A light and electron microscopic study of the CB1 cannabinoid receptor in the primate spinal cord

The distribution of cannabinoid receptors was studied in the monkey spinal cord by immunocytochemistry and electron microscopy, using an antibody to the CB1 brain cannabinoid receptor. Large numbers of labelled neurons were observed in all portions of the grey matter of the spinal cord. These included small diameter 9–16µm neurons in the dorsal horn, larger (40–60µm) neurons in the intermediate grey, and very large (60–100µm), motor neurons in the ventral horn. Reaction product was observed in dendrites postsynaptic to unlabelled axon terminals. Since cannabinoid receptor activation decreases neuronal excitability by several mechanisms, including inhibition of voltage dependent calcium channels, the dense staining of CB1 in dorsal horn neurons suggests that CB1 could reduce calcium influx through such channels in these neurons. This, in turn, could decrease calcium-dependent changes in synaptic transmission and decrease sensitisation to nociceptive stimuli in these neurons. Similarly, the dense staining of CB1 in ventral horn cells suggests that cannabinoid receptors could limit calcium influx through voltage dependent calcium channels in these neurons, and could be significant in terms of neuroprotection to these neurons.     

A light and electron microscopic study of the CB1 cannabinoid receptor in monkey basal forebrain

The distribution of the CB1 cannabinoid receptor was studied in the monkey basal forebrain by immunocytochemistry and electron microscopy, using an antibody to the CB1 brain cannabinoid receptor. Large numbers of labelled neurons were observed in the medial septum, nucleus of the diagonal band, and the nucleus basalis of Meynert. The labelled neurons had dimensions similar to those of cholinergic neurons and were larger than those of GABAergic neurons. Double immunolabelling with an antibody to the synthetic enzyme for acetylcholine, choline acetyl transferase (ChAT) showed that CB1-positive neurons were also positive for ChAT, whilst electron microscopy confirmed that CB1-labelled neurons contained lipofuscin granules and dense clusters of rough endoplasmic reticulum, characteristic of cholinergic neurons. The dense labelling of cholinergic neurons for CB1 is interesting from the standpoint of neuroprotection. The CB1 receptor has been shown to couple in an inhibitory manner to voltage dependent calcium channels, and the dense labelling of CB1 in cholinergic neurons would therefore suggest that CB1 receptors could be important in limiting calcium influx through voltage dependent calcium channels in these neurons. This could serve to limit intracellular calcium concentrations, and consequent calcium mediated injury, in these neurons.     

Characterization of CB1 cannabinoid receptor immunoreactivity in postmortem human brain homogenates

The CB1 cannabinoid receptor (CB1) is the predominant type of cannabinoid receptor in the CNS, in which it displays a unique anatomical distribution and is present at higher densities than most other known seven transmembrane domain receptors. Nevertheless, as with almost all seven transmembrane domain receptors, the tertiary and quaternary structure of this receptor is still unknown. Studies of CB1 in rat cerebral tissue are scarce, and even less is known regarding the expression of CB1 in the human brain. Thus, the aim of the present work was to characterize CB1 expression in membranes from postmortem human brain using specific antisera raised against this protein. Western blot analysis of P1 and P2 fractions, and crude plasma membrane preparations from the prefrontal cortex showed that CB1 migrated as a 60 kDa monomer under reducing conditions. These data were confirmed by blotting experiments carried out with human U373MG astrocytoma cells as a positive control for CB1 expression and wild-type CHO cells as negative control. In addition, when proteins were solubilized in the absence of dithiothreitol, the anti-human CB1 antiserum detected a new band migrating at around 120 kDa corresponding in size to a putative CB1 dimer. This band was sensitive to reducing agents (50 mM dithiothreitol) and showed sodium dodecylsulphate stability, suggesting the existence of disulfide-linked CB1 dimers in the membrane preparations. Important differences in the anatomical distribution of CB1 were observed with regard to that described previously in monkey and rat; in the human brain, CB1 levels were higher in cortex and caudate than in the cerebellum.     

A light and electron microscopic study of mannosidosis

The present work investigated the light and electron microscopic changes in hypertrophied gingiva in a patient with mannosidosis. The biopsy specimens studied covered a period of 20 months; biopsy specimens were taken before and after a therapeutic trial with oral and local zinc sulfate. The intensity of the disease was progressive, in spite of the zinc, and was characterized by marked hyperplasia of the epithelium and severe inflammation of the stroma. Many of the cells in the inflammatory infiltrate, as well as cells indigenous to the gingiva, showed a striking vacuolation of their cytoplasm. Histiocytes were most numerous and also were most heavily vacuolated, but fibroblasts, endothelial cells, plasma cells, and epithelial cells also manifested the vacuolar change. In the histiocytes, the vacuoles occupied most of the cytoplasm, ranged widely in size, and were contiguous, molded, and intercommunicating. The vacuoles were bound by a single membrane and were filled predominantly by a finely granular material of medium density but also by varying amounts of coarser, darker granules, fragmented membranes, myelin-like figures, lipid droplets, and small vesicles. The vacuoles were interpreted as being consistent with secondary lysosomes that contained excessively stored substrate, similar to what has been observed in the mucopolysaccharidoses, in which the vacuoles have also been demonstrated histochemically and cytochemically to contain acid phosphatase, a known lysosomal marker.     

Estrogen-producing adrenocortical carcinoma. A light and electron microscopic study

A case of adrenocortical carcinoma with feminization seen in a man aged 35, is reported. The levels of estron (E1) and estradiol (E2) in the venous blood draining the tumor were high, and it was confirmed by in vitro assay of tumor cells taken from the primary tumor of the left adrenal gland that the tumor produced estrone. The light microscopic examination demonstrated that the primary tumor was composed of mixture of large cells with pleomorphic nuclei and vacuolated cytoplasm and uniform cells with ovoid nuclei and eosinophilic cytoplasm. The electron microscopic examination on the latter cells revealed numerous large and irregularly shaped mitochondria with mostly tubular or lamellar and occasionally vesicular cristae and electron-dense matrix, well-developed smooth-surfaced endoplasmic reticulum in the cytoplasm. However, lipid droplets and lysosomes or lipofuscin granules were scanty. From these findings, it is suggested that cells of the present tumor have characteristics of those in the zona reticularis of the adrenal cortex as well as in the fetal cortex, and the functional property of this tumor is well correlated with its morphological features.     

A light and electron microscopic study of GAT-1 in the monkey basal ganglia

The distribution of the GABA transporter GAT-1 was studied by immunocytochemistry and electron microscopy in the monkey basal ganglia. Dense staining was observed in the globus pallidus externa and interna, intermediate in the subthalamic nucleus, and substantia nigra, and light staining in the caudate nucleus and putamen. Staining was observed in axon terminals, but not cell bodies. Electron microscopy showed that the GAT-1 positive axon terminals formed symmetrical synapses, suggesting that they were the terminals of GABAergic neurons. Comparison of areas high in GAT-1 protein with that of GABA showed a good correlation between the density in neuropil staining for GAT-1, and that of GABA.     

Mesangial involvement in hemolytic-uremic syndrome. A light and electron microscopic study.

Electron microscopic analysis of the mesangial injury in the hemolytic-uremic syndrome was performed in 10 patients. Proteinaceous material similar to that found in the subendothelial region was also seen focally in the mesangium altering the matrix and imparting a reticular appearance. This degenerative process was associated with reparative changes in the glomerular tuft. Many of the mesangial cells were hypertrophied and demonstrated phagocytic activity and peripheral extension of their cytoplasmic processes. Mitotic figures in endothelial as well as mesangial cells were regarded as evidence of a reparative process. Severe mesangial insudation of material containing fibrinogen derivatives resulted in segmental tuft necrosis with almost complete replacement and destruction of the mesangial matrix. On some occasions, a break of the glomerular basement membrane was accompanied by the escape of intraluminal contents into the urinary space, leading to crescentic epithelial cell proliferation.     

Poorly differentiated synovial sarcoma. A light and electron microscopic study.

Few studies of the ultrastructural features of synovial sarcoma have appeared in the literature. The case under study represented a poorly differentiated synovial sarcoma with a predominant fibrosarcomatous component and a few areas with epithelioid and pseudoacinar patterns. Ultrastructurally, the cellular elements of the varied histologic patterns were similar. Basement membranes and desmosomes were absent, and the cell surfaces facing the acinar lumen exhibited multiple microvilli. It appears from a comparison of our studies with the previous reports that the fine structure of this tumor varies according to the degree of histologic differentiation.     

Ochronotic arthropathy. A comparative scanning electron microscopic and light microscopic study of the synovium in ochronosis

The synovium in two cases of ochronosis was studied by scanning electron microscopy and light microscopy. Several features not yet described were seen by scanning electron microscopic examination and correlated with the light microscopic findings. This is the first report in the English language literature comparing scanning electron microscopic findings with the light microscopic findings in ochronosis.     

CB1 and CB2 cannabinoid receptor expression during development and in epileptogenic developmental pathologies

Recent data support the involvement of the endocannabinoid signaling in early brain development, as well as a key role of cannabinoid receptors (CBR) in pathological conditions associated with unbalanced neuronal excitability and inflammation. Using immunocytochemistry, we explored the expression and cellular pattern of CBR 1 and 2 (CB1 and CB2) during prenatal human cortical development, as well as in focal malformations of cortical development associated with intractable epilepsy (focal cortical dysplasia; cortical tubers in patients with the tuberous sclerosis complex and glioneuronal tumors). Strong CB1 immunoreactivity was detected in the cortical plate in developing human brain from the earliest stages tested (gestational week 9) and it persisted throughout prenatal development. Both cannabinoid receptors were not detected in neural progenitor cells located in the ventricular zone. Only CB1 was expressed in the subventricular zone and in Cajal–Retzius cells in the molecular zone of the developing neocortex. CB2 was detected in cells of the microglia/macrophage lineage during development. In malformations of cortical development, prominent CB1 expression was demonstrated in dysplastic neurons. Both CBR were detected in balloon/giant cells, but CB2 appeared to be more frequently expressed than CB1 in these cell types. Reactive astrocytes were mainly stained with CB1, whereas cells of the microglia/macrophage lineage were stained with CB2. These findings confirm the early expression pattern of cannabinoid receptors in the developing human brain, suggesting a function for CB1 in the early stages of corticogenesis. The expression patterns in malformations of cortical development highlight the role of cannabinoid receptors as mediators of the endocannabinoid signaling and as potential pharmacological targets to modulate neuronal and glial cell function in epileptogenic developmental pathologies.     

The pathology of Tangier disease. A light and electron microscopic study.

Tangier disease (deficiency of high density plasma lipoproteins) is characterized clinically by: low levels of plasma cholesterol; enlarged, orange-yellow to yellow-gray tonsils and, frequently, peripheral neuropathy. Histologic and ultrastructural studies were made of various tissues from 5 patients with Tangier disease, and comparisons were made of these findings with those in the 12 other patients thus far known to have this disease. Deposits of cholesteryl esters were found in: reticuloendothelial cells (foam cells) in tonsils, bone marrow, skin and jejunal submucosa; Schwann cells in peripheral nerves and myenteric plexus; and in nonvascular smooth muscle cells. These deposits appeared electron lucent and intensely birefringent, varied from spherical to crystalline in shape, often were extensively confluent throughout large areas of cytoplasm, and were not limited by membranes. Certain foam cells in bone marrow also contained membrane-limited clusters of lipid particles resembling chylomicrons. The foam cells in Tangier disease differ morphologically from those in numerous lysosomal enzyme deficiency states, particularly Wolman's disease and cholesteryl ester stroage disease, and in proliferative diseases of the reticuloendothelial system in which cholesteryl esters also accumulate in abnormal histiocytes. Morphologic and biochemical data suggest several hypotheses to explain the accumulation of cholesteryl esters in tissues of patients with Tangier disease. Among these hypotheses, the most likely are considered to be the presence in plasma of abnormal lipoprotein particles that are subject to phagocytic removal by reticuloendothelial cells, and the failure of a process that normally removes locally synthesized cholesterol from cells to plasma. (Am J Pathol 78:101-158, 1975)