year after irradiation. The relative biological effectiveness (RBE) of neutrons is about 2 for these long-term hemopoietic deficiencies.

Animals↗
PubMed1986

Radiosensitivity of murine hemopoietic colony-forming units assayed in situ in the rib and in other marrow sites.

The radiosensitivity of murine hemopoietic colony-forming cells, which produce colonies in situ and which were counted at Day 8 after irradiation in sections of the femur, humerus, sternum, and spleen, is characterized by a D0 value of 91 +/- 9 cGy. The radiosensitivity of such cells in the rib was assessed using a new technique measuring regeneration or ablation of marrow in transverse sections of ribs observed at Day 8 after irradiation. The mean D0 value over a range determined using several different criteria was 108 cGy. These results provide evidence for the common assumptions that radiosensitivity measured using conventional transplantation assays reflects radiosensitivity in situ, and that the radiosensitivity of stem cells in different medullary marrow sites is similar. The techniques could be used with other species where assays for stem cells are not available.

Animals↗
PubMed1985

The reversion phenomenon in irradiated fern prothalli: effects of acute or chronic anoxia and LET.

In several systems a paradoxical reduction of radiation damage with increasing dose, termed reversion, has been observed. In the fern Osmunda regalis the percentage of cells which does not die but stays alive, although reproductively sterile, increases with dose. The assumed mechanism of this effect is a continuation of cytoplasmic growth during radiation-induced mitotic delay which induces terminal differentiation (early differentiation) thus preventing mitosis and the expression of chromosomal injury. Suppression of cytoplasmic growth after irradiation should abrogate reversion. This was tested using anoxia. Reversion was suppressed by storage of the sporelings in nitrogen for 8 h or more after X-rays, but was not suppressed by storage in 0.27 microM oxygen nor by a 60-min exposure to air after irradiation and before storage in nitrogen. Anoxia before irradiation in air had no effect. Anoxia only during irradiation showed an OER of about 2 for the reversion peak. The partial abrogation of reversion is consistent with the assumed mechanism. Marked reversion also was observed after 14.7 MeV neutrons.

Cell Survival↗
PubMed1985

The cellular basis of long-term marrow injury after irradiation.

Haemopoietic recovery from radiation injury can appear complete when measured by blood cell counts, but this can hide deficiencies in the precursor cell populations because of compensatory mechanisms of increased numbers of divisions in the maturing cell populations and increased cycling of the stem cells. These mechanisms can operate for quite long but finite periods, before they fail which then leads to hypoplasia. Also, while these mechanisms are operating, small further injuries could precipitate marrow failure. Persistent injury in the stem cell population can be induced by quite small doses, and in mice the threshold total dose is probably in the region of 1.5 Gy using fractionated whole-body irradiations. The sensitivity of the environment varies enormously, depending largely on the proliferative stress applied to the cell populations involved in the particular assay technique used. When similar tests of reproductive integrity are applied, stromal progenitor cells are more radioresistant than haemopoietic stem cells. The contribution of environmental injuries to haemopoietic defects is uncertain and difficult to assess.

Animals↗
PubMed1985

Thermal sensitivity of haemopoietic and stromal progenitor cells in different proliferative states.

Stromal progenitor cells (CFU-F) in normal mouse bone marrow were more sensitive to heat at 43 degrees C than haemopoietic progenitor cells (CFU-S and GM-CFC) by a factor of approximately 1.2. In marrow regenerating after 4.5 Gy X-rays, the changes in sensitivity were by less than a factor of 1.4 and the sensitivity of CFU-F changed slightly to become intermediate between that of CFU-S and GM-CFC. A comparison of sensitivities reported in the literature revealed an inexplicable large variation of up to a factor of 6 in the thermal sensitivities of CFU-S and GM-CFC.

Animals↗
PubMed1985

Survival curves for normal-tissue clonogens: a comparison of assessments using in vitro, transplantation, or in situ techniques.

A survey of survival curves in the literature, for clonogenic cells (clonogens) in normal tissues, highlights the following features: the sensitivity of some human and dog clonogens apparently is greater than that of their counterparts in mice and sheep, assessed in vitro. However, this should be interpreted with caution because of the possibility of cell selection and the ability to modify sensitivity markedly in some systems by variations in growth conditions; extrapolation numbers are in general higher when assessed in vivo than in vitro. This is due partly to the lack of measurements of repair of potentially-lethal damage using many assays in vitro. This feature increases the extrapolation number when measured using transplantation assays in vivo; epithelial clonogens in vivo demonstrate a remarkable similarity in sensitivity between tissues. The range is similar for clonogens assayed in situ or by transplantation, and this argues against the possibility that a resistant subpopulation may be selected in most assays in situ. It is emphasized from the comparisons that caution must be exercised in extrapolating results, obtained for clonogens assayed in vitro or by transplantation in vivo, to the situation in situ.

Animals↗
PubMed1985

Strain differences in the radiosensitivity of mouse spermatogonia.

The radiosensitivity of spermatogonia was found to be greater by up to a factor of 2 in C3H mice than in B6D2F1 mice, whether assessed for the highly sensitive spermatogonia (types A2 to In) or the much more resistant clonogenic spermatogonia which repopulate tubules. The latter were similarly resistant in the B6D2F1 hybrid and in the DBA2 parent, but were much more sensitive in the C57BL parent strain. A difference in sensitivity by up to a factor of 2 results in a variation by a factor of 10 or more in the level of survival of clonogenic cells after high doses. This variation is also observed when comparing data in the literature from different authors using various strains of mice. Using the radiosensitizer misonidazole, it was shown that hypoxia did not play a major role in the lesser sensitivity demonstrated in B6D2F1 mice. The variation in sensitivity is similar to the range reported in the literature for reciprocal translocations.

Animals↗
PubMed1985

Dose and time related responses of the irradiated prepubertal rat testis. I. Leydig cell function.

The testes of prepubertal rats were locally irradiated with 300 kVp x-rays to doses of between 1 and 15 Gy. Leydig cell function was assessed between 2 and 36 weeks post-irradiation. Dysfunction was observed at two weeks as evidenced by a reduction in serum levels of testosterone to between 40 and 70% of control, with a threshold dose of about 5 Gy. Endocrine deficiencies in the Leydig cell population were indicated at later times by increased serum levels of LH, although serum testosterone concentrations recovered to control levels. The elevations in serum LH increased with time suggesting progressive Leydig cell failure.

Age Factors↗