Morphology of the ependymal cells of the bovine area postrema.

This communication describes the ultrastructure of the ependyma of the bovine area postrema. The polygonal cells possessed an abundant apical array of microvilli but were nonciliated with the exception of occasional cells at the periphery of the area, which had a central kinocilium. The low squamous cells contained moderate numbers of cytoplasmic organelles. The cells do not appear to be typically secretory, but may function in fluid exchange.

Accuracy of an automated counting method by television-computer equipment in the quantitative autoradiography.

Commercially available television-computer equipment was used in the counting of silver grains in autoradiograms. The counting was made very rapidly and easily. The counts were compared with the counts made visually. With some limitations both counts showed excellent agreement. The accuracy of the method used is discussed.

Familial undulatory nystagmus in Ayrshire bulls in Finland.

The article describes a familial, undulatory nystagmus in Finnish Ayrshire bulls. The nystagmus appeared as a high-frequency tremor with a small amplitude and it was similar in both eyes. The vision didn't seem to be affected. In three of the affected five bulls a slight paramyoclonia posterior ('stretches') was also noticed. A histological examination of the vestibular nuclei with the adjacent brain area revealed no abnormalities. The pedigree of the bulls suggests a recessive autosomal inheritance.

The surface fine structure of the ependymal lining of the lateral ventricle in rats with hereditary hydrocephalus.

The ependyma of the lateral ventricle of rats with hereditary hydrocephalus was studied using scanning electron microscopy. Normal rats from the same litters were used as control animals. The surface morphology of the lateral ventricle of normal rats corresponded to results reported by other authors. The most prominent changes in the surface morphology of the ependyma of the hydrocephalic rats were seen in the cilia. They were shortened, fewer in number and clumped or matted. The surface of the ependymal cells was flattened and contained small, irregular projections. The number of large supraependymal cells, regarded as neurons, appeared to have diminished in the hydrocephalic rats. The number of supraependymal macrophages was greatly increased in these rats, suggesting the existence of an ependymitis.

The surface fine structure of the bovine subcommissural organ.

The bovine subcommissural organ was studied by using scanning electron microscopy. The most prominent findings was the existence of protruded and dilated endings of the ependymal cells. The majority of these cells were ciliated with two or more cilia; only a few unciliated cells were seen. Some pore-like structures were also seen on the surface. From the functional point of view, the most interesting finding was an amorphous heterogeneous material on the subcommissural ependyma. Especially in the caudal part of the organ this material accumulated in abundance. No real filamentous structures such as Reissner's fibre could be seen, however, it was assumed that the heterogeneous material corresponds to this formation. No supraependymal neurones were demonstrated.

The kinetics of 35S-labelled cysteine in the hypothalamic-neurohypophyseal neurosecretory system of the dehydrated rat.

Thirst stimulation of the supraoptic nucleus (SON) and paraventricular nucleus (PVN) was induced in rats by withholding all fluids during three days. 35S-cysteine was then intraperitoneally administered and the rats were killed at predetermined times and examined by autoradiography, applying the authors' previously described method. This experimental series totalling 51 animals was compared with a control series of 70 rats, similarly treated, who had had free access to water. The kinetic phenomena in SON and PVN were analysed in terms of the two-compartment model previously used, which gives an estimate of the neurosecretory material (NSM) secretion parameters and of those of the lumped structural cell protein turnover in the nuclei. The kinetics of the precursor amino acids after administration of labelled cysteine were also assessed. Determinations of the label uptake at two specific times in the experiment, in the infundibular nucleus, ventromedial nucleus and optic nerve tissue in both series served as a check on the specifity of the structural protein turnover changes observed. Compared with the controls, the turnover rate of the slow compartment was more than tripled in the dehydrated rats, while that of the fast compartment had gone down to about one-third; both effects very nearly equal in SON and PVN. These results are compatible with the concept according to which thirst stimulates the SON and PVN equally. A distinct, and strikingly equal, hump was observed (2 hours after label administration) in all specific activity curves, also in the precursor serum concentration, and it is probably due to recycling of 35s from cysteine to methionine. This and other circumstances render the phenomena rather too complex for a straight-forward evaluation by the two-compartment model. Even so, the observations are believed to furnish good evidence of the biological verity of this model as well as the thirst-induced changes elicited.