Vascular ontogeny of the septal region in rats.

The development of the arterial and venous systems of the septum was studied in rat brains injected daily with India ink, from the 11th embryonic (E) until the first postnatal day. Arterial blood is supplied to the septum by the unpaired hemispheric artery, the stem and septal branches of which are to be recognized on the 14th and 15th embryonic days respectively. At earlier stages, e.g. on E12, a capillary network, the hemispheric plexus, can be seen between the two hemispheres contributing to the blood supply of the septum during the early phase (E14 to E18) of development. From E18 onwards, the arterial supply of the septum is derived only from direct branches of the hemispheric artery; one group of them being dorsal (infracallosal) and the other ventral (subcallosal). The venous drainage of the septum is bidirectional: 1) Veins of the ventral group leading to the interperioptic sinus are seen on E14. At first they collect blood only from a small rostral portion of the septum, but later their territory expands to include the anteroventral two-thirds of the septum. 2) The dorsal septal veins drain into the great cerebral vein (of Galen), or into the superior sagittal sinus directly. Initially, twigs run directly into the great cerebral vein. These later become the tributaries of the internal cerebral vein, which appears on E17 or E18. Until E18 this dorsally-directed drainage predominates, whereas at birth it becomes restricted to one third of the septum as a result of a gradual regression. The development of both arterial and venous circulations of the septum is complete at birth.

The vascular architecture of the developing pituitary-median eminence complex in the rat.

The development of the pituitary gland and its blood vessels is described in rat embryos (gestational day 12 through day 21) injected with India-ink via the umbilical vessels. The vascularization of all components of the pituitary gland develops from the surface network covering the prosencephalic vesicle. However, vascular connections exist between the prospective median eminence and the anterior pituitary gland in the earliest stages examined (day 12) but are not augmented by vessels from the stomatodeal roof until day 13. Primary portal veins appear initially on day 13, the vascularization of the pars distalis is visible on day 15. The "Mantelplexus" covering the floor of the diencephalon is discernible on day 16. Large-caliber portal veins appear immediately before birth, but otherwise there is no significant change in the vascular pattern during the last five days of gestation. The pars intermedia and the median eminence-pituitary stalk region remain avascular throughout embryonic life.

Quantitative analysis for innervation of smooth muscle cells in the wall of the urinary bladder.

The distribution of nerve terminals to different parts of the urinary bladder was studied by electron microscopy with the aid of 6-hydroxydopamine treatment. A quantitative analysis was made for each region. In the sphincter and trigone areas nerve terminals were found to be much more numerous (3 times more) than in sections from the body and the apex of the bladder. In much of the bladder there were 6--7 smooth muscle cells for each nerve fiber, however in the trigone area 1--2 muscle cells were supplied by terminal nerve fiber. The narrowest gap between nerve terminals and smooth muscle cells was found to be 150--250 nm. It was commonly seen that Desmosome-like attachments, called nexuses, connected adjacent smooth muscle cells. After 6-hydroxydopamine treatment degenerated terminals could be found mostly in the fine periarterial plexuses but some were also observed that were not related to blood vessels, especially in the trigone area. Summation of our figures and results for terminal density suggests to us that contractions of the urinary bladder are initiated or controlled in the trigone region and that other parts of the wall are activated by local nerve processes and the numerous nexal contacts.

Degeneration analysis of the efferent nerves to the urinary bladder in the cat.

The extrinsic efferent nerve fibres to the urinary bladder in the cat were studied by secondary degeneration after transection of the seventh lumbar, all three sacral and the first coccygeal ventral roots of spinal nerves and after extirpation of both hypogastric ganglia. Under the electron microscope, degenerated nerve fibres of spinal origin could be observed in the trigone region among the ganglion cells and all layers and in the different areas of the urinary bladder wall. These degenerated nerve fibres containing mainly clear vesicles, 30-60 nm in diameter, and a few 80- to 120-nm granular vesicles were situated in synapsing contacts on the surface of the local nerve cells and in synapsing with other probably local nerve processes. After extirpation of the hypogastric ganglia several degenerated nerve fibres could be found along the blood vessels and lymph vessels in all layers. However, occasionally on the surface of the local nerve cells degeneratd nerve fibres could also be found. 2 months after both interferences most of the nerve fibres and synapses remained unaffected. According to these observations the extrinsic efferent nerve fibres and synapse seem to have a modulatory effect on the local ganglia. The large amount of the local intact synapses suggests that the micturition reflex is not a spinal but a local peripheral reflex.

Innervation of the small intestine.

It was shown in acute and chronic degeneration studies that the nerve elements of the cat small intestine belong to two according to whether they are extrinsic or intrinsic in origin. Part of the extrinsic nerve fibres originate from the vagus nerve and can be found on both intestinal plexuses, the other fibres are processes of the coeliac ganglion and occur in the first place in the vascular tunica adventitia. The intrinsic nerve cells may be classified into three groups on grounds their ultrastructure the number of synapses and processes on their surface. The synaptic connections between the different nerve cells of the internal plexuses were confirmed on chronic isolated of intestinal loops. The local reflexes provided by these connections are held responsible for peristalsis, the functional modifications of the mucosal pattern and the movements of the villi.

Intrinsic innervation of the urinary bladder.

The intrinsic innervation of the urinary bladder of the cat was studied with the aid of total extrinsic denervation (L7, S1, S2, S3 and the first coccygeal spinal nerves were transected and the hypogastric ganglia were extirpated on both sides); the materials were studied by electron microscopy. Several synapses could be observed between nerve processes and perikarya and between two adjacent nerve processes. The terminals could be classified into four groups according to the existence of a dense core and according to the size of the synaptic vesicles; the first group is made up of small clear vesicles; the second group of terminals contains some large granulated vesicles in addition to a few small clear vesicles; the third group of terminals contains small granulated vesicles and in the fourth type of terminals, large, 150- to 250-nm 'peptiderg' vesicles could be observed. The latter type of terminals was always observed in postsynaptic situation. Spine synapses could also be found in the ureterovesical ganglia. Several desmosome-liek attachments also could be observed between the nerve processes and perikaraya and between two nerve fibers. Up to three different types of nerve fibers have been observed on the same neuron. These morphological results suggest that the ureterovesical junction should be considered a single functional unit which plays an important role in coordinating the function of the bladder; further local circuits might exist in the urinary bladder wall.

Ultrastructure of the nerve cells and fibres in the urinary bladder wall of the cat.

The nerve elements in the urinary bladder of the cat were studied by electron microscopy. According to their ultrastructure, nerve cell somata can be classified into three types: the large cells with a cytoplasm rich in organelles, several processes and numerous synaptic contacts on their surface; the cytoplasm contained 80- 120-nm granulated vesicles. The second type is poor in cytoplasmic organelles and has very few processes and virtually no synaptic contacts on the soma. The third type contains numerous large 160- to 220-nm 'neurosecretory' vesicles in the cytoplasm. According to the morphology of the vesicle population, four types of nerve processes could be distinguished: Type a, with a dominant population of small (40-60 nm) agranular vesicles. These are thought to be sacral parasympathetic fibres. Type b, with small (40-60 nm) granular vesicles, which may be the noradrenergic sympathetic fibres. Type c, with 80- to 120-nm granulated vesicles, probably of local origin. Typed d, with large 160- to 220-nm 'neurosecretory' vesicles also of local origin. Different types of nerve fibres are converging on the local nerve cells. This suggests that the local circuits can play an important role in coordinating the function of the bladder. Therefore, ganglia may be considered as an elementary functional unit.

Morphological changes in the small intestine of the cat following transection of the vagal nerve.

An attempt was made to identify the vagal fibres of the small intestine and to investigate their course by secondary degeneration after transection of both vagus nerves just below the ganglion nodosum. Under the electron microscope, degenerated fibres could be observed in the myenteric and submucous plexuses, in the longitudinal and circular muscular coats of the duodenum and jejunum. No signs of degeneration were encountered in the wall of the ileum. Direct synaptic relationship between these degenerated fibres and the nerve cells and intact nerve processes could scarcely be found. The degenerated axons do not differ basically from other, intrinsic nerve processes containing round clear vesicles (30--60 nm in diameter) and granular vesicles (80--120 nm in diameter). The sporadic occurrence of the degenerated axons on the surface of cell somata and processes might indicate that the vagal nerve innervates only a few neurons in the small intestine and that the intrinsic neurons contact a large number of other neurons via processes in the intestinal wall. The vagal nerve fibres thus seem to have a modulatory effect on the activity of the intestinal wall.

Ultrastructural effects of parachlorophenylalanine, 5-hydroxytryptamine and the imipramine group on the nerve processes of the small intestine.

The structure of the nerve fibres in the chronically isolated cat ileum was studied by fluorescence and electron microscopy after imipramine group compounds, parachlorophenylalanine, and 5-hydroxytryptamine treatment. Following treatment with parachlorophenylalanine and imipramine group compounds in the nerve fibres of the small intestine, specific granules were selectively decreased (p less than 0.001) in number. In concordance with ultrastructural observations, a marked diminution of fluorescence intensity was demonstrable in the small intestine. In addition, the number of the granular vesicles was significantly increased following 5-hydroxytryptamine treatment, and yellow fluorescent neurones and processes were observed in the myenteric and submucous plexuses. On the basis of these observations, the serotoninergic nature of certain nerve fibres could be demonstrated.