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PubMed1962

Electron microscopy of lysosome-rich fractions from rat thymus isolated by density-gradient centrifugation before and after whole-body x-irradiation.

Fractions from rat thymuses were isolated by sucrose density-gradient centrifugation, before and after 1000 r whole-body x-irradiation, and examined by electron microscopy. Cytochrome oxidase and acid phosphatase activities of these fractions were tested as well. Electron-opaque bodies with diameters ranging from 0.10 to 0.35 micro, with a mean of 0.25 micro, were found in fractions having high acid phosphatase activity, while the fractions rich in cytochrome oxidase consisted mostly of mitochondria. After irradiation, there was an increased ratio of dense bodies to mitochondria. These particles are considered to be lysosomes similar to those identified in other rat tissues. Their relationship to the mitochondria is discussed.

Animals↗
PubMed1962

The effect of a medium dose (430 roentgens) of x-ray irradiation on resting cells of the liver.

The mitotic activity of regenerating liver cells after a single dose (430 r) of x-ray irradiation was studied. In every group of the experimental animals (white rats), the mitotic activity (mitotic index) and the number of abnormal mitotic figures were determined. The results indicated that resting cells irradiated a short time before mitotic activity showed reactions similar to those of cells irradiated during mitotic activity. The disturbances in the irradiated mitotically active cells were only quantitatively different from those in the irradiated resting cells. The disturbances in the irradiated resting cells depended upon the time interval between the irradiation and the beginning of mitotic activity stimulated by partial hepatectomy. It was found that the shorter the time interval, the more pronounced were the disturbances and the more similar they became to those of irradiated mitotically active cells. Conversely, the longer the time interval between the irradiation and the beginning of mitotic activity, the less pronounced were the disturbances and the more similar they became to those of the non-irradiated control cells. A discussion is presented as to whether or not the lesions of resting cells caused by a single medium dose of x-ray irradiation are reversible, and whether such lesions are only brought to light by the process of mitosis or whether the process of mitosis renders it possible for these lesions to develop.

Animals↗
PubMed1961

The influence of x-rays on organelle induction an differentiation in grasshopper spermatogenesis.

The effect of x-irradiation on grasshopper spermatogenesis was studied with the aid of light and electron microscopy. The insects were irradiated at the second instar prior to the presence of maturation stages and observed at the last instar and imago stages. Dosages of 100 to 600 roentgens were found to retard the differentiation of the nucleus and mitochondrial nebenkern in spermatids. Evidence is presented that irradiation causes a curtailment and disorganization in the differentiation of the nebenkern from mitochondria. The above doses also induced the formation of supernumerary centrioles, flagellar filaments and acrosomes; nuclear disorganization as well as pycnosis and fragmentation also occur. The nucleus appears to be drawn toward each radiation-induced supernumerary acrosome, with consequent multipolarity of the nucleus. Induction of a set of flagellar filaments is seen only where the centriolar structure is in contact with the nucleus. Details are given of an organelle, heretofore not described, that is composed of anastomosed and interwoven cytoplasmic strands.

Acrosome↗
PubMed1960

Studies on susceptibility to infection following ionizing radiation. V. Comparison of intraperitoneal and intravenous challenge at intervals following different doses of x-radiation.

Ten week old female CF-1 mice were subjected to a single total body exposure of x-radiation in one of the following doses: 300, 400, and 500 r. At intervals thereafter, susceptibility to bacterial infection was determined by intraperitoneal challenge with graded inocula of Pseudomonas aeruginosa. Mice exposed to 400 or 500 r were also challenged by intravenous inoculation. The LD(50) of the test microorganism in each challenge was estimated from the mortality data. Exposure to 300 r caused little increase in susceptibility to this experimental infection. 400 r caused a moderate increase on the 3rd day post-irradiation with return to normal on the 17th. Leucocyte counts (geometric means) following this dose of radiation did not fall below 1200. 500 r caused a marked increase in susceptibility which lasted from the 3rd to 11th day, during which period the leucocyte counts were below 800. On the 20th day, susceptibility to infection was normal, although the geometric mean of leucocyte counts was only 2200. Comparison of mortalities resulting from equivalent inocula introduced by the two routes (intravenous and intraperitoneal) showed no difference in unirradiated mice. However, among mice irradiated with 400 or 500 r, higher mortalities resulted from intravenous inoculation. The difference was found to be due to the establishment of a small focus of infection at the site of intravenous injection as a result of leakage of a minute fraction of inoculum into the perivenous tissues of the tail. Bacterial multiplication occurred in such foci in irradiated (leucopenic) mice, but not in unirradiated mice, nor at the site of intraperitoneal inoculation even in irradiated mice.

Animals↗