Effects of castration on alpha(1)-adrenoceptor subtypes in the rat aorta

The expression of alpha(1)-adrenoceptor subtypes in several tissues is regulated by gonadal hormones. In this study, we investigated whether castration regulates the alpha(1)-adrenoceptor subtypes mediating the contractions of the aorta from male rats to noradrenaline. Noradrenaline induced similar concentration-dependent contractions in the aorta from control and castrated rats. Treatment of the aorta from both control and castrated rats with the alpha(1B)/alpha(1D)-adrenoceptor alkylating agent chloroethylclonidine resulted in approximate to1600-fold rightward shift in the concentration-response curves to noradrenaline. The pA(2) values found for WB 4101, benoxathian (alpha(1A)-selective) and BMY 7378 (alpha(1D)-selective) indicate that alpha(1D)-adrenoceptors are involved in the contractions of the aorta from control and castrated rats to noradrenaline. However, there was a 15-fold difference between the pK(B) estimated through the lowest effective concentrations of the alpha(1A)-adrenoceptor selective antagonist 5-methyl-urapidil in the aorta from control and castrated rats. The pK(B) estimated in aorta from control rats is consistent with the interaction with alpha(1D)-adrenoceptors (7.58 +/- 0.06), while that calculated in organs from control rats is consistent with alpha(1A)-adrenoceptors (8.76 +/- 0.09). These results suggest that castration induces plasticity in the alpha(1)-adrenoceptor subtypes involved in the contractions of the aorta to noradrenaline. (C) 2003 Elsevier B.V. All rights reserved.

Effects of indoramin in rat vas deferens and aorta: concomitant alpha(1)-adrenoceptor and neuronal uptake blockade

1 the actions of the alpha(1)-adrenoceptor antagonist indoramin have been examined against the contractions induced by noradrenaline in the rat vas deferens and aorta taking into account a putative neuronal uptake blocking activity of this antagonist which could. result in self-cancelling actions.2 Indoramin behaved as a simple competitive antagonist of the contractions induced by noradrenaline in the vas deferens and aorta yielding pA(2) values of 7.38 +/- 0.05 (slope = 0.98 +/- 0.03) and 6.78 +/- 0.14 (slope = 1.08 +/- 0.06), respectively.3 When the experiments were repeated in the presence of cocaine (6 mu M) the potency (pA(2)) of indoramin in antagonizing the contractions of the vas deferens to noradrenaline was increased to 8.72 +/- 0.07 (slope = 1.10 +/- 0.05) while its potency remained unchanged in the aorta (pA(2) = 6.69 +/- 0.12; slope = 1.04 +/- 0.05).4 In denervated vas deferens, indoramin antagonized the contractions to noradrenaline with a potency similar to that found in the presence of cocaine (8.79 +/- 0.07; slope = 1.09 +/- 0.06).5 It is suggested that indoramin blocks alpha(1)-adrenoceptors and neuronal uptake in rat vas deferens resulting in Schild plots with slopes not different from unity even in the absence of selective inhibition of neuronal uptake. As a major consequence of this double mechanism of action, the pA(2) values for this antagonist are underestimated when calculated in situations where the neuronal uptake is active, yielding spurious pK(B) values.

The sympathetic adrenomedullary system, but not the hypothalamic-pituitary-adrenal axis, participates in aorta adaptive response to stress: nitric oxide involvement

Stress induced a decrease in the reactivity of the aorta to noradrenaline (NA), as a consequence of an endothelial nitric oxide (NO) system hyperactivity. The main characteristic of the stress response is activation of the hypothalamic-pituitary-adrenal (HPA) axis and sympathetic adrenomedullary (SA) system. The participation of the HPA axis and SA system in the decreased reactivity to NA in the aorta of rats exposed to 4-h immobilization was investigated. Concentration-response relationships for NA were obtained in the aorta, with and without endothelium, isolated from normal and stressed rats, following these procedures: (1) in the absence and presence of L-NAME; (2) after adrenalectomy (ADX) or not, in the absence or presence of L-NAME; (3) ADX rats treated or not with corticosterone; (4) ADX associated with stress; and (5) treated or not with reserpine. The reactivity of aorta without endothelium was unaffected by the procedures. The reactivity of aorta with endothelium was decreased by either stress or ADX. This effect was reversed by both L-NAME and corticosterone. ADX did not potentiate the decrease in the aorta reactivity induced by stress. Reserpine did not change the reactivity of aorta with endothelium from normal rats, but prevented the decrease in reactivity induced by stress. It is concluded that the HPA axis participates in endothelium-dependent modulation of aorta reactivity in normal conditions and that thr SA system participates in hyperactivity of the endothelial NO-system induced by stress, which is responsible for the decreased aorta reactivity to NA. (C) 2000 Elsevier B.V. B.V. All rights reserved.

The Anatomy of the Thoracic Spinal Canal Investigated with Magnetic Resonance Imaging

BACKGROUND: We investigated, with magnetic resonance imaging, the distance of the dura mater to the spinal cord in patients without spinal or medullar disease at the 2nd, 5th, and 10th thoracic segments.METHODS: Fifty patients in the supine position underwent magnetic resonance imaging. Medial sagittal slices of the 2nd, 5th, and 10th thoracic segments were measured for the relative distances using the 1.5-T superconducting system (Gyroscan Intera, Philips Medical Systems, Best, the Netherlands). In 10 patients, the angles relative to the tangent at the insertion point on the skin were measured.RESULTS: The posterior dural-spinal cord distance is significantly greater at the midthoracic region (5th thoracic = 5.8 +/- 0.8 mm) than at the upper (2nd thoracic = 3.9 +/- 0.8 mm) and lower thoracic levels (10th thoracic = 4.1 +/- 1.0 mm) (P < 0.015). There were no differences between interspaces T2 and 110. There was no correlation between age and the measured distance between the dura mater and the spinal cord. The entry angle of the needle at T2 was 9.0 degrees +/- 2.5 degrees; at T5, 45.0 degrees +/- 7.4 degrees; and at T10, 9.50 degrees +/- 4.2 degrees.CONCLUSIONS: This study demonstrated that there is greater depth of the posterior subarachnoid space at the T2, T5, and T10 levels. The greater distance was found at T5. (Anesth Analg 2010;110:1494-5)

Aortic aneurysm surgery: problems and innovations

Um longo caminho foi percorrido desde as primeiras intervenções cirúrgicas feitas para o tratamento do aneurisma de aorta abdominal. Ao longo deste tempo, várias inovações foram criadas, no sentido de reduzir a invasividade dos procedimentos e melhorar sua segurança e durabilidade. Nesta revisão, são discutidos os principais e recentes avanços em intervenções sobre aneurismas aórticos, incluindo a restauração aórtica endovascular, a cirurgia aórtica videolaparoscópica, as técnicas híbridas convencionais e endovasculares, as técnicas combinadas videolaparoscópicas e endovasculares, bem como as perspectivas futuras, tanto para aorta torácica como abdominal. Diante de tantas transformações e evolução, o cirurgião vascular moderno terá que ter sua mente aberta para as novidades e desenvolver capacitação ampla com diferentes técnicas para proporcionar a melhor opção terapêutica para seus pacientes.

Morphological and biomechanical study of abdominal aorta of rats submitted to experimental chronic alcoholism

OBJETIVO: avaliar a influência do alcoolismo crônico experimental na morfologia e biomecânica da artéria aorta de ratos. MÉTODOS:ratos Wistar foram divididos em dois grupos de 22 animais. Grupo alcoolista: os ratos receberam água com concentração crescente de etanol e ração ad libitum durante 6 meses. Grupo controle: os animais receberam água e ração ad libitum pelo mesmo período. Os animais foram sacrificados com overdose de pentobarbital e as aortas abdominais foram excisadas para realização de histologia (hematoxilina-eosina, tricrômio de Masson, Calleja, Picrosirius red), histomorfometria e avaliação biomecânica (carga máxima, alongamento na carga máxima, limite de proporcionalidade, alongamento no limite de proporcionalidade e coeficiente de rigidez). RESULTADOS: A histologia e a histomorfometria não mostraram diferenças significantes na morfologia da aorta em ambos os grupos. A avaliação biomecânica mostrou aumento do alongamento no limite de proporcionalidade no grupo alcoolista (p<0.05). CONCLUSÃO: o alcoolismo crônico experimental não provocou alterações morfológicas na parede da aorta, mas causou aumento da sua elasticidade, sem modificar as outras propriedades mecânicas avaliadas.

Some segmental structural features of the aortic wall of domestic chicken (Gallus domesticus)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of diethylpropion treatment and withdrawal on aorta reactivity, endothelial factors and rat behavior

Diethylpropion (DEP) is an amphetamine-like compound used as a coadjutant in the treatment of obesity and which presents toxicological importance as a drug of abuse. This drug causes important behavioral and cardiovascular complications; however, the vascular and behavioral alterations during DEP treatment and withdrawal, have not been determined. We evaluated the effects of DEP treatment and withdrawal on the rat aorta reactivity to noradrenaline, focusing on the endothelium, and the rat behavior during DEP treatment and withdrawal. DEP treatment caused a hyporreactivity to noradrenaline in aorta, reversible after 2 days of withdrawal and abolished by both the endothelium removal and the presence of L-NAME, but not by the presence of indomethacin. Furthermore, DEP treatment increased the general activity of rats. Contrarily, DEP withdrawal caused a decrease in the locomotor activity and an increase in grooming behavior, on the 2nd and 7th days after the interruption of the treatment, respectively. DEP treatment also caused an adaptive vascular response to noradrenaline that seems to be dependent on the increase in the endothelial nitric oxide system activity, but independent of prostaglandins synthesis. The data evidenced chronological differences in the adaptive responses of the vascular and central nervous systems induced by DEP treatment. Finally, a reversion of the adaptive response to DEP was observed in the vascular system during withdrawal, whereas a neuroadaptive process was still present in the central nervous system post-DEP. These findings advance on the understanding of the vascular and behavioral pathophysiological processes involved in the therapeutic and abusive uses of DEP. (C) 2003 Elsevier B.V. (USA). All rights reserved.

Differential antagonism by conotoxin p-TIA of contractions mediated by distinct alpha(1)-adrenoceptor subtypes in rat vas deferens, spleen and aorta

The ability of the conotoxin p-TIA, a 19-amino acid peptide isolated from the marine snail Conus tulipa, to antagonize contractions induced by noradrenaline through activation of alpha(1A)-adrenoceptors in rat vas deferens, alpha(1B)-adrenoceptors in rat spleen and alpha(ID)-adrenoceptors in rat aorta, and to inhibit the binding of [I-125]HEAT (2-[[beta-(4-hydroxyphenyl)ethyl]aminomethyl]-1-tetralone) to membranes of human embryonic kidney (HEK) 293 cells expressing each of the recombinant rat alpha(1)-adrenoceptors was investigated. p-TIA (100 nM to 1 muM) antagonized the contractions of vas deferens and aorta in response to noradrenaline without affecting maximal effects and with similar potencies (pA(2)similar to7.2, n=4). This suggests that p-TIA is a competitive antagonist of alpha(1A)- and alpha(1D)-adrenoceptors with no selectivity between these subtypes. Incubation of p-TIA (30 to 300 nM) with rat spleen caused a significant reduction of the maximal response to noradrenaline, suggesting that p-TIA is a non-competitive antagonist at alpha(1B)-adrenoceptors. After receptor inactivation with phenoxybenzamine, the potency of p-TIA in inhibiting contractions was examined with similar occupancies (similar to25%) at each subtype. Its potency (pIC(50)) was 12 times higher in spleen (8.3 +/- 0.1, n=4) than in vas deferens (7.2 +/- 0.1, n=4) or aorta (7.2 0.1, n=4). In radioligand binding assays, p-TIA decreased the number of binding sites (B,,,,,,) in membranes from HEK293 cells expressing the rat alpha(1B)-adrenoceptors without affecting affinity (K-D), In contrast, in HEK293 cells expressing rat alpha(1A)- or alpha(1D)-adrenoceptors, p-TTA decreased the KD without affecting the B-max. It is concluded that p-TIA will be useful for distinguishing the role of particular alpha(1)-adrenoceptor subtypes in native tissues. (C) 2004 Elsevier B.V. All rights reserved.

Collagen is reduced and disrupted in human aneurysms and dissections of ascending aorta

In ascending aorta aneurysms, there is an enlargement of the whole vessel, whereas aortic dissections (ADs) are characterized by the cleavage of the wall into 2 sheets at the external half. We searched if alterations in collagen could be related to these diseases. Sections of aortas from 14 case patients with acute dissections, 10 case patients with aneurysms, and 9 control subjects were stained with picrosirius. Slides were analyzed under polarized microscopy to evaluate the structure of collagen fibers. The proportion of collagen was calculated in each half of the medial layer by color detection in a computerized image analysis system. Collagen appearance under polarized light was consistent with collagenolysis. The mean collagen proportions at the inner and outer halves, respectively, were 0.50 +/- 0.13 and 0.40 +/- 0.08 in the control group, 0.20 +/- 0.10 and 0.18 +/- 0.12 in the AD group, and 0.33 +/- 0.12 and 0.19 +/- 0.12 in the aneurysm group. The AD (P < .01) and control (P = .04) groups had less collagen at the external half, no difference was found in the aneurysm group (P = .71). In both halves, there was less collagen in the case patients than in the control subjects (all P < .01), but at the internal half, the decrease was significantly greater in the case patients with aneurysms than in those with dissections (P = .03; at the external half, P = .99). Aortic dissections and aneurysms show a decrease in collagen content that could be related to a weakness of the wall underlying the diseases, but the locations of the decrease differ: in dissections, it is situated mostly at the external portion of the media (site of cleavage), whereas in aneurysms, it is more diffuse, consistent with the global enlargement. (c) 2008 Elsevier B.V. All rights reserved.