Pierre Hélie

Single intravenous low-dose injections of connexin 43 mimetic peptides protect ischemic heart in vivo against myocardial infarction

The opening of unapposed connexin 43 hemichannels (Cx43Hc) under ischemic stress leads to cell death and irreversible tissue injury. Here, we investigate for the first time in vivo the cardioprotective potentials of two unique Cx43 structural-mimetic peptides (Cx43MPs) presumed specific blockers of Cx43Hc, Gap26 and Gap27, when injected intravenously using a rat model of myocardial infarction.Sprague Dawley rats were utilized. Myocardial infarction was induced by occluding the left anterior descending coronary for 40 min followed by 2 days of reperfusion. Interestingly, single bolus injections of Gap26 or Gap27 (1 μg/kg) into the jugular vein caused infarct size reductions by up to 61% with reference to control rats injected with saline at similar timings. Infarct reductions did not vary significantly whether peptides were administered before or after the onset of ischemia. Although the two peptides allegedly interact with distinct structures of Cx43, co-administration of Gap26/Gap27 in equal doses did not confer additive protection to hearts (maximum infarct reduction by 64%). Using patch clamp technique, we provide unique and direct evidence for the inhibitory effect of Cx43MPs on genuine human Cx43Hc transiently expressed in the ion channel-deficient tsA201 cells. In concordance with the cardioprotective effect observed in vivo, co-application of both peptides did not cause cumulative current inhibition. A safety profile of Cx43MPs was also addressed.Our results reveal great therapeutic potential of Cx43MPs in treatment of myocardial infarction. Their practical way and timing of administration and their apparent safe profile make them promising tools to fight ischemic heart disease.

Noninvasive correction of a fractured endoluminal nitinol tracheal stent in a dog.

An 11-year-old, castrated male Pomeranian was presented for intractable cough and dyspnea secondary to severe tracheal collapse. An endoluminal nitinol tracheal stent was placed with good results. Five months following placement of the prosthesis, clinical signs acutely recurred and failure of the implant was noted. A second stent was superimposed over the fractured stent and resulted in resolution of all clinical signs. The dog died several months later from progression of the tracheal collapse to the carina and mainstem bronchi.

Thoracoscopic lung biopsies in heaves-affected horses using a bipolar tissue sealing system.

Objective: To validate the use of the LigaSure™ Vessel Sealing System (LVSS) to perform thoracoscopic lung tissue biopsies in heaves-affected horses. Study design: Prospective clinical study. Animals: Heaves-affected horses (n=12). Methods: Lung biopsies (n=34) were collected with the LVSS (2–4 biopsies/horse) in horses with and without clinical signs of heaves. Thoracoscope (13th intercostal space [ICS]) and 2 instruments (between the 12–15th ICS) portals were used. Selected clinical and arterial blood gas variables were monitored. Postoperative pneumothorax was evaluated. Depth of thermal injury to the surrounding tissue and representativeness of the biopsies were determined. Results: Mean surgical time was 22.9±8.0 minutes. The complication rate was 5.6%, and primarily related to a focal inadequate sealing of the biopsy margin. Five horses in exacerbation required intraoperative intranasal O2. Mean PaO2 was significantly lower in heaves-affected horses with clinical signs compared with those without clinical signs. Postoperative pneumothorax was detected radiographically after 20 of the 34 procedures. One horse with clinical signs of heaves developed a fatal tension pneumothorax 5 days postoperatively despite close radiographic monitoring. Conclusion: Thoracoscopic lung biopsy using LVSS is a rapid and effective technique to harvest peripheral lung tissues from heaves-affected horses. Although the complication rate was tolerable, tension pneumothorax was a potential life-threatening complication because of incomplete lung sealing. Clinical Relevance: LVSS can be used with relative safety to perform thoracoscopic lung biopsy, but close postoperative monitoring is necessary to avoid tension pneumothorax.OBJECTIVE To validate the use of the LigaSure™ Vessel Sealing System (LVSS) to perform thoracoscopic lung tissue biopsies in heaves-affected horses. STUDY DESIGN Prospective clinical study. ANIMALS Heaves-affected horses (n=12). METHODS Lung biopsies (n=34) were collected with the LVSS (2-4 biopsies/horse) in horses with and without clinical signs of heaves. Thoracoscope (13th intercostal space [ICS]) and 2 instruments (between the 12-15th ICS) portals were used. Selected clinical and arterial blood gas variables were monitored. Postoperative pneumothorax was evaluated. Depth of thermal injury to the surrounding tissue and representativeness of the biopsies were determined. RESULTS Mean surgical time was 22.9±8.0 minutes. The complication rate was 5.6%, and primarily related to a focal inadequate sealing of the biopsy margin. Five horses in exacerbation required intraoperative intranasal O(2) . Mean PaO(2) was significantly lower in heaves-affected horses with clinical signs compared with those without clinical signs. Postoperative pneumothorax was detected radiographically after 20 of the 34 procedures. One horse with clinical signs of heaves developed a fatal tension pneumothorax 5 days postoperatively despite close radiographic monitoring. CONCLUSION Thoracoscopic lung biopsy using LVSS is a rapid and effective technique to harvest peripheral lung tissues from heaves-affected horses. Although the complication rate was tolerable, tension pneumothorax was a potential life-threatening complication because of incomplete lung sealing. CLINICAL RELEVANCE LVSS can be used with relative safety to perform thoracoscopic lung biopsy, but close postoperative monitoring is necessary to avoid tension pneumothorax.

Effects of endotoxemia on the pharmacodynamics and pharmacokinetics of ketamine and xylazine anesthesia in Sprague-Dawley rats

Purpose To evaluate the effects of endotoxemia on the pharmacokinetics and pharmacodynamics of ketamine and xylazine anesthesia in Sprague-Dawley rats. Methods Sprague-Dawley rats received ketamine (80 mg/kg) and xylazine (5 mg/kg) intramuscularly following the intraperitoneal administration of different lipopolysaccharide concentrations (1, 10, and 100 µg/kg) to simulate different levels of endotoxemia. Results were compared to control animals receiving saline intraperitoneally. During anesthesia, a toe pinch was performed to evaluate anesthesia duration, and selected physiological parameters (heart and respiratory rates, oxygen saturation, and rectal temperature) were taken. Blood samples were also taken during anesthesia at selected time points for the analysis of plasmatic ketamine and xylazine concentrations by liquid chromatography-mass spectrometry. Blood samples were taken 1 week prior to and 24 hours following anesthesia for blood biochemistry. Results Anesthesia duration significantly increased for moderate (10 µg/kg) and high (100 µg/kg) lipopolysaccharide groups. Liver histopathology showed minor to moderate necrosis in all lipopolysaccharide groups in some animals. The most important physiological change that occurred was a decrease in oxygen saturation, and for blood biochemistry a decrease in serum albumin. Ketamine pharmacokinetics were not affected except for the moderate (10 µg/kg) lipopolysaccharide group where a decrease in the area under the plasma concentration-time curve from time zero to the last measurable concentration, a decrease in half-life, and an increase in the clearance were observed. For xylazine, the area under the plasma concentration-time curve increased and the clearance decreased in the moderate (10 µg/kg) and high (100 µg/kg) lipopolysaccharide groups. Conclusion During ketamine-xylazine anesthesia, endotoxemia may alter xylazine pharmacokinetics and selected biochemical and physiological parameters, suggesting that anesthetic drug dosages could be modified for a more rapid recovery.

Genetic diversity of Mycoplasma hyopneumoniae isolates of abattoir pigs.

Mycoplasma hyopneumoniae, the causative agent of porcine enzootic pneumonia, is present in swine herds worldwide. However, there is little information on strains infecting herds in Canada. A total of 160 swine lungs with lesions suggestive of enzootic pneumonia originating from 48 different farms were recovered from two slaughterhouses and submitted for gross pathology. The pneumonic lesion scores ranged from 2% to 84%. Eighty nine percent of the lungs (143/160) were positive for M. hyopneumoniae by real-time PCR whereas 10% (16/160) and 8.8% (14/160) were positive by PCR for M. hyorhinis and M. flocculare, respectively. By culture, only 6% of the samples were positive for M. hyopneumoniae (10/160). Among the selected M. hyopneumoniae-positive lungs (n=25), 9 lungs were co-infected with M. hyorhinis, 9 lungs with PCV2, 2 lungs with PRRSV, 12 lungs with S. suis and 10 lungs with P. multocida. MLVA and PCR-RFLP clustering of M. hyopneumoniae revealed that analyzed strains were distributed among three and five clusters respectively, regardless of severity of lesions, indicating that no cluster is associated with virulence. However, strains missing a specific MLVA locus showed significantly less severe lesions and lower numbers of bacteria. MLVA and PCR-RFLP analyses also showed a high diversity among field isolates of M. hyopneumoniae with a greater homogeneity within the same herd. Almost half of the field isolates presented less than 55% homology with selected vaccine and reference strains.

Bilateral central pain sensitization in rats following a unilateral thalamic lesion may be treated with high doses of ketamine

BackgroundCentral post-stroke pain is a neuropathic pain condition caused by a vascular lesion, of either ischemic or hemorrhagic origin, in the central nervous system and more precisely involving the spinothalamocortical pathway responsible for the transmission of painful sensations. Few animal models have been developed to study this problem. The objectives of this study were to evaluate different modalities of pain in a central neuropathic pain rat model and to assess the effects of ketamine administered at different doses. Animals were evaluated on the rotarod, Hargreaves, Von Frey and acetone tests. A very small hemorrhage was created by injecting a collagenase solution in the right ventral posterolateral thalamic nucleus. Following the establishment of the neuropathy, ketamine was evaluated as a therapeutic drug for this condition.ResultsHistopathological observations showed a well localized lesion with neuronal necrosis and astrocytosis following the collagenase injection that was localized within the VPL. No significant change in motor coordination was observed following surgery in either the saline or collagensae groups. In the collagenase group, a significant decrease in mechanical allodynia threshold was observed. A sporadic and transient cold allodynia was also noted. No thermal hyperalgesia was seen following the collagenase injection. Ketamine was then tested as a potential therapeutic drug. A significant decrease in motor coordination was seen only following the administration of 25 mg/kg of ketamine in both groups. An alleviation of mechanical allodynia was achieved only with the high ketamine dose. The minimal effective ketamine serum concentration (150 ng/mL) was only achieved in animals that received 25 mg/kg.ConclusionsAn intrathalamic hemorrhage induced a bilateral mechanical allodynia in rats. Cold hyperalgesia was observed in 60% of these animals. Mechanical allodynia was alleviated with high doses of ketamine which corresponded with therapeutic plasmatic concentrations.

Physiological, pharmacokinetic and liver metabolism comparisons between 3-, 6-, 12- and 18-month-old male Sprague Dawley rats under ketamine-xylazine anesthesia

The main objective of this study was to compare the physiological changes (withdrawal and corneal reflexes, respiratory and cardiac frequency, blood oxygen saturation, and rectal temperature) following intraperitoneal administration of ketamine (80 mg/kg) and xylazine (10 mg/kg) to 3-, 6-, 12- and 18-month-old male Sprague Dawley rats (n=6/age group). Plasma pharmacokinetics, liver metabolism, and blood biochemistry were examined for a limited number of animals to better explain anesthetic drug effects. Selected organs were collected for histopathology. The results for the withdrawal and corneal reflexes suggest a shorter duration and decreased depth of anesthesia with aging. Significant cardiac and respiratory depression, as well as decreased blood oxygen saturation, occurred in all age groups however, cardiac frequency was the most affected parameter with aging, since the 6-, 12-, and 18-month-old animals did not recuperate to normal values during recovery from anesthesia. Pharmacokinetic parameters (T1/2 and AUC) increased and drug clearance decreased with aging, which strongly suggests that drug exposure is associated with the physiological results. The findings for liver S9 fractions of 18-month-old rats compared with the other age groups suggest that following a normal ketamine anesthetic dose (80 mg/kg), drug metabolism is impaired, leading to a significant increase of drug exposure. In conclusion, age and related factors have a substantial effect on ketamine and xylazine availability, which is reflected by significant changes in pharmacokinetics and liver metabolism of these drugs, and this translates into shorter and less effective anesthesia with increasing age.

Anesthetic and pathological changes following high doses of ketamine and xylazine in Sprague Dawley rats.

The main objective of this study was to compare the effects of ketamine and xylazine in aging rats when coadministered intraperitoneally at high anesthetic doses. Three groups (n=6 rats/group) consisting of rats at 3, 6 and 12 months of age were used. During anesthesia, animals were monitored for heart rate, respiratory frequency, blood oxygen saturation, and rectal temperature. The corneal and paw withdrawal reflex were also examined during anesthesia. During anesthesia, withdrawal and corneal reflexes were absent for progressively longer durations with increasing age. Significant decreases in cardiac and respiratory frequency and, blood oxygen saturation occurred for the 6- and 12-month-old animals. Respiratory frequency and blood oxygen saturation returned to normal at the end of the anesthesia; however, the significant decrease in cardiac frequency persisted in the 6- and 12-month-old animals. Rectal temperature was decreased significantly only in the 3-month-old animals. Pulmonary edema and effusion occurred in 50% of the 12-month-old animals. In conclusion, if ketamine-xylazine are used for anesthesia, the doses should be optimized for the age of the subjects prior to initiation of the research project.

Development of a Semiquantitative Histological Score for the Diagnosis of Heaves Using Endobronchial Biopsy Specimens in Horses.

Background Remodeling of the peripheral airways persists during the asymptomatic phase of heaves. Assessing the histology of large bronchi could facilitate the diagnosis of heaves during remission of the disease. Hypothesis Airway inflammation and remodeling in endobronchial biopsy (EBB) specimens differentiate horses with heaves from controls, independently of their clinical status (exacerbation or remission). Animals Fourteen healthy horses and 24 horses with heaves. Methods A 14‐point scoring system assessing central bronchial wall inflammation and remodeling was developed. The score was validated by 2 pathologists using specimens obtained from 18 horses (6 controls, 6 with heaves exacerbation, and 6 with heaves remission) in which lung function had been assessed with impulse oscillometry. Clinical and research application of the score was evaluated using biopsy specimens obtained from 20 additional horses (8 controls, 6 with heaves exacerbation, and 6 with heaves remission). Results The score was repeatable (interclass correlation coefficient = 69%). It differentiated horses with heaves in exacerbation (mean ± SD: 6.2 ± 2.2) from those in remission (4.0 ± 1.0) and controls (3.6 ± 1.7, P < 0.0001). The histological scores of horses with heaves correlated with the ratio of respiratory resistance (R) at 5 and 10 Hz (R 5 : R 10 ratio, r = 0.65, P = 0.03), a parameter assessing airway obstruction. Conclusions and Clinical Significance The proposed histological scoring system correlates with the degree of airway obstruction measured by impulse oscillometry. However, it does not discriminate horses with heaves in remission from controls. Evaluation of EBB specimens might be considered in future research and clinical studies of respiratory diseases in horses.

Postoperative pain in Sprague Dawley rats after liver biopsy by laparotomy versus laparoscopy

Laparoscopic surgery offers advantages for both animal welfare and quality of experimental data. Compared with laparotomy, laparoscopy is associated with less postoperative pain and faster recuperation in humans and is also associated with less postoperative pain in dogs. Postoperative pain associated with laparotomy and laparoscopy has not been compared in rodents, however. The authors used a validated pain grimace scale to evaluate postoperative pain in male Sprague Dawley rats after liver biopsy by laparotomy or laparoscopy. Rats that underwent laparoscopy showed fewer recognized signs of pain than did rats that underwent laparotomy. The authors suggest that laparoscopy could be used for repeated biopsies in rats, minimizing the number of animals used in pharmacological and toxicological studies.