Copper absorption in young men fed adequate and low zinc diets

Copper absorption was measured at two levels of dietary zinc in six healthy young men who were confined to a metabolic unit for a 75 d study of zinc utilization. A diet of conventional foods was fed, providing either 16.5 or 5.5 mg zinc and 1.3 mg copper daily. Copper absorption was determined by feeding⁶⁵Cu, a stable isotope of copper, once during the 16.5 mg Zn diet and near the beginning and end of the 5.5 mg Zn diet. Apparent copper absorption averaged 48.1% when the 16.5 mg Zn diet was fed. This was significantly higher than the averages of 37.2 and 38.5% when the 5.5 mg Zn diet was fed. Absorption also differed significantly among subjects. Fecal copper did not differ between diets or among subjects. All subjects were in positive copper balance at both levels of dietary zinc. These results suggest that a dietary zinc intake slightly above the Recommended Dietary Allowance of 15 mg/d does not increase fecal copper loss and does not interfere with copper absorption.     

Calicotyle urolophi n. sp. (Monogenea: Monocotylidae) from stingarees,Urolophus spp. (Elasmobranchii: Urolophidae) taken in coastal waters of Southern Australia

Calicotyle urolophi n. sp. is proposed for calicotylines found in the cloaca of three stingaree species, Urolophus cruciatus, U. bucculentus and U. paucimaculatus, collected off the southeastern coast of Tasmania. Variations in the soft body parts were observed between specimens taken from U. cruciatus and U. bucculentus but were not considered sufficient for separation into two species. C. urolophi is differentiated from other Calicotyle spp. found in the South Pacific by the configuration of the tubular male copulatory organ, the structure of the intestinal caeca and the arrangement of the vaginae. Amended diagnoses for the subfamily Calicotylinae and the genus Calicotyle are provided.     

Oral Ultrastructure and Oral Development of the Misaligned Undulating Membrane Mutant of Tetrahymena thermophila1

The misaligned undulating membrane (mum) mutant of Tetrahymena thermophila is a non-conditional, single gene recessive mutation. The major effect of the mum mutation is the production of multiple undulating membrane (UM) fragments in the oral apparatus (OA). The ultrastructure of the UM fragments of mum OAs is identical to that of the single UM of wild-type OAs. Analysis of OA development at midbody using a combination of light microscopy of protargol-stained cells and SEM of demembranated whole cells showed that the phenotypic effect of the mum mutation first becomes evident during mid to late stage 4 and is fully manifested in early stage 5. The effect of the mutation involves a proliferation of excess basal bodies in the UM field. Subsequent events in the development of the mum OA from mid to late stage 5 are identical to those in wild-type OAs. This study suggests that the mum mutation establishes conditions that allow the production of multiple UMs and thus reveals that the UM field is competent for the complete and coordinated development of several adjacent UMs. This level of regional control is not clearly evident when a single UM is present. The comparison of development of wild-type and mum OAs required an extensive reanalysis of stages 4 and 5 of normal oral development. On the basis of current and previous observations, we propose a new and more subdivided staging system for oral development in Tetrahymena.     

Comparative aspects of the area postrema: fine-structural considerations help to determine its function

The area postrema is a circumventricular organ of the fourth ventricle of the mammalian brain. Although there are distinct gross anatomical differences in the appearance of this organ between "lower" mammals such as rodents and lagomorphs and "higher" mammals such as carnivores and primates, its fine structure is remarkably similar in all species studied. There are many suggestions in the literature for a specific function for this area of the brain, ranging from its being a chemoreceptive trigger zone for the emetic response to its being a regulatory nucleus for the sleep cycle. The present report describes some comparative studies on the ultrastructure of this organ. This information is discussed in relation to what is known about the neurochemistry of the area postrema and its connections with other brain regions and visceral structures. A suggestion is offered that our current knowledge of the area postrema is consistent with its performing many of its proposed functions in the context of a regulatory ("fine-tuning") center for many autonomic functions.