Late ultrastructural changes in the myocardium and myocardial microvasculature in the B6CF/sub 1/ mouse have been compared through 24 months following total-body exposure to fission spectrum neutrons or /sup 60/Co-..gamma.. rays. Radiation treatment, initiated when the mice were 4 months old, included single doses of 788 ..gamma.. rad, or 80 to 240 neutron rad, and fractionated doses of 823 or 2690 total ..gamma.. rad or 20, 80, or 240 total neutron rad (24 fractions given in 23 weeks). Early damage to myofibers and capillaries of the heart were previously described to be most severe at 30 to 90 days after a single exposure. Ultrastructural findings at later times after initiation of irradiation are compared here with the effects of normal aging. At 18 and 24 months into the experiment (mice 22 and 28 months of age), only minor aging changes were noted. Extracellular areas showed minimal increases in proteoglycan matrix and collagen fibers, while myocytes had increases in inclusion bodies and lipid droplets. Late (18 and 24 months) radiation damage seen at the ultrastructural level included myofibrillolysis, capillary degeneration, and increased accumulations of debris and lipids. The effects of 240 neutron rad, either single or fractionated, were more severe thanmore » those of a fractionated dose of 2690 ..gamma.. rad. Matrix (proteoglycans) accumulation and fibrosis were more prominent in neutron-than in ..gamma..-treated animals. Myocardial changes generally corresponded to the degree of coronary artery damage previously reported, although there was greater individual variation. The excess fibrosis and matrix accumulation observed in neutron-treated animals agree with previous reports of a similar reaction following neutron therapy.« less

A high incidence of leukemia in adult beagle dogs was induced by continuous whole-body exposure to low doses of 60Co gamma irradiation. At 5, 10, and 17 R per 22-hr exposure day, 20 animals of 53 died of either myelogenous leukemia (15 of 20) or erythroleukemia (5 of 20); the latter occurred only at 5 R/day. Consistent preclinical changes occurred in the peripheral blood, including (1) a partial recovery from an initial severe leukopenia, (2) a prolonged accommodation-to-irradiation phase, and (3) marked oscillations in platelet values in the preleukemic period. In the terminal condition the dogs were severely anemic, thrombocytopenic, and commonly leukopenic. Peripheral blood buffy-coat preparations contained circulating “blast” cells and juvenile forms. Abnormal erythrocyte and platelet morphology was consistently present. The bone marrow was altered most severely; other organs showed variable degrees of leukemic infiltration and proliferation and loss of normal tissue architecture. The marrow was hyperplastic with little or no fat remaining. Differential marrow cell counts showed increased numbers of immature cell forms. Myeloid: erythroid (M:E) ratios ranged from 2.6:1 to 61.5:1 in the granulocytic leukemias, and 0.2:1 to 1:1 in the erythroleukemias. Juvenile leukemic cells (both circulating and tissue forms) displayed a number of distinctive cytologic features, including asynchronous patterns of nuclear–cytoplasmic maturation, increased incidence of nuclear clefts, coalescence of cytoplasmic granules, and bizarre arrangements of endoplasmic reticulum. These experimentally induced canine leukemias have many hematologic and cytologic features in common with both spontaneous and radiation-induced leukemias of man. Thus, they may provide a useful model for the study of human leukemia.

Microvascular changes in the pinna were studied in vivo and recorded photographically over a period of 12-18 months after irradiation of 4-month-old B6CF$sub 1$ mice. Radiation treatment consisted of total-body exposure to 240 rad fission neutrons either in a single dose or in 72 fractions of 3.3 rad each over 24 weeks. Neutrons with a mean energy of 0.8 MeV were supplied from the JANUS reactor. A fission neutron dose of 240 rad is below the acutely lethal range. At 20 months after treatment, after a series of in vivo observations of the microvasculature, animals were sacrified for study of changes in vascular fine structure in the pinna. Blood vessels were selected from regions that had been identified on photomicrographs. After single or fractionated neutron exposures, the surviving functional blood vessels had relatively minor late ultrastructural changes in the endothelium. Many arterioles, however, showed extensive degenerative changes in the subendothelial intima (including the elastica) and marked necrosis of smooth muscle. Accumulations of fibrillar material and debris frequently occupied much of the media and replaced regions of smooth muscle lost by focal necrosis. Arteriolar degeneration and sclerosis appeared to be more extensive after fractionated treatments. Corresponding small veins or venules alsomore » showed smooth muscle degeneration and increased fibrosis, but changes were somewhat less severe than in arterioles. Capillary changes included a thickened basal lamina and increased fibrosis. Endothelial swelling and increased vacuolization were sometimes observed. (auth)« less

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.

The structure of a cilium in Nyctotherus ovalis is that usually found: two single central filaments surrounded peripherally by nine double filaments; the whole is encased in a ciliary membrane continuous with the pellicle. The two central filaments end in a single enlarged bulb just above a septum, located at about the level of the pellicle, whereas the nine double filaments extend inward to form the cylindrical basal body, which is open at its inner end. Inside the basal body are granules àrranged in rows parallel to its sides. These granules may have significance in the origin of new basal bodies as well as in the outgrowth of new cilia. The latter may have been observed in a few instances. Parallel to the pellicle are two series of fibrils, one median and one inner, connecting adjacent basal bodies. Fibrils extend from the inner end of each basal body, these converge and extend deep into the ectoplasm, often becoming lost in a pattern of equilateral triangles, arranged to form hexagons. These features are clearly seen in the peristomial membranelles, where the basal bodies of the four rows of cilia are close together, separated from adjacent membranelles by a protoplasmic shelf and supported by a mass of fibrillar material comprising the peristomial ectoplasmic band. This broad band extends to the inner end of the peristome whence it returns along the opposite wall as a narrow mass of fibrillar ectoplasm without basal bodies. Peripherally the fibrils are condensed into fan‐like bundles; internally they often form a network of equilateral triangles arranged to form hexagons, with corpuscles at the intersections. Trichite‐like structures are also found in the peristomial groove and tube; these are connected to both the basal bodies and the fibrillar network.The functions, origin and development of this complex infraciliature during fission constitute one of the yet unsolved morphological problems in such complex ciliates.

SYNOPSIS. Materials within the endoplasm of both the protomerite and deutomerite may be displaced and stratified by ultracentrifugation. Animals are not killed by this treatment, and in time a redistribution of stratified materials may occur. The electron microscope reveals numerous ultramicroscopic folds in the surface envelope which is composed of 3 membranes; the outer and middle cover the surface of the folds while the inner one continues as a smooth membrane over the ectoplasm. The contact surfaces of animals in syzygy do not show the small folds to be interlocked; instead, they are in fold‐to‐fold contact. Numerous relatively dense bodies which appear to be filamentous are sometimes observed immediately underneath or within the middle or inner membrane. Within the ectoplasm is an ultramicroscopic net‐like fibrillar structure much denser than the surrounding cytoplasm. This system of fibrils is composed of anastomosing elements varying from ∼ 50 to 200 Å in diameter. Certain of the larger fibrils are directly attached to the surface envelope at positions between the folds. A second filamentous structure within the ectoplasm appears to be tubular. Elements of this system also appear to join and penetrate the surface envelope by means of pores.A large amount of gelatinous secretion forms at the surface of the sporont; as it glides forward a trail of mucous is left behind. The actual mechanism involved in the gliding movement was unobserved, but evidence is lacking to support the view that the gliding movement is engendered by posteriorly directed “jets” of mucus.

The pharyngeal gland cells of the worker honeybee function as unicellular glands; each is possessed of a relatively long, sacculated and unbranched ductule. The ductule takes a sinuous course around the nucleus in a position more or less midway between it and the cell membrane. Electron micrographs reveal the wall of the ductule to be composed of an inner relatively dense and incomplete layer arranged as circular bands or spirals, so that in sections it appears as plates of relatively dense material; in addition, there is a middle granular layer as well as an outer less well-defined membrane layer. The secretion collects in relatively large masses about the ductule and probably diffuses into its lumen through that portion of the granular layer free of the inner bands or plates. Because the density of the inner layer of the ductule and that of the epicuticle appear similar, it is suggested that they are probably homologous structures. If this be true, diffusion of the secretion through the wall of the ductule must take place in the interval between the plates of the inner layer. The pharyngeal gland cells are highly basophilic and possess a relatively large amount of endoplasmic reticulum. Tubules of the endoplasmic reticulum are sometimes entrapped within the secretion masses, and, in which case, they are probably discharged from the cell along with the secretion. Mitochondria and Golgi bodies were also observed in the pharyngeal gland cells in addition to intracellular tracheoles.