Transient Attenuation Research Articles

In-situ laser spectroscopy of CO, Ch4, and H2O in a particle laden laboratory-scale fluidized bed combustor

The pyrolysis, devolatilization and char combustion of bituminous coal and biomass (beechwood, firwood) were investigated in a laboratory-scale fluidized bed combustor by tunable diode laser spectroscopy. Individual fuel particles were suspended in the freeboard of the unit. The bed temperature was 800 ?C, the oxygen partial pressure 0 to 20 kPa (0-10 vol.%). Two Fabry Perot type tunable near infrared diode lasers were deployed for quantitative in-situ species concentration measurements. CH4 and CO were measured simultaneously during devolatilization and char combustion in-situ 10 mm above the surface of the fuel particles as well as H2O using laser spectroscopy. Sand particles were passing the probing laser beam path. Besides the resonant absorption of the laser light by CO, CH4 and H2O severe and strongly transient non-resonant attenuation by partial blocking of the beam and beam steering effects occurred. By wavelength tuning the two laser sources, species concentrations could be determined. The measured absorbances had to be corrected for the real temperature measured at the position of the probing laser beam. In addition, CO, CO2 and O2 were determined ex-situ by con ventional methods. A spatial profile inside the FBC of major species (CH4, CO, CO2, O, H, OH) was calculated using a chemical kinetics program for a single fuel particle in a plug flow reactor geometry. The results were compared to the experimental findings. Good agreement was found. Tunable diode laser spectroscopy was found to be an apt method of determining quantitative species concentrations of multiple gases in a high temperature multi phase environment.

CT Spectrum of Transient Peritumoral Hyperemia after Radiofrequency Thermal Ablation of Hepatic Tumors

Purpose: To determine the incidence and pattern of peritumoral hyperemia at CT after radiofrequency thermal ablation of hepatic tumors, as well as its correlation with local marginal recurrence. Materials and Methods: Forty-five tumor nodules in 28 patients with hepatocellular carcinoma (n=34) or metastasis (n=11) were treated by RF thermal ablation. Serial follow-up contrast- enhanced CT scans were reviewed by three radiologists for 1) the presence, 2) the morphological characteristics [circumferential, THAD (transient hepatic attenuation difference), nodular form], and 3) the temporal course (acute, persistent, delayed onset pattern) of peritumoral hyperemia after RF thermal ablation. These findings were correlated with the frequency of recurrence at the margin of the treated tumors. Results: The frequency of acute hyperemia observed on immediate follow-up CT scans after RF ablation was 71% (32/45). There was the local recurrence in nine of 32 tumors (28%) with hyperemia and in one of 13 (8%) without hyperemia (p>0.05). Among 32 tumors, the circumferential form was observed in 22 (69%); the THAD form in eight (25%); and the nodular form in two (6%). Marginal recurrence was noted in five of 22 tumors circumferential tumors (23%), in three of eight (38%) with the THAD form, and in one of two (50%) which were nodular. Among 32 nodules, an acute transient pattern was noted in 21 (66%), a persistent pattern in nine (28%), and a nodular pattern in two (6%). There was marginal recurrence in two (10%) of 21 tumors with acute transient hyperemia, in six (67%) of nine with persistent hyperemia, and in both tumors with delayed-onset hyperemia. There was significant correlation between the pattern of persistent/delayed-onset hyperemia and marginal tumor recurrence of (p=0.001). Conclusion: Although peritumoral hyperemia after RF thermal ablation therapy is a frequent transient finding at follow-up imaging studies, its temporal pattern may help detect early marginal tumor recurrence.

Comparison of effects of spinal manipulation and massage on motoneuron excitability

The purpose of this study was to compare the magnitude and duration of motoneuron inhibition occurring as a sequel to spinal manipulation or paraspinal and limb massage. The physiologic mechanisms involved in spinal manipulative therapy and massage therapy are largely unknown. One possible hypothesis is based upon the theory that these two distinct and different modalities may attenuate the activity of alpha motoneurons. Both modalities have been reported to produce short-term inhibition of motoneurons. Asymptomatic volunteers were randomly assigned to either a spinal manipulation, massage, or control group. Baseline tibial nerve H-reflex amplitudes were obtained prior to the application of either lumboscaral spinal manipulation or paralumbar and limb massage. Post-interventional H-reflex recordings were recorded immediately following the application of either modality. Spinal manipulation significantly (p < 0.05) attenuated alpha motoneuronal activity immediately post-therapy, as measured by the amplitude of the tibial nerve H-reflex. Massage subjects exhibited no significant reduction in motoneuronal activity immediately following administration. Spinal manipulation produced a transient attenuation of alpha motoneuronal excitability. Paraspinal and limb massage did not inhibit the motoneuron pool as measured immediately post-therapy. These findings support the supposition that spinal manipulation procedures lead to short-term inhibitory effects on motoneuron excitability to a greater magnitude than massage.

Temporal CT changes after hepatic and renal interstitial radiotherapy in a canine model.

The purpose of this work was to define the temporal CT characteristics of hepatic and renal ablation following point-source radioablation utilizing a low energy, photon X-ray source emitted from a miniature probe. Twelve mongrel dogs underwent each of three hepatic and two renal point-source radiation ablations. Animals underwent serial, dual phase, spiral CT scans and were killed at 1, 3, and 6 months after treatment. Ablative lesions were clearly visible at 1 month following therapy and consistently diminished in size over the 6 months of follow-up. Lesion size tended to be proportional to dose delivered. Both hepatic and renal lesions were low in attenuation with frequent rim enhancement that diminished over time. Hepatic lesions frequently showed transient hepatic attenuation differences (THADs). Lesion size appeared independent of proximity to vessels. Following hepatic or renal interstitial radiotherapy, lesions are generated that are similar in CT appearance to those produced by other ablative techniques. The presence of rim or THAD enhancement can be seen early on as part of the normal tissue-healing response.

Multiphase helical CT findings after percutaneous ablation procedures for hepatocellular carcinoma.

Multiple-phase helical computed tomography (CT) has been regarded as the method of choice in the evaluation of patients with hepatocellular carcinoma (HCC) treated by nonsurgical procedures. The aim of this article was to report our experience in the assessment of nodular and parenchymal changes recognizable after various percutaneous ablation therapies. We reviewed the studies of 116 consecutive patients with HCC treated with multisession percutaneous ethanol injection (56 patients, 98 nodules), single-session percutaneous ethanol injection (14 patients, 31 nodules), radiofrequency thermal ablation (32 patients, 48 nodules), and interstitial laser photocoagulation (14 patients, 25 nodules). CT had been performed 3-28 days after the last session (mean = 18 days) with unenhanced helical acquisition and with contrast-enhanced double- or triple-phase helical acquisition. Persisting neoplastic tissue was identified within 54.5% of the nodules. It was located centrally in 4.5% of these nodules, peripherally in 11%, and eccentrically in 84.5%, and its shape was crescent in 58%, globular in 24.5%, and other in 16%. On arterial phase scans, viable tumor was hyperdense in 97% of the lesions and isodense in 3%; on portal phase scans, the tumor was hyperdense in 20%, isodense in 28%, and hypodense in 52%; on delayed phase scans, the tumor was consistently hypodense. Tumor necrosis was always hypodense on contrast-enhanced scans. On unenhanced images, 7.4% of the nodules were undetectable. Nodule diameter appeared as unchanged in 53% of the nodules and as larger in 47%; its shape was unchanged in 54% and modified in 46%; its margins were unchanged in 36% and modified in 64%. A rim of granulation tissue was detected around 15% of the nodules, and a perilesional transient attenuation difference was detected in 21%. Perihepatic effusion was seen in 13% of the patients, segmental biliary duct dilation and local atrophy each in 9%, arterioportal fistula in 6%, portal vein thrombosis, subcapsular collection and pleural effusion each in 7%, hepatic infarction in 5%, and inferior vena cava thrombosis in 2%. Percutaneous ablation of HCC may cause several changes. Knowledge of their CT appearance is mandatory to correctly assess and manage this tumor.

Steady-state transfer and depletion kinetics of mercury from amalgam fillings

In 29 volunteers with a low amalgam load, the number of amalgam-covered tooth surfaces and the occlusal area of the fillings were determined. Before and at select times after removal of all amalgams, concentrations of total mercury were measured by cold-vapor atomic absorption in plasma and erythrocytes as well as in urine together with the excretion rate. Absorbed daily doses were estimated from intraoral Hg emission by two separate methods. The transfer of Hg from the fillings via the oral cavity and blood to urinary excretion was evaluated according to the most representative combination of parameters. This consisted of occlusal area (1), absorbed dose (2), Hg concentration in plasma (3) and urinary excretion (4). Pairwise correlation coefficients were 0.49 for parameters 1 vs. 2, and 0.75 each for parameters 2 vs. 3 and 3 vs. 4. Within 9 days after removal of the fillings, a transient increase in Hg levels was observed in plasma only; in the group without a rubber dam, concentrations increased significantly above pre-removal values at days 1 and 3, whereas they decreased significantly below pre-removal values at day 30 in the rubber-dam group and at day 100 in both groups. Excretion rates decreased significantly at day 100 in the protected group. Peak plasma-Hg was 0.6 ng/ml on average at day 1 and decreased with halftimes of 3 and 43 days in subjects protected by a rubber dam. The results indicated that concentrations of total mercury in plasma responded rapidly to changes in the amalgam status and reflected the actual absorption most reliably. Notably, plasma-Hg levels were sensitive enough to detect a transient attenuation of the additional exposure after using a rubber dam during the removal of only a few fillings. However, being small in magnitude and lasting 100 days at best, the rubber-dam effect had minor toxicological relevance.

Effects of vitamin E on chronic and acute endothelial dysfunction in smokers

OBJECTIVESThe aims of this study were to determine whether chronic or acute impairment of flow mediated vasodilation (FMD) in the brachial artery of smokers can be restored or preserved by the antioxidant vitamin E.BACKGROUNDTransient impairment of endothelial function after heavy cigarette smoking and chronic endothelial dysfunction in smokers result at least in part from increased oxidative stress.METHODSWe studied 22 healthy male smokers (mean ± SD, 23 ± 9 cigarettes per day) randomly assigned to receive either 600 IU vitamin E per day (n = 11, age 28 ± 6 years) or placebo (n = 11, age 27 ± 6 years) for four weeks and 11 age-matched healthy male nonsmokers. Flow mediated vasodilation and endothelium-independent, nitroglycerin-induced dilation were assessed in the brachial artery using high resolution ultrasound (7.5 MHz) at baseline and after therapy. Subjects stopped smoking 2 h before the ultrasound examinations. At the end of the treatment period, a third scan was obtained 20 min after smoking a cigarette (0.6 mg nicotine, 7 mg tare) to estimate transient impairment of FMD.RESULTSFlow mediated vasodilation at baseline was abnormal in the vitamin E (5.3 ± 3.8, p < 0.01) and in the placebo group (6.4 ± 3.5, p < 0.05) compared with nonsmoking controls (11.6 ± 4.7). Using a two-way repeated measures analysis of variance (ANOVA) to examine the effects of vitamin E on FMD, we found no effect for the grouping factor (p = 0.5834) in the ANOVA over time but a highly significant difference with respect to time (p = 0.0065). The interaction of the time factor and the grouping factor also proved to be significant (p = 0.0318). Flow mediated vasodilation values remained similar after treatment for four weeks in both groups but declined faster after smoking a cigarette in subjects taking placebo compared with those receiving vitamin E (p values from successive differences for the time/group factor: 0.0001/0.0017). The transient attenuation of FMD (calculated as the percent change in FMD) was related to the improvement of the antioxidant status, estimated as percent changes in thiobarbituric acid-reactive substances (r = −0.67, p = 0.0024). Nitroglycerin-induced dilation did not differ between study groups at baseline or after therapy.CONCLUSIONSThese results demonstrate that oral supplementation of vitamin E can attenuate transient impairment of endothelial function after heavy smoking due to an improvement of the oxidative status but cannot restore chronic endothelial dysfunction within four weeks in healthy male smokers.

Effect of rubber dam on mercury exposure during amalgam removal.

It was the aim of this investigation to treat 20 volunteers with maximally 5 amalgam fillings by the same comprehensive protocol in which all removals with (n = 8) and without (n = 12) rubber dam had been performed within a few months. Nine amalgam-related parameters indicated a close matching of both groups before removal. In the group without rubber dam, mercury (Hg) levels in plasma increased significantly above preremoval values at days 1 and 3 after removal; they decreased significantly below preremoval values at day 30 in the rubber-dam group and at day 100 in both groups. Excretion rates did not increase significantly in either group, but decreased significantly at day 100 in the protected group. Peak plasma-Hg was 0.6 ng/mL on average at day one and decreased with halftimes of 3 and 43 d in subjects protected by rubber dam. The results indicated that concentrations of total mercury in plasma responded rapidly to changes in the amalgam status and reflected the actual absorption most reliably. Notably, plasma-Hg levels were sensitive enough to detect a transient attenuation of the additional exposure by using rubber dam during the removal of only a few fillings. However, being small in magnitude and lasting 100 d at best, the rubber-dam effect had minor toxicological relevance.

Hepatic perfusion abnormalities in acute pancreatitis: CT appearance and clinical importance.

The purpose of the present study was to describe the computed tomography (CT) appearances of transient hepatic attenuation differences (THADs) in patients with acute pancreatitis and to discuss the mechanism of THAD. Two-phase dynamic CT images of 28 patients with acute pancreatitis were reviewed. Among them, THAD was seen in nine patients. All patients underwent ultrasonography, and four patients with THAD underwent surgery. Three types of THAD (THAD adjacent to the gallbladder in five of 28 patients, THAD with left lobar distribution in three of 28, wedge-shaped THAD in one of 28) were seen on the two-phase dynamic CT scans of patients with acute pancreatitis. In five patients, THAD disappeared when acute pancreatitis had subsided. THAD in acute pancreatitis is probably caused by increased arterial blood flow attributable to the inflamed lobe of the liver or the inflamed gallbladder. THAD in acute pancreatitis should not be confused with primary liver abnormalities.

Robust adaptive control of robots with arbitrary transient performance and disturbance attenuation

We consider the tracking problem for robot manipulators with unknown and (possibly) time-varying parameters, which are subject to bounded disturbances. We provide a state feedback adaptive control algorithm which guarantees arbitrary transient performance as well as arbitrary disturbance attenuation. If the disturbances vanish and the parameters remain constant, the proposed controller achieves asymptotic tracking.

Spectrum of transient hepatic attenuation differences in biphasic helical CT.

A, Helical CT scan obtained in hepatic arterial phase shows large hemangioma in left lobe of liver. Liver parenchyma adjacent to lesion (arrowheads) shows early enhancement B, Helical CT scan obtained in portal venous phase reveals that area of early enhancement has become isodense. Left portal vein is compressed by lesion and is faintly opacified (arrowheads). C, Superior mesenteric angiogram shows only main and right portal veins. Left lobe counterpart is not revealed.

Inhibitors of protein synthesis preserve the N-methyl-D-aspartate-induced cerebral arteriolar dilation after ischemia in piglets.

BACKGROUND AND PURPOSE--Cerebral arteriolar dilation to N-methyl-D-aspartate (NMDA) is a neuronally mediated process that is sensitive to cerebral ischemia. We tested the hypothesis that pretreatment with transcription or translation inhibitors preserves the vascular response to NMDA after global cerebral ischemia. METHODS--Pial arteriolar diameters were measured in anesthetized piglets by use of a closed cranial window and intravital microscopy. Arteriolar responses to NMDA (10(-5) and 10(-4) mol/L) were measured before and 1, 2, and 4 hours after 10 minutes of ischemia. Ischemia was induced by increasing intracranial pressure. Subgroups were pretreated with vehicle, topical actinomycin D (Act-D) 10(-5) or 10(-6) mol/L, or intravenous cycloheximide (CHX) 1.0 or 0.3 mg/kg 15 minutes before ischemia. The effects of Act-D and CHX on vascular responses to NMDA without preceding ischemia were also examined. RESULTS--In the vehicle group, arteriolar responses to NMDA were clearly attenuated 1 hour after ischemia but returned to baseline at 2 to 4 hours. Preischemic compared with 1 hour postischemic arteriolar dilation to NMDA was 10+/-2% versus 1+/-0% at 10(-5) mol/L and 40+/-4% versus 20+/-4% at 10(-4) mol/L NMDA (mean+/-SEM; both P<0.05, n=7). In contrast, pretreatment with Act-D resulted in preservation of the arteriolar responses to NMDA 1 hour after ischemia. For 10(-6) mol/L (n=5) of Act-D, dilations were 6+/-2% versus 6+/-2% at 10(-5) mol/L and 51+/-9% versus 39+/-10% at 10(-4) mol/L of NMDA. For 10(-5) mol/L (n=5) of Act-D, arterioles dilated by 7+/-2% versus 7+/-2% at 10(-5) mol/L and 38+/-4% versus 35+/-4% at 10(-4) mol/L NMDA. Similarly, CHX preserved NMDA-induced vasodilation. For 0.3 mg/kg of CHX (n=5), dilations were 8+/-2% versus 8+/-1% at 10(-5) mol/L and 39+/-4% versus 28+/-6% at 10(-4) mol/L NMDA. For 1.0 mg/kg of CHX (n=5), arterioles dilated by 10+/-2% versus 6+/-2% at 10(-5) mol/L and 37+/-7% versus 35+/-6% at 10(-4) mol/L NMDA. In experiments without ischemia, NMDA-induced vasodilation before and 85 minutes after administration of Act-D or CHX was not significantly different. CONCLUSIONS--Vascular responses of cerebral arterioles to NMDA after ischemia are preserved by pretreatment with either Act-D or CHX. Without preceding ischemia, Act-D and CHX do not potentiate neuronal-vascular responses to NMDA. Our results suggest that continued or augmented protein synthesis is involved in the transient attenuation of NMDA-induced dilation during the early reperfusion phase and that inhibitors of protein synthesis may protect neurons against ischemic stress.

Presentation of an Ethanol-Paired Stimulus Complex Alters Response Patterns During Extinction

It has been hypothesized that environmental stimuli previously paired with ethanol consumption play a role in excessive ethanol intake. This study examined the ability of orally self-administered ethanol to establish a tone-light stimulus complex as a conditioned reinforcer (CSR). Male Long–Evans rats were trained to orally self-administer 10% ethanol (10E) using the sucrose-substitution procedure. During training, a tone–light stimulus complex was paired with ethanol presentation in a stimulus complex paired (SC-paired) group but not in a control group. Responding during extinction in the presence and absence of the stimulus complex was then examined. Following the initiation of ethanol self-administration, 10E maintained greater responding in the SC-paired group compared to the control group. When the stimulus complex was presented contingent on responding during extinction, the rate of extinction was slightly attenuated in the SC-paired group but not in the control group. The altered rate of extinction in the SC-paired group was characterized by: 1) a slight decrease in total session responding over successive days of extinction and 2) a transient attenuation of extinction burst response rate during the first extinction session. These data suggest the stimulus complex could function as a weak CSR, but overall its ability to maintain lever pressing was minimal.

Minor role of a Ca2+-depleted sarcoplasmic reticulum in heterologous desensitization of smooth muscle to K+.

Exposure of porcine carotid artery smooth muscle (PCASM) to histamine was followed by a large reduction in the rate of force generation in response to 40 mM KCl. This was shown to be a manifestation of slow attainment of a steady-state myoplasmic Ca2+ concentration ([Ca2+]i). We hypothesized that if net transsarcolemmal Ca2+ flux into the depolarized PCASM cells is the same before and after a desensitizing histamine treatment, then the transient attenuation of the increase in [Ca2+]i may be due to accelerated uptake of Ca2+ by a partially depleted sarcoplasmic reticulum (SR) acting as a Ca2+ sink or superficial buffer barrier. We tested this hypothesis by eliciting responses of "desensitized PCASM" to 40 mM KCl in the presence of cyclopiazonic acid (CPA), an SR Ca2+-ATPase inhibitor. Contractions of CPA-treated tissues were attenuated less than those of tissues not treated with CPA, but they were not abolished. CPA-insensitive mechanism(s) dominated the desensitization. We conclude that histamine pretreatment reduced net transsarcolemmal Ca2+ flux into PCASM in response to 40 mM KCl.

Generalization of Impedance Matching to Nonlinear Dynamics of Robot Tasks

This paper aims at generalizing the concept of impedance matching to nonlinear circuits that express nonlinear dynamics of robot tasks, where a tool endpoint (or fingertip) with soft material presses a rigid and fixed object or environment. Under such a situation that characteristics of reproducing force of the elastic material with respect to displacement is nonlinear and unknown, impedance control is established by constructing a negative feedback connection of two hyperstable blocks. Then, the minimum upper-bound of the average power of force error under the existence of measurement noises of both displacement and force is derived in a sense of H-infinity disturbance attenuation, which corresponds to a generalization of the well-known theorem of maximum power transfer for impedance matching of linear electric circuits. Choice of design parameters is discussed from the viewpoint of better matching of two passive blocks to attain optimal transient response and attenuation of the effect of disturbances.

Attenuation of single event induced pulses in CMOS combinational logic

Results are presented of a study of SEU generated transient pulse attenuation in combinational logic structures built using common digital CMOS design practices. SPICE circuit analysis, heavy ion tests, and pulsed, focused laser simulations were used to examine the response characteristics of transient pulse behavior in long logic strings. Results show that while there is an observable effect, it cannot be generally assumed that attenuation will significantly reduce observed circuit bit error rates.

Internal Friction/Attenuation in a β‐Spodumene Glass‐Ceramic

Transient creep and attenuation (internal friction) of a β‐spodumene glass‐ceramic has been examined. Four‐point flexural creep tests have been performed at high tempera‐ture(T = 925°‐1000°C) and modest stress levels (σl,max= 7‐25 MPa). The flexural creep response of the glass‐ceramic is characterized by a large decelerating transient that precedes the establishment of a steady state. The creep response is transformed via a numerical algorithm to give the attenuation spectrum. In addition, low‐stress (2.5‐30 MPa), subresonant‐frequency (10 −5 Hz ≤ f ≤ 1 Hz), com‐pression‐compression attenuation experiments have been performed. A first‐order thermodynamic analysis of the effect of effective pressure on the volume fraction of re‐sidual glass suggests that the dilatational process that is associated with the flexural deformation mode should be characterized by a single loss mechanism. The predictions that are available from the flexural creep tests, as well as those that have been directly measured in experiments, in‐dicate that attenuation behavior is insensitive to both fre‐quency and temperature and exhibits a characteristic band of absorption. The weak frequency dependence of this an‐elastic response is well‐characterized by a power law of the form Q−1χfα, where 0.15 ≥ a ≥ 0.3, which suggests a physical mechanism that possesses a distribution of relax‐ation times. A plausible explanation exists in the fluid‐mechanics description of deformation‐induced melt migra‐tion, in which the crystalline β‐spodumene “matrix” undergoes compaction or dilatation while the residual glass phase, which forms an interpenetrative network along grain triple junctions of the matrix, flows: the evolution with time of the compacted (and/or dilated) layer thickness of the deforming matrix produces a distribution of compli‐ances.

Long-term effects of neonatal axoplasmic transport attenuation on the organization of the rat's trigeminal system

The current study examined the long-term effects of infraorbital nerve (ION) axoplasmic transport attenuation with vinblastine on the organization of trigeminal (V) primary afferents and central vibrissae-related patterns. Retrograde tracing and single unit recording were used to evaluate the innervation of vibrissae follicles in adult (P > 60) rats that sustained application of vinblastine to the ION at birth. Single units recorded from vinblastine-treated animals yielded responses to deflection of a single vibrissa, and a significantly (P < 0.001) higher percentage of these cells (85.7%) showed rapidly adapting responses compared with normal rats (42.2%). Retrograde tracing revealed a qualitatively and normal distribution of V ganglion cells innervating A-row and E-row vibrissae follicles in vinblastine-treated rats. Transganglionic tracing with horseradish peroxidase (HRP) demonstrated a qualitatively and quantitatively normal somatotopic organization of vibrissae follicle input to V nucleus principalis (PrV) and V subnucleus interpolaris (SpI) in the vinblastine-treated animals. Despite the nearly normal mapping of V ganglion cell axons onto the vibrissae follicles and brainstem, staining for either cytochrome oxidase (CO) or parvalbumin failed to reveal vibrissae-related patterns in PrV, SpI, or the magnocellular portion of V subnucleus caudalis in these animals. Labelling of thalamocortical afferents with HRP and staining for CO also failed to reveal a cortical vibrissae-related pattern in the vinblastine-treated rats. The present results indicate that although transient attenuation of axoplasmic transport with vinblastine has limited effects on the peripheral and central projections of surviving V primary afferents, it permanently disrupts the normal development and maintenance of central vibrissae-related patterns.

Cerebral embolization is reduced with use of the stab technique for aortic cannulation compared with the side-clamp technique

heart rate response can be similar to that of the transplanted heart, 2 the attenuated heart rate response to exercise early after the maze procedure may be caused by denervation of the sinoatrial node as a result of multiple incisions in the atrial wall. If the attenuated heart rate response to exercise early after the maze procedure was caused by denervation of the sinoatrial node, recovery of the heart rate response late after operation can be explained by the time course of reinnervation of the sinoatrial node. 3 ANPs have been extracted from atrial myocytes of mammals, including human beings, and play an important role in natriuresis and vasodilation. Because ANP was excreted markedly after exercise, the determination of plasma ANP level after exercise allows evaluation of the atrial function as the excretion ability. Percent increase of ANP after exercise was higher in the late phase than that in the control and early phases, which suggests that atrial function of ANP excretion was restored over time. Transient atrial dysfunction occurred in patients with atrial fibrillation who underwent electrical cardioversion, and mechanical atrial function is reduced when conversion is achieved after atrial fibrillation has been sustained for more than a week. 4 The mechanism of atrial dysfunction after elimination of atrial fibrillation is unknown. Shapiro and colleagues 4 postulated that postischemic stunned atrial myocardium, as in the occurrence of ischemia during ventricular fibrillation, may explain this phenomenon. The delayed recovery of atrial function may influence the improved exercise capacity in the late phase after combined treatment consisting of surgical repair for organic heart disease and atrial fibrillation. We conclude that transient attenuation of atrial function, seen as sinoatrial node response, excretion of ANP, and mechanical contractility, occurred in patients after combined treatment with surgical repair for heart disease and the maze procedure for atrial fibrillation. The late recovery of atrial function may improve exercise capacity over time.

Conditioned Blocking in patients with paranoid, non-paranoid psychosis or obsessive compulsive disorder: Associations with symptoms, personality and monoamine metabolism

Conditioned blocking (CB) refers to a delay in learning that a new stimulus, added during learning, has the same consequences as the conditioned stimulus already present. In animals such “learned inattention” depends on monoaminergic and limbic function and, thus, CB performance should be informative on selective information processing impairments found in subgroups of psychotic patients. Attenuated CB in acute schizophrenia has been reported to normalize rapidly. This study examines in young patients the specificity of CB performance to illness, and its associations with symptoms, personality traits and monoaminergic metabolic status. CB was attenuated in psychotic patients with non-paranoid symptoms (NP: n = 12, mean age 17 years) with respect to obsessive-compulsive (OCD: n = 13, mean age 16 years) and healthy subjects (CON, n = 29, mean age 18 years), but only a transient attenuation was observed in paranoid hallucinatory patients (PH: n = 14, mean age 19 years). Outgoing personality traits in CON and OCD subjects correlated with CB. In NP patients attenuated CB was associated with increasing neurotic lability. In PH patients CB correlated positively with “manic” but negatively with psychotic or neurotic scores. The severity of negative symptoms in psychosis and specific negative/positive symptoms in the NP/PH groups was associated with reduced CB. Increased dopamine activity (24-h urine samples) correlated positively with CB, but relative increases of noradrenaline metabolism in NP and serotonin metabolism in OCD patients interfered. In summary, marked psychotic or neurotic traits and some symptom-states were associated with reduced CB. The particular selective processing problems of NP patients may reflect inappropriate NA activity.