Mesothelium of the murine allantois exhibits distinct regional properties

The rodent allantois is thought to be unique amongst mammals in not having an endodermal component. Here, we have investigated the mesothelium, or outer surface, of murine umbilical precursor tissue, the allantois (～7.25–8.5 days postcoitum, dpc) to discover whether it exhibits the properties of an epithelium. A combination of morphology, challenge with biotinylated dextran amines (BDAs), and immunohistochemistry revealed that the mesothelium of the mouse allantois exhibits distinct regional properties. By headfold stages (～7.75–8.0 dpc), distal mesothelium was generally squamous in shape, and highly permeable to BDA challenge, whereas ventral proximal mesothelium, referred to as “ventral cuboidal mesothelium” (VCM) for the characteristic cuboidal shape of its cells, was relatively impermeable. Although “dorsal cuboidal mesothelium” (DCM) resembled the VCM in cell shape, its permeability to BDA was intermediate between the other two regions. Results of immunostaining for Zonula Occludens‐1 (ZO‐1) and Epithelial‐cadherin (E‐cadherin), together with transmission electron microscopy (TEM), suggested that impermeability in the VCM may be due to greater cellular contact area between cells and close packing rather than to maturity of tight junctions, the latter of which, by comparison with the visceral yolk sac, appeared to be rare or absent from the allantoic surface. Both VCM and DCM exhibited an ultrastructure more favorable for protein synthesis than did the distal squamous mesothelium; however, at most stages, VCM exhibited robust afadin (AF‐6), whereas the DCM uniquely contained alpha‐4‐integrin. These observations demonstrate that the allantoic mesothelium is not a conventional epithelium but possesses regional ultrastructural, functional and molecular differences that may play important roles in the correct deployment of the umbilical cord and its associated vascular, hematopoietic, and other cell types. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

alpha2,6-Sialylation promotes binding of placental protein 14 via its Ca2+-dependent lectin activity: insights into differential effects on CD45RO and CD45RA T cells

Placental protein 14 (PP14; glycodelin) is a pregnancy-associated immunoregulatory protein that is known to inhibit T cells via T-cell receptor desensitization. The recent demonstration of PP14 as lectin has provided insight into how it may mediate its CD45 glycoprotein-dependent T-cell inhibition. In this study, we have investigated PP14's lectin-binding properties in detail. Significantly, PP14 reacts with N-acetyllactosamine (LacNAc) as was also found for members of the galectin family, such as the potent immunoregulatory protein, galectin-1. However, in contrast to galectin-1, PP14's binding is significantly enhanced by alpha2,6-sialylation and also by the presence of cations. This was demonstrated by preferential binding to fetuin as compared with its desialylated variant asialofetuin (ASF) and by using free alpha2,6- versus alpha2,3-sialylated forms of LacNAc in competitive inhibition and direct solid-phase binding assays. Interestingly, from immunological point of view, PP14 also binds differentially to CD45 isoforms known to differ in their degree of sialylation. PP14 preferentially inhibits CD45RA+, as compared with CD45RO+ T cells, and preferentially co-capped this variant CD45 on the T-cell surface. Finally, we demonstrate that PP14 promotes CD45 dimerization and clustering, a phenomenon that may regulate CD45 activity.     

A multiple watershed field test of hydrogeomorphic functional assessment of headwater streams—Variability in field measurements between independent teams

Ephemeral and intermittent headwater streams are under increasing pressure from disturbance and development. Rapid, repeatable assessment techniques are needed in order to gauge the condition of these stream systems. Several attributes of these headwater streams constrain the use of the most widely used macroinvertebrate or water quality stream assessment techniques. The hydrogeomorphic (HGM) functional assessment is a reference-based alternative technique. To evaluate this alternative, repeated assessments were conducted in eight high-gradient headwaters in West Virginia by four independent teams. Across-site and measurement variance among teams was assessed using a coefficient of variation (CV, expressed as percent). A variability of >50% CV, which suggests less repeatable results, occurred in only 13.8% of measurements, primarily associated with 2 of the 9 variables examined (snag density and substrate size). Between site measurement variance was the greatest at more highly disturbed sample locations, particularly with regard to the large woody debris, tree species richness, and channel bank erosion variables. Variables with the lowest CV were tree diameter, detrital cover, canopy cover, and channel embeddedness. Based on these results, measurements included when applying HGM approach to these streams should focus on direct measurements or directed estimates that yield a large response range across a spectrum of sites while maintaining consistent repeatability among different teams, with special attention paid to their use in highly disturbed sites.     

Blood-brain barrier permeability and nerve cell damage in rat brain 14 and 28 days after exposure to microwaves from GSM mobile phones

We investigated the effects of global system for mobile communication (GSM) microwave exposure on the permeability of the blood-brain barrier and signs of neuronal damage in rats using a real GSM programmable mobile phone in the 900 MHz band. Ninety-six non-anaesthetized rats were either exposed to microwaves or sham exposed in TEM-cells for 2 h at specific absorption rates of average whole-body Specific Absorption Rates (SAR) of 0.12, 1.2, 12, or 120 mW/kg. The rats were sacrificed after a recovery time of either 14 or 28 d, following exposure and the extravazation of albumin, its uptake into neurons, and occurrence of damaged neurons was assessed. Albumin extravazation and also its uptake into neurons was seen to be enhanced after 14 d (Kruskal Wallis test: p = 0.02 and 0.002, respectively), but not after a 28 d recovery period. The occurrence of dark neurons in the rat brains, on the other hand, was enhanced later, after 28 d (p = 0.02). Furthermore, in the 28-d brain samples, neuronal albumin uptake was significantly correlated to occurrence of damaged neurons (Spearman r = 0.41; p < 0.01).     

Staphylococcus aureus cell wall structure and dynamics during host-pathogen interaction

Peptidoglycan is the major structural component of the Staphylococcus aureus cell wall, in which it maintains cellular integrity, is the interface with the host, and its synthesis is targeted by some of the most crucial antibiotics developed. Despite this importance, and the wealth of data from in vitro studies, we do not understand the structure and dynamics of peptidoglycan during infection. In this study we have developed methods to harvest bacteria from an active infection in order to purify cell walls for biochemical analysis ex vivo. Isolated ex vivo bacterial cells are smaller than those actively growing in vitro, with thickened cell walls and reduced peptidoglycan crosslinking, similar to that of stationary phase cells. These features suggested a role for specific peptidoglycan homeostatic mechanisms in disease. As S. aureus missing penicillin binding protein 4 (PBP4) has reduced peptidoglycan crosslinking in vitro its role during infection was established. Loss of PBP4 resulted in an increased recovery of S. aureus from the livers of infected mice, which coincided with enhanced fitness within murine and human macrophages. Thicker cell walls correlate with reduced activity of peptidoglycan hydrolases. S. aureus has a family of 4 putative glucosaminidases, that are collectively crucial for growth. Loss of the major enzyme SagB, led to attenuation during murine infection and reduced survival in human macrophages. However, loss of the other three enzymes Atl, SagA and ScaH resulted in clustering dependent attenuation, in a zebrafish embryo, but not a murine, model of infection. A combination of pbp4 and sagB deficiencies resulted in a restoration of parental virulence. Our results, demonstrate the importance of appropriate cell wall structure and dynamics during pathogenesis, providing new insight to the mechanisms of disease.     

The Importance of Mentorship and Interest Group Involvement for the Orthopedic Surgery Applicant

BackgroundMentorship in medical education is important for students’ professional development career planning. Orthopedic Surgery Interest Groups (OSIG) exist as formal organizations and serve as a conduit for undergraduate mentorship, though the role of mentorship via OSIGs within orthopedic medicine has not been thoroughly evaluated. Similarly, OSIGs within institutions are not standardized nor well defined. We sought to answer: (1) What offerings does OSIG provide for students interested in orthopaedic surgery? (2) How does OSIG involvement impact the orthopaedic surgery residency applicant? (3) Does OSIG involvement increase match rates for orthopaedic surgery residency applicants?MethodsAn online survey was distributed to faculty advisors at all allopathic US medical schools with available contact information. Results were analyzed using SPSS.ResultsOf the 28 respondent organizations, the majority (53.6%) have between 1-25 student members. On average, OSIGS offer 3.64 + 1.59 (mode = 4) executive positions. The most important initiative for OSIG groups was clinical/surgical shadowing, followed by faculty mentorship, and guidance for the residency application. OSIG involvement does impact the applicant, as all faculty mentors believed this to be an important component of the residency application. Leadership positions within OSIG was not perceived as being equally important. OSIG involvement did increase match rates; the match rate for all students at the schools surveyed (n=17) was 81.21% while the match rate for students within OSIG (n=17) was 82.39% (p<0.05). Of all students who applied to orthopedic surgery residency programs, 98.9% were members of OSIG, and of all students who successfully matched into orthopedic surgery residency programs in the 2019-2020 cycle, 100% (p<0.05) of students (n=17) were involved in OSIG.ConclusionThis study indicates the importance of involvement in OSIG as a conduit for clinical exposure and mentorship throughout medical education, and is especially relevant for applicants given the impact of the COVID-19 pandemic on the residency application process. Data suggests that participation in an OSIG is a valuable experience for the medical student interested in orthopedics and that students involved in OSIGs are more likely to match into orthopedic residency programs. Level of Evidence: V     

Prolonged maintenance of water balance by adult females of the American spider beetle, Mezium affine Boieldieu, in the absence of food and water resources

Moisture requirements were evaluated for female adults of spider beetles Mezium affine Boieldieu and Gibbium aequinoctiale Boieldieu to determine how they are differentially adapted for life in a dry environment. Features showing extreme desiccation resistance of M. affine were an impermeable cuticle wherein activation energies (43 kJ/mol) were suppressed, daily water losses as little as 0.3%/day with an associated group effect, a low 64% water content and an impressive ability to survive nearly 3 months with no food and water. Behaviorally, the extended period of water stress and fasting was marked by long intervals of physical inactivity (quiescence), as though dead. These characteristics emphasizing water retention rather than gain are shared by G. aequinoctiale and reflect a typical xerophilic water balance profile. Water uptake was restricted to imbibing liquid, as evidenced by uptake of dye-stained droplets of free water and a critical equilibrium activity of 1.00a_v, where the inability to absorb water vapor from the air fails to equilibrate declining water levels (gain≠loss) except at saturation. Four-fold reduction in survival time within dry air and accelerated water loss rates with high activation energies for female adults of the closely related winged Prostephanus truncatus (Say) suggest that the enhanced water conservation of spider beetles is due, in part, to fusion of their elytra supplemented by entering into quiescence.