Comparison of thoracoscopic and open thoracic discectomy in a live ovine model for anterior spinal fusion

STUDY DESIGN: The authors undertook a randomized comparison of 30 thoracoscopic and 30 open thoracic discectomies for anterior spinal fusion in a live sheep model. OBJECTIVES: To compare in a live sheep model discectomies performed using a thoracoscopic technique with those using an open thoracotomy technique to validate the efficacy of thoracoscopic disc and end plate removal for potential fusion. SUMMARY OF BACKGROUND DATA: In 1993, Mack and Regan described a technique for video-assisted thoracic surgery that resulted in less morbidity than open techniques. Subsequent reports support the finding that thoracoscopic spinal surgery results in less morbidity. METHODS: Sixty discectomies were performed in 10 live sheep. In each sheep, three randomly selected discectomies were performed thoracoscopically, and, subsequently, three open discectomies were performed. The animal then was killed, and the spine was sectioned and analyzed by computer imaging. RESULTS: Statistical analysis found no significant difference in the amount of disc resected (t' = 1.9639, t0.025, 60 = 2.000, alpha = 0.05). The mean percentage of disc resected was 67.8% (range, 0-92.2%) in the thoracoscopic group and 76.1% (range, 44.9-95.4%) in the open group. More than 50% of the disc was excised in 27 of 30 spines (90%) in the thoracoscopic group and in 29 of 30 (96.7%) in the open group. This difference was not statistically significant (theta 2(0.05, 1) = 3.84, theta 2' = 1.07). CONCLUSION: The findings in this study indicate that the thoracoscopic discectomy technique is equivalent to the open technique in the amount of disc and end plate resected. In addition, these findings suggest that thoracoscopic discectomies provide adequate disc resection to provide for an acceptable fusion rate according to the criteria demonstrated by Bunnell in 1982 and therefore support the efficacy of a thoracoscopic technique for anterior spinal fusion.     

A biomechanical comparison of open and thoracoscopic anterior spinal release in a goat model

STUDY DESIGN: A biomechanical assessment of anterior release and discectomy in the thoracic spine was performed on an animal model using thoracoscopic and open thoracotomy techniques. OBJECTIVES: To compare the relative efficacy of these two techniques of release in achieving increased spinal mobility. BACKGROUND DATA: The clinical use of video-assisted thoracoscopy in the correction of spinal deformity is increasing. The effectiveness of thoracoscopic anterior spinal release with discectomy has not been evaluated biomechanically. METHODS: Anterior release with discectomy was performed on six midthoracic motion segments in five mature goats. The thoracoscopic technique was used for three levels on one side, and an open thoracotomy was used for the alternating three levels of the contralateral side. The duration of surgery for disc excision and the amount of blood loss for each technique were recorded. The intact cranial and caudal motion segments served as controls. The motion segments were individually subjected to nondestructive biomechanical testing. Torsional, sagittal, and coronal bending torques were applied, and the resulting angular displacement was measured. RESULTS: The duration of surgery to remove a disc thoracoscopically decreased as experience was gained by the surgeon. The amount of intraoperative blood loss was comparable using the two methods. There was significantly increased flexibility in the released segments with both techniques, compared with the flexibility in the intact levels for all three loading directions. There was no difference in the motion obtained after release between the two techniques. CONCLUSION: Open and thoracoscopic anterior release and discectomy have been demonstrated, through biomechanical in vitro testing, to increase the flexibility of the spine to a similar extent.     

Video-assisted thoracoscopic surgery versus thoracotomy for recurrent spontaneous pneumothorax. A comparison of results and costs

OBJECTIVE: Video-assisted thoracoscopic surgery (VATS) represents at present the most suitable treatment of recurrent spontaneous pneumothorax. After three years we consider this interesting to draw up a trial balance of our VATS experience in comparison with the cases treated before 1991 with the classic thoracotomic approach. METHODS: We have considered retrospectively the results obtained in a series of 30 consecutive patients with recurrent spontaneous pneumothorax treated with VATS between November 1991 and August 1994 in comparison with those obtained in a group of 30 patients previously treated with a traditional thoracotomy. The groups have been selected in such a way that surgical indications, sex ratio, age and number of episodes were homogeneous. The parameters we have compared were the postoperative complications, the duration of chest drainage and hospitalization, the operating times and the relapses. Besides these technical parameters we considered the economic data too. RESULTS: On average drains removal occurred one day before in VATS-Group: the time spent in the Hospital was significantly shorter in VATS-Group, being on average 1 week. Short term complications may be considered similar in the two Groups. Prolonged air leaks occurred in 13% and 16% respectively. Emothorax requesting reoperation occurred in 1 case for each Group. One death occurred in thoracotomy-Group in an old patient presenting a severe chronic respiratory insufficience with exacerbation in postoperative time. We have registered 2 relapses after VATS and none after thoracotomy. CONCLUSIONS: The study has demonstrated the therapeutic efficacy of VATS and in the same time that in VATS the total economic cost is lower (22.7%) in comparison with traditional thoracotomy.     

Maturation of the posterolateral spinal fusion and its effect on load-sharing of spinal instrumentation. An in vivo sheep model

We investigated the temporal relationship among the biomechanical, radiographic, and histological properties of a posterolateral spinal fusion mass to elucidate the changes in load-sharing of the spinal instrumentation and that of the fusion mass throughout the healing process. Destabilization of the posterior spinal column and transpedicular screw fixation at the segments between the third and fourth and the fifth and sixth lumbar vertebrae was performed in twenty-four sheep. A posterolateral spinal arthrodesis with use of autologous corticocancellous bone graft was done randomly at one of the two segments; the other segment (without bone graft) served as the instrumented control. Six animals each were killed at four, eight, twelve, and sixteen weeks postoperatively. Biomechanical testing showed that the posterolateral fusion mass had increased mechanical stiffness after the fourth week. The strain on the hardware, measured with use of rods instrumented with strain-gauges, decreased significantly (p < 0.01) beginning at eight weeks. Radiographically, three independent observations of each of the six animals at each time-period showed that, although all of the fusion masses were considered solid unions at sixteen weeks, bridging of trabecular bone was noted during only ten of eighteen observations at twelve weeks, three of eighteen observations at eight weeks, and none of eighteen observations at four weeks. Computerized tomography and histomorphometric analyses demonstrated that mineralization in the fusion mass increased in a linear fashion even after eight weeks. Histologically, the fusion mass consisted predominantly of woven bone at eight weeks; thereafter, it was gradually trabeculated. CLINICAL RELEVANCE: We found a great discrepancy between biomechanical stability and histological maturation of the posterolateral fusion mass. The biomechanical properties of a stable spinal fusion preceded the radiographic appearance of a solid fusion by at least eight weeks, suggesting that immature woven bone provided substantial stiffness to the fusion mass. The spinal instrumentation was subjected predominantly to bending stress rather than to axial stress, and the load-sharing of the spinal instrumentation decreased concurrently with the development of the spinal fusion.     

A biomechanical evaluation of graft loading characteristics for anterior cervical discectomy and fusion. A comparison of traditional and reverse grafting techniques

STUDY DESIGN: A biomechanical study of graft loading characteristics for anterior cervical discectomy and fusion comparing the amount and location of transmitted forces. OBJECTIVES: To evaluate the difference between traditional iliac grafting and reverse iliac grafting used for anterior cervical discectomy and fusion in the amount and location of forces applied to the grafts. SUMMARY OF BACKGROUND DATA: Traditional fusion after anterior cervical discectomy involves placing a tricortical iliac crest strut into the disc space with the cortical portion facing anteriorly and the cancellous portion posteriorly. Recently, reverse iliac grafting has been introduced in which the cortical portion is placed in the posterior disc space and the cancellous portion in the anterior disc space. There is no biomechanical or clinical study showing an advantage of using one technique over the other. This study is the first to produce data supporting one technique as biomechanically superior. METHODS: Five fresh cadaveric cervical spines were tested using pressure-sensitive film placed between the bone graft and the vertebral endplate after an anterior discectomy was performed. A 10-pound load was applied to the cervical spine at predetermined sagittal positions. Recordings were made at neutral, 10 degrees of flexion, and 10 degrees and 20 degrees of extension after traditional and reverse iliac grafting. RESULTS: Graft forces were identical in both traditional and reverse grafting in the location and amount of force applied. Total force increased to the maximum in flexion and gradually decreased in more extended positions. The location of the forces was completely anterior with flexion, moving to the posterior portion of the graft with positions of extension. With 10 degrees of flexion, the load applied to the grafts was 20.4 N. In the neutral position, the load was 12 N. The loads decreased further with extension with forces of 11 N in 10 degrees extension, and 4 N in 20 degrees of extension. CONCLUSIONS: The optimal position of the tricortical iliac graft for an anterior cervical fusion is with the stronger cortical portion placed in the anterior disc space and the weaker cancellous portion placed in the posterior disc space. In this traditional position, the graft will best resist the loads applied to the cervical spine, preventing graft collapse.     

A case report on surgery for chylothorax after anterior spinal fusion: usefulness and effectiveness of intraoperative milk administration and postoperative OK-432 administration]

After having reported preliminary results of soft system stabilization according to Graf in a series of 27 patients with degenerative disc disease of the lumbar spine in early 1995 the authors report long term clinical and radiological results of this patient series (n = 25). At a mean period of postoperative observation of 50 months excellent, good, satisfactory, moderate and poor results were obtained in 62, 9%, 11, 1% and 11, 1%, 7, 4% and 7, 4% of the patients, respectively. The well-known phenomenon of loss of disc height at the level of posterolateral fusion and instrumentation as well as overcharge of adjacent segments were not observed after soft system stabilization. Regional as well as global lumbar lordosis were maintained and, although statistically not significant, an increase of intervertebral distance was observed in adjacent segments in flexion of the lumbar spine. These phenomena might represent pressurization of instrumented as well as adjacent discs after the insertion of ligament prostheses. It is the impression of the authors, that the Graf technique leads to good surgical results in degenerative disc disease with destabilization of lumbar motion segment(s) if the following criteria are strictly respected: 1. No or only mild arthrotic changes of the facet joints 2. Preferably minor disc degeneration/only mild loss of intervertebral distance. 3. Well trained low back muscles and 4. A clear-cut, repeatedly demonstrated pain-relief on trial anaesthesia of the corresponding articular nerves and while wearing a probatory jacket.     

Wound metastases following laparoscopic and open surgery for abdominal cancer in a rat model

The recent application of laparoscopic resection techniques to malignant disease has raised safety concerns due to metastasis to surgical access wounds. The significance and incidence of this problem are controversial. In the present study a rat model, in which an implanted tumour was lacerated, was used to investigate whether application of laparoscopic techniques for malignant abdominal disease leads to an increased risk of tumour dissemination and implantation within the peritoneal cavity, and abdominal wall wounds. Malignant cells were implanted into the abdominal wall of 42 rats, resulting 7 days later in the growth of a tumour measuring 20-25 mm in diameter. There were three control groups: no surgery (n = 6); blunt manipulation of the tumour laparoscopically (n = 6); and blunt manipulation of the tumour at laparotomy (n = 6). Twenty-four rats underwent surgical laceration of the tumour capsule at either laparoscopy (n = 12) or laparotomy (n = 12). All rats were killed 1 week later, and examined for macroscopic evidence of tumour metastasis. The abdominal surgical wounds were excised for independent microscopic examination by a histopathologist. Growth of the primary tumour was greater in rats that had an operation than in unoperated controls, and was greater after laparotomy. However, wound metastases were five times more likely after laparoscopic tumour laceration than after the same procedure through an open incision (ten of 12 rats versus two of 12, P = 0.0033). Wound metastases following laparoscopic tumour manipulation are an important and real problem, with significant implications for the application of laparoscopic techniques to excise malignant disease in humans.     

Posterior stabilization of degenerative lumbar spondylolisthesis with a Leeds-Keio artificial ligament. A biomechanical analysis in a porcine vertebral model

BACKGROUND: Endoscopic ultrasonography (EUS) appears to be the best imaging method for the diagnosis of choledocholithiasis. The aim of this preliminary, prospective, controlled study was to assess the accuracy of EUS and magnetic resonance cholangiopancreatography (MRCP) in the diagnosis of common bile duct stones. METHODS: From December 1995 through April 1997, all patients referred because of suspicion of the presence of common bile duct stones were included in the study. EUS and MRCP were performed. Each examination was performed by a different operator unaware of the result of the other procedure. The definitive diagnosis was established by means of endoscopic retrograde cholangiography with sphincterotomy or a surgical procedure. RESULTS: Forty-three patients (18 men, 25 women) with a mean age of 60.9 +/- 14.5 years (range 25 to 81 years) were included in the study. Eleven patients were excluded because of unavailability of magnetic resonance imaging(n = 5) or EUS (n = 6). Ten patients (31.2%) had choledocholithiasis. For this diagnosis, the sensitivity of EUS was 100%, the specificity was 95.4%, the positive predictive value was 90.9%, and the negative predictive value was 100%. The corresponding values for MRCP were 100%, 72.7%, 62.5%, and 100%, not significantly different from EUS results. The accuracy of EUS was 96.9%, and that of MRCP was 82.2%. CONCLUSION: This preliminary study confirmed EUS as an accurate and noninvasive procedure for the diagnosis of common bile duct stones. MRCP, which had a high sensitivity and high negative predictive value, might be an accurate technique for patients with a contraindication to EUS.     

Video-assisted lateral intertransverse process arthrodesis. Validation of a new minimally invasive lumbar spinal fusion technique in the rabbit and nonhuman primate (rhesus) models

STUDY DESIGN: Cadaveric anatomic and in vivo survival animal studies were performed to develop a new arthrodesis technique for the lumbar spine. OBJECTIVES: To examine the feasibility, efficacy, and safety of a minimally invasive lumbar intertransverse process arthrodesis technique using an osteoinductive growth factor (rhBMP-2) delivered in a collagen sponge carrier. The technique was first developed using a rabbit model and modified for the nonhuman primate (rhesus monkey), a larger animal with the most similar bone biology to humans. SUMMARY OF BACKGROUND DATA: The morbidity of conventional posterolateral lumbar intertransverse process arthrodesis includes graft donor site morbidity; paraspinal muscle devascularization, denervation, and scarring and nonunion in up to 36% of patients. Minimally invasive anterior lumbar interbody arthrodesis techniques have been developed, but these often require a metal implant and carry risks to major vessels and development of retrograde ejaculation. A minimally invasive technique for posterolateral intertransverse process arthrodesis has not been described previously. METHODS: In Part 1, we examined seven New Zealand white rabbits and five rhesus monkeys at necropsy and during nonsurvival surgeries to determine the best access routes and to develop special instruments for video-assisted lateral intertransverse process arthrodesis. In Part 2, 38 New Zealand white rabbits underwent L4-L5 intertransverse process arthrodesis: the "OPEN" group (n = 16) underwent a standard open muscle-splitting approach using rhBMP-2 (bone morphogenetic protein) and collagen as a bone graft substitute; the "video-assisted control" group (n = 6) underwent video-assisted lateral intertransverse process arthrodesis with the collagen implant only (no growth factor); and the "video-assisted-BMP" group (n = 16) underwent video-assisted lateral intertransverse process arthrodesis with rhBMP-2 and collagen as the graft material. In Part 3, rhesus monkeys (n = 4) underwent video-assisted lateral intertransverse process arthrodesis using rhBMP-2 and collagen after laminectomy of L4-L5. RESULTS: In Part 1, we identified expedient, minimally invasive routes to the intertransverse process interval appropriate for each species: an intermuscular approach for the rabbit and a lateral, extramuscular approach for the rhesus monkey. In Part 2, all rabbits in the OPEN and video-assisted-BMP groups achieved solid intertransverse process lumbar fusions when assessed at 10 weeks. There were no neurologic impairments nor any difference between the two groups in the frequency of postoperative infection or other complications. None of the animals in the video-assisted control group showed evidence of fusion. In Part 3, exposure, decortication and grafting with rh-BMP-2 and collagen was accomplished successfully in all four monkeys through the video-assisted minimally invasive approach without complications. CONCLUSION: Video-assisted lateral intertransverse process arthrodesis is a feasible, effective, and safe method of lumbar spinal fusion in the rabbit and rhesus monkey. Use of this arthrodesis procedure will minimize the morbidity of paraspinal muscle denervation and devascularization seen with open intertransverse process fusion techniques, and the use of an osteoinductive growth factor will eliminate the problem of graft donor site morbidity and possibly increase the chances for successful fusion.     

Inability to establish ectopic endometrium in a natural killer cell-deficient murine model. Immunologic, histologic and histochemical assessment

OBJECTIVE: To investigate what effect natural killer (NK) cells have on the implantation of heterologous endometrial scrapings. STUDY DESIGN: Anti-asialo GM1 (AA-GM1) anti-sera have been shown to eliminate NK cell activity in various strains of rats and mice. Either AA-GM1 antibodies (+) or rabbit antiglobulin (-) was administered to beige mice (NK cell deficient) or beige control mice (not NK cell deficient of the same strain). The heterologous endometrial scrapings were prepared by scraping seven pairs of uterine horns from normal mice of the same strain. Beige and normal mice were then injected intraperitoneally every 3 days with the heterologous endometrial scraping and antibodies for a period of 50 days. The four experimental groups (n = 10 per group) can be summarized as being beige (+), beige (-), normal (+) and normal (-). RESULTS: There was no evidence of ectopic endometrial tissue in any of the four test groups by histologic examination or by using immunohistochemical staining techniques. Histologic evidence of an impaired immune response was clearly demonstrated in the beige mice receiving AA-GM1 antibodies. CONCLUSION: Using this model, a deficiency of NK cell activity did not appear to enhance the implantation of endometrial tissue on the abdominal peritoneum of mice.     

Glucocorticoid receptors and actions in the spinal cord of the Wobbler mouse, a model for neurodegenerative diseases

We have studied glucocorticoid receptors (GR) and actions in the spinal cord of the Wobbler mouse, a model for amyotrophic lateral sclerosis and infantile spinal muscular atrophy. Basal and stress levels of circulating corticosterone (CORT) were increased in Wobbler mice. Single point binding assays showed that cytosolic type II GR in the spinal cord of Wobbler mice of both sexes were slightly reduced compared with normal littermates. Saturation analysis further demonstrated a non-significant reduction in Bmax with increased Kd. In the hippocampus, however, we found down-regulation of GR, a probable response to increased CORT levels. We also found that the basal activity of ornithine decarboxylase (ODC), a rate-limiting enzyme of polyamine biosynthesis, was higher in Wobbler mice than in control animals. Both groups showed a two-fold stimulation of ODC activity after treatment with dexamethasone (DEX). Additionally, Wobbler mice presented with an intense proliferation of astrocytes immunoreactive (ir) for glial fibrillary acidic protein (GFAP) in grey and white matter of the spinal cord. The enhanced GFAP-ir was attenuated after four days of treatment with a corticosterone (CORT) pellet implant, producing a pharmacological increase in peripheral circulating CORT. Taking into consideration the content of GR and the changes in ODC activity and GFAP-ir brought about by glucocorticoids, we suggest that Wobbler mice are hormone responsive. Further elucidation of glucocorticoid effects in this model may be relevant for understanding the possible use of hormones in human neurodegenerative diseases.     

HIV testing for HIV prevention: a comparative analysis of policies in Britain, Hungary and Sweden

Growth of vegetative cells and outgrowth of spores of enterotoxigenic psychrotrophic Bacillus cereus in refrigerated minimally processed food products is a public health concern. A study was undertaken to determine the combined effects of pH, nisin, and temperature on growth and survival of 20 strains of B. cereus. The minimum growth temperatures in tryptic soy broth (pH 7.3) and brain heart infusion broth (BHI broth, pH 7.4) were 5 degrees C for two strains and 8 degrees C for five other strains. Vegetative cells of four of eight strains grew at 8 degrees C in BHI broth (pH 6.01 and 6.57) containing 10 micrograms of nisin per ml. At 15 degrees C, all strains grew at pH 5.53 to 6.57; three strains tolerated nisin at 50 micrograms/ml (pH 6.57), whereas two other strains had a maximum tolerance of 10 micrograms of nisin per ml. Tolerance of vegetative cells of B. cereus to nisin increased as the pH of the broth was increased from 5.53 to 6.01 and again to pH 6.57. Outgrowth of spores (six of six strains tested) was inhibited by 5 and 50 micrograms of nisin per ml at 8 and 15 degrees C, respectively. At 15 degrees C, outgrowth of spores of two strains occurred at pH 6.52 in BHI broth containing 10 micrograms of nisin per ml. The effectiveness of nisin in controlling the growth of psychrotrophic strains of B. cereus capable of causing human illness was more pronounced at 8 degrees C than at 15 degrees C and as the pH was decreased from 6.57 to 5.53. Studies to determine the effectiveness of nisin in controlling growth of psychrotrophic B. cereus in nonpasteurized foods held at refrigeration temperatures are warranted.     

Adrenaline markedly improves thoracic epidural analgesia produced by a low-dose infusion of bupivacaine, fentanyl and adrenaline after major surgery. A randomised, double-blind, cross-over study with and without adrenaline

BACKGROUND: Basic pharmacological research indicates that there are synergistic antinociceptive effects at the spinal cord level between adrenaline, fentanyl and bupivacaine. Our clinical experience with such a mixture in a thoracic epidural infusion after major surgery confirms this. The objectives of the present study were to evaluate the effects on postoperative pain intensity, pain relief and side effects when removing adrenaline from this triple epidural mixture. METHODS: A prospective, randomised, double-blind, cross-over study was carried out in 24 patients after major thoracic or abdominal surgery. Patients with only mild pain when coughing during a titrated thoracic epidural infusion of about 10 ml.h-1 of bupivacaine 1 mg.ml-1, fentanyl 2 micrograms.ml-1, and adrenaline 2 micrograms.ml-1 were included. On the 1st and 2nd postoperative days each patient was given a double-blind epidural infusion, at the same rate, with or without adrenaline. The effect was observed for 4 h or until pain when coughing became unacceptable in spite of a rescue analgesic procedure. Rescue analgesia consisted of up to two epidural bolus injections per hour and i.v. morphine if necessary. All patients received rectal paracetamol 1 g, every 8 h. Fentanyl serum concentrations were measured with a radioimmunoassay technique at the start and end of each study period. Main outcome measures were extent of sensory blockade and pain intensity at rest and when coughing, evaluated by a visual analogue scale, a verbal categorical rating scale, the Prince Henry Hospital pain score, and an overall quality of pain relief score. RESULTS: The number of hypaesthetic dermatomal segments decreased (P < 0.001) and pain intensity at rest and when coughing increased (P < 0.001) when adrenaline was omitted from the triple epidural mixture. This change started within the first hour after removing adrenaline. After 3 h pain intensity when coughing had increased to unacceptable levels in spite of rescue analgesia (epidural bolus injections and i.v. morphine). Within 15-20 min after restarting the triple epidural mixture with adrenaline, pain intensity was again reduced to mild pain when coughing. Serum concentration of fentanyl doubled from 0.22 to 0.45 ng.ml-1 (P < 0.01), and there was more sedation during the period without adrenaline. CONCLUSIONS: Adrenaline increases sensory block and improves the pain-relieving effect of a mixture of bupivacaine and fentanyl infused epidurally at a thoracic level after major thoracic or abdominal surgery. Serum fentanyl concentrations doubled and sedation increased when adrenaline was removed from the epidural infusion, indicating more rapid vascular absorption and systemic effects of fentanyl.     

Endocrine reactions, circulatory and resuscitation behavior in ketamine-midazolam anesthesia. A comparative study of ketamine racemate vs. (S)-ketamine in knee surgery

Clinically used ketamine is a racemic mixture of two isomers, (S)- and (R)-ketamine, in equal amounts. Previous investigations showed the anaesthetic potency of (S)-ketamine to be three times higher than that of (R)-ketamine. The aim of this study was to compare the effects of (S)-ketamine/midazolam and racemic ketamine/midazolam on endocrine and cardiovascular parameters, recovery, and side effects in unpremedicated patients during knee surgery. METHODS: 41 patients scheduled for elective knee surgery were investigated in a prospective, double-blind, and randomised design. For induction of intravenous anesthesia, patients received 0.1 mg/kg midazolam, 0.003 mg/kg atropine, 1 mg/kg (S)-ketamine or 2 mg/kg racemic ketamine, respectively. For tracheal intubation, 1 mg vecuronium and 1.5 mg/kg suxamethonium were injected. After intubation and relaxation with a total dose of 0.1 mg/kg vecuronium, a continuous infusion of 0.5 mg/kg/h (S)- or 1 mg/kg/h racemic ketamine was administered throughout the surgery. In addition, 0.05 mg/kg/h midazolam was infused continuously in both groups throughout surgery. Ventilation was performed with N2O/O2 (FiO2 0.3). Blood samples were taken using a central venous line five times before induction as well as during and after surgery for analysis of adrenaline, noradrenaline (by high-pressure liquid chromatography with electrochemical detection), anti-diuretic hormone (ADH), adrenocorticotropic hormone (ACTH), and cortisol (by radioimmunoassay). In addition, systolic and diastolic arterial pressure (SAP, DAP), heart rate (HR), and arterial oxygen saturation were measured. The time intervals between the end of ketamine and midazolam infusion and the return of consciousness and orientation were recorded. The incidence and quality of dreams and other side effects were reported by the patients. RESULTS: Biometric data of the groups were comparable. Plasma adrenaline and noradrenaline did not change significantly during anaesthesia. ADH increased significantly (p < 0.05) after skin incision in both groups.     

A model of synchronization of motor acts to a stimulus sequence. II. Stability analysis, error estimation and simulations

In Part I (Mates 1994), a linear model of timing and error-corrections was constructed that aims at an explanation of the mechanisms underlying a subject's performance in an experimental paradigm, in which the task is to synchronize a sequence of motor acts to a sequence of stimuli. The model consists of two error-corrective mechanisms: (1) corrections of period (inverted frequency) of the sequence of responses; (2) corrections of phase shift of that sequence (synchronization error). In this paper, the influence of the physiologically justifiable model variables and of initial conditions on the steady-state response sequence as well as the stability of performance of the model are analyzed. The model is stable for error-correction gains in the range from 0 to 2. Comparison with known empirical data supports the assumption that reasonable values are less than 1. Furthermore, an alternative to the basic linear model is introduced in which the possible character of the process of subjective acquisition of the synchronization error is discussed. On the basis of findings from other experimental paradigms (fusion and order threshold) it can be assumed that the subjective estimate is a nonlinear function of the difference between the temporal central availability of internal representations of the stimulus and response-feedback events. Some other known synchronization data are simulated by the nonlinear modification of the model in this paper. A good fit of the simulation results achieved further justifies the model structure proposed. Finally, the possible effect of the subjective synchronization-error estimation on empirical data is discussed.     

Temporal changes in spinal cord expression of mRNA for substance P, dynorphin and enkephalin in a model of chronic pain

We have used a partial sciatic nerve ligation model to examine the time course for changes in the expression of mRNA for three peptides related to pain transmission at spinal sites (dynorphin, enkephalin and substance P), during the development of allodynia. Enhanced expression of mRNA for dynorphin and substance P was observed in the dorsal horn on the same side as the partial nerve ligation. Increased expression of dynorphin mRNA was biphasic. The initial increases in expression of dynorphin mRNA occurred at 3 h, and a secondary peak was observed 1-3 days after surgery. The secondary increases coincided roughly with increased substance P mRNA expression. However, both dynorphin and substance P mRNA returned to control values after 1 week despite continuing allodynia. No significant changes in expression of mRNA for enkephalin were observed. The elevation of substance P mRNA in intrinsic spinal cord neurons may be secondary to changes in immediate early genes c-fos and jun-B, whereas the expression of dynorphin and enkephalin mRNA is differently regulated. The results also suggest that changes in the expression of the three neuropeptides are not critically involved in the development and maintenance of chronic pain or allodynia.     

A new marker for mosaic analysis in Caenorhabditis elegans indicates a fusion between hyp6 and hyp7, two major components of the hypodermis

A fusion of the sur-5 protein to the green fluorescent protein containing a nuclear localization signal is demonstrated as a marker for genetic mosaic analysis in the nematode Caenorhabditis elegans. Because of an extensive accumulation of bright fluorescence in many nuclei, normal growth plates, each containing hundreds of worms, can be rapidly screened with a dissecting microscope for rare mosaic individuals. As the marker can also be used to detect transgenic worms, the construction of strains for mosaic analyses can be minimized. In the course of examining rare mosaic animals, an unexpected pattern of fluorescence was noticed for hyp6, a syncytial component of the hypodermis, which indicated that the marker may serve as a means of assessing cellular fusions during development. Immunofluorescent staining of adherens junctions confirmed a postembryonic fusion of hyp6 with hyp7, the major syncytium of the hypodermis.     

Relative taste thresholds for ethanol, saccharin, and quinine solutions in three strains of rats nonselected for ethanol: A comparative study.

C. P. Richter and K. H. Campbell (1940b) originally defined taste threshold as "the point at which the rats first indicated that they recognized a difference between the distilled water and the solutions" (p. 34). The present study sought to apply this simple behavioral measure to the investigation of strain differences in taste sensitivities, particularly with respect to predictive relationships in ethanol, saccharin, and quinine preference. Fawn-Hooded, Lewis, and Wistar rats were presented with gradual increments in concentration of ethanol (0.01-15%; C. P. Richter & K. H. Campbell, 1940a), saccharin (0.002-3%) or quinine (0.000 1-0.0055). Results showed that although intake for saccharin was similar in all strains, consumption of ethanol and quinine differed among the groups. Although previous research has proposed that sweet preference is a promising behavioral marker for ethanol preference, these results suggested that bitter preference may be a more reliable predictor of ethanol preference in rats. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maternal control, cognitive style, and childhood anxiety: A test of a theoretical model in a multi-ethnic sample.

This study tested a theoretical model of the interrelations among controlling parenting, negative cognitive styles, children's anxiety, and race/ethnicity. The model suggests that, in general, cognitive style mediates the relation between maternal control and child anxiety but that the set of associations may differ as a function of ethnicity. African American (n = 235), Latin American (n = 56), and European American (n = 136) children completed measures of their anxiety, cognitive schemas reflecting impaired autonomy/performance and disconnection/rejection domains, and maternal control. Results indicated that a disconnection/rejection negative cognitive style mediated the effect of perceived maternal control on childhood anxiety only for the European American group. Maternal control was associated with the impaired autonomy/performance cognitive style for each of the three ethnic groups and with a disconnection/rejection cognitive style only for the European American and Latin American groups. Maternal control had an indirect effect on anxiety through the disconnection/rejection cognitive style for the Latin American group. The results are discussed in terms of how the model presented extends current theories of anxiety problems to African American and Latin American children by noting that significant cultural variations may exist in how parenting practices and cognitive styles relate to children's anxiety levels. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive complaints, depression, medical symptoms, and their association with neuropsychological functioning in HIV infection: A structural equation model analysis.

The main objective of this study was to use structural equation modeling (SEM) to clarify the relationship between subjective cognitive complaints and neuropsychological functioning in 160 adults with HIV infection. Participants completed questionnaires assessing cognitive complaints, symptoms of depression, and HIV-related medical symptoms. Neuropsychological tests included measures of attention, verbal fluency, psychomotor skills, learning, memory, and executive skills. SEM was used to test models of the relationships among cognitive complaints, mood, and medical symptoms with neuropsychological functioning. The model indicated that although depressed mood (β = 0.32, p