Topic Review
The Cat Mandible
The cat mandible is small and has some peculiarities relative to the dentition (only three incisors, a prominent canine, two premolars and one molar); a conical and horizontally oriented condyle, and a protudent angular process in its ventrocaudal part. Most of the body of the mandible is occupied by the mandibular dental roots and the mandibular canal that protects the neurovascular supply: the inferior alveolar artery and vein, and the inferior alveolar nerve that exits the mandible rostrally as the mental nerves. They irrigate and innervate all the teeth and associated structures such as the lips and gingiva. Tooth roots and the mandibular canal account for up to 70% of the volume of the mandibular body. Consequently, when fractured it is difficult to repair without invading the dental roots or vascular structures.
  • 1546
  • 01 Mar 2021
Topic Review
The Biological Basis for Antioxidant Therapy
Reactive oxygen species (ROS) are a class of highly reactive free radicals, such as hydroxyl radical (•OH), the superoxide radical (O2•−) and hydrogen peroxide (H2O2). The high intracellular ROS level-induced oxidative stress leads to the upregulation of antioxidant capacity to maintain redox homeostasis by metabolic rerouting or activation of genetic programs.
  • 302
  • 06 Jul 2022
Topic Review
Telocytes in the Rainbow Trout Intestinal Stem-Cell Niche
Histological and ultrastructural studies revealed peculiar mesenchymal cells adjacent to the epithelium that generated an intricate mesh spanning from the folds’ base to their apex. Their voluminous nuclei, limited cytoplasm and long cytoplasmic projections characterized them as telocytes (TCs). 
  • 211
  • 10 Feb 2022
Topic Review
T-Cell Receptor Signalosome
Human immunodeficiency virus type-1 (HIV-1) can undergo either a lytic pathway to cause productive systemic infection or enter a latent state in which the integrated provirus remains transcriptionally silent for decades. The ability to latently infected T-cells enables HIV-1 to establish persistent infections in resting memory CD4+ T-lymphocytes which become reactivated following disruption or cessation of intensive drug therapy. Maintenance of viral latency occurs through epigenetic and non-epigenetic mechanisms. Epigenetic mechanisms of HIV latency regulation involve deacetylation and methylation of histone proteins within Nucleosome 1 (nuc -1) at the viral long terminal repeats (LTR) such that inhibition of histone deacetyltransferase and histone lysine methyltransferase activities, respectively, reactivates HIV from latency. Non-epigenetic mechanisms involve nuclear restriction of critical cellular transcription factors such as Nuclear factor-kappa Beta (NF-kB) or Nuclear factor of activated T-cells (NFAT) which activate transcription from the viral LTR, limiting nuclear levels of viral transcription transactivator protein Tat and its cellular co-factor; positive transcription elongation factor b (P-TEFb) which together regulate HIV transcriptional elongation. The T-cell receptor (TCR) activation efficiently induces NF-kB, NFAT, and activator protein 1 (AP-1) transcription factors through multiple signal pathways and how these factors efficiently regulate HIV LTR transcription through the non-epigenetic mechanism. Elongation factor P-TEFb induced through an extracellular signal-regulated kinase (ERK) dependent mechanism regulates HIV transcriptional elongation before Tat is synthesized and the role of AP-1 in the modulation of HIV transcriptional elongation through functional synergy with NF-kB. The TCR signaling induces critical posttranslational modifications of the Cyclin-dependent kinase 9 (CDK9) subunit of P-TEFb which enhances interactions between P-TEFb and viral Tat protein and the resultant enhancement of HIV transcriptional elongation.
  • 459
  • 13 Aug 2020
Topic Review
Surgical Management of Rectal Cancer
Successful oncologic resection in rectal cancer relies on the surgical tenants of wide local excision of the disease to establish clear margin status and resection of adequate lymph nodes for staging. The introduction of, and adherence to, complete total mesorectal excision, which is the resection of the total mesorectal envelope containing the local lymphatic drainage of the rectum, has contributed a large part to the improved operative outcomes and long-term survival for rectal cancer patients. Notably, total mesorectal excision has produced a notable reduction in rectal cancer recurrence by 30 to 40%.
  • 180
  • 06 Apr 2022
Topic Review
Surfactant and the Glycocalyx
Gas exchange in the lung takes place via the air-blood barrier in the septal walls of alveoli. The tissue elements that oxygen molecules have to cross are the alveolar epithelium, the interstitium and the capillary endothelium. The epithelium that lines the alveolar surface is covered by a thin and continuous liquid lining layer. Pulmonary surfactant acts at this air-liquid interface. By virtue of its biophysical and immunomodulatory functions, surfactant keeps alveoli open, dry and clean. What needs to be added to this picture is the glycocalyx of the alveolar epithelium. Here, we briefly review what is known about this glycocalyx and how it can be visualized using electron microscopy. The application of colloidal thorium dioxide as a staining agent reveals differences in the staining pattern between type I and type II alveolar epithelial cells and shows close associations of the glycocalyx with intraalveolar surfactant subtypes such as tubular myelin. These morphological findings indicate that specific spatial interactions between components of the surfactant system and those of the alveolar epithelial glycocalyx exist which may contribute to the maintenance of alveolar homeostasis, in particular to alveolar micromechanics, to the functional integrity of the air-blood barrier, to the regulation of the thickness and viscosity of the alveolar lining layer, and to the defence against inhaled pathogens. Exploring the alveolar epithelial glycocalyx in conjunction with the surfactant system opens novel physiological perspectives of potential clinical relevance for future research.
  • 613
  • 03 May 2021
Topic Review
Structure-Dynamic Determinants of Regulatory Divergence in Eukaryotic NCXs
The plasma-membrane Na+/Ca2+ exchangers (NCXs) mediate Ca2+ extrusion/entry to dynamically shape Ca2+ signaling in biological systems ranging from bacteria to humans. The NCX gene orthologs, isoforms, and their splice variants are expressed in a tissue-specific manner and exhibit nearly 104-fold differences in the transport rates and diverse regulatory specificities to match the cell-specific requirements. About 280 residues are directly involved in the folding of Ca2+ binding CBD1 and CBD2 domains that form a two-domain regulatory tandem (CBD12). The X-ray and NMR structures of the CBD1, CBD2, and CBD12 domains reveal a β-immunoglobulin (Ig)-like folding, where two antiparallel β-sheets (with A-B-E and D-C-F-G strands) form a seven-strand β-sandwich motif. The remarkable similarity between the folding structures of CBD1 and CBD2 is evident since the overlay of the CBD1 and CBD2 crystal structures display nearly identical folding with RMSD = 1.3 Å, although all the Ca2+ binding sites in both CBDs reside at the C-terminal ends of distal loops. However, the striking difference between the CBDs is that the CBD1 domain contains four Ca2+ binding sites in all known variants, whereas in the CBD2 domain, the splicing segment varies the number of Ca2+ binding sites from zero to three. The challenge is to resolve the underlying structure-dynamic mechanisms that can explain how the Ca2+ interactions with different variants of eukaryotic NCXs can result in positive, negative, and neutral responses. 
  • 94
  • 09 Jan 2023
Topic Review
Spinal-Deformities and Advancement in Corrective-Orthoses
Spinal deformity is an abnormality in the spinal curves and can seriously affect the activities of daily life. The conventional way to treat spinal deformities, such as scoliosis, kyphosis, and spondylolisthesis, is to use spinal orthoses (braces). Braces have been used for centuries to apply corrective forces to the spine to treat spinal deformities or to stabilize the spine during postoperative rehabilitation. Braces have not modernized with advancements in technology, and very few braces are equipped with smart sensory design and active actuation. There is a need to enable the orthotists, ergonomics practitioners, and developers to incorporate new technologies into the passive field of bracing. 
  • 1011
  • 30 Jan 2021
Topic Review
Sjögren’s Syndrome Lymphomagenesis
Sjögren’s Syndrome (SS) is a chronic autoimmune disorder characterized by focal mononuclear cell infiltrates that surround the ducts of the exocrine glands, impairing the function of their secretory units. Compared to other autoimmune disorders, SS is associated with a notably high incidence of non-Hodgkin lymphoma (NHL) and more frequently mucosa associated lymphoid tissue (MALT) lymphoma, leading to increased morbidity and mortality rates. High risk features of lymphoma development include systemic extraepithelial manifestations, low serum levels of complement component C4 and mixed type II cryoglobulinemia. The discrimination between reactive and neoplastic lymphoepithelial lesion (LEL) is challenging, probably reflecting a continuum in the evolution from purely inflammatory lymphoid infiltration to the clonal neoplastic evolution. Early lesions display a predominance of activated T cells, while B cells prevail in severe histologic lesions. This strong B cell infiltration is not only a morphologic phenomenon, but it is also progressively associated with the presence of ectopic germinal centers (GCs). 
  • 303
  • 08 Dec 2020
Topic Review
Seeking Sense in the Hox Gene Cluster
The Hox gene cluster, responsible for patterning of the head–tail axis, is an ancestral feature of all bilaterally symmetrical animals (the Bilateria) that remains intact in a wide range of species.
  • 334
  • 20 Dec 2022
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