Structure of human CALHM1 reveals key locations for channel regulation and blockade by ruthenium red

Calcium homeostasis modulator 1 (CALHM1) is a voltage-dependent channel involved in neuromodulation and gustatory signaling. Despite recent progress in the structural biology of CALHM1, insights into functional regulation, pore architecture, and channel blockade remain limited. Here we present the cryo-EM structure of human CALHM1, revealing an octameric assembly pattern similar to the non-mammalian CALHM1s and the lipid-binding pocket conserved across species. We demonstrate by MD simulations that this pocket preferentially binds a phospholipid over cholesterol to stabilize its structure and regulate the channel activities. Finally, we show that residues in the amino-terminal helix form the channel pore that ruthenium red binds and blocks.

Activation of Piezo1 Increases Na,K-ATPase-Mediated Ion Transport in Mouse Lens

Lens ion homeostasis depends on Na,K-ATPase and NKCC1. TRPV4 and TRPV1 channels, which are mechanosensitive, play important roles in mechanisms that regulate the activity of these transporters. Here, we examined another mechanosensitive channel, piezo1, which is also expressed in the lens. The purpose of the study was to examine piezo1 function. Recognizing that activation of TRPV4 and TRPV1 causes changes in lens ion transport mechanisms, we carried out studies to determine whether piezo1 activation changes either Na,K-ATPase-mediated or NKCC1-mediated ion transport. We also examined channel function of piezo1 by measuring calcium entry. Rb uptake was measured as an index of inwardly directed potassium transport by intact mouse lenses. Intracellular calcium concentration was measured in Fura-2 loaded cells by a ratiometric imaging technique. Piezo1 immunolocalization was most evident in the lens epithelium. Potassium (Rb) uptake was increased in intact lenses as well as in cultured lens epithelium exposed to Yoda1, a piezo1 agonist. The majority of Rb uptake is Na,K-ATPase-dependent, although there also is a significant NKCC-dependent component. In the presence of ouabain, an Na,K-ATPase inhibitor, Yoda1 did not increase Rb uptake. In contrast, Yoda1 increased Rb uptake to a similar degree in the presence or absence of 1 µM bumetanide, an NKCC inhibitor. The Rb uptake response to Yoda1 was inhibited by the selective piezo1 antagonist GsMTx4, and also by the nonselective antagonists ruthenium red and gadolinium. In parallel studies, Yoda1 was observed to increase cytoplasmic calcium concentration in cells loaded with Fura-2. The calcium response to Yoda1 was abolished by gadolinium or ruthenium red. The calcium and Rb uptake responses to Yoda1 were absent in calcium-free bathing solution, consistent with calcium entry when piezo1 is activated. Taken together, these findings point to stimulation of Na,K-ATPase, but not NKCC, when piezo1 is activated. Na,K-ATPase is the principal mechanism responsible for ion and water homeostasis in the lens. The functional role of lens piezo1 is a topic for further study.

Introduction of correlative light and airSEM™ microscopy imaging for tissue research under ambient conditions

A complete fingerprint of a tissue sample requires a detailed description of its cellular and extracellular components while minimizing artifacts. We introduce the application of a novel scanning electron microscope (airSEM™) in conjunction with light microscopy for functional analysis of tissue preparations at nanometric resolution (<10 nm) and under ambient conditions. Our metal-staining protocols enable easy and detailed visualization of tissues and their extracellular scaffolds. A multimodality imaging setup, featuring airSEM™ and a light microscope on the same platform, provides a convenient and easy-to-use system for obtaining structural and functional correlative data. The airSEM™ imaging station complements other existing imaging solutions and shows great potential for studies of complex biological systems.

Mast cells respond to urticating extract from lepidoptera larva Morpheis ehrenbergii in the rat

Mast cells and histamine participate in toxic effects of hairs from some caterpillars. This study reports that a crude extract of Morpheis ehrenbergii caterpillar hairs induces in vitro mast cells activation, triggers the release of histamine and causes a rapid urticarial reaction in the rat skin. Heating of the extract abolishes the inflammatory reaction. These results suggest that the use of antihistamines may improve the adverse skin reactions caused by the Mexican caterpillar M. ehrenbergii.

The glycocalyx of human, bovine and murine microvascular endothelial cells cultured in vitro

This study investigated the morphology and thickness of the glycocalyx linings of microvascular endothelial cells (MVEC). Three distinct cell types were used: the human dermal cells (HDMVEC), the murine cardiac cells (MCMVEC) and the bovine luteal cells (BLMVEC). Cells were cultivated for 48 h. Glycocalyx was stained with ruthenium red and examined under a transmission electron microscope. The glycocalyx of HDMVEC was thin and constant (10-22 nm). No glycocalyx was detected within intracellular vesicles. Two cell populations of MCMVEC were recorded. The minor MCMVEC population was well differentiated and covered with heterogenous glycocalyx (2-200 nm). Conglomerates formed above the baseline along the cell extensions. The major MCMVEC population was undifferentiated and coated by a smooth and thin (12-25 nm) layer of glycocalyx. Intracellular vesicles were also coated with glycocalyx. In the BLMVEC population, 10% had 3-170 nm of discontinuous glycocalyx. Rough conglomerates were observed along cell sprouts. Their intracellular vesicles were coated with glycocalyx. The study found vast differences in the morphology and thickness of endothelial glycocalyx among different MVEC under in vitro cultivation. The only record of active endocytosis was in BLMVEC and MCMVEC. No evidence of active endocytosis was found in HDMVEC.

Caffeine-activated large-conductance plasma membrane cation channels in cardiac myocytes: characteristics and significance

Caffeine-activated, large-conductance, nonselective cation channels (LCCs) have been found in the plasma membrane of isolated cardiac myocytes in several species. However, little is known about the effects of opening these channels. To examine such effects and to further understand the caffeine-activation mechanism, we carried out studies using whole-cell patch-clamp techniques with freshly isolated cardiac myocytes from rats and mice. Unlike previous studies, thapsigargin was used so that both the effect of opening LCCs and the action of caffeine were independent of Ca2+ release from intracellular stores. These Ca2+-permeable LCCs were found in a majority of the cells from atria and ventricles, with a conductance of ∼370 pS in rat atria. Caffeine and all its direct metabolic products (theophylline, theobromine, and paraxanthine) activated the channel, while isocaffeine did not. Although they share some similarities with ryanodine receptors (RyRs, the openings of which give rise to Ca2+ sparks), LCCs also showed some different characteristics. With simultaneous Ca2+ imaging and current recording, the localized fluorescence increase due to Ca2+ entry through a single opening of an LCC (SCCaFT) was detected. When membrane potential, instead of current, was recorded, SCCaFT-like fluorescence transients (indicating single LCC openings) were found to accompany membrane depolarizations. To our knowledge, this is the first report directly linking membrane potential changes to a single opening of an ion channel. Moreover, these events in cardiac cells suggest a possible additional mechanism by which caffeine and theophylline contribute to the generation of cardiac arrhythmias.

Anionic sites on Toxoplasma gondii tissue cyst wall: Expression, uptake and characterization

Toxoplasmosis, caused by Toxoplasma gondii, is an important parasitic disease worldwide, which causes widespread human and animal diseases. The need for new therapeutic agents along with the biology of these parasites has fueled a keen interest in the understanding of the nutrients acquisition by these parasites. Studies on the characterization of the T. gondii cyst wall as well as the contribution of the host cell to this formation have been little explored. The aim of this paper was to investigate the electric surface charge of the T. gondii tissue cysts by ultrastructural cytochemistry, through polycationic markers, employing ruthenium red (RR) and cationized ferritin (CF). Glycosaminoglycans revealed by RR were localized on the cyst wall as a homogeneous granular layer electrondense, all over its surface. The incubation of living tissue cysts with CF for 20 min at 4 degrees C followed by the increase of temperature to 37 degrees C indicated that T. gondii cyst wall is negatively charged and that occurs an incorporation of anionic sites by the cyst wall, through vesicles and tubules, and their posterior location in the cyst matrix. So, as to identify which group of molecules produces negative charge in the cyst wall, we used enzymes for cleavage on different types of molecules, demonstrating that the negative charge in the cyst wall is mainly produced by phospholipids. Our results, described in this work show, for the first time, the negativities of the cyst wall, the incorporation and the traffic of intracellular surface molecules by T. gondii cyst wall. Our model of study can give an important contribution to the knowledge of the biology and the processes involved in nutrients acquisition by bradyzoites living inside the cysts and, and also be applied as a target for the direct action of drugs against the cyst.

Cell surface differences of Naegleria fowleri and Naegleria lovaniensis exposed with surface markers

Differences in the distribution of diverse cell surface coat markers were found between Naegleria fowleri and Naegleria lovaniensis. The presence of carbohydrate-containing components in the cell coat of the two species was detected by selective staining with ruthenium red and alcian blue. Using both markers, N. fowleri presented a thicker deposit than N. lovaniensis. The existence of exposed mannose or glucose residues was revealed by discriminatory agglutination with the plant lectin Concanavalin A. These sugar residues were also visualized at the cell surface of these parasites either by transmission electron microscopy or by fluorescein-tagged Concanavalin A. Using this lectin cap formation was induced only in N. fowleri. The anionic sites on the cell surface detected by means of cationized ferritin were more apparent in N. fowleri. Biotinylation assays confirmed that even though the two amoebae species have some analogous plasma membrane proteins, there is a clear difference in their composition.

HIV-1 buds predominantly at the plasma membrane of primary human macrophages

HIV-1 assembly and release are believed to occur at the plasma membrane in most host cells with the exception of primary macrophages, for which exclusive budding at late endosomes has been reported. Here, we applied a novel ultrastructural approach to assess HIV-1 budding in primary macrophages in an immunomarker-independent manner. Infected macrophages were fed with BSA-gold and stained with the membrane-impermeant dye ruthenium red to identify endosomes and the plasma membrane, respectively. Virus-filled vacuolar structures with a seemingly intracellular localization displayed intense staining with ruthenium red, but lacked endocytosed BSA-gold, defining them as plasma membrane. Moreover, HIV budding profiles were virtually excluded from gold-filled endosomes while frequently being detected on ruthenium red-positive membranes. The composition of cellular marker proteins incorporated into HIV-1 supported a plasma membrane-derived origin of the viral envelope. Thus, contrary to current opinion, the plasma membrane is the primary site of HIV-1 budding also in infected macrophages.

Effects of allyl isothiocyanate from horseradish on several experimental gastric lesions in rats

Allyl isothiocyanate is well known to be a principal pungent constituent of horseradish and an agonist for transient receptor potential (TRP) A1. Ally isothiocyanate markedly inhibited the formation of gastric lesions induced by ethanol (1.5 ml/rat, p.o.), 0.6 M HCl (1.5 ml/rat, p.o.), 1% ammonia (1.5 ml/rat, p.o.), and aspirin (150 mg/kg, p.o.) (ED(50)=1.6, 2.2, 1.7, ca. 6.5 mg/kg, p.o.). It also significantly inhibited the formation of gastric lesions induced by indomethacin (20 mg/kg, p.o.), though the inhibition was ca. 60% at a high dose (40 mg/kg, p.o.). Furthermore, several synthetic isothiocyanate compounds also significantly inhibited ethanol and indomethacin-induced gastric lesions. Whereas, TRPV1 agonists, capsaicin and piperine, inhibited gastric lesions induced by ethanol, 1% ammonia, and aspirin, but had less of an effect on 0.6 M HCl-induced gastric lesions. With regard to mode of action, the protective effects of ally isothiocyanate on ethanol-induced gastric lesions were attenuated by pretreatment with indomethacin, but not with N(G)-nitro-L-arginine methyl ester hydrochloride (L-NAME), or ruthenium red. Pretreatment with indomethacin reduced the protective effects of piperine, and L-NAME reduced the effects of capsaicin and omeprazole. Furthermore, ruthenium red reduced the effects of capsaicin, piperine, and omeprazole. These findings suggest that endogenous prostaglandins play an important role in the protective effect of allyl isothiocyanate in ethanol-induced gastric lesions different from capsaicin, piperine, and omeprazole.

The voltage-dependent anion channel, a major component of the tRNA import machinery in plant mitochondria

In plants, as in most eukaryotic cells, import of nuclear-encoded cytosolic tRNAs is an essential process for mitochondrial biogenesis. Despite its broad occurrence, the mechanisms governing RNA transport into mitochondria are far less understood than protein import. This article demonstrates by Northwestern and gel-shift experiments that the plant mitochondrial voltage-dependent anion channel (VDAC) protein interacts with tRNA in vitro. It shows also that this porin, known to play a key role in metabolite transport, is a major component of the channel involved in the tRNA translocation step through the plant mitochondrial outer membrane, as supported by inhibition of tRNA import into isolated mitochondria by VDAC antibodies and Ruthenium red. However VDAC is not a tRNA receptor on the outer membrane. Rather, two major components from the TOM (translocase of the outer mitochondrial membrane) complex, namely TOM20 and TOM40, are important for tRNA binding at the surface of mitochondria, suggesting that they are also involved in tRNA import. Finally, we show that proteins and tRNAs are translocated into plant mitochondria by different pathways. Together, these findings identify unexpected components of the tRNA import machinery and suggest that the plant tRNA import pathway has evolved by recruiting multifunctional proteins.

Oleanolic acid, a pentacyclic triterpene attenuates capsaicin-induced nociception in mice: possible mechanisms

The anti-inflammatory pentacyclic triterpene, oleanolic acid (OA) was examined on acute nociception induced by intraplantar injection of capsaicin in mice. OA administered orally to mice at 10, 30 and 100 mgkg(-1), significantly attenuated the paw-licking response to capsaicin (1.6 microg/paw) by 53%, 68.5% and 36.6%, respectively. Ruthenium red (3 mgkg(-1), s.c.), a non-competitive vanilloid receptor (V1, TRPV1)-antagonist also suppressed the capsaicin nociception by 38.6%. The maximal antinociception produced by 30 mgkg(-1) OA was significantly blocked in animals pre-treated with naloxone (2 mgkg(-1), i.p.), the opioid antagonist; l-arginine (600 mgkg(-1), i.p.), the substrate for nitric oxide synthase; or glibenclamide (2 mgkg(-1), i.p.), the K(ATP)-channel blocker, but was unaffected by yohimbine (2 mgkg(-1), i.p.), an alpha(2)-adrenoceptor antagonist. In open-field and rota-rod tests that detect motor deficits, mice received 30 mgkg(-1) OA did not manifest any effect per se, indicating that the observed antinociception is not a consequence of motor abnormality. These data suggest that OA inhibits capsaicin-evoked acute nociception due to mechanisms possibly involving endogenous opioids, nitric oxide, and K(ATP)-channel opening.

Assessing Nezara viridula (Hemiptera: Pentatomidae) feeding damage in macadamia nuts by using a biological stain

Damage caused by southern green stink bug, Nezara viridula (L.), to macadamia nuts, Macadamia integrifolia Maiden & Betche, is normally determined after nuts are harvested and processed, which may be many months after damage occurred in the field. We developed a method using ruthenium red dye to stain stink bug feeding probes and indirectly assess feeding activity in macadamia nuts. By using the staining method, feeding probes were easily detected on the husk, shell, and kernel. Husk probing was highly correlated (0.80-0.90) with feeding and damage to the kernel. Failure rate to detect kernel damage from stained husk probes was generally <6%. The staining method was equally effective for immature and mature nuts; therefore, N. viridula feeding activity can be monitored throughout the season to evaluate pest management tactics and forecast outbreak populations.

TRPV1 regulators mediate gentamicin penetration of cultured kidney cells

Transient receptor potential (TRP) receptors are, typically, calcium-permeant cation channels that transduce environmental stimuli. Both kidney epithelial and inner ear sensory cells express TRPV1, are mechanosensors and accumulate the aminoglycoside antibiotic gentamicin. Recently, we showed that Texas Red-conjugated gentamicin (GTTR) enters kidney cells via an endosome-independent pathway. Here, we used GTTR to investigate this non-endocytotic mechanism of gentamicin uptake. In serum-free buffers, GTTR penetrated MDCK cells within 30 s and uptake was modulated by extracellular, multivalent cations (Ca2+, La3+, Gd3+) or protons. We verified the La3+ modulation of GTTR uptake using immunocytochemical detection of unconjugated gentamicin. Membrane depolarization, induced by high extracellular K+ or valinomycin, also reduced GTTR uptake, suggesting electrophoretic permeation through ion channels. GTTR uptake was enhanced by the TRPV1 agonists, resiniferatoxin and anandamide, in Ca2+-free media. Competitive antagonists of the TRPV1 cation current, iodo-resiniferatoxin and SB366791, also enhanced GTTR uptake independently of Ca2+, reinforcing these antagonists' potential as latent agonists in specific situations. Ruthenium Red blocked GTTR uptake in the presence or absence of these TRPV1-agonists and antagonists. In addition, GTTR uptake was blocked by RTX in the presence of more physiological levels (2 mM) of Ca2+. Thus gentamicin enters cells via cation channels, and gentamicin uptake can be modulated by regulators of the TRPV1 channel.

Role of mitochondrial Na+ concentration, measured by CoroNa red, in the protection of metabolically inhibited MDCK cells

In ischemic or hypoxic tissues, elevated cytosolic calcium levels can induce lethal processes. Mitochondria, besides the endoplasmic reticulum, play a key role in clearing excessive cytosolic Ca2+. In a previous study, it was suggested that the clearance of cytosolic Ca2+, after approximately 18 min of metabolic inhibition (MI) in renal epithelial cells, occurs via the reverse action of the mitochondrial Na+/Ca2+ exchanger (NCX). For further investigating the underlying mechanism, changes in the mitochondrial Na+ concentration ([Na+](m)) were monitored in metabolically inhibited MDCK cells. CoroNa Red, a sodium-sensitive fluorescence probe, was used to monitor [Na+]m. In the first 15 min of MI, a twofold increase of [Na+]m was observed reaching 113 +/- 7 mM, whereas the cytosolic Na+ concentration ([Na+]c) elevated threefold, to a level of 65 +/- 6 mM. In the next 45 min of MI, [Na+]m dropped to 91 +/- 7 mM, whereas [Na+]c further increased to 91 +/- 4 mM. The striking rise in [Na+]m is likely sufficient to sustain the driving force for mitochondrial Ca2+ uptake via the NCX. Furthermore, when CGP-37157, a specific inhibitor of the mitochondrial NCX, was applied during MI, the second-phase drop of [Na+]m was completely abolished. The obtained results support the hypothesis that the mitochondrial NCX reverses after approximately 15 min of MI. Moreover, because the cellular homeostasis can recover after MI, the mitochondria likely protect MDCK cells from injury during MI by the reversal of the mitochondrial NCX. This study is the first to report [Na+]m measurements in nonpermeabilized living cells.

Bacterial internalization in periodontitis

BACKGROUND

Bacterial invasion of host epithelial cells plays an important role in the pathogenesis of periodontitis; however, the exact mechanism of the invasion has not been investigated.

METHODS

Pocket epithelium biopsies in periodontitis were analysed via scanning and transmission electron microscopy using ultra-histochemical staining with ruthenium red for glycocalyx visualization.

RESULTS

We demonstrated that oral bacteria adhered via fimbriae-mediated adhesion only. The bacterial internalization in periodontitis was marked by the hallmark of the fimbriae-induced zipper mechanism--the phagocytic cup formation--but we found no sign of the trigger mechanism of internalization. In addition, we frequently observed apoptosis in the phagocytizing epithelial cells.

CONCLUSION

Fimbriae-mediated adhesion is a prerequisite for bacterial invasion in periodontitis. This occurs by the fimbriae-induced zipper mechanism of internalization. As internalization induces apoptosis, the subsequent exfoliation might play a significant role in the clearance of periodontal pathogens.

Strain discrimination among B. anthracis and related organisms by characterization of bclA polymorphisms using PCR coupled with agarose gel or microchannel fluidics electrophoresis

The bclA gene codes for the protein backbone of the exosporium glycoprotein BclA of B. anthracis. BclA has a central collagen-like region formed by polymorphic GXX repeats and conserved amino- and carboxy-termini. It is noted here that the bclA gene is also present in the genome of Bacillus cereus and Bacillus thuringiensis. There is considerable size heterogeneity among the BclA proteins, both for species and strains, due to different numbers of GPT repeats and [GPT]5GDTGTT repeats (BclA repeats). PCR products that included the entire variable region were analyzed by conventional agarose gel electrophoresis and by micro-channel fluidics (MCF) LabChip to assess differences in molecular weight (MW). Both methods provided discrimination at the strain level for B. cereus group organisms. Results obtained by MCF electrophoresis were superior to conventional agarose gel analysis demonstrating improved reproducibility and much faster analysis time. The expression of a carbohydrate-rich exosporium (corresponding to BclA) in other members of the B. cereus group, in addition to B. anthracis, was also demonstrated ultra-structurally. Analysis of sequence variability within the bclA gene CLR revealed even greater potential for strain and species identification.

Calcium buffering activity of mitochondria controls basal growth hormone secretion and modulates specific neuropeptide signaling

Goldfish somatotropes contain multiple functionally distinct classes of non-mitochondrial intracellular Ca(2+) stores. In this study, we investigated the role of mitochondrial Ca(2+) handling in the control of hormone secretion. Inhibition of mitochondrial Ca(2+) uptake with 10 microM ruthenium red (RR) and 10 microM carbonyl cyanide m-chlorophenylhydrazone (CCCP) caused a small and reversible increase in cytosolic [Ca(2+)]. Despite relatively modest global Ca(2+) signals, RR and CCCP stimulated robust GH secretion under basal culture conditions. CCCP-stimulated hormone release was abolished in cells pre-incubated with 50 microM BAPTA-AM, suggesting that elevations in cytosolic [Ca(2+)] mediate this release of GH. Both caffeine-sensitive intracellular Ca(2+) stores and L-type Ca(2+) channels can be the source of the Ca(2+) buffered by mitochondria in somatotropes. The stimulatory effect of RR on caffeine-stimulated GH release was enhanced dramatically in the presence of ryanodine, pointing to a complex interaction between these three Ca(2+) stores. Inhibition of mitochondrial Ca(2+) uptake with RR augmented GH release evoked by only one of the two endogenous gonadotropin-releasing hormones. Thus, we provide the first evidence that mitochondrial Ca(2+) buffering is differentially involved in specific agonist Ca(2+) signaling pathways and plays an important role in the control of basal GH release.

High-resolution visualization of the microbial glycocalyx with low-voltage scanning electron microscopy: dependence on cationic dyes

The microbial glycocalyx is composed of a variety of polyanionic exopolysaccharides and plays important roles in microbial attachment to different substrata and to other cells. Here we report the successful use of low-voltage scanning electron microscopy (LVSEM) to visualize the glycocalyx in two microbial models (Klebsiella pneumoniae and Enterococcus faecalis biofilms) at high resolution, and also the dependence on fixation containing polycationic dyes for its visualization. Fixation in a paraformaldehyde-glutaraldehyde cocktail without cationic dyes was inadequate for visualizing the glycocalyx, whereas addition of various dyes (alcian blue, safranin, and ruthenium red) to the aldehyde cocktail appeared necessary for stabilization. The cationic dyes varied in size, shape, and charge density, and these factors appeared responsible for different phenotypic appearances of the glycocalyx with each dye. These results suggest that aldehyde fixation with cationic dyes for high-resolution LVSEM will be a useful tool for investigation of microbial biofilms as well as investigation of the extent and role of the glycocalyx in microbial attachment to surfaces.

Light-regulated Ca2+ uptake and O2 secretion at the surface of a scleractinian coral Galaxea fascicularis

The surface concentration dynamics of Ca(2+) and O(2) in the scleractinian coral Galaxea fascicularis were investigated by means of 2 mm-sized sensors (mini-electrodes). Mini-electrodes were used to measure the light-regulated uptake of Ca(2+) for calcification, and the secretion of O(2), produced by photosynthesising zooxanthellae, at the surface of the oral ectoderm of Galaxea polyps. The concentration of Ca(2+) measured in the boundary layer of seawater adjacent to the polyp surface was variable but always higher than in bulk seawater in the dark and fell to levels closer to the value in bulk seawater on illumination. The fall in concentration, representing an influx of Ca(2+) into the ectoderm, increased with increasing photosynthetic photon flux density of illumination. The decrease in Ca(2+) concentration on illumination was insensitive to ruthenium red but sensitive to verapamil and acetazolamide. Oxygen secretion at the ectoderm, manifested by an increase in O(2) concentration in the boundary layer, increased on illumination but was not sensitive to any of the inhibitors used in the calcium experiments. The results suggest that Ca(2+) uptake involves calcium channels and is coupled in someway to the uptake of inorganic carbon for calcification. Uptake is also strongly coupled to photosynthesis.

Texture of the zona pellucida of the mature pig oocyte. The mammalian egg envelope revisited

The zona pellucida (ZP) of mature pig oocytes is believed to consist of a dense filamentous meshwork, less compact on the inner and outer faces. The uneven surface of the ZP is made of unordered and stretched fibrils surrounding deep funnels which are the openings of the radial canaliculi. The topography of the ZP surface may contribute to the initial interplay between male and female gametes. Using cytochemical techniques for transmission electron microscopy (TEM), such as tannic acid and ruthenium red treatments, we found that the ZP of pig oocytes was essentially made of bundles of fibrils distributed in concentric layers (except in the innermost and outer parts). A correlation appears between the dense structure of the core layer of the ZP and its texture: it is constituted of superposed layers of fibril bundles, whereas only a random meshwork is found in a very thin innermost and in the outer layer. The fascicular configuration may control the permeability of the ZP, giving its semi-rigidity and elasticity, and may facilitate sperm penetration. The liquid crystal-like design of the core layer of the ZP is similar to textures found in the the vitelline envelope (zona radiata) of other vertebrates and possibly of all the deuterostomes. Such texture is probably related to the unique ZP protein composition and to a coordinated synthesis.

Glycocalyx morphology of Candida albicans

In this study, we examine new cytochemical aspects of the fimbria-mediated adhesion of the oral facultative pathogen Candida albicans. A wild-type strain of the yeast was grown with and without sucrose supplementation for 8 days. Osmium tetroxide, uranyl acetate (UA), ruthenium red (RR), and cupromeronic blue (CB) staining with critical electrolytic concentrations (CECs) and tannic acid-metal salt technique (TAMST) were applied to specimens separately or in combination for transmission electron microscopy (TEM) examination. Cytochemically, two types of fimbriae of C. albicans were distinguished: RR-positive fimbriae of polyanionic glycoconjugates and CB-positive fimbriae with a ceasing point of 0.3 M MgCl2 where no staining of sulfated carboxyl-rich and/or phospho-glycoconjugates occurred. Additionally, CB-positive intercellular fibers were observed, which seemed to be involved in intercellular adhesion. The present protocol enables, for the first time, a partial cytochemical differentiation between at least two kinds of yeast fimbriae.

Protective effects of polygodial on gastric mucosal lesions induced by necrotizing agents in rats and the possible mechanisms of action

The effects of polygodial isolated from the leaves of Tasmannia lanceolata on necrotizing agents-induced gastric lesions in rats were compared with capsaicin. Polygodial markedly inhibited the gastric mucosal lesions induced by several necrotizing agents, such as ethanol (ED(50)=0.029 mg/kg, p.o.), 0.6 M HCl (ED(50)=0.26 mg/kg, p.o.), and aspirin (ED(50)=0.38 mg/kg, p.o.), and partly inhibited the gastric mucosal lesions induced by indomethacin, but showed no significant effect on acid output in pylorus-ligated rats at doses of 0.05-0.5 mg/kg. The gastroprotection of polygodial was attenuated by pretreatment with indomethacin (10 mg/kg, s.c.), N(G)-nitro-L-arginine methyl ester (70 mg/kg, i.p.), N-ethylmaleimide (10 mg/kg, s.c.) and ruthenium red (3.5 mg/kg, s.c.). Polygodial (0.2 mg/kg, p.o.) increased the amount of reduced glutathione in gastric mucosa of ethanol-treated group. These results suggested that endogenous prostaglandins, nitric oxide, sulfhydryl compounds and vanilloid receptor-mediated effects are involved in the protective effect of polygodial.

Improved staining of negative binding sites with ruthenium red on cryosections of frozen cells

Hexavalent cationic dye ruthenium red (RR) binds to anionic sites of cellular components, predominantly to the surface coat rich in glycoconjugates, and can be used as a marker of negative binding sites. Due to limited penetration of RR only superficial layers of cells are stained satisfactorily. To improve RR staining of L1210 leukemic cells isolated from culture and concentrated by centrifugation, cryosections of frozen cells were treated by RR to expose simultaneously all the cells and their components to the dye treatment. Cells were fixed with 2% glutaraldehyde in cacodylate buffer (CB), soaked in 2.2 mol/l sucrose and frozen by plunging into liquid nitrogen. Ultrathin cryosections were cut at a temperature of -90 degrees C, transferred to Formvar coated copper grids, postfixed with 1% OsO4 and stained with 0.05% RR in CB for 60-120 min. After removing RR solution with filter the grids were dried and examined electron microscopically. The resulting staining was a combination of a negative contrast (the plasma membrane and membranes of intracellular organelles) and of a positive contrast (cytoplasmic matrix and the extracellular coat). RR staining of negative binding sites on cryosections has proved useful for uniform exposure of all cells and cellular compartments to the dye and especially of external coat containing glycoconjugates.

The human zona pellucida and scanning electron microscopy. Reality or artifacts?

The surface micro-morphology of the zona pellucida (ZP) was investigated in 158 inseminated but unfertilized mature human oocytes derived from assisted reproduction trials (ART) by means of traditional scanning electron microscopy (SEM) techniques (gold coating and conductive staining methods) and saponin-ruthenium red-osmium tetroxide-thiocarbohydrazide method (Sap-RR-Os-TC). The main aspect of the ZP by traditional SEM (122 oocytes) consisted in a porous, net-like structure (97 oocytes), whereas a nearly smooth or compact structure of ZP was detected in 25 oocytes (79.5% vs 20.5%). Using Sap RR-Os-TC method on 36 oocytes, 31 oocytes showed ZP with alternating tight and large meshed networks, whereas 5 oocytes displayed only tight meshed network (86.1% vs 13.9%). Due to our well standardized procedures, to the stabilizing action of the conductive staining on the zona material and similar results obtained with the use of Sap RR-Os-TC method, we confidentially regard the ZP changes, occurring in oocytes of various groups, as genuine features, likely related to their actual maturation status, rather than as artifacts. In addition, we emphasize the concept that a modern view of the ZP surface implies the best evidence of crossing filaments' network. We think that the ZP "spongy" or "compact" appearance is only the result of microfilaments network collapse, not the true three-dimensional (3-D) representation of ZP structure.

Isolation and characterization of mutants defective in seed coat mucilage secretory cell development in Arabidopsis

In Arabidopsis, fertilization induces the epidermal cells of the outer ovule integument to differentiate into a specialized seed coat cell type producing extracellular pectinaceous mucilage and a volcano-shaped secondary cell wall. Differentiation involves a regulated series of cytological events including growth, cytoplasmic rearrangement, mucilage synthesis, and secondary cell wall production. We have tested the potential of Arabidopsis seed coat epidermal cells as a model system for the genetic analysis of these processes. A screen for mutants defective in seed mucilage identified five novel genes (MUCILAGE-MODIFIED [MUM]1-5). The seed coat development of these mutants, and that of three previously identified ones (TRANSPARENT TESTA GLABRA1, GLABRA2, and APETALA2) were characterized. Our results show that the genes identified define several events in seed coat differentiation. Although APETALA2 is needed for differentiation of both outer layers of the seed coat, TRANSPARENT TESTA GLABRA1, GLABRA2, and MUM4 are required for complete mucilage synthesis and cytoplasmic rearrangement. MUM3 and MUM5 may be involved in the regulation of mucilage composition, whereas MUM1 and MUM2 appear to play novel roles in post-synthesis cell wall modifications necessary for mucilage extrusion.

GABA(C) rho(1) subunits form functional receptors but not functional synapses in hippocampal neurons

The ability to control the physiological and pharmacological properties of synaptic receptors is a powerful tool for studying neuronal function and may be of therapeutic utility. We designed a recombinant adenovirus to deliver either a GABA(C) receptor rho(1) subunit or a mutant GABA(A) receptor beta(2) subunit lacking picrotoxin sensitivity [beta2(mut)] to hippocampal neurons. A green fluorescent protein (GFP) reporter molecule was simultaneously expressed. Whole cell patch-clamp recordings demonstrated somatic expression of both bicuculline-resistant GABA(C) receptor-mediated and picrotoxin-resistant GABA(A) receptor-mediated GABA-evoked currents in rho(1)- and beta(2)(mut)-transduced hippocampal neurons, respectively. GABAergic miniature inhibitory postsynaptic currents (mIPSCs) recorded in the presence of 6-cyano-7-nitroquinoxalene-2,3-dione, Mg(2+), and TTX revealed synaptic events with monoexponential activation and biexponential decay phases. Despite the robust expression of somatic GABA(C) receptors in rho(1)-neurons, no bicuculline-resistant mIPSCs were observed. This suggested either a kinetic mismatch between the relatively brief presynaptic GABA release and slow-activating rho(1) receptors or failure of the rho(1) subunit to target properly to the subsynaptic membrane. Addition of ruthenium red, a presynaptic release enhancer, failed to unmask GABA(C) receptor-mediated mIPSCs. Short pulse (2 ms) application of 1 mM GABA to excised outside-out patches from rho(1) neurons proved that a brief GABA transient is sufficient to activate rho(1) receptors. The simulated-IPSC experiment strongly suggests that if postsynaptic GABA(C) receptors were present, bicuculline-resistant mIPSCs would have been observed. In contrast, in beta(2)(mut)-transduced neurons, picrotoxin-resistant mIPSCs were observed; they exhibited a smaller peak amplitude and faster decay compared with control. Confocal imaging of transduced neurons revealed rho(1) immunofluorescence restricted to the soma, whereas punctate beta(2)(mut) immunofluorescence was seen throughout the neuron, including the dendrites. Together, the electrophysiological and imaging data show that despite robust somatic expression of the rho(1) subunit, the GABA(C) receptor fails to be delivered to the subsynaptic target. On the other hand, the successful incorporation of beta(2)(mut) subunits into subsynaptic GABA(A) receptors demonstrates that viral transduction is a powerful method for altering the physiological properties of synapses.

Isolation and characterization of mutants defective in seed coat mucilage secretory cell development in Arabidopsis

In Arabidopsis, fertilization induces the epidermal cells of the outer ovule integument to differentiate into a specialized seed coat cell type producing extracellular pectinaceous mucilage and a volcano-shaped secondary cell wall. Differentiation involves a regulated series of cytological events including growth, cytoplasmic rearrangement, mucilage synthesis, and secondary cell wall production. We have tested the potential of Arabidopsis seed coat epidermal cells as a model system for the genetic analysis of these processes. A screen for mutants defective in seed mucilage identified five novel genes (MUCILAGE-MODIFIED [MUM]1-5). The seed coat development of these mutants, and that of three previously identified ones (TRANSPARENT TESTA GLABRA1, GLABRA2, and APETALA2) were characterized. Our results show that the genes identified define several events in seed coat differentiation. Although APETALA2 is needed for differentiation of both outer layers of the seed coat, TRANSPARENT TESTA GLABRA1, GLABRA2, and MUM4 are required for complete mucilage synthesis and cytoplasmic rearrangement. MUM3 and MUM5 may be involved in the regulation of mucilage composition, whereas MUM1 and MUM2 appear to play novel roles in post-synthesis cell wall modifications necessary for mucilage extrusion.

Fimbria-mediated bacterial adhesion to human oral epithelium

Oral mucosa biopsies and saliva samples from 12 individuals were processed for transmission (TEM) and scanning (SEM) electron microscopy with and without ruthenium red staining. Additionally performed microbiological estimations indicated in all bacteriological samples a facultative pathogenic flora. SEM and TEM investigation showed a diverse bacterial flora attached to the mucosal surface. Fimbriae comprising the glycocalyx and enabling bacterial attachment to the epithelial cells could be clearly visualised by ruthenium red. The only mode of bacterial attachment to the oral mucosa detected in the present investigation was fimbria-mediated adhesion and co-adhesion. The fimbria-mediated adhesion enables the bacterial persistence in the oral cavity and is the first step in the bacterial colonisation process.

Influence of calcitonin gene-related peptide release on pH-induced mechanical depression in rat atria

Rat atria is richly innervated by sensory nerve fibers that release CGRP when stimulated either by capsaicin or acid pH. We studied the physiological relevance of acid pH-induced CGRP release on changes in atrial contractility and relaxation produced by lowering the pH. Isolated atria electrically paced at 2.77 Hz were exposed to a 10-minute period of metabolic acidosis (pH=6.73+/-0.01, n=28) after: 1) CGRP release induced by capsaicin 0.5 microM; 2) blockage of CGRP release with ruthenium red (RR) 5 microM; 3) no pretreatment; and 4) CGRP receptor blockage with CGRP(8-37) 1 microM. Contractility and relaxation were significantly less depressed by acid pH when CGRP release was prevented by RR or CGRP receptor activation was blocked by CGRP(8-37). The results suggest that CGRP release and the activation of CGRP receptors may be physiologically involved in contributing to the depression of contractility and relaxation induced by acid pH in rat atria.

Demonstration of biofilm in infectious crystalline keratopathy using ruthenium red and electron microscopy

OBJECTIVE

Bacterial biofilm formation has been implicated in the pathogenesis of infectious crystalline keratopathy. Biofilm cannot be visualized by electron microscopy without the addition of a fixative that stabilizes the polysaccharide-rich bacterial extracellular matrix that surrounds the bacterial colonies in a biofilm. We used ruthenium red as a fixative to evaluate corneal biopsy specimens for the presence of bacterial biofilm in three cases of infectious crystalline keratopathy (ICK) and five cases of chronic microbial keratitis without crystalline changes.

DESIGN

Case series with clinicopathologic correlation.

PARTICIPANTS

Eight patients underwent corneal biopsy or therapeutic keratoplasty as part of their management for chronic unresponsive microbial keratitis.

METHODS

The corneal specimens removed were trisected for microbiology, pathology, and transmission electron microscopy (TEM). The TEM specimens were fixed in 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer with 0.05% ruthenium red.

MAIN OUTCOME MEASURES

Demonstration of bacterial biofilm with TEM.

RESULTS

TEM demonstrated organisms with a surrounding extracellular matrix consistent with a bacterial biofilm in the three cases of ICK but not in the five other cases of chronic microbial keratitis.

CONCLUSIONS

The presence of biofilm in ICK can be demonstrated with TEM with appropriate fixation techniques that stabilize the bacterial extracellular matrix. Biofilm stains intensely with periodic acid-Schiff because of the polysaccharide-rich extracellular matrix and weakly with Gram stain because of the high proportion of nonviable organisms. Biofilm formation occurs in ICK but probably not in chronic bacterial keratitis without crystalline changes. Secretion of an extracellular matrix by bacteria to form a biofilm is a response to a nutrient-deprived environment in which growth and replication is depressed. The extracellular matrix of the biofilm may mask bacterial antigens, explaining the relative lack of inflammatory response in these infections. It may also be one of the mechanisms explaining the resistance to in vivo antimicrobial therapy when in vitro sensitivities have been proven.

IP3-gated channels and their occurrence relative to CNG channels in the soma and dendritic knob of rat olfactory receptor neurons

Olfactory receptor neurons respond to odorants with G protein-mediated increases in the concentrations of cyclic adenosine 3',5'-monophosphate (cAMP) and/or inositol-1,4,5-trisphosphate (IP3). This study provides evidence that both second messengers can directly activate distinct ion channels in excised inside-out patches from the dendritic knob and soma membrane of rat olfactory receptor neurons (ORNs). The IP3-gated channels in the dendritic knob and soma membranes could be classified into two types, with conductances of 40 +/- 7 pS (n = 5) and 14 +/- 3 pS (n = 4), with the former having longer open dwell times. Estimated values of the densities of both channels from the same inside-out membrane patches were very much smaller for IP3-gated than for CNG channels. For example, in the dendritic knob membrane there were about 1000 CNG channels x microm(-2) compared to about 85 IP3-gated channels x microm(-2). Furthermore, only about 36% of the dendritic knob patches responded to IP3, whereas 83% of the same patches responded to cAMP. In the soma, both channel densities were lower, with the CNG channel density again being larger ( approximately 57 channels x microm(-2)) than that of the IP3-gated channels ( approximately 13 channels x microm(-2)), with again a much smaller fraction of patches responding to IP3 than to cAMP. These results were consistent with other evidence suggesting that the cAMP-pathway dominates the IP3 pathway in mammalian olfactory transduction.

The rapid mode of calcium uptake into heart mitochondria (RaM): comparison to RaM in liver mitochondria

A mechanism of Ca(2+) uptake, capable of sequestering significant amounts of Ca(2+) from cytosolic Ca(2+) pulses, has previously been identified in liver mitochondria. This mechanism, the Rapid Mode of Ca(2+) uptake (RaM), was shown to sequester Ca(2+) very rapidly at the beginning of each pulse in a sequence [Sparagna et al. (1995) J. Biol. Chem. 270, 27510-27515]. The existence and properties of RaM in heart mitochondria, however, are unknown and are the basis for this study. We show that RaM functions in heart mitochondria with some of the characteristics of RaM in liver, but its activation and inhibition are quite different. It is feasible that these differences represent different physiological adaptations in these two tissues. In both tissues, RaM is highly conductive at the beginning of a Ca(2+) pulse, but is inhibited by the rising [Ca(2+)] of the pulse itself. In heart mitochondria, the time required at low [Ca(2+)] to reestablish high Ca(2+) conductivity via RaM i.e. the 'resetting time' of RaM is much longer than in liver. RaM in liver mitochondria is strongly activated by spermine, activated by ATP or GTP and unaffected by ADP and AMP. In heart, RaM is activated much less strongly by spermine and unaffected by ATP or GTP. RaM in heart is strongly inhibited by AMP and has a biphasic response to ADP; it is activated at low concentrations and inhibited at high concentrations. Finally, an hypothesis consistent with the data and characteristics of liver and heart is presented to explain how RaM may function to control the rate of oxidative phosphorylation in each tissue. Under this hypothesis, RaM functions to create a brief, high free Ca(2+) concentration inside mitochondria which may activate intramitochondrial metabolic reactions with relatively small amounts of Ca(2+) uptake. This hypothesis is consistent with the view that intramitochondrial [Ca(2+)] may be used to control the rate of ADP phosphorylation in such a way as to minimize the probability of activating the Ca(2+)-induced mitochondrial membrane permeability transition (MPT).

Citrinin-induced mitochondrial permeability transition

The effects of mycotoxin citrinin on Ca2+ efflux and membrane permeabilization were studied in isolated rat liver mitochondria. The efflux rate observed when in presence of ruthenium red was higher when citrinin was added. Swelling experiments demonstrated Ca(2+)-dependent membrane permeabilization by citrinin. Catalase, butylhydroxitoluene (BHT), and dithiothreitol (DTT) did not protect swelling caused by Ca2+ plus citrinin. The protection conferred by ATP-Mg2+ and cyclosporin A in the latter experiments are strong indications of pore formation. These results suggest that citrinin can induce permeability transition by a mechanism that does not involve oxidative damage.

Opisthorchis viverrini: ultrastructure and cytochemistry of the glycocalyx of the tegument

The ultrastructure and cytochemistry of the glycocalyx of the tegument of Opisthorchis viverrini during maturation from newly excysted juvenile to adult stages were investigated using colloidal iron, ruthenium red and lectin stainings. The results showed that the glycocalyx was intensely stained by the first two dyes, thus indicating the presence of relatively high amounts of negative charges. However, the thickness and intensity of the staining decreased during the fluke's maturation. Binding studies using lectin probes on the surface of adult parasites showed that binding sites for Canavalia ensiformis (Con A), Triticum vulgaris (WGA) and Ricinus communis I (RCA I) were present in relative large amounts on the glycocalyx of the adult tegument, whereas those for Dolichos biflorus (DBA) were relatively fewer in number, and those for Ulex europaeus I (UEA I) were absent. The binding patterns of Con A, WGA, RCA I and DBA were generally similar, and the reaction product was uniformly distributed over the dorsal and ventral surfaces of the parasite's body. These bindings, therefore, indicate the presence of D-mannose/D-glucose, N-acetyl-D-glucosamine/sialic acid, D-galactose and N-acetyl-D-galactosamine residues on the glycocalyx of the adult tegument.

Responses to putative second messengers and odorants in water nose olfactory neurons of Xenopus laevis

Using the whole-cell mode of the patch-clamp technique, we attempted to record inward currents in response to cAMP, inositol 1,4, 5-trisphosphate (IP(3)) and odorants from sensory neurons in the olfactory epithelium of the Xenopus laevis lateral diverticulum (water nose). Dialysis of 100 microM of IP(3) induced inward currents, while dialysis of 1 mM of cAMP into olfactory neurons did not induce any response under the voltage-clamp conditions. Changes in membrane conductance were examined by applying ramp pulses. The slope of the current-voltage (I-V) curve during the IP(3)-induced response was steeper than that after the response, indicating that IP(3) increased the membrane conductance. The water nose olfactory neurons have been shown to respond to both amino acids and volatile odorants. The slopes of I-V curves during responses to amino acids and a volatile odorant, lilial, were similar to those before the responses, suggesting that the total membrane conductance was not changed during responses to amino acids and the volatile odorant.

Differential quantal release of histamine and 5-hydroxytryptamine from mast cells of vesicular monoamine transporter 2 knockout mice

The recent availability of mice lacking the neuronal form of the vesicular monoamine transporter 2 (VMAT2) affords the opportunity to study its roles in storage and release. Carbon fiber microelectrodes were used to measure individual secretory events of histamine and 5-hydroxytryptamine (5-HT) from VMAT2-expressing mast cells as a model system for quantal release. VMAT2 is indispensable for monoamine storage because mast cells from homozygous (VMAT2(-/-)) mice, while undergoing granule-cell fusion, do not release monoamines. Cells from heterozygous animals (VMAT2(+/-)) secrete lower amounts of monoamine per granule than cells from wild-type controls. Investigation of corelease of histamine and 5-HT from granules in VMAT2(+/-) cells revealed 5-HT quantal size was reduced more than that of histamine. Thus, although vesicular transport is the limiting factor determining quantal size of 5-HT and histamine release, intragranular association with the heparin matrix also plays a significant role.

Dynamic changes in sarcoplasmic reticulum function in cardiac hypertrophy and failure

Previous studies have demonstrated that cardiac function changes with development of pressure overload-induced hypertrophy. The present study was undertaken to discover the basis for the changes in sarcoplasmic reticulum (SR) functions: uptake, (as related to the SR Ca2+ pump properties) and release in isolated, perfused hypertrophied rat hearts. Our results demonstrated significant prolongation of the time-to-90%-relaxation, both during the period of compensation (8 weeks after banding the ascending aorta, group HR1), when systolic function was preserved, and later with progressive hypertrophy (20 weeks after banding, group HR2) and contractile failure (20-22 weeks after banding, group F). The initial rates of the oxalate-supported SR Ca2+ uptake and the maximum transport rate (Vmax) of the SR Ca2+ pump, measured in the left ventricular homogenates, during blockade of the SR Ca2+ release channels with ruthenium red, were preserved in group HR1. To correlate early relaxation abnormalities with SR function, the [Ca2+] required for half-maximal pump activation (EC50) was examined and increased significantly in HRI vs. Sham1 (0.95+/-0.06 vs. 0.81+/-0.04 microM, P<0.05) indicating that the affinity of the SR Ca2+ pump for Ca2+ was reduced. The same tendency was demonstrated in groups HR2 (0.94+/-0.06 vs. 0.79+/-0.05) and F (0.89+/-0.05 vs. 0.78+/-0.05). In addition, with progression of hypertrophy we observed a significant decline in the amount of SR Ca2+ pump, as assessed by the Vmax, from 31.22+/-1.20 (Sham2) to 26.47+/-1.58 HR2) nmol/mg protein per min (P<0.05), and from 33.81+/-1.23 (Sham3) to 25.15+/-1.57 (F) nmol/mg protein per min, (P<0.01). This decrease was accompanied by a parallel reduction in the number of SR Ca2+ release channels by 14% (HR2) and 23% (F), as determined by maximum [3H] ryanodine binding (Bmax). These results suggest that pressure overload-induced changes in SR Ca2+ uptake (as reflected by Vmax and EC50) and SR Ca2+ release (as reflected by Bmax), both leading to diminished Ca2+ sequestration, may contribute to impaired cardiac relaxation with compensatory hypertrophy and failure.

The effects of cold-restraint stress on urinary bladder wall compared with interstitial cystitis morphology

Stress is associated with many diseases of unknown aetiology. This study demonstrates the effects of cold-restraint stress on the morphology of the urinary bladder. Additionally, it compares the results obtained with the morphology of the interstitial cystitis. The animals were subjected to three hours of cold-restraint stress and then starved for 48 h. The morphology and histochemistry of the urinary bladder was investigated with light and electron microscopy. The proliferative activity was analysed via flow cytometry. Increased and degranulated mast cells in the mucosa, leucocyte infiltration in the lamina propria, vacuole formation in the urothelial cells, loose tight junction, dilated intercellular spaces and altered proliferative activity were observed in the stress group when compared with the control. The increase in the number of mast cells and especially degranulated mast cells and vacuole formation and the loose tight junction of the urothelium correlated with the histopathological findings of interstitial cystitis.

The extracellular matrix of rat pacinian corpuscles: an analysis of its fine structure

The Pacinian corpuscle consists of a sensory axon terminal that is enveloped by two different structures, the inner core and the capsule. Since proteoglycans are extremely water soluble and are extracted by conventional methods for electron microscopy, the current picture of the structural composition of the extracellular matrix in the inner core and the capsule of the Pacinian corpuscle is incomplete. To study the structural composition of the extracellular matrix of the Pacinian corpuscles, cationic dyes (ruthenium red, alcian blue, acridine orange) and tannic acid were applied simultaneously with the aldehyde fixation. The interosseal Pacinian corpuscles of the rat were fixed either in 2% formaldehyde and 1.5% glutaraldehyde, with the addition of one of these cationic dyes or, in Zamboni's fixative, with tannic acid added. The cationic dyes and tannic acid revealed a different structural pattern of proteoglycans in the extracellular matrix in the inner core and in the capsule of the rat Pacinian corpuscles. The inner core surrounding the sensory axon terminal is a compartment containing proteoglycans that were distributed not only in the extracellular matrix but also in the cytoplasm of the lamellae. In addition, this excitable domain was separated from the capsular fluid by a thick layer of proteoglycans on its surface. An enlarged interlamellar space of the capsule contained large amounts of proteoglycans that were removed by digestion with chondroitinase-ABC. Ruthenium red and alcian blue provided only electron dense granules, probably corresponding to collapsed monomeric proteoglycan molecules. Acridine orange and tannic acid preserved proteoglycans very well and made it possible to visualize them as "bottlebrush" structures in the electron microscope. These results show that the inner core and the capsule of rat Pacinian corpuscles have different structural patterns of proteoglycans, which are probably involved in different functions.

On the characterisation of the mechanism underlying passive activation of the Ca2+ release-activated Ca2+ current ICRAC in rat basophilic leukaemia cells

1. Tight-seal whole-cell patch clamp experiments were performed to investigate the mechanism whereby passive depletion of stores activates the Ca2+ release-activated Ca2+ current (ICRAC) in rat basophilic leukaemia (RBL) cells. 2. Passive depletion of stores was achieved by dialysing cells with different concentrations of Ca2+ chelators. Low concentrations generally evoked a submaximal ICRAC, which developed slowly and monophasically. Higher concentrations resulted in a biphasic current in which the initial slow monophasic component developed into a faster and bigger second phase. 3. The kinetics of ICRAC as well as its final amplitude were not affected by Ca2+ chelators that had different affinities or speeds of binding. 4. Exogenous Ca2+ binding ratios > or = 16,670 were necessary to fully activate ICRAC. Because the Ca2+ binding ratio within the stores is presumably low, this indicates that other factors like Ca2+ transport across the stores membrane are rate limiting for passive store depletion. 5. Heparin and Ruthenium Red both failed to affect passive Ca2+ leak from the intracellular stores. 6. Treatment with sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) pump blockers dramatically altered the kinetics of activation of biphasic currents, and increased the amplitude of monophasic ones. 7. Our results suggest that SERCA pumps are very effective in preventing ICRAC from activating passively, and are responsible for the phasic nature of the current, its time course of development and its overall extent.

Species dependence of mitochondrial calcium transients during excitation-contraction coupling in isolated cardiomyocytes

Whether mitochondrial Ca(2+) transport is rapid enough to respond to changes in cytosolic [Ca(2+)] ([Ca(2+)](c)) which occur during excitation-contraction coupling in the heart is controversial; different results wereobtained with different techniques and different species. In this study mitochondrial [Ca(2+)] ([Ca(2+)](m)) was measured in indo-1/AM-loaded myocytes from rat and guinea-pig hearts where the cytosolic indo-1 had been removed by extended incubation of cells at 37 degrees C ("heat treatment"). The mitochondrial origin of the remaining fluorescence was confirmed by sensitivity of the indo-1 signal to ruthenium red. In resting rat myocytes, [Ca(2+)](m) was lower than [Ca(2+)](c), whereas in guinea-pig cells [Ca(2+)](m) was higher than [Ca(2+)](c). Upon electrical stimulation of cells, no change occurred in [Ca(2+)](m) in rat myocytes. However, in guinea-pig cells mitochondrial Ca(2+) transients were clearly visible with a mean indo-1 ratio amplitude of 0.153 +/- 0.2 (n = 20), compared with 0.306 +/- 0.02 (n = 25), p < 0.001, prior to heat treatment. These observations suggest significant differences in mitochondrial Ca(2+) transport in cardiomyocytes from different species.

Differential utilization of cyclic ADP-ribose pathway by chemokines to induce the mobilization of intracellular calcium in NK cells

We show here that cyclic adenosine diphosphate-ribose (cADPR) may be a second messenger for chemokines. Extracts collected from NK cells stimulated with IL-8 for 2 min were incubated with beta-NAD for an additional 2 min (designated as IL-8 extracts). This mixture elevated the mobilization of (Ca(2+))(i) in alpha-toxin permeabilized NK cells. This activity was inhibited upon prior incubation of these cells with ruthenium red but not with heparin. Purified cADPR and not Ins 1,4,5 P(3) desensitized NK cells to the calcium mobilization effect of IL-8 extracts. Further analysis showed that ruthenium red and heparin differentially inhibit RANTES-, SDF-1alpha-, or MDC-induced calcium mobilization in IL-2-activated NK cells. Also, introduction of anti-ryanodine receptor antibody inside streptolysin O-permeabilized NK cells resulted in complete inhibition of MDC, and only partial inhibition of RANTES and SDF-1alpha-induced calcium fluxes in NK cells. Collectively, these results suggest that chemokines may utilize the cADPR/ryanodine receptor pathway as well as the Ins 1,4,5 P(3)/Ins 1,4,5 P(3) receptor signaling pathway to induce the accumulation of calcium in NK cells.

Use of Ca2+ modulation to evaluate biliary excretion in sandwich-cultured rat hepatocytes

Previous work in our laboratory has indicated that biliary excretion of a substrate in sandwich-cultured hepatocytes can be quantitated by measurement of substrate accumulation in the presence and absence of extracellular Ca2+. The present study was designed to examine the effects of Ca2+ on taurocholate accumulation and tight junction integrity in cultured hepatocytes. Kinetic modeling was used to characterize taurocholate disposition in the hepatocyte monolayers in the presence and absence of extracellular Ca2+. The accumulation of taurocholate in freshly isolated hepatocytes, which lack an intact canalicular network, was the same in the presence and absence of extracellular Ca2+. Electron microscopy studies showed that Ca2+ depletion increased the permeability of the tight junctions to ruthenium red, demonstrating that tight junctions were the major diffusional barrier between the canalicular lumen and the extracellular space. Cell morphology and substrate accumulation studies in the monolayers indicated that Ca2+ depletion disrupted the tight junctions in 1 to 2 min. The integrity of the disrupted tight junctions was not re-established completely after reincubation in the presence of Ca2+ for 1 h. The accumulation of taurocholate was described best by a two-compartment model (cytosol and bile) with Michaelis-Menten kinetics for both uptake and biliary excretion. In summary, Ca2+ depletion does not alter hepatocyte transport properties of taurocholate. Ca2+ modulation may be a useful approach to study biliary excretion of substrates in sandwich-cultured hepatocytes.

Clearance of large Ca2+ loads in a single smooth muscle cell: examination of the role of mitochondrial Ca2+ uptake and intracellular pH

Redistribution of cytosolic free Ca2+ following Ca2+ influx into the cytoplasm was studied in single smooth muscle cells isolated from guinea-pig urinary bladder. Voltage-clamped cells were loaded with a low-affinity fluorophore Indo-1FF. A decay of free intracellular Ca2+ ([Ca2+]i) after the termination of the depolarizing pulse (1 s from -50 mV to +20 mV) was fitted with a single exponential and the effect of various substances on the time constant was compared. At a holding potential of +80 mV the [Ca2+]i decay was 1.56 times slower compared to that at -50 mV suggesting the presence of a voltage-dependent process redistributing Ca2+. In the presence of cyclopiazonic acid (CPA, 10 microM), an inhibitor of sarco(endo)plasmatic Ca2+ pump (SERCa), the [Ca2+]i decay was 3.93 times slower than that in the absence of the inhibitor. Introduction of a polycation Ruthenium Red (RR) (20 microM), an inhibitor of the mitochondrial Ca2+ uniporter, into a cell or collapsing a transmitochondrial H+ gradient with the protonophore CCCP (2 microM) slowed down the [Ca2+]i decay 6.05-fold and 9.78-fold, respectively. The apparent amplitude of [Ca2+]i increments was also increased by CCCP. Increasing H+ buffering power in the intracellular solution from 10 mM to 40 mM of HEPES greatly reduced the effect of CCCP on [Ca2+]i decay. A further increase in HEPES concentration to 100 mM eliminated the effects of CCCP both on the time course of [Ca2+]i decay and on the amplitude of [Ca2+]i increment. Perfusion of RR together with 100 mM HEPES into the cytoplasm was without effect on the decay time course of [Ca2+]i. The effect of CPA on [Ca2+]i decay was also reduced in cells loaded with 100 mM HEPES; the time constant in the presence of CPA was slowed down by a factor of 2.18. Application of 10 mM Na(+)-butyrate to the cells loaded with 10 mM HEPES resulted in a slowing down of [Ca2+]i decay: the time constant was increased by a factor of 5.84. Measurement of intracellular pH with SNARF-1 confirmed cytoplasmic acidification during application of Na(+)-butyrate and CCCP. It is concluded that the contribution of mitochondrial Ca2+ uptake to the rapid [Ca2+]i decay is much less than could be extrapolated from action of protonophores in these smooth muscle cells. The results also demonstrate the importance of intracellular pH for Ca2+ handling in the cytoplasm of smooth muscle cells.

[Capsule formation in Pasteurella multocida, serovar A]

In this work the process of capsule formation in P.multocida bovine strain, serovar A, has been studied. The cultures were grown on liquid and solid nutrient media prepared on the basis of Hottinger hydrolysate and synthetic culture medium 199. Extracellular material was detected by the method electron cytochemistry with ruthenium red and polycationic ferritin. As revealed by specific staining and labeling, P.multocida capsule of serovar A was found to contain material of the polysaccharide nature. But the capsular structures of obtained from agar-grown and broth cultures were different. The capsular layer on the surface of cells grown in Hottinger's broth was found to be more pronounced.

Ratiometric confocal Ca2+ measurements with visible wavelength indicators in d-amphetamine-treated central snail neuron

1. The bursting firing of action potentials and cytosolic calcium content in d-amphetamine-treated RP4 neurons of the African snail, Achatina fulica Ferussac, were studied elelctrophysiologically and optopharmacologically. 2. d-Amphetamine elicited bursting of firing of action potentials in central RP4 neuron. The bursting firing of action potentials was blocked following extracellular application of ruthenium red, the calcium uptake and release inhibitor from mitochondria. 3. At the same neuron, image analysis using ratiometric measurement on calcium green 1 and Texas red dextran (70,000 MW) with laser-scanning confocal microscopy revealed that cytosolic calcium content was increased after d-amphetamine treatment. 4. Our results support the view that the bursting firing of action potentials elicited by d-amphetamine is associated with cytosolic calcium content.

Polyamine modulation of mitochondrial calcium transport. I. Stimulatory and inhibitory effects of aliphatic polyamines, aminoglucosides and other polyamine analogues on mitochondrial calcium uptake

In this study, the regulation of mitochondrial Ca2+ transport by polyamines structurally related to spermine and by analogous polycationic compounds was characterized. Similar to spermine, a number of amino groups containing cationic compounds exerted a dual effect on Ca2+ transport of isolated rat liver mitochondria: a decrease in Ca2+ uptake velocity and an enhancement of Ca2+ accumulation. In contrast to the effects of spermine and other aliphatic polyamines, however, the accumulation-enhancing effect of aminoglucosides, basic polypeptides, and metal-amine complexes turned into an inhibition of Ca2+ accumulation at higher concentrations. Within groups of structurally related compounds, the potency to decrease Ca2+ uptake velocity and to enhance Ca2+ accumulation correlated with the number of cationic charges. The presence of multiple, distributed cationic charges was a necessary, but not sufficient criterion for effects on mitochondrial Ca2+ transport, because cationic polyamines and basic oligopeptides which did not enhance mitochondrial Ca2+ accumulation could be identified. Spermine was not able to antagonize the blocking of Ca2+ uptake by ruthenium red, but rather showed an apparent synergism, which can be explained as a displacement of membrane-bound Ca2+ by spermine. The aminoglucosides, gentamicin and neomycin, but not the inactive polyamine bis(hexamethylene)-triamine, inhibited the binding of spermine to intact mitochondria. Apparently, the binding of spermine, gentamicin, and a number of polyamine analogues to low-affinity binding sites at mitochondria, which have low, but distinct structural requirements and which may correspond to phospholipid headgroups, indirectly influences the activity state of the mitochondrial Ca2+ uniporter. The ability of aminoglucosides to displace spermine from the mitochondria and to inhibit mitochondrial Ca2+ accumulation may contribute to the mitochondrial lesions, which are known to occur early in the course of aminoglucoside-induced nephrotoxicity.