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Biomedical subjects

N Hunter

Publications and source records attributed to N Hunter.

At least 199 records · Page 11Linked to original sources
PubMed1986

Radiation safety and protection in U.S. dental hygiene programs.

A survey of radiation safety and protection measures used by programs teaching dental hygiene indicated some areas for concern. No barriers or radiation shieldings were used between operator and patient in four programs. Radiation monitoring devices were not worn by faculty operators in 16% of the programs. Fewer than half of the programs used thyroid shields for patients on a routine basis. Insufficient filtration for the kilovolt peak employed was used by 14% of the programs, and for 19% more the filtration was unknown or unspecified. Three programs used closed cones. Rectangular collimation was not used at all by 63% of the programs, and only 20% used E speed film routinely. Quality assurance for equipment maintenance and for film processing were in place at only 54% and 49% of the programs, respectively.

Dental Hygienists↗
PubMed1986

Effect of the radiosensitizer misonidazole and the radioprotector diethyldithiocarbamate on spontaneous metastasis formation of murine tumors.

The effect of treatment with the hypoxic cell radiosensitizer misonidazole (MISO) and the radioprotector diethyldithiocarbamate (DDC) on the formation of spontaneous lung metastases of four different spontaneously metastasizing murine tumors was investigated. The tumors were mammary carcinoma MCA-K, hepatocarcinoma HCA-1, and sarcomas SA-4020 and SA-NH. Multiple daily treatments with MISO significantly enhanced the incidence of metastases only in MCA-K. Because only MCA-K, but not the three remaining tumors, is immunogenic, the treatment with MISO may be associated with the promotion of metastasis primarily in the immunogenic tumors. Treatment of mice with DDC had no influence on metastatic spread. However, when given prior to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), DDC reduced BCNU-induced enhancement of HCA-1 metastases.

Animals↗
PubMed1986

Response of previously irradiated mouse skin to a second course of irradiation: early skin reaction and skin shrinkage.

The responses of previously irradiated hind legs of mice to second courses of gamma ray irradiation were studied using early skin reaction and skin shrinkage as end points. The hind legs of mice were treated with various doses in single and multifractionated irradiation at one-day intervals, 12 months after a variety of doses in various treatment schedules and in a single exposure, respectively. The re-irradiated skin was relatively radioresistant compared to the previously non-irradiated skin, depending on the skin site used and the end point used to evaluate the skin's radiation sensitivity. Early skin reactions that occurred after test doses administered to pre-irradiated skin developed sooner, and remained longer, than skin reactions that developed in the previously non-irradiated controls, regardless of treatment regimens. The degree of early skin reaction to the test dose was greater in the pre-irradiated skin, when the test dose was relatively small, and lower, when the test dose was relatively large, regardless of treatment regimens with one exception: the ventral aspect of the mouse's hind leg responded more to multifractionated test doses in the pre-irradiated skin. The degree of skin shrinkage, assessed 50-60 days after the test dose, was less in the pre-irradiated skin than in the previously non-treated controls, for each dose in each test treatment schedule. The amount of skin shrinkage, resulting from a given test dose (25 or 40 Gy), decreased with increasing dose during the first course of each treatment schedule. The degree of skin shrinkage caused by the first and second exposure, however, increased when the total dose of the first course and the test exposure was increased.

Animals↗
PubMed1986

Age dependency of response of the mouse skin to single and multifractionated gamma irradiation.

The age dependency of the response of the mouse skin to gamma-ray irradiation was studied using early skin reaction as an end point. The isoeffect doses for almost all the given levels of early skin reaction were, even though statistically not significant, approximately 10% larger on the average for 38- and 64-week-old mice than for 12-week-old mice. No significant difference between 12-week-old mice and 64-week-old mice was observed in the proportion of dose recovered during multifractionated exposures and in the slope of the fraction number and isoeffect dose relationships plotted on a log-log scale, as well as in the effects of anatomical location on the radiosensitivity. A preliminary shaving made the mouse skin relatively sensitive to radiation, and the dose-modifying factor was smaller for 64-week-old mice than for 12-week-old mice.

Aging↗
PubMed1986

A semi-quantitative assessment of the histopathology of oral lichen planus.

In a retrospective study of 112 cases, an attempt has been made to further delineate the histopathological parameters which are useful in making a diagnosis of oral lichen planus. The results of this study show that mononuclear infiltration beneath and adjacent to the epithelium, parakeratosis and degeneration of the basal layer of the epithelium were consistent features. Linear regression analyses of the parameters studied provided partial support for a cell-mediated immune mechanism.

Adult↗
PubMed1986

Treatment of experimental lung metastasis with local thoracic irradiation followed by systemic macrophage activation with liposomes containing muramyl tripeptide.

The purpose of these studies was to determine whether the combination of a low-dose local thoracic irradiation (LTI) followed by systemic activation of macrophages with liposomes containing muramyl tripeptide phosphatidylethanolamine (MTP-PE) would significantly decrease established experimental fibrosarcoma lung metastases. Male C3Hf/Kam mice were given i.v. injections of 1 X 10(5) fibrosarcoma cells. Five days later, groups of mice were treated with saline, with 8 Gy LTI, or with liposomes containing MTP-PE or first with 8 Gy LTI and followed by multiple i.v. injections of liposomes containing MTP-PE. Most of the mice in the groups treated with liposomes died by day 42 of the experiment. In contrast, 60% of the mice treated with the combination of LTI and liposomes containing MTP-PE were alive by day 140 of the study. These mice were killed and were found to be free of tumors. Control studies demonstrated that liposomes administered i.v. to mice given LTI were trapped in the capillary bed of the lungs and activated the tumoricidal properties of lung macrophages. We conclude that, in this combination, low-dose LTI, which can lead to both tumor cell death and inflammatory changes in the lung capillaries, could precede i.v. administration of liposomes containing MTP-PE. This combination of treatments can lead to destruction of tumor foci in the lung that cannot be achieved with either treatment alone.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1986

Retardation of tumor growth in mice caused by radiation-induced injury of tumor bed stroma: dependency on tumor type.

Dependency on tumor type of tumor growth retardation caused by the radiation-induced damage of tumor bed stroma, a phenomenon known as the tumor bed effect (TBE), was investigated using two mammary carcinomas designated MCA-4 and MCA-K and two fibrosarcomas designated FSA and NFSA, all syngeneic to C3Hf/Kam mice. Inoculations of tumor cells were given s.c. into the right hind thighs of mice either treated or not treated 1 day earlier with graded doses of gamma-rays; tumor latency and growth rate were determined. Tumor latency was prolonged and tumor growth was retarded, but the magnitude of these two features of TBE greatly depended on radiation dose and tumor type. TBE began to appear at doses of 5-10 Gy and then sharply increased as the dose of radiation was increased up to between 20 and 30 Gy, at which point a plateau was achieved. TBE was also significant after 40 and 60 Gy total dose given in daily fractions of 2 Gy 5 times per week, a schedule commonly used in radiotherapy treatment of cancer patients. Carcinomas exhibited more pronounced TBE than fibrosarcomas, with NFSA showing only minimal TBE. Radiation-inactivated MCA-4 and FSA cells admixed with viable MCA-4 cells reduced tumor latency, but not the tumor growth delay, of resulting MCA-4 tumors in preirradiated legs. In contrast, admixture of irradiated NFSA and viable MCA-4 cells abolished growth delay but did not influence tumor latency of the TBE phenomenon. Thus the type of a tumor growing in the irradiated tissue is a very important factor that determines the expression of TBE.

Animals↗
PubMed1985

Current concepts in periodontal diseases.

Periodontal diseases are common oral diseases that afflict all humans to some degree. The major aetiological agent is dental plaque--the complex microflora which forms on teeth in the absence of effective oral hygiene. The interaction of the microbial flora and the periodontal tissues produces an inflammatory response and tissue breakdown. Recent information has categorized periodontal diseases on the basis of increased knowledge about the particular microorganisms associated with the different clinical conditions. In addition, the important role of host defences, in particular the phagocytic cellular elements, has allowed for a better understanding of the pathological processes. This knowledge is contributing towards the development of rational and effective therapy for all forms of periodontal diseases. Because of the widespread occurrence of periodontal diseases and their potential relationships to systemic conditions, it is important that medical practitioners should be able to recognize, and be conversant with methods of treatment of, these diseases.

Acute Disease↗
PubMed1985

Dental radiology instructors in United States dental hygiene programs.

A survey of dental radiology instructors in accredited United States dental hygiene programs found the majority of such faculty members to be registered dental hygienists with only very limited formal training in radiology. Most of the radiography faculty had less than 5 years' experience teaching that subject. Most instructors spent less than a quarter of each week teaching radiology. Student: faculty ratios varied considerably from program to program.

Dental Hygienists↗
PubMed1985

Radiology requirements in United States dental hygiene programs.

A survey of accredited dental hygiene programs in the United States revealed little standardization of requirements for dental radiology. However, most programs satisfied suggested minimum guidelines for didactic instruction in radiology. Six programs had no preclinical laboratory requirements, and seven had no clinical requirements. An area of concern was the high percentage of programs in which classmates exposed one another to ionizing radiation for training purposes.

Accreditation↗
PubMed1984

A fluorescent screening assay for collagenase using collagen labeled with 2-methoxy-2,4-diphenyl-3(2H)-furanone.

This report describes the use of the compound 2-methoxy-2,4-diphenyl-3(2H)-furanone to label collagen as a substrate for the detection of mammalian collagenase in a fluorescent assay which is suitable for screening large numbers of samples. The compound 2-methoxy-2,4-diphenyl-3(2H)-furanone presents distinct advantages over other fluorophores, since both the unbound reagent and its hydrolysis products are nonfluorescent. The labeling procedure uses commercially available collagen, is fast and simple, and gives a 90% yield of labeled substrate. The fluorescent collagen substrate is stable and retains fluorescence over a wide range of pH. The assay detects, reproducibly, metal-dependent collagenase activity in microliter volumes of conditioned media from cultured neoplastic cells or in chromatographic fractions from such media.

Animals↗
PubMed1984

Protection of spermatogonial survival and testicular function by WR-2721 against high and low doses of radiation.

The radioprotection of normal cells with WR-2721 at doses of radiation extending down to less than 1 Gy was investigated using testicular cells. Survival of stem spermatogonia after single doses of radiation was measured by counts of repopulating tubules and by sperm head counts, with consistent results obtained for both endpoints. Protection factors (PF) obtained by injection of 400 mg/kg WR-2721 at 15 min prior to irradiation decreased from about 1.4 at radiation doses above 10 Gy to 1.0 at 2 Gy. Similarly, the radioprotection by 300 mg/kg WR-2721 was reduced from a PF of about 1.35 when the drug was given prior to a single high dose of radiation to 1.0-1.1 when the drug was given prior to each of 5 daily fractions of 2 Gy. Thus, less protection of testicular stem cells by WR-2721 was observed at lower doses of radiation. This lowered protection may be explained, at least in part, by a direct cytotoxic effect of WR-2721 on testicular stem cells. Protection of differentiated spermatogonia was observed with 400 mg/kg WR-2721; the PF was 1.4 at 1 Gy and decreased at lower doses. The protection of testicular function by WR-2721, as assayed by the return of fertility and the maximum recovered level of sperm production, was compared to the protection of stem cell survival. At about 8 Gy the PF with 400 mg/kg WR-2721 for both functional endpoints was about 1.5, which was not significantly different from the value of 1.3 obtained using the stem cell assays.

Amifostine↗
PubMed1984

In vivo radioprotective activities of diethyldithiocarbamate (DDC).

Studies were performed to determine whether diethyldithiocarbamate (DDC) protects against radiation damage to bone marrow, jejunal crypts, testicular tubules, hair follicles, tissues in the leg responsible for leg contractures, and a fibrosarcoma (FSA) of C3Hf/Kam mice. In most experiments, DDC at a dose of 400 mg/kg or 1000 mg/kg body weight was given i.p. 30 minutes before single doses of gamma radiation. DDC (1000 mg/kg) given 30 minutes before whole-body irradiation protected hematopoietic stem cells by a factor (PF) of 1.59, as assessed by the LD50/30 assay, and by PFs of 1.32-1.55, as assessed by the endogenous spleen colony assay. A dose of 400 mg/kg DDC was less effective. Protection was also significant against hair loss and leg contractures; PFs produced by 1000 mg/kg DDC were 1.44 and 1.38-1.51, respectively. Jejunum was protected by 400 mg/kg DDC (PF = 1.2), but not by 1000 mg/kg. The opposite was observed with testis: 1000 mg/kg was protective (PF = 1.2), but not 400 mg/kg. DDC also protected the FSa tumor, either as lung micrometastases or as a solitary tumor in the leg. Both 400 mg/kg and 1000 mg/kg DDC protected 4 day-old micrometastases by a PF of approximately 1.1. DDC at a dose of 1000 mg/kg protected 8 mm leg tumors by a PF of 1.24 at the TCD50 level. Therefore, DDC protected both normal tissues and FSA, but the degree of protection varied greatly. A therapeutic gain was achieved in some instances.

Animals↗
PubMed1984

Effect of tumor type, size, and endpoint on tumor radioprotection by WR-2721.

Experiments are reported showing that the degree of tumor radioprotection afforded by WR-2721 varies with the type of tumor and assay endpoint, and that for a given tumor system, microaggregates are protected better than larger cell masses. The tumors used were a methylcholanthrene-induced fibrosarcoma (FSa), and two tumors of spontaneous origin, another fibrosarcoma (NFSa), and a mammary carcinoma (MCa-4), all syngeneic to C3Hf/Kam mice. WR-2721 was given in a dose of 400 mg/kg 30 minutes before irradiation in all experiments. In TCD50 assays, WR-2721 protected 5 mm diameter and impalpable 3 day-old transplants of 5 X 10(5) FSa cells growing in the leg by factors of 1.11 and 1.13, respectively. Using the tumor latency endpoint, 3 day-old s.c. transplants of 10(3) FSa in the abdominal wall were protected by a factor of 1.27, a degree of protection similar to that reported earlier for sterilization of lung micrometastases of the same tumor. MCa-4 tumors growing in the leg were protected better than FSa in TCD50 assays with protection factors of 1.3 for 4 day-old transplants, 1.24 for 5 mm tumors, and 1.23 for 8 mm tumors. MCa-4 tumors recurrent after irradiation as 4 day-old transplants grew more rapidly in mice that had received WR-2721, and this was shown to be most likely due to protection by the drug against expression of the tumor bed effect. Using the lung micrometastases assay, NFSa was protected by a factor of 1.22. This variability in protection with different tumor types, sizes, and assay endpoints is discussed in terms of drug delivery and uptake, and also in relation to the influence of tumor hypoxia on the radioprotective ability of WR-2721.

Amifostine↗
PubMed1984

Cytotoxic effects of WR-2721 on mouse testicular cells.

WR-2721 (S-2-(3-aminopropylamino)ethylphosphorothioic acid) has been demonstrated to be cytotoxic to stem spermatogonia in the mouse. Five and 10 injections of 300 mg/kg killed sufficient numbers of stem cells to reduce sperm production 56 days after treatment by 16 and 43%, respectively. Single injections of 300 or 400 mg/kg of WR-2721 given 15 min after irradiation produced negligible toxicity to stem cells as measured by counts of repopulated tubules; 600 mg/kg reduced stem cell survival by 47%. Four daily injections of 300 mg/kg given 4, 3, 2, and 1 days prior to irradiation (with or without a fifth injection 15 min after irradiation) reduced stem cell survival by about 60%. The cytotoxic effects of WR-2721 on testicular stem cells at least partially explains the reduced protection factors observed in the testis with low doses of radiation and during fractionated treatments involving multiple injections of drug.

Amifostine↗
PubMed1984

Inhibition of radiation carcinogenesis in mice by S-2-(3-aminopropylamino)-ethylphosphorothioic acid.

We have demonstrated that S-2-(3-aminopropylamino)ethylphosphorothioic acid (WR-2721) given to mice prior to ionizing radiation inhibits development of radiation-induced sarcomas. The right hind legs of C3Hf/Kam mice were exposed to single doses of gamma-rays ranging from 3400 to 5700 rads. Thirty min before irradiation, approximately one-half of the mice were given i.p. injections of WR-2721 (400 mg/kg). Mice were checked for development of radiation-induced tumors within the irradiated tissue of legs from 250 up to 786 days after irradiation. Tumors first appeared in both groups of mice at approximately 300 days after irradiation. Thereafter, the rate of tumor development was slower in mice that received both WR-2721 and leg irradiation. At the end of the observation period, the overall actuarial tumor incidence in these mice was 26%, compared to 87% in mice exposed to radiation only. Since WR-2721 has the ability to protect against radiation carcinogenesis, it may also afford protection against the carcinogenic effect of alkylating agents.

Amifostine↗