Arthur Hess

Altered catecholaminergic innervation of superior colliculus after enucleation in adult and neonatal hamsters

Abstract The catecholaminergic (CA) innervation of the superior colliculus was examined using histofluorescence techniques in normal hamsters and in animals subjected to removal of the left eye either within 12 h of birth or as adults. In both the neonatal and adult enucleates, the CA innervation of the superficial collicular laminae contralateral to the removed eye was considerably increased. The changes observed in the adult enucleates appeared more substantial thanthose in the animals which sustained eye removals on the day of birth.

Histochemical localization of cholinesterase in the brain of the cockroach (Periplaneta americana).

The histochemical localization of cholinesterase in the cockroach (Periplaneta americana) brain was investigated and compared to the localization of catecholamines as described by others. An inverse relationship occurs in many areas. The calyx, negative after catecholamine staining, stains with cholinesterase in its ventral two-thirds. The alpha and beta lobes appear striped after catecholamine staining and are unstained by cholinesterase. Neuronal cell groups stained by catecholamines are unstained by cholinesterase. A few cells of the pars intercerebralis are stained by cholinesterase, but not by catecholamines. Neuropiles in all lobes of the brain are stained intensely by cholinesterase, while only a few fibers in these areas are seen after catecholamine procedures. The medulla of the optic lobe, unstained by catecholamines, is stained intensely by cholinesterase. An external semilunar zone of the lobula of the optic lobe is stained intensely by cholinesterase and after catecholamine procedures. Neither transmitter can be found in the globuli cells, the dorsal one-third of the calyx, the stem of the mushroom body, and between the catecholaminergic stripes of the alpha and beta lobes. Both transmitters can be found in parts of the central body.

Chronically denervated rat carotid bodies

The ninth nerve was severed and the rat carotid body studied in the light and electron microscopes and after formaldehyde-induced fluorescence for its catecholamine content from 3 weeks to 13 months after operation. Minimal changes in the carotid body were observed. Hyperthrophy of the capsule cell was noticed up to about 2 months, after which time these cells appeared normal. Lysosomes in the capsule cells occurred more frequently and were larger than in normal carotid bodies. Discernible pathological alterations did not occur in the glomus cells, despite the absence of afferent terminals upon them. Atrophy of the carotid body was not noticed. The catecholamine content of the denervated carotid body was comparable to its innervated control and no nerve terminals were found on the glomus cells. Autonomic ganglion cells intrinsic to the carotid body varied in number from 1 to 8 and in location. The glomus cells do not receive any significant autonomic innervation, and the ganglion cells in the carotid body, perhaps sympathetic, probably innervate blood vessels. It is concluded that deafferentation has minimal morphological effects on the carotid body. The reactions of other receptor cells to deafferentation are compared with those of the glomus cells.

Neuropathological changes in the caudate nucleus elicited by MPTP and their prevention by monoamine oxidase inhibition.

MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), a neurotoxin producing parkinsonism, causes an obvious reduction in tyrosine hydroxylase (TH) activity in the caudate nucleus. This depletion of TH activity is due to degeneration of TH-positive punctate dopaminergic terminals. The disappearance of these terminals unmasks the presence of long branching, varicose preterminal fibers, which may be sprouting after degeneration of their terminal arborizations. Glial cells, normally sparse with delicate processes, undergo intense increase in number and a robust hypertrophy. All of these changes are prevented completely by administration of deprenyl, a monoamine oxidase inhibitor, before and after MPTP. These neuropathological effects are additional manifestations of the dopaminergic neurotoxicity induced by MPTP. The metabolism of MPTP, which is blocked by monoamine oxidase inhibition, is apparently necessary for the expression of toxicity in the brain by this neurotoxin.

Localization of noradrenaline and serotonin in nerves in the pineal gland of rats and guinea-pigs studied by glyoxylic acid histofluorescence and electron microscopy

SummaryThe nerves in the pineal gland of the rat and guinea-pig contain both noradrenaline and serotonin and fluoresce intensely after histofluorescence procedures. Vesicle-filled terminals in the perivascular space of the pineal body contain numerous clear and dense-cored vesicles. A 5mg/kg dose of reserpine causes disappearance of histofluorescence from the pineal nerves and a virtual elimination of dense-cored vesicles from vesicle-filled terminals. A 1mg/kg dose of reserpine results in loss of fluorescence and virtual depletion of dense cores in nerves in the rat, but the guinea-pig pineal nerves continue to fluoresce lightly and the dense-cored vesicles are still present but reduced to about 1/3 in number. Subsequent treatment of lightly reserpinized guinea-pigs withp-chlorophenylalanine, a specific depletor of serotonin, results in dis ppearance of fluorescence in nerves in the pineal gland and virtual depletion of the remaining dense cores. A dose of 1mg/kg reserpine succeeds in depleting noradrenaline from most peripheral nervous structures of the guinea-pig. Hence, the remaining monoamine in guinea-pig pineal nerves after depletion of noradrenaline appears to be serotonin located in the remaining dense-cored vesicles. Since, in lightly reserpinized guinea-pig pineal nerves, a number of dense-cored vesicles containing serotonin are still present after depletion of noradrenaline, it is suggested that noradrenaline and serotonin are not in the same vesicles at the same time.

Calcium inhibits catecholamine depletion by reserpine from carotid body glomus cells

Histofluorescent and quantitative microfluorimetric studies have been performed on glomus cells of the rat carotid body, which fluoresce intently after treatment by paraformaldehyde vapor. Reserpine causes a reduction in intensity of fluorescence of about 90%. Subcutaneous injections of calcium chloride (100-300 mg/kg) were given before reserpine. Calcium prevents the depletion of catecholamies from the glomus cells by reserpine. This effect is dose related in that the depletion of catecholamines by heavy reserpine doses (15 mg/kg) cannot be overcome by calcium, medium doses (5 mg/kg) can be overcome but variably, and light doses (1 mg/kg) are always overcome substantially and can result in virtually complete inhibition of the depletion by reserpine. If calcium might counteract the effects of reserpine by occupying attachment sites of the vesicular membrane, thereby preventing reserpine from reaching its site of action, resulting in the usual uptake of catecholamines by the vesicles and suppression of the depleting action of reserpine.

The effects of 6-hydroxydopamine on the appearance of granulated vesicles in glomus cells of the rat carotid body

The glomus cells of the rat carotid body reveal an intense fluorescence after exposure to paraformaldehyde vapor and contain catecholamines. After initial fixation in glutaraldehyde, many granulated vesicles are seen in the glomus cells. After initial fixation in osmium tetroxide, most of the vesicles are depleted of their dense interiors and granulated vesicles occur infrequently. Administration of 6-hydroxydopamine followed by initial fixation in osmium tetroxide leads to the reapperance of dense interiors in virtually all vesicles. 6-Hydroxydopamine apparently is taken up by the membrane pump of the glomus cell and is incorporated into the amine storage granules, thereby displacing the endogenous monoamines. Osmium tetroxide does not dissolve the 6-hydroxydopamine from the vesicles, as it apparently does for the normal vesicular contents. The 6-hydroxydopamine does not fluoresce, hence 6-hydroxydopamine administration results in a decreased intensity of formaldehyde induced fluorescence in the glomus cells. Administration of reserpine after 6-hydroxydopamine treatment (and subsequent initial fixation in osmium tetroxide) depletes the previously restored dense material from the vesicles of the glomus cells. 6-Hydroxydopamine acts like a monoamine in that it is taken up by the glomus cell, incorporated into the vesicles, and can be depleted from the vesicles by reserpine.

The effects of monoamine oxidase inhibition and dopamine uptake blockade on MPTP-induced increase of 2-[3H]deoxyglucose uptake in specific mesencephalic catecholaminergic nuclei

Intraperitoneal injection in C57 black mice of 30 or 7.5 mg/kg MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) followed 1-2 h later by 0.5 mCi/100 g 2-[3H]deoxyglucose (2-DG) produces an intense increase of 2-DG uptake in the dopaminergic zona compacta (ZC) of the substantia nigra and the adjacent ventral tegmental area (VTA) as seen in autoradiographs. Anesthetized animals also exhibit this reaction. Clorgyline (10 mg/kg), a monoamine oxidase (MAO)-A inhibitor, 30 min before MPTP does not block this reaction. Deprenyl (10 mg/kg), an MAO-B inhibitor, blocks increased 2-DG uptake in ZC and VTA if injected 30 min or 12 h before 7.5 mg/kg MPTP, but has no effect if injected 12 h before 30 mg/kg MPTP. Mazindol (10 mg/kg), a dopamine uptake blocker, is effective in blocking the action of 7.5 mg/kg MPTP, but ineffective against 30 mg/kg MPTP. Heavier doses of MPTP can, in some instances, overcome the actions of MAO inhibitors or dopamine uptake blockers in preventing the increased 2-DG uptake elicited by MPTP. But, essentially, the intensely increased glucose metabolism acutely induced in specific catecholaminergic neurons appears to be another significant pathological feature of the dopaminergic neurotoxicity caused by MPTP which can be prevented by MAO inhibition or dopamine uptake blockade.

Neuromuscular Junctions and Electric Organs

The neuromuscular junction has been much studied anatomically and physiologically, not only because of its influence on muscle action, but also because of its ready accessibility as a peripheral synapse and the significant information that it contributes to synaptic morphology and function in general. Fine structural studies employing the electron microscope and histochemical studies, usually involving the localization of Cholinesterase, have contributed most significantly in recent times to our knowledge of the anatomy of the neuromuscular junction. These studies have dealt not only with the structure of the myoneural junction itself, but also with the distribution and location of the nerve terminals on the muscle fibers. Variations have been found, both in the structure and in the disposition of the nerve terminals, and these varieties of endings have attracted attention because they are correlated in many instances with functional variations in the action of the muscle fibers.

Some Aspects of Localization, Depletion, Uptake and Turnover of Catecholamines by Glomus Cells of the Rat Carotid Body

The carotid body has been shown biochemically to contain catecholamines, predominantly dopamine1. Further evidence for the presence of catecholamines in glomus cells is provided by studies of histofluorescence, and glomus cells fluoresce intently after exposure to hot paraformaldehyde vapor,2 3, 4, a histochemical test specific for catecholamines5. The glomus cells of the rat carotid body contain numerous dense-core or granulated vesicles6, 7, resembling somewhat the vesicles seen in other catecholaminergic cells and nerve fibers. Presumably these vesicles are the site of location, wholly or in part, of the neurotransmitter substances. The biochemical tests show that the catecholamines are in the carotid body, and the histofluorescence studies demonstrate that the catecholamines are in the glomus cells. However, definitive proof has still not yet been presented that the dense-core vesicles are indeed the site of storage of catecholamines in glomus cells.