Radiosensitization of hypoxic tumor cells by depletion of intracellular glutathione

Depletion of glutathione in Chinese hamster ovary cells in vitro by diethyl maleate resulted in enhancement of the effect of x-rays on cell survival under hypoxic conditions but not under oxygenated conditions. Hypoxic EMT6 tumor cells were similarly sensitized in vivo. The action of diethyl maleate is synergistic with the effect of the electron-affinic radiosensitizer misonidazole, suggesting that the effectiveness of misonidazole in cancer radiotherapy may be improved by combining it with drugs that deplete intracellular glutathione.

Pegylated nanoparticles based on poly(methyl vinyl ether-co-maleic anhydride): preparation and evaluation of their bioadhesive properties

Pegylated nanoparticles based on poly(methyl vinyl ether-co-maleic anhydride) (PVM/MA) were prepared by simple solvent displacement method, in the absence of catalysts or specific chemical conditions. Pegylation efficiency increased with the increasing of molecular weight and bulk concentration of poly(ethylene glycols) (PEGs) investigated. In fact, the use of PEG with molecular weight less than 1000 Da did not lead to its attachment. 1H NMR spectroscopy was performed in order to estimate the conformation state of PEG-chains and to predict the nanoparticle structure. Pegylation with PEG 2000 gave surface modified nanoparticles ("brush" conformation), while the chains of PEG 1000 were distributed either in the core or physically adsorbed on the nanoparticle surface. The capacity of nanoparticles to adsorb mucin at pH 7.4 was significantly higher for PEG 1000-NP than for PEG 2000-NP. The "brush" layer seemed to decrease the interaction between PEG 2000-NP and mucin, which facilitated their penetration through the mucus gel. As a consequence, PEG 2000-NP displayed higher capacity to develop adhesive interactions with rat intestinal mucosa in vivo. Independent on the weaker bioadhesive potential of PEG 1000-NP, both types of pegylated nanoparticles demonstrated very high affinity to the intestinal mucosa rather than to the stomach wall, which could be established for drug targeting to the small intestine.

Human cutaneous vulvar reactivity to irritants

To better understand the cutaneous reactivity of vulvar skin, two chemical irritants were applied topically to 21 subjects. The forearm of each subject served as a comparative control. Test sites remained open and were read at 24 hours. A significantly increased response to the irritants was noted on the vulvar skin.

Copoly(styrene-maleic acid)−Pirarubicin Micelles: High Tumor-Targeting Efficiency with Little Toxicity1

The copolymer of styrene-maleic acid (SMA) was used to construct micelles containing pirarubicin (4'-O-tetrahydropyranyladriamycin, or THP) as a new anticancer drug formulation. The procedure for the preparation of the micelles was simple, the component consisting of only SMA and pirarubicin in a noncovalent association, possibly by hydrophobic interaction between the styrene portion of SMA and pirarubicin chromophore. This method ensures more than 80% recovery of pirarubicin by weight, and 60% of drug loading (by weight) was achieved. The micelles obtained (SMA-THP) showed high solubility in water and a constant pirarubicin release rate of about 3-4%/day in vitro. SMA-THP micelles had an average molecular size of about 34 kDa according to gel chromatography; this size is a marked increase from the 627.6 Da of free THP, which suggests the formation of a micellar structure. When albumin was added, the molecular size of the micelles increased to about 94 kDa, which indicates binding to albumin, a unique characteristic of SMA. SMA-THP micelle preparation had a cytotoxic effect (93-101%) on MCF-7 breast cancer cells and SW480 human colon cancer cells in vitro that was comparable to that of free THP. An in vivo assay of SMA-THP at doses of 20 mg/kg in ddY mice bearing S-180 tumor revealed complete tumor eradication in 100% of tested animals. Mice survived for more than 1 year after treatment with micellar drug doses as high as 100 mg/kg pirarubicin equivalent. This marked antitumor activity can be attributed to the enhanced permeability and retention (EPR) effect of macromolecular drugs seen in solid tumors, which enables selective delivery of drugs to tumor and thus much fewer side effects. Complete blood counts, liver function test, and cardiac histology showed no sign of adverse effects for intravenous doses of the micellar preparation. These data thus suggest that intravenous administration of the SMA-THP micellar formulation can enhance the therapeutic effect of pirarubicin more than 50-fold.

Hepatic xenobiotic metabolism of cylindrospermopsin in vivo in the mouse

Cylindrospermopsin (CYN) is a hepatotoxin isolated from the blue-green alga Cylindrospermopsis raciborskii. The role of both glutathione (GSH) and the cytochrome P450 enzyme system (P450) in the mechanism of toxicity of CYN has been previously investigated in in vitro systems. We have investigated the role of GSH and P450 in vivo in mice. Mice pre-treated with buthionine sulphoximine and diethyl maleate to deplete hepatic GSH prior to dosing with 0.2mg/kg CYN showed a seven-day survival rate of 5/13 while the control group rate was 9/14. Dosing mice with 0.2mg/kg CYN produced a small decrease in hepatic GSH with a characteristic rebound effect at 24h. The magnitude of this effect is however small and combined with the non-significant difference in survival rates after GSH depletion suggest depletion of GSH by CYN could not be a primary mechanism for CYN toxicity. Conversely, pre-treatment with piperonyl butoxide, a P450 inhibitor, protected mice against CYN toxicity giving a survival rate of 10/10 compared with 4/10 in the control group (p < 0.05 Chi squared) and was protective at doses up to 0.8 mg/kg, suggesting activation of CYN by P450 is of primary importance in the mechanism of action.

Poly(styrene-co-maleic acid)-based pH-sensitive liposomes mediate cytosolic delivery of drugs for enhanced cancer chemotherapy

pH-responsive polymers render liposomes pH-sensitive and facilitate the intracellular release of encapsulated payload by fusing with endovascular membranes under mildly acidic conditions found inside cellular endosomes. The present study reports the use of high-molecular weight poly(styrene-co-maleic acid) (SMA), which exhibits conformational transition from a charged extended structure to an uncharged globule below its pK(1) value, to confer pH-sensitive property to liposomes. The changes in the co-polymer chain conformation resulted in destabilization of the liposomes at mildly acidic pH due to vesicle fusion and/or channel formation within the membrane bilayer, and ultimately led to the release of the encapsulated cargo. The vesicles preserved their pH-sensitivity and stability in serum unlike other polymer-based liposomes and exhibited no hemolytic activity at physiological pH. The lysis of RBCs at endosomal pH due to SMA-based liposome-induced alterations in the bilayer organization leading to spherocyte formation indicated the potential of these vesicles to mediate cytosolic delivery of bio-active molecules through endosome destabilization. The SMA-loaded liposomes exhibiting excellent cytocompatibility, efficiently delivered chemotherapeutic agent 5-Fluorouracil (5-FU) within colon cancer cells HT-29 in comparison to neat liposomes. This caused increased cellular-availability of the drug, which resulted in enhanced apoptosis and highlighted the clinical potential of SMA-based vesicles.

Gantrez® AN nanoparticles as an adjuvant for oral immunotherapy with allergens

The aim of this study was to investigate the adjuvant properties of oral-administered Gantrez AN nanoparticles with ovalbumin (as allergen model) and, in some cases, lipopolysaccharide of Brucella ovis as immunomodulator. For this purpose, BALB/c mice were administered by oral gavage with OVA nanoparticles and both Th1 and Th2 markers (IgG2a and IgG1, respectively) were enhanced. On the other hand, these carriers administered by oral route were able to protect a model of sensitized mice to ovalbumin from anaphylactic shock. These results are highly suggestive for the valuable use of Gantrez nanoparticles in oral immunotherapy with allergens.

Characterization of metallothionein-I-transgenic mice

A metallothionein-I-transgenic mouse strain (MT-TG) was characterized to determine whether they would be suitable to study the functions of this protein. MT-TG mice were visually indistinguishable from nontransgenic littermate controls, but had 10- to 20-fold higher basal levels of MT protein in pancreas, liver, and stomach, as well as 2- to 6-fold higher MT protein levels in other organs (kidney, intestine, uterus, testes, spleen, heart, and lung) than control mice, as determined by the Cd/hemoglobin assay. The MT-TG mice had 50% more Zn in liver and 300% more Zn in pancreas than control mice. Interestingly, female MT-TG mice have 4- to 5-fold higher MT levels in liver than those of males. To determine whether MT can be further increased by well-known MT inducers, control and MT-TG mice were given Zn (200 mumol/kg), Cd (20 mumol/kg), or diethyl maleate (DEM, 5 mmol/kg), and tissue MT concentrations were measured 24 hr later. MT-TG mice responded to MT inducers in a manner similar to control mice. The hepatic antioxidant components (glutathione (GSH), GSH-peroxidase, GSH-reductase, GSH S-transferase, superoxide dismutase, DT-diaphorase, and catalase) of MT-TG mice were not different from those of controls. The cytochrome P450 enzymes (total P450, b5, NADPH cytochrome c reductase) were normal in these MT-TG mice. The activities of CYP1A, CYP2B, and CYP2E enzymes in MT-TG mice were also similar to those of controls, as determined by ethoxy- and pentoxyresorufin O-dealkylation and chlorzoxazone 6-hydroxylation. Thus, MT-TG mice appear to be a good model for studying functions of MT.

The relationship between bond strength and orthodontic bracket base surface area with conventional and microetched foil-mesh bases

The aim of this study was to test the effects on the shear bond strength by sandblasting bracket base surfaces, reducing base surface area, and etching enamel with various acid types. Four different base sizes, used as either standard (untreated), sandblasted or microetched were bonded with Phase II resin (Reliance Orthodontic Products, Inc.) in four groups of 12 bovine enamel specimens after enamel etching with phosphoric acid gel (37%), 37% phosphoric acid aqueous solution, 10% maleic acid gel, or 10% maleic acid aqueous solution. Storage of samples was for 7 days in distilled water at room temperature before shear bond testing with an Instron universal testing machine with a crosshead speed of 0.5 mm/min. Statistical analyses included the analysis of variance, the Student t test, and the Chi-square test at p < 0.05. An increase in shear bond strength was associated with sandblasting and microetching of foil-mesh bases for all base sizes (p < 0.05). No statistically significant difference in shear bond strength existed between the three larger base sizes, which indicated that shear bond strength is independent of surface area between 6.82 and 12.35 mm2. A reduction in bond strength was associated with the reduction of base surface area from 6.82 to 2.38 mm2 (p < 0.05). There appears to be no need to increase base surface area beyond 6.82 mm2. Aqueous maleic acid (10%) etching of the enamel was associated with the highest shear bond strength, with no statistically significant difference between the other three acids used.

Chitosan and poly(methyl vinyl ether-co-maleic anhydride) microparticles as nasal sustained delivery systems

An original dosage form for nasal delivery based on the encapsulation of hydrophilic drug in chitosan-poly(methyl vinyl ether-co-maleic anhydride) (CH-PVM/MA) microparticles prepared by spray-drying technique was developed. Microparticles were characterized in terms of morphology, size, swelling properties, encapsulation efficiency and drug release. The physical state of the drug and the polymer was determined by scanning electron microscopy (SEM) and infrared spectroscopy (IR). Propranolol hydrochloride (PH) was a beta-blocker, used for the treatment of hypertension and was chosen as a model of hydrophilic drug. SEM studies showed spherical particles with smooth surfaces for chitosan hydrochloride (CH-HCl), whereas rather gross surface defects resulted from the incorporation of poly(methyl vinyl ether-co-maleic anhydride) (PVM/MA). In vitro release studies revealed a sustained release of propranolol HCl from microparticles and in particular chitosan hydrochloride provided the lowest release of drug.

In vitro and in vivo evaluation of tumor targeting styrene-maleic acid copolymer-pirarubicin micelles: Survival improvement and inhibition of liver metastases

Pirarubicin is a derivative of doxorubicin with improved intracellular uptake and reduced cardiotoxicity. We have prepared a micellar formulation of pirarubicin using styrene-maleic acid copolymer (SMA) of mean molecular weight of 1.2 kDa, which exhibits a mean diameter of 248 nm in solution. Being a macromolecule, SMA-pirarubicin micelles exhibit excellent tumor targeting capacity due to the enhanced permeability and retention (EPR) effect. Here we report the antitumor activity of SMA-pirarubicin micelles on human colon and breast cancer cell lines in vitro, and a murine liver metastasis model in vivo. Metastatic tumor microvasculature, necrosis, apoptosis, proliferation, and survival were also investigated using immunohistochemistry for Ki-67, active caspase-3, and CD34, respectively. Drug cytotoxicity in vitro was assessed using MTT (3-[4,5-dimethyl-2-thiazolyl]-2, 5-diphenyl-2H-tetrazolium bromide) assay. In vivo, SMA-pirarubicin was administered at 100, 150, or 200 mg/kg (pirarubicin equivalent). Tumor microvasculature was also assessed using scanning electron microscopy. Styrene-maleic acid copolymer (SMA)-pirarubicin micelles were toxic against human colorectal and breast cancer cells in vitro. IC(50) was at or below 1 muM, free pirarubicin equivalent. In vivo, SMA-pirarubicin at 100 mg/kg reduced tumor volume by 80% and achieved a survival rate of 93% at 40 days after tumor inoculation. Styrene-maleic acid copolymer (SMA)-pirarubicin micelles demonstrated potent antitumor activity in this liver metastases model, contributing to prolonged survival. Histological examination of tumor nodules showed significant reduction and proliferation of tumor cells (>90%). The present results suggest that investigation of the effect of multiple dosing at later time points to further improve survival is warranted.

Bioadhesive properties of Gantrez nanoparticles

Bioadhesive nanoparticles have been proposed as carriers for the oral delivery of poorly available drugs and facilitate the use of this route. This work summarises some experiments describing the bioadhesive potential of Gantrez nanoparticles fluorescently labeled with rhodamine B isothiocyanate. The adhesive potential of Gantrez was found to be stronger when folded as nanoparticles than in the solubilised form. Conventional nanoparticles displayed a tropism for the upper areas of the gastrointestinal tract, with a maximum of adhesion 30 min post-administration and a decrease in the adhered fraction along the time depending on the given dose. The cross-linkage of nanoparticles with increasing amounts of 1,3-diaminopropane stabilised the resulting carriers and prolonged their half-life in an aqueous environment; although, the adhesive capacity of nanoparticles, the intensity and the relative duration of the adhesive interactions within the gut as a function of the cross-linking degree. Finally, nanoparticles were coated with either gelatin or albumin. In the first case, the presence of gelatin dramatically decreased the initial capacity of these carriers to interact with the gut mucosa and the intensity of these phenomenons. In the latter, bovine serum albumin coated nanoparticles (BSA-NP) showed an important tropism for the stomach mucosa without further significant distribution to other parts of the gut mucosa.

Mapping of tubule and intertubule surface areas available for bonding in Class V and Class II preparations

OBJECTIVES AND METHODS

The aim of this in vitro study was to evaluate the morphology of dentine in Class V and the Class II preparation walls in terms of tubule orientation, density and increase in surface area after conditioning. Six circular V-shaped preparations were cut at the cementum-enamel junction (CEJ) of anterior teeth and six Class II cavities with the cervical margin 1 mm below the CEJ were prepared in posterior teeth. The preparations were conditioned with 10% maleic acid. The samples were directly studied by SEM. The observations were organized according to location in the preparation, tubule density was counted and the increase in area available for bonding after acid etching was calculated.

RESULTS

Dentine morphology of Class V and Class II preparation walls was mostly regular according to predictable patterns. Between the tubules, along the walls of the cavity, the etched dentine surface exhibited a porous network of collagen fibers. More than 50% of Class V and Class II cavity surface presented oblique or parallel tubule orientation with respect to the cut surface. Because of the presence of a structureless cementum layer. the morphology of the cervical area turned out to be less predictable. The tubule density varied considerably in different regions of the preparations. The intertubular dentine surface area increased after conditioning in Class V preparations from 20.9% to 50.3% on the walls where tubules were cut parallel to their long axis, and from 5.8% to 47.8% where tubules were cut perpendicularly. These same values for Class II preparations ranged from 0.6% to 46.4% on the walls where tubules were cut parallel to their long axis, and 29.8% of the tubules were cut perpendicularly.

CONCLUSIONS

Based on this morphological investigation, the increase in intertubular dentine surface area might very well be responsible for the enhanced bond strength after acid etching of dentine, but not all areas exhibited equal responses to etching. In particular, the bonding substrate at the gingival margins may contribute little in terms of micromechanical retention.

Maleic acid and succinic acid in fermented alcoholic beverages are the stimulants of gastric acid secretion

Alcoholic beverages produced by fermentation (e.g., beer and wine) are powerful stimulants of gastric acid output and gastrin release in humans. The aim of this study was to separate and specify the gastric acid stimulatory ingredients in alcoholic beverages produced by fermentation. Yeast-fermented glucose was used as a simple model of fermented alcoholic beverages; it was stepwise separated by different methods of liquid chromatography, and each separated solution was tested in human volunteers for its stimulatory action on gastric acid output and gastrin release. Five substances were detected by high-performance liquid chromatography and were analyzed by mass spectrometry and 1H-13C nuclear magnetic resonance spectroscopy. At the end of the separation process of the five identified substances, only the two dicarboxylic acids, maleic acid and succinic acid, had a significant (P < 0.05) stimulatory action on gastric acid output (76% and 70% of fermented glucose, respectively), but not on gastrin release. When given together, they increased gastric acid output by 100% of fermented glucose and by 95% of maximal acid output. We therefore conclude that maleic acid and succinic acid are the powerful stimulants of gastric acid output in fermented glucose and alcoholic beverages produced by fermentation, and that gastrin is not their mediator of action.

A proton NMR study of the effect of a new intravasal injectable male contraceptive RISUG on seminal plasma metabolites

Nuclear magnetic resonance (NMR) spectroscopy was used to quantify citrate, glucose, lactate, glycerophosphorylcholine and choline in seminal plasma from subjects injected with a new male contraceptive RISUG, a copolymer of styrene maleic anhydride dissolved in dimethyl sulphoxide, and in seminal plasma from normal ejaculates. No significant difference in the concentration of citrate was observed between the groups, indicating that the prostate is not affected by the contraceptive. The concentrations of glucose, lactate, glycerophosphorylcholine and choline were significantly lower (P < 0.01) in subjects injected with RISUG compared with controls. In addition, metabolite ratios such as choline:citrate, citrate:lactate, choline:lactate and glycerophosphorylcholine:choline were calculated. Citrate:lactate and glycerophosphorylcholine:choline ratios were significantly lower in RISUG-injected subjects than in controls (P < 0.01), thereby indicating the occurrence of partial obstructive azoospermia. The most important finding of the present study was that the intervention of RISUG in the vas deferens even for a period as long as 8 years is absolutely safe and does not lead to prostatic diseases.

Glutathione and cysteine depletion in rats and mice following acute intoxication with diethylmaleate

We examined the dose-dependent glutathione (GSH) depletion in liver, kidney, heart and brain of rats and mice, and cysteine depletion in rat kidney, following i.p. administration of diethylmaleate (DEM). In either rodent, the fall in total GSH concentration in liver and heart reached an upper value of 90 and 80% with 3 and 4 mmol DEM/kg respectively, which did not increase with higher doses. This study suggests that the residual level of GSH corresponds to the mitochondrial pool, in which case DEM might serve as a tool for the measurement of mitochondrial GSH ex vivo. In further experiments, we studied the time course of GSH and cysteine after administration of 3 mmol DEM/kg in rat tissues. Maximal depletion was reached approximately 1 hr after the i.p. injection. Subsequent GSH repletion was fast in liver and kidney, whereas it was slow in heart and brain, with a return to control values by 8-12 and by 48 hr after intoxication, respectively. This study provides new data for cardiac GSH and renal cysteine decrease after intoxication with DEM and should help to optimize GSH depletion models for further pharmacological investigations, especially when the use of inhibitors of glutathione metabolic turnover is undesirable and when side-effects other than GSH depletion must be avoided.

Comparative toxicity of fumigants and a phosphine synergist using a novel containment chamber for the safe generation of concentrated phosphine gas

Background

With the phasing out of ozone-depleting substances in accordance with the United Nations Montreal Protocol, phosphine remains as the only economically viable fumigant for widespread use. However the development of high-level resistance in several pest insects threatens the future usage of phosphine; yet research into phosphine resistance mechanisms has been limited due to the potential for human poisoning in enclosed laboratory environments.

Principal Findings

Here we describe a custom-designed chamber for safely containing phosphine gas generated from aluminium phosphide tablets. In an improvement on previous generation systems, this chamber can be completely sealed to control the escape of phosphine. The device has been utilised in a screening program with C. elegans that has identified a phosphine synergist, and quantified the efficacy of a new fumigant against that of phosphine. The phosphine-induced mortality at 20°C has been determined with an LC₅₀ of 732 ppm. This result was contrasted with the efficacy of a potential new botanical pesticide dimethyl disulphide, which for a 24 hour exposure at 20°C is 600 times more potent than phosphine (LC₅₀ 1.24 ppm). We also found that co-administration of the glutathione depletor diethyl maleate (DEM) with a sublethal dose of phosphine (70 ppm, <LC₅), results in a doubling of mortality in C. elegans relative to DEM alone.

Conclusions

The prohibitive danger associated with the generation, containment, and use of phosphine in a laboratory environment has now been substantially reduced by the implementation of our novel gas generation chamber. We have also identified a novel phosphine synergist, the glutathione depletor DEM, suggesting an effective pathway to be targeted in future synergist research; as well as quantifying the efficacy of a potential alternative to phosphine, dimethyl disulphide.

Multi-targeted inhibition of tumor growth and lung metastasis by redox-sensitive shell crosslinked micelles loading disulfiram

Metastasis, the main cause of cancer related deaths, remains the greatest challenge in cancer treatment. Disulfiram (DSF), which has multi-targeted anti-tumor activity, was encapsulated into redox-sensitive shell crosslinked micelles to achieve intracellular targeted delivery and finally inhibit tumor growth and metastasis. The crosslinked micelles demonstrated good stability in circulation and specifically released DSF under a reductive environment that mimicked the intracellular conditions of tumor cells. As a result, the DSF-loaded redox-sensitive shell crosslinked micelles (DCMs) dramatically inhibited cell proliferation, induced cell apoptosis and suppressed cell invasion, as well as impairing tube formation of HMEC-1 cells. In addition, the DCMs could accumulate in tumor tissue and stay there for a long time, thereby causing significant inhibition of 4T1 tumor growth and marked prevention in lung metastasis of 4T1 tumors. These results suggested that DCMs could be a promising delivery system in inhibiting the growth and metastasis of breast cancer.

Maleic acid-induced impaired conversion of 25(OH)D3 to 1,25(OH)2D3: implications for Fanconi's syndrome

Conversion of 25-hydroxyvitamin D3 [25(OH)D3] to 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] occurs exclusively in the renal cortex. To determine whether a disorder of the renal cortical tubule capable of causing Fanconi's syndrome can also impair the synthesis of 1,25(OH)2D3, we investigated whether conversion of 25(OH)D3 to 1,25(OH)2D3 was reduced by maleic acid. In vitamin D-deficient rats, maleic acid was administered i.v. over two hours. Thirty minutes after its initiation, when the complex renal tubule dysfunction had occurred, 3H-25(OH)D3 was administered i.v. as a bolus. Five hours afterwards, the amount of 3H-1,25(OH)2D3 recovered in the kidney, small intestine mucosa, and blood was one-third to one-half that in tissues of control rats that received acetazolamide or only saline or were subjected only to the surgical procedure. The glomerular filtration rate, as measured by inulin clearance, did not decrease significantly with maleic acid. In intact vitamin D-deficient chicks, 24 and 22 hr after i.p. administration of maleic acid and 14C-vitamin D3, respectively, the amount of 14C-1,25(OH)2D3 recovered in small intestine mucosa was reduced by one-half when compared to saline-treated controls. In kidney homogenates and isolated renal tubules of vitamin D-deficient chicks, activity of 25-hydroxyvitamin D3-1-hydroxylase was diminished immediately after maleic acid was administered in vivo or added in vitro to the incubation medium, respectively. These data provide the first demonstration that the renal capacity to convert 25(OH)D3 to 1,25(OH)2D3 can be substantially impaired in vivo by a renal disorder in which the glomerular filtration rate is not reduced.

Antihepatotoxic activity of monomethyl fumarate isolated from Fumaria indica

Monomethyl fumarate, isolated for the first time from the methanolic extract of the whole plant of Fumaria indica, was characterised and screened for its antihepatotoxic activity in albino rats. The compound showed significant (P < 0.01) antihepatotoxic activity against thioacetamide in vitro, and against hepatotoxicities induced by carbon tetrachloride, paracetamol and rifampicin in vivo to an extent almost similar to that of silymarin, a known antihepatotoxic agent.

Glutathione depletion and acute exercise increase O-GlcNAc protein modification in rat skeletal muscle

Post-translational modification of intracellular proteins with O-linked β-N-acetylglucosamine (O-GlcNAc) profoundly affects protein structure, function, and metabolism. Although many skeletal muscle proteins are O-GlcNAcylated, the modification has not been extensively studied in this tissue, especially in the context of exercise. This study investigated the effects of glutathione depletion and acute exercise on O-GlcNAc protein modification in rat skeletal muscle. Diethyl maleate (DEM) was used to deplete intracellular glutathione and rats were subjected to a treadmill run. White gastrocnemius and soleus muscles were analyzed for glutathione status, O-GlcNAc and O-GlcNAc transferase (OGT) protein levels, and mRNA expression of OGT, O-GlcNAcase and glutamine:fructose-6-phosphate amidotransferase. DEM and exercise both reduced intracellular glutathione and increased O-GlcNAc. DEM upregulated OGT protein expression. The effects of the interventions were significant 4 h after exercise (P < 0.05). The changes in the mRNA levels of O-GlcNAc enzymes were different in the two muscles, potentially resulting from different rates of oxidative stress and metabolic demands between the muscle types. These findings indicate that oxidative environment promotes O-GlcNAcylation in skeletal muscle and suggest an interrelationship between cellular redox state and O-GlcNAc protein modification. This could represent one mechanism underlying cellular adaptation to oxidative stress and health benefits of exercise.

Adaptation and radiographic evaluation of four adhesive systems

OBJECTIVES

The purpose of this study was to compare microleakage, gap formation, thickness of the adhesive layer and its radiographic appearance associated with four adhesive restorative procedures for class I cavities.

METHODS

Adhesive systems with easy handling characteristics were selected for the restoration of class I cavities in extracted third molars. Bitewing radiographs were taken of each tooth and four observers were asked to assess the presence of the adhesive layer. Microleakage, gap width and the thickness of the adhesive layer of each restoration were measured upon sectioning of the teeth.

RESULTS

Microleakage in the experimental restorations was minimal. The thickness of the adhesive layers and gap formation varied among different adhesive systems. The adhesive system with self-etching primer produced the highest percentage gap-free restorations. Thick adhesive layers could be detected on the radiograph. ROC analysis of the results validates the diagnosis from the radiograph.

CONCLUSIONS

The four restorative systems performed well in the prevention of microleakage. The use of a resin modified glass-ionomer cement base did not prevent gap formation compared with the all-etch bonding systems used in this study. The presence of an adhesive layer contributed to the prevention of gap formation, independently of the bonding system used. Thick adhesive layers could be detected on the radiograph.