Small molecule targeting amyloid fibrils inhibits Streptococcus mutans biofilm formation

Amyloid fibrils are important scaffold in bacterial biofilms. Streptococcus mutans is an established cariogenic bacteria dwelling within biofilms, and C123 segment of P1 protein is known to form amyloid fibrils in S. mutans biofilms, among which C3 segment could serve as a promising anti-amyloid target due to its critical role in C123-P1 interactions. Recently, small molecules have been found to successfully inhibit biofilms by targeting amyloid fibrils. Thus, our study aimed to screen small molecules targeting C3 segment with the capacity to influence amyloid fibrils and S. mutans biofilms. In silico screening was utilized to discover promising small molecules, which were evaluated for their effects on bacterial cells and amyloid fibrils. We selected 99 small molecules and enrolled 55 small molecules named D1–D55 for crystal violet staining. Notably, D25 selectively inhibit S. mutans biofilms but had no significant influence on biofilms formed by Streptococcus gordonii and Streptococcus sanguinis, and D25 showed no bactericidal effects and low cytotoxicity. In addition, amyloid fibrils in free-floating bacteria, biofilms and purified C123 were quantified with ThT assays, and the differences were not statistically significant in the presence or absence of D25. Morphological changes of amyloid fibrils were visualized with TEM images, where amorphous aggregates were obvious coupled with long and atypical amyloid fibrils. Moreover, amyloid-related genes were upregulated in response to D25. In conclusion, D25 is a promising antimicrobial agent with the capacity to influence amyloid fibrils and inhibit S. mutans biofilms.

APPLICATION OF CONTRAST-ENHANCED CONSTRUCTIVE INTERFERENCE IN STEADY STATE MAGNETIC RESONANCE IMAGING TO LEKSELL GAMMAPLAN FOR LOCALIZING C2-C3 ANEURYSMS

OBJECTIVE We used gadolinium (Gd)-enhanced constructive interference in steady state (CISS) magnetic resonance imaging with the Leksell GammaPlan (LGP; Elekta AB, Stockholm, Sweden) system for accurate preoperative evaluation of the anatomic localization of intradural and/or extradural C2–C3 aneurysms. METHODS Anatomic localization of 8 unruptured aneurysms of the C2–C3 segment was evaluated using Gd-enhanced CISS imaging with LGP. Four patients diagnosed with intradural aneurysms, 1 with a combined intraextradural aneurysm, and 1 with an intracavernous aneurysm underwent operation. The aneurysmal localizations diagnosed preoperatively by Gd-enhanced CISS imaging with LGP were compared with intraoperative findings. RESULTS By use of Gd-enhanced CISS imaging with LGP, 3-dimensional visualization of the internal carotid artery, aneurysms at the C2–C3 segment, optic nerve, oculomotor nerve, cavernous sinus, and anterior clinoid process was possible in 8 patients. The localization of intradural or combined intra-extradural aneurysms was diagnosed on the basis of the oculomotor nerve and the cavernous sinus depicted in 3-dimensional images. The oculomotor nerve and the cavernous sinus serve as landmarks for the proximal ring on images of the carotico-oculomotor membrane. Intradural or intra-extradural localization of C2–C3 aneurysms with this novel technique was in complete agreement with intraoperative findings in 6 surgical cases. CONCLUSION This study demonstrated the utility of Gd-enhanced CISS imaging used with LGP for accurate preoperative localization of intradural and/or extradural aneurysms at the C2–C3 segments.

Compartmentalization of motor units in the cat neck muscle, biventer cervicis

1. The neck muscle biventer cervicis is supplied by five separate nerve bundles that originate from segments C2-C5 and enter the muscle at different rostrocaudal levels. We have used the glycogen-depletion method to investigate the distribution of muscle fibers supplied by each nerve bundle and also the extent of motor-unit territories supplied by single motoneurons in the C3 segment. 2. Prolonged intermittent stimulation of each nerve bundle produced glycogen depletion in a compartment of muscle fibers that ran only a fraction of the whole-muscle length. The depleted compartment was separated by tendinous inscriptions from adjacent, serially arranged compartments that were supplied by different nerve bundles. Thus the muscle was divided into five in-series compartments, arranged in the same rostrocaudal sequence as the nerves by which they were supplied. 3. Six fast, glycolytic (FG) and five fast, oxidative-glycolytic (FOG) motor units were depleted by repetitive intracellular stimulation of their antidromically identified motoneurons in the C3 segment. The fibers of each motor unit were confined to a striplike subvolume whose cross-sectional area was only 20-40% of that for the whole compartment in which it was located. Single motor units contained an average of 408 extrafusal fibers (range: 262-582 fibers), and these were distributed with an average density of 20 fibers/mm2 in cross sections through their motor domains. No significant differences were found between the numbers or densities of fibers in FG and FOG motor units. 4. The specialized in-series organization of compartments has functional implications because the forces generated by one compartment of motor units must be transmitted through other in-series compartments of muscle fibers rather than directly onto skeletal attachments. The confined distribution of muscle fibers belonging to a single motor unit suggests that an additional level of organization may exist within individual compartments. The implications of these features for the physiological behavior and neural control of biventer cervicis are discussed.

The Paraclinoid Carotid Artery: Anatomical Aspects of a Microneurosurgical Approach

The paraclinoid area is investigated anatomically for possible microneurosurgical approaches to the C3 segment of the internal carotid artery and to structures in the vicinity of the anterior siphon knee. Removal of the anterior clinoid process reveals a tight connective tissue ring that fixes the internal carotid artery to the surrounding osseous structures at the point of its transdural passage. Transection of this fibrous ring opens a microsurgical pathway to the carotid C3 segment. The artery is surrounded by a loose connective tissue layer that allows blunt preparation along the C3 segment, without compromising the cranial nerves and without damaging venous compartments of the cavernous sinus. This approach provides neurosurgical access to paraclinoidal aneurysms, to partly intracavernous aneurysms, and to carotid-ophthalmic aneurysms, allowing control of the proximal aneurysm neck and of the parent artery itself. In cases of tumors involving the medial sphenoid ridge, the apex of the orbit, or the cavernous sinus, the pericarotid connective tissue can serve as a guide layer for access along the internal carotid artery.