Structural basis of the redox switches in the NAD+-reducing soluble [NiFe]-hydrogenase.

NAD+ (oxidized form of NAD:nicotinamide adenine dinucleotide)-reducing soluble [NiFe]-hydrogenase (SH) is phylogenetically related to NADH (reduced form of NAD+):quinone oxidoreductase (complex I), but the geometrical arrangements of the subunits and Fe-S clusters are unclear. Here, we describe the crystal structures of SH in the oxidized and reduced states. The cluster arrangement is similar to that of complex I, but the subunits orientation is not, which supports the hypothesis that subunits evolved as prebuilt modules. The oxidized active site includes a six-coordinate Ni, which is unprecedented for hydrogenases, whose coordination geometry would prevent O2 from approaching. In the reduced state showing the normal active site structure without a physiological electron acceptor, the flavin mononucleotide cofactor is dissociated, which may be caused by the oxidation state change of nearby Fe-S clusters and may suppress production of reactive oxygen species.

Composite material stent comprising metallic wire and polylactic acid fibers, and its mechanical strength and retrievability.

BACKGROUND: Although metallic stents are characterized by strong expanse of force, thin walls, and easy stent deployment, their removal from the body is usually difficult or impossible due to the difficulty of unraveling their mesh structure. A stent built of a composite material comprising a metallic wire and a polylactic acid (PLA) fiber, in which the metallic wire component could be unraveled after PLA fiber degradation in the body, should allow easy stent removal. PURPOSE: To evaluate the mechanical strength and retrievability of a composite material stent comprising a metallic wire and a PLA fiber. MATERIAL AND METHODS: We produced a composite material stent comprising a metallic wire and a biodegradable fiber (hybrid stent). As the metallic wire is not cross-linked with itself, but with the PLA fibers only, the hybrid stent can be easily unraveled after PLA fiber degradation. This stent was built with a 0.2-mm stainless-steel wire and a 0.23-mm PLA fiber knitted in the same textile as an Ultraflex stent. For comparison, an identical stent was built using PLA fiber only (PLA stent). The mechanical strength of these stents was tested by the radial expansive force response against circumferential shrinkage stress load. Change in radial force due to PLA fiber degradation was estimated by adding an artificial PLA degeneration process, by immersing each stent in a water bath at 80 degrees C for 48 hours. Retrievability of the hybrid stent after PLA degeneration was examined by hooking and pulling out the residual stainless-steel wire from a silicon tube. RESULTS: The hybrid stent exhibited a linear response in radial expansive force within the range of 15% diameter reduction. The PLA stent did not exhibit linear response at over 15% diameter reduction. Decrease of radial expansive force after PLA degradation was within 5% of the original force in the hybrid stent, but the PLA stent did not create effective radial expansive force. Hybrid stents, even after PLA degradation, exhibited a linear response in radial expansive force, within the range of 15% diameter reduction. The metallic component of the heat-processed hybrid stent was easily unraveled by pulling out the wire. CONCLUSION: The hybrid stent comprising a stainless-steel wire and a PLA fiber appears to provide effective radial expansive force and retrievability.

Transcatheter coil embolization for steal syndrome in patients with hemodialysis access.

BACKGROUND: Drainage of large amounts of shunt blood into deep veins via collaterals reduces resistance to venous outflow and decreases blood flow to the artery distal to the arterial anastomotic site, potentially resulting in steal syndrome. PURPOSE: To evaluate the effectiveness of transcatheter coil embolization for collateral veins of hemodialysis access in the treatment of steal syndrome. MATERIALS AND METHODS: Five hemodialysis patients (four male, one female; mean age 58.8 years, range 40-71 years) with symptomatic steal syndrome were treated. Steal syndrome was diagnosed based on decreased or absent distal pulse, coolness, pain, abnormal skin color, ischemic ulceration of digits, numbness, sensory impairment, or motor impairment. Coil embolization was performed to block collaterals communicating with deep veins, with conscious sedation and local anesthesia. Fistulography was performed before, immediately after, and 1 month after embolization. Ultrasonography was performed 2 days after embolization. Symptoms and signs were assessed 2 days after embolization. Clinical findings related to steal syndrome and access failure were observed at each hemodialysis. RESULTS: Blood flow in the collaterals was successfully blocked by coil embolization in all patients. Distal pulse, coolness, pain, and skin color improved in all patients. Numbness, sensory impairment, and motor impairment were unimproved in two patients. In all patients, hemodialysis following embolization was performed normally. The mean observation period after embolization was 33 months (range 9-75 months). CONCLUSION: Coil embolization of collaterals that drain shunt blood into deep veins is effective for steal syndrome for hemodialysis access originating in the brachial artery.

Cerebral microembolisation during radiofrequency ablation of lung tumours: detection by carotid duplex ultrasound.

The aim of this study was to investigate the appearance of microbubbles during radiofrequency ablation (RFA) of lung tumours. Eight consecutive patients (mean age, 73.1 years; 3 men and 5 women; 10 malignant lesions; mean lesion size, 24.8 mm) who underwent RFA of lung tumours using internally cooled single electrodes were enrolled. During the RFA procedure, the right internal carotid artery was continuously monitored by duplex ultrasound. High-intensity transient signals (HITS) that occurred in the Doppler blood flow waveform were taken to indicate microbubbles. 21 RFA applications were performed for the 10 lesions. HITS were observed in 19 of 21 RFA applications; the mean frequency in a single application was 10+/-13.3. A statistical correlation was seen between the duration of energy deposition and the number of HITS, and between tumour size and the number of HITS. Microbubbles were detected in all patients in the late phase of the first session of RFA.

Improvement in respiratory function by percutaneous vertebroplasty.

BACKGROUND: Percutaneous vertebroplasty (PVP) improves back pain and corrects spinal misalignment to some extent, and thus may improve respiratory function. PURPOSE: To retrospectively investigate changes in respiratory function after PVP. MATERIAL AND METHODS: 41 patients (mean age 72.0 years, range 59-86 years; 39 women, two men) who had undergone PVP for vertebral compression fractures (37 thoracic vertebral bodies [Th6-Th12] and 50 lumbar vertebral bodies [L1-L5]) caused by osteoporosis visited our hospital for follow-up consultation between January and June 2005. At this follow-up consultation, respiratory function testing, including percent forced vital capacity (FVC%) and percent forced expiratory volume in 1 s (FEV(1)%), was performed. We retrospectively compared these values with those taken before PVP using a Wilcoxon signed-rank test. RESULTS: FVC% was 85.2+/-30.3% before PVP and 91.5+/-16.8% at follow-up (mean 10 months after PVP), which represented a significant difference (P<0.003). No significant difference in FEV(1)% was detected. Regarding the number of treatment levels, that is, single vertebroplasty versus multiple vertebroplasty, no significant difference in improvement of FVC% was confirmed (P=0.1). FVC% was abnormally low (

Percutaneous transluminal cutting-balloon angioplasty for hemodialysis access stenoses resistant to conventional balloon angioplasty.

PURPOSE: To examine the value of cutting-balloon percutaneous transluminal angioplasty (PTA) for hemodialysis access with residual stenosis after conventional balloon PTA. MATERIAL AND METHODS: Angioplasty with conventional balloons was performed on 48 hemodialysis access stenoses in 28 patients. If the balloon waist still remained at the rated burst pressure, the balloon was reinflated up to three times. Fifteen of 48 stenoses had residual stenoses of more than 30% after conventional balloon PTA. In these 15 stenoses, additional cutting-balloon PTA was performed. RESULTS: The mean residual percent diameter stenoses before and after conventional balloon PTA were 77.6+/-3.4% and 48.6+/-8.5%, respectively. Additional cutting-balloon PTA decreased the mean residual percent diameter to 27.9+/-10.0%, and the cutting balloon was completely inflated without complication. In 12 patients, the 6-month primary patency rate (+/-SE) was 90.0% (9.5), and the 1-year primary patency rate (+/-SE) was 25.0% (14.8). CONCLUSION: Additional cutting-balloon PTA was found useful for reducing residual stenosis.

Percutaneous vertebroplasty for compression fracture: analysis of vertebral body volume by CT volumetry.

PURPOSE: To evaluate the relationships between volume of vertebral bodies with compression fracture (measured by CT volumetry) before percutaneous vertebroplasty, the amount of bone cement injected, and the effect of treatment. MATERIAL AND METHODS: We examined 49 consecutive patients, with 104 vertebral body compression fractures, who underwent percutaneous injection of bone cement. Vertebral body volume was measured by CT volumetry. The patient's pain level was assessed using a visual analog scale (VAS) before and after the procedure. Improvement in VAS was defined as the decrease in VAS after the procedure. Relationships between vertebral body volume, the amount of bone cement, and the effect of treatment were evaluated using Pearson's correlation coefficient test. RESULTS: Average vertebral body volume was 26.3 +/- 8.1 cm3; average amount of bone cement was 3.2 +/- 1.1 ml; and average improvement in VAS was 4.9 +/- 2.7. The vertebral body volume was greater if a larger amount of bone cement was injected. There was a significant positive correlation between vertebral body volume and amount of bone cement (r = 0.44; P < 0.0001). However, there was no correlation between vertebral body volume and improvement in VAS, or between amount of bone cement and improvement in VAS. CONCLUSION: In percutaneous vertebroplasty for vertebral body compression fracture, there is a positive correlation between vertebral body volume and amount of bone cement, but improvement in VAS does not correlate with vertebral body volume or amount of bone cement.

[A device to prevent an air-leakage after a thoracoscopic surgery for spontaneous pneumothorax].

PURPOSE: In a thoracoscopic surgery for the patient with spontaneous pneumothorax, an air-leakage from the staple-line is one of the most troublesome complications. Recently we have been using a polyglycolic acid (PGA) sleeve for staple-line reinforcement. The purpose of this study was to investigate an efficacy of staple-line reinforcement in the patients who underwent thoracoscopic lung resection using an automatic stapler. OBJECTS: Last 4 years, 55 patients with primary spontaneous pneumothorax underwent thoracoscopic surgery using an automatic stapler. PGA sleeve was used in 19 patients as PGA group, fibrin glue was applied to the staple-line in 6 patients as fibrin group and no staple-line reinforcement was applied in 30 patients as no-reinforce group. We investigated the efficacy of staple-line reinforcement according to the results after surgery in these 3 groups. RESULTS: Average drainage time in PGA group, fibrin group and no-reinforce group were 2.1, 2.2 and 2.8 days, respectively. In PGA group, the drainage time after surgery tended to be short term. The relapse of pneumothorax after surgery developed in 2 patients in PGA group (10.5%) and 8 patients in non-reinforce group (26.7%). In PGA group, the relapse after surgery tended to be low rate. CONCLUSIONS: Bioabsorbable PGA sleeve could be an useful device for a staple-line reinforcement in the patients who underwent lung resection using automatic stapler.

A four-dimensional study of the aortic root dynamics.

OBJECTIVE: Although aortic root expansion has been well studied, its deformation and physiologic relevance remain controversial. Three-dimensional (3-D) sonomicrometry (200Hz) has made time-related 4-D study possible. METHODS: Fifteen sonomicrometric crystals were implanted into the aortic root of eight sheep at each base (three), commissures (three), sinuses of Valsalva (three), sinotubular junction (three), and ascending aorta (three). In this acute, open-chest model, the aortic root geometric deformations were time related to left ventricular and aortic pressures. RESULTS: During the cardiac cycle, aortic root volume increased by mean+/-1 standard error of the mean (SEM) 33.7+/-2.7%, with 36.7+/-3.3% occurring prior to ejection. Expansion started during isovolumic contraction at the base and commissures followed (after a delay) by the sinotubular junction. At the same time, ascending aorta area decreased (-2.6+/-0.4%). During the first third of ejection, the aortic root reached maximal expansion followed by a slow, then late rapid decrease in volume until mid-diastole. During end-diastole, the aortic root volume re-expanded by 11.3+/-2.4%, but with different dynamics at each area level. Although the base and commissural areas re-expanded, the sinotubular junction and ascending aorta areas kept decreasing. At end-diastole, the aortic root had a truncated cone shape (base area>commissures area by 51.6+/-2.0%). During systole, the root became more cylindrical (base area>commissures area by 39.2+/-2.5%) because most of the significant changes occurred at commissural level (63.7+/-3.6%). CONCLUSION: Aortic root expansion follows a precise chronology during systole and becomes more cylindrical - probably to maximize ejection. These findings might stimulate a more physiologic approach to aortic valve and aortic root surgical procedures.

A new liquid embolic material for liver tumors.

PURPOSE: To evaluate the feasibility of a new liquid embolic material, Onyx, for treating liver tumors. MATERIAL AND METHODS: Onyx is a mixture of 6% (w/v) ethylene-vinyl-alcohol copolymer dissolved in anhydrous dimethyl sulfoxide (DMSO) with 28% (w/v) tantalum powder. In addition to 6% Onyx, we also tried 4%, 2% and 1% solutions, prepared by adjusting the amount of DMSO. We used 15 white rabbits with liver tumors created by percutaneous injection of VX2 tumor cells. In 4 groups with 3 rabbits in each, the liver arteries were embolized with 6%, 4%, 2% and 1% Onyx, respectively, and in 3 rabbits DMSO alone was injected. The injections were performed just proximal to the bifurcation of the proper hepatic artery, followed by celiac arteriography. Post mortem, the livers were examined by soft-tissue radiography, and liver-tissue section microscopy. RESULTS: The maximum number of arterial branching points passed by embolic material in either the right or left hepatic arteries was 11, 15 and 16, for 6%, 4% and 2% Onyx, respectively, but was non-measurable for 1% Onyx. Minimum diameters of arteries reached by 6%, 4%, 2% and 1% Onyx in tumorous areas were 40 microm, 35 microm, 20 microm and 10 microm, respectively, and in non-tumorous areas 35 microm, 5 microm, 5 microm and 5 microm, respectively. CONCLUSION: This study suggests that Onyx may be feasible for treatment of hepatic tumors.

Aortic and pulmonary root: are their dynamics similar?

OBJECTIVES: The long-term behavior of the pulmonary autograft in the aortic position (Ross procedure) remains uncertain. Using three-dimensional (3D) sonomicrometry (200 Hz) we compared the dynamics of the aortic and pulmonary roots. METHODS: Twenty-four crystals were implanted in each aortic (eight sheep) and pulmonary roots (six sheep) at: base (3 x 2), commissures (3 x 2), sinotubular junction (3 x 2), ascending aorta (3) and pulmonary trunk (3). Under stable hemodynamic conditions, geometric changes were time-related to left ventricular pressure (LV) and aortic pressure. RESULTS: The expansion of the aortic root is twice that of the pulmonary root. During the cardiac cycle, the aortic root volume increased by 37.7 +/- 2.7% (mean +/- SEM) versus 20.9 +/- 1.0% for the pulmonary root. Both were cone-shaped at end diastole. Because expansion at commissures was twice that of the base, both roots became more cylindrical during ejection. Although both roots started to expand prior to ejection and reached maximal expansion during the first third of ejection, the commissural and sinotubular junction dynamics were different in each root. While in the aortic root, expansion at commissural and sinotubular junction levels was significantly different (63.7 +/- 3.6% versus 37.0 +/- 2.1%), in the pulmonary root, they were similar (29.0 +/- 1.3% versus 27.7 +/- 1.4%). Expansion of the three sinuses was also different (P<0.001). In the aortic root: the right expanded more than the left and more than the non-coronary sinus. In the pulmonary root: the right sinus expanded more than the anterior more than the left. CONCLUSIONS: Dynamic differences might explain the global pulmonary root dilatation when subjected to systemic pressure, particularly at the level of the sinotubular junction which might result in the autograft failure. Differences in the asymmetrical expansion of the aortic and pulmonary roots should be considered for the implantation of the pulmonary autograft in the most physiological position.

[Reoperation for metachronous pulmonary or tracheal lesions after pneumonectomy].

Although aggressive reoperation for metachronous multiple primary lung cancer or intrathoracic recurrence without distant metastases have been recommended to the patients of primary lung cancer and metastatic lung tumor, surgical indication after a previous pneumonectomy is restricted because of residual pulmonary function. We report about 3 reoperated cases for metachronous pulmonary or tracheal lesions after left pneumonectomy. Case 1: A 61-year old male who underwent left pneumonectomy for primary lung cancer was reoperated for tracheal cancer 41 months after the pneumonectomy. Case 2: A 61-year old male who underwent left pneumonectomy for primary lung cancer was reoperated for metachronous multiple primary lung cancer 59 months after the pneumonectomy. Case 3: A 59-year old male who underwent left pneumonectomy for metastatic lung tumor from rectal cancer was re-operated for intrathoracic recurrence 28 months after the pneumonectomy. All cases are alive without recurrence.

Glycine at the 65th position plays an essential role in ATP-dependent protein folding by Archael group II chaperonin.

In the previous study, we have found that G65C and I125T double mutant of alpha chaperonin homo-oligomer from a hyperthermophilic archaeum, Thermococcus sp. strain KS-1, lacks ATP-dependent protein refolding activity despite showing ATPase activity and the ability to bind the denatured proteins. In this study, we have characterized several mutant Thermococcus chaperonin homo-oligomers with the amino acid substitutions of Gly-65 or Ile-125. The results showed that amino acid residue at 65th position should be a small amino acid such as glycine or alanine for the ATP-dependent refolding activity. The alpha chaperonin homo-oligomers with amino acid substitution of Gly-65 by amino acids whose side chains are larger than the methyl group did not have ATP-dependent protein refolding activity, but exhibited an increase of the binding affinity for unfolded proteins in the presence of ATP or AMP-PNP. (c)2001 Elsevier Science.

Hemodynamic evaluation of a new stentless autologous pericardial mitral valve.

BACKGROUND: There is no satisfactory mitral valve prosthesis. An ideal mitral valve substitute should be biologic, nonantigenic, and anatomically correct. METHODS: We developed a stentless, chordal-supported (including anterior basal stay chords) mitral valve made with glutaraldehyde-treated autologous pericardium. Eight such prostheses were implanted in sheep. RESULTS: Seven animals survived the operation and were studied postoperatively immediately, at 1 week, and at 1 month. Simultaneous left ventricular and left atrial pressures showed peak and mean transvalvular pressure gradients of 6+/-2 mm Hg and 1+/-1 mm Hg, respectively. Echocardiography performed intraoperatively and then 1 week and 1 month postoperatively showed normal valve leaflet movements. Color and pulsed Doppler echocardiography showed no sign of transvalvular stenosis or regurgitation. Effective orifice area was 5.39+/-0.35 cm2 at intraoperative, 5.51+/-0.29 cm2 1 week after operation (n = 5), and 5.51+/-.28 cm2 1 month after operation (n = 3). Three animals were sacrificed at 19 days and at 1 and 3 months. One animal is alive at 10 months. CONCLUSIONS: This new stentless pericardial mitral valve performed satisfactorily with low gradients and no regurgitation. Possible advantages of this pericardial valve are excellent hemodynamics, ease of construction and implantation, lack of immunogenicity, and low cost. Similarly designed valves but with a shorter nonglutaraldehyde treatment time have been used in 3 sheep monitored for more than 3 months.

A new method for the preservation of aortic valve homografts.

BACKGROUND AND AIM OF THE STUDY: Aortic valve homografts were treated with 50% ethanol and glycerol followed by freeze-drying (D-Hydro). Comparative results of fresh versus D-Hydro-treated aortic roots implanted for up to nine months in the descending aorta of sheep with induced aortic regurgitation (AR) are reported. METHODS: Six fresh and six D-Hydro valves were implanted in 12 sheep for three, six and nine months, and echocardiography and pressures were taken at surgery and sacrifice. Tissue sections were stained with hematoxylin and eosin, von Kossa, Masson's trichrome, Movat's pentachrome, von Willebrand factor, CD3 (a T-cell marker) and smooth muscle alpha-actin. RESULTS: No grafts had increased gradients after implantation, or at sacrifice. At explantation, fresh homografts showed early pannus formation followed by thrombus, annular dilatation and wall calcification. Leaflets were thickened and progressively retracted. All had severe AR. The appearance of D-Hydro-treated homografts was normal, except for mild leaflet retraction in three, resulting in AR (in two animals the induced AR had healed). Histologically, a T-cell-mediated reaction was evident in the fresh homografts, and collagen distortion was noted. Calcification was present in all fresh specimens and was severe at nine months. D-Hydro roots showed only minor calcification in the six-month samples. Normal collagen, and a complete layer of von Willebrand factor-stained cells were present at three months. At nine months, cell rehabitation extended for two-thirds of the leaflets (alpha-actin +). The inflammatory reaction was very mild, with CD3+-stained cells absent in most samples. CONCLUSION: Aortic valve homografts treated with the D-Hydro freeze-drying method performed better than fresh homografts due to the absence of thrombus and annulus dilatation, limited calcification, and rehabitation of the aortic wall and parts of the leaflet by myofibroblasts, as well as the presence of a complete endothelial layer on the aortic wall and leaflet.

[Surgical results and perioperative complications in patients presenting lung cancer and cardiovascular diseases].

Among 525 patients with lung cancer who underwent an operation between 1985 and 1998, 24 patients who also had a cardiovascular disease, most commonly ischemic heart disease. We gave all of these patients a preoperative assessment for ischemic heart disease, done according to a diagnostic flow chart. Eighteen patients (3.4%) were found to have IHD. We performed myocardial revascularization before or simultaneously with an operation for lung cancer in patients who also have known IHD. None of these patients had major perioperative cardiac trouble. Inspite of our efforts, perioperative myocardial ischemic events occurred in 6 patients (1.2% of all patients) who were not detected by our preoperative IHD assessment. We conclude that this IHD assessment flow chart may be useful for proper perioperative management of patients undergoing lung surgery. However, more precise methods to detect patients with IHD will be necessary to improve their perioperative cardiac risk.

A study of the junction between glutaraldehyde-treated allogeneic aorta and host aorta.

BACKGROUND AND AIM OF THE STUDY: Stentless aortic valve bioprostheses have become popular because of their superior hemodynamics and expected increased durability. However, the stentless bioprosthesis differs from stented valves in that glutaraldehyde (GA)-treated tissue is implanted in direct contact with the native aorta. The effect of GA-treated tissue on host tissue has not been reported. METHODS: In order to analyze the effect of GA in the healing process, sheep descending aortic conduits treated with 0.625% GA were inserted in the descending thoracic aorta of 10 adult sheep. The implants were removed after 4, 5, 10, 12, 15, 25, 30, 32, 60 and 120 days. The upstream and downstream junctions were evaluated macro- and microscopically, and by immunohistology for smooth muscle cell alpha-actin and von Willebrand factor. RESULTS: By day 60 of implantation, the GA-treated conduits were calcified. By days 60 and 120, the calcification had spread to the host aorta, and was seen as foci of calcification in the junctional area. Acellular areas were also seen in the host aorta near the anastomosis. A fibrotic layer spanning the abluminal aspect of the junction between the implant and host aorta was present at day 4 and continued through 120 days. This layer was characterized by a progressive increase in collagenous matrix and cellularity, as well as new blood vessel formation. The luminal aspect of the junction had a neointimal layer of variable thickness containing alpha-actin-expressing cells covered by a monolayer of von Willebrand factor-expressing cells, seen at 15-30 days and present through 120 days. CONCLUSION: In our model, implanting GA-fixed tissue in direct contact with living tissues resulted in cell death and calcification of host tissue within 60 days. The integrity of the junction did not appear to be compromised. This may be of interest in light of the increased popularity of the stentless aortic bioprosthesis.

Significant increase of aortic root volume and commissural area occurs prior to aortic valve opening.

BACKGROUND AND AIM OF THE STUDY: The increased use of autologous, homologous or heterologous aortic root demands a detailed knowledge of its anatomy and function. The advent of 3-D digital sonomicrometry offered the opportunity to acquire precise information on the root and leaflet movements during the cardiac cycle. METHODS: Under cardiopulmonary bypass, sonomicrometry crystals were implanted in the aortic root and valve of eight sheep. Crystals were sutured at each commissure (n = 3), the top of the sinotubular junction (n = 3), lowest point of the annulus (n = 3), and leaflet tip (n = 3). 3-D coordinates of each crystal were recorded, together with left ventricular and aortic root pressures and ECG. When the animal had returned to a stable hemodynamic condition, the maximum and minimum distances between two crystals, and areas between three crystals, were calculated. Changes in root volume and leaflet position were time-related to the pressure changes. RESULTS: The most significant change between maximum and minimum distance between crystals during the cardiac cycle occurred at the commissural level. Similarly, the triangle defined by the three commissural crystals showed the greatest change in area (47%). The root volume increased by an average of 22%; about 40% of this increase occurred during the isovolumic phase. The aortic leaflets began to open before ejection. CONCLUSION: We postulate that aortic valve opening is initiated by the outward pull of the commissures. These findings should impact on aortic root surgery.

Afferent and efferent nerve activity of arterial baroreceptor reflex under nonpulsatile systemic circulation.

We studied the changes in arterial baroreceptor reflex (ABR) afferent activity and efferent activity induced by nonpulsatile systemic circulation (NC) during total left heart bypass (TLHB) in rabbits. To evaluate the influence of the circuit priming fluid and exposure to NC, we directly measured aortic depressor nerve activity (ADNA) (n = 5) and renal sympathetic nerve activity (RSNA) (n = 5) before the start of partial left heart bypass (PLHB) (Before), after PHLB (After), and 5 min after the start of TLHB (During THLB) while maintaining the mean aortic pressure. The circuit priming fluid did not affect the ABR. ADNA exhibited periodic discharge at Before and After, but at During THLB, this periodic discharge transformed into a continuous discharge, and ADNA increased significantly. However, there were no significant differences in RSNA. Our results suggested that in the acute phase under NC, the ABR differed from that under natural circulation.