Elapid snake envenomation in horses: 52 cases (2006-2016).

BACKGROUND: Snake envenomation is a cause of morbidity and mortality in domestic animals worldwide. The clinical features of crotalid snake (pit viper) envenomation are widely reported and well described in horses but elapid snake envenomation is poorly characterised. OBJECTIVES: To describe the presentation, clinical and laboratory findings, treatment and outcome of horses with a diagnosis of elapid snake envenomation in Australia. STUDY DESIGN: Retrospective case series. METHODS: Medical records of horses with a diagnosis of elapid snake envenomation (2006-2016) at several university and private veterinary practices were reviewed. Inclusion criteria comprised one or more of the following: 1) observed snakebite, 2) positive snake venom detection kit (SVDK) result, 3) appropriate clinical response to treatment with antivenom or 4) supportive post-mortem findings. RESULTS: Fifty-two cases met the inclusion criteria. Most cases (94%) demonstrated clinical signs of neurotoxicity, characterised by generalised neuromuscular weakness. Associated neurologic signs included staggering gait, muscle fasciculations, recumbency, mydriasis, ptosis and tongue paresis. Concurrent clinically important conditions included rhabdomyolysis (50%) and haemolysis (19%). Of 18 urine samples evaluated with a SVDK, only three (17%) were positive. Overall survival was favourable (86%) among 49 horses who received antivenom. Eighteen surviving horses (43%) required more than one vial of antivenom. MAIN LIMITATIONS: Possible cases within the searchable database were not included if horses died acutely or responded to symptomatic treatment without receiving antivenom. CONCLUSIONS: Elapid snake envenomation is primarily a syndrome of neuromuscular weakness. Supportive anamnesis or an obvious bite site is rarely encountered. In endemic areas, this diagnosis should be considered for horses with generalised neuromuscular weakness, altered mentation, rhabdomyolysis and/or haemolysis; especially during spring and summer months. Diagnostic suspicion is best confirmed by response to treatment with antivenom.

Effects of polymyxin-B on TNF-α production in equine whole blood stimulated with three different bacterial toxins.

Polymyxin-B is used to treat equine systemic inflammation. Bacterial toxins other than lipopolysaccharide (LPS) contribute to systemic inflammation but the effects of polymyxin-B on these are poorly defined. Whole blood aliquots from six healthy horses diluted 1:1 with RPMI were incubated for 21 hr with 1 µg/ml of LPS, lipoteichoic acid (LTA) or peptidoglycan (PGN) in the presence of increasing concentrations of polymyxin-B (10-3000 µg/ml). A murine L929 fibroblast bioassay was used to measure TNF-α activity. Polymyxin-B significantly inhibited the effects of all three bacterial toxins. Analysis of variance showed the IC50 value for polymyxin-B for TNF-α inhibition caused by LTA (11.19 ± 2.89 µg/ml polymyxin-B) was significantly lower (p = .009) than the values for LPS (46.48 ± 9.93 µg/ml) and PGN (54.44 ± 8.97 µg/ml). There was no significant difference in IC50 values between LPS and PGN (p > .05). Maximum inhibition of TNF-α was 77.4%, 73.0% and 82.7% for LPS, PGN and LTA, respectively and was not significantly different between toxins. At the two highest concentrations of polymyxin-B, TNF-α began to increase. These data suggest that polymyxin-B may inhibit the effects of bacterial toxins other than LPS and might be a more potent inhibitor of LTA than LPS or PGN.

Sequential plasma lactate concentrations as prognostic indicators in adult equine emergencies.

BACKGROUND: Sequential lactate concentration ([LAC]) measurements have prognostic value in that hospitalized humans and neonatal foals that have a delayed return to normolactatemia have greater morbidity and case fatality rate. HYPOTHESIS: Prognosis for survival is decreased in horses with a delayed return to normal [LAC]. ANIMALS: Two hundred and fifty adult horses presented for emergency evaluation excepting horses evaluated because of only ophthalmologic conditions, superficial wounds, and septic synovitis without systemic involvement. METHODS: Prospective observational study. [LAC] was measured at admission and then at 6, 12, 24, 48, and 72 hours after admission. The change in [LAC] over time ([LAC]deltaT) was calculated from changes in [LAC] between sampling points. RESULTS: Median [LAC] was significantly (P < .001) higher at admission in nonsurvivors (4.10 mmol/L [range, 0.60-18.20 mmol/L]) when compared with survivors (1.30 mmol/L [range, 0.30-13.90 mmol/L]) and this difference remained at all subsequent time points. The odds ratio for nonsurvival increased from 1.29 (95% confidence interval 1.17-1.43) at admission to 49.90 (6.47-384) at 72 hours after admission for every 1 mmol/L increase in [LAC]. [LAC]deltaT was initially positive in all horses but became negative and significantly lower in nonsurvivors for the time periods between 24-72 hours (- 0.47, P = .001) and 48-72 hours (- 0.07, P = .032) when compared with survivors (0.00 at both time periods) consistent with lactate accumulation in nonsurvivors. CONCLUSIONS AND CLINICAL IMPORTANCE: These results indicate that lactate metabolism is impaired in critically ill horses and [LAC]deltaT can be a useful prognostic indicator in horses.

Hyperhydration prior to a simulated second day of the 3-day moderate intensity equestrian competition does not cause arterial hypoxemia in Thoroughbred horses.

Dehydration and the associated impairment of cardiovascular and thermoregulatory function comprise major veterinary problems in horses performing prolonged exercise, particularly under hot and humid conditions. For these reasons, there is considerable interest in using pre-exercise hyperhydration to help maintain blood volume in the face of the excessive fluid loss associated with sweat production during prolonged exertion. However, recently it was reported that pre-exercise hyperhydration causes arterial hypoxemia in horses performing moderate intensity exercise simulating the second day of an equestrian 3-day event competition (E3DEC) which may adversely affect performance (Sosa Leon et al. in Equine Vet J Suppl 34:425-429, 2002). These findings are contrary to data from horses performing short-term maximal exertion, wherein hyperhydration did not affect arterial O2 tension/saturation. Thus, our objective in the present study was to examine the impact of pre-exercise hyperhydration on arterial oxygenation of Thoroughbred horses performing an exercise test simulating the second day of an E3DEC. Control and hyperhydration studies were carried out on seven healthy Thoroughbred horses in random order, 7 days apart. In the control study, horses received no medications. In the hyperhydration experiments, nasogastric administration of NaCl (0.425 g/kg) 5 h pre-exercise induced a plasma volume expansion of 10.9% at the initiation of exercise. This methodology for inducing hypervolemia was different from that of Sosa Leon et al. (2002). Blood-gas tensions/pH as well as plasma protein, hemoglobin and blood lactate concentrations were measured pre-exercise and during the exercise test. Our data revealed that pre-exercise hyperhydration neither adversely affected arterial O2 tension nor hemoglobin-O2 saturation at any time during the exercise test simulating the second day of an E3DEC. Further, it was observed that arterial blood CO2 tension, pH, and blood lactate concentrations also were not affected by pre-exercise hyperhydration. However, hemodilution in hyperhydrated horses caused an attenuation of the expansion in the arterial to mixed-venous blood O2 content gradient during phases B and D of the exercise protocol, which was likely offset by an increase in cardiac output. It is concluded that pre-exercise hyperhydration of horses induced in the manner described above is not detrimental to arterial oxygenation of horses performing an exercise test simulating the second day of an E3DEC.

Pre-exercise hypervolaemia is not detrimental to arterial oxygenation of horses performing a prolonged exercise protocol simulating the second day of a 3-day equestrian event.

REASONS FOR PERFORMING STUDY: Hyperhydration, prior to prolonged moderate-intensity exercise simulating the 2nd day of a 3-day equestrian event (E3DEC), may induce arterial hypoxaemia detrimental to performance. OBJECTIVES: Because moderate-intensity exercise does not induce arterial hypoxaemia in healthy horses, the effects of pre-exercise hypervolaemia on arterial oxygenation were examined during a prolonged exercise protocol. METHODS: Blood-gas studies were carried out on 7 healthy, exercise-trained Thoroughbred horses in control and hyperhydration experiments. The study conformed to a randomised crossover design. The sequence of treatments was randomised for each horse and 7 days were allowed between studies. Hyperhydration was induced by administering 0.425 g/kg bwt NaCl via nasogastric tube followed by free access to water. The exercise protocol was carried out on a treadmill set at a 3% uphill grade and consisted of walking at 2 m/sec for 2 min, trotting for 10 min at 3.7 m/sec, galloping for 2 min at 14 m/sec (which elicited maximal heart rate), trotting for 20 min at 3.7 m/sec, walking for 10 min at 1.8 m/sec, cantering for 8 min at 9.2 m/sec, trotting for 1 min at 5 m/sec and walking for 5 min at 2 m/sec. RESULTS: NaCl administration induced a significant mean +/- s.e. 15.5 +/- 1.1% increase in plasma volume as indicated by a significant reduction in plasma protein concentration. In either treatment, whereas arterial hypoxaemia was not observed during periods of submaximal exercise, short-term maximal exertion caused significant arterial hypoxaemia, desaturation of haemoglobin, hypercapnoea, and acidosis in both treatments. However, the magnitude of exercise-induced arterial hypoxaemia, desaturation of haemoglobin, hypercapnoea, and acidosis in both treatments remained similar, and statistically significant differences between treatments could not be demonstrated. CONCLUSIONS: It was concluded that significant pre-exercise expansion of plasma volume by this method does not adversely affect the arterial oxygenation of horses performing a prolonged exercise protocol simulating the 2nd day of an E3DEC.

An evaluation of drug treatments for adolescents in 4 US cities.

BACKGROUND: Little is known about outcomes of community-based treatment programs for adolescents with drug problems. METHODS: We studied 1167 adolescents (age range, 11-18 years; 368 females, 799 males) from 4 US cities (Pittsburgh, Pa; Minneapolis, Minn; Chicago, Ill; and Portland, Ore) using a naturalistic, nonexperimental evaluation design. These adolescents were consecutive admissions during the period from 1993 to 1995 at 23 community-based treatment programs in the Drug Abuse Treatment Outcome Studies for Adolescents. Included were 418 admissions to 8 residential programs, 292 admissions to 9 outpatient drug-free programs, and 457 admissions to 6 short-term inpatient programs. RESULTS: Adolescents in treatment typically had multiple problems (eg, 58.4% of them were involved in the legal system, and 63.0% met diagnostic criteria for a mental disorder). Nevertheless, less than half (43.8%) of all patients reported weekly marijuana use in the year following treatment (dropping from 80.4% in the year before admission). Similarly, there were decreases in heavy drinking (dropping from 33.8% to 20.3%), use of other illicit drugs (dropping from 48.0% to 42.2%), and criminal involvement (dropping from 75.6% to 52.8%). Additionally, patients reported better psychological adjustment and school performance after treatment. Longer stays in treatment were positively associated with several favorable outcomes, although length of time in treatment was generally short. CONCLUSIONS: Substance abuse treatment for adolescents is effective in achieving many important behavioral and psychological improvements. Strategies specific to adolescents to improve their treatment retention and completion are needed to maximize the therapeutic benefits of drug treatment.

The Trypanosoma brucei mitochondrial ATP synthase is developmentally regulated at the level of transcript stability.

The mitochondrial ATP synthase is developmentally regulated throughout the life cycle of the Trypanosoma brucei. The alpha and beta subunits of the F(1) moiety, and subunit 9 of the F(0) moiety of the T. brucei ATP synthase have been previously cloned and characterized. Here we have determined the chromosomal localization and developmental regulation of these three key subunits of the complex. Southern blot analysis indicates that all three of these genes are present as single copies in the T. brucei genome. Pulsed field gel analysis demonstrates that these genes are encoded in different chromosomes, and are thus not part of the same gene cluster. A comparison between the protein and steady state transcript levels for these subunits suggests that regulation of expression occurs predominantly posttranscriptionally. Comparison of mRNA stability for procyclic and bloodstream forms shows that the half life of the three transcripts is much shorter in bloodstream forms. The differences in transcript stability in the procyclic form for subunit 9 is greater than that for alpha and beta subunits, while the differences at the protein levels are comparable. These results suggest that there may be further posttranscriptional regulation of subunit 9.

Factors associated with frequency of 12-Step attendance by drug abuse clients.

Comparison was made of treatment clients attending Narcotics Anonymous and/or Alcoholics Anonymous meetings less than weekly (n = 41) with treatment clients attending meetings at least three times a week (n = 30). The frequent attenders (attending an average of 30.6 meetings monthly) differed from non- and infrequent attenders (attending an average of 0.4 meetings monthly) in terms of histories of greater lifetime drug use, more arrests and treatment experiences, and an earlier age of first use of alcohol. Although the frequent attender was also older, age was not found to influence the differences found between groups. Measures of religiosity, use of community services, and support from others for recovery and psychological functioning, other than ratings of the helpfulness of 12-Step, were not differentiated among groups. The findings suggest that 12-Step groups are more likely to be selected by clients with more severe histories of drug use and criminal activity, i.e., those most in need of the support to behavior change those groups provide. The role of treatment programs in facilitating the use of 12-Step groups is discussed.

Cloning and characterization of the subunits comprising the catalytic core of the Trypanosoma brucei mitochondrial ATP synthase.

The Trypanosoma brucei mitochondrial F(1)-ATPase has been previously isolated and characterized. It is composed of five subunits of molecular weights 55000, 42000, 32000, 22000, and 17000 [1]. We have identified the alpha and beta subunits of the T. brucei F(1)-ATPase by N-terminal sequence determination together with analysis of cDNA and genomic clones. The genes for both subunits are homologous to the same subunits from other organisms. They contain the Walker A and B boxes of homology and a putative mitochondrial import sequence. The isolated T. brucei alpha subunit is unusually small at 42 kDa. The alpha cDNA clone encodes a protein of predicted size 59 kDa with a mitochondrial import presequence at the N-terminus. The predicted size was confirmed by expression of a 59 kDa protein from the cDNA clone in vitro. These results suggest that the alpha subunit may have an unusually large mitochondrial presequence of 159 amino acids. In contrast, the estimated size of the native beta subunit (55 kDa) correlates well with the size predicted from the cDNA clone, 57 kDa, from which a 21 amino acid presequence has been removed in vivo. The size of the beta subunit was confirmed by expression in an in vitro and an Escherichia coli expression system. The purified recombinant beta subunit, like the native F(1)-ATPase, can be labeled by the photoaffinity nucleotide analogue 8-azido ATP. Binding of the 8-azido ATP probe is best competed by the natural substrate ATP, and is significantly reduced by pretreatment with the inhibitor 7-chloro-4-nitrobenzo-2-oxa-1,3-diazide as has been shown with beta subunits of other organisms. The differential binding of this photoaffinity analogue was used to resolve the identities of the alpha and beta subunits of the ATP synthase from T. brucei. These results are in contrast to results previously obtained for a related trypanosomatid Crithidia fasciculata.

Factors associated with frequent and infrequent HIV testing.

Drug user treatment clients with 5 or more HIV tests (frequent testees N=43) and 0-2 HIV tests (infrequent testees-N = 56) were compared on demographic characteristics, risk behaviors, perceived risk of HIV infection to self, involvement with family members, and psychological functioning. Extreme groups of HIV testees did not differ on any variables other than an index of perceived vulnerability to HIV infection (e.g., " You think that you really could get AIDS"). That measure of felt vulnerability was not correlated significantly with needle or sexual risk behaviors, family involvement, psychological functioning or other measures of perceived risk. It was reasoned that, in a community in which both dangers and protective behaviors are widely understood, frequent testees experience a generalized and heightened concern unrelated to specific behaviors or characteristics.

Effectiveness of a stand-alone aftercare program for drug-involved offenders.

A study was made of the effectiveness of an aftercare program operating in conjunction with area outpatient drug free treatment programs while organizationally independent of those programs. Parolees and probationers mandated to treatment were assigned to aftercare on the basis of residence in the catchment areas in which aftercare facilities were located (n = 32) and randomly to aftercare (n = 62) and control (n = 51) when not a resident in a catchment area. No outcome differences were found between aftercare groups based on proximity to facility. At 6 months postbaseline the combined aftercare group showed significantly lower levels of criminal activity and frequent drug use as compared to controls. At 12 months postbaseline there was an attenuation of group differences with only tendencies toward significance obtained for lower levels of frequent drug use by the aftercare group. The findings are discussed in terms of the relevance of community variables for programming and for understanding long-term treatment outcomes.

Modulation and genetic identification of the M channel.

Potassium channels constitute a superfamily of the most diversified ion channels, acting in delicate and accurate ways to control or modify many physiological and pathological functions including membrane excitability, transmitter release, cell proliferation and cell degeneration. The M-type channel is a unique ligand-regulated and voltage-gated K(+) channel showing distinct physiological and pharmacological characteristics. This review will cover some important progress in the study of M channel modulation, particularly focusing on membrane transduction mechanisms. The K(+) channel genes corresponding to the M channel have been identified and will be reviewed in detail. It has been a long journey since the discovery of M current in 1980 to our present understanding of the mysterious mechanisms for M channel modulation; a journey which exemplifies tremendous achievements in ion channel research and exciting discoveries of elaborate modulatory systems linked to these channels. While substantial evidence has accumulated, challenging questions remain to be answered.

Molecular basis for differential sensitivity of KCNQ and I(Ks) channels to the cognitive enhancer XE991.

Channels formed by coassembly of the KCNQ1 (KvLQT1) subunit and the minK subunit underlie slowly activating cardiac delayed rectifier (I(Ks)) in the heart, whereas two other members of the KCNQ channel family, KCNQ2 and KCNQ3, coassemble to underlie the M current in the nervous system. Because of their important physiological function, KCNQ channels have potential as drug targets, and an understanding of possible mechanisms that would enable tissue-specific targeting of these channels will be of significant value to drug development. In this study, we examined the role of the minK subunit in determining the response of KCNQ1 channels to blockade by the cognitive enhancer XE991. Coexpression with minK markedly decreased the sensitivity of KCNQ1 to blockade by XE991. When measured at the end of a 500-ms step, XE991 blockade of the KCNQ1+minK current had a K(D) value of 11.1 +/- 1.8 microM, approximately 14-fold less sensitive than the block of the KCNQ1 current (K(D) = 0.78 +/- 0.05 microM). In addition, XE991 reduced activation and deactivation time constants and caused a rightward shift in the activation curve of KCNQ1+minK, but affected none of these parameters for KCNQ1 alone. Also, XE991 block of KCNQ1+minK, but not of KCNQ1, was time- and voltage-dependent. We conclude that the presence of minK in the I(Ks) channel complex gives rise to differential sensitivity of KCNQ and I(Ks) channels to blockade by XE991. Our results have implications for drug development by demonstrating the important potential role of accessory subunits in determining the pharmacological properties of KCNQ channels.

Possible role of valvular serotonin 5-HT(2B) receptors in the cardiopathy associated with fenfluramine.

Dexfenfluramine was approved in the United States for long-term use as an appetite suppressant until it was reported to be associated with valvular heart disease. The valvular changes (myofibroblast proliferation) are histopathologically indistinguishable from those observed in carcinoid disease or after long-term exposure to 5-hydroxytryptamine (5-HT)(2)-preferring ergot drugs (ergotamine, methysergide). 5-HT(2) receptor stimulation is known to cause fibroblast mitogenesis, which could contribute to this lesion. To elucidate the mechanism of "fen-phen"-associated valvular lesions, we examined the interaction of fenfluramine and its metabolite norfenfluramine with 5-HT(2) receptor subtypes and examined the expression of these receptors in human and porcine heart valves. Fenfluramine binds weakly to 5-HT(2A), 5-HT(2B), and 5-HT(2C) receptors. In contrast, norfenfluramine exhibited high affinity for 5-HT(2B) and 5-HT(2C) receptors and more moderate affinity for 5-HT(2A) receptors. In cells expressing recombinant 5-HT(2B) receptors, norfenfluramine potently stimulated the hydrolysis of inositol phosphates, increased intracellular Ca(2+), and activated the mitogen-activated protein kinase cascade, the latter of which has been linked to mitogenic actions of the 5-HT(2B) receptor. The level of 5-HT(2B) and 5-HT(2A) receptor transcripts in heart valves was at least 300-fold higher than the levels of 5-HT(2C) receptor transcript, which were barely detectable. We propose that preferential stimulation of valvular 5-HT(2B) receptors by norfenfluramine, ergot drugs, or 5-HT released from carcinoid tumors (with or without accompanying 5-HT(2A) receptor activation) may contribute to valvular fibroplasia in humans.

Prevalence of Neospora antibodies in beef cattle in New Zealand.

AIM: To estimate the prevalence of Neospora infection in a sample of New Zealand beef cattle. METHODS: The prevalence of Neospora caninum infection in New Zealand beef cattle was estimated by collecting blood at slaughter from 499 beef cattle from 40 different farms at 2 slaughter plants in the North Island and 1 in the lower South Island . Sera were tested using an ELISA against Neospora tachyzoite antigen. RESULTS: The prevalence of seropositive cattle was 2.5% (n=120), 3.6% (n=166) and 2.3% (n=213) at the plants surveyed, the overall prevalence being 2.8%. The serologically positive cattle came from 9 farms, 3 of which had more than 1 positive animal. The highest prevalence recorded amongst animals from 1 farm was 4/13 (31%), in a group of young steers. CONCLUSION: Neosporosis appears to be present at a lower level in the New Zealand beef cattle population than in the New Zealand dairy cattle population. Nevertheless, from the high seroprevalence evident amongst young cattle on 1 farm, we suggest that Neospora may be a cause of infertility in beef cattle in this country.

Synthesis of phosphonate 3-phthalidyl esters as prodrugs for potential intracellular delivery of phosphonates.

A new prodrug approach for intracellular delivery of phosphonates was developed via the synthesis of 3-phthalidyl esters of 1-naphthalenemethylphosphonate. This approach is advantageous over the traditional acyloxymethyl phosphonate prodrugs, because these prodrugs do not generate formaldehyde and have improved plasma half-lives.

Prior treatment experience related to process and outcomes in DATOS.

Using data collected from cocaine-abusing patients who participated in the Drug Abuse Treatment Outcome Studies (DATOS), we contrasted patients in treatment for the first time and patients having extensive histories of prior treatment to identify factors associated with better outcomes in each group. Compared with first-timers, treatment-experienced patients had less favorable post-treatment outcomes. Indicators of early engagement in DATOS treatment predicted post-treatment abstinence for both groups. Importantly, the interaction of treatment history and several process measures affected post-treatment abstinence. For example, individual counseling and program compliance had greater impacts on abstinence among treatment repeaters in outpatient drug-free programs than for first-timers. Social support and environmental context were significantly related to abstinence. These findings confirm the importance of considering treatment process and aftercare in developing and implementing strategies to optimize treatment for patients with different treatment histories.

KCNQ2 and KCNQ3 potassium channel subunits: molecular correlates of the M-channel.

The M-current regulates the subthreshold electrical excitability of many neurons, determining their firing properties and responsiveness to synaptic input. To date, however, the genes that encode subunits of this important channel have not been identified. The biophysical properties, sensitivity to pharmacological blockade, and expression pattern of the KCNQ2 and KCNQ3 potassium channels were determined. It is concluded that both these subunits contribute to the native M-current.