CHANGES IN FINE STRUCTURE DURING SILK PROTEIN PRODUCTION IN THE AMPULLATE GLAND OF THE SPIDER ARANEUS SERICATUS

The ampullate silk gland of the spider, Araneus sericatus, produces the silk fiber for the scaffolding of the web. The fine structure of the various parts of the gland is described. The distal portion of the duct consist of a tube of epithelial cells which appear to secrete a substance which forms the tunica intima of the duct wall. At the proximal end of the duct there is a region of secretory cells. The epithelium of the sac portion contains five morphologically distinct types of granules. The bulk of the synthesis of silk occurs in the tail of the gland, and in this region only a single type of secretory droplet is seen in the epithelium. Protein synthesis can be stimulated by the injection of 1 mg/kg acetylcholine into the body fluids. 10 min after injection, much of the protein stored in the cytoplasm of the epithelial cells has been secreted into the lumen. 20 min after stimulation, the ergastoplasmic sacs form large whorls in the cytoplasm. Protein, similar in electron-opacity to protein found in the lumen, begins to form in that portion of the cytoplasm which is enclosed by the whorls. The limiting membrane of these droplets is formed by ergastoplasmic membranes which lose their ribosomes. No Golgi material has been found in these cells. Protein appears to be manufactured in the cytoplasm of the tail cells in a form which is ready for secretion.     

The conversion of injected glucose into renal glycogen and mucopolysaccharides

Summary Tritiated glucose has been injected into rabbits in various states of hydration. The renal papilla of all animals showed an uptake of the label, converted into glycogen, and into mucopolysaccharides, in a manner dependent on the water balance of the animal.In papillae of control animals, the glycogen of the collecting duct epithelial cells and the mucopolysaccharides of the interstitium were labelled.In papillae of animals in an aqueous diuresis, the collecting duct glycogen was lightly labelled and there was no label over the interstitium.Antidiuretic hormone caused a diversion of label from the collecting ducts into interstitial mucopolysaccharides.The significance of these findings, with respect to renal concentrating ability, is discussed.The author wishes to thank Dr. M. K. S. Hathorn for help with the statistical analysis. Mr. K. Gamblin and Mr. P. L. Hyam gave valuable technical assistance. This research formed a part of the work approved for the degree of Ph. D. (London).     

Cytochemical and ultrastructural studies of ribonucleoprotein containing structures in oocytes of Acheta domesticus

Summary Two distinct types of ribonucleoprotein containing structures are found in oocytes of the house cricket, Acheta domesticus, a large secondary or accessory nucleolus and many small primary nucleoli. The secondary nucleolus increases in size during oocyte development and is similar in appearance to the nucleolus of somatic cells. The primary nucleoli are intimately associated with a large, extrachromosomal DNA containing body. The DNA body is no longer visible in nuclei of late diplotene stage cells when the primary nucleoli are dispersed within the nucleoplasm. Both types of nucleoli contain cytochemically detectable RNA and acid protein, little or no DNA and basic protein, and particulate structures similar to but smaller than cytoplasmic ribosomes.The authors acknowledge the technical assistance of Miss Celeste Malinoski and Mrs. Marcia Andrews. This work was supported by a U.S.P.H.S. grant, number GM-16440-01 and grants number L-16 and J-1 from the Health Research Services Foundation.     

Nitrogen chlorosis in blue-green algae

Summary Nitrogen deficient Anacystis nidulans contained normal levels of chlorophyll-a and carotenoids but did not contain any phycocyanin. These organisms also contained large amounts of polysaccharide. The addition of nitrate to a deficient culture resulted in the recovery of normal pigmentation over a period of several hours.The relation between these changes and growth was established by a kinetic study of the changes in cell composition during pigment loss and recovery. Loss of phycocyanin commenced with the cessation of growth due to nitrogen limitation and was complete after 15 hours. In contrast there were only minor changes in chlorophyll-a and carotenoid. After growth had ceased polysaccharide continued to increase and viability dropped sharply although total cell counts did not change. These trends were reversed by the addition of nitrate to deficient cultures. Phycocyanin was detected after a short lag and normal levels of phycobiliprotein were present within 8 hours. Cell division did not begin until normal levels of phycocyanin had been restored. During the recovery of normal pigmentation there was a decrease in reducing sugar content and a sharp rise in viability. Qualitative studies with 9 additional blue-green algae suggest that loss of phycocyanin is a characteristic feature of nitrogen deficiency in blue-green algae.     

Electron microscopy of phages for Agrobacterium tumefaciens

Summary Bacteriophages for three strains of A. tumefaciens were concentrated by ultracentrifugation, stained with 1% phosphotungstic acid (PTA), or 0.5% uranyl acetate, and examined with the electron microscope. Phage PT11 was a bacillary-shaped particle with a whip-like tail containing a knob at its distal end. Phage PIIBNV6 appeared to have an icosahedral head. The wide non-contractile tail terminated in a plate with pegs. Phage PIIBNV6-C was an icosahedral particle with a short, spike-like tail. Host cells of A. tumefaciens were encapsulated rods bearing polar or lateral flagella.Published with approval of the Director, Wisconsin Agricultural Experiment Station, Madison, Wisconsin, U.S.A. 53706.     

Enzyme Activity,Acidic Nuclear Proteins,and Prognosis in Human Breast Cancer

The activities of the enzymes lactate dehydrogenase, 6-phosphogluconate dehydrogenase, and phosphohexose isomerase in primary human breast cancer biopsies are shown to be related to the time between mastectomy and recurrence of the cancer. These enzymes have higher activity in malignant breast tissues generally than in non-malignant breast tissues. In tumours from patients with long free periods these differences are not apparent.Evidence is presented which suggests that two different types of breast cancer can be distinguished according to the relative amounts of phosphohexose isomerase and acidic nuclear proteins. It is suggested that this difference may be related to hormone responsiveness.