Sustained substrate cycles between hexose phosphates and free sugars in phosphate-deficient potato (Solanum tuberosum) cell cultures.

MAIN CONCLUSION: Futile cycling between free sugars and hexose phosphates occurring under phosphate deficiency could be involved in the maintenance of a threshold level of free cellular phosphate to preserve respiratory metabolism. We studied the metabolic response of potato cell cultures growing in Pi sufficient (2.5 mM, +Pi) or deficient (125 µM, -Pi) conditions. Under Pi deficiency, cellular growth was severely affected, however -Pi cells were able to maintain a low but steady level of free Pi. We surveyed the activities of 33 primary metabolic enzymes during the course of a 12 days Pi deficiency period. Our results show that many of these enzymes had higher specific activity in -Pi cells. Among these, we found typical markers of Pi deficiency such as phosphoenolpyruvate phosphatase and phosphoenolpyruvate carboxylase as well as enzymes involved in the biosynthesis of organic acids. Intriguingly, several ATP-consuming enzymes such as hexokinase (HK) and phosphofructokinase also displayed increased activity in -Pi condition. For HK, this was associated with an increase in the steady state of a specific HK polypeptide. Quantification of glycolytic intermediates showed a pronounced decrease in phosphate esters under Pi deficiency. Adenylate levels also decreased in -Pi cells, but the Adenylate Energy Charge was not affected by the treatment. To investigate the significance of HK induction under low Pi, [U-14C]-glucose tracer studies were conducted. We found in vivo evidence of futile cycling between pools of hexose phosphates and free sugars under Pi deficiency. Our study suggests that the futile cycling between hexose phosphates and free sugars which is active under +Pi conditions is sustained under Pi deficiency. The possibility that this process represents a metabolic adaptation to Pi deficiency is discussed with respect to Pi homeostasis in Pi-deficient conditions.

Choosing a lung isolation device for thoracic surgery: a randomized trial of three bronchial blockers versus double-lumen tubes.

BACKGROUND: There is no consensus on the best technique for lung isolation for thoracic surgery. In this study, we compared the clinical performance of three bronchial blockers (BBs) available in North America with left-sided double-lumen tubes (DLTs) for lung isolation in patients undergoing left-sided thoracic surgery. METHODS: One hundred four patients undergoing left-sided thoracotomy or video-assisted thoracoscopic surgery were randomly assigned to one of the four lung isolation groups (n = 26/group). Lung isolation was with an Arndt wire-guided BB (Cook Critical Care, Bloomington, IN), a Cohen Flexi-tip BB (Cook Critical Care) or a Fuji Uni-blocker (Fuji Systems, Tokyo) or with a left-sided DLT (Mallinckrodt Medical, Cornamadde, Athlone, Westmeath, Ireland). Anesthetic management and lung isolation were performed according to a standardized protocol. Each group was randomly subdivided into two subgroups (n = 13/subgroup): immediate suction (at the time of insertion of the lung isolation device) (Subgroup I) or delayed suction (20 min after insertion of the lung separation device) (Subgroup D) according to when suction was applied to the BB suction channel or the bronchial lumen of the DLT. Using a verbal analog scale, lung collapse was assessed by the surgeons, who were blinded to the lung isolation technique. RESULTS: There was no difference among the lung isolation devices in lung collapse scores at 0 (P = 0.66), 10 (P = 0.78), or 20 min (P = 0.51) after pleural opening. The time to initial lung isolation was less for DLTs (93 +/- 62 s) than BBs (203 +/- 132) (P = 0.0001). There were no differences among the BBs in the time to lung isolation (P = 0.78). There were significantly more repositions after initial placement of the lung isolation device with BBs (35 incidents) than with DLTs (two incidents) (P = 0.009). The Arndt BB required repositioning more frequently (16 incidents) than the Cohen BB (8) or the Fuji BB (11) (P = 0.032). CONCLUSIONS: The three BBs provided equivalent surgical exposure to left-sided DLTs during left-sided open or video-assisted thoracoscopic surgery thoracic procedures. BBs required longer to position and required intraoperative repositioning more often. The Arndt BB needed to be repositioned more often than the other BBs.

Performance of the PAxpress vs the ProSeal laryngeal mask airway during general anesthesia.

PURPOSE: The PAxpress (PAx) is a relatively new pharyngeal airway device that is easily inserted and effective in routine airway management. A prospective, randomized study was undertaken to compare the PAx with the ProSeal laryngeal mask airway (PLMA) during anesthesia with positive pressure ventilation. METHODS: One hundred adult patients scheduled for elective surgery under general anesthesia were randomized to airway management with either the PAx (n=50) or the PLMA (n=50). All patients swallowed a methylene blue capsule before anesthesia. After insertion, leak and inspiratory pressures were measured. Fibrescopy was used to view the glottis. Devices were inspected for blood or methylene blue staining upon removal at the end of surgery. An interview was conducted postoperatively to evaluate the occurrence of sore throat, dysphagia and dysphonia. RESULTS: Insertion time was longer for the PAx than for the PLMA (52 +/- 44s vs 34 +/- 23 sec; P=0.003). Leak pressure was lower while peak inspiratory pressures, and EtCO2 values were higher (P=0.016; 0.027 and 0.04 respectively) with the PAx. Both devices provided comparable fibreoptic viewing of the glottis. There were no differences with respect to the incidence or pattern of blue stains upon removal. Blood was seen more often on the PAx (58% vs 19%) and dysphagia was also more frequent and severe with the PAx. CONCLUSION: In comparison with the PLMA, PAx insertion time is longer and the ventilatory characteristics of this new device may be marginally inferior. The PAx is also more traumatic and is associated with more postoperative discomfort compared to the PLMA.

Case report: epidural blood patch in the treatment of abducens palsy after a dural puncture.

PURPOSE: To describe a case of iatrogenically induced abducens nerve palsy following a diagnostic lumbar puncture, and to review the evidence for blood patching in the management of sixth cranial nerve palsy after dural puncture. CLINICAL FEATURES: A 45-yr-old woman developed post-dural puncture headache with bilateral abducens palsy following a diagnostic lumbar puncture. Magnetic resonance imaging showed findings compatible with intracranial hypotension. An epidural blood patch was performed five days after the onset of diplopia and ten days following the dural puncture. After blood patching, the patient reported relief of the headache, but still complained of diplopia. The palsies recovered spontaneously 21 months after the dural puncture. CONCLUSION: Experience from this case as well as other case report evidence suggest that an epidural blood patch performed more than 24 hr after the onset of a sixth cranial nerve palsy consistently fails to relieve diplopia. An epidural blood patch executed within 24 hr from the onset of diplopia could possibly lead to partial improvement and/or earlier resolution of symptoms.