The majority of pollinating insects are generalists whose lifetimes overlap flowering periods of many potentially suitable plant species. Such generality is instrumental in allowing exotic plant ...species to invade pollination networks. The particulars of how existing networks change in response to an invasive plant over the course of its phenology are not well characterized, but may shed light on the probability of long-term effects on plant-pollinator interactions and the stability of network structure. Here we describe changes in network topology and modular structure of infested and non-infested networks during the flowering season of the generalist non-native flowering plant, Cirsium arvense in mixed-grass prairie at Badlands National Park, South Dakota, USA. Objectives were to compare network-level effects of infestation as they propagate over the season in infested and non-infested (with respect to C. arvense) networks. We characterized plant-pollinator networks on 5 non-infested and 7 infested 1-ha plots during 4 sample periods that collectively covered the length of C. arvense flowering period. Two other abundantly-flowering invasive plants were present during this time: Melilotus officinalis had highly variable floral abundance in both C. arvense-infested and non-infested plots and Convolvulus arvensis, which occurred almost exclusively in infested plots and peaked early in the season. Modularity, including roles of individual species, and network topology were assessed for each sample period as well as in pooled infested and non-infested networks. Differences in modularity and network metrics between infested and non-infested networks were limited to the third and fourth sample periods, during flower senescence of C. arvense and the other invasive species; generality of pollinators rose concurrently, suggesting rewiring of the network and a lag effect of earlier floral abundance. Modularity was lower and number of connectors higher in infested networks, whether they were assessed in individual sample periods or pooled into infested and non-infested networks over the entire blooming period of C. arvense. Connectors typically did not reside within the same modules as C. arvense, suggesting that effects of the other invasive plants may also influence the modularity results, and that effects of infestation extend to co-flowering native plants. We conclude that the presence of abundantly flowering invasive species is associated with greater network stability due to decreased modularity, but whether this is advantageous for the associated native plant-pollinator communities depends on the nature of perturbations they experience.
Successful macrophage colonization by Coxiella burnetii , the cause of human Q fever, requires pathogen-directed biogenesis of a large, growth-permissive parasitophorous vacuole (PV) with ...phagolysosomal characteristics. The vesicular trafficking pathways co-opted by C. burnetii for PV development are poorly defined; however, it is predicted that effector proteins delivered to the cytosol by a defective in organelle trafficking/intracellular multiplication (Dot/Icm) type 4B secretion system are required for membrane recruitment. Here, we describe involvement of clathrin-mediated vesicular trafficking in PV generation and the engagement of this pathway by the C . burnetii type 4B secretion system substrate Coxiella vacuolar protein A (CvpA). CvpA contains multiple dileucine DERQXXXLLI and tyrosine (YXXΦ)-based endocytic sorting motifs like those recognized by the clathrin adaptor protein (AP) complexes AP1, AP2, and AP3. A C. burnetii Δ cvpA mutant exhibited significant defects in replication and PV development, confirming the importance of CvpA in infection. Ectopically expressed mCherry-CvpA localized to tubular and vesicular domains of pericentrosomal recycling endosomes positive for Rab11 and transferrin receptor, and CvpA membrane interactions were lost upon mutation of endocytic sorting motifs. Consistent with CvpA engagement of the endocytic recycling system, ectopic expression reduced uptake of transferrin. In pull-down assays, peptides containing CvpA-sorting motifs and full-length CvpA interacted with AP2 subunits and clathrin heavy chain. Furthermore, depletion of AP2 or clathrin by siRNA treatment significantly inhibited C. burnetii replication. Thus, our results reveal the importance of clathrin-coated vesicle trafficking in C. burnetii infection and define a role for CvpA in subverting these transport mechanisms.
The excitatory amino acid transporter 2 (EAAT2) is the major glutamate transporter in the brain expressed predominantly in astrocytes and at low levels in neurons and axonal terminals. EAAT2 ...expression is reduced in aging and sporadic Alzheimer’s disease (AD) patients’ brains. The role EAAT2 plays in cognitive aging and its associated mechanisms remains largely unknown. Here, we show that conditional deletion of astrocytic and neuronal EAAT2 results in age-related cognitive deficits. Astrocytic, but not neuronal EAAT2, deletion leads to early deficits in short-term memory and in spatial reference learning and long-term memory. Neuronal EAAT2 loss results in late-onset spatial reference long-term memory deficit. Neuronal EAAT2 deletion leads to dysregulation of the kynurenine pathway, and astrocytic EAAT2 deficiency results in dysfunction of innate and adaptive immune pathways, which correlate with cognitive decline. Astrocytic EAAT2 deficiency also shows transcriptomic overlaps with human aging and AD. Overall, the present study shows that in addition to the widely recognized astrocytic EAAT2, neuronal EAAT2 plays a role in hippocampus-dependent memory. Furthermore, the gene expression profiles associated with astrocytic and neuronal EAAT2 deletion are substantially different, with the former associated with inflammation and synaptic function similar to changes observed in human AD and gene expression changes associated with inflammation similar to the aging human brain.
Coxiella burnetii is an obligate intracellular bacterium and the etiological agent of Q fever in humans. C. burnetii transitions between a replicative, metabolically active large-cell variant (LCV) ...and a spore-like, quiescent small-cell variant (SCV) as a likely mechanism to ensure survival between host cells and mammalian hosts. C. burnetii encodes three canonical two-component systems, four orphan hybrid histidine kinases, five orphan response regulators, and a histidine phosphotransfer protein, which have been speculated to play roles in the signaling required for C. burnetii morphogenesis and virulence. However, very few of these systems have been characterized. By employing a CRISPR interference system for genetic manipulation of C. burnetii, we created single- and multigene transcriptional knockdown strains targeting most of these signaling genes. Through this, we revealed a role for the C. burnetii PhoBR canonical two-component system in virulence, regulation of P
maintenance, and P
transport. We also outline a novel mechanism by which PhoBR function may be regulated by an atypical PhoU-like protein. We also determined that the GacA.2/GacA.3/GacA.4/GacS orphan response regulators coordinately and disparately regulate expression of SCV-associated genes in C. burnetii LCVs. These foundational results will inform future studies on the role of C. burnetii two-component systems in virulence and morphogenesis.
C. burnetii is an obligate intracellular bacterium with a spore-like stability allowing it to survive long periods of time in the environment. This stability is likely due to its biphasic developmental cycle, whereby it can transition from an environmentally stable small-cell variant (SCV) to a metabolically active large-cell variant (LCV). Here, we define the role of two-component phosphorelay systems (TCS) in C. burnetii's ability to survive within the harsh environment contained in the phagolysosome of host cells. We show that the canonical PhoBR TCS has an important role in C. burnetii virulence and phosphate sensing. Further examination of the regulons controlled by orphan regulators indicated a role in modulating gene expression of SCV-associated genes, including genes essential for cell wall remodeling.
Background Larger within-patient variability of lipid levels has been associated with increased risk of cardiovascular disease (CVD); however, measures of lipid variability require ≥3 measurements ...and are not currently used clinically. We investigated the feasibility of calculating lipid variability within a large electronic health record-based population cohort and assessed associations with incident CVD. Methods and Results We identified all individuals ≥40 years of age who resided in Olmsted County, MN, on January 1, 2006 (index date), without prior CVD, defined as myocardial infarction, coronary artery bypass graft surgery, percutaneous coronary intervention, or CVD death. Patients with ≥3 measurements of total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, or triglycerides during the 5 years before the index date were retained. Lipid variability was calculated using variability independent of the mean. Patients were followed through December 31, 2020 for incident CVD. We identified 19 652 individuals (mean age 61 years; 55% female), who were CVD-free and had variability independent of the mean calculated for at least 1 lipid type. After adjustment, those with highest total cholesterol variability had a 20% increased risk of CVD (Q5 versus Q1 hazard ratio, 1.20 95% CI, 1.06-1.37). Results were similar for low-density lipoprotein cholesterol and high-density lipoprotein cholesterol. Conclusions In a large electronic health record-based population cohort, high variability in total cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol was associated with an increased risk of CVD, independent of traditional risk factors, suggesting it may be a possible risk marker and target for intervention. Lipid variability can be calculated in the electronic health record environment, but more research is needed to determine its clinical utility.
Although one third of Medicare beneficiaries are enrolled in Medicare Advantage (MA) plans, there is limited information about the cost of treating Alzheimer disease and related dementias (ADRD) in ...these settings.
The objective of this study was to estimate direct health care costs attributable to ADRD among older adults within a large MA plan.
A retrospective cohort design was used to estimate direct total, outpatient, inpatient, ambulatory pharmacy, and nursing home costs for 3 years before and after an incident ADRD diagnosis for 927 individuals diagnosed with ADRD relative to a sex-matched and birth year-matched set of 2945 controls.
Adults 65 years of age and older enrolled in the Kaiser Permanente Washington MA plan and the Adult Changes in Thought (ACT) Study, a prospective longitudinal cohort study of ADRD and brain aging.
Data on monthly health service use obtained from health system electronic medical records for the period 1992-2012.
Total monthly health care costs for individuals with ADRD are statistically greater (P<0.05) than controls beginning in the third month before diagnosis and remain significantly greater through the eighth month following diagnosis. Greater total health costs are driven by significantly (P<0.05) greater nursing home costs among individuals diagnosed with ADRD beginning in the third month prediagnosis. Although total costs were no longer significantly greater at 8 months following diagnosis, nursing home costs remained higher for the people with dementia through the 3 years postdiagnosis we analyzed.
Greater total health care costs among individuals with ADRD are primarily driven by nursing home costs.
ACR guidance document on MR safe practices: 2013 Kanal, Emanuel; Barkovich, A. James; Bell, Charlotte ...
Journal of magnetic resonance imaging,
March 2013, Letnik:
37, Številka:
3
Journal Article
Invasion of macrophages and replication within an acidic and degradative phagolysosome-like vacuole are essential for disease pathogenesis by Coxiella burnetii, the bacterial agent of human Q fever. ...Previous experimental constraints imposed by the obligate intracellular nature of Coxiella limited knowledge of pathogen strategies that promote infection. Fortunately, new genetic tools facilitated by axenic culture now allow allelic exchange and transposon mutagenesis approaches for virulence gene discovery. Phenotypic screens have illuminated the critical importance of Coxiella's type 4B secretion system in host cell subversion and discovered genes encoding translocated effector proteins that manipulate critical infection events. Here, we highlight the cellular microbiology and genetics of Coxiella and how recent technical advances now make Coxiella a model organism to study macrophage parasitism.
Macrophage parasitism by
, the cause of human Q fever, requires the translocation of proteins with effector functions directly into the host cell cytosol via a Dot/Icm type 4B secretion system ...(T4BSS). Secretion by the analogous
T4BSS involves signal sequences within the C-terminal and internal domains of effector proteins. The cytoplasmic chaperone pair IcmSW promotes secretion and binds internal sites distinct from signal sequences. In the present study, we investigated requirements of
IcmS for host cell parasitism and effector translocation. A
deletion mutant (Δ
) exhibited impaired replication in Vero epithelial cells, deficient formation of the
-containing vacuole, and aberrant T4BSS secretion. Three secretion phenotypes were identified from a screen of 50 Dot/Icm substrates: IcmS dependent (secreted by only wild-type bacteria), IcmS independent (secreted by both wild-type and Δ
bacteria), or IcmS inhibited (secreted by only Δ
bacteria). Secretion was assessed for N-terminal or C-terminal truncated forms of CBU0794 and CBU1525. IcmS-inhibited secretion of CBU1525 required a C-terminal secretion signal whereas IcmS-dependent secretion of CBU0794 was directed by C-terminal and internal signals. Interchange of the C-terminal 50 amino acids of CBU0794 and CBU1525 revealed that sites within the C terminus regulate IcmS dependency. Glutathione
-transferase-tagged IcmSW bound internal sequences of IcmS-dependent and -inhibited substrates. Thus, the growth defect of the
Δ
strain is associated with a loss of T4BSS chaperone activity that both positively and negatively regulates effector translocation.
The intracellular pathogen
employs a type 4B secretion system (T4BSS) that promotes growth by translocating effectors of eukaryotic pathways into host cells. T4BSS regulation modeled in
indicates IcmS facilitates effector translocation. Here, we characterized type 4B secretion by a
Δ
mutant that exhibits intracellular growth defects. T4BSS substrates demonstrated increased, equivalent, or decreased secretion by the Δ
mutant relative to wild-type
Similar to the
T4BSS, IcmS dependency in
was determined by C-terminal and/or internal secretion signals. However, IcmS inhibited secretion of some effectors by
that were previously shown to be translocated by
Thus,
has a unique IcmS regulatory mechanism that both positively and negatively regulates T4BSS export.
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