Monensin associated or not with virginiamycin or functional oil for feedlot beef cattle

The objective of this study was to evaluate diets containing monensin (MON) associated or not with virginiamycin (VM) or functional oil based on cashew nut shell and castor beans (FO_cc) for beef cattle in feedlots on nutritional (intake and digestibility) and productive parameters. A total of 1410 non-castrated Nellore cattle were selected, with an average age of 18 months and with an initial mean body weight (BW) of 305 ± 41.52 kg. The diet showed a roughage to concentrate ratio of 23:77, with the supply of corn silage as a source of roughage. The following additive inclusions in the diet were evaluated: (1) MON: 27 mg MON/kg dry matter (DM); (2) MON + VM: 22 mg MON/kg DM + 19 mg VM/kg DM; and (3) MON + FO_cc: 22 mg MON/kg DM + 500 mg FO_cc/kg DM. Statistical analyses were obtained through a linear model using initial BW and days of feedlot as covariables and comparisons between treatments using mutually orthogonal linear contrasts with a 5% significance level. The association or not of MON with VM or FO_cc does not affect any of the nutritional and productive parameters evaluated. Animals that receive diets with MON + VM have higher average daily gain and feed efficiency (FE) than those that receive MON + FO_cc without showing differences in nutritional parameters. The supply of MON associated with VM or FO_cc does not increase intake and productive performance and, consequently, efficiency of feedlot beef cattle. However, in the case of use associated with MON, the VM provides greater performance than FO_cc without changing food intake.

Genetic parameters for performance, feed efficiency, and carcass traits in Senepol heifers

Improving feed efficiency is a key breeding goal in the beef cattle industry. In this study, we estimated the genetic parameters for feed efficiency and carcass traits in Senepol cattle raised in tropical regions. Various indicators of feed efficiency [gain to feed ratio (G:F), feed conversion ratio (FCR), residual weight gain (RG), residual intake and body weight gain (RIG), and residual feed intake (RFI)] as well as growth [final BW, average daily gain (ADG), and DM intake (DMI)], and carcass [rib-eye area (REA), backfat thickness (BF), intramuscular fat score, and carcass conformation score] traits were included in the study. After data editing, records from 1 393 heifers obtained between 2009 and 2018 were used for the analyses. We fitted an animal model that included contemporary group (animals from the same farm that were evaluated in the same test season) as the fixed effect, and a linear effect of animal age at the beginning of the test as a covariate; in addition to random direct additive genetic and residual effects. The (co)variance components were estimated by Bayesian inference in uni- and bivariate analyses. Our results showed that feed efficiency indicators derived from residual variables such as RG, RIG, and RFI can be improved through genetic selection (h² = 0.14 ± 0.06, 0.13 ± 0.06, and 0.20 ± 0.08, respectively). Variables calculated as ratios such as G:F and FCR were more influenced by environmental factors (h² = 0.08 ± 0.05 and 0.09 ± 0.05), and were, therefore, less suitable for use in breeding programs. The traits with the greatest and impact on genetic progress in feed efficiency were ADG, REA, and BF. The traits with the greatest and least impact on growth and carcass traits were RG and RFI, respectively. Selection for feed efficiency will result in distinct overall effects on the growth and carcass traits of Senepol heifers. Direct selection for lower RFI may reduce DMI and increase carcass fatness at the finishing stage, but it might also result in reduced growth and muscle deposition. Residual BW gain is associated with the highest weight gain and zero impact on REA and BF, however, it is linked to higher feed consumption. Thus, the most suitable feed efficiency indicator was RIG, as it promoted the greatest decrease in feed intake concomitant with faster growth, with a similar impact on carcass traits when compared to the other feed efficiency indicators.

Synergic effect of simvastatin in combination with amphotericin B against environmental strains of Cryptococcus neoformans from northeastern Brazil: a prospective experimental study

BACKGROUND

Statins are used as cholesterol-lowering drugs and may also have direct antimicrobial effects.

OBJECTIVE

To evaluate synergic interactions between simvastatin and both amphotericin B and fluconazole, against environmental strains of Cryptococcus neoformans isolated from captive birds' droppings.

DESIGNAND SETTING

Experimental study conducted at Federal University of Piauí, Parnaíba, in collaboration with Federal University of Triângulo Mineiro, Uberaba, Brazil.

METHODS

Statin susceptibility tests of Cryptococcus neoformans samples were performed as prescribed in standards. Interactions of simvastatin with amphotericin and fluconazole were evaluated using the checkerboard microdilution method. Presence of these interactions was quantitatively detected through determining the fractional inhibitory concentration index (FICI).

RESULTS

Isolates of Cryptococcus neoformans were obtained from 30 of the 206 samples of dry bird excreta (14.5%) that were collected from pet shops and houses. Ten isolates were selected for susceptibility tests. All of them were susceptible to amphotericin and fluconazole. All presented minimum inhibitory concentration (MIC) > 128 µg/ml and, thus, were resistant in vitro to simvastatin. An in vitro synergic effect was shown through combined testing of amphotericin B and simvastatin, such that six isolates (60%) presented FICI < 0.500. Two isolates showed considerable reductions in MIC, from 1 µg/ml to 0.250 µg/ml. No synergic effect was observed through combining fluconazole and simvastatin.

CONCLUSION

These results demonstrate that simvastatin should be considered to be a therapeutic alternative, capable of potentiating the action of amphotericin B. However, further studies are necessary to clarify the real effect of simvastatin as an antifungal agent.

Alanyl-glutamine attenuates 5-fluorouracil-induced intestinal mucositis in apolipoprotein E-deficient mice

Apolipoprotein E (APOE=gene, apoE=protein) is a known factor regulating the inflammatory response that may have regenerative effects during tissue recovery from injury. We investigated whether apoE deficiency reduces the healing effect of alanyl-glutamine (Ala-Gln) treatment, a recognized gut-trophic nutrient, during tissue recovery after 5-FU-induced intestinal mucositis. APOE-knockout (APOE-/-) and wild-type (APOE+/+) C57BL6J male and female mice (N=86) were given either Ala-Gln (100 mM) or phosphate buffered saline (PBS) by gavage 3 days before and 5 days after a 5-fluorouracil (5-FU) challenge (450 mg/kg, via intraperitoneal injection). Mouse body weight was monitored daily. The 5-FU cytotoxic effect was evaluated by leukometry. Intestinal villus height, villus/crypt ratio, and villin expression were monitored to assess recovery of the intestinal absorptive surface area. Crypt length, mitotic, apoptotic, and necrotic crypt indexes, and quantitative real-time PCR for insulin-like growth factor-1 (IGF-1) and B-cell lymphoma 2 (Bcl-2) intestinal mRNA transcripts were used to evaluate intestinal epithelial cell turnover. 5-FU challenge caused significant weight loss and leukopenia (P<0.001) in both mouse strains, which was not improved by Ala-Gln. Villus blunting, crypt hyperplasia, and reduced villus/crypt ratio (P<0.05) were found in all 5-FU-challenged mice but not in PBS controls. Ala-Gln improved villus/crypt ratio, crypt length and mitotic index in all challenged mice, compared with PBS controls. Ala-Gln improved villus height only in APOE-/- mice. Crypt cell apoptosis and necrotic scores were increased in all mice challenged by 5-FU, compared with untreated controls. Those scores were significantly lower in Ala-Gln-treated APOE+/+ mice than in controls. Bcl-2 and IGF-1 mRNA transcripts were reduced only in the APOE-/- -challenged mice. Altogether our findings suggest APOE-independent Ala-Gln regenerative effects after 5-FU challenge.

PPAR gamma activation protects the brain against microvascular dysfunction in sepsis

Sepsis is a severe disorder characterized by systemic inflammatory responses in the presence of an infection and may progress to multiple organ dysfunction and death. Alterations in cerebral microcirculation fulfill a crucial role in the pathogenesis of severe sepsis, and include a decrease in capillary density and disturbances in leukocyte movement along capillaries. Nevertheless, the mechanisms involved in sepsis-associated cerebral microcirculatory alterations have so far not been defined. We investigated the effect of the peroxisome proliferator-activated receptor gamma (PPARγ) selective agonist rosiglitazone on leukocyte/endothelial cell interaction and functional capillary density in the brain in the cecal ligation and puncture (CLP) model of sepsis. Anti-inflammatory effects of rosiglitazone on the cerebral microcirculation were marked. Functional capillary density increased and leukocyte rolling and adhesion were decreased in animals submitted to CLP and treated with rosiglitazone. Our data provide evidence for involvement of PPARγ activation in leukocyte-endothelium interactions and alterations in capillary density. Improved cerebral perfusion in animals treated with rosiglitazone, suggests that PPARγ activation is protective against cerebral microvascular dysfunction in sepsis.

Effects of centrally acting antihypertensive drugs on the microcirculation of spontaneously hypertensive rats

We investigated the acute effects of centrally acting antihypertensive drugs on the microcirculation of pentobarbital-anesthetized spontaneously hypertensive rats (SHR). The effects of the sympatho-inhibitory agents clonidine and rilmenidine, known to activate both alpha2-adrenoceptors and nonadrenergic I1-imidazoline binding sites (I1BS) in the central nervous system, were compared to those of dicyclopropylmethyl-(4,5-dimethyl-4,5-dihydro-3H-pyrrol-2-yl)-amine hydrochloride (LNP 509), which selectively binds to the I1BS. Terminal mesenteric arterioles were observed by intravital microscopy. Activation of the central sympathetic system with L-glutamate (125 microg, ic) induced marked vasoconstriction of the mesenteric microcirculation (27 +/- 3%; N = 6, P < 0.05). In contrast, the marked hypotensive and bradycardic effects elicited by intracisternal injection of clonidine (1 microg), rilmenidine (7 microg) and LNP 509 (60 microg) were accompanied by significant increases in arteriolar diameter (12 +/- 1, 25 +/- 10 and 21 +/- 4%, respectively; N = 6, P < 0.05). The vasodilating effects of rilmenidine and LNP 509 were two-fold higher than those of clonidine, although they induced an identical hypotensive effect. Central sympathetic inhibition elicited by baclofen (1 microg, ic), a GABA B receptor agonist, also resulted in vasodilation of the SHR microvessels. The acute administration of clonidine, rilmenidine and LNP 509 also induced a significant decrease of cardiac output, whereas a decrease in systemic vascular resistance was observed only after rilmenidine and LNP 509. We conclude that the normalization of blood pressure in SHR induced by centrally acting antihypertensive agents is paralleled by important vasodilation of the mesenteric microcirculation. This effect is more pronounced with substances acting preferentially (rilmenidine) or exclusively (LNP 509) upon I1BS than with those presenting important alpha2-adrenergic activity (clonidine).

Protective effects of yangambin on cardiovascular hyporeactivity to catecholamines in rats with endotoxin-induced shock

The protective effects of a new, selective, plant-derived platelet-activating factor (PAF) antagonist, yangambin, on the cardiovascular alterations and mortality due to endotoxic shock were investigated in anaesthetized rats. We also studied the involvement of PAF in the induction of the vascular and cardiac hyporesponsiveness to adrenergic stimulation observed during endotoxaemia. The animals were sensitized to the lethal effects of Escherichia coli lipopolysaccharide (LPS) with D(+)-galactosamine (50 mg/kg, i.v.) 15 min before LPS injection. LPS (3 mg/kg, i.v.) induced a progressive and marked decrease in mean arterial blood pressure from 85+/-4 to 30+/-3 mmHg and a reduction of cardiac output (CO) from 180+/-7 to 37+/-3 ml/min (120 min) accompanied by a maintenance of systemic vascular resistance, suggesting that cardiovascular collapse resulted mainly from myocardial depression. The maximum pressor responses to noradrenaline (0.3-3.0 microg/kg, i.v.) fell from 72+/-9 (control) to 5+/-1 mmHg (LPS) while the CO responses decreased from 81+/-5 to 8+/-3 ml/min. Pre-treatment with yangambin (30 mg/kg, i.v.) or with WEB 2086 (5 mg/kg, i.v.), a reference PAF receptor antagonist, completely prevented the LPS-induced cardiovascular collapse and abolished the sharp reductions of the arterial blood pressure and CO responses to noradrenaline observed during endotoxaemia. Post-treatment with yangambin 90 min after LPS administration did not reverse the arterial hypotension, cardiac failure or cardiovascular hyporesponsiveness to catecholamines. Finally, the acute (150 min) survival rates of endotoxic shock increased from 0% (LPS group) to 100% in the groups pretreated with either yangambin or WEB 2086. The long-term (7-day) survival also increased from 0% (LPS group) to 85% (yangambin pre-treatment group). In conclusion, these data suggest a role for PAF in the pathogenesis of endotoxin-induced vascular and cardiac hyporesponsiveness to catecholamines and confirm its involvement in the complex cascade of multiple mediators released during endotoxic/septic shock. Yangambin proved to be an effective pharmacological agent against cardiovascular collapse and mortality in endotoxin shock.

The acute increases in vasomotor tone and blood pressure induced by carotid artery occlusion are modulated by platelet-activating factor (PAF) independently of nitric oxide release

The purpose of the present study was to investigate the involvement of nitric oxide (NO) in the modulatory role of platelet-activating factor (PAF, 1-O-hexadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine), a vasoactive phospholipid mediator synthesized by endothelial cells, on the vascular tone and arterial blood pressure. In pentobarbitone-anaesthetized rabbits, unloading of the carotid sinus baroreceptors by a bilateral carotid artery occlusion elicited a reflex rise in systemic vascular resistance, which was markedly potentiated by pretreating the animals with the PAF receptor antagonist WEB 2086 ([3-4-(2-chlorphenyl-)-9-methyl-6H-thieno-3,2-f-1,2,4-triazolo-4,3 -alpha-1,4 -diazepin-2-yl-(4-morpholinyl)-1-propanone]; 5 mg/kg, i.v.). In contrast, the inhibition of the biosynthesis of NO via NO synthase using N omega-nitro-L-arginine methyl ester (L-NAME) neither affected the systemic vasoconstriction induced by carotid artery occlusion nor modified the potentiating effect of WEB 2086. The haemodynamic alterations induced by L-NAME administration were corrected by continuous infusions of the directly-acting vasodilators sodium nitroprusside or diazoxide. The results of the present study confirm previous studies from our group suggesting the involvement of PAF in a negative feedback mechanism effective in the local regulation of vasomotor tone in anaesthetized rabbits, but exclude the participation of NO in this process.

Yangambin: a new naturally-occurring platelet-activating factor receptor antagonist: in vivo pharmacological studies

The pharmacological profile of a novel specific platelet-activating factor (PAF) receptor antagonist-yangambin-isolated from the Brazilian plant Ocotea duckei Vattimo (Lauraceae), was investigated in the pentobarbitone-anaesthetized rabbit. The i.v. administration of PAF (0.03-3.0 microgram kg-1) induced marked but reversible hypotensive effects and mild reductions in the heart rate. Both effects are independent of the respiratory conditions imposed on the animals. Moreover, PAF (3.0 microgram kg-1, i.v.) induced a reversible decrease of the circulating levels of platelets and of polymorphonuclear leukocytes. Pretreatment with yangambin (10 and 20 mg kg-1, i.v.) dose-dependently attenuated PAF-induced cardiovascular changes and thrombocytopaenia. Nevertheless, the neutropenic leukopaenia elicited by PAF (3.0 microgram kg-1, i.v.) was not prevented by yangambin whereas the reference PAF antagonists WEB 2086 (2 mg kg-1, i.v.) and SR 27417 (1 mg kg-1, i.v.) significantly inhibited the phenomenon. The hypotensive effects of acetylcholine, histamine, and 5-hydroxytryptamine were not affected by prior administration of yangambin. It is concluded that yangambin is a selective antagonist of the cardiovascular effects of PAF which could be useful in pathological states characterized by abnormal PAF release, such as anaphylactic and septic shocks. Furthermore, yangambin might discriminate a PAF receptor subtype present in the cardiovascular system and platelets from the one existing in polymorphonuclear leukocytes in the rabbit.