Diagnostic imaging descriptions and prevalence of presumed phrenic lymph nodes in dogs.

The phrenic lymph node (PLN) has been described in bovine, equine, and feline anatomic references but descriptions in canine anatomic references are currently lacking. Authors have observed a well-defined, soft tissue attenuating, contrast-enhancing structure in a location consistent with previous anatomic descriptions of the PLN in dogs that underwent thoracic CT for neoplastic staging. The aims of this two-part, retrospective/prospective, anatomic, prevalence study were (1) to describe the presence of a soft tissue structure close to the thoracic caudal vena cava, defined as the presumed PLN, in a series of dogs that underwent CT as part of the staging for metastatic disease; (2) to confirm the lymphatic origin of the presumed PLN in a dog through postmortem examination; (3) to assess the prevalence of the presumed PLN in a population of dogs that underwent thoracic CT or MRI for different clinical purposes; and (4) to assess the possibility to visualize the presumed PLN with ultrasonography. The lymphatic origin of the presumed PLN was confirmed by postmortem examination in one dog. The presumed PLN was visible in 29 of 777 canine CT examinations (prevalence 3.7%). The presumed PLN was not visible in 9 of 10 prospectively recruited ultrasound cases. Most dogs with visible presumed PLNs were large-medium breeds that were presented for neoplastic staging purposes. Findings indicated that a structure consistent with the previously reported anatomic features of PLN in cattle, horses, and cats may be detected with a low prevalence in canine CT and MRI examinations.

Scapular morphology of great apes and humans: A three-dimensional computed tomography-based comparative study.

The primate scapula has been studied widely since its shape has been shown to correlate with how the forelimb is used in daily activities. In this study, we expand on the existing literature and use an image-based methodology that was originally developed for orthopaedic practice to quantify and compare the three-dimensional (3D) morphology of the scapula across humans and great apes. We expect that this image-based approach will allow us to identify differences between great apes and humans that can be related to differences in mobility and loading regime of the shoulder. We hypothesize that gorillas and chimpanzees will have a similar scapular morphology, geared towards stability and weight-bearing in knuckle-walking, whilst the scapular morphology of orangutans is expected to be more similar to that of humans given their high glenohumeral mobility associated with their suspensory lifestyle. We made 3D reconstructions of computed tomography scans of 69 scapulae from four hominid genera (Pongo, Gorilla, Pan and Homo). On these 3D bone meshes, the inferior glenoid plane was determined, and subsequently, a set of bony landmarks on the scapular body, coracoid, and acromion were defined. These landmarks allowed us to measure a set of functionally relevant angles which represent acromial overhang, subacromial space and coracoacromial space. The angles that were measured are: the delto-fulcral triangle (DFT), comprising the alpha, beta, and delta angle, the acromion-glenoid angle (AGA), the coracoid-glenoid centre-posterior acromial angle (CGA), the anterior tilt (TA CGA) and the posterior tilt of the CGA (PT CGA). Three observers placed the landmarks on the 3D bone meshes, allowing us to calculate the inter-observer error. The main differences in the DFT were found between humans and the great apes, with small differences between the great apes. The DFT of humans was significantly lower compared to that of the great apes, with the smallest alpha (32.7°), smallest delta (45.7°) and highest beta angle (101.6°) of all genera. The DFT of chimpanzees was significantly higher compared to that of humans (p < 0.01), with a larger alpha (37.6°) and delta angle (54.5°) and smaller beta angle (87.9°). The mean AGA of humans (59.1°) was significantly smaller (p < 0.001) than that of gorillas (68.8°). The mean CGA of humans (110.1°) was significantly higher (p < 0.001) than in orangutans (92.9°). Humans and gorillas showed mainly a posterior tilt of their coracoacromial complex whilst chimpanzees showed mainly an anterior tilt. The coracoacromial complex of the orangutans was not tilted anteriorly or posteriorly. With our image-based method, we were able to identify morphological features of the scapula that differed significantly between hominid genera. However, we did not find an overall dichotomy in scapular morphology geared towards high stability (Pan/Gorilla) or high mobility (Homo/Pongo). Further research is needed to investigate the functional implications of these differences in scapular morphology.

The shrimp nephrocomplex serves as a major portal of pathogen entry and is involved in the molting process.

Viruses, such as white spot syndrome virus, and bacteria, such as Vibrio species, wreak havoc in shrimp aquaculture [C. M. Escobedo-Bonilla et al., J. Fish. Dis. 31, 1-18 (2008)]. As the main portal of entry for shrimp-related pathogens remain unclear, infectious diseases are difficult to prevent and control. Because the cuticle is a strong pathogen barrier, regions lacking cuticular lining, such as the shrimp's excretory organ, "the antennal gland," are major candidate entry portals [M. Corteel et al., Vet. Microbiol. 137, 209-216 (2009)]. The antennal gland, up until now morphologically underexplored, is studied using several imaging techniques. Using histology-based three-dimensional technology, we demonstrate that the antennal gland resembles a kidney, connected to a urinary bladder with a nephropore (exit opening) and a complex of diverticula, spread throughout the cephalothorax. Micromagnetic resonance imaging of live shrimp not only confirms the histology-based model, but also indicates that the filling of the diverticula is linked to the molting cycle and possibly involved therein. Based on function and complexity, we propose to rename the antennal gland as the "nephrocomplex." By an intrabladder inoculation, we showed high susceptibility of this nephrocomplex to both white spot syndrome virus and Vibrio infection compared to peroral inoculation. An induced drop in salinity allowed the virus to enter the nephrocomplex in a natural way and caused a general infection followed by death; fluorescent beads were used to demonstrate that particles may indeed enter through the nephropore. These findings pave the way for oriented disease control in shrimp.

Description of different ultrasound guided transversus abdominis plane block in pig cadavers - A pilot study.

OBJECTIVE: To develop an ultrasound (US)-guided transversus abdominis plane (TAP) block in pigs. STUDY DESIGN: Prospective, descriptive, experimental study. ANIMALS: A total of 26 hemi-abdomens belonging to 13 Seghers Hybrid cadavers. METHODS: The study consisted of two parts. In part 1, a preliminary anatomical understanding of the abdominal wall innervation in pigs was established (two hemi-abdomens of one pig). Part 2 was divided into three phases, and a US-guided TAP technique using methylene blue dye (0.3 mL kg-1 for each hemi-abdomen) was developed. In chronological order, a pilot study (phase I) was conducted to establish good injection points (four hemi-abdomens). In phase II a two-point injection technique (10 hemi-abdomens) was performed. A cranial injection was made at two-thirds of the distance between the xyphoid process and the iliac crest, immediately ventral to the rib arch. A caudal injection was performed ventral to the last rib. In phase III a three-point injection technique was performed (10 hemi-abdomens) with an extra injection point halfway between the cranial and caudal injection point. Staining of the different nerves was recorded during dissection. RESULTS: In part 1 the nerves innervating the pig's abdominal wall, thoracic vertebrae 12-16 (T12-16) and lumbar vertebrae 1-3 (L1-3), were identified. In part 2, data from the pilot study, adequate nerve staining with the two- or three-point injection technique, were obtained in T12 (29 versus 45% respectively), T13 (29 versus 100%), T14 (73 versus 45%), T15 (75 versus 78%), T16 (58 versus 78%), L1 (100 versus 75%), L2 (88 versus 84%) and L3 (23 versus 0%). CONCLUSIONS AND CLINICAL RELEVANCE: US-guided TAP block can be used in swine but only a moderate success rate for adequate nerve staining was achieved in this study. Further studies are necessary to determine a correct injection volume and assess clinical intra- and postoperative efficacy.

Quantitative analysis of hepatic macro- and microvascular alterations during cirrhogenesis in the rat.

Cirrhosis represents the end-stage of any persistent chronically active liver disease. It is characterized by the complete replacement of normal liver tissue by fibrosis, regenerative nodules, and complete fibrotic vascularized septa. The resulting angioarchitectural distortion contributes to an increasing intrahepatic vascular resistance, impeding liver perfusion and leading to portal hypertension. To date, knowledge on the dynamically evolving pathological changes of the hepatic vasculature during cirrhogenesis remains limited. More specifically, detailed anatomical data on the vascular adaptations during disease development is lacking. To address this need, we studied the 3D architecture of the hepatic vasculature during induction of cirrhogenesis in a rat model. Cirrhosis was chemically induced with thioacetamide (TAA). At predefined time points, the hepatic vasculature was fixed and visualized using a combination of vascular corrosion casting and deep tissue microscopy. Three-dimensional reconstruction and data-fitting enabled cirrhogenic features to extracted at multiple scales, portraying the impact of cirrhosis on the hepatic vasculature. At the macrolevel, we noticed that regenerative nodules severely compressed pliant venous vessels from 12 weeks of TAA intoxication onwards. Especially hepatic veins were highly affected by this compression, with collapsed vessel segments severely reducing perfusion capabilities. At the microlevel, we discovered zone-specific sinusoidal degeneration, with sinusoids located near the surface being more affected than those in the middle of a liver lobe. Our data shed light on and quantify the evolving angioarchitecture during cirrhogenesis. These findings may prove helpful for future targeted invasive interventions.

Intussusceptive Pillar Formation in Developing Porcine Glomeruli.

BACKGROUND/AIMS: Intussusceptive angiogenesis (IA) is a dynamic process which contributes to vascular expansion and remodeling. Intraluminal pillars have long been the distinctive structural indicator of IA. However, the mechanism of their formation has not been fully elucidated. METHODS: Using light and electron microscopy, we studied intussusceptive vascular growth in the developing porcine metanephric kidney. RESULTS: We observed intraluminal pillars formed by endothelial cells in the vasculature of developing glomeruli. Their diameter was < 2.5 µm, consistent with the diameter of nascent pillars. TEM revealed that the majority of these pillars consisted only of endothelium. However, a central core of extracellular matrix (ECM) covered by endothelium, reminiscent of a more mature intussusceptive pillar, was also found in the lumen of a glomerular capillary. Perivascular cells or pericytes were not involved in the pillar structure during these stages of formation. CONCLUSION: This study shows ECM presence in a mature intussusceptive pillar without any perivascular cell involvement in the structure. This leads to the hypothesis that ECM deposition precedes the participation of these cells in the formation of intraluminal pillars during IA in porcine metanephric glomerular capillaries.

25-OH-vitamin D, parathyroid hormone, and calcium serum levels in captive common marmosets (Callithrix jacchus): Reference values and effect of age, sex, season, and closure of long bone epiphyses.

BACKGROUND: To date, reference values for 25-OH-vitamin D, parathyroid hormone (PTH), and calcium in serum of common marmosets (Callithrix jacchus) based on a large sample size are not available. METHODS: Serum reference values for these parameters were determined and correlated with sex, age, season of sampling, and time of long bone epiphyseal closure in captive-housed marmosets. RESULTS AND CONCLUSIONS: The 90% reference range for serum 25-OH-vitamin D is 47.40-370.4 nmol/L, for PTH 2.10-30.51 pmol/L, and for calcium 2.08-2.63 mmol/L. Lower levels of vitamin D were measured in fall compared with the other seasons. Levels of PTH were higher in males than in females, and calcium levels were lower in younger animals compared with older marmosets. No other effects of age, sex, season, or timing of growth plate closure were found.

A preliminary study of pulmonary vein implant applicability and safety as a potential ablation platform in a follow-up study in pigs.

BACKGROUND: Recurrence of atrial fibrillation after an ablation procedure remains a major problem which emphasizes the need for improved pulmonary vein isolation techniques. AIMS: The aim of this study was to describe an implantation procedure of a pulmonary vein-stent which may possibly serve as an ablation technique in the future and to examine stent safety in a follow-up study in pigs. METHODS AND RESULTS: Eight pigs were catheterized and nine self-expanding nitinol stents were implanted through a transfemoral or transatrial approach into the antra of the pulmonary veins. After 3 months' follow-up, the animals were euthanized for further examination. During the follow-up phase, no complications were observed. Absence of thrombus formation or pulmonary vein wall dissection was noticed during anatomical and histological evaluation of the heart-lung packages. All implants were almost completely covered by neo-intima, of which thickness varied between 0.2 and 3.9 mm. CONCLUSIONS: Stents can safely be positioned and deployed into the antra of the pulmonary veins without any acute or long-term (3 months) adverse effects. In the future, these implants could function as a permanently implanted ablation device and provide new therapeutic strategies for pulmonary vein isolation in patients with atrial fibrillation.

The fate of the vitelline and umbilical veins during the development of the human liver.

Differentiation of endodermal cells into hepatoblasts is well studied, but the remodeling of the vitelline and umbilical veins during liver development is less well understood. We compared human embryos between 3 and 10 weeks of development with pig and mouse embryos at comparable stages, and used Amira 3D reconstruction and Cinema 4D remodeling software for visualization. The vitelline and umbilical veins enter the systemic venous sinus on each side via a common entrance, the hepatocardiac channel. During expansion into the transverse septum at Carnegie Stage (CS)12 the liver bud develops as two dorsolateral lobes or 'wings' and a single ventromedial lobe, with the liver hilum at the intersection of these lobes. The dorsolateral lobes each engulf a vitelline vein during CS13 and the ventromedial lobe both umbilical veins during CS14, but both venous systems remain temporarily identifiable inside the liver. The dominance of the left-sided umbilical vein and the rightward repositioning of the sinuatrial junction cause de novo development of left-to-right shunts between the left umbilical vein in the liver hilum and the right hepatocardiac channel (venous duct) and the right vitelline vein (portal sinus), respectively. Once these shunts have formed, portal branches develop from the intrahepatic portions of the portal vein on the right side and the umbilical vein on the left side. The gall bladder is a reliable marker for this hepatic vascular midline. We found no evidence for large-scale fragmentation of embryonic veins as claimed by the 'vestigial' theory. Instead and in agreement with the 'lineage' theory, the vitelline and umbilical veins remained temporally identifiable inside the liver after being engulfed by hepatoblasts. In agreement with the 'hemodynamic' theory, the left-right shunts develop de novo.

A multilevel framework to reconstruct anatomical 3D models of the hepatic vasculature in rat livers.

The intricate (micro)vascular architecture of the liver has not yet been fully unravelled. Although current models are often idealized simplifications of the complex anatomical reality, correct morphological information is instrumental for scientific and clinical purposes. Previously, both vascular corrosion casting (VCC) and immunohistochemistry (IHC) have been separately used to study the hepatic vasculature. Nevertheless, these techniques still face a number of challenges such as dual casting in VCC and limited imaging depths for IHC. We have optimized both techniques and combined their complementary strengths to develop a framework for multilevel reconstruction of the hepatic circulation in the rat. The VCC and micro-CT scanning protocol was improved by enabling dual casting, optimizing the contrast agent concentration, and adjusting the viscosity of the resin (PU4ii). IHC was improved with an optimized clearing technique (CUBIC) that extended the imaging depth for confocal microscopy more than five-fold. Using in-house developed software (DeLiver), the vascular network - in both VCC and IHC datasets - was automatically segmented and/or morphologically analysed. Our methodological framework allows 3D reconstruction and quantification of the hepatic circulation, ranging from the major blood vessels down to the intertwined and interconnected sinusoids. We believe that the presented framework will have value beyond studies of the liver, and will facilitate a better understanding of various parenchymal organs in general, in physiological and pathological circumstances.

A novel approach for regional anaesthesia of the auricular region in horses: an anatomic and imaging study.

OBJECTIVE: To investigate the anatomy of the ear innervation in horses and develop a new approach for the block of the internal and external pinna and acoustic meatus. STUDY DESIGN: Prospective, descriptive, cadaveric study. ANIMALS: A total of 25 heads and necks from horse cadavers. METHODS: Phase I: anatomical dissection and dye deposition on 19 heads. With the head positioned in lateral recumbency, 10 mL methylene blue (1:1 sterile water) for the internal auricular and 2 mL for the great auricular nerve block were injected in 21 ears (seven left, 10 right and two bilaterally). The anatomy of all the ears (bilaterally) and the accuracy of dye deposition (successful nerve staining defined as > 2 cm) was assessed following dissection. Occurrence of intraparotid, intravascular, or intraneural injection was recorded. Phase II: the same technique and volumes were applied, bilaterally, using a lidocaine 2%:iohexol solution mixture (3:1) in six different cadavers. Computed tomography was performed and the needle position and spread of the mixture evaluated and recorded. RESULTS: Phase I: Inter- and intraindividual differences were found in the anatomy of the great auricular nerve, but not in the internal and lateral auricular nerve branches and the caudal auricular nerve. No auriculotemporal nerve was found. Nerve staining was successful in 95% of the cases for the great auricular nerve, 85% of the cases for the internal auricular nerve, and 100% of the cases for the lateral auricular branch and caudal auricular nerve. Failure was observed in horses with abundant periauricular fat. No intravascular, intraparotid or intraneural injections occurred. Phase II: A 100% success rate was recorded from computed tomography images. CONCLUSIONS AND CLINICAL RELEVANCE: The described approach seems suitable for blockade of the sensory innervation of the equine ear.

The need for transparency and good practices in the qPCR literature.

Two surveys of over 1,700 publications whose authors use quantitative real-time PCR (qPCR) reveal a lack of transparent and comprehensive reporting of essential technical information. Reporting standards are significantly improved in publications that cite the Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) guidelines, although such publications are still vastly outnumbered by those that do not.

Infrahepatic inferior caval and azygos vein formation in mammals with different degrees of mesonephric development.

Controversies regarding the development of the mammalian infrahepatic inferior caval and azygos veins arise from using topography rather than developmental origin as criteria to define venous systems and centre on veins that surround the mesonephros. We compared caudal-vein development in man with that in rodents and pigs (rudimentary and extensive mesonephric development, respectively), and used Amira 3D reconstruction and Cinema 4D-remodelling software for visualisation. The caudal cardinal veins (CCVs) were the only contributors to the inferior caval (IVC) and azygos veins. Development was comparable if temporary vessels that drain the large porcine mesonephros were taken into account. The topography of the CCVs changed concomitant with expansion of adjacent organs (lungs, meso- and metanephroi). The iliac veins arose by gradual extension of the CCVs into the caudal body region. Irrespective of the degree of mesonephric development, the infrarenal part of the IVC developed from the right CCV and the renal part from vascular sprouts of the CCVs in the mesonephros that formed 'subcardinal' veins. The azygos venous system developed from the cranial remnants of the CCVs. Temporary venous collaterals in and around the thoracic sympathetic trunk were interpreted as 'footprints' of the dorsolateral-to-ventromedial change in the local course of the intersegmental and caudal cardinal veins relative to the sympathetic trunk. Interspecies differences in timing of the same events in IVC and azygos-vein development appear to allow for proper joining of conduits for caudal venous return, whereas local changes in topography appear to accommodate efficient venous perfusion. These findings demonstrate that new systems, such as the 'supracardinal' veins, are not necessary to account for changes in the course of the main venous conduits of the embryo.

A Preclinical Study of an Implanted Device in the Pulmonary Veins, Intended for the Treatment of Atrial Fibrillation in an Ovine Model.

BACKGROUND: Atrial fibrillation is the most frequent arrhythmia in adults of which the interventional cure is hampered by high recurrence rates. Recurrence after ablation is due to an incomplete isolation of the pulmonary veins. A new ablation technique was performed, in the antra of ovine pulmonary veins, by device implantation, which was heated through a wireless heat-generating system. METHODS AND RESULTS: Implants were placed transatrially in the pulmonary veins of sheep. Using a wireless heating system, the energy was afterward transferred through wires to the implanted device according to a defined protocol. The position of the implant and the applied lesions were macroscopically evaluated. Samples of the ablated tissue of the atrio-pulmonary vein junction were histologically and immunohistochemically examined. CONCLUSIONS: Six ablation procedures in four sheep were successfully performed without adverse cardiac reactions. Implantation of the device and the wireless heat generation was feasible. Sufficient heat was produced at the level of the antra of the pulmonary veins to create ablation lesions, which were histologically and immunohistochemically confirmed.

Steroids affect gene expression, ciliary activity, glucose uptake, progesterone receptor expression and immunoreactive steroidogenic protein expression in equine oviduct explants in vitro.

The oviduct undergoes dramatic functional and morphological changes throughout the oestrous cycle of the mare. To unravel the effects of steroids on the morphology, functionality and gene expression of the equine oviduct, an in vitro oviduct explant culture system was stimulated with physiological concentrations of progesterone and 17ß-oestradiol. Four conditions were compared: unsupplemented preovulatory explants, preovulatory explants that were stimulated with postovulatory hormone concentrations, unsupplemented postovulatory explants and postovulatory explants that were stimulated with preovulatory hormone concentrations. The modulating effects of both steroids on oviduct explants were investigated and the following parameters examined: (1) ciliary activity, (2) glucose consumption and lactate production pattern, (3) ultrastructure, (4) mRNA expression of embryotrophic genes, (5) steroidogenic capacities of oviductal explants and (6) progesterone receptor expression. The present paper shows that the equine oviduct is an organ with potential steroidogenic capacities, which is highly responsive to local changes in progesterone and 17ß-oestradiol concentrations at the level of morphology, functionality and gene expression of the oviduct. These data provide a basis to study the importance of endocrine and paracrine signalling during early embryonic development in the horse.

The Omental Pedicle Flap in Dogs Revised and Refined: A Cadaver Study.

OBJECTIVE: To expand current knowledge on the canine omental vasculature and refine the existing lengthening technique of the canine omentum. STUDY DESIGN: Ex vivo study. ANIMALS: Canine cadavers (n=20). METHODS: In 10 canine cadavers the omental arteries were mapped using intravascular latex injection and these results were used to create an omental pedicle flap based on the splenic artery in 10 additional cadavers. The operating range of the flap was recorded with particular attention to the main regions of interest for omental transposition in dogs (axillary and inguinal regions). RESULTS: The superficial and deep omental leaves were each predominantly supplied by a left and a right marginal omental artery that anastomosed near the caudal omental border into a superficial and a deep omental arch, respectively. Anastomoses between arteries of the superficial and the deep omental leaves were weak and inconsistent, except for 1 anastomosis that was found in 8 of 10 dogs. By transposing the intact omentum, the right axilla could be reached in 3 dogs, both axillae in 1 dog, and both groins in all cadavers. In all cases, the omental pedicle reached to and beyond the axillary and inguinal regions. By unfolding the pedicle leaves, the width of the pedicle tip could be doubled. CONCLUSION: When lengthening the omentum is necessary to reach extra-abdominal structures, the omental pedicle flap based on the splenic artery appears to preserve the omental vascular supply. These observations warrant further clinical trials to evaluate this new omtental flap technique in vivo.

Development of the human infrahepatic inferior caval and azygos venous systems.

Differences in opinion regarding the development of the infrahepatic inferior caval and azygos venous systems in mammals centre on the contributions of 'caudal cardinal', 'subcardinal', 'supracardinal', 'medial and lateral sympathetic line' and 'sacrocardinal' veins. The disagreements appear to arise from the use of topographical position rather than developmental origin as criterion to define separate venous systems. We reinvestigated the issue in a closely spaced series of human embryos between 4 and 10 weeks of development. Structures were visualized with the Amira(®) reconstruction and Cinema4D(®) remodelling software. The vertebral level and neighbouring structures were used as topographic landmarks. The main results were that the caudal cardinal veins extended caudally from the common cardinal vein between CS11 and CS15, followed by the development of the subcardinal veins as a plexus sprouting ventrally from the caudal cardinal veins. The caudal cardinal veins adapted their course from lateral to medial relative to the laterally expanding lungs, adrenal glands, definitive kidneys, sympathetic trunk and umbilical arteries between CS15 and CS18, and then became interrupted in the part overlaying the regressing mesonephroi (Th12-L3). The caudal part of the left caudal cardinal vein then also regressed. The infrarenal part of the inferior caval vein originated from the right caudal cardinal vein, while the renal part originated from subcardinal veins. The azygos veins developed from the remaining cranial part of the caudal cardinal veins. Our data show that all parts of the inferior caval and azygos venous systems developed directly from the caudal cardinal veins or from a plexus sprouting from these veins.

Steroids in the equine oviduct: synthesis, local concentrations and receptor expression.

Steroids play an important role in mammalian reproduction and early pregnancy. Although systemic changes in steroid concentrations have been well documented, it is not clear how these correlate with local steroid concentrations in the genital tract. We hypothesised that, in the horse, the preimplantation embryo may be subjected to high local steroid concentrations for several days. Therefore, we measured progesterone, 17-hydroxyprogesterone, 17?-oestradiol, testosterone and 17?-testosterone concentrations in equine oviductal tissue by ultra-HPLC coupled with tandem mass spectrometry, and progesterone, 17?-oestradiol, oestrone and testosterone concentrations in oviduct fluid by radioimmunoassay, with reference to cycle stage and side of ovulation. Progesterone concentrations were high in oviductal tissue and fluid ipsilateral to the ovulation side during dioestrus, whereas other steroid hormone concentrations were not influenced by the side of ovulation. These results suggest that the high ipsilateral progesterone concentration is caused by: (1) contributions from the follicular fluid in the oviduct and diffusion of follicular fluid steroids after ovulation; (2) local transfer of steroids via blood or lymph; (3) local synthesis of progesterone in the oviduct, as evidenced by the expression of steroidogenic enzymes; and (4) a paracrine contribution from follicular cells. These data provide a basis for the study of the importance of endocrine and paracrine signalling during early embryonic development in the horse.

A multilevel modeling framework to study hepatic perfusion characteristics in case of liver cirrhosis.

Liver cirrhosis represents the end-stage of different liver disorders, progressively affecting hepatic architecture, hemodynamics, and function. Morphologically, cirrhosis is characterized by diffuse fibrosis, the conversion of normal liver architecture into structurally abnormal regenerative nodules and the formation of an abundant vascular network. To date, the vascular remodeling and altered hemodynamics due to cirrhosis are still poorly understood, even though they seem to play a pivotal role in cirrhogenesis. This study aims to determine the perfusion characteristics of the cirrhotic circulation using a multilevel modeling approach including computational fluid dynamics (CFD) simulations. Vascular corrosion casting and multilevel micro-CT imaging of a single human cirrhotic liver generated detailed datasets of the hepatic circulation, including typical pathological characteristics of cirrhosis such as shunt vessels and dilated sinusoids. Image processing resulted in anatomically correct 3D reconstructions of the microvasculature up to a diameter of about 500 µm. Subsequently, two cubic samples (150 × 150 × 150 µm³) were virtually dissected from vascularized zones in between regenerative nodules and applied for CFD simulations to study the altered cirrhotic microperfusion and permeability. Additionally, a conceptual 3D model of the cirrhotic macrocirculation was developed to reveal the hemodynamic impact of regenerative nodules. Our results illustrate that the cirrhotic microcirculation is characterized by an anisotropic permeability showing the highest value in the direction parallel to the central vein (kd,zz = 1.68 × 10-13 m² and kd,zz = 7.79 × 10⁻¹³ m² for sample 1 and 2, respectively) and lower values in the circumferential (kd,ϑϑ = 5.78 × 10⁻¹4 m² and kd,ϑϑ = 5.65 × 10⁻¹³ m² for sample 1 and 2, respectively) and radial (kd,rr = 9.87 × 10⁻¹4 m² and kd,rr = 5.13 × 10⁻¹³ m² for sample 1 and 2, respectively) direction. Overall, the observed permeabilities are markedly higher compared to a normal liver, implying a locally decreased intrahepatic vascular resistance (IVR) probably due to local compensation mechanisms (dilated sinusoids and shunt vessels). These counteract the IVR increase caused by the presence of regenerative nodules and dynamic contraction mechanisms (e.g., stellate cells, NO-concentration, etc.). Our conceptual 3D model of the cirrhotic macrocirculation indicates that regenerative nodules severely increase the IVR beyond about 65 vol. % of regenerative nodules. Numerical modeling allows quantifying perfusion characteristics of the cirrhotic macro- and microcirculation, i.e., the effect of regenerative nodules and compensation mechanisms such as dilated sinusoids and shunt vessels. Future research will focus on the development of models to study time-dependent degenerative adaptation of the cirrhotic macro- and microcirculation.

Analyzing the human liver vascular architecture by combining vascular corrosion casting and micro-CT scanning: a feasibility study.

Although a full understanding of the hepatic circulation is one of the keys to successfully perform liver surgery and to elucidate liver pathology, relatively little is known about the functional organization of the liver vasculature. Therefore, we materialized and visualized the human hepatic vasculature at different scales, and performed a morphological analysis by combining vascular corrosion casting with novel micro-computer tomography (CT) and image analysis techniques. A human liver vascular corrosion cast was obtained by simultaneous resin injection in the hepatic artery (HA) and portal vein (PV). A high resolution (110 µm) micro-CT scan of the total cast allowed gathering detailed macrovascular data. Subsequently, a mesocirculation sample (starting at generation 5; 88 × 68 × 80 mm³) and a microcirculation sample (terminal vessels including sinusoids; 2.0 × 1.5 × 1.7 mm³) were dissected and imaged at a 71-µm and 2.6-µm resolution, respectively. Segmentations and 3D reconstructions allowed quantifying the macro- and mesoscale branching topology, and geometrical features of HA, PV and hepatic venous trees up to 13 generations (radii ranging from 13.2 mm to 80 µm; lengths from 74.4 mm to 0.74 mm), as well as microvascular characteristics (mean sinusoidal radius of 6.63 µm). Combining corrosion casting and micro-CT imaging allows quantifying the branching topology and geometrical features of hepatic trees using a multiscale approach from the macro- down to the microcirculation. This may lead to novel insights into liver circulation, such as internal blood flow distributions and anatomical consequences of pathologies (e.g. cirrhosis).