Ferric ammonium citrate (FAC)-induced inhibition of osteoblast proliferation/differentiation and its reversal by soybean-derived peptides (SDP).

Ferric citrate has been used to treat hyperphosphatemia, a prevalent symptom in patients with chronic kidney disease while ferric ammonium citrate (FAC), a more dissolvable format, is widely used as food additive. However, excess iron is associated with osteoporosis. Dietary soybean products have been shown to prevent the progression of osteoporosis. In this study, a group of peptides, referred as P3, was identified from the enzymolysis of soybean protein isolates, and its biological functions were investigated. The results showed that MC3T3-E1 cell cycle progression from G0/G1 to S phase was accelerated by P3 treatment. MC3T3-E1 cell proliferation was enhanced by P3 via ERK1/2 activation. Importantly, P3 treatment abolished the antiproliferative effect of FAC on MC3T3-E1 cell. In addition, P3 treatment increased the expression of ALP, COL-1, OCN, consequently promoting the differentiation and mineralization of MC3T3-E1 cells via activation of p38 MAPK pathway. Consequently, P3 treatment was able to reverse the inhibitory effect of FAC on osteoblasts differentiation and mineralization. Our findings suggest P3, as a dietary supplement, has a potential therapeutic function to attenuate the adverse effects of FAC on bone metabolism and to prevent osteoporosis progression.

Engineered Polymer Nanoparticles with Unprecedented Antimicrobial Efficacy and Therapeutic Indices against Multidrug-Resistant Bacteria and Biofilms.

The rapid emergence of antibiotic-resistant bacterial "superbugs" with concomitant treatment failure and high mortality rates presents a severe threat to global health. The superbug risk is further exacerbated by chronic infections generated from antibiotic-resistant biofilms that render them refractory to available treatments. We hypothesized that efficient antimicrobial agents could be generated through careful engineering of hydrophobic and cationic domains in a synthetic semirigid polymer scaffold, mirroring and amplifying attributes of antimicrobial peptides. We report the creation of polymeric nanoparticles with highly efficient antimicrobial properties. These nanoparticles eradicate biofilms with low toxicity to mammalian cells and feature unprecedented therapeutic indices against red blood cells. Most notably, bacterial resistance toward these nanoparticles was not observed after 20 serial passages, in stark contrast to clinically relevant antibiotics where significant resistance occurred after only a few passages.

Heme oxygenase-1 mitigates ferroptosis in renal proximal tubule cells.

Ferroptosis is an iron-dependent form of regulated nonapoptotic cell death, which contributes to damage in models of acute kidney injury (AKI). Heme oxygenase-1 (HO-1) is a cytoprotective enzyme induced in response to cellular stress, and is protective against AKI because of its antiapoptotic and anti-inflammatory properties. However, the role of HO-1 in regulating ferroptosis is unclear. The purpose of this study was to elucidate the role of HO-1 in regulating ferroptotic cell death in renal proximal tubule cells (PTCs). Immortalized PTCs obtained from HO-1+/+ and HO-1-/- mice were treated with erastin or RSL3, ferroptosis inducers, in the presence or absence of antioxidants, an iron source, or an iron chelator. Cells were assessed for changes in morphology and metabolic activity as an indicator of cell viability. Treatment of HO-1+/+ PTCs with erastin resulted in a time- and dose-dependent increase in HO-1 gene expression and protein levels compared with vehicle-treated controls. HO-1-/- cells showed increased dose-dependent erastin- or RSL3-induced cell death in comparison to HO-1+/+ PTCs. Iron supplementation with ferric ammonium citrate in erastin-treated cells decreased cell viability further in HO-1-/- PTCs compared with HO-1+/+ cells. Cotreatment with ferrostatin-1 (ferroptosis inhibitor), deferoxamine (iron chelator), or N-acetyl-l-cysteine (glutathione replenisher) significantly increased cell viability and attenuated erastin-induced ferroptosis in both HO-1+/+ and HO-1-/- PTCs. These results demonstrate an important antiferroptotic role of HO-1 in renal epithelial cells.

Surfactants in aquatic and terrestrial environment: occurrence, behavior, and treatment processes.

Surfactants belong to a group of chemicals that are well known for their cleaning properties. Their excessive use as ingredients in care products (e.g., shampoos, body wash) and in household cleaning products (e.g., dishwashing detergents, laundry detergents, hard-surface cleaners) has led to the discharge of highly contaminated wastewaters in aquatic and terrestrial environment. Once reached in the different environmental compartments (rivers, lakes, soils, and sediments), surfactants can undergo aerobic or anaerobic degradation. The most studied surfactants so far are linear alkylbenzene sulfonate (LAS), quaternary ammonium compounds (QACs), alkylphenol ethoxylate (APEOs), and alcohol ethoxylate (AEOs). Concentrations of surfactants in wastewaters can range between few micrograms to hundreds of milligrams in some cases, while it reaches several grams in sludge used for soil amendments in agricultural areas. Above the legislation standards, surfactants can be toxic to aquatic and terrestrial organisms which make treatment processes necessary before their discharge into the environment. Given this fact, biological and chemical processes should be considered for better surfactants removal. In this review, we investigate several issues with regard to: (1) the toxicity of surfactants in the environment, (2) their behavior in different ecological systems, (3) and the different treatment processes used in wastewater treatment plants in order to reduce the effects of surfactants on living organisms.

Aged-look vat dyed cotton with anti-bacterial/anti-fungal properties by treatment with nano clay and enzymes.

In this research, nanotechnology as a route to functional finishing of textiles was used along with bio-finishing to enhance the cotton fabrics performance. For this purpose, quaternary modified montmorillonite and common enzymes such as cellulase, laccase and their mixture were applied on vat dyed cotton fabric. Characteristic analysis of the treated samples and the dispersed nano clays in the effluent of the treatment was performed by various analyzing methods. The nano/bio-finishing is believed to impart antibacterial and antifungal activities with simultaneously higher lightness, advanced softness and handle properties into cotton fabrics. Moreover, cotton fabrics were proved to have no adverse effects (low toxicity) on human dermal fibroblasts. Findings suggest the potential of the proposed method in reducing the risk of microorganism for textile applications and imparting better handle and appearance properties.

The effects of ammonium perchlorate on thyroid homeostasis and thyroid-specific gene expression in rat.

Perchlorate, a kind of inorganic chemical, is mainly used in defense industry and widely used in other civilian areas. It was well known that perchlorate exerts its thyrotoxicant effect on thyroid homeostasis via competitive inhibition of iodide uptake. However, some details of mechanism by which perchlorate disturb thyroid homeostasis are unknown and remain to be elucidated. The present study aimed to investigate if iodide insufficiency in the thyroid is the main mechanism by which perchlorate exerts its effect on the thyroid gland. We highlighted and measured the gene expression of NIS, Tg, and TPO which involved in thyroid hormone biosynthesis. Thyroid effects of perchlorate were identified by assessing different responses of these genes at the treatments of perchlorate and iodine deficiency. The results indicated that high dose perchlorate (520 mg kg(-1) b.wt.) can induce a significant decrease in body weight and cause hypertrophy of thyroid gland, with a decreased level of FT3, FT4 and a remarkable increased level of TSH. In addition, the significant decreased gene expression of Thyroglobulin (Tg) and thyroperoxidase (TPO) were both observed at the treatment of high dose perchlorate. These results suggested that perchlorate can suppress gene expression of Tg and TPO which directly involved in biosynthesis of thyroid hormones, and may therefore aggravate the perturbation of thyroid homeostasis in addition to competitive inhibition of iodide uptake.

[The effects of ammonium perchlorate on thyroid function and mRNA expression of thyroglobulin and thyroperoxidase].

OBJECTIVE: To investigate the effects of ammonium perchlorate (AP) on thyroid functions and mRNA expression levels of thyroglobulin (Tg) and thyroperoxidase (TPO) genes of rats. METHODS: Thirty SD male rats were randomly divided into six groups: control group, iodine-deficient group, low dose AP group (130 mg/kg), moderate dose AP group (260 mg/kg), high dose AP group (520 mg/kg) and high iodine-combined group. After the rats were exposed orally for 90 days, serum free-thyroxine (FT(4)), free-triiodothyronine (FT(3)) and thyroid stimulating hormone (TSH) were measured using radioimmunoassays. mRNA expression levels of thyroglobulin (Tg) and thyroperoxidase (TPO) genes were detected by real-time quantitative PCR. RESULTS: Serum FT(4) levels in moderate dose AP group and high dose AP group were [(9.540 ± 1.327) fmol/ml] and [(6.509 ± 1.949) fmol/ml] respectively, which were significantly lower than that [(13.505 ± 1.276) fmol /ml] in control group (P < 0.05 or P < 0.01). Serum TSH level in high dose AP group was [(1.227 ± 0.295) mIU/L], which was significantly higher than that [(0.545 ± 0.282) mIU/L] in control group (P < 0.05). The mRNA expression levels of thyroglobulin (Tg) gene in all groups exposed to AP were significantly lower than that in control group (P < 0.01). The mRNA expression level of thyroperoxidase (TPO) gene in high dose AP group was significantly higher than that in control group (P < 0.05). CONCLUSION: AP can reduce the serum FT(3) and FT(4) levels of rats, increase the serum TSH level of rats and decrease obviously the mRNA expression levels of Tg and TPO genes. In addition, high iodine can reduce the toxic effects of AP on thyroid gland of rats to some extent.

Cytotoxicity of set polymer nanocomposite resin root-end filling materials.

AIM: To evaluate the cytotoxicity of two forms of the novel root-end filling materials, polymer nanocomposite (PNC) resins [C-18 Amine montmorillonate (MMT) and VODAC MMT] both containing Chlorhexidine Diacetate Salt Hydrate 2%, and to compare it to that of two widely accepted commercially available materials, ProRoot® MTA and Geristore®. METHODOLOGY: Elutes of experimental materials extracted after 24 h, 1, 2 and 3 weeks were interacted with the mouse fibroblasts L-929 using a colorimetric cell viability assay (MTS) based on mitochondrial dehydrogenases activity. Using 100% and 50% concentrations of the extracted elutes of the experimental materials the effect of different concentrations of elutes on the cells was analysed. In the positive control group Hygrogold® was added to the cell culture to arrest cells bioactivity. In the negative control group, fresh Dulbecco's Eagle's minimum essential medium supplemented with 10% foetal bovine serum was used to enhance cell bioactivity. Differences in mean bioactivity values were assessed using a t-test and one-way anova (P<0.05). RESULTS: No significant difference was found in cytotoxicity between ProRoot® MTA, Geristore® and PNC resin C-18 Amine MMT on 24 h, 1, 2 and 3 weeks samples. Sample elutes of PNC resin VODAC MMT, however, revealed cytotoxic activity during most of these experiments. CONCLUSION: Cytotoxicity of the elutes of PNC resin C-18 Amine MMT was not significantly different from that of ProRoot® and Geristore®. PNC resin VODAC MMT, revealed significantly more cytotoxicity compared to the other tested materials.

Nitric oxide supplementation alleviates ammonium toxicity in the submerged macrophyte Hydrilla verticillata (L.f.) Royle.

The likely protective effects of nitric oxide (NO) against ammonium toxicity were investigated in the submerged macrophyte Hydrilla verticillata. The plants were subjected to ammonium stress (3mM ammonium chloride) in the presence of sodium nitroprusside (SNP, 10 µM), an NO donor. Treatment with SNP significantly increased the NO content and partially reversed the ammonium-induced negative effects, including membrane damage and the decrease in levels of chlorophyll, malondialdehyde, glutathione and ascorbic acid. Further, SNP application increased the catalytic activities of ascorbate peroxidase, superoxide dismutase, guaiacol peroxidase, catalase and glutathione S-transferase, but decreased that of NADH-oxidase. Histochemical staining showed that SNP application caused a significant decrease in the levels of superoxides and hydrogen peroxide. In contrast, application of other breakdown products of SNP (10 µM sodium ferrocyanide, 10 µM sodium nitrite and 10 µM sodium nitrate) failed to show any protective effect. The results suggest that the increased intracellular NO, resulting from SNP application, improved the antioxidant capacity of H. verticillata plants in coping with ammonium-induced oxidative stress.

Enzymatic detergent in rat peritoneum. A comparative study with physiological solution.

BACKGROUND: Peritoneal washing out with physiological solution with different substances added is useful in peritoneal infections, but the effect of enzymatic detergents, such as quaternary didecyl-dimethyl ammonium compounds (DDAC), used in the sterilization of surgical material is unknown. We undertook this study to determine histological changes (inflammation, fibrosis and new vessel formation) in the peritoneum of Wistar rats after the application of physiological solution or DDAC. METHODS: The minimum inhibitory concentration (MIC) of DDAC for E. coli (512 µg/ml) and E. faecalis (128 µg/ml) was determined. Sixty-three Wistar rats weighing 200 ± 20 g were studied. They were divided into three groups: control: 7 rats were instilled with 3 ml of physiological solution in peritoneal cavity; groups 1 and 2 were instilled with 3 ml of MIC for E. coli and E. faecalis, respectively. These groups were divided into four subgroups of seven animals. In every rat, 1 cm(2) of peritoneum was obtained at 2, 7, 14, and 21 days for histological study with hematoxylin-eosin. Ten fields were evaluated. The data obtained were analyzed with the Mann-Whitney test. RESULTS: There were no significant differences in inflammation, fibrosis and new vessel formation with the physiological solution vs. DDAC at 2, 7, 14, and 21 days (p >0.05), except for inflammation at 2 days in group 2 (p = 0.026), which remitted. CONCLUSIONS: There was no significant difference in changes in rat peritoneum after physiological solution or DDAC application.

Decontamination of tetramethylammonium hydroxide (TMAH) splashes: promising results with Diphoterine in vitro.

Tetramethylammonium hydroxide (TMAH), used in microelectronic industries and research and development, has both corrosive properties and systemic toxicity. Two fatal TMAH occupational exposure cases have been published. Studies comparing initial TMAH decontamination with Diphoterine versus tap water were performed: an in vitro pH titration study and an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) in vitro cytotoxicity cell viability assay. For pH normalization, 17 times more tap water than Diphoterine was required. In the cytotoxicity test, two-thirds of the cells remained viable after Diphoterine washing, compared with only one-third after tap water washing (p < .001). Diphoterine washing is a promising TMAH decontamination method.

Integrated Constructed Wetlands (ICW) for livestock wastewater management.

Social, economic and environmental coherence is sought in the management of livestock wastewater. Wetlands facilitate the biogeochemical processes that exploit livestock wastewater and provide opportunities to achieve such coherence and also to deliver on a range of ecosystem services. The Integrated Constructed Wetland (ICW) concept integrates three inextricably linked objectives: water quantity and quality management, landscape-fit to improve aesthetic site values and enhanced biodiversity. The synergies derived from this explicit integration allow one of the key challenges for livestock management to be addressed. An example utilizing twelve ICW systems from a catchment on the south coast of Ireland demonstrates that over an eight year period mean reduction of total and soluble phosphorus (molybdate reactive phosphorus) exceeded 95% and the mean removal of ammonium-N exceeded 98%. This paper reviews evidence regarding the capacity of ICWs to provide a coherent and sustainable alternative to conventional systems.

Characterization of the oat1 gene of Penicillium chrysogenum encoding an omega-aminotransferase: induction by L-lysine, L-ornithine and L-arginine and repression by ammonium.

The Penicillium chrysogenum oat1 gene, which encodes a class III omega-aminotransferase, was cloned and characterized. This enzyme converts lysine into 2-aminoadipic semialdehyde, and plays an important role in the biosynthesis of 2-aminoadipic acid, a precursor of penicillin and other beta-lactam antibiotics. The enzyme is related to ornithine-5-aminotransferases and to the lysine-6-aminotransferases encoded by the lat genes found in bacterial cephamycin gene clusters. Expression of oat1 is induced by lysine, ornithine and arginine, and repressed by ammonium ions. AreA-binding GATA and GATT sequences involved in regulation by ammonium, and an 8-bp direct repeat associated with arginine induction in Emericella (Aspergillus nidulans and Saccharomyces cerevisiae, were found in the oat1 promoter region. Deletion of the oat1 gene resulted in the loss of omega-aminotransferase activity. The null mutants were unable to grow on ornithine or arginine as sole nitrogen sources and showed reduced growth on lysine. Complementation of the null mutant with the oat1 gene restored normal levels of omega-aminotransferase activity and the ability to grow on ornithine, arginine and lysine. The role of the oat1 gene in the biosynthesis of 2-aminoadipic acid is discussed.

Wastewater treatment polymers identified as the toxic component of a diamond mine effluent.

The Ekati Diamond Mine, located approximately 300 km northeast of Yellowknife in Canada's Northwest Territories, uses mechanical crushing and washing processes to extract diamonds from kimberlite ore. The processing plant's effluent contains kimberlite ore particles (< or =0.5 mm), wastewater, and two wastewater treatment polymers, a cationic polydiallydimethylammonium chloride (DADMAC) polymer and an anionic sodium acrylate polyacrylamide (PAM) polymer. A series of acute (48-h) and chronic (7-d) toxicity tests determined the processed kimberlite effluent (PKE) was chronically, but not acutely, toxic to Ceriodaphnia dubia. Reproduction of C. dubia was inhibited significantly at concentrations as low as 12.5% PKE. Toxicity identification evaluations (TIE) were initiated to identify the toxic component of PKE. Ethylenediaminetetraacetic acid (EDTA), sodium thiosulfate, aeration, and solid phase extraction with C-18 manipulations failed to reduce PKE toxicity. Toxicity was reduced significantly by pH adjustments to pH 3 or 11 followed by filtration. Toxicity testing with C. dubia determined that the cationic DADMAC polymer had a 48-h median lethal concentration (LC50) of 0.32 mg/L and 7-d median effective concentration (EC50) of 0.014 mg/L. The anionic PAM polymer had a 48-h LC50 of 218 mg/L. A weight-of-evidence approach, using the data obtained from the TIE, the polymer toxicity experiments, the estimated concentration of the cationic polymer in the kimberlite effluent, and the behavior of kimberlite minerals in pH-adjusted solutions provided sufficient evidence to identify the cationic DADMAC polymer as the toxic component of the diamond mine PKE.

Analysis of the biologic functions of H- and L-ferritins in HeLa cells by transfection with siRNAs and cDNAs: evidence for a proliferative role of L-ferritin.

We describe the use of small interfering RNAs (siRNAs) to down-regulate H- and L-ferritin levels in HeLa cells. siRNAs repressed H- and L-ferritin expression to about 20% to 25% of the background level in both stable and transient transfections. HeLa cells transfected with H- and L-ferritin cDNAs were analyzed in parallel to compare the effects of ferritin up- and down-regulation. We found that large modifications of L-ferritin levels did not affect iron availability in HeLa cells but positively affected cell proliferation rate in an iron-independent manner. The transient down-regulation of H-ferritin modified cellular iron availability and resistance to oxidative damage, as expected. In contrast, the stable suppression of H-ferritin in HeLa cell clones transfected with siRNAs did not increase cellular iron availability but made cells less resistant to iron supplementation and chelation. The results indicate that L-ferritin has no direct effects on cellular iron homeostasis in HeLa cells, while it has new, iron-unrelated functions. In addition, they suggest that H-ferritin function is to act as an iron buffer.

Combination of dithiothreitol and detergent treatment of spermatozoa causes paternal chromosomal damage.

Treatment of spermatozoa with either the nonionic detergent Triton X-100 (TX) or dithiothreitol (DTT) has been suggested to confer enhanced success on intracytoplasmic sperm injection (ICSI) in mice and humans. Here, we attempted to use both reagents together, to our knowledge for the first time, and found that this caused severe chromosomal breaks in paternal pronuclei. We documented this effect further by treating mouse spermatozoa with several combinations of DTT with and without detergent. Spermatozoa were treated with vigorous pipetting to induce membrane disruption or with TX or the ionic detergent mixed alkyltrimethylammonium bromide (ATAB). Swim-up spermatozoa were used as controls. In each treatment, two samples were tested, with or without the addition of DTT during the treatment procedure. In all samples with DTT, protamine reduction was confirmed by the decondensation assay. Sperm nuclei obtained after different treatments were injected into oocytes for cytogenetic analysis, and paternal and maternal chromosomes of the zygote were visualized and examined. We found that the numbers of normal paternal karyoplates resulting from ICSI with spermatozoa treated with either DTT (87%, 153/176), TX (79%, 112/142), or ATAB (85%, 99/116) alone were similar to swim-up controls (92%, 103/112). However, only 22% (23/103) and 40% (59/149) of examined metaphases were scored as normal in TX + DTT or ATAB + DTT treatments, respectively. Spermatozoa in which the membranes were disrupted by vigorous pipetting in the presence of DTT had a slightly reduced frequency of normal chromosomes (61%, 64/104), whereas those without DTT were normal (79%, 125/159). However, this difference was not statistically significant. When spermatozoa were treated with TX + DTT in the presence of EGTA or a mixture of EGTA and EDTA, the frequency of normal chromosomes was 39% (45/114) and 47% (38/81), respectively, suggesting that endogenous sperm nucleases may play a role in chromosomal damage. Our results indicate that simultaneous treatment of spermatozoa with detergent and DTT induces extensive chromosomal breakage and, therefore, should not be attempted in ICSI.

TAK-779 (Takeda).

TAK-779 is a CCR5 antagonist under investigation by Takeda and Kagoshima University for the potential treatment of HIV [324663], [342114]. TAK-779 inhibits chemokine binding to the CCR5 receptor at nanomolar concentrations. However, it has no effect on the binding of chemokines to the CXCR4 receptor [346835]. A US IND for injectable TAK-779 was filed in june 1999, with Takeda initially planning to commence phase I trials in August 1999. However, the FDA did not clear the IND and recommended that Takeda altered the study protocol to include non-invasive measurement of local toxicities and to evaluate other routes of administration. By September 1999, Takeda had conducted some studies in response to the FDA's recommendations and had made efforts to develop an oral formulation. At this time, the company planned to file a new IND application upon completion of the oral formulation [342114]. In August 1995, Lehman Brothers predicted potential worldwide peak sales of US $300 million in

Safety of a filtrate of fermented garambullo fruit: biotransformation and toxicity studies.

Betalains are important natural pigments for the food industry. The purpose of this study was to evaluate the toxicological and toxicokinetic effects of betalain pigments from a cactaceous fruit (garambullo) on male and female Wistar rats. The pigments did not cause death with any of the doses tested, up to 5 g/kg body weight. In the digestibility studies, there was a degradation of the pigment of 26-29% in the large intestine, 20-26% in the small intestine and 24-29% in the stomach. The pigments were eliminated in the urine as betalains. The pigments had no metabolic effect on the hepatocytes for up to 7 hours. Furthermore, there was no increase in the heart rate when the pigments were administered by oral intubation, up to a dose of 5 g/kg. The data suggest that garambullo fruit pigments do not cause acute toxicity.

Mitochondrial bioenergetics as affected by cationic detergents.

This paper examines the accumulation and toxicity mechanism of a cationic detergent, cetyltrimethylammonium (bromide) (CTAB), in energized rat liver mitochondria. The results suggest that: (1) the CTAB ion is accumulated in the mitochondrial matrix by a membrane potential-driven uptake mechanism; (2) accumulation may lead to a toxic effect, since it gives rise to collapse of the mitochondrial membrane potential (delta phi) which is correlated with ATP synthesis and which regulates Ca++ uptake; (3) collapse of delta phi may be due to enhanced permeability of the mitochondrial membrane to the ions (detergent effect); and (4) delta phi collapse and Ca++ and K+ release were also observed in another cationic detergent, NTAB, but not in the presence of anionic detergents.

Irritant and protective action of urea-urease ammonia in rat gastric mucosa. Different effects of ammonia and ammonium ion.

The effects of urea-urease-ammonia on the rat gastric mucosa were examined and compared with those of NH4OH and NH4Cl. The mucosal application of urea with urease produced a reduction in potential difference (PD) in a dose-related manner for urea, and a significant drop was observed by > 0.1% urea in the presence of 100 units urease. Such PD reduction was also observed when the mucosa was exposed to either NH4OH (> 0.03%) or NH4Cl (> 1%); delta PD (20 mV) caused by 0.3% NH4OH and 3% NH4Cl was equivalent to that induced by 0.5% urea+urease (100 units). The combined oral administration of urea (approximately 6%) and urease (100 units) did not induce any macroscopic damage in the gastric mucosa. NH4Cl given orally had no or little effect on the mucosa at any dose levels even at 10%, while NH4OH given orally caused hemorrhagic lesions in the mucosa at the dose of > 0.3%. In contrast, both urea+urease and NH4Cl given prior to HCl/ethanol protected the gastric mucosa against damage in a dose-related manner, and a significant effect was obtained by urea at > 0.5% and by NH4Cl at > 1%. NH4OH was also effective in reducing the severity of HCl/ethanol-induced gastric lesions at lower dose (0.3%). The protective effect of urea+urease was attenuated significantly by prior administration of indomethacin or coadministration of hydroxyurea, while that of NH4Cl or NH4OH was mitigated by indomethacin.(ABSTRACT TRUNCATED AT 250 WORDS)