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Biomedical subjects

R Armentano

Publications and source records attributed to R Armentano.

At least 19 recordsLinked to original sources
PubMed2006

[Vascular access for haemodyalisis. Comparative analysis of the mechanical behaviour of native vessels and prosthesis].

INTRODUCTION: The prosthesis nowadays used in the vascular access for haemodialysis have low patency rates, mainly due to the luminal obstruction, determined by the intimal hyperplasia. Several factors have been related to de development of intimal hyperplasia and graft failure. Among them are the differences in the biomechanical properties between the prosthesis and the native vessels. In the searching for vascular prosthesis that overcomes the limitations of the currently used, the cryopreserved vessels (cryografts) appear as an alternative of growing interest. However, it is unknown if the mechanical differences or mismatch between prosthesis and native vessels are lesser when using cryografts. OBJECTIVE: To characterize and compare the biomechanical behaviour of native vessels used in vascular access and cryografts. Additionally, segments of expanded polytetrafluoroethylene (ePTFE) were also evaluated, so as to evaluate the potential biomechanical advantages of the cryografts respect to synthetic prosthesis used in vascular access. METHODS: Segments from human humeral (n = 12), carotid (n = 12) and femoral (n = 12) arteries, and saphenous vein (n = 12), were obtained from 6 multiorgan donors. The humeral arteries were studied in fresh state. The other segments were divided into two groups, and 6 segments from each vessel were studied in fresh state, while the remaining 6 segments were evaluated after 30 days of criopreservation. For the mechanical evaluation the vascular segments and 6 segments of ePTFE were mounted in a circulation mock and submitted to haemodynamic conditions similar to those of the in vivo. Instantaneous pressure (Konigsberg) and diameter (Sonomicrometry) were measured and used to calculate the viscous and elastic indexes, the compliance, distensibility and characteristic impedance. For each mechanical parameter studied, the mismatch between the prosthesis and the native vessel was evaluated. RESULTS: The ePTFE was the prosthesis with the higher mechanical mismatch (p < 0.05). The venous and arterial cryografts showed the least mismatch with native veins and arteries, respectively. The prosthesis with the least mechanical mismatch was different, depending on the native vessel evaluated, and for a native vessel, on the parameter considered. CONCLUSION: The mechanical mismatch between the native vessel and the vascular prosthesis used in a vascular access could be reduced using cryografts.

Adult↗
PubMed2005

Immunohistochemical and serological 90K/Mac-2BP detection in hepatocellular carcinoma patients: different behaviour of two monoclonal antibodies.

To clarify the biological role of the 90K/Mac-2BP glycoprotein, we evaluated the ability of two MAbs SP-2 and 1A4.22, to reveal this glycoprotein in both serum and tissue from hepatocellular carcinoma (HCC) patients. Tissue expression of 90K was detected by the immunohistochemical method in 20 HCC patients, while the 90K serum level was assessed by the ELISA assay in 13 HCC patients. MAb SP-2 was reactive only in serum, with a mean value of 12.8+/- 6.7 microg/ml . On the contrary, MAb 1A4.22 revealed immunoreactivity both in 92% of sera and in 60% of neoplastic samples. Positive staining was seen only in the epithelial cells and was cytoplasmic and granular in all instances. The mean 90K serum level assayed with MAb 1A4.22 was 29.4 +/- 13.7 microg/ml. Patients with a 90K serum level 30 microg/ml. Moreover, a possible poor prognostic role was observed for negative 90K in tissue. Our results suggest that only MAb 1A4.22 could demonstrate 90K glycoprotein expression in paraffin-embedded tissue and that this MAb could have a diagnostic and prognostic role in both sera and tissues from HCC patients.

Aged↗
PubMed2004

Smooth muscle role on pulmonary arterial function during acute pulmonary hypertension in sheep.

AIM: We determined the wall mechanical response of the pulmonary artery (PA) to acute pulmonary hypertension induced pharmacologically and by an occlusion maneuver, to study the vascular response of the local segment and its influence in the whole pulmonary circulation. METHODS: Pulmonary pressure and diameter were measured in six anaesthetized sheep under steady-state conditions. Transient hypertension in the PA was induced by phenylephrine (PHE) and a high pressure (HP) mechanical occlusion aimed at producing the same pulse and mean pressure responses. A viscoelastic arterial wall model was applied and the elastic (E(pd)) and viscous (micro) indexes were obtained. The micro/E(pd) ratio was adopted to quantify the damping performance of the arterial wall segment. The diastolic time constant was used as an indicator of the whole pulmonary buffering function. The systemic pressure was always measured. RESULTS: The pulmonary mean, systolic and pulse pressure increases (P < 0.05) were similar during PHE and HP, with respect to control. PHE also induced a systemic pressure rise (P < 0.05). The E(pd) elastic index increased during HP (P < 0.05) and tended to increase during PHE with respect to control. The viscous index micro only increased with PHE (P < 0.05) with respect to control and occlusion. The diastolic time constant increased with PHE with respect to control (P < 0.05). CONCLUSIONS: A pressure rise in the PA, induced by an occlusion maneuver, increased local stiffness. Similar pressure rises with smooth muscle activation (PHE), produced both a stiffness and viscous index increase. In PHE resistance increases more than compliance decreases so that the global net effect is a longer decay time. Smooth-muscle activation enhances the local damping effect (micro/E(pd)), concomitant with the buffering function improvement.

Acute Disease↗
PubMed2002

Tauroursodeoxycholic acid reduces damaging effects of taurodeoxycholic acid on fundus gastric mucosa.

We investigated the effects of tauroursodeoxycholic acid (TUDCA) to assess whether this acid may also have "protective" effects similar to those found with ursodeoxycholic acid (UDCA). We used a well-known amphibian model of gastric mucosa, and studied the effects of taurodeoxycholic acid (TDCA) on electrical transepithelial parameters, acid secretion and histology in absence or in presence of TUDCA. Mucosal exposure to TDCA, after stimulation with histamine, caused a reduction in transepithelial potential difference (V(t)) and transepithelial resistance (R(t)) and a decrease in acid secretion while mucosal exposure to TUDCA did not cause a significant change in the electrical parameters. Moreover, TDCA primarily affected the neck cells, while TUDCA affected only oxyntic cells, causing a similar degree of injury to that observed in controls. Mucosal exposure to TUDCA plus TDCA caused a reduction in short circuit current (I(sc)) and R(t), whereas acid secretion did not change. These results suggest that: (1) TUDCA reduces the damaging effects of TDCA on fundus gastric mucosa; (2) TUDCA may play an important role in the treatment of gastritis associated with bile reflux.

Animals↗
PubMed2001

Gender differences in wall shear-mediated brachial artery vasoconstriction and vasodilation.

OBJECTIVES: We sought to investigate wall shear rate (WSR) and brachial artery diameter (BAD) changes simultaneously and to determine whether any gender differences exist in arterial reactivity. BACKGROUND: Wall shear rate/stress and arterial reactivity are rarely assessed at the same time. Furthermore, flow-mediated vasoconstriction has received less attention than flow-mediated vasodilation in humans. METHODS: A new noninvasive evaluation of WSR in the brachial artery, using multigated, pulsed Doppler velocimeter and a double-transducer probe moved and fixed by a robotic system, was developed. RESULTS: The validity of the system was tested in vitro with calibrated tubes and showed a high correlation (r = 0.98, p < 0.001). In 10 men and 10 women of similar age, induction of low and high shear rates by forearm occlusion produced significant vasoconstriction and vasodilation, respectively. The time lag for maximal BAD changes was 3 min for vasoconstriction and 1 min for vasodilation. A greater half-time for vasodilation (96 +/- 6 for men and 86 +/- 12 s for women) than for shear rate (31 +/- 5 s for men and 34 +/- 4 s for women) was observed after discontinuation of occlusion. Relative BAD was correlated with WSR changes, showing a significantly higher slope in women than in men (p < 0.01). Moreover, a larger normalized arterial diameter per shear rate was observed for vasoconstriction (p < 0.01) and vasodilation (p < 0.01) in women than in men. CONCLUSIONS: Shear-mediated arterial vasodilation and vasoconstriction were more pronounced in women than in men, suggesting different gender-related sensitivity in the regulation of large-artery vascular tone.

Adult↗
PubMed2001

Do arterial effects of antihypertensive drugs depend on subject's serum cholesterol?

Effects of antihypertensive treatment on large arteries may be influenced by the type of drug and concomitant risk factors such as blood cholesterol. To explore these possibilities we investigated the common carotid artery of 20 subjects with low cholesterol and 19 subjects with high cholesterol, all with essential hypertension, randomly allocated to 3 months of treatment with nitrendipine (20 mg/d) or trandolapril (2 mg/d). Carotid parameters were determined by recording instantaneous pressure (applanation tonometry) and diameter (echotracking device) and by modeling the pressure-diameter loop to obtain the Peterson modulus, stiffness index, measured and isobaric compliances, and wall viscosity. Effects of drugs on carotid parameters did not differ, except on systolic and diastolic diameters (p < 0.01), which increased insignificantly under nitrendipine but decreased (p < 0.01) under trandolapril. Blood cholesterol status did not influence carotid effects of trandolapril, whereas patients with low and high cholesterol treated with nitrendipine exhibited significant differences in drug effects on (a) systolic and pulse pressures (p < 0.05), which decreased in patients with low cholesterol (p < 0.01, p < 0.05) but not in those with high cholesterol; (b) diastolic diameter (p = 0.05), which increased insignificantly in patients with low cholesterol but was unchanged in those with high cholesterol; and (c) wall viscosity (p < 0.01), which decreased in patients with low cholesterol (p < 0.05) but increased insignificantly in those with high cholesterol. Also, wall viscosity change under nitrendipine was positively related to the baseline blood cholesterol ( r = 0.64, p < 0.01). Thus, nitrendipine and trandolapril show noteworthy differences in their effects on the carotid artery, in particular with respect to the status of blood cholesterol, but these differences should be confirmed by larger studies.

Adult↗
PubMed1999

Carotid wall inertial index increase is related to intima-media thickening in hypertensive patients.

OBJECTIVE: The aim of this study is to evaluate the relationship between carotid intima-media thickness (IMT) and arterial wall inertial behaviour. METHODS: The simultaneous and noninvasive assessment of the intima-media complex and arterial diameter waveform was performed using high-resolution ultrasonography. The common carotid artery of eleven normotensive subjects (NTA) and eleven mild-to-moderate essential hypertensive patients (HTA) were measured noninvasively using tonometry and an automatic densitometric analysis of B-mode images to obtain IMT and instantaneous pressure (P) and diameter (D) loops. A linear discrete time model was used to estimate the inertial index (K(M)) using a system modelling-identification approach. RESULTS: In NTA K(M) was 0.333+/-0.256 (mmHg x s2/mm) and IMT 0.643+/-0.061 (mm), whereas in HTA K(M) was 0.798+/-0.590 (P < 0.05) and IMT 0.760+/-0.034 (P < 0.025). When all data of K(M) versus IMT of NTA and HTA were pooled in a linear regression analysis, a correlation coefficient of r = 0.61 (P < 0.05) was obtained. CONCLUSION: Wall inertia increase was associated with a higher IMT, suggesting that the intima-media thickening might be partially related to vascular hypertrophy manifested as increase of inertial behaviour.

Adult↗
PubMed1998

[Vascular dysfunction in hypertension evaluated by nonivasive assessment of arterial impedance].

The effects of high blood pressure on arterial vessels has become an important topic of research. These effects can be evaluated by analyzing three major components: systemic vascular resistance, arterial compliance and wave reflection. The increase in systemic vascular resistance and arterial stiffness produces modifications of left ventricular afterload and morphologic changes of pressure and flow waves. These effects can eventually cause structural changes of the left ventricle, an increase in oxygen consumption and a decrease in coronary perfusion. Until recently, invasive methods were the only means to evaluate arterial function. The aim of this review is to assess the usefulness of non invasive methods to determine the components of arterial impedance in order to evaluate the hemodynamic changes due to high blood pressure.

Arteries↗
PubMed1997

Polyamine levels and ODC activity in intestinal-type and diffuse-type gastric carcinoma.

Gastric carcinomas are divided into two types according to Lauren's classification: intestinal and diffuse types. Polyamines (putrescine, spermidine, and spermine) are polycations involved in neoplastic growth of gastrointestinal mucosa. A key role is also played by ornithine decarboxylase, the rate limiting enzyme in polyamine metabolism. Our aim was to investigate whether there were differences between the two types of tumor in polyamine metabolism. Twenty-seven patients with gastric carcinoma entered the study. Seventeen carcinomas were classified as diffuse type and 10 as intestinal type. Polyamine levels were evaluated by high-performance liquid chromatography. Ornithine decarboxylase activity was measured by a radiometric technique. Polyamine levels and ornithine decarboxylase activity were significantly higher in intestinal type samples than diffuse type samples. A similarity of polyamine levels in intestinal type samples with levels previously observed in patients with colorectal adenocarcinoma was also found. These findings show a different proliferative behavior of these two types of tumor, and therefore different therapeutic strategies can be hypothesized.

Adenocarcinoma↗
PubMed1995

Effects of hypertension on viscoelasticity of carotid and femoral arteries in humans.

We compared the properties of common carotid and femoral arteries of 16 normotensive and 14 hypertensive men. Arterial pressure and diameter were recorded noninvasively in each vessel by tonometric and echotracking devices. The x-y composition of pressure and diameter waves provided the diameter-pressure hysteresis loop. The elastic diameter-pressure curve and wall viscosity index were deduced after hysteresis elimination. The compliance-pressure and distensibility-pressure curves were derived from the diameter-pressure curve, allowing the calculation of effective compliance and distensibility at the prevailing pressure of each subject and isobaric compliance and distensibility at the same standard pressure in all subjects. Systolic, diastolic, mean, and pulse pressures and diameters in each vessel were higher in the hypertensive than the normotensive group, except carotid pulse diameter, which did not differ. The carotid diameter-pressure, compliance-pressure, and distensibility-pressure curves did not differ between groups. In the carotid artery hypertensive patients had isobaric compliance and distensibility values similar to those of normotensive subjects, despite lower effective compliance (P < .05) and distensibility (P < .01). The femoral diameter-pressure curve was higher (P < .05) and the femoral compliance-pressure and distensibility-pressure curves were lower (P < .01) in the hypertensive than the normotensive group. Hypertensive patients had effective and isobaric femoral compliance and distensibility values lower than to those of normotensive subjects (P < .001). In both arteries, viscosity index was higher in the hypertensive than the normotensive group (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[DNA content in colorectal carcinomas: application of image analysis to archival material].

The most studied biological parameter of human tumours is the DNA nuclear content. In the present study we assessed the DNA content of 197 colorectal cancers from 180 patients using archival material (tissues routinely processed and paraffin-embedded) for image analysis. The metastatic lymph nodes were also included in the study in 54 Dukes "C" stage cases and 19/25 Dukes "D" stage cases. A total of 452 sections, 5 mu thick, were submitted to image analysis in static cytometry. DNA diploid pattern was found in 72/452 samples (15.9%) and the DNA-aneuploid pattern in 380/452 (84.1%). Two different areas for each tumour were examined but we found a concordance of diploid pattern in only 23 cases. DNA-aneuploidy, regarded as presence of at least one sample with an aneuploid peak in the same tumour, reached 88% in our study. In conclusion the image analysis of several samples obtained from different areas of the same tumour clearly revealed: a pronounced heterogeneity of ploidy patterns in colon cancer; an overall prevalence of DNA-aneuploidy in colon cancer; a prevalence of diploid pattern in tumours localized in right portion of the colon and in younger patients.

Adenocarcinoma↗
PubMed1991

Mechanical pressure versus intrinsic effects of hypertension on large arteries in humans.

Brachial artery diameter and compliance were measured in 23 normotensive control subjects and 49 hypertensive patients. The results were compared in isobaric conditions by a modeling analysis extrapolating from the measured data a short segment of the pressure-diameter and pressure-compliance curves in the artery. A logarithmic diameter-pressure function was used as well as measurements of brachial artery blood pressure and lumen diameter (by pulsed Doppler), and of brachial-to-radial pulse wave velocity (by mechanography). The measured values of diameter and compliance in the hypertensive patients were 109% and 63%, respectively, of the control group values. By extrapolating the data via the model at the same pressure level in all subjects (the average level of mean blood pressure of the two groups), the isobaric values of diameter and compliance in the hypertensive patients were 107% and 81%, respectively, of the control group values. Overall, measured isobaric diameters and measured compliance correlated with systolic, diastolic, and mean blood pressure values (p less than 0.001), whereas isobaric compliance correlated only with systolic (p less than 0.05) and pulse (p less than 0.01) pressure values. Thus, the increased diameter and reduced compliance of the brachial artery observed in hypertensive humans cannot be attributed solely to the stretching effect of elevated blood pressure, but also to intrinsic alteration of the arterial walls. These could represent either adaptative structural or functional changes secondary to the chronic increase in arterial pressure, or primary abnormalities of the vessel wall.

Adolescent↗
PubMed1990

Effects of muscarinic and beta-adrenergic blockade on the aortic elastic response to epinephrine induced acute hypertension in conscious dogs.

To determine the effects of parasympathetic blockade and beta-blockade on the elastic response of aortic stiffness to vasopressive interventions, we studied 5 unanesthetised adult mongrel dogs by means of a pressure microtransducer and two ultrasonic crystals positioned at opposing sites in the proximal descending thoracic aorta which were used for diameter measurements. Systolic and diastolic changes in pressure and diameter were used to calculate Peterson and incremental elastic moduli. Acute hypertension was induced using infusions of epinephrine during the control period and later propranolol (1.5 mg/kg) plus atropine (0.2 mg/kg). Percent variations of mean aortic diameter were correlated to percent variations in mean aortic pressure in the control period and after autonomic blockade (P less than .001). The slopes of these correlations in the control group were higher than after autonomic blockade (P less than .05). Correlations were also found between Peterson and incremental elastic moduli and mean pressure in the control group and after autonomic blockade (P less than .001). The slopes of the correlations of incremental elastic modulus and Peterson's modulus versus mean aortic pressure were lower in the control group than after blockade (P less than .001). We conclude that in conscious dogs, autonomic blockade with propranolol and atropine decreased the distension and increased the stiffness of the aortic wall in response to acute hypertension mediated by epinephrine.

Acute Disease↗
PubMed1990

Telemetry of aortic pressure in unrestrained animals: validation of the method over a wide range of blood pressure (from 40 to 200 mmHg).

A telemetric method has been designed for continuous measurement of intra-arterial aortic blood pressure in the unrestrained dog. The system used a Konigsberg P7 transducer, a temperature-compensated voltage-controlled oscillator, an FM transmitter, and an FM tuner to convert the signal received into a voltage proportional to aortic blood pressure. The method was validated by comparison with a standard direct method (using cables for transmission). Over a wide range of blood pressure obtained by hypotensive and hypertensive drugs (in total about 2500 data points, ranging from 40 to 200 mmHg), the telemetric method gave almost the same result as the direct method. Absolute error (telemetric measure minus standard measure) was normally distributed, with a mean value of -0.44 mmHg, and a standard deviation of 3.37 mmHg. The telemetric method was designed for future studies on the chronobiology of blood pressure in normal condition, in stress conditions and under drugs.

Animals↗
PubMed1989

[Visco-elastic characteristics of the aorta in conscious dogs in a model of experimental calcinosis].

Effects of experimental calcinosis induced by daily overdose of 500.000 IU Vit D3 during 10 days were studied in 6 mongrel conscious dogs chronically instrumented with intra-aortic Konigsberg microtransducer and two ultrasonic piezo-electric crystals diametrically opposed in the adventitia of the descending thoracic aorta. Simultaneous recording of instantaneous aortic pressure and diameter waves in basal state and during transient acute hypertension induced by intravenous angiotensin bolus (0.1 microgram/kg) allowed to obtain the pressure (y) diameter (x) relationship of the aorta according to an exponential regression: P = expo (beta D + A), with a highly significant correlation coefficient in all animals (r greater than 0.99). (table; see text) Anatomopathological studies of aortas revealed abnormal calcium deposition, ruptures of elastic fibers and disorganization of collagen. Thus, a striking decrease in aortic rigidity is observed after calcinosis in relation with structural changes of elastic materials and responsible in part for a reduction in pulsatile pressure; moreover this unexpected phenomena might represent an initiative process of development of aortic aneurysms.

Animals↗
PubMed1988

Aortic pulsatile pressure and diameter response to intravenous perfusions of angiotensin, norepinephrine, and epinephrine in conscious dogs.

The aortic elastic behavior has been studied in conscious dogs chronically instrumented with a pressure microtransducer and two ultrasonic crystals. Pressure and diameter measurements were analyzed in terms of their mean values and systolic-diastolic variations, enabling calculation of Peterson elastic modulus, and were displayed in the x-y form to obtain pressure diameter hysteresis loops. After recovery from surgery and under autonomic blockade, intravenous perfusions of angiotensin, norepinephrine, and epinephrine were made at incremental steps of doses until steady-state pressure-diameter changes were achieved. The slopes of the positive pressure-diameter correlations obtained at each dose of the same vasoactive substance were higher for angiotensin than norepinephrine (p less than 0.01) and epinephrine (p less than 0.001) and were higher for norepinephrine than epinephrine (p less than 0.05). Similarly, the slopes of the elastic modulus to mean pressure relation were significantly lower for angiotensin than for norepinephrine (p less than 0.05) and epinephrine (p less than 0.001) and were significantly lower for norepinephrine than epinephrine (p less than 0.001). Thus, at the same transmural pressure, the distension and stiffness of the aorta were lower and higher with epinephrine than with norepinephrine, respectively, and with norepinephrine than with angiotensin suggesting different potencies of these drugs in terms of smooth muscle activation in the aorta.

Angiotensin II↗
PubMed1988

Constricting and stiffening action of atropine on aortic response to angiotensin in dogs.

The elasticity of the thoracic aorta was studied in nine dogs instrumented with a pressure microtransducer and two ultrasonic crystals diametrically fixed in the adventitia. Systolic and diastolic changes in pressure and diameter were used to calculate Peterson and incremental elastic moduli. Acute hypertension was induced by infusions of angiotensin performed 1) during the control period, 2) after propranolol (1.5 mg/kg), 3) after atropine (0.2 mg/kg), and 4) after propranolol plus atropine. Absolute and percent variations of mean diameter were correlated to pressure in the control period and after autonomic blockade (p less than 0.01). The slopes of these correlations were not different between propranolol and control groups, but were lower with atropine (p less than 0.01) and with atropine plus propranolol (p less than 0.001) than in the control period. Correlations were also found between Peterson and incremental elastic moduli and mean pressure in the control period and after blockade (p less than 0.001). No differences of slopes existed between propranolol and control groups, but the slope of the correlation relative to the incremental elastic modulus was higher with atropine than in the control period (p less than 0.05), and the slopes of the correlations relative to the Peterson and the incremental elastic moduli were respectively higher with atropine plus propranolol than in the control period (p less than 0.05, p less than 0.05). Thus, atropine decreased the distention and increased the stiffness of the aorta in response to acute angiotensin-mediated hypertension.

Angiotensin II↗