Bacterioplankton Dynamics in the McMurdo Dry Valley Lakes, Antarctica: Production and Biomass Loss over Four Seasons

Abstract Research of the microbial ecology of McMurdo Dry Valley lakes has concentrated primarily on phototrophs; relatively little is known about the heterotrophic bacterioplankton. Bacteria represent a substantial proportion of water column biomass in these lakes, comprising 30 to 60% of total microplankton biomass. Bacterial production and cell numbers were measured 3 to 5 times, within four Antarctic seasons (October to January), in Lakes Fryxell, Hoare, and Bonney. The winter-spring transition (September to October) was included during one year. Lake Fryxell was the most productive, but variable, lake, followed by Lakes Bonney and Hoare. Bacterial production ranged from 0 to 0.009 μg C ml-1 d-1; bacterial populations ranged from 3.2 x 10(4) to 4.4 x 10(7) cells ml-1. Bacterial production was always greatest just below the ice cover at the beginning of the season. A second maximum developed just above the chemocline of all the lakes, as the season progressed. Total bacterioplankton biomass in the lakes decreased as much as 88% between successive sampling dates in the summer, as evidenced by areal integration of bacterial populations; the largest decreases in biomass typically occurred in mid-December. A forward difference model of bacterial loss in the trophogenic zone and the entire water column of these lakes showed that loss rates in the summer reached 6.3 x 10(14) cells m-2 d-1 and 4.16 x 10(12) cells m-2 d-1, respectively. These results imply that bacteria may be a source of carbon to higher trophic levels in these lakes, through grazing.     

拐芹根化学成分研究Ⅱ

从伞型科当归属植物拐芹(Angelica polymorpha Maxim)的根及根茎中又分得4个结晶性化合物。经物理常数测定、光谱分析,分别鉴定为欧前胡素Ⅰ,异氧化前胡内酯Ⅱ,Pabulenol Ⅲ,Phellopterin Ⅳ。     

Establishment and spread of Gyranusoidea tebygi noyes and Anagyrus mangicola noyes (hymenoptera: encyrtidae), two biological control agents released against the mango mealybug Rastrococcus invadens williams (homoptera: pseudococcidae) in Africa

Two specific endophagous parasitoids Gyranusoidea tebygi and Anagyrus mangicola, of Indian origin, were mass‐reared at the International Institute of Tropical Agriculture in Cotonou and released against the mango mealybug Rastrococcus invadens, in collaboration with national biological control programmes. G. tebygi was released in the following countries: Benin, Gabon, Ghana, Nigeria, Sierra Leone and Zaire. In Togo, it had been released earlier and studied during another project. This parasitoid is now established in all areas infested by the mango mealybug. In addition, it established itself without previous release in Congo and Côte d'Ivoire. A. mangicola has been released in Benin, Gabon and Sierra Leone since 1991, and by mid‐1993 was recovered from a few sites. It seems locally established in southern Benin.     

ADAM15 overexpression in NIH3T3 cells enhances cell-cell interactions.

ADAM15 is a member of the family of metalloprotease-disintegrins that have been shown to interact with integrins in an RGD- and non-RGD-dependent manner. In the present study, we examined the effects of ADAM15 overexpression on cell-matrix and cell-cell interactions in NIH3T3 cells. Tetracycline-regulated ADAM15 overexpression in NIH3T3 cells leads to an inhibition of migration on a fibronectin-coated filter in a Boyden chamber assay and in a scratch wound model. The effects of ADAM15 overexpression on cell migration are not due to changes in matrix attachment or to the lack of extracellular signal-regulated kinase signaling response to PDGF or fibronectin. However, a decrease in monolayer permeability with ADAM15 overexpression and altered cell morphology suggest a possible increase in cell-cell interaction. Analysis of adhesion of NIH3T3 cells to a polyclonal population of cells retrovirally transduced to overexpress ADAM15 demonstrates a 45% increase in cell adhesion, compared with enhanced green fluorescent protein-expressing control cells. In addition, we demonstrate localization of HA-epitope-tagged ADAM15 to cell-cell contacts in an epithelial cell line that forms extensive cell-cell contact structures. Thus, overexpression of ADAM15 in NIH3T3 cells appears to enhance cell-cell interactions, as suggested by decreased cell migration, altered cell morphology at the wound edge, decreased monolayer permeability, and increased cell adhesion to monolayers of cells expressing ADAM15 by retroviral transduction.     

IL-18 binding protein protects against contact hypersensitivity

Allergic contact dermatitis, the clinical manifestation of contact hypersensitivity, is one of the most common disorders of the skin. It is elicited upon multiple cutaneous re-exposure of sensitized individuals to the sensitizing agent. In this study, we demonstrate that using IL-18 binding protein (IL-18BP) to neutralize IL-18 significantly reduced clinical symptoms in a murine model of contact hypersensitivity. Furthermore, IL-18BP alleviated the relapses during established disease, as indicated by significant protection during re-exposure of mice that had previously undergone a contact hypersensitivity response without treatment. Although edema was not influenced, IL-18BP reduced the number of T cells homing to sites of inflammation, resulting in diminished local production of IFN-gamma. Thus, by preventing the accumulation of effector T cells to the target tissue, IL-18BP appears to be a potent protective mediator to counter skin inflammation during contact hypersensitivity. Taken together with the evidence that IL-18 is present in tissue samples of the human disease, our data reinforces IL-18BP as a candidate for this therapeutic indication.     

Is it possible to exclude a diagnosis of myocardial damage within six hours of admission to an emergency department? Diagnostic cohort study

ObjectiveTo assess the clinical efficacy and accuracy of an emergency department based six hour rule-out protocol for myocardial damage.DesignDiagnostic cohort study.SettingEmergency department of an inner city university hospital.Participants383 consecutive patients aged over 25 years with chest pain of less than 12 hours'' duration who were at low to moderate risk of acute myocardial infarction.InterventionSerial measurements of creatine kinase MB mass and continuous ST segment monitoring for six hours with 12 leads.ResultsOutcome of the gold standard test was available for 292 patients. On the diagnostic test for the protocol, 53 patients had positive results and 239 patients had negative results. There were 18 false positive results and one false negative result. Sensitivity was 97.2% (95% confidence interval 95.0% to 99.0%), specificity 93.0% (90.0% to 96.0%), the negative predictive value 99.6%, and the positive predictive value 66.0%. The positive likelihood ratio was 13.9 and the negative likelihood ratio 0.03.ConclusionsThe six hour rule-out protocol for myocardial infarction is accurate and efficacious. It can be used in patients presenting to emergency departments with chest pain indicating a low to moderate risk of myocardial infarction.

What is already known on this topic

Many patients with chest pain in emergency departments indicating a low to moderate risk of myocardial infarction are admitted to rule out myocardial damageSome 6% of those discharged have undiagnosed myocardial damage

What this study adds

An emergency department based chest pain assessment unit protocol to rule out myocardial damage is sensitive enough to allow safe discharge of patients at low to moderate risk of myocardial infarction within six hoursSuch units can also reduce the number of patients admitted unnecessarily     

Rye Pm8 and wheat Pm3 are orthologous genes and show evolutionary conservation of resistance function against powdery mildew

The improvement of wheat through breeding has relied strongly on the use of genetic material from related wild and domesticated grass species. The 1RS chromosome arm from rye was introgressed into wheat and crossed into many wheat lines, as it improves yield and fungal disease resistance. Pm8 is a powdery mildew resistance gene on 1RS which, after widespread agricultural cultivation, is now widely overcome by adapted mildew races. Here we show by homology‐based cloning and subsequent physical and genetic mapping that Pm8 is the rye orthologue of the Pm3 allelic series of mildew resistance genes in wheat. The cloned gene was functionally validated as Pm8 by transient, single‐cell expression analysis and stable transformation. Sequence analysis revealed a complex mosaic of ancient haplotypes among Pm3‐ and Pm8‐like genes from different members of the Triticeae. These results show that the two genes have evolved independently after the divergence of the species 7.5 million years ago and kept their function in mildew resistance. During this long time span the co‐evolving pathogens have not overcome these genes, which is in strong contrast to the breakdown of Pm8 resistance since its introduction into commercial wheat 70 years ago. Sequence comparison revealed that evolutionary pressure acted on the same subdomains and sequence features of the two orthologous genes. This suggests that they recognize directly or indirectly the same pathogen effectors that have been conserved in the powdery mildews of wheat and rye.     

TLR4/MD-2 monoclonal antibody therapy affords protection in experimental models of septic shock

Overactivation of the immune system upon acute bacterial infection leads to septic shock. Specific bacterial products potently stimulate immune cells via toll-like receptors (TLRs). Gram-negative bacteria induce a predominantly TLR4-driven signal through LPS release. To neutralize LPS signaling in experimental models of sepsis, we generated mAbs toward the TLR4/myeloid differentiation protein-2 (MD-2) complex. The binding properties of an array of selected rat mAbs differed in respect to their specificity for TLR4/MD-2 complex. The specificity of one such mAb, 5E3, to murine TLR4 was confirmed by its recognition of an epitope within the second quarter of the ectodomain. 5E3 inhibited LPS-dependent cell activation in vitro and prevented proinflammatory cytokine production in vivo following LPS challenge in a dose-dependent manner. Furthermore, 5E3 protected mice from lethal shock-like syndrome when applied using both preventative and therapeutic protocols. Most notably, in the colon ascendens stent peritonitis model of polymicrobial abdominal sepsis, administration of a single dose of 5E3 (50 mug) protected mice against mortality. These results demonstrate that neutralizing TLR4/MD-2 is highly efficacious in protecting against bacterial infection-induced toxemia and offers TLR4/MD-2 mAb treatment as a potential therapy for numerous clinical indications.     

Properties of human IgG1s engineered for enhanced binding to the neonatal Fc receptor (FcRn)

We describe here the functional implications of an increase in IgG binding to the neonatal Fc receptor. We have defined in a systematic fashion the relationship between enhanced FcRn binding of a humanized anti-respiratory syncytial virus (RSV) monoclonal antibody (MEDI-524) and the corresponding biological consequences in cynomolgus monkeys. The triple mutation M252Y/S254T/T256E (YTE) was introduced into the Fc portion of MEDI-524. Whereas these substitutions did not affect the ability of MEDI-524 to bind to its cognate antigen and inhibit RSV replication, they resulted in a 10-fold increase in its binding to both cynomolgus monkey and human FcRn at pH 6.0. MEDI-524-YTE was efficiently released from FcRn at pH 7.4 in both cases. We show that MEDI-524-YTE consistently exhibited a nearly 4-fold increase in serum half-life in cynomolgus monkeys when compared with MEDI-524. This constituted the largest half-life improvement described to date for an IgG in a primate. For the first time, we demonstrate that these sustained serum levels resulted in an up to 4-fold increase in lung bioavailability. Importantly, we also establish that our non-human primate model is relevant to human. Finally, we report that the YTE triple substitution provided a means to modulate the antibody-dependent cell-mediated cytotoxicity (ADCC) activity of a humanized IgG1 directed against the human integrin alpha(v)beta3. Therefore, the YTE substitutions allow the simultaneous modulation of serum half-life, tissue distribution and activity of a given human IgG1.     

Study of antigenic epitopes recognized by monoclonal antibodies to recombinant interferon-gamma

Seven hybridomas (BG 1-7) which secreted monoclonal antibodies against recombinant interferon-gamma were produced. The ascites fluids containing four of the seven monoclonal antibodies (BG 1-4) neutralized the antiviral activity of both natural and recombinant interferon-gamma. Competition between labeled and unlabeled monoclonal antibodies for interferon-gamma in a solid phase immunoassay showed that BG 1 was competed by both BG 3 and BG 4 but not by BG 2; BG 2 was competed by BG 3 but not by BG 1 nor by BG 4. These results suggest that human interferon-gamma has at least two antigenic epitopes; one of the epitopes reacted with BG 1 & BG 4 while the other reacted with BG 2; BG 3 either binds to a region overlapping with the other two epitopes or reacts with both epitopes. The antigenic epitopes recognized by these four neutralizing monoclonal antibodies are likely at or closely related to the active sites of interferon-gamma.