W.C. Wong

Immunocytochemical localization of CR3 complement receptors with OX-42 in amoeboid microglia in postnatal rats.

SummaryThe present study described the labelling of amoeboid microglial cells in the postnatal rat brain with OX-42, an antibody that recognizes type 3 complement receptors CR3 in mononuclear phagocytes. Of the diverse morphological forms of amoeboid microglia present in the corpus callosum in early postnatal (2–5 days) rats, cells with a round regular outline, or showing short stout processes, were the most intensely stained. When traced from the main cell colony into the borderline zone with the cortex, the immunoreactivity of amoeboid microglia that assumed a ramified form was drastically reduced. Examination of materials from the late postnatal (8–12 days) age group showed that the majority of the OX-42 positive cells in the corpus callosum became oval, elongated and ramified. Immunoelectron microscopy confirmed the above observations, and also showed that the immunoreactivity in the round amoeboid microglia was localized in their plasma membrane, surface projections and invaginations, as well as in some of the subsurface vacuoles. The immunoreactivity was reduced in the oval cells, and diminished in the elongated or ramified form. It is proposed that the presence of CR3 membrane receptors in amoeboid microglial cells is related to their active role in endocytosis. These, however, diminish with the growth of the brain.

Development of the Various Glial Cell Types in the Cerebral Cortex of Postnatal Rats

The present quantitative study in the postnatal rats showed the rapid growth of the various glial cell types in the cerebral cortex. Among them, the increase of microglia was most dramatic. The increase was about 15 times, covering a period of 15 days extending from 5 days of age to 20 days. The majority of the microglia observed were in the outer third of the cortex. During the same period, the number of oligodendrocytes and astrocytes also showed a steady but moderate increase. The increase of oligodendrocytes was most significant between 5 and 10 days. Their density was greater in the inner third of the cortex. Astrocytes were distributed uniformly throughout. Examination of the cerebral cortex in 1- to 3-day-old rats by electron microscopy showed sporadic ameboid microglia cells and glioblasts. The possibility that they served as the precursor cells of microglia and macroglia (astrocytes and oligodendrocytes), respectively, was considered.

Labelling of amoeboid microglial cells in rats of various ages following an intravenous injection of horseradish peroxidase.

The macrophagic amoeboid microglial cells in the corpus callosum of postnatal rats were labelled following an intravenous injection of horseradish peroxidase (HRP). The earliest time when these cells were labelled was 3 h after the injection of HRP in postnatal (1-10 days) rats. Similar cells around the mesencephalic aqueduct and the fourth ventricle were also labelled. These cells, however, were weakly labelled in developing (11-20 days) and unlabelled in weaning (21-30 days) rats. The results suggest that in the postnatal rats, the HRP passed through the endothelial lining of the blood vessels and was then ingested by the amoeboid microglial cells. In the developing and older rats, the wall of blood vessels had developed fully thereby preventing the free passage of HRP into the brain tissues.

Histochemical observations on the mucins of the gastrointestinal tract in the toad (Bufo melanostictus).

The pattern of mucin secretion of the gastrointestinal tract of the toad (B. melanostictus) was investigated by histochemical methods. The goblet cells of the oesophagus secreted mainly acid mucins which were sialomucins, while the cells lining the surface of the stomach produced neutral mucins only. Goblet cells of the small intestine and cloaca secreted acid mucins, which were predominently sulphated mucins.

NADPH-diaphorase activity in the nodose ganglion of normal and vagotomized guinea-pigs.

Abstract.The activity and distribution of reduced nico-tinamide adenine dinucleotide phosphate diaphorase (NADPH-diaphorase) in the nodose ganglion of normal and vagotomized guinea-pigs were examined by light and electron microscopy. Light microscopy confirmed a remarkable increase in the number of NADPH-diaphorase-reactive neurons in the nodose ganglion following unilateral cervical vagotomy. The increase was present at 5 days but became more prominent at 10 days and was sustained until at least 30 days after vagotomy when compared with the non-lesioned side. The NADPH-diaphorase reaction product was associated with the membrane of the rough endoplasmic reticulum, Golgi apparatus, mitochondria and nucleus of the nodose neurons. In animals killed 5 days post-operation, there was no noticeable degeneration in the nodose neurons. However, at 10 days, the mitochondria in some neurons appeared swollen and vacuolated with disrupted cristae. These changes were accentuated in some nodose neurons 20 and 30 days after vagotomy but there was no evidence of cell death. All the degenerating neurons exhibited NADPH-diaphorase activity. The increase in NADPH-diaphorase activity in the neuronal somata after vagotomy suggests that the enzyme is involved in either the retrograde degeneration or the recovery of the lesioned neurons.

Localization of choline acetyltransferase and NADPH diaphorase activities in the submucous ganglia of the guinea-pig colon

A combined immunohistochemical and histochemical demonstration of choline acetyltransferase (ChAT) and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) was carried out, respectively, to determine the localization of the neurotransmitters, acetylcholine and nitric oxide (NO) in the submucous neurons of guinea-pig colon. Almost half of the submucous neurons in the guinea-pig colon exhibited ChAT-immunoreactivity. Some of the ChAT-immunoreactive neurons were also stained for NADPH-d, although most of them showed only weak to moderate diaphorase activity. Many of the submucous neurons displayed exclusively either ChAT or NADPH-d activity. A close spatial relationship was observed between the cholinergic and nitrergic submucous neurons. Thus, in light microscopy, some ChAT-immunoreactive fibres were closely associated with the NADPH-d-positive nerve cell bodies. Ultrastructural study extended the fact that many of the ChAT-immunoreactive terminals made synaptic contacts with the soma of the NADPH-d-positive submucous neurons. A remarkable feature was the demonstration of ChAT and NADPH-d in some of the neurons and their presynaptic axon terminals, suggesting the co-localization of acetylcholine and NO as neurotransmitters in the submucous neurons and their presynaptic axon terminals. It is suggested that the submucous neurons with their specific neurochemical codings would subserve different functions.

Localisation of substance P-like immunoreactivity in the ciliary ganglia of monkey (Macaca fascicularis) and cat: a light- and electron-microscopic study

The present study describes substance P-like immunoreactivity in the ciliary ganglia of monkey (Macaca fascicularis) and cat. About 60% of neurons in the monkey ciliary ganglion and 40% in the cat ciliary ganglion were substance P-like immunoreactive, ranging from faint to moderate staining. Substance P-like immunoreactivity was located in cell bodies, dendritic profiles and axons. In the monkey, substance P-like immunoreactive pericellular arborisations were associated with about 0.5%–3% of the ganglion cells, which were either negatively, faintly or moderately stained. An electron-microscopic study demonstrated the presence of either substance P-like immunoreactive positive or negative axon terminals synapsing or closely associated with positive dendritic profiles in both the monkey and cat ciliary ganglia. The results suggest that substance P plays an important role in the ciliary ganglion, perhaps as a modulator or transmitter.

Localization of nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) activity in the gastrointestinal sphincters in the guinea pig

The distribution of nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d), a marker for nitric oxide synthase (NOS), in the nerves of gastrointestinal sphincters in guinea pigs was investigated to throw some light on the role of nitric oxide (NO) in these sphincteric regions. The nerve fibres with NADPH-d activity were observed chiefly in the circular muscle layer of the wall of gastrointestinal sphincters. Compared with the adjacent non-sphincteric regions, the proportions of NADPH-d positive myenteric neurons in the lower esophageal sphincter (LES), pyloric sphincter (PS) and internal anal sphincter (IAS) were higher (P < 0.05). The densities of NADPH-d-positive fibres in the circular muscle of above sphincteric regions were also higher (in LES P < 0.01; in PS and IAS P < 0.05). Within the circular muscle of LES, some discrete NADPH-d-positive intrinsic nerve cell bodies, usually smaller than their outlying myenteric neurons, were also observed. The dense distribution of NADPH-d-positive fibres within the circular muscles of gastrointestinal sphincteric regions suggests that NO, as a non-adrenergic non-cholinergic (NANC) inhibitory neurotransmitter, might play an important role in the neuronal regulation of the guinea-pig gastrointestinal sphincters.

Ultrastructural Changes in the Gracile Nucleus of Alloxan-Induced Diabetic Rats

The present study reports ultrastructural changes in the gracile nucleus of male Wistar rats after alloxan-induced diabetes. During the acute phase (3-7 days) degenerating electron-dense dendrites and axon terminals were dispersed in the neuropil. Degenerating dendrites were characterized by an electron-dense cytoplasm, swollen mitochondria, dilated endoplasmic reticulum and randomized ribosomes. Degenerating axon terminals were characterized by an electron-dense cytoplasm and clustering of small spherical agranular vesicles. Degenerating axon terminals may form the central element or part of a synaptic glomerulus. Macrophages were present in the neuropil and in the process of engulfing neuronal elements. During the medium phase (1-6 months), most of the degenerating dendrites and axon terminals had been engulfed or removed by macrophages. During the late phase (9-12 months), a second wave of degeneration occurred in the gracile nucleus, similar to the acute phase.

Degeneration in the adult rat spinal cord following systemic treatment with 6-hydroxydopamine

3 and 5 days following intravenous injection of 6-OHDA (100 mg/kg) in adult rats, the Nauta technique demonstrated sparse axon degeneration in laminae V, VII, IX and X of Rexed in the mid-thoracic spinal cord and also in the lateral and ventral white columns. This showed that in adult rats 6-OHDA may pass the blood-brain barrier at the level of the spinal cord. An unexpected finding was the absence of degeneration in the laminae dorsal to lamina V, where noradrenergic nerve terminals are known to occur.