SYNTHETIC ACTIVITIES DURING SPERMATOGENESIS IN THE LOCUST

Isolated testes of the locust Schistocerca gregaria were immersed in solutions of tritiated thymidine, cytidine, uridine, or arginine for short periods to study nucleic acid and protein synthesis during spermatogenesis. DNA synthesis in this tissue is completed prior to initiation of meiosis. Protein synthesis continues throughout the whole meiotic cycle as well as during spermatid development. Meiotic cells, except those in metaphase through early telophase, and early spermatids are also actively synthesizing RNA. The heteropycnotic X-chromosome does not produce RNA at any stage of spermatogenesis. The rates of protein and particularly RNA synthesis decrease as chromosome condensation progresses. Depression of RNA synthesis, however, is not always accompanied by cytologically detectable condensation of chromatin, since very little or no RNA is synthesized in spermatids in which chromatin condensation has barely begun.     

SEED GERMINATION STUDIES IN MUSA. I. SCARIFICATION AND ASEPTIC GERMINATION OF MUSA BALBISIANA

Stotzky , G., Elsie A. Cox , and Roger D. Goos . (Central Research Labs., United Fruit Co., Norwood, Mass.) Seed germination studies in Musa. I. Scarification and aseptic germination of Musa balbisiana . Amer. Jour. Bot. 49(5): 515–520. Illus. 1962.—Methods for germinating seeds of Musa balbisiana Colla under aseptic conditions have been developed. Scarification was required for germination under these conditions, and mechanical was superior to chemical scarification. Various methods of mechanical scarification and cultural procedures were developed which facilitated the operation when large numbers of aseptic seedlings were required. Removing a chip from the lateral portion of the seed coat to expose the endosperm was the most effective method of scarification: germination percentages averaged 80%, and the time required for germination in sterile culture was shortened from the 3–6 weeks required for intact seeds in soil to 6–10 days. However, scarification did not shorten the time required for germination in soil, and seeds treated with some methods of mechanical scarification failed to germinate, as a result of their decomposition by microorganisms. The effectiveness of scarification in causing germination in aseptic culture is not presently understood, but, as the excised embryo exhibits no dormancy, the factors delaying germination apparently reside in other portions of the seed.     

Novel excitatory Conus peptides define a new conotoxin superfamily

A new class of Conus peptides, the I-superfamily of conotoxins, has been characterized using biochemical, electrophysiological and molecular genetic methods. Peptides in this superfamily have a novel pattern of eight Cys residues. Five peptides that elicited excitatory symptomatology, r11a, r11b, r11c, r11d and r11e, were purified from Conus radiatus venom; four were tested on amphibian peripheral axons and shown to elicit repetitive action potentials, consistent with being members of the 'lightning-strike cabal' of toxins that effect instant immobilization of fish prey. A parallel analysis of Conus cDNA clones revealed a new class of conotoxin genes that was particularly enriched (with 18 identified paralogues) in a Conus radiatus venom duct library; several C. radiatus clones encoded the excitatory peptides directly characterized from venom. The remarkable diversity of related I-superfamily peptides within a single Conus species is unprecedented. When combined with the excitatory effects observed on peripheral circuitry, this unexpected diversity suggests a corresponding molecular complexity of the targeted signaling components in peripheral axons; the I-conotoxin superfamily should provide a rich lode of pharmacological tools for dissecting and understanding these. Thus, the I-superfamily conotoxins promise to provide a significant new technology platform for dissecting the molecular components of axons.     

Moving as a reason for pet relinquishment: a closer look

One of the most frequently given reasons for relinquishing a companion animal to an animal shelter is that the person or family is moving. Telephone interviews conducted with 57 caregivers who relinquished animal companions to a shelter in the midwestern United States covered details of the move, characteristics both of the caregivers and the animals, and efforts to avoid relinquishment. A human-nonhuman animal bonding scale also was administered. Although some participants had additional reasons for relinquishment, the majority had given up their pets solely because they were moving. Most had relatively low income, were moving for employment reasons, and were renting their homes. Landlord restrictions were an important factor in relinquishment. High scores on the bonding scale and spontaneous expressions of discomfort and sorrow suggest that external pressures overrode attachment to the animal and the pain of relinquishment.