Large Extracellular Spaces Research Articles

Mode of cell migration to the superficial layers of fetal monkey neocortex.

AbstractGolgi and electronmicroscopic methods were used to define the shapes and intercellular relationships of cells migrating from their sites of origin near the ventricular surface across the intermediate zone to the superficial neocortical layers of the parietooccipital region in the brains of 75‐ to 97‐day monkey fetuses. After mitotic division in either ventricular or subventricular zones, the cells enter the intermediate zone and assume an elongated bipolar form oriented toward the cortical plate. The leading processes, 50 to 70 μ long, are irregular cytoplasmic cylinders containing prominent Golgi apparatus, mitochondria, microtubules, ribosomal rosettes, immature endoplasmic reticulum and occasional centrioles. They usually terminate in several attenuated expansions, the longest one oriented toward the cortical plate. The trailing processes are more slender, relatively uniform in caliber and display few organelles.Throughout the 3500 μ pathway across the intermediate zone the migrating cells are apposed to elongated, radially oriented, immature glial processes which span the full thickness of the cerebral wall. Most of the perikarya of these glial cells in the younger specimens lie in the ventricular or subventricular zones, but in older fetuses of this series many are found in the intermediate zone. The main characteristics of these fibers are: elongated cylindrical form contaiing numerous microtubules; electronlucent cytoplasmic matrix; short lamellate expansions protruding at right angles from the segment of the fiber which runs through the intermediate zone; and terminal endfeet joined at the pial surface to form a continuous sheet coated externally with basement membrane. It is suggested that glial radial fibers provide guidelines for cell migration through the complex mixture of closely packed cell processes and cell bodies that compose the developing cerebral wall. Strong surface affinity between radial fiber and migrating cell is suggested in regions where both follow precisely the same curving course from subventricular to intermediate zones and also in areas where large extracellular spaces separate other cells and processes but in which migrating cells and radial fibers remain closely paired nonetheless. Specific affinity between them is implied in the failure of migrating cells to follow any of the myriad differently‐oriented processes they encounter. Several generations of postmitotic cells appear to migrate along the same radial fiber, a developmental mechanism that would allow for the vertical cell columns of adult neocortex.

A cytological study of the ovary of Rhodnius prolixus. I. The ontogeny of the follicular epithelium.

AbstractThe relatively undifferentiated cells comprising the prefollicular epithelium of the fourth and fifth instar of the reduvid bug Rhodninus prolixus are flattened and contain the regularly occurring organelles, lipid droplets, and aggregates of glycogen‐like particles. These cells transform into the adult prefollicular tissue.During vitellogenesis there is a gradual shortening of the cells of the follicular epithelium and an increase in the size of the intercellular space between them and between follicle cells and oocyte. The follicle cells are binucleate, contain numerous microtubules, rough endoplasmic reticulum, many free and aggregate ribosomes, and Golgi complexes. They are associated with each other by gap junctions. Only the follicle cells on the lateral aspects of the oocyte exhibit the development of large extracellular spaces while those at the apical end, that produces the cap, remain tall and closely apposed to each other during vitellogenesis. The normal morphology of the follicle cells over various areas of the oocyte suggests that shape and/or volume changes of these cell may be important in regulating the access of yolk proteins to the colemma.Subsequent to vitellogenesis the follicle cells become cuboidal and once again become closely apposed to each other. They contain much rough endoplasmic reticulum and produce the secondary coat.

A physiological difference in the hippocampus of rats with a low inborn learning ability.

Rats with a low ability to learn conditioned avoidance responses in a shuttle-box were in-bred. After five or six generations, a fairly homogeneous population was obtained consisting of bad learners both in the shuttle-box and in a Lashley III maze. When the hippocampus of these bad-learner rats was perfused with high potassium solutions, it was observed that more stimuli were needed, under each potassium concentration, in order to elicit a seizure, than in normal animals. This was apparently the result of a lower release of potassium per stimulus into the extracellular space, in as much as other possibilities (low sensitivity to the epileptogenic effect of potassium, large extracellular space, high Na-K-Mg-ATPase activity) were excluded. This reduced potassium release by stimulation in the hippocampus of bad-learner rats was not due to a lower potassium gradient across cell membranes, and therefore, could in principle be attributed to a defect in the property of local neural membranes (pre- and/or postsynaptic) to increase potassium conductance when stimulated. The present data fit with the hypothesis advanced previously, that the hippocampus plays a role in learning through heterosynaptic interactions mediated by the release, and subsequent accumulation of potassium.

Morphological aspects of exocytosin in the adrenal medulla.

In the adrenal medulla of the hamster, we have clearly observed profiles which show exocytosis. Such profiles have been seen on all surfaces of the chromaffin cells, near the large extracellular spaces which are mainly occupied by the blood vessels and connective tissue and also near the narrow intercellular cleft of about 20 to 25 nm which separates neighbouring chromaffin cells. (1) Near the large extracellular spaces, the plasma membrane shows granule-containing invaginations. An electron-translucent space separates the plasma membrane and the granule which is alone in the invagination. The same diversity in size and shape may be seen among the expelled granules and the intracellular granules (see figures 1 to 7 and, plates 47 to 50). These figures look like the exocytosis aspects which have been already described in other types of cells, in particular adenohypophysis (Farquhar 1961).

Round and amoeboid microglial cells in the neonatal rabbit brain

Round and amoeboid microglial cells in brains of neonatal rabbits have been studied with light and electron microscopy. They are present mainly in the white matter where there are large extracellular spaces, but a few occur in the vicinity of blood vessels in the basal ganglia. They are easily recognized by the shape of their processes. Both round and amoeboid cells are highly differentiated cells whose size and cytoplasmic vacuoles are similar to phagocytes. They lack the fibrils and microtubules of young nerve and glial cells and contain a rich complement of cytoplasmic organelles. Large numbers of lipid bodies and vacuoles are their most characteristic features. Small vacuoles are concentrated near the cell surface and contain material identical to that filling the extracellular space. They appear to arise as invaginations at the cell surface, to unite to form large vacuoles, and to increase in density as their contents are degraded. The role of these cells in the embryonic development of the brain is not clear and further work is in progress to establish their origin and fate.

Development of the blood vessels and extracellular spaces during postnatal maturation of rat cerebral cortex

AbstractAs part of a larger study of the development of postnatal rat cerebral cortex, this report deals with the maturation of the cortex as a tissue from birth to twenty‐one days of age. The changes in the numerical density of cells and blood vessels and the thickness of the cortex at successive ages were followed on light micrographs, and both were related to the ultrastructural observations on routine electron microscopic preparations. The maturation of the cortex is divided into two periods: The first ten days during which the growth to adult dimensions occurs and few patent blood vessels but large extracellular spaces are to be found, and the second ten days in which the majority of the vessels develop patent lumina, the perivascular sheath of astrocyte end‐feet develops, and the large extracellular spaces disappear concomitant with the maturation of the neuropil.The blood vessels appear to develop during the first ten days as solid cords of mesodermal elements which form a network of primordial vessels with thick walls and slit‐like lumina containing a flocculent material. The formation of a blood filled, patent lumen apparently occurs synchronously over a brief period of time for the majority of the vessels during the early part of the second ten‐day period. The basal lamina is ill‐defined initially but takes on mature appearance parallel with the development of the perivascular glial sheath.The volume of the extracellular space was found to be largest during the phase of rapid growth of axons and dendrites when few patent vessels exist. The disappearance of these large extracellular spaces during maturation of the blood vessels and neuropil is discussed in terms of the possible artifactitious nature of these spaces in both immature and mature cortex.

Morphology of superficial postnatal cerebral cortex with special reference to synapses.

The ultrastructure of layers I and II of the motor cerebral cortex of rat brain has been studied at birth, 4, 7 and 14 days postnatal and in the adult. Compared with the adult, neonatal rat motor cortex exhibited a large extracellular space which decreases with increasing age. At all stages studied the neurons were seen to contain the organelles usually found in adult neurons. Growth cones were present in decreasing numbers up to 14 days old. Synapses were detectable at birth and there was an obvious increase in their number throughout the postnatal development. At the earliest stages studied there was a lack of specialization characteristic of the adult. Many synapses were either avesicular or relatively so and lacked the high degree of modification of adult pre- and postsynaptic membranes. By 7 days after birth many synapses existed which in all morphological respects resembled those of the adult, and by 14 days, the majority were of the adult type. These findings, particularly with reference to the postnatal development of synapses, have been discussed in relation to the known electrophysiological findings.

Microcystic meningioma mimicking pleomorphic xanthoastrocytoma

Microcystic meningioma is a distinct morphological variant of meningioma, characterized by loose texture and microcysts with formation of large extracellular spaces containing edematous fluid. The tumor cells have stellate and vacuolated cytoplasm with long cytoplasmic processes. We report a case of microcystic meningioma occurring in a 60 year-old man. Histological features showed tumor cells with abundant foamy cytoplasm, pleomorphic nucleus with vesicular chromatin and prominent nucleoli which mimicked pleomorphic xanthoastrocytoma. The clinical presentation and histopathological diagnostic dilemma along with immunohistochemistry is discussed. Keywords: MicrocysticMeningioma; Pleomorphic xanthoastrocytoma Immunohistochemistry DOI: http://dx.doi.org/10.3126/jpn.v1i2.5413 JPN 2011; 1(2): 158-160

The extracellular space in the developing rat brain: Its variation with changes in osmolarity of the fixative, method of fixation and maturation

Considerable extracellular space was demonstrated in the newborn rat cerebral cortex. The extent of this space could be easily modified by changes in the osmolarity of the glutaraldehyde fixative. With maturation this space became progressively less, generally from the deeper layers outward, and attained adult dimensions by the end of the second week. However, in the white matter, between subpial astrocytes, between ependymal cells and between the cells of the choroid plexus, much narrower spaces were present at all ages. These results compare well with the morphologic findings reported by others following primary glutaraldehyde fixation or freeze-substitution, as well as with the physiologic measurements of the cerebral extracellular spaces in the immature brain also reported by other investigators. Following immersion fixation, the extracellular space was somewhat narrower. The most marked decrease in the extracellular space was noted after immersion fixation in isotonic fixative. All these observations of a relatively large extracellular space in the immature brain contrast with the narrow space seen following primary osmium tetroxide fixation reported by other investigators. It is concluded that the cerebral cortical extracellular space in the immature brain is quite large, but that its true in vivo extent cannot be definitely demonstrated because of the sensitivity of the immature brain to the processes of fixation and embedding.

The glio-vascular system of cephalopods

The branches of the cerebral arteries run to the centre of each lobe of the brain and from there radiate outwards. The arteries are lined by endothelial cells, surrounded by pericytes. Outside these are large extracellular spaces containing collagen. These spaces continue as a system of ‘glio-vascular’ channels among the tissues. These channels contain collagen and other extracellular material and nuclei belonging probably to muscle cells and fibroblasts. This system permeates the neuropil and in the cell layers provides wrappings for the perikarya. The channels and extracellular material form tunnels of ‘trophospongium’ within the neuronal cytoplasm. Glial fingers also penetrate into these channels but are not well seen by light microscopy. The system of spaces among the tissues communicates with an elaborate set of branching ‘lymphoid' channels. These collect into veins either in the membrane around the brain or at the centre of the optic lobe. The veins discharge to the pharyngo-ophthalmic vein and the brain is thus provided with a venous system partly isolated from the main haemocoele. The true neuroglia cells are of two types. The protoplasmic glia cells have much-branched processes, especially in the neuropil. They have abundant end-feet attached to the outside of the perivascular channels and to the glio-vascular strands. They occur in the cell layers and their processes probably penetrate the neurons. The fibrous glia have very long processes, mostly smooth and with little branching. The processes run in bundles accompanying the main tracts of nerve fibres in the neuropil and extending into the cell layers.

Lymph mobilization following acute blood loss in the toad, Bufo marinus

1. 1. Blood loss (3·5 ml/100 g) by the toad, Bufo marinus, results in a rapid hemodilution with falls in hematocrit of up to 50 per cent after 1 hr. 2. 2. There is no net change in total extracellular volume (inulin “space”) during this time. 3. 3. An immediate change in albumin kinetics occurs following hemorrhage with a dilution of tagged plasma protein which, along with the above findings, suggests peripheral lymph as the source of the mobilized fluid. 4. 4. Blood loss in a potent stimulus for augmenting the rate of lymph heart contraction. 5. 5. Neither the lymph hearts nor the nephrostomes are necessary for the rapid net mobilization of lymph following blood loss. 6. 6. The pituitary is unnecessary for either the lymph heart or the blood volume responses. 7. 7. The physiological importance of the large (35 per cent) extracellular space of the toad, in relation to dehydration, is discussed.

The extracellular space of the smooth muscle of the guinea-pig taenia coli.

1. The measured extracellular space of the taenia coli is large when small ions or molecules are used for the determination, and small when large molecules are used, even with identical experimental procedures.2. Extracellular hyaluronic acid has been detected histologically. It is apparently reduced by hyaluronidase.3. The extracellular inulin space increases after the tissue has been pretreated with hyaluronidase, although the ionic composition and wet weight are unchanged.4. It is suggested that the hyaluronic acid prevents the free entry of macromolecules such as inulin into the extracellular space by steric hindrance. Monatomic ions such as Na(+), Li(+), Cl(-), Ca(2+) therefore have a larger extracellular space available than is calculated on the basis of the inulin space.5. A slight shrinkage of the muscle cells can be detected when the incubation period is prolonged.

ELECTRON MICROSCOPY OF THE STRATIFIED EPITHELIUM LINING THE EXCRETORY CANAL OF THE DOGFISH RECTAL GLAND.

AbstractIn spite of a renewed interest in the rectal (salt‐secreting) gland of the spiny dogfish, Squalus acanthias, the morphology of the stratified epithelium lining the central lumen and large ducts of this gland has been mentioned only briefly. The fluid removed from the duct of the rectal gland has been shown by Burger and Hess ('60a, b) and Burger ('62) to be a concentrated sodium chloride solution. The function of the stratified epithelium in the elaboration of this fluid is unknown. It is of interest to know if the stratified epithelium has morphological specializations which might suggest its function.The stratified epithelium of the central canal consists of surface cells, intermediate cells, and basal cells. Four types of surface cells can be distinguished: granular cells, mucous cells, flask‐shaped cells, and cells with large mitochondria. The intermediate cells form a loose network. In the large extracellular spaces between the intermediate cells, free cells presumably of blood origin, can be seen. The basal cells lie on a basement membrane. There is a structural resemblance of the epithelium to that of the toad bladder.

Fixation of the central nervous system for electron microscopy by aldehyde perfusion: II. Effect of osmolarity, pH of perfusate, and fixative concentration

Hypertonic fixatives perfused well, but gross brain shrinkage was excessive with extreme hypertonicity. Increasing the amount of buffer in a perfusate to 1200 mOsM resulted in shrinkage of cells and large amounts of extracellular space. Increasing the fixative concentration did not cause extensive extracellular space formation but had only relatively subtle effects on fine structure. Moderate hypertonicity resulted in little gross brain volume change. Isotonic (300–320 mOsM) perfusates acted similarly to hypotonic fixatives, which caused gross swelling of the brain and poor preservation on the ultrastructural scale and would not flow well at perfusion. While extreme pH's (2 and 11) were detrimental to preservation of structure, pH's of 6 and 8 caused little change. A brief “wash” of pH 2.0 buffer immediately preceding pH 7.4 perfusion caused the appearance of large scale extracellular space, but also fair preservation of ultrastructure.

The ultrastructure of the superior cervical sympathetic ganglion of the cat: I. The structure of the ganglion cell processes as studied by serial sections

The structure of the ganglion cell processes in the superior cervical ganglion of the cat has been studied by means of serial sections. The structural pattern of the cell processes is characterized by a tight packing of thick filaments. The cell processes in addition contain α-cytomembranes and RNA particles in varying numbers. Other structural components are mitochondria, vesicular structures, and opaque granules. A large filamentous corpuscle has been observed in some of the cell processes. A satellite cell sheath appears around the cell processes, separated from a relatively large extracellular space by a basement membrane. The majority of the cell processes observed in this study are assumed to be dendrites. The dendrites show an extensive branching system by means of which they come into direct contact with each other and with the ganglion cell bodies. The dendrodendritic and dendrosomatic contact zones are of two types. One type consists of a simple close packing of the plasma membranes of the dendrites without any interposed satellite cell cytoplasm. In the second type of contact, which usually has a length of about 800–2000 A, the cytoplasmic surfaces of the plasma membranes are associated with opaque material in the neuronal cytoplasm. A space about 60–80 A wide separates the plasma membranes and contains some slightly stained material. The contact zones may consist of either one of the two types or may show both types alternating with each other. A great number of synaptic contacts between preganglionic fibers and the dendrites are found throughout the ganglion.

The ultrastructure of ameloblasts from the growing end of rat incisors

Ameloblasts from the growing end of rat incisors were examined with the electron microscope. They exhibit marked polarity with the nucleus at the basal end of the cell. Mitochondria are proximal to the nucleus. Just distal to the nucleus is a well defined Golgi apparatus. Rough-surfaced endoplasmic reticulum and granules fill the remainder of the cytoplasm. Some 150 Å particles are independently present in the cytoplasm. The cells are close to each other with a minimum of extracellular space. Terminal bars are present at the junction of the ameloblasts with Tomes' process. Each cell contributes a cell membrane and opaque cytoplasm to the terminal bar. At least two components are seen in enamel matrix: small rodlets 60 Å wide and up to 1000 Å long, and a more extensive amorphous material. Ameloblasts from a more incisal location are separated by a large extracellular space into which microvilli project. In the most incisal region examined, small granules measuring 70 Å are found in the ameloblasts and the cells are connected by desmosomes.

The Effect of Age on the Concentration of Chloride and Water in Chick Tissues

Experiments by Barlow, Slinger, and Manery, on chicks from hatching to 1825 days of age, show that there is a rapid decrease in the water and chloride concentrations of skin and muscle during the first month after hatching. More gradual decreases were found in tendon water and chloride. From histochemical calculations applied to these analyses it is suggested that tissues of young birds contain a much larger extracellular space than those of older birds. Human muscle and rat muscle have been reported to increase in chloride concentration in the period of senescence, whereas in older chicks a drop occurred. Although desiccation of tissues has long been considered to accompany senility, this was not true of the musclfs of the older birds, and only a small decrease in water was observed in the connective tissues studied.