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Chlorella has two mechanisms of K uptake, depending on concentration. Mechanism 1 operates at low concentration and may be responsible for net transport. Mechanism 2 is dominant at high concentration (above 1 × 10−3M) and may be attributed to the K/K exchange system. In either case, Rb, which has a more favourable radioisotope, substitutes for K. Both mechanisms are temperature sensitive, dependent on metabolism, and carrier-mediated. At low Rb concentration (3 × 10−5M), γ-irradiation (60 krad) reduced Rb uptake at 30 °, but increased it at 10 °. At high concentration (3 × 10−3M) uptake was stimulated by irradiation at both temperatures. With K-deficient cells the Rb net transport contributed to a higher degree to total Rb influx, compared with normal cells. On γ-irradiation of K-deficient cells, at low concentration a decrease of the uptake was observed at both 30 ° and 10 °, and at high concentration the stimulation was less pronounced than with normal cells at both temperatures. It is suggested that the K/K exchange system is stimulated, but the K (Rb) net transport system is injured by irradiation. The increased K efflux after irradiation is about equal to the stimulated K (Rb) influx via the exchange system. Thus it is not necessary to assume enlarged membrane permeability to explain the increase of the K efflux after γ-irradiation.

The reproductive capacity and resistance to an acute dose of gamma irradiation were determined for populations of Callosobruchus maculatus treated with substerilizing doses of irradiation each generation for 30 generations. Reproductive capacity was decreased by an ancestral history of irradiation, the reduction being positively correlated with both the size of dose per generation and the number of ancestral generations treated. Irradiation of the selected populations with an acute dose revealed no increase in tolerance, even after 30 generations. In general, the greater the amount of accumulated ancestral exposure to irradiation, the greater the sensitivity to further irradiation. The ability to develop a tolerance to ionizing irradiation may not be a general phenomenon in insects. (auth)

The specific suppressor cells which had been demonstrated by us in the spleens of mice tolerant to human serum albumin (HSA) could be shown to originate in the thymus of these animals. They were not depleted by passing such spleen cell suspensions on columns with an adsorbed antigen-antibody complex, a device which retains B cells, while they could be inactivated by treatment with anti θ serum and complement. These suppressor T cells were found to survive the pretreatment of their donors with hydrocortisone acetate. Nevertheless, indications were found that their precursors are apparently cortisone-sensitive since in a suitably designed experiment cortisone could be shown to interfere with tolerance induction. The suppressor cells of tolerant mice block the anamnestic response to the tolerizing antigen which can be activated after differential irradiation of tolerant animals. Analysis by means of cell transfer experiments indicated that this memory of tolerance induction was associated with a B cell population which remained functional after gamma irradiation.

Because starch of low viscosity is important for industrial purposes this research was carried out to study the possibility of producing this sort of starch by treating rice starch with γ-irradiation. Results indicated that when rice starch was modified by γ-irradiation, the reducing power increased and degradation as well as molecular breakdown occured followed by sharp decrease of its viscosity, specific viscosity and intrisinc viscosity. Results showed that starch became more soluble by treating with γ-irradiation and lost its resistance to water as its swelling capacity decreased. All these changes were proportional to the doses of γ-irradiation.

Carbon fibres heat treated to temperatures in the range 1000-2600°C have been irradiated in the spent fuel pond to gamma doses between 1-1000 Megarads (MI). The mechanical properties of the irradiated fibres have been determined by single filament tests. There is a reduction in strength and modulus for fibres irradiated in air, probably due to radiation enhanced oxidation effects. This produces an increase in fibre diameter (≲10%) for fibre originally heat treated to 1000 and 1500°C. This is probably due to fine scale voidage (∼20 A) for which there is some evidence in thin sections prepared from regions close to the surface of these fibres (irradiated to 1000 Mr). The mechanical properties of fibres irradiated to 1000 Mr in argon were unaffected by the irradiation showing that the displacement damage from the irradiation has had little effect on the processes controlling modulus and strength.

Wood, particularly in the presence of excessive moisture, deteriorates due to action of biological agents and sunlight. Decay manifests itself not only in impairment of physical strength but also in discoloration. Protection of the paint during consolidation by impregnation and polymerization, albeit difficult, is possible. Details of a home-built 23 cm-diameter and 48 cm-long chamber for vacuum impregnation are given. The permeating methylmethacrylate monomer solution used with good results contained bis-4-t-butylcyclohexyl peroxidicarbonate as catalyst, and pyridine as activator in addition to methylmethacrylate polymer, which reduced the rate of heat generation by the reaction. Polymerization induced by gamma irradiation also yielded satisfactory results. Case histories of three artifacts are described.

Populations of soil algae were sampled along the radiation gradient in the Brookhaven Irradiated Forest in the sixth year of irradiation. Seventeen taxa were identified from over 300 individual isolations. Changes in the soil algal populations were limited to the Devastated Zone from which most higher plants had been eliminated. Principal changes occurred at exposures in excess of 1000 R/day. Coefficient of community and percentage similarity dropped to 50 per cent of control at about 2250 R/day. Although diversity remained approximately constant or increased slightly at the highest exposures, there was a tendency toward replacement of eucaryotic forms by procaryotic forms at exposures in excess of 1000–2000 R/day. The soil algal community appears to be more resistant than communities of higher plants and to have about the same sensitivity as the lichen community of the oak-pine forest.

Se estudiaron los efectos de la radiación gamma en la germinación de la variedad del ñame (D. alata) Florido cultivado en Puerto Rico y en los cambios químicos que tienen lugar en el tubérculo. La radiación con dosis de 7.5 Krad no afectó aprobablemente su composición y prolongó por 4 meses más el período de inactividad del ñame. Se sugiere una dosis de 7.5 Krad como la óptima para inhibir la germinación de los tubérculos del ñame de esta variedad. Esto hace posible que haya disponible ñame de buena calidad fuera de temporada. Las pérdidas en peso fueron relativamente bajas y el sabor del tubérculo muy aceptable.

The shape of survival curves for several mammalian cell types has been studied by assessing the “recovered dose” (early recovery) for different sizes of the fractions. The following “gross” end-points have been used: skin reactions and intestinal death in mice, tumour regression, gross skin and mucosal reactions in patients. The increase of dose necessary to attain the chosen biological effect has been determined when a single irradiation dose Ds is split into two equal doses 2Di or when N fractions (N × Ds) are “split” into 2N equal “subfractions” (N × 2Di); i is the interval between the two “subfractions” Di and the overall treatment time is kept constant. From the data obtained conclusions are drawn about the shape of cell survival curves in the low dose region and some implications for fast neutron therapy are discussed.

The sensitivity of Trichoplusia ni (Hubner) eggs to gamma irradiation depended upon age and dose: no hatch occurred when 0- to 24-h-old eggs were exposed to 4 krad, 24- to 48-h-old eggs were exposed to 30 krad, or 48- to 72-h-old eggs were exposed to 70 krad. Also, when 24- to 48-h-old eggs were treated with 15 and 20 krad, none of the larvae pupated, but when they were treated with 10 krad, 6% pupated; even when these eggs were exposed to only 4–5 krad, the percentage that pupated, that emerged as normal adults, or that mated was lower than in the control. There were little differences in results between eggs irradiated when 24–48 hand 48–72 h old. Eggs 48–72 h old irradiated with 1.5–3.5 krad produced females that were more sterile than similarly exposed males, but the sterility was not sufficient to permit the use of the females in a sterile-insect release program. All Fl progeny of parents from treated eggs were fertile

Populations ofTribolium castaneum(Herbst) exposed to sublethal doses of irradiation (0.5–4.0 krad) each generation for as many as 25 generations had decreases in reproductive capacity and increases in sterility that were positively correlated with the size of the dose per generation, but not with the number of ancestral generations treated. Exposure of the selected populations to an acute dose of irradiation (2.0 krad) revealed no increase in tolerance to irradiation even after 25 generations of selection. Radioresistant populations would probably not arise from fertile survivors of irradiation disinfestation of bulk grain.

Presence of Formic Acid in Irradiated Maize Starch. Formic acid occurs in relatively large amounts during gamma irradiation of maize starch (100 μg/g/Mrad, in oxygen). It represents the main part of radio-induced free acidity. We determined the influence of several parameters: irradiation conditions (dose, dose rate, temperature, surrounding gas), storage temperature, starch characteristics (moisture, impurities), heat treatment. A formation process is prosposed.

Soybean ( Glycine max L. Merrill cv. Hill) plants in the unifoliolate leaf stage were subjected to various total doses of 90 Y beta and 60 Co gamma radiation, separately and in combination, at dose rates of either 8·4 or 17·8 rads/min and grown to maturity under outdoor conditions. Biological effects were evaluated on the basis of survival, height, lateral growth from cotyledonary node, and vegetative and seed yield. Survival and height were dependent on total dose and independent of dose rate and the beta/gamma component of total dose. Survival was slightly affected with total dose, and a dose of 2·8 krads reduced height to approximately 50 per cent of control. Lateral growth and vegetative and seed yield were dependent on total dose, dose rate, and the beta/gamma component of total dose. For lateral growth, especially at 2·4 krads, as the dose rate and beta component of total dose increased, the per cent of plants with lateral growth increased. Also, especially at 8·4 rads/min, as the beta component of total dose increased, the length of lateral growth increased. For the 50 per cent reduction level, with the exception of seed yield at 17·8 rads/min where the beta and gamma radiation were equivalent, gamma radiation was approximately 1·2-times more effective than beta radiation for both vegetative and seed yield.

An experiment was conducted to test the influence of continuous γ-irradiation over a wide range of exposures throughout one life cycle on inducing chlorophyll-deficient mutations in barley ( Hordeum vulgare ). 200 seeds per treatment were planted at various distances from the radiation source. Treatments ranged from 0.17 R/day (16.5 R total exposure) to 23.2 R/day (2240 R total exposure). The plants were exposed 20 h per day from time of emergence until harvest (96 days) and the apical spikes harvested from each surviving plant. 20 seeds (at random) from each spike were removed and bulked with those from other spikes within the same treatment to make up the M 1 population. Seeds from non-irradiated plants were also included as a treatment. Up to 5 spikes were harvested from each M 1 plant, planted in greenhouse benches, and M 2 seedlings scored for chlorophyll-deficient mutants. M 1 plant survival and reduction in seed set were approximately the same regardless of the treatment. The frequency of mutations per 10 000 M 2 seedlings from 1.3 for the non-irradiated population to 4.3 for progeny of plants receiving 0.17 R/day. This frequency remained about the same through 1.45 R/day. At 3.17 R/day, the frequency increased to 7.0 and was 45.4 at 23.2 R/day. Although there appears to be a plateau and the low exposures, it is not possible to determine the exact shape of the dose response. A mathematical model with an equation of the form Y = Be cx2 and also a linear-linear model were used to summarize the data. The mutation spectrum from all treatments was 70.6% albina, 17.6% viridis and 11.7% others.

Germination of spores of the toxinogenic organism Aspergillus flavus NRRL-3145, previously exposed to specific gamma radiation levels, resulted in a greater production of aflatoxins B1 and B2 follo...

A possibility of the application of the pruning techniques for the isolation, fixation and propagation of wholly mutant plant from a small sectorial mutation induced by gamma irradiation on Begonia rex has been investigated.Among the irradiated Begonia plants, variety‘Winter Queen’, partially changed plants each having a small green chimeric mutation with a number of small silver- white spots on leaf were found and one of these plants was employed throughout the present experiments (Fig. 1).For extending and fixing the mutation, this plant was subjected to repeated cutting-back, layering and division in order to accelerate the development of axillary or adventitious buds and to grow them up to the shoots having the wider mutated area (Figs. 2-4). After the application of these techniques, the wholly mutated shoot was finally obtained (Fig. 4). This changed shoot was layerd and grown to the wholly changed plant (Fig. 5). The leaf color of new plants was green with a number of small silver-white spots as that of the original small sector (Figs. 6 and 9, and Table 1). The procedures of these experiments are illustrated in Figs. 7 and 8.From this investigation, it is suggested that the combination of irradiation and various pruning techniques can be useful in the breeding of horticultural crops, which are propagated vegetatively, under ordinary cultural conditions.\

Results of electron scavenging experiments for gamma irradiation at 4 K are reviewed. An anomalous increase in the scavenging efficiency at 4 K is discussed. Intermediate anions which have very short lifetimes at usual temperatures are very stable at 4 K. As an example of these anions, the optical absorption spectrum of the benzyl chloride anion is described.

Radiolysis products resulting from the deamination pathway were isolated and identified after irradiation of cytosine by gamma rays in neutral aqueous solutions. They were identical to those identified in uracil radiolysis i. e. 5,6-dihydroxy-5,6-dihydro-uracil (cis and trans forms), iso-dialuric acid, alloxan, 5-hydroxy-hydantoin, parabanic acid and oxaluric acid. The absence of 4,4′-di-iso-barbituric acid, alloxantin or iso-barbituric acid could be explained by the good stability of uracil glycols. The identification of buiret proof of potential degradation mechanisms different from these involving of the free radical attack on the 5,6 double bond. Gamma Irradiation of Cytosine in an Aerated Aqueous Solution, I

Gamma irradiation of lithium acetate dihydrate single crystals at room temperature reveals initially an intense ESR signal due to CH2CO−2 radicals. On standing, these radicals disappear and RCHCO−2 radicals are formed. UV and IR absorption spectra of irradiated crystal samples are discussed and correlated with the postulated CH2CO−2 and RCHCO−2 radicals.

Long-term effects of continuous gamma-irradiation with a dose-rate of 6 R/day were studied of mouse ovaries which had been irradiated during whole reproductive period, namely from conception until adult age. In the non-irradiated control group age-related changes were observed in their ovaries from 35 to 400 days of age. In the irradiated group, severe histopathological damages were detected in the ovaries. At 35 to 65 days of age, only a few abnormal oocytes were counted in their ovaries. All the females had permanent sterility (the accumulated dose of 330R), and ovarian tumours appearred at early ages (120 days old) as compared to controls (400 days old). The irradiation experiments for a limited period of mice's life-span showed that the irradiation during the suckling period (from birth to weaning) induced a permanent sterility, while the irradiation during the foetal period or the weaning-juvenile period resulted in a partial deletion of oocytes and a partial decrease of ovary weight.

The radiation energy absorbed in solutions of phosphorus-32, iodine-125 and -131, mercury-197 and -203 was calculated and tabulated for various time of storage. The influence of geometrical shape of solutions was also evaluated. An experimental verification of calculations was carried out for solutions of iodine-131, the good agreement was obtained. The possibilities and limitations of the use of external gamma irradiation for estimating the self-radiation effect were discussed.

A dosage of 0.5 M rad was found sufficient to eliminate three species of Salmonella in smoked lake whitefish (Coregonus clupeaformis) regardless of the stage of processing at which steaks were inoculated with the bacteria. All three species survived smoking at temperatures up to 167 F. The dosages required for elimination of the bacteria when steaks were inoculated at various stages of processing were: before freezing at 0 F for 48 hr, 0.4 M rad for S. give, 0.3 for S. typhimurium, and 0.2 for S. java; before brining at 60 Salometer for 25 min, 0.4, 0.3, and 0.3; after smoking, 0.5, 0.4, and 0.35. Salmonella give was more resistant to heat than the other two species.

The average longevity of adult Laspeyresia pomonella (L.) was extended 2.1-7.3 days when mature pupae of either sex were treated with 25, 30, 35, 40, or 45 krad of gamma radiation. The longevity of males treated as adults was unaffected by 25, 35, or 45 krad but was increased 0.8-2.0 days by 30 or 40 krad. The longevity of females treated as adults was unaffected at 25 or 45 krad, but was increased 2.2-6.2 days by a treatment of 30, 35, or 40 krad. The number of eggs deposited by females from treated pupae was not determined, but among females irradiated as adults and allowed to mate with normal males, the number of eggs deposited was significantly reduced. Reductions in numbers of eggs deposited by treated females ranged 2- to 18-fold below that of untreated females mated with untreated males. Among normal adult females allowed to mate with treated males, the effect of treatment on oviposition was not significant.

The effects of acute doses of γ-irradiation ranging from 250 to 2000 rad delivered to wheat at various stages of growth were investigated. Before tiller initiation was complete, doses of 2000 rad caused premature death, while 750–1250 rad led to the number of tillers and ears being increased by factors of up to three. Some enhancement of tillering was also caused by 500 rad delivered at the 2-leaf stage. These effects were shown to depend on the doses received by the apical meristems; increased tillering was always associated with some retardation in the development of the main axis. In contrast when plants were irradiated after tillering was complete neither the number of tillers nor the number of ears was affected by doses up to 2000 rad. The weight of seed per plant was unaffected by exposure to 500 rad. The effects of 1000 rad were variable, but on average yield was reduced to about 60 per cent of that in the control; no consistent relationship was found between the effects of this dose and the age when plants were irradiated. In contrast the effects of 2000 rad varied greatly during the growing season; exposure, before tillering was complete, inhibited all ear development, at the time of ear emergence yield was reduced to less than a quarter of that of the controls; whereas when irradiation was deferred to the time of anthesis or later yield was much less affected. All treatments which reduced the yield of seed per plant also caused the weight per seed to be smaller.

Plants of spring barley were exposed to acute doses of γ-irradiation, ranging from 250–2000 rads at various stages of the life cycle. Although there were quantitative differences between experiments, sensitivity to radiation was always greatest in plants irradiated at the vegetative stages of growth. Doses of 1000–2000 rads delivered at the 2- and 4-leaf stages of growth caused premature death, whilst plants exposed to these doses at the later stages survived. Lower doses delivered at the time of ear emergence or earlier caused the number of tillers to be increased by up to twice that of the control plants, although ultimately the yield of grain was reduced to an average of over 50 per cent. The severe reduction of yield in these plants was due to marked decreases in the number of ears and of the weight of individual seeds. Radiation had no effect on tillering in plants irradiated at anthesis or later and caused only a small reduction of seed yield. In studies on winter wheat and spring oat, similar though less severe effects of radiation were observed. Possible causes of the differences in the extent of radiation injury between these crops and those of wheat are discussed.

Mice exposed to 12, 24, 43, and 74 r gamma radiation per day were observed with reference to the following parameters and compared with controls: testis weights, testis areas in section, tubular areas in section, Chalkley counts on cell types and on empty space within and surrounding the tubules, and srecial counts of type A and intermediate spermatogonia, type B spermatogonia, and leptotene spermatocytes. The results show that under prolonged gamma irradiation testis weights decrease concomitantly with the loss of spermatogenic cells from the tubules. Measurements of cross sectional areas of testes and tubules were found to decrease along with testis weight. There is an increase in the relative area occupied by the Sertoli cells surviving the gamma doses, because of decreasing tubular dimensions. Spermatogonia under 12 and 24 r/day survive with low levels of mitotic activity. At higher intensities they do not survive beyond 2000 r cumulated dose. Spermatocytes vanish due to lack of recruitment as well as through irradiation death. Their disappearance time is intensity-dependent, The same is true of spermatids and spermatozoa. (auth)

Pupae of the tobacco budworm, Heliothis virescen (F.), were irradiated with Cobalt-60 gamma rays about 2 days before adult emergence. Male moths were 99% sterile after a dose of 35 kilorads. Female moths produced very few eggs when the dose was greater than 35 krad, though there was some egg hatch at this dose level. The emergence and lifespan of both sexes were reduced by sterilizing doses. The initiation and length of the oviposition periods for females mated with either treated males or untreated males were similar. However, females crossed with treated males produced significantly fewer eggs. Virgin females laid eggs, but their oviposition began later and was shorter than that of females crossed with males. The average lifetime production of eggs for single pairs of control moths was about 800 eggs, though some females did produce more than 1600. When the sterility data from irradiated males were plotted, the resulting dose-response curve appeared to be sigmoidal. Cytological observations on spermatogenesis indicated that sperm were present in the testes of the pupae at the time of irradiation.

Acceptability scores for irradiated hot-smoked whitefish ( Coregonus clupeaformis ) were significantly higher (P Fish from a single catch were smoked commercially, sampled, frozen and withdrawn from —40° C storage at 28, 21, 14, 7 and 0 days before examination. Gamma irradiation was applied after thawing, immediately before refrigerated storage. The sensory evaluat on was replicated three times. Scoring of acceptability, flavor and texture by eight semitrained judges using the multiple comparison difference test showed that flavor scores followed the same pattern as the acceptability scores. No effects of either irradiation or storage were apparent from texture scores. No differences in sensory qualities were found between fish irradiated at 0.3, 0.4 and 0.5 megarads.

(1) 米国産輸入トウモロコシおよびマイロにおいて,非照射試料でも照射試料でもそのミクロフローラを構成する主要な糸状菌はAspergillus属であり,細菌はBaoillus属であって,酵母菌と放線菌はほとんどみられなかった.糸状菌ではA. restrictus groupとA. glaucus groupが非照射試料での全糸状菌のほとんど全部をしめた. (2) A. glaucus group strain No. 6801の形成する被子器のL値は110Kradであり,子ノウ胞子の35Krad,分生子の7Kradに比べるとかなり大きく,D10値についても被子器では120Kradであり,子ノウ胞子の2.5倍,また分生子の3.6倍であった. (3) 分生子のγ線感受性において,A. glaucus group strain No. 6801の場合にはリン酸緩衝液中でも穀粒上でも差はみられなかったが, A. restrictus group strain No. 6802では穀粒に付着した状態の方が抵抗性が大きかった. (4) これら好浸透圧性の両菌種の穀粒上での完全殺菌線量を実験室結果から推定すると,マイロでは540Krad,トウモロコシでは1550Kradであった.

When adult Pectinophora gossypiella (Saunders) irradiated with a substerilizing dose (10 krad) of gamma irradiation were released in field cages and in a 5-acre field of cotton, larvae with chromosomal aberrations that could cause sterility in the adult stage were found in both cages and the field. Also, when 3500 partially sterile moths (mixed sexes) were released in a 1/200-acre cage over a 7-week period, sufficient larvae did not develop to cause significant damage to the cotton. Of 743 males recaptured after releases in the field, 34% were recaptured on the 2nd day following release.

Late 4th-stage larvae of Pectinophora gossipiella (Saunders) were treated with Cobalt-60 gamma irradiation at doses of 0-32 krad. Forty percent of the treated male larvae showed chromosomal damage at 2 krad. At 5 krad or higher, 100% of the examined spermatogonial divisions showed chromosomal damage. The percentage of morphologically normal adults mating was reduced by 85% or more at doses above 4 krad for males and 2 krad for females. Some F1 progeny were produced from crosses between treated and control insects although numbers were generally reduced as compared with controls. Sterility was present in F1 larvae, and egg production was reduced. Chromosomal aberrations present in the F1 progeny occurred also in the F2 but at a lower rate.

Exposure of toxigenic Aspergillus flavus spores to specific gamma radiation levels induced higher yields of aflatoxin G1 from the developing cultures per unit of time, while nontoxigenic A. flavus ...

Experiments were conducted on the effects of acute X-, and chronic γ -irradiation of different stages of flower development in Cosmos bipinnatus with particular reference to the induction of somatic mutations. Clone I was heterozygous both for flower colour and flower type, while Clone II was heterozygous for flower colour only. Stage of flower development was controlled by giving short-day treatment prior to irradiation. Plants were irradiated with 2 kR of X-rays at the vegetative stage and after 10, 20 and 27 days of short-day treatment. For chronic irradiation two groups of growing plants of Clone I were transplanted to the gamma field, and received a total exposure of about 3 and 2 kR of γ -rays. Somatic mutations appeared as narrow streaks to wide sectors of red, light pink and white colours on a background of normal colour of the ray florets. The maximum number of flowers with mutations was observed in Clone I after 20 days of short-day treatment. The relative frequency of flowers with colour mutations varied with the clone and stage of flower development at the time of irradiation. Narrower sectors of mutated colour with a higher frequency were observed at advanced stages of flower development; wider sectors of mutated colour with a lower frequency were induced at vegetative and younger stages of flower development. The number of mutations decreased as greater time elapsed between irradiation and flowering but the frequency of mutant sectors of larger size increased. Various types of physiological injuries were observed. The most commonly observed morphological abnormality was the dissection of ray florets. Mutation rate was very low after chronic γ -irradiation as compared with the acute X-irradiation.

Gross fission products may one day be cheap and plentiful enough to allow them to be used for large-scale industrial pasteurization. Some of the effects of gamma rays from a 60-curie cobalt60 source on beer and associated materials are described. The dosage necessary to pasteurize pulp-filtered beer was found to be about 55,000 roentgens, but such an exposure was accompanied by undesirable changes in flavour and odour. At the same time, there was a loss of colour and a reduction in the Indicator Time Test value. The origin of the off odour has been investigated, and the results of irradiation have been compared with those of the melanoidin reaction and the phenomenon of sun-struck beer.

Description of the design of a mobile gamma irradiation unit capable of processing 1000 lb/hr of field products at radio-pasteurization doses up to 225 000 rads. The mobile irradiator uses a 128 000 C cobalt-60 source. It consists of a quadrant irradiator system, a lead shielding cask, hydraulic system, refrigeration and ventilating system, instrumentation, conveying system, etc., mounted on a trailer bed which can be moved using a standard trailer tractor.

After gamma irradiation of barley seeds, a comparison has been made between the chlorophyll-mutant frequencies in X1 spikes that had multicellular bud meristems in the seeds at the time of treatment (denoted as pre-formed spikes) and X1 spikes having no recognizable meristems at the time of treatment (denoted as post-formed spikes). The task was attempted in two ways. First, comparisons were made between plant groups with different numbers of tillers. This analysis revealed no significant differences. Secondly, we compared the mutant frequencies of spikes ranked within each X1 plant according to their number of flowers, a ranking which was shown to reflect the embryological status of the spike. In this comparison it was found that (a) the frequency of mutated X1 spikes is larger by a factor of 1·5–2 in pre-formed than in post-formed spikes, (b) the frequency of mutated X2 plants among all recovered X2 plants is the same in pre-formed and post-formed spikes, and (c) the frequency of mutant X3 plants in mutated X1-spike progenies (the segregation frequency) is lower by a factor of almost 2 in pre-formed than in post-formed spikes.

SummaryThe influence was studied of changes of the bacterial host strain on the course of inactivation of Staphylococcus phages A/5 and ϕ131 after u.v.-irradiation, gamma-irradiation and photodynamic inactivation by AO. Effectiveness of phage plating was alike on all the host strains used. An influence of the various bacterial host strains on the survival of inactivated phages was found for u.v.-irradiated phages only. The bacterial host strains could be divided into strain groups having a favourable effect on the inactivation course of u.v.-irradiated phages, i.e. increasing the number of surviving phage particles, and into bacterial strains which may further reduce the survival of inactivated phage particles. The possible presence of repair mechanism in Staphylococcus bacterial cells is discussed.

Organic acids were measured in serum from sheep that had been exposed to neutron—gamma irradiation, air blast, or both to determine which concentrations change after experimental injury. Samples were directly analyzed by partition chromatography and indicator titration. The semiautomated instrument efficiently separates mixtures of monocarboxylic acids. Monocarboxylic acids in serum seem to be sensitive indicators of biological injury. Survey experiments showed that lactate and propionate accumulate in sheep serum after severe air-blast injury, but only propionate after irradiation. Propionate-loading studies suggested that the utilization of injected propionate is impaired, to various degrees, in fasting, irradiation, and air blast. However, presumptive impairment of propionate utilization occurred earlier in sheep exposed to irradiation and blast than in only irradiated animals, and earlier in irradiated animals than in fasting controls. Air blast exposure resulted in effects of only borderline significance.

New data have clearly confirmed the earlier finding that specific locus mutation rates obtained with chronic gamma irradiation of spermatogonia are lower than those obtained with acute x-rays. Since this result is in contrast to classical findings for Drosophila spermatozoa, and apparently contradicts one of the basic tenets of radiation genetics, it was important to determine what factors were responsible for it. Experiments undertaken for this purpose reveal the following: (i) the lower mutation frequency is due mainly to difference in dose rate of radiation, rather than quality; (ii) a dose-rate effect is not obtained in experiments with mouse spermatozoa, confirming classical findings for spermatozoa, and indicating that the explanation for intensity dependence in spermatogonia resides in some characteristic of gametogenic stage; and (iii) a dose-rate effect is found not only in spermatogonia but also in oocytes, where cell selection is improbable, indicating that the radiation intensity effect is on the mutation process itself. A threshold response for all mutations in spermatogonia and oocytes is not a necessary consequence of the findings. Plausible hypotheses consistent with the present results can lead to other predictions. From a practical point of view, the results indicate that the genetic hazards, at least under some radiation conditions, may not be as great as those estimated from the mutation rates obtained with acute irradiation. However, it should not be forgotten that even the lower mutation rates obtained with the present intensity levels are still appreciable (16).