Characteristics of the New Mast Cell-Rich Nodal Structure in the Rat Skin Surface.

Background: : Acupuncture, practiced for millennia, lacks a clear anatomical definition for acupoints. A prevailing theory suggests that acupoints overlap with skin areas with higher mast cell density. Skin spots stained with intravenously infused Evans blue (EB), indicative of neurogenic inflammation, have recently been posited as acupoints in rats. Objectives: : To demonstrate the concordance between EB-reactive skin spots and mast cell-enriched acupoints. Methods: : We employed staining and RNA-seq analysis to delineate the morphological characteristics and gene expression profiles of EB-reactive skin spots in rats. Results: : EB infusion revealed a novel nodal structure on the rat skin surface, visible to the naked eye, with dimensions of approximately 1 mm in both diameter and height. Around 30 such nodes were identified on one side of the abdominal area, spaced roughly 3 mm apart, excluding the linea alba. RNA-seq analysis indicated that the gene expression patterns within these nodes markedly differed from both non-nodal skin areas and lymph nodes. Histological examination using toluidine blue revealed a significantly greater mast cell count in the nodes than in non-nodal skin regions. Additionally, the nodes stained positively with Alcian blue and Hemacolor, reagents known to mark primo vascular tissues. Conclusion: : Our findings suggest that EB-reactive nodes are indeed rich in mast cells. Further research is warranted to establish these skin nodes as surface primo nodes.

Tissue Concentration Analysis of Sulfur, Calcium and Oxygen in Novel Skin Primo Nodes After Acupuncture.

Over the past 5000 years, acupuncture has been practiced in Korea, China, and Japan to relieve various diseases, and it is now widely used and accepted worldwide. Although the anatomical substance and function of meridians has been actively studied, it is still not clearly defined. One of the keys to acupuncture is determining the specific anatomical location exactly on or under the skin. We discovered that the skin primo node is a new anatomical structure in the skin of rats. The present study aimed to analyze the relationship between skin primo nodes and acupoints through changes in the expression of tissue concentrations of skin primo nodes. Analysis of this skin primo node confirmed that the skin primo node after acupuncture had a significantly higher concentration of sulfur and calcium than found in normal skin. And the significant pO2 in the skin primo node was confirmed by measuring pO2 using a needle oxygen sensor. Through sulfur, calcium, and pO2 concentration values of skin primo nodes, we confirmed whether these nodes could be related to acupoint. To understand the clear structure and function of this node, it is necessary to further study through the known properties of acupoints and the function of Primo Vascular System (PVS).

Primo Vessels Inside Lymphatic Vessels Are Absent in an ALS Mouse Model.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the selective death of motor neurons in the central nervous system. It is also a representative rare disease among degenerative diseases of the nervous system. Although many drugs for the treatment of degenerative brain diseases are being developed, they are not delivered correctly to the target due to the blood-brain barrier. The present study aimed to analyze changes in the primo vascular system (PVS) in ALS mice with symptoms and the partial oxygen pressure (pO2) in normal mice. In normal mice, we consistently observed primo vessels in lymphatic vessels (L-PVS). However, in ALS mice with symptoms, L-PVS were mostly lost, rendering them difficult to observe. The pO2 of the L-PVS in normal mice was significantly higher than that of normal dermis and lymph nodes.In conclusion, the relatively higher oxygen levels measured in the L-PVS than in normal dermis and lymph nodes suggest a role for the PVS in oxygen transport and enable a hypothesis that the L-PVS can function as a drug delivery pathway.

Structural dynamics of receptor recognition and pH-induced dissociation of full-length Clostridioides difficile Toxin B.

Clostridioides difficile secretes Toxin B (TcdB) as one of its major virulence factors, which binds to intestinal epithelial and subepithelial receptors, including frizzled proteins and chondroitin sulfate proteoglycan 4 (CSPG4). Here, we present cryo-EM structures of full-length TcdB in complex with the CSPG4 domain 1 fragment (D1401-560) at cytosolic pH and the cysteine-rich domain of frizzled-2 (CRD2) at both cytosolic and acidic pHs. CSPG4 specifically binds to the autoprocessing and delivery domains of TcdB via networks of salt bridges, hydrophobic and aromatic/proline interactions, which are disrupted upon acidification eventually leading to CSPG4 drastically dissociating from TcdB. In contrast, FZD2 moderately dissociates from TcdB under acidic pH, most likely due to its partial unfolding. These results reveal structural dynamics of TcdB during its preentry step upon endosomal acidification, which provide a basis for developing therapeutics against C. difficile infections.

Interplay between an ATP-binding cassette F protein and the ribosome from Mycobacterium tuberculosis.

EttA, energy-dependent translational throttle A, is a ribosomal factor that gates ribosome entry into the translation elongation cycle. A detailed understanding of its mechanism of action is limited due to the lack of high-resolution structures along its ATPase cycle. Here we present the cryo-electron microscopy (cryo-EM) structures of EttA from Mycobacterium tuberculosis (Mtb), referred to as MtbEttA, in complex with the Mtb 70S ribosome initiation complex (70SIC) at the pre-hydrolysis (ADPNP) and transition (ADP-VO4) states, and the crystal structure of MtbEttA alone in the post-hydrolysis (ADP) state. We observe that MtbEttA binds the E-site of the Mtb 70SIC, remodeling the P-site tRNA and the ribosomal intersubunit bridge B7a during the ribosomal ratcheting. In return, the rotation of the 30S causes conformational changes in MtbEttA, forcing the two nucleotide-binding sites (NBSs) to alternate to engage each ADPNP in the pre-hydrolysis states, followed by complete engagements of both ADP-VO4 molecules in the ATP-hydrolysis transition states. In the post-hydrolysis state, the conserved ATP-hydrolysis motifs of MtbEttA dissociate from both ADP molecules, leaving two nucleotide-binding domains (NBDs) in an open conformation. These structures reveal a dynamic interplay between MtbEttA and the Mtb ribosome, providing insights into the mechanism of translational regulation by EttA-like proteins.