Association between heart rate, heart rate variability, cortisol, glucose and electrolytes in healthy newborn calves / Associação entre frequência cardíaca, variabilidade da frequência cardíaca, cortisol, glicose e eletrólitos em bezerros recém-nascidos saudáveis

This study aims at evaluating the effects of electrolytes, glucose and cortisol levels over heart rate (HR) and heart rate variability (HRV) in healthy newborn calves. Seventeen healthy Holstein calves were evaluated during their first month of life, and the plasma concentrations of glucose, cortisol, calcium, magnesium, inorganic phosphorus, sodium and potassium were analyzed. HRV indexes were determined in the time and frequency domains through the analysis of neonatal electrocardiogram recordings. In the first day, low blood levels of phosphorus presented a strong correlation with the HR and the increased high-frequency components of HRV. The plasma concentrations of magnesium decreased significantly throughout the 35 days, revealing a positive association with a decreasing low-frequency components of HRV at day 28. There was a strong correlation between HR, HRV indexes, some plasma electrolytes, glucose and cortisol during the studied period. Variations in the concentrations and correlations observed may be attributed to the adaptive neonatal period in calves.(AU)

Este estudo teve como objetivo avaliar os efeitos dos níveis de eletrólitos, glicose e cortisol sobre a frequência cardíaca (FC) e a variabilidade da frequência cardíaca (VFC) em bezerros recém-nascidos e saudáveis. Dezessete bezerros da raça Holandesa foram avaliados durante o primeiro mês de vida e foram analisadas as concentrações plasmáticas de glicose, cortisol, cálcio, magnésio, fósforo inorgânico, sódio e potássio. Os índices VFC foram determinados em domínios de tempo e frequência por meio da análise de gravações do eletrocardiograma neonatal. No primeiro dia, baixos níveis sanguíneos de fósforo correlacionaram-se fortemente com FC e aumento dos componentes de alta frequência da VFC. As concentrações plasmáticas de magnésio diminuíram significativamente ao longo dos 35 dias, revelando correlação positiva com a diminuição dos componentes de baixa frequência da VFC no dia 28. Houve uma forte correlação entre FC, índices de VFC, eletrólitos plasmáticos, glicose e cortisol durante o período estudado. As variações nas concentrações e correlações observadas podem ser atribuídas ao período neonatal adaptativo em bezerros.(AU)

Virulence markers associated with Trueperella pyogenes infections in livestock and companion animals.

Trueperella pyogenes is an opportunistic pathogen that causes diverse pyogenic infections in livestock. The genes that encode the exotoxin pyolysin (plo) and other putative factors that promote adhesion of pathogen to host cells (fimbriae fimA, fimC, fimE, fimG, neuraminidases nanH, nanP, and collagen-binding protein cbpA) have been associated with virulence, particularly in mastitis and uterus infections of dairy cows. However, the role of these virulence markers in the pathogenicity of the agent in domestic animals infections still is incompletely understood. The genes plo, fimA, fimC, fimE, fimG, nanH, nanP, and cbpA were investigated in 71 T. pyogenes strains recovered from cattle, sheep, goats, dogs, equines, and a pig, recovered from mastitis (n = 35), and non-mastitis (n = 36) cases (abscesses, reproductive tract diseases, pneumonia, lymphadenitis, encephalitis). The most common genes harboured by the isolates were: plo (71/71 = 100·0%), fimA (70/71 = 98·6%), nanP (56/71 = 78·9%), fimE (53/71 = 74·6%), fimC (46/71 = 64·8%) and nanH (45/71 = 63·4%), whereas cbpA (6/71 = 8·4%) and fimG (4/71 = 5·6%) were uncommon. The most frequent genotypes were plo/fimA/fimE/fimC/nanH/nanP (17/71 = 23·9%), plo/fimA/fimE/nanH/nanP (13/71 = 18·3%), and plo/fimA/fimE/fimC/nanP (11/71 = 15·5%). No association was observed between the presence of genes vs clinical signs or host species. To the best of our knowledge, this is the first report on aforementioned virulence factors of pathogen detected in diseased horses and dogs. SIGNIFICANCE AND IMPACT OF THE STUDY: The role of particular virulence factors of Trueperella pyogenes that determine different pyogenic infections among domestic animals is poorly understood. Eight putative virulence genes and genotype profiles of 71 isolates were investigated among different clinical manifestations in domestic animals. The most common genes were plo (71/71 = 100·0%), fimA (70/71 = 98·6%), nanP (56/71 = 78·9%), fimE (53/71 = 74·6%), fimC (46/71 = 64·8%) and nanH (45/71 = 63·4%), whereas plo/fimA/fimE/fimC/nanH/nanP (17/71 = 23·9%), plo/fimA/fimE/nanH/nanP (13/71 = 18·3%), and plo/fimA/fimE/fimC/nanP (11/71 = 15·5%) were the most frequent genotypes. Studies involving virulence factors are critical in the investigation of molecular epidemiology, pathogenicity, and hypothetical differences in the virulence among T. pyogenes strains from different geographical areas.

In vitro algicidal effect of guanidine on Prototheca zopfii genotype 2 strains isolated from clinical and subclinical bovine mastitis.

Prototheca species have increasingly been reported to be opportunistic pathogens that cause mastitis in dairy herds, and it poses an emergent problem because at present, there are no effective therapies for the treatment of protothecal mastitis. This study investigated the in vitro algicidal effect of guanidine on 75 Prototheca zopfii genotype 2 strains isolated from 75 cases of clinical and subclinical bovine mastitis. All strains were susceptible to guanidine in vitro with minimal algaecide concentrations ranging from 0·001 to 0·035%. Guanidine is known to have a high microbicidal effect and is considered to be a new generation microbicidal compound. It is not toxic to human mucous membranes and conjunctivas at low concentrations and has been used as a disinfectant in swimming pools and as an antiseptic for human wounds. The algicidal action of guanidine at low concentrations indicates that it could be an alternative disinfectant or antiseptic for cleaning of the dairy environment and milking equipment, in pre- and postdipping solutions, in the chemical dry therapy of bovine teats and even in the intramammary therapy of P. zopfii infections. This is the first report of the in vitro algicidal effect of guanidine on P. zopfii strains of animal origin. SIGNIFICANCE AND IMPACT OF THE STUDY: Prototheca zopfii genotype 2 is an opportunistic pathogen of bovine mastitis. To date, no effective therapies against protothecal mastitis have been developed. The in vitro algicidal effect of guanidine on 75 P. zopfii genotype 2 strains isolated from cows revealed that all of the isolates were susceptible to the compound at low concentrations, which indicates that guanidine may be used as an antiseptic/disinfectant for dairy milking equipment, in pre- and postdipping solutions, and as a chemical dry therapy or an intramammary therapy. This study describes the in vitro algicidal effect of guanidine on P. zopfii for the first time.

Trueperella pyogenes multispecies infections in domestic animals: a retrospective study of 144 cases (2002 to 2012).

BACKGROUND: Formerly, Arcanobacterium pyogenes was recently renamed Trueperella pyogenes. This opportunistic bacterium is related to miscellaneous pyogenic infections in animals. Most studies involving T. pyogenes are case reports, whereas few surveys have focused the major aspects of T. pyogenes infections involving a case series study design. OBJECTIVE: The aim of this study was to retrospectively evaluate selected epidemiological and clinical aspects, as well as the in vitro antimicrobial susceptibility pattern of 144 cases of T. pyogenes infections among domestic animals from 2002 to 2012. ANIMALS AND METHODS: T. pyogenes was isolated from different clinical specimens from cattle, goats, sheep, pigs, horses, dogs, and buffaloes. Correlations were assessed by the Chi-square or Fisher's exact tests. RESULTS: Mastitis (45.1%), abscesses (18.0%), pneumonia (11.1%), and lymphadenitis (9.0%) were the most common clinical manifestations. In addition, the organism was also isolated from other miscellaneous clinical specimens from cases of septicemia, encephalitis, pyometra, prostatitis, orchitis, seminal vesiculitis, pericarditis, and omphalitis. No statistical association was observed between T. pyogenes infections and age, gender, or season across the study. The most effective drugs against the pathogen were florfenicol (99.1%), cefoperazone (96.0%), cephalexin (95.0%), and ceftiofur (94.8%). High resistance rates were observed against trimethoprim-sulfamethoxazole (49.3%), followed by norfloxacin (10.9%) and tetracycline (9.2%). CONCLUSIONS: This study highlights the diversity of clinical manifestations and the opportunistic behavior of T. pyogenes infections in domestic animals, with predominance of mastitis, abscesses, pneumonia, and lymphadenitis. It also reinforces the importance of knowing the susceptibility profile before initiating therapy, to improve antimicrobial therapy approaches.

Effects of prenatal cocaine exposure on dopamine system development: a meta-analysis.

Several studies have investigated the effects of prenatal cocaine (PCOC) exposure on the nigrostriatal dopaminergic system in animal models of maternal drug abuse, yet independent examinations of striatal dopamine (DA) receptors and tissue DA levels have produced equivocal results. The current meta-analysis provides a quantitative review of the literature on these topics, and analyzes potential moderators of the effects of PCOC exposure on these variables. The results indicate that the effects of PCOC exposure on striatal DA levels, D1 and D2 receptor-binding densities, and D2 receptor-binding affinity are negligible when collapsed over age, sex, species, and several other methodological variables. However, effects of PCOC exposure on some dopaminergic measures were significantly influenced by factors such as age and sex. As expected, and as suggested by the selectivity and specificity of PCOC-induced changes reported in the published literature, the direction and magnitude of differences between genders or age groups in this study were not systematic across all dependent measures. Generally, PCOC exposure was more often linked to decreases, rather than increases, in the selected dependent measures. These findings indicate that PCOC exposure produces selective alterations in striatal dopaminergic system function which do not appear under all experimental circumstances, but which may be important factors in behavioral alterations seen in selected groups after PCOC exposure.

Prenatal cocaine exposure alters behavioral and neurochemical sensitization to amphetamine in adult rats.

This study examined the neurochemical correlates of amphetamine (AMPH)-induced behavioral effects in prenatally saline (PSAL)-exposed or cocaine (PCOC)-exposed male rats. Pregnant Long-Evans rats received saline or saline containing cocaine hydrochloride (20 mg/kg s.c., b.i.d.) from gestational days 15-21. Animals were left with their biological mothers. Adult offspring were exposed to daily saline or AMPH (0.5, 1.5, or 5 mg/kg, i.p.) injections for 7 days. Behaviors were recorded in an open field during the first hour post-injection. PCOC rats did not exhibit behavioral anomalies during habituation to injection-stress or placement in the open field. PCOC rats displayed significant alterations in stereotyped responses to acute or intermittent exposure to various doses of AMPH. Within 48 h of the final testing day, striatal tissue was obtained from these animals and electrically-evoked [3H]acetylcholine (ACh) release was measured from striatal slices. Superfusion of tissue slices with various concentrations of AMPH (1-1000 nM) produced dose-dependent inhibition of ACh release in both PSAL and PCOC rats repeatedly injected with saline as adults. However, AMPH-induced inhibition of ACh release was decreased in PCOC rats repeatedly injected with AMPH as adults. At 5 mg/kg AMPH, PCOC rats exhibited increased mortality compared to PSAL rats. These data suggest that PCOC exposure produces long-lasting alterations in nigrostriatal transmission and behaviors mediated by this system.

Prenatal cocaine exposure increases serotonergic inhibition of electrically evoked acetylcholine release from rat striatal slices at adulthood.

This study tests the hypothesis that prenatal cocaine (pCOC) exposure (20 mg/kg, bidaily from embryonic days 15-21) modifies 5-HT(3) receptor regulation of electrically-evoked [(3)H]acetylcholine (ACh) overflow from adult male and female (proestrus, diestrus) rat striatal slices. Also, the influence of endogenous dopamine (DA) on serotonin (5-HT) regulation of ACh overflow was determined by assessing the effects alpha-methyl-para-tyrosine (AMPT) pretreatment or sulpiride. Phenylbiguanide (PBG, 5-HT(3) agonist) superfusion dose-dependently inhibited ACh overflow in all groups except the diestrus pCOC group in which there was an enhanced sensitivity to PBG. PBG (10, 30, and 60 microM) produced greater effects in the pCOC male than in the prenatal saline (pSAL) group. The pCOC male group also exhibited greater sensitivity to PBG (30 and 60 microM) than the pCOC proestrus group. PBG inhibition of ACh overflow was comparable in the pSAL male and female (proestrus) groups. PBG inhibition of ACh overflow was greater in the pCOC diestrus group than in the pCOC proestrus (10, 30, and 60 microM), the pSAL diestrus (10 and 30 microM), and the pCOC male (10 microM) conditions. In slices from untreated rats superfused with 30 microM PBG, AMPT pretreatment (68% DA loss) reduced inhibition of ACh overflow, and 1 microM sulpiride increased ACh overflow. ICS205-930 (5-HT(3) antagonist) reduced effectiveness of PBG indicating 5-HT(3) receptor specificity for PBG. In summary, pCOC exposure enhances modulatory effects of 5-HT (via 5-HT(3) receptors) on striatal ACh release in male and females rats and the inhibitory actions of 5-HT(3) receptors are mediated by DA.

Subsensitivity to dopaminergic drugs in periadolescent rats: a behavioral and neurochemical analysis.

It has been reported that post-natal day (PD) 30-40 rats respond differently to the behavioral effects of dopaminergic drugs when compared to younger or older rats. In this study, the behavioral effects of amphetamine (AMPH) on motor behavior and the effects of dopaminergic drugs on striatal acetylcholine (ACh) release were evaluated in periadolescent (PD35) and adult rats. AMPH increased dopamine (DA)-mediated motor behaviors (locomotor activity and stereotypy) in periadolescent and adult rats; however, these responses were of a lesser magnitude in periadolescent rats. In adult rats, cocaine and nomifensine inhibited ACh overflow in a dose-dependent manner. In periadolescent rats, ACh overflow was maximally inhibited at a lower drug concentration (5 microM) than in adult rats (10 microM) signifying increased sensitivity in these rats. Apomorphine inhibited ACh overflow in a dose-dependent fashion in slices from adult rats. In contrast, apomorphine did not consistently inhibit ACh overflow in striatal slices prepared from periadolescent rats. Collectively, the results of this study demonstrate behavioral subsensitivity to AMPH in periadolescent rats. Examination of the effects of DA reuptake blockers on DA modulation of striatal cholinergic neurons failed to reveal a corresponding subsensitivity. In fact, ACh release was more sensitive to DA reuptake blockers in periadolescent rats. This latter finding suggests that undisclosed factors override dopaminergic modulation of striatal neurons in the mediation of behavior in periadolescent rats. We propose that during periadolescence, DA transmission is transiently elevated. This results in post-synaptic supersensitivity of cholinergic receptors and consequently induces behavioral subsensitivity when challenged with dopaminergic drugs. Increased cholinergic tone may mediate behavioral subsensitivity despite drug-induced elevations in DA.

Paradoxical effects of kappa-opioid stimulation on the locomotor activity and Fos immunoreactivity of the preweanling rat: role of dopamine receptors.

The kappa-opioid agonist U-50,488 increases the locomotor activity of preweanling rats. The authors attempted to determine whether this effect was modulated by dopamine (DA) system functioning. Surprisingly, U-50,488's locomotor activating effects were attenuated by both the DA receptor antagonist flupenthixol and the DA receptor agonist R(-)-propylnorapomorphine (NPA). In order to determine those brain areas stimulated by U-50,488, Fos immunoreactivity was assessed in 17- and 80-day-old rats. U-50,488 not only enhanced the locomotor activity of the younger rats, but it also enhanced Fos expression in various brain areas, including the nucleus accumbens and medial striatum. NPA blocked U-50,488-induced Fos expression in the latter region. When considered together, these results indicate that U-50,488 does not increase locomotion by stimulating a DA mechanism. Instead, either agonizing or antagonizing DA receptors is sufficient to disrupt U-50,488's locomotor activating effects in the preweanling rat.

Effects of the kappa-opioid receptor agonist U-50,488 on morphine-induced place preference conditioning in the developing rat.

The ability of the kappa-opioid receptor agonist trans-(+/-)- 3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzeneacetamide methanesulfonate (U-50,488) to modulate morphine-induced reward was assessed in preweanling (10- and 17-day-old) and periadolescent (35-day-old) rats using the conditioned place preference paradigm. Conditioning and testing were conducted in a three compartment chamber, with each end compartment having its own distinct tactile and odor cues (almond or lemon). An abbreviated conditioned place preference procedure was used in which rats received two saline-odor pairings on the first conditioning day, and two saline- or morphine-odor pairings on the second day. In some experiments, rats were given U-50,488 (2-10 mg/kg, s.c.) 30 min prior to being conditioned with morphine (0.1-8 mg/kg, i.p.). On the third day, rats were allowed free access to the entire chamber for 900 s and compartment preferences were determined. Similar to adult rats, morphine (0.5 mg/kg) was consistently able to induce conditioned place preferences in the two preweanling age groups. This effect was attenuated by kappa-opioid receptor agonist pretreatment, as U-50,488 not only enhanced the locomotor activity of 10- and 17-day-old rats, but it blocked the morphine-induced place preference conditioning of these younger animals. In contrast, periadolescent (35-day-old) rats did not exhibit morphine-induced place preferences, nor did they show enhanced locomotor activity after U-50,488 treatment; however, using the same procedure, a different group of similarly aged rats showed conditioned preference produced by 20 mg/kg cocaine (i.p.). Therefore, these results suggest that reward processes are functionally mature in the preweanling rat (at least by 10 days of age), but that periadolescent rats are generally unresponsive to mu- and kappa-opioid drugs.

Effects of dopamine D1 and D2 receptor antagonists on cocaine-induced place preference conditioning in preweanling rats.

The effects of dopamine D1 and D2 receptor antagonists on the reward processes of 10- and 17-day-old rats were assessed using the conditioned place preference paradigm. Conditioning and testing were conducted in a three-compartment chamber, with each end compartment having its own distinct tactile and odor cues (almond and lemon). During six experiments, 10- and 17-day-old rats (age at initial conditioning) were injected intraperitoneally with either saline, the dopamine D1 receptor antagonist R(+/-)-SCH 23390 hydrochloride (0.01-1.0 mg/kg), or the dopamine D2 receptor antagonists (+/-)-sulpiride (1-100 mg/kg) or S(-)-eticlopride hydrochloride (0.1-0.5 mg/kg) 30 min prior to being injected with cocaine hydrochloride (20 mg/kg) or saline. After the latter injections, rats were immediately confined in the lemon-scented (nonpreferred) compartment for 30 min. On the alternate conditioning day, rats were injected with saline and confined in the almond-scented compartment. On the third day (i.e., the test day), rats were given saline and allowed free access to the entire chamber for 15 min. The results showed that the dopamine D1 receptor antagonist SCH 23390 blocked the cocaine-induced place preference conditioning of both 10- and 17-day-old rats. Surprisingly, the dopamine D2 receptor antagonists sulpiride and eticlopride blocked the place preference conditioning of 10-day-old rats, while leaving the 17-day-old rats unaffected. These results indicate that dopamine D1 receptors are critically involved in the reward processes of preweanling rats, but that the importance of dopamine D2 receptors changes across ontogeny.

The effects of the kappa agonist U-50,488 on cocaine-induced conditioned and unconditioned behaviors and Fos immunoreactivity.

The ability of kappa opioid agonists to modulate dopamine-mediated behavior and Fos immunoreactivity was assessed in adult rats. It was predicted that kappa agonist treatment would block the unconditioned and conditioned behaviors produced by cocaine (an indirect dopamine agonist). In the initial experiments, cocaine-induced locomotor activity was assessed after either acute or chronic injections of the kappa receptor agonist U-50,488 (5 mg/kg, SC). As expected, U-50,488 decreased cocaine-induced activity, while leaving baseline activity levels unaffected. Interestingly, chronic treatment with U-50,488 did not induce behavioral tolerance. The conditioned effects of cocaine (20 mg/kg, IP) were assessed using the conditioned place preference (CPP) paradigm. As expected, rats showed a preference for the cocaine-paired compartment, an effect blocked by U-50,488 (5 mg/kg, SC). One hour after CPP testing, rats were killed and Fos immunoreactivity was assessed. Rats conditioned with cocaine, but not U-50,488, showed increased Fos activity in the anterior cingulate cortex, piriform cortex, lateral septal area, and olfactory tubercles. When considered together, these results suggest that U-50,488 was effective at blocking the unconditioned and conditioned effects of cocaine, as well as cocaine-induced neuronal activity (as measured by Fos induction).

Behavioral effects of the reversible dopamine antagonist flupenthixol are not potentiated by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline in the preweanling rat.

In the preweanling rat, the irreversible dopamine (DA) receptor antagonist N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) does not diminish behaviors induced by the nonselective DA agonist R(-)-propylnorapomorphine (NPA). To determine whether EEDQ was simply inactivating an insufficient percentage of DA receptor antagonist) and/or EEDQ. When given alone, flupenthixol (0.04, 0.1, and 0.4 mg/kg, intraperitoneally [IP]) produced a dose-dependent decrease in the behavioral effects induced by 1.0 mg/kg NPA. Unexpectedly, EEDQ (7.5 mg/kg, IP) did not potentiate flupenthixol's actions. This suggests that EEDQ's inability to block the NPA-induced behaviors of preweanling rats was not the result of an insufficient percentage of DA receptors being inactivated.

Ontogeny of behavioral sensitization in the rat: effects of direct and indirect dopamine agonists.

In the present study, the abilities of NPA (a direct DA receptor agonist) and amphetamine (an indirect DA receptor agonist) to induce short- and long-term behavioral sensitization were assessed in 11- and 17-day-old rats (age at initial injection). Rats were injected on 4 consecutive days with amphetamine (1.0, 2.5, or 5.0 mg/kg), NPA (1.0 mg/kg), or saline. A final test day occurred either 2 days (experiment 1) or 8 days (experiment 2) later. On the test day, rats given successive agonist injections received a single injection of the same agonist again; whereas rats given successive saline injections received either amphetamine or NPA for the first time. Five minutes after injection, locomotor activity (line-crosses), stereotyped sniffing, and vertical activity were measured during a 30-min testing session. The results showed that 11- and 17-day-old rats exhibited behavioral sensitization when tested with NPA or amphetamine after a 2-day interval. In contrast, neither NPA nor amphetamine was able to sensitize the behaviors of preweanling rats when measured 8 days after initial drug treatments. Therefore, these results show that both direct and indirect DA agonists are able to induce short-term behavioral sensitization in preweanling rats, but that the mechanisms responsible for mediating long-term behavioral sensitization have not yet matured.