The phenoxazine dye resazurin exhibits bactericidal activity against the Gram-negative pathogens Francisella tularensis and Neisseria gonorrhoeae. One resazurin derivative, resorufin pentyl ether, significantly reduces vaginal colonization by Neisseria gonorrhoeae in a mouse model of infection. The narrow spectrum of bacteria susceptible to resazurin and its derivatives suggests these compounds have a novel mode of action. To identify potential targets of resazurin and mechanisms of resistance, we isolated mutants of F. tularensis subsp. holarctica live vaccine strain (LVS) exhibiting reduced susceptibility to resazurin and performed whole genome sequencing. The genes pilD (FTL_0959) and dipA (FTL_1306) were mutated in half of the 46 resazurin-resistant (RZR) strains sequenced. Complementation of select RZR LVS isolates with wild-type dipA or pilD partially restored sensitivity to resazurin. To further characterize the role of dipA and pilD in resazurin susceptibility, a dipA deletion mutant, ΔdipA, and pilD disruption mutant, FTL_0959d, were generated. Both mutants were less sensitive to killing by resazurin compared to wild-type LVS with phenotypes similar to the spontaneous resazurin-resistant mutants. This study identified a novel role for two genes dipA and pilD in F. tularensis susceptibility to resazurin.

The basioccipital bone is an essential developmental component to the occipital bone, occipital condyles, foramen magnum, clivus, and cranial base. The basioccipital bone joins each exoccipital bone with a basiexoccipital synchondrosis and the basisphenoid/sphenoid bone with a spheno‐occipital synchondrosis. The basioccipital is found intermediate to the petrous temporal bones and forms the bilateral petrooccipital/petroclival fissures otherwise known as the petrooccipital complex. Thus, the basioccipital bone is a central component to the developing cranial base. Despite the importance of basioccipital development in cranial ontogeny, there has been limited study of basioccipital ontogeny. This study assessed 98 disarticulated human basioccipital bones from a perinatal population ranging in age‐at‐death from 5‐months intrauterine to 5‐months post‐natal development. Size and shape of basioccipital bones were assessed with traditional and extended eigenshape geometric morphometric analysis. The results of this study demonstrate that the basioccipital bone grows in width at a faster rate than it grows in length. The maximum basioccipital width surpassed the midsagittal length at approximately 7‐months intrauterine development. Canonical variate analysis revealed statistically significant shape change occurring from a relatively narrow/elongate (anterior‐to‐posterior) basiocciput shape with mild concavity at the foramen magnum in the fifth and sixth intrauterine months to a relatively broad/stout basiocciput shape with more pronounced concavity in the postnatal months. Likewise, growth rate in total length was greater than midsagittal length, demonstrating enlargement of concavity in the anterior foramen magnum over time. This report provides insight into cranial development and aids in estimating age‐at‐death among fetuses and infants.

The basioccipital bone is particularly important with regard to the developing cranium. There is broad anatomical diversity in the anatomy of fetal and infantile basioccipitals. Specifically, some basioccipitals have transverse basilar clefts, clival foramina, and clival canals. Additionally, basioccipitals are diverse with regard to foveae and foveolae patterns. The size and shape of the basioccipital also changes throughout development. Canonical variate analysis revealed shape change from a relatively narrow/long with mild concavity at the foramen magnum in the 5th and 6th intrauterine months to relatively broad/short with more pronounced concavity in the 5th postnatal month. This report highlights the development of the basioccipital bone in addition to detailing the prevalence of the aforementioned anatomical features of the basioccipital and discusses the implications for anthropology, forensic osteology, as well as clinical implications of variant basioccipital anatomy.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

The marginal tubercle, otherwise known as the processus marginalis, is an inconsistent structure that exists along the posterior aspect of the frontal process of the zygomatic bone. The marginal tubercle can be drilled in standard mini‐pterional craniotomy to enhance exposure. Surgical difficulty has been reported to occur when encountering tubercles greater than 13 mm wide (anterior‐to‐posterior dimension), in which case drilling of the tubercle is required for adequate surgical exposure. Despite the surgical importance of the marginal tubercle, few studies have assessed its anatomy. This study analyzed 744 frontal processes, classifying them by the presence of a marginal tubercle and the relationship with the sphenozygomatic suture into four categories based (A, B, C, and D, respectively). Type A had an average width of 11.18±2.27 mm (mean±SD), type B averaged 12.85±2.10 mm, type C averaged 12.09±2.19 mm, and type D averaged 13.51±2.40 mm. There were statistically significant differences in width between all types. In the context of mini‐pterional craniotomies, type D marginal tubercles are implicated as the most likely bony obstacle in the region. Moreover, type D marginal tubercles were found to exist in 31.2% of zygomatic bones. The information from this study will help with the preoperative planning of mini‐pterional craniotomies.Support or Funding InformationWV Research Challenge Fund [HEPC.dsr.17.06] and [HEPC.dsr.14.13]This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.