Cell Body Shape Research Articles

Corticotropin‐releasing factor immunoreactivity in monkey neocortex: An immunohistochemical analysis

Corticotropin-releasing factor (CRF) has been implicated in the pathophysiology of certain human neuropsychiatric disorders that affect neocortical function. However, the anatomical organization of CRF-containing structures in the expanded and highly differentiated primate neocortex has not been previously described. In this study, the distribution of CRF-immunoreactive neurons and processes was characterized in the neocortex of New World squirrel monkeys (Saimiri sciureus). Substantial regional differences were present in the density, laminar distribution, and morphological appearance of CRF-immunoreactive neurons. The greatest density of labeled neurons was present in anterior cingulate cortex. A wide range of intermediate densities of CRF-immunoreactive neurons was evident in the association regions of the prefrontal, parietal, and temporal cortices. The lowest numbers of CRF-immunoreactive neurons were observed in the primary visual and primary motor cortices. For example, the density of labeled neurons was nearly five times greater in the anterior cingulate cortex than in the precentral cortex. CRF-immunoreactive neurons were also distributed in at least four different laminar patterns. For example, in the agranular anterior cingulate cortex, labeled cell bodies were distributed throughout layers II, III, and V. In other regions, such as the posterior cingulate cortex, labeled neurons were present in layers II, III, and IV. In contrast, labeled neurons were predominantly present in layers II and superficial III of the visual cortex, whereas in the inferior temporal cortex, they were present predominantly in layer IV. Regional and laminar differences were also present in the relative distributions of the two major morphological types (as defined by cell body shape) of CRF-immunoreactive neurons. Vertically oriented oval neurons, which frequently had a single dendritic process arising from each somal pole, were most frequently found in layer III. In contrast, the labeled neurons in layers II and IV tended to have a round- or triangular-shaped soma. In layer IV of some association cortices, these multipolar neurons were associated with a high density of rod-like structures composed of large immunoreactive varicosities clustered together in vertical arrays. These structures were frequently found to be located immediately below the soma of pyramidal neurons. Comparison of these findings with Golgi impregnation studies strongly suggests that CRF is present in the soma and axonal cartridges of a subset of chandelier neurons. The heterogeneous distribution and morphological diversity of CRF-containing neurons suggest that CRF may mediate distinct functions in different regions and layers of monkey neocortex.

A system of indoleamine-accumulating neurons in the rabbit retina

The indoleamine-accumulating neurons of the rabbit retina were labeled by intraocular injection of 5,7-dihydroxytryptamine (5,7-DHT). The retinas were fixed with 2.5% paraformaldehyde and 0.2% glutaraldehyde and inspected by fluorescence microscopy. Five kinds of cell accumulated the indoleamine. They were labeled to essentially the same brightness and remained so despite variations in the concentration at which 5,7-DHT had been applied or the duration of its application. Experiments in which 5,7-DHT was applied to retinas incubated in vitro gave identical results. To see the whole shape of the cells, we visually guided micropipettes to the fluorescent cell bodies and injected the cells with Lucifer yellow CH. To study the cells as a population, we used a new method in which the fluorescence of 5,7-DHT is photochemically converted to an insoluble diaminobenzidine product. The dendrites of all of the indoleamine-accumulating cells were then simultaneously visible. Used together, these techniques revealed an interrelated system of indoleamine-accumulating neurons. All of the cells contribute processes to a dendritic plexus that lies at the inner margin of the inner plexiform layer. The plexus is roughly 4 micron thick. It is pierced by the stalks of the Müller cells and is occasionally interrupted by ganglion cell bodies, where they extend above the average margin of the ganglion cell layer. Otherwise it fills much of the space at the junction of the plexiform and ganglion cell layers. The type 1 and type 2 cells are amacrine cells with cell bodies at the inner margin of the inner nuclear layer. They have 5-8 radially branching primary dendrites which extend horizontally across the inner plexiform layer before descending to join the dendritic plexus. They differ from each other in cell body shape, dendritic morphology, and the course of their dendrites within the inner plexiform layer. Each has a "displaced" counterpart, with a morphology similar to the type 1 or type 2 cell but with a cell body located in the ganglion cell layer. The displaced cells are separate functional elements because, in contrast to the type 1 and type 2 cells, they have no dendrites (and hence can have no synaptic connections) in the outer part of the inner plexiform layer. The fifth kind of cell (type 3) appears not to have been described before. Its cell body is located at the outer margin of the inner nuclear layer.(ABSTRACT TRUNCATED AT 400 WORDS)

A Golgi study of the neuronal population of the marginal zone (lamina I) of the rat spinal cord.

On the basis of dendroarchitecture and cell body shape, complemented with morphometry of dendritic ramification, four major neuronal types were distinguished in lamina I of the spinal cord of the rat. (I) Fusiform spiny cells (39% of impregnated neurons) have longitudinal spindle-shaped perikarya with bipolar, less frequently unipolar, dendritic trees rich in pedicled spines and a thin, beaded longitudinal axon; such neurons occur mainly in the lateral marginal zone. In type IA cells (33% of the total), the dendritic domain occupies a narrow longitudinal area, while in type Ib cells (6%) the polar dendritic trees partly arborize ventrally. Fusiform neurons are considered intrinsic cells connected with the longitudinal afferent plexus in lateral lamina I, and in type IB cells also receiving primary input in the substantia gelatinosa. (II) Multipolar cells (23%) have a dense dendritic arbor originating from numerous primary trunks and they predominate in the medial marginal zone. The dendritic arbor is moderately extended dorsoventrally in type IIA cells and reaches lamina III in the larger type IIB cells. The former possess a variety of spines, axonlike processes and sometimes an unmyelinated axon, and are presumably interneurons, while type IIB cells show a thick tapering axon that is probably myelinated. (III) Flattened aspiny neurons (13%) with a polygonal body flattened in the horizontal plane, and a horizontal dendritic arbor confined to lamina I; these cells predominate in middle lamina I. (IV) Pyramidal neurons (25%) have longitudinally elongated perikarya that bulge into the white matter. The arbor has a large longitudinal and lateromedial spread and includes branches which ramify in the white matter. Types III and IV show the classical lateromedially elongated orientation of the marginal cells of the old literature; they show thick tapering axons and probably make up the bulk of the projection neurons of rat lamina I.

Comparative Retinal Pigment Epithelium and Photoreceptor Ultrastructure in Nocturnal and Fossorial Rodents: The Eastern Woodrat, Neotoma floridana, and the Plains Pocket Gopher, Geomys bursarius

In fossorial plains pocket gophers ( Geomys bursarius ) the eyes are extremely small and the cells of the retinal pigment epithelium (RPE) have extensive, highly developed apical microvilli and numerous melanolysosomes. The neural retina consists of both cone (up to 25%) and rod photoreceptor cells. The cones often are clustered and surrounded by rods. Ultrastructurally, the cones differ from rods in position and appearance of nuclei, overall shape of cell body, disc membrane, and presence of pedicle-type synaptic terminals. By way of comparison, in nocturnal eastern woodrats ( Neotoma floridana ) the RPE cells have poorly developed apical microvilli and relatively few melanolysosomes. The neural retina consists almost entirely (99%) of abundant and densely packed rod photoreceptors characterized by unusually long outer segments with a high number of discs. Numerous significant quantitative differences between RPE and photoreceptors of Neotoma and Geomys serve to underscore further the dissimilarities of the retinas of these rodents. Although G. bursarius and other species of gophers live in dark or semi-dark burrow systems and have eyes that are reduced in size, the RPE and neural retina is characterized by an intermediate (diurnal-nocturnal) structural pattern suggestive of good visual acuity. The lack of any obvious specialization in RPE or photoreceptor morphology is striking and could imply that the generalized eye in gophers is representative of the eyes found in their ancestors. If so, gophers probably evolved from ground-dwelling diurnal species.

Morphometry of intracellularly labeled neurons of the auditory nerve: correlations with functional properties.

Single auditory-nerve fibers were injected with horseradish peroxidase after their tuning properties, characteristic frequencies, and spontaneous discharge rates were measured. From these functional properties virtually all other aspects of auditory-nerve response can be predicted. Labeled fibers were reconstructed from the point of peripheral termination on cochlear hair cells to the point at which they enter the cochlear nucleus. Several morphological properties were measured at the light-microscopic level, including axonal diameter, axonal length, internodal distances, cell-body area, and cell-body shape. All of these parameters were correlated, though some weakly, with characteristic frequency. However, only axonal diameter was correlated with spontaneous discharge rate.

The cat locus coeruleus. Light and electron microscopic study of the neuronal somata.

The neuronal cell bodies of the locus coeruleus (LC) and subcoeruleus (SC) of the cat were investigated using Nissl and Golgi preparations, and electron microscopy. On the basis of morphological criteria--size and shape of cell body, branching pattern of dentrites, distribution of cytoplasmic organelles and number of axosomatic synapses--four types of neuronal perikarya were recognized in each region: medium-sized, small-sized and two groups of intermediate-sized neurons. The medium-sized neurons (30--50 micron) had an elongated cell body, thick dendrites with a moderate number of branchings, abundant organelles arranged in concentric rings around the nucleus and a moderate number of axosomatic synapses. They were found throughout the LC and SC and most probably correspond to the larger class of catecholaminergic neurons demonstrated by fluorescence histochemistry. The small neurons (10--25 micron) were also seen in both LC and SC and are believed to represent non-monoaminergic local interneurons. They displayed sparsely branching dendrites and a thin rim of cytoplasm containing few organelles. In the SC, some of these cells occurred in closely associated pairs. Ultrastructural analysis of such pairs revealed a close apposition (80--100 A degrees) of the cell membranes for long distances (up to 10 micron) and a narrowing of the intercellular space (30--40 A degrees) at some discrete points, perhaps indicative of an electrical interaction. The intermediate-sized neurons exhibited some regional morphological differences, but two distinct subgroups could be distinguished. One was characterized by a low number of axosomatic synapses, while the other exhibited a high number of such contacts. It may be assumed that the two subgroups of intermediate-sized neurons comprise catecholaminergic and indolaminergic neurons.

Morphology of cochlear inner hair cells following outer hair cell destruction by kanamycin intoxication in the chinchilla

Inner hair cells were examined in cochlear regions of outer hair cell destruction caused by kanamycin intoxication. The majority of inner hair cells were ultrastructurally normal, except that some exhibited a slight increase in inclusion bodies in the region between the cell nucleus and the cuticular plate. Only in the extreme cochlear base, where kanamycin damage was maximal, were major changes in inner hair cell morphology seen: while many inner hair cells were normal in appearance, others showed extrusion of the cuticular plate from the reticular lamina, fusion and/or encapsulation of stereocilia, or distortion of cell body shape. Such damage appeared secondary to changes in structural cells of the organ of Corti.

CHARACTERISTICS OF FROG CARCINOMA IN TISSUE CULTURE

The adenocarcinoma of leopard frogs may be cultivated with ease in plasma media. In such cultures two types of growth occur with regularity. The first is in the form of tubules which promptly grow out in the solid medium and retain their tubular form as long as they remain completely enveloped by plasma. When, however, they make contact with the surface of the glass, they adhere to it, the part in contact becomes flat, and its cells now grow no longer as tubules but as membranes. The manner of growth in vitro resembles the growth of transplants of the same tumor in the anterior chamber of the living eye, thus suggesting that in each case the habit of growth is determined by the same morphogenetic factors, i.e. those inherent in the cells themselves, and those depending on interfacial forces. The malignant cells of the frog carcinoma have the attributes which in general distinguish malignant cells from normal cells of corresponding type. In comparison with adult kidney cells, their normal homologues, the conspicuous properties of frog carcinoma cells are: larger and more variable size and shape of cell body, of nucleus, and nucleolus; coarser and denser structure of cytoplasm, of nucleoplasm, and of nuclear membrane; increase in number of mitochondria, and more frequent occurrence of mitosis. These cytological characteristics remain unaltered in cultures maintained for as long as six months. Frog carcinoma is a transmissible disease due to an agent which induces inclusion bodies, and which has other attributes indicating that it is a virus. The general correspondence in character between its cells and the malignant cells of mammalian tumors of diverse origin suggests that neoplastic phenomena are essentially alike, no matter in what group of animals they occur or what their causal factors may be.