Staphylococcus aureus is capable of infecting nearly every organ in the human body. In order to infiltrate and thrive in such diverse host tissues, staphylococci must possess remarkable flexibility ...in both metabolic and virulence programs. To investigate the genetic requirements for bacterial survival during invasive infection, we performed a transposon sequencing (TnSeq) analysis of S. aureus during experimental osteomyelitis. TnSeq identified 65 genes essential for staphylococcal survival in infected bone and an additional 148 mutants with compromised fitness in vivo. Among the loci essential for in vivo survival was SrrAB, a staphylococcal two-component system previously reported to coordinate hypoxic and nitrosative stress responses in vitro. Healthy bone is intrinsically hypoxic, and intravital oxygen monitoring revealed further decreases in skeletal oxygen concentrations upon S. aureus infection. The fitness of an srrAB mutant during osteomyelitis was significantly increased by depletion of neutrophils, suggesting that neutrophils impose hypoxic and/or nitrosative stresses on invading bacteria. To more globally evaluate staphylococcal responses to changing oxygenation, we examined quorum sensing and virulence factor production in staphylococci grown under aerobic or hypoxic conditions. Hypoxic growth resulted in a profound increase in quorum sensing-dependent toxin production, and a concomitant increase in cytotoxicity toward mammalian cells. Moreover, aerobic growth limited quorum sensing and cytotoxicity in an SrrAB-dependent manner, suggesting a mechanism by which S. aureus modulates quorum sensing and toxin production in response to environmental oxygenation. Collectively, our results demonstrate that bacterial hypoxic responses are key determinants of the staphylococcal-host interaction.
Full text
Available for:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Development of adrenal cortex zonation Xing, Yewei; Lerario, Antonio M; Rainey, William ...
Endocrinology and metabolism clinics of North America,
06/2015, Volume:
44, Issue:
2
Journal Article
Peer reviewed
Open access
The human adult adrenal cortex is composed of the zona glomerulosa (zG), zona fasciculata (zF), and zona reticularis (zR), which are responsible for production of mineralocorticoids, glucocorticoids, ...and adrenal androgens, respectively. The final completion of cortical zonation in humans does not occur until puberty with the establishment of the zR and its production of adrenal androgens; a process called adrenarche. The maintenance of the adrenal cortex involves the centripetal displacement and differentiation of peripheral Sonic hedgehog-positive progenitors cells into zG cells that later transition to zF cells and subsequently zR cells.
The bending rigidity k c of bilayer vesicles self-assembled from amphiphilic diblock copolymers has been measured using single- and dual-micropipet techniques. These copolymers are nearly a factor of ...5 greater in hydrophobic membrane thickness d than their lipid counterparts and an order of magnitude larger in molecular weight M n. The macromolecular structure of these amphiphiles lends insight into and extends relationships for traditional surfactant behavior. We find the scaling of k c with thickness to be nearly quadratic, in good agreement with existing theories for bilayer membranes. The results here are key to understanding and designing soft interfaces such as biomembrane mimetics.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Curli are functional amyloid fibers assembled by enteric bacteria such as Escherichia coli and Salmonella spp. In E. coli, the polymerization of the major curli fiber subunit protein CsgA into an ...amyloid fiber depends on the minor curli subunit protein, CsgB. The outer membrane-localized CsgB protein shares almost equal to30% sequence identity with the amyloid-forming protein CsgA, suggesting that CsgB might also have amyloidogenic properties. Here, we characterized the biochemical properties of CsgB and the molecular basis for CsgB-mediated nucleation of CsgA. Deletion analysis revealed that a CsgB molecule missing 19 amino acids from its C terminus (CsgBtrunc) was not outer membrane-associated, but secreted away from the cell. CsgBtrunc was overexpressed and purified from the extracellular milieu of cells as an SDS-soluble, nonaggregated protein. Soluble CsgBtrunc assembled into fibers that bound to the amyloid-specific dyes Congo red and thioflavin-T. CsgBtrunc fibers were able to seed soluble CsgA polymerization in vitro. CsgBtrunc displayed modest nucleator activity in vivo, as demonstrated by its ability to convert extracellular CsgA into an amyloid fiber. Unlike WT CsgB, CsgBtrunc was only able to act as a nucleator when cells were genetically manipulated to secrete higher concentrations of CsgA. This work represents a unique demonstration of functional amyloid nucleation and it suggests an elegant model for how E. coli guides efficient amyloid fiber formation on the cell surface.
Full text
Available for:
BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Approximately one-tenth of the general population exhibit adrenal cortical nodules, and the incidence has increased. Afflicted patients display a multifaceted symptomatology—sometimes with rather ...spectacular features. Given the general infrequency as well as the specific clinical, histological, and molecular considerations characterizing these lesions, adrenal cortical tumors should be investigated by endocrine pathologists in high-volume tertiary centers. Even so, to distinguish specific forms of benign adrenal cortical lesions as well as to pinpoint malignant cases with the highest risk of poor outcome is often challenging using conventional histology alone, and molecular genetics and translational biomarkers are therefore gaining increased attention as a possible discriminator in this context. In general, our understanding of adrenal cortical tumorigenesis has increased tremendously the last decade, not least due to the development of next-generation sequencing techniques. Comprehensive analyses have helped establish the link between benign aldosterone-producing adrenal cortical proliferations and ion channel mutations, as well as mutations in the protein kinase A (PKA) signaling pathway coupled to cortisol-producing adrenal cortical lesions. Moreover, molecular classifications of adrenal cortical tumors have facilitated the distinction of benign from malignant forms, as well as the prognostication of the individual patients with verified adrenal cortical carcinoma, enabling high-resolution diagnostics that is not entirely possible by histology alone. Therefore, combinations of histology, immunohistochemistry, and next-generation multi-omic analyses are all needed in an integrated fashion to properly distinguish malignancy in some cases. Despite significant progress made in the field, current clinical and pathological challenges include the preoperative distinction of non-metastatic low-grade adrenal cortical carcinoma confined to the adrenal gland, adoption of individualized therapeutic algorithms aligned with molecular and histopathologic risk stratification tools, and histological confirmation of functional adrenal cortical disease in the context of multifocal adrenal cortical proliferations. We herein review the histological, genetic, and epigenetic landscapes of benign and malignant adrenal cortical neoplasia from a modern surgical endocrine pathology perspective and highlight key mechanisms of value for diagnostic and prognostic purposes.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Infections are a major concern in orthopedics. Antibacterial agents such as silver ions are of great interest as broad‐spectrum biocides and have been incorporated into bioactive glass–ceramic ...particles to control the release of ions within a therapeutic concentration and provide tissue regenerative properties. In this work, the antibacterial capabilities of silver‐doped bioactive glass (Ag‐BG) microparticles were explored to reveal the unedited mechanisms of inhibition against methicillin‐resistant Staphylococcus aureus (MRSA). The antibacterial properties were not limited to the delivery of silver ions but rather a combination of antibacterial degradation by‐products. For example, nano‐sized debris punctured holes in bacteria membranes, osmotic effects, and reactive oxygen species causing oxidative stress and almost 40% of the inhibition. Upon successive Ag‐BG treatments, MRSA underwent phenotypic and genomic mutations which were not only insufficient to develop resistance but instead, the clones became more sensitive as the treatment was re‐delivered. Additionally, the unprecedented restorative functionality of Ag‐BG allowed the effective use of antibiotics that MRSA resists. The synergy mechanism was mainly identified for combinations targeting cell‐wall activity and their action was proven in biofilm‐like and virulent conditions. Unraveling these mechanisms may offer new insights into how to tailor healthcare materials to prevent or debilitate infections and join the fight against antibiotic resistance in clinical cases.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Methicillin-resistant
(MRSA) is a threat to global health. Consequently, much effort has focused on the development of new antimicrobials that target novel aspects of
physiology. Fatty acids are ...required to maintain cell viability, and bacteria synthesize fatty acids using the type II fatty acid synthesis (FASII) pathway. FASII is significantly different from human fatty acid synthesis, underscoring the therapeutic potential of inhibiting this pathway. However, many Gram-positive pathogens incorporate exogenous fatty acids, bypassing FASII inhibition and leaving the clinical potential of FASII inhibitors uncertain. Importantly, the source(s) of fatty acids available to pathogens within the host environment remains unclear. Fatty acids are transported throughout the body by lipoprotein particles in the form of triglycerides and esterified cholesterol. Thus, lipoproteins, such as low-density lipoprotein (LDL), represent a potentially rich source of exogenous fatty acids for
during infection. We sought to test the ability of LDLs to serve as a fatty acid source for
and show that cells cultured in the presence of human LDLs demonstrate increased tolerance to the FASII inhibitor triclosan. Using mass spectrometry, we observed that host-derived fatty acids present in the LDLs are incorporated into the staphylococcal membrane and that tolerance to triclosan is facilitated by the fatty acid kinase A, FakA, and Geh, a triacylglycerol lipase. Finally, we demonstrate that human LDLs support the growth of
fatty acid auxotrophs. Together, these results suggest that human lipoprotein particles are a viable source of exogenous fatty acids for
during infection.
Inhibition of bacterial fatty acid synthesis is a promising approach to combating infections caused by
and other human pathogens. However,
incorporates exogenous fatty acids into its phospholipid bilayer. Therefore, the clinical utility of targeting bacterial fatty acid synthesis is debated. Moreover, the fatty acid reservoir(s) exploited by
is not well understood. Human low-density lipoprotein particles represent a particularly abundant
source of fatty acids and are present in tissues that
colonizes. Herein, we establish that
is capable of utilizing the fatty acids present in low-density lipoproteins to bypass both chemical and genetic inhibition of fatty acid synthesis. These findings imply that
targets LDLs as a source of fatty acids during pathogenesis.
We present the geomagnetic field model COV-OBS.x2 that covers the period 1840–2020. It is primarily constrained by observatory series, satellite data, plus older surveys. Over the past two decades, ...we consider annual differences of 4-monthly means at ground-based stations (since 1996), and virtual observatory series derived from magnetic data of the satellite missions CHAMP (over 2001–2010) and Swarm (since 2013). A priori information is needed to complement the constraints carried by geomagnetic records and solve the ill-posed geomagnetic inverse problem. We use for this purpose temporal cross-covariances associated with auto-regressive stochastic processes of order 2, whose parameters are chosen so as to mimic the temporal power spectral density observed in paleomagnetic and observatory series. We aim this way to obtain as far as possible realistic posterior model uncertainties. These can be used to infer for instance the core dynamics through data assimilation algorithms, or an envelope for short-term magnetic field forecasts. We show that because of the projection onto splines, one needs to inflate the formal model error variances at the most recent epochs, in order to account for unmodeled high frequency core field changes. As a by-product of the core field model, we co-estimate the external magnetospheric dipole evolution on periods longer than 2 years. It is efficiently summarized as the sum of a damped oscillator (of period 10.5 years and decay rate 55 years), plus a short-memory (6 years) damped random walk.
Context:
The use of next-generation sequencing has resulted in the identification of recurrent somatic mutations underlying primary aldosteronism (PA). However, significant gaps remain in our ...understanding of the relationship between tumor aldosterone synthase (CYP11B2) expression and somatic mutation status.
Objective:
The objective of the study was to investigate tumor CYP11B2 expression and somatic aldosterone-driver gene mutation heterogeneity.
Methods:
Fifty-one adrenals from 51 PA patients were studied. Immunohistochemistry for CYP11B2 was performed. Aldosterone-producing adenomas with intratumor CYP11B2 heterogeneity were analyzed for mutation status using targeted next-generation sequencing. DNA was isolated from CYP11B2-positive, CYP11B2-negative, and adjacent normal areas from formalin-fixed, paraffin-embedded sections.
Results:
Of 51 adrenals, seven (14 %) showed distinct heterogeneity in CYP11B2 by immunohistochemistry, including six adenomas with intratumor heterogeneity and one multinodular hyperplastic adrenal with both CYP11B2-positive and -negative nodules. Of the six adrenocortical adenomas with CYP11B2 heterogeneity, three had aldosterone-regulating mutations (CACNA1D p.F747C, KCNJ5 p.L168R, ATP1A1 p.L104R) only in CYP11B2-positive regions, and one had two different mutations localized to two histologically distinct CYP11B2-positive regions (ATP2B3 p.L424_V425del, KCNJ5 p.G151R). Lastly, one adrenal with multiple CYP11B2-expressing nodules showed different mutations in each (CACNA1D p.F747V and ATP1A1 p.L104R), and no mutations were identified in CYP11B2-negative nodule or adjacent normal adrenal.
Conclusions:
Adrenal tumors in patients with PA can demonstrate clear heterogeneity in CYP11B2 expression and somatic mutations in driver genes for aldosterone production. These findings suggest that aldosterone-producing adenoma tumorigenesis can occur within preexisting nodules through the acquisition of somatic mutations that drive aldosterone production.
PDF
