Biomedical subjects

C D Tweedle

Publications and source records attributed to C D Tweedle.

40 records · Page 3Linked to original sources

PubMed1972

Branching of central neurons: intracellular cobalt injection for light and electron microscopy.

Cobalt chloride can be injected into an identified nerve cell body in an insect ganglion and reacted with ammonium sulfide to stain the soma and its branches with a black precipitate. The stained cell body and its branches throughout the neuropil are visible in both the light and electron microscope. In whole mount preparations, the resolution of neurites within the neuropil is of a quality that permits the comparison of branching patterns between cells and during various functional states.

Action Potentials↗

PubMedDate not supplied

Ultrastructural comparisons of neurons of supraoptic and circularis nuclei in normal and dehydrated rats.

A quantitative ultrastructural investigation was undertaken to compare the nucleus circularis (NC) and supraoptic nucleus (SON) of the rat both under normal and water-deprived conditions. NC was found to have dramatically more of its cells and membrane surface involved in direct soma-somatic contact than the SON. Water deprivation, even for one day, brought about a significant increase in both percentage of cells and membrane surface in contact in both nuclei, apparently by the retraction of fine glial processes from between the somata. The normal NC was made up of only one ultrastructurally identifiable cell type. The normal NC had no cells showing expanded endoplasmic reticulum, although these were seen following 5 days (but not 1 day) of water deprivation. The normal SON did have 4.4% of its cells showing expanded endoplasmic reticulum. This percentage significantly increased following water deprivation. The vesicle population per area of cytoplasm was very similar between the two normal nuclei. One day of water deprivation brought about a significant increase in less than 800 A vesicles in NC but not the SON. Five days of water deprivation resulted in a significant decrease in the lysosomal population per unit area in both nuclei. Vesicle changes have been discussed in relation to the volume changes in the cells.

Animals↗

PubMedDate not supplied

Ultrastructure of neurons in the paraventricular nucleus of normal, dehydrated and rehydrated rats.

Previous reports have shown that the percentage of neuronal somatic membrane in soma-somatic apposition (without intervening glia) increased with brief periods of dehydration (4--24 hr) and decreased with rehydration in the rat supraoptic and circularis nuclei. In the present study, the percentage of somal membrane in soma-somatic appositions was found to increase in the primarily vasopressin-containing lateral portion of the rat paraventricular nucleus with twelve hours of dehydration. Further evidence for altered cellular function in this nucleus was a decrease in the number of smaller dense core vesicles (< 2600A) per unit cytoplasmic area during initial dehydration (4--12 hr). No changes were detected, however, in the number of larger dense core vesicles (> 4000 A) or lysosomes (> 4000 A) per unit cytoplasm. Intranuclear membrane-bound vacuoles were found primarily in hydrated and rehydrated animals. No reliable changes were seen in the dilation of granular endoplasmic reticulum. Cilia were found in the neuropil and were occasionally traced to magnocellular somata. Differences in the patterns of morphological responses among the magnocellular hypothalamic nuclei suggest specializations in their roles, and further support a functional significance of neuronal membrane appositions.

Animals↗

PubMedDate not supplied

Brain slice preparation: hypothalamus.

Methods, materials and procedures for producing viable hypothalamic slices are described in detail. Also described are the results of methodological experiments dealing with combatting the problem of evaporative water loss which produces subsequent increases in concentration of the bathing medium. A formula is given by which the amounts of evaporative loss may be calculated and compensated for without direct measurement of the medium osmotic pressure. Finally, ultrastructural data are presented which indicate that paraventricular nucleus neurosecretory cells in the slices undergo a loss of dense core vesicles during the initial 3 hr in vitro, then recover by 5 hr and maintain a relatively constant state for up to 9 hr, the longest time sampled.

Animals↗