Comparison of cerebral base arteries in antelopes of Tragelaphus,Taurotragus and Boselaphus genera

Studies were conducted on preparations of head arteries, including cerebral base arteries of sitatunga (n = 14), nyala n = 16) and Greater kudu n = 4) of Tragelaphus genus, Common eland n = 7) from the tribe of Tragelaphini and the largest Asiatic Nilgai antelope n = 9) from Boselaphini tribe. Blood vessels of the cerebral arterial circle in studied antelopes were found to arise from terminal division of intracranial segments of internal carotid arteries, which emerge from the pairwise rostral epidural rete mirabile. Due to obliteration of the extracranial segment of internal carotid artery, the cerebral arterial circle of studied antelopes is supplied with blood mainly through maxillary artery, with mediation of blood vessels of rostral epidural rete mirabile. The system of cerebral base arteries in selected representatives of Tragelaphus, Taurotragus and Boselaphus, in contrast to other species of Bovinae subfamily, manifests the absence of caudal epidural rete mirabile. The pattern of cerebral base arteries in studied antelopes is consistent with position of the species in taxonomy worked out by Simpson (Bull Am Mus Nat Hist 85:1–350, 1945) and McKenna and Bell (Classification of mammals above the species level. Columbia University Press, New York, pp I–XII, 1997).     

Anatomy of the arteries of the head in the domestic fowl

The anatomy of the cephalic arterial system in the fowl was studied in 24 specimens by means of latex-injected preparations and by dissection. Branches of the external carotid artery supply the extracranial regions. The vertebral arteries unite with the occipitals and have no major communications with the encephalic system. Blood can reach the brain directly from the internal carotid artery and indirectly by way of the extensive cerebral-extracranial anastomoses; especially prominent are those to the palatine and sphenomaxillary arteries from the maxillary and facial branches of the external carotid artery. A large external ophthalmic artery supplies the temporal rete and eye musculature, and an internal ophthalmic artery links the rete and the cerebral vessels. The circle of Willis is incomplete both anteriorly and posteriorly; the anterior cerebral arteries do not unite and the basilar artery is generally asymmetrical in origin. The basilar artery tapers caudally and is continued as the ventral spinal artery.     

The vascularization of the human tela choroidea of the lateral ventricle

The human tela choroidea of the lateral ventricle is vascularized by arteries arising from the two systems which form the arterial circle of the base, i.e. the internal carotid system and the vertebral basilar system. This blood supply is given by one anterior choroidal artery and by several posterior choroidal arteries. These arteries anastomose to form multiple indirect and remote links between the carotid and vertebral basilar systems. The capillary networks of the tela choroidea of the lateral ventricle consists of a velar network and of a choroidal network. This duality is constantly observed in the choroid formations of the human brain. The venous vascularization of the tela is tributary of the venous circle of the base of the brain through choroidal veins that drain either into the internal cerebral veins or into the basal veins.     

Pro‐inflammation and pro‐fibrosis factors were highly induction in heart tissues of carotid arteries balloon‐injured animal model

To investigate the changes of cardiomyocyte inflammation and fibrosis factors in heart of carotid artery balloon injury inflammatory rat model. Using rat carotid artery balloon injury model to detect left ventricular characteristics at 2 h, 2 days and 14 days after surgery using hematoxylin‐eosin (H&E) gross stain, Masson's trichome stain and Western blot analysis for inflammatory and fibrosis‐induced factors, tumour necrosis factor α (TNFα), JNK1, P38α, connective tissue growth factor (CTGF), SP1 and transforming growth factor β (TGFβ) protein expressions. The rat carotid arteries were injured after 2 h, 2 days and 14 days. Balloon‐angioplasty to H&E stain results showed the increasing trend of left ventricular wall at 2 h and 2 days; then, the left ventricular wall became thinner, and the left ventricular chamber became enlarged and dilated after 14 days of carotid artery balloon injury. In addition, the Masson's trichome stain results showed that the left ventricular section has fibrosis‐related blue staining (collagen) at 2 and 14 days after rat carotid artery balloon injury, and became even more severe at 14 days. Furthermore, we observed the protein expression level changs, which include TNFα, JNK1, P38α, CTGF, SP1 and TGFβ using Western blotting assay. All proteins were induced at 2 h, 2 days and then reached the maximal level at 14 days. The vessel inflammation was associated with cardiac inflammatory and fibrosis effects during or after carotid artery balloon injury. Copyright © 2012 John Wiley & Sons, Ltd.     

Cryopreservation procedure does not modify human carotid homografts mechanical properties: an isobaric and dynamic analysis

The viscoelastic and inertial properties of the arterial wall are responsible for the arterial functional role in the cardiovascular system. Cryopreservation is widely used to preserve blood vessels for vascular reconstruction but it is controversially suspected to affect the dynamic behaviour of these allografts. The aim of this work was to assess the cryopreservation's effects on human arteries mechanical properties. Common carotid artery (CCA) segments harvested from donors were divided into two groups: Fresh (n = 18), tested for 24–48 h after harvesting, and Cryopreserved (n = 18) for an average time of 30 days in gas-nitrogen phase, and finally defrosted. Each segment was tested in a circulation mock, and its pressure and diameter were registered at similar pump frequency, pulse and mean pressure levels, including those of normotensive and hipertensive conditions. A compliance transfer function (diameter/pressure) derived from a mathematical adaptive modelling was designed for the on line assessment of the arterial wall dynamics and its frequency response. Assessment of arterial wall dynamics was made by measuring its viscous (η), inertial (M) and elastic (E) properties, and creep and stress relaxation time constant (τ_C and τ_SR, respectively). The frequency response characterization allowed to evaluate the arterial wall filter or buffer function. Results showed that non-significant differences exist between wall dynamics and buffer function of fresh and cryopreserved segments of human CCA. In conclusion, our cryopreservation method maintains arterial wall functional properties, close to their fresh values.     

The Vascularization of the Anuran Brain: Olfactory Bulb and Telencephalon: A scanning electron microscopical study of vascular corrosion casts

Lametschwandtner, A., Albrecht, U., Adam, H. 1980. The vascularization of the anuran brain. Olfactory bulb and telencephalon. A scanning electron microscopical study of vascular corrosion casts. (Department of Zoology, University of Salzburg, Austria.) — Acta zool. (Stockh.) 61(4): 225–238. The vascularization of the olfactory bulb and the telencephalon of the anuran brain is studied by means of scanning electron microscopy of vascular corrosion casts.—The olfactory bulb is supplied via a terminal branch of the ramus hemisphaerii medialis ventralis, while the drainage is via the lateral telencephalic vein. The vascular plexus which caps the olfactory bulb shows “basket-like” vascular formations facing the rostral olfactory bulb. This plexus is supplied via two sources which are a) terminal branches of the ramus hemisphaerii medialis ventralis and b) a branch of the inner carotid artery. — In the telencephalon the vascular pattern of medial and lateral cortex, the striatum, the septum, and the amygdala are described. It is demonstrated that in the cerebral cortex of the anuran brain the centrifugal blood flow is not present in that strictness found in the other parts of the brain. The arterial supply is via the ramus hemisphaerii medialis ventralis and the posterior telencephalic artery (ramus hemisphaerii medialis dorsalis) and their branches as well as by branches of the preoptic artery. The venous drainage of the telencephalon is by the lateral telencephalic vein.     

Homology of lungs and gas bladders: Insights from arterial vasculature

Gas bladders of ray‐finned fishes serve a variety of vital functions and are thus an important novelty of most living vertebrates. The gas bladder has long been regarded as an evolutionary modification of lungs. Critical evidence for this hypothesized homology is whether pulmonary arteries supply the gas bladder as well as the lungs. Pulmonary arteries, paired branches of the fourth efferent branchial arteries, deliver blood to the lungs in osteichthyans with functional lungs (lungfishes, tetrapods, and the ray‐finned polypterid fishes). The fact that pulmonary arteries also supply the respiratory gas bladder of Amia calva (bowfin) has been used to support the homology of lungs and gas bladders, collectively termed air‐filled organs (AO). However, the homology of pulmonary arteries in bowfin and lunged osteichthyans has been uncertain, given the apparent lack of pulmonary arteries in critical taxa. To re‐evaluate the homology of pulmonary arteries in bowfin and lunged osteichthyans, we studied, using micro‐CT technology, the arterial vasculature of Protopterus, Polypterus, Acipenser, Polyodon, Amia, and Lepisosteus, and analyzed these data using a phylogenetic approach. Our data reveal that Acipenser and Polyodon have paired posterior branches of the fourth efferent branchial arteries, which are thus similar in origin to pulmonary arteries. We hypothesize that these arteries are vestigial pulmonary arteries that have been coopted for new functions due to the dorsal shift of the AO and/or the loss of respiration in these taxa. Ancestral state reconstructions support pulmonary arteries as a synapomorphy of the Osteichthyes, provide the first concrete evidence for the retention of pulmonary arteries in Amia, and support thehomology of lungs and gas bladders due to a shared vascular supply. Finally, we use ancestral state reconstructions to show that arterial AO supplies from the celiacomesenteric artery or dorsal aorta appear to be convergent between teleosts and nonteleost actinopterygians. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.     

Contribution of the vertebral artery to cerebral circulation in the rat snake Elaphe obsoleta

Blood supplying the brain in vertebrates is carried primarily by the carotid vasculature. In most mammals, cerebral blood flow is supplemented by the vertebral arteries, which anastomose with the carotids at the base of the brain. In other tetrapods, cerebral blood is generally believed to be supplied exclusively by the carotid vasculature, and the vertebral arteries are usually described as disappearing into the dorsal musculature between the heart and head. There have been several reports of a vertebral artery connection with the cephalic vasculature in snakes. We measured regional blood flows using fluorescently labeled microspheres and demonstrated that the vertebral artery contributes a small but significant fraction of cerebral blood flow (∼13% of total) in the rat snake Elaphe obsoleta. Vascular casts of the anterior vessels revealed that the vertebral artery connection is indirect, through multiple anastomoses with the inferior spinal artery, which connects with the carotid vasculature near the base of the skull. Using digital subtraction angiography, fluoroscopy, and direct observations of flow in isolated vessels, we confirmed that blood in the inferior spinal artery flows craniad from a point anterior to the vertebral artery connections. Such collateral blood supply could potentially contribute to the maintenance of cerebral circulation during circumstances when craniad blood flow is compromised, e.g., during the gravitational stress of climbing. J. Morphol. 238:39–51, 1998. © 1998 Wiley-Liss, Inc.     

Microvascular anatomy of the brain of the adult pipid frog,Xenopus laevis (Daudin): A scanning electron microscopic study of vascular corrosion casts

To demonstrate the 3D microvascular anatomy of the brain of the model organism Xenopus laevis Daudin scanning electron microscopy of vascular corrosion casts was correlated with light microscopy of stained 7 µm thick serial tissues sections. Results showed that supplying arteries descended from the leptomeningeal surface without remarkable branchings straight to the subventricular zone where they branched and capillarized. Capillaries showed few H‐ and/or Y‐shaped anastomoses during their centrifugal course toward the leptomeningeal surface where they drained into cerebral venules and veins. Apart from the accessory olfactory bulb and the vestibule‐cochlear nucleus where capillaries were densely packed, capillaries formed a wide‐meshed 3D network throughout the brain parenchyma and thus contrasted to urodelian brains where hairpin‐shaped capillaries descend from the leptomeningeal vessels into varying depths of the brain parenchyma. In about two‐third of specimens, a closed arterial circle of Willis was found at the base of the brain. If this circle in Xenopus might serve the same two functions as in men is briefly discussed. Choroid plexuses of third and fourth ventricle were found to have a high venous, but a low arterial inflow via one small choroidal artery only. Findings are compared with previous studies on the vascularization of the anuran brain and discrepancies in respect to presence or absence of particular arteries and/or veins in Ranids, Bufonids, and Pipids studied so far are discussed with particular emphasis on the techniques used in the various studies published so far.     

Blood vessel size of circulus arteriosus cerebri (circle of Willis): a statistical research on 100 human subjects

The brain weight of 100 fresh cadavers of Italian subjects (60 males and 40 females), aged between 17 and 84 years, was obtained and the corrected circumference of the following blood vessels was measured: basilar artery, internal carotid arteries, anterior and posterior cerebral arteries, and anterior and posterior communicating arteries. The cerebral 'potential flow' was expressed in each case by adding the circumference of the basilar artery to that of the internal carotid arteries. Moreover, the sides and the perimeter of the circle of Willis as well as the length of the basilar artery were calculated. The statistical analysis of the obtained data yielded the following main results: (1) the brain weight decreases with aging, is lower in females than in males and and is statistically correlated neither with the circumferences of the considered arteries and the 'potential flow' nor with the perimeter of the arterial polygon (circle of Willis); (2) the arteries of the left side appear to be larger than those of the right one; (3) no significant difference exists in the circumference and length of the arteries between males and females; (4) the increase of the perimeter of the arterial polygon is achieved by means of a harmonious increase of all its sides; (5) the anterior and posterior communicating arteries have an anarchic pattern, because of the relatively frequent anomalies and the lack of a correlation between their circumference and that of the vessel of origin or of outlet.     

川金丝猴脑的动脉供应

为了探讨川金丝猴脑动脉供应的形态学特征,为脑生物学研究提供结构基础,用血管铸型和组织透明方法追踪观察了川金丝猴幼体脑动脉的来源和分支分布。结果表明川金丝猴与人脑的动脉供应基本相同,也由颈内动脉和椎动脉供应。上述动脉的分支于垂体周围形成大脑动脉环。颈内动脉通过大脑前动脉和大脑中动脉主要供应大脑半球前部的血液,椎动脉参与形成基底动脉、小脑动脉系和大脑后动脉,供应脑干、小脑和大脑后部的血液。另外,川金丝猴幼体左、右大脑前动脉间缺少前交通动脉。     

Meningeal arterial patterns in great apes: Implications for hominid vascular evolution

Arterial meningeal patterns were observed for 100 hemispheres from great ape endocasts (Pan paniscus, Pan troglodytes, Gorilla gorilla, and Pongo pygmaeus). Eight patterns emerged based on the relative contributions to the walls and dura mater of the middle part of the braincase of meningeal arteries that stem from two sources. These arteries enter the braincase through either the orbit (delivering blood from the internal carotid artery) or through the base of the middle cranial fossa (via the middle meningeal artery whose blood comes from the external carotid artery). The three genera of apes manifest different frequencies of the eight, patterns, with orangutans highly dependent on orbital meningeal arteries at one extreme, and chimpanzees showing the greatest reliance on the middle meningeal artery at the other. As was the case in an earlier study of rhesus monkeys, there is a trend across the two genera of African apes for increased mean cranial capacity to be associated with increased reliance on the internal carotid artery for supplying the middle portion of the braincase. However, unlike the case for macaques, this trend does not reach statistical significance in African apes. Because it is rare for humans to manifest significant arterial contributions from the orbit to the middle cranial fossa, the comparative data on monkeys, apes, and humans suggest that, during the course of vascular evolution in Homo, the middle meningeal artery eventually took over supply of the entire middle cranial fossa. This hypothesis should be tested in the hominid fossil record. Earlier work on meningeal arterial patterns in apes has traditionally relied on Adachi's system that was determined from humans and focuses on the origin of the middle branch of the middle meningeal artery. As a result, the extensive orbital contributions to the middle portion of the braincase that characterize apes were not recognized and the eight patterns described in this paper were often erroneously assigned to the three patterns that adequately describe only humans. Adachi's system should therefore be abandoned for nonhuman primates and early hominids. A correct understanding of meningeal arterial evolution cannot be achieved until the orbital contributions to the meningeal arteries are recognized and incorporated into an evolutionary study that spans from apes to fossil hominids to living people. © 1993 Wiley-Liss, Inc.     

The blood vascular system in the head of the herring gull (Larus argentatus)

The structure and development of the blood vascular system in the head of the herring gull (Larus argentatus) have been studied using injection techniques and histological sections. Three different but interconnected divisions of the arterial system are recognized in the adult: the cerebral carotid artery system, the external ophthalmic artery system, and the external carotid artery system. Embryologically, the arterial system is characterized by changes in the relative development of these three divisions; the cerebral carotid system being the most prominent in the first half of the embryonic period. The venous system is divided into two parts, the rostral cephalic system and the caudal cephalic system, which drain separate regions of the head. The Rete ophthalmicum, which is an arteriovenous network associated with the external ophthalmic artery system, can be identified from the fifth day of incubation, and its development appears to be coupled with changes in the arterial supply to the eye. The possibility of a homology between the Rete ophthalmicum of birds and the Rete caroticum of mammals is briefly discussed.     

Pharmacological characterization of the mechanisms involved in the vasorelaxation induced by progesterone and 17β-estradiol on isolated canine basilar and internal carotid arteries

Progesterone and 17β-estradiol induce vasorelaxation through non-genomic mechanisms in several isolated blood vessels; however, no study has systematically evaluated the mechanisms involved in the relaxation induced by 17β-estradiol and progesterone in the canine basilar and internal carotid arteries that play a key role in cerebral circulation. Thus, relaxant effects of progesterone and 17β-estradiol on KCl- and/or PGF_2α-pre-contracted arterial rings were investigated in absence or presence of several antagonists/inhibitors/blockers; the effect on the contractile responses to CaCl₂ was also determined. In both arteries progesterone (5.6–180 μM) and 17β-estradiol (1.8–180 μM): (1) produced concentration-dependent relaxations of KCl- or PGF_2α-pre-contracted arterial rings; (2) the relaxations were unaffected by actinomycin D (10 μM), cycloheximide (10 μM), SQ 22,536 (100 μM) or ODQ (30 μM), potassium channel blockers and ICI 182,780 (only for 17β-estradiol). In the basilar artery the vasorelaxation induced by 17β-estradiol was slightly blocked by tetraethylammonium (10 mM) and glibenclamide (K_ATP; 10 μM). In both arteries, progesterone (10–100 μM), 17β-estradiol (3.1–31 μM) and nifedipine (0.01–1 μM) produced a concentration-dependent blockade of the contraction to CaCl₂ (10 μM–10 mM). These results suggest that progesterone and 17β-estradiol produced relaxation in the basilar and internal carotid arteries by blockade of L-type voltage dependent Ca²⁺ channel but not by genomic mechanisms or production of cAMP/cGMP. Potassium channels did not play a role in the relaxation to progesterone in both arteries or in the effect of 17β-estradiol in the internal carotid artery; meanwhile K_ATP channels play a minor role on the effect of 17β-estradiol in the basilar artery.     

The morphology,innervation and neural control of the anterior arterial system of Aplysia californica

Summary The morphology, innervation, and neural control of the anterior arterial system of Aplysia californica were investigated. Immunocytochemical and histochemical techniques generated positive reactions in the anterior arterial system for several neuroactive substances, including SCP_B, FMRFamide, R151 peptide, dopamine and serotonin. Three neurons were found to innervate the rostral portions of the anterior arterial tree. One is the identified peptidergic neuron R15 in the abdominal ganglion, and the other two are a pair of previously unidentified neurons, one in each pedal ganglion, named pedal arterial shorteners (P_AS)- The endogeneously bursting neuron R15 was found to innervate the proximal anterior aorta. It also innervates a branch of the distal anterior aorta, the left pedal-parapodial artery. Activity in R15 causes constriction of the left pedal-parapodial artery. This effect is presumed to direct hemolymph towards the genital groove and penis on the right side in vivo. This vasoconstrictor action of R15 is mimicked by the R151 peptide. The P_AS neuron pair causes longitudinal contraction of the rostral anterior aorta and the pedal-parapodial arteries. In vivo, the pair is active during behaviors involving head withdrawal and turning. By adjusting the length of the arteries during postural changes, the P_AS neurons may prevent disturbances in blood flow due to bending or kinking of the arterial walls.     

Vascular corrosion replicas of chemo-baroreceptors in fish: The carotid labyrinth in Ictaluridae and Clariidae

Summary Scanning electron microscopy of vascular corrosion replicas and light microscopy revealed a pair of highly vascularized tissues, the carotid labyrinths, in the dorsal head region of the channel catfish, Ictalurus punctatus, the black bullhead, I. melas, and the walking catfish, Clarias batrachus. The labyrinth consists of a myriad of arterioles that arise from the common carotid artery immediately distal to the origin of the common carotid from the efferent branchial (epibranchial) artery of the first gill arch. The arterioles anastomose with each other to form: (1) the internal carotid artery which supplies the brain, and (2) several anteriolateral arteries that extend into the anterior head. In the ictalurids the common carotid artery emerges from the labyrinth intact and continues anteriorly as the large olfactory artery, whereas in Clarias all postlabyrinthine vessels result from arborization of the common carotid and subsequent anastomosis of the arterioles. Similarities between piscine and amphibian carotid labyrinths and the anatomical proximity of the former with the gills suggest that, in Ictaluridae, the labyrinth has a chemoor baroreceptor function.Supported by NSF Grant No. PCM 79-23073The authors wish to thank K. Drajus, D. Kullman, E. Boland and Dr. J. O'Malley for their most capable help. The authors also express their gratitude to P. Shafland and the Florida Game and Fresh Water Fish Commission for providing Clarias     

Dense granule-containing cells in arterial chemoreceptor areas of the tortoise (Testudo hermanni)

Light- and electron-microscopic observations of the chemosensory areas of the arteries of the tortoise (Testudo hermanni) reveal that clusters of nonmuscular cells are found in the adventitial layer of restricted regions of the carotid artery, aortic arch, and pulmonary artery. In these clusters, three types of cells are complexly interwoven: the G-cell closely resembles the glomus cell, which has been found in the arterial chemoreceptor area of several animal species; the LG-cell has very large electron-dense granules; the third type is a G- and LG-cell supporting cell. Membrane specializations are often observed at apposing membranes between G-cells. Two kinds of nerve endings synapse with G-cells, one with numerous clear synaptic vesicles, the other without vesicles. Some G-cells are in membrane-to-membrane contact with smooth-muscle cells (g-s connection), and here a membrane thickening is visible. Nerve terminals with numerous synaptic vesicles synapse with the LG-cells. The G-cell in the carotid artery, the aorta, and the pulmonary artery is a chemoreceptor element ultrastructurally the same as the glomus cell in the arterial chemoreceptor area of various vertebrate species.     

Selective Defecation and Selective Foraging: Antiparasite Behavior in Wild Ungulates?

Selective defecation and selective foraging are two potential antiparasite behaviors used by grazing ungulates to reduce infection by fecal–oral transmitted parasites. While there is some evidence that domestic species use these strategies, less is known about the occurrence and efficacy of these behaviors in wild ungulates. In this study, I examined whether wild antelope use selective defecation and selective foraging strategies to reduce exposure to gastrointestinal nematode parasites. By quantifying parasite levels in the environment in relation to the defecation patterns of three species, dik‐dik (Madoqua kirkii), Grant's gazelle (Gazella granti), and impala (Aepyceros melampus), I found that nematode larval concentrations in pasture were higher in the vicinity of clusters of feces (dung middens) compared to single fecal pellet groups or dung‐free areas. In addition, experimental feeding trials in free‐ranging dik‐dik showed that individuals selectively avoided feeding near concentrations of feces. Given that increased parasite contamination was found in the immediate vicinity of fecal clusters, fecal avoidance could help reduce host consumption of parasites and may therefore be an effective antiparasite behavior for certain species. On the other hand, while the concentration of parasite larvae in the vicinity of middens coupled with host avoidance of these areas during grazing could reduce host contact with parasites, results showing a positive correlation between the number of middens in a habitat and larval abundance at control sites suggest that dung middens might increase and not decrease overall host exposure to parasites. If this is the case, dung midden formation may not be a viable antiparasite strategy.     

New notharctine (primates,adapiformes) skull from the Uintan (middle Eocene) of San Diego County,California

A new genus and species of notharctine primate, Hesperolemur actius, is described from Uintan (middle Eocene) aged rocks of San Diego County, California. Hesperolemur differs from all previously described adapiforms in having the anterior third of the ectotympanic anulus fused to the internal lateral wall of the auditory bulla. In this feature Hesperolemur superficially resembles extant cheirogaleids. Hesperolemur also differs from previously known adapiforms in lacking bony canals that transmit the internal carotid artery through the tympanic cavity. Hesperolemur, like the later occurring North American cercamoniine Mahgarita stevensi, appears to have lacked a stapedial artery. Evidence from newly discovered skulls of Notharctus and Smilodectes, along with Hesperolemur, Mahgarita, and Adapis, indicates that the tympanic arterial circulatory pattern of these adapiforms is characterized by stapedial arteries that are smaller than promontory arteries, a feature shared with extant tarsiers and anthropoids and one of the characteristics often used to support the existence of a haplorhine-strepsirhine dichotomy among extant primates. The existence of such a dichotomy among Eocene primates is not supported by any compelling evidence. Hesperolemur is the latest occurring notharctine primate known from North America and is the only notharctine represented among a relatively diverse primate fauna from southern California. The coastal lowlands of southern California presumably served as a refuge area for primates during the middle and later Eocene as climates deteriorated in the continental interior. Hesperolemur probably was an immigrant taxon that entered California from either the northern (Wyoming/Utah) or southern (New Mexico) western interior during the middle Eocene © 1995 Wiley-Liss, Inc.     

Impaired UTP-induced relaxation in the carotid arteries of spontaneously hypertensive rats

Uridine 5′-triphosphate (UTP) has an important role as an extracellular signaling molecule that regulates inflammation, angiogenesis, and vascular tone. While chronic hypertension has been shown to promote alterations in arterial vascular tone regulation, carotid artery responses to UTP under hypertensive conditions have remained unclear. The present study investigated carotid artery responses to UTP in spontaneously hypertensive rats (SHR) and control Wistar Kyoto rats (WKY). Accordingly, our results found that although UTP promotes concentration-dependent relaxation in isolated carotid artery segments from both SHR and WKY after pretreatment with phenylephrine, SHR exhibited significantly lower arterial relaxation responses compared with WKY. Moreover, UTP-induced relaxation was substantially reduced by endothelial denudation and by the nitric oxide (NO) synthase inhibitor N^G-nitro-L-arginine in both SHR and WKY. The difference in UTP-induced relaxation between both groups was abolished by the selective P2Y₂ receptor antagonist AR-C118925XX and the cyclooxygenase (COX) inhibitor indomethacin but not by the thromboxane-prostanoid receptor antagonist SQ29548. Furthermore, we detected the release of PGE₂, PGF_2α, and PGI₂ in the carotid arteries of SHR and WKY, both at baseline and in response to UTP. UTP administration also increased TXA₂ levels in WKY but not SHR. Overall, our results suggest that UTP-induced relaxation in carotid arteries is impaired in SHR perhaps due to impaired P2Y₂ receptor signaling, reductions in endothelial NO, and increases in the levels of COX-derived vasoconstrictor prostanoids.