A LIGHT AND ELECTRON MICROSCOPIC STUDY OF PEROXIDASE LOCALIZATION IN THE ONION ROOT TIP

Peroxidase activity in the onion root tip was localized by the diaminobenzidine procedure and studied at the light and electron microscope levels. Reaction product was observed in the cell wall, on the plasmalemma, in the Golgi apparatus cisternae and vesicles, in young and developing vacuoles, in the endoplasmic reticulum, and on both soluble and membrane-bound ribosomes. The reaction product at the various cellular and subcellular sites occurs in distinct tissue and developmental patterns.     

Ultrastructural Localization of ATPase Activity in the Cells of the Apical Meristem Zone,Elongation Zone and Root Hair Zone of Tomato Roots

A comparative study on the cytochemical localization of adenosine triphosphatase (ATPase) activity reaction in the cells of the apical meristem zone, elongation zone and root hair zone of tomato roots was carried out by electron microscopic observations of lead phosphate precipitation. The following experimental results have been obtained: In the meristematic cells of tomato roots, the heavy lead phosphate deposits indicating a very high activity of ATPase were localized at plasmalemma, plasmodesmata, endoplasmic reticulum, Golgi bodies, nucleoli and chromatin (Figs. 1—2). The reaction products of ATPase activity were also observed at some sites of ground cytoplasm and cell wall, but they were not found in little vacuoles and on tonoplast. In the cells of elongation zone, the ATPase activity at plasmalemma and plasmodesmata was as high as that in the meristematic cells of root tip, while the ATPase activity at nucleoli, chromatin, endoplasmic reticulum and Golgi bodies was markedly lowered. On the other hand, the high ATPase activity was produced on the tonoplast of the developing and enlarging vacuoles (Fig. 3). In the cells of root hair zone, the high ATPase activity was shown at plasmalemma, tonoplast and intercellular spaces, but the ATPase activity at nucleoli, chromatin and endoplasmic reticulum was wholly inactivated. (Figs. 4—7). The above results indicate that the ATPase activity with membranes and organelles is altered when the functions of cells and organelles change. Therefore, it is evident that the ATPase activity may be closely related to many physiological functions.     

STRUCTURE AND DEVELOPMENT OF THE SIEVE ELEMENTS IN PSILOTUM NUDUM

Shoot tissue of Psilotum nudum (L.) Griseb. was fixed in glutaraldehyde and postfixed in osmium tetroxide for electron microscopy. Young sieve elements can be distinguished from contiguous parenchyma cells by their distinctive plastids, the presence of refractive spherules, and the overall dense appearance of their protoplast. The refractive spherules apparently originate in the intracisternal spaces of the endoplasmic reticulum (ER). With increasing age the sieve-element wall undergoes a marked increase in thickness. Concomitantly, a marked increase occurs in the production of dictyosome vesicles, many of which can be seen in varying degrees of fusion with the plasmalemma. Other fibril- and vesicle-containing vacuoles also are found in the cytoplasm. In many instances the delimiting membrane of these vacuoles was continuous with the plasmalemma. Vesicles and fibrillar materials similar to those of the vacuoles were found in the younger portions of the wall. At maturity the plasmalemma-lined sieve element contains a parietal network of ER, plastids, mitochondria, and remnants of nuclei. The protoplasts of contiguous sieve elements are connected by solitary pores on lateral walls and pores aggregated into sieve areas on end walls. All pores are lined by the plasmalemma and filled with numerous ER membranes which arise selectively at developing pore sites, independently of the ER elsewhere in the cell. P-protein and callose are lacking at all stages of development.     

ACETYLCHOLINESTERASE IN FROG SYMPATHETIC AND DORSAL ROOT GANGLIA : A Study by Electron Microscope Cytochemistry and Microgasometric Analysis with the Magnetic Diver

The localization and chemical determination of acetylcholin esterase in the frog sympathetic and dorsal root ganglia were studied by a combination of the methods of electron microscopy, histochemistry, and microgasometric analysis with the magnetic diver. The Koelle-Friedenwald copper thiocholine histochemical method was modified by eliminating the sulfide conversion and by treatment of the tissue with potassium permanganate. In fixed tissue, enzymatic activity was demonstrated on the inner surface of the endoplasmic reticulum, nuclear envelope, subsurface cisternae, and agranular reticulum of the perikaryon and axon. In briefly fixed tissue, end product appeared also at the axon-sheath and the sheath-sheath interface. Activity at the synaptic junction was most readily obtained in unfixed tissue. Isolated neurons recovered from the diver following chemical analysis were studied with the electron microscope. Cells having a high enzyme activity showed a badly ruptured or absent neural plasmalemma and sheath. In this case the measured activity was apparently due to the enzyme present in the endoplasmic reticulum. Neurons having low activity exhibited an intact plasmalemma and sheath. This may reflect the effectiveness of the neural plasmalemma and sheath as a penetration barrier. The effects of fixation on enzyme activity are discussed. Electron microscopic examination of cells following microgasometric analysis is shown to be essential for the interpretation of the biochemical data.     

Biochemical and cytochemical studies of digestive-absorptive functions of esophagus, cecum, and tequment in Schistosoma mansioni: acid phosphatase and tracer studies.

Acid phosphatase activity was examined, both cytochemically and biochemically, using beta-glycerophosphate (betaGP) and p-nitrophenyl phosphate (NPP) as substrates. The hydrolysis of these substrates differs in pH optimum and sensitivity to some inhibitors. A latent component of the enzyme activity could be demonstrated with betaGP but not with NPP as substrate. These differences suggest the presence of multiple enzymes operative at acid pH in S. mansoni. Cytochemical localization of the sites of hydrolysis of these substrates shows the major activity of the digestive system to be in the posterior portion of the esophagus and in the cecum. The reaction product in the posterior esophagus is found in small dumbbell-shaped vesicles and in the basal infoldings, while in the cecum it occurs on the apical plasmalemma, basal infoldings, and in pleiomorphic vesicles. The electron-dense tracers, ferritin, peroxidase, Thorotrast, and latex beads were all ingested but none was phagocytized. Tracer material was found in some "apparent" vesicles with subsequently were shown by the lanthanum staining technique to be in communication with the extracellular space.     

The phosphate uptake mechanism

The slow rate of diffusion of phosphate in soil results in a zone of depletion of phosphate ions in solution around the roots of plants in low phosphate soils. Transfer of phosphate to the site of uptake into the root symplasm limits phosphate uptake in such soils. This transfer involves movement across the depletion zone and through the root apoplasm. The apoplasm is made up of the cell walls of epidermal and cortical cells, together with the associated intercellular spaces. Although the pores in the open latticework of these cell walls permit movement of nutrients around cells, they increase the path length across which phosphate ions have to diffuse. The structural components and net negative charges of the cell walls also influence the effective concentrations of phosphate in the apoplasm. This concentration may be further modified by excreted organic compounds around cell walls and the presence of micro-organisms that use such compounds as carbon sources. A membrane on the inner surface of the cell wall, the plasmalemma, separates the apoplasm from the symplasm. Uptake of nutrients into the root symplasm occurs through transporter proteins embedded in this membrane. Understanding of the mechanisms by which phosphate is transported across the plasmalemma into the plant symplasm has advanced considerably over the past 4 years due to the application of molecular techniques. Genes encoding the transporters involved in this process have been isolated from a number of plant species. These transporters belong to a family of membrane proteins characterized by having 12 membrane-spanning domains arranged in a '6+6' configuration. H₂PO₄ ^– ions, together with protons, are transported through this protein. This transport process is driven by the potential across the membrane maintained by the action of a H⁺-ATPase, the `proton pump', that extrudes protons to the outer surface of the membrane. The expression of genes encoding high-affinity root phosphate transporters is regulated by the phosphorus (P) status of the plant. The transduction pathway involved in this regulation is not known at present. It is a systemic response rather than a localized response, however, the overall phosphate status of the plant being the controlling factor. Under phosphate stress, the expression of genes encoding these phosphate transporters is up-regulated. This results in a greater number of transporter proteins in the plasmalemma and enhanced phosphate uptake rates, if phosphate is available at the membrane surface. Uptake occurs around the root tip, into epidermal cells with their associated root hairs and into cells in the outer layers of the root cortex. Further back along the root axis, phosphate can also be taken up by transfer from mycorrhizal fungi to root cortical cells.Strategies for increasing nutrient uptake by overexpressing genes encoding high-affinity phosphate transporters are likely to be mainly applicable to situations where a reasonable phosphate concentration can be maintained at the outer surface of the plasmalemma. Maintaining such a concentration is a major problem in the phosphate deficient soils of the semi-arid tropics (SAT), so emphasis in these soils is on strategies to improve the movement of phosphate to the surface of the plasmalemma. There may be scope, however, for manipulating the expression of genes involved in the internal mobilisation of phosphate within the plant, thereby improving phosphate utilisation.     

Calcium as a plant nutrient

Abstract. Calcium occurs as a relatively large, divalent ion which readily enters the apoplast and is bound in exchangeable form in cell walls and on the exterior surface of the plasmalemma. It occurs in only very low concentrations in the cytoplasm and chloroplasts and appears to have a limited role as an enzymatic cofactor. The soil solution usually provides an adequate supply of Ca to plants. The well known physiological disorders resulting from localized Ca deficiencies within the plant are thus attributable to poor Ca distribution rather than restriction in uptake. Calcium is moved largely in the xylem and only to a very limited extent in the phloem. The phloem/xylem ratio of the solute input can be particularly critical in organs which are naturally low in Ca, such as fruits and young leaves. Factors which influence the distribution of Ca such as humidity, root pressure, phytohormone activity, can also affect the occurrence of these disorders.     

Secretion of acid phosphatase in<Emphasis Type="Italic">Claviceps purpurea</Emphasis> — an ultracytochemical study

The lead phosphate precipitation method showed the reaction product of acid phosphatase (which reflects the presence of the enzyme glycoprotein) in peripheral cytoplasmic vesicles in the ascomycetous fungus Claviceps purpurea. The product appeared to diffuse from these vesicles (diameter 100-200 nm) towards the cell wall, usually to its sites covered by the capsular fibres exhibiting also acid phosphatase activity. This observation of diffusion of secretory glycoprotein in the cytoplasmic matrix and its orientation to the plasmalemma and capsular fibrils suggests an alternative to the well-described secretory mechanism of transport and exocytosis of glycoproteins via membrane-bound transport conveyors fusing with the cell membrane. It confirms and enlarges our previous finding of the reaction product of acid phosphatase performed by ultrastructural cytochemistry in vacuoles (lysosomes), in the growing cell septum, in cytoplasmic vesicles and in the fibres of the external capsule.     

Electron microscopic localization of adenylate cyclase activity of white and brown adipose tissue of the rat and chicken

Summary Brown adipose tissue of newborn rats and chicken embryos and white adipose tissue of adult rats were studied. Adenylate cyclase (EC 4.6.1.1.) activity stimulated by 0.1 mmol/l noradrenaline was demonstrated using an electron microscopic histochemical method.The reaction product was visualized as a cobalt salt in the plasmalemma of the adipocytes. The adipocytes of the brown adipose tissue of the newborn rats showed most intense reaction in the outer surfaces of their plasmalemma. Alloxan totally inhibited the enzymatic reaction.The histochemical reaction used in the present study probably demonstrated the hormonal receptor sites in the plasmalemmas of the adipocytes which are stimulated by noradrenaline.     

Electron microscopic localization of adenylate cyclase activity of white and brown adipose tissue of the rat and chicken.

Brown adipose tissue of newborn rats and chicken embryos and white adipose tissue of adult rats were studied. Adenylate cyclase (EC 4.6.1.1.) activity stimulated by 0.1 mmol/l noradrenaline was demonstrated using an electron microscopic histochemical method. The reaction product was visualized as a cobalt salt in the plasmalemma of the adipocytes. The adipocytes of the brown adipose tissue of the newborn rats showed most intense reaction in the outer surfaces of their plasmalemma. Alloxan totally inhibited the enzymatic reaction. The histochemical reaction used in the present study probably demonstrated the hormonal receptor sites in the plasmalemmas of the adipocytes which are stimulated by noradrenaline.     

Structural differentiation of membranes involved in the secretion of polysaccharide slime by root cap cells of cress (Lepidium sativum L.)

The peripheral secretion tissue of the root cap of Lepidium sativum L. was investigated by electronmicroscopy and freeze-fracturing in order to study structural changes of membranes involved in the secretion process of polysaccharide slime. Exocytosis of slime-transporting vesicles occurs chiefly in the distal region of the anticlinal cell walls. The protoplasmic fracture face (PF) of the plasmalemma of this region is characterized by a high number of homogenously distributed intramembranous particles (IMPs) interrupted by areas nearly free of IMPs. Near such areas slime-transporting vesicles are found to be underlying the plasma membrane. It can be concluded that areas poor in particles are prospective sites for membrane fusion. During the formation of slime-transporting vesicles, the number of IMPs undergoes a striking change in the PF of dictyosome membranes and their derivatives. It is high in dictyosome cisternae and remarkably lower in the budding region at the periphery of the cisternae. Slime-transporting vesicles are as poor in IMPs as the areas of the plasmalemma. Microvesicles rich in IMPs are observed in the surroundings of dictyosomes. The results indicate that in the plasmalemma and in membranes of the Golgi apparatus special classes of proteins — recognizable as IMPs — are displaced laterally into adjacent membrane regions. Since the exoplasmic fracture face (EF) of these membranes is principally poor in particles, it can be concluded that membrane fusion occurs in areas characterized by a high quantity of lipid molecules. It is obvious that the Golgi apparatus regulates the molecular composition of the plasma membrane by selection of specific membrane components. The drastic membrane transformation during the formation of slime-transporting vesicles in the Golgi apparatus causes the enrichment of dictyosome membranes by IMPs, whereas the plasma membrane probably is enriched by lipids. The structural differentiations in both the plasma membrane and in Golgi membranes are discussed in relation to membrane transformation, membrane flow, membrane fusion, and recycling of membrane constituents.Abbreviations PF protoplasmic fracture face - EF exoplasmic fracture face - IMP intramembranous particle     

Function of Rhizodermal Transfer Cells in the Fe Stress Response Mechanism of Capsicum annuum L

A variety of red pepper (Capsicum annuum L., cv Yaglik) responds to Fe deficiency stress with simultaneously enhanced H⁺ extrusion, reduction of ferric ions and synthesis of malic and citric acid in a swollen subapical root zone densely covered with root hairs. It is demonstrated that these stress responses temporally coincide with the development of rhizodermal and hypodermal transfer cells in this root zone. During stress response the transfer cells show a marked autofluorescence which could arise from endogenous iron chelators of the phenolic acid type. The presence of organelle-rich cytoplasm which often exhibits rotational cytoplasmic streaming points to high physiological activity and makes these cells, with their increased plasmalemma surface, particularly well suited for the entire stress response mechanism. Since Fe stress-induced acidification is diminished by vanadate and erythrosin B, both specific inhibitors of plasmalemma ATPases, it seems reasonable to suppose that H⁺ pumping from transfer cells is activated by an ATPase located in their plasmamembrane. H⁺ extrusion is also shown to be inhibited by abscisic acid. Raised phosphoenolpyruvate carboxylase activity and simultaneous accumulation of malate in the swollen root zone point to the action of a pH stat preventing a detrimental rise in cytoplasmic pH of transfer cells during enhanced H⁺ extrusion. The simultaneous increase in citric acid concentration favors chelation of iron at the site of its uptake and thus ensures long distance transport to the areas of metabolic demand. A direct link between citrate accumulation and ferric ion reduction as proposed in recent literature further supports the crucial role of transfer cells in the response to Fe deficiency stress.     

Ultrastructural localization of phosphatase activity in the guinea pig pineal gland by the cerium technique

Thiamine pyrophosphatase (TPPase), nucleoside diphosphatase (NDPase), and glucose-6-phosphatase (G-6-Pase) were localized by the cerium technique in guinea pig pinealocytes and compared with the corresponding lead technique. NDPase and TPPase were also compared at different pH values using the cerium technique. Vibratome sections of perfusion-fixed tissue were incubated with cerium chloride or lead nitrate. Substrates used were thiamine pyrophosphate (for TPPase), sodium inosine diphosphate (NDPase), and disodium glucose-6-phosphate (G-6-Pase). The 1-2 trans saccules of the Golgi apparatus showed TPPase and NDPase activity but none for G-6-Pase. The endoplasmic reticulum (ER) cisternae and perinuclear space had NDPase and G-6-Pase activity but not TPPase. The abluminal plasmalemma of endothelial cells and the plasmalemma of Schwann cells demonstrated TPPase and NDPase activity but the luminal plasmalemma of the endothelial cells and the plasmalemma of pinealocyte processes showed only NDPase activity. TPPase was active at all pH values tested, but NDPase was most active at pH values of 6.5 and 7.0. Lead phosphate precipitate was frequently seen in nuclei, perinuclear space, ER cisternae, and "synaptic" vesicles when lead was used as the capturing agent. These sites were usually not labeled when cerium was used.     

Endoplasmic Reticulum Forms a Dynamic Continuum for Lipid Diffusion between Contiguous Soybean Root Cells

Intercellular communication between plant cells for low molecular weight hydrophilic molecules occurs through plasmodesmata. These tubular structures are embedded in the plant cell wall in association with the plasmalemma and endoplasmic reticulum (ER). Transmission electron microscopy has provided strong evidence to support the view that both the ER and plasmalemma are structurally continuous across the wall at these sites. In experiments to be described, the technique of fluorescence redistribution after photobleaching was used to examine the lateral mobility and intercellular transport capability of a number of fluorescent lipid and phospholipid analogs. These probes were shown by confocal fluorescence microscopy to partition in either the ER or plasmalemma. Results from these measurements provide evidence for cell communication between contiguous cells for probes localized predominantly in the ER. In contrast, no detectable intercellular communication was observed for probes residing exclusively in the plasmalemma. It was of particular interest to note that when 1-acyl-2-(N-4-nitrobenzo-2-oxa-l,3-diazole)aminoacylphosphatidylcholine was utilized as a potential reporter molecule for phospholipids in the plasmalemma, it was quickly degraded to 1-acyl-2-(N-4-nitrobenzo-2-oxa-1,3-diazole)aminoacyldiglyceride (NBD-DAG), which then appeared predominantly localized to the ER and nuclear envelope. This endogenously synthesized NBD-DAG was found to be capable of transfer between cells, as was exogenously incorporated NBD-DAG. Results from these investigations provide support for the following conclusions: (1) ER, but apparently not the plasmalemma, can form dynamic communication pathways for lipids across the cell wall between connecting plant cells; (2) the plasmodesmata appear to form a barrier for lipid diffusion through the plasmalemma; and (3) lipid signaling molecules such as diacylglycerol are capable of transfer between contiguous plant cells through the ER. These observations speak to issues of plant cell autonomy for lipid synthesis and mechanisms of intercellular signaling and communication.     

Structure and cytochemistry of the procambium in Salix buds during dormancy and dormancy breaking

This report presents a combined investigation of ultrastructural and enzymatic changes in the procambium from late winter to early spring. In January the procambial cells of dormant Salix buds have a convoluted plasma membrane with many plasmalemmasomes, numerous lipid bodies, large stacks of rough ER and plastids surrounded by smooth ER profiles. Several small lysosomes show activity of ATPase and acid phosphatases. In addition ER, nuclear envelopes, dictyosomes, and thylakoids have ATPase activity, and ER and plasmalemma, and nuclei also show acid phosphatase activity. In February metabolism seems to increase as indicated by lysosomes with membranous formations, dilated ER, nuclear envelopes, spiny vesicles, and polysomes. ATPase activity occurs in plasmalemma and vacuoles, and acid phosphatases in the middle lamella region of walls, in plasmalemma, vacuoles, ER, and nuclei. At the end of March, when growth starts inside the buds, but before they break, the stacks of rough ER disappear, and the vacuoles coalesce. Most of the lipid bodies have disappeared and the plastids have accumulated starch. Cell division and differentiation of procambial cells to protophloem and protoxylem have started. The distribution of ATPase increases; activity is found in walls and plasmalemma, and only a few small vacuoles still have ATPase and acid phosphatase activity. Notable is the appearance of ATPase in mitochondrial cristae and nucleoli and the occurrence of rather high levels also in endomembranes and dictyosomes.     

Integration of sperm and egg plasma membrane components at fertilization

Studies examining the integration of the sperm and egg plasma membranes, subsequent to gamete fusion in the surf clam, Spisula solidissima, were carried out employing the concanavalin A-horseradish peroxidase-diaminobenzidine procedure (Con A-HRP-DAB). When unfertilized Spisula eggs were incubated in Con A, either prior to or after aldehyde fixation and reacted with HRP-DAB, enzymatic precipitate was found associated with the vitelline layer and plasmalemma. The plasma membranes of sperm treated in a similar manner failed to stain. The plasma membranes of fertilized eggs reacted with Con A-HRP-DAB and examined by 1 min postinsemination were associated uniformly with enzymatic precipitate except at sites of sperm incorporation. These portions of unstained plasma membrane were derived from the spermatozoon and delimited the contents of the fertilization cone. From 2 to 4 min postinsemination, HRP-DAB reaction product became associated with the plasma membrane delimiting the fertilization cone. By 4 min postinsemination no difference in staining of the plasma membranes derived from the egg or the sperm (plasmalemma delimiting the fertilization cone) was detected. Evidence is presented suggesting that the acquisition of HRP-DAB reaction product by the former sperm plasmalemma is due to the movement of Con A binding sites from the egg plasma membrane.     

Further characterization of phosphatase activities using non-specific substrates

Synopsis The demonstration of non-lysosomal acid phosphatase has been the subject of a number of recent investigations. In the present study we compared the enzyme activities in rat liver and kidney that are revealed after incubation in the presence of either -glycerophosphate,p-nitrophenylphosphate or phenylphosphate at varying pH. As seen by others, the activity towardsp-nitrophenylphosphate at pH 5–6 was confined to lysosomes, Golgi apparatus, endoplasmic reticulum (ER), nuclear envelope and plasmalemma. The reactivity of the plasmalemma and the ER was increased at pH 7. The ER of Küpffer cells in the liver stained intensely in contrast to the ER of the parenchymal cells, which stained only weakly. In the presence of NaF, all sites except the plasmalemma became negative. Addition of a levamisole-analogue,l-p-bromotetramisole, which is a specific inhibitor of alkaline phosphatase, resulted in the disappearance of the plasmalemmal activity whereas the activity at the other sites appeared unaltered. The rather unusual locations of activities with so-called non-specific substrates were further compared with those obtained with specific substrates such as glucose-6-phosphate and thiamine pyrophosphate. The possible implication of these data in relation to the specificity of marker-enzymes for subcellular organelles is discussed.     

OBSERVATIONS ON THE STRUCTURE OF SOME FORMS OF GOMPHONEMA PARVULUM KÜTZ. III. FRUSTULE FORMATION1

Gomphonema parvulum Kütz. was investigated by electron microscopy for details of frustule formation. An expansion of the cell along the pervalvar plane occurs prior to cell division. After nuclear division the organelles are, separated into 2 entities, either by division or by dispersion. The cell divides into 2 halves by the invagination of the plasmalemma which is derived from Golgi vesicular activity. When cytoplasmic cleavage, is complete, the Golgi actively produces electronlucent vesicles which collect and coalesce beneath the. plasmalemma to form the silicalemma around the silicon deposition vesicle. The endoplasmic reticulum is also closely associated with this vesicular activity. The vesicle gradually expands and becomes extremely electron dense as silica is deposited within it—first in the region, followed by the mantle edge. When the valve is mature, Golgi vesicles collect and fuse to form the silicalemma of the first girdle band. The first girdle band becomes aligned against the mantle edge on completion, by the “sloughing off” of the external silicalemma and plasmalemma. The second and third bands are formed, individually in a similar manner. Separation of the 2 daughter cells commences at the apical pole and progresses to the basal pole. The plasmalemma and external silicalemma are “sloughed off” so that the 2 cells can separate. The inner segment of the silicalemma becomes the new plasmalemma of the daughter cell.     

Fine structural localization of potassium-stimulated rho nitrophenylphosphatase activity in denrites of the cerebral cortex

A histochemical technique for the demonstration of K+-rho-nitrophenylphosphatase (K+-rhoNPPase) activity, a component of the Na+,K+-ATPase, has been applied at the fine structural level in the somatosensory cortex of the rat. Reaction product was consistenly found in dendrites and in association with the cytoplasmic aspect of the dendritic plasmalemma. Reaction product often filled portions of the tubular smooth endoplasmic reticulum in these processes. The results of these studies are interpreted to indicate that enzymatic activity is associated with large-and small-diameter dendrites. No convincing evidence of high activity was found in glial profiles. The importance of neurons and their dendrites in active transport of sodium and potassium ions in the cerebral cortex may be more significant than indicated by studies with isolated neurons and glia.     

NUCLEOSIDE PHOSPHATASE AND CHOLINESTERASE ACTIVITIES IN DORSAL ROOT GANGLIA AND PERIPHERAL NERVE

In dorsal root ganglia and peripheral nerve of the rat and other species, nucleoside phosphatase and unspecific cholinesterase reaction products are found in the plasma membranes and spaces between them at two sites: (1) Schwann cell-axon interfaces and mesaxons of unmyelinated fibers, and (2) sheath cell-perikaryon interfaces and interfaces between adjacent sheath cells. Acetylcholinesterase reaction product is found in the perikaryon (within the endoplasmic reticulum) and the axon (axoplasmic surface). Nucleoside phosphatase reaction product is also found in the numerous vacuoles at the surface of perineurium cells, ganglion sheath cells, and cells surrounding some ganglion blood vessels. Nucleoside phosphatase activities in the sections fail to respond, in the manner described for "transport ATPase," to diisopropylphosphofluoridate, sodium and potassium ions, and ouabain. Nucleoside diphosphates are hydrolyzed more slowly than triphosphates in unmyelinated fibers, and are not hydrolyzed at the perikaryon surface. Nucleoside monophosphates are either not hydrolyzed or hydrolyzed very slowly. In contrast to these localizations, which are believed to demonstrate sites of enzyme activity, it is considered likely that diffusion artifacts account for the nucleoside phosphatase reaction product frequently found along the outer surfaces of myelinated fibers and within vacuoles at the Schwann cell surfaces of these fibers. The diffuse reaction product seen in basement membranes of ganglion and nerve may also be artifact.