Biomedical subjects

W F Harvey

Publications and source records attributed to W F Harvey.

17 recordsLinked to original sources

PubMed1999

Mutant yields and mutational spectra of the heterocyclic amines MeIQ and PhIP at the S1 locus of human-hamster AL cells with activation by chick embryo liver (CELC) co-cultures.

Cooking meat and fish at high temperature creates heterocyclic amines (HA) including 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Several HA are mutagens in the Ames' S9/Salmonella assay. While PhIP is a substantial Ames' test mutagen, it is 1000-fold less active than the extraordinarily potent MeIQ. In contrast, MeIQ is significantly less mutagenic than PhIP in several mammalian cell assays, especially in repair-deficient Chinese hamster ovary (CHO) cells. HA are suspect human carcinogens on the basis of (i) epidemiological evidence, (ii) induction of tumors in rodents and monkeys, (iii) DNA adduct formation and (iv) mutagenic capacity. In this study, MeIQ and PhIP were significant mutagens at the S1 locus of co-cultivated human/hamster hybrid AL cells following metabolic activation by beta-napthoflavone (betaNF)-induced chick embryonic liver cultures (CELC). MeIQ was more mutagenic than PhIP in the CELC+AL cell assay. The mutant response curves increase with dose and then plateau (PhIP), or decrease (MeIQ). The inflections in these response curves coincide with dose-dependent decreases in cytochrome CYP1A1 activity. Molecular analysis of S1- mutants indicates that a substantial fraction, >65%, of the mutations induced by PhIP are deletions of 4.2 to 133 (Mbp); half are larger than 21 Mbp. Mutations induced by MeIQ were smaller, most (56%) being less than 5.7 Mbp. When appropriate metabolic activation is combined with a target locus, which can detect both small and large chromosomal mutations, both MeIQ and PhIP are significant mutagens and clastogens in repair proficient mammalian cells.

Animals↗

PubMed1995

Gamma-ray mutagenesis measurement in mammalian cells.

Application of conventional in vitro mutagenesis testing has so far failed to result in marked reduction of the total incidence of cancer. At least part of the reason may lie in the frequent use of a cell target too small to yield adequate sensitivity, and in failure to take into account the effects of cell killing in the assessment of mutagenic action. A single theoretical analysis fits the results of experimental data on gamma-irradiation applied to single marker gene testing in bacteria and to cytogenetic analysis of irradiated mammalian cells, and permits determination of the mean mutagenic dose, DoM, without complication due to cell killing. Cytogenetic monitoring of human lymphocytes which can detect mutagenic effects of gamma-radiation down to doses of < 0.1 Gy (10 rad) will also furnish an estimate of repair effectiveness at these low levels and may well be a useful tool in a program for prevention of cancer and other genetic disease.

Animals↗

PubMed1993

Radiobiology of alpha particles. IV. Cell inactivation by alpha particles of energies 0.4-3.5 MeV.

In this report the effectiveness of low-energy alpha particles in the range 0.4 to 3.5 MeV for cell killing is investigated. Four cell lines of different nuclear dimensions (AG1522, C3H 10T1/2, CHO-10B, and HS-23) are studied. Monte Carlo simulations are carried out to interpret the experimental results. They are presented as a function of dose to the nucleus, the total track length of alpha particles in the nucleus, and other parameters. It is found that the effectiveness of alpha particles for cell killing decreases with decreasing alpha-particle energy. The maximum RBE value is found to extend to LET values as high as 180 keV/microns. Although the LET might be the same, the effectiveness of alpha particles for cell killing is higher in the ascending part of the Bragg curve compared to descending part of the Bragg curve. The terminal tracks of alpha particles are observed to be less effective for cell killing.

Alpha Particles↗

PubMed1991

Wood duck hatch date: relationship to pairing chronology, plasma luteinizing hormone, and steroid hormones during autumn and winter.

We examined variation in courtship activity and hormone levels of male and female wood ducks (Aix sponsa) in relation to hatch date. Young wood ducks were assigned in groups of 8 (4 males and 4 females) to 4 experimental pens; 2 pens contained early-hatched ducks (3-12 April) and 2 pens contained late-hatched ducks (7-16 June). Courtship behaviors occurred less frequently in October and November than in December and January-February for both early- and late-hatched groups. Early-hatched wood ducks participated in courtship more frequently and formed pair bonds sooner than late-hatched individuals. Testosterone (T) and androstenedione (AD) levels of males did not differ between treatment groups; however, average levels of luteinizing hormone (LH) were greater for early-hatched males. Differences in LH occurred in 2 of 12 samples (6 October and 3 November); otherwise, LH did not vary by treatment. Levels of T and LH in males varied temporally, but there was no significant temporal variation in AE levels. Temporal variation in hormone levels was similar for early- and late-hatched males. Estradiol (E), progesterone (P), and LH levels of females did not differ between treatment groups. There was temporal variation in levels of E and LH, but not of P; this variation was similar for early- and late-hatched females. These data indicate that behavioral differences occurring temporally and between early- and late-hatched wood ducks were not related to corresponding differences in hormone levels.

Animals↗

PubMed1991

Radiobiology of alpha particles. II. Dosimetry of low-energy alpha particles using parallel-plate ionization chambers and a surface barrier detector.

Three small parallel-plate ionization chambers were developed for measuring dose rates, of primarily low-energy alpha particles in the energy range 0.4-3.5 MeV, at a defined cell-Mylar interface. Spectral energy distributions of these alpha particles were also measured at the same position using a specially designed small-area silicon surface barrier detector. Dose rates were derived from the spectral distributions and compared with those derived from the ionization chambers. Different alpha-particle energies were obtained using a 144-MBq 238Pu collimated source and a variety of Mylar moderator foils of different thicknesses. These measurements, extended to mean alpha-particle energies as low as 0.4 MeV, will enable us to correlate radiobiological data with effects of alpha particles terminating in different regions of cell nuclei.

Alpha Particles↗

PubMed1990

Protein glycosylation in heat-sensitive and thermotolerance-deficient mutants of Chinese hamster ovary cells.

Chinese hamster ovary (CHO) cells are capable of developing a high degree of thermotolerance in response to appropriate heat conditioning. In this study we examined the relationship between thermotolerance development and protein glycosylation using four sublines of CHO cells. Two of these CHO sublines are characterized by an increased heat sensitivity and impaired cellular capacity for thermotolerance development. The data show that thermotolerance development after heat conditioning in the heat-sensitive, thermotolerance-deficient mutants was accompanied by reduced labeling of a Mr 50,000 glycoprotein (GP50), in both soluble and insoluble cell fractions. Similarly, activation of UDP-N-acetylgalactosaminyltransferase (Gal-NAcT) after hyperthermia was almost completely abolished in these cell lines. Both of these endpoints have been correlated previously with thermotolerance expression. The data are consistent with the glycosylation hypothesis that attributes increased heat resistance of thermotolerant cells, at least in part, to enhanced glycosylation and accumulation of endogenous glycoproteins, such as GP50.

Animals↗

PubMed1990

Radiobiology of alpha particles. I. Exposure system and dosimetry.

A 238Pu alpha-particle exposure apparatus was designed and constructed for use in radiobiological studies with cultured cell systems. The system provides a wide dynamic range of absorbed doses and a uniform radiation field. Average dose rate in air was measured with a small-volume ionization chamber. Estimates of dose rate at the cell surface were obtained from measurements taken with a silicon surface barrier detector. Particle fluence uniformity and fluence rate were measured using track etch procedures. The design and dosimetric characterization of the apparatus are discussed.

Alpha Particles↗

PubMed1990

Alterations in specific and general protein synthesis after heat shock in heat-sensitive mutants of CHO cells and their wild-type counterparts.

The rates of general and specific protein synthesis were studied in two heat-sensitive strains of CHO cells (Harvey and Bedford, Radiat. Res. 113, 526-542, 1988), both of which show a reduced ability to develop thermotolerance following an initial 45 degrees C heat shock. After various labeling periods with [35S]methionine, wild-type and mutant labeled proteins were separated by one- and two-dimensional polyacrylamide gel electrophoresis. Autoradiograms showed differences in levels of synthesis of several proteins after a 45 degrees C heat shock. In particular, these were in the hsp-70 group referred to as hsp-70a, b, and c, having molecular weights of 76, 73, and 72 kDa and isoelectric focusing pH values of 5.7, 5.5, and 5.7, respectively. Of particular note were changes in the hsp-70c region of the autoradiograms. We found that there was perhaps a low level of synthesis of hsp-70c in unheated wild-type cells but none was detectable in the mutant lines. After an isosurvival (approximately 10%) pulse of 45 degrees C heat there was a gradual increase in the synthesis of hsp-70c for wild-type but a smaller increase for the heat-sensitive strain 36 (HS-36) cells. In contrast, for HS-23 cells there was a very large initial increase by 5 to 7 h after the heat pulse and then a rapid decrease to undetectable levels by 11 to 13 h. The inhibition and recovery of general protein synthesis for both mutant and wild-type cells was also measured following various heat treatments at 45 degrees C. We observed that inhibition and resumption to a "normal" rate of protein synthesis for HS-23 cells paralleled the same response observed for the wild-type 10B2 cells. In sharp contrast, the time for recovery from the inhibition of protein synthesis for HS-36 cells was severely reduced for all heating times tested. Our results show that the period of delay before resumption of protein synthesis after heating does not always correlate with heat sensitivity or the degree of thermotolerance development. Several explanations for these observations are possible. One is that while synthesis of certain heat-shock proteins may indeed be responsible for the development of thermotolerance, the timing of the synthesis of these proteins in relation to the period of inhibition of general protein synthesis is crucial to such development.(ABSTRACT TRUNCATED AT 400 WORDS)

Acclimatization↗

PubMed1989

Radiobiology of ultrasoft X rays. IV. Flat and round-shaped hamster cells (CHO-10B, HS-23).

The results reported earlier in this series indicated that the relative biological effectiveness (RBE) of ultrasoft X rays decreases with decreasing cell thickness, approaching unity for the thinnest cells used, plateau-phase human skin fibroblasts (HSF). The possible dependence of RBE on the configuration of the cell nucleus is investigated further in this paper using two CHO cell lines that attach well and have similar intrinsic radiosensitivities to 60Co gamma rays. One of the lines forms monolayers similar to V79 cells, while the other remains more spherical during growth. We find an increasing RBE with decreasing X-ray energy for both of these cell lines, consistent with our results using V79 cells. Also consistent with our results obtained with 10T1/2 and HSF cells, we find an increasing RBE with increasing cell thickness. The possible dependence of RBE on radiosensitivity and the use of the concept of mean dose for ultrasoft X rays is discussed.

Animals↗

PubMed1988

Isolation and characterization of heat-sensitive, thermotolerant defective mutants of CHO cells.

A replica plating technique was utilized to isolate stable CHO cell mutants that are heat-sensitive and have altered capacities to develop thermotolerance. From a mutagen (EMS) treated population of CHO cells, two strains were isolated. One (HS-36) shows a greatly reduced ability to develop thermotolerance following an initial 45.0 degrees C heat shock. The other (HS-23) also shows a greatly reduced thermotolerance development following a short 45.0 degrees C induction dose, but a greater thermotolerance development following longer 45.0 degrees C induction doses. The dose-survival response following single-dose 45.0 degrees C heating of HS-23 cells suggests the presence of a resistant subpopulation which is not due to contamination from, or reversion to, wild-type cells. Both strains have unique morphological characteristics. Spheroids develop in the central portion of HS-36 colonies, though cells in monolayers are indistinguishable from wild-type parental cells. HS-23 cells grow in firmly attached monolayers, but more than 95% maintain a "rounded" morphology. The remainder show a "flattened" morphology typical of CHO cells. Both strains have parental CHO characteristics as determined by chromosome number, population doubling times, and survival responses to UV light and to gamma rays. Each has maintained its heat-sensitive and altered thermotolerance phenotype for a period of over 6 months in continuous log-phase culture.

Acclimatization↗

PubMed1968