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Biomedical subjects

M B Maron

Publications and source records attributed to M B Maron.

At least 19 recordsLinked to original sources
PubMed2001

beta(2)-adrenergic receptor overexpression increases alveolar fluid clearance and responsiveness to endogenous catecholamines in rats.

beta-Adrenergic agonists accelerate the clearance of alveolar fluid by increasing the expression and activity of epithelial solute transport proteins such as amiloride-sensitive epithelial Na(+) channels (ENaC) and Na,K-ATPases. Here we report that adenoviral-mediated overexpression of a human beta(2)-adrenergic receptor (beta(2)AR) cDNA increases beta(2)AR mRNA, membrane-bound receptor protein expression, and receptor function (procaterol-induced cAMP production) in human lung epithelial cells (A549). Receptor overexpression was associated with increased catecholamine (procaterol)-responsive active Na(+) transport and increased abundance of Na,K-ATPases in the basolateral cell membrane. beta(2)AR gene transfer to the alveolar epithelium of normal rats improved membrane-bound beta(2)AR expression and function and increased levels of ENaC (alpha subunit) abundance and Na,K-ATPases activity in apical and basolateral cell membrane fractions isolated from the peripheral lung, respectively. Alveolar fluid clearance (AFC), an index of active Na(+) transport, in beta(2)AR overexpressing rats was up to 100% greater than sham-infected controls and rats infected with an adenovirus that expresses no cDNA. The addition of the beta(2)AR-specific agonist procaterol to beta(2)AR overexpressing lungs did not increase AFC further. AFC in beta(2)AR overexpressing lungs from adrenalectomized or propranolol-treated rats revealed clearance rates that were the same or less than normal, untreated, sham-infected controls. These experiments indicate that alveolar beta(2)AR overexpression improves beta(2)AR function and maximally upregulates beta-agonist-responsive active Na(+) transport by improving responsiveness to endogenous catecholamines. These studies suggest that upregulation of beta(2)AR function may someday prove useful for the treatment of pulmonary edema.

Adenoviridae↗
PubMed2001

Effect of high transcapillary pressures on capillary ultrastructure and permeability coefficients in dog lung.

To determine the correlation between ultrastructural and physiological changes in blood-gas barrier function in lungs transiently exposed to very high vascular pressures, we increased capillary transmural pressure (Ptm) of 6 canine isolated perfused left lower lung lobe preparations (high-pressure group) to 80.3 Torr for 3.8 min and then determined the capillary filtration (K(fc)) and osmotic reflection (sigma(d)) coefficients at a Ptm of 19.1 Torr in the ventilated lung lobes. This was followed by perfusion fixation of the lobes at a Ptm of 20.5 Torr for ultrastructural analysis. These data were compared with those obtained in six lobes in which Ptm was not transiently elevated before K(fc), sigma(d), and ultrastructural evaluation. K(fc) was higher [0.249 +/- 0.042 (SE) vs. 0.054 +/- 0.009 g. min(-1). Torr(-1). 100 g(-1); P < 0.01] and sigma(d) was lower (0.52 +/- 0.07 vs. 0.85 +/- 0.08; P < 0.01) in the high-pressure group. In contrast, although endothelial and epithelial breaks were occasionally observed in some experiments, their incidence was not increased in the high-pressure group. These data suggest that the increased transvascular water and protein flux occurred through pathways of a size not resolvable by electron microscopy after vascular perfusion-fixation at a Ptm of 20.5 Torr.

Animals↗
PubMed2000

Inactivation of one copy of the mouse neurotrophin-3 gene induces cardiac sympathetic deficits.

Whether two copies of the neurotrophin-3 (NT3) gene are necessary for proper development of cardiac sympathetic innervation was investigated in mice carrying a targeted inactivation of the NT3 gene. Heterozygous (+/-) and null (-/-) mutant mice had fewer stellate ganglion neurons than did wild-type (+/+) mice at postnatal day 0 (P0 or birth), and this deficit was maintained between adult (P60) +/- and +/+ mice. The sympathetic innervation of the heart matured postnatally in +/+ and +/- mice. Tyrosine hydroxylase (TH)-positive axons were restricted largely to the epicardium at P0, were concentrated around large blood vessels in the myocardium at P21, and were present among cardiac myocytes at P60. Cardiac norepinephrine (NE) concentrations paralleled the growth of the sympathetic axons into the heart. NE concentrations were equivalent among +/+, +/-, and -/- mice at birth, but differences between +/- and +/+ mice increased with age. Adult +/- mice also exhibited lower resting heart rates and sympathetic tonus than +/+ mice. Thus deletion of one copy of the NT3 gene translates into anatomical, biochemical, and functional deficits in cardiac sympathetic innervation of postnatal mice, thereby indicating a gene-dosage effect for the NT3 gene.

Aging↗
PubMed2000

Otorhinolaryngological assessment and psychological adjustment in tanning industry workers.

The purpose of the study was to verify the presence of any symptoms and otorhinolaryngological pathologies and to determine any discomfort and psychophysical changes among workers in the tanning industry. The study involved 129 subjects working in tanning industries in the Chiampo valley (Veneto region of Italy). Their clinical history was recorded and they underwent objective ENT examination and pure-tone audiometry. For the psychodiagnostic evaluation, four questionnaires were administered (EPI, STAI, ZUNG and GHQ). ENT assessment revealed no objective problems and findings were within the normal range in the majority of cases. Hearing function was also generally normal or within the normal range for an individual's age. Psychological evaluation revealed a valid psychological adjustment in almost all cases, despite the majority of workers reporting some subjective discomfort attached mainly to the particularly unpleasant smell in a micro-climate with a high rate of humidity. The findings of this preliminary investigation enable us to claim that the working environment in the tanning industries is not severely harmful for the upper airways and hearing function. It is worth noting the normality of the workers' psychological adjustment, which indicates a valid psycho-physical balance in these subjects who operate in an environment with unpleasant features.

Adaptation, Psychological↗
PubMed1999

Effect of epinephrine on alveolar liquid clearance in the rat.

Endogenous epinephrine has been found to increase alveolar liquid clearance (ALC) in several pulmonary edema models. In this study, we infused epinephrine intravenously for 1 h in anesthetized rats to produce plasma epinephrine concentrations commonly observed in this species under stressful conditions and measured ALC by mass balance. Epinephrine increased ALC from 31.5 +/- 3.2 to 48.9 +/- 1.1 (SE)% of the instilled volume (P < 0.05). The increased ALC was prevented by either propranolol or amiloride. To determine whether ALC returns to normal after plasma epinephrine concentration normalizes, we measured ALC 2 h after stopping an initial 1-h epinephrine infusion and found ALC to be at baseline values. Finally, to determine whether desensitization of the liquid clearance response occurs, we evaluated the effects of both repeated 1-h infusions and a continuous 4-h infusion of epinephrine on ALC and found no reduction in ALC under either condition. We conclude that epinephrine increases ALC by stimulating beta-adrenoceptors and sodium transport, that the increase is reversible once plasma epinephrine concentration normalizes, and that desensitization of the ALC response does not appear to occur after 4 h of continuous epinephrine exposure.

Adrenergic beta-Agonists↗
PubMed1999

Importance of behavior in response to tinnitus symptoms.

Among subjects affected by tinnitus, two groups are distinguished: patients who can cope positively with the symptom and patients who cannot cope with it. These differing attitudes suggest the necessity to study affected patients' "illness behavior" (i.e., a subjective interpretation of symptoms concerning body functioning). Our study considered 125 idiopathic tinnitus sufferers who requested a visit by an otorhinolaryngologist expressly for this symptom. All patients were invited to complete the illness behavior questionnaire (IBQ). IBQ mean score results were lower for affective inhibition and irritability and resulted in higher denial. Patients with more psychological suffering presented higher levels of hypochondria, disease convinction, and dysphoria. Results revealed a correlation between psychological suffering and tinnitus intensity: The group of patients with stronger psychological suffering included more subjects with a higher intensity level. The other group included more subjects with a moderate intensity level. Within the psychological evaluation of tinnitus sufferers, the IBQ results demonstrated particular sensitivity in revealing patients' nonadaptation area in coping with the symptom.

Adaptation, Psychological↗
PubMed1998

Effect of neuropeptide Y on hemodynamics of the rabbit lung.

We evaluated the effect of neuropeptide Y (NPY) on the hemodynamics of the isolated rabbit lung perfused at constant flow and outflow pressure. Doses of 10(-8) and 10(-7) M NPY increased pulmonary arterial pressure (Ppa) from 11.5 +/- 1.0 (SE) mmHg to, respectively, 16.4 +/- 1.5 and 26.0 +/- 3.8 mmHg (P < 0.05, n = 5 mmHg lungs), with 78 +/- 4% of the increase at 10(-7) M resulting from an increased arterial resistance. At the latter dose, pulmonary capillary pressure increased from 5.8 +/- 0.9 to 9.4 +/- 1.0 mmHg (P < 0.05). When administered in the presence of norepinephrine, 10(-8) and 10(-7) M NPY (n = 6) produced extreme increases in Ppa to 66.1 +/- 20.5 and 114.7 +/- 25.5 mmHg, respectively, that were due primarily to an increased arterial resistance. To determine the significance of circulating NPY as a pulmonary vasoactive agent, we measured plasma NPY-like immunoreactivity in anesthetized rabbits after massively activating the sympathetic nervous system with veratrine. NPY-like immunoreactivity increased from 74 +/- 10 to 111 +/- 10 (SE) pM (P < 0.05). Thus, although NPY is a potent vasoconstrictor in the rabbit lung, it is not likely that plasma NPY concentrations rise sufficiently, even after massive sympathetic nervous system activation, to produce pulmonary vasoconstriction in the intact rabbit.

Animals↗
PubMed1998

Dose-response relationship between plasma epinephrine concentration and alveolar liquid clearance in dogs.

Previously, alveolar liquid clearance (ALC) was observed to increase in a canine model of neurogenic pulmonary edema (NPE) by adrenal epinephrine (S. M. Lane, K. C. Maender, N. E. Awender, and M. B. Maron. Am. J. Respir. Crit. Care Med. 158: 760-768, 1998). In this study the dose-response relationship between plasma epinephrine concentration and ALC was determined in anesthetized dogs by infusing epinephrine to produce plasma concentrations of 256 +/- 37, 1,387 +/- 51, 15,737 +/- 2,161, and 363,997 +/- 66,984 (SE) pg/ml (n = 6 for each concentration) for 4 h and measuring the resultant ALC. The latter was determined by mass balance after instillation of autologous plasma into a lower lung lobe. These plasma concentrations produced ALCs of 14.3 +/- 1.2, 20.5 +/- 1.9, 30.1 +/- 1.5, and 37.9 +/- 2.7% of the instilled volume, respectively. ALC after the lowest infusion rate was not different from that previously observed under baseline conditions (14.1 +/- 2.1%), whereas in a previous study of NPE, plasma epinephrine concentration increased to 7,683 +/- 687 pg/ml and ALC was 30.4 +/- 1.6%. These data indicate that, during recovery from canine NPE, ALC is not maximally stimulated and suggest that it might be possible to pharmacologically produce further increases in the rate of resolution of this form of edema.

Algorithms↗
PubMed1998

Adrenal epinephrine increases alveolar liquid clearance in a canine model of neurogenic pulmonary edema.

Case reports of neurogenic pulmonary edema (NPE) often indicate that the edema resolves quickly. Because plasma epinephrine concentration may be elevated in NPE, and epinephrine has been shown to increase the rate of alveolar liquid clearance (ALC), we determined if ALC was increased in a canine model of NPE produced by the intracisternal administration of veratrine. ALC was determined by instilling autologous plasma into a lower lung lobe and using the increase in instillate protein concentration after 4 h to calculate the volume of fluid cleared from the airspaces by mass balance. To prevent pulmonary hypertension and edema, which would confound the mass balance analysis, carotid arterial blood was allowed to drain into a reservoir as pulmonary arterial pressure started to rise after veratrine administration. ALC in animals administered veratrine (n = 6) was 30.4 +/- 1.6 (SE)% of the instilled volume compared with 14.1 +/- 2.1% observed in control animals. The increase in ALC could be inhibited by adrenalectomy, beta2-adrenergic blockade using ICI 118,551, or sodium channel blockade using amiloride and could be duplicated by infusing epinephrine to increase plasma epinephrine concentration to levels observed in NPE. These data indicate that the increased ALC was mediated by adrenal epinephrine and suggest that edema resolution in patients with NPE might be accelerated by endogenous epinephrine.

Adrenal Glands↗
PubMed1998

Psychological distress in patients with tinnitus.

OBJECTIVE: This study was conducted to evaluate the psychological distress in patients with tinnitus that is often correlated with sleeping disorders, difficulties in concentration, and compromized social relations. METHODS: Eighty-four patients were studied using preliminary clinical and audiologic evaluations, and successive psychological tests. RESULTS: The cluster analysis indicated two essential groups composed of 45 patients (CLST-1) and 38 patients (CLST-2), respectively. The CLST-1 group had higher scores for depression, anxiety, and neuroticism. The IBQ CLST-1 revealed a greater degree hypochondria, conviction of disease dysphoria, and irritability. CONCLUSIONS: Our results indicate that the relationship between the intensity of the tinnitus and the extent of the distress is supported by the larger number of patients with more intense tinnitus in the first cluster. The CLST-2 with its normal psychological test results, apart from marked denial, would support the hypothesis of a somatic expression of the distress.

Adult↗
PubMed1997

Alveolar liquid clearance in multiple nonperfused canine lung lobes.

We evaluated the ability of canine isolated nonperfused lung lobes to absorb fluid from their air spaces by simultaneously measuring alveolar liquid clearance (ALC) in three lobes removed from the same dog. Autologous plasma was instilled in the air spaces of each lobe, and the increase in plasma protein concentration resulting from fluid reabsorption was used to calculate ALC. ALC after 4 h was 16.5 +/- 0.6% (SE) of the instilled fluid volume under baseline conditions and was 30.2 +/- 1.3% after terbutaline (10(-5) M) administration. These values were similar to those previously reported for intact dogs. Propranolol (10(-4) M) and ouabain (10(-3) M) reduced ALC in terbutaline-stimulated lobes to 20.4 +/- 0.8 and 3.9 +/- 1.4%, respectively. There was no significant difference in ALC among the three lobes under either baseline conditions or after terbutaline administration. These data indicate that the sodium and water transport mechanisms of the canine alveolar epithelium remain viable during 4 h of nonperfusion and that there are no intrinsic differences in the transport properties of individual lung lobes. The ability to study several lobes simultaneously without the need for perfusion will allow for the design of experiments in which multiple interventions can be studied by using lung lobes from the same animal.

Animals↗
PubMed1996

Illness behaviour, personality traits, anxiety, and depression in patients with Menière's disease.

OBJECTIVE: This study was conducted to evaluate illness behaviour, personality traits, anxiety and depression in patients with Menière's disease. DESIGN: A prospective study of patients and review of the literature is presented. METHODS: Fifty patients presenting to the ENT department of the Padua University were studied using the Illness Behaviour Questionnaire (IBQ), Eysenck Personality Inventory (EPI), State Trait Anxiety Inventory, and the Zung Self-Rating Depression Scale. RESULTS: Mean scores were found to be higher than normal for neuroticism with a stronger psychological perception of disease and a lower level of affective inhibition. Cluster analysis of the IBQ scores identified a subgroup of Meniere's patients with normal scores and another with severe psychological distress associated with high levels of neuroticism and psychoticism in the EPI and an abnormal illness behaviour: these were older patients with a longer history of Menière's disease and more hospital stays. CONCLUSION: Our results indicate the possibility of distinguishing those patients whose personality traits could facilitate the development of abnormal illness behaviour and psychological symptoms in relation to Menière's disease. Analysis of the data suggests that there is no specific link between such psychological aspects and the clinical disease.

Adult↗
PubMed1995

Role of EDRF in the cardiopulmonary dysfunction produced by massive sympathetic activation.

This study was undertaken to determine whether endothelium-derived relaxing factor (EDRF) modulates the pulmonary and systemic hemodynamic responses to massive sympathetic nervous system (SNS) activation and, in so doing, also modulates the degree of SNS-induced left ventricular (LV) dysfunction and the likelihood for pulmonary edema formation. The SNS of 13 anesthetized untreated rabbits and 14 anesthetized rabbits pretreated with the EDRF inhibitor, N omega-nitro-L-arginine (L-NNA, 20 mg/kg), was massively activated with an intracisternal injection of veratrine. Pulmonary and systemic arterial pressures increased to the same extent in both groups, but LV end-diastolic pressure was significantly lower in untreated rabbits. During this time, cardiac output decreased by 37% in L-NNA pretreated rabbits compared with 8% in untreated animals. Peak systemic and pulmonary vascular resistances increased significantly in L-NNA rabbits, whereas only systemic vascular resistance increased significantly in untreated rabbits. However, this increase in systemic vascular resistance was threefold less than that observed for L-NNA-treated animals. Although the degree of LV dysfunction was greater in the L-NNA rabbits, pulmonary edema developed less frequently in this group. We suggest that when EDRF release is inhibited during massive SNS activity, pulmonary vascular resistance increases markedly, which causes the right ventricle to fail. We further suggest that the reduced right ventricular output maintains pulmonary microvascular pressure below levels required for edema development.

Animals↗
PubMed1994

Temporal changes in left ventricular function after massive sympathetic nervous system activation.

Intense activation of the sympathetic nervous system (SNS) decreases the contractile state of the rabbit left ventricle (LV). In this study, we determined the time course of LV dysfunction after massive central activation of the SNS in dogs. Veratrine (40-80 micrograms/kg) was injected intracisternally to activate the SNS in six chloralose-anesthetized dogs, and LV end-diastolic pressure (LVEDP), cardiac output, heart rate, and aortic pressure (Pa) were measured at 30-min intervals for 3 h. Pa increased from 147 +/- 8 (SE) to 272 +/- 7 mmHg (1 mmHg = 133.3 Pa) within 15 min, then declined to 148 +/- 16 mmHg by 1 h LV function curves (stroke work versus LVEDP or stroke work verus LV transmural pressure) showed a marked decrease in slope and a shift to the right within minutes after activating the SNS, which persisted for the duration of the experiment. These data indicate that LV contractility was diminished in these animals. No changes in LV function were observed in three dogs serving as time-matched controls. In three additional dogs, LV pressure was raised to a degree similar to that observed after SNS activation by constricting the ascending aorta for 1 h. These animals exhibited only modest shifts in the LV function curve during and after aortic constriction. Mean plasma catecholamine concentration increased by one to two orders of magnitude in animals after SNS activation, but only minor changes were observed in the other two groups. We conclude that myocardial contractility declines markedly soon after massive SNS activation and is not solely a function of the initial hypertensive period.

Acidosis↗
PubMed1994

Edema development and recovery in neurogenic pulmonary edema.

We determined the time course of changes in extravascular lung water (EVLW) that occur after massive sympathetic activation produced by intracisternal veratrine administration in chloralose-anesthetized dogs. Three groups of dogs were studied. In the first group (n = 9), acute increases in EVLW (occurring within minutes) were determined both by measuring extravascular thermal volume and by gravimetric analysis. In the second (n = 6) and third (n = 7) groups, changes in EVLW were followed for 2-3 h after veratrine administration. Extravascular thermal volume was measured in the second group. In the third group, right atrial injections of a vascular indicator (125I-labeled serum albumin) and an extravascular indicator (3HOH) were made while blood was sampled from the pulmonary artery (PA) and left atrium, and EVLW was determined by deconvolution of the left atrial and PA concentration-time curves. Indicator-dilution and gravimetric EVLW increased acutely only in dogs in which PA pressure exceeded 60 Torr, with two- to four-fold increases in EVLW being observed in dogs that developed the highest PA pressures (maximum 94 Torr). Thus, severe edema can develop rapidly after massive sympathetic nervous system activation but requires extreme degrees of pulmonary hypertension. In several dogs after the acute increase in EVLW associated with the pulmonary hypertension, the indicator-dilution EVLW decreased with time. These decreases appear to effect clearance of edema fluid rather than alterations in perfusion.

Animals↗
PubMed1994

Time course of blood volume changes in an isolated lung lobe after venous pressure elevation.

The elevation of venous pressure (Pv) in isolated perfused organs causes organ weight to increase in a biphasic manner. The initial rapid phase results primarily from an increase in blood volume (BV), whereas the second slower phase is generally considered to reflect fluid filtration. Recent studies have suggested, however, that BV may continue to increase during the slow weight gain phase. To address this question, we made serial measurements of circulating BV by indicator dilution with indocyanine green dye in a canine isolated perfused left lower lung lobe (LLL) preparation during 40 min of Pv elevation. Pv was raised to approximately 18 Torr in six LLLs beginning an average of 28 min after the start of perfusion. After an initial rapid increase, BV continued to increase at a slower rate for approximately 30 min. The increase in BV observed between 3 and 40 min of Pv elevation [4.3 +/- 0.3 (SE) ml] was 47.9 +/- 9.1% of the weight gain that occurred during this period. In six additional LLLs, Pv elevation was delayed until approximately 70 min after the perfusion was started. In these LLLs, BV generally achieved constancy 3 min after Pv was elevated. These data indicate that the dynamics of the BV response of this preparation to Pv elevation is time dependent and that gravimetric determinations of the rate of fluid filtration may substantially overestimate the true filtration rate in the presence of continuing increases in BV. The increases in BV observed in the first group of LLLs appear to be due to vascular recruitment rather than stress relaxation.

Animals↗
PubMed1993

Model-free numerical deconvolution of recirculating indicator concentration curves.

This paper investigates two model-free methods for numerical deconvolution of recirculating indicator concentration curves. The two methods, damped least squares and discrete orthogonal polynomial deconvolution, are applied to simulated data to verify the reliability of the algorithms. Both deconvolution methods provide damping that results in estimated transport functions that are smooth and reasonable estimates of the actual simulated transport function. On convolution with the simulated input curve, the estimated transport functions provide good fits to the simulated output curve. In addition, methods for identifying an optimal solution and for truncating the artifactually long oscillatory tails of the estimated transport functions are proposed, which appear to allow for reasonably accurate estimation of the mean transit times and variances of the transport functions as well. When either method was applied to indicator dilution data obtained from the pulmonary artery and left atrium, it was computationally stable while producing transport functions that when convolved with the input concentration curves provided good fits to the output concentration curves. The combined simulation and experimental results suggest that the proposed methods should be useful for estimating circulation transport functions from indicator dilution data.

Algorithms↗