A new method to measure regional myocardial time-varying elastance using minute vibration

We developed a new technique to evaluate regional myocardial elastance using minute vibration. In 13 isolated cross-circulated canine hearts, we applied small sinusoidal vibrations of displacement to the left ventricular surface at various frequencies (50-100 Hz). Using the measured displacement and force between the vibrator head and myocardium, we derived myocardial elastance on the basis of the equation of motion for a given moment of the cardiac cycle. Simultaneous solution of the equations of motion at different frequencies yielded a unique value of elastance. Time-varying myocardial elastance increased from diastole (0.028 +/- 0.211 x 10(6) dyn/cm) to systole (0.833 +/- 0.391 x 10(6) dyn/cm). The end-systolic elastance (ees) linearly correlated with end-systolic left ventricular elastance (r = 0.717, P < 0.001) and also with the end-systolic Young's modulus (r = 0.874, P < 0.0001). We also measured ees at both ischemic and nonischemic regions during coronary occlusion. Young's modulus, estimated by normalizing ees by the wall thickness and by the estimated mass, did not change significantly at the nonischemic regions, whereas it decreased significantly from 2.303 +/- 0.556 to 1.173 +/- 0.370 x 10(6) dyn/cm2 at the ischemic region after coronary occlusion (P < 0.005). We conclude that this technique is useful for the quantitative assessment of regional myocardial elastance.

Dynamic transduction properties of in situ baroreceptors of rabbit aortic depressor nerve

We developed a new method for isolating in situ baroreceptor regions of the rabbit aortic depressor nerve (ADN) and estimated the transfer function from pressure to afferent nerve activity in the frequency range of 0.01-5 Hz by a white noise technique. Complete isolation of the baroreceptor area of the right ADN was made in situ by ligation of the innominate artery and the right subclavian and common carotid arteries. We altered the pressure in the isolated baroreceptor area according to a binary quasi-white noise between 80 and 100 mmHg in 12 urethan-anesthetized rabbits. The gain increased two to three times as the frequency of pressure perturbation increased from 0.01 to 2 Hz and then decreased at higher frequencies. The phase slightly led below 0.2 Hz. The squared coherence value was > 0.8 in the frequency range of 0.01-4 Hz. The step responses estimated from the transfer function were indistinguishable from those actually observed. We conclude that the baroreceptor transduction of the ADN is governed by linear dynamics under the physiological operating pressure range.

Experimental myelitis caused by herpes simplex virus type 2 in C57BL/6N and BALB/cN mice

Intraperitoneal and intracranial inoculation of herpes simplex virus type 2 (HSV 2) into BALB/cN and C57BL/6N mice was carried out to induce experimental myelitis. The myelitis was clearly observed in C57BL/6N mice following intraperitoneal inoculation. Within 24 hours before death, the mice showed urinary and rectal incontinence and paraplegia of the hind legs. Randomly distributed, severe necrosis was demonstrated in the spinal cord, mainly at the lower cord. In BALB/cN mice the clinical symptoms were not clearly observed, as the mice died shortly after their onset. Although spinal cord necrosis was more prominent in C57BL/6N mice than BALB/cN mice, brain necrosis was only found in the latter, and not in the former. Both strains of mouse showed marked nuclear pyknosis of the nerve cells and slight nuclear pyknosis of the astrocytes in the brain where HSV 2 antigen was demonstrated immunohistochemically. The antigen was also detected in the necrotic spinal cord. In contrast, intracranial inoculation of the virus into both strains did not cause myelitis. Spinal cord necrosis was not demonstrated and virus DNA was not detected, by PCR, in spinal cord samples. In the brain, however, the virus was demonstrated by both PCR and immunohistochemistry.

Estimation of arterial mechanical properties from aortic and tonometric arterial pressure waveforms

Although arterial mechanical properties have been evaluated using arterial input impedance, the relative difficulty in accurate flow measurement made the value of impedance somewhat limited. To develop an alternative method to evaluate arterial mechanical properties, we analyzed the aortic pressure (AoP)-radial arterial pressure (RAP) relationship because of relative ease in obtaining peripheral pressure waveform by tonometry. In 8 patients we simultaneously recorded aortic root and radial arterial pressure waveforms. We calculated the transfer function from AoP to RAP. We then fitted the transfer function to a model of a lossless uniform elastic tube terminated with a modified Windkessel model. The fact that the model transfer function predicted AoP from RAP waveform with considerable accuracy indicated that the model represented the arterial mechanical properties well. We conclude that we can estimate the arterial mechanical properties by the pressure-pressure transfer function analysis.

Negative inotropic effect of basic fibroblast growth factor on adult rat cardiac myocyte

BACKGROUND

Basic fibroblast growth factor (bFGF) is highly expressed in the myocardium in some cardiac disorders, such as ischemia-reperfusion and cardiac allograft rejection. However, whether bFGF has any effects on myocardial contraction is unknown.

METHODS AND RESULTS

We examined the effects of bFGF on myocardial contractility using isolated adult rat cardiac myocyte preparations. bFGF exerted a direct negative inotropic effect that was concentration and time dependent. The pretreatment of myocytes with a neutralizing anti-bFGF antibody (100 ng/mL) abolished the negative inotropic effects of bFGF (100 ng/mL). Platelet-derived growth factor (12.5 ng/mL) and transforming growth factor-beta (1 ng/mL) did not exert such effects, which indicated that bFGF-induced negative inotropism was considered to be specific for this growth factor. bFGF decreased the peak intracellular Ca2+ transient by 46% during systole. The enhanced production of nitric oxide was unlikely to be responsible for the bFGF-induced negative inotropic effect.

CONCLUSIONS

bFGF, primarily a potent growth promoter, produced acute negative inotropic effects in the adult cardiac myocyte that could have resulted from alterations in intracellular Ca2+ homeostasis. The negative inotropic effect of bFGF may contribute to myocardial dysfunction associated with ischemia-reperfusion injury and heart transplant rejection.

Interstitial norepinephrine level by cardiac microdialysis correlates with ventricular contractility

Although a cardiac microdialysis technique has made it possible to estimate myocardial interstitial norepinephrine (NE) levels, whether such levels reflect the local NE concentration that would regulate ventricular contractility remains unknown. If such levels indicate locally regulating NE concentration, then ventricular contractility should be a unique function of the interstitial NE level regardless of how the latter is altered. To examine this hypothesis, we altered the interstitial NE level endogenously by stimulating the cardiac sympathetic nerves at 1 and 2 Hz while monitoring ventricular contractility. We also altered the interstitial NE level exogenously by means of intravenous NE infusions at 10 and 40 micrograms.kg-1.h-1. The basal NE levels did not differ between the stimulation and the infusion experiments (42.9 +/- 11.2 vs. 40.1 +/- 6.2 pg/ml, means +/- SE). The slopes of regression lines relating ventricular contractility and interstitial NE level were also not different between the two experiments [1.13 +/- 0.20 vs. 1.17 +/- 0.20%/(pg/ml), means +/- SE]. We conclude that the interstitial NE level estimated by cardiac microdialysis reflects the local NE concentration regulating ventricular contractility.

Closed-loop identification of carotid sinus baroreflex open-loop transfer characteristics in rabbits

In the circulatory system, a change in blood pressure operates through the baroreflex to alter sympathetic efferent nerve activity, which in turn affects blood pressure. Existence of this closed feedback loop makes it difficult to identify the baroreflex open-loop transfer characteristics by means of conventional frequency domain approaches. Although several investigators have demonstrated the advantages of the time domain approach using parametric models such as the autoregressive moving average model, specification of the model structure critically affects their results. Thus we investigated the applicability of a nonparametric closed-loop identification technique to the carotid sinus baroreflex system by using an exogenous perturbation according to a binary white-noise sequence. To validate the identification method, we compared the transfer functions estimated by the closed-loop identification with those estimated by open-loop identification. The transfer functions determined by the two identification methods did not differ statistically in their fitted parameters. We conclude that exogenous perturbation to the baroreflex system enables us to estimate the open-loop baroreflex transfer characteristics under closed-loop conditions.

Vagal stimulation decreases left ventricular contractility mainly through negative chronotropic effect

Although an increase in vagal tone is known to slow heart rate (HR), whether it also depresses left ventricular contractility through mechanisms independent of the bradycardic effect remains unknown. The chief aim of this investigation, therefore, was the separation of the observed vagally mediated depression of ventricular contractility into direct and indirect vagal effects, the latter resulting via negative chronotropism. In 12 anesthetized, sympathectomized open-chest rabbits, we measured left ventricular contractility through determination of the end-systolic elastance (Ees). We found that tonic vagal stimulation administered at 0, 5, and 10 Hz decreased both HR (226.9 +/- 39.7, 201.9 +/- 25.7, and 171.3 +/- 18.5 beats/min, respectively; P = 0.0003) and Ees (109.5 +/- 25.7, 85.1 +/- 34.1, and 71.9 +/- 33.1 mmHg/ml, respectively; P = 5 x 10(-6)) in a frequency-dependent fashion. However, we observed that as long as HR was kept constant through fixed-rate atrial pacing, vagal stimulation resulted in little or no change in Ees. Thus we conclude that the negative inotropic effect of vagal stimulation is attributable primarily to its negative chronotropic effect when sympathetic tone is minimal.

omega-Conotoxin GVIA and desipramine insensitive norepinephrine efflux from cardiac sympathetic nerve terminal

Using dialysis technique, prominent accumulation of norepinephrine (NE) in the myocardial interstitial space was observed under local administration of a monoamine oxidase inhibitor (pargyline, 10 mM), and a vesicle uptake inhibitor (reserpine, 10 microM). Accumulation of NE in the myocardial interstitial space was associated with a reduction of dihydroxyphenylglycol levels. Pretreatment with omega-conotoxin GVIA (10 microM) or desipramine (10 microM) did not suppress this response. A brisk increase in dialysate NE levels might occur as a consequence of exocytotic or neurotransporter insensitive efflux of NE.

Inhibition of NO synthesis does not potentiate dynamic cardiovascular response to sympathetic nerve activity

We examined whether the inhibition of nitric oxide (NO) synthesis potentiates the dynamic sympathetic regulation of the cardiovascular system through the baroreflex. In anesthetized rabbits, we imposed random pressure perturbations on the isolated carotid sinuses to evoke random changes in sympathetic nerve activity (SNA). We estimated the transfer functions from SNA to both aortic pressure (AoP) and heart rate (HR). The inhibition of NO synthesis by NG-monomethyl-L-arginine (L-NMMA, 40 mg/ kg) altered neither the transfer function from SNA to AoP nor that from SNA to HR. In contrast, sodium nitroprusside (3-6 micrograms.kg-1.min-1) significantly decreased the steady-state gain (40.3 +/- 11.7% of the control, P < 0.05) of the transfer function from SNA to AoP without affecting the HR responses. We conclude that the basal release of NO may have a role in the tonic blood pressure regulation, whereas it may not be involved in the dynamic sympathetic regulation of AoP or HR through the baroreflex.

Vasodilator effects of adrenomedullin on small pulmonary arteries and veins in anaesthetized cats

1. This study was conducted to determine adrenomedullin (AM) action sites in the pulmonary vascular bed and the relation between its vasodilator effects and vascular tone. Moreover, an examination was made into whether calcitonin gene-related peptide (CGRP) receptors mediate pulmonary vasodilatations induced by AM. To this end, we directly measured internal diameter (i.d.) changes in small pulmonary arteries and veins (100-1100 microns i.d.) by use of an X-ray television system on the in vivo cat lung. 2. Under control (resting vascular tone) conditions, AM injections into the left main pulmonary artery caused dose-related i.d. increases in both small arteries and veins. The mean i.d. increase of the 100-1100 microns arteries (4 +/- 1, 11 +/- 2, and 17 +/- 2% with 0.01, 0.1, and 1 nmol kg-1 AM, respectively) was significantly larger than that for the veins (1 +/- 1, 5 +/- 2, and 7 +/- 2% with 0.01, 0.1 and 1 nmol kg-1 AM, respectively) whatever the injected dose of AM. 3. When unilobar hypoxia (5% O2) had decreased the i.d. of the 100-1100 microns arteries and veins by 16 +/- 3 and 6 +/- 3%, respectively, AM (0.1 nmol kg-1) was able to induce significantly larger i.d. increases in the arteries (28 +/- 3%) and veins (11 +/- 3%) than those under control conditions. 4. The AM-induced i.d. response pattern in the serially connected pulmonary arteries was quite different from that induced by CGRP; AM caused a greater increase in smaller vessels (100-500 microns) than in larger vessels (500-1100 microns). In the case of CGRP, a greater increase was observed in the larger vessels. 5. CGRP8-37 (100 nmol kg-1, i.v., followed by a continuous infusion of 0.2 nmol kg-1 min-1) had no significant effect on the i.d. increase induced by AM (0.1 nmol kg-1) in any serial segments of the arteries and veins. 6. The results indicate that, in the cat, AM induces greater vasodilatation in small pulmonary arteries and lesser vasodilatation in small veins, the maximum dilatation being in the more peripheral arterial segment (100-500 microns). The vasodilator effect of AM was enhanced when vascular tone was elevated. The data suggest that the AM-induced pulmonary vasodilatation is not mediated by CGRP receptors but by its own specific receptor.

Inhibition of NO synthesis minimally affects the dynamic baroreflex regulation of sympathetic nerve activity

The purpose of this investigation was to examine the role of nitric oxide (NO) in the dynamic baroreflex regulation of cardiac sympathetic nerve activity. In anesthetized rabbits, we imposed random pressure perturbations on the isolated carotid sinuses before and after the intravenous administration of NG-monomethyl-L-arginine. We characterized the dynamic properties relating carotid sinus pressure input to sympathetic nerve activity by means of a transfer function analysis. NG-monomethyl-L-arginine decreased the corner frequency of the transfer function (0.100 +/- 0.054 vs. 0.074 +/- 0.035 Hz; P < 0.05), whereas other parameters such as the steady-state gain and transmission lag time remained unchanged. Although cursory examination of these findings would suggest a possible contribution of NO in the dynamic baroreflex regulation of sympathetic nerve activity, quantitative assessment of the transfer function reveals only a minimal effect on the baroreflex regulation of arterial pressure, particularly under closed-loop conditions. We conclude that NO noticeably affects the dynamic baroreflex regulation of sympathetic nerve activity. However, it may not significantly affect arterial pressure regulation through central modulation of the carotid sinus baroreflex.

Dynamic vagosympathetic interaction augments heart rate response irrespective of stimulation patterns

We previously demonstrated that tonic stimulation of either the sympathetic or the vagal nervous system augmented the dynamic heart rate response to the other of the two systems. We characterized the phenomenon as bidirectional augmentation of heart rate regulation. The question remained unanswered, however, as to whether such augmentation could occur under simultaneous dynamic stimulation of the two systems. The transfer characteristics from nerve stimulation to heart rate were well described by linear systems analysis, although no attention was paid to the aphasic nature of the stimuli in relation to each R-R interval. When we stimulated the two nerves with statistically independent Gaussian white noises, gain of the transfer function increased by 63.2 +/- 47.4% relative to individual stimulation (P < 0.05). When we stimulated the two nerves with mutually reciprocal Gaussian white noises, gain of the transfer function increased by 54.9 +/- 49.1% (P < 0.05). Thus simultaneous dynamic stimulation of the sympathetic and vagal systems bidirectionally augmented heart rate regulation irrespective of the pattern of the stimulation signals.

Characteristics of pulmonary artery pressure waveform for differential diagnosis of chronic pulmonary thromboembolism and primary pulmonary hypertension

OBJECTIVES

The accurate diagnosis of chronic pulmonary thromboembolism (CPTE) is a prerequisite for life-saving surgical interventions. To help in the differential diagnosis of CPTE and primary pulmonary hypertension (PPH), we characterized the configuration of the pulmonary artery pressure waveform.

BACKGROUND

Because CPTE predominantly involves the proximal arteries, whereas PPH involves the peripheral arteries, we hypothesized that patients with CPTE would have stiff or high resistance proximal arteries, whereas those affected by PPH would have high resistance peripheral arteries. These differences in the primary lesions would make arterial pulsatility relative to mean pressure larger in CPTE than in PPH.

METHODS

In 34 patients with either CPTE (n = 22) or PPH (n = 12) whose pulmonary systolic pressure was > or = 50 mm Hg, we measured pulmonary artery pressure using a fluid-filled system that included a balloon-tipped flow-directed catheter.

RESULTS

To quantify the magnitude of pulsatility relative to mean pressure, we normalized pulse pressure by mean pressure, hereinafter referred to as fractional pulse pressure (PPf). PPf was markedly higher in CPTE than in PPH (mean [+/-SD] 1.41 +/- 0.20 and 0.80 +/- 0.18, respectively, p < 0.001) and was diagnostic in separating the two groups without overlap. Similarly, the coefficient of variation of pulmonary artery pressure also separated the two groups without overlap (0.45 +/- 0.06 and 0.25 +/- 0.06, respectively, p < 0.001). Fractional time to half the area under the pressure curve separated the two groups reasonably well (0.35 +/- 0.02 and 0.43 +/- 0.03, respectively, p < 0.001).

CONCLUSIONS

The analysis of pulsatility of pulmonary artery pressure is useful in the differential diagnosis of CPTE and PPH.

A new, concise dialysis approach to assessment of cardiac sympathetic nerve terminal abnormalities

We applied a dialysis technique to the hearts of anesthetized cats and examined whether the concentration of dialysate norepinephrine (NE) reflected NE disposition at the cardiac sympathetic nerve terminals. Dialysis probes were implanted in the left ventricular wall, and dialysate NE concentrations were measured as an index of myocardial interstitial NE levels. Stimulation of stellate ganglia significantly increased dialysate NE responses that were suppressed by local administration of an NE-releasing inhibitor (omega-conotoxin GVIA, 10 microM). Increments in basal dialysate NE levels were correlated with concentrations of a locally administered neuronal uptake blocker (desipramine; 1, 10, and 100 microM). Desipramine (100 microM) augmented stimulation-induced dialysate NE responses. Local administration of a neuronal vesicle uptake blocker (reserpine, 1 and 10 microM) did not alter dialysate NE levels but increased dialysate dihydroxyphenylglycol levels. An NE-releasing amine (tyramine, 100 microg/ml) was locally administered to examine NE storage capacity at the nerve terminal. The tyramine-induced NE-releasing response was completely abolished by pretreatment with reserpine (1 mg/kg i.p.). Thus cardiac dialysis with local administration of a pharmacological tool offers a new, concise approach to assessment of neuronal NE release, uptake, vesicle uptake, and storage capacity by cardiac sympathetic nerve terminals.

Aortic blood momentum--the more the better for the ejecting heart in vivo?

OBJECTIVES

The aim of the present study was to test two hypotheses: (1) the momentum of the blood flowing out of the left ventricle toward the aorta (inertia force) plays an important role in the initiation of decay and the maximum rate of decay (peak (-dP/dt)) of left ventricular pressure (P); (2) a normal heart itself generates the inertia force which enhances its function.

METHODS

The contribution of the inertia force to (-dP/dt) was theoretically given as rho c alpha, where rho is the blood density, c the pulse wave velocity, and alpha the deceleration rate of aortic blood flow. The correlations of peak (-dP/dt) with rho c alpha and with the time constant (tau) of the pressure decay during isovolumic relaxation, which was considered to represent myocardial relaxation characteristics, were compared in seven dogs. We developed a method of grading the strength of the inertia force, using the phase loop of left ventricular pressure (dP/dt vs. P relation). The method was applied to the records of 25 patients with ischemic heart disease, from which high fidelity left ventricular pressure recordings were available.

RESULTS

The correlation of peak (-dP/dt) with rho c alpha was much higher than with tau (0.75 vs. -0.46). 16 of the 25 patients showed evidence of the inertia force. However, other patients showed no inertia force. The strength of the inertia force showed a significant (P < 0.05) correlation with left ventricular end-diastolic pressure (r = -0.46), cardiac index (r = 0.62), stroke volume index (r = 0.69), ejection fraction (r = 0.46), and peak (-dP/dt) (r = 0.56).

CONCLUSION

The inertia force of late systolic aortic flow contributed to ventricular relaxation in the normal heart.

[Estimation of right ventricular contractility by continuous-wave Doppler echocardiography]

The right ventricular dP/dtmax and relatively load-independent index, dP/dtmax/IP (IP: instantaneous pressure difference between the right ventricle and right atrium) can be measured from the tricuspid regurgitant velocity by continuous-wave Doppler echocardiography. The present study investigated these indices as measures of right ventricular contractility. Thirty-one patients were classified into three groups: 11 patients without right ventricular disease (control group), 9 with dilated cardiomyopathy and 1 with hypertrophic cardiomyopathy in the dilated phase (DCM group), and 10 with pulmonary hypertension (PH group). Right ventricular contractility was impaired in both the PH group and DCM group, but dP/dtmax was significantly larger in the PH group compared with the control group and DCM group (519 +/- 113 vs 249 +/- 66 and 234 +/- 78 mmHg/sec, p < 0.01). There was no significant difference between dP/dtmax in the control group and DCM group. dP/dtmax/IP in the PH group was smaller than the control group (31 +/- 8 vs 39 +/- 7/sec, p < 0.05) and larger than the DCM group (22 +/- 12/sec, p < 0.05). Mean New York Heart Association grading was 1.0 in the control group, 3.1 in the DCM group, and 2.8 in the PH group, respectively. Thus, dP/dtmax/IP, noninvasively obtained by continuous-wave Doppler echocardiography, may be a better index for evaluating right ventricular contractility than dP/dtmax.

Neural arc of baroreflex optimizes dynamic pressure regulation in achieving both stability and quickness

The baroreflex loop consists of a fast neural arc and a slow mechanical arc. We hypothesized that the neural baroreflex arc compensates the slow mechanical response and thus improves the quality of blood pressure regulation. We estimated the open-loop transfer characteristics of the neural baroreflex arc (HP), i.e., from carotid sinus pressure to sympathetic nerve activity (SNA), and that of the effective peripheral baroreflex arc (Hp), i.e., from SNA to arterial pressure, in anesthetized rabbits. The gain of Hn was constant below 0.12 +/- 0.057 Hz and increased with a slope of 6.1 +/- 0.06 dB/octave above its frequency up to 1 Hz. In contrast, the gain of Hp was constant below 0.071 +/- 0.03 Hz and decreased with a slope of -11.0 +/- 1.48 dB/octave above the frequency. These data indicate that Hn accelerates slow peripheral responses in the frequency range of 0.1-1 Hz. Although too much acceleration in the high-frequency range could result in instability of the system, numerical analysis of the closed-loop baroreflex response indicated that the neural arc optimized arterial pressure regulation in achieving both stability and quickness.

Bidirectional augmentation of heart rate regulation by autonomic nervous system in rabbits

Although the characteristics of the static interaction between the sympathetic and parasympathetic nervous systems in regulating heart rate (HR) have been well established, how the dynamic interaction modulates the HR response remains unknown. We therefore investigated dynamic interaction by estimating the transfer function from nerve stimulation to HR using a band-limited Gaussian white-noise technique. The transfer function relating dynamic sympathetic stimulation to HR had characteristics of a second-order low-pass filter. Simultaneous tonic vagal stimulation at 5 and 10 Hz increased gain of the transfer function by 55.0 +/- 40.1 and 80.7 +/- 50.5%, respectively (P < 0.05). The transfer function from dynamic vagal stimulation to HR had characteristics of a first-order low-pass filter. Simultaneous tonic sympathetic stimulation at 5 and 10 Hz increased the gain by 18.2 +/- 17.9 and 24.1 +/- 18.0%, respectively (P < 0.05). Thus interaction augmented dynamic gain bidirectionally, even though it affected mean HR antagonistically. By virtue of this interaction, the autonomic nervous system appears to extend its dynamic range of operation.

[Questionnaire survey of AIDS examination recipients at government-run public health center regarding AIDS awareness promotion and HIV examinations]

An anonymous questionnaire survey was conducted among persons who had undergone screening for AIDS at public health centers under the auspices of 7 local government bodies (Hokkaido, Metropolitan Tokyo, Aichi Prefecture, Osaka Prefecture, Kobe City, Saga Prefecture, Okinawa Prefecture). There were 1,230 replies, for a response rate of 46.8%. Questions in the survey pertained to general knowledge of AIDS, information desired by the recipients, desired ways to foster awareness, and a desirable examination system. A comparison was made in terms of gender, marriage status (married, single) and age (less than 40 years of age, more than 40 years of age), respectively. The survey results were as follows. 1. Concerning the infection route, accurate response rate was low with regard to the mother-child infection, mosquito transmission, and use of contaminated needles. 2. Desired methods to promote AIDS awareness expressed among replies were given in the following order or frequency: "information via radio and TV," "spread of knowledge through telephone consultation," and "holding an AIDS Week or similar kinds of campaigns." 3. Information sought by respondents frequently included AIDS treatment, pathology, and spread. This trend was most obvious among those under 40 years of age. 4. As for the AIDS examination system, replies most often reflected the hope that the examination site would be the Public Health Center, the charge would be gratis, and that one could be examined at night during the week, and on days off. 5. For those undergoing examination where there was no actual concern of possibility of HIV infection, single persons, accounted for around 80% of the overall. 6. More than half of those who had been examined mentioned having experienced concerns about maintaining confidentiality at the time they were examined.

Inhaled nitric oxide: diameter response patterns in feline small pulmonary arteries and veins

Using an X-ray television system on the in vivo cat lung, we directly measured internal diameter (ID) changes in the small pulmonary arteries and veins (100-1,100 microns ID) in response to 5, 15, and 40 ppm nitric oxide (NO) inhalations. We also measured to what extent 40 ppm NO inhalation can attenuate large ID constrictions at the different serial segments of the small vessels due to unilobar anoxic (0% O2) exposure. Under normoxic conditions, 5-40 ppm NO inhalations significantly increased the ID of both arteries and veins less than approximately 900 microns dose dependently but caused no significant, or only slight, ID increases in the vessels larger than this, if any at all. The ID increase in the serially connected arteries was nonuniform (4-18, 8-28, and 7-35% with 5, 15, and 40 ppm NO inhalations, respectively), whereas that for the veins was relatively uniform (4-9, 6-17, and 7-18% with 5, 15, and 40 ppm NO, respectively). The maximum ID increase occurred in the 200- to 500- and 200- to 700-microns arteries in response to 5-15 and 40 ppm NO, respectively. Unilobar anoxic exposure significantly decreased the ID of the 100- to 700-microns arteries and veins, but not the ID of the other-sized vessels. The ID decrease in the serially connected arteries was nonuniform (13-29%) but relatively uniform in the veins (8-12%). The maximum ID decrease occurred in the 200- to 300-microns arteries. However, adding 40 ppm NO to the lobe completely eradicated the ID decreases at all segments of the arteries and veins and, instead, caused significant ID increase (11-21%) in the arteries and (10-12%) in the veins. The data indicate that, according to dosage, 5-40 ppm NO inhalations cause selective dilation of approximately 100- to 900-microns pulmonary arteries and veins, particularly the 200- to 700-microns arteries. During anoxic exposure, the vasodilator effect of NO is preserved and can completely reverse the marked pulmonary vasoconstriction.

Explorations into development of a neurally regulated cardiac pacemaker

Although the artificial cardiac pacemaker has contributed to the management of patients with serious arrhythmias, its rate-responsive function is not sufficient to provide physiological regulation of heart rate (HR). To achieve truly physiological rate response in any given patient, we propose a framework to develop a pacemaker directly regulated by sympathetic nerve activity (SNA). In eight anesthetized rabbits, we quantified the dynamic transduction characteristics from SNA to HR as a transfer function. We then characterized the decoding rule as an impulse response, that is the transfer characteristics in the time domain. The transfer function was approximated by a first-order, low-pass filter with lag time (corner frequency: 0.024 +/- 0.013 Hz, lag time: 0.98 +/- 0.09 s). Predicted HR correlated well with measured HR (r = 0.80-0.98). The standard error of the prediction relative to mean HR was only 1.2 +/- 0.7%, indicating that the prediction was reasonably accurate. Direct decoding of SNA to predict instantaneous HR is possible through this analysis. This framework should enable development of a neurally regulated artificial pacemaker.