Performance, carcass characteristics and meat quality of Nellore cattle supplemented with supranutritional doses of sodium selenite or selenium-enriched yeast.

The enrichment of meat with selenium is important to improve the intake of selenium by humans. The effects of supranutritional doses of sodium selenite or selenium-enriched yeast on performance, carcass characteristics and meat quality were evaluated using 63 Nellore cattle in a completely randomized design with two sources (sodium selenite and selenium-enriched yeast), three levels (0.3, 0.9 and 2.7 mg Se/kg DM) and control treatment (without addition of selenium). Final body weight (BW), average daily gain, dry matter intake and gain to feed ratio (G : F) at the end of 84 days of supplementation were not influenced by treatments (P>0.05). Values of pH, ribeye area, back fat thickness and marbling score were also not influenced by treatments ( P>0.05). Dressing percentage was greater (P=0.02) in Nellore cattle supplemented with organic Se (58.70%) compared to animals supplemented with inorganic Se (57.94%). Hot carcass weight increased ( P=0.05) with the increasing of Se levels in the diet. Colour, shear force (SF), cooking and drip loss remained unchanged ( P>0.05); however thiobarbituric acid reactive substances was 15.51% higher with inorganic Se compared with organic Se. The selenium concentration in the meat of animals receiving organic selenium was higher ( P<0.001) than that of animals receiving sodium selenite, at all levels (0.3; 0.9 and 2.7 mg/kg DM). The meat of animals receiving 2.7 mg of organic Se/kg of DM presented concentration of 372.7 µg Se/kg in the L.dorsi muscle, and the intake of 150 g of this meat by humans provides approximately 100% of the recommended Se intake (55 µg Se/day for adults). Therefore, the use of supranutritional doses of 2.7 mg Se/kg of DM, regardless of source, is a way of naturally producing selenium-enriched meat without compromising performance, carcass characteristics and quality of Nellore bovine meat.

Effects of ractopamine hydrochloride and dietary protein content on performance, carcass traits and meat quality of Nellore bulls.

Ractopamine hydrochloride (RH) alters protein metabolism and improves growth performance in Bos taurus cattle with high carcass fat. Our objective was to evaluate the effects of RH, dietary CP and RH×CP interaction on performance, blood metabolites, carcass characteristics and meat quality of young Nellore bulls. A total of 48 bulls were randomly assigned to four treatments in a 2×2 factorial arrangement. The factors were two levels of dietary CP (100% and 120% of metabolizable protein requirement, defined as CP100 and CP120, respectively), and two levels of RH (0 and 300 mg/animal·per day). Treated animal received RH for the final 35 days before slaughter. Animals were weighed at the beginning of the feedlot period (day 63), at the beginning of ractopamine supplementation (day 0), after 18 days of supplementation (day 18) and before slaughter (day 34). Animals were slaughtered and hot carcass weights recorded. After chilling, carcass data was collected and longissimus samples were obtained for determination of meat quality. The 9-11th rib section was removed for carcass composition analysis. Supplementation with RH increased ADG independently of dietary CP. There was a RH×CP interaction on dry matter intake (DMI), where RH reduced DMI at CP120, with no effect at CP100. Ractopamine improved feed efficiency, without RH×CP interaction. Ractopamine had no effect on plasma creatinine and urea concentration. Greater dietary CP tended to increase blood urea, and there was a RH×CP interaction for plasma total protein. Ractopamine supplementation increased plasma total protein at CP120, and had no effect at CP100. Ractopamine also decreased plasma glucose concentration at CP100, but had no effect at CP120. Ractopamine increased alkaline phosphatase activity at CP120 and had no effect at CP100. There was a tendency for RH to increase longissimus muscle area, independently of dietary CP. Ractopamine did not alter fat thickness; however, fat thickness was reduced by greater CP in the diet. Supplementation with RH decreased meat shear force, but only at day 0 of aging, having no effect after 7, 14 or 21 days. Greater dietary protein increased meat shear force after 0 and 7 days of aging, with no effect after 14 or 21 days. These results demonstrate for the first time the efficacy of ractopamine supplementation to improve gain and feed efficiency of intact Bos indicus males, with relatively low carcass fat content. Ractopamine effects were not further improved by increasing dietary protein content above requirements.

Zilpaterol hydrochloride improves feed efficiency and changes body composition in nonimplanted Nellore heifers.

This research aimed to evaluate the effects of zilpaterol hydrochloride (ZH; MSD Animal Health, São Paulo, SP, Brazil) on the performance, carcass traits, serum metabolites, body composition, and gain composition of nonimplanted Nellore heifers. Nellore heifers ( = 72; average BW = 267 ± 16 kg; average 18 mo of age) were maintained in a feedlot system for 118 d. Heifers were separated into 2 groups: Control and ZH. The ZH group received ZH (8.3 mg/kg diet DM) for 30 d with 3 d of withdrawal before slaughter. Heifers were allotted to 18 pens, 9 pens per treatment, and assigned to a randomized block design. The animals were weighed, blood samples were collected, and subgroups of heifers were slaughtered at the beginning of supplementation and after 20 and 33 d to evaluate performance, blood metabolites, empty BW (EBW), and EBW composition. Hot carcass and kidney-pelvic fat weights were recorded at slaughter. At 24 h postmortem, carcasses were fabricated and the 9-10-11th rib (HH) section was removed from the primal rib to analyze moisture, protein, ash, and ether extract (EE) content in empty body (EB) and gain composition. Heifers fed ZH had gains in HCW that were 19.7 kg greater than controls, reflecting the 30% increase ( < 0.01) in ADG. There was no change in DMI, resulting in a 20% greater G:F ratio ( < 0.01) for heifers fed ZH. Heifers supplemented with ZH had carcass dressing percentages that were 3% greater than controls ( < 0.01), and there was also a 19% reduction in kidney-pelvic fat ( = 0.05) in ZH-treated heifers. Zilpaterol increased serum creatinine ( < 0.01), tended to increase ( = 0.06) serum triacylglycerol, decreased serum NEFA ( = 0.04), and tended to decrease ( = 0.06) serum glucose. The EBW composition was changed after 20 d of ZH supplementation ( = 0.02), with ZH increasing the moisture, ash, and protein contents, whereas carcass fat was decreased by ZH by 14%. Consequently, the carcass CP:EE ratio after 20 d was increased ( = 0.03) by 24% with ZH supplementation. There was no change on EBW composition after 30 d of ZH supplementation ( = 0.17). Regarding carcass gain composition, ZH increased EBW gain ( = 0.02) by 842 g/d from d 0 to d 30, EB protein gain by 221 g/d ( = 0.05) from d 0 to d 20, and by 180 g/d ( = 0.01) from d 0 to d 33. In conclusion, ZH supplementation in nonimplanted Nellore heifers altered the composition of body weight gain, promoting greater lean tissue deposition and improving feed efficiency.

Mechanisms of adaptation to the effects of ethanol on activation of phospholipase C in NG 108-15 cells.

In this study the effect of different times of exposure to ethanol (1-7 days, 100 mM) on bradykinin and GTP(S)-stimulated activation of phospholipase C in NG 108-15 cells and on the binding of [3H]bradykinin to its receptors was investigated. Ethanol attenuated both agonist and GTP-analogue-induced hydrolysis of phosphoinositides for a period of up to 4 days of treatment, while exerting no effect on binding to bradykinin receptors. However, after 7 days of exposure to ethanol, the agonist-induced activation of phospholipase C was completely resistant to the inhibitory effects of alcohol. This finding correlated to a change in the affinity of the bradykinin receptor population after 7 days of treatment. The results indicate that bradykinin-induced breakdown of phosphatidylinositol 4,5-bisphosphate adapts to the effects of ethanol, after long-term treatment. Possible adaptative changes taking place at the level of the G protein(s), may induce a shift in the affinity of the receptor population and, consequently, serve as a compensatory mechanism to counteract the inhibitory effect of ethanol.

Characterisation of kappa-opioid binding sites in rat and guinea-pig spinal cord.

The binding of radiolabelled ligands with high affinity for kappa-opioid binding sites has been studied in homogenates of lumbo-sacral spinal cord from the rat. The unselective ligands [3H]bremazocine and [3H]diprenorphine labelled a large number of sites which could not be fully resolved in terms of mu-, delta- and kappa-types by displacement assays. In particular binding at the kappa-site appeared anomalous in that sites which could be identified as high affinity kappa-type represented only 40% of total kappa-binding, defined using the unselective [3H]ligands. This was confirmed by the low levels of binding seen with the kappa-agonists [3H]dynorphin A(1-9) and [3H]U-69593. In guinea-pig cord, under conditions in which binding to mu- and delta-sites was suppressed, [3H]dynorphin A(1-9) and [3H]U-69593 labelled only 60% of the kappa population, defined by the [3H]unselective ligands. The reasons for the observed discrepancies are discussed.

Antinociceptive activity of glycosidic enkephalin analogues.

The antinociceptive activity of two new enkephalin analogues: N1.5-(beta-D-glucopyranosyl)[D-Met2, Pro5]enkephalinamide and N1.5-(beta-D-galactopyranosyl)[D-Met2, Pro5]enkephalinamide was assessed using the tail immersion and paw pressure behavioural tests. Both enkephalin analogues appear to be more active than morphine when injected either into the fourth ventricle or intrathecally; the galactose analogue is more than 5000 times more active than morphine when injected into the fourth ventricle. The analgesic effects produced by the analogues are partially reversed by SC naloxone (0.1 mg/kg) and totally reversed when the dose of naloxone used was 1 mg/kg, suggesting that the analogues act upon more than one type of opiate receptor (mu/delta).

Intrathecal administration of 5,6-DHT or 5,7-DHT reduces morphine and substance P-antinociceptive activity in the rat.

The administration of SP (15 and 50 ug) and morphine sulphate (10 ug) either into the IV ventricle or intrathecally produces an analgesic effect. This effect was attenuated when the rats received previously an intrathecal dose of 5,6-DHT or 5,7-DHT. The consequences of neurotoxin administration upon monoamine descending systems were evaluated by measuring 14C-5HT and 3H-NA synaptosomal uptake in different structures of the CNS. SP levels were also determined in the animals injected with the neurotoxins. Our results confirm the existence of a relationship injected with the neurotoxins. Our results confirm the existence of a relationship between the 5HT and SP descending systems, which control the nociceptive information at the level of the dorsal horn of the spinal cord.

New glycosylpeptides with high antinociceptive activity.

The antinociceptive activity of two new synthetic glucoside and galactoside enkephalinamide analogues was studied. The effects produced by the new analogues were compared with those obtained with [D-Met2,Hyp5]enkephalinamide and with morphine. The analogues were injected into the fourth ventricle and intrathecally. Tail immersion and paw pressure behavioural tests were used to assess antinociception. One of the analogues studied, O1,5-[beta-D-galactopyranosyl] [D-Met2,Hyp5]enkephalinamide appears to be 57,000 times more potent than morphine.

The inhibition of [³H] inositol 1,4,5-trisphosphate binding by Ca²âº is modified after long-term ethanol treatment and ethanol withdrawal.

We have analysed the influence of long-term ethanol exposure on the effect exerted by Ca²âº on the binding of tritiated inositol 1,4,5-trisphosphate to its receptors in rat cerebellar membranes. After 21 days of ethanol treatment the binding of the agonist was reduced in the absence of Ca²âº. The decrease was due to reduction in B max without any alteration of K d. In membranes from control animals Ca²âº inhibited the binding of InsP3 in a dose-dependent manner by altering the affinity of the protein for the ligand. However, the inhibitory effect of Ca²âº was abolished following chronic ethanol exposure. Five days after withdrawing ethanol, the B max recovered to control values, but the inhibitory effect of Ca²âº was recovered at only 10 days after withdrawal. The results indicate that long-term ethanol exposure may have differential effects on the InsP3binding site and on the Ca²âº binding site, or alternatively on a Ca²âº -related regulatory cycle.

Targeting opioid and neurokinin-1 receptors to treat alcoholism.

Alcoholism is a multifarious and ongoing disease tightly related to the amount of alcohol ingested, the drinking pattern, the history of alcohol drinking and the individual features, such as some genetic traits. Worldwide alcohol is the necessary cause of approximately 60 diseases and causes circa 2.5 million deaths every year. Studies show that alcohol interacts with brain neurotransmission in a complex manner. Dopaminergic, GABAergic, serotonergic, cholinergic and glutamatergic systems are all key participants in the action of ethanol on the brain. Furthermore, several neuropeptides, such as endogenous opioid peptides, substance P, corticotropin-releasing hormone, or the appetite-regulating peptides (eg., neuropeptide Y, ghrelin or orexin) also play a role in alcohol drinking. Treatment of alcohol use disorders (AUD) is based on the application of combined approaches, including pharmacological intervention directed to different molecular targets. Results, however, are variable, not always satisfactory, and not applicable to all stages and pathologies or to all patients. New strategies focused on the control of neuropeptide performance in the brain are being explored and may be an advance in the therapy of alcoholism. The application of treatments ad personam represents a challenge that currently stimulates research in different realms, including epidemiology, psychology, chemistry, biochemistry, cell biology and pharmacology. In this review the potential value and application of ligands that modulate the function of opioid and neurokinin-1 receptors in alcoholism therapy is analyzed.

The role of cellular plasticity in cancer development.

It has traditionally been accepted that, in the process of cellular differentiation, developmental options are progressively restricted until commitment to a specific fate is established and then only terminal differentiation along this lineage is possible. Although this is usually the case in normal physiological development, the latest experimental evidences indicate that the differentiated state of mature cells is not always as stable and durable as it was thought to be. In fact, recently, a hidden plasticity has been revealed in differentiated cells which allows them to deviate to other cell types that might be, functionally, very far away in other developmental pathways. This plasticity has biological significance since it is necessary for normal development to occur, but it also makes possible the emergence of aberrant lineages when interferences with the normal transcriptional and epigenetic mechanisms in charge of maintaining cellular identity do appear. Cancer is one of the possible outcomes of this aberrant reprogramming. The plasticity of the initial cell suffering the first oncogenic alteration plays an essential role in cancer development, since only if this cell possesses enough plasticity a tumoral reprogramming will be possible and a full-blown tumor will develop. Also, plasticity makes it possible for differentiated cells to acquire cancer stem cell properties in the presence of the appropriate oncogenic insults. In this review we discuss the role of cellular plasticity in the normal development of adult tissues and how cellular susceptibility to reprogramming plays an essential part in cancer development.

Ethanol alters the inhibitory effect of calcium ions on [(3) H]-inositol 1,4,5-trisphosphate binding.

In this study we have analysed the effects of ethanol and divalent cations on the binding of [(3) H]-inositol 1,4,5 trisphosphate to rat cerebellar membranes. Rats were injected intraperitoneally, daily, with 3g of ethanol/kg of body weight for different periods of time. Repeated in vivo administration of ethanol caused a reduction of about 30% of binding in an in vitro assay carried out in the presence of 1 mM EDTA. With an IC approximately 250 nM calcium ions produced a reduction in binding to cerebellar membranes isolated from control rats. The inhibitory effect was not observed in membranes taken from animals injected with alcohol for 21 days. Magnesium and manganese ions also lowered IP binding. The metabolic degradation of IP to IP was increased by magnesium and manganese but not by calcium and was similar in control and ethanol 2 treated rats. The results indicate that ethanol repeatedly administered to rats modifies the sensitivity of the IP receptor to calcium ion, but that it does not alter the metabolic fate of IP to IP. This supports the idea that ethanol may have preferable targets within the cell.

Differential effects of Mg2+ and other divalent cations on the binding of tritiated opioid ligands.

The effects of MgCl2 on the binding of tritiated ligands to opioid binding sites in homogenates of guinea-pig brain in HEPES buffer have been studied. The binding of tritiated mu-, delta-, and kappa-opioid agonists was promoted in a concentration-dependent manner over a range of MgCl2 concentrations from 0.1 mM to 10 mM, as was binding of the nonselective antagonists [3H]diprenorphine and [3H]naloxone. At concentrations of MgCl2 above 10 mM reversal of this effect was observed. The effects of MgCl2 on binding parameters differed at each site. The promoting effects of MgCl2 were mimicked by MnCl2, CaCl2, and MgSO4, but CoCl2 and ZnCl2 were inhibitory. Following treatment of guinea-pig brain synaptosomes at pH 11.5 to eliminate G proteins, the binding of the mu-opioid agonist [3H][D-Ala2, MePhe4, Gly-ol5]enkephalin and [3H]naloxone was much reduced but binding of [3H]diprenorphine was unaffected. Under these conditions MgCl2 still promoted binding of [3H]diprenorphine. The results suggest that Mg2+ ions promote binding by an action at the opioid receptor, even in the absence of G protein, and that opioid antagonists may differ in their recognition of opioid receptor binding sites.

A method for maintaining constant ethanol concentrations in cell culture media.

The present study reports on the development of a model for maintaining constant ethanol concentrations over time in cell culture media. When neuroblastoma x glioma cells (NG 108-15) were grown in ethanol containing media under standard cultivation conditions in the incubator at 37 degrees C, a 90% evaporation was observed after 24 hr. To counteract evaporation, the cell culture dishes were placed inside polystyrene boxes together with an open dish containing an appropriate amount of ethanol. By using such procedure, the decrease in ethanol concentration in the culture media was completely avoided. Cultivating cells in ethanol-free media inside sealed plastic boxes did not change their viability, growth rate, protein and phospholipid composition of the cells or the pH of the media, compared to cultures grown outside the boxes.

G proteins coupled to phospholipase C: molecular targets of long-term ethanol exposure.

Long-term ethanol exposure is known to inhibit bradykinin-stimulated phosphoinositide hydrolysis in cultures of neuroblastoma x glioma 108-15 cells. In the present study, [3H]bradykinin binding, GTP-binding protein function, and phospholipase C activity were assayed in cells grown for 4 days in 100 mM ethanol with the aim of elucidating the molecular target of ethanol on signal transduction coupled to inositol trisphosphate and diacylglycerol formation. Ethanol exposure reduced guanosine 5'-O-(3-thiotriphosphate) [GTP(S)]- and, to a lesser extent, NaF/AlCl3-stimulated phosphoinositide hydrolysis, whereas it had no effect on the enzymatic activity of a phosphatidylinositol 4,5-bisphosphate-specific phospholipase C. [3H]Bradykinin binding in the absence of GTP(S) was not influenced by ethanol exposure. However, the reduction in [3H]bradykinin binding seen in control cells after addition of GTP analogue was inhibited in cells grown in ethanol-containing medium. The results indicate that long-term ethanol exposure exerts its effects on receptor-stimulated phosphoinositide hydrolysis primarily at the level of the GTP-binding protein.

Continuous and intermittent exposure to ethanol: effect on NG 108-15 cell membrane phospholipids.

The effect of continuous and intermittent ethanol exposure on the phospholipid composition of Neuroblastoma x Glioma (NG 108-15) cell membranes was investigated. The cells were treated with ethanol for three weeks. Continuous ethanol exposure (150 mM) produced an increase (27%) in the amount of phosphatidylcholine, whereas intermittent ethanol treatment (150 mM) induced a 22% reduction of this lipid. Decreases of phosphatidylethanolamine plasmalogen (8.5%), phosphatidylinositol (16%) and phosphatidylserine (24%) were also seen after intermittent exposure. After binge administration, the concentration of total phospholipids was reduced by 17%, whereas continuous exposure produced a 19% increase. Both intermittent and continuous exposure induced a reduction in the total protein content. No changes in phosphatidic acid, sphingomyelin, phosphatidylcholine plasmalogen or phosphatidylethanolamine (diacyl form) were detected with either treatment. The importance of this study is that ethanol, irrespective of amount, can elicit different effects depending on the pattern of administration.

Ethanol potentiates the uptake of [14C]serine into phosphatidylserine by base-exchange reaction in NG 108-15 cells.

Phospholipid base-exchange enzymes catalyze the incorporation of nitrogenous bases into phosphoglycerides by a calcium-dependent mechanism. In this study, we describe the effect of ethanol on the incorporation of radioactive serine, choline and ethanolamine into their respective phospholipids in a neuroblastoma x glioma hybrid cell line (NG 108-15). Long term ethanol exposure induced a potentiation of the incorporation of [14C]serine into phosphatidylserine. Moreover, the phosphorus content of PS was found to be increased after long-term ethanol exposure. No concomitant changes in the phosphorus content of other phospholipids were observed. The results indicate that in NG 108-15 cells, the incorporation of radiolabelled serine into PS is potentiated during chronic ethanol exposure.

Ethanol and phosphatidylethanol reduce the binding of [3H]inositol 1,4,5-trisphosphate to rat cerebellar membranes.

In this study, we have analysed the effect of ethanol and phosphatidylethanol, a unique phospholipid formed only in the presence of ethanol, on the binding of [3H]inositol 1,4,5-trisphosphate to rat cerebellar membranes. Rats were intraperitoneally injected daily with 3 g of ethanol/kg body weight for different periods of time. Repeated administration of ethanol induced a reduction in the binding capacity (Bmax) without affecting the affinity constant (Kd). A significant 32% reduction was observed after 21 days of exposure (from control Bmax values of 25 +/- 3 pmol/mg and Kd values of 9 +/- 2 nM). In an in-vitro assay, phosphatidylethanol (500 microM) and phosphatidic acid (500 microM, but no other phospholipids tested, induced a reduction in Bmax (39% and 43%, respectively). The observed effect displayed by phosphatidylethanol was not due to its degradation to phosphatidic acid or other phospholipids. The results emphasize the importance of examining phosphatidylethanol (PEth) as a possible mediator of the effects of ethanol on cellular processes. However, the role of PEth in the observed effect of long-term ethanol exposure still needs further consideration.