Serotonin-containing nerve fibers in the rat spinal cord: electron microscopic immunohistochemistry.

The ultrastructure of the serotonin (5HT) system in the spinal cord of rats was studied by an immunohistochemical peroxidase-antiperoxidase (PAP) method. Under the light microscope, 5HT immunoreactive staining was observed as brown-colored dots in the anterior horn, lateral horn, posterior horn and pericentral canal region. These positively staining dots were probably indicative of 5HT immunoreactive varicosities and nerve terminals. At the ultrastructural level, 5HT immunoreactive nerve fibers appeared as darkly stained varicosities with PAP positive large electron dense vesicles (80-100 nm), as well as small clear vesicles (30-40 nm) finely coated with PAP immunoreactive products. In the anterior horn, some of the 5HT immunoreactive structures were clearly nerve terminals forming asymmetric synaptic contact with soma or dendrites of the anterior horn cells. In the lateral horn, posterior horn and pericentral canal region, however, only 5HT positive varicosities were detected.</p

Ultrastructure of monoaminergic terminals in the intermediolateral nucleus of the cat spinal cord.

Monoaminergic innervation of the intermediolateral nucleus of the cat spinal cord was investigated by fluorescence histochemistry and electron microscopy. Large numbers of monoaminergic terminals were labeled by prior administration of the false neurotransmitter 5-hydroxydopamine (5-OHDA). Ultrastructurally, 5-OHDA-labeled terminals fell into three types. Type I, which made up 55% of the labeled terminals, contained abundant, large and densely labeled vesicles and only a few small and unlabeled vesicles. This type was &#34;bouton de passage&#34;. Type II, which made up 40% of the terminals, made asymmetrical synaptic contacts with typical postsynaptic structures. This type contained many small vesicles, some of which were labeled, and a few large dense-core vesicles. Type III, which made up 5% of the terminals, made close contact with presynaptic nerve endings containing abundant small unlabeled clear vesicles. The type III terminals contained many large and densely labeled vesicles and a few small flattened vesicles, most of which were unlabeled.</p

Electron microscopic study of mossy fiber endings of the hippocampal formation in El mice.

The effects of seizure activity on the mossy fiber endings of El mice were studied by electron microscopy. During epileptic seizures of El mice, the number of clear round vesicles (50 nm) in the mossy fiber endings of the hippocampal formation decreased, while the number of large densecore vesicles (100 nm) increased. In these endings, the large dense-core vesicles were scattered during the resting state, but after seizure activity they tended to accumulate together and attach to the presynaptic membrane. Omega-shaped profiles, which seemed to be due to exocytosis of the large dense-core vesicles, were seen in the presynaptic membrane.</p

Light and electron microscopic observation of specific atrial granules using water-miscible resin as an embedding medium.

A mixture of glycol methacrylate (GMA) and Quetol 523 was examined as an embedding medium for atrial tissue to be selectively stained for specific atrial granules. Semi-thin sections of rat atrial tissue embedded in this resin were stained with lead hematoxylin and observed under a light microscope. Atrial granules were found to be specifically stained blue black with lead hematoxylin. The same semithin sections stained with OsO4 vapor were examined electron microscopically and the atrial granules could be distinguised clearly from other cytoplasmic components. The GMA-Quetol 523 mixture is a useful embedding medium for studying the distribution of specific atrial granules by light and electron microscopy.</p

Detection of metastatic neuroblastoma cells in bone marrow aspirates by formaldehyde induced fluorescence histochemistry.

Metastatic neuroblastoma cells in bone marrow aspirates were examined by the formaldehyde induced fluorescence histochemical method. With this method we could easily identify abnormal cells as metastatic neuroblastoma cells by observing catecholamine green colored fluorescence in their cytoplasma. This formaldehyde induced fluorescence histochemical method is significantly useful for the diagnosis of metastatic neuroblastoma of the bone marrow.</p

A scanning electron microscopic study of the two-step effect of cytochalasin B on Ehrlich ascites tumor cells.

The effect of cytochalasin B (CB) on the surface structure of Ehrlich ascites tumor cells was investigated using the scanning electron microscope. The effect occurs in two steps: formation of zeiotic knobs on the cell surface and subsequent grouping of the knobs at one pole of the cell. The early step of zeiotic knob formation occurs at low concentrations of CB (0.5-1 microgram/ml) at 37 degrees C and at high concentrations of the drug (5-10 microgram/ml) at low temperature but within 1 min at 37 degrees C. This step is only partially inhibited by 5 x 10(-3) M sodium azide. The subsequent grouping of zeiotic knobs lasts for more than 2 min at 37 degrees C and occurs only in the case of high concentrations of CB. It is inhibited by sodium azide and is often associated with grouping of the microvilli, which are then lost from all of the cell surface except the area of knob-grouping.</p

Exocytotic features of rat specific atrial granules.

To clarify the mode of secretion of specific atrial granules, rat atrial muscle cells were examined by transmission electron microscopy. Atrial granule formation and exocytotic features of granules were clearly seen. Abrupt breaks in the unit membrane structure of mature granules were observed in thin sections, but these breaks were not detected in freeze-fracture replicas. These findings support the concept that the granule contents are released to the extracellular space by exocytosis.</p

The experimental and histochemical study in the rat hippocampal formation.

The hippocampal formation of the rat brain was studied by the Falck-Hillarp method and Karnovsky method after administration of dithizone, alloxan, and oxine. The purpose of this experiment was to clear the relation between cholinergic, adrenergic terminals and zinc in the mossy fiber synaps. The acetylcholinesterase and catecholamine reaction increased in oxine and dithizone administration. On the other hand, when dithizone and oxine were administrated, zinc decreased in the mossy fiber synaps. From this result, the relation between zinc in mossy fiber synaps and acetylcholinesterase, catecholamine in the hippocampus were discussed