Evaluation of reproducibility of spontaneous baroreflex sensitivity at rest and during laboratory tests

OBJECTIVE

The aim of the present study was to examine the reproducibility of arterial baroreflex sensitivity (BRS) provided by the spontaneous baroreflex method at rest and during laboratory tests.

METHODS

Twenty healthy volunteers were studied 24 h apart, in the same laboratory and under the same environmental conditions, at rest, during active standing, while performing mental arithmetics and during static hand-gripping. Systolic blood pressure, mean arterial pressure and pulse interval were continuously and non-invasively measured by using a Finapres device. BRS was evaluated by analysing the slopes of spontaneously occurring sequences of three or more consecutive beats in which systolic blood pressure and pulse interval of the following beat both increased or decreased, in the same direction, in a linear fashion. Individual BRS were obtained by averaging all slopes computed within a given test.

RESULTS

Under each test condition BRS did not differ significantly between the two consecutive days, showing strikingly similar values. The mean group coefficients of variation (CVAR), obtained by averaging individual CVAR, between the two experimental days were 15.0, 13.9 and 19.7% for resting, standing, static hand-gripping and mental arithmetic, respectively. No relationships were found between individual CVAR and individual mean arterial pressure, pulse interval and number of baroreflex sequences under any tested condition, on both experimental days.

CONCLUSIONS

These results show that the spontaneous baroreflex method provides good BRS reproducibility under various stimuli that affect the neural control of circulation differently. They also suggest that BRS variability is dependent neither on haemodynamic modifications nor on the degree of baroreflex engagement, but it seems to reflect an inherent feature of the way in which arterial baroreflex modulate the heart period.

Childhood neuronal ceroid-lipofuscinoses in Argentina

We report on 30 cases of neuronal ceroid lipofuscinoses (NCL), mainly diagnosed in 1985-1993 in Argentina, whose population is predominantly of European descent. Twenty-four cases were late infantile Jansky-Bielschowsky (LINCL) and 6 were juvenile Spielmeyer-Vogt (JNCL). Sex ratio was female:male, 20:10. Age range and mean at onset and at diagnosis for the LINCL cases were 1-6 years, mean 3.1, and 2-11 years, mean 5.5, and for the JNCL cases, 5-9 years, mean 7, and 9-18 years, mean 13, respectively. Cases were referred for biopsy after neurological examination, and most included complete electrophysiological [electroencephalography (EEG) with photic stimulation, electroretinography (ERG), and visual-evoked potential (VEP)], neuroimaging, and neurometabolic investigation. NCL was the first suspected clinical diagnosis, followed by mitochondrial encephalopathy in some cases of recent onset. Except for 1 case, clinical findings were homogeneous in LINCL, characterized by refractive epilepsy, mental regression and progressive deterioration, ataxia, myoclonia, and visual loss. Abnormal VEP, ERG, and EEG, with polyphasic high-voltage spikes when photic stimulation was performed at low frequency, were observed. Visual impairment and retinitis pigmentosa were early manifestations in 4/6 JNCL, followed by mental abnormalities, motor deterioration, and myoclonic jerks, while 2/4 followed an atypical course. In both variants inheritance was autosomal-recessive. Five out of 27 families had more than 1 affected member, 3 of whom were included in our series. Diagnosis was initially performed in conjunctival biopsy in 3 cases, skin in 5, muscle in 17, and brain in 5, though most cases had a concomitant biopsy from another tissue including nerve, and there was a single brain autopsy.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute "axonal" Guillain-Barré syndrome in childhood

We identified 5 of 44 consecutive children (11%) with Guillain-Barré syndrome who had electrophysiologic evidence of severe reduction of the mean amplitude of the compound motor action potentials (mean CMAP amplitude < 10% of lower limit of normal). EMG studies revealed profuse fibrillation activity in distal and proximal muscles after 2 weeks of onset. We compared this group with 16 consecutive children with GBS prospectively evaluated over 1 year, all of whom presented a mean CMAP amplitude > 10% of lower limit of normal. Children in the first group were more likely to require assisted ventilation (60% vs. 6.2%) and were more frequently quadriplegic at the peak of their disability (80% vs. 18.7%). They also required longer periods to improve one functional grade (mean 63.6 days vs. 16.6 days) and to become ambulatory (mean 156 days vs. 17.6 days). Moreover, only the children in the first group had distal atrophy of four limbs after 1 year of follow-up. Severe reduction of the mean amplitude of the CMAPs in children with GBS identifies a subgroup of patients with axonal damage that produces more severe weakness and delayed recovery.

Physiological unloading of cardiopulmonary mechanoreceptors by posture change does not influence the pressor response to isometric exercise in healthy humans

In recent studies in humans the role of cardiopulmonary baroreflexes in modulating the cardiovascular responses to isometric exercise (somatic pressor reflex) has been investigated by performing static handgrip exercise during deactivation of cardiopulmonary receptors produced by low levels of lower body negative pressure; however, findings from these studies have not been consistent. The purpose of this study was to investigate whether a more physiological unloading stimulus of cardiopulmonary baroreceptors, obtained by sequentially changing posture, could influence the pressor response to somatic afferent stimulation induced by isometric exercise. To accomplish this, ten healthy subjects performed a 2-min isometric handgrip (IHG) at 30% maximal voluntary contraction after 10 min of supine rest and, in rapid sequence, after 10 min of sitting and 10 min of standing, at the time when, owing to their transitory nature, the cardiovascular effects, due to arterial baroreceptor intervention should have been minimal. During IHG arterial pressure (BPa) was continuously and noninvasively measured to quantify accurately the blood pressure response to IHG both in magnitude and time course. Results showed that the pressor response to IHG was not significantly influenced by change in posture, either in magnitude or in time course. The mean arterial pressure increased by 17.4 (SEM 2.5), 18.6 (SEM 1.2) and 17.0 (SEM 1.3) mmHg in supine, sitting and standing [2.3 (SEM 0.3), 2.5 (SEM 0.2) and 2.3 (SEM 0.2) kPa] positions, respectively. Also the heart rate response to IHG was unaffected by change in posture.(ABSTRACT TRUNCATED AT 250 WORDS)

Scintigraphic assessment of "effort" axillary-subclavian vein thrombosis

"Effort" axillary-subclavian vein thrombosis (Paget-Schroetter syndrome) is an uncommon deep venous thrombosis due to repetitive activity of the upper limb. Clinical suspicion is usually confirmed by contrast venography. This report describes a case where the diagnosis was made by radionuclide venography (Tc-99m DTPA). The examination was carried out in the acute phase and clearly demonstrated the presence and the site of the obstruction as well as the collateral vessels. Despite a complete clinical recovery, obtained by medical therapy, further examinations performed in the follow-up period showed persistence of the thrombotic obstruction and a rich development of collateral vessels. In the authors' opinion, radionuclide venography is worth considering as a first-choice procedure when an axillary-subclavian vein thrombosis is suspected, and contrast venography should be performed only when surgical treatment is indicated.

[The physiopathological aspects and new therapeutic approaches in cardiac-circulatory failure]

Pathophysiological mechanisms are reviewed concerning the onset and the perpetuation of the clinical features of congestive heart failure. This syndrome is a severe condition of poor prognosis and bad life quality which in the last decades has reached, in the western industrial countries, the highest levels of general mortality, mainly due to the high prevalence of hypertensive and ischaemic myocardiopathies in the last years. To the clinical features of heart failure mainly contributes a deregulation of the physiological compensatory mechanisms contemporarily and concurrently activated following the primary deficiency of the heart pump function. In physiological conditions, following the myogenic adapting mechanisms reflex mechanisms intervene, activated by intracardiac and aortic and carotid-sinus mechanoreceptors following the variations in intracardiac and intravascular pressure and generally evoking negative feed-back effects. In patients with heart failure arterial high pressure mechanoreceptors respond to the reduction in effective arterial pressure thus provoking a deactivation of the tonic inhibition on the sympathetic cardiovascular drive. This leads to an activation of peripheral and renal vasoconstrictor tone, to a raised medullary catecholamine incretion, to heart rate and inotropism stimulation, and to an increase in pituitary gland ADH production as well as to an activation of renin-angiotensin-aldosterone system (RAAS). Analogous vasoconstrictive, and sodium and water retentive effects can be elicited by endothelin produced by endothelial cells and found in high plasma levels in CHF. These excitatory effects, leading to a rise in systemic vascular resistance and to hydro-electrolytic retention with volume expansion, are not efficiently counteracted by the opposite effects triggered by cardiopulmonary vagally mediated mechanoreceptors activated by the raised cardiac filling pressure and leading to sympathetic nervous inhibition, peripheral and renal vasodilation, ADH and RAAS inhibition. Analogous effects should be provoked by the raised production, due to enhanced heart wall distension, of atrial natriuretic factor leading to vasodilation, natriuresis and diuresis. Reduced sensitivity of cardiopulmonary baroreceptors and lowered production of ANF due to structural cardiac changes could represent, according to most opinions, the main factors responsible for the prevailing sympathetic activation and hydro-saline retention in CHF. The activation of cardiopulmonary sympathetic positive-feed back afferents, could be also involved in the characteristic alteration of the vago-sympathetic balance in heart failure. The persistent reduction in heart pump function could lead to the instauration of vicious circles among the various regulatory systems and create an overcompensation condition.(ABSTRACT TRUNCATED AT 400 WORDS)

[Integrated cardiorespiratory changes induced by chemical stimulation of muscular receptors]

Muscular exercise is accompanied by evident and perfectly matched cardiovascular and respiratory adjustments to avoid changes in arterial blood gases. The mechanisms responsible for this perfect regulation have not yet been defined. Our previous experimental investigations have shown that a consistent rate of cardiorespiratory reflex responses to exercise is caused by chemosensitive muscular receptors activation. The 2 different types of classical muscular exercise (rhythmic and isometric exercise) are joined with the 2 different patterns of cardiorespiratory reflex responses attributed in our opinion to the activation of 2 different kinds of muscle receptors (K and P). It has been observed that the increase in ventilation (VE), elicited by activation of both types of chemoreceptors during muscular experimental exercise is not accompanied by significant variations of partial pressure of CO2 (PaCO2) in the arterial blood (isocapnic hyperpnea). This suggest that muscular chemoreceptor activation during physical exercise determines an adequate cardiopulmonary matching. The main purpose of the present study has been to verify, in anesthetized rabbits, if also the chemical activation of muscular receptors was able to evoke reflexly an adequate degree of cardiopulmonary matching. The ventilation reflex changes and the concomitant variations of PaCO2 induced by injection of bradikinin (BK 250 ng) and hypertonic solutions (NaCl 10% 1 ml) in femoral artery have been evaluated in 10 anesthetized rabbits. The PaCO2 modifications observed during reflex hyperpnea have been compared with those recorded during hyperpnea induced by artificial ventilation.(ABSTRACT TRUNCATED AT 250 WORDS)

Active specific immunotherapy with antiidiotypic antibodies in patients with solid tumors

Tumor-associated antigens (TAA) provide appropriate targets for selective manipulation of the patient's immune response in the immunotherapy of cancer. Active specific immunotherapy utilizing antiidiotypic antibodies to anti-TAA antibodies has been implemented in phase I clinical trials both in patients with colorectal carcinoma and in those with melanoma. The theoretical basis for immunotherapy with antiidiotypic antibodies, the results of these clinical trials, and an evaluation of appropriate parameters for future clinical trials of active specific immunotherapy with antiidiotypic antibodies in patients with solid tumors are reviewed.

[Bone echinococcosis]

Hydatidosis of the bone is a rare form of human echinococcosis. Due to the clinical, diagnostic, therapeutic and prognostic problems involved, the costal and occipital locations are of particular interest. Both are rare and differ from visceral locations in that they are always "primary" and have the capacity to destroy the bone matrix and infiltrate the adjacent tissues. The course of the disease is particularly slow and without specific signs and symptoms so that it can look like any bone condition. Laboratory tests are frequently negative and not wholly specific. While some authors claim that the radiological picture is of no diagnostic significance, others state that it offers pathognomonic signs. Diagnosis will be obtained through the combined assessment of clinical, radiological, laboratory and anamnestic data. Provenance from a rural area should reinforce the suspicion. Surgery, whether radical or conservative, is the key factor in treatment though local recurrences are common. Better results are obtained by combining surgery with Mebendazole for pre and postoperative prophylaxis. Large doses over a long period will give a better clinical course and reduce the incidence of recurrences. The prognosis is good for both sites as long as surgical treatment is given in good time.

[Muscular and subcutaneous hydatidosis]

Among unusual echinococcus cysts, muscular hydatidosis merits particular attention. Careful analysis of the statistics provided by the literature shows that the condition is not all that rare: its incidence varies from 0.5 to 4.7%, making it less common than hepatic or pulmonary cysts but more frequent than cysts of the kidneys, bone, pancreas, spleen or mesenterium. There are disagreements about the percentage distribution in the various muscular districts but it seems that the incidence gradually decreases as we go from the muscles of the torso and the root of the limbs to the distal extremities. The Palermo University case series includes 6 cases of which 5 muscular and one in the connective tissue. Of the 4 muscular cases, only one is to be considered secondary. For the purposes of correct preoperative diagnosis we should not neglect either anamnestic data or laboratory tests. Though the latter are not specific they are helpful for differential diagnosis from other muscular neoformation. Exploratory centesis that must be performed very cautiously in order to prevent dissemination appears to be more specific. Radiography and ultrasound examinations permit the direct study of cystic formations and a general assessment of the possibility of multiple hydatid locations. The only possible treatment is surgical. Though total removal of the cyst is the operation of choice, this is not always possible if the cyst is very big and adhering to other structures. In this case the procedure to be adopted is sterilisation and aspiration of the content, removal of the membrane and treatment of the pericystium.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiorespiratory reflexes from muscles during dynamic and static exercise in the dog

Cardiorespiratory reflex responses during the initial phase of dynamic and static contraction of hindlimb muscles were studied in anesthetized dogs. Muscle contractions were elicited by stimulating the femoral and gastrocnemius nerves at 3 and 100 Hz with the intensity of 2.0-2.5 times the motor threshold for a 20-s period. Rhythmic contractions caused a decrease in arterial pressure (Pa) and heart rate (HR) and increased pulmonary ventilation (VE) by increasing frequency (f) without significantly changing VT. Tetanic contractions provoked an increase in Pa and HR and a hyperpnea resulting from a rise in both f and VT. Similar responses were also obtained in anesthetized dogs with carotid sinuses denervated and cervical vagi cut. The abrupt increase in VE at the start of both types of exercise was not associated with immediate significant decreases in end-tidal CO2 values. These two patterns of cardiocirculatory and respiratory responses were closely similar to those reported in anesthetized rabbits in previous studies. Both patterns of responses were reflexes initiated by activation of muscle receptors verified by interrupting the afferents from the contracting muscles. It is concluded that, during dynamic and static work, two distinct muscular reflex mechanisms might exert their drives, related to the muscular metabolic rate, on the circulatory and respiratory function.

Evidence that nitroarene metabolites form mutagenic adducts with DNA-adenine as well as with DNA-guanine

Nitropyrenes as well as several other nitroarenes and their metabolites exhibit considerable mutagenicity for Salmonella tester strains (TA102 and TA96) which have adenine-thymine base pairs at the mutational target. This finding is unexpected as previous biochemical studies had shown that arylation at the C8 position of DNA-guanine is the only chemically and biologically significant reaction. This conclusion is supported by the extraordinary mutagenic potency of these chemicals in Salmonella strains with guanine at the mutational site (e.g., TA98). The present results indicate that a minor reaction with DNA-adenine may result in the formation of an unusually potent promutagenic DNA adduct.

Different patterns of respiratory reflexes originating in exercising muscle

In anesthetized rabbits, rhythmic contractions of the gastrocnemius muscle elicited by stimulating the gastrocnemius nerves (40 trains/min of 0.5-ms rectangular pulses at 2.0-2.5 mult of motor threshold), increased pulmonary ventilation by increasing frequency (f). Expiratory duration (TE) was greatly reduced, while inspiratory time (TI) was much less changed. Mean expiratory flow (VT/TE) was increased consistently more than mean inspiratory flow (VT/TI). Arterial pressure (Pa) and heart rate (HR) were decreased. During tetanic contractions (100 Hz, 2.0-2.5 X T) tidal volume (VT) increased considerably more and f considerably less than during rhythmic exercise, TE was shortened, and TI was only slightly affected. Pa and HR, after a transitory reduction, increased over the resting levels. Similar responses were also obtained in deafferented rabbits with carotid sinus, aortic, and cervical vagus nerves cut. These two patterns of cardiorespiratory changes were initiated by activation of muscle receptors verified by interrupting the afferents from the contracting muscles. It is concluded that, in the anesthetized rabbit, two different muscular reflex mechanisms are involved in controlling the pattern of breathing and ventilation during muscular exercise. One mechanism, predominantly activated during dynamic exercise, decreases TE and increases f, the other mechanism, mainly activated during static exercise, increases the inspiratory drive, thus increasing the depth of breathing.

[Comparative study of cardiocirculatory response and respiratory reflex to the injection of bradykinin, inorganic phosphates and prostaglandins into the femoral artery]

In 15 anesthetized rabbits the reflex changes in arterial pressure, heart rate and respiratory rate in response to injections of bradykinin inorganic phosphate and prostaglandins into femoral artery have been studied. Intraarterial injection of bradykinin produced a reflex fall in arterial pressure, bradycardia and tachypnea. The latency of response ranged from 6 to 7 sec. The threshold dose was about 50 ng. This effect was accompanied by a consistent increase in the afferent discharge in the saphenus nerve. Isotonic mixtures of Na2HPO4 and NaH2PO4 at pH 7, PGE1, PGE2, and PGA, when injected into femoral artery even in high doses, failed to produce any significant cardiocirculatory or respiratory reflex responses. Infusion of PGE1 (1 ug/min) into femoral artery, although inactive by itself, enhanced the reflex effect of bradykinin.

Cardiovascular and respiratory reflexes from muscles during dynamic and static exercise

In anesthetized and deafferented rabbits, rhythmic and static contractions of the hindlimb muscles were elicited by stimulating the femoral nerve at 3 and 100 Hz with the intensity of 2.0-2.5 times threshold for the motor fibers. Rhythmic contractions caused a decrease in systemic blood pressure, heart rate, and vascular resistance of the resting hindlimb with hyperpnea. Tetanic contractions caused a rise in arterial pressure, in vascular resistance of the nonexercising hindlimb, and in pulmonary ventilation with small increases in heart rate. These responses were not obtained after sectioning the somatic nerves of the exercised limb or when the cut central end of the femoral nerve or the intact nerve in curarized animals was stimulated with the same intensity of 2.0-2.5 times the motor threshold. Both depressor and pressor responses were, therefore, reflexes initiated in the contracting limbs. Removal of the skin from the exercising limb did not change the typical patterns of response. The most likely source of the observed reflexes is that from receptors activated by metabolites released in the exercising muscles.