Early ultrastructural changes of developing oocytes in the dog

Many aspects of the developmental stages of the oocyte of the dog resemble those of other mammalian species. The oocyte of the dog, however, contains large amounts of lipid yolk material. A study of the ultrastructural morphology of early growth and maturation of dog oocytes was undertaken to clarify the nature and appearance of this yolk material. The lipid yolk first appears in early primary oocytes as aggregated dense bodies that gradually fill the ooplasm as the oocyte matures. The site of the yolk's initial appearance is consistently related to a single centriole and often to the lamellae of smooth endoplasmic reticulum that surrounds groups of forming lipid yolk bodies. Dense cortical granule-like vesicles are found to lie deep within the maturing oocyte and often are enclosed within the lamellar yolk space. Granules within this space undergo changes in size, matrix configuration, and vacuolization. These changes suggest a mechanism whereby material is added to the lipid yolk bodies. Light microscope histochemistry for lipid and polysaccharide material is described.     

Early contacts between fibroblasts. An ultrastructural study

Pairs of chick heart fibroblasts have been studied with the light microscope and then fixed in situ for electron microscopy at varying times after they have been seen to make contact with each other. The resultant electron micrographs show that areas of specialisation begin to develop within 20 sec of the contact being made. These specialisations resemble those seen in isolated chick heart fibroblasts where the cell comes close to the substrate and are thought to be areas of adhesion. The development of these areas and their associated microfilaments is described and an attempt is made to correlate this with the stages of the contact inhibition phenomenon.     

An ultrastructural study of the carotid body of horse and dog

Summary Carotid body tissue from horse and dog has been investigated ultrastructurally. Several cell types are recognized: glomus cells which are regarded as chemoreceptors, sustentacular cells which enclose the glomus cells, and nerve fibers.The glomus cells contain electron dense granules which are interpreted as packages of biogenic monoamines. There are both dark and light glomus cells, the former containing more granules and ribosomes. Invaginations of the plasma membranes as well as free coated vesicles are often seen in the cytoplasm of glomus cells. Nerves within the glomus lobules are generally wrapped by sustentacular cells, but nerve endings are also seen in close contact with the glomus cells. Some endings contain synaptic vesicles as well as a great concentration of mitochondria. The corresponding fibers are thought to be efferent. Another type of contact is interpreted as en passant synapses of afferent fibers.The author wishes to express his gratitude to Professor L. Nicander who initiated this project and took most of the micrographs and to Professor Nils Obel and associate Professor Gustav Björk at the Royal Veterinary College for their valuable help with the surgical procedure and to Dr. Martin Ritzén of the Royal Medical College for making the tests for biogenic monoamines.     

Secretory cell activity in the hamster seminal vesicle following castration. A morphometric ultrastructural study

The ultrastructure of hamster seminal vesicle epithelium was studied 7, 14, 21 and 28 days after castration using a stereological approach. The results show that castration promotes epithelial reorganization, mainly characterized by reduced epithelial cell size and number, decreased rough endoplasmic reticulum and Golgi complex, increased lysosomes and lipid droplets, increased apical secretory granule size and number, and increased intracellular secretory products per average epithelial cell. It is concluded that after testosterone withdrawal the secretory activity of hamster seminal vesicle epithelial cells, although reduced, is not abolished, and that exocytosis is relatively more reduced than secretory protein production. We suggest that an extracellular androgen source is responsible for secretory activity not being lost in the epithelial cells of castrated hamster seminal vesicle.     

Early ultrastructural changes in the myocardium following thyroxine-induced hypertrophy

The model of myocardial hypertrophy induced by thyroxine was studied with particular regard to the early ultrastructural changes in fractional volume of the mitochondria and myofibrils, and capillary distribution. Following injections of L-thyroxine (25 mg/kg IP) for 9 consecutive days, rats were sacrificed by vascular perfusion and cardiac tissue samples from the mid-wall zone of the left ventricle were processed routinely for electron microscopy. Heart weight/body weight ratios of thyroxine treated (T) rats showed a significant increase (P less than 0.001) over the ratios in control (C) rats. Likewise, the fractional volume of mitochondria (42%) was significantly increased (P less than 0.001) in the myocardium of T rats when compared with C rats (31%). However, the fractional volume of myofibrils was significantly decreased in the myocardium of T rats (P less than 0.001) and there was no significant difference between the hearts of T and C rats with respect to capillary luminal area/myocyte area. The mitochondria/myofibril ratio was increased in the hearts of T rats (0.82) over that found in control hearts (0.52). These results suggest that in the early stages of thyroxine-induced myocardial hypertrophy there is not an immediate increase in capillary area which may account for the ischemia and significant increase in mitochondrial volume which characterized myocardial hypertrophy in this model.     

Penile lentiginosis. An ultrastructural study.

This study on five patients has revealed more extensive alterations to melanocytes than previously reported, and emphasizes the fact that depigmentation is an essential element of the condition. In hyperpigmented areas, melanocytes were increased in number along the basal layer of the epithelium, were hyperactive, and in some cases contained bizarre melanosomes. In two cases there was suggestion of a defect in melanosome transfer to keratinocytes. Lymphocytes were closely apposed to melanocytes, and, in hypopigmented areas, were clearly involved in their disintegration. In depigmented areas, there was complete absence of melanocytes and of melanosomes in keratinocytes, and lymphocytes were present in the basal layer. In general, the appearances did not resemble melanoma in situ with spontaneous regression, although a second biopsy of one patient after one year did reveal features of melanocytes suggestive of an early stage of this condition. The study has provided no clear information as to the initial cause of the condition, but the manner of destruction of melanocytes suggests an immune reaction. Neither has it been of assistance in suggesting a more precise name for it.     

Ultrastructural changes of the neurohypophysis of the rat after castration

Summary The infundibular processes of the neurohypophysis of male and female rats were studied after different periods of castration. After seven days an increase in neurosecretory granules was observed. Two types of neurosecretory nerve endings were identified: dark ones, with dense neurosecretory elementary granules of 1600 A, and clear ones, with lighter neurosecretory granules of 1800 A. Protoplasmatic pituicytes showed a large increase in lipid granules together with a general hypertrophy. After one week of castration but with hormonal therapy the protoplasmatic pituicytes appeared normal or even showed less lipid granules than in the controls.With one month of castration the changes already mentioned in the nerve endings and pituicytes were more pronounced and after six months even more accentuated. Two types of neurosecretory nerve endings were clearly identified and the protoplasmatic pituicytes were loaded with lipid granules.The probable significance of the two different neurosecretory axons was discussed in relation to recent studies on the isolation of neurosecretory terminals from the neurohypophysis. The changes in the protoplasmatic pituicytes were considered in relation to the possible significance of the lipid granules.Supported by grants from the Consejo Nacional de Investigaciones Cientificas y Técnicas and by the Air Force Office of Scientific Research (AF-AFOSR 963-67).We are deeply indebted to Mrs. Defilippi-Novoa and Mr. Alberto Saenz for their skillful assistence.Associated Investigator, Consejo Nacional de Investigaliones Científicas y Técnicas, Argentina.     

Acute eosinophilic leukemia. An ultrastructural study.

Observations on a 32 year old male are described. Hematological examination demonstrated leukocytosis with circulating blastosis and dystrophic hypereosinophilia of the blood and bone marrow, with cells at various stages of maturation. Cytotoxic chemotherapy led to complete remission for 5 months followed by a terminal relapse. No features in favor of an "eosinophilic collagenosis" were revealed at autopsy. Repetitive ultrastructural studies performed during evolution of the illness demonstrated considerable anomalies of the eosinophil line. The present observation thus shows the clinical, evolutional, cytological and autopsy criteria of an acute eosinophilic leukemia.     

Plasma testosterone levels and ultrastructural studied on the prostate gland following castration in the marsupial Isoodon macrourus

Attempts were made to collect fetal fluids during the third month of 37 pregnancies in 34 heifers by inserting an aspirating needle through the sacrosciatic ligament and uterine wall into the fetal sac. In 10 trial attempts, six samples were collected and submitted for cytogenetic studies; four fetal deaths occurred, one in a case from which no fluid had been obtained. Subsequently, in 27 test attempts, 25 samples were collected of which 23 were submitted for cytogenetic studies. Three fetal deaths occurred, one in a case from which no fluid had been obtained. In spite of the risks involved, the technique is considered to be a practical method for the collection of fetal fluids in cattle.     

An ultrastructural study of the prostate gland of megascolicid earthworm Lampito mauritii (Kinberg)

The ultrastructure of prostate gland of Lampito mauritii revealed two types of secretory cells. Type 1 cells with a broad basal region and a long apical region contain electron dense oval secretory granules with an increased density at the core region. Numerous electron lucent granules with fine filamentous and electron dense amorphous materials also occur at the basal region of these cells. Type 2 cells contain electron lucent mucous-like secretory granules. This cell type contains exceptionally large Golgi complexes having 20-23 stacked cisternae. Both cell types open into a common lumen and numerous microtubules are visible at the apical end. Junctional complexes, such as desmosomes and septate junctions, are observed in this glandular tissue.     

Immunocompetent cells in the starfish Asterias rubens. An ultrastructural study

Cells from the axial organ of the starfish Asterias rubens were fractionated into two populations, adherent and non-adherent to nylon wool. In both populations the ultrastructural study revealed the presence of cells resembling the lymphocytes of the vertebrates, as well as phagocytic, peroxidase positive cells. The lymphocyte-like cells in the non-adherent population (average diameter 4 mu) have a high nucleo-cytoplasmatic ratio and are morphologically similar to Th lymphocytes while the adherent cells (average diameter 5.5 mu) are more similar to Bm lymphocytes. These observations are in line with the hypothesis that there exist, in the starfish, a primitive immune system with characteristics resembling those of the immune system of vertebrates.