Expression of Fas antigen and apoptosis caused by 5,10,15, 20-tetra(4-methoxyphenyl)porphyrin (TMP) on carcinoma cells: implication for photodynamic therapy

The photodynamic effects of 5,10,15, 20-tetra(4-methoxyphenyl)porphyrin (TMP) on a Hep-2 cell line were investigated. TMP toxicity in the dark and in relation to illumination with visible light was examined. Hep-2 cells were treated with different TMP concentrations (1, 5 and 10 microM). The uptake of TMP by Hep-2 cells increased with TMP concentration and an increase of the initial uptake rate was observed with increasing TMP concentrations. However, after 24 h of incubation, a similar value of intracellular TMP concentration was reached at all three concentrations of TMP added. Cell toxicity induced by TMP was analyzed in the dark at different concentrations of the photosensitizer and at several incubation periods. The cell mortality obtained after exposure of the cell cultures to visible light was exclusively due to the photosensitization effect of TMP produced by light irradiation. Staining with the hematoxylin-eosin method demonstrated that treatment with TMP, followed by exposure to visible light, notably increased the apoptotic figures. Fas antigen was only expressed in these conditions. The results contribute to the understanding of the photodynamic therapy (PDT) mechanism produced by TMP on Hep-2 carcinoma cell line.

Breast cancer cell line MDA-231 stimulates osteoclastogenesis and bone resorption in human osteoclasts

Breast cancers commonly cause osteolytic metastases in bone, a process that is dependent upon osteoclast-mediated bone resorption, but the mechanism responsible for tumor-mediated osteoclast activation has not yet been clarified. In the present study we utilized a well-known human breast cancer cell line (MDA-231) in order to assess its capability to influence osteoclastogenesis in human bone marrow cultures and bone resorption in fully differentiated osteoclasts. We demonstrated that conditioned medium (CM) harvested from MDA-231 increased the formation of multinucleated TRAP-positive cells in bone marrow cultures. Bone resorption activity of fully differentiated human osteoclasts and of osteoclast-like cell lines, from giant cell tumors of bone (GCT), was highly increased by the presence of MDA-231 CM. Moreover, while MDA-231 by themselves did not produce IL-6 tumor cell, CM increased the secretion of IL-6 by primary human osteoclasts and GCT cell lines compared to untreated controls. These data suggest that MDA-231 produce osteoclastic activating factor(s) that increase both osteoclast formation in bone marrow culture and bone resorption activity by mature cells. Moreover, breast cancer cells stimulate IL-6 secretion by osteoclasts that is one of the factors known to supports osteoclastogenesis.

Effects of alpha-difluoromethylornithine on the cyclin A expression in Hep-2 cells

DFMO is an irreversible inhibitor of ornithine decarboxilase (ODC), the key enzyme in mammalian polyamine biosynthesis. The goal of this study was to determine the effects of DFMO on the expression of cyclin A at different stages of the cell cycle of Hep-2 cells. The cell cycle analysis, done by measuring the incorporation of thymidine in the cell DNA, revealed that DFMO produced a lower and constant level of that incorporation; this effect is probably due to the incapacity of the cells to culminate the phase S of the cell cycle. The expression of cyclin A increased in the phases S and G2 in control cells, almost disappearing in phase M. However, in DFMO treated cultures, the expression of cyclin A was increased in M and this effect remained still after 48 h treatment. We conclude that polyamines could exert an effect on the cyclin destruction mechanism, and the depletion caused by DFMO would alter this mechanism.

Apoptosis is regulated by polyamines in the cell cycle of Chinese hamster ovary cells

This paper deals with the relationship between the polyamine metabolism and apoptosis in the different phases of the cell cycle in a Chinese hamster ovary (CHO) cell line. Synchronously growing cells were obtained by the addition of 1.2 mM hydroxyurea and the progression through the cell cycle was monitored by determining the incorporation of 3H-thymidine in the DNA. Ornithine decarboxylase (ODC) activity showed a peak in S phase, while intracellular putrescine and spermine contents increased constantly, reaching to a maximum level at G2 phase; spermidine content doubled during G2 and increased four times during M, compared to G1. The increment in the endogenous polyamine content was associated to a diminished uptake from the medium. The apoptotic index was higher in G2 phase, coinciding with the maximum level observed in putrescine content. The results support the idea that intracellular putrescine level is closely related to apoptosis.

Terminal end of the human odontoblast process: a study using SEM and confocal microscopy

Towards the middle of the eighteenth century, Tomes described the presence of membranous structures of cellular origin inside the dentinal tubules. Subsequent studies have been controversial regarding the terminal end of the odontoblasts. According to Fusayama, this cellular process reaches even the dentinal-enamel junction; others, such as Brännström, believed that this cellular process is present only in the inner third of the dentin. The aim of the present study was to determine the exact area up to which the terminal ends of the odontoblasts extend. With the aid of advanced confocal laser scanning microscopy (CLSM) cylindrical structures were demonstrated inside the tubules even in the absence of odontoblasts. This would confirm that the structures previously described as cellular processes can be identified with the lamina limitans of the peritubular dentin. High resolution field-emission scanning electron microscopy (FE-SEM) provided further evidence that tubular structures are only seen in the inner third of the dentin, towards the pulp.

Esthetic and functional reproduction of occlusal morphology with composite resins

The increasing use of composite resin restorations in posterior sectors produces some difficulties in the exact reproduction of occlusal morphology. In this article we present a new operative method that allows a quick and precise reproduction of occlusal morphology with minimal carious destruction of the occlusal enamel of posterior dental elements in the case of initial carious lesions. This method is indicated for class I and II carious lesions and is based on a preoperative record of the occlusal morphology made with a transparent silicone mold. This mold is placed on the tooth after the application of the last layer of composite resin, which is then polymerized through the silicone. Illustrated as a clinical case, the method is particularly rapid, easy to perform, and contributes to the improved quality and subsequent success of composite restorations in posterior sectors.

[Polishing of composite resins. Instrumental notes]

BACKGROUND

The polishing is the last procedure in the application of composite fillings. The surface morphology and the marginal seal, that are indispensable for integration of composite fillings with dental tissue and oral environment, are tightly dependent on polishing procedure.

METHODS

The authors tried out experimental therapeutic procedure in order to examine the surface of any composite resin polymerizated under matrix on a slide before and after polishing made by abrasive disease and finally after application of a new resin layer on a polished composite surface. These composite surfaces was examined with AFM and SEM.

RESULTS

The images prove that in the polished specimens there is a restoration of composite morphology surface because of the partial removal of organic part during the polishing. The polymerization of a new resin layer on polished surface make this one more regular and even as a substitute for partial removal of organic part during the polishing.

CONCLUSIONS

The experimental procedure prove that the ideal composite surface is that polymerizated under matrix because every treatment on this surface affect the composite filling's quality.

Hyaluronic acid by atomic force microscopy

Hyaluronic acid (HA) of different molecular weights has been examined by atomic force microscopy (AFM) in air. This technique allows 3-D surface images of soft samples without any pretreatment, such as shadowing or staining. In the present study we examined the supermolecular organization of HA chains when deposited on mica and graphite, to better understand the interchain and intrachain interactions of HA molecules in solution. The concentration of the solution deposited varied from 0.001 to 1 mg/ml. On both substrates, and independent of the concentration, high-molecular-mass HA formed networks in which molecules ran parallel for hundreds of nanometers, giving rise to flat sheets and tubular structures that separate and rejoin into similar neighboring aggregates. Accurate measurements of the thickness of the thinnest sheets were consistent with a monolayer of HA molecules, 0.3 nm thick, strongly indicating lateral aggregation forces between chains as well as rather strong hydrophilic interactions between mica and HA. The results agree with an existing model of HA tertiary structure in solution in which the network is stabilized by both hydrophilic and hydrophobic interactions. Our images support this model and indicate that hydrophobic interactions between chains may exert a pivotal role in aqueous solution.

Extent of the odontoblastic process. Analysis by SEM and confocal microscopy

BACKGROUND

Towards the middle of the eighteenth century, Tomes described membranous structures of cellular origin inside the dentinal tubules. Subsequent studies of the terminal segment of the odontoblasts have been controversial. According to Fusayama, this cellular process reaches as far as the junction; others, including Brännström, affirm that this process is present only in the inner third of the dentin.

AIMS

The aim of the present study was to verify the exact length of the odontoblastic terminal segment with the aid of advanced confocal microscopy (CLSM) and high resolution field-emission scanning electron microscopy (FE-SEM).

METHODS

Premolars due for extraction for orthodontic reasons, were used for this study; vestibular class V cavities about 2 mm in diameter and 3 mm in depth prepared and subsequently filled with IRM (Caulk Dentsply). All teeth were extracted after four weeks fixed and prepared for examination under SEM and CLSM.

RESULTS

CLSM revealed cylindrical structures inside the tubules even in the absence of odontoblasts. SEM evidenced the presence tubular structures only in the inner third of the dentin (towards the pulp).

CONCLUSIONS

Structures previously described as cellular processes can be identified as the lamina limitans of the peritubular dentin.

Alendronate reduces adhesion of human osteoclast-like cells to bone and bone protein-coated surfaces

Bisphosphonates (BPs) are potent inhibitors of bone resorption and are therapeutically effective in disease of increased bone turnover, but their mechanism(s) of action remain to be elucidated. Using as experimental model human osteoclast-like cell lines derived from giant cell tumors of bone, extensively characterized for their osteoclast features, we investigated the adhesive properties of osteoclasts on bone slices and on different proteins of the extracellular matrix in the presence of BPs. Adhesion assays using bone slices pretreated with ALN, at the established active concentration, showed that, although the morphology of osteoclasts plated onto pretreated bone slices was not modified, the number of adherent cells was reduced by the treatment of about 50% vs. controls. The effect of ALN on the adhesion of osteoclast-like cells onto specific extracellular matrix proteins, such as bone sialoprotein-derived peptide, containing the RGD sequence, conjugated to BSA (BSP-BSA) and fibronectin (FN), was also tested. In the case of FN the treatment with ALN of protein-coated wells did not modify the percentage of cell adhesion compared with the control, whereas onto BSP-BSA the presence of ALN significantly reduced adhesion of about 40-45%, suggesting that the inhibitory effect of ALN on cell adhesion could probably be due to the interference with receptors specifically recognizing bone matrix proteins as alphaVbeta3 integrins. Furthermore, ALN induced Ca-mediated intracellular signals in osteoclasts, triggering a 2-fold increase in intracellular calcium concentration.

Study of elastic fiber organization by scanning force microscopy

Elastic fibers of beef ligamentum nuchae were observed by atomic force microscopy and data compared with those obtained by conventional and freeze-fracture electron microscopy. Fresh isolated elastin fibers as well as thin sections of ligament fragments, which were fixed and embedded either in relaxed or in stretched conditions, were analysed. The results confirm that, at least in beef ligamentum nuchae, elastic fibers consist of beaded filaments which can be oriented by stretching in the direction of the force applied. Moreover, atomic force microscopy revealed that these beaded filaments are laterally connected by periodical bridges which become more pronounced upon stretching. The data clearly show that elastin molecules are organized in a rather ordered array, at least at the super-molecular level, and a depiction of the elastin organization in beef ligamentum nuchae is attempted.

Response of Azospirillum brasilense Cd to sodium chloride stress

Growth of Azospirillum brasilense Cd in the presence of different NaCl concentrations showed that it tolerates up to 200 mM NaCl in the medium, without appreciable decline in growth rate. At 300 mM NaCl, a decrease of 66% in growth was observed at 24 h of culture. At 48 h of culture, bacteria in the presence of 300 mM NaCl reached the maximum optical density value that was attained at 12 h by control cultures. This investigation was designed to elucidate the effect of saline stress on Azospirillum brasilense Cd and the physiologic mechanism involved in its possible salinity tolerance. For this reason, studies of other osmolytes, as well as of putrescine metabolism and protein patterns were done with bacteria grown with this NaCl concentration in the medium, at 24 and at 48 hours. A. brasilense responded to saline stress elevating the intracellular concentration of glutamate at 24 h, and of K+ at 48 h. Glucan pattern, putrescine metabolism, and total and periplasmic protein patterns of the treated group showed several changes with respect to the control. In spite of the several cellular functions affected by saline stress, the results imply that A. brasilense Cd shows salinity tolerance in these experimental conditions.

Hyaluronan-phospholipid interactions

Hyaluronan-phospholipid interactions have been studied in vitro by negative staining and rotary shadowing electron microscopy. Hyaluronan (HA) molecules of different molecular weights (around 170,000; 740,000, and 1.9 x 10(6) Da) were added to phospholipid suspensions (DPPC or egg lecithin) that were in the form of either unilamellar particles or multilamellar vesicles. Suspensions were then gently stirred and incubated at different temperatures from 24 hr up to 7 days. After 24 hr, at temperatures just above the melting point of the phospholipid used, both unilamellar particles and multilamellar vesicles were already shown to change their organization in the presence of HA, giving rise to the formation of (1) huge perforated membrane-like structures lying on the substrate; (2) 12-nm-thick "cylinders" (rollers) with a tendency to aggregate and to form sheets. These structures were seen only in the presence of high-molecular-weight HA, whereas low-molecular-weight HA (170 kDa) induced fragmentation of liposomes and formation of a few short rollers. These data show that phospholipids and HA interact and suggest they may also do so in vivo within the joint cavity, where both chemical species are present, giving rise to complexes which might exhibit peculiar lubricating and protective properties. It is also proposed that such interactions may not be as efficient in arthritic joints, where HA is degraded to low-molecular-weight fragments.

Retinoic acid induces cell proliferation and modulates gelatinases activity in human osteoclast-like cell lines

The effect of Retinoic Acid (RA) on human osteoclast-like cell lines, obtained from Giant Cell tumors (GCT) of bone, has been investigated evaluating its action on bone resorption, cell proliferation, microtubular organization and gelatinases expression and activity. Increasing concentrations of RA significantly dose-dependently decreased GCTs bone resorption, while 10(-7) M RA promoted an increase of cell proliferation. By immunofluorescence we demonstrated that GCTs express A and B gelatinases and, by zymography, that their activity was enhanced in medium collected from GCTs cultured in the presence of 10(-7) M RA. These data indicate that RA increases cell proliferation and modulates metalloproteinases (MMPs) activity, crucial events during the migration of osteoclast precursors toward bone surfaces.

Scanning electron microscopic evaluation of resin-dentin and calcium hydroxide-dentin interface with resin composite restorations

Calcium hydroxide has been used as a liner in resin composite restorations to protect the pulp. Recent research has demonstrated that pulpal inflammation is caused by microleakage of restorations and by the subsequent passage of bacteria. The present study involved scanning electron microscopic observation of cross-sections of resin composite-dentin interfaces after the interposition of a layer of calcium hydroxide. A new-generation adhesive system that involves etching of the dentin was used. Ultrastructural analysis indicated that polymerization shrinkage of the resin composite caused the separation of the calcium hydroxide from the dentinal surface, forming 8- to 15-micron-wide interfacial gaps in 100% of the areas studied. Where the adhesive was applied directly to dentin, it adhered closely, forming a gap-free attachment with evidence of an acid-resistant hybrid layer (4 to 6 microns in thickness) and resin tags of various lengths that hermetically sealed the dentinal tubules.

2,4-Dichlorophenoxyacetic acid affects the attachment of Azospirillum brasilense Cd to maize roots

2.4-Dichlorophenoxyacetic acid (2,4-D) is a herbicide widely applied to forage, grain and cereals. We previously determined that 1 mM 2,4-D diminished cell growth and cellular activity of Azospirillum brasilense Cd. The present work was designed to determine the possible effect of this herbicide--at concentrations used on crops--on the attachment of the bacteria to maize roots, since this step is of prime importance for the growth stimulation of the plant obtained with Azospirillum brasilense. In this paper we demonstrate that 2,4-D alters the bacterial adhesion to maize roots.

Characterization of 2,4-dichlorophenoxyacetic acid transport and its relationship with polyamines in Azospirillum brasilense

We have previously shown that 2,4-dichlorophenoxyacetic acid (2,4-D) inhibits Azospirillum brasilense growth, the synthesis of DNA, RNA and proteins. These toxic effects are prevented when polyamines are added to the culture medium. The purposes of our research were to determine the effects of the herbicide on the number of viable Azospirillum brasilense cells, characterize the 2,4-D transport system and to study the effects of polyamines upon the latter in this microorganism. We found that 2,4-D reduced the number of viable cells and that 2,4-D transport is energy-independent, since it was not affected by metabolic inhibitors. Polyamines did not alter 2,4-D uptake, further supporting the hypothesis that the herbicide most likely produces its toxic effects by interfering with the polyamine metabolism.

Marginal seal and biocompatibility of a fourth-generation bonding agent

OBJECTIVES

The pulpal reaction and the marginal sealing of in vivo restored samples using resin composite and Scotchbond Multi-Purpose adhesive system (3M Dental Products) were analyzed in this study.

METHODS

Twelve Class I non-exposed cavity preparations were placed on premolars to be removed for orthodontic reasons. They were restored and observed at 7 d and 28 d.

RESULTS

The examination of the resin-dentin interface under the scanning electron microscope (SEM) revealed: 1) a gap-free attachment between adhesive resin and dentinal surface in 80% of the areas studied, 2) penetration of resin tags into the dentinal tubules, and 3) formation of a 3-5 micrometer thick acid-resistant hybrid layer. Microfissures measuring about 10 micrometers were observed in only 20a% of the areas studied; these were located along the walls of the cavities, especially near the enamel in zones where there was a lower concentration of dentinal tubules. The histological analysis, carried out 7 d after preparation of the restoration, did not show any alteration of the pulp. After 4 wk, reparative dentin was produced in the pulpal areas corresponding to the restored cavities.

SIGNIFICANCE

The quantity of newly formed dentin is correlated with the distance from the cavity to the pulp. The results indicate that acid-etching of vital dentin using 10% maleic acid does not impair pulpal healing in deep Class I cavities and that the Scotchbond Multi-Purpose adhesive system is able to preserve the morphological and biological integrity of the pulpo-dentinal complex.

Dentinal adhesive with composite restorations: a clinical and microstructural evaluation

It is generally accepted that the application of dentin-enamel adhesive should involve not only the etched enamel but also the dentinal surface. For this purpose, new bonding agents requiring dentin etching and the combined use of bifunctional groups (Primers) as well as hydrophilic resins have been introduced. This study used scanning electron microscopy to analyze the relationship between dentin and fluid resin of three bonding agents. The results demonstrated that the adhesive monomers easily penetrated the etched dentin, sealing the dentinal tubules and creating a resin dentin interdiffusion zone (hybrid layer). As a result, the microleakage between dentin and resin composite restorations, responsible for postoperative tooth sensitivity, pulpal inflammatory reaction, and secondary decay, is greatly reduced.

[Micromorphological aspects of dentin]

Samples of dentine of healthy teeth were analysed in this study with at the scanning electron microscope. In order to see the morphological changes in the structure of both the dentine and the dentinary tubules, the dentine was observed at different levels according to the distance from the pulp. After the removal of the odontoblasts the predentine appears to be composed only by collagen fibres and is about 15 microns thick. At this level, the dentinary tubules can reach a diameter of 4 microns. This measure decreases progressively in proportion to the distance from the pulp, reaching about 2 microns at a distance of 1 mm, and 1 micron at 2 mm from the pulp. A decrease in the tubular lumina is observed when the peritubular dentine changes from 0.8 to 1 in thickness. The internal surface of the tubules appears smooth and shows the confluence of very thin lateral canaliculi. The dentinary tubules end forming forks which spread out until they enter into contact with the enamel.

Effects of 2,4-dichlorophenoxyacetic acid on polyamine transport and metabolism in Azospirillum brasilense Cd

We had previously demonstrated that 1 mM 2,4-D inhibited cell growth, nucleic acid synthesis and protein synthesis (at the ribosomal level) of Azospirillum brasilense. These alterations were prevented by the presence of polyamines in the culture medium. On the other hand, polyamines did not affect the 2,4-D uptake. In this paper we demonstrate that 2,4-D alters the metabolism of polyamines and increases their uptake.