Crystalline arrays of proteoglycan and collagen in the tectorial membrane

Ultrastucture of the tectorial membrane in the chinchilla cochlea was studied by transmission electron microscopy using different fixatives and staining procedures. It was shown that the tectorial membrane is a highly structured matrix composed of collagen type A fibrils, noncollagenous type B fibrils and proteoglycan. The localization of type B fibrils surrounding bundles of parallel type A fibrils was observed. Staining of the tectorial membranes with the cationic dye Cuprolinic blue in a "critical electrolyte concentration" method revealed proteoglycan, D-periodically associated with collagen type A fibrils and orthogonal to them. The appearance and size of the proteoglycan, and its binding to collagen, were similar to small proteoglycans observed in cartilage and other tissues. In many regions of the tectorial membrane the collagen-bound proteoglycan forms crystalline-like arrays. The images of these arrays processed by Fourier analysis show long linear aggregates of proteoglycan arranged parallel each other.

[Endotoxin causes release of calcitonin gene-related peptide (CGRP) from the isolated mesenteric arterial bed in rat]

Our previous work has shown that CGRP is released into the circulation during endotoxin or hemorrhagic shock in animals and septic shock in patients. We have also identified the blood vessels as a major source of production of circulating CGRP in the endotoxic rat. In the present study we determined whether ETX could directly trigger release of CGRP from CGRP-containing perivascular nerves in isolated mesenteric arterial bed (MAB) of rat. The results showed that ETX caused time- and concentration (10-100 micrograms/ml) -dependent release of CGRP. ETX (50 micrograms/ml) is increased by 20 fold CGRP in perfusate 10-15 min after ETX. Characterization of CGRP in perfusates by reverse-phase HPLC showed one predominant peak which coeluted with synthetic rat CGRP. Pretreated MAB with capsaicin or ruthenium red inhibited ETX-induced release of CGRP by 90% and 65% respectively. ETX-induced CGRP release was decreased under Ca2+-free perfusion by 80%. The data suggest that ETX directly trigger the release of CGRP from capsaicin-sensitive sensory nerve innervating blood vessels. The release of CGRP is dependent on extra-cellular Ca2+ and Ca2+-induced Ca2+ release from the intracellular Ca2+ store which is sensitive to ruthenium red.

Comparison of chemical dehydration and critical point drying for the stabilization and visualization of aging biofilm present on interior surfaces of PVC distribution pipe

In this study, fixation of attached glycocalyx on the interior surfaces of polyvinyl chloride distribution pipe remnants was compared with and without ruthenium red/osmium tetroxide and, in the final preparatory phase, with chemical dehydration and critical point drying. SEM examination of interior surface of the polyvinyl chloride pipe showed varying concentrations of adherent bacteria, depending on the preparatory technique used. It was concluded that using a combination of ruthenium red/osmium tetroxide and critical point drying is the optimum method for visually demonstrating aging biofilm on the interior surface of contaminated polyvinyl chloride pipe.

Inosine-induced vasoconstriction is mediated by histamine and thromboxane derived from mast cells

Mast cell degranulation has been shown to release products that cause arteriolar constriction. We previously reported that two nucleosides, adenosine and inosine, cause vasoconstriction of isolated hamster cheek pouch arterioles by stimulating degranulation of periarteriolar mast cells. The objectives of the present study were to characterize the nucleoside-dependent vasoconstriction in vivo and to determine the mediator or mediators responsible. We examined the vasomotor effect of inosine on arterioles in the cheek pouches of anesthetized hamsters (70 mg/kg pentobarbital sodium) in the control situation and in the presence of receptor antagonists for histamine (H1), thromboxane A2 (Tx), and leukotrienes (LT). Most experiments were carried out using inosine applied once locally via micropipette to arterioles and observing the subsequent response. Over a range of inosine concentrations from 10(-5) to 10(-3) M in the pipette, we observed a dose-dependent increase in the incidence and magnitude of constriction. In addition, mast cell staining with ruthenium red was observed after stimulation with inosine, an indication of mast cell degranulation. Neither the H1, Tx, nor LT antagonist alone had a significant effect on the vasomotor response to inosine. However, combined H1 and Tx blockade significantly reduced the incidence and magnitude of inosine-induced constriction. These data establish that inosine-induced constriction occurs in vivo and support the role of mast cells in this response. Furthermore they suggest that multiple mediators, primarily histamine and thromboxane, are responsible for the observed constriction.

A comparison of three staining methods in estimation of structures on the cell wall surface of Acinetobacter junii by using electron microscope

Two strains of Acinetobacter junii isolated from groin and nasal cavity were studied for the presence of structures on the cell wall surface. Three staining methods were used. In the first thin section were contrasted with uranyl acetate and lead citrate. In this method, only electron dense amorphous material could be seen. Using only 1% uranyl acetate, thin fimbriae were observed which in few cases were collected in bundles. Staining with ruthenium red showed bacteria with thick short and long numerous peritrichous structures. Bacteria with structures concentrated near the polar regions were seen as well. From the comparative study of three methods, two of them were found to be useful: methods with ruthenium red and with 1% uranyl acetate.

Use of Ruthenium Red staining to detect mast cell degranulation in vivo

OBJECTIVE

To establish a method of detecting mast cell degranulation in tissues during in vivo microscopy.

METHODS

Hamster tissues were prepared for intravital microscopy. Ruthenium red (RR) was superfused over the cheek pouch at concentrations of 0.0001-0.01% to determine the optimal concentration. Mast cells were stimulated with compound 48/80, as well as with vasoactive agents not known to be stimulatory to mast cells, following which, mast cell staining was observed. Mesenteries were stained with Toluidine Blue (TB) or RR and mast cell degranulation was assessed during treatment with compound 48/80, or control.

RESULTS

During superfusion with varying concentrations of RR, a dose dependence for background staining of unstimulated cells was observed. A RR concentration of 0.001% was optimal for in vivo detection of mast cell degranulation. Mast cells exposed to 0.001% RR were stained following stimulation with compound 48/80 but not after treatment with KCl or acetylcholine. The latter agents are not known to stimulate mast cells. Thus, arteriolar vasomotor responses, per se, did not appear to play a role in mast cell RR uptake. Comparable results were obtained with RR versus TB in control or 48/80-treated mesenteries.

CONCLUSIONS

This RR technique facilitates rapid detection of mast cell degranulation in vivo and provides an opportunity to assess both mast cell and microvascular function simultaneously.

Identification of a 44 kDa protein localized within the endoplasmic reticulum of Trypanosoma brucei brucei

Immunoaffinity chromatography and gel electrophoresis were used to isolate a 44 kDa protein that was bound to a 72 kDa chaperone in Trypanosoma brucei brucei. A polyclonal antiserum to the 44 kDa protein was raised in rats and employed in conjunction with chromatography using DEAE-cellulose, Sephacryl S-300, and hydroxyapatite to purify the protein from membranes of bloodstream forms of the trypanosomes. Immunoblot analysis using this antiserum revealed a protein doublet of 44/45 kDa in T. b. brucei and a single protein band of 53 kDa in almost equivalent amounts throughout the life-cycle stages of T. congolense. Indirect immunofluorescence using affinity-purified antibodies specific for the 44 kDa protein showed labelling of the perinuclear area and reticular system extending throughout the parasites, suggesting that this protein was located in the endoplasmic reticulum. Localization of the 44 kDa molecule in the endoplasmic reticulum was confirmed by immunoelectron microscopy. Protease protection experiments demonstrated that the epitopes bound by antibody were buried within the membrane or towards the lumenal face of the endoplasmic reticulum. Ruthenium Red overlay of nitrocellulose blots containing the 44/45 kDa doublet suggested that the molecules have the potential to bind calcium. The N-terminal amino acid sequence of the 44 kDa protein showed no sequence similarity to any proteins in the database.

Myocardial mitochondrial calcium accumulation modulates nuclear calcium accumulation and DNA fragmentation

BACKGROUND

Previously, we have shown that normothermic global ischemia increases cytosolic calcium accumulation in both the mature and aged heart. Increased nuclear and mitochondrial calcium accumulation was shown to occur in the aged but not the mature heart, and these age-related differences were associated with increased DNA fragmentation and decreased cellular viability only in the aged heart.

METHODS

To investigate the relationship between increased mitochondrial and nuclear calcium and DNA fragmentation, mature and aged rabbit hearts were subjected to normothermic global ischemia with and without the addition of ruthenium red to block mitochondrial calcium influx. Cytosolic calcium accumulation was measured in a parallel experiment using fura-2.

RESULTS

Ruthenium red ameliorated mitochondrial calcium accumulation and was associated with both decreased DNA fragmentation and decreased nuclear calcium accumulation.

CONCLUSIONS

Nuclear calcium accumulation was correlated with increased mitochondrial calcium accumulation but not increased cytosolic calcium accumulation in the aged heart. Modulation of mitochondrion "futile calcium cycling" may be of significance in the modulation of ischemic myocardial injury.

[An electron microscopic histochemical study on proteoglycans in salivary gland myoepithelioma]

Four myoepitheliomas and four parotid gland were studied histochemically be electron microscopy after stain with ruthenium red. It was found that the normal myoepithelial cells of parotid gland had no secretion function, whereas the myoepithelioma cells were capable of secreting proteoglycans and might form the myxoid region in this tumor. The authors propose that in the pathological diagnosis and differentiat diagnosis of salivary gland epithelial tumors, the appearance of the myxoid region is not only the pathological feature of pleomorphic adenoma, but also the pathological change of myoepithelioma.

Media calcium attenuates mitochondrial 1,25(OH)2D production in phosphorus or vitamin D-deprived rats

Although PTH and hypophosphatemia are the best known stimulators of 25-hydroxyvitamin D-1 alpha-hydroxylase, 1,25(OH)2D3 production in rats and humans can be modulated by circulating calcium, independent of PTH. To test whether calcium modulates this function directly in mitochondria, we examined effects of calcium on 1 alpha-hydroxylase in isolated mitochondrial preparations under basal and stimulated conditions. Rats were fed a low phosphorus (or matched control) diet for 4 or 7 d or a vitamin D-deficient (or matched control) diet for 2, 4, or 7 wk. Renal mitochondria were isolated and assayed for 1 alpha-hydroxylase activity in the presence or absence of added calcium. Calcium did not alter 1 alpha-hydroxylase in rats on control diets. After 4 d of low phosphorus diet, 1 alpha-hydroxylase was increased 2-fold over basal activity; media calcium prevented this stimulatory response. By 7 d the calcium effect was not evident. After 4 wk of vitamin D deprivation, activity was approximately 30-fold greater than controls; calcium reduced this response significantly (15-fold). A significant, but less marked inhibition of activity by calcium was present in rats subjected to 7 wk of vitamin D deprivation. Extramitochondrial calcium can directly modulate 1,25(OH)2D3 production, but this effect appears to be secondary to the primary physiologic regulators of this function. The calcium effect can be overcome after longer term exposure to phosphorus deprivation, but is sustained in the presence of long term vitamin D deprivation.

[Histogenesis of pleomorphic adenoma of the salivary gland]

Six parotid pleomorphic adenomas were studied histochemically by electron microscopy after staining with ruthenium red. It was found that the myxoid region was filled with ruthenium red granules. Similar positive ruthenium red-stained intracellular granules were observed within the Golgi-derived vacuoles of the neoplastic myoepithelial cells in the myxoid region. Some cells located at the periphery of the double-layer ductal structure had the features of myoepithelial cell, they also showed similar positive ruthenium red-stained granules in the intracellular vacuoles and intercellular space. No ruthenium red-stained granules was obtained in neoplastic ductal epithelium and the mucus in ductal cavities were negative for ruthenium red stain. The observations indicate that the neoplastic myoepithelial cells in the myxoid region probably derive from the periphery of the double-layer ductal structure, they secrete the proteoglycans forming the myxoid region and play an important role in the histogenesis of pleomorphic adenoma.

Three-dimensional architecture of the tubular endocytic apparatus and paramembranous networks of the endoplasmic reticulum in the rat visceral yolk-sac endoderm

The three-dimensional architecture of the tubular endocytic apparatus and the endoplasmic reticulum in the rat yolk-sac endoderm was investigated after loading with horseradish peroxidase-conjugated concanavalin A by intrauterine administration. After 30 min, small vesicles (50-150 nm in diameter), small tubules (80-100 nm in diameter) and large vacuoles (0.2-1.0 microns in diameter) in the apical cytoplasm were labeled with the tracer, but lysosomes (1.0-3.5 microns in diameter) in the supranuclear cytoplasm were not labeled until 60 min after loading. Stereo-viewing of the labeled small tubules in thick sections revealed that they were not isolated structures but formed three-dimensional anastomosing networks, which were also confirmed by scanning electron microscopy after maceration with diluted osmium tetroxide. Their earlier labeling with the endocytic tracer, localization in the apical cytoplasm and three-dimensional network formation indicated that the labeled small tubules represented tubular endosomes (tubular endocytic apparatus). These well-developed membranous networks provided by the tubular endosomes are suggested to facilitate the receptor-mediated endocytosis and transcytosis of the maternal immunoglobulin in the rat yolk-sac endoderm. Scanning electron microscopy further revealed lace-like networks of the smooth endoplasmic reticulum near the lateral plasma membrane. Their possible involvement in transport of small molecules or electrolytes is discussed.

Tight junctions and paracellular permeability in cultured bovine corneal endothelial cells

Intramembrane specializations of cultured bovine corneal endothelial cells were studied with thin section and freeze-fracture electron microscopy and related to the paracellular permeability and the transendothelial resistance (Rt) of the monolayers. The following intercellular junctions were found: single and discontinuous networks of tight junctions (TJ) which girdle the apico-lateral cell perimeter incompletely, gap junctions, and membrane undulations suggesting intermediate junctions. The macromolecular tracer ruthenium red penetrated into the lateral intercellular space beyond the level of the incomplete belt of TJ. Rt of these monolayers was 20.9 +/- 1.0 omega.cm2. Protamine induced a reversible increase of Rt to 118 +/- 5% of its control value. We conclude that incomplete belts of TJ may be the morphological counterpart of the high paracellular permeability of this monolayer and functionally and morphologically resemble those of their native endothelium. Cultured corneal endothelial cells are an excellent model for studying the influence of incomplete belts of TJ on paracellular permeability of cells.

Distribution of carbohydrates in the zona pellucida of human oocytes

The purpose of the present study was to investigate the distribution pattern of carbohydrates in the zona pellucida of human oocytes using lectins and ruthenium red as histochemical probes. For lectin analyses, oocytes that failed to undergo fertilization following in vitro insemination were collected, washed, fixed with glutaraldehyde and embedded in araldite. For ruthenium red labelling, the oocytes were fixed with glutaraldehyde containing ruthenium red, post-fixed with OsO4 and embedded in araldite. Araldite sections (1 micron) were de-resined with sodium methoxide, rehydrated, labelled with ten different biotinylated lectins as probes and avidin-biotin-peroxidase complex as visualant, and examined under a light microscope. The zonae pellucidae of all oocytes studied exhibited a common lectin-binding pattern, expressed in intense binding of lectins from Concanavalia ensiformis (ConA), Lens culinaris (LCA), Ricinus communis (RCA-I), wheat germ agglutinin (WGA), and of succinylated WGA (S-WGA). Peanut lectin (PNA) bound to the zona pellucida only after neuraminidase treatment, whereas the lectins from Griffonia simplisifolia (GS-I), Dolichos biflorus (DBA), Ulex europhaeus (UEA-I) and soybean (SBA) did not bind at all. There was almost no binding of ruthenium red to the matrix of the zona pellucida. The results indicate that the human zona pellucida is characterized by normally exposed mannosyl, N-acetylglucosaminyl and beta-galactosyl residues. In addition, it contains masked beta Gal-(1-3)GalNAc sugar sequences that can be exposed only after removing terminal sialic acid residues.(ABSTRACT TRUNCATED AT 250 WORDS)

A ruthenium-103 red dot blot assay specific for nanogram quantities of sulfated glycosaminoglycans

Ruthenium-103 red has been used previously to detect nanogram quantities of glycosaminoglycans after they have been separated by electrophoresis on cellulose diacetate. We have applied the critical electrolyte principle to the binding of this dye to polyanions. This eliminates interaction with nucleic acids and hyaluronan. After samples are digested with chondroitinase ABC the method allows the measurement of chondroitin sulfates and heparan sulfates at the 2-ng level in dot blots of tissue extracts.

Effects of luxabendazole on the tegument of Fasciola hepatica

The effects in vivo of 5, 10, and 20 mg/kg of luxabendazole (LBZ) on the tegument of Fasciola hepatica have been examined 48 h, 7 days and 14 days post-treatment of experimentally-infected rats. As early as 48 h post-treatment, the drug is shown to provoke significant damage to the tegument. The pathological phenomena characterizing LBZ damage are blebbing of the apical plasmalemma, formation of microvillus-like projections over the free surface, swelling of the basal infolds and stimulation of autophagy. The spines are often fractured; the tegument in the vicinity of spines seems more strongly altered than that in other foci. The basal layer is often changed, from increase of electron density to lack of integrity with the apical cytoplasm. The progress of the ultrastructural damage with time is not expressed. However, cytochemical data show that a longer post-treatment intervals the surface-coat structure becomes irregular and patches of ruthenium red positive material of variable thickness are focally accumulated. Only a slight dose-effect is noted 48 h after LBZ application when the alterations provoked by 5 mg/kg are less evident than those by 10 and 20 mg/kg.

Production of slime polysaccharides by Shigella dysenteriae type 1

Electron microscopy of ruthenium red-stained ultrathin section of strains of Shigella dysenteriae type 1 grown in the Casamino Acids-yeast extract broth medium showed the presence of an extracellular slime layer. The slime appeared as a dense sheath covering bacteria. The presence of slime promoted hemagglutinating activity of the bacteria. The slime polysaccharide (SPS) isolated from the cell-free culture supernatant or the bacterial surface was less than 162,000 daltons in size and immunochemically similar. The SPS showed cross-reaction with lipopolysaccharide (LPS) antigen in immunological tests; however, it also appeared to be different from LPS since it did not contain 2-keto-3-deoxyoctonate, a core sugar of LPS. A different pattern of separation from LPS was also observed by silver staining of SDS-polyacrylamide gels. From these data it appeared that either LPS and SPS are contaminated with each other or that SPS is the polysaccharide portion of LPS.

Adenosine discriminates between the caffeine and adenine nucleotide sites on the sheep cardiac sarcoplasmic reticulum calcium-release channel

Calcium-release channels of sheep cardiac sarcoplasmic reticulum were incorporated into phosphatidylethanolamine bilayers and single channel currents were recorded under voltage-clamp conditions. The effect of adenosine on single channel conductance and gating was investigated, as were the interactions between adenosine and caffeine and adenosine and alpha, beta-methylene ATP. Addition of adenosine (0.5-5 mM) to the cytosolic but not the luminal side of the membrane increased the open probability of single calcium-activated calcium-release channels by increasing the frequency and duration of open events, yielding an EC50 of 0.75 mM at 10 microM activating Ca2+. Addition of 1 mM caffeine potentiated the effects of adenosine at 10 or 100 microM-activating cytosolic calcium, but had no effect on the inability of adenosine to activate the channel at 80 pM calcium, suggesting discrete sites of action on the calcium-release channel for adenosine and caffeine. In contrast, addition of 100 microM alpha, beta-methylene-ATP decreased single channel open probability in the presence of adenosine, suggesting that these compounds act on the same site on the channel. Activation of single channel opening by adenosine, or by adenosine together with caffeine, had no effect on single channel conductance or the Ca2+/Tris+ permeability ratio. Channels activated by adenosine were characteristically modified by ryanodine and blocked by microM ruthenium red or mM magnesium. These results show that adenosine activates the sheep cardiac sarcoplasmic reticulum Ca(2+)-release channel by increasing the frequency and duration of open events in a Ca(2+)-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Protective effect of various calcium antagonists against an experimentally induced calcium overload in isolated hepatocytes

The effect of the hepatotoxic substance diamidinothionaphthene (98/202) on cytosolic, mitochondrial and extra-mitochondrial calcium distribution was measured in isolated rat hepatocytes. The drastic disturbance of the intracellular calcium homeostasis caused by this substance (increase of the cytosolic and mitochondrial calcium contents and depletion of extra-mitochondrial calcium stores, which at last lead to cell death) gave rise to an investigation of the possible cytoprotective effect of calcium antagonists of various chemical classes: verapamil, diltiazem, and nifedipine on isolated hepatocytes. Our results show that all three calcium antagonists prevented cell death caused by 98/202. The 98/202-induced increase of cytosolic and mitochondrial calcium content was inhibited by all three calcium antagonists. However, only verapamil was able to inhibit the depletion of extra-mitochondrial calcium stores. Since 98/202-induced cell death occurs only in the presence of extracellular calcium, it is concluded that calcium antagonists are also able to inhibit the influx of extracellular calcium in liver cells, which leads to a calcium overload of the cytosol and mitochondria. The various ways of interfering with the calcium homeostasis of liver cells qualifies the hepatotoxic substance 98/202 as a suitable in vitro hepatotoxicity model for testing the hepatoprotective effect of different calcium antagonists.

cGMP mobilizes intracellular Ca2+ in sea urchin eggs by stimulating cyclic ADP-ribose synthesis

Many hormones or neurotransmitters act at cell surface receptors to increase the intracellular free calcium concentration, triggering a wide range of cellular responses. As the source of this Ca2+ is often internal stores, additional messengers are required to convey the hormonal message from the plasma membrane. Cyclic ADP-ribose (cADPR) has been proposed as the endogenous activator of Ca(2+)-induced Ca2+ release by the ryanodine receptor in sea urchin eggs and in several mammalian cell types. A second messenger role for cADPR requires that its intracellular levels be under the control of extracellular stimuli. Here we demonstrate a novel action of 3',5'-cyclic guanosine monophosphate (cGMP) in stimulating the synthesis of cADPR from beta-NAD+ by activating its synthetic enzyme ADP-ribosyl cyclase in sea urchin eggs and egg homogenates. We suggest that cADPR may transduce signals generated by cell surface receptors or gaseous transmitters linked to cGMP production.

Morphological and histochemical changes in intercellular junctional complexes in epithelial cells of mouse small intestine upon X-irradiation: changes of ruthenium red permeability and calcium content

Changes of calcium-content and permeability of tight junction following X-irradiation were investigated in mouse intestinal epithelial cells by electron microscopy. In the control animals the lower parts of tight junctional area as well as the other junctional elements and the intercellular space are labeled by pyroantimonate precipitates, which contain calcium as revealed by electron spectroscopy and electron energy loss spectrometry. X-irradiation, parallel with morphological changes, lead to rapid decrease of pyroantimonate precipitable calcium content and increase of the permeability of tight junctions indicated by the penetration of ruthenium red into the intercellular space. These changes were readily reversible following 0,5 Gy doses of irradiation however, they persisted up to 24 hours following 5 Gy irradiation. We conclude that irradiation at the applied doses can transiently destabilize the tight junctions in the epithelial layer of the small intestine, presumably through a calcium dependent mechanism.

Structural heterogeneity of the diffuse intimal thickening and correlation with distribution of TGF-beta 1

This study examines the ultrastructural features of diffuse intimal thickenings of human coronary arteries and correlates structural heterogeneity along the radial axis with the distribution and known actions of transforming growth factor beta 1 (TGF-beta 1). Morphometric and immunohistochemical data were collected from thickenings of varying widths, sampled at autopsy from 19 persons ranging in age from 3 months to 81 years. Thickenings were characterised by an inner proteoglycan layer (PGL), up to approximately 70 mm wide, and an underlying variable-width musculofibrous layer (MFL). The PGL was characterised by low volume fractions (v/fs) for collagen, elastin, basement membranes and cells and a high v/f for matrix space; v/fs for the MFL components were more evenly distributed. Proteoglycans were visualised by ruthenium red staining, quantified and sized. Densities of large (versican; > 20 nm) and small (< 20 nm) granules changed little across intimal thickenings. Mean diameters of matrix space granules increased with increasing intimal thickness and notably were significantly (p < 0.001) larger in the PGL than the MFL. In contrast, diameters of collagen-associated small granules (decorin) did not differ between the PGL and MFL. TGF-beta 1 staining was detected in 70% of vessels examined and occurred almost exclusively in the PGL, although showed a patchy distribution. Both the distribution of TGF-beta 1 and its known differential effects on versican and decorin synthesis suggest that it may play a significant role in the formation and maintenance of the PGL.

Intracellular penetration of ruthenium red in embryonic nervous tissue

Electron microscopic investigations, using ruthenium red revealed that dye is usually observed in immature neuronal cells in autonomic ganglia of rat embryos and fetuses. Ruthenium red does not penetrate undamaged neurons in mature ganglia. Ruthenium red positive material covers neuronal cell plasmalemma even in early primordial phases of autonomic ganglia. Plasmalemma of growth zones does not react with ruthenium red. Intracellular penetration of immature neurons by ruthenium red, according to expectation, depends on damage to cell membrane due to the fixation procedure, especially in the growth zones.

Effects of epidermal growth factor versus phorbol ester on kidney epithelial (LLC-PK1) tight junction permeability and cell division

In polarized epithelia, the tight junctions (TJs) constitute a barrier that controls the paracellular flux of solutes and water. In the renal LLC-PK1 cells, the TJ permeability can be correlated directly with the unidirectional transepithelial flux of solutes, such as D-mannitol, which have negligible affinity for cell membrane transport systems, and inversely to the transepithelial electrical resistance (TER). This study investigates TJ permeability and cell proliferation in LLC-PK1 cells treated with the phorbol ester, tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA) or with epidermal growth factor (EGF), a mitogen without secondary carcinogenic effects. Both TPA and EGF induced mitogenesis in LLC-PK1 cells. The TJs in TPA-treated cells were leaky, as indicated by decreased TER, increased D-mannitol flux, and TJ penetration by ruthenium red. In contrast, EGF treatment did not result in a decrease in TER, only slightly increased the D-mannitol flux, and did not result in ruthenium red penetration of the TJs. This inability of ruthenium red to penetrate TJs between EGF-treated epithelial cells was true even for cells in mitosis. The data therefore indicate that mitogenesis per se does not increase TJ permeability, suggesting that the TJ leakiness observed during tumor promotion with phorbol esters does not arise from cell proliferation and is perhaps associated distinctly with or causal to the transformation of those cells.