Immunocytochemical localization of somatostatin-28 in the rat hypothalamus

Somatostatin-28 (SS28) is considered as a precursor of somatostatin-14 (SS14) and also of the remaining NH2 terminus of SS28, the dodecapeptide SS28 which has been recently characterized. In order to study the cellular and subcellular localization of SS28 in the rat hypothalamus, we have conducted a light and electron microscopic immunocytochemical study, using both the peroxidase-antiperoxidase and the immunogold technique. Several antisera which selectively recognize one or more of these 3 somatostatin-related peptides were used. In serial paraffin sections, it was observed that SS28 was contained in the same neuronal cell bodies which also contain SS28. These neurons were exclusively located in the periventricular nucleus. All the antisera used also produced a strong staining in the external zone of the median eminence. At the electron microscopic level, the 3 peptides were exclusively localized in all the dense core vesicles in cell bodies and axons in the periventricular nucleus and terminals in the median eminence. These results strongly suggest that SS28 and SS14 originate from the precursor SS28 and that processing of the precursor occurs in the cell body. They also support the hypothesis that the 3 peptides are released simultaneously under appropriate stimulation.

Immunohistochemical identification of the uncoupling protein in rat brown adipose tissue

Brown adipose tissue mitochondria are characterized by the presence of an uncoupling protein that gives them an exceptional capacity for substrate-controlled respiration and thermogenesis. The specific localization of this protein in rat brown adipocytes was demonstrated using an immunohistochemical technique, the peroxidase-antiperoxidase (PAP) method. Light microscopy observations showed that serum antibodies raised against the uncoupling protein selectively reacted with multilocular brown adipocytes. No labeling could be detected in either unilocular adipocytes, capillaries, or muscle fibers (striated and vascular smooth muscle). Staining was more intensive in certain adipocytes than in others, suggesting the presence of cellular heterogeneity. The specificity of the staining technique was demonstrated by showing that treatment of the preparations with antiserum saturated with an excess of uncoupling protein almost entirely inhibited brown adipocyte labeling. The specificity and selectivity of the PAP method allow the clear differentiation of uncoupling protein-containing adipocytes from other cellular types, suggesting that this immunohistochemical technique will represent an extremely useful tool for studying adipocyte function and differentiation.

Electron microscope immunocytochemical localization of neuropeptide Y (NPY) in the rat brain

In order to identify the neuronal structures as well as the intracellular organelles which contain the newly discovered brain peptide, neuropeptide Y (NPY), we have localized this peptide by immunoelectron microscopy in brain areas containing high levels of NPY. Ultrastructural studies using both the pre- and post-embedding immunoperoxidase techniques have shown that NPY-like immunoreactivity could be observed in neuronal cell bodies, dendrites and axonal processes. In terminals, the reaction product was associated with the large dense core vesicles. Only a small percentage of the positive terminals were seen making synaptic contacts. These results support the hypothesis that NPY can act as a neurotransmitter or neuromodulator.

Acute and chronic experimental optic neuritis. Alteration in the blood-optic nerve barrier

Horseradish peroxidase (HRP) tracer studies in experimental allergic optic neuritis showed alterations in the blood-optic nerve barrier. Light and electron microscopic examination of the optic disc disclosed intense leakage of HRP at the lamina scleralis, with extracellular staining of both axonal and glial columns, despite the lack of inflammation at this region. The intraorbital optic nerve showed leakage of HRP at the sites of both acute and chronic demyelination. Ultrastructurally, leakage of HRP was confined to the perivascular and extracellular spaces. The mechanism of leakage seems to be by diffusion through the endothelial cell junctions or vesicular transport across the endothelial cells. The high predilection for involvement of the optic nerve in chronic demyelinating disorders may be due to the inherent weakness of the blood-brain barrier at the optic nerve head.

Primary position vertical nystagmus and cerebellar ataxia

Hereditary cerebellar ataxia was evaluated clinically and by electro-oculography in three members of a family. There was no clinical evidence of exttra-cerebellar dysfunction although quantitative eye movement analysis did shown internuclear ophthalmoparesis and slow saccadic velocity suggestive of brainstem dysfunction. In addition, oculomotor examination showed primary position vertical nystagmus in all patients. Other findings were in accord with previous reports of cerebellar-related oculomotor dysfunction.

Biological and immunological characterization of alpha-melanocyte-stimulating hormone (alpha-MSH) in two neuronal systems of the rat brain

Recent immunocytochemical studies have demonstrated the existence of two different neuronal systems containing alpha-MSH-like material in the brain: one originating from the arcuate nucleus and the other one from the dorsolateral hypothalamus. The aim of the present study was to further characterize alpha-MSH in these two discrete regions of the rat diencephalon. Intracerebroventricular administration of colchicine resulted in a marked decrease in the number of ACTH and beta-endorphin nerve fibers and a significant reduction in ACTH and beta-endorphin content in the dorsolateral hypothalamus. Conversely, colchicine treatment did not alter alpha-MSH, ACTH or beta-endorphin content in the arcuate nucleus and did not significantly affect alpha-MSH concentration in the dorsal region. Reverse-phase high-performance liquid chromatography showed that the major alpha-MSH-like compound localized in the dorsal hypothalamus co-migrated exactly with synthetic alpha-MSH, whereas the arcuate nucleus contained 5 peptides cross-reacting with alpha-MSH antibodies, 4 of them being different from standard alpha-MSH. Significant amounts of biologically active melanotropin, which migrated on Sephadex G-25 columns like synthetic alpha-MSH, were also detected in both the arcuate nucleus and dorsolateral hypothalamus. Taken together, these data demonstrate that the alpha-MSH cell bodies located in the dorsolateral hypothalamus specifically produce authentic alpha-MSH, whereas the alpha-MSH cell bodies in the arcuate nucleus also contain ACTH, beta-endorphin and several peptides immunologically related but not identical to alpha-MSH.

Further studies on the identification of neurons containing immunoreactive alpha-melanocyte-stimulating hormone (alpha-MSH) in the rat brain

In order to identify more accurately the organelles containing immunoreactive alpha-melanocyte-stimulating hormone (alpha-MSH) in the rat brain, attempts were made to improve the ultrastructural preservation of the neural tissue used for immunostaining of the peptide. With the post-embedding staining technique, the quality of the preservation was not adequate since only low concentrations (0.2-0.5%) of OsO4 could be used for postfixation. Higher concentrations of OsO4 completely destroyed the antigenicity of alpha-MSH. With the pre-embedding technique in which the immunostaining is performed prior to postfixation with OsO4, a good preservation could be obtained making possible the identification of organelles and classification of endings containing immunoreactive alpha-MSH. In the dendrites, the staining was rather diffuse without any clear association with organelles. In the endings, the staining was mostly restricted to dense core vesicles with some degree of diffusion in the cytoplasm. None of the positive endings were seen making synaptic contact. These results support the hypothesis that alpha-MSH could be released in sites other than the classical synaptic junction and act as a local hormone.

Effects of chronic demyelination on axonal transport in experimental allergic optic neuritis

Axonal transport studies were undertaken to determine the effect of chronic demyelination on axonal function in experimental allergic optic neuritis in the guinea pig, an animal model for multiple sclerosis. Fast and slow components of axonal transport over the prelaminar, laminar, and retrolaminar portions of the optic nerve head and at the foci of demyelination in the retrobulbar optic nerve were evaluated by the autoradiographic grain-counting technique. At 6 hr there was a significant increase in grain counts over the demyelinated foci and in the regions proximal to the demyelination, including the swollen disc. At day 1 there was no significant difference in the grain counts at the site of demyelination when compared to the myelinated portion of the nerve. However, at days 3 and 7 there was a decrease in the number of grains over the demyelinated areas. These results indicate impairment of axonal function in chronic demyelination. Moreover, in this pathologic process, most of the synthesized materials appear to move in the fast transport phase, unlike in the normal optic nerve where the bulk of materials move by slow transport.

Differential projections of two immunoreactive alpha-melanocyte stimulating hormone (alpha-MSH) neuronal systems in the rat brain

Immunocytochemical localization of alpha-MSH was performed in the brain of rats of which the arcuate nucleus has been destroyed by treatment with monosodium glutamate in the neonatal period. In these animals, alpha-MSH cell bodies normally found in the arcuate nucleus were almost completely absent. The reactive fibers found in the ACTH-beta-LPH pathway were also markedly decreased. On the other hand, alpha-MSH cell bodies located in the dorsolateral hypothalamus as well as fibers located outside the ACTH-beta-LPH pathway were not decreased. These results strongly suggest that alpha-MSH cell bodies in dorsolateral hypothalamus have projections completely different from those located in the arcuate nucleus.

Pulmonary core biopsy by percutaneous needle aspiration

Percutaneous aspiration needle biopsy for pulmonary lesions has been practised for many years but has not until recently gained popularity. Further proof of its simplicity, safety and accuracy for both central and peripheral lesions is given in this retrospective study of 181 biopsies performed in a community hospital. The diagnostic yield was higher in neoplastic (87.5%) than in nonneoplastic (68.4%) lesions and higher in malignant (91%) than in benign (58.3%) neoplasms. The larger the lesion the higher was the success rate--95.6% if the lesion was larger than 3 cm. The complication rate was low (14.9%) and there were no deaths. There was no difference in the success rate or the incidence of complications between biopsy done for central or peripheral lesions. The complication rate did not differ between large and small lesions, localized or diffuse. The sample could be used for cell block histologic sectioning, which gave the same diagnostic accuracy as cytologic examination. There were no false-positive cytologic diagnoses. During the procedure the operator (a radiologist in all cases) was able to predict the diagnosis in cases of hamartoma and neurofibroma.

Endobronchial metastasis from renal adenocarcinoma simulating a foreign body

A patient was seen with right lower lobe collapse which partially re-expanded after removal of an endobronchial mass, initially thought to be a foreign body. The pathology revealed clear cell carcinoma identical with the primary removed from his kidney three years before.

Identification of a second category of alpha-melanocyte-stimulating hormone (alpha-MSH) neurons in the rat hypothalamus

An immunocytochemical localization of alpha-melanocyte-stimulating hormone (alpha-MSH) as well as ACTH and a fragment (16K) of the common precursor of ACTH and beta-lipotropin (beta-LPH) was performed in rat brain. Two different groups of neuronal cell bodies showing alpha-MSH-like immunoreactivity (alpha-MSH-LI) were observed in the hypothalamus. One group of neurons located in the arcuate nucleus was shown to contain not only alpha-MSH-LI, but also ACTH and the 16K fragment. A second category of alpha-MSH-LI-containing neurons was characterized by the complete absence of staining for ACTH and 16K fragment. These neurons were mainly located in the dorsal-lateral portion of the hypothalamus. Immunoelectron microscopy showed that immunostaining for alpha-MSH was restricted to dense core vesicles in the positive perikarya. Nerve fibers staining for alpha-MSH (but not for ACTH and 16K fragment) were also observed outside the ACTH-beta-LPH pathway, especially in the cortex, caudate-putamen nucleus and hippocampus. These findings strongly suggest the presence of two different neuronal systems reacting with antibodies to alpha-MSH.

Localization of a 16,000-dalton fragment of the common precursor of adrenocorticotropin and beta-lipotropin in the rat and human pituitary gland

To clearly identify cells and organelles containing the common precursor (31,000 dalton) for both adrenocorticotropin (ACTH) and beta-lipotropin (beta-LPH), an immunohistochemical localization of a fragment (16,000 dalton) of the precursor that is not common to beta-LPH and ACTH was conducted in rat and human pituitary glands. With the help of specific antibodies that do not cross-react with beta-LPH and ACTH, the 16,000-dalton fragment was localized in the cells that also produce ACTH and beta-LPH in both the pars distalis and pars intermedia of the rat pituitary. At the electron microscope level, the secretory granules that contain ACTH were also stained for 16,000-dalton fragment. In the human pituitary, the 16,000-dalton fragment was also observed in all the secretory granules of lipocorticotrophs. These results suggest that, after enzymatic cleavage, fragment(s) of the common precursor and/or the whole common precursor remain packaged within the secretory granules with peptides of known activity.

Immunohistochemical localization of gamma-endorphin in the rat pituitary gland and hypothalamus

To gain more information about cells and organelles involved in the secretion of gamma-endorphin in the rat pituitary gland, an immunohistochemical localization of this peptide was conducted at both light and electron microscopic levels. Using an antiserum to gamma-endorphin which shows little cross-reactivity with beta-lipotropin (beta-LPH) and beta-endorphin, it has been demonstrated that gamm-endorphin is present in all cells of the intermediate lobe and the corticotropic cells of the anterior lobe. At the electron microscopic level, staining for gamma-endorphin was restricted to the secretory granules which also contain ACTH and beta-LPH, suggesting that all of these peptides are released concomitantly during exocytosis. In the hypothalamus, immunostaining possibly related to both gamma- and beta-endorphin but not to beta-LPH was also observed in nerve fibers and not in cell bodies.