The IL-10R2 binding hot spot on IL-22 is located on the N-terminal helix and is dependent on N-linked glycosylation

IL-22 is a class 2 alpha-helical cytokine involved in the generation of inflammatory responses. These activities require IL-22 to engage the cell surface receptors IL-22R1 and the low-affinity signaling molecule IL-10R2. IL-10R2 also interacts with five other class 2 cytokines: IL-10, IL-26, and the interferon-like cytokines IL-28A, IL-28B, and IL-29. Here, we define the IL-10R2 binding site on IL-22 using surface plasmon resonance (SPR) and site-directed mutagenesis. Surprisingly, the binding hot spot on IL-22 includes asparagine 54 (N54), which is post-translationally modified by N-linked glycosylation. Further characterization of the glycosylation reveals that only a single fucosylated N-acetyl glucosamine on N54 is required for maximal IL-10R2 binding. Biological responses of IL-22 mutants measured in cell-based luciferase assays correlate with the in vitro SPR studies. Together, these data suggest that IL-22 activity may be modulated via changes in the glycosylation state of the ligand during inflammation.     

Geographic Variation in Egg Size and Lipid Provisioning in the Diamondback Terrapin Malaclemys terrapin

Abstract Understanding phenotypic differentiation among populations of wide-ranging species remains at the core of life-history research, because adaptation to local environmental conditions is expected. For example, when energy resources influence offspring fitness (as in oviparous ectotherms), the egg and hatchling environments are expected to influence selection by acting on the amount of energy allocated to offspring. Here we identify population variation in egg mass, length, width, and volume from diamondback terrapin Malaclemys terrapin eggs collected in Rhode Island (RI), Maryland (MD), and South Carolina (SC). Egg size (mean volume: 7.6, 8.1, and 9.1 cc in RI, MD, and SC, respectively) and clutch size (mean no. eggs: 16.1, 12.2, and 6.0 in RI, MD, and SC, respectively) differed among populations, which indicated that females produce larger clutches with smaller eggs at high latitudes and smaller clutches of larger eggs at lower latitudes. Lipid analyses indicated that eggs from SC contained yolks with a higher proportion of nonpolar lipids than did eggs from MD or RI (mean percentage of nonpolar lipids: 22.3%, 22.5%, and 31.8% in RI, MD, and SC, respectively). Thus, female terrapins in SC are laying larger eggs with increased lipid content to provide more energy for the developing embryo. Interestingly, total triacylglycerol (energetic lipid) was greater in southern populations but occurred in higher proportions in northern populations (total triacylglycerol: 88.0%, 85.4%, and 81.9% in RI, MD, and SC, respectively). This variation in triacylglycerol levels demonstrates the necessity for quantifying each lipid component. These data indicate a difference in reproductive strategy by which females in northern populations invest in higher fecundity with less energetic resources per offspring, whereas females in southern populations invest in larger eggs with considerably greater energy reserves.     

Role of echocardiography in the diagnosis and management of infective endocarditis

Infective endocarditis is one of the most common causes of serious infection and carries a high risk of morbidity and mortality. It represents the fourth leading cause of life-threatening infections after urosepsis, pneumonia, and intra-abdominal sepsis. There is still a continuous rise in the incidence of infective endocarditis, with a rate of about 20,000 new cases in the United States alone. This rise in incidence of infective endocarditis is mainly caused by increasing numbers of intravenous drug abusers, patients with artificial valves and elderly patients. In this paper, we will briefly review the crucial role of echocardiography in the diagnosis and management of infective endocarditis.     

Resolution of three nonproliferative immature splenic B cell subsets reveals multiple selection points during peripheral B cell maturation.

Although immature/transitional peripheral B cells may remain susceptible to selection pressures before full maturation, the nature and timing of these selection events remain unclear. We show that correlated expression of surface (s) IgM (sIgM), CD23, and AA4 defines three nonproliferative subpopulations of immature/transitional peripheral B cells. We designate these populations transitional (T) 1 (AA4(+)CD23(-)sIgM(high)), T2 (AA4(+)CD23(+)sIgM(high)), and T3 (AA4(+)CD23(+)sIgM(low)). Cells within all three subsets are functionally immature as judged by their failure to proliferate following sIgM cross-linking in vitro, and their rapid rate of turnover in vivo as assessed by 5-bromo-2'-deoxyuridine labeling. These labeling studies also reveal measurable cell loss at both the T1-T2 and T2-T3 transitions, suggesting the existence of multiple selection points within the peripheral immature B cell pool. Furthermore, we find that Btk-deficient (xid) mice exhibit an incomplete developmental block at the T2-T3 transition within the immature B cell pool. This contrasts markedly with lyn(-/-) mice, which exhibit depressed numbers but normal ratios of each immature peripheral B cell subset and severely reduced numbers of mature B cells. Together, these data provide evidence for multiple selection points among immature peripheral B cells, suggesting that the B cell repertoire is shaped by multiple unique selection events that occur within the immature/transitional peripheral B cell pool.     

Cell cycle parameters of Escherichia coli K-12.

A computer simulation routine was used to calculate the DNA distributions of exponentially growing cultures of Escherichia coli K-12. Simulated distributions were compared with distributions obtained experimentally by flow cytometry. Durations of the DNA replication period (C) and the postreplication period (D) were found by minimizing the difference between theoretical and experimental DNA histograms. It was demonstrated that the K-12 strains AB1157 and CM735 had C and D periods that differed widely from each other and from those of the previously measured strain B/rA, while strain MC1000 was shown to have the same durations of the C and D periods as strain B/rA. The variation between K-12 strains may explain the divergence in the literature regarding their C and D periods. Strains W3110 and AB1157 recA1 had DNA histograms that could not be adequately simulated by the classical Cooper-Helmstetter model, which is consistent with the asymmetrically located origin and terminus for W3110 and the asynchrony of initiation for AB1157 recA1.     

On the stabilization by fixation of configurational states in beef heart mitochondria

The energized configuration of the cristal membrane of beef heart mitochondria can be maintained only as long as oxygen is available for electron transfer. When the oxygen supply is exhausted, the membrane undergoes a transition to the nonenergized configuration. Since the exhaustion of the available oxygen supply is complete in 5–20 sec, it is impossible to apply the method of sedimenting the mitochondria prior to fixation for studying the energized configurational states of mitochondria. The direct addition of glutaraldehyde followed by osmium tetroxide to the mitochondrial suspension is the most effective way of freezing the configurational state of the cristal membrane. Fixation with glutaraldehyde appears to be complete within 1–2 sec even at 0°. Osmium tetroxide alone can also freeze the energized configuration by fixation but the concentration of the fixative is critical. The problem of capturing the configurational state applies not only to energized transitions (nonenergized to energized) but also to nonenergized transitions (orthodox to aggregated). The freezing by fixation of the cristal membrane in the aggregated configuration is best accomplished by the sequential use of glutaraldehyde and osmium tetroxide. When the levels of glutaraldehyde and osmium tetroxide are respectively too low or too high, the mitochondrion will undergo a transition from the aggregated to the orthodox configuration before fixation is complete. Light-scattering studies provide an independent method for monitoring configurational changes in mitochondria; these light-scattering measurements confirm that the conditions for fixation which lead to stabilization of the energized state as judged by electron microscopy, also show maintenance of configuration as judged by absence of light-scattering changes after the fixatives are introduced. Reagents used in negative staining will induce the geometrical form of the energized configuration of the mitochondrion even under nonenergizing conditions. These reagents are thus unsuitable for use in studies of configurational transitions in mitochondria.     

Hitchhiking in space: Ancestry in adapting,spatially extended populations*

Selective sweeps reduce neutral genetic diversity. In sexual populations, this “hitchhiking” effect is thought to be limited to the local genomic region of the sweeping allele. While this is true in panmictic populations, we find that in spatially extended populations the combined effects of many unlinked sweeps can affect patterns of ancestry (and therefore neutral genetic diversity) across the whole genome. Even low rates of sweeps can be enough to skew the spatial locations of ancestors such that neutral mutations that occur in an individual living outside a small region in the center of the range have virtually no chance of fixing in the population. The fact that nearly all ancestry rapidly traces back to a small spatial region also means that relatedness between individuals falls off very slowly as a function of the spatial distance between them.