Remodeling in the AV block dog is essential for tolerating moderate treadmill activity.

Background: A preclinical model standardized at different remodeling stages after AV block induction in awake state is suitable for the evaluation of improved cardiac devices. We studied exercise-induced cardiorespiratory parameters at three different timepoints after inducing AV block in dogs. Methods: Mongrel dogs (n = 12) were placed on a treadmill with a 10% incline and performed a moderate exercise protocol (10-minute run at 6 km/h). Dogs ran at sinus rhythm (SR), at two days (AVB2d, initiation of remodeling), three weeks (CAVB3) and six weeks (CAVB6, completed remodeling) after AV block. Results: All dogs completed the exercise protocol at SR, CAVB3 and CAVB6, while 6/12 dogs at AVB2d failed to complete the exercise protocol. The atrial rate was higher at all AV block timepoints (126 ± 20 to 141 ± 19 bpm at rest and 221 ± 10 to 231 ± 13 bpm during exercise) compared to SR (100 ± 29 bpm at rest and 162 ± 28 bpm during exercise, p < 0.05). Upon exercise, stroke volume increased from 66 ± 15 ml at SR, to 96 ± 21 ml at AVB2d (p < 0.05), 91 ± 13 ml at CAVB3 (p < 0.05) and 85 ± 24 ml at CAVB6 but failed to compensate for the AV block-induced bradycardia. Therefore, cardiac output was lower after AV block compared to SR. Exercising dogs at AVB2d showed most arrhythmic events, lowest VO2, and signs of desaturation and acidification in venous blood. Conclusion: Dogs with limited remodeling after AV block have a reduced exercise tolerance, which is reflected in changes in cardiorespiratory parameters.

Pressure measurement in the reticulum to detect different behaviors of healthy cows.

The aim of the current study was to investigate the relation between reticulorumen contractions and monitored cow behaviors. A purpose-built pressure measuring device was used and shown to be capable of detecting the known contraction patterns in the reticulorumen of four rumen-fistulated cows. Reticular pressure data was used to build a random forest algorithm, a learning algorithm based on a combination of decision trees, to detect rumination and other cow behaviors. In addition, we developed a peak-detection algorithm for rumination based on visual inspection of patterns in reticular pressure. Cow behaviors, differentiated in ruminating, eating, drinking, sleeping and 'other', as scored from video observation, were used to develop and test the algorithms. The results demonstrated that rumination of a cow can be detected by measuring pressure differences in the reticulum using either the random forest algorithm or the peak-detection algorithm. The random forest algorithm showed very robust performances for detecting rumination with an accuracy of 0.98, a sensitivity of 0.95 and a specificity of 0.99. The peak-detection algorithm could detect rumination robustly, with an accuracy of 0.92, a sensitivity of 0.97 and a specificity of 0.90. In addition, we provide proof of principle that a random forest algorithm can also detect eating, drinking and sleeping behavior from the same data with performances above 0.90 for all measures. The measurement device used in this study needed rumen-fistulated cows, but the results indicate that behavior detection using algorithms based on only measurements in the reticulum is feasible. This is promising as it may allow future wireless sensor techniques in the reticulum to continuously monitor a range of important behaviors of cows.

Surgical resection and radiofrequency ablation initiate cancer in cytokeratin-19+- liver cells deficient for p53 and Rb.

The long term prognosis of liver cancer patients remains unsatisfactory because of cancer recurrence after surgical interventions, particularly in patients with viral infections. Since hepatitis B and C viral proteins lead to inactivation of the tumor suppressors p53 and Retinoblastoma (Rb), we hypothesize that surgery in the context of p53/Rb inactivation initiate de novo tumorigenesis.We, therefore, generated transgenic mice with hepatocyte and cholangiocyte/liver progenitor cell (LPC)-specific deletion of p53 and Rb, by interbreeding conditional p53/Rb knockout mice with either Albumin-cre or Cytokeratin-19-cre transgenic mice.We show that liver cancer develops at the necrotic injury site after surgical resection or radiofrequency ablation in p53/Rb deficient livers. Cancer initiation occurs as a result of specific migration, expansion and transformation of cytokeratin-19+-liver (CK-19+) cells. At the injury site migrating CK-19+ cells formed small bile ducts and adjacent cells strongly expressed the transforming growth factor ß (TGFß). Isolated cytokeratin-19+ cells deficient for p53/Rb were resistant against hypoxia and TGFß-mediated growth inhibition. CK-19+ specific deletion of p53/Rb verified that carcinomas at the injury site originates from cholangiocytes or liver progenitor cells.These findings suggest that human liver patients with hepatitis B and C viral infection or with mutations for p53 and Rb are at high risk to develop tumors at the surgical intervention site.

Neurophysiological assessment of the sedative and analgesic effects of a constant rate infusion of dexmedetomidine in the dog.

The sedative and analgesic effects of continuous rate infusion (CRI) of dexmedetomidine (DEX) were investigated in Beagle dogs (n=8) using auditory and somatosensory evoked potentials (AEPs and SEPs) recorded before, during and after a CRI of saline or DEX (1.0, 3.0, 5.0 µg/kg bolus, followed by 1.0, 3.0, 5.0 µg/kg/h CRI, respectively). The results showed a significant reduction in AEP at doses of 1.0 µg/kg/h and above and a significant reduction of the SEP at doses of 3.0 and 5.0 µg/kg/h. Neither the AEP nor the SEP was further reduced at 5.0 µg/kg/h when compared to 3.0 µg/kg/h, although a slower return towards baseline values was observed at 5.0 µg/kg/h. The mean plasma levels (±SEM) of DEX during infusion were 0.533±0.053 ng/mL for the 1.0 µg/kg/h dose, 1.869±0.063 ng/mL for the 3.0 µg/kg/h dose and 4.017±0.385 for the 5.0 µg/kg/dose. It was concluded that in adult dogs, a CRI of DEX had a sedative and analgesic effect that could be described quantitatively using neurophysiological parameters. Sedation was achieved at lower plasma levels than required for analgesia, and DEX had a longer (but not larger) effect with infusion rates above 3.0 µg/kg/h.

Reducing chloride conductance prevents hyperkalaemia-induced loss of twitch force in rat slow-twitch muscle.

Exercise-induced loss of skeletal muscle K(+) can seriously impede muscle performance through membrane depolarization. Thus far, it has been assumed that the negative equilibrium potential and large membrane conductance of Cl(-) attenuate the loss of force during hyperkalaemia. We questioned this idea because there is some evidence that Cl(-) itself can exert a depolarizing influence on membrane potential (V(m)). With this study we tried to identify the possible roles played by Cl(-) during hyperkalaemia. Isolated rat soleus muscles were kept at 25 degrees C and twitch contractions were evoked by current pulses. Reducing [Cl(-)](o) to 5 mM, prior to introducing 12.5 mM K(o), prevented the otherwise occurring loss of force. Reversing the order of introducing these two solutions revealed an additional effect, i.e. the ongoing hyperkalaemia-related loss of force was sped up tenfold after reducing [Cl(-)](o). However, hereafter twitch force recovered completely. The recovery of force was absent at [K(+)](o) exceeding 14 mM. In addition, reducing [Cl(-)](o) increased membrane excitability by 24%, as shown by a shift in the relationship between force and current level. Measurements of V(m) indicated that the antagonistic effect of reducing [Cl(-)](o) on hyperkalaemia-induced loss of force was due to low-Cl(-)-induced membrane hyperpolarization. The involvement of specific Cl(-) conductance was established with 9-anthracene carboxylic acid (9-AC). At 100 microm, 9-AC reduced the loss of force due to hyperkalaemia, while at 200 microm, 9-AC completely prevented loss of force. To study the role of the Na(+)-K(+)-2Cl(-) cotransporter (NKCC1) in this matter, we added 400 microm of the NKCC inhibitor bumetanide to the incubation medium. This did not affect the hyperkalaemia-induced loss of force. We conclude that Cl(-) exerts a permanent depolarizing influence on V(m). This influence of Cl(-) on V(m), in combination with a large membrane conductance, can apparently have two different effects on hyperkalaemia-induced loss of force. It might exert a stabilizing influence on force production during short periods of hyperkalaemia, but it can add to the loss of force during prolonged periods of hyperkalaemia.

Prevention of biofilm formation in dialysis water treatment systems.

BACKGROUND: Biofilm formations in dialysis systems may be relevant because they continuously release bacterial compounds and are resistant against disinfection. The aim of the study was to compare the development of biofilm between a water treatment system based on a single reverse osmosis unit producing purified dialysate water [bacterial count, 350 colony-forming unit (CFU)/L] (center A) and a water treatment system based on double reverse osmosis and electric deionization, which is continuously disinfected with ultraviolet light and treated with ozone once a week (bacterial count, 1 CFU/L) (center B). METHODS: During a period of 12 weeks, biofilm formation was studied in the tubing segment between the water piping and the dialysis module, using four dialysis monitors in each center. On a weekly basis, tubing samples of 5 cm length (N = 96) were taken under aseptic conditions and investigated for microbiologic contamination [cystine lactose electrolyte-deficient (CLED) Agar], endotoxin levels [limulus amoeben lysate (LAL) gel test, cutoff value, 0.0125 EU/mL], and biofilm formation [electron scanning microscopy (SEM)]. RESULTS: In center A, tube cultures were positive (>100 CFU/mL) in 16% of samples at 22 degrees C and 37 degrees C, compared to 3% of samples of center B (P < 0.05; chi-square). Endotoxin levels were positive in 76% of the tubing samples of center A and negative in all of the samples of center B (P < 0.05). Biofilm was present in 91.7% of the samples of center A (Fig. 1), and only present in one sample (taken after 9 weeks) of center B (P < 0.05) (Fig. 2). In center A, biofilm formation was already observed after 1 week. CONCLUSION: In contrast to a standard water treatment system producing purified water, the use of a system producing highly purified water, which is also treated with regular disinfection procedures, leads to a significant reduction in biofilm formation, bacterial growth, and endotoxin levels in a highly vulnerable part of a water treatment system.