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J H Hendry

Publications and source records attributed to J H Hendry.

At least 73 records · Page 4Linked to original sources
PubMed1997

Cellular radiosensitivity in human severe-combined-immunodeficiency (SCID) syndromes.

PURPOSE: The aim of the work was to establish to what extent a variety of human severe-combined-immunodeficiency (SCID) disorders are associated with in vitro cellular hypersensitivity to ionizing radiation. MATERIALS AND METHODS: A study was made of fibroblast strains established from individuals with adenosine deaminase deficiency, T(-)B(-) SCID, Omenn's syndrome and a SCID heterozygote. For comparison, an assessment was also made of the radiosensitivity of a series of fibroblast strains derived from: normal donors, a patients with ataxia-telangiectasia (A-T) and an A-T heterozygote. Radiosensitivity was determined using a clonogenic assay following both high (HDR) and low (LDR) dose-rate irradiation. RESULTS: Following HDR irradiation, the fibroblast strains derived from the different human SCID disorders displayed a wide range of radiosensitivity: the adenosine deaminase deficiency cells were similar in radiosensitivity to normal fibroblasts, T(-)B(-) cells were as hypersensitive to radiation as A-T cells and the Omenn's syndrome cells showed intermediate radiosensitivity. However, whereas all four normal cell strains studied showed significant LDR sparing, none of the SCID fibroblasts did. CONCLUSIONS: These data indicate that human SCID is variable in terms of radiosensitivity depending on the particular defect. In addition, the lack of LDR sparing of radiation-induced damage suggests the involvement of some form(s) of DNA repair defect in all the human SCID syndromes.

Adenosine Deaminase↗
PubMed1997

Haemopoietic injury after irradiation: analysis of dose responses and repair using a target-cell model.

Published dose-incidence data for haemopoietic lethality in mice have been analysed using a mathematical model based on target-cell survival. The analysis of three comprehensive data sets produced an initial D(o) value of about 1.4 Gy, decreasing to about 1.1 Gy at 3 Gy, 0.9 Gy at 5 Gy, and about 0.7 Gy at a dose of 10 Gy. The alpha/beta ratio was about 14 Gy, and the repair half-time was about 0.3 h. The level of target-cell depletion at LD37 was at about 6 x 10(-4). The D(o) values are compatible with those measured directly for several stages of early haemopoietic progenitor cells in the marrow. The additional use of 13 or alternatively 24 other less-comprehensive data sets increased the overall degree of heterogeneity, so flattening dose-response curves and increasing the deduced overall D(o) values by a factor of about 2. However, when these data sets were stratified with respect to ln(N(o)) where N(o) is the number of tissue rescuing units (TRU), the results were comparable to those obtained when the three comprehensive data sets were analysed individually. Also, the repair halftime was higher at about 1 h. Further, the implied radiosensitivity of the projected target-cell population comprising the TRU was similar to the survival curves obtained for CFU-S and other closely-related haemopoietic progenitor cell types. It has been shown that the number of critical TRU at risk in the marrow is the main feature modulating heterogeneity even when it is assumed that the cellular radiosensitivity does not vary between strains. The number of stem cells comprising a TRU may vary between strains and this may also be influenced by environmental and/or immunological factors. However, it is certainly the case that the initial complement of TRU plays a major role in the incidence of whole body radiation induced mortality.

Animals↗
PubMed1997

Apoptosis and mitotic cell death: their relative contributions to normal-tissue and tumour radiation response.

The target-cell theory of tissue responses is reviewed with reference to the radiosensitivity of proposed target cells in bone marrow, intestine, epidermis, and spermatogenesis. The difficulties in precisely identifying target cells using histological/cell marker criteria, and hence determining the role of their mode of death in tissue responses, are being circumvented to some extent by the recent use of mice deficient in gene products required for radiation-induced apoptosis. In this case cell death results from 'mitotic cell death' and e.g. in the case of p53, any remaining p53-independent apoptosis. In the p53 null mouse, cell survival levels are increased in bone marrow and intestine but decreased in the testis. Different interpretations, based on the lack of p53-dependent apoptosis or the lack of a permanently induced G1-arrest in the case of marrow fibroblasts, can be applied to the results for different cell types. Hence both apoptosis and mitotic cell death can variously be involved as contributing to target-cell sensitivity and hence to early reactions in these tissues after irradiation. It is still unclear whether, or how, the mode of cell death (apoptotic versus mitotic) determines the radiosensitivity and response of tumours. In experimental tumours, the levels of radiation-induced apoptosis have been shown to correlate both with the in vivo response to radiation and the degree of spontaneous apoptosis in the tumours. Measurements of spontaneous apoptosis in human tumours, however, have yielded conflicting data with high apoptotic levels significantly correlating with both good and poor prognosis in different studies. There is one report of a lack of relationship between intrinsic radiosensitivity and spontaneous apoptosis in cervical cancers. In contrast several studies have reported correlations between apoptosis levels and the degree of tumour cell proliferation. Tumour hypoxia has also been shown to increase apoptosis. These data suggest that tumour apoptosis may be a reflection of intrinsic radiosensitivity, tumour cell proliferation and tumour hypoxia. Its relative importance will probably be tumour type, size and stage related.

Animals↗
PubMed1997

Differential survival of murine small and large intestinal crypts following ionizing radiation.

Radiation survival curves have been obtained for crypts in the small and large intestine of male BDF1 mice using the microcolony assay. Four regions of the small intestine and three regions of the large intestine were studied. One of the major objectives was to determine the optimal conditions for the microcolony assay in the large bowel. Various times post-irradiation were studied using different approaches and threshold criteria for surviving crypts. Small, but statistically significant, differences were observed along the length of the small intestine, but no differences were observed between different regions of the large intestine. There was a marked difference (p < 0.001) in the response in the large compared with the small intestine (D0 = 291 +/- 14 compared with 151 +/- 4 cGy respectively with corresponding extrapolation numbers of 18 +/- 4 and 377 +/- 65). The use of tritiated thymidine or vincristine helped in the identification of true survivors in the large bowel, but these approaches are not necessary in the small bowel. The longer the time after irradiation that the samples were fixed the easier it was to identify survivors in the colon. However, the longer the time the more animals died. The optimum compromise in these studies was to use partial-body irradiation (abdomen only) and to sample on the fifth day after irradiation. With these criteria the mid-colon survival curve had a D0 = 274 +/- 28 cGy and an extrapolation number of 22 +/- 10. The results can be considered in relation to published data on the levels of p53 and bcl-2 expression and apoptosis in murine small and large bowel.

Animals↗
PubMed1997

Comparative measurements of radiation-induced DNA double-strand breaks by graded voltage and pulsed-field gel electrophoresis.

We compared the ability of graded-voltage gel electrophoresis (GVGE) and pulsed-field gel electrophoresis (PFGE), to resolve DNA containing double-strand breaks (dsb) induced in human MS751 cells after exposure to gamma-radiation. For quantitation, prelabelling of the cells with [2-14C]-thymidine prior to electrophoresis and subsequent scintillation counting of excised bands was found to give closely similar results to Southern blotting and radiolabelled probe hybridization followed by phosphorimager quantitation. Compared with PFGE, DNA subjected to GVGE migrated further and generated distinct DNA bands. Dsb were detected and quantifiable with GVGE at much lower doses than with PFGE the radiation dose limits were approximately 2 and 10 Gy respectively. At all doses used, the amounts of dsb detected by GVGF, were higher than those by PFGE. GVGE coupled with Southern hybridization and phosphorimager analysis is thus a more sensitive approach to assessing dsb and their relationship with radiation sensitivity. The approach is also convenient when processing large numbers of samples and has the additional advantage of avoiding cell prelabelling such as in the case of cells extracted directly from human tumour biopsies and normal tissues.

DNA↗
PubMed1997

Predicting late rectal complications following prostate conformal radiotherapy using biologically effective doses and normalized dose-surface histograms.

A model to predict the late normal tissue complication probability (NTCP) of the rectum following conformal therapy is described. The model evaluates the biological consequence of inhomogeneities in the physical dose by computing dose histograms of the biologically effective dose to the surface of the rectum for a given fractionation scheme. A method of normalizing the surface area of the rectum is employed so that the predicted NTCP is independent of the differing cross-sectional size of sections of the rectum, ensuring the NTCP is dependent only on the dose delivered to sensitive rectal tissues. The model has been used to assess severe late rectal complications and the milder RTOG grades 2 and 3 reactions. This model was found to predict severe toxicity levels of 1.7 +/- 0.6% for an accelerated treatment of 50 Gy in 16 fractions commonly employed at this centre. This result lies between the severe toxicities predicted for 60 and 62 Gy delivered in 2 Gy fractions. The model predicts that the average NTCP for severe late effects for nine prostate patients becomes greater than 5% with a fractionation scheme of 70 Gy in 35 fractions, for the four fields treatment. The effects of not treating all fields at each therapy session on rectal toxicity were also investigated. Biologically effective dose-surface histograms show that the dose to the lower surface of the rectum is increased by not treating all fields at each therapy session, but the predicted differences in rectal NTCP are negligible.

Dose-Response Relationship, Radiation↗
PubMed1997

p53 deficiency sensitizes clonogenic cells to irradiation in the large but not the small intestine.

The role of p53 in the survival of irradiated crypts in the small intestine and three regions of the large intestine (cecum, mid-colon and rectum) was assessed by comparing the responses in p53 null, p53 heterozygous and wild-type mice. There was no difference in the levels of crypt survival in the small intestine between the three genotypes, although the rate of cell depletion and regeneration in the null mice appeared slower. In the large intestine, crypt survival was lowest in the null mice compared to the other genotypes, in particular after high doses. The levels of crypt survival in the heterozygotes were not significantly different from those in the wild-type mice. Hence the greater radioresistance of crypts in the colon than in the small intestine, reported previously by us and others using various other mouse strains, may be partly attributable to the presence of p53. This effect is not readily explained by current knowledge concerning the decreased p53 expression and the greater expression of the survival gene Bcl2 in the stem cell zone of crypts in the colon compared to those in the small intestine. Reduced repair associated with the lack of a G2-phase checkpoint delay, the predominant arrest point for intestinal cells, is a possible explanation for the decrease in survival.

Animals↗
PubMed1996

A modelled comparison of the effects of using different ways to compensate for missed treatment days in radiotherapy.

There is much evidence for the detrimental effect on tumour control of missed treatment days during radiotherapy, amounting for example to approximately a 1.6% absolute decrease in local control probability per day of treatment prolongation in the case of head and neck squamous cell cancer. Various methods to compensate for missed treatment days are compared quantitatively in this article, using the linear-quadratic formalism. The overall time and fraction size can be maintained by either treating on weekend days (the preferred way (Method 1a), although with unsocial hours and at extra cost) or using two fractions per day to "catch up' (Method 1b). The latter might incur a small loss of tolerance regarding late reactions, when intervals of 6-8 h are used rather than 24 h, and there may be logistical/scheduling difficulties with larger numbers of patients in some centres when using this method. A second type of strategy retains overall treatment time, and also one fraction per day, but the size of the dose per fraction is increased. For example, this may be done for the same number of "post-gap' days as gap days (Method 2). However, with this method, calculated isoeffect doses regarding late reactions indicate a probable decrease in tumour control rate (Method 2a). Otherwise, isoeffective doses regarding tumour control result in an increase in late reactions (Method 2b). In addition, this method is unsuitable for short regimens already using high doses per fraction. To reduce this problem, overall treatment time can also be retained by using fewer fractions, all of greater size in the case of planned gaps (statutory holidays), or larger remaining fractions after unplanned gaps (Method 2c). The problem also with this method is that equivalence for tumour control gives an increase in late reactions. The least satisfactory strategy (Method 3) is to accept the protraction caused by the missed treatment days, and give either the same prescribed number of (slightly larger) fractions or the planned treatment followed by one (or more) extra fraction to compensate for the gap. This would retain the expected local control rate, but there would be an increase in late reactions. An example of this, using average parameter values, is that a 3-day gap (necessitating four extra days to complete treatment with one fraction of 2.4 Gy) might maintain a 70% local control rate for glottic carcinoma, but severe reactions might rise from 1% to 4% and minor/moderate reactions from 37% to 50%. In this example, the inclusion of an extra weekend would increase the required extra dose and hence may further increase the morbidity rates. A final point is that the effect of treatment interruptions for an individual patient is expected to be greater than that for a group of patients because of interpatient heterogeneity tending to flatten dose-response curves. Calculations show that the above value of 1.6% loss of local control per day for a group of patients may reflect values for individual patients that range around a median value of as much as 5% per day, so stressing further the importance of gaps in treatment. It is concluded that, wherever possible, treatment days should not be missed. If they are missed, it is important to compensate for them, preferably by one of the first of the above methods (1a or 1b), in order to keep as close as possible to the original/standard prescription in terms of total dose, dose per fraction and overall time.

Brachytherapy↗
PubMed1996

P53 deficiency produces fewer regenerating spermatogenic tubules after irradiation.

The survival of clonogenic spermatogonia was assessed by scoring regenerating tubules at 35 days after irradiation, in the p53 null, heterozygote and wild-type mouse. Survival levels in the p53 null mouse after doses between 6 and 16 Gy were reduced by a factor of 3-4 compared with the levels in the heterozygote or wild-type mouse, which responded similarly. However the radiosensitivity of the cells was similar in all three types of mice, and was characterised by a D0 = 1.7 Gy. A two-dose experimental protocol was used to show that the reduced level of survival in the null mouse at day 35 after irradiation was compatible with the interpretation that there were fewer functional radioresistant clonogenic spermatogonia in the testis of the unirradiated null mouse by about a factor of 3 compared with that in the testis of the wild-type. The lower cell number was similar to the number deduced in other mice (BDF1), where the cells were much more resistant (D0 = 3.2 +/- 0.2 Gy). It is concluded that the lack of p53 causes a reduced level of tubule regeneration at 35 days after irradiation. This is probably not due to cellular radiosensitization, but possibly to a change in the stem cell cycle phase distribution resulting in a smaller proportion of resistant stem cells, which are assayed after high doses.

Animals↗
PubMed1996

Transferrin-mediated uptake of plutonium by spermatogenic tubules.

Using isolated rat seminiferous tubules as an in vitro model, we have found that 238Pu can cross the blood-tubule barrier and accumulate within tubules in a time dependent manner. Furthermore, similar to 59Fe, tubule 238Pu uptake was inhibited by the addition of excess transferrin, suggesting that plutonium may utilize the physiological iron-transferrin pathway to cross the blood-tubule barrier. However unlike 59Fe, 238Pu was only transiently associated with the tubules, suggesting differences in the intracellular processing of these radionuclides. The assumptions made in the estimation of doses to the human testis from incorporated plutonium are considered.

Animals↗
PubMed1996

The influence of the number of fractions and bi-exponential repair kinetics on biological equivalence in pulsed brachytherapy.

A linear-quadratic radiobiological model incorporating single or bi-exponential repair kinetics has been used to show the following and other features when a continuous low dose rate (CLDR) 70 Gy/140 h brachytherapy protocol is replaced by a radiobiologically equivalent pulsed dose rate (PDR) system using 140 fractions for reasons of dosage homogeneity. (1) For equivalent effects in late-reacting tissues, the PDR dose (at 5 or 0.05 Gy min-1) x 1 h intervals needs to be reduced by up to only 3%. Progressively further reductions in dose are required when fewer larger fractions are used. (2) When equivalence using pulsed doses is achieved for one normal tissue type, and extrapolated response doses (ERD) are calculated for other tissue types in the irradiated volume, values of the ERD remain within 5% of each other using the above PDR protocol and associated parameters. (3) For tumours with alpha/beta = 10 Gy and a single repair halftime of 0.1-1.0 h, there is no significant loss of therapeutic benefit using the PDR protocol equivalenced for late normal tissue reactions. The strategy of replacing an LDR boost protocol of about 24 Gy by a PDR protocol gives similar levels to the 70 Gy PDR protocol for the expected percentage increase in the biological dose to normal tissues (due to the PDR protocol alone). These calculations also highlight the importance of the values assumed for the conventional alpha/beta ratio and the repair kinetics when estimating equivalent PDR protocols. The use of an inappropriate radiobiological parameterization will lead to erroneous conclusions with the potential to advocate PDR protocols which will, in practice, lead to an increase in late complications.

Brachytherapy↗
PubMed1996

Transferrin-mediated uptake of radionuclides by the testis.

UNLABELLED: In an attempt to explain the deleterious effects of gonadal radionuclide localization, we examined the role of transferrin in testicular radionuclide uptake. METHODS: In vivo testicular uptake and retention of the transferrin binding radionuclides 114mIn-citrate and 59Fe-citrate were compared with that of the nontransferrin binding isotopes 137Cs-citrate and Na125I for 63 days postinjection. Isotope uptake mechanisms were investigated in vitro using isolated seminiferous tubules and Sertoli cell monolayers grown in bicameral culture chambers. RESULTS: Indium-114m, 59Fe and 137Cs were localized in the testis by 24 hr postinjection, but accumulation of 125I was minimal. Although testicular 114mIn remained constant, 59Fe declined slowly over the following 63 days and 137Cs fell very rapidly. When 114mIn- or 59Fe-loaded testes were fractionated, and markedly more 114mIn was associated with the seminiferous tubules than 59Fe, suggesting that 114mIn may be retained. In vitro uptake of 59Fe, 67Ga and 114mIn by isolated seminiferous tubules was inhibited by transferrin, but uptake of 137Cs and 125I was unaffected. Iron-59, 67Ga and 114mIn were retained by isolated tubules in contrast to 137Cs and 125I. Whereas 137Cs, 59Fe and 114mIn all crossed Sertoli cell monolayers, the rate of transcellular transport of 137Cs was faster than that of 59Fe or 114mIn, suggesting differences in the intracellular processing of transferrin binding and nontransferrin binding radionuclides. CONCLUSION: These data suggest that some radionuclides may access the seminiferous epithelium through receptor-mediated endocytosis of transferrin. Such radionuclide localization could lead to continuous irradiation of the testes, resulting in mutagenic damage to spermatogenic cells.

Animals↗
PubMed1996

Gamma-ray-induced cell killing and chromosome abnormalities in the bone marrow of p53-deficient mice.

Resistance to the lethal effects of ionizing radiation has been demonstrated in a wide variety of cell types with defects in the p53 gene (thymocytes, splenic B and T cells, in vitro hemopoietic colony-forming cells and intestinal cells of the mouse, embryo cells of the rat, and human Burkitt's lymphoma cells). In contrast, Slichenmeyer et al. (Cancer Res. 53, 4164-4167, 1993) found no evidence of resistance in fibroblasts derived from p53 null mice. The aim of our study was to compare the radiation response of hemopoietic colony-forming cells (in vitro CFC) and of fibroblastoid colony-forming cells or units (CFU-F) within the same tissue (marrow) in p53 null mice (-/-), heterozygotes (+/-) and wild-type animals (+/+). We have also tested the hypothesis that, in proliferating cells, radiation-induced cell killing is mediated through chromosome damage by examining the relationship between these end points in hemopoietic cells of the three mouse types. Both in vitro CFC and CFU-F of -/- mice were resistant to cell killing compared with +/+ and +/- mice whose cellular sensitivities were indistinguishable. The resistance was characterized by a broader "shoulder" on the cell survival curve, i.e. a higher extrapolation number but similar D0 values using the multitarget model or a lower alpha coefficient using the linear-quadratic model. The frequency of chromosomally abnormal marrow cells after irradiation was similar for the three genotypes. However, marrow cells with aberrations carried more aberrations in -/- mice than in +/+ or +/- mice such that the total number of aberrations per 100 cells was higher in -/- mice. Since there were no differences in the yields of aberrations between genotypes in spleen lymphocytes or in CFU-F (both noncycling at the time of irradiation) and less mitotic inhibition in -/- marrow cells than in +/+ or +/- cells, the chromosomal radiosensitivity of -/- marrow hemopoietic cells might be related to reduced cell cycle delay allowing insufficient time for repair, but other explanations have been considered. We postulate that the radiation resistance of both hemopoietic CFC and CFU-F in -/- mice is a consequence of the failure of DNA/chromosome damage to trigger apoptosis or permanent cell cycle arrest to the same extent as in the +/+ or +/- mice: hence the lack of correlation between chromosome damage and cell death in the three mouse types.

Analysis of Variance↗
PubMed1995

Apoptosis induced by high- and low-LET radiations.

Cell death after irradiation occurs by apoptosis in certain cell populations in tissues. The phenomenon also occurs after high linear energy transfer (LET) irradiation, and the relative biological effectiveness (RBE) is 3 to 4 (with respect to low-LET radiation and apoptosis in intestinal crypts) for neutrons with energies of 14 MeV and up to 600 MeV. It is thought that p53 plays a role in the phenomenon, as radiation-induced apoptosis is not observed in p53-null animals.

Animals↗
PubMed1995

Apoptosis, intrinsic radiosensitivity and prediction of radiotherapy response in cervical carcinoma.

Apoptosis is an important mechanism of cell death in tumours and it is seen both prior to and following radiotherapy. In this study patients with proven carcinoma of the cervix had measurement made of the percentage of apoptotic cells (apoptotic index or AI) in pre-therapy biopsies. Measurements of intrinsic radiosensitivity (SF2), already shown to be a predictor of outcome, had previously been made on the same pre-therapy biopsies. Mitotic index (MI) and Ki-67 antigen staining were also recorded as markers for proliferation. Patients were divided into those with an AI above or below the median and in general increasing apoptosis was associated with poor prognosis. The 5-year survival rate for tumours with an AI below the median was 79% and was significantly greater than the rate of 47% for those with an AI above the median (p = 0.003). There was also a significantly increased 5-year local recurrence-free rate for patients with an AI below the median compared with those with an AI above the median (79 versus 61%, p = 0.012). In addition, AI and SF2 acted as independent prognostic indicators. Patients with both an SF2 and AI value above the median did badly (25% 5-year survival, 46% local control) compared with those with an SF2 and AI below the median (80% 5-year survival, 100% local control). Apoptosis showed correlation with MI (n = 66, r = 0.34, p = 0.002) and cell staining for the Ki-67 antigen (n = 57, r = 0.25, p = 0.03), but neither MI nor Ki-67 were related to patient outcome. This suggests that while apoptosis may be a reflection of tumour proliferation this cannot in itself explain the ability of apoptosis to predict clinical outcome for this series of patients. The study raises the possibility of AI and SF2 being used together as predictors of tumour response to radiotherapy.

Adult↗
PubMed1995

Relationships between the cytotoxic effects of restriction endonucleases and radiation on mammalian cells.

Wild-type Chinese hamster ovary (CHO) cells, a radiosensitive mutant CHO line (xrs6), and two human cervical carcinoma cell lines, MS751 and ME180, differ in sensitivity to ionizing radiation with surviving fractions at 2 Gy (SF2) of 0.84, 0.06, 0.90 and 0.24 respectively. Restriction endonucleases (REs) were introduced into the cells by treatment with streptolysin O (SLO) and the effects of this on clonogenic cell survival were compared. A comparison was made of REs inducing either blunt- (AluI) or cohesive-ended (Sau3AI) double-strand breaks. Whilst MS751 cells were resistant to the effects of both REs, AluI caused significantly greater cell killing than Sau3AI in the other three lines (p < 0.05 for all). Both ME180 and xrs6 were significantly more sensitive to REs than their radioresistant counterparts, MS751 and CHO (p < 0.05 for both). In order to investigate the effect of DNA methylation on dsb induction, the isoschizomers MspI and HpaII (cohesive-ended dsb inducers) were introduced into the cell lines. Both REs recognize the same sequence but HpaII cannot cleave if the internal cytosine is methylated. MS751 was also resistant to the effects of both of these enzymes and MspI was more cytotoxic than HpaII in the other three lines (p < 0.03 for all). The differential sensitivity to the two REs was more marked in the radiosensitive cell lines, suggesting that there may be a greater degree of DNA methylation in radiosensitive cells. The variation in sensitivities to REs between the cell lines could not be explained in terms of differences in cell poration following SLO treatment because, although MS751 was resistant to SLO (25% of cells porated), the other three lines showed the same level of cell poration (98% of cells). With these four cell lines, there was a significant correlation between sensitivity to RE and radiosensitivity for AluI, Sau3AI and MspI but not for HpaII.

Animals↗