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Using the subcellular fractionation technique the fine structure of the isolated nerve endings (synaptosomes) from the hemispheres and brain stem of the 1–day old and adult rat was examined. In the synaptosomal fractions of the brain of 1–day old rats we observed a new type of nerve endings containing predominantly large agranular vesicles about 1 000 A in diameter. After incubation with a-methylnoradrenaline or 5–hydroxydopamine these vesicles remained agranular. It is assumed that the new type of large vesicles represent developing synaptic vesicles. References

Carotid bodies of adult albino rats were examined using the formaldehyde-induced fluorescence (FIF) method for the demonstration of fluorogenic monaomines and staining with I% Toluidine Blue for morphological observations.

The human fetal adrenal medulla evidently contains a pool of primitive sympathetic elements, which possess the capacity for differentiation to both catecholamine storing medullary cells and neurons. Furthermore, these cells are organized into large, rounded, tightly packed avascular cell islands which were easily found and/or isolated.The purpose of the present study was to follow the development of primitive sympathetic cells in human fetal adrenal medulla to find the origin of the adrenal neurons.

The fine structure of the preterminal nerve fibers of the rabbit myometrial smooth muscle was studied using potassium permanganate fixation or glutaraldehyde fixation with postosmification. The preterminal fibers were mostly formed by 2–10 axons enveloped by Schwann cells. Two kinds of axons and axon terminals were found. (1) Adrenergic axons, which contained many small, granular vesicles (diameter 300–600 A) and large granular vesicles (diameter 700–1200 A) which represented ca. 2% of the total count of the vesicles. (2) Nonadrenergic axons, which contained small agranular vesicles (diameter 300–600 A) and large granular vesicles (diameter 700–1200 A). Both types of axons formed preterminal varicosities along their course. The real terminal varicosities, representing the anatomical end of the axons, were usually larger than the preterminal ones and showed close contact to the plasma membranes of the smooth muscle cells. Both adrenergic and nonadrenergic terminals were found close to the smooth muscle cells, but a gap of at least 2000 A was always present between the two cell membranes. The axons and preterminal varicosities of both types of nerves were in intimate contact with each other within the preterminal nerve fiber. Axo-axonal interactions between the two types of axons are possible in the rabbit myometrium. The relative proportion of the nonadrenergic axons from the total was about one fourth.

The effect of hydrocortisone, prednisolone, estrogen, progesterone and testosteron on the differentiation of the paracervical ganglion of the rat uterus was examined by the formaldehyde induced fluorescence (FIF) method. Prednisolone and hydrocortisone treatment caused about a tenfold increase in the number of small, intensively fluorescent (SIF) cells. The SIF-cells were larger and organized in larger groups than in untreated animals. The SIF-cells were also arranged in a satellite cell position around the ganglion cells, which were non-fluorescent or showed a weak to moderate FIF. The amount of solitary SIF-cells was increased. No effects detectable by the FIF-method were found with certainty after administration of estrogen, progesterone or testosterone.

The effects of 17-B-estradiol on the fine structure of the autonomic nerves of the rabbit oviduct and myometrium were studied by means of KMnO4-fixation. The main changes due to prolonged estrogen treatment were the following: (1) the dimensions of the axons increased, (2) the amount of smooth endoplasmic reticulum in the axons increased, (3) the amounts of both large granular vesicles (LGV) and large agranular vesicles (LAV) in the axons increased and (4) electron dense grains were found within the endoplasmic tubuli of the axons. Furthermore, it seems probable that the amount of small granular vesicles was also considerably higher after two weeks of estrogen treatment.

The responses of human fetal catecholamine storing tissues, the paraganglia and adrenal medulla to severe oxygen deficiency were tested by using perfusion techniques. The changes in catecholamine content of the target organs were registered by demonstrating the formaldehyde induced fluorescence exhibited by catecholamines. A definite decrease in the intensity of the catecholamine specific fluorescence was observed regularly in the paraganglia after 10–15 min hypoxia. Only very slight changes occurred occasionally in the corresponding adrenal medullae. The role of the target organs and the catecholamine release during oxygen deficiency are discussed.

The distribution and structure of small, intensively fluorescent, granule-containing cells within the human feta! ganglion cenicale superius was studied. The ganglia contained numerous small collections of these cells evenly scattered over the whole region of the organ. The granule-containing cells were as a rule located on the capillaries and showed regularly tight contacts with the basement membrane. The mean diameter of the catecholamine storing granules was 2700 A. The differentiation and role of the granule-containing cells within sympathetic nervous system was discussed.

The fine structure of the paracervical ganglion was studied in the rat after 3 % KMnO4 fixation. Three types of neuronal cells were observed: (1) The majority of cells were devoid of dense-core vesicles (DCV). (2) The minority of cells with typical neuronal structure contained small (500 A) and large (1000 A) DCV. (3) The cells resembling those of the adrenal medulla contained vesicles up to 3000 A in diameter with irregular and dense core. The synaptic axon terminals to the different cell types contained agranular vesicles. Because no small DCVs were found, these synapses are presumably not adrenergic.

The autonomic nerves of the myometrium of the rabbit were studied in order to demonstrate simultaneously the adrenergic nature of an axon and the localization of acetylcholinesterase (AChE) in the same axons. The synaptic vesicles of the adrenergic axons and nerve terminals remained partially filled with the electron dense material typical for them after formaldehyde fixation and short incubation time for AChE. AChE stain was localized regularly on the axons which contained agranular synaptic vesicles and also on axons which contained dense cored synaptic vesicles beeing probably adrenergic. The role of AChE on the adrenergic axons is discussed.

The response of the atypically short adrenergic neurons in rabbit myometrium to 10-14 days of estradiol treatment (1 mcg/kg) was contrasted with neurons in untreated preovulatory adults in their appearance under electron microscopy. Estrogen doubled the size of the terminal axons originating from the preterminal nerve fiver and made them more consistent in size. Small granular vesicles containing transmitter were more evenly dispersed. Numbers and diversity of new ne urotubuli increased particularly along the length of the axon. The proportion of large vesicles 700-1200 Angstrom in diameter increased from 2%-3% to 5%-7% and numerous large agranular vesicles appeared. The large vesicles were occassionally in contact with the neurotubuli apparently continuous with neurotubuli plasma membrane.

A new combination of freeze-drying, formaldehyde induced fluorescence method for catecholamines and autoradiography of water soluble substances was developed and tested with different tissues containing biogenic amines. The freeze-dried tissue pieces were fixed with vaporours paraformaldehyde and OsO4 before embedding procedure. The effect of OsO4-vapour on the formaldehyde induced fluorescence was tested. The method produces semi-thin sections in which the fluorescence is well preserved and the tissue lightly stained with OsO4 which also fixes the steroid hormones used for radioautography.

The ultrastructure and protein content of the five subfractions of the crude mitochondrial fraction from the brain stem of the 1-day old and adult rat was examined. The morphological composition of the subfractions after fixation in glutaraldehyde and osmiumtetroxide in the adult rat brain stem resembled that previously reported for the whole brain; synaptosomes sedimented in a sucrose gradient in subfractions C and D. In the 1-day old rat, mature synaptosomes were found in subfractions A, B, C and D; E contained mainly free mitochondria. 80–95% of the processes in the adult and 10–30% in the 1-day old rat contained synaptic vesicles which were of four types: (1) small agranular vesicles (2) large dense core vesicles (3) large agranular vesicles (4) coated vesicles. Pre- and postsynaptic membrane thickenings were demonstrated in many nerve-ending particles. In the subfractions of the 1-day old rat the protein content was one half and the distribution resembled that in the adult. Evidently nerve endings develop faster in the brain stem than in cortical areas; a serotoninor adrenergic origin of the early synaptosomes is suggested.

The histochemistry and fine structure of human fetal superior cervical ganglion has been studied in 5 fetuses aged from the 13th to the 15th week.

The formaldehyde-induced fluorescence method was used for light microscopy and fixation in glutaraldehyde and osmium tetroxide for electron microscopy to study the effect of 75 mg/kg 6-hydroxydopamine on the paracervical ganglion of the rat uterus. No changes were observed in the fluorescence intensity of the ganglion. Ultrastructurally the ganglion cells and the synapses remained unchanged. The small, intensely fluorescent (SIF) cells were severely damaged, displaying large vacuoles with an irregular contour as well as smaller, more regular vacuoles studded with ribosomes. The granular vesicles showed a lower density of their central parts suggesting that their catecholamine content had diminished.

Two new types of structure of the cytoplasm of an autonomic neuron were described: (1) Inclusions of the rough ergastoplasmic reticulum, which were named “ergastosomes”, contain finely granular material with moderately electron opaque staining with both glutaraldehyde-OsO4 and KMnO4 fixations. A short comment was made on the nature of the contents of the ergastosomes. (2) Tubular formations of endoplasmic reticulum were found in the axons and/or dendrites of the paracervical ganglion.

Adult albino rats were given a single intraperitoneal injection of 400 mg/kg of 6-methylprednisolone sypionate in oil suspension. They were killed one week after the injection, fixed by perfusion with 2.5 % glutaraldehyde in 0.1 M phosphate buffer and by subsequent immersion first in the same solution and then in 1 % osmium tetroxide, also in phosphate buffer.Methylprednisolone caused the appearance of numerous granular vesicles in some glomus cells of the carotid body. While there was a general tendency towards an increase in the number of granular vesicles per unit area of cell profile and towards a decrease in the mean size of the vesicles, the differences from normal were not statistically significant. Formation of parallel arrays of rough-surfaced cisternae of the endoplasmic reticulum was the most conspicuous change due to methylprednisolone.Since similar methylprednisolone treatment causes a marked increase in the intensity of the catecholamine fluorescence in the cytoplasm of the glomus cells, but...

The monoamine containing structures of the human fetal hypothalamohypophyseal tract were studied histochemically by demonstrating the formaldehyde induced fluorescence. First specific fluorescence in the hypothalamus and median eminence was observed at the age of 15 weeks. A sparce network of fluorescent nerve fibres was found to line the walls of the ventricle. Weakly fluorescent cells were found within the stromal cell cords of the adenohypophysis at the age of 11 weeks. Both the number and the fluorescence intensity of these cells increased up to the age of 15 weeks. The apperance of the monoamines in the cytoplasm of the adenohypophyseal cells correlates well with the previous observations on the onset of the function of the fetal adenohypophysis. The lack of monoaminergic innervation of the hypothalamus and median eminence suggests that the hypothalamoadeno-hypophyseal neurohumoral regulation might not be functional during the first trimester of pregnancy.

The carotid bifurcation areas of 25 human fetuses aged from 8 to 22 weeks were studied using the formaldehyde-induced fluorescence method. A long process from the sympathetic trunk reached the area at the age of 8 weeks contacting with the carotid body primordium. Brightly fluorescent cells can be seen both in the carotid body and in the ganglionic process. Migration of these cells from the sympathetic trunk to the carotid body is suggested. The connection from the sympathetic trunk to the carotid body totally disappeared after the tenth week, leaving no fluorescent elements between these two. Control electron microscopy and light microscopy were performed to identify the fluorescent and nonfluorescent components of the human fetal carotid body.