Dynamic aspects of the LHRH system associated with ovulation in the little brown bat (Myotis lucifugus).

Adult female bats were collected from natural roosting sites in pre-ovulatory and post-ovulatory conditions. LHRH neurones of these animals were examined using light and electron microscopic immunocytochemistry, and LHRH tissue contents were measured by radioimmunoassay. Comparisons between the two groups of bats revealed that the number of LHRH perikarya detected immunocytochemically, as well as hypothalamic LHRH content, were significantly reduced in post-ovulatory animals. Distributions of immunoreactive perikarya were, however, strikingly similar in both groups. The reduction in immunoreactive cell number observed after ovulation was therefore not restricted to an anatomically defined subset of neurones, but was evident throughout the population. The projection of LHRH-immunoreactive fibres that extend into the pituitary neural lobe in this species also exhibited changes related to endocrine condition. Morphometric indices of fibre density in the neural lobe were significantly reduced in post-ovulatory bats, as was LHRH content of the lower infundibular stalk and neural lobe. Fine structural study of perikarya revealed complex anatomical interactions between LHRH-immunopositive elements, especially in post-ovulatory bats. These interactions included direct apposition of perikarya, as well as more elaborate networks involving various combinations of perikarya and large- and small-caliber processes. These changes in the LHRH system associated with ovulation suggest reduction of stored peptide within perikarya and depletion from terminals within the lower infundibular stem and neural lobe. Parallel reductions in hypothalamic and neural lobe LHRH content during the periovulatory period support the hypothesis that the neural lobe component of the system contributes to control of gonadotrophin secretion in this species. Finally, increased complexity of anatomical contact between components of the LHRH system may be related to activation of this cell population in spring.

Distribution of pulmonary cholinergic nerves in the rabbit.

Investigations of the nerves of the rabbit lung, by light and electron microscopy, showed a dense acetylcholinesterase-positive innervation of the bronchi through the bronchiolar level. Large nerve bundles were found to decrease in size as they progressed from extrachondral to subchondral connective tissue, forming complex networks of mostly terminal fibres in the muscle layer. In several instances single fibres penetrated the submucosal layer and approached the mucosa. Gangliocytes, which also reacted positively for cholinesterase, were visible in the vicinity of the large peribronchial bundles. Gangliocytes rarely were seen in association with the vasculature. Blood vessels received a much less dense cholinesterase-positive nerve supply than the bronchi. Single, non-terminal fibres were noted at the adventitiomedial junction of the pulmonary artery and vein. In addition, segments of nerve fibres (networks) were observed in the arterial and venous smooth muscle layers. Cholinesterase-positive innervation was even less extensive in the veins than in the arteries.

Effect of retinal location on cone critical flicker frequency.

This experiment investigated the differential sensitivity of various areas of the retina using flicker. For 12 subjects testing was carried out in the fovea, and 5 degrees and 6 degrees temporal to the fovea using a wavelength of 555 nm. Testing was done both in the presence of a surround beam and in its absence. In all cases, there was a 2.5- to 4-fold increase in the amount of energy needed to perceive flicker as testing was shifted from the fovea to the periphery. A number of possible explanations are suggested to account for these findings.

Intranuclear rodlets in a pulmonary neuroepithelial body of a rabbit.

Filamentous intranuclear rodlets were found in a majority of cells in a bronchiolar neuroepithelial body of a rabbit. These rodlets appear to be similar to structures that have been described primarily in neural tissues. They are composed of large bundles of microfibrils made up of smaller subbundles. No close association with any nuclear structure is seen. Although no function can as yet be ascribed to intranuclear rodlets, their demonstration in a neuroepithelial body may be of importance of the understanding of the function of both structures.