The effect of hypothermia on myogenic motor-evoked potentials to electrical stimulation with a single pulse and a train of pulses under propofol/ketamine/fentanyl anesthesia in rabbits

In the present study, we investigated the effect of hypothermia on myogenic motor-evoked potentials (MEPs) in rabbits. The influence of stimulation paradigms to induce MEPs was evaluated. Twelve rabbits anesthetized with ketamine, fentanyl, and propofol were used for the study. Myogenic MEPs in response to electrical stimulation of the motor cortex with a single pulse and a train of three and five pulses were recorded from the soleus muscle. After the control recording of MEPs at 38 degrees C of esophageal temperature, the rabbits were cooled by surface cooling. Esophageal temperature was maintained at 35 degrees C, 32 degrees C, 30 degrees C, and 28 degrees C, and MEPs were recorded at each point. MEP amplitude to single- pulse stimulation was significantly reduced with a re-duction of core temperature to 28 degrees C compared with the control value at 38 degrees C (0.8 +/- 0.4 mV versus 2.3 +/- 0.3 mV; P < 0.05), whereas MEP amplitude to train-pulse stimulation did not change significantly during the cooling. MEP latency was increased linearly with a reduction of core temperature regardless of stimulation paradigms. In conclusion, these results indicate that a reduction of core temperature to 28 degrees C did not influence MEP amplitudes as long as a train of pulses, but not a single pulse, was used for stimulation in rabbits under propofol/ketamine/fentanyl anesthesia.

IMPLICATIONS

Intraoperative monitoring of myogenic motor-evoked potentials (MEPs) may be required under hypothermic conditions because of its neuroprotective efficacy. However, data on the influence of hypothermia on myogenic MEPs are limited. The results indicate that multipulse stimulation may be better than single-pulse stimulation when monitoring MEPs during hypothermia.

The effects of a specific neutrophil elastase inhibitor (ONO-5046) in pulmonary ischemia-reperfusion injury

Ischemia-reperfusion injury is a significant problem in lung transplantation. Polymorphonuclear elastase derived from neutrophils plays a major mechanistic role in this process. Hence, we have investigated the effects of ONO-5046, a neutrophil elastase inhibitor, on ischemia-reperfusion injury. Fifteen rabbits were divided into three groups: 2 h of single left-lung perfusion (control group, n=3); 2 h of ischemia followed by 2 h of reperfusion (ischemic group, n=6); and drip intravenous administration of ONO-5046 during the 2 h of ischemia and 2 h of reperfusion (ONO-5046 group, n=6). Hemodynamic parameters were determined and a histopathological examination of the lung was performed. In the ONO-5046 group, arterial oxygen pressure, cardiac output, and tissue blood perfusion were higher and pulmonary vascular resistance was lower than in the ischemic group. The ONO-5046 group also showed large decreases in neutrophil infiltration, pulmonary edema, and intra-alveolar hemorrhage. Treatment with ONO-5046 improves lung function in a rabbit-lung ischemia-reperfusion model.

Long-term assessment of hind limb motor function and neuronal injury following spinal cord ischemia in rats

Recent evidence suggests that brain injury caused by ischemia is a dynamic process characterized by ongoing neuronal loss for at least 14 days after ischemia. However, long-term outcome following spinal cord ischemia has not been extensively examined. Therefore, we investigated the changes of hind limb motor function and neuronal injury during a 14-day recovery period after spinal cord ischemia. Male Sprague-Dawley rats received spinal cord ischemia (n = 64) or sham operation (n = 21). Spinal cord ischemia was induced by inflation of a 2F Fogarty catheter placed into the thoracic aorta for 6, 8, or 10 minutes. The rats were killed 2, 7, or 14 days after reperfusion. Hind limb motor function was assessed with the 21-point Basso, Beattie, and Bresnahan (BBB) scale during the recovery period. The number of normal and necrotic neurons was counted in spinal cord sections stained with hematoxylin/eosin. Longer duration of spinal cord ischemia produced severer hind limb motor dysfunction at each time point. However, BBB scores gradually improved during the 14-day recovery period. Neurologic deterioration was not observed between 7 and 14 days after reperfusion. The number of necrotic neurons peaked 2 days after reperfusion and then decreased. A small number of necrotic neurons were still observed 7 and 14 days after reperfusion in some of the animals. These results indicate that, although hind limb motor function may gradually recover, neuronal loss can be ongoing for 14 days after spinal cord ischemia.

The influence of induced hypothermia for hemostatic function on temperature-adjusted measurements in rabbits

In hypothermic patients, a tendency to bleed may be observed even when hemostatic tests seem to be normal. Coagulation and platelet function tests are usually performed at 37 degrees C. We investigated the influence of induced hypothermia on temperature-adjusted hemostasis function testing using Sonoclot Analyzer (Sonoclot) and Thromboelastography (TEG). Anesthesia was induced and maintained with IV ketamine and fentanyl on 15 male New-Zealand White rabbits. A water blanket was used to induce hypothermia to 30 degrees C and to rewarm to 37 degrees C. Blood samples were obtained at four points: before hypothermia, at 34 degrees C, at 30 degrees C, and after rewarming. Standard coagulation tests were performed at 37 degrees C (C method), and simultaneously, real temperature hemostasis function tests (R method) were run. In Sonoclot(R), activated clotting time and time to peak increased and clot rate decreased significantly at 30 degrees C in the R method compared with those in the C method. In TEG(R), reaction time and clot formation time were prolonged and clot formation rate was diminished at 30 degrees C in the R method compared with those in the C method. Induced hypothermia delayed the coagulation cascade and reduced platelet function. During hypothermia, hemostatic measurements should be performed at real temperature to avoid overestimating patient hemostatic function based on results measured at the standard 37 degrees C.

IMPLICATIONS

We investigated the influence of induced hypothermia on temperature-adjusted hemostasis function tests in rabbits using Sonoclot Analyzer and Thromboelastography. Induced hypothermia delayed the coagulation cascade and reduced platelet function. The conventional coagulation tests performed at 37 degrees C failed to detect these hypothermia-induced degradations in hemostasis performance.

Induction of neuropilin-1 and vascular endothelial growth factor by epidermal growth factor in human gastric cancer cells

The epidermal growth factor receptor (EGF-R) pathway plays a pivotal role in the progression of human gastric cancer. The angiogenic factor vascular endothelial growth factor (VEGF) has been shown to be induced by EGF in various cancer cell lines. Neuropilin-1 (NRP-1) acts as a coreceptor for VEGF-165 and increases its affinity for VEGF receptor 2 (VEGFR-2) in endothelial cells. Furthermore, NRP-1 has been found to be expressed by tumour cells and has been shown to enhance tumour angiogenesis and growth in preclinical models. We examined the expression of NRP-1 mRNA and EGF-R protein in seven human gastric cancer cell lines. NRP-1 expression was expressed in five of seven cell lines, and EGF-R expression closely mirrored NRP-1 expression. Moreover, in EGF-R-positive NCI-N87 and ST-2 cells, EGF induced both NRP-1 and VEGF mRNA expression. C225, a monoclonal antibody to EGF-R, blocked EGF-induced NRP-1 and VEGF expression in NCI-N87 cells in a dose-dependent manner. The treatment of NCI-N87 cells with EGF resulted in increases in phosphorylation of Erk1/2, Akt, and P38. Blockade of the Erk, phosphatidylinositol-3 kinase/Akt, or P38 pathways in this cell line prevented EGF induction of NRP-1 and VEGF. These results suggest that regulation of NRP-1 expression in human gastric cancer is intimately associated with the EGF/EGF-R system. Activation of EGF-R might contribute to gastric cancer angiogenesis by a mechanism that involves upregulation of VEGF and NRP-1 expression via multiple signalling pathways.

Plasma propofol concentration and EEG burst suppression ratio during normothermic cardiopulmonary bypass

BACKGROUND

During cardiopulmonary bypass (CPB), several factors affect drug disposition and action. This topic has not been studied extensively during normothermic CPB. In this study, we related propofol dose to plasma propofol concentration and burst suppression of the EEG during normothermic bypass.

METHODS

After institutional approval and informed consent, 45 patients having cardiac surgery were assigned randomly to receive propofol infusions at 4 (Group A), 5 (Group B) and 6 (Group C) mg kg(-1) h(-1) during normothermic CPB. In all patients, small to moderate doses of fentanyl were also administered. Plasma propofol concentration and burst suppression ratio (BSR) were measured at the following times: (1) 10 min before CPB, (2) 10 min after the start of CPB, (3) 30 min after the start of the CPB, (4) just after aortic declamping, and (5) 60 min after CPB.

RESULTS

At baseline, plasma propofol concentrations were similar among the three groups. After the start of CPB, the concentrations of propofol decreased significantly by 41, 35, and 30% of control values in Groups A, B, and C, respectively. In Group A, the concentration of propofol during CPB remained unchanged at less than the concentration before bypass. In Groups B and C, plasma propofol concentrations gradually increased during CPB to the pre-bypass concentrations. In Group A, BSR values did not change significantly during CPB. In Groups B and C, BSR values gradually increased and became significantly greater than baseline values. No patient reported intraoperative awareness.

CONCLUSION

The pharmacokinetics and pharmacodynamics of propofol change during normothermic CPB. During normothermic CPB, the efficacy of propofol may be enhanced compared with before CPB.

Noxious stimuli do not modify myogenic motor evoked potentials by electrical stimulation during anesthesia with propofol-based anesthesia

PURPOSE

To investigate whether motor evoked potentials (MEP) to transcranial electrical stimulation under constant blood propofol concentration are affected by the arousing effect of surgical noxious stimuli.

METHODS

Twenty patients who underwent elective spinal surgery were studied. Patients were anesthetized with 50% nitrous oxide in oxygen, fentanyl, and propofol to maintain the bispectral index (BIS) score around 50. MEP in response to a multipulse transcranial electrical stimulation at stimulus sites of C3-C4 were recorded over the right abductor pollicis brevis muscle. Changes of peak-to-peak amplitude and onset latency of MEP, BIS score before and after surgical stimuli were evaluated. Propofol plasma concentration was measured at the same time points.

RESULTS

Both MEP amplitude and latency did not change significantly after surgical stimuli although BIS increased significantly (48 +/- 6 to 58 +/- 5; P < 0.05). Plasma propofol concentration was maintained at the same level between the two measurement points (3.3 +/- 0.7 to 3.3 +/- 0.7 micro g*mL(-1)). There was no relation between BIS change and changes of MEP amplitude and latency, and propofol plasma concentration.

CONCLUSION

MEP to the transcranial electrical stimulation under a constant and clinically appropriate blood propofol concentration are not affected by surgical noxious stimuli.

Comparison of the effects of sevoflurane and propofol on cooling and rewarming during deliberate mild hypothermia for neurosurgery

BACKGROUND

Because the time available for cooling and rewarming during deliberate mild hypothermia is limited, studies of the rate of the cooling and rewarming are useful. The decrease in core hypothermia caused by heat redistribution depends on the anaesthetic agent used. We therefore investigated possible differences between sevoflurane and propofol on the decrease and recovery of core temperature during deliberate mild hypothermia for neurosurgery.

METHODS

After institutional approval and informed consent, 26 patients were assigned randomly to maintenance of anaesthesia with propofol or sevoflurane. Patients in the propofol group (n=13) received propofol induction followed by a continuous infusion of propofol 3-5 mg kg(-1) h(-1). Patients in the sevoflurane group (n=13) received propofol induction followed by sevoflurane 1-2%. Nitrous oxide and fentanyl were also used for anaesthetic maintenance. After induction of anaesthesia, patients were cooled and tympanic membrane temperature was maintained at 34.5 degrees C. After surgery, patients were actively rewarmed.

RESULTS

There was no difference in the rate of decrease and recovery of core temperature between the groups. There was also no difference in skin surface temperature gradient (forearm to fingertip), heart rate and mean arterial blood pressure between the groups.

CONCLUSIONS

Sevoflurane-based anaesthesia did not affect cooling and rewarming for deliberate mild hypothermia compared with propofol-based anaesthesia.

Intraoperative monitoring of myogenic motor-evoked potentials from the external anal sphincter muscle to transcranial electrical stimulation

STUDY DESIGN

Motor-evoked potentials from the external anal sphincter were analyzed using transcranial electrical stimulation during spinal surgery in patients under general anesthesia.

OBJECTIVE

To investigate whether motor-evoked potentials from the external anal sphincter could be elicited by transcranial electrical stimulation under general anesthesia.

SUMMARY OF BACKGROUND DATA

Lumbosacral surgery often places nerve rootlets at risk for injury during operative dissection. Specifically, injury for sacral rootlets can result in bowel and bladder dysfunction, but the techniques for monitoring bowel and bladder function are limited.

METHODS

Thirty patients who underwent elective spinal surgery were studied. Patients were anesthetized with 50% nitrous oxide in oxygen, fentanyl, and 4 mg/kg/h of propofol (n = 19) or 1 mg/kg/h of ketamine (n = 11). The level of neuromuscular blockade, assessed by recording the M-response from the right abductor pollicis brevis muscle, was maintained at an M-response amplitude of 40-50% of control. Motor-evoked potentials in response to a multipulse transcranial electrical stimulation at stimulus sites of C3-C4 or Fz-Cz were recorded from the skin over the subcutaneous part of the external anal sphincter using a plug-type electrode probe. The success rate of motor-evoked potentials' recording and peak-to-peak amplitude and the onset latency of motor-evoked potentials were evaluated.

RESULTS

Success rates of motor-evoked potentials from the external anal sphincter were 73% and 53% after transcranial stimulation at stimulus sites of C3-C4 and Cz-Fz, respectively. Amplitudes of motor-evoked potentials after C3-C4 stimulation were significantly greater than those after Cz-Fz stimulation. Motor-evoked potential latency from the external anal sphincter was 18.6 +/- 1.5 and 19.0 +/- 2.7 msec after C3-C4 and Cz-Fz stimulation, respectively.

CONCLUSIONS

The results suggest that, using a transcranial multipulse stimulation, monitoring of motor-evoked potentials from the external anal sphincter is feasible during ketamine- and propofol-based anesthesia. However, further improvement of techniques would be required for intraoperative elicitation of motor-evoked potentials from the external anal sphincter.

Human peripheral blood polymorphonuclear leukocytes at the ovulatory period are in an activated state

The ovulatory process has been compared with inflammation. We investigated the state of female peripheral polymorphonuclear leukocytes (PMN) during menstrual cycles, and found that PMN contained high levels of superoxide, hydrogen peroxide and nitric oxide (NO) during at the peri-ovulatory period. Assuming the cause of this elevation to be a luteinizing hormone (LH), the surge of which preceded the ovulation, we examined the responsiveness of PMN to pituitary LH. The results revealed that this hormone elevated dose-dependently the production of reactive oxygen intermediates (ROI). Furthermore, we demonstrated the mRNA expression of LH receptors and their presence on PMN. The data indicated that the LH surge before on the ovulatory day resulted in general activation of PMN, suggesting that this state of PMN may be a necessary step for initiation of ovulation, rather than a defensive role against infection.

Treatment for complex atypical hyperplasia of the endometrium

OBJECTIVE

To clarify the clinical outcome of women with complex atypical hyperplasia of the endometrium who were treated either by hysterectomy or a non-surgical treatment with medroxyprogesterone acetate (MPA).

STUDY DESIGN

Thirty of the 53 patients with complex atypical hyperplasia of the endometrium were treated by undergoing hysterectomy and 20 were treated with MPA alone as the primary therapy. Their clinical features and outcomes were evaluated.

RESULTS

The ages of the 53 patients ranged from 28 to 62 years (mean 46.2). Fifteen (75%) of the 20 patients (8 of 12 with low-dose MPA and 6 of 8 with high-dose MPA) responded initially to MPA therapy. Two of the 12 patients who were treated with low-dose MPA progressed to endometrial adenocarcinoma. Three patients treated with high-dose MPA conceived after treatment having three healthy infants.

CONCLUSION

Primary treatment with high-dose MPA is a safe and effective therapy for women with complex atypical hyperplasia of the endometrium who wish to preserve their fertility.

Toxicological study of a new maintenance fluid, Veen 3G, in rats

A study of the different volume and infusion rates of a new maintenance fluid, Veen 3G, on the general conditions of rats was investigated during the 14 days after infusion. In Experiment I, 100 ml/kg and 200 ml/kg of Veen 3G were infused at a rate of 300 ml/kg/h in male and female rats. Results were compared with those for Gurunon Ringer solution (GRS) in male and female rats. We observed only transient polyuria in animals administered by each dose of Veen 3G and GRS for 0-15 min after infusion. Necropsy was not observed in any of the animals tested 14 days after infusion. In Experiment II, 200 ml/kg of Veen 3G was infused at rates of 200, 400, 800 and 1600 ml/kg/h in male rats. At 800 and 1600 ml/kg/h, irregular respiration and decrease in movement were observed concomitantly with polyuria. Three out of 4 rats died immediately after the infusion of Veen 3G at a rate of 1600 ml/kg/h, and one rat was still alive 14 days after the infusion. In this experiment, 200 ml/kg Veen 3G was safe when we infused at a rate of less than 400 ml/kg/h in male rats. Since this rate is about 27-80 times higher than that used clinically in maintenance treatment, Veen 3G is suggested to be safe, with the exception of polyuria, in clinical situations at the standard infusion rate (5-15 ml/kg/h).

Effect of mild hypothermia on inodilator-induced vasodilation of pial arterioles in cats

BACKGROUND

Mild hypothermia has been proposed as a means of providing cerebral protection after traumatic brain injury. However, hypothermia has been shown to alter not only physiologic but also pharmacologic responses. The purpose of this study was to investigate whether mild hypothermia (3-4 degrees C temperature reduction) could alter cerebral vasodilation induced by inodilators, which are characterized by having an inotropic effect in addition to a vasodilatory effect. Isoproterenol (a beta-adrenergic receptor agonist), colforsin dapropate (an adenylate cyclase stimulant), and amrinone (a phosphodiesterase inhibitor) were chosen as inodilators.

METHODS

The cranial window technique, combined with microscopic video recording, was used. Forty-eight cats were randomly assigned to either a normothermic or a hypothermic group (33 degrees C). Isoproterenol, colforsin dapropate, or amrinone was topically applied in the cranial window and the diameter of pial arterioles was measured.

RESULTS

Topical administration of isoproterenol, colforsin dapropate, and amrinone produced a significant dilation in a dose-dependent manner during normothermia. The vasodilation induced by these inodilators was not affected by mild hypothermia.

CONCLUSION

The vasodilation induced by topical administration of isoproterenol, colforsin dapropate, and amrinone was not affected by mild hypothermia.

Mild hypothermia can enhance pial arteriolar vasodilation induced by isoflurane and sevoflurane in cats

OBJECTIVE

Volatile anesthetics have been shown to dilate cerebral vessels. Recent evidence suggests that mild hypothermia can alter vascular reactivity of the cerebral vessels. However, the effect of mild hypothermia on volatile anesthetic-induced vasodilation of cerebral vessels is unknown. In the present study, we investigated the effect of mild hypothermia on pial arteriolar vasodilation induced by isoflurane and sevoflurane in cats.

DESIGN

Prospective, randomized, experimental study with repeated measures.

SETTING

Investigational animal laboratory.

SUBJECTS

Forty cats were used for the study of systemic administration of volatile anesthetics, and 22 cats were used for the study of topical administration of volatile anesthetics.

INTERVENTIONS

This study was approved by the Animal Experiment Committee of Nara Medical University. Animals were anesthetized with pentobarbital to maintain suppressive electroencephalographic patterns, which were introduced to measure direct effects of anesthetic agents after removing metabolic effects. The cranial window technique, combined with microscopic video recording, was used for the measurement of small (50-100 microm) and large (100-200 microm) pial arteriolar diameter in an experiment. Animals were randomly assigned to either a normothermic (37 degrees C) or a hypothermic group (33 degrees C). Desired temperatures were maintained by using a water blanket. In the first phase of the study, the effect of hypothermia on pial arteriolar vasodilation induced by systemic administration of isoflurane or sevoflurane was assessed. Each cat received isoflurane or sevoflurane at 0.5, 1.0, 1.5, and 2.0 minimum alveolar anesthetic concentrations, and the diameter of pial arterioles was measured. In the second group of animals, the direct effect of isoflurane and sevoflurane on pial vessels was evaluated. The artificial cerebrospinal fluid bubbled with isoflurane or sevoflurane (minimum alveolar anesthetic concentrations of 1 or 3) was topically administered in the cranial window.

MEASUREMENTS AND MAIN RESULTS

Systemic and topical administration of isoflurane and sevoflurane produced significant dilation of both small and large pial arterioles in a dose-dependent manner during normothermia. In the hypothermic group, vasodilation of small pial arterioles by systemic administration of isoflurane and sevoflurane at a high concentration was significantly larger than in the normothermic group (p <.05). Vasodilation of both small and large pial arterioles by topical administration of isoflurane and sevoflurane was significantly greater in the hypothermic group than in the normothermic group (p <.05).

CONCLUSIONS

These results suggest that pial arteriolar vasodilation induced by isoflurane and sevoflurane can be enhanced by mild hypothermia in cats anesthetized with pentobarbital.

High-dose amrinone is required to accelerate rewarming from deliberate mild intraoperative hypothermia for neurosurgical procedures

BACKGROUND

Since the time available to provide the cooling and rewarming is limited during deliberate mild hypothermia, the technique to accelerate the cooling and rewarming rate of core temperature has been studied. Amrinone has been reported to accelerate the cooling rate but not the rewarming rate of core temperature during deliberate mild hypothermia. The failure of amrinone effect on the rewarming rate might be due to an insufficient dose of amrinone during hypothermic conditions. The authors therefore tested whether higher doses of amrinone can accelerate the rewarming rate of core temperature during deliberate mild hypothermia for neurosurgery.

METHODS

After institutional approval and informed consent, 30 patients were randomly assigned to one of three groups. Patients in the control group (n = 10) did not receive amrinone; patients in the AMR 15 group (n = 10) received 15 microg x kg(-1) x min(-1) amrinone with a 1.0-mg/kg loading dose of amrinone at the beginning of cooling; and patients in the ReAMR group (n = 10) received 5 microg x kg(-1) x min(-1) amrinone with 1.0-mg/kg loading and reloading doses of amrinone at the beginning of cooling and rewarming, respectively. Administration of amrinone was started just after the induction of cooling and continued until the end of anesthesia. Anesthesia was maintained with nitrous oxide in oxygen, propofol, and fentanyl. After induction of anesthesia, patients were cooled, and tympanic membrane temperature was maintained at 34.5 degrees C. After completion of the main surgical procedures, patients were actively rewarmed and extubated in the operating room.

RESULTS

The cooling and rewarming rates of core temperature were both significantly faster in both amrinone groups than in the control group. During the cooling and rewarming periods, forearm minus fingertip temperature gradient was significantly smaller in both amrinone groups than in the control group. During the rewarming period, heart rate and mean arterial pressure in the AMR 15 group were significantly faster and lower, respectively, than in the control group. Systemic vascular resistance in the AMR 15 group was smaller than in the control group throughout the study; on the other hand, only the value after the start of rewarming in the ReAMR group was smaller than in the control group.

CONCLUSIONS

Amrinone at an infusion rate of 15 or 5 microg x kg(-1) x min(-1) with a reloading at the beginning of rewarming accelerated the rewarming rate of core temperature during deliberate mild hypothermia. This suggests that high-dose amrinone is required to accelerate rewarming from deliberate mild intraoperative hypothermia for neurosurgical procedures.

Amplitudes and intrapatient variability of myogenic motor evoked potentials to transcranial electrical stimulation during ketamine/N2O- and propofol/N2O-based anesthesia

The aim of the current study was to investigate whether there are differences in amplitudes and intrapatient variability of motor evoked potentials to five pulses of transcranial electrical stimulation between ketamine/N2O- and propofol/N2O-based anesthesia. Patients in the propofol group (n = 13) and the ketamine group (n = 13) were anesthetized with 50% N2O in oxygen, fentanyl, and 4 mg/kg/hr of propofol or 1 mg/kg/hr of ketamine, respectively. The level of neuromuscular blockade was maintained at an M-response amplitude of approximately 50% of control. Motor evoked potentials in response to multipulse transcranial electrical stimulation were recorded from the right adductor pollicis brevis muscle, and peak-to-peak amplitude and onset latency of motor evoked potentials were evaluated. To estimate intrapatient variability, the coefficient of variation (standard deviation/mean x 100%) of 24 consecutive responses was determined. Motor evoked potential amplitudes in the ketamine group were significantly larger than in the propofol group (mean, 10th-90th percentile: 380 microV, 129-953 microV; 135 microV, 38-658 microV, respectively; P <.05). There were no significant differences in motor evoked potential latency (mean +/- standard deviation: 20.9 +/- 2.2 msec and 21.4 +/- 2.2 msec, respectively) and coefficient of variation of amplitudes (median [range]: 32% [22-42%] and 26% [18-41%], respectively) and latencies (mean +/- standard deviation: 2.1 +/- 0.7% and 2.1 +/- 0.7%, respectively) between the ketamine and propofol groups. In conclusion, intrapatient variability of motor evoked potentials to multipulse transcranial stimulation is similar between ketamine/N2O- and propofol/N2O-based anesthesia, although motor evoked potential amplitudes are lower during propofol/N2O-based anesthesia than ketamine/N2O-based anesthesia.

Attenuation of glucan-binding protein C reduces the cariogenicity of Streptococcus mutans: analysis of strains isolated from human blood

A blood isolate of Streptococcus mutans strain TW871 shows relatively low homology with MT8148, a reference oral isolate strain, and lacks the serotype-specific polysaccharide antigen, suggesting that other cell-surface structures correlate with cariogenicity. We compared cariogenicity of TW871 with MT8148 (serotype c) and blood isolate TW964 (serotype f) in rats. Strain TW871 showed significantly lower cariogenicity than MT8148 or TW964 and expressed significantly lower sucrose-independent cellular adhesion to saliva-coated hydroxyapatite and dextran-binding activity than strain MT8148. Strains TW871 and TW964 showed a defect in the gbpA gene by Southern hybridization analysis, while sequencing analysis revealed gbpC variation in TW871. These results suggest that variation in GbpC may alter cellular adherence properties and can be correlated with the cariogenicity of S. mutans in this strain.

Effect of nitrous oxide on myogenic motor evoked potentials during hypothermia in rabbits anaesthetized with ketamine/fentanyl/propofol

BACKGROUND

A number of authors have reported that anaesthetics suppress myogenic motor evoked potentials (MEPs). However, the influence of hypothermia on these effects is unknown. Therefore we investigated the effects of hypothermia on nitrous oxide-induced suppression of myogenic MEPs.

METHODS

Twenty-two rabbits anaesthetized with ketamine, fentanyl and propofol were randomly allocated to one of three groups, with oesophageal temperatures of 40 degrees C (n = 8), 35 degrees C (n = 7) and 30 degrees C (n = 7). Myogenic MEPs in response to electrical stimulation of the motor cortex with a train of five pulses were recorded from the soleus muscle. Following the control recording, nitrous oxide was administered at concentrations of 30%, 50%, and 70% in random order, and MEPs were recorded. Control MEP amplitudes and percentage of control MEP amplitudes (%MEP amplitude) during the administration of nitrous oxide were compared between the three groups.

RESULTS

Control MEP amplitudes were similar between the three groups. Nitrous oxide suppressed MEPs in a dose-dependent manner in all groups. During the administration of nitrous oxide, % MEP amplitudes at 35 degrees C and 30 degrees C (hypothermia) were significantly lower than those at 40 degrees C (normothermia).

CONCLUSION

These results suggest that nitrous oxide-induced suppression of MEPs may be augmented during hypothermia.

Butyl benzyl phthalate, an endocrine disrupter, inhibits pulsatile luteinizing hormone secretion under an insulin-induced hypoglycaemic state in ovariectomized rats

Butyl benzyl phthalate (BBP) and bisphenol A (BPA), termed endocrine disrupters, are known to mimic oestrogen in their actions, and therefore there is concern about their effect on reproductive functions. Since it is reported that the inhibitory action of oestrogen on the pulsatile secretion of luteinizing hormone (LH) is enhanced under insulin-induced hypoglycaemia, whether this also applies to BBP and BPA was examined in the present study. In adult ovariectomized (OVX) rats, the pulsatile LH secretion 24 h after subcutaneous injection of 10 mg BBP (BBP-treated), 10 mg BPA (BPA-treated) or 100 ng 17beta-oestradiol (E2-treated), all of which were dissolved in sesame oil, was not changed significantly compared to that after the injection of sesame oil only. Furthermore, in oil-treated OVX rats, the pulsatile LH secretion immediately after intravenous injection of insulin (1.0 U) was not changed compared to that after saline injection. In BBP-treated OVX rats, the injection of insulin (1.0 U) significantly decreased the number of LH pulses as in E2-treated OVX rats. The injection of insulin did not significantly affect the amplitude of LH pulses in BBP-, BPA- and E2-treated OVX rats. The results indicate that the oestrogenic action of BBP is significantly enhanced by insulin-induced hypoglycaemia and thus the pulsatile LH secretion is inhibited. We suggest that weak oestrogenic endocrine disrupters may become harmful to reproductive functions even in adult female rats, if acting under a low energy state.

Influence of chronic inflammation in peripheral target tissue on recovery of crushed nerve injury

An experimental study was performed to investigate the influence of chronic inflammation in peripheral target tissue on recovery of the sciatic nerve after crush injury. Thirty-four male Wistar rats, weighing 300-370 g were used. The sciatic nerve was crushed unilaterally with an aneurysm clip (250 gf; holding force; 5 min). One week before the operation, chronic inflammation, localized in the tibiotarsal joint of one hind limb, was produced by the intraarticular injection of complete Freund's adjuvant. The animals were divided into five groups, as follows: CIA (crush injury with ipsilateral arthritis), CCA (crush injury with contralateral arthritis), C (crush injury without arthritis), A (sham operation and ipsilateral arthritis), and S (sham operation without arthritis). Specimens for histological examination were taken from the nerve at a site 5 mm distal to the crush injury 4 weeks postoperatively. Histological study showed that the diameters of the axons in group CIA were significantly smaller than those in group CCA and those in group C. No significant differences were observed between group CCA and group C. In conclusion, peripheral nerve recovery after crush injury was suppressed by chronic inflammation in peripheral target tissue.