Fine structural and cytochemical mapping of enamel organ during the enameloid formation stages in gars, Lepisosteus oculatus, Actinopterygii

During cap enameloid formation in gars (Lepisosteus oculatus), the dental epithelial cells that constitute the enamel organ were observed by means of transmission electron microscopy and enzyme cytochemistry to detect the hydrolytic enzyme activities, alkaline phosphatase (ALPase), acid phosphatase (ACPase), calcium-dependent adenosine triphosphatase (Ca-ATPase) and potassium-dependent p-nitrophenylphosphatase (K-NPPase) (sodium, potassium-activated adenoshine triphosphatase (Na-K-ATPase)). The enameloid formation process in gars was divided into three stages: matrix formation, mineralisation and maturation. The enamel organ consisted of the outer dental epithelial (ODE) cells, stellate reticulum (SR), stratum intermedium (SI) and the inner dental epithelial (IDE) cells during the whole of the cap enameloid formation stages. During the matrix formation stage, many cisternae of rough endoplasmic reticulum and widely distributed Golgi apparatus, in which the procollagen granules containing cross-striations were often found, were remarkable elements in the IDE cells. During the stage of mineralisation, the IDE cells were tall columnar, and infoldings of distal plasma membrane of the IDE cells became marked. The most developed Golgi apparatus was visible at this stage, and large secretory granules containing fine granular or tubular materials were found in the distal cytoplasm that was close to the infoldings of the distal end. Many lysosomes that were ACPase positive were seen near the Golgi apparatus and in the distal cytoplasm of the IDE cells. ACPase positive granules often contained the cross-striation structure resembling procollagen, suggesting that the procollagen is degenerated in the IDE cells. During the maturation stage, the distal infoldings became unclear, and there were no large granules containing tubular materials, but many ACPase positive lysosomes were still present in the IDE cells. Non-specific ALPase was detected at the plasma membrane of the IDE cells at the mineralisation and maturation stages. K-NPPase was markedly detected at the plasma membrane of the IDE cells at the maturation stage. These results demonstrate that the IDE cells might be mainly involved in the removal of degenerated organic matrix from enameloid during the later formation stages. Strong Ca-ATPase activity was observed at the entire plasma membrane of the stratum intermedium cells, and there was slightly weak activity at the plasma membrane of the IDE cells during the mineralisation and maturation stages, implying that these cells are related to the active Ca transport to the maturing enameloid. It is likely that although the structure of the enamel organ is different, the function, especially at the mineralisation and maturation stages, is similar to other actinopterygians having well-mineralized cap enameloid.

R25 is an intracellular membrane receptor for a snake venom secretory phospholipase A(2)

Ammodytoxin is a presynaptically neurotoxic (beta-neurotoxic) snake venom secretory phospholipase A(2) (sPLA(2)). We detected a 25 kDa protein which binds the toxin with very high affinity (R25) in porcine cerebral cortex. Here we show that R25 is an integral membrane protein with intracellular localisation. It is the first sPLA(2) receptor known to date that localises to intracellular membranes. Centrifugation on sucrose gradients was used to fractionate porcine cerebral cortex. The subcellular composition of the fractions was determined by following the distribution of organelle-specific markers. The distribution of R25 in the fractions matched the distribution of the mitochondrial marker succinate dehydrogenase, but not the markers for plasma membrane, lysosomes, endoplasmic reticulum, synaptic and secretory vesicles. R25 most likely resides in mitochondria, which are known to be targets for sPLA(2) neurotoxins in the nerve ending and are potentially implicated in the process of beta-neurotoxicity.

Expression and sub cellular localization of the sodium hydrogen exchanger isoform-1 in rat tissues: a possible functional relevance

In an attempt to understand the mechanism underlying the tissue-dependent function, the expression of NHE-1 protein and its sub cellular localization was examined in the rat GI-tract and other tissues. Rat NHE-1 polyclonal antibodies were raised in rabbits using a NHE-1 fusion protein antigen. The antibodies recognized a 110 kD protein in rats and mice, but not in human or rabbit RBCs. Colon, stomach, brain, spleen and kidney expressed NHE-1 protein abundantly, whereas the skeletal muscle the least abundant. Ouabain-sensitive-K+-stimulated p-nitrophenylphosphatase (PNPPase), the partial activity of the sodium pump and alkaline phosphatase (Apase) were used as the markers of the basolateral and apical membranes. NHE-1 was detected predominantly in the PNPPase enriched membrane fractions, but was also detected in the apical membrane enriched fractions in the kidney cortex, jejunum and colon at a lower level. NHE-1 was detected in the plasma membrane enriched fractions from the skeletal muscle and ventricle. Immunofluorescence data showed a similar localization pattern of NHE-1 in the colon and kidney sections. These findings suggest that NHE-1 is localized both on the apical and basolateral membrane. In view of its similar sub cellular localization in the GI-tract and kidney, but a different level of expression, might suggest that the level of protein, but not the sub cellular distribution is important to regulate its tissue-dependent function.

Differentiation of mucous neck cells into parietal cells: a new concept of mitochondrial biogenesis

Parietal cells of the gastric fundic mucosa are small and contain only a few tiny mitochondria when they begin to differentiate from mucous neck cells. The canalicular ATPase activity characteristic of mature parietal cells is discrete in these young cells, whereas areas of very high activity are apparent in the Golgi complex, reticulum, nuclear envelope, mitochondrial wall, and plasma membrane. Close relations and contacts occur between mitochondria and these organelles, and the size and number of mitochondria increase progressively. These relations, as well as mitochondrial ATPase activity (a true differentiation marker), cease once the mitochondria become as numerous and large as those of a mature parietal cell. Our observations suggest that a secondary form of mitochondrial biogenesis, involving the massive participation of other organelles and independent of the classical mechanisms inherent in mitosis, occurs in parietal cells at the beginning of G1 phase during the 6 days of their maturation.

Human liver high molecular weight zinc-dependent acid p-nitrophenylphosphatase. Purification and properties

Human liver contains high molecular weight-type Zn2+-dependent acid p-nitrophenylphosphatase (HMW-ZnAP). The enzyme was purified 1000-fold by a new procedure, including preparative isoelectrofocusing. The HMW-ZnAP was homogeneous in non-denaturing disk-gel electrophoresis with an MW of about 93 kDa determined by Sephadex G-100 chromatography. A single polypeptide chain of 43 kDa was detected on sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), suggesting a homodimeric structure. The isoelectric point (pI) was 7.2-7.4. Human liver HMW-ZnAP requires Zn2+-ions for activity; other divalent cations are ineffective or act as inhibitors. It dephosphorylated p-nitrophenylphosphate (pNPP) (Km = 0.24 mM), o-carboxyl phenylphosphate (oCPP) (Km = 0.92 mM) and phenylphosphate (PhP) (Km = 1.42 mM). Other substrates including [32P]-labelled casein or phosvitin, adenyl nucleotides and myo-inositol-1-phosphate, were not dephosphorylated. Human liver HMW-ZnAP obeys Michaelis-Menten kinetics with pNPP as substrate; the enzyme was competitively inhibited by inorganic phosphate (Ki = 0.55 mM), and by oCPP (Ki = 0.65 mM) and PhP (K = 1.16 mM). Adenosine monophosphate (AMP), adenosine diphosphate (ADP) and ATP displayed mixed-type inhibition. The enzyme was also inhibited by some modifiers such as EDTA, oxalate, p-chloromercurybenzoate, tartrate, imidazole, cyanide, cysteine, histidine and diethylpyrocarbonate, but not by fluoride or okadaic acid. Human liver HMW-ZnAP is sensitive to temperatures higher than 40 degrees C. The pH-dependence of the steady-state kinetic parameters indicates the existence of an essential ionizable group with a pKa of 7.25-7.50, similar to that of histidine. However, diethylpyrocarbonate inactivation experiments suggest that other amino acid residues may also be involved in enzyme catalysis.

Light and electron microscopical demonstration of the ouabain-sensitive, potassium-dependent p-nitrophenylphosphatase activity (K-NPPase) using a Ce-Mg-double capture technique

The cerium-based method of Kobayashi et al. for the histochemical demonstration of K-NPPase activity was improved. Besides Ce3+ additionally Mg2+ ions as orthophosphate capture were employed (double capture technique). For light microscopical purposes the Mg-phosphate was converted into Ce-phosphate by treatment of the sections with Ce-citrate yielding higher quantity of reaction product. Unspecific background staining was eliminated by EGTA. In the electron microscope this technique brought about fine granular reaction products without diffusion artefacts.

Acrosome damage and enzyme leakage of goat spermatozoa during dilution, cooling and freezing

Semen of Jamunapari goat bucks was frozen in three diluents egg yolk-tris, egg yolk/citrate/glucose, and skim milk/egg yolk. In fresh ejaculated semen over 90% of the spermatozoa had normal head and acrosome morphology. Quantification of goat sperm structure with Giemsa stain revealed significant (P < 0.01) damage to acrosome on freezing which varied between 38 to 43% in three diluents. Scanning electron microscopy defined and revealed greater damage during freezing with 50% sperm heads having normal acrosome structure in three diluents. The ultrastructural changes detected in frozen goat sperm was protrusion at the anterior cap, broken tail, swelling of acrosome, and loss of acrosomal contents. The leakage of five enzymes GOT, GPT, hyaluronoglucosaminidase, acid phosphatase, and alkaline phosphatase measured simultaneously revealed a positive correlation between enzyme release and acrosomal damage.

Adaptations of plasma membrane glucose transport facilitate cryoprotectant distribution in freeze-tolerant frogs

Natural freeze tolerance in several anuran species involves the accumulation of high concentrations of glucose as a cryoprotectant in body fluids and tissues. The present study identifies an important new molecular mechanism supporting freeze tolerance, an adaptive increase in the capacity for facilitated transport of cryoprotectant across plasma membranes by increasing the numbers and/or activity of plasma membrane glucose transporters. Glucose transport by membranes isolated from liver and skeletal muscle was analyzed in two species, the freeze-tolerant wood frog Rana sylvatica and the freeze-intolerant leopard frog Rana pipiens. Membranes from both liver and muscle of R. sylvatica displayed much higher rates of carrier-mediated glucose transport, measured by a rapid filtration technique, compared with corresponding rates for R. pipiens membranes. For the liver Vmax values for glucose transport by membrane vesicles were 69 +/- 18 and 8.4 +/- 2.3 nmol.mg protein-1.s-1 at 10 degrees C for R. sylvatica and R. pipiens, respectively. This difference was due primarily to a greater number of glucose transporters in R. sylvatica liver membranes; the total number of transporter sites, determined by cytochalasin B binding, was 4.7-fold higher in the freeze-tolerant species. For muscle membranes, the Vmax for glucose transport was 4.9 +/- 1 and 0.6 +/- 0.16 nmol.mg-1 x s-1 at 22 degrees C for R. sylvatica and R. pipiens, respectively. However, in muscle there were no differences in the number of membrane transporters between species.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural and enzymatic studies on the plasma membrane domains and sodium pump enzymes of absorptive epithelial cells in the avian lower intestine

The coprodaeum of the domestic hen maintained on a low-NaCl diet adapts by enhanced sodium transport. This study examines the adaptive response at the single cell and whole organ levels. Surface areas of apical (microvillous) and basolateral plasma membranes of columnar absorptive epithelial cells were estimated by use of ultrastructural stereology. The activities of succinic dehydrogenase (a mitochondrial enzyme) and ouabain-sensitive, potassium-dependent paranitrophenyl phosphatase (a sodium pump enzyme) were determined in tissue homogenates. Sodium, potassium-ATPase (pump enzyme) activity in cell membranes was localized by ultrastructural cytochemistry. Apical and basolateral membranes responded differently. In high-NaCl hens, the membrane signature of the average cell was 32 microns 2 (apical), 932 microns 2 (lateral) and 17 microns 2 (basal). Cells from low-NaCl hens had more apical membrane (49 microns 2 per cell) but essentially the same area of basolateral membrane. However, total surfaces per organ were greater for all membranes. Sodium pump enzymes were localized in basolateral membranes. Enzyme activities per unit mitochondrial volume and per unit basolateral membrane surface were higher in low-NaCl birds. These findings are discussed in the context of known mechanisms of transcellular sodium transport via apical ion channels and basolateral pumps.

Glucose transporter number, function, and subcellular distribution in rat skeletal muscle after exercise training

Endurance exercise training can result in increased rates of insulin-stimulated glucose uptake in skeletal muscle; however, this effect may be lost rapidly once training ceases. To examine a mechanism for these changes, the skeletal-muscle glucose transport system of female rats exercise-trained in wheelcages for 6 wk were studied against a group of untrained female rats. The trained rats were studied immediately following and 2 and 5 days after removal from wheelcages; both trained and untrained rats were studied 30 min after insulin (90 nmol/rat, intraperitoneal) or saline injection. The total number of skeletal-muscle plasma-membrane glucose transporters (R0), total muscle-homogenate and plasma-membrane GLUT4 protein, and rates of plasma-membrane vesicle D-facilitated glucose transport were higher in the exercise-trained rats immediately after exercise training and did not decrease significantly during the 5 days after cessation of training. On the other hand, exercise training did not alter microsomal-membrane total glucose-transporter number or GLUT4 protein, nor did training alter GLUT1 protein in total muscle homogenates nor either membrane fraction. The carrier-turnover number, an estimate of average functional activity of glucose transporters in the plasma membrane, was elevated slightly, but not significantly, in the trained muscle. In both the trained and untrained muscle, insulin administration resulted in translocation of glucose transporters from the microsomal-membrane fraction to the plasma membrane and an increase in the carrier-turnover number.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytochemical investigation of p-NPPase activity in rat cardiac muscle

The cytochemical demonstration of the atrial cardiac myocyte pumping activity has been made by detecting p-nitrophenylphosphatase (NPPase), which is used by investigating of Na(+)-K(+)-ATPase and H(+)-K(+)-ATPase activities. The fine ultrastructural localization of these enzymes was studied using cytochemical methods with cerium as a capturing agent. Na(+)-K(+)-ATPase was localized on the atrial muscle cell plasma membrane, T-tubule membrane, endothelial cell nuclear membrane, and cardiac myocyte nuclear membrane. H(+)-K(+)-ATPase was localized on the atrial muscle cells plasma membrane, T-tubule membrane, and sarcoplasmatic reticulum. The present findings indicate that the transporting metabolic activity of the heart as an endocrine organ is realized by the interaction between p-NPPases.

Prenatal diagnosis by isoenzymic differentiation of Treacher Collins' syndrome induced by retinoids in rats

A series of branchial arch malformations was induced in 618 embryos from 72 pregnant rats by a single intraperitoneal injection of 10 mg/kg etretinate at 8.5 days of gestation. The litters developed several malformations, including microtia, low set and dorsally placed outer ears, defective middle ear ossicles, short cochleas, defectively differentiated Meckel's cartilages, micrognathia, rudimentary malar bones, lateral facial clefts, fistulas and skin tags, all of which were similar to Treacher Collins' syndrome in man. The defects were accompanied by a pathological differentiation pattern of various isoenzymes in maxillary and mandibular processes. These isoenzymes could be detected in amniotic fluid from the 9th to the 20th days of pregnancy and showed a pathological differentiation pattern here as well. We conclude that a teratogenically induced syndrome affecting the first and second branchial arches is accompanied by a pathological differentiation pattern that can be traced by determinations of isoenzymes in the branchial arches as well as in amniotic fluid.

Activity of some lysosomal enzymes and postnatal ontogenetic development of epileptic reactivity in rabbit brain

The beta-glycerophosphatase (GP), p-nitrophenyl phosphatase (PNFP) and beta-glucuronidase (BG) activities in four neocortical rabbit areas have been determined in six successive electrocorticographic stages of postnatal ontogenetic development of epileptic reactivity. The lysosomal enzyme activity decreases gradually from rabbits aged 1 day to adult ones and is similar within the four neocortical areas. The activity of the three lysosomal enzymes is not parallel. Statistically significant decreases in beta-glycerophosphatase activity are present in rabbits at the age of 30 days versus adult age in all the areas investigated while beta-glucuronidase is higher at the same developmental stage only in beta retrosplenial (III) and motor (II) areas. Correlation of the electrophysiological and biochemical data cannot provide explanation for the particular phenomena of the epileptogenic reactivity in rabbit cerebral neocortex.

Ultrastructural localization of ouabain-sensitive, K-dependent p-nitrophenyl phosphatase activity in monkey eccrine sweat gland

We studied the electron microscopic localization of ouabain-sensitive, potassium-dependent p-nitrophenyl phosphatase (K-pNPPase) activity of the Na K-ATPase complex in Rhesus monkey eccrine sweat gland by use of the one-step lead citrate method of Mayahara et al. (Histochemistry 1980; 67:125). Reaction product was observed predominantly in the cytoplasmic side of the basolateral membranes of clear (secretory) cells, especially in the interdigitating membrane folds in the basal labryinth, and were completely abolished by 10 mM ouabain or by removal of K+. Little or no enzyme activity was noted in membrane processes in the intercellular canaliculi and in the secretory coil lumen. Basolateral membranes of the dark cells also showed moderate enzyme activity. The myoepithelial cell membrane was devoid of reaction product, except in a few membrane processes arising from the inner aspect of myoepithelial cells. In the coiled duct, K-pNPPase activity was present predominantly in the entire cell membrane of the peripheral ductal cells. The predominantly basolateral distribution of Na-K-ATPase in the eccrine sweat secretory cells is consistent with the concept that a Na-K-Cl co-transport model may be involved in the mechanism of eccrine sweat secretion.

Inactivation of detergent-solubilized sarcoplasmic reticulum ATPase

Inactivation of sarcoplasmic ATPase in the solubilized state was studied in the absence and presence of Ca2+, Mg2+ and glycerol. The effects of the detergents octa(ethyleneglycol) mono-n-dodecyl ether (C12E8), 1-O-tetradecylpropanediol-(1,3)-3-phosphorylcholine and myristoylglycerophosphocholine were compared. All three detergents caused a rapid decline of the dinitrophenyl phosphatase activity of the unprotected enzyme. The stabilizing effect of Ca2+ ions was kinetically analysed. It was found that the stability of the solubilized enzyme depends on the Ca2+ concentration in a manner which is best explained by assuming rapid inactivation of Ca2+-free enzyme accompanied by slow inactivation of a calcium-enzyme complex (E1Ca). The apparent affinity constants obtained are in the order of 10(6)M-1, suggesting that high-affinity Ca2+ binding must be involved. No indications of a contribution were found, either of low-affinity Ca2+-binding sites of the conformational state E2 or of the high-affinity calcium complex E1Ca2. If Ca2+ was replaced by Mg2+, which exerts a weaker protection, the apparent affinity constants for Mg2+ are in the range of 1 mM-1. The stoichiometry of the effect of Mg2+ depends on the detergent.

Subcellular fractionation of the longitudinal smooth muscle/myenteric plexus of dog ileum: dissociation of the distribution of two plasma membrane marker enzymes

The distribution of plasma membrane markers, the sodium pump [evaluated as ouabain-sensitive, potassium-stimulated p-nitrophenyl phosphatase (K+-pNPPase)], [3H]saxitoxin binding, and 5'-AMPase, was studied in the subcellular fractions prepared from the homogenates of the longitudinal smooth muscle/myenteric plexus of dog ileum. The K+-pNPPase activity and [3H]-saxitoxin binding were found to be predominantly associated with the synaptosomal fraction as indicated by the high level of these activities in the crude synaptosomal fraction and by the copurification of K+-pNPPase and [3H]saxitoxin binding, but not 5'-AMPase, with several synaptosomal markers during the fractionation of the crude synaptosomal fraction on density gradients. In contrast to the K+-pNPPase activity and [3H]saxitoxin binding, the 5'-AMPase activity was found to be concentrated in the microsomal pellet. Further fractionation of microsomes on density gradient resulted in copurification of 5'-AMPase but not K+-pNPPase or [3H]saxitoxin binding, with other smooth muscle plasma membrane-bound enzymes, such as high-affinity Ca2+-ATPase, Mg2+-ATPase, and Ca2+-ATPase. It was concluded that in the longitudinal smooth muscle/myenteric plexus, the sodium pump activity is present in higher density in the neuronal plasma membranes whereas 5'-AMPase activity is concentrated in the smooth muscle plasma membranes.

Ultracytochemical distribution of ouabain-sensitive, K+-dependent, p-nitrophenylphosphatase in the synaptic layers of goldfish retina

Ouabain-sensitive, K+-dependent p-nitrophenylphosphatase (K+-pNPPase) activity, which represents the second dephosphorylation step of Na+,K+-ATPase, was localized histochemically at the light and electron microscopical levels in the goldfish retina. K+-pNPPase staining was most intense in the outer and inner plexiform layers and less intense over the photoreceptor inner segments. K+-pNPPase staining was observed on the membranes of horizontal cell dendrites and presynaptic membrane of all cone pedicles but only rarely over rod spherules. Bipolar cell dendrites in the outer plexiform layer were not stained for K+-pNPPase. In the inner plexiform layer (IPL), K+-pNPPase staining was observed at 90% of the bipolar cell ribbon synapses but only at 40% of amacrine cell synapses. The proportion of K+-pNPPase staining at amacrine cell synapses increased from 26 to 49% as one progressed from the outer to inner layers of the IPL, while staining at bipolar cell synapses showed no such trend. Only 16% of the amacrine synapses onto mixed, rod-cone (mb) bipolar cell synaptic terminals were positive for K+-pNPPase. We suggest that the differential distribution of K+-pNPPase staining at retinal synapses can be explained, in part, by the ionic conductances gated at the postsynaptic sites. In addition, the presence of K+-pNPPase on lateral horizontal cell dendrites in cone pedicles is consistent with the hypothesis that the sodium pump is involved in the release of GABA at feedback synapses from horizontal cells to cone photoreceptors.

Membrane-bound phosphotyrosyl-protein phosphatase activity in human erythrocytes. Dephosphorylation of membrane band 3 protein

Human erythrocyte membranes exhibit, in addition to "acid" p-nitrophenyl-phosphatase activity, remarkable phosphotyrosyl-protein phosphatase activity, assayed on synthetic polymer poly (Glu-Tyr) 4:1, previously phosphorylated on Tyr residues by rat spleen tyrosine-protein kinase. The results reported here indicate that such a 32P-Tyr-phosphatase activity, rather than p-nitrophenyl-phosphatase, is involved in the dephosphorylation of transmembrane band 3 protein on 32P-tyrosine residues.

Ultracytochemistry of ouabain-sensitive K+-dependent p-nitrophenyl phosphatase in rat incisor enamel organ

Sprague-Dawley strain rats of 4-5 weeks old were perfusion-fixed with either a mixture containing 0.1 or 0.25% glutaraldehyde and 2% formaldehyde, or a 2% formaldehyde in 0.1 M sodium cacodylate buffer for 10 minutes. Non-decalcified 30-50-micron sections of the enamel organ taken from lower incisors were then processed for ultracytochemical demonstration of ouabain-sensitive, K+-dependent, p-nitrophenyl phosphatase, by use of the one-step lead method, representing the second dephosphorylative step of Na+-K+-ATPase. Throughout the secretory, transition, and maturation stages of amelogenesis, the enzymatic activity was demonstrated along the cytoplasmic side of the plasma membranes of the stratum intermedium and the papillary layer cells, especially along their numerous microvilli. The plasma membranes forming gap junctions and desmosomes were free of reaction or showed slight focal precipitates of reaction products. The stellate reticulum and the outer enamel epithelium exhibited either a weak reaction or were reaction negative. Secretory ameloblasts showed a weak trace-like reaction along the basal and lateral cell surfaces; however, the latter surfaces were sometimes completely free of reaction. Tomes' processes were usually reaction negative. Ameloblasts in the transition and maturation stages were devoid of enzymatic activity, except for a slight reaction along the plasma membranes of the basal cell surfaces of transition ameloblasts facing the papillary layer. The enzymatic activity described above was completely dependent on the presence of potassium and substrate in the incubation media and was almost completely inhibited by an addition of 10 mM ouabain to the incubation media.

Histochemical distribution of potassium-dependent p-nitrophenylphosphatase in the calf intestine

Potassium-dependent p-nitrophenylphosphatase was demonstrated, using the lead citrate method of Mayahara et al. (1980), in frozen sections of calf intestine fixed in formalin-calcium. The calcium chloride included in the fixative was shown to improve the localization of the reaction markedly. The phosphatase activity observed in the basolateral cell borders of the surface epithelium in the small intestine and colon was reduced by 10 mM ouabain and by substitution of sodium ions for potassium ions, confirming that the reaction was representative for the second step in the Na+/K+-ATPase complex. The intensity of the basolateral enzyme reaction was in the order: colon greater than duodenum, proximal jejunum greater than ileum greater than middle and distal jejunum. The crypts reacted weakly. A reaction in the brush border of the proximal jejunum and duodenum and a granular reaction in the supranuclear cytoplasm of the epithelial cells was not influenced by ouabain. The staining pattern for the potassium-dependent phosphatase differed from that of alkaline phosphatase and Mg2+-dependent ATPase, which gave a reaction that was restricted to the brush border.

A rapid, flexible method for biochemical assays using a microtiter plate reader and a microcomputer. Application for assays of protein, Na,K-ATPase and K-p-nitrophenylphosphatase

A computerized system which greatly accelerates and eases the collection, storage, and analysis of data has been applied to several standard biochemical assays. The system uses a commercially available microtiter plate reader connected to an Apple IIe microcomputer via a standard serial port. Data are transmitted automatically from the reader to the microcomputer, where they can be viewed, printed, further analyzed immediately, or stored on a diskette for later retrieval and processing. Some or all of the data may be entered manually. The program calculates a linear least squares best fit to a standard curve after correcting all data for blanks, then determines the quantities of substrate or product contained in each well of a microtiter plate. Data from two plates may be combined, enabling calculation of enzyme specific activities. This system can be adapted to any assay whose final step can be performed by a microtiter plate reader. Its use is described for determination of protein concentration, Na,K-ATPase activity, and K-stimulated p-nitrophenylphosphatase activity.

Tryptic modification of red-cell sodium pump behaviour

Inside-out membrane vesicles derived from human red cells were used to probe the effects of controlled tryptic digestion on the sodium pump as it exists in situ. Digestion of the enzyme in its E1 conformation resulted in several alterations which are generally similar to those reported for the purified kidney enzyme, namely (i) greater loss in overall hydrolytic activity compared to level of phosphoenzyme intermediate and (ii) cleavage of the alpha-subunit by trypsin as well as chymotrypsin at the cytoplasmic surface to yield a fragment of approx. 78 kDa. Tryptic digestion effected similar rates of inactivation of pump-mediated Na+-K+(Rb+) exchange, (ATP- plus ADP)-dependent Na+-Na+ exchange and, in the absence extracellular alkali cation, 'uncoupled' Na+ flux (Na+/0 flux). Alteration in the Na+:Rb+(K+) stoichiometry following trypsin cleavage could not be detected. The conformational transitions of phosphoenzyme and dephosphoenzyme are affected similarly by trypsin, as evidenced by similar inactivation rates of reactions through the 'forward' sequence involving the E1P to E2P transition as well as through the 'reserve' sequence involving the E1 to E2 transition.

An ultracytochemical investigation of ouabain-sensitive p-nitrophenylphosphatase in chick osteoclasts

Cytochemical methods for the demonstration of p-nitrophenylphosphatase (p-NPPase) at the electron-microscopic level were applied to avian osteoclasts to elucidate some of the functional differences among ruffled border, other membrane systems, and cellular organelles. The localization of p-NPPase activity occurred in mitochondria, in lysosomes, and on the cytoplasmic side of the ruffled-border membrane. Enzymatic activity in the ruffled-border membrane was sensitive to ouabain and was partially dependent on potassium. Thus, Na+,K+-ATPase, the proposed sodium pump, appears to be present in the osteoclast ruffled border. The activity in ruffled border occurred only when osteoclasts were attached to bone. Following calcitonin treatment many osteoclasts were detached from the bone surface and lacked reaction product along the ruffled-border membrane. The lysosomal p-NPPase activity was not sensitive to ouabain and was distinct from that of other lysosomal phosphatases. The p-NPPase activity in mitochondria was not inhibited by ouabain but was sensitive to duramycin. The mitochondrial p-NPPase may, therefore, represent the mitochondrial proton pump.

Histochemical localization of phosphatases in the pig placenta: II. Potassium-dependent and potassium-independent p-nitrophenyl phosphatases at high pH; relation to sodium-potassium-dependent adenosine triphosphatase

Histochemical localization by Mg2+ capture methods of K+-dependent, ouabain-sensitive phosphatase activity in the pig placenta shows that strong Na+,K+-dependent adenosine triphosphatase (Na+,K+-ATPase) activity is restricted to the basal zone of the columnar epithelium covering the areolar chorionic villi. It is proposed that active Na+ absorption at this epithelium may be the source of the ouabain-sensitive, fetal-side-positive potential difference which can be measured across the placental membrane in vitro. The one-step procedure for Na+,K+-ATPase localization is unsatisfactory in this organ as any specific ATPase reaction is swamped by activity probably attributable to uteroferrin and other non-specific phosphatases.

Enzyme cytochemical and immunocytochemical studies of flask cells in the amphibian epidermis

The localization of oxidoreductases and transport enzymes in flask cells of the amphibian epidermis was studied at the light-microscopic level. In these cells, the deposition of cytochemical reaction products was very similar to that found in fish epidermal ionocytes, thus demonstrating histochemical similarities between these two types of cells. The present histochemical results revealed high levels of activity of alkaline phosphatase (ALPase), potassium-dependent nitrophenylphosphatase (K+-p-NPPase) and carbonic-anhydrase isozymes (CA-I and CA-II) in the apical region of the flask cells, indicating that enzyme zonation may be the main site of the ion pumping.

Cytosolic protein phosphotyrosine phosphatases from rabbit kidney. Purification of two distinct enzymes that bind to Zn2+-iminodiacetate agarose

Cytosolic protein phosphotyrosine (PPT) phosphatase was measured using a new substrate, Tyr(32P)-labeled bovine serum albumin. Kidney was found as a particularly rich tissue source of PPT-phosphatase activity, containing twice as much as liver and over 10-fold more than brain, heart, lung, or skeletal muscle. An affinity column of Zn2+-iminodiacetate agarose adsorbed up to 60% of the PPT-phosphatase present in kidney extracts. Subsequent chromatography on DEAE-Sepharose separated the phosphatase into two peaks, labeled I and II, that had Mr = 34,000 and 37,000, respectively, upon gel filtration with Sephadex G-75 Superfine. Overall purification of 850- and 1100-fold was achieved with a net 4% yield. Both phosphatases hydrolyzed p-nitrophenylphosphate as well as the protein substrate in the presence of EDTA. Peak I phosphatase activity displayed a neutral pH optimum, had an absolute requirement for sulfhydryl compounds, and was sensitive to trypsin, whereas Peak II activity had an acidic pH optimum and was active without mercaptans. The two proteins also gave different fragmentation patterns by gel electrophoresis after digestion with S. aureus V8 protease. The results show that multiple forms of PPT phosphatase specifically interact with Zn2+ and provide a basis for further structural and functional comparisons among different members of the phosphoprotein phosphatase family.

Localization of ATPases in retinal receptor cells

Ouabain-sensitive, K-dependent p-nitrophenylphosphatase (K- NPPase ) activity of the Na-K-ATPase complex and the Ca-ATPase activity were studied ultracytochemically in the inner and outer segments of guinea pig photoreceptor cells by means of newly developed methods. The K- NPPase activity was demonstrated on the plasmalemma of the inner segments, whereas the Ca-ATPase activity was restricted to the matrix side of the inner membrane of the mitochondria which were accumulated in the inner segments. In contrast to the enzyme activities in the inner segments no such activity could be detected on the plasma and disk membranes of the outer segments. The functional meaning of the enzyme activities is discussed.

Preparation and properties of highly enriched cardiac sarcolemma from isolated adult myocytes

Isolated myocytes were prepared from adult canine hearts using a combined technique of myocardial perfusion followed by incubation with collagenase. More than 60% of the cells routinely excluded trypan blue dye. Disruption of the myocytes was accomplished using high pressure nitrogen cavitation. After differential and sucrose gradient centrifugation, the peak sarcolemmal fraction averaged 100-fold enrichment in ouabain-inhibited K+-stimulated p-nitrophenyl phosphatase and 82-fold in ouabain-inhibited (Na+,K+)-ATPase. These sarcolemmal membranes are enriched in phospholipid phosphorus (1.98 mumol/mg of protein) and more than 4-fold in sphingomyelin and cholesterol. Polyacrylamide gels revealed three major protein peaks at 50,000, 91,000, and 140,000 apparent molecular weights. This work demonstrates the feasibility of preparing highly pure cardiac sarcolemma from isolated adult myocytes. The problem of cellular cross-contamination due to heterogeneity of cell types in whole myocardial tissue has been circumvented. The level of enrichment exceeds all reported preparations of cardiac sarcolemma from whole myocardium and cultured myocytes. This preparation should prove to be useful as an in vitro model for studies of physiological, pharmacological, and pathological perturbations of sarcolemmal structure and function.

Influence of inorganic phosphate on the activity determination of isoenzymes of alkaline phosphatase in various buffer systems

The inhibitory effect of inorganic phosphate on the activity determination of isoenzymes of alkaline phosphatase (AP) in diethanolamine (DEA), glycine and 2-amino-2-methyl-1,3-propandiol (AMPD) buffer was studied. This effect depends on the buffer used and isoenzyme investigated. Especially the placental isoenzyme is inhibited; the inhibitory effect in DEA buffer is stronger than in the other buffers used. The requirement of purity for 4-nitrophenylphosphate with respect to its content of inorganic phosphate and conclusions for using control sera enriched with AP isoenzymes are discussed.

Isolation and characterization of cardiac sarcolemma

A procedure was developed for the isolation of cardiac sarcolemmal vesicles. These vesicles are enriched about ten-fold (with respect to the tissue homogenate) in K+-stimulated p-nitrophenylphosphatase, (Na+ + K+)-ATPase, 5'-nucleotidase activities and sialic acid content, all of which are believed to be components of the sarcolemma. The sarcolemma of tissue culture cardiac cells were radioiodinated and the distribution of this radioiodine paralleled the distribution of the other membrane markers above. There was very little contamination of the sarcolemmal fraction by sarcoplasmic reticulum (as judged by Ca2+-ATPase and glucose-6-phosphatase activities) or inner mitochondrial membranes (as judged by succinate dehydrogenase activity). There may, however, be some contamination by outer mitochondrial membranes (as judged by monoamine oxidase and rotenone-insensitive NADH cytochrome c reductase activities) which have rarely been monitored in cardiac sarcolemmal preparations. The purity of this preparation is good when compared with other cardiac sarcolemmal preparations. This preparation should be very useful in studying the roles of the cardiac sarcolemma (e.g. in excitation contraction coupling and Ca2+ binding).

Cell fractions and enzymatic activities of Ureaplasma urealyticum

The localization of some enzymic activities in cell fractions of Ureaplasma urealyticum was studied. A quantitative evaluation of the effectiveness of several cell lysis procedures was obtained by using labeled membranes and sucrose density gradient centrifugation. Ultrasonic treatment was found to be the most effective procedure for lysing the cells, whereas digitonin and osmotic shock caused the lysis of only 70 and 50% of the cells, respectively. The localization of selected enzymes in Ureaplasma cells resembled that found in other Mycoplasma species. Adenosine triphosphatase, ribonuclease, deoxyribonuclease, and p-nitrophenylphosphatase activities were located exclusively in the membrane fraction, whereas urease and L-histidine ammonia-lyase were located in the cytoplasm.

4-Nitrophenol in 4-nitrophenyl phosphate, a substrate for alkaline phosphatase, as measured by paired-ion high-performance liquid chromatography

We used paired-ion high-performance liquid chromatography to determine the 4-nitrophenol content of 4-nitrophenyl phosphate, a substrate for alkaline phosphatase analysis. This was done on a reversed-phase column with a mobile phase of methanol/water, 45/55 by vol, containing 3 ml of tetrabutylammonium phosphate reagent per 200 ml of solvent. At a flow rate of 1 ml/min, 4-nitrophenol was eluted at 9 min and monitored at 404 nm; 4-nitrophenyl phosphate was eluted at 5 min and could be monitored at 311 nm. Samples of 4-nitrophenyl phosphate obtained from several sources contained 0.3 to 7.8 mole of 4-nitrophenol per mole of 4-nitrophenyl phosphate.

Effect of phosgene on rat lungs after single high-level exposure

Rats were exposed under static conditions to phosgene at concentrations within the LCt50 range and above. Lungs were removed at various postexposure intervals. Degrees of pulmonary edema were estimated by increases in percentage of water in the lungs of exposed groups as opposed to control animals. Lungs were fractionated into four major subcellular organelle fractions: nuclear debris, mitochondrial-lysosomal, microsomal, and soluble (cytoplasmic). Activities of p-nitrophenyl phosphatase, cytochrome C oxidase, ATP'ase, and LDH within these fractions were decreased after phosgene exposure. There was a concomitant increase in serum LDH levels. One possible mechanism that may play a role in phosgene damage can be associated with either inhibition or loss of enzyme activities from the lung.

Transport adenosine triphosphatase activity in the rat cornea

The sodium-potassium activated adenosine triphosphatase (NaKATPase) activity of the rat cornea was investigated histochemically using a Pb2+-precipitation technique in which adenosine triphosphate (ATP) is used as substrate and two methods for potassium-dependent para-nitrophenyl-phosphatase (K-NPPase) activity. With all the three techniques used it was demonstrated that the sodium-potassium-activated adenosine triphosphatase (NaK-ATPase) activity is localized in the cell membranes of the endothelium whereas a much weaker activity was observed in the epithelium. When the Pb2+-technique was used, the epithelial cell membranes showed a weaker reaction in the presence of ouabain. This activity was only Mg2+-dependent and was presumably due to an Mg2+-dependent ATPase. The validity of the histochemical techniques for NaK-ATPase activity is discussed. The results emphasize the importance of the endothelium as the main site of Na+ transport in the cornea. Small amounts of the enzyme are also present in the epithelium, which seems to be rich in Mg2+-ATPase. Provided that careful controls are performed, all the methods give consistent results in the cornea.

Localization of ouabain-sensitive, potassium-dependent nitrophenyl phosphatase in the rectal gland of the spiny dogfish, Squalus acanthias

Tissue from the digitiform rectal gland of the spiny dogfish, Squalus acanthias, was fixed briefly by formaldehyde perfusion and studied for the specificity and localization of p-nitrophenyl phosphatase (NPP'ase) activity. The enzymatic activity was K+-dependent (56%) and ouabain-sensitive (67%-inhibition). The electron-dense reaction product (SrPO4) of the cytochemical reaction (Ernst, 1972b) was localized along the inner surfaces of the basolateral membranes of the secretory cells. It was absent from mitochondria nuclei, vesicles, and other organelles. The luminal surface of the secretory cells was slightly reactive. On the basis of (1) this pattern of localization for the sodium transport system, (2) the presence of extensive intercellular labyrinthine channels (Bulger, 1963) that would facilitate "standing gradients" (Diamond and Bossert, 1968), and (3) the specific distribution of the energy-providing mitochondria, we conclude that the concentration and electrochemical gradients recorded from the secreting gland (Hayslett et al., 1974) are maintained across the domains of the basolateral surfaces of the secretory cells.

Localization of K+-stimulated p-NPPase in the lachrymal 'salt' gland of Malaclemys, using cytochemical and autoradiographical techniques

Using two independent techniques, histochemistry and autoradiography, an enzyme (E.C. 3.6.1.3.) has been localized on basolateral cell membranes of salt secreting cells in the lachrymal gland of Malaclemys. This enzyme is ouabain sensitive. In addition an L-tetramisole sensitive alkaline phosphatase is found in the same sites, and an ethacrynic acid sensitive K+-stimulated p-NPPase is found on the apical membrane. The significance of these results with regard to the location of the pump responsible for net transepithelial sodium transport is discussed.

The demonstration of acid phosphatase in cultured 3T3 mouse cells

Acid phosphatase has been demonstrated ultrastructurally in 3T3 and SV40-3T3 mouse cells using sodium beta-glycerophosphate and p-nitrophenyl phosphate as substrate. The former substrate only demonstrates the enzyme in lysosomes and elements of the Golgi apparatus while the latter demonstrates it in the cisternae of the endoplasmic reticulum and in the cell surface as well as at lysosomal sites. The significance of surface acid phosphatase activity is discussed in terms of sublethal autolysis.

A microplate method of enzyme-linked immunosorbent assay and its application to malaria

A microplate method of enzyme-linked immunosorbent assay is described. This method, which may be of value in the measurement of antibodies in various infectious diseases, is simple, cheap, and easy to carry out on a large scale. For field use, results can be assessed subjectively. The potential of the test is illustrated by a small seroepidemiological study of malaria.