Structure of cephalic abnormalities in Drosophila melanogaster (Diptera: Drosophilidae)

Scanning and transmission electron microscopy were utilized in studying the cephalic abnormalities of the tu-h strain of Drosophila melanogaster. Abnormalities, appearing as protuberances (growths) of different shapes and sizes, were observed only on or in close proximity to receptor cites. Compound eyes of some flies, besides having such protuberances, either had modified corneal lenses or were absent altogether. Cuticles of the growths were thinner than that of the normal surrounding layer. The epidermal cells associated with setae on the growths or underlying modified corneal lenses remained undifferntiated. Both setae and growths lacked innervation. The receptor portions (retinular sensory cells and secondary pigment cells) of the abnormal compound eye, where the dioptric portions were replaced by protuberances or remained undifferentiated, were unaffected by the mutation. Nuclei of several cells, including oenocytes and fat bodies, close to or underlying epidermal cells of abnormalities, were large and contained compact nucleoli without nucleonemas. Viruslike particles were observed in several nuclei of growth cells. It was concluded from the present study that the alterations induced by the mutation can be only a localized phenomenon restricted to at least several cephalic epidermal cells and/or their derivatives.     

A Survey of the Postpartum Reproductive Performance of Dairy Cows with Fertility Problems in Southern Iceland

The purpose of this survey was to evaluate the reproductive performance of dairy cows on problem farms in southern Iceland. In all 229 cows on 6 farms were studied. The animals were examined clinically by rectal palpation, once a month. Blood samples were taken 2–5 and 7–10 weeks after calving. The blood samples were analysed for the contents of glucose, urea, inorganic phosphate, calcium and magnesium. Milk samples for progesterone profiles were taken, by the farmer, every 4th day from day 10 postpartum until first oestrus. Because of this sampling method, 128 cows had no rise in progesterone levels, when milk sampling was stopped. These 128 animals were excluded from the study. The results are based on 101 animals. There was a large variation between cows in postpartum reproductive performance. In the total material 1st ovulation occurred later than reported in many other countries. Fifty percent of the cows had ovulated 35 days after calving and 90 percent 70 days after calving. The first luteal phase was short in about 60 % of the cows. The progesterone values assayed from those short cycles were lower than the values assayed from the following cycle. First artificial insemination (ai) was on the average 77 days postpartum (pp). The conception rate to first service was 49 %. Of 100 milk samples taken at the time of ai, 20 had high progesterone value. This indicates a high frequency of luteal phase inseminations. Clinical ketosis was diagnosed in 35 cows. Of these, 31 had a low glucose value. Cows with clinical ketosis ovulated, on the average, later than other animals and 24 ovulated later than 40 days pp. The results indicated that the fertility problems of these cows studied were late ovulations, low conception rate, probably in part, due to luteal phase inseminations, and a high frequency of ketosis which could be caused by low quality feedstuff.     

Animal evolution: the enigmatic phylum placozoa revisited

A recent report of high levels of genetic variation between strains of Trichoplax adhaerens challenges the traditional view that the phylum Placozoa comprises only one species. At the morphological level, placozoans are amongst the simplest extant animals, but molecular evidence suggests that they may have more complex origins.     

Cultivable fungi present in Antarctic soils: taxonomy,phylogeny, diversity,and bioprospecting of antiparasitic and herbicidal metabolites

Extremophiles - Molecular biology techniques were used to identify 218 fungi from soil samples collected from four islands of Antarctica. These consisted of 22 taxa of 15 different genera belonging...     

LIGNIFICATION DURING SECONDARY WALL FORMATION IN COLEUS: AN ELECTRON MICROSCOPIC STUDY

The fine structure of lignin deposition was examined in developing secondary walls of wound vessel members in Coleus. KMnO₄, which was used as the fixative, selectively reacts with the lignin component of the cell wall and thus can be used as a highly sensitive electron stain to follow the course of lignification during secondary wall deposition. Lignin was first detected as conspicuuos electron-opaque granules in the primary wall in the region where the secondary wall thickening arises and as fine granular striations extending into the very young secondary wall. As the secondary wall develops lignification becomes progressively more extensive. In cross sections the lignified secondary wall appears as concentric, fine granular striations; in tangent al or oblique sections it is seen as delicate, beaded fibrils paralleling the long axis of the thickening. High magnification of tangential or oblique sections shows that the fibrillar appearance is due to the presence of alternating light and dark layers each approximately 25-35 A wide. It is assumed that the light layers are the cellulose microfibrils and the dark regions contain lignin which fills the space between the microfibrils. KMnO₄, by selectively reacting with lignin, thus negatively stains the cellulose microfibrils revealing their orientation and dimensions.