Heritable protein variants induced by exposure to ethylnitrosourea: heritability, subcellular location, and tissue distribution

The heritability, subcellular location, and tissue distribution of liver protein alterations found in the two-dimensional electrophoresis patterns of 4 offspring from male mice treated with N-ethyl-N-nitrosourea (ENU) were studied. Mice homozygous for each of the 4 ENU-induced protein variants were found to be viable and fertile, although the number of homozygous offspring from crosses between heterozygous carriers of one variant (ENU 2) was less than that expected for a nondetrimental trait. Two of the proteins altered by ENU-induced mutations were associated with the crude mitochondrial fraction, another was found predominantly in the microsomal fraction, and the fourth was associated with the mitochondrial, microsomal, and cytosol fractions. All of the ENU-induced mutations affected proteins that were not liver-specific; i.e., the proteins were found in other tissues in addition to the liver.     

Organogenesis of the pituitary, adrenal, and lung at birth in the wallaby, Macropus rufogriseus

The ultrastructure of the pituitary, the adrenal, and the lung was examined in the newborn wallaby, Macropus rufogriseus. Tissue from six wallaby neonates (less than 8 hr of age), two near-term fetuses (26 days after removal of suckling pouch young [RPY]), and a two-day-old pouch young was examined; and tissue levels of cortisol in the adrenal glands of five neonates and a near-term fetus (26 days) were measured by radioimmunoassay. At birth the adenohypophysis comprised the bulk of the pituitary gland. The pars distalis was well vascularized and many cells contained electron-dense, membrane-bound granules. The adrenal glands lacked specific zones but comprised two distinct populations of cells. The cytoplasm of one cell type contained electron-dense, membrane-bound granules, similar to those observed inside catecholamine-secreting cells of the adrenal medulla; the other cell type possessed large amounts of smooth endoplasmic reticulum and mitochondria with tubulo-vesicular cristae. These features are characteristic of cells which are actively synthesizing steroid hormones. The concentration of cortisol was 0.58 ng/adrenal in the wallaby at birth. The fetal lungs near term were at the glandular stage of development, and epithelial differentiation of type I and type II pneumocytes was imminent although attenuation was not evident. The canalicular neonatal lung did not contain true alveoli, but type II pneumocytes contained osmiophilic lamellar inclusions of surfactant. The fetal pituitary and adrenal are functional at birth and are thus capable of initiating parturition and of influencing lung maturation in the fetus.     

Cloning and characterization of the platypus mitochondrial genome

The vertebrate mitochondrial genome is highly conserved in size and gene content. Among the chordates there appears to be one basic gene arrangement, but rearrangements in the mitochondrial gene order of the avian lineages have indicated that the mitochondrial genome may be more variable than once thought. Different gene orders in marsupials and eutherian mammals leave the ancestral mammalian order in some doubt. We have investigated the mitochondrial gene order in the platypus (Ornithorhynchus anatinus), a representative of the third major group of mammals, to determine which mitochondrial gene arrangement is ancestral in mammals. We have found that the platypus mtDNA conforms to the basic chordate gene arrangement, common to fish, amphibians, and eutherian mammals, indicating that this arrangement was the original mammalian arrangement, and that the unusual rearrangements observed in the avians and marsupials are probably lineage-specific. Correspondence to: N.J. Gemmell     

Changes in the fine structure of the testicular Leydig cells of the seasonally-breeding bat,Myotis adversus

Summary Leydig cells of the bat, Myotis adversus, have been examined by electron microscopy throughout fourteen months. During the breeding season the Leydig cells become hypertrophied and are characterised by prominent areas of agranular endoplasmic reticulum and numerous small, membrane-bound granules. Microperoxisomes are also observed. During the period of testicular regression. Leydig cell size and the number of membrane-bound granules are greatly reduced. Lipid droplets and dense bodies are more numerous.     

Transformation of mammalian cells by alpha particles.

Mammalian cells in culture have been shown here for the first time to be transformed by alpha irradiation. Mouse embryo (C3H 10T1/2) cells were transformed with 5.6 MeV alpha particles from a Tandem Van de Graaff machine. Malignant tumours were induced following inoculation of the transformed cells into syngeneic hosts. Unirradiated control cells failed to produce tumours. The morphology of the transformed foci was similar to that obtained by X-rays and chemicals but different from virally transformed cells. The transformation frequency increased approximately as the cube of the dose to a maximum of about 4 per cent ofthe surviving cells which occurred between 1.5 and 2.5 x 10(7) alpha particles per cm2 (205-342 rad). It appears that alpha particle irradiation may exert a direct effect on the genome of the cell to produce malignancy without any external immunological or hormonal influences.