Necrotic Agents Research Articles

Selected aspects of avascular tumor growth reproduced by a hybrid model of cell dynamics and chemical kinetics

We here propose a hybrid computational framework to reproduce and analyze aspects of the avascular progression of a generic solid tumor. Our method first employs an individual-based approach to represent the population of tumor cells, which are distinguished in viable and necrotic agents. The active part of the disease is in turn differentiated according to a set of metabolic states. We then describe the spatio-temporal evolution of the concentration of oxygen and of tumor-secreted proteolytic enzymes using partial differential equations (PDEs). A differential equation finally governs the local degradation of the extracellular matrix (ECM) by the malignant mass. Numerical realizations of the model are run to reproduce tumor growth and invasion in a number scenarios that differ for cell properties (adhesiveness, duplication potential, proteolytic activity) and/or environmental conditions (level of tissue oxygenation and matrix density pattern). In particular, our simulations suggest that tumor aggressiveness, in terms of invasive depth and extension of necrotic tissue, can be reduced by (i) stable cell–cell contact interactions, (ii) poor tendency of malignant agents to chemotactically move upon oxygen gradients, and (iii) presence of an overdense matrix, if coupled by a disrupted proteolytic activity of the disease.

Shiga-Like Toxin Produced by Local Isolates of Escherichia coli O157:H7 Induces Apoptosis of the T47 Breast Cancer Cell Line.

Purpose:It has been suggested that Shiga-like toxins produced by Escherichia coli O157:H7 could be used as novel therapeutic agents against malignant tumors. In addition, the antitumor potency of local isolates from Indonesia, which are known to be less toxic than the control isolate ATCC 43894, has not yet been tested. The study aimed to analyze local strains of E. coli O157:H7 as a proapoptosis agent on the T47 breast cancer cell line.Methods:As many as 30 culture cells of T47D breast cancer cell line were subjected to purified extracts of Shiga-like toxin originating from 5 local isolates of E. coli O157:H7: KL-48(2), SM-25(1), SM-7(1), DS-21(4), and 1 isolate ATCC 43894 which was used as a control. Toxin production of each isolate was detected using a sandwich enzyme-linked immunosorbent assay, and the treatment of cell lines was observed for 24 hours, with 2 replications; 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide tests and acridine orange/ethidium bromide double staining assays were used for detection and analyses of apoptosis.Results:The study showed 2 local strains of E. coli O157:H7 (codes KL-48(2) and SM-25(1)) had toxins positive at titer 5 and 10 μg/100 μL. These titers were lower than the control isolate ATCC 43894, but they had a necrosis effect higher (P < .05), ie, 80.3%, than control isolate, ie, 63.3%. Other local strain SM-25(1) also had a good necrosis effect. It has a nondifferent necrosis effect (P > .05) with the control isolate ATCC 43894, ie, 13.0% from 13.3%.Conclusion:This study concludes that the Shiga toxin produced by E. coli O157:H7 local isolate (Indonesia) has potential as a proapoptotic and/or necrotic agent for treating T47 breast cancer cell lines, as effectively as ATCC 43894 control isolates.

RETRACTED: Gastric mucosal defense and cytoprotection

The gastric mucosa is continuously exposed to many noxious factors and substances. 'Mucosal defense' is a term used to describe the various factors that permit the mucosa to remain intact despite its frequent exposure to substances with a wide range of temperature, pH and osmolarity, as well as to substances with detergent or cytotoxic actions, and bacterial products capable of causing local and systemic inflammatory reactions. Mucosal defense is multifactorial and can be modulated by a wide range of substances and mediators. We review basic components of gastric mucosal defense. Knowledge regarding gastric mucosal defense mechanisms has let to the development of current and potential future therapies to reduce gastrointestinal injury. The concept of 'cytoprotection' has been developed to describe the ability of pharmacologic agents to reduce damage to the stomach induced by ulcerogenic or necrotizing agents.

Antifungal 3,5-disubstituted furanones: From 5-acyloxymethyl to 5-alkylidene derivatives

5-Acetoxymethyl-3-(4-bromophenyl)-2,5-dihydrofuran-2-one previously described as highly antifungally active was found to provide the corresponding 5-methylene derivative via an unusual DMSO-promoted elimination of the ester group at C5 under antifungal assay conditions. Since the latter possessed nearly the same antifungal effect as that originally reported for the former, the 5-acetoxymethyl furanone just served as a precursor of the actual antifungally active species. A few series of compounds with alkyloxy, aryloxy and alkylidene substituents at C5 of the parent furanone structure were therefore prepared and evaluated. In line with the ease of elimination of the substituent from C5, low activities of the 5-alkoxy compounds were observed. On the other hand, their 5-aryloxymethyl congeners were found to be capable of liberating the antifungally active 5-methylene furanone into the testing medium. The antifungal effect of the 5-alkylidene derivatives was highly sensitive to substitution of the alkylidene moiety; a substituent in the allylic position was necessary for a compound to retain high activity. Parallel evaluation of cytostatic activity showed moderate activities of the antifungally active derivatives against HeLa S3 and CCRF-CEM lines. Cell cycle analysis of CCRF-CEM cells following the treatment with 5-methylene-3-(4-bromophenyl)-2,5-dihydrofuran-2-one revealed that this compound is a necrotic agent.

Anti tumor necrotic factor agents promote the ability of the BMP-2 induced ectopic bone formation

Anti tumor necrotic factor agents promote the ability of the BMP-2 induced ectopic bone formation

Mandibular bone necrosis caused by use of arsenic paste during endodontic treatment: two case reports

To report that arsenical pastes are still employed in endodontics and to highlight the potentially serious consequences of their use. Chemotherapeutic agents such as arsenic trioxide and paraformaldehyde were once commonly employed as pulp-necrotizing agents. Their cytotoxic effects are well recognized, and leakage from teeth has been associated with widespread necrosis of periodontal tissues and bone. This report describes two cases of severe bone necrosis affecting the mandible following the use of an arsenical paste. Pulp-necrotizing agents such as arsenic trioxide can cause severe bone necrosis. Arsenical pastes have no place in contemporary dental practice. Dentists should employ appropriate local anaesthetic techniques for pulp extirpation instead of relying on toxic necrotizing agents.

Comparison of the gastroprotective effect of a diterpene lactone isolated from Croton cajucara with its synthetic derivatives

The effect of three new derivatives from dehydrocrotonin (DHC—compound I) on gastric damage in different animal models including gastric ulceration induced by a necrotic agent and hypothermic restrained-stress was studied: compound II (produced by reducing the cyclohexenone moiety of DHC with NaBH 4); compound III (produced by reducing the carbonyls with LiAlH 4); and compound IV (produced by transforming the lactone moiety into an amide). Their structures were confirmed on the basis of chemical and physicochemical evidence. When previously administered (p.o.) at a dose of 100 mg/kg, compound II significantly ( P<0.01) reduced gastric injury induced by HCl/ethanol (78%) and indomethacin (88%) better than did reference compound I (48 and 43%, respectively). But the anti-ulcerogenic activity of compound II was completely abolished by the stress-induced ulcer. Reduction of carbonyls with LiAlH 4 (compound III) caused decreased activity, markedly when no protective effect in any of the models was applied ( P>0.05). However, compound IV, in which the lactone moiety was changed into an amide, when administered at the same dose (100 mg/kg, p.o.), was more effective. The presence of a lactone moiety or Michael acceptor is probably essential for the anti-ulcerogenic effect of these compounds.

Detection of ghost cells in the standard alkaline comet assay is not a good measure of apoptosis.

The single cell gel electrophoresis assay, or Comet assay, is a powerful tool for measurement of DNA strands breaks, oxidative damage, and alkali labile sites, and the assay was recently modified to detect DNA cross-links. It has also been proposed as a measure of apoptosis since apoptotic cells are suspected to result in total migration of the DNA from the nucleus into the tail. Cells with this appearance are called ghost cells, clouds, hedgehogs, or NDCN (nondetectable cell nuclei). The aim of this study was to determine if ghost cells can be used to measure apoptosis in the standard alkaline comet assay. To answer this question, we made use of two cell lines: CTLL-2 cells that can enter apoptosis upon addition of apoptosis stimuli or IL-2 deprivation, and CTLL-2 bcl2 cells that are protected from apoptosis due to the overexpression of the apoptosis inhibitor gene bcl2. The two cell lines were treated with cytotoxins (nongenotoxic apoptosis inducers, nongenotoxic necrotic agents) or genotoxins. They were also subjected to growth factor withdrawal, which induced apoptosis in the CTLL-2 cell line. The level of apoptosis was measured by the Annexin V-FITC method in parallel with performing the Comet assay. The results obtained in the two cell lines suggest that apoptotic or necrotic death does not correlate well with the detection of ghost cells, presumably because these cells are lost upon electrophoresis. A variant of the alkaline Comet assay that was performed without electrophoresis (halo method) was able to efficiently detect cells undergoing apoptosis, but it was unable to clearly distinguish between apoptosis and genotoxic damage.

Nitric Oxide Donating Compounds Inhibit HCl-Induced Gastric Mucosal Lesions Mainly via Prostaglandin

Prostaglandin (PG) and nitric oxide (NO) have been known to inhibit the lesion formation induced by necrotic agents. However, no clear correlation between PG and NO has been shown in the gastro-protective action against necrotic agent-induced gastric mucosal lesions in rats. Thus, the present study was performed to clarify this correlation. Gastric mucosal lesions were induced by the oral administration of 0.6 M HCl in rats. 16,16-Dimethyl PGE2 (0.3 - 3 μ g /kg, p.o.; dim-PGE2), sodium nitrite (0.3 and 1 mg /kg, s.c.) and sodium nitroprusside (30 and 100 mg /kg, i.v.; SNP) dose-dependently inhibited the lesion formation. Orally administered sodium nitrite or SNP (3 mg/kg) also significantly inhibited the lesion formation. The gastroprotective action by dim-PGE2 was not affected by the pre-treatment with NG-nitro-L-arginine methylester (10 mg/kg, i.v.). The gastroprotective effect by sodium nitrite or SNP was markedly attenuated by the pre-treatment with indomethacin (10 mg/kg, s.c.). These findings suggest that NO donating compounds inhibit the HCl-induced mucosal lesions mainly through prostaglandin, but dim-PGE2 directly inhibits the lesions without involvement of NO in rats.

Differential modulation of alpha, beta and gamma enolase isoforms in regenerating mouse skeletal muscle.

Nothing is known about the expression of the glycolytic enzyme enolase in skeletal muscle alterations such as myofiber degeneration and regeneration. Enolase is a dimeric enzyme which exhibits cell type specific isoforms. The embryonic form, alphaalpha, remains expressed in most adult tissues, whereas a transition towards specific isoforms occurs during ontogenesis in two cell types with high energy requirements: alphagamma and gammagamma in neurons, alphabeta and betabeta in striated muscle cells. During murine myogenesis, beta enolase transcripts are detected early in the forming muscles, and the beta gene is further upregulated at specific stages of muscle development. The alpha and beta subunits exhibit characteristic developmental microheterogeneity patterns. High levels of beta enolase subunits characterize the glycolytic fast-twitch fibers of adult muscles. We have investigated the expression of enolase subunits in a mouse experimental model of muscle regeneration. Following a single intramuscular injection of the necrotic agent cardiotoxin, we observed a rapid decrease in the level of the major muscle enolase subunit beta, accounting for the drop in total enolase activity that correlated with the degeneration of myofibers. Concomitant with the regeneration of new fibers, beta subunit levels began to increase, reaching normal values by 30 days after injury. Changes in the embryonic and ubiquitous subunit, alpha, mimicked those occurring during development by two aspects: modifications in electrophoretic variants and redistribution between soluble and insoluble compartments of muscle extracts. Imunocytochemical analyses of alpha and beta enolase subunits first revealed a homogeneous labeling within myofibers. Striations characteristic of normal adult muscle tissue were visible again by day 14 after injury. A perinuclear alpha and beta immunoreactivity was often observed in regenerating myofibers but its functional significance remains to be elucidated. Double labeling experiments with anti-gamma enolase and FITC-alpha bungarotoxin allowed us to follow the neuromuscular junction remodeling that occurs during muscle regeneration despite the absence of nerve injury.

Gastroduodenal mucosal defense

Research performed in the laboratory and the clinic over the past several years has added to our understanding of the mechanisms that are operative in protecting the epithelial lining of the stomach and duodenum from injury and ulceration, most frequently caused by necrotic agents in the lumen. The defensive mechanism of the gastroduodenal mucosa comprises a series of physical, chemical, biologic, and immunologic barriers or mechanisms that act in concert to either prevent or limit cellular injury or transformation. The field of gastroduodenal defense can be subdivided into the following four areas: extracellular mucus barrier properties; membrane and ion transport properties; cellular factors promoting growth and restitution; and vascular, neural, and inflammatory factors ensuring optimal tissue perfusion and immune responsiveness, respectively. In addition, a great deal can be learned about gastroduodenal defense by studying the effects of ulcerogenic factors and conditions on the defensive mechanisms described here and specifically how they may be compromised by nonsteroidal anti-inflammatory drugs and Helicobacter pylori infection. This review presents interesting and noteworthy findings impacting on these properties contributing to gastroduodenal defense since the prior review article on this subject appearing in this journal.

Protection by Rhinax in various models of ulceration in rats

The effect of Rhinax on gastric damage in different animal models including gastric ulceration induced by a necrotic agent such as 0.6 N HCl, indomethacin, and intragastric distension was studied. Treatment with Rhinax at a dose of 160 mg/kg protected gastric mucosa against the damage induced by oral administration of indomethacin and intragastric distension. The volume and acidity of gastric juice in pyloric ligated rats was reduced by Rhinax. It also significantly promoted gastric mucus secretion in normal animals. On the basis of these observations, we conclude that Rhinax possesses anti-ulcer activity and that the observed activity may be due to the modulation of defensive factors by improvement in gastric cytoprotection.

Role of Mucus Secretion and Sulfhydryl Groups in Gastroprotection Mediated by a Flavonoid Fraction of Bidens aurea

Abstract The aerial parts of Bidens aurea (Aiton) Sherff have been used in folk medicine as an antiulcer agent. The efficacy of an ether extract to prevent gastric mucosal damage produced by several necrotic agents was studied in rats. The best efficiency was against lesions induced by 30% NaCl with a significant decrease of damage at all doses tested (250, 125 and 62.5 mg kg-1). In contrast, only the highest dose (250 mg kg-1) was effective on gastric erosions induced by 0.6 ɴ HCl. This effect could not be related with the mucus gel production only since the groups treated with of absolute ethanol or 30% NaCl before and then received 250 mg kg-1 of the ether extract increased significantly the amount of gastric mucus and its glycoprotein content. However, the ether extract of Bidens aurea enhanced the production of mucosal non-protein SH groups at all doses assayed after treatment with absolute ethanol and 0.6 ɴ HCl. With NaCl-induced gastric injury, also the highest dose (250 mg kg-1) produced an increase of this parameter. The results suggest that a slight augmentation of the mucus gel concentration and the increase of non-protein sulfhydryl compounds, could con­ tribute to the functional protection mechanism mediated by a flavonoid fraction of B.aurea in these experimental models.

Gastroprotection and prostaglandin E2 generation in rats by flavonoids of Dittrichia viscosa.

Investigations were carried out to determine the gastroprotective effects of the flavonoid fraction of Dittrichia viscosa (L.) W. Greuter against gastric lesions produced by necrotizing agents. The action of the fraction on the production of mucus, and the involvement of endogenous PGs in gastric mucosal defensive mechanisms were also determined. Gastric ulcers induced by oral administration of three necrotic agents (100% ethanol, 0.6 N HCl, 30% NaCl) were markedly reduced by pretreatment with the flavonoid extract at doses from 125 to 500 mg/kg p.o. and the reduction at the highest dose (500 mg/kg p.o.) was practically complete. Flavonoid fraction pretreatment also increased mucus production and glycoprotein content. In addition, intraperitoneal administration of indomethacin (10 mg/kg i.p.) to animals treated with the extract (500 mg/kg) partially inhibited gastric protection but the PGE2 determination did not show an increase in prostanoid level. These observations suggest that the gastroprotective effects of the flavonoid fraction from D. viscosa could be partly explained through non-prostaglandin-dependent mechanisms.

Gastric Cytoprotective Anti-Ulcerogenic Actions of Hydroxychalcones in Rats

The preventive effects of hydroxychalcone derivatives on ulcer formation induced by severe necrotizing agents such as 60% ethanol in 150 mM HCl (HCl-ethanol) and 0.2 N NaOH in rats were examined. Among the compounds tested, 2',4'-dihydroxychalcone gave the strongest activity in both experimental models and protected the gastric mucosa from the insult of either necrotizing agent at oral doses ranging from 1 to 10 mg/kg, as evidenced by a dose-related reduction in the ulcer index. The mucosal protective activity of 2',4'-dihydroxychalcone was not affected by pretreatment with indomethacin (5 mg/kg, s.c.). To investigate the detailed mechanism of the mucosal protective action of 2',4'-dihydroxychalcone, its inhibitory effects on the decrease in the hexosamine content from the gastric mucus induced by HCl-ethanol were studied by using it in combination with a dye, Alcian blue. As a result, 2',4'-dihydroxychalcone at an oral dose of 10 mg/kg inhibited the decrease in the dye-recovery from the gastric mucus induced by HCl-ethanol. PGE2 at an oral dose of 0.1 mg/kg exhibited a similar action. These results established that 2',4'-dihydroxychalcone is a potent cytoprotective agent similar to PGE2 effectively preventing gastric ulcer formation induced by strong necrotizing agents and seems to suggest that this compound protects the stomach against its own peptic secretions by reinforcement of gastric resistances. In fact, 2',4'-dihydroxychalcone prevented ulcer formation induced by water-immersion stress in rats and also showed a marked enhancement of the healing of acetic acid-induced gastric ulcers in rats.

Clara cell cultures from the mouse and their reaction to bronchiolar toxins.

The major aim of this study was to determine if small numbers of freshly isolated mouse Clara cells could be used to rapidly screen the toxic effects of a number of diverse pulmonary toxins. A short-term (20 hr) culture of functionally competent (nitotetrazolium reductase positive) Clara cells was developed. In this culture the Clara cells were allowed to attach to an extracellular matrix in 96-well multiwell plates containing a culture medium of DCCM 1 and Ultroser G (0.4%). Pulmonary toxins (a total of 26 agents with concentrations ranging from 10(-7) M to 10(-3) M) were examined for their ability to reduce the attachment efficiency of functionally competent Clara cells and TD50 values (the amount of toxin required to reduce normal attachment efficiency by 50%) were calculated. With the possible exception of some halogenated hydrocarbons, the simple toxicity test in vitro correlated well with the known effects of the bronchiolar necrotic agents in vivo. For 13 compounds studied there was a direct correlation between TD50 values in vitro and LD50 values (mostly oral) in rodents in vivo, the correlation coefficient of the regression line being 0.783.

Serum amyloid P component: its role in platelet activation stimulated by sphingomyelinase D purified from the venom of the brown recluse spider (Loxosceles reclusa)

C. A. Gates and R. S. Rees. Serum amyloid P component: its role in platelet activation stimulated by sphingomyelinase D purified from the venom of the brown recluse spider ( Loxosceles reclusa). Toxicon 28, 1303–1315, 1990.—Serum amyloid P component or serum amyloid protein is a ubiquitous, highly conserved glycoprotein whose function is unknown. Although the related pentraxin, C-reactive protein, is an acute phase reactant in man, there is no direct evidence that human serum amyloid protein is involved in an inflammatory response. Here we show that serum amyloid protein is required by sphingomyelinase D, the principal necrotic agent of the venom of Loxosceles reclusa, for the in vitro-activation of human platelets. Furthermore, this platelet activation is dependent upon the presence of only serum amyloid protein; no other plasma components are necessary. Secretion of [ 3H]-serotonin and aggregation of platelets are nearly maximal following incubation of the platelets with purified sphingomyelinase D (0.3 μg/ml) and 5 μg/ml pure serum amyloid protein in the presence of calcium. Since the platelets are no longer activated when this 10% physiologic amount of serum amyloid protein is omitted, serum amyloid protein is likely to have a role in the necrosis caused by brown recluse spider venom.

Allyl formate-induced hepatotoxicity in rainbow trout

Rainbow trout liver is tubular without apparent lobules. Hepatotoxins are often defined by the portion of the hepatic lobule affected. One of these, carbon tetrachloride, has been studied in trout and has produced no consistent pattern of toxicity similar to the centrilobular pattern seen in rodent liver. By contrast, allyl formate, a periportal necrotic agent in rodent liver, induced distinctive necrosis in trout liver. At 24 h, following oral administration of 100 μliter/kg allyl formate, light microscopy revealed pallor of hepatocytes, hemorrhage in parenchymal space, swollen and shrunken hepatocytes, hepatocellular lysis and nuclear changes signifying necrosis. Calcification and apparently increased collagen deposition were observed at 48 h near bile ducts. By 72 h, hepatocyte morphology suggested partial recovery. Electron microscopy confirmed and extended histologic observations and revealed destruction of sinusoidal endothelium, hepatocyte glycogen depletion and condensed mitochondria. Surviving hepatocytes appeared condensed and shrunken. Serum glutamate-pyruvic transaminase increased at 24 and 48 h and returned to normal by 72 h. Liver Na + and K + and serum bilirubin were also changed and correlated with observed morphological alterations.

Effects of zinc acexamate on gastric mucosal resistance factors

The effects of zinc acexamate on gastric defensive systems were evaluated in the rat. Gastric ulcers induced by oral administration of three necrotic agents (0.6 N HCl, 25% NaCl, 100% ethanol) were markedly reduced by different pretreatments with zinc acexamate. This cytoprotective effect was not modified by previous treatment with indomethacin (30 mg/kg orally). Zinc acexamate pretreatment also prevents the disruption of the gastric mucosal barrier induced by aspirin (40 mM) and increases mucus production in the gastric glands and tracheal walls. These observations suggest that the antiulcer effects described for zinc salts could be the result, at least partly, of an action increasing gastric mucosal defensive systems.

Partial characterization of the gastrointestinal weight changes produced in the female rat by 16,16-dimethylprostaglandin E 2

Oral and subcutaneous administration of 16,16-dimethylprostaglandin E 2 (16,16-dimethyl PGE 2) resulted in an increase in the dry weight of the stomach and small intestine of the female rat. This weight response was rapid, controlled rather than continuously progressing, dose dependent and reversible. The dry weight of the colon also increased but this was not studied in detail. Two-day treatment with 16,16-dimethyl PGE 2 caused an increase in the incorporation of 3H-thymidine into the duodenum, jejunum and colon suggesting an increase in cell number. Incorporation into the stomach and ileum was not changed. The number of goblet cells per crypt was increased by prostaglandin treatment in all parts of the small intestine. Since these are mucus producing cells, the small intestine may have increased in cell number and mucus production. Both anti-secretory and cytoprotective doses of 16,16-dimethyl PGE 2 caused weight increases in the stomach and small intestine. However, the weight gain by itself was not sufficient to protect the stomach or small intestine from necrotic agents after the prostaglandin was discontinued.