An arch worth revisiting: A study on the feline humeral supracondylar foramen and its evolutionary significance.

The supracondylar foramen with a (seemingly) osseous peripheral arch noticed on the medio-distal feline humeri had remained disputed among anatomists. Some scholars have argued in favor of homology between this foramen and the supracondyloid foramen formed in the presence of the ligament of Struthers in humans. Other theories include its presence as a retinaculum holding the median nerve and brachial artery to their anatomical position in a flexed elbow. Unfortunately, these theories lack investigative rigor. The emergence of non-invasive imaging modalities, such as micro-computed tomography, has enabled researchers to inspect the internal anatomy of bones without dismantling. Thus, a micro-computed tomographic investigation was conducted on three feline (Felis catus) humeri specimens while the internal anatomy of the supracondylar foramina was examined. Unlike the humerus, the thin peripheral arch of the feline supracondylar foramen failed to elicit any osseous trabeculae or foci of calcification. While adhering to the humeral periosteum at its origin, the non-osseous arch, typical of a muscular tendon, inserts into the bony saddle related to the medial humeral epicondyle suggestive of a tendon or aponeurotic extension of a (vestigial) brachial muscle, with the coracobrachialis longus emerging to be the most likely candidate.

Comparison of Siglec-1 protein networks and expression patterns in sperm and male reproductive tracts of mice, rats, and humans.

Background: Sialic acid-binding immunoglobulin-like lectin 1 (Siglec-1) is a transmembrane glycoprotein involved in the sialic acid (Sia)-dependent regulation of the immune system. Siglec-1 expression has recently been identified in the male reproductive tract (MRT) of several species, including humans, cattle, horses, and sheep, and may play a role in modulating fertility in a Sia-dependent manner. Materials and Methods: In this study, protein-protein interaction (PPI) analysis of Siglec-1 was conducted to identify associated network protein conservation, and the expression of Siglec-1 in the MRT of mice and rats, including their accessory sex glands and spermatozoa was determined by immunostaining. Results: Network analysis of proteins with Siglec-1 in mice and rats demonstrated significant similarity to human Siglec-1 networks, suggesting a similar conservation of network proteins between these species and, hence, a potential conservation role in immune modulation and function. Specific immunostaining patterns of mouse and rat testes, epididymis, ductus deferens, accessory sex gland tissues, and sperm were detected using human Siglec-1. These results confirmed that the human Siglec-1 antibody could cross-react with mouse and rat Siglec-1, suggesting that the specific expression patterns of Siglec-1 in the MRT and sperm of both mice and rats are similar to those observed in other species. Conclusions: The conservation of Siglec-1 expression patterns in sperm and within the MRT and the similarity of protein networks for Siglec-1 across species suggest that Siglec-1 may function in a similar manner across species. These results also suggest that rodents may serve as a valuable model system for exploring the function of Siglecs in the reproductive system across species and their potential role in modulating fertility in a Sia-dependent manner.

An Anatomical Study Using Computed Tomography, Magnetic Resonance Imaging, and Rhinoscopy of the Nasal Cavity of Domestic Cat (Felis silvestris catus L.) and Big Cats: Lion (Panthera leo leo L.), Leopard (Panthera pardus kotiya L.), and Cheetah (Acinonyx jubatus jubatus S.).

The objective of this work was to study the normal anatomy of the nasal cavity of the three species of big cats (leopard, lion, and cheetah) compared to the domestic cat through the use of computed tomography, magnetic resonance imaging, and rhinoscopy. Computed tomography allowed us to clearly visualize the entire bony and cartilaginous framework that supports the nasal cavity. Magnetic resonance imaging permitted better visualization of the soft tissues of this cavity. On the other hand, rhinoscopy enabled the direct visualization of the mucosa of the vestibule and nasal cavity, which is very useful in the diagnosis of masses or foreign bodies. Furthermore, with this technique, it has been possible to observe several small orifices from the nasolacrimal duct, the pharyngeal auditory tube, and the lateral nasal gland. Computed tomography, magnetic resonance imaging, and rhinoscopy are useful tools in analysis of the anatomical characteristics of the nasal cavity in these species.

Anatomical and Three-Dimensional Study of the Female Feline Abdominal and Pelvic Vascular System Using Dissections, Computed Tomography Angiography and Magnetic Resonance Angiography.

This study describes the anatomical characteristics of the abdominal and pelvic vascular system of two healthy mature female cats via three-dimensional contrast enhanced computed tomography angiography, non-contrast enhanced magnetic resonance angiography and three-dimensional printing. Volume-rendering computed tomography angiography images were acquired from the ventral aspect using RadiAnt, Amira and OsiriX MD Dicom three-dimensional formats, and three-dimensional printing was obtained and compared with the corresponding computed tomography angiography images. Non-contrast enhanced magnetic resonance angiography was made using the time-of-flight imaging in ventral, oblique and lateral views. In addition, three cadavers with colored latex injection were dissected to facilitate the identification of the vascular structures. Three-dimensional computed tomography angiography showed the main vascular structures, whereas with the time-of-flight blood appeared with a high signal intensity compared with associated abdominal and pelvic tissues. Three-dimensional computed tomography angiography images and time-of-flight sequences provided adequate anatomical details of the main arteries and veins that could be used for future feline anatomical and clinical vascular studies of the abdomen and pelvis.

Creation of Three-Dimensional Anatomical Vascular and Biliary Models for the Study of the Feline Liver (Felis silvestris catus L.): A Comparative CT, Volume Rendering (Vr), Cast and 3D Printing Study.

In this study, six adult feline cadavers were examined using CTA, 3D printing, and casts injected with epoxy. The aorta, the portal vein, and the gallbladder of 3 feline cadavers were separately injected with a 50% mixture of colored vulcanized latex and hydrated barium sulfate as contrast medium to analyze by CT the arterial, venous and biliary systems. The other three cadavers were injected with a mixture of epoxy resin in the aorta, gallbladder and hepatic veins, separately. After the corrosion and washing process, hepatic vascular and biliary casts were obtained. The images obtained by CT showed the vascular and biliary system using a soft tissue window. For the identification of vascular and biliary structures, the 3D prints together with the 3D reconstructions were analyzed, and the results were compared with the casts obtained with epoxy resin. Each of the arterial, venous and biliary branches associated with each of the liver lobes were identified with the help of the printings. In conclusion, the creation of 3D prototypes of nonpathological feline hepatic parenchyma can be used in the veterinary clinic as a basis for the detection of pathological problems in addition to obtaining future pathological hepatic 3D models.

On the importance of integrating comparative anatomy and One Health perspectives in anatomy education.

As a result of many factors, including climate change, unrestricted population growth, widespread deforestation and intensive agriculture, a new pattern of diseases in humans is emerging. With increasing encroachment by human societies into wild domains, the interfaces between human and animal ecosystems are gradually eroding. Such changes have led to zoonoses, vector-borne diseases, infectious diseases and, most importantly, the emergence of antimicrobial-resistant microbial strains as challenges for human health. Now would seem to be an opportune time to revisit old concepts of health and redefine some of these in the light of emerging challenges. The One Health concept addresses some of the demands of modern medical education by providing a holistic approach to explaining diseases that result from a complex set of interactions between humans, environment and animals, rather than just an amalgamation of isolated signs and symptoms. An added advantage is that the scope of One Health concepts has now expanded to include genetic diseases due to advancements in omics technology. Inspired by such ideas, a symposium was organised as part of the 19th International Federation of Associations of Anatomists (IFAA) Congress (August 2019) to investigate the scope of One Health concepts and comparative anatomy in contemporary medical education. Speakers with expertise in both human and veterinary anatomy participated in the symposium and provided examples where these two disciplines, which have so far evolved largely independent of each other, can collaborate for mutual benefit. Finally, the speakers identified some key concepts of One Health that should be prioritised and discussed the diverse opportunities available to integrate these priorities into a broader perspective that would attempt to explain and manage diseases within the scopes of human and veterinary medicine.

The presence of Wormian bones increases the fracture resistance of equine cranial bone.

Wormian (intrasutural) bones are small, irregular bones, that are found in the cranial sutures of the skull. The occurrence of Wormian bones in human skulls has been well documented but few studies have detected the presence of such bones in domestic animals. Although some research has linked the presence of Wormian bones to bone pathology, its anatomical significance in healthy individuals is not known. To the best of our knowledge, no previous study has examined the biomechanical features of Wormian bone. This study uses microCT imaging of the parietal bone region to determine the frequency of occurrence of Wormian bones in horse skulls and, through 3-point bending tests, to calculate the mechanical differences that result from the presence of such bones. In addition, bone properties such as bone mineral density (BMD) and stiffness were measured and analysed to determine the influence of Wormian bone. Our findings on 54 specimens taken from 10 horses (ages ranging from 4 to 29 years) showed that Wormian bone was present in 70% of subjects and that its occurrence was unrelated to age or sex. 3-point bend tests revealed that the stiffness normalised by cross section area (P = 0.038) was lower in samples where Wormian bone was present. An idealised Finite Element simulation confirmed that the presence of Wormian bone reduced the maximum stress and strain, as well as their distribution throughout the sample. We consequently conclude that the presence of Wormian bones, which are confined to the calvaria, increase the compliance of the bone and reduce the likelihood of skull fracture. As all skull samples were collected from a local abattoir, ethical approval was not required for this work.

The struggle to equilibrate outer and inner milieus: Renal evolution revisited.

The journey of life, from primordial protoplasm to a complex vertebrate form, is a tale of survival against incessant alterations in climate, surface topography, food chain, and chemistry of the external environment. Kidneys present with an ensemble embodiment of the adaptations devised by diverse life-forms to cope with such challenges and maintain a chemical equilibrium of water and solutes, both in and outside the body. This minireview revisits renal evolution utilizing the classic: From Fish to Philosopher; the story of our internal environment, by Prof. Homer W. Smith (1895-1962) as a template. Prof. Smith's views exemplified the invention of glomeruli, or its abolishment, as a mechanism to filter water. Moreover, with the need to preserve water, as in reptiles, the loop of Henle was introduced to concentrate urine. When compared to smaller mammals, the larger ones, albeit having loops of Henle of similar lengths, demonstrated a distinct packing of the nephrons in kidneys. Moreover, the renal portal system degenerated in mammals, while still present in other vertebrates. This account will present with a critique of the current concepts of renal evolution while examining how various other factors, including the ones that we know more about now, such as genetic factors, synchronize to achieve renal development. Finally, it will try to assess the validity of ideas laid by Prof. Smith with the knowledge that we possess now, and understand the complex architecture that evolution has imprinted on the kidneys during its struggle to survive over epochs.