Rete Mirabile Research Articles

The arterial system of the sperm whale (Physeter macrocephalus)

The angioarchitecture of the sperm whale is basically similar to that of other mammals, but it has specific attributes associated with the aquatic environment of this animal and its tolerance for deep and long diving. Specialized features include an expansive aortic arch, unusually far anterior localization of the arch, symmetrical branching of common carotid and subclavian arteries from the aorta, the absence of direct connection between internal carotid arteries and brain arteries, the absence of a costocervical artery, and the presence of a well-developed occipital artery. The sperm whale has extraordinarily well-developed retia mirabilia, distributed in the cranial cavity, vertebral canal, neck and thoracic cavity, around the optic nerve, and in the walls of the uterus. These retia are more extensively developed in the sperm whale than in any other cetacean previously studied. J. Morphol. 234:37–50, 1997. © 1997 Wiley-Liss, Inc.

The arterial system of the sperm whale (Physeter macrocephalus).

The angioarchitecture of the sperm whale is basically similar to that of other mammals, but it has specific attributes associated with the aquatic environment of this animal and its tolerance for deep and long diving. Specialized features include an expansive aortic arch, unusually far anterior localization of the arch, symmetrical branching of common carotid and subclavian arteries from the aorta, the absence of direct connection between internal carotid arteries and brain arteries, the absence of a costocervical artery, and the presence of a well-developed occipital artery. The sperm whale has extraordinarily well-developed retia mirabilia, distributed in the cranial cavity, vertebral canal, neck and thoracic cavity, around the optic nerve, and in the walls of the uterus. These retia are more extensively developed in the sperm whale than in any other cetacean previously studied.

Enzyme adaptation along a heterothermic tissue: the visceral retia mirabilia of the bluefin tuna.

We measured enzyme activities along a heterothermic tissue, the visceral retia mirabilia of the bluefin tuna, to test current theories of enzyme temperature adaptation. The heterothermic tissue model is ideal for the study of fundamental temperature adaptation because it eliminates confounding effects of whole animal acclimation. Enzymes were measured at six positions along the rete at four temperatures (15, 20, 25, and 30 degrees C). Five enzymes (aspartate aminotransferase, citrate synthase, glucose-6-phosphate dehydrogenase, glutamate dehydrogenase, and pyruvate kinase) exhibited a significant positive compensatory effect, with activity at the cold end of the rete 1.2-3.1 times higher than at the warm end. Two enzymes (alanine aminotransferase and lactate dehydrogenase) exhibited no significant compensation. On the basis of activation energies of enzymes along the rete, differences in activity were due to differences in enzyme concentration and not isozymes or enzyme modification. Analysis of the compensatory responses of the enzymes in light of their thermal sensitivities leads us to conclude that the pentose phosphate shunt is especially enhanced at the cold end of the rete.

Distribution of the arterial supply to the vomeronasal organ in the cat.

The main goal of this work was to investigate the general distribution of arterial blood around and inside the vomeronasal organ (VNO) of the cat. Macro- and microdissection methods together with light and scanning electron microscopy were used. Heads were injected with an India ink/agar mixture (the VNO subsequently being cut in transverse, sagittal and horizontal sections), with clear latex (the VNO subsequently being cut in transverse sections), or with an epoxy resin to obtain casts for examination by scanning electron microscopy. Dissection and microdissection show that the infraorbital, minor palatine, and descending palatine arteries have a common origin, rostral to the Rete mirabile arteria maxillaris. In transverse series and in the rostral half of the VNO, an arteriole is consistently observed between the vomeronasal duct and the lateral sheet of the vomeronasal cartilage. In this same segment, arterial branches with different orientations (perpendicular, horizontal, or transverse with respect to the main axis of the organ) are observed. Scanning electron microscopy of arterial casts shows that arterial vessels of the mucosa of the nasal septum have a direct relationship with the VNO. Branches of the sphenopalatine artery are the chief route of blood supply to the VNO. The vomeronasal parenchyma has few arterial vessels, and these are usually situated in the same position. Differences observed between the arteries inside and outside the VNO and the dilation of both by isoproterenol support the idea that the VNO is similar to erectile tissue organs and that it may act as a physiological pump.

Distribution of the arterial supply to the vomeronasal organ in the cat

Background The main goal of this work was to investigate the general distribution of arterial blood around and inside the vomeronasal organ (VNO) of the cat. Methods Macro- and microdissection methods together with light and scanning electron microscopy were used. Heads were injected with an India ink/agar mixture (the VNO subsequently being cut in transverse, sagittal and horizontal sections), with clear latex (the VNO subsequently being cut in transverse sections), or with an epoxy resin to obtain casts for examination by scanning electron microscopy. Results Dissection and microdissection show that the infraorbital, minor palatine, and descending palatine arteries have a common origin, rostral to the Rete mirabile arteria maxillaris. In transverse series and in the rostral half of the VNO, an arteriole is consistently observed between the vomeronasal duct and the lateral sheet of the vomeronasal cartilage. In this same segment, arterial branches with different orientations (perpendicular, horizontal, or transverse with respect to the main axis of the organ) are observed. Scanning electron microscopy of arterial casts shows that arterial vessels of the mucosa of the nasal septum have a direct relationship with the VNO. Conclusions Branches of the sphenopalatine artery are the chief route of blood supply to the VNO. The vomeronasal parenchyma has few arterial vessels, and these are usually situated in the same position. Differences observed between the arteries inside and outside the VNO and the dilation of both by isoproterenol support the idea that the VNO is similar to erectile tissue organs and that it may act as a physiological pump. Anat. Rec. 247:129–136 © 1997 Wiley-Liss, Inc.

Evidence of brain-warming in the mobulid rays, Mobula tarapacana and Manta birostris (Chondrichthyes: Elasmobranchii: Batoidea: Myliobatiformes)

The presence of cranial retia mirabilia in rays of the genus Mobula is well established. Although previously regarded as consisting exclusively of arteries, the presence of veins has now been established in gross dissections of the rete in the mobulid, Manta birostris. Histological examination of the retia in Manta birostris and Mobula tarapacana confirms the presence of veins. These findings suggest the presence of a counter-current heat-exchanger that warms the brain.

Transport of insulin and albumin by the microvascular endothelium of the rete mirabile.

Vascular permeability for albumin and insulin in the continuous capillary network of the rete mirabile of the eel swimbladder was evaluated by ultrastructural immunocytochemistry and countercurrent perfusion experiments. Upon perfusion of the rete capillaries with a buffer solution containing albumin and insulin, these serum proteins were revealed at the electron microscope level, by the Protein A-gold immunocytochemical technique on a post-embedding step. For the simultaneous detection of both proteins, the double labeling technique with different sized gold particles was used. Furthermore, labeling was performed with the mixture of anti-albumin and anti-insulin anti-bodies. The labelings obtained were morphometrically evaluated and demonstrate that: (1) serum proteins such as albumin and insulin are transported by the endothelial cells through their plasmalemmal vesicular system; (2) insulin is transported preferentially to albumin; and (3) this transport involves different populations of plasmalemmal vesicles. Measurements of diffusion permeability coefficients have confirmed the preferential transport of insulin, its coefficient being higher than that of albumin. Conversely, when compared to that of insulin or sucrose, which are assumed to be markers of the paracellular diffusion, it was found to be much lower, indicating that transcytosis through the vesicular system is less efficient than diffusion along the intercellular junctions. These results indicate that transcytosis of insulin and albumin occurs via different sets of plasmalemmal vesicles, probably through receptor-mediated mechanisms, and that the overall rate of transport across the rete capillaries, with respect to paracellular diffusion, is higher for insulin than for albumin.

Induction of cytochrome P4501A in endothelium: the rete mirabile as a model for the study of endothelial CYP1A

Induction of cytochrome P4501A in endothelium: the rete mirabile as a model for the study of endothelial CYP1A

Brain cooling in humans--anatomical considerations.

Vascular arrangements allowing a bulky transfer of venous blood from the skin of the head and from nasal and paranasal mucous membranes to the dura matter provide an excellent anatomical basis for the convection process of cooling, caused by evaporation of sweat or mucus. The dura mater, with its extraordinarily high vascularization controlled by a potent vasomotor apparatus, may transmit temperature changes to the cerebrospinal fluid (CSF) compartment. Temperature gradients of the CSF may in turn influence the temperature of brain parenchyma (1) directly, along the extensive contact area between the cerebrocortical surface and the CSF-compartment, or (2) indirectly, via brain arteries that extend over long distances and arborize within the subarachnoid space before entering the pial vascular network and brain parenchyma. Numerous subarachnoid and pial arterial branches exposed to the CSF have diameters in the range of the vessels of the retia mirabilia of animals in which selective brain cooling has been clearly established experimentally. It is also shown that the arrangements of venous plexuses within the vertebral canal provide anatomical preconditions for a cooling of the spinal cord via the CSF. The possibility of spinal cord and spinal ganglia cooling by temperature convection via venous blood--cooled in the venous networks of the skin of the back--flowing through numerous anastomoses to the external and internal vertebral plexuses and, finally, into the vascular bed of the spinal dura is discussed on the basis of anatomical facts.

Use of the swine carotid rete mirabile in experimental interventional neuroradiology: A renew of normal and applied anatomy

Use of the swine carotid rete mirabile in experimental interventional neuroradiology: A renew of normal and applied anatomy

Linear gap and tight junctional assemblies between capillary endothelial cells in the eel rete mirabile.

Interendothelial tight junctions and gap junctions have been described in large blood vessels and in cultures of endothelium derived from large blood vessels. Transfer of microinjected small-molecular weight tracers between adjacent endothelial cells also has been demonstrated indicating the presence of gap junctional interendothelial communication. Similar transfer of tracers is evident between microvessel endothelial cells in culture and in microvessels in situ. However, gap junctions have not been detectable by electron microscopy of intact capillary systems. This may be due to limited sampling available in diffuse capillary systems and a small area of overlap between adjacent endothelial membranes. Thin slices of the parallel, tightly packed capillary bed of the eel rete mirabile were cryofixed and prepared for conventional TEM by freeze-substitution. Other samples were freeze-fractured and replicated for examination of endothelial junctional components. A novel tight-gap junctional complex between rete capillary endothelial cells is described. In freeze-fracture replicas of the membrane P face, rows of gap junction subunits are flanked on either side by linear depressions representing grooves previously occupied by tight junctional strands that partition to the E face. In thin sections, the junctions appear in profile as short lengths of closely apposed membranes characteristic of gap junctions. The tight junctional components imply a barrier to paracellular transport across the capillary wall between the endothelial cells. The gap junctional component may provide a mechanism for communication between endothelial cells along the length of the vessel wall.

The histopathological prevalence of malignant catarrhal fever in swamp buffaloes slaughtered in the private slaughterhouses in Bogor district

Surveys were conducted in five private slaughterhouses in Bogor district to reveal the histopathological prevalence rates of malignant catarrhal fever (MCF) cases in buffaloes . The study was carried out from 1992-1994 in five sub-districts, namely: Ciawi, Caringin, Cijeruk, Megamendung and Cisatua, covering 47 villages . Thirty- two samples (18 .1%) from a total of 177 were histologically being positive for MCF, although the distribution and the severity of lesions were varied amongst them . From those 32 cases examined, lesions observed in the rete mirabile, lung, kidney, liver, urinary bladder, spleen, abomasum, heart, and small intestine were as follows : 84.4%, 77 .3%, 65 .6%, 53 .1%, 28.196, 18 .8%, 9 .4%, 9 .1%, and 3.1% respectively.

88 PRECEREBRAL AND CEREBRAL VESSEL ANATOMY IN THE PIG

The anatomy of the precerebral and cerebral vessels are not identical in humans and pigs. Vessel anatomy in newborn pigs were studied by dissection and angiography. It is possible by ligation of the external carotid, occipital and condylic artery to transform the common carotid into a precerebral artery for continous neasurements of cerebral blood flow. The pig has a large rete mirabilis between the internal carotid and the circle of Willis. We found by selective angiography in either the vertebral, internal or external carotid 1) good flow to the contralateral hemisphere, 2) some flow between the extra- and intracerebral arteries. These findings of well developed vessel communication may explain that it is not possible to produce a focal ischemic brain damage in the piglet.

TUNAS AS SMALL AS 207 mm FORK LENGTH CAN ELEVATE MUSCLE TEMPERATURES SIGNIFICANTLY ABOVE AMBIENT WATER TEMPERATURE

Tunas (family Scombridae) maintain muscle temperatures (Tm) elevated significantly above ambient water temperature (Ta) by using vascular counter-current heat exchangers (retia mirabilia) to conserve metabolic heat generated by continuous contraction of red muscle fibers. Previous work has documented endothermy and both behavioral and physiological thermoregulation in tunas, but only individuals greater than approximately 1 kg body mass had been studied. The purpose of this study was to measure Tm and to examine heat exchanger morphology in smaller fish in order to determine the minimum size at which tunas can elevate Tm significantly above Ta. Measurements of Tm made immediately after capture in field-caught and laboratory-raised tunas (Euthynnus lineatus, Auxis thazard, A. rochei and Thunnus albacares) spanning a size range of 15.5­667 mm fork length (FL) show that tunas 207 mm FL (162.3 g) and larger can elevate red muscle temperature by at least 3.0°C above Ta. E. lineatus, A. thazard and A. rochei of this size possess blood vessels serving the red muscle that are arranged as both lateral and central heat exchangers; the smallest tuna with evidence of a rete was a 108.5 mm FL E. lineatus. In the ectothermic scombrid Scomberomorus sierra (108.7­132.0 mm FL), Tm was elevated 0.2­0.5°C above Ta, and the greatest Tm elevation reported in any ectothermic species is only 2.7°C. Taken together, these data provide evidence that tunas greater than 207 mm FL are endothermic.

Adrenergic control of swimbladder perfusion in the European eel Anguilla anguilla.

Adrenergic control of swimbladder blood flow was analysed in blood-perfused preparations of the European eel as well as in situ by recording the changes in swimbladder blood flow and blood pressure following an injection of catecholamine into the dorsal artery. In blood-perfused swimbladder preparations, injection of the alpha-adrenergic agonist phenylephrine into the perfusion loop caused a marked dose-dependent increase in perfusion pressure at constant flow, while injection of the beta-agonist isoproterenol slightly decreased perfusion pressure. The beta-effect was not as pronounced as the alpha-adrenergic vasoconstriction and was observed only during the first application of catecholamine in each preparation. In situ injection of adrenaline (final concentration 10(-8)-10(-9) mol kg-1 body mass) into the dorsal aorta caused a dose-dependent transient increase in dorsal aortic blood pressure and in cardiac output which, after 5-10 min, returned to resting levels. Swimbladder perfusion also increased initially after an injection of adrenaline, but after about 1-2 min suddenly decreased and then slowly recovered to preinjection levels. Following the injection of adrenaline into the dorsal aorta, blood pressure changes in vessels at the swimbladder pole of the rete mirabile revealed a similar biphasic pattern with an initial increase, a subsequent decrease and a slow return to preinjection levels, while pressure in the arterial influx vessel of the rete resembled dorsal aortic pressure. After injection of the beta-blocker propranolol, adrenaline evoked a smaller initial increase in blood flow, but the subsequent reduction in flow was even more pronounced. Injection, in addition, of the alpha-adrenergic blocker phentolamine abolished the sharp adrenaline-induced decrease in swimbladder perfusion. It is concluded that alpha- and beta-adrenergically controlled resistance vessels are located close to the rete mirabile, probably at the arterial entrance into the rete. These vessels control perfusion of the rete mirabile and of the swimbladder and are thus involved in the control of gas deposition into the swimbladder.

A quantitative study on the retial arteries in the bovine fetus

The rostral epidural rete mirabile was injected with latex and the retial arteries were studied quantitatively in three groups of bovine fetuses. It was seen that the differences between the diameters of the right and left retial arteries were not significant. An interesting observation was that the diameter of the internal carotid artery decreased gradually with an increase in the gestational age, but this reduction was made up for the maxillary artery via the rostral rete branches. The proportion of the blood supply to the rete was also determined in three groups of fetuses.

Multiple aneurysms associated with bilateral carotid occlusion and venous angioma: surgical management risk—case report

A unique case of multiple aneurysms associated with bilateral carotid artery occlusion and venous angioma is described. A 42 year old female presented with subarachnoid haemorrhage. Cerebral angiograms demonstrated(1) a ruptured saccular aneurysm in the right posterior cerebral artery,(2) bilateral occlusion of internal carotid arteries,(3) a rete mirabile in the subtemporal fossa fed by left external carotid artery which connected with the internal carotid artery at the cavernous portion where a saccular aneurysm had formed, and(4) a venous angioma in the posterior fossa. The ruptured aneurysm of the posterior cerebral artery was obliterated preserving the anterior choroidal arteries. However, a left hemiparesis developed and CT scan revealed a small low density area in the right posterior limb of the internal capsule postoperatively. A ruptured aneurysm associated with bilateral extracranial carotid occlusion poses a clinical dilemma and treatment of such cases is challenging and difficult. The non-surgical and surgical outcomes of ruptured cerebral aneurysms associated with internal carotid occlusion are reviewed.

Necrosis of trout retina (Oncorhynchus mykiss) after sublethal exposure to nitrite

Rainbow trout exposed to sublethal concentrations of nitrite accumulate this substance to different degrees. The result is a formation of methemoglobin in amounts ranging from 6 to 100% of total hemoglobin. In contrast to tolerant specimens (low nitrite accumulation), the eyes of most of the intolerant trout were severely affected. Alterations ranged from necroses of single retinal neurons to complete destruction of the retina. Since severe direct or hypoxic damages to other organs have not been observed, the striking reaction of the retina may be attributable to its high oxygen demand. The impaired function of the choroidal rete mirabile is believed to lead to a reduced oxygen supply or to acidification of the ocular fluids.

Roles of Buffering Capacity and Pentose Phosphate Pathway Activity in the Gas Gland of the Gulf Toadfish Opsanus Beta

ABSTRACT The teleost gas gland is truly remarkable in its abilities to secrete gases into the swim bladder of physoclistous fish. The physiological and metabolic adaptations of this tissue have been elegantly summarized in a recent review article by Pelster and Scheid (1992). There are two key contributors to the function of the gland. First, a specialized metabolism of the swim bladder, involving copious and simultaneous production of lactate and CO2 from anaerobic glycolysis and the pentose phosphate pathway (also known as the hexose monophosphate shunt), respectively, contributes to gas exchange through pH and salting-out effects on the oxygen-carrying capacity of the blood. Second, a countercurrent multiplier system (i.e. a rete mirabile) enables gas tensions to be elevated further by back diffusion. Several features of metabolism and acid–base physiology remain unclear. First, despite the remarkable ability of this tissue to produce acid, it is not clear if or how intracellular pH (pHi) is regulated. Since ultimately the blood must be acidified, one would predict that the pHi of the tissue would be well regulated via high rates of membrane exchange of protons and/or high tissue buffering capacity. Second, although the functioning of the pentose phosphate pathway has been strongly inferred from measurements of enzyme activities (Boström et al. 1972; Pelster and Scheid, 1991), and from measurements of enhanced rates of CO2 excretion relative to the rates of oxygen uptake (Pelster et al. 1989), direct evidence for the existence of the shunt is lacking. Lastly, although the pentose phosphate pathway is expected to produce CO2, and thus contribute to the acidification of blood entering the gland, the pathway may have a different primary, or perhaps a dual, role, namely to maintain high tissue levels of NADPH for protection against oxygen radical damage to cells (Pelster and Scheid, 1992). The composition of the gas stored in the swim bladder can approach pure oxygen in some species, so it is not surprising that the teleost gas gland contains substantial levels of the enzymes catalase, superoxide dismutase and glutathione peroxidase, which scavenge deleterious radicals of oxygen and related harmful compounds (Morris and Albright, 1984). Noteworthy is glutathione peroxidase, which requires a constant supply of NADPH (presumably from the shunt) to maintain glutathione in a reduced state. Reduced glutathione is then used in a variety of oxygen radical detoxification mechanisms. If the pentose phosphate pathway has a role in oxygen detoxification, one would predict that flux rates through the pathway would increase with increased oxygen levels.

Immunolocalization of cytokeratin 19 in bovine and human pulmonary microvascular endothelial cells in situ

1. 1. Immunocytochemical analysis of bovine and human lung sections revealed the presence of the 41 kD intermediate filament protein cytokeratin 19 in microvessel and subpleural lymphatic endothelial cells as well as the mesothelial cell layer of the lung visceral pleura. 2. 2. Cytokeratin 19 was expressed by human and bovine pulmonary microvessels with diameters ranging from 5 to 50 μm. 3. 3. Cytokeratin 19 was also found in microvessels of the rete mirabile, an oxygen exchange organ of the eel. 4. 4. Immunoperoxidase electron microscopy demonstrated cytokeratin 19 associated with the lateral membranes of adjacent bovine alveolar capillary endothelial cells.