Oblique double layers: a comparison between terrestrial and auroral measurements.

The S3-3, POLAR, and FAST satellite auroral observations of parallel and perpendicular electric field structures have been identified as belonging to a large "U"-shaped potential structure that supports oblique electric double layers. This interpretation is verified by terrestrial laboratory measurements of a self-consistently supported three-dimensional oblique current-free double layer. Its width is a few tens of Debye lengths, its oblicity (with respect to the magnetic field) varies from 0 up to 30 degrees, and its strength is a few times the electron temperature.

Upstream ionization instability associated with a current-free double layer.

A low frequency instability has been observed using various electrostatic probes in a low-pressure expanding helicon plasma. The instability is associated with the presence of a current-free double layer (DL). The frequency of the instability increases linearly with the potential drop of the DL, and simultaneous measurements show their coexistence. A theory for an upstream ionization instability has been developed, which shows that electrons accelerated through the DL increase the ionization upstream and are responsible for the observed instability. The theory is in good agreement with the experimental results.

Experimental evidence of a double layer in a large volume helicon reactor.

The self-consistently generated current-free electric double layer (DL) is shown to scale up with the source tube diameter and appears not to be affected by rf driving frequency and changes in reactor geometry. This Letter presents the first simultaneous measurements of local plasma potential and beam energy as a function of axial position. The DL is shown to be no more than 5 mm thick (20 D lengths) and positioned just downstream of the maximum in the magnetic field gradient. Furthermore, its position relative to the magnetic field is observed to be invariant as the magnetic field is translated axially. Measurements of the potential drop across the DL are presented for pressures down to 0.09 mTorr and the DL strength (phiDL/T(e)) is determined to be between 5 and 7.

Ion cyclotron production by a four-wave interaction with a helicon pump.

Ion cyclotron waves at approximately 0.7 the ion gyrofrequency have been observed experimentally in the large volume helicon reactor WOMBAT. These waves are highly localized along the axis of the device where a 8 cm diameter, 2 m long. Ar II plasma column is produced. Spectral measurements reveal a four-wave interaction where energy is down-converted to the ion cyclotron mode from the helicon pump. The experimental results are explained in terms of a filamentation type instability.

The effect of environmentally induced changes in the bark of young conifers on feeding behaviour and reproductive development of adult Hylobius abietis (Coleoptera: Curculionidae).

Young plants of Sitka spruce, Scots and Corsican pine were subject to high and low light, and high and low nitrogen treatments in a polyhouse experiment. The effect of treatments on resin duct size and nitrogen concentration in stem bark was determined together with feeding by Hylobius abietis Linnaeus on the stems of 'intact' plants and on 'detached' stems cut from the plant. Resin duct size was largest on Corsican pine and smallest on Sitka spruce and inherent variation in duct size between the three conifer species appears to determine the pattern of weevil feeding between species. Resin ducts and the flow of resin from them protect the stems of young conifers from weevil feeding not by affecting the total amount of bark eaten but by limiting the depth of feeding and so protecting the inner phloem and cambium. Shallow feeding may increase the likelihood of effective wound repair. Duct size was positively related to plant growth and in particular increased with bark thickness. Overall, ducts were largest in the high light treatment although species differed in their response to the treatment. It is suggested that the effects of plant size, growing conditions and transplantation on susceptibility to attack by H. abietis, reported in various studies, may be due to underlying variation in resin duct size or flow rate. The effect on weevils of superficial feeding on stems is to increase the time for reproductive maturation by reducing consumption of the inner bark which has a higher nitrogen content.

Maturation feeding and reproductive development in adult pine weevil, Hylobius abietis (Coleoptera: Curculionidae).

Maturation feeding on conifer bark by newly emerged Hylobius abietis(Linnaeus) is essential for reproductive development. When feeding occurs on young conifer transplants, this weevil causes significant economic damage. Between emergence and oviposition however, weevils feed on bark from different sources but of unknown nutritional 'quality'. The factors influencing the rate of feeding by males and females and female reproductive development were determined in laboratory bioassays using two contrasting food sources - the bark on different species of seedling conifer and on logs of mature trees. The nutritional 'quality' of bark was characterized by the concentration of nitrogen, total sugars, total polyphenols and resin. Regression models were used to show that overall, the rate of feeding on the bark of both seedlings and logs increased with weevil size and was negatively related to nitrogen concentration. The nitrogen concentration in seedling bark (mean 1.1%) was about three times higher than that of logs (mean 0.4%). The rate of reproductive development increased with nitrogen intake during feeding and the preoviposition period for weevils feeding on seedlings and logs was ~ 13 days and 46 days, respectively. Analysis of weevil mortality and of the weight gain of surviving weevils suggests that a nitrogen content of around 0.3% may be limiting for H. abietis. The possibility that nutritionally adequate food resources may be limiting for H. abietis is briefly discussed.

The RNA-binding protein Tsunagi interacts with Mago Nashi to establish polarity and localize oskar mRNA during Drosophila oogenesis.

In Drosophila melanogaster, formation of the axes and the primordial germ cells is regulated by interactions between the germ line-derived oocyte and the surrounding somatic follicle cells. This reciprocal signaling results in the asymmetric localization of mRNAs and proteins critical for these oogenic processes. Mago Nashi protein interprets the posterior follicle cell-to-oocyte signal to establish the major axes and to determine the fate of the primordial germ cells. Using the yeast two-hybrid system we have identified an RNA-binding protein, Tsunagi, that interacts with Mago Nashi protein. The proteins coimmunoprecipitate and colocalize, indicating that they form a complex in vivo. Immunolocalization reveals that Tsunagi protein is localized within the posterior oocyte cytoplasm during stages 1-5 and 8-9, and that this localization is dependent on wild-type mago nashi function. When tsunagi function is removed from the germ line, egg chambers develop in which the oocyte nucleus fails to migrate, oskar mRNA is not localized within the posterior pole, and dorsal-ventral pattern abnormalities are observed. These results show that a Mago Nashi-Tsunagi protein complex is required for interpreting the posterior follicle cell-to-oocyte signal to define the major body axes and to localize components necessary for determination of the primordial germ cells.

mag-1, a homolog of Drosophila mago nashi, regulates hermaphrodite germ-line sex determination in Caenorhabditis elegans.

The Caenorhabditis elegans gene mag-1 can substitute functionally for its homolog mago nashi in Drosophila and is predicted to encode a protein that exhibits 80% identity and 88% similarity to Mago nashi (P. A. Newmark et al., 1997, Development 120, 3197-3207). We have used RNA-mediated interference (RNAi) to analyze the phenotypic consequences of impairing mag-1 function in C. elegans. We show here that mag-1(RNAi) causes masculinization of the germ line (Mog phenotype) in RNA-injected hermaphrodites, suggesting that mag-1 is involved in hermaphrodite germ-line sex determination. Epistasis analysis shows that ectopic sperm production caused by mag-1(RNAi) is prevented by loss-of-function (lf) mutations in fog-2, gld-1, fem-1, fem-2, fem-3, and fog-1, all of which cause germ-line feminization in XX hermaphrodites, but not by a her-1(lf) mutation which causes germ-line feminization only in XO males. These results suggest that mag-1 interacts with the fog, fem, and gld genes and acts independently of her-1. We propose that mag-1 normally allows oogenesis by inhibiting function of one or more of these masculinizing genes, which act during the fourth larval stage to promote transient sperm production in the hermaphrodite germ line. When the Mog phenotype is suppressed by a fog-2(lf) mutation, mag-1(RNAi) also causes lethality in the progeny embryos of RNA-injected, mated hermaphrodites, suggesting an essential role for mag-1 during embryogenesis. The defective embryos arrest during morphogenesis with an apparent elongation defect. The distribution pattern of a JAM-1::GFP reporter, which is localized to boundaries of hypodermal cells, shows that hypodermis is disorganized in these embryos. The temporal expression pattern of the mag-1 gene prior to and during morphogenesis appears to be consistent with an essential role of mag-1 in embryonic hypodermal organization and elongation.

The transmembrane molecule kekkon 1 acts in a feedback loop to negatively regulate the activity of the Drosophila EGF receptor during oogenesis.

We have identified the Drosophila transmembrane molecule kekkon 1 (kek1) as an inhibitor of the epidermal growth factor receptor (EGFR) and demonstrate that it acts in a negative feedback loop to modulate the activity of the EGFR tyrosine kinase. During oogenesis, kek1 is expressed in response to the Gurken/EGFR signaling pathway, and loss of kek1 activity is associated with an increase in EGFR signaling. Consistent with our loss-of-function studies, we demonstrate that ectopic overexpression of kek1 mimics a loss of EGFR activity. We show that the extracellular and transmembrane domains of Kek1 can inhibit and physically associate with the EGFR, suggesting potential models for this inhibitory mechanism.

Zimp encodes a homologue of mouse Miz1 and PIAS3 and is an essential gene in Drosophila melanogaster.

The related mouse proteins Miz1 and PIAS3, which have predicted zinc finger domains, interact with the transcription factors Msx2 and STAT3, modulating the ability of Msx2 and STAT3 to regulate transcription. Here, we describe a Drosophila gene, zimp, that encodes a protein with similarity to Miz1 and PIAS3. The zimp gene appears to be post-transcriptionally regulated, as three alternatively spliced forms are detected in a cDNA library screen and on an RNA blot. In addition, all three zimp transcripts are detected in embryonic mRNA, but only two of the transcripts are detected in adult mRNA. The three transcripts have the ability to encode two proteins, of 554 and 522 amino acids. The two Zimp amino acid sequences share an amino-terminal 515-amino-acid region and differ in their carboxy-termini. These proteins and related proteins in other organisms, including mammals, C. elegans, yeast, and plants, share a highly conserved region predicted to form a zinc finger. Deletion of the zimp gene or P-element insertion in zimp is lethal; thus, zimp is an essential gene in Drosophila. These data underscore the potential importance of Zimp-related proteins cross-species, and conservation of the putative zinc finger domain suggests that it is functionally important.

mago nashi mediates the posterior follicle cell-to-oocyte signal to organize axis formation in Drosophila.

Establishment of the anteroposterior and dorsoventral axes in the Drosophila egg chamber requires reciprocal signaling between the germ line and soma. Upon activation of the Drosophila EGF receptor in the posterior follicle cells, these cells signal back to the oocyte, resulting in a reorganization of the oocyte cytoplasm and anterodorsal migration of the oocyte nucleus. We demonstrate that the gene mago nashi (mago) encodes an evolutionarily conserved protein that must be localized within the posterior pole plasm for germ-plasm assembly and Caenorhabditis elegans mago is a functional homologue of Drosophila mago. In the absence of mago+ function during oogenesis, the anteroposterior and dorsoventral coordinates of the oocyte are not specified and the germ plasm fails to assemble.

Expansion of restricted cellular immune responses to HIV-1 envelope by vaccination: IL-7 and IL-12 differentially augment cellular proliferative responses to HIV-1.

The failure of immune effector mechanisms to control HIV-1 infection has important consequences for the human host. In a randomized cohort of HIV-infected patients, there was striking in vitro restriction of the proliferative response to HIV-1 envelope protein (Env), gp160; only 34% of patients recognized Env. Therapeutic vaccination with recombinant gp160 or gp120 (rgp160, rgp120) reversed the restriction in vitro, with Env recognition rising to 81%. Peripheral blood mononuclear cells (PBMC) from HIV-infected vaccine recipients, placebo recipients, and seronegative volunteers were cultured with exogenous IL-7 or IL-12 and either tetanus toxoid (TT) or gp160. IL-7 significantly augmented proliferative responses to TT and gp160, whereas IL-12 only affected proliferation to gp160. IL-7, but not IL-12, increased the number of HIV-infected placebo recipients who recognized rgp160. IL-12 had its greatest effect in the induction of rgp160-specific responses from seronegative individuals. The data suggest that these two cytokines have differential activity in the relief of restricted cellular immunity to Env; the predominant effect of IL-7 is in individuals who have been primed by exposure to antigen, while the effect of IL-12 is most evident in seronegative, unprimed individuals. Modification of restricted proliferative responses to Env by vaccination or cytokines in vitro suggests that strategies incorporating IL-7 or IL-12 as adjuvants may selectively boost cellular reactivity to HIV-1.

Transcriptional effects of superinfection in HIV chronically infected T cells: studies in dually infected clones.

We had previously shown that chronically infected ACH-2 cells (HIVLAI) could be superinfected with HIVRF, that the frequency of superinfection increased with time, and that the transcription of the superinfecting virus exceeded that of the host HIVLAI provirus. In contrast, ACH-2 cells superinfected with a nef-substituted neomycin-resistant (proNEO) provirus were not detectable by DNA polymerase chain reaction (PCR) until geneticin (G418) was added, suggesting that the ability to propagate progressively in culture may be HIV strain specific. Clonal populations of ACH-2 superinfected with proNEO did not demonstrate preferential transcription of the superinfecting virus. However, clones of ACH-2 superinfected with HIVRF (ACH2/RF) showed a preponderance of HIVRF transcripts similar to that seen in bulk populations. Induction of the superinfecting virus by phorbol ester (PMA) occurred more rapidly than the hose provirus and did not equalize transcriptional activity. PCR-derived long terminal repeat (LTR) fragments and Tat cDNAs from A3.01 cells acutely infected with HIVRF or from ACH-2 cells were sequenced and tested for transactivation. The HIVLAI LTR was two to three times more Tat-responsive than the HIVRF LTR. TatRF was two to three times more transcriptionally active on either LTR than TatLAI. Demethylation with 5-azacytidine did not significantly affect HIV expression from the HIVLAI host provirus of superinfected ACH2/RF cell clones. These data suggest that the mechanism of preferential transcription in HIVRF superinfected ACH2/RF may be attributed to the Tat/TAR axis and the effect of the specific locus of host proviral integration.

Patterns of virus burden and T cell phenotype are established early and are correlated with the rate of disease progression in human immunodeficiency virus type 1-infected persons.

Human immunodeficiency virus (HIV)-1 DNA and RNA levels and T lymphocyte cell surface markers were measured in blood serum and cell fractions from asymptomatic infected patients to find novel virologic and immunologic features in early disease predictive of subsequent clinical disease course. Thirty-two patients with rapid disease progression (rapid CD4+ cell loss and progression to clinical AIDS) were compared with 25 patients with stable infections (constant or rising CD4+ cell counts, no clinical disease manifestations). All HIV-1 burdens measured by polymerase chain reaction were consistently higher in specimens from rapid progressors than slow progressors. For each patient, virus burden remained relatively constant throughout the study period (mean, 42-44 months). Flow cytometry also disclosed stable lymphocyte immunophenotype patterns that correlated strongly with subsequent rapid progression to clinical disease. Thus, in early HIV-1 infection, a constellation of high virus burden and in vivo costimulatory antigen and lymphocyte activation abnormalities is predictive of rapid disease course.

Bronchiolitis obliterans from exposure to incinerator fly ash.

Inhalation of toxic substances in the workplace can result in a variety of respiratory disorders. One relatively rare sequela of the inhalation of toxic fumes is bronchiolitis obliterans, a condition characterized by fibrosis and narrowing of the small airways. Several substances have been reported to cause bronchiolitis obliterans, including ammonia, chlorine, hydrogen fluoride, hydrogen sulfide, nitrogen dioxide, ozone, phosgene, and other irritant fumes. Little has been reported on the pulmonary effects of fly ash produced by the incineration of coal and oil. We report a case of bronchiolitis obliterans with a component of partially reversible airway obstruction in a 39-year-old male occupationally exposed to incinerator fly ash.

In vitro T cell function, delayed-type hypersensitivity skin testing, and CD4+ T cell subset phenotyping independently predict survival time in patients infected with human immunodeficiency virus.

Human immunodeficiency virus type 1 (HIV-1)-infected patients (n = 335) in the US Air Force HIV Natural History Program were followed for 3 years (mean) after skin testing, immunophenotyping of CD4+ cell subsets, and measurement of in vitro interleukin-2 production after stimulation by phytohemagglutinin, alloantigens, tetanus toxoid, and influenza A virus. The T cell functional assay predicted survival time (P < .001) and time for progression to AIDS (P = .014). Skin testing for tetanus, mumps, and Candida antigen and the total number of positive tests (P < .001 for each) stratified patients for survival time. In a multivariable proportional hazards model, the T cell functional assay (P = .008), the absolute number of CD4+ T cells (P = .001), the percentage of CD4+ CD29+ cells (P = .06), and the number of reactive skin tests (P < .001) predicted survival time. Thus, cellular immune functional tests have significant predictive value for survival time in HIV-1-infected patients independent of CD4+ cell count.

Multivariate models for predicting progression to AIDS and survival in human immunodeficiency virus-infected persons.

Nine hundred thirty persons enrolled in the US Air Force Human Immunodeficiency Virus (HIV) Natural History Study were evaluated with a standard battery of 30 potential surrogate markers of disease progression. A risk score for predicting progression to AIDS was then calculated for each patient in the cohort by using the four highest-ranking variables from multivariate analysis: percentage of CD4 CD29 cells, anergy status, age, and hemoglobin. For predicting survival, beta 2-microglobulin replaced age in the Cox model. Stratification according to the risk score demonstrated that rates of progression to AIDS and survival were significantly different between risk groups (P < .0001). The novel combination of these markers results in extremely accurate risk scores, which may serve as the basis for the development of true surrogate markers of disease progression.

Preparation of casein using carbon dioxide.

The effects of pressure, temperature, residence time, and mass of skim milk on some characteristics of casein, prepared by precipitation with high pressure CO2, were examined in a batch reactor. For a 500-g milk sample, precipitation occurred at pressures > 2760 kPa and temperatures > 32 degrees C. Residence time was not significant and was held at 5 min. Yields were maximum at 2750 to 5520 kPa and at 38 to 49 degrees C for a 500-g milk sample. The resulting whey had a pH of 6.0. The casein product had an acceptable appearance and had greater solids, ash, and Ca contents than commercial acid caseins. Particle size distribution studies showed that the mean particle size was sensitive to precipitation pressure and temperature and was similar to that of acid caseins produced under laboratory conditions. The HPLC studies of the casein and whey fractions showed that precipitation by CO2 did not result in fractionation of casein or whey proteins to their component proteins.

Observer variability in measuring elevation and external rotation of the shoulder. Primary Care Rheumatology Society Shoulder Study Group.

The aim of the study was to assess the observer variation between trained primary care physicians in their assessment of two key shoulder movements: elevation and external rotation. Six observers each examined and recorded their visual estimate of the range of movements in six patients assessed in random order. There was good agreement on the range of passive elevation assessed to the start of pain (if present): intraclass correlation coefficient (ICC) = 0.84, and to the point of maximum elevation: ICC = 0.95. There was no evidence of an important systematic bias between observers. By contrast, external rotation was poorly reproducible: ICC = 0.43, with important systematic differences between observers. In the second experiment, six observers simultaneously witnessed a range of movements in a single volunteer subject, and the agreement on their visual estimation of the angles achieved was assessed. There was a marked reduction in the systematic bias in external rotation, but agreement was still poor. Agreement for elevation remained high with a reduction in the small amount of bias observed in the first experiment when variability in both examination and visual assessment had been investigated. We conclude that shoulder elevation is a reliable measurement for use in multicentre studies by trained primary care physicians. By contrast, external rotation is poorly reproducible because of systematic variation in examination technique and random variation in visual assessment.