The carotid body and associated tumors: updated review with clinical/surgical significance.

Purpose: The carotid body functions as a chemoreceptor and receives richer blood supply, by weight, than any other organ in the body. We review the literature regarding the anatomy, histology, and function of the carotid body and the incidence, functionality, and clinical relevance of carotid body tumors and paragangliomas. These lesions are often nonfunctional but can be associated with catecholamine secretion. Most patients are asymptomatic or present initially with a cervical mass. As the tumors grow, they can impinge on nearby cranial nerves. Although there is some debate, the dominant clinical strategy is to surgically resect these tumors as early as possible. If they are resected early, the risk of postoperative neurovascular injury is minimized. Methods: Literature search was performed using the PubMed database with focus on articles including descriptions of the carotid body and associated tumors. Results: We reviewed recent literature that related to the anatomy of the carotid body while also including carotid pargangliomas and associated diagnosis with treatment interventions. Conclusion: As the carotid body serves as a vital modulator of cardiovascular and respiratory functions, illustrates the importance of identifying potential carotid paragangliomas due its ability to impede function of the carotid body. By understanding carotid paraganglioma's distinct etiologies while also understanding proper diagnosis of tumors allows for early detection and appropriate treatment options.

The Carotid Sinus Nerve-Structure, Function, and Clinical Implications.

Interest has been renewed in the anatomy and physiology of the carotid sinus nerve (CSN) and its targets (carotid sinus and carotid body, CB), due to recent proposals of surgical procedures for a series of common pathologies, such as carotid sinus syndrome, hypertension, heart failure, and insulin resistance. The CSN originates from the glossopharyngeal nerve soon after its appearance from the jugular foramen. It shows frequent communications with the sympathetic trunk (usually at the level of the superior cervical ganglion) and the vagal nerve (main trunk, pharyngeal branches, or superior laryngeal nerve). It courses on the anterior aspect of the internal carotid artery to reach the carotid sinus, CB, and/or intercarotid plexus. In the carotid sinus, type I (dynamic) carotid baroreceptors have larger myelinated A-fibers; type II (tonic) baroreceptors show smaller A- and unmyelinated C-fibers. In the CB, afferent fibers are mainly stimulated by acetylcholine and ATP, released by type I cells. The neurons are located in the petrosal ganglion, and centripetal fibers project on to the solitary tract nucleus: chemosensory inputs to the commissural subnucleus, and baroreceptor inputs to the commissural, medial, dorsomedial, and dorsolateral subnuclei. The baroreceptor component of the CSN elicits sympatho-inhibition and the chemoreceptor component stimulates sympatho-activation. Thus, in refractory hypertension and heart failure (characterized by increased sympathetic activity), baroreceptor electrical stimulation, and CB removal have been proposed. Instead, denervation of the carotid sinus has been proposed for the "carotid sinus syndrome." Anat Rec, 302:575-587, 2019. © 2018 Wiley Periodicals, Inc.

Evaluation of osteologic parameters of jugular foramen and its significance with respect to expanded endoscopic endonasal approach

The jugular foramen (JF) is a large irregular hiatus, lies at the posterior end of the petro-occipital suture, posterior to the opening of carotid canal (CC) and it transmits major neurovascular structures. Tumors are the most common pathology involving structures present in JF. In the current scenario, lesions of structures present in JF progressing towards midline are suitably removed by expanded endoscopic endonasal approach (EEEA). In lieu of EEEA, we studied new parameters in relation to JF. The study was done on 50 human dry skulls with the help of sliding Vernier caliper and statistical analysis was done using SPSS software. Morphological study on the presence of dome, septa and relation of CC to JF was done. Morphometric parameters of JF and its distance from vomer, medial pterygoid plate (MPP), lateral pterygoid plate (LPP) and CC were studied. We also determined the distance from lateral and medial end of CC to the midsagittal plane (MSP). The dome of the jugular fossa (JFo) was seen in 42% skulls, each bilaterally and unilaterally. Complete and incomplete septa in JF were seen in 4% & 16% bilaterally and 8% & 18% unilaterally respectively. In the majority of the skulls, position of CC was anterior to JF and anteromedial was the next common position seen. Length & width of JF, depth of JFo, distance of JF from vomer, MPP, LPP & CC and the distance of CC to the MSP were more on the right side. This study may help neurosurgeons & ENT surgeons while approaching lesions around JF by EEEA

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Control of breathing and ventilatory acclimatization to hypoxia in deer mice native to high altitudes.

AIM: We compared the control of breathing and heart rate by hypoxia between high- and low-altitude populations of Peromyscus mice, to help elucidate the physiological specializations that help high-altitude natives cope with O2 limitation. METHODS: Deer mice (Peromyscus maniculatus) native to high altitude and congeneric mice native to low altitude (Peromyscus leucopus) were bred in captivity at sea level. The F1 progeny of each population were raised to adulthood and then acclimated to normoxia or hypobaric hypoxia (12 kPa, simulating hypoxia at ~4300 m) for 5 months. Responses to acute hypoxia were then measured during stepwise reductions in inspired O2 fraction. RESULTS: Lowlanders exhibited ventilatory acclimatization to hypoxia (VAH), in which hypoxia acclimation enhanced the hypoxic ventilatory response, made breathing pattern more effective (higher tidal volumes and lower breathing frequencies at a given total ventilation), increased arterial O2 saturation and heart rate during acute hypoxia, augmented respiratory water loss and led to significant growth of the carotid body. In contrast, highlanders did not exhibit VAH - exhibiting a fixed increase in breathing that was similar to hypoxia-acclimated lowlanders - and they maintained even higher arterial O2 saturations in hypoxia. However, the carotid bodies of highlanders were not enlarged by hypoxia acclimation and were similar in size to those of normoxic lowlanders. Highlanders also maintained consistently higher heart rates than lowlanders during acute hypoxia. CONCLUSIONS: Our results suggest that highland deer mice have evolved high rates of alveolar ventilation and respiratory O2 uptake without the significant enlargement of the carotid bodies that is typical of VAH in lowlanders, possibly to adjust the hypoxic chemoreflex for life in high-altitude hypoxia.

Cuerpo carotídeo: un enfoque anatómico y fisiológico / Carotid body: an anatomical and physiological approach

Resumen:Este trabajo describe la presencia del cuerpo carotídeo y su relación con el seno carotídeo. Además, se presenta una revisión bibliográfica de la historia, anatomía y fisiologia del órgano y su importancia como quimioreceptor del cuerpo humano.

Abstract:This work describes the presence of carotid body and its relationship to the carotid sinus. In addition, a literature review of the history, anatomy and physiology of the body and its importance as chemoreceptory the human body is presented.

Carotid body modulation in systolic heart failure from the clinical perspective.

Augmented sensitivity of peripheral chemoreceptors (PChS) is a common finding in systolic heart failure (HF). It is related to lower left ventricle systolic function, higher plasma concentrations of natriuretic peptides, worse exercise tolerance and greater prevalence of atrial fibrillation compared to patients with normal PChS. The magnitude of ventilatory response to the activation of peripheral chemoreceptors is proportional to the level of heart rate (tachycardia) and blood pressure (hypertension) responses. All these responses can be measured non-invasively in a safe and reproducible fashion using different methods employing either hypoxia or hypercapnia. Current interventions aimed at modulation of peripheral chemoreceptors in HF are focused on carotid bodies (CBs). There is a clear link between afferent signalling from CBs and sympathetic overactivity, which remains the priority target of modern HF treatment. However, CB modulation therapies may face several potential obstacles: (1) As evidenced by HF trials, an excessive inhibition of sympathetic system may be harmful. (2) Proximity of critical anatomical structures (important vessels and nerves) makes surgical and transcutaneous interventions on CB technically demanding. (3) Co-existence of atherosclerosis in the area of carotid artery bifurcation increases the risk of central embolic events related to CB modulation. (4) The relative contribution of CBs vs. aortic bodies to sympathetic activation in HF patients is unclear. (5) Choosing optimal candidates for CB modulation from the population of HF patients may be problematic. (6) There is a risk of nocturnal hypoxia following CB ablation - mostly after bilateral procedures and in patients with concomitant obstructive sleep apnoea.

Three-dimensional architectures of P2X2-/P2X3-immunoreactive afferent nerve terminals in the rat carotid body as revealed by confocal laser scanning microscopy.

We investigated the three-dimensional architectures of P2X2-/P2X3-immunoreactive nerve terminals in the rat carotid body using immunohistochemistry with confocal laser microscopy. Nerve endings immunoreactive for P2X2 and P2X3 were associated with clusters of type I cells, whereas some nerve endings were sparsely distributed in a few clusters. Most nerve endings surrounding type I cells were hederiform in shape and extended several flattened axon terminals, which were polygonal or pleomorphic in shape and contained P2X2-/P2X3-immunoreactive products. Three-dimensional reconstruction views revealed that some flattened nerve endings with P2X3 immunoreactivity formed arborized, sac- or goblet-like terminal structures and were attached to type I cells immunoreactive for tyrosine hydroxylase (TH). However, P2X3-immunoreactive axon terminals were sparsely distributed in type I cells immunoreactive for dopamine beta-hydroxylase. Multi-immunolabeling for P2X2, S100, and TH revealed that P2X2-immunoreactive axon terminals were attached to TH-immunoreactive type I cells on the inside of type II cells with S100 immunoreactivity. These results revealed the detailed morphology of P2X2-/P2X3-immunoreactive nerve terminals and suggest that sensory nerve endings may integrate chemosensory signals from clustered type I cells with their variform nerve terminals.

Microsurgical anatomy of the human carotid body (glomus caroticum): Features of its detailed topography, syntopy and morphology.

The human glomus caroticum (GC) is not readily accessible during ordinary anatomical teaching courses because of insufficient time and difficulties encountered in the preparation. Accordingly, most anatomical descriptions of its location, relationship to neighboring structures, size and shape are supported only by drawings, but not by photographs. The aim of this study is to present the GC with all associated roots and branches. Following microscope-assisted dissection and precise photo-documentation, a detailed analysis of location, syntopy and morphology was performed. We carried out this study on 46 bifurcations of the common carotid artery (CCA) into the external (ECA) and internal (ICA) carotid arteries and identified the GC in 40 (91%) of them. We found significant variations regarding the location of the GC and its syntopy: GC was associated with CCA (42%), ECA (28%) and ICA (30%) lying on the medial or lateral surface (82% or 13%, respectively) or exactly in the middle (5%) of the bifurcation. The short and long diameter of its oval form varied from 1.0 × 2.0 to 5.0 × 5.0mm. Connections with the sympathetic trunk (100%), glossopharyngeal (93%), vagus (79%) and hypoglossal nerve (90%) could be established in 29 cadavers. We conclude that precise knowledge of this enormous variety might be very helpful not only to students in medicine and dentistry during anatomical dissection courses, but also to surgeons working in this field.

The simultaneous presence of a bicarotid trunk and a retroesophageal right subclavian artery: a case report with clinical impact

Many variations exist in the branching pattern of the aortic arch. One variation exists in which there is a common origin of the carotid arteries, known as a bicarotid trunk, coexisting with a retroesophageal right subclavian artery. This anomaly is associated with a right non-recurrent laryngeal nerve. Aortic arch anomalies are clinically applicable to the fields of anatomy, radiology, general medical practice, as well as thoracic and cardiovascular surgery. Here, we report a case of an uncommon branching pattern of the aortic arch identified during anatomical dissection and supported by ante-mortem diagnostic imaging. The anatomical variant was discovered in an 89-year-old Caucasian male during a routine anatomical dissection and was characterized by a bicarotid arterial trunk, left subclavian artery, followed by a retroesophageal right subclavian artery. Additionally, a right non-recurrent inferior laryngeal nerve was present. In the absence of clinical symptoms, the relevance of this variant is most evident in the case of cardiovascular or laryngeal surgeries. With advanced imaging such as CT and MRI, this type of vascular anomaly should be properly identified and described. The variation presented has particular interest to general practitioners, radiologists, and cardiovascular and thoracic surgeons

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Endoscopic, endonasal variability in the anatomy of the internal carotid artery.

BACKGROUND: Classic three-dimensional schemas of the internal carotid artery (ICA) for transcranial approaches do not necessarily apply to two-dimensional endoscopic views. Modifying an existing ICA segment classification, we define endoscopic orientation for the lacerum (C3) to clinoid (C5) segments through an endonasal approach. METHODS: In 20 cadaveric heads, we classified endoscopic appearance based on shape and angulation of C3 to C5 segments. Distances were measured between both arteries, and between the ICA and pituitary gland. RESULTS: We identified 4 common ICA patterns: types I through III matched side-to-side, whereas type IV was asymmetric. In 80% of specimens, the pituitary gland had direct contact with the ICA. In 20% of specimens, a space existed between the pituitary gland and the cavernous segment. Access to the posterior aspect of the cavernous sinus medial to the cavernous segment was possible without retraction of the artery or pituitary gland. Spaces between the lacerum and cavernous segments were trapezoid (80%) and hourglass (20%). CONCLUSIONS: Distinguishing which ICA type courses between the lacerum and clinoid segments can help clarify the relationships between the artery and its surrounding structures during endoscopic approaches. Adapting the classic terminology of ICA segments provided consistency of endoscopic relevance, defined potential endoscopic corridors, and highlighted the critical step of arterial contact.

Ventilatory behavior and carotid body morphology of Brown Norway and Sprague Dawley rats.

Differences in acute ventilatory behavior are associated with carotid body (CB) structural and immunohistologic profiles in some, but not all, reports. Brown Norway (BN) rats exhibit lower acute ventilatory responses to hypoxia and hypercapnia compared to Sprague Dawley (SD) rats. We hypothesized that BN rats possess CB with fewer glomus cells. Ventilation was recorded in 6-month-old BN and SD rats exposed to hypoxia-reoxygenation and hypercapnia. Extracted CBs were examined using H&E staining, and immunohistochemistry with antibodies specific for tyrosine hydroxylase (TH), neural nitric oxide synthase (nNOS), and pyruvate dehydrogenase (PD). Sections were analyzed for cell and immunostaining density. SD displayed greater hypoxic and hypercapnic responses, and post-hypoxic short term potentiation, whereas BN exhibited post-hypoxic frequency decline. Contrary to our hypothesis, BN demonstrated a denser arrangement of glomus cells with a larger TH stained area (31.7% BN, 22.6% SD; p<0.0001), and nNOS stained area (37.3% BN, 32.1%; SD; p=0.01). Hence, respiratory phenotype does not correlate intuitively with these anatomic features.

Grosor íntima-media carotídeo en diabéticos e hipertensos / Carotid intima-media thickness in diabetics and hypertensive patients

El objetivo del estudio es describir los valores medios del grosor íntima-media carotídeo (GIMc), la evolución con la edad y la presencia de lesión carotídea en diabéticos e hipertensos comparados con controles. Estudiamos a 562 sujetos (121 diabéticos, 352 hipertensos y 89 controles). El valor medio del GIMc fue 0,781±0,119 mm en diabéticos, 0,738±0,108mm en hipertensos y 0,686±0,093mm en controles. La diferencia del GIMc entre diabéticos y controles e hipertensos y controles ajustado por edad fue 0,040 y 0,026 mm respectivamente. Por cada año que aumenta la edad, cabe esperar un incremento del GIMc de 0,005 mm en diabéticos, 0,006 mm en hipertensos y 0,005 mm en controles. Presentaron lesión carotídea el 23% de los diabéticos, el 12% de los hipertensos y el 3,4% de los controles. En conclusión, el GIMc es mayor en diabéticos, pero el incremento anual del grosor es superior en hipertensos (AU)

The aims of this study are to describe the mean values of carotid intima-media thickness and how it increases with age, and to compare carotid injury in diabetics and hypertensive patients with that of controls. We included 562 subjects (121 diabetics, 352 hypertensive patients, 89 controls). The mean intima-media thickness was 0.781mm in diabetics, 0.738mm in hypertensive patients and 0.686mm in controls. The difference in intima-media thickness between diabetics and controls and between hypertensive patients and controls, adjusted for age, was 0.040 and 0.026mm, respectively. We observed an increase in intima-media thickness of 0.005 mm in diabetics and of 0.005 mm in controls with every additional year of age. We found carotid damage in 23% of the diabetics, 12% of the hypertensive patients and 3.4% of the controls. In conclusion, the intima-media thickness is greater in diabetics, but the annual increase in the thickness is greater in hypertensive patients (AU)

Morphological differences of the carotid body among C57/BL6 (B6), A/J, and CSS B6A1 mouse strains.

The C57/BL6 (B6) mouse strain exhibits post-hypoxic frequency decline and periodic breathing, as well as greater amount of irregular breathing during rest in comparison to the A/J and to the B6a1, a chromosomal substitution strain whereby the A/J chromosome 1 is bred onto the B6 background (Han et al., 2002; Yamauchi et al., 2008a,b). The hypothesis was that morphological differences in the carotid body would associate with such trait variations. After confirming strain differences in post-hypoxic ventilatory behavior, histological examination (n=8 in each group) using hematoxylin and eosin (H&E) staining revealed equivalent, well-defined tissue structure at the bifurcation of the carotid arteries, an active secretory parenchyma (type I cells) from the supportive stromal tissue, and clustering of type I cells in all three strains. Tyrosine hydroxylase (TH) immunohistochemical staining revealed a typical organization of type I cells and neurovascular components into glomeruli in all three strains. Image analysis from 5 µm sections from each strain generated a series of cytological metrics. The percent carotid body composition of TH+ type I cells in the A/J, B6 and B6a1 was 20±4%, 39±3%, and 44±3%, respectively (p=0.00004). However, cellular organization in terms of density and ultrastructure in the B6a1 is more similar to the B6 than to the A/J. These findings indicate that genetic mechanisms that produce strain differences in ventilatory function do not associate with carotid body structure or tyrosine hydroxylase morphology, and that A/J chromosome 1 does not contribute much to B6 carotid body morphology.

Position and blood supply of the carotid body in a Kenyan population / Posición y suministro sanguíneo del cuerpo carotídeo en una población de Kenia

Position and source of blood supply to the human carotid body displays population variations. These data are important during surgical procedures and diagnostic imaging in the neck but are only scarcely reported and altogether missing for the Kenyan population. The aim of this study was to describe the position and blood supply of the carotid body in a Kenyan population. A descriptive cross-sectional study at the Department of Human Anatomy, University of Nairobi, was designed. 136 common carotid arteries and their bifurcations were exposed by gross dissection. The carotid body was identified as a small oval structure embedded in the blood vessel adventitia. Position and source of blood supply were photographed. Data are presented by tables and macrographs. 138 carotid bodies were identified. Commonest position was carotid bifurcation (75.4 percent) followed by external carotid artery (10.2 percent), internal carotid artery (7.2 percent) and ascending pharyngeal artery (7.2 percent). Sources of arterial blood supply included the carotid bifurcation (51.4 percent), ascending pharyngeal (21.0 percent), external carotid (17.4 percent) and internal carotid (10.2 percent) arteries. Position and blood supply of the carotid body in the Kenyan population displays a different profile of variations from those described in other populations. Neck surgeons should be aware of these to avoid inadvertent injury.

La posición y la fuente de suministro sanguíneo del cuerpo carotídeo humano muestra variaciones en la población. Estos datos son importantes durante los procedimientos quirúrgicos y de diagnóstico por imagen en el cuello, pero son poco informados e inclusive faltan por completo en la población de Kenia. El objetivo de este estudio fue describir la posición y el aporte sanguíneo del cuerpo carotídeo en una población de Kenia. Se diseñó un estudio descriptivo de corte transversal en el Departamento de Anatomía Humana de la Universidad de Nairobi. 136 arterias carótidas comunes y sus bifurcaciones fueron expuestas mediante disección simple. El cuerpo carotídeo fue identificado como una pequeña estructura oval ubicada en la adventicia del vaso sanguíneo. La posición y la fuente de suministro sanguíneo fueron fotografiados. Los datos obtenidos fueron presentados en las tablas y fotomacrografías. 138 cuerpos carotídeos fueron identificados. La posición más frecuente fue la bifurcación carotídea (75,4 por ciento), seguida de la arteria carótida externa (10,2 por ciento), arteria carótida interna (7,2 por ciento) y la arteria faríngea ascendente (7,2 por ciento). Las fuentes de suministro sanguíneo arterial incluyeron la bifurcación carotídea (51,4 por ciento), arteria faríngea ascendente (21,0 por ciento), arteria carótida externa (17,4 por ciento) y arterias carótidas internas (10,2 por ciento). La posición y el suministro sanguíneo del cuerpo carotídeo en la población de Kenia muestra un perfil de variaciones diferente a las descritos en otras poblaciones. Los cirujanos de cuello deben conocer estas variaciones para así evitar lesiones accidentales.

Estudio genético del complejo enzimático succinato deshidrogenasa en los paragangliomas carotídeos. Implicaciones diagnósticas / Genetic study of the succinate dehydrogenase enzyme complex in carotid paragangliomas: diagnostic implications

Introducción: Los paragangliomas (PG) en general y los carotídeos (PGC) en particular son tumores infrecuentes, generalmente únicos y de evolución benigna, que presentan controversias en su comportamiento biológico e historia natural. Objetivo: Correlacionar la presencia de mutaciones de los genes del complejo enzimático succinato deshidrogenasa (SDH) con la aparición de presentaciones atípicas de PG (bilaterales, multicéntricos y malignos). Pacientes y método: Estudio genético en 20 pacientes, 18 con PGC esporádico y 2 con PGC familiar; 2 pacientes presentaban localizaciones múltiples y 3 fueron de evolución maligna. Después de consentimiento informado específico, se obtuvo sangre periférica de los pacientes para realizar un estudio genómico según protocolo estándar. Resultados: Se detectaron mutaciones en 6 pacientes (30 % de la serie), repartiéndose de forma homogénea (2 por subunidad B, C o D). Las mutaciones fueron del 100 % en las formas familiares (2/2) y del 22,2 % en las esporádicas (4/18). Los 2 pacientes con PG múltiples presentaron mutaciones (SDHB y SDHC). En 2 de 3 pacientes con PG de evolución maligna se presentaron mutaciones en SDHB. En los casos familiares se estudió a 3 hijos de los pacientes, resultando positivo (SDHB) un caso. Finalmente, 3 de las 6 mutaciones descritas por nosotros no han sido referidas previamente en la literatura consultada (SDHB c.472 del A, SDHC c.A377G y SDHC c.A21G). Conclusiones: La mutación de las subunidades de SDH es responsable de la tendencia a padecer un PG tanto en las formas familiares como en las esporádicas, teniendo una importante relevancia en la presencia de formas múltiples y el pronóstico evolutivo de estos tumores(AU)

Introduction: Carotid paragangliomas (CPGs) are uncommon tumours which tend to be isolated and benign. However, there are controversies over their biological behaviour and natural history. Aim: To correlate the presence of mutations of succinate dehydrogenase (SDH) complex genes with the appearance of atypical CPGs (bilateral, multicentral and malignant). Patients and methods: We carried out mutation analyses in 18 patients with sporadic CPGs and 2 patients with familial CPGs. Two patients had multiple locations and three had a malignant outcome. After obtaining informed consent, peripheral blood was obtained to perform a genomic study according to a standard protocol. Results: We identified SHD mutations in six patients (30 %), 100 % in familial CPGs (2/2) and 22.2 % in sporadic CPGs (4/18). Both patients with multiple CPGs showed mutations in SDH (SDH subunit B and SDH subunit C). Two of three patients with CPGs and malignant outcome showed mutation in the SDH subunit B gene. In familial CPGs, we studied three children and we found a positive case (SDHB). Finally, we identified three novel SHD mutations (SDHB c.472 del A, SDHC c.A377G; and SDHC c.A21G). Conclusion: SDH mutations are responsible for the trend to suffer CPGs in both familial and sporadic forms and may play an important role in multiple CPGs and malignant PGs(AU)

Care of the patient undergoing surgical excision of a carotid body chemodectoma.

The carotid body is a small mass of tissue inside the carotid bifurcation that reacts to the body's level of oxygen. In rare cases, the carotid body may develop a tumor known as a chemodectoma or paraganglioma. These tumors can vary in size and, typically, they are benign. Although carotid body tumors usually are painless and slow growing, they may cause a compression syndrome that results in symptoms such as dysphagia. The treatment of choice for many carotid body tumors is surgical removal, but there are risks involved with resecting these tumors because of their close location to the carotid vessels and cranial nerves. The use of newer imaging modalities to allow earlier detection of carotid body tumors and careful surgical technique can decrease the complications associated with this challenging surgical procedure.

Grosor íntima-media carotídeo en sujetos sin factores de riesgo cardiovascular / Carotid intima-media thickness in subjects with no cardiovascular risk factors

El grosor íntima-media de la arteria carótida permite la cuantificación del engrosamiento arterial en fases preclínicas de la enfermedad, pero no se conoce sus valores en población sin factores de riesgo cardiovascular. El objetivo es describir la distribución y los factores determinantes del grosor íntima-media carotídeo en población sana y sin factores de riesgo cardiovascular. Estudiamos el grosor íntima-media carotídeo de 138 sujetos (64 varones y 74 mujeres) de 20-79 años de edad distribuidos homogéneamente según edad y sexo. El límite superior de la normalidad de la media del grosor íntima-media osciló entre 0,59 y 0,95 mm en varones y entre 0,52 y 0,93 mm en mujeres. Los valores máximos oscilaron entre 0,81 y 1,11 mm en varones y entre 0,66 y 1,13 mm en mujeres. Los principales factores determinantes del grosor íntima-media fueron edad, sexo masculino, presión arterial sistólica y colesterol de las lipoproteínas de baja densidad (AU)

Measurement of the carotid intima-media thickness enables arterial wall thickening to be quantified during preclinical disease stages. However, little is known about how the thickness varies in individuals with no cardiovascular risk factors. The objective of this study was to report on the range of carotid intima-media thicknesses observed in a population of healthy subjects with no cardiovascular risk factors and to identify parameters that influence it. The carotid intima-media thickness was assessed in 138 subjects (64 men and 74 women) aged 20-79 years whose age and sex were homogeneously distributed. The upper limit of normal for the mean carotid intima-media thickness ranged from 0.59-0.95 mm in men and from 0.52-0.93 mm in women. The upper limit for the maximum thickness varied from 0.81-1.11 mm in men and from 0.66-1.13 mm in women. The main parameters determining the intima-media thickness were age, male sex, systolic blood pressure and low-density lipoprotein cholesterol level (AU)

Comparative analysis of neonatal and adult rat carotid body responses to chronic intermittent hypoxia.

Previous studies suggest that carotid body responses to long-term changes in environmental oxygen differ between neonates and adults. In the present study we tested the hypothesis that the effects of chronic intermittent hypoxia (CIH) on the carotid body differ between neonates and adult rats. Experiments were performed on neonatal (1-10 days) and adult (6-8 wk) males exposed either to CIH (9 episodes/h; 8 h/day) or to normoxia. Sensory activity was recorded from ex vivo carotid bodies. CIH augmented the hypoxic sensory response (HSR) in both groups. The magnitude of CIH-evoked hypoxic sensitization was significantly greater in neonates than in adults. Seventy-two episodes of CIH were sufficient to evoke hypoxic sensitization in neonates, whereas as many as 720 CIH episodes were required in adults, suggesting that neonatal carotid bodies are more sensitive to CIH than adult carotid bodies. CIH-induced hypoxic sensitization was reversed in adult rats after reexposure to 10 days of normoxia, whereas the effects of neonatal CIH persisted into adult life (2 mo). Acute intermittent hypoxia (IH) evoked sensory long-term facilitation of the carotid body activity (sensory LTF, i.e., increased baseline neural activity following acute IH) in CIH-exposed adults but not in neonates. The effects of CIH were associated with hyperplasia of glomus cells in neonatal but not in adult carotid bodies. These observations demonstrate that responses to CIH differ between neonates and adults with regard to the magnitude of sensitization of HSR, susceptibility to CIH, induction of sensory LTF, reversibility of the responses, and morphological remodeling of the chemoreceptor tissue.

Sensing hypoxia in the carotid body: from stimulus to response.

The carotid body is a peripheral sensory organ that can transduce modest falls in the arterial PO(2) (partial pressure of oxygen) into a neural signal that provides the afferent limb of a set of stereotypic cardiorespiratory reflexes that are graded according to the intensity of the stimulus. The stimulus sensed is tissue PO(2) and this can be estimated to be around 50 mmHg during arterial normoxia, falling to between 10-40 mmHg during hypoxia. The chemoafferent hypoxia stimulus-response curve is exponential, rising in discharge frequency with falling PO(2), and with no absolute threshold apparent in hyperoxia. Although the oxygen sensor has not been definitely identified, it is believed to reside within type I cells of the carotid body, and presently two major hypotheses have been put forward to account for the sensing mechanism. The first relies upon alterations in the cell energy status that is sensed by the cytosolic enzyme AMPK (AMP-activated protein kinase) subsequent to hypoxia-induced increases in the cellular AMP/ATP ratio during hypoxia. AMPK is localized close to the plasma membrane and its activation can inhibit both large conductance, calcium-activated potassium (BK) and background, TASK-like potassium channels, inducing membrane depolarization, voltage-gated calcium entry and neurosecretion of a range of transmitter and modulator substances, including catecholamines, ATP and acetylcholine. The alternative hypothesis considers a role for haemoxygenase-2, which uses oxygen as a substrate and may act to gate an associated BK channel through the action of its products, carbon monoxide and possibly haem. It is likely however, that these and other hypotheses of oxygen transduction are not mutually exclusive and that each plays a role, via its own particular sensitivity, in shaping the full response of this organ between hyperoxia and anoxia.