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Biomedical subjects

M Corda

Publications and source records attributed to M Corda.

At least 37 records · Page 2Linked to original sources
PubMed1991

[Acute effects of transdermal administration of nitroglycerin on effort tolerance and myocardial perfusion, evaluated by Tl-201 scintigraphy, in patients with stable effort angina].

The aim of this study was to evaluate the effects of the transdermal application of nitroglycerin (NGT) on exercise tolerated and regional myocardial perfusion, as evaluated by 201 thallium stress scintigraphy, in patients with stable effort angina. We studied 20 patients, 15 men and 5 women, aged between 43 and 68 years, with average age of 55 +/- 8 years, suffering from effort angina, whose angina threshold was stable in 3 stress testing performed in the week before the study started. The patients, after a pharmacological washout of 1 week, underwent 2 exercise testing 20 hours after the application of a patch containing placebo or 10 mg NGT, with an interval of 7 days. 60-90 s before stress testing was interrupted, 2 mCi of thallium 201 were injected in an antecubital vein of the arm. The scintigraphic images were obtained soon in the 0, 45 and 90 degree views and after 4 hours reperfusion. Under placebo patch all patients interrupted ergometer test for angina, while under the patch containing active NGT angina was present in 11/20 patients and 9 patients stopped the test because of muscular exhaustion. NGT induced an increase of the ergometer test duration (+26%); this difference was statistically significant. The ST segment downsloping decreased significantly both at maximal common work and at exercise peak after NGT application in comparison with placebo. The perfusional defects observed on the scintigraphic images obtained soon after the exercise (and reversible after 4 hours of reperfusion) on placebo patch, diminished significantly after NGT and the captation index lung/heart decreased also significantly (from 49 to 41%), showing so an improvement of cardiac performance. In conclusion the transdermal application of NGT, in patients with effort angina, demonstrated to have antianginal and antiischemic effect, reducing the number of patients interrupting the stress testing for angina, increasing the exercise tolerated and diminishing the ST segment downsloping, objective demonstration of myocardial ischemia. This antianginal and antiischemic effect might follow to the reduction of the preload induced by nitrates, in part also the reduction of the afterload, factors determining a decrease of the wall tension and so of MVO2, but also to a redistribution of the subendocardial flow as demonstrated by 201-Tl scintigraphic images. These effects induce also a global improvement of the left ventricular function as demonstrated by the reduction of the lung/heart index of thallium captation.

Administration, Cutaneous↗
PubMed1991

Cardiovascular structural changes in hypertension: possible regression during long-term antihypertensive treatment.

Arterial hypertension is often complicated by left ventricular hypertrophy (LVH) and by vascular structural changes resulting in decreased proximal and distal compliance. LVH is an adverse prognostic factor because it increases the incidence of sudden death and other morbid events related to ischaemic heart disease, whereas vascular alterations may induce target organ damage and contribute to the maintenance of elevated blood pressure values. Thus, antihypertensive treatment must both reduce blood pressure and halt regression of cardiovascular structural changes. A review of the literature suggests long-term use of calcium antagonists, ACE inhibitors, and beta-blockers may revert LVH. We have found that such long-term drug use not only reduces blood pressure and LVH, but also ventricular arrhythmias that are often related to cardiac hypertrophy; however, diuretics do not have this beneficial effect. As regards vascular disturbances ACE inhibitors partially revert these alterations, whereas beta-blockers do not. Further studies are needed to determine whether there are regional differences in the regression of cardiovascular structural changes or whether different antihypertensive drugs have different effects on these changes.

Animals↗
PubMed1991

[Vascular damage in arterial hypertension: its noninvasive assessment].

Arterial hypertension is a definite risk factor for the atherosclerotic disease and thus has a primary role in the genesis of cardiovascular diseases, but it acts also though a direct structural damage of great and small arteries and arterioles. Up to date, clinical research and technological advancements have made possible the development of instruments and methods for the evaluation of the vascular damage. Ultrasonographic methods are now the better non invasive tools for the study of arterial diseases, allowing a definition power comparable to angiography, and giving useful data on characters and composition of plaques, also minimal, at the level of the arterial district of lower limbs, epiaortic, renal, and abdominal vessels. These methods allow the study of the vascular lesion under the hemodynamic (CW or pulsed Doppler with spectral signal analysis) and the morphological profile (high resolution echotomography) or both echo-Doppler duplex scanning or color flow imaging). Arterial compliance of great vessels can be studied through the Doppler evaluation of pulsed wave velocity along the arterial tree. Other useful parameters are the aortic distensibility (ratio between % change in arterial volume and blood pressure), the elastic module, the index of arterial rigidity and the aortic index (ratio between pulse pressure and stroke volume). By using this latter parameter we demonstrated a significant decrease of arterial compliance that is proportional to the severity of blood pressure values. Small vessels may be studied through strain-gauge plethysmography, that allows to obtain the regional blood flows at the hand and forearm (skin circulation) and the calf (muscular circulation) both in basal conditions and after ischaemic stimulus. From the ratio between mean arterial pressure and post-ischemic blood flow it is possible to obtain minimal vascular resistances, expression of the maximal vasodilatation capacity in the arteriolar bed. With this method we showed that minimal vascular resistances increase proportionally with the increase of blood pressure in borderline hypertensives, in mild, moderate and severe stable arterial hypertension and in hypertension of the aged. The cutaneous microcirculation may be studied also by laser Doppler and capillaroscopy, that show a reduced capillary perfusion in hypertension. Clinically, these diagnostic tools are also extremely useful for studying the effects of antihypertensive treatment on structure and function of arterial vessels, as it seems that some drugs are able to counteract the structural alterations related to hypertension.

Arteriosclerosis↗
PubMed1990

Flight and heat dissipation in birds. A possible molecular mechanism.

Birds during normal sustained flight must be able to dissipate more than 8 times as much heat as during rest in order not to be overheated. The experiments reported in this note on the hemoglobin systems from two different birds indicate the existence of a molecular mechanism by which hemoglobin is used simultaneously for oxygen transport and heat dissipation.

Animals↗
PubMed1990

Expiration-related neurons in the caudal ventral respiratory group of the cat: influences of the activation of Bötzinger complex neurons.

The functional role of Bötzinger complex (Böt. c.) projections to the expiration-related (ER) area of the caudal ventral respiratory group (cVRG) was investigated in anesthetized, vagotomized, paralyzed and artificially ventilated cats. ER neurons in both the ipsi- and the contralateral cVRG displayed excitatory responses to Böt. c. electrical microstimulation. They were also activated by microinjections of D,L-homocysteic acid into the Böt. c. region. We propose that at least part of the Böt. c. projections to the cVRG have an excitatory function.

Animals↗
PubMed1989

Hemoglobins from bats (Myotis myotis and Rousettus aegyptiacus): a possible example of molecular adaptation to different physiological requirements.

The functional properties of the hemoglobin systems from two different species of bat i.e. Rousettus aegyptiacus and Myotis myotis have been studied as a function of chloride, polyphosphates, pH and temperature. Apart from overall similarities shared with most mammalian hemoglobins, the two systems show significant differences with respect to the effect of chloride and temperature sensitivity. These findings have been related to the different physiological needs of the two species.

Animals↗
PubMed1988

Influences of superior laryngeal afferent stimulation on expiratory activity in cats.

The effects of superior laryngeal nerve (SLN) stimulation on the activity of the expiratory muscles and medullary expiration-related (ER) neurons were investigated in 24 pentobarbital-anesthetized cats. In some experiments the animals were also paralyzed and artificially ventilated. Sustained tetanic stimulation of SLN consistently caused an apneic response associated with the appearance of tonic CO2-dependent activity in the expiratory muscles and in ER neurons located in the caudal ventral respiratory group (VRG) and the Bötzinger complex. Single shocks or brief tetani at the same stimulation intensities failed to evoke excitatory responses in the expiratory muscles and in the vast majority of ER neurons tested. At higher stimulation strengths, single shocks or short tetani elicited excitatory responses in the expiratory muscles (20- to 35-ms latency) and in the majority of ER neurons of the caudal VRG (7.5- to 15.5-ms latency). These responses were obtained only during the expiratory phase and proved to be CO2 independent. On the contrary, only inhibitory responses were evoked in the activity of Bötzinger complex neurons. The observed tonic expiratory activity most likely represents a disinhibition phenomenon due to the suppression of inspiratory activity; activation of expiratory muscles at higher stimulation intensities appears to be a polysynaptic reflex mediated by ER neurons of the caudal VRG but not by Bötzinger complex neurons.

Animals↗
PubMed1988

Oxidation of some seleno-diamines by pig kidney diamine oxidase.

The enzymatic deamination of Se-lanthionamine (Se-L), Se-homolanthionamine (Se-HL) and Se-homocystamine (Se-HC) catalyzed by pig kidney diamine oxidase (PKAO) has been studied to collect information about the possible metabolic reactions of selenocompounds in comparison with the sulfur ones. The results indicate that: Se-L, Se-HL and Se-HC are substrates for PKAO. The first product of Se-L, Se-HL and Se-HC oxidative deamination, in analogy with other thio and seleno diamines, may be the cyclized aminoaldehyde. The final product of Se-L, Se-HL and Se-HC degradation are ammonia, elemental selenium and C2 or C3 compounds.

Amine Oxidase (Copper-Containing)↗
PubMed1986

Respiration-related neurons in the medial nuclear complex of the solitary tract of the cat.

Respiration-related (RR) neuronal activity was systematically searched for in the nuclear complex of the solitary tract (nTS) with special interest focused on regions located medially to the ventrolateral subnucleus (vlnTS) which is widely considered to be the anatomical location of the dorsal respiratory group (DRG). The experiments were carried out on cats under pentobarbitone anaesthesia, paralyzed and artificially ventilated. RR activity was recorded consistently not only in the vlnTS, but also in more medial regions. R alpha-type neurons were often encountered in ventral and medial aspects of the nTS. R beta-type neurons and expiration-related neurons were found also in ventral regions of the nTS. A small number of 'late onset' and 'early burst' inspiration-related neurons was found respectively in ventral and ventromedial regions of the nTS. The activity of neurons presenting a rhythmic pattern completely determined by lung volume changes due to the respirator was consistently recorded both in ventral and medial areas of the nTS. Most of these neurons were excited by lung inflation and displayed a discharge pattern characteristic of P-neurons. A few neurons, designated as 'inverse' P-neurons displayed an opposite behaviour, being inhibited by lung inflation. The results are consistent with both histological and neurophysiological studies showing that pulmonary stretch receptor afferents terminate also on the medial side of the solitary tract. It is suggested that the DRG is not restricted to the vlnTS, but comprises also neurons located in more medial regions of the nTS.

Animals↗
PubMed1985

Expiration-related neurons in the region of the retrofacial nucleus: vagal and laryngeal inhibitory influences.

The influences of vagal and laryngeal afferent inputs on expiration-related neurons of Bötzinger complex were studied in anesthetized, paralyzed and artificially ventilated cats. Unilateral electrical stimulation (single shocks or short trains of stimuli at 200 Hz) applied to the cervical vagus nerve or to the superior laryngeal nerve induced inhibitory effects on the activity of these neurons. During apnoea due to hyperventilatory hypocapnia, expiration-related units displayed a low level of tonic activity which was rhythmically inhibited by pump-induced lung inflations. The functional significance of these findings is briefly discussed.

Animals↗
PubMed1979

[Effect of motor stimulation and stretching on afferent activity of the neuromuscular spindle isolated from the frog].

The arrangement of muscle spindles in m. ext. long. dig. IV has been examined by microdissection. It is confirmed that spindle systems generally appear to consist of individual receptors. Stimulation effects of fast motor fibres (conduction velocities greater than 12 m/sec) on the spindles of the same muscle were studied. Receptors were isolated with their nerves and the appropriate spinal roots, the latter ones were used for stimulating efferent fibres and recording sensory discharges. Single shocks to the ventral root filaments caused afferent responses ranging from a single action potential to a train of impulses. During repetitive stimulation (train of stimuli at frequency of 10 to 150/sec) a marked increase in afferent activity was found. Afferent activity could be driven by the frequency of stimuli ("driving") and the stimulus/action potentials ratio varied from 1:1 to 1:3 or more. The rate of sensory discharge depended on the frequency of stimuli: the maximum effect, was attained at 30 to 50 stimuli/sec and, in the most responsive receptors, up to 80 stimuli/sec. Slight increases of the initial lengths of the receptors caused facilitation of sensory responses to motor stimulation. Moreover, impairing effects, which appear during sustained or high-frequency stimulation, possibly related to fatigue in intrafusal neuromuscular transmission, could be relieved by increasing the initial length. The repetitive stimulation of fast fusimotor fibres increased both dynamic and static responses and also raised the afferent activity after a period of stretching, when usually a depression occurs; these effects varied according to the preparation, its initial tension and the frequency of stimulation. The main feature of the examined motor fibres, when stimulated, is the constant excitatory action on muscle spindle static response. Results are discussed. It is suggested that the different characteristics of intrafusal muscle fibres, the receptor initial tension and the frequency of motor units discharges, may together affect muscle spindles static or dynamic performance.

Afferent Pathways↗
PubMed1979

[Effects of acetylcholine and succinylcholine on isolated frog neuromuscular spindle].

The mode of action of acetylcholine (ACh) and succinylcholine (SCh) on the isolated frog's muscle spindle has been studied. Receptor afferent nervous supply was maintained; the appropriate spinal roots were dissected for stimulating motor axons and recording from sensory fibres. Excitatory effects on the afferent activity, when the receptor was held still and during stretching, were found with ACh or SCh concentrations of 10(-8) to 10(-3); 10(-6) g/ml being usually effective. These effects are similar to those obtained by stimulating fusimotor nerve fibres. The contractile activity of intrafusal muscle fibres which occurred during these effects was observed. Seldom, and only for high concentrations of ACh and SCh, a decrease in afferent activity following the excitatory effects was found. Tubocurarine chloride (10(-5)-10(04) g/ml) in the bath prevented both motor fibres and drugs effects. Sometimes slight transient excitation occurred at very high concentrations of the two tested substances; however, this effect was prevented by stronger curarization. The observed blocking effects were always reversed by removing tubocurarine from the bath. No more excitatory effects by motor fibres stimulation and by ACh and SCh action could be found after destruction of intrafusal muscle fibres, by pinching them as close as possible to the ends of the spindle. It is suggested that ACh and SCh act indirectly by causing mechanical changes in intrafusal muscle fibres, and that a direct action on sensory nerve endings, if any, cannot, by itself, increase the afferent activity of the receptor.

Acetylcholine↗