Dexmedetomidine attenuates neuronal injury after spinal cord ischaemia‐reperfusion injury by targeting the CNPY2‐endoplasmic reticulum stress signalling

Dexmedetomidine (Dex) has been proven to exert protective effects on multiple organs in response to ischaemia‐reperfusion injury, but the specific mechanism by which this occurs has not been fully elucidated. The purpose of this study was to investigate whether Dex attenuates spinal cord ischaemia‐reperfusion injury (SCIRI) by inhibiting endoplasmic reticulum stress (ERS). Our team established a model of SCIRI and utilized the endoplasmic reticulum agonist thapsigargin. Dex (25 g/kg) was intraperitoneally injected 30 minutes before spinal cord ischaemia. After 45 minutes of ischaemia, the spinal cord was reperfused for 24 hours. To evaluate the neuroprotective effect of Dex on SCIRI, neurological function scores were assessed in rats and apoptosis of spinal cord cells was determined by TUNEL staining. To determine whether the endoplasmic reticulum apoptosis pathway CNPY2‐PERK was involved in the neuroprotective mechanism of Dex, the expression levels of related proteins (CNPY2, GRP78, PERK, CHOP, caspase‐12, caspase‐9 and caspase‐3) were detected by western blot analysis and RT‐PCR. We observed that Dex significantly increased the neurological function scores after SCIRI and decreased apoptosis of spinal cord cells. The expression of ERS‐related apoptosis proteins was significantly increased by SCIRI but was significantly decreased in response to Dex administration. Taken together, the results of this study indicate that Dex may attenuate SCIRI by inhibiting the CNPY2‐ERS apoptotic pathway.     

OSMIUM STAINING OF ENDOPLASMIC RETICULUM AND MITOCHONDRIA IN THE RAT ADRENAL CORTEX

The zona fasciculata of the rat adrenal cortex synthesizes and secretes glucocorticoids. As observed after aldehyde fixation, the cells in this zone contain an extensive endoplasmic reticulum (ER), a small Golgi apparatus, a moderate number of lipid droplets, and abundant mitochondria with tubulovesicular cristae. Numerous areas within the endoplasmic reticulum and mitochondrial cristae appear clear. In addition, a small percentage of mitochondria encompasses large, clear areas. After immersion of finely minced adrenal cortex in unbuffered 2% OsO₄ (40–48 hr at 40°C), deposits of osmium are seen within the Golgi apparatus, the entirety of the ER, and occasionally within mitochondria. In some mitochondria, the deposits are within cristae; in others, within vacuoles; in still others, in both cristae and vacuoles. These localizations correspond best to the clear areas found in aldehyde-fixed tissue. Osmium is not deposited in lipid droplets, in bar-containing inclusions, in mitochondrial matrix inclusions, or in the peripheral, outer mitochondrial spaces. Addition of zinc-iodide to OsO₄ increases the amount of Golgi apparatus and mitochondrial staining. Adrenocorticotropin (ACTH) does not affect the localization of deposits; hypophysectomy decreases mitochondrial staining. This study (a) emphasizes the necessity for electron microscopic confirmation of osmium localization when this technique is used as a Golgi apparatus stain; and (b) suggests that the ER-staining pattern may be consistent in cells actively synthesizing steroids or steroid-like compounds.     

LYSOSOMES AND GERL IN NORMAL AND CHROMATOLYTIC NEURONS OF THE RAT GANGLION NODOSUM

The rat ganglion nodosum was used to study chromatolysis following axon section. After fixation by aldehyde perfusion, frozen sections were incubated for enzyme activities used as markers for cytoplasmic organelles as follows: acid phosphatase for lysosomes and GERL (a Golgi-related region of smooth endoplasmic reticulum from which lysosomes appear to develop) (31–33); inosine diphosphatase for endoplasmic reticulum and Golgi apparatus; thiamine pyrophosphatase for Golgi apparatus; acetycholinesterase for Nissl substance (endoplasmic reticulum); NADH-tetra-Nitro BT reductase for mitochondria. All but the mitochondrial enzyme were studied by electron microscopy as well as light microscopy. In chromatolytic perikarya there occur disruption of the rough endoplasmic reticulum in the center of the cell and segregation of the remainder to the cell periphery. Golgi apparatus, GERL, mitochondria and lysosomes accumulate in the central region of the cell. GERL is prominent in both normal and operated perikarya. Electron microscopic images suggest that its smooth endoplasmic reticulum produces a variety of lysosomes in several ways: (a) coated vesicles that separate from the reticulum; (b) dense bodies that arise from focal areas dilated with granular or membranous material; (c) "multivesicular bodies" in which vesicles and other material are sequestered; (d) autophagic vacuoles containing endoplasmic reticulum and ribosomes, presumably derived from the Nissl material, and mitochondria. The number of autophagic vacuoles increases following operation.     

大豆根瘤侵染细胞中一种细胞质内含物的电镜观察

在中国丰收11号大豆根瘤侵染细胞中,我们发现了一种电子密度很高,体积很大,形状为圆形或近似圆形,外面没有界膜,常位于胞间隙附近的特殊的细胞质内含物。高尔基体及其小泡,丰富的粗糙型内质网和核糖体常在它的附近,其中一些核糖体正沉积在它的表面。它主要是由核糖体凝聚而成,高尔基体和内质网在它的形成中也起了一定作用。它的内部含有颗粒状,纤维状,泡状和管状物质。它的出现似乎与侵染细胞固氮有关。     

THE STRUCTURE OF SOME CYTOPLASMIC COMPONENTS OF PLANT CELLS IN RELATION TO THE BIOCHEMICAL PROPERTIES OF ISOLATED PARTICLES

1. Electron micrographs of thin sections of material fixed with buffered osmium tetroxide have been used for comparison of the fine structure of isolated cytoplasmic particles from silver beet petioles and roots of germinating wheat with that of the cytoplasm of the intact cells. 2. Mitochondria of wheat roots have an external double membrane and poorly oriented internal double membranes. As compared with the structures seen in situ, the isolated mitochondria showed evidence of some disorganisation of the fine internal structure, probably due to osmotic effects. The possible influence of such changes on the enzymic properties of the isolated mitochondria is discussed. 3. The isolated plant microsomes are mainly spherical vesicular structures consisting of (a) an outer membrane enclosing (b) either an homogeneous slightly dense material (wheat root microsomes) or some granular dense material (silver beet microsomes) and (c) small dense particles, mostly associated with the vesicle membranes. 4. The cytoplasm of the wheat root cells does not contain any structures similar to the isolated microsomes but has a very dense reticular network, consisting of membranes with associated small dense particles, here called the endoplasmic reticulum. The observations indicate that the isolated microsomes arise mainly by rupture and transformation of the membranes of this structure. The effects of such extensive changes in the lipoprotein membranes on the enzymic activities of the endoplasmic reticulum, as studied in isolated microsomes, is discussed. 5. Meristematic wheat root cells contain structures which consist of smooth membranes with associated vacuoles and are similar to the Golgi zones of animal cells. The membranes of these zones probably contribute to the microsomal fraction under the conditions of preparation used for the enzymic and chemical studies previously reported.     

NOGO-A immunolabeling is present in glial cells and some neurons of the recovering lumbar spinal cord in lizards

The transected lumbar spinal cord of lizards was studied for its ability to recover after paralysis. At 34 days post-lesion about 50% of lizards were capable of walking with a limited coordination, likely due to the regeneration of few connecting axons crossing the transection site of the spinal cord. This region, indicated as “bridge”, contains glial cells among which oligodendrocytes and their elongation that are immunolabeled for NOGO-A. A main reactive protein band occurs at 100–110 kDa but a weaker band is also observed around 240 kDa, suggesting fragmentation of the native protein due to extraction or to physiological processing of the original protein. Most of the cytoplasmic immunolabeling observed in oligodendrocytes is associated with vesicles of the endoplasmic reticulum. Also, the nucleus is labeled in some oligodendrocytes that are myelinating sparse axons observed within the bridge at 22–34 days post-transection. This suggests that axonal regeneration is present within the bridge region. Immunolabeling for NOGO-A shows that the protein is also present in numerous reactive neurons, in particular motor-neurons localized in the proximal stump of the transected spinal cord. Ultrastructural immunolocalization suggests that NOGO is synthesized in the ribosomes of these neurons and becomes associated with the cisternae of the endoplasmic reticulum, probably following a secretory pathway addressed toward the axon. The present observations suggest that, like for the regenerating spinal cord of fish and amphibians, also in lizard NOGO-A is present in reactive neurons and appears associated to axonal regeneration and myelination.     

Organelle Membranes from Germinating Castor Bean Endosperm: II. ENZYMES, CYTOCHROMES, AND PERMEABILITY OF THE GLYOXYSOME MEMBRANE

Glyoxysome ghosts were isolated from germinating castor bean endosperms using established methods. Electron microscopic examination showed that some matrix material was retained within the glyoxysomal membrane. Two cytochrome reductases and phosphorylcholine glyceride transferase co-sedimented with the alkaline lipase, a known component of the glyoxysome membrane, in sucrose gradient centrifugation of osmotically shocked glyoxysomes. The activities of these enzymes in the glyoxysome membranes were compared to those in the endoplasmic reticulum relative to phospholipid content. On this basis, the phosphorylcholine glyceride transferase was 10-fold more active in the endoplasmic reticulum, whereas the lipase was 50-fold more active in the glyoxysome membrane. The cytochrome reductases were only 2-fold more active in the endoplasmic reticulum, indicating that they are components of the two membranes. Difference spectroscopy of the glyoxysome membrane suspension revealed the presence of a b5-type cytochrome similar to that found in the endoplasmic reticulum. Since the glyoxysome membrane is apparently derived from the endoplasmic reticulum, components of the endoplasmic reticulum such as these are likely to be incorporated into the glyoxysome membrane during biogenesis.     

The chaperone protein clusterin may serve as a cerebrospinal fluid biomarker for chronic spinal cord disorders in the dog

Chronic spinal cord dysfunction occurs in dogs as a consequence of diverse aetiologies, including long-standing spinal cord compression and insidious neurodegenerative conditions. One such neurodegenerative condition is canine degenerative myelopathy (DM), which clinically is a challenge to differentiate from other chronic spinal cord conditions. Although the clinical diagnosis of DM can be strengthened by the identification of the Sod1 mutations that are observed in affected dogs, genetic analysis alone is insufficient to provide a definitive diagnosis. There is a requirement to identify biomarkers that can differentiate conditions with a similar clinical presentation, thus facilitating patient diagnostic and management strategies. A comparison of the cerebrospinal fluid (CSF) protein gel electrophoresis profile between idiopathic epilepsy (IE) and DM identified a protein band that was more prominent in DM. This band was subsequently found to contain a multifunctional protein clusterin (apolipoprotein J) that is protective against endoplasmic reticulum (ER) stress-mediated apoptosis, oxidative stress, and also serves as an extracellular chaperone influencing protein aggregation. Western blot analysis of CSF clusterin confirmed elevated levels in DM compared to IE (p < 0.05). Analysis of spinal cord tissue from DM and control material found that clusterin expression was evident in neurons and that the clusterin mRNA levels from tissue extracts were elevated in DM compared to the control. The plasma clusterin levels was comparable between these groups. However, a comparison of clusterin CSF levels in a number of neurological conditions found that clusterin was elevated in both DM and chronic intervertebral disc disease (cIVDD) but not in meningoencephalitis and IE. These findings indicate that clusterin may potentially serve as a marker for chronic spinal cord disease in the dog; however, additional markers are required to differentiate DM from a concurrent condition such as cIVDD.

Electronic supplementary material

The online version of this article (doi:10.1007/s12192-013-0457-4) contains supplementary material, which is available to authorized users.     

AN ELECTRON MICROSCOPE STUDY OF THE ENDOPLASMIC RETICULUM IN NEWT NOTOCHORD CELLS AFTER DISTURBANCE WITH ULTRASONIC TREATMENT AND SUBSEQUENT REGENERATION

Ultrasonic treatment of the tails of Triturus alpestris tadpoles, at intensities of 8 to 15 watts/cm², at 1 megacycle/sec., for 5 minutes, disrupted the epidermis and caused pycnosis in individual cells of the muscle and neural tube, but caused no damage to the notochord that could be detected by light microscopy. Electron microscopy showed that this ultrasonic treatment disordered nearly all the endoplasmic reticulum (ER) of the notochord cells into irregularly rounded vesicles, but within 3 hours after treatment some parallel arrays of normal endoplasmic reticulum were seen near, and continuous with, the outer nuclear membrane. In addition, a re-ordering of the previously disordered ER took place throughout the cytoplasm, in some cases. A classification was made of the state of the ER as shown in electron micrographs of material fixed immediately, 3, and 24 hours after treatment. This showed that more than half the total endoplasmic reticulum in notochord cells was normal again by 24 hours after treatment.     

LYSOSOMES IN THE RAT SCIATIC NERVE FOLLOWING CRUSH

Peripheral nerves undergoing degeneration are favorable material for studying the types, origins, and functions of lysosomes. The following lysosomes are described: (a) Autophagic vacuoles in altered Schwann cells. Within these vacuoles the myelin and much of the axoplasm which it encloses in the normal nerve are degraded (Wallerian degeneration). The delimiting membranes of the vacuoles apparently form from myelin lamellae. Considered as possible sources of their acid phosphatase are Golgi vesicles (primary lysosomes), lysosomes of the dense body type, and the endoplasmic reticulum which lies close to the vacuoles. (b) Membranous bodies that accumulate focally in myelinated fibers in a zone extending 2 to 3 mm distal to the crush. These appear to arise from the endoplasmic reticulum in which demonstrable acid phosphatase activity increases markedly within 2 hours after the nerve is crushed. (c) Autophagic vacuoles in the axoplasm of fibers proximal to the crush. The breakdown of organelles within these vacuoles may have significance for the reorganization of the axoplasm preparatory to regeneration. (d) Phagocytic vacuoles of altered Schwann cells. As myelin degeneration begins, some axoplasm is exposed. This is apparently engulfed by the filopodia of the Schwann cells, and degraded within the phagocytic vacuoles thus formed. (e) Multivesicular bodies in the axoplasm of myelinated fibers. These are generally seen near the nodes of Ranvier.     

RELATION OF TOBACCO MOSAIC VIRUS TO THE HOST CELLS

The relation of tobacco mosaic virus (TMV) to host cells was studied in leaves of Nicotiana tabacum L. systemically infected with the virus. The typical TMV inclusions, striate or crystalline material and ameboid or X-bodies, which are discernible with the light microscope, and/or particles of virus, which are identifiable with the electron microscope, were observed in epidermal cells, mesophyll cells, parenchyma cells of the vascular bundles, differentiating and mature tracheary elements, and immature and mature sieve elements. Virus particles were observed in the nuclei and the chloroplasts of parenchyma cells as well as in the ground cytoplasm, the vacuole, and between the plasma membrane and the cell wall. The nature of the conformations of the particle aggregates in the chloroplasts was compatible with the concept that some virus particles may be assembled in these organelles. The virus particles in the nuclei appeared to be complete particles. Under the electron microscope the X-body constitutes a membraneless assemblage of endoplasmic reticulum, ribosomes, virus particles, and of virus-related material in the form of wide filaments indistinctly resolvable as bundles of tubules. Some parenchyma cells contained aggregates of discrete tubules in parallel arrangement. These groups of tubules were relatively free from components of host protoplasts.     

STUDIES ON THE FINE STRUCTURE OF ULTRACENTRIFUGED SPINAL GANGLION CELLS

The following structures were observed in electron micrographs of the mouse spinal ganglion cells: Nissl bodies composed of both aggregated rough-type, largely oriented, membranes of the endoplasmic reticulum and discrete particles; short rodlike mitochondria with well-developed transverse, obliquely or longitudinally arranged cristae, and a relatively typical Golgi complex. The components of ultracentrifuged ganglion cells (400,000 times gravity for 20 minutes) are stratified, the layers appearing in the order of their decreasing density as follows: (1) A microsomal or ergastoplasmic layer which may be further divided into three sublayers without sharp boundaries, namely, a discrete particle layer, a layer of discrete particles and highly distorted membranes of the endoplasmic reticulum, and a layer composed of relatively intact, but stretched membranes of the endoplasmic reticulum and discrete particles. (2) Mitochondria constitute a relatively broad layer. They are sometimes stretched; however, they retain most of their fine structure. The stratified nucleus is found within the mitochondrial layer. (3) A relatively wide layer of tightly packed vesicles. (4) At the centripetal end, resting against the cell membrane, are a few lipid vacuoles. A comparison is made between the ultrastructure of the stratified layers in situ and those described by others in differentially ultracentrifuged homogenates.     

Two types of intracytoplasmic inclusions in the cells of a patient with acute lymphoblastic leukemia

A patient with acute lymphoblastic leukemia (ALL) with cells containing two types of cytoplasmic inclusions is described. The inclusions appeared as globular bodies containing electron dense material with homogeneous structure and as crystalloid formations confined in organelles with structure similar to that of the surrounding mitochondria. In distinction to other reports, these structures were not related to the endoplasmic reticulum. The possibility that some of them represented altered mitochondria is discussed.     

COMPARATIVE CYTOPHYSIOLOGY OF STRIATED MUSCLE WITH SPECIAL REFERENCE TO THE ROLE OF THE ENDOPLASMIC RETICULUM

1. The structure and distribution of the components of striated muscle cells vary with the species and with the specialization of muscle fiber function. 2. There appear to be two, easily distinguishable, general categories of striated muscle structure. A. High frequency muscle (represented by flight muscle of higher insects and hummingbird, and cicada tympanal muscle) is characterized by widely spaced, non-branching fibrils of large diameter and short period, little endoplasmic reticulum, and large quantities of large mitochondria (low fibril-sarcoplasm ratio). This structure is correlated with heavy tracheolization or vascularization, high oxidative activity, and dark color as compared with other muscles of the same species. B. Low frequency muscle is characterized, in general, by high fibril-sarcoplasm ratio, relatively long period, few mitochondria increasing with activity and decreasing with absolute power of the fiber. Oxidative capacity and color are proportional to the quantity of mitochondria. These fibers are further differentiated into (a) fibrillar arrangement of contractile material which permits a regular pattern of interfibrillar and segmental reticulum, and (b) afibrillar arrangement of contractile material leading to an unsystematic distribution of reticulum. 3. The endoplasmic reticulum appears as a complex coordination system in the muscle fiber. Peripherally, it links the Z and M lines of the fibrils to the sarcolemma and between the fibrils it links the cross-bands, forming the Grundmembran of earlier authors. By longitudinal linkage, it connects with the sarcolemma at the muscle extremity to form a digital arrangement into which the tendon fibrils are spliced. The extent of its development and its position have a definite relationship to the degree and site of fiber shortening. At present the reticulum is the only structure that one can consider to be an internal conducting system. It may distribute the excitation transversely from fibril to fibril, and lengthwise saltatorially to the symmetry centers of the sarcomeres. 4. The nucleus is the mediating element between the cytoplasmic phases within and without the tubular system of the endoplasmic reticulum. A possible mechanism which correlates nucleus, adenylic acid system, ion exchange, and reticulum with the initiation of contraction is postulated.     

Fine structure of the female sex pheromone-producing glands in Sesamia nonagrioides lef. (Lepidoptera : Noctuidae)

The morphology and cytology of the female sex pheromone-producing glands of Sesamia nonagrioides (Lepidoptera : Noctuidae) consist of modified intersegmental membranes; they are unusual compared with those described in other moths. There are 2 different glandular areas (a ventral area, GI, around the ostium bursae and a ring-shaped area, GII, around the ovipositor), instead of a single area (between segments 8 and 9 + 10) as in most other species. Ultrastructural features, such as developed basal invaginations and dilated intercellular spaces indicate transport of material from the hemolymph to the glandular cells, while the presence of abundant mitochondria, numerous free ribosomes, rough endoplasmic reticulum, and inclusions reveal high cellular activity. The smooth endoplasmic reticulum is absent in S. nonagrioides, in contrast to its extensive development in glands producing similar compounds in other moths. The cuticle, abnormally thick (7–8 times thicker than the glandular epithelium), is traversed by dilated pore canals forming cuticular gaps, connected with epicuticular canals. This system allows the storage and the passage of pheromone in and through the cuticle.     

Organelle distribution in chick neuroepithelial cells: effects of colchicine and cytochalasin B

The intracellular distribution of mitochondria, cytoplasmic inclusions and rough endoplasmic reticulum cisternae of chick neuroepithelial cells was investigated at neurulation stages 6, 8, 10 and 12. These neuroepithelial cells were subdivided into three zones: apical, median and basal and the distribution percentages of distribution of these organelles were obtained. Mitochondrial distribution was related to the energy supply that mitochondria provide for apical microfilament contraction. Cytoplasmic inclusions were distributed preferentially in the apical zone of the neuroepithelial cells during the four stages. Rough endoplasmic reticulum cisternae were homogeneously distributed in the three zones at stages 10 and 12, but at stages 6 and 8 there are more elevated percentages of rough endoplasmic reticulum in the apical zones than in the other zones. Experimental treatments with colchicine and cytochalasin B does not modify the patterns of mitochondria and rough endoplasmic reticulum cisternae but alters the distribution of cytoplasmic inclusions. Finally, there is a correlation in the normal neurulating neuroepithelial cells between the distributions of mitochondria and rough endoplasmic reticulum distribution and between the distributions of mitochondria and cytoplasmic inclusions distribution. This relationship is retained in the treated neuroepithelial cells.     

UDP-Galactose:Ceramide Galactosyl Transferase of Isolated Oligodendroglia

Abstract: The activity of UDP-galactose:ceramide galactosyl transferase (CGalT) has been studied in isolated oligodendroglia from bovine brain white matter and myelinating rat brain. The specific activity and activity per mg DNA are 4- and 10-fold higher in rat oligodendroglia compared with neuronal perikarya from rat brain, and is higher in oligodendroglia from myelinating rat brain compared with bovine oligodendroglia. In membranes isolated from oligodendroglia, the specific activity decreased in the order endoplasmic reticulum > plasma membrane > myelin.     

Viral Glycoproteins Accumulate in Newly Formed Annulate Lamellae following Infection of Lymphoid Cells by Human Herpesvirus 6

Ultrastructural analysis of HSB-2 T-lymphoid cells and human cord blood mononuclear cells infected with human herpesvirus 6 revealed the presence, in the cell cytoplasm, of annulate lamellae (AL), which were absent in uninfected cells. Time course analysis of the appearance of AL following viral infection showed that no AL were visible within the first 72 h postinfection and that their formation correlated with the expression of the late viral glycoprotein gp116. The requirement of active viral replication for AL neoformation was further confirmed by experiments using inactivated virus or performed in presence of the viral DNA polymerase inhibitor phosphonoacetic acid. Both conventional electron microscopic examination and immunogold fracture labeling with anti-endoplasmic reticulum antibodies indicated a close relationship of AL with the endoplasmic reticulum and nuclear membranes. However, when the freeze-fractured cells were immunogold labeled with an anti-gp116 monoclonal antibody, AL membranes were densely labeled, whereas nuclear membranes and endoplasmic reticulum cisternae appeared virtually unlabeled, showing that viral envelope glycoproteins selectively accumulate in AL. In addition, gold labeling with Helix pomatia lectin and wheat germ agglutinin indicated that AL cisternae, similar to cis-Golgi membranes, contain intermediate, but not terminal, forms of glycoconjugates. Taken together, these results suggest that in this cell-virus system, AL function as a viral glycoprotein storage compartment and as a putative site of O-glycosylation.     

Oligodendroglial Signal Transduction Systems Are Developmentally Regulated

Abstract: Studies from several laboratories indicate that oligodendroglia exhibit signal transduction systems that can be activated by classical neurotransmitters. Previous studies from this laboratory indicate that oligodendroglia express neuroligand receptors linked to the regulation of Ca²⁺_i. Experiments presented in this article were designed to determine if developmental processes that influence the ability of oligodendroglia to respond to neuroligands with an increase in Ca²⁺_i proceed either in vitro or in vivo. Findings support the view that developmental processes markedly affected the sensitivity of these cells to both purinergic and cholinergic receptor agonists, whereas their responsiveness to either histamine or bradykinin appeared relatively stable over time. Approximately 90 and 75% of oligodendroglia responded to ATP or carbachol, respectively, after 4 days in vitro, whereas <10% of these cells responded to either of these neuroligands after 8 days in vitro. The decrease in the percentage of oligodendroglia responding to ATP, but not carbachol, could be prevented by including dibutyryl cyclic AMP in the culture medium during the final 4 days in vitro. However, once the loss in responsiveness to ATP had occurred, it could not be reversed by exposure to dibutyryl cyclic AMP. Developmental changes in the ATP sensitivity of oligodendroglia occurred in cells expressing galactocerebroside and myelin basic protein. The neuroligand sensitivity of oligodendroglia isolated from either neonatal, 2-, 3-, or 5-week-old spinal cord was examined to determine if developmental changes in oligodendroglial Ca²⁺ regulation occurred in vivo. The results of these experiments indicate that the percentage of oligodendroglia responding to either ATP or carbachol markedly decreased as a function of the age of the animal used to prepare the cultures; this was not the case for the stimulation of Ca²⁺_i by histamine. The decreased sensitivity of oligodendroglia isolated from older animals could not be reversed through the addition of dibutyryl cyclic AMP. Overall, the results of these experiments indicate that developmental processes selectively influence the sensitivity of oligodendroglia to specific neuroligands and suggest that oligodendroglial processes unrelated to myelin formation may be regulated by neuroligands in vivo.     

INTRACISTERNAL GRANULES IN THE EXOCRINE CELLS OF THE PANCREAS

Dense, homogeneous granules of 250 to 350 mµ in diameter have been found inside the cavities of the endoplasmic reticulum in the acinar cells of the pancreas of the guinea pig. They apparently correspond to the fine granules described in the same material in light microscopy by Mankowski and Bensley. The location of these granules indicates that the endoplasmic reticulum is a cavitary system and suggests its participation in secretory processes.