Postembryonic brain development in the monarch butterfly,Danaus plexippus plexippus L.

Development Genes and Evolution -     

Melanogenesis in amphibians

Summary The pigmented epithelium of Rana pipiens tadpole eyes normally develops at least two types of melanosomes: (1) an elongated melanin granule of relatively homogeneous electron density, and (2) a complex melanosome which has an outer electrondense area and one or more less dense cores. Evidence indicates that complex melanosomes are formed by new melanin enclosing preexisting melanosomes. An organized fibrillar premelanosome is demonstrated with the aid of the antimelanogenic compound phenylthiourea (PTU). These premelanosomes are the developing forms of the elongated melanosomes. There is evidence that the premelanosomes originate in the smooth endoplasmic reticulum. Phenylthiourea blocks melanin synthesis in the premelanosomes; however, removal of the PTU allows pigment deposition. This finding of an organized, fibrillar premelanosome in an amphibian marks the lowest phylogenetic group in which these organelles have been described.An Oak Ridge Graduate Fellow from Catholic University of America, Washington, D.C., under appointment from Oak Ridge Associated Universities.The MAN Program is supported by the National Cancer Institute, the National Institute of General Medical Sciences, the National Institute of Allergy and Infectious Diseases, and the U.S. Atomic Energy Commission.Oak Ridge National Laboratory is operated by Union Carbide Corporation Nuclear Division for the U.S. Atomic Energy Commission.     

Maintenance Digoxin in Elderly Patients

Digitalis glycosides remain the cornerstone of treatment in cardiac failure. The increasing frequency of toxic effects is a cause for concern. Review of 80 elderly patients receiving digoxin on a maintenance basis, some of whom had toxic effects, shows that in almost three-quarters of the group digoxin was stopped without detriment. Elderly patients on maintenance treatment should be reviewed, and in the absence of a known primary cardiac lesion an attempt should be made to withdraw digoxin.     

Sub-specialization or Super-specialization in Surgery?

A special centre for prosthetic hip replacement set up 10 years ago has been successful in its primary objectives, producing high quality work at low cost and stimulating research. The project has not yet been successful in achieving a permanent staffing structure, but this is the effect of certain British ideologies in surgical training, with the result that craftsmanship and technology cannot be reconciled with pure intellectual attainment.The success of the project suggests the importance of isolating elective surgery from emergency surgery in the interests of cost-effectiveness. Problems of isolation from teaching hospitals are not insurmountable, but isolation to some degree is essential to achieve the minimum size necessary for efficiency and to ensure unbroken professional team-work among all levels of staff. While maximum efficiency in this field can be achieved only in special centres, too many primary operations will be required every year to insist that total hip replacement should be done only in special centres. A special feature of this field is the need for a permanent staffing structure to hand on technical expertise as an unbroken tradition.     

Monitored Environment System to Control Cell Growth, Morphology, and Metabolic Rate in Fungi by Oxidation-Reduction Potentials

A device for the adjustment, maintenance, and monitoring of a desired oxidation-reduction potential in a liquid environment is described. The filamentous species, Penicillium lilacinum and Trichophyton schoenleinii, and the dimorphic species, Histoplasma capsulatum, developed budding yeastlike cells when grown in a liquid medium with a low oxidation-reduction potential. When the organisms were inoculated into fresh medium, they returned to the filamentous condition as the oxidation-reduction potential was restored to a more positive (oxidizing) environment.