Jan Cammermeyer

Is the solitary dark neuron a manifestation of postmortem trauma to the brain inadequately fixed by perfusion

SummaryDark neurons, classified as solitary because of their sparse occurrence, were discerned in the transitional zones between gray and white matter in various species of laboratory animals fixed by perfusion. These neurons, histologically indistinguishable from dark neurons in immersion fixed material, tended to develop when the saline perfusion was delayed or slow, the amount of the Bouin fixative was excessive, or the autopsy was performed shortly after the perfusion. Under these conditions, the white matter manifested a softer consistency and a paler color than the gray matter. These observations suggest that, as the consequence of regional differences in intensity and speed of fixation, distortion during extraction of the brain may activate a stress force in the transitional zones where incompletely fixed neurons become affected and acquire an abnormal affinity for aniline dyes and silver.

The post-mortem origin and mechanism of neuronal hyperchromatosis and nuclear pyknosis.

Abstract In an attempt to elucidate the mechanism by which post-mortem traumatization induces transformation of a normal neuron to a “dark” neuron, several series of cats and guinea pigs were fixed and prepared histologically in various manners. The initial change was demonstrated in frozen sections of tissues fixed by immersion in formalin; cytoplasmic and nuclear membranes were detached from their surroundings forming cleavage spaces which were enlarged by dehydration. The transfer of tissues directly into rapidly acting fixatives or their prolonged storage in fixatives was of no avail for restoration of attachments. The perfusion of fixatives was of significance for avoiding “dark” neurons, provided the procedure was successful and the autopsy delayed; 4 hours sufficed after use of Heidenhains Susa fixative. Perfect perfusion and fixation were obtained, even if the brain was exposed to air and thus to atmospheric pressure prior to death or if perfusion was performed 10 min after death. “Dark” neurons were present in areas of imperfect perfusion. They were present when the perfusion was delayed 30 min. For proper fixation many factors had to be considered; among them, hydrostatic pressure, composition of the solution to flush blood vessels, use of a coagulant fixative, and delayed autopsy. The aim of fixation is to affix cellular membranes in such a manner that neurons are no longer vulnerable to traumatization incurred during autopsy and removal of the organ.

Mast cells in the mammalian area postrema

SummaryMast cells, identified by metachromasia of perikarya in material fixed by two-step perfusion with Bouins solution, were studied in the area postrema of 25 mammalian species. (A) The appearance of mast cells varied greatly, and when the population of these cells was high, they were predominantly of the pale type with pyknotic nuclei. (B) The mast cells tended to accumulate near the ventricular surface in primates and carnivores, while in other species the distribution was diffuse

Is the perivascular oligodendrocyte another element controlling the blood supply to neurons

General characteristics of distribution. By way of introduction, the distribution of oligodendrocytes is studied in sections of the central nervous system of Macaca cyrto~nolgus and rrzulatta. The cells are irregularly distributed. They aggregate around neurons in a haphazard manner and along vessels and nerve fibers at irregular intervals. Many microscopic fields have to be scanned before characteristics are recognized; these are demonstrated in the following composite pictures. The oligodendrocytes next to large neurons may often form a compact group in a manner known as satellitosis, pseudosatellitosis, or neuronophagia (arrow in fig. lA). In other fields the neuron is adherent to a small vessel and the group of oligodendrocytes is arranged along the wall of the vessel (arrow in fig. 1B). Actually similar arrangements can be found provided that the plane of sectioning is corresponding to the course of the vessel around the neuron. The

Histochemical phospholipid reaction in ischemic neurons as an indication of exposure to postmortem trauma

Abstract Affinity for acid hematein is assumed by neurons displaying the ischemic neuronal disease of Spielmeyer in 1- to 8-hr old embolic lesions elicited by intracardial injections of oil in cynomolgus monkeys fixed by perfusion. Dark neurons situated in normal tissue surrounding the lesions exhibit a similar affinity. In their morphological and tinctorial qualities, ischemic neurons are, in the acute stages, prior to manifest loss or dispersal of Nissl substance, indistinguishable from dark neurons. Since both types of neurons occur in tissues which have been inadequately fixed by perfusion, a common factor, postmortem traumatization, affecting the structure of pathologically altered and normal neurons is proposed, and the affinity for acid hematein is regarded as artifactitious for both cell types. Besides shrunken ischemic neurons, which may be either blue or yellow, another pathological neuronal type is manifested by severe distintegration of the cytoplasm and lack of affinity for acid hematein. The process of postmortem autolysis, as evidenced in an immersed-fixed monkey brain with myriad embolic lesions, does not alter the histological characteristics of ischemic or dark neurons until after a lapse of several hr and does not reproduce the pathological neuronal changes of embolic lesions. In the compressed cerebral cortex of cats fixed by perfusion, scattered neurons with inflated, pale, nonvacuolated perikarya and nuclei are regarded as prototype of the anoxic neuron. No affinity for acid hematein is demonstrable in these neurons.

Argentophil neuronal perikarya and neurofibrils induced by postmortem trauma and hypertonic perfusates

Argentophil neuronal perikarya and perikaryal neurofibrils similar to those illustrated in Ramón y Cajals classical studies have in the present investigation been found to be manifestations of the chromophil neuron. Conclusive evidence of such association was obtained by silver impregnation with the Bodian technique of sections previously stained with cresyl violet. Regardless of the fixative used, silver-impregnated neurofibrils were evident when (1) normal tissues were fixed by immersion or unsuccessfully fixed by perfusion, (2) normal tissues were exposed and touched after death but before perfusion with the fixative, or (3) flow of perfusates was compromised by the effect of an experimental procedure, as well as when (4) a hypertonic saline solution was used in the first perfusate. These cytologic peculiarities were still discernible after 24 h of postmortem autolysis following a delay in removal of the brain or in immersion of the exposed brain in the fixative. After immersion fixation, argentophilia and chromophilia occurred ubiquitously in the brain of the newborn guinea pig; however, argentophil neurofibrils were noted in the absence of chromophil neurons in the brain stem of the newborn rat, rabbit and cat. After fixation by perfusion, perikaryal neurofibrils were not impregnated in either newborn or old animals or in animals with facial nerve transection. Affinity for Congo red or birefringency, exhibited by neurons with marked neurofilbrillary changes in human senile brain atrophy, were absent in the present material. On the basis of the current light-microscopic observations, it is concluded that argentophilia of neuronal perikarya and perikaryal neurofibrils is another manifestation of the chromophil neuron induced by postmortem trauma and of the ocellate neuron elicited by perfusion with hypertonic saline.

Mast cells and postnatal topographic anomalies in mammalian subfornical body and supraoptic crest

SummaryIn the central nervous system of 22 animal species, mast cells occur (1) in both the subfornical body and the supraoptic crest in chimpanzee, stumpatailed monkey, agouti and flying squirrel and in cynomolgus monkey from 1 day of age; (2) in the subfornical body in paca, ground squirrel, woodchuck and prairie dog; and (3) in the supraoptic crest in cats from 2 days of age through the fourth month, and capybara. The medial habenular nucleus and the area postrema contain mast cells in many of the animals, but differences in number with species and with age do not follow the same pattern as in the above regions. Not infrequently, the thalamus has a considerable number of mast cells, and occasionally other regions, such as the dentate nuclei and the medulla oblongata, have a few mast cells.The number of mast cells, amounting to several hundreds in the circumventricular regions, varies with region, species, individual animal and age. The marked qualitative and quantitative differences, which complicate interpretation of experimental results, are associated with differences in functional requirements; the migratory faculty of the mast cell would enable each of its many biogenic amines to act separately on specific elements at different sites as demand arises.Study of newborn animals disclosed mitotic cells in several of the circumventricular regions. The formation of dysmitotic elements, as an expression of anomalous mitosis, may be the cause of disproportionate growth of the tissue and the overlying ependyma, whereby aberrations in the development of the ventricular wall ensue.

The effect of postmortem trauma on neuronal cell types stained histochemically for phospholipids

Abstract With Bakers acid hematein method, blue and yellow neurons occur after fixation by immersion or after inadequate fixation by perfusion as the consequence of postmortem trauma. They increase in number when such trauma is intentionally applied to cerebral surfaces prior to fixation by either procedure, and their formation is prevented by successful perfusion of the fixative prior to removal of the cranium. The formation of blue and yellow cell types is not influenced by variations in composition of the fixative, embedding procedure or tissue preparation, age or species of animal, or treatment with pyridine. Prolonged delays in fixation do not affect the affinity for acid hematein in neurons next to superficial injuries caused by dissection. The two cell types are therefore regarded as artifactitious, comparable to dark neurons demonstrable by other staining techniques. It is concluded that the neuronal stainability with Bakers acid hematein is nonspecific and that the identification of neurons according to histochemical composition is equivocal in both normal and experimental material.

Improved preservation of neuronal glycogen by fixation with iodoacetic acid-containing solutions.

Abstract A new principle of fixation was developed for the histochemical demonstration of neuronal glycogen in the rabbit because of the poor results obtained after routine perfusion with saline and Bouins solution. Accordingly, all perfusates are mixed with 0.01 m iodoacetic acid, and as soon as possible after narcosis and exposure of the heart, epinephrine is injected into the left ventricle; 30 s later the heart is incised for perfusion with aqueous 0.9% NaCl solution (30 s), followed by perfusion with Bouins solution (6 to 8 min), and 15 to 180 min thereafter by perfusion with 100% ethanol (60 min). Then, the brain is removed and dehydrated by immersion in the same alcohol solution and embedded in paraffin within 24 h after the perfusion. The dimedone-PAS-stained neuronal glycogen, which is unstained after saliva treatment, is regarded as being better preserved because (i) it is demonstrable in the perikarya of cortical neurons and Purkinje cells, (ii) it occurs throughout the perikarya in the deeply situated Purkinje cells, and (iii) it is more intensely stained in motor neurons than with previous techniques. The beneficial effect of the iodoacetic acid on preservation of neuronal glycogen depends on the vasoconstricting action of epinephrine on the peripheral vasculature so that flow of perfusates is directed to the brain exclusively. In superficially situated Purkinje cells, glycogen, because of the action of the infiltrating alcohol, is dispersed to one side of the perikarya and aggregated in the proximal parts of axons, but is unchanged in dendrons. The differential effect of alcohol on glycogen at the three cellular levels and the observation that glycogen is reduced in astrocytes but not in neurons after the intracardial injection of epinephrine suggest that factors controlling the storage of glycogen are variable.

The effect of cortisone treatment and reoperation on reactive changes in the facial nucleus after axotomy

The material, with few exceptions, consists of PAS-gallocyanin stained paraffin sections from 4- to 6-month-old male rabbits fixed by perfusion first with saline and then with Bouins solution. (1) In animals treated with cortisone prior to and subsequent to axotomy, the neurons exhibit an accelerated dispersal and delayed reconstitution of Nissl substance (ribosomes). While mitotic activity is depressed at various sites, formation of new microglial cells is evident. Neuronal degeneration with karyorrhexis is occasionally noted in single neurons in the lateral parts of the facial nucleus. An increase in intraneuronal glycogen deposition is manifested by a greater number of glycogen-rich neurons; such neurons are depleted of their glycogen after axotomy. (2) In other animals, reoperation of the facial nerve on the 6th, 22nd, 60th and 120th day, followed by survival of 3 days, results in dispersal of restored Nissl substance and in increased extravascular mitotic activity which is of less intensity than in single-operated animals.