Development of the faecal microbiota in foals.

REASONS FOR PERFORMING STUDY: The intestinal microbiota is a complex polymicrobial ecosystem that exerts extremely important roles in the development and maintenance of health. Recently, as new sequencing technologies have become more available, there has been a revolution in the understanding of the equine intestinal microbiota. However, studies characterising the pioneer intestinal bacteria colonising foals and its development over time are still limited. OBJECTIVES: The objectives of this study were to characterise the intestinal bacterial colonisation of newborn foals and to follow individual animals over time until age 9 months. STUDY DESIGN: Longitudinal study. METHODS: Eleven pregnant mares from one farm were enrolled and faecal samples were collected longitudinally from mares and foals during their first day post partum and again periodically until foals were age 9 months. The V4 region of the 16S rRNA gene was amplified and sequenced using the Illumina MiSeq platform. RESULTS: Newborn foals had a rich and diverse bacterial community, which was mainly comprised of the Firmicutes phylum with several low abundant genera being unique at this age. Foals aged 2-30 days had significantly decreased diversity compared to older animals, with the majority of organisms classified as Akkermansia spp. After 60 days of life, the intestinal microbiota structure tended to remain stable, but differences in community membership were still present between 9-month-old animals and mature mares. Several differences at the phylum level were observed between different ages, including a higher abundance of Fibrobacteres after weaning. CONCLUSIONS: The intestinal microbiota of the equine newborn is already complex by the first day of life. Microbiota adaptation occurs during the first month and the microbiota of foals older than 60 days resemble the mother's microbiota, although differences in community membership are still present.

Kinetics of esmolol, an ultra-short-acting beta blocker, and of its major metabolite.

Esmolol is an ultra-short-acting beta blocker. Its kinetics was studied in eight healthy subjects after continuous intravenous infusion of 400 micrograms/kg/min over 2 hr. The concentrations of esmolol and its major metabolite, 3-[4-(2-hydroxy-3-[isopropylamino]propoxy)phenyl]propionic acid, in blood and urine were determined by gas chromatographic-mass spectrometric assay and HPLC. The distribution and elimination t1/2s of esmolol averaged 2.03 and 9.19 min. The apparent volume of distribution of esmolol averaged 3.43 l/kg and was four times the volume of the central compartment. The total clearance of esmolol averaged 285 ml/min/kg, indicating that nonhepatic routes play a predominant role in its clearance. The t1/2s of formation and elimination of the metabolite averaged 2.82 min and 3.72 hr. The ratio of the metabolite formation and elimination rate constants of the parent drug (kf/k10) averaged 0.829, suggesting that 82.9% of esmolol was converted to the metabolite (which is consistent with the urinary recovery of 71% of the dose as unconjugated metabolite). The volume of distribution and total clearance of the metabolite averaged 0.411 l/kg and 1.28 ml/min/kg. Esmolol was followed by a significant reduction of isoproterenol-induced increase in heart rate and systolic blood pressure at doses of 50, 150, and 400 micrograms/kg/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Mono- and bis(aminomethyl)phenylacetic acid esters as short-acting antiarrhythmic agents. 2.

The synthesis, antiarrhythmic activity, and blood hydrolysis properties of a series of mono- and bis(aminomethyl)phenylacetic acid esters related to a previously reported class Ic antiarrhythmic agent (ACC-9358) are described. Of the various oxa-, aza-, thia-, and carbacyclic esters initially prepared in the bis(pyrrolidinomethyl)-4-hydroxyphenylacetic acid series, the 1,4-benzodioxanyl-2-methyl(3q) and the thienyl-2-methyl(31) esters were evaluated in vivo for antiarrhythmic efficacy. In addition, a number of monoappended phenylacetic esters of 3q with or without the 4-hydroxy group were also prepared for evaluation of antiarrhythmic, lipophilic, and metabolic properties. Of these compounds, 3q possessed the most desirable pharmacological and pharmacokinetic profile.

Ester derivatives of 2,6-bis(1-pyrrolidinylmethyl)-4-benzamidophenol as short-acting antiarrhythmic agents. 1.

In an effort to find a replacement for the iv antiarrhythmic drug lidocaine having reduced systemic and central nervous system effects, activity against supraventricular as well as ventricular arrhythmias, and a biological half-life of less than 15 min, derivatives of the orally active class Ic clinical agent 2,6-bis(1-pyrrolidinylmethyl)-4-benzamidophenol, 1 (ACC-9358), were synthesized and tested. Compounds with ester groups attached to the phenyl ring were either weakly active or toxic. Replacement of the formanilide function with alkyl esters afforded compounds with antiarrhythmic activity in the range of 1. When the ester carboxyl was separated from the bis(aminomethyl)phenol by methylene units, very short half-lives were observed in human blood. In general, these compounds also had low lipophilic character.

[(Arylcarbonyl)oxy]propanolamines. 1. Novel beta-blockers with ultrashort duration of action.

Novel [(arylcarbonyl)oxy]propanolamines were synthesized and investigated as potential ultrashort-acting beta-adrenergic receptor blockers. Many of these analogues exhibited good potency and short duration. The N-ureidoalkyl analogue 85 (ACC-9089) has a potency equal to propranolol and a duration of action of about 21 min in the dog. It has been selected as a candidate for further clinical study. Structure-activity relationships and structure-duration relationships for these new beta-blockers are also discussed.

A-69024: a non-benzazepine antagonist with selectivity for the dopamine D-1 receptor.

A-69024 HBr, 1-(2-bromo-4,5-dimethoxybenzyl)-7-hydroxy-6-methoxy-2-methyl-1,2,3,4- tetrahydroisoquinoline hydrobromide, is a selective antagonist of the dopamine D-1 receptor. A-69024 HBr shows an apparent affinity toward the D-1 receptor (identified using [125I]SCH 23390) of 12.6 (4.15-38.3) nM (mean (90% CL), n = 3); the apparent affinity toward the D-2 receptor (identified using [3H]spiroperidol is 1 290 (1,200-1,380) nM (n = 3); using [125I]lysergic acid diethylamine to identify the 5-HT1C receptor gives apparent affinity of 17,800 (9,700-32,600) nM (n = 3). In assays of adenylate cyclase activity, A-69024 HBr antagonizes the D-1 receptor with a calculated affinity of 43.9 (17.5-110) nM (n = 5), while the molecule antagonizes the D-2 receptor with a calculated affinity greater than 400 nM. Behavioral studies demonstrate that A-69024 HBr (5 mg/kg s.c.) is able to block both amphetamine-induced locomotor activity and apomorphine-induced stereotypy. Furthermore, A-69024 HBr blocks SF&F 38393-, but not quinpirole-, induced rotation in rats having unilateral 6-hydroxydopamine lesions of the substantia nigra. When administered at behaviorally effective doses. A-69024 HBr neither increases the concentration of serum prolactin nor potentiates dihydroxyphenylalanine (DOPA) accumulation in the caudate-putamen of rats pretreated with the DOPA decarboxylase inhibitor NSD 1015. Because A-69024 is a dopamine receptor antagonist discriminating between the D-1 and D-2 receptors, it may be a useful research tool.

Pharmacokinetics of [14C]bretylium tosylate in rats.

The pharmacokinetics of bretylium tosylate were investigated in eight male Charles River rats. Each animal received an intravenous dose (10 mg/kg) of [14C)bretylium tosylate. Serial blood samples, urine, and feces were collected for up to 72 hr. Bretylium concentrations in plasma and amounts excreted in urine and feces were determined by scintillation counting. On the average, 88 and 95% of the dose were recovered in urine and feces in 24 and 72 hr, respectively. Urinary recovery accounted for 65.6 of the dose while 29.7% was excreted in the feces. Bretylium concentrations in plasma declined triexponentially and were fitted to a three-compartment open model. Bretylium has a very high apparent volume of distribution (15 liters/kg), and its beta half-life averaged 5.5 hr. Mean values of the apparent volume of the central compartment, plasma clearance, renal clearance, and excretion rate constants of bretylium in rats were 1 liter/kg, 1.93 liters/hr/kg, 1.27 liters/hr/kg, and 1.24 hr-1, respectively. The results indicate that: (a) bretylium is strongly bound to the tissues and is eliminated by active urinary secretion and by biliary excretion in rats, and (b) there are strong similarities between the pharmacokinetics of bretylium in humans and rats and that this animal model might be suitable for interaction studies with other drugs.

Tissue distribution of [14C]bretylium tosylate in rats.

The distribution of [14C]bretylium tosylate in the body and the relationship between tissue and plasma concentrations was determined following intravenous administration of the drug to Charles River rats. The renal excretion of bretylium was rapid in rats and follows an active process. On the average, 50% of the administered dose was excreted in the urine within 1 hr. In the postequilibrium phase, the plasma concentration declined with a half-life of 5 hr. Bretylium concentrations in all tissues, except the heart, declined rapidly according to a triexponential equation. The liver and kidney bretylium concentrations declined in parallel to the plasma concentration with mean tissue-plasma concentration ratios of 6.04 and 12.3, respectively, in the beta phase. However, the concentration of bretylium in the heart increased gradually and peaked at 2 hr, with a tissue-plasma concentration ratio of 121, which, in turn, declined to a value of greater than 60 after 8 hr. The data indicated that (a) bretylium is rapidly distributed into the liver and kidney immediately after reaching the systemic circulation; (b) the distribution into the heart occurs at a slower rate compared with the other organs, and the drug has a high affinity to the myocardium; and (c) since the heart is the site of action and there is no direct correlation between the concentrations in myocardium and plasma, the antiarrhythmic effect of bretylium may not be related to the plasma concentration.

Age-related pharmacokinetics of N-acetylprocainamide in rats.

The pharmacokinetics of N-acetylprocainamide, administered orally or intravenously, were studied in 3-, 6-, and 12-month-old rats using a two-way crossover study design. At 3, 6, and 12 months of age, the half-life values of N-acetylprocainamide were 1.66, 1.82, and 2.29 hr, respectively; the apparent volumes of distribution were 4.75, 3.35, and 1.98 liter/kg, respectively. The elimination rate constant, clearance, and absolute bioavailability of the drug (determined by AUC measurements and the amounts excreted unchanged in the urine) decreased significantly with age. The rate of absorption remained unchanged. The amounts of N-acetylprocainamide in the liver and kidneys were significantly higher in the 12-month-old animals. These results clearly demonstrate a significant alteration with age in the bioavailability, distribution, and elimination of N-acetylprocainamide in rats. In long-term toxicity studies of this and other drugs that show age-dependent pharmacokinetics, an adjustment in the chronically administered dose is essential.

Outbreak of acute colitis on a horse farm associated with tetracycline-contaminated sweet feed.

Exposure of a group of horses to tetracycline-contaminated feed resulted in acute colitis and subsequent death in one horse and milder diarrhea in 3 others. The most severely affected animal demonstrated clinical and pathological findings typical of colitis X. The other herdmates responded well to administration of zinc bacitracin.

[From flayer to veterinarian]. / Vom Abdecker zum Tierarzt.

The duty of the flayer was to dispose of horse and dog offal that was not intended for consumption. In addition he was to see to the disposal of animal carcases. The steady increase in the numbers of horses and dogs as well as devastating diseases, obliged the authorities to improve the control on the flaying of animals. A better knowledge of the dismembering of animals and improved diagnostic capabilities were expected of the flayer. Despite the greater importance of his duties, however, the flayer remained at the bottom of the social ladder. It was only during the era of enlightenment that he became an accepted member of society. Thus emancipated, he was able to leave his accustomed working place and attempted to gain entry into the realm of veterinary medicine. These attempts were sometimes met with success.

Physicochemical interpretation of acid-base abnormalities in 54 adult horses with acute severe colitis and diarrhea.

BACKGROUND: The quantitative effect of strong electrolytes, pCO2 , and plasma protein concentration in determining plasma pH and bicarbonate concentrations can be demonstrated with the physicochemical approach. Plasma anion gap (AG) and strong ion gap (SIG) are used to assess the presence or absence of unmeasured anions. HYPOTHESES: The physicochemical approach is useful for detection and explanation of acid-base disorders in horses with colitis. AG and SIG accurately predict hyperlactatemia in horses with colitis. ANIMALS: Fifty-four horses with acute colitis and diarrhea. METHODS: Retrospective study. Physicochemical variables were calculated for each patient. ROC curves were generated to analyze sensitivity and specificity of AG and SIG for predicting hyperlactatemia. RESULTS: Physicochemical interpretation of acid-base events indicated that strong ion metabolic acidosis was present in 39 (72%) horses. Mixed strong ion acidosis and decreased weak acid (hypoproteinemia) alkalosis was concomitantly present in 17 (30%) patients. The sensitivity and specificity of AG and SIG to predict hyperlactatemia (L-lactate > 5 mEq/L) were 100% (95% CI, 66.4-100; P < .0001) and 84.4% (95% CI, 70.5-93.5 P < .0001). Area under the ROC curve for AG and SIG for predicting hyperlactatemia was 0.95 (95% CI, 0.86-0.99) and 0.93 (95% CI, 0.83-0.99), respectively. CONCLUSION AND CLINICAL RELEVANCE: These results emphasize the importance of strong ions and proteins in the maintenance of the acid-base equilibria. AG and SIG were considered good predictors of clinically relevant hyperlactatemia.

Contribution of unmeasured anions to acid-base disorders and its association with altered demeanor in 264 calves with neonatal diarrhea.

BACKGROUND: The quantitative effect of strong electrolytes, unmeasured anions (UAs), pCO2 , and plasma protein concentrations in determining plasma pH and bicarbonate (HCO3 (-) ) can be demonstrated using the physicochemical approach. Demeanor of calves with diarrhea is associated with acidemia, dehydration, and hyper-d-lactatemia. HYPOTHESIS: Unmeasured anions are a major factor influencing changes in plasma pH and HCO3 (-) of calves with diarrhea and UAs and strong UAs, estimated by anion gap (AG) and strong ion gap (SIG), respectively, are more strongly associated with alteration of demeanor compared to other acid-base variables. ANIMALS: A total of 264 calves with diarrhea from two data sets (DS1 and DS2). METHODS: Retrospective study. Forward stepwise regression was performed to determine the relationship between measured pH or HCO3 (-) , and physicochemical variables. A two-way ANOVA was performed to investigate the association between acid-base variables and attitude (bright, obtunded, and stuporous), posture (standing, sternal or lateral recumbency), and strength of suckling reflex (strong, weak, or absent). RESULTS: Increased strong UAs estimated by SIG was the most important contributor to changes in measured pH and HCO3 (-) (DS1: r(2) 66 and 59%, DS2: 39 and 42%, P < .0001). SIG and AG were correlated to deteriorating calf demeanor for all three clinical scoring categories: attitude, posture, and suckle reflex (P < .0001). CONCLUSION AND CLINICAL RELEVANCE: Elevated concentrations of strong UAs were the primary cause of acidemia and had an important influence on the demeanor of calves with diarrhea. These findings emphasize the importance of the calculation of UAs when evaluating acid-base abnormalities in calves.

Epidemiology of Clostridium difficile on a veal farm: prevalence, molecular characterization and tetracycline resistance.

Concern has been raised about the potential for Clostridium difficile to be a bovine and foodborne pathogen, yet limited study has been performed in cattle, and none in veal calves. This study evaluated the epidemiology and microbiology of C. difficile on one veal farm. Rectal swabs were obtained from calves within 48 h of arrival and at one, 17 and 21 weeks later. Selective culture for C. difficile was performed. Isolates were characterized by PCR ribotyping and PCR for tcdA, tcdB and cdtA. Tetracycline resistance and resistance genes were investigated. Multivariable logistic regression models were constructed to determine the relationship between shedding of the bacterium and specific ribotypes and the independent variables: time of sampling and area of housing. Calves were twice more likely to test positive 1 week after arrival (51%) when compared to initial results (32%). Shedding at 17 and 21 weeks was significantly lower (2% at both samplings). Ribotype 078 was the most common. Twelve different ribotypes were present initially with only three ribotypes found subsequently. Seventy-six percent (40/53) of isolates initially recovered were tetracycline resistant compared to 93% (81/87) from 2nd sampling. Tetracycline resistance genes were detected in 24% (13/53) of isolates during 1st and in 55% (50/91) during 2nd sampling. The high prevalence of pathogenic C. difficile in veal calves could be of zoonotic concern. The low prevalence before slaughter may be of importance for the evaluation of foodborne risks. Oxytetracycline administration to calves may have an impact on prevalence of C. difficile colonization.

Effects of chronic acetazolamide administration on gas exchange and acid-base control in pulmonary circulation in exercising horses.

REASONS FOR PERFORMING STUDY: Carbonic anhydrase (CA) catalyses the hydration/dehydration reaction of CO(2) and increases the rate of Cl(-) and HCO(3)(-) exchange between the erythrocytes and plasma. Therefore, chronic inhibition of CA has a potential to attenuate CO(2) output and induce greater metabolic and respiratory acidosis in exercising horses. OBJECTIVES: To determine the effects of Carbonic anhydrase inhibition on CO(2) output and ionic exchange between erythrocytes and plasma and their influence on acid-base balance in the pulmonary circulation (across the lung) in exercising horses with and without CA inhibition. METHODS: Six horses were exercised to exhaustion on a treadmill without (Con) and with CA inhibition (AczTr). CA inhibition was achieved with administration of acetazolamide (10 mg/kg bwt t.i.d. for 3 days and 30 mg/kg bwt before exercise). Arterial, mixed venous blood and CO(2) output were sampled at rest and during exercise. An integrated physicochemical systems approach was used to describe acid base changes. RESULTS: AczTr decreased the duration of exercise by 45% (P < 0.0001). During the transition from rest to exercise CO(2) output was lower in AczTr (P < 0.0001). Arterial PCO(2) (P < 0.0001; mean ± s.e. 71 ± 2 mmHg AczTr, 46 ± 2 mmHg Con) was higher, whereas hydrogen ion (P = 0.01; 12.8 ± 0.6 nEq/l AczTr, 15.5 ± 0.6 nEq/l Con) and bicarbonate (P = 0.007; 5.5 ± 0.7 mEq/l AczTr, 10.1 ± 1.3 mEq/l Con) differences across the lung were lower in AczTr compared to Con. No difference was observed in weak electrolytes across the lung. Strong ion difference across the lung was lower in AczTr (P = 0.0003; 4.9 ± 0.8 mEq AczTr, 7.5 ± 1.2 mEq Con), which was affected by strong ion changes across the lung with exception of lactate. CONCLUSIONS: CO(2) and chloride changes in erythrocytes across the lung seem to be the major contributors to acid-base and ions balance in pulmonary circulation in exercising horses.

Displacement currents in the node of Ranvier. Voltage and time dependence.

The time course of the membrane currents in the node of Ranvier in which the sodium and potassium conductances have been blocked reveals asymmetries during and after the application of depolarizing and hyperpolarizing voltage-clamp pulses of identical size. Since 1. the integrals of the "on" and "off" current transients were found to be equal and opposite, 2. the change displaced reached saturation (about 140-10-minus 15 C/node) when the internal potential was taken to a sufficiently positive value during the depolarizing pulses and, 3. the size of the charge transferred was unaffected by temperature although its time constant had a large temperature coefficient (Q10 = 2.4), these currents to our opinion must result form charge movements confined to the membrane and, therefore, can be considered as non-liner displacement currents. The steady-state rearrangement of the charges is consistent with a Boltzmann distribution of charges (effective valence z = 1.65) between two configurations characterized by different energy levels. The midpoint potential of the distribution curve is -33.7mV and its maximum slope, kT/ZE, is 14.9 mV. Following changes in membrane potential the charges undergo a first order transition between these states. We propose that these displacement currents arise from a redistribution of the charges involved in the sodium gating system.

Biochemical characterization of flestolol esterase.

The blood esterase that mediates the metabolism of flestolol, an ultra short-acting beta blocker, was characterized. Esterase activity occurred in plasma of human, dog, rat, and guinea pig and not in erythrocytes of the same species. The esterase activity was greatest in humans and guinea pigs followed by dogs and rats. Purified human serum cholinesterase was very active against flestolol while human serum albumin was slightly active. Human and bovine erythrocyte membrane acetylcholinesterases, electric eel acetylcholinesterase, human hemoglobin, dog, rat, chicken, and bovine serum albumin were all inactive. Esterase activity with flestolol was inhibited in human, dog, and rat blood by echothiophate, eserine, and sodium fluoride. Guinea pig blood esterase activity was inhibited by echothiophate and sodium fluoride, but not by eserine. Metabolic interaction studies indicated that succinylcholine, procaine, and chloroprocaine interfere with the metabolism of flestolol in human blood. Succinylcholine prolonged the in vitro half-life of flestolol in dog blood, but acetylcholine, procaine, and chloroprocaine had no effect. Flestolol did not affect the metabolism of procaine or chloroprocaine in human and dog blood. The metabolism rate of flestolol decreased in individuals with atypical, fluoride-resistant and silent forms of serum cholinesterase.

Polymorphic metabolism of flestolol and other ester containing compounds by a carboxylesterase in New Zealand white rabbit blood and cornea.

Flestolol, N(1,1-dimethyl-2-ureidocthyl)-2-hydroxy-3-(o-fluorobenzoyloxy++ +) propylamine, (F), is an ester containing an ultra short-acting beta blocker intended for the treatment of myocardial dysfunctions. In vitro incubation of F, procaine, chloroprocaine, and atropine with blood from different New Zealand White (NZW) rabbits resulted in a bimodal distribution (70% fast, 30% slow) of ester hydrolysis rates. Using F as a model substrate, bimodal hydrolysis rates were also observed in NZW rabbit cornea but not aqueous humor, iris-ciliary body complex and ocular tissues of pigmented rabbits. In addition, the bimodal distribution of esterase activity was not observed in blood from rats, dogs, and humans. Incubation of esters at various positions of the phenoxypropanolamine nucleus of beta blockers with NZW rabbit blood indicated structural specificity of the carboxylesterase in terms of unimodal or biomodal distribution of activity. These results strongly suggest that the carboxylesterase in NZW rabbit blood that hydrolyzes F and similar compounds is atropine esterase as described in the literature.