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Biomedical subjects

A Just

Publications and source records attributed to A Just.

At least 19 recordsLinked to original sources
PubMed2006

Imaging pathologic pulmonary air and fluid accumulation by functional and absolute EIT.

The increasing use of EIT in clinical research on severely ill lung patients requires a clarification of the influence of pathologic impedance distributions on the validity of the resulting tomograms. Significant accumulation of low-conducting air (e.g. pneumothorax or emphysema) or well-conducting liquid (e.g. haematothorax or atelectases) may conflict with treating the imaging problem as purely linear. First, we investigated the influence of stepwise inflation and deflation by up to 300 ml of air and 300 ml of Ringer solution into the pleural space of five pigs on the resulting tomograms during ventilation at constant tidal volume. Series of EIT images representing relative impedance changes were generated on the basis of a modified Sheffield back projection algorithm and ventilation distribution was displayed as functional (f-EIT) tomograms. In addition, a modified simultaneous iterative reconstruction technique (SIRT) was applied to quantify the resistivity distribution on an absolute level scaled in Omega m (a-EIT). Second, we applied these two EIT techniques on four intensive care patients with inhomogeneous air and fluid distribution and compared the EIT results to computed tomography (CT) and to a reference set of intrathoracic resistivity data of 20 healthy volunteers calculated by SIRT. The results of the animal model show that f-EIT based on back projection is not disturbed by the artificial pneumo- or haematothorax. Application of SIRT allows reliable discrimination and detection of the location and amplitude of pneumo- or haematothorax. These results were supported by the good agreement between the electrical impedance tomograms and CT scans on patients and by the significant differences of regional resistivity data between patients and healthy volunteers.

Algorithms↗
PubMed2003

[Kinematic analysis before and after bicondylar resurfacing knee arthroplasty].

Knee joint motion appears as a hinge movement around the flexion-extension axis. Corresponding to the rolling-sliding mechanism and alternative models of knee joint kinematics, an instant center pathway must be expected. The current photogrammetric investigation aimed to analyze these pathways when assessed in the sagittal plane in patients with preoperative varus or valgus deformity. A total of 40 patients either with varus or valgus deformity (20 in each group) were examined before and 6 months after implantation of PFC-SIGMA prostheses. Apart from the influence of knee joint deformity, a so-called soft tissue ratio was investigated. Therefore, the relation of thigh and femur as well as lower limb and tibia diameters was calculated and combined in one value. The investigation unit consisted of a standardized chair with passive knee joint movement (90-0 degrees flexion) supported by an electric motor. The position of predefined skin markers was assessed by digital camera with online transmission to a PC. The instant center pathway was then evaluated applying the Reuleaux technique based on the changes of skin marker positions. Results showed the following characteristics: small values of soft tissue ratio were represented by round or oval courses of the pathway whereas increasing ratios led to triangular and slightly increased dimensions of the courses. Varus deformity was primarily combined with an increase of the pathway's dimension and in contrast, valgus deformity showed decreased pathways. In each case, dimensions normalized after prosthesis implantation. The instant center pathway of knee joint motion showed for both patient groups characteristic phenomena. They were clearly associated with constitutional and clinical features of each patient.

Aged↗
PubMed2003

[Photogrammetry of knee joint kinematics after hinge arthroplasty].

Hinge prostheses are the oldest total knee arthroplasties based on the easiest model of knee joint kinematics. The complex knee joint movement is simplified by a hinge rotating around the flexion-extension axis. Nevertheless, different studies showed that in unscathed joints an instant center pathway in the sagittal plane must be expected. The objective of the current photogrammetric investigation was the assessment of these pathways after hinge arthroplasty. Moreover, they were compared with reference pathways from healthy participants. A total of 20 patients were examined on average 12.1 years after implantation of St. Georg hinge prostheses. Apart from this, 50 test persons with unscathed knee joints were investigated. The examination unit consisted of a standardized chair with passive knee joint movement (90-0 degrees flexion) supported by an electric motor. The position of predefined skin markers was assessed by digital camera with online transmission to a PC. The instant center pathway was then evaluated applying the Reuleaux technique based on the changes of skin marker positions. Patients with hinge prostheses showed small pathways almost comparable to dots. Apart from this, courses of the pathways depended on the extent of soft tissue in the knee joint area. Small values were associated with round or oval courses,whereas increasing soft tissue led to triangular and slightly increased dimensions of the courses. Pathways of the reference participants confirmed this observation and additionally showed clearly greater dimensions of the pathways. The instant center pathway of unscathed knee joints showed a dependence of the course on the extent of soft tissue. The same observation was made in patients with hinge prostheses. Moreover,the latter were characterized by very small, almost fixed pathways. These results confirm the neglect of additional movement components in hinge prostheses.

Adult↗
PubMed2002

Central hypercapnic chemoreflex modulation of renal sympathetic nerve activity in experimental heart failure.

Activation of the sympathetic nervous system plays an important role in the pathophysiology and progression of congestive heart failure (CHF). The precise mechanisms responsible for sympathetic activation in CHF are not yet clearly established. An altered central hypercapnic chemoreflex modulation of sympathetic nerve activity (SNA) might be an explanation. Therefore, the response of postganglionic renal SNA to elevation of CO2 concentration in the inspiratory air to 2, 4, and 6% was determined in anesthetized, artificially ventilated rats after denervation of peripheral baro- and chemoreceptors 2 weeks (group A; n=8) or 6 weeks (group B; n=11) after induction of an aorto-caval shunt, or 4 weeks after aortic banding (group C; n=7). In all CHF models, left ventricular enddiastolic pressure was increased (A 8 +/- 1, B 8 +/- 1, C 10 +/- 2 mmHg) as compared to sham operated controls (A 3 +/- 1, B 4 +/- 1, C 5 +/- 1 mmHg). Indicative of left ventricular hypertrophy and pulmonary congestion, wet weight of heart (A + 60%, B + 93%, C + 49%) and lungs (A + 15%, B + 36%, C + 12%) were also enhanced as compared to controls. Elevation of inspiratory CO2 concentration to 2,4, and 6% increased renal SNA by approximately 10, 20, and 30% from resting activity in all groups. The maximum SNA responses at 6% CO2 in the groups with CHF (A + 390 +/- 95, B + 425 +/- 133, C + 368 +/- 158 microVs) did not differ from those in the respective controls (A + 510 +/- 130, B + 570 +/- 180, C + 275 +/- 25 microVs). It is concluded that under these experimental conditions the central hypercapnic chemoreflex sensitivity is not altered in either of the employed models of CHF and therefore may not play a major role for the well-known elevation of SNA in CHF.

Animals↗
PubMed2002

[Kinematic changes after bicondylar resurfacing knee arthroplasty].

AIM: Knee joint motion appears as a hinge movement around the flexion - extension axis. But corresponding to the rolling-sliding-mechanism and alternative models of knee joint kinematics an instant center pathway must be expected. Objective of the study was the comparison of this pathway when assessed in the sagittal plane in patients with preoperative varus or valgus deformity. METHOD: A total of 40 patients either with varus or valgus deformity (20 in each group) were examined before and 6 months after implantation of PFC(R)-SIGMA prostheses. Apart from the influence of knee joint deformity (35 degrees varus to 24 degrees valgus), a so called soft tissue ratio was investigated. Therefore the relation of thigh and femur as well as lower limb and tibia diameters was calculated and combined in one value. The examination by means of photogrammetry consisted of a standardized chair with passive knee joint movement (90 degrees to 0 degrees flexion) supported by an electric motor. The position of defined skin markers was assessed by digital camara with online transmission to PC. The instant center pathway was then evaluated applying the Reuleaux-technique based on the changes of skin marker positions. RESULTS: Results showed a dependence of the course and dimension of the instant center pathway on the extent of soft tissue ratio as well as knee joint deformity. Small values of the ratio (W = 2.9) were represented by round or oval courses of the pathway whereas increasing ratios (W = 4.0) led to triangular and slightly increased dimensions of the courses. Varus deformitywas primarily combined with an increase of the pathways dimension and in contrast, valgus deformity showed decreased pathways. In each case, dimension normalized after prostheses implantation. CONCLUSION: The instant center pathway of knee joint motion showed for both patient groups characteristic phenomen. They were clearly combined with constitutional and clinical features of each patient.

Aged↗
PubMed2001

In vitro dose response to different GPIIb/IIIa-antagonists: inter-laboratory comparison of various platelet function tests.

AIMS: The aim of this study was to assess the inter- and intra-laboratory variation of the concentration-response to the GPIIb/IIIa-antagonists abciximab and eptifibatide on platelet aggregometry and to compare results with flow cytometric tests as well as the rapid platelet function analyser (RPFA). METHODS: In five different laboratory sites, blood from three to five healthy donors was spiked with abciximab or eptifibatide, followed by the assessment of: (1) aggregometry (anticoagulant: sodium citrate 3.18% or hirudin 5 microg/ml); (2) flow cytometry (fibrinogen binding or PAC1-expression), or (3) RPFA. Dose-response curves were established on the basis of a sigmoidal Imax)-model [I=(Imax)*Cg)/(IC50g + Cg)]. RESULTS: For citrated blood, aggregation induced by 20 microM ADP was blocked up to 100% by both GPIIb/IIIa-antagonists, IC50 values varied between 0.11-0.22 microg/ml for eptifibatide and 1.25-2.3 microg/ml for abciximab. I(max) of the response to 5 microg/ml collagen ranged from 46% to 100%, and IC50 values varied between 0.28-0.34 microg/ml for eptifibatide and 2.3-3.8 microg/ml for abciximab. In hirudinized blood, IC50 values for eptifibatide were 1.5- to 3-fold higher than those obtained with citrated plasma. Inhibition of PAC1-expression by abciximab (IC50) 0.84 microg/ml) showed results similar those of the RPFA (approx. 1.0 microg/ml); larger differences between PAC1 and RPFA results were observed for eptifibatide. Based on aggregometry, eptifibatide concentrations for 80% inhibition varied from 0.27 to 0.55 microg/ml, and were considerably less when the RPFA was taken as basis (0.15 or 0.22 microg/ml). A similar pattern was observed for abciximab. CONCLUSIONS: We found quite a low inter- and intra-laboratory variation in the in vitro pharmacodynamic characterization of GPIIb/IIIa-antagonists by aggregometry, making results of these tests obtained from different laboratories during clinical trials at least comparable. The RPFA exhibits a higher sensitivity to inhibitory GPIIb/IIIa-effects, in keeping with the "real" inhibition of the activated receptor (PAC1) as assessed with more elaborate flow cytometry.

Abciximab↗
PubMed2001

[Crossed screw osteosynthesis of proximal humerus fractures].

Between March 1997 and October 1999 thirty-one patients with displaced proximal humeral fractures were treated with crossed screw osteosynthesis. Insertion of the screws was realized by using a deltoideo-pectoral approach placing the screws anteriorly and posteriorly in a crossed manner from the distal fragment into the humeral head. Additionally, in all two-part-fractures a tension band was applied. In all three-part-fractures, the greater tuberosity was reattached by additional screws. In 21 patients (14 female, 7 male, median age 62 years, 18-86) a clinical and radiological follow-up (median 18 months, 10-29) was obtained. Fractures were classified as two-part-fractures in 10 patients and as three-part-fractures in 11 patients. According to the Constant-Score, "excellent" and "good" results were achieved in 15 patients, "moderate" results were found in 3 patients. However, in 3 patients results were only "poor" (1 two-part-, 2 three-part-fractures). The complication rate was 29% (premature hardware removal due to head perforation in 3 cases; humeral head necrosis necessitating prosthetic replacement in 2 patients; secondary displacement in 1 case). Crossed screw osteosynthesis represents an justified alternative in the surgical treatment of displaced proximal humeral fractures permitting early functional therapy.

Adolescent↗
PubMed2001

[Experimental flow and perfusion measurements in the animal model with magnetic resonance tomography].

AIM: Validation of non-invasive methods for morphologic and functional imaging of the kidney under physiologic and pathophysiologic conditions. MATERIAL AND METHODS: In chronically instrumented animals (foxhounds) comparative measurements of renal flow and perfusion were performed. Magnetic resonance imaging techniques were compared to data obtained from implanted flow probes and total kidney weight post mortem. In the MR system, different degrees of renal artery stenosis could be induced by means of an implanted inflatable cuff. The degree of stenosis was verified with high-resolution 3D contrast-enhanced MR angiography (3D-CE-MRA) using an intravascular contrast agent. RESULTS: The MR-data agreed well with the invasively obtained results. Artifacts resulting from the implanted flow probes and other devices could be kept to a minimum due to appropriate selection of the probe materials and measurement strategies. Stenoses could be reproduced reliably and quantified from the induced morphologic and functional changes. CONCLUSION: Morphologic and functional MR techniques are well suited for non-invasive in vivo assessment of renal blood flow physiology.

Animals↗
PubMed2001

[Ethical decision models in nursing and medicine].

A literature review on ethical decision making models shows that there is a great number of monodisciplinary ethical models in nursing and in medicine and new ones are constantly being developed. It is, however, to be questioned if by using these models divergent possibilities and consequences arise for practice. To answer this question this article deals with two selected models in ethical decision making. The model by Illhardt (1998) derives from a physician's viewpoint and understanding. The procedure from Tschudin (1996) was developed on the background of nursing. The practical application of these two models in this case study shows common ground as well as differences and interrelated effects on the decision making process. In relation to this case study the development of specific ethical decision making models for nursing is therefore questionable, most of all if an interdisciplinary implementation is the actual aim.

Aged↗
PubMed2001

Dynamic characteristics and underlying mechanisms of renal blood flow autoregulation in the conscious dog.

The time course of the autoregulatory response of renal blood flow (RBF) to a step increase in renal arterial pressure (RAP) was studied in conscious dogs. After RAP was reduced to 50 mmHg for 60 s, renal vascular resistance (RVR) decreased by 50%. When RAP was suddenly increased again, RVR returned to baseline with a characteristic time course (control; n = 15): within the first 10 s, it rose rapidly to 70% of baseline (response 1), thus already comprising 40% of the total RVR response. Thereafter, it increased at a much slower rate until it started to rise rapidly again at 20-30 s after the pressure step (response 2). After passing an overshoot of 117% at 43 s, RVR returned to baseline values. Similar responses were observed after RAP reduction for 5 min or after complete occlusions for 60 s. When tubuloglomerular feedback (TGF) was inhibited by furosemide (40 mg i.v., n = 12), response 1 was enhanced, providing 60% of the total response, whereas response 2 was completely abolished. Instead, RVR slowly rose to reach the baseline at 60 s (response 3). The same pattern was observed when furosemide was given at a much higher dose (>600 mg i.v.; n = 6) or in combination with clamping of the plasma levels of nitric oxide (n = 6). In contrast to RVR, vascular resistance in the external iliac artery after a 60-s complete occlusion started to rise with a delay of 4 s and returned to baseline within 30 s. It is concluded that, in addition to the myogenic response and the TGF, a third regulatory mechanism significantly contributes to RBF autoregulation, independently of nitric oxide. The three mechanisms contribute about equally to resting RVR. The myogenic response is faster in the kidney than in the hindlimb.

Animals↗
PubMed2000

Large vasodilatations in skeletal muscle of resting conscious dogs and their contribution to blood pressure variability.

Large (up to +400 %) transient ( approximately 20 s) increases of blood flow were observed in the external iliac arteries of resting conscious dogs (n = 10) in the absence of major alerting or muscular activity. At the same time arterial pressure (AP) fell slightly while heart rate (HR) rose. The vasodilatations were resistant to atropine, ganglionic, beta-adrenergic and NO-synthase inhibition, but were suppressed by spinal or general anaesthesia. Vasodilatations of similar appearance were elicited by an alerting sound; these were abolished by atropine. The spontaneous vasodilatations occurred simultaneously and their magnitudes were well correlated between both legs, but were not correlated to the amount of concomitant activation of the surface electromyogram. The duration of this activation almost never outlasted 10 s. The reactive hyperaemia observed after a total occlusion of the artery even for 16 s was not large enough to explain the size of the spontaneous vasodilatations. Occlusion during peak flow of the vasodilatations did not affect the size of the reactive hyperaemia. Spectral analysis made separately for data segments with and without vasodilatation revealed that the vasodilatations substantially enhanced the variability of AP and HR at frequencies below approximately 0.1 Hz. In conclusion, large coordinated skeletal muscle vasodilatations were identified in resting conscious dogs, which are initiated neurally, but not by sympathetic-cholinergic or nitroxidergic fibres and which do not show any clear correlation to muscular contraction. The vasodilatations substantially affect the regulation of skeletal muscle blood flow and explain a significant portion of AP and HR variability.

Animals↗
PubMed2000

[Quantitative recording of renal function with magnetic resonance tomography].

AIM: To show the potential of various methods in magnetic resonance imaging for the evaluation of renal function. MATERIAL AND METHODS: A combined assessment of renal morphology, renal hemodynamics and function is proposed. Various techniques are explained, including multiphasic 3D gadolinium MR angiography, MR phase-contrast flow measurements, quantitative perfusion measurements with intravascular contrast agents, and MR renography and MR urography. The use of these techniques is demonstrated for renovascular diseases. RESULTS: The combined use of these techniques allows renal artery stenosis to be accurately detected and evaluation of renal blood flow, perfusion, glomerular filtration rate, and renal excretion. Based on true quantitative parameters, the hemodynamic and functional significance of the stenosis can be assessed. Renovascular diseases can be differentiated from renoparenchymal disease. CONCLUSION: For the assessment of renal function, functional magnetic resonance imaging techniques are an important alternative to nuclear medicine. The predictive value regarding the effect of revascularization is currently under investigation.

Contrast Media↗
PubMed2000

Autonomic cardiovascular control in conscious mice.

Autonomic cardiovascular control was characterized in conscious, chronically catheterized mice by spectral analysis of arterial pressure (AP) and heart rate (HR) during autonomic blockade or baroreflex modulation of autonomic tone. Both spectra were similar to those obtained in humans, but at approximately 10x higher frequencies. The 1/f relation of the AP spectrum changed to a more shallow slope below 0.1-0.2 Hz. Coherence between AP and HR reached 0.5 or higher below 0.3-0.4 Hz and also above 2.5 Hz. Muscarinic blockade (atropine) or beta-adrenergic blockade (atenolol) did not significantly affect the AP spectrum. Atropine reduced HR variability at all frequencies, but this effect waned above 1 Hz. beta-Adrenergic blockade (atenolol) slightly enhanced the HR variability only above 1 Hz. alpha-Adrenergic blockade (prazosin) reduced AP variability between 0.05 and 3 Hz, most prominently at 0. 15-0.7 Hz. A shift of the autonomic nervous tone by a hypertensive stimulus (phenylephrine) enhanced, whereas a hypotensive stimulus (nitroprusside) depressed AP variability at 1-3 Hz; other frequency ranges of the AP spectrum were not affected except for a reduction below 0.4 Hz after nitroprusside. Variability of HR was enhanced after phenylephrine at all frequencies and reduced after nitroprusside. As with atropine, the reduction with nitroprusside waned above 1 Hz. In conclusion, in mice HR variability is dominated by parasympathetic tone at all frequencies, during both blockade and physiological modulation of autonomic tone. There is a limitation for further reduction but not for augmentation of HR variability from the resting state above 1 Hz. The impact of HR on AP variability in mice is confined to frequencies higher than 1 Hz. Limits between frequency ranges are proposed as 0.15 Hz between VLF (very low frequency range) and LF (low frequency range) and 1.5 Hz between LF and HF (high frequency range).

Adrenergic beta-Antagonists↗
PubMed1999

[MRI of the kidneys. New diagnostic strategies].

AIM: New diagnostic strategies for evaluation of the kidney by fast MR imaging techniques. MATERIAL AND METHODS: A comprehensive morphologic and functional evaluation of the kidney is proposed using fast MR imaging of renal morphology, multiphase 3D gadolinium MR angiography, MR urography and MR flow measurements. A single MR examination is designed to grade renovascular disease and assess the hemodynamic and functional significance, detect and characterize renal lesions and evaluate the urinary tract. RESULTS: The combined analysis of morphologic and functional data allows reliable assessment of renal artery stenosis, benign and malignant renal masses and diseases of the renal collecting system and ureters, as well as congenital abnormalities in good agreement to the results of conventional imaging modalities. The improved tissue contrast and additional functional information compensates for the disadvantage of a lower spatial resolution. CONCLUSION: Combined morphologic and functional MR examination represents a reliable, non-invasive and cost-effective alternative imaging modality for comprehensive diagnostic evaluation of renal disease.

Acute Kidney Injury↗
PubMed1999

Aortic pressure-diameter relationship assessed by intravascular ultrasound: experimental validation in dogs.

Intravascular ultrasound (IVUS) has emerged as an important diagnostic method for evaluating vessel diameter and vessel wall motion. To evaluate the validity of IVUS in assessing changes in the pressure-diameter relationship we compared measurements of abdominal aortic diameters derived from IVUS with those simultaneously obtained at the same site using implanted sonomicrometers in five chronically instrumented conscious dogs and in seven acutely instrumented anesthetized dogs. Five hundred eighty beats were analyzed to obtain peak systolic and end-diastolic diameters and to calculate aortic compliance at different blood pressure levels induced either by an aortic pneumatic cuff or by intravenous injections of nitroglycerin or norepinephrine. IVUS agreed closely with sonomicrometer measurements at different blood pressure levels. However, IVUS slightly but significantly underestimated aortic diameters by 0.6 +/- 0.7 mm for systolic diameters (P < 0.001) and by 0.7 +/- 0.6 mm for diastolic diameters (P < 0.001) compared with the sonomicrometer measurements. We conclude that IVUS is a feasible and reliable method to measure dynamic changes in aortic dimensions and has the potential to provide ready access to assess aortic compliance in humans.

Animals↗
PubMed1999

Contribution of endothelin to renal vascular tone and autoregulation in the conscious dog.

Exogenous endothelin-1 (ET-1) is a strong vasoconstrictor in the canine kidney and causes a decrease in renal blood flow (RBF) by stimulating the ETA receptor subtype. The aim of the present study was to investigate the role of endogenously generated ET-1 in renal hemodynamics under physiological conditions. In six conscious foxhounds, the time course of the effects of the selective ETA receptor antagonist LU-135252 (10 mg/kg iv) on mean arterial blood pressure (MAP), heart rate (HR), RBF, and glomerular filtration rate (GFR), as well as its effects on renal autoregulation, were examined. LU-135252 increased RBF by 20% (from 270 +/- 21 to 323 +/- 41 ml/min, P < 0.05) and HR from 76 +/- 5 to 97 +/- 8 beats/min (P < 0. 05), but did not alter MAP, GFR, or autoregulation of RBF and GFR. Since a number of interactions between ET-1 and the renin-angiotensin system have been reported previously, experiments were repeated during angiotensin converting enzyme (ACE) inhibition by trandolaprilat (2 mg/kg iv). When ETA receptor blockade was combined with ACE inhibition, which by itself had no effects on renal hemodynamics, marked changes were observed: MAP decreased from 91 +/- 4 to 80 +/- 5 mmHg (P < 0.05), HR increased from 85 +/- 5 to 102 +/- 11 beats/min (P < 0.05), and RBF increased from 278 +/- 23 to 412 +/- 45 ml/min (P < 0.05). Despite a pronounced decrease in renal vascular resistance over the entire pressure range investigated (40-100 mmHg), the capacity of the kidneys to autoregulate RBF was not impaired. The GFR remained completely unaffected at all pressure levels. These results demonstrate that endogenously generated ET-1 contributes significantly to renal vascular tone but does not interfere with the mechanisms of renal autoregulation. If ETA receptors are blocked, then the vasoconstrictor effects of ET-1 in the kidney are compensated for to a large extent by an augmented influence of ANG II. Thus ET-1 and ANG II appear to constitute a major interrelated vasoconstrictor system in the control of RBF.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1999

Tonic and phasic influences of nitric oxide on renal blood flow autoregulation in conscious dogs.

The aim of this study was to investigate the influence of the mean level and phasic modulation of NO on the dynamic autoregulation of renal blood flow (RBF). Transfer functions were calculated from spontaneous fluctuations of RBF and arterial pressure (AP) in conscious resting dogs for 2 h under control conditions, after NO synthase (NOS) inhibition [NG-nitro-L-arginine methyl ester hydrochloride (L-NAME)] and after L-NAME followed by a continuous infusion of an NO donor [S-nitroso-N-acetyl-DL-penicillamine (SNAP)]. After L-NAME (n = 7) AP was elevated, heart rate (HR) and RBF were reduced. The gain of the transfer function above 0.08 Hz was increased, compatible with enhanced resonance of the myogenic response. A peak of high gain around 0.03 Hz, reflecting oscillations of the tubuloglomerular feedback (TGF), was not affected. The gain below 0.01 Hz, was elevated, but still less than 0 dB, indicating diminished but not abolished autoregulation. After L-NAME and SNAP (n = 5), mean AP and RBF were not changed, but HR was slightly elevated. The gain above 0.08 Hz and the peak of high gain at 0.03 Hz were not affected. The gain below 0.01 Hz was elevated, but smaller than 0 dB. It is concluded that NO may help to prevent resonance of the myogenic response depending on the mean level of NO. The feedback oscillations of the TGF are not affected by NO. NO contributes to the autoregulation below 0.01 Hz due to phasic modulation independent of its mean level.

Animals↗