Lasalocid immediately and completely prevents the myocardial damage caused by coronary ischemia reperfusion in rat heart.

Lasalocid, a specific mobile membrane ionophore for calcium, dopamine and norepinephrine was assayed in its capacity to reduce or maintain unaltered the cardiovascular function in conditions of imminent myocardial injury. In experiments of coronary blockade and reperfusion carried out in rat heart, it was found that when administered from 5 to 30 minutes prior to the induction of coronary blockade, at a concentration of 2 mg/kg of body weight, the ionophore immediately, simultaneously, and completely interrupts the blood pressure decay, cardiac frequency increase, electrical ventricular tachycardia and fibrillation, as well as the fall of mitochondrial oxidative phosphorylation and decay of mitochondrial oxygen uptake provoked by the induced myocardial injury. It appears that the molecular mode of action of the lasalocid is associated with its unique ability to transport both calcium and the catecholamines, dopamine and norepinephrine, across mitochondrial and bimolecular lipid membranes, as well as through synaptic cell membrane terminals from rat heart, myocardial fibers of the heart and heart chromaffin membrane vesicles. It is suggested that for the potential medical use of lasalocid to detain incoming ischemic myocardial damage, there exists a need to develop a personal electronic device able to simultaneously monitor, detect, and inform on the very early and simultaneous signs of cardiac alterations of electrical, mechano-chemical, metabolic and hydraulic nature, all which precede heart failure and to administer the lasalocid.

Trypanosoma brucei: trypanocidal and cell swelling activities of lasalocid acid.

Chemotherapeutic treatment of human and animal trypanosomiasis is unsatisfactory because only a few drugs are available. As these drugs have poor efficacy and cause adverse reactions, more effective and tolerable medications are needed. As the polyether ionophore antibiotic lasalocid acid is used as medicated feed additive in cattle, the compound was tested for its trypanocidal and cytotoxic activity against bloodstream forms of Trypanosoma brucei and human myeloid HL-60 cells. The concentrations required of lasalocid acid to reduce the growth rate of trypanosomes by 50% and to kill the parasites were 1.75 and 10 µM, respectively. The ionophore displayed also cytotoxic activity against HL-60 cells but the human cells were about 10 to 14 times less sensitive indicating moderate selectivity. As the trypanocidal mechanism of action of polyether ionophore antibiotics is due to a sodium influx-induced cell swelling, the effect of lasalocid acid on cell volume change in bloodstream-form trypanosomes was investigated. Interestingly, lasalocid acid induced a much faster cell swelling in trypanosomes than the more trypanocidal related ionophore salinomycin. These results support further investigations of lasalocid acid and derivatives thereof as potential agents against African trypanosomiasis.

Assessment of probiotics supplementation via feed or water on the growth performance, intestinal morphology and microflora of chickens after experimental infection with Eimeria acervulina, Eimeria maxima and Eimeria tenella.

In this study, the effect of probiotic supplementation via drinking water or feed on the performance of broiler chickens experimentally infected with sporulated oocysts of Eimeria acervulina (5 × 10(4)), Eimeria maxima and Eimeria tenella (2 × 10(4) each one) at 14 days of age was evaluated. Two hundred and forty 1-day-old Ross 308 male chicks were separated into eight equal groups with three replicates. Two of the groups, one infected with mixed Eimeria oocysts and the other not, were given a basal diet and served as controls. The remaining groups were also challenged with mixed Eimeria species and received the basal diet and either water supplemented with probiotic (three groups) or probiotic via feed (two groups); the probiotic used consisted of Enterococcus faecium #589, Bifidobacterium animalis #503 and Lactobacillus salivarius #505 at a ratio of 6:3:1. Probiotic supplementation was applied either via drinking water in different inclusion rates (groups W1, W2 and W3) or via feed using uncoated (group FN) or coated strains (group FC). The last group was given the basal diet supplemented with the anticoccidial lasalocid at 75 mg/kg. Each experimental group was given the corresponding diet or drinking water from day 1 to day 42 of age. Throughout the experimental period of 42 days, body weight and feed intake were recorded weekly and feed conversion ratios were calculated. Seven days after infection, the infected control group presented the lowest weight gain values, while probiotics supplied via feed supported growth to a comparable level with that of the lasalocid group. Probiotic groups presented lesion score values and oocyst numbers that were lower than in control infected birds but higher than in the lasalocid group. In the duodenum, jejunum and ileum, the highest villous height values were presented by probiotic groups. In conclusion, a mixture of probiotic substances gave considerable improvement in both growth performance and intestinal health in comparison with infected control birds and fairly similar improvement to an approved anticoccidial during a mixed Eimeria infection.

One-pot synthesis and cytotoxicity studies of new Mannich base derivatives of polyether antibiotic--lasalocid acid.

Seven Mannich base derivatives of polyether antibiotic Lasalocid acid (2a-2g) were synthesized and screened for their antiproliferative activity against various human cancer cell lines. A novel chemoselective one-pot synthesis of these Mannich bases was developed. Compounds 2a-2c and 2g with sterically smaller dialkylamine substituent, displayed potent antiproliferative activity (IC50: 3.2-7.3 µM), and demonstrated higher than twofold selectivity for specific type of cancer. The nature of Mannich base substituent on C-2 atom at the aromatic ring may be critical in the search for selectivity towards a particular cancer cell.

Effects of lasalocid, narasin, or virginiamycin supplementation on rumen parameters and performance of beef cattle fed forage-based diet.

Two experiments were designed to evaluate the impacts of supplementing lasalocid (LAS), narasin (NAR), or virginiamycin (VRM) on rumen fermentation parameters, apparent nutrient digestibility, and blood parameters (Exp. 1), as well as feed intake and performance (Exp. 2) of Nellore cattle consuming a forage-based diet. In Exp. 1, 32 rumen-fistulated Nellore steers (initial shrunk body weight [BW] = 355 ± 4.4 kg) were assigned to a randomized complete block design. Within block, animals were randomly assigned to one of four treatments: 1) forage-based diet without feed additives (CON), 2) CON diet plus 13 mg/kg of dry matter (DM) of NAR, 3) CON diet plus 20 mg/kg of DM of sodium LAS, or 4) CON diet plus 20 mg/kg of DM of VRM. No treatment effects were detected (P ≥ 0.32) for intake and apparent digestibility of nutrients. Steers fed NAR had the lowest (P ≤ 0.01) molar proportion of acetate on day 28, 56, and 112 vs. CON, LAS, and VRM steers, whereas acetate did not differ (P ≥ 0.25) between LAS, VRM, and CON steers from day 28 to 84. On day 112, steers fed LAS had a lower (P < 0.02) molar proportion of acetate vs. VRM and CON, whereas it did not differ between CON and VRM (P > 0.33). Steers receiving NAR had a greater (P ≤ 0.04) ruminal propionate vs. CON, LAS, and VRM, whereas LAS steers had greater (P < 0.04) propionate vs. CON and VRM steers on day 28 and 112, and it did not differ (P > 0.22) between CON and VRM. In Exp. 2, 160 Nellore bulls were blocked by initial shrunk BW (212 ± 3.1 kg) in a 140-d feedlot trial. Diets contained the same treatments used in Exp. 1. Bulls fed NAR had greater (P < 0.02) average daily gain (ADG) vs. CON and VRM, and similar (P = 0.17) ADG between NAR and LAS, whereas ADG did not differ (P > 0.28) between LAS, VRM, and CON bulls. A treatment effect was detected (P = 0.03) for dry matter intake, being greater in NAR vs. CON, LAS, and VRM bulls, and similar (P > 0.48) between CON, LAS, and VRM bulls. A tendency was detected (P = 0.09) for feed efficiency, which was greater (P < 0.02) in NAR bulls vs. CON and VRM, and similar (P = 0.36) between NAR and LAS bulls. From day 112 to 140, bulls receiving NAR were heavier (P < 0.03) vs. CON, LAS, and VRM bulls, but no differences were observed (P > 0.51) between CON, LAS, and VRM bulls. Collectively, ruminal fermentation profile and intake were impacted by NAR supplementation, which partially contributed to the enhanced performance of Nellore bulls receiving a forage-based diet.

Feed additives are nutritional tools that benefit dietary digestibility and nutrient utilization, alter ruminal fermentation routes, and improve cattle growth and efficiency, thus increasing productivity and profitability in beef cattle systems. Nonetheless, most of the current research focuses on supplementing feed additives in high-concentrate diets. Leaving a significant gap in understanding the influence of feed additives in cattle consuming forage-based diets, especially molecules capable of altering the fermentation process and, consequently, beef cattle performance. Therefore, this experiment aimed to evaluate the impacts of supplementing narasin (NAR), lasalocid (LAS), or virginiamycin (VRM) on rumen fermentation parameters, apparent nutrient digestibility, feed intake, and performance of Bos indicus Nellore cattle consuming a forage-based diet. Including commercially available feed additives into forage-based diets did not impact nutrient intake and digestibility of nutrients. The inclusion of NAR affected ruminal fermentation parameters toward propionate production, positively contributing to animal performance. Ruminal fermentation characteristics and animal growth were not impacted by dietary LAS and VRM, which could be attributed to the dose used in the current experiment, despite the manufacturer's recommendation. This research provides insights into NAR as an important feed additive for forage-based beef cattle diets.

Comparison effect of lasalocid, diclazuril, probiotic and symbiotic on histomorpholical changes of small intestine induced by E. tenella.

This study aimed to investigate the comparison of effect of anticoccidal drugs including lasalocid and diclazuril with probiotic and synbiotic on the growth performance and intestinal morphology in broiler chicken. One hundred eighty chickens (Ross 308, 1 day old) were randomly divided into 6 equal groups (n=30) including the negative control (basal diet), the positive control (basal diet+oral inoculation of 3×104 sporulated oocytes of E. tenella, and four treatment groups. At days of 28 and 49 of age, 9 chickens were blindly chosen from each group were scarified by decapitation and their various segments of small intestine including ileum, jejunum, and duodenum were evaluated histomorphologically. We found that the economic losses resulted from coccidial infection in the poultry industry are caused by the decreased performance of broiler chicken induced by morphological changes in the any three segments specially jejunum. The anticoccidial drugs, synbiotic and probiotic can partially prevent morphological changes in any three segments of small intestine in broiler chicken with coccidiosis. Since morphological changes in the jejunum begin earlier than in other parts and surface area of jejunal villi is important for nutrition absorbance as well as growth performance, lasolacid was found to a be more efficient treatment in this regard.

The co-administration effects of florfenicol and lasalocid on performance, biochemical and pathological parameters of muscle, heart, liver, kidney and sciatic nerve in broiler chickens.

The study aimed to examine the effect of simultaneous application of florfenicol and lasalocid on the performance and vital organ function of chickens. For this, 300 chicks were divided into four groups. Group one to three received florfenicol, lasalocid and lasalocid plus florfenicol, respectively. Group four as the control group received a basic diet without lasalocid or florfenicol. Lasalocid was used from 7 to 35 days old, continuously. Florfenicol was used at 21 days old for 5 days. The growth indices were measured at the end of each week. The chickens were euthanized at the ages of 28 and 35 days old after collecting blood samples with and without anticoagulants. The liver, heart, muscle, kidney and sciatic nerve were collected in formalin 10% for histopathological examination. The blood and serum samples were used to determine clinical pathologic and hematologic indices. The ratio of internal organs to body weight and ratio of the right ventricle to the total ventricles (RV/TV) of the heart was measured. Results showed, the use of lasalocid decreased feed conversion rate and triglyceride, and increased total protein. Simultaneous administration of lasalocid and florfenicol affected histopathology of the liver and heart and significantly increased creatine phosphokinase, uric acid and the ratio of RV/TV of heart. The eosinophil percentage in the chickens who received florfenicol plus lasalocid was significantly higher than chickens who received florfenicol alone (p < 0.05). In conclusion, it seems that simultaneous administration of the florfenicol and lasalocid induces side-effects especially on cardiac function and it is not recommended.

Revisiting Old Ionophore Lasalocid as a Novel Inhibitor of Multiple Toxins.

The ionophore lasalocid is widely used as a veterinary drug against coccidiosis. We found recently that lasalocid protects cells from two unrelated bacterial toxins, the cytotoxic necrotizing factor-1 (CNF1) from Escherichia. coli and diphtheria toxin. We evaluated lasalocid's capacity to protect cells against other toxins of medical interest comprising toxin B from Clostridium difficile, Shiga-like toxin 1 from enterohemorrhagic E. coli and exotoxin A from Pseudomonas aeruginosa. We further characterized the impact of lasalocid on the endolysosomal and the retrograde pathways and organelle integrity, especially the Golgi apparatus. We found that lasalocid protects cells from all toxins tested and impairs the drop of vesicular pH along the trafficking pathways that are required for toxin sorting and translocation to the cytoplasm. Lasalocid also has an impact on the cellular distribution of GOLPH4 and GOLPH2 Golgi markers. Other intracellular trafficking compartments positive for EEA1 and Rab9A display a modified cellular pattern. In conclusion, lasalocid protects cells from multiple deadly bacterial toxins by corrupting vesicular trafficking and Golgi stack homeostasis.

Polymerization of actin. VI. The polarity of the actin filaments in the acrosomal process and how it might be determined.

The polarity of the actin filaments which assemble from the nucleating body or actomere of Thyone and Pisaster sperm was determined using myosin subfragment 1 decoration. The polarity was found to be unidirectional with the arrowheads pointing towards the cell center. When polymerization is induced at low temperature with concentrations of actin near the critical concentration for polymerization, elongation of filaments occurs preferentially off the apical end. If the sperm are induced to undergo the acrosomal reaction with an ionophore, the polarity of the actin filaments attached to the actomere is the same as that already described, but the filaments which polymerize parallel to, but peripheral to, those extending from the actomere are randomly polarized. These randomly polarized filaments appear to result from spontaneous nucleation. When sperm are induced to undergo the acrosomal reaction with eggs, the polarity of the actin filaments is also unidirectional with the arrowheads pointing towards the cell center. From these results we conclude: (a) that the actomere, by nucleating the polymerization of actin filaments, controls the polarity of the actin filaments in the acrosomal process, (b) that the actomere recognizes a surface of the actin monomer that is different from that surface recognized by the dense material attached to membranes, and (c) that egg myosin could not act to pull the sperm into the egg. Included is a discussion of how the observation that monomers add largely to one end of a decorated filament in vitro relates to these in vivo observations.

Convergent differentiation in cultured rat cells from nonkeratinized epithelia: keratinocyte character and intrinsic differences.

Epithelial cells derived from a variety of glandular and other nonkeratinized rat tissues (pituitary, thyroid, bladder, endometrium, trachea, seminal vesicle, prostate, and mammary epithelium) were serially cultivated using a feeder layer of lethally irradiated 3T3 cells. The epithelial cells grew as progressively expanding colonies, in some cases stratified, and were shown to form cornified envelopes upon ionophore-induced activation of cross-linking. Cultures derived from each tissue were distinguishable from the others by characteristic cellular appearance and colony morphology. Those examined in greater detail could be distinguished biochemically in three ways. (a) A majority of cells in sparse cultures of bladder, tracheal, endometrial, and vaginal epithelial cells were capable of envelope formation, whereas those from pituitary, thyroid, seminal vesicle, and mammary epithelia did not attain maximal envelope forming ability until after confluence. (b) Bladder, thyroid, and pituitary cells exhibited different electrophoretic profiles of keratins, which accounted for 20-50% of the cellular protein. (c) Bladder cells were distinguished from thyroid and pituitary cells by a greater suppression of envelope-forming ability by vitamin A. These observations showed that cells from many epithelia have the potential to express properties of keratinocytes in culture while maintaining morphological and physiological differences. Serial passage of these cells generated continuous lines.

Polymerization of actin. V. A new organelle, the actomere, that initates the assembly of actin filaments in Thyone sperm.

Between the acrosomal vacuole and the nucleus is a cup of amorphous material (profilactin) which is transformed into filaments during the acrosomal reaction. In the center of this cup in untreated Thyone sperm is a dense material which I refer to as the actomere; it is composed of 20-25 filaments embedded in a dense matrix. To visualize the substructure of the actomere, the profilactin around it must be removed. This is achieved either by demembranating the sperm with Triton X-100 and then raising the pH to 8.0, or by adding inophores to intact sperm at pH 8.0. Under these conditions, the actomere remains as a unit while the rest of the profilactin is solubilized or polymerized. When demembranated sperm are incubated under conditions in which the actin should polymerize, filaments grow from the end of the actomere: the actomere thus appears to behave as a nucleating body. This observation is strengthened by experiments in which untreated sperm are incubated in seawater or isotonic NaCl at pH 7.0 and the ionophore X537A is added; in this case, only a partial polymerization of the actin occurs and the acrosomal vacuole does not fuse with the cell surface. The actin filaments that do form, however, are attached to the apical end of the actomere. In fact, the elongating filaments push their way into and frequently through the acrosomal vacuole. Thus, it appears that the sperm organizes the actin filaments by controlling their nucleation. My model is that the cell controls the ammount of unbound actin such that it is slightly above the critical concentration for polymerization. Then, spontaneous nucleation is unfavored and polymerization would proceed from existing nuclei such as the actomer.

Membrane events in the acrosomal reaction of Limulus sperm. Membrane fusion, filament-membrane particle attachment, and the source and formation of new membrane surface.

The membranes of Limulus (horseshoe crab) sperm were examined before and during the acrosomal reaction by using the technique of freeze-fracturing and thin sectioning. We focused on three areas. First, we examined stages in the fusion of the acrosomal vacuole with the cell surface. Fusion takes place in a particle-free zone which is surrounded by a circlet of particles on the P face of the plasma membrane and an underlying circlet of particles on the P face of the acrosomal vauole membrane. These circlets of particles are present before induction. Up to nine focal points of fusion occur within the particle-free zone. Second, we describe a system of fine filaments, each 30 A in diameter, which lies between the acrosomal vacuole and the plasma membrane. These filaments change their orientation as the vacuole opens, a process that takes place in less than 50 ms. Membrane particles seen on the P face of the acrosomal vacuole membrane change their orientation at the same time and in the same way as do the filaments, thus indicating that the membrane particles and filaments are probably connected. Third, we examined the source and the point of fusion of new membrane needed to cover the acrosomal process. This new membrane is almost certainly derived from the outer nuclear envelope and appears to insert into the plasma membrane in a particle-free area adjacent to an area rich in particles. The latter is the region where the particles are probably connected to the cytoplasmic filaments. The relevance of these observations in relation to the process of fertilization of this fantastic sperm is discussed.

Golgi organelle response to the antibiotic X537A.

The effects of the ionophoric antibiotic X537A on cell structure were studied with phase-contrast, fluorescence, and electron microscopy. X537A induced selective vacuolation of the Golgi apparatus of vascular and intestinal smooth muscle, epithelium, plasma cells, and cultured chick heart and guinea pig vascular smooth muscle cells. The swelling of the Golgi apparatus induced by X537A was reversible in the systems examined for reversibility: vascular smooth muscle and cultured chick heart. Myelin figures were common in the Golgi apparatus vacuolated by X537A. Fluorescence microscopy of cultured cells incubated with X537A showed the characteristic blue X537A fluorescence associated with lipid globules in the cultured cells. Incubation of cultured chick heart cells with X537A reduced the beating rate and, after 24-72 h, abolished the sarcomere pattern. The swelling of the Golgi membranes produced by X537A in cultured vascular smooth muscle was associated with inhibition of D-[6-3H]glucosamine and [35S]sulfate incorporation into glycosaminoglycans.

Premature specification of the retina in embryonic Xenopus eyes treated with ionophore X537A.

Eyes excised from Xenopus embryos at stages 24 to 25 were cultured for 4 to 6 hours in a medium containing the ionophore X537A or in a control medium. The eyes were implanted either upside down or normally in host embryos at stages 28 to 30, and their retinotectal projections were mapped after metamorphosis. Treatment with X537A prevented realignment of retinal axes in eyes implanted into hosts that were capable of producing retinal axial alignment in all control eyes.

Ethanol: modifications of acute intoxication by divalent cations.

Calcium, other divalent cations, and calcium antagonists were tested for their ability to alter ethanol-induced sleeping time, hypothermia, and behavioral intoxication in mice and rats. Calcium given intraventricularly significantly enhanced sleeping time and behavioral intoxication in a dose-related manner. The ionophores X537A and A23187 accentuated the effect of a low dose of calcium, whereas the calcium chelators EDTA and EGTA decreased sleeping time. Calcium also enhanced tertiary butanol- and chloral hydrate-induced sleeping time. The effects of cations on ethanol-induced hypothermia were less significant. The results suggest the existence of a central calcium pool that is involved in ethanol intoxication in rodents.

Botulinum toxin: mechanism of presynaptic blockade.

The mechanism of action of botulinum toxin was analyzed by the use of calcium ionophores and black widow spider venom. Addition of calcium ionophores to nerve-muscle preparations blocked by botulinum toxin did not increase the frequency of miniature end plate potentials. However, the spider venom elicited a barrage of miniature end plate potentials after blockade by botulinum. Electron micrographs of preparations treated with botulinum toxin and then the spider venom revealed clumping of synaptic vesicles at release sites in the otherwise depleted nerve terminals. These findings indicate that the action of botulinum toxin is not due to deficient storage of acetylcholine in vesicles or blockade of calcium entry into nerve terminals. They suggest that the toxin interferes with the acetylcholine release process itself, possibly by blocking exocytosis at the release sites.

Screening of a Drug Library Identifies Inhibitors of Cell Intoxication by CNF1.

Cytotoxic necrotizing factor 1 (CNF1) is a toxin produced by pathogenic strains of Escherichia coli responsible for extra-intestinal infections. CNF1 deamidates Rac1, thereby triggering its permanent activation and worsening inflammatory reactions. Activated Rac1 is prone to proteasomal degradation. There is no targeted therapy against CNF1, despite its clinical relevance. In this work we developed a fluorescent cell-based immunoassay to screen for inhibitors of CNF1-induced Rac1 degradation among 1120 mostly approved drugs. Eleven compounds were found to prevent CNF1-induced Rac1 degradation, and five also showed a protective effect against CNF1-induced multinucleation. Finally, lasalocid, monensin, bepridil, and amodiaquine protected cells from both diphtheria toxin and CNF1 challenges. These data highlight the potential for drug repurposing to fight several bacterial infections and Rac1-based diseases.

Bone resorption in organ culture: inhibition by the divalent cation ionophores A23187 and X-537A.

The ionophores A23187 and X-537A were used as probes to investigate the possible role of calcium uptake by bone as a mediator for the stimulation of bone resorption induced by parathyroid hormone (PTH) and other agents in cultured mouse calvaria. The ionophores alone at concentrations from 1 nM to 20 muM did not stimulate bone resorption, nor did they potentiate bone resorption stimulated by submaximal concentrations of PTH after either brief (15-60 min) or extended (1-3 day) exposure to the ionophores. Unexpectedly, we found that the ionophores inhibit in a dose-dependent manner bone resorption stimulated by PTH and a wide variety of other compounds (prostaglandin E2, 1alpha-hydroxycholecalciferol, 3-isobutyl-1-methyl-xanthine, and phorbol myristate acetate). This inhibition was not due to irreversible damage to the bones by the ionophores, because the inhibition was reversible even after 24 h of treatment. Inhibition of bone resorption by the ionophores was observed in media of both high and low calcium concentration, indicating that the inhibition was not due to a critical extracellular calcium concentration. Inhibition by the ionophores differs qualitatively in several ways from that produced by calcitonin, a natural inhibitor of bone resorption. Furthermore, A23187 at 1.0 mug/ml had no effect on the accumulation of cyclic AMP in the medium of either control, PTH- or calcitonin treated calvaria. We conclude that the ionophores A23187 or X537A do not stimulate bone resorption nor potentiate the effects of stimulators of bone resorption; instead they are inhibitors of bone resorption stimulated by a wide variety of compounds.

Mucosal mast cell proteases are involved in colonic permeability alterations and subsequent bacterial translocation in endotoxemic rats.

LPS-induced endotoxemia is associated with gut immune stimulation, mucosal inflammation, colonic paracellular permeability (CPP) alteration, and it promotes bacterial translocation (BT). Gut permeability increase linked to LPS promotes mucosal barrier dysfunction resulting to BT. However, the mechanisms involved in these alterations remain unknown. We aimed to evaluate the role of colonic mucosal mast cells and luminal serine protease activity (PA) in the alterations of CPP and BT induced by LPS. Rats receiving doxantrazole, a mast cell stabilizer, combined or not with LPS from Escherichia coli and CPP as well as BT were evaluated after each treatment. Mucosal mast cell activation was assessed by histological methods and by rat mast cell protease 2 level measurement in colonic content. Colonic luminal PA and mucosal inflammation (myeloperoxidase activity) were biochemically determined. In addition, the ability of luminal contents to act on CPP was evaluated in vitro in Ussing chambers. Peripheral administration of LPS promoted mast cell degranulation and increased CPP, BT, mucosal myeloperoxidase activity as well as rat mast cell protease 2 levels, and PA in colonic content. LPS-induced CPP increase and BT were prevented by doxantrazole. In vitro, exposure of the apical side of colonic tissues with supernatants from colonic contents of LPS-treated rats increased CPP. This effect was blocked by the serine protease inhibitor soybean trypsin inhibitor. Our data bring evidence of a key role of mucosal mast cells in LPS-induced increase of CPP and BT through the release of serine proteases into the colonic lumen.

Effects of lasalocid or monensin supplementation on digestion, ruminal fermentation, blood metabolites, and milk production of lactating dairy cows.

Six ruminally fistulated midlactating multiparous Holstein cows were used in a double 3 x 3 Latin square design (35-d periods) to study the effects of lasalocid (LAS) and monensin (MON) supplemented at 24 mg/ kg of dry matter on digestion, ruminal fermentation, blood metabolites, and milk production. Cows were blocked according to milk production and fed a red clover silage-based total mixed ration (17.8% crude protein) without supplementation or supplemented with LAS or MON. Daily dry matter intake, milk production, and milk fat and protein concentrations were similar among treatments and averaged 23.5 kg, 36.6 kg, 3.36%, and 3.38%, respectively. Rumen lipogenic:glucogenic volatile fatty acids and NH(3)-N concentration were lower, and apparent digestibility of dry matter, organic matter, crude protein, and gross energy were higher with than without ionophore supplementation. Compared with LAS, MON increased concentrations of plasma urea-N and milk urea-N, and excretion of urinary urea-N and total N. Monensin also decreased N retention and tended to reduce plasma concentration of nonessential AA in comparison with LAS. Both ionophores reduced daily fecal excretion of N by 13 g compared with the control, but MON increased daily losses of urinary N by 36 g compared with LAS. Results from this study suggest that postabsorptive metabolism of N might be altered by the type of ionophore fed.