Concentrations of dexmedetomidine and effect on biomarkers of cartilage toxicity following intra-articular administration in horses.

OBJECTIVE: The goal of this study was to determine plasma, urine, and synovial fluid concentrations and describe the effects on biomarkers of cartilage toxicity following intra-articular dexmedetomidine administration to horses. ANIMALS: 12 research horses. PROCEDURES: Horses received a single intra-articular administration of 1 µg/kg or 5 µg/kg dexmedetomidine or saline. Plasma, urine, and synovial fluid were collected prior to and up to 48 hours postadministration, and concentrations were determined. The effects on CS846 and C2C were determined in synovial fluid at 0, 12, and 24 hours postadministration using immunoassays. RESULTS: Plasma concentrations of dexmedetomidine fell below the limit of quantification (LOQ) (0.005 ng/mL) by 2.5 and 8 hours postadministration of 1 and 5 µg/kg, respectively. Synovial fluid concentrations were above the LOQ (0.1 ng/mL) of the assay at 24 hours in both dose groups. Drug was not detected in urine samples at any time postdrug administration. CS846 concentrations were significantly decreased relative to baseline at 12 hours postadministration in the saline group and significantly increased in the 5-µg/kg-dose group at 24 hours. Concentrations of C2C were significantly decreased at 12 and 24 hours postadministration in the saline treatment group. There were no significant differences in CS846 or C2C concentrations between dose groups at any time. CLINICAL RELEVANCE: Systemic concentrations of dexmedetomidine remained low, compared to synovial fluid concentrations. CS846, a marker of articular cartilage synthesis, increased in a dose-dependent fashion. Based on these findings, further dose titration and investigation of analgesic and adverse effects are warranted.

Metabolic and cardiovascular effects of body weight supported treadmill walking in healthy older adults.

BACKGROUND: The purpose of this study was to determine if body weight supported treadmill training (BWSTT) decreased metabolic and cardiovascular demand in older (50-74 years) healthy adults while walking a self-selected speed. The results of this study could impact clinician application to exercise therapy. METHODS: Twenty subjects (50% female, 58.3±7.3 years) completed 3, 5-minute treadmill walking trials at a self-selected pace, with 0%, 15%, and 30% body weight support (BWS). Blood pressure (BP), heart rate (HR), and oxygen uptake (V̇O2) were measured at rest, and during walking trials. Mean data from minutes 3-5 were analyzed for difference by repeated measures ANOVA and Bonferroni post-hoc test. RESULTS: At rest, HR was 70.8±8.2 bpm and BP was 126.8±12.2/84.3±8.6 mmHg. Mean walking speed was 67.1 m/min. Tested parameters during exercise trials were significantly (P<0.05) different from rest, but no significant differences were detected among the 3 exercise trials. CONCLUSIONS: In older adults walking at self-selected speeds, up to 30% BWS had no significant impact on metabolic or cardiovascular demand.

Pharmacokinetics of betamethasone in plasma, urine, and synovial fluid following intra-articular administration to exercised thoroughbred horses.

The use of corticosteroids, such as betamethasone, in performance horses is tightly regulated. The objective of the current study was to describe the plasma pharmacokinetics of betamethasone as well as time-related urine and synovial fluid concentrations following intra-articular administration to horses. Twelve racing-fit adult Thoroughbred horses received a single intra-articular administration (9 mg) of a betamethasone sodium phosphate and betamethasone acetate injectable suspension into the right antebrachiocarpal joint. Blood, urine, and synovial fluid samples were collected prior to and at various times up to 21 days post drug administration. All samples were analyzed using tandem liquid chromatography-mass spectrometry. Plasma data were analyzed using compartmental pharmacokinetic modeling. Maximum measured plasma betamethasone concentrations were 3.97 ± 0.23 ng/mL at 1.45 ± 0.20 h. The plasma elimination half-life was 7.48 ± 0.39 h. Betamethasone concentrations were below the limit of detection in all horses by 96 h and 7 days in plasma and urine, respectively. Betamethasone fell below the limit of detection in the right antebrachiocarpal joint between 14 and 21 days. Results of this study provide information that can be used to regulate the use of intra-articular betamethasone in the horse. Copyright © 2017 John Wiley & Sons, Ltd.

Differential expression of skeletal muscle genes following administration of clenbuterol to exercised horses.

BACKGROUND: Clenbuterol, a beta2-adrenergic receptor agonist, is used therapeutically to treat respiratory conditions in the horse. However, by virtue of its mechanism of action it has been suggested that clenbuterol may also have repartitioning affects in horses and as such the potential to affect performance. Clenbuterol decreases the percent fat and increases fat-free mass following high dose administration in combination with intense exercise in horses. In the current study, microarray analysis and real-time PCR were used to study the temporal effects of low and high dose chronic clenbuterol administration on differential gene expression of several skeletal muscle myosin heavy chains, genes involved in lipid metabolism and the ß2-adrenergic receptor. The effect of clenbuterol administration on differential gene expression has not been previously reported in the horse, therefore the primary objective of the current study was to describe clenbuterol-induced temporal changes in gene expression following chronic oral administration of clenbuterol at both high and low doses. RESULTS: Steady state clenbuterol concentrations were achieved at approximately 50 h post administration of the first dose for the low dose regimen and at approximately 18-19 days (10 days post administration of 3.2 µg/kg) for the escalating dosing regimen. Following chronic administration of the low dose (0.8 µg/kg BID) of clenbuterol, a total of 114 genes were differentially expressed, however, none of these changes were found to be significant following FDR adjustment of the p-values. A total of 7,093 genes were differentially expressed with 3,623 genes up regulated and 3,470 genes down regulated following chronic high dose administration. Of the genes selected for further study by real-time PCR, down-regulation of genes encoding myosin heavy chains 2 and 7, steroyl CoA desaturase and the ß2-adrenergic receptor were noted. For most genes, expression levels returned towards baseline levels following cessation of drug administration. CONCLUSION: This study showed no evidence of modified gene expression following chronic low dose administration of clenbuterol to horses. However, following chronic administration of high doses of clenbuterol alterations were noted in transcripts encoding various myosin heavy chains, lipid metabolizing enzymes and the ß2-adrenergic receptor.

Disposition of isoflupredone acetate in plasma, urine and synovial fluid following intra-articular administration to exercised Thoroughbred horses.

The use of isoflupredone acetate in performance horses and the scarcity of published pharmacokinetic data necessitate further study. The objective of the current study was to describe the plasma pharmacokinetics of isoflupredone acetate as well as time-related urine and synovial fluid concentrations following intra-articular administration to horses. Twelve racing-fit adult Thoroughbred horses received a single intra-articular administration (8 mg) of isoflupredone acetate into the right antebrachiocarpal joint. Blood, urine and synovial fluid samples were collected prior to and at various times up to 28 days post drug administration. All samples were analyzed using liquid chromatography-Mass Spectrometry. Plasma data were analyzed using a population pharmacokinetic compartmental model. Maximum measured plasma isoflupredone concentrations were 1.76 ± 0.526 ng/mL at 4.0 ± 1.31 h and 1.63 ± 0.243 ng/mL at 4.75 ± 0.5 h, respectively, for horses that had synovial fluid collected and for those that did not. The plasma beta half-life was 24.2 h. Isoflupredone concentrations were below the limit of detection in all horses by 48 h and 7 days in plasma and urine, respectively. Isoflupredone was detected in the right antebrachiocarpal and middle carpal joints for 8.38 ± 5.21 and 2.38 ± 0.52 days, respectively. Results of this study provide information that can be used to regulate the use of intra-articular isoflupredone in the horse.

Low dose, early mucosal exposure will minimize the risk of microbial disease.

In the 21st century we will rediscover the germ theory of disease: germs not only cause infection as described in standard textbooks but also have a pathogenic role in autoimmunity, atherosclerosis, cancer and even acute psychiatric conditions. In order to reduce morbidity and mortality caused by common organisms we should ensure that exposure is early, often, by the mucosal route and in low dose. Micro-organisms should be delivered daily throughout life by respiratory mucosal spray or enteric coated pill, in precise dose and in a predetermined schedule.

Postmortem cerebrospinal fluid pleocytosis: a marker of inflammation or postmortem artifact?

The aim of this paper is to reassess the significance of postmortem cerebrospinal fluid pleocytosis. Published articles of CSF changes after death were reviewed, and reanalysis, in the light of modern views on the significance of bacterial postmortem isolates, was undertaken. There is theoretical and experimental evidence that the blood brain barrier to the movement of protein and cells is preserved in the first few hours after death. The number of mononuclear cells in the cerebrospinal fluid does rise in the first 24 hours after death, and this is most probably due to detachment of leptomeningeal lining cells. But the marked increase in lymphocyte counts seen in some cases of sudden infant death syndrome (SIDS) and in other deaths in the paediatric age range could well be a marker of inflammation.

The effect of Staphylococcus aureus carriage in late pregnancy on antibody levels to staphylococcal toxins in cord blood and breast milk.

We investigated the effect of carriage of Staphylococcus aureus in the later stages of pregnancy on levels of antibody specific to the S. aureus toxins, staphylococcal enterotoxin B (SEB), staphylococcal enterotoxin C (SEC) and toxic shock syndrome toxin-1 (TSST-1), in cord blood and breast milk and also explored the relationship between levels of antibody in antenatal serum and cord blood. Nasopharyngeal swabs and stool samples were collected on two occasions, from 96 women, during the last 6 weeks of pregnancy. Samples were cultured and S. aureus isolates were identified. Antenatal and cord blood samples from the same women and their infants were analysed for IgG antibody to SEB, SEC and TSST-1 by enzyme-linked immunosorbent assay. Breast milk samples were analysed for IgA antibody to the same toxins. We found that S. aureus carriage in pregnancy is common and exposure to a toxin-producing isolate boosts immunity. Over 89% of women and infants have some protective antibody to the toxins, and antitoxin IgG levels are higher in cord blood samples compared with antenatal samples. Levels of cord blood IgG and breast milk IgA specific for the staphylococcal toxins vary. Some infants lack protection and could be at risk of toxin-induced disease.

Transient bacteraemia: a possible cause of sudden life threatening events.

The concept proposed is that transient bacteraemia occurring in otherwise healthy individuals can cause acute life threatening events due to bacterial toxaemia even though the bacteraemia is rapidly cleared (<20 min). This is most likely to occur in infancy at around two to three months of age when anti-toxin IgG reaches its nadir. Sudden unexpected death in infancy, acute life threatening events, haemorrhagic shock and encephalopathy, and the triad of retinal haemorrhage, encephalopathy and bilateral thin film subdural haematomata are conditions which could be caused by this mechanism. Investigations need to be directed to measuring bacterial toxins in blood, CSF and urine; anti-toxin IgG in blood; and bacterial specific nucleic acid sequences in blood, CSF and urine using polymerase chain reaction in order to confirm recent bacteraemia. Furthermore the upper respiratory tract bacterial flora should be mapped in cases and appropriately matched live healthy community controls. Sudden onset, profound life threatening physiological dysfunction occurring in later life could also be caused by a similar mechanism and should be investigated in a similar way; candidate conditions include epilepsy, migraine, stroke and cardiac arrhythmias.

Changes in EMG coherence between long and short thumb abductor muscles during human development.

In adults, motoneurone pools of synergistic muscles that act around a common joint share a common presynaptic drive. Common drive can be revealed by both time domain and frequency domain analysis of EMG signals. Analysis in the frequency domain reveals significant coherence in the range 1-45 Hz, with maximal coherence in low (1-12 Hz) and high (16-32 Hz) ranges. The high-frequency range depends on cortical drive to motoneurones and is coherent with cortical oscillations at approximately 20 Hz frequencies. It is of interest to know whether oscillatory drive to human motoneurone pools changes with development. In the present study we examined age-related changes in coherence between rectified surface EMG signals recorded from the short and long thumb abductor muscles during steady isometric contraction obtained while subjects abducted the thumb against a manipulandum. We analysed EMG data from 36 subjects aged between 4 and 14 years, and 11 adult subjects aged between 22 and 59 years. Using the techniques of pooled coherence analysis and the chi(2) difference of coherence test we demonstrate that between the ages of 7 and 9 years, and 12 and 14 years, there are marked increases in the prevalence and magnitude of coherence at frequencies between 11 and 45 Hz. The data from subjects aged 12-14 years were similar to those obtained from adult controls. The most significant differences between younger children and the older age groups were detected at frequencies close to 20 Hz. We believe that these are the first reported results demonstrating significant late maturational changes in the approximately 20 Hz common oscillatory drive to human motoneurone pools.

Detection of specific antibodies in cord blood, infant and maternal saliva and breast milk to staphylococcal toxins implicated in sudden infant death syndrome (SIDS).

The common bacterial toxins hypothesis of sudden infant death syndrome (SIDS) is that nasopharyngeal bacterial toxins can trigger events leading to death in infants with absent/low levels of antibody that can neutralise the toxins. The aim of this study was to investigate nasopharyngeal carriage of Staphylococcus aureus and determine levels of immunity in the first year of life to toxic shock syndrome toxin (TSST-1) and staphylococcal enterotoxin C (SEC). Both toxins have been implicated in SIDS cases. Seventy-three mothers and their infants (39 males and 34 females) were enrolled onto the study. The infants had birth dates spread evenly throughout the year. In infants, S. aureus carriage decreased significantly with age (P<0.001). Between 40% and 50% of infants were colonised with S. aureus in the first three months of life and 49% of the isolates produced one or both of the staphylococcal toxins. There was a significant correlation between nasopharyngeal carriage of S. aureus in mothers and infants in the three months following the birth (P<0.001). Carriage of S. aureus in infants and their mothers was not significantly associated with levels of antibody to TSST-1 or SEC in cord blood, adult saliva or breast milk. Infants colonised by S. aureus had higher levels of salivary IgA to TSST-1 than infants who were culture negative. Analysis of cord blood samples by a quantitative ELISA detected IgG bound to TSST-1 and SEC in 95.5% and 91.8% of cases respectively. There was a marked variation in levels of maternal IgG to both TSST-1 and SEC among cord blood samples. Maternal age, birth weight, and seasonality significantly affected the levels of IgG binding to TSST-1 or SEC. Analysis of infant saliva samples detected IgA to TSST-1 and SEC in the first month after birth; 11% of samples tested positive for salivary IgA to TSST-1 and 5% for salivary IgA to SEC. By the age of two months these proportions had increased to 36% and 33% respectively. More infants who used a dummy tested positive for salivary IgA to TSST-1 compared to infants who did not use a dummy. Levels of IgA to TSST-1 and SEC detected in the breast-milk samples varied greatly among mothers. There was a trend for infants receiving breast milk with low levels of antibody to TSST-1 or SEC to have higher levels of salivary antibody to the toxins. In conclusion, passive immunity to toxins implicated in SIDS cases varies greatly among infants. Infants are able to mount an active mucosal immune response to TSST-1 and SEC in the first month of life.

Cutaneomuscular reflexes following stroke: a 2-year longitudinal study.

Cutaneomuscular reflex responses (CMRs) have been studied in nine stroke patients (55-84 years) starting from the first 1-7 weeks after stroke and continuing at intervals of 6-8 weeks for up to 2 years. Multi-unit surface EMG signals were recorded from the stroke and non-stroke first dorsal interosseous (1DI) hand muscle while subjects gripped a dowel, and concomitant stimulation of the digital nerves of the index finger was delivered at 2.5 x threshold for perception. Motor function was measured using the Motor Assessment Scale (MAS) and patients were classified as having a good or a poor recovery according to their final functional outcome. None of the patients showed a change in the sizes of the E1, I1 and E2 reflex components over time. At initial testing, the size of the E1 component for all patients who showed good recovery fell within the 95% reference range (0-16.5% modulation of background EMG) found for normal age matched controls. In contrast, when first tested, 5/5 patients who showed no significant recovery over the 2-year period, had exaggerated spinal E1 components greater than 16.5%. We conclude that exaggerated E1 components could be predictive of a poor functional outcome at 2 years.

Changes in cutaneomuscular reflex responses in relation to normal ageing in man.

Changes in cutaneomuscular reflex responses (CMRs) have been studied in relation to normal ageing in man. Multiunit surface EMG signals were recorded from right and left first dorsal interosseous (1DI) hand muscles from 23 elderly adults (mean age 71.1, range 58-88 years) and 11 young adults (mean age 25.9, range 19-31 years). Subjects (1) performed index finger abduction and (2) gripped a dowel while concomitant stimulation of the digital nerves of the index finger was delivered at x2.5 threshold for perception. The E1 spinally mediated components of the CMRs recorded from 1DI were significantly smaller in the elderly subjects compared with young subjects for both tasks. The I1 and E2 transcortical components did not show a significant change in size with age although the incidence of I1 components was significantly reduced in the elderly subjects.