Biomedical subjects

M Urano

Publications and source records attributed to M Urano.

At least 37 records · Page 2Linked to original sources

PubMed1997

Synergistic cytotoxicity between a protein kinase C inhibitor, UCN-01, and monoclonal antibody to the epidermal growth factor receptor on MDA-468 cells.

Cytotoxic effect of the monoclonal antibody to the epidermal growth factor receptor (anti-EGFR MAb) given alone or in combination with UCN-01, a selective protein kinase C inhibitor, was investigated in vitro. MDA-468 human breast cancer cells expressing both a large amount of EGF receptors and its ligand, transforming growth factor a, were used. A given number of the cells were plated and treated with the MAb and/or UCN-01 for 48 h. These cells were replated and incubated for colony formation assay. Cytotoxicity of the anti-EGFR MAb alone was hardly detected. However, when cells were treated with both anti-EGFR MAb and UCN-01, the combined cytotoxic effect was synergistic.

Alkaloids↗

PubMed1997

[Oro-pharyngeal burn during electrodissection of the adenoid and tonsil].

We present a case of oro-pharyngeal burn which occurred during electrodissection of the adenoid and tonsil in a 5-year-old boy. We intubated the patient with an uncuffed spiral tube of appropriate size and noticed a slight gas leak during positive-pressure ventilation. Anesthesia was maintained with a mixture of 60% nitrous oxide, 40% oxygen and 2.5% sevoflurane. During manipulations of the right tonsil, orange-colored flame blew out about 5 cm from the mouth. Fortunately, the patient underwent the operative procedures without any further troubles, recovered fully from the grade 1 burn in the oral mucosa, and was discharged 23 days after surgery. The surgeons speculated that sevoflurane had been ignited. Although it is well known that sevoflurane is nonflammable in the concentration of clinical use, several reports show that sevoflurane is flammable in concentration of 10% under pure oxygen or nitrous oxide. We concluded that this accident was caused by electrocautery-induced ignition of the gauze packed into the larynx under a high concentration of oxygen which leaked through an uncuffed endotracheal tube. We have to bear in mind that any flammable substance may ignite when using electrocautery in a small space such as the mouth under oxygen-rich environment.

Adenoidectomy↗

PubMed1996

[An immunohistochemical study of proliferating cell nuclear antigen (PCNA) and MIB-1 in epithelial hyperplasia and dysplasia of the vocal cords].

We investigated the proliferative activities in epithelial hyperplasia and dysplasia of the human vocal cords as precancerous lesions, using immunohistochemical staining with anti-PCNA and MIB-1 (anti-Ki-67) monoclonal antibody. The series for this study consisted of nine patients with hyperplasia, 12 with mild dysplasia, ten with moderate dysplasia, eight with severe dysplasia, eight with vocal cord polyps, and 14 with invasive squamous cell carcinoma. The following results were obtained: 1) The mean PCNA labeling index was 1.12 +/- 1.05 (MEAN +/- STD%) in polyp, 4.88 +/- 2.02 in hyperplasia, 2.76 +/- 1.76 in mild dysplasia, 3.80 +/- 2.03 in moderate dysplasia, 6.12 +/- 3.01 in severe dysplasia, and 19.07 +/- 10.37 in invasive cancer. 2) The mean MIB-1 positive rates were 5.50 +/- 2.47 (MEAN +/- STD%) in polyp, 13.08 +/- 6.86 in hyperplasia, 16.55 +/- 7.34 in mild dysplasia, 15.94 +/- 6.73 in moderate dysplasia, 21.43 +/- 8.16 in severe dysplasia, and 41.48 +/- 14.05 in invasive cancer. In cases of hyperplasia, dysplasia and invasive cancer, PCNA labeling index values and MIB-1 positive rates increased in proportion to the histological atypical grade increasing. Some lesions which recurred or progressed to cancer were found show high expression of PCNA and MIB-1. In cancer cases, there was no significant correlation between the PCNA labeling index, MIB-1 positive rates and either the degree of tumor cell differentiation or the T-classification. There was a positive correlation between the PCNA labeling index and MIB-1 positive rates among all cases. In this study, those cases showing a high PCNA labeling index and/or MIB-1 positive rates may indicate the possibility of recurrence or progression to malignancy in precancerous lesions of the vocal cords.

Aged↗

PubMed1995

Expression of manganese superoxide dismutase reduces tumor control radiation dose: gene-radiotherapy.

This study investigated the in vitro and in vivo radiation response of tumor cells transfected with human manganese superoxide dismutase (MnSOD) cDNA. A major objective was to test the potential tumor suppressive effect of MnSOD in vivo. Tumor cells studied were an in vitro line derived from a murine spontaneous fibrosarcoma, FSa-II, which expressed an undetectable MnSOD activity. These cells were transfected with pSV2-NEO plasmid (NEO line) or cotransfected with MnSOD plasmid plus pSV2-NEO plasmid (SOD lines) as described previously. The cell lines used were SOD-L and SOD-H, which expressed, respectively, low and high MnSOD activities after transfection, and NEO and parental FSa-II controls. Both SOD-L and SOD-H cell lines were slightly more resistant to ionizing radiation than were the two control cell lines when irradiated in vitro in the presence of oxygen. The dose-modifying factors calculated at the survival level of 0.01 were 1.13 and 1.15 for the SOD-L and SOD-H cells, respectively. To investigate potential tumor suppressive effects, animal tumors of 4 mm diameter were irradiated in vivo under hypoxic conditions, and the radiation dose to control one-half of the irradiated tumors (TCD50) was determined for each tumor. The TCD50S obtained on the basis of the tumor control rate in 120 days after irradiation were substantially lower for the SOD-H and SOD-L tumors compared to the NEO tumors. They were 22.9, 28.6, and 47.5 Gy for SOD-H, SOD-L and NEO tumors, respectively. To analyze these data, survival curves were obtained for hypoxic cells by irradiating NEO and SOD-H tumors under hypoxic conditions in vivo and assaying in vitro. Analysis of these curves suggests that the decrease in the TCD50S of SOD tumors is attributable to the reduced tumorigenicity in these tumors. The hypoxic cell survival curves also showed that SOD did not protect cells from radiation in the absence of oxygen. Electron microscopy showed no morphological differences between these cells. These results suggest that the fraction of tumorigenic cells could be reduced by expression of MnSOD, resulting in a substantial decrease in the TCD50.

Animals↗

PubMed1995

Spontaneous and ionizing radiation induced mutations involve large events when selecting for loss of an autosomal locus.

The mouse P19H22 embryonal carcinoma cell line contains two distinct chromosome 8 homologs, one derived from Mus musculus domesticus (M. domesticus) and the other derived from Mus musculus musculus (M. musculus). It also contains a deletion for the M. musculus aprt allele, which is located on chromosome 8. In this study, cells with spontaneous or induced aprt deficiencies were isolated from P19H22 and examined to determine the nature of the mutational events that had occurred. Ultraviolet radiation (UV), ethyl methanesulfonate (EMS), and two forms of ionizing radiation, 137Cs and 252Cf, were used for mutation induction. DNA preparations from the aprt deficient cells were initially screened with a Southern blot analysis and separated into two broad classes: those that had lost the M. domesticus aprt allele and those that had retained it. The overwhelming majority (> 95%) of the spontaneous and ionizing radiation-induced mutants exhibited aprt gene loss, indicating that relatively large events had occurred and that homozygosity for the deleted region was not a lethal event. Loss of heterozygosity for syntenic markers was found to be a common event in cells exhibiting aprt gene loss. In contrast, a majority of the UV-induced mutants (61%) and a substantial minority of the EMS-induced mutants (38%) retained the aprt gene. A sequence analysis confirmed that base-pair substitutions were responsible for this class of mutation. Gene inactivation associated with hypermethylation of the promoter region was found to be a rare event and was not induced by any of the mutagenic agents tested. The results demonstrate the suitability of the P19H22 cell line for mutational studies, particularly those that are large in nature.

Adenine Phosphoribosyltransferase↗

PubMed1995

The relative significance of repopulation and hypoxic clonogens in the fractionated radiotherapy of a mouse tumor.

The aim of this study was to analyze the significance of the repopulation of tumor cell clonogens, reoxygenation and hypoxic cells for the outcome of fractionated radiotherapy. Our previous fractionation study using a murine tumor was used for the analysis (Nishimura and Urano, Int. J. Radiat. Oncol. Biol. Phys. 29, 141-148, 1994). In the previous study, single cell suspensions were prepared from the early-generation isotransplants of a spontaneous fibrosarcoma, FSa-II, in a C3Hf/Sed mouse and transplanted into the foot of C3Hf/Sed mice. Fractionation schedules consisted of equal graded daily doses (1-20 fractions) given in air or under hypoxic conditions with 137Cs. Treatment was initiated when tumors reached an average diameter of 4 mm. A twice-a-day (b.i.d.) irradiation was tested for 20 doses. Tumor control was the end point, and the TCD50 (50% tumor control dose) was obtained. The surviving fractions resulting from these TCD50 doses were calculated using the alpha and beta values for the FSa-II cells, assuming that these values were constant throughout the fractionation period. These surviving fractions were used to calculate the clonogen repopulation and the reoxygenation of the hypoxic cells. Tumor clonogens repopulated rapidly and the hypoxic cells appeared to reoxygenate substantially during 10-20 doses. In the fractionation regimens consisting of more than 5 doses, the repopulation became significant. This rapid repopulation was reflected as a small alpha/beta ratio on the Fe plot. During 20 daily doses given under hypoxic conditions, clonogens (including both oxygenated and hypoxic) repopulated by a factor of 1.9 x 10(6). The hypoxic clonogens (based on the TCD50 after doses in air) repopulated to a much lesser extent than did the total clonogens. Reoxygenation was not substantial up to 5 daily doses but appeared to become significant during 10 to 20 doses. The magnitude of reoxygenation appeared to be substantially greater during 20 daily doses than during 20 b.i.d. doses. The significance of the hypoxic cells appeared to be less with increasing fractionation for the tumor control, but still remained critical in 20 daily doses. This study also suggested that the inhibition of clonogen repopulation could improve the outcome of radiotherapy, but this inhibition should be accompanied by further reoxygenation as long as hypoxic clonogens remain critical for the tumor control.

Animals↗

PubMed1994

Suppression of fibrosarcoma metastasis by elevated expression of manganese superoxide dismutase.

A mouse fibrosarcoma cell line (FSa-II), which exhibits low endogenous levels of manganese superoxide dismutase, was transfected with a human manganese superoxide dismutase complementary DNA. Fifty clones were screened for manganese superoxide dismutase activity by the superoxide dismutase activity gel assay. Activity of the positive clones was measured by the nitro blue tetrazolium-reduction assay in the presence of cyanide. Three cell lines exhibiting a range of activity were chosen to be transplanted into syngeneic mice. The results indicated that the metastasis rate for all transfected cells was significantly less than that of control cells.

Animals↗

PubMed1994

The effect of hyperthermia on reoxygenation during the fractionated radiotherapy of two murine tumors, FSa-II and MCa.

PURPOSE: To investigate the effect of hyperthermia on the tumor reoxygenation during fractionated irradiations. It has been shown that hyperthermia increases the size of hypoxic cell fraction in some murine tumors and reoxygenation is critical for successful radiotherapy. METHODS AND MATERIALS: Tumors were early generation isotransplants of spontaneous murine fibrosarcoma (FSa-II) and mammary carcinoma (MCa) in C3Hf/Sed mice. Treatments were initiated when they reached an average diameter of 4 mm. A local heat treatment at 43.5 degrees C for 45 min was given in a constant temperature water bath 24 h before irradiation(s). This interval was selected to avoid heat-radiation interaction and to simply investigate the heat effect on the reoxygenation process. Tumors were irradiated under hypoxic conditions or in air and observed for recurrences for 120 days. The foot reaction of animals with controlled-tumors was scored on the last day of experiments. The TCD50 (50% tumor control dose) and RD50 (dose to induce partial foot atrophy in 50% of treated animals) were calculated. RESULTS: The TCD50s following a various number of fractions were obtained for FSa-II and MCa with or without hyperthermia. The difference between the TCD50 (hypoxia) and TCD50 (in air) without hyperthermia increased with an increasing number of fractions, suggesting that significant reoxygenation occurred during the fractionated irradiation. The TCD50s (with heat, in air) were smaller than the TCD50s (radiation alone, in air) following fractionated irradiations, indicating that hyperthermia did not affect tumor reoxygenation. The difference between these TCD50 values was greater for heat-sensitive MCa than for heat-resistant FSa-II, suggesting that this difference was due to additive heat cytotoxicity. An unexpected observation was that heat significantly enhanced the foot reaction with no resultant therapeutic gain for both MCa and FSa-II tumors. CONCLUSION: Hyperthermia given independently prior to fractionated irradiation did not affect tumor reoxygenation, nor was there a therapeutic gain for the two murine tumors. These results suggest that selective tumor heating is essential in clinical thermoradiotherapy.

Animals↗

PubMed1994

Repopulation of tumour cells following irradiation with X-rays or low energy neutrons.

The repopulation of C3H mouse mammary carcinoma cells following X-ray or fast neutron irradiation was investigated in vivo using TCD50 as an endpoint. Tumours in the C3H mouse leg were irradiated in air with an X-ray dose of 9.6, 28.8 or 48.0 Gy, or a neutron dose of 2.6 or 5.2 Gy, and, various times thereafter, graded X-ray doses were given under hypoxic conditions to determine TCD50. Substantial recovery from sublethal and potentially lethal radiation damages was observed within 48 h following X-ray irradiation, and less recovery was found after neutrons. The effective number of tumourigenic cells was calculated at the time of the second irradiation using the TCD50 equation based on the multitarget model. The effective cell doubling time following X-rays depended on radiation dose. Repopulation appeared to be faster after small and intermediate X-ray doses (9.6 and 28.8 Gy) than after the largest dose, but substantial division delay was observed after the largest X-ray dose. A significant finding was that the tumour cells treated with a neutron dose, either 2.6 or 5.2 Gy, appeared to repopulate slightly more rapidly than those irradiated with X-rays, and the doubling times following two different neutron doses were not significantly different. These results suggest the use of a short overall treatment time for the high LET radiotherapy, and that caution must be exercised if the high LET radiation is given before photon doses.

Animals↗

PubMed1994

[Surgical evaluation and clinical features of cholesteatoma in children].

There are two types of cholesteatoma in children, congenital and acquired. The pathogenesis of each type is thought to be different. The pathogenesis of congenital cholesteatoma is thought to be the embryonic inclusion of squamous epithelium, whereas acquired cholesteatoma is thought to develop from various factors including recurrent otitis media and tubal insufficiency. We reviewed a series of 23 patients with congenital cholesteatoma and 27 patients with acquired cholesteatoma, aged 2-15 years, who were operated on at our institution between January 1981 and December 1990. Planned staged surgery was performed in all patients. In the first-stage operation, the canal-wall-up technique was used in all cases. About 12 months after the first operation, the second-stage operation was performed to investigate the course of the disease. The presence of recurrent and residual cholesteatoma was evaluated at this time. In the congenital cholesteatoma series, 11 cases of residual cholesteatoma (48%) were detected at the second-stage operation. Since recurrent cholesteatoma was not observed in the series of congenital cholesteatoma cases, the prognosis of these cases was considered to be good. On the other hand, in the acquired cholesteatoma series, 9 cases (33%) of recurrent cholesteatoma and 13 (48%) of residual cholesteatoma were detected at the second-stage operation. For the second-stage operation, the canal-wall-up technique was performed on 18 patients with no recurrence, whereas the canal-wall-down technique was used on all 9 patients with recurrence. Additional mastoid obliteration was performed on 7 of these 9 patients. The prognosis of the patients who underwent obliteration was good, and there was no recurrence of cholesteatoma after the second operation. From these observations, it was concluded that planned staged tympanoplasty was useful for eliminating recurrent and residual cholesteatoma. It is also apparent that, in order to prevent recurrent cholesteatoma, it is necessary to reduce the air space to compensate for poor eustachian tube ventilation.

Child↗

PubMed1993

Timing and sequence of hyperthermia in fractionated radiotherapy of a murine fibrosarcoma.

PURPOSE: This study investigated the effect of timing and sequence of hyperthermia on fractionated radiotherapy, since it has been shown that the heat increases the size of hypoxic cell fraction which could affect the effect of subsequent radiation doses. METHODS AND MATERIALS: Animal-tumors were early generation isotransplants of a spontaneous fibrosarcoma, FSa-II, in C3Hf/Sed mice. Tumor response was studied by tumor growth time and TCD50 (50% tumor control dose) assays. The tumor growth time is the time required for one-half of the treated tumors to reach 500 mm3 from the first treatment day. The TCD50 is a radiation dose to control one-half of the treated tumors for 120 days following treatments. One heat treatment at 43.5 degrees C for 45 min was given in a water bath in combination with fractionated doses independently (24 hr interval) or simultaneously (2 min interval). For the normal tissue study, the mouse foot was treated, and the acute foot reaction was scored daily and averaged. The late foot reaction was scored in animals used in the TCD50 assay that developed no recurrence for 120 days. The RD50(2.0) and RD50(5.0), or total radiation doses to induce an average score of 2.0 (complete epilation) and 5.0 (partial foot atrophy) in 50% of treated animals, were calculated. RESULTS: Thermal radiosensitization was most prominent when heat was combined simultaneously with the first or last radiation dose in both the tumor growth time and TCD50 assays. However, the thermal enhancement was greatest when heat was given either with the first or last radiation dose in the TCD50 assay; whereas it was greatest when heat was administered with the last radiation dose in the tumor growth time assay. Both acute and late skin reactions were significantly potentiated by heat administered 24 hr before the first radiation dose. CONCLUSION: A significant observation in this study was that, in both the tumor growth time and TCD50 assays, heat given independently or simultaneously did not result in any therapeutic gain compared to the radiation alone treatment.

Animals↗

PubMed1993

Recovery of the vestibular function after vestibular neuronitis.

We performed steroid therapy on 34 cases with vestibular neuronitis and compared them with 77 patients not subjected to this therapy to examine the role of recovery of their vestibular function. Since no relation was noted between use of steroid and changes in subjective symptom of dizziness, the use of steroid is likely to facilitate the disappearance of spontaneous nystagmus in the early recovery stage. Canal paralysis recovered significantly by steroid and in cases of slight and moderate paralysis at the onset, recovery was more significant. Steroid therapy is argued to be effective for the recovery of vestibular function in cases of vestibular neuronitis.

Administration, Oral↗

PubMed1992

Enhancement of misonidazole chemosensitization effect by mild local hyperthermia.

In an attempt to increase the chemosensitization effect of the alkylating agents 1,3 bis(2-chloroethyl)-1-nitrosourea (BCNU) and cyclophosphamide (CY), by misonidazole (MISO) at the tumor site, mild hyperthermic treatment (41.5 degrees C, 1 hr) was applied at various administration sequences. C3Hf/Sed mice bearing subcutaneous FSa-II tumors in the foot were used for a tumor growth time assay. Local hyperthermic treatment increased the antitumor activities of BCNU and CY by 1.4 and 2.4 fold, respectively. MISO at 2.5 mmole/kg potentiated the antitumor activities of BCNU, but not CY, at normal body temperature. There were no significant improvement of MISO chemosensitization when heat was given before the administration of BCNU and CY. However, a significant enhancement of chemosensitization was observed when heat was given after the administration of MISO and the alkylating agents. Enhancement ratios of about 2.4 and 4.7 were observed with BCNU and CY, respectively. There may be two mechanisms responsible for this thermal enhancement. First, the MISO pre-incubation time that was required for the expression of chemosensitization effect decreased substantially at elevated temperatures. This hypothesis was supported by the pharmacokinetic studies that MISO was rapidly eliminated from tumors in the first 10 min during the local heat treatment and remained at a plateau with a concentration of about 5-fold less than the peak MISO concentration in the control tumors. This rapid elimination might result from the increase in the rate of hypoxic metabolism of MISO in heated tumors. Second, heat may increase the MISO-alkylating agent interactions, which are independent of pre-incubation time. This effect was especially pronounced in CY because pre-incubation-induced chemosensitization of CY in unheated tumor was insignificant in this study. The significant improvement of MISO chemosensitization at moderately elevated temperatures can be useful clinically in combined hyperthermia and chemotherapy treatment.

Animals↗

PubMed1992

Late reaction following twice-a-day irradiations in the murine foot: possible repopulation or consequential late effect.

The effect of twice-a-day irradiation on the foot reaction was studied in C3Hf/Sed mice. A numerical scoring system was used to evaluate the foot reaction that became visible shortly after irradiation. Peak reaction occurred on the 21st to 23rd day and reappeared after approximately the 200th postirradiation day. These reactions are called early- and late-appearing reactions, respectively. Animals studied for early-appearing reactions were continuously scored for more than 600 days after irradiation. The late-appearing reaction increased continuously or remained constant, but never decreased during the course of the experiments. Animal feet were irradiated with a fraction size from 1.0 to 5.0 Gy twice-a-day daily with a treatment interval of 6 and 18 hours, and varying numbers of fractions were given. A top-up dose of 20 Gy was given as the last dose. The late-appearing foot reaction following a fraction size of 1.5 Gy or greater increased with increasing total dose. However, the increase in the late reaction score with increasing total dose was trivial following multiple doses with a fraction size of 1.0 Gy, suggesting a possible repopulation during prolonged irradiation or that the observed reaction was a consequential late effect. The Fe-plot based on doses which induced fibrosis in one-half of the irradiated animals, showed an alpha/beta ratio of 6.57 +/- 0.62 Gy, and the presence of a breaking point at approximately 1.5 Gy. The alpha/beta ratios calculated by Joiner's method and Thames direct analysis were identical. The slope of the Fe-plot below 1.5 Gy was significantly steeper than that above 1.5 Gy.

Animals↗

PubMed1992

Lack of thermal inhibition of radiation damage repair in the late-appearing foot reaction.

Our previous study on early- and late-appearing murine foot reactions following combined hyperthermia and irradiation suggested that hyperthermia may not inhibit repair of sublethal and/or potentially lethal radiation damage for the late-appearing reaction. A series of split dose experiments was performed by using C3Hf/Sed mouse foot reaction, which showed both early and late responses in the same tissue. Hyperthermia given in a 43.5 degrees C water bath for 45 min inhibited radiation damage repair in the early-appearing reaction, but was not able to modify repair in the late-appearing reaction. The failure of thermal inhibition of radiation damage repair in the late-appearing reaction was observed regardless of the sequence of heat and irradiation. Complete repair appeared to require approximately 9 hr. Although it is unknown whether radiation damage repair can be completely inhibited in all late-responding normal tissues, the reduction in thermal repair inhibition in some late-responding tissues may be an advantage of "heat prior to irradiation" treatment over radiation alone.

Animals↗

PubMed1992

Radiation and thermal sensitivities of murine tumor (FSa-II) cells recurrent after a heavy irradiation.

Radiation and thermal sensitivities, and cell doubling times (Tds) of C3Hf/Sed mouse FSa-II cells recurring after a heavy irradiation were examined in vitro. Tumors in the leg were irradiated with gamma-rays and observed for late recurrence (in vivo clones), or removed immediately after irradiation and single cell suspensions were plated for colony formation (in vitro clones). Five subclones were selected from original cells in vitro. Survival curves were fitted to the multi-target and linear quadratic models. Surviving fractions at 2 (SF2) and 10 Gy (SF10) irradiations, and those at 30 and 60 min heatings at 44 degrees C (SF30 and SF60), were obtained for each clone. Although, Tds of subclones were slightly longer than those of the parental cells, those of recurrent clones were prolonged substantially with an exception of one cell line. Radiosensitivities of FSa-II parental cells tested in vitro and in vivo were equally radioresistant. Thermal sensitivities of parental cells tested in vitro and in vivo were also identical. All subclones were more radiosensitive compared to the parental cells. The in vitro recurrent clones showed smaller D0 (radiation dose to reduce survival from S to S/e in the exponential portion of survival curve) than the D0 of the parental cells. The SF2 values of four in vitro recurrent clones were greater than that of the parental cells whereas those of two lines were smaller. It was of interest that the in vivo recurrent tumor cells showed a wide variation in the radiation sensitivity. Among 9 tumor cell lines examined, 4 lines were more sensitive and 4 were more resistant compared to the original. FSa-II subclones as well as both in vitro and in vivo recurrent clones showed a wide variation in thermal sensitivity. No consistent changes in the shoulder or in the slope were found. The SF30 or SF60 showed that 5 out of 9 in vivo recurrent clones and 4 out of 9 in vitro clones were more resistant compared to the original cells. No correlation was observed between thermal and radiation sensitivities. The Td was not related with radiation or thermal sensitivity.

Adaptation, Physiological↗

PubMed1992

Radiosensitivity of mouse skin epithelial cell line established in serum-free culture: an alternative to animal use.

A cultured line of murine skin epithelial cells was established to investigate the potential use of cultured cells as an alternative to animal use in radiation research. C3Hf/Sed newborn mouse skin cells have been successfully cultured in serum- and Ca(2+)-free medium with no terminal differentiation to keratinized cells. Presently, more than 25 passages have passed with no loss of stem cell capability. The radiosensitivity and repair of sublethal and potentially lethal radiation damages were investigated in this epithelial cell line. The population cell doubling time was 25 +/- 2.9 hr at 37 degrees C. The clonal growth of epithelial cells after irradiation was performed in the serum-free medium in the presence of lethally irradiated skin fibroblasts. Single dose survival curves of exponentially growing epithelial cells were investigated from the seventh to the twenty-third passages, and no significant changes in radiosensitivity and doubling time were found. The confluent epithelial cells also showed an identical sensitivity to radiation. The alpha/beta ratios of survival curves fitted by the linear quadratic model were 6.1 +/- 1.0 and 5.9 +/- 1.3 Gy for cells in exponential and confluent phases, respectively. The survival curve of epithelial cells left in confluence for 8 hr after irradiation showed a smaller beta value than that of cells plated immediately after irradiation with a resultant alpha/beta ratio of 9.5 +/- 3.8 Gy. This alpha/beta ratio was identical to those found in many animal experiments, suggesting a potential use of this cell line as an alternative to animal use. The magnitude of repair of sublethal damage following 6 Gy was greater than that following 3.9 Gy. Survival curves were also obtained following twice-a-day irradiations with no sign of rapid repopulation. These results are discussed by comparing with published in vivo and in vitro data.

Animal Testing Alternatives↗

PubMed1992

Megavoltage grid total body irradiation of C3Hf/SED mice.

The effect of a grid on whole-body megavoltage radiation tolerance in C3Hf/SED mice was studied. Adult mice were irradiated beneath a 50% megavoltage grid. LD50 (50% lethality) values were measured at ten and 30 days. LD50/30 day increased by a factor of 1.5 for mice receiving both single and two fraction irradiation beneath the grid. LD50/ten day increased by factors of 1.1 to 1.2 for single, two, and five fraction irradiation beneath the grid.

Animals↗