X-ray phase imaging of biological soft tissue using a direct-sensing x-ray HARP tube camera.

A HDTV camera having a direct-sensing x-ray high-gain avalanche rushing amorphous photoconductor (HARP) tube was used, for the first time, to acquire x-ray phase maps. The tube can achieve a high sensitivity as a result of the avalanche multiplication process in the HARP target. A beryllium plate, rather than a glass plate, was used as the face plate of the tube to minimize the loss of x-rays due to absorption, and a 15 microm thick HARP target was directly formed on it. In the experiment, the x-ray phase shifts produced by a rat liver were measured using synchrotron x-rays (lambda = 0.0766 nm) and a triple Laue-case (LLL) x-ray interferometer. Interference patterns produced by the sample were observed with the direct-sensing x-ray HARP tube camera. A voltage of 1300 V was applied to the HARP target to give an output signal gain of two. The camera was operated in 1125 scanning-line mode, and real-time images were stored on a workstation at a rate of 30 images/s with an image format of 960 (H) x 1100 (V) pixels. A phase-map image of the sample was successfully obtained using the fringe scanning method and phase unwrapping. The observed phase shifts ranged from 50 degrees to 200 degrees . Trees of blood vessels in the rat liver were clearly depicted without using a contrast agent. The spatial resolution of the x-ray camera was estimated to be better than 35 microm in the vertical direction and 100 microm in the horizontal direction.

Effects of gamma-irradiation on the rejection of transplanted scale melanophores in the teleost, Oryzias latipes.

The effects of gamma-irradiation on allograft rejection in the teleost, Oryzias latipes, were examined at 25 degrees C. The survival of melanophores in the transplanted scale was observed as an index of rejection. Allografts were rejected in non-irradiated fish within 7 days. In the gamma-irradiated recipients (2kR), the grafts were rejected more slowly, but still within 20 days. The gamma-ray effects, however, disappeared almost completely within 25 days after the irradiation. If the same recipient again received transplants, the secondary response occurred clearly and the melanophores were rejected very rapidly. The secondary response was suppressed by gamma-rays if the fish was irradiated just before the second transplantation. Immunologic memory against the first transplants disappeared within 30 days, a period shorter than that of mammals.

Effect of corticosteroids on the thymus of the fish Oryzias latipes.

Morphology and development of the thymus in fish Oryzias latipes was studied in response to corticosteroids. Adult fish were subjected to different concentrations of two corticosteroids, deoxycorticosterone acetate (DOCA) and cortisone acetate (CA). Histology of the thymus and thymocyte counts in treated fish were compared to normal ones. There was no change in histology of thymus due to CA treatment even those subjected to 10 mg/l water which is a lethal dose of DOCA. In contrast, the effect of DOCA at low doses (0.01 and 0.1 mg/l water) was examined and resulted in reduction of thymus volume due to depopulation of thymocytes from the entire gland. Thymus subjected to DOCA at a high dose (1 mg/l water) caused destruction of all thymocytes and reticular cells resulting in complete disappearance of the thymus. There was dose dependent mortality associated with DOCA. The maximum lethal dose was 10 mg/l causing death of all treated fish within a few hours. This information is relevant to the use of CS in fish therapy in response to stress.

Age related changes in morphology of the thymus of the fish, Oryzias latipes.

The thymus of the teleost fish Oryzias latipes is a paired structure found at the dorsoposterior part of the gill chamber. In 3-month-old fish, the thymus shows a great development. The thymus displays atrophy during aging, and the thymus involution continues until 5 years of age. Male thymus shows heavier involution than female thymus of the same age. Emigration of thymus cells takes place at all ages but increases with age.

Effect of gamma irradiation on the reproductive system of the pond snail Physa acuta.

Changes in the survival rate in adults and embryos of the pond snail Physa acuta were studied after acute whole-body gamma irradiation. The LD50 value of the adult snails was about 40 kR. The LD50 values of the embryos irradiated 0 and 1 day after oviposition were about 0.9 and 2 kR, respectively. Histological changes in the ovotestis, the number of eggs laid, and their hatchability were examined in the irradiated adult snails. A fall and a subsequent recovery were observed for these characteristics after irradiation with 8 kR of gamma rays. The relative constitution of the germ-cell populations was greatly changed by the same dose of gamma rays. The proportion of immature germ cells was reduced, and the total number of germ cells also diminished 11 days after irradiation. After depletion, the ovotestis was first repopulated with gonia , and then with oocytes, spermatocytes, and spermatids.

Dominant lethal mutations induced by MMS and mitomycin C in the fish Oryzias latipes.

Males of the fish Oryzias latipes were treated with various chemicals and then mated with normal females. The fertility and hatchability of the eggs laid by the parents were examined, and the dominant lethal effects were estimated. Mitomycin C induced dominant lethals in the fish spermatids and spermatocytes after the males had been treated with concentrations of 2.5 and 25 micrograms/ml. Methyl methanesulfonate (MMS) induced dominant lethals in spermatozoa and spermatozoa and spermatids after the injection of 200 and 400 mg/kg. These results are in good agreement with the results obtained with mice. However, the effects of ethyl methanesulfonate (EMS) were not clear on spermatogenic cells at any stage. We could not recognize any significant induction of dominant lethals by urethanes, bleomycin, caffeine, and two kinds of food-color additives, at least under the present experimental conditions.

Hertwig effect caused by UV-irradiation of sperm of Oryzias latipes (teleost) and its photoreactivation.

When sperm of the fish Oryzias latipes were irradiated with ultraviolet light and allowed to fertilize normal eggs, the so-called "Hertwig effect" was observed, with a dose-dependent decrease in survival rate at low doses (0-27 J . m-2) but a better survival rate at higher dose ranges. Illumination with visible light after fertilization (10-70 min after insemination) showed the existence of photoreactivation (PR), demonstrating that pyrimidine dimers are a lesion in sperm DNA that is mainly responsible for the UV-caused Hertwig effect. Genetic analysis, in which sperm from a wild-type of this fish was used, showed that, after UV-irradiation at the high dose range, male nuclei did not participate in embryonic development (a gynogenetic haploid condition). Embryos having only a maternal set of chromosomes could develop no further than stage 27. Only the visible light during the early part (until around 20-30 min after insemination, at 25 degrees C) of the single-cell stage was effective for PR; illumination thereafter was not.

Dominant lethal mutation rate after gamma-irradiation of the fish, Oryzias latipes.

When laying females or males of the small fish Oryzias latipes were irradiated with gamma-rays and then mated with a non-irradiated partner, the fertility and hatchability of the embryos were reduced as the doses increased. In respect to hatchability (the induction of dominant lethality), the male was more sensitive than the female, and mature sperm were most sensitive among the various stages of spermatogenetic cells. The dose-rate effects on the production of the dominant lethality were observed in spermatogonia and spermatocytes. The inbred strain of the fish, HB-1, was sensitive to gamma-rays. Since the relationship between dose and the decrease in hatchability was almost linear, at least within a limited range, we think that this system would be useful for monitoring mutagenic factors in an aquatic environment.