A systematic study of brain base arteries in the wild boar (Sus scrofa scrofa)

From Anomalous Arteries to Selective Brain Cooling: Parallel Evolution of the Artiodactyl Carotid Rete

Terrestrial artiodactyls (even-toed ungulates) inhabit some of the world's most extreme environments, including arid deserts and high elevations. As medium-to-large-bodied mammals, artiodactyls have a suite of specialized physiologies to facilitate occupation of regions unavailable to other large mammals. One such physiology is selective brain cooling, wherein reduction of brain temperature below core body temperature has been demonstrated to reduce evaporative water loss. This physiology is enabled by an arterial heat-exchanger called the carotid rete. The ubiquity of the carotid rete throughout the clade, as well as its evolutionary history, is currently uninvestigated. Here, I use osteological correlates to survey clade-wide presence and morphology of the carotid rete, prior to conducting a preliminary evolutionary analysis. Nearly all living artiodactyls possess a carotid rete and are capable of selective brain cooling; however, major arteries supplying the rete are derived from different embryonic aortic arches on a suborder-specific basis. Ancestral character estimation infers this pattern of variation to be the result of independent evolutionary processes, suggesting carotid rete homoplasy arising via parallelism. This is a surprising finding given the role this structure plays in driving a physiology that has been implicated in mitigating artiodactylan responses to extreme environmental conditions. Future studies should incorporate extinct species represented in the fossil record to better parse between parallel and convergent mechanisms, as well as to better understand the relationship between the carotid rete, selective brain cooling, and survivorship of climate perturbation. Anat Rec, 2018. © 2018 Wiley Periodicals, Inc. Anat Rec, 303:308-317, 2020. © 2018 American Association for Anatomy.

A Systematic Review of the Complex Effects of Cannabinoids on Cerebral and Peripheral Circulation in Animal Models

While cannabis is perceived as a relatively safe drug by the public, accumulating clinical data suggest detrimental cardiovascular effects of cannabinoids. Cannabis has been legalized in several countries and jurisdictions recently. Experimental studies specifically targeting cannabinoids' effects on the cerebral vasculature are rare. There is evidence for transient vasoconstrictive effects of cannabinoids in the peripheral and cerebral vasculature in a complex interplay of vasodilation and vasoconstriction. Vasoreactivity to cannabinoids is dependent on the specific molecules, their metabolites and dose, baseline vascular tone, and vessel characteristics as well as experimental conditions and animal species. We systematically review the currently available literature of experimental results in in vivo and in vitro animal studies, examining cannabinoids' effects on circulation and reactive vasodilation or vasoconstriction, with a particular focus on the cerebral vascular bed.

Role of terminal and anastomotic circulation in the patency of arteries jailed by flow-diverting stents: animal flow model evaluation and preliminary results

OBJECTIVE

The authors describe herein the creation of an animal model capable of producing quantifiable data regarding blood flow rate and velocity modifications in terminal and anastomotic types of cerebrofacial circulation. They also present the preliminary results of a translational study aimed at investigating the role of terminal and anastomotic types of circulation in arterial branches jailed by flow-diverting stents as factors contributing to arterial patency or occlusion.

METHODS

Two Large White swine were used to validate a terminal-type arterial model at the level of the right ascending pharyngeal artery (APhA), created exclusively by endovascular means. Subsequently 4 Large White swine, allocated to 2 groups corresponding to the presence (Group B) or absence (Group A) of terminal-type flow modification, underwent placement of flow-diverting stents. Blood flow rates and velocities were quantified using a dedicated time-resolved 3D phase-contrast MRA sequence before and after stenting. Three months after stent placement, the stented arteries were evaluated with digital subtraction angiography (DSA) and scanning electron microscopy (SEM). Patent (circulating) ostia quantification was performed on the SEM images.

RESULTS

Terminal-type flow modification was feasible; an increase of 75.8% in mean blood velocities was observed in the right APhAs. The mean blood flow rate for Group A was 0.31 ± 0.19 ml/sec (95% CI −1.39 to 2.01) before stenting and 0.21 ± 0.07 ml/sec (95% CI −0.45 to 0.87) after stenting. The mean blood flow rate for Group B was 0.87 ± 0.32 ml/sec (95% CI −1.98 to 3.73) before stenting and 0.76 ± 0.13 ml/sec (95% CI −0.41 to 1.93) after stenting. Mean flow rates after stenting showed a statistically significant difference between Groups A and B (Welch test). Mean and maximal blood velocities were reduced in Group A cases and did not decrease in Group B cases. Control DSA and SEM findings showed near occlusion of the jailed APhAs in both cases of anastomotic circulation (mean patent ostium surface 32,776 μm2) and patency in both cases of terminal-type circulation (mean patent ostium surface 422,334 μm2).

CONCLUSIONS

Terminal-type arterial modification in swine APhAs is feasible. Sufficient data were acquired to perform an a priori analysis for further research. Flow diversion at the level of the APhA ostium resulted in significant stenosis in cases of anastomotic circulation, while sufficient patency was observed in terminal-type circulation.

A comparison of postnatal arterial patterns in a growth series of giraffe (Artiodactyla: Giraffa camelopardalis)

Nearly all living artiodactyls (even-toed ungulates) possess a derived cranial arterial pattern that is highly distinctive from most other mammals. Foremost among a suite of atypical arterial configurations is the functional and anatomical replacement of the internal carotid artery with an extensive, subdural arterial meshwork called the carotid rete. This interdigitating network branches from the maxillary artery and is housed within the cavernous venous sinus. As the cavernous sinus receives cooled blood draining from the nasal mucosa, heat rapidly dissipates across the high surface area of the rete to be carried away from the brain by the venous system. This combination yields one of the most effective mechanisms of selective brain cooling. Although arterial development begins from the same embryonic scaffolding typical of mammals, possession of a rete is typically accompanied by obliteration of the internal carotid artery. Among taxa with available ontogenetic data, the point at which the internal carotid obliterates is variable throughout development. In small-bodied artiodactyls, the internal carotid typically obliterates prior to parturition, but in larger species, the vessel may remain patent for several years. In this study, we use digital anatomical data collection methods to describe the cranial arterial patterns for a growth series of giraffe (Giraffa camelopardalis), from parturition to senescence. Giraffes, in particular, have unique cardiovascular demands and adaptations owing to their exceptional body form and may not adhere to previously documented stages of cranial arterial development. We find the carotid arterial system to be conserved between developmental stages and that obliteration of the giraffe internal carotid artery occurs prior to parturition.

Focused post mortem dissection technique for harvest of rete mirabile in domestic swine (Sus scrofa)

BACKGROUND

Rete mirabile (RM) of the domestic pig is a popular animal model of arteriovenous malformations. The RM (Latin for 'wonderful net)' comprises the arterioarterial portal connecting ascending pharyngeal arteries and the internal carotid arteries, which exists in the skull base of even-toed ungulates. Although angiographic access of the RM is relatively easy, its post mortem procurement is complicated and its detailed technique has not been well described.

OBJECTIVE

To present our focused post mortem dissection technique for undamaged and complete harvest of the RM.

MATERIALS AND METHODS

Fourteen domestic (40-70 lb (18-32 kg)) swine were used in this study. Angiographies were performed under general anesthesia in all animals. A 5F Berenstein catheter was used for angiography and a 014 microcatheter was used to obtain superselective angiography. A stepwise surgical dissection technique has been developed to efficiently harvest RM. Angiographic and surgical anatomy were also compared.

RESULTS

The RM was supplied by bilateral ascending pharyngeal arteries. Bilateral anterior cerebral arteries, middle cerebral arteries, and the basilar system were identified rostral to the RM. Our surgical dissection technique was developed during a project to streamline harvesting of the RM and a stepwise description is as follows: (1) decapitate the swine by removing the head through the plane of the occiput and C1 vertebral body; (2) remove the tongue and oropharynx via a ventral approach; (3) dissect through the posterior pharyngeal wall identifying bilateral tympanic bullae and the basisphenoid bone; and (4) remove the basisphenoid bone about one and half inches above the rostral end of the tympanic bullae to fully expose the rete.

CONCLUSIONS

The RM can be procured efficiently and effectively with our technique, without requiring any sophisticated surgical devices.

Morfometria do encéfalo e formação do circuito arterial em equinos mestiços

O objetivo desta investigação foi caracterizar a morfometria do encéfalo e a formação do circuito arterial em equinos adultos mestiços de ambos os sexos. A fixação foi feita através de cânula plástica introduzida na artéria carótida comum com solução de formaldeído a 10%. Em seguida, foram feitas repleções vasculares com solução aquosa de Petrolátex S65 corado com pigmento Suvinil vermelho. Procedeu-se a craniotomia, remoção e morfometria dos encéfalos e dissecção para a observação das ramificações principais da artéria basilar e formação do circuito arterial. A média mais erro padrão da média do comprimento da artéria basilar foi de3,629 cm ± 0,1550 nos machos e 4,423 cm ± 0,1990 nas fêmeas (p=0,0037). Em todos os equinos dissecados, a artéria basilar originou-se da convergência das artérias vertebrais, emitindo a artéria cerebelar caudal, ramos variados para bulbo e ponte, ramos terminais e artérias cerebelares rostrais. As artérias da base do encéfalo estiveram na dependência dos sistemas carótico e vértebrobasilar. O circuito arterial do cérebro apresentou-se fechado rostral e caudalmente em 100% dos animais dissecados.

Brain base arteries: pattern and variation in the European otter (Lutra lutra)

The pattern and variation of the brain base arteries were investigated in 30 specimens of European otter. It was found that the vascular pattern in this species is similar to the vascular pattern found in other Carnivora. A very well-developed basilar artery, which was formed as a result of the anastomosis of equally well-developed vertebral arteries and the ventral spinal artery, was demonstrated to be characteristic of the species. Most of the variation in the pattern of origin concerned the origin of the middle cerebral arteries and labyrinthine arteries. In a single individual, a double middle cerebral artery was observed. Overall, the specimens demonstrated a clear regularity in the pattern of vessels in the base of the brain and a small range of variation.