Ultrastructural studies on the brachiopod pedicle

Studies of the ultrastructure of representative articulate and inarticulate pedicles show that there are similarities in secretory activity between pedicle epithelia of both classes and the outer mantle epithelium of the inarticulates. Rootlet epithelial cells of the articulate pedicle produce small vesicles which pass to the junction between rootlet and substrate and probably play a part in the breakdown of the substrate. Scanning electron microscopy shows that dissolution of a bivalve shell acting as a substrate often follows the boundary of a single nacre tablet, and transmission electron microscopy shows that the rootlet extends its infiltration along the conchiolin walls. The inarticulate pedicle ending is modified to collect adherent sand grains.     

Successful co-culture of 1-4-cell cattle ova to the morula or blastocyst stage

Bovine ova (n = 326) collected at the 1-4-cell stage were cultured in TCM-199 + 10% foetal calf serum with or without oviducal cells. The bovine oviducal cells were collected and seeded either on the day of ovum recovery (BOC-0) or 3 days earlier (BOC-3). In Exp. 1, the effect of age of oviducal cells in co-culture on ovum development was examined. In the BOC-0 and BOC-3 treatments, respectively, 36/46 (78%) and 30/37 (81%) of ova developed to morulae or blastocysts, while no ova developed past the 8-16-cell stage in the absence of oviducal cells. In Exp. 2, the effect of age of oviducal cells and of physical contact between the oviducal cells and ova on ovum development was examined. In the BOC-0 and BOC-3 treatments, respectively, 29/42 (69%) and 23/43 (53%) of the ova developed to morulae or blastocysts, while 1/42 (2%) developed to the morula stage in the absence of oviducal cells. Physical separation of the ova using a microporous membrane inserted between the oviducal cells and the ova did not affect ovum development, with 26/42 (62%) and 22/42 (52%) of ova developing to morulae or blastocysts in the BOC-0 and BOC-3 treatments, respectively. A high proportion of the morulae and blastocysts in Exp. 1 (57/66, 86%) and Exp. 2 (67/100, 67%) were of quality grades 1 or 2, with mean nuclei counts of 85 for morulae and 111 for blastocysts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrastructural studies on oogenesis in symphyla

Summary In the oocytes of Hanseniella nivea, cortical granules are formed in the peripheral ooplasm during late stages of oogenesis. Single Golgi elements are involved in the process. Concurrent with the formation of cortical granules is the appearance of a chorion on the oocyte surface. Precursors of this envelope are most likely synthesized by follicle cells.     

Ultrastructural studies on oogenesis in Symphyla

Summary The paired ovaries of Symphyla are sac-shaped. Their interior is filled with synchronously developing oocytes surrounded by a simple follicular epithelium. Previtellogenic oocytes have spherical or oval nuclei, the latter containing a large number of small nucleoli. Part of the nuclear surface is covered by a thick coat made up of a granular substance of medium electron density. The coat is penetrated by cisternae of the smooth endoplasmic reticulum. Micropinocytosis is the principal source of yolk in Symphyla; a small amount of yolk material arises within the mitochondrial cristae. Vitellogenic oocytes are characterized by a highly active rough endoplasmic reticulum synthesizing a material, probably lipoprotein in nature, which is incorporated into lipid droplets.Supported by Government Problem Grant II-1.3.13. The author is grateful to Dr. F. Kaczmarski of the Medical Academy, Kraków, for the use of EM facilities in his laboratory and to Dr. W. Hüther, Ruhr-Universität, Bochum, for the identification of the specimens     

Ultrastructural studies on erythropoiesis in the avian thymus

Summary Thymus lobes from three species of birds, Quelea quelea, Passer domesticus and Sturnus vulgaris, have been examined ultrastructurally. The component cell types are compared with their counterparts in mammalian thymus glands, and found to be similar. Greater differences exist between small, intermediate and enlarged lobes of one species than exist between species. Developing erythroid cells are present in most enlarging and some enlarged glands. They appear to be developing at the expense of lymphoid cells in some birds. The origin of these cells is discussed. Cells that are possible candidates for the production of some thymic hormones are also described.Formerly: Houghton Poultry Research Station, Houghton, Huntingdon, Cambs     

Ultrastructural studies on erythropoiesis in the avian thymus

The cortex of enlarging thymic lobes from adult haemorrhaged Quelea quelea were found to be similar to those of wild birds where the thymic enlargement was occurring naturally. A detailed stereological analysis of cells broadly designated as lymphoid, and the construction of models to account for the results, indicates that the enlarging thymic lobe contains both large and small blast cells, a heterogenous group of medium lymphocytes, erythroid cells, and two types of very small lymphocytes. The distinction between early erythroid cells and some lymphocytes, despite this detailed analysis is very difficult, but it is possible in enlarging thymic lobes that up to 42% of the lymphoid cells may have erythroid characteristics.     

Ultrastructural studies on mitochondrial swelling

Mitochondrial swelling induced by valinomycin, calcium chloride and P(i) was studied after potassium permanganate fixation in suspension. Valinomycin induces a rapid K(+) influx, increase of the matrix space and out-folding of the cristae, with good preservation of the matrix material. This swelling is reversible but the cristae do not completely re-form and have a blebbed appearance. On repeated swelling and contraction cycles there is a gradual loss of matrix material. Calcium chloride and P(i) produce a slow swelling of the matrix space. Shrinkage induced by ATP was partial and not associated with return to the original structure.     

Ultrastructural studies on the epididymal spermatozoa in the rhesus monkey

Ultrastructural studies on the spermatozoa in different regions of the epididymis of the rhesus monkey have shown that the process of sperm maturation is associated with the caudad migration of the cytoplastmic droplet, a reduction in the volume of the cytoplasmic droplet, and an obvious wrinkling of the plasma membrane surrounding the head of the spermatozoa. These changes are completed by the time the spermatozoa reach the distal-middle segment of the epididymis. The present studies also indicate that spermatozoa are incorporated into the intraepithelial cells in the epidymis. This finding suggests that spermiophagy is a normal occurrence in the epidymis of rhesus monkey.     

Ultrastructural studies on the heart of bony-fish larvae

The ultrastructure of the heart in 2 and 6 d old larvae of Melanogrammus aeglefinus and 1, 7, 14, and 21 d old larvae of Poecilia reticulata, is described. Additional studies were done on prenatal specimens of P. reticulata. In the atrium of M. aeglefinus the endocardium is separated from the muscle wall by a wide, electron lucent space, which probably contains cardiac jelly (Davis 1924). The myocardium is an 1 cell-thick layer in the atrium, whereas it consists of 2 to 4 cells in the ventricle. Cardiac trabeculae seem to be absent. The contractile material appears more developed at the endocardial side of the muscle wall than at the epicardial side. Thus, in the latter area the myofibrils are thin, few in number, and embedded in large amounts of free ribosomes. Often they radiate from a spot of electron dense material or an intercalated disc. Generally, intercalated discs, short nexuses and specific heart granules (Jamieson and Palade 1964) occur in ventricular as well as in atrial myocardial tissue. In P. reticulata cardiac jelly seems absent, whereas cardiac trabeculae occur regularly, particularly in the ventricle. The myofibrillar apparatus displays a nearly adult structure. However, in the ventricular wall, there occur spots and bands of intracellular, electron dense material at that sarcolemma facing the subepicardial space. Normally, myofibrils extend from this material into the cellular cytoplasm. Subsarcolemmal electron dense material was only scarcely seen in the atrial wall.(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrastructural studies in rheumatoid polyneuropathy

The biopsy material from the sural nerve of 8 patients suffering from rheumatoid arthritis and showing, with one exception, positive serological reactions, were studied by means of electron microscopy. All the patients were displaying sensory and sensomotor neuropathy. Besides hypermyelination the damage of Schwann cells, the destruction on unmyelinated fibres and the proliferation and degeneration of the vascular endothelium were observed. No inflammatory signs were seen around the peri- and endoneurial vessels.     

Ultrastructural studies on the cell walls in Fusarium sulphureum.

The cell walls of Fusarium sulphureum have a microfibrillar component that is randomly arranged. X-ray-diffraction diagrams of the microfibrils are consistent with a high degree of crystallinity and show that they are chitin. The chitin microfibrils of the peripheral walls envelop the hyphal apex and extend across the septae. During the first 8h in culture, the conversion of conidial cells to chlamydospores is evidenced by a swelling of the cells and the original microfibrils remain randomly arranged. Within 24h new wall material is deposited as the cells expand and the wall thickens. The new microfibrils are indistinguishable from those of the original conidial cells. After 3 days in culture, the chlamydospores are fully developed and have the characteristic thick wall which is a continuous layer of randomly arranged microfibrils. Chlamydospores maintained in a conversion medium for 8 days have microfibrils identical with those in 3-day-old cultures; thus a further change in the microfibril orientation did not occur during that period. Alkaline hydrolysis of the walls removes most of the electron-dense staining constituents from the inner wall layer and leaves the outer wall layer intact. This treatment also reveals some of the wall microfibrils. An additional treatment of the walls with HAc/H2O2 completely removes the wall components that react positively to heavy metal stains. The results are discussed in relation to the structure of other fungal cell walls.