Magnetically propagating Hund's exciton in van der Waals antiferromagnet NiPS3

Magnetic van der Waals (vdW) materials have opened new frontiers for realizing novel many-body phenomena. Recently NiPS3 has received intense interest since it hosts an excitonic quasiparticle whose properties appear to be intimately linked to the magnetic state of the lattice. Despite extensive studies, the electronic character, mobility, and magnetic interactions of the exciton remain unresolved. Here we address these issues by measuring NiPS3 with ultra-high energy resolution resonant inelastic x-ray scattering (RIXS). We find that Hund's exchange interactions are primarily responsible for the energy of formation of the exciton. Measuring the dispersion of the Hund's exciton reveals that it propagates in a way that is analogous to a double-magnon. We trace this unique behavior to fundamental similarities between the NiPS3 exciton hopping and spin exchange processes, underlining the unique magnetic characteristics of this novel quasiparticle.

U-CAN-seq: A Universal Competition Assay by Nanopore Sequencing

RNA viruses quickly evolve subtle genotypic changes that can have major impacts on viral fitness and host range, with potential consequences for human health. It is therefore important to understand the evolutionary fitness of novel viral variants relative to well-studied genotypes of epidemic viruses. Competition assays are an effective and rigorous system with which to assess the relative fitness of viral genotypes. However, it is challenging to quickly and cheaply distinguish and quantify fitness differences between very similar viral genotypes. Here, we describe a protocol for using reverse transcription PCR in combination with commercial nanopore sequencing services to perform competition assays on untagged RNA viruses. Our assay, called the Universal Competition Assay by Nanopore Sequencing (U-CAN-seq), is relatively cheap and highly sensitive. We used a well-studied N24A mutation in the chikungunya virus (CHIKV) nsp3 gene to confirm that we could detect a competitive disadvantage using U-CAN-seq. We also used this approach to show that mutations to the CHIKV 5' conserved sequence element that disrupt sequence but not structure did not affect the fitness of CHIKV. However, similar mutations to an adjacent CHIKV stem loop (SL3) did cause a fitness disadvantage compared to wild-type CHIKV, suggesting that structure-independent, primary sequence determinants in this loop play an important role in CHIKV biology. Our novel findings illustrate the utility of the U-CAN-seq competition assay.

Atmospheric effects on the laser-driven avalanche-based remote detection of radiation

The effect of realistic atmospheric conditions on mid-IR (λ = 3.9 µm) and long-wave-IR (λ = 10 µm) laser-induced avalanche breakdown for the remote detection of radioactive material is examined experimentally and with propagation simulations. Our short-range in-lab mid-IR laser experiments show a correlation between increasing turbulence level and a reduced number of breakdown sites associated with a reduction in the portion of the focal volume above the breakdown threshold. Simulations of propagation through turbulence are in excellent agreement with these measurements and provide code validation. We then simulate propagation through realistic atmospheric turbulence over a long range (0.1-1 km) in the long-wave-IR regime (λ = 10 µm). The avalanche threshold focal volume is found to be robust even in the presence of strong turbulence, only dropping by ∼50% over a propagation length of ∼0.6 km. We also experimentally assess the impact of aerosols on avalanche-based detection, finding that, while background counts increase, a useful signal is extractable even at aerosol concentrations 10⁵ times greater than what is typically observed in atmospheric conditions. Our results show promise for the long-range detection of radioactive sources under realistic atmospheric conditions.

Emergence of Spinons in Layered Trimer Iridate Ba_{4}Ir_{3}O_{10}

Spinons are well known as the elementary excitations of one-dimensional antiferromagnetic chains, but means to realize spinons in higher dimensions is the subject of intense research. Here, we use resonant x-ray scattering to study the layered trimer iridate Ba_{4}Ir_{3}O_{10}, which shows no magnetic order down to 0.2 K. An emergent one-dimensional spinon continuum is observed that can be well described by XXZ spin-1/2 chains with a magnetic exchange of ∼55  meV and a small Ising-like anisotropy. With 2% isovalent Sr doping, magnetic order appears below T_{N}=130  K along with sharper excitations in (Ba_{1-x}Sr_{x})_{4}Ir_{3}O_{10}. Combining our data with exact diagonalization calculations, we find that the frustrated intratrimer interactions effectively reduce the system into decoupled spin chains, the subtle balance of which can be easily tipped by perturbations such as chemical doping. Our results put Ba_{4}Ir_{3}O_{10} between the one-dimensional chain and two-dimensional quantum spin liquid scenarios, illustrating a new way to suppress magnetic order and realize fractional spinons.

Effect of fluctuation of oxygenation and time spent in the target range on retinopathy of prematurity in extremely low birth weight infants

BACKGROUND

The association between saturation of peripheral oxygenation (SpO2) fluctuation and severity of retinopathy of prematurity (ROP) is well elucidated in extremely low birth weight (ELBW) infants. Time spent in the Target range of SpO2 is also associated with the severity of ROP.

METHODS

In a prospective observational study, the SpO2 of all ELBW infants admitted to our unit were monitored for the first four weeks of life, and averaged every minute for analysis. The percent time spent at SpO2 <90%, 90-95%, and >95% and weekly SpO2 fluctuations [as SpO2 coefficient of variation (CoV)] were calculated.

RESULTS

During the study period 21 infants had moderate to severe ROP and 35 infants served as controls. Infants with moderate to severe ROP were smaller and younger than their controls [676±124 grams vs. 796±148 grams (p < 0.001); and 24.0±1.0 weeks vs. 25.0±1.7 weeks (p < 0.001) respectively]. There were no significant differences in time spent in the 90-95% range between groups (p = 0.66). However there was a significant increase in weekly SpO2 CoV in infants with moderate to severe ROP vs. controls (p = 0.007).

CONCLUSION

In ELBW infants, there was an association between SpO2 fluctuation during the first four weeks of life and severity of ROP, although, no association was established with time spent in the target range of SpO2.

Distribution, Cultivar Susceptibility, and Epidemiology of Apium virus Y on Celery in Coastal California

Apium virus Y (ApVY) is a potyvirus that was recently found to cause crop loss to celery (Apium graveolens) in California. Symptoms on leaves exhibit varying forms of chlorosis and necrosis. Depending on the cultivar, celery petioles could also exhibit extensive necrotic, sunken, elongated lesions. Severely affected plants were unmarketable. Disease incidence surveys found that a susceptible celery (cv. 414) showed 55% (2007) and 71% (2008) disease. Because it was noted that the Apiaceae weed poison hemlock (Conium maculatum) was present in almost all areas where ApVY affected celery, a 4-year survey collected overwintered hemlock from six coastal county regions and tested composite samples for ApVY using reverse transcription-polymerase chain reaction (RT-PCR) and ApVY-specific primers. These plants were consistently positive for ApVY. Seeds collected from these plants were also positive when tested with the same RTPCR method. However, when ApVY-positive hemlock seeds were germinated and the resulting seedlings tested, all results were negative. The failure of ApVY to be transmitted from hemlock seeds to seedlings was further documented by collecting newly germinated hemlock seedlings from the field and testing them with RT-PCR. All such seedlings were negative for ApVY even though large, adjacent, overwintered hemlock plants tested positive. Two crops of celery seed were produced from ApVY-positive mother plants; celery seed from these infected plants likewise tested positive for ApVY, but seedlings grown from the seed lots were negative for ApVY. Twenty-one celery and celeriac cultivars were inoculated with ApVY using viruliferous aphids, planted in a replicated field trial, and then grown to maturity. Seven cultivars remained symptomless, tested negative for ApVY, and showed signs of possible resistance. The epidemiology of disease caused by ApVY in California evidently involves poison hemlock as a common overwintering host with subsequent vectoring of the virus from hemlock to celery via aphids. ApVY was not seedborne in this weed host or in celery in our experiments. Our data suggest that growers can manage this disease by controlling poison hemlock weed populations and by planting celery cultivars that are not susceptible to ApVY.

Flux rope dynamics: experimental study of bouncing and merging

We show experimentally for the first time that two mutually attracting flux ropes may bounce back instead of merging together, leading to a variety of dynamics not expected from a two-dimensional model. Attraction forces due to flux rope currents compete with repulsion from field line bending of in-plane and out-of-plane magnetic fields and elastic plasma compression. Bouncing dynamics occurs if the line-bending force due to an out-of-plane field dominates. Otherwise, the ropes merge. Further reduction in the field line-bending force results in violently erratic magnetic states.

The amino terminus of Epstein-Barr Virus (EBV) nuclear antigen 1 contains AT hooks that facilitate the replication and partitioning of latent EBV genomes by tethering them to cellular chromosomes

During latency, Epstein-Barr virus (EBV) is stably maintained as a circular plasmid that is replicated once per cell cycle and partitioned at mitosis. Both these processes require a single viral protein, EBV nuclear antigen 1 (EBNA1), which binds two clusters of cognate binding sites within the latent viral origin, oriP. EBNA1 is known to associate with cellular metaphase chromosomes through chromosome-binding domains within its amino terminus, an association that we have determined to be required not only for the partitioning of oriP plasmids but also for their replication. One of the chromosome-binding domains of EBNA1 associates with a cellular nucleolar protein, EBP2, and it has been proposed that this interaction underlies that ability of EBNA1 to bind metaphase chromosomes. Here we demonstrate that EBNA1's chromosome-binding domains are AT hooks, a DNA-binding motif found in a family of proteins that bind the scaffold-associated regions on metaphase chromosomes. Further, we demonstrate that the ability of EBNA1 to stably replicate and partition oriP plasmids correlates with its AT hook activity and not its association with EBP2. Finally, we examine the contributions of EBP2 toward the ability of EBNA1 to associate with metaphase chromosomes in human cells, as well as support the replication and partitioning of oriP plasmids in human cells. Our results indicate that it is unlikely that EBP2 directly mediates these activities of EBNA1 in human cells.

Accumulation of oxidized lipid-protein complexes alters phagosome maturation in retinal pigment epithelium

Lipid peroxidation has been implicated in many age-associated disorders including macular degeneration of the retina. We sought to elucidate the mechanism by which accumulation of oxidized LDL (oxLDL) reduces the ability of retinal pigment epithelium (RPE) to process photoreceptor outer segments (OS) as a model of peroxidation-induced disruption of phagocytosis. OxLDL did not reduce the lysosomal hydrolytic capacity of the RPE, but efficiently inhibited processing of various internalized proteins. OxLDL caused a delay in the acquisition of late lysosomal markers by newly formed phagosomes. At the same time, an excessive accumulation of markers of early phagosomal compartments was also observed. The activity of phosphatidylinositol 3-kinase (PI3K) was reduced in phagosomes of the RPE treated with oxLDL. These results suggest that accumulation of oxidized lipid-protein complexes in the RPE impedes phagosome maturation by blocking PI3K recruitment to the phagosomal membrane, leading to delayed processing of internalized OS.

Metaphase chromosome tethering is necessary for the DNA synthesis and maintenance of oriP plasmids but is insufficient for transcription activation by Epstein-Barr nuclear antigen 1

Epstein-Barr Virus (EBV) infects resting B cells, within which it establishes latency as a stable, circular episome with only two EBV components, the cis element oriP and the latently expressed protein EBNA1. It is believed that EBNA1's ability to tether oriP episomes to metaphase chromosomes is required for its stable replication. We created fusions between the DNA-binding domain (DBD) of EBNA1 and the cellular chromatin-binding proteins HMGA1a and HMG1 to determine the minimal requirements for stable maintenance of an oriP-based episome. These two proteins differ in that HMGA1a can associate with metaphase chromosomes but HMG1 cannot. Interestingly, coinciding with metaphase chromosome association, HMGA1a-DBD but not HMG1-DBD supported both the transient replication and stable maintenance of oriP plasmids, with efficiencies quantitatively similar to that of EBNA1. However, HMGA1a-DBD activated transcription from EBNA1-dependent episomal reporter to only 20% of the level of EBNA1. Furthermore, EBNA1 but not HMGA1a-DBD activated transcription from a chromosomally integrated EBNA1-dependent transcription reporter. This indicates that EBNA1 possesses functional domains that support transcription activation independent of its ability to tether episomal oriP plasmids to cellular chromosomes. We provide evidence that metaphase chromosome tethering is a fundamental requirement for maintenance of an oriP plasmid but is insufficient for EBNA1 to activate transcription.

Comparing beneficiaries of the Medicare savings programs with eligible nonparticipants

This note focuses on participation in two entitlement programs that help reduce out-of-pocket expenses for low-income Medicare beneficiaries: the Qualified Medicare Beneficiary (QMB) program and the Specified Low-Income Medicare Beneficiary (SLMB) program. As of 1999, about 2.75 million eligible, noninstitutionalized individuals were not enrolled in these Medicare savings programs. The eligible nonparticipants differed substantially from the QMB and SLMB participants in that they were less likely to be Supplemental Security Income beneficiaries and more likely to be elderly, nonblack, and in relatively good health. These findings, which could help target future outreach efforts, are based on Survey of Income and Program Participation data matched with administrative records from the Social Security Administration.

Modeling SSI financial eligibility and simulating the effect of policy options

This article simulates eligibility for Supplemental Security Income (SSI) among the elderly, analyzes factors affecting participation, and looks at the potential effects of various options to modify financial eligibility standards for the federal SSI program. We find that in the estimated noninstitutional elderly population of 30.2 million in the United States in 1991, approximately 2 million individuals aged 65 or older were eligible for SSI (a 6.6 percent rate of eligibility). Our overall estimate of the rate of participation among eligible elderly is approximately 63 percent, suggesting that more than a third of those who are eligible do not participate in the program. The results of our analysis of factors affecting participation among the eligible elderly show that expected SSI benefits and a number of demographic and socioeconomic variables are associated with the probability of participation. We also simulate the effects of various policy options on the poverty rate, poverty gap, annual program cost, the number of participants, and the average estimated benefits among participants. The simulations consider the potential effects of five policy alternatives: Increase the general income exclusion (GIE) from $20 to $80. Increase the earned income exclusion (EIE) from $65 to $260. Increase the federal benefit rate (FBR) by $50 for individuals and $75 for couples and eliminate the GIE. Increase the asset threshold to $3,000 for individuals and $4,500 for couples. Increase the asset threshold to $6,000 for individuals and $9,000 for couples. Using 1991 microdata from the Survey of Income and Program Participation (SIPP) matched to Social Security Administration administrative records and making adjustments reflecting aggregate program statistics, we present the results of our simulations for December 1999. The results show substantial variation in the simulated effects of the five policy alternatives along the various outcome dimensions considered. The simulated effects on the poverty gap of the elderly population range from a 7.9 percent reduction ("Increase the GIE from $20 to $80") to a 0.1 percent reduction ("Increase the EIE from $65 to $260"). All simulated interventions are expected to increase the rate of SSI participation among the elderly from a high of 20.3 percent ("Increase the GIE from $20 to $80") to a low of 0.5 percent ("Increase the EIE from $65 to $260"). We also find that the interventions that have greater estimated effects in terms of increased participation and reduced poverty tend to cost more. At the high end, we estimate that increasing the GIE from $20 to $80 could raise annual federal SSI cash benefit outlays by about 46 percent, compared with only 0.9 percent for increasing the EIE from $65 to $260. Similar to the EIE intervention, raising the resource thresholds by 50 percent would reduce the overall poverty gap of the elderly by only 0.2 percent, would increase SSI participation only modestly (by 1.3 percent), but would entail slightly higher program costs (by 1.4 percent). Increasing the asset threshold by 200 percent would have higher estimated effects on all three outcomes, but it would still be associated with relatively low increases in both costs and benefits. Finally, the simulated effects on the three key outcomes of increasing the FBR by $50 for individuals and $75 for couples, combined with eliminating the GIE, are relatively large but are clearly less substantial than increasing the GIE from $20 to $80. This work relies on data from the SIPP matched to administrative data on federal SSI benefits that provide a more accurate picture of SSI participation than has been feasible for previous studies. We simulate eligibility for federal SSI benefits by applying the program rules to detailed information on the characteristics of individuals and couples based on the rich array of demographic and socioeconomic data in the SIPP, particularly the comprehensive information SIPP provides on assets and monthly income. A probit model is estimated to analyze factors affecting participation among the eligible elderly. Finally, we conduct the policy simulations using altered program rules represented by the policy alternatives and predicted participation probabilities to estimate outcomes under simulated program rules. We compare those simulated outcomes to observed outcomes under current program rules. The results of our simulations are conditional on the characteristics of participants and eligibles in 1991, but they also reflect aggregate adjustments capturing substantial changes in overall participation and program benefit levels between 1991 and 1999.

Multiple substrate growth kinetics of Leptothrix discophora SP-6

The growth parameters of Leptothrix discophora SP-6 were quantified on the basis of the steady-state concentrations and utilization rates of pyruvate, dissolved oxygen, and concentration of microorganisms in a chemostat operated at 25 degrees C, pH 7.2, and an agitation rate of 350 rpm. The results showed that the microbial growth was limited by both pyruvate and dissolved oxygen. A combined growth kinetics model using Monod growth kinetics for pyruvate and Tessier growth kinetics for oxygen showed the best correlation with the experimental data when analyzed using an interactive multiple substrate model. The growth kinetics parameters and the respective confidence limits, estimated using the Monte Carlo simulation, were mu(max) = 0.576 +/- 0.021 h(-1), K(sMp) = 38.81 +/- 4.24 mg L(-1), K(sTo) = 0.39 +/- 0.04 mg L(-1), Y(X/p) = 0.150 (mg microorganism mg(-1) pyruvate), Y(X/o) = 1.24 (mg microorganism mg(-1) oxygen), the maintenance factors for pyruvate and oxygen were m(p) = 0.129 (mg pyruvate consumed mg(-1) microorganism h(-1)) and m(o) = 0.076 (mg oxygen consumed mg(-1) microorganism h(-1)), respectively.

Limited macular translocation with scleral retraction suture

BACKGROUND/AIMS

Macular translocation with scleral imbrication is a new technique for treating subfoveal choroidal neovascular membranes (CNV). This procedure shortens the sclera but may result in a minimal decrease in the internal circumference of the globe and limits the amount of foveal displacement. The authors propose a new scleral retraction suture aimed at decreasing the internal circumference of the globe in an effort to increase foveal displacement.

METHODS

Using a cadaver model, they compared the amount of scleral shortening using a standard scleral imbrication technique and a modified three suture scleral retraction technique. Sections of the globes were digitised and specialised software was used to estimate the amount of scleral shortening. Three patients with subfoveal choroidal neovascularisation underwent limited macular translocation using pars plana vitrectomy and macular detachment with the modified scleral suture technique. The main outcome measures were visual acuity, foveal displacement, and complications.

RESULTS

In the cadaver model, the scleral retraction suture resulted in a flatter internal scleral fold compared to the standard suture technique and created approximately 890 microm of effective scleral shortening. In the patients who underwent macular translocation and laser photocoagulation of the CNV, visual acuity improved in two patients and worsened in one patient. The range of foveal displacement was 1400-2400 microm.

CONCLUSION

The foveal displacements achieved in this limited study compared to median displacement previously published using standard suture techniques demonstrates that the scleral retraction suture technique may be a useful adjunct to limited macular translocation. The advantage of this type of suture in conjunction with translocation may depend on the effective scleral shortening offered by this retraction suture.

Volatile antimicrobials from Muscodor albus, a novel endophytic fungus

Muscodor albus is a recently described endophytic fungus obtained from small limbs of Cinnamomum zeylanicum (cinnamon tree). This xylariaceaous fungus effectively inhibits and kills certain other fungi, and bacteria, by virtue of a mixture of volatile compounds that it produces. The majority of these compounds were identified by gas chromatography/mass spectrometry and then made into an artificial mixture that mimicked the antibiotic effects of the mixture of volatile compounds given off by the fungus. Each of the five classes of volatile compounds produced by the fungus (alcohols, esters, ketones, acids and lipids) had some inhibitory effect against the test fungi and bacteria, but none was lethal. However, collectively they acted synergistically to kill a broad range of plant- and human-pathogenic fungi and bacteria. The most effective class of inhibitory compounds was the esters, of which 1-butanol, 3-methyl-, acetate was the most active biologically. This report describes the ecological implications and potential practical benefits of the 'mycofumigation' effects of M. albus.

Medicare premium buy-in programs: results of SSA demonstration projects

Three programs known collectively as the Medicare buy-in programs are available to pay Medicare Part B premiums and, in some cases, other medical expenses for certain low-income individuals. The Health Care Financing Administration administers those programs, with most functions performed by the states. The Social Security Administration (SSA) plays an indirect role in the buy-in programs: with certain exceptions, people who qualify for Medicare and hence for buy-in are beneficiaries of Social Security retirement or disability programs. SSA is often cited as an agency that might be able to increase enrollment in the buy-in programs through outreach to its beneficiaries and by acting as an intermediary in the enrollment process. The three buy-in programs have different requirements for eligibility. The Qualified Medicare Beneficiary (QMB) program includes individuals who have Part A Medicare benefits and whose income does not exceed 100 percent of federal poverty guidelines. People in the Specified Low-Income Medicare Beneficiary (SLMB) program are individuals who would otherwise be QMBs but whose income is more than 100 percent but less than 120 percent of poverty guidelines. People in the Qualified Individual (QI) program are those who meet the other criteria but whose income is less than 175 percent of poverty guidelines. Various reports and studies by government agencies and advocacy organizations conclude that the buy-in programs are not reaching many of the people who are eligible. Low enrollment appears to be a particular issue for the SLMB and QI programs. States have tried various outreach efforts, but the effectiveness of those efforts has not been adequately assessed. In 1998, Congress mandated that SSA conduct a demonstration project to determine how to increase participation in the buy-in programs. The project tested six different administrative models in which outreach letters were sent to potential beneficiaries asking them to contact SSA and then be screened for eligibility and referred for enrollment. SSA was able to screen about 7.1 percent of letter recipients for buy-in eligibility: 4.2 percent were potentially eligible for the programs based on income and resources, and 3.7 percent enrolled in a buy-in program. An evaluation of the probability that letter recipients would contact SSA to be screened found that: Among the elderly, older individuals were less likely to be screened but more likely to enroll. Among the disabled, older individuals were more likely to be screened but less likely to enroll. The disabled were less likely to be screened but more likely to enroll. Individuals with higher Social Security benefits were more likely to be screened but less likely to enroll. Women were more likely to be screened and to enroll. Being married did not appear to affect screening but negatively affected enrollment. Individuals with a preference for materials in Spanish were much more likely to be screened and enrolled. In some of the demonstration sites, enrollment in a Medicare+Choice plan increased the probability of being both screened and enrolled. SSA conducted a survey of some people who did not respond to the outreach letter. Most of those from whom explanations of the nonresponse were obtained had not responded because they were not eligible on the basis of their income or resources. If SSA were to reproduce the demonstrations in a nationwide outreach effort, a national mailing would include nearly 20 million individuals. If response rates were similar to those seen in the 1999 demonstrations, outreach would produce over 740,000 new buy-in enrollees. That number might be increased modestly by conducting additional outreach efforts in conjunction with the mailing.

Eligibility for the Medicare buy-in programs, based on a survey of income and program participation simulation

Medicare buy-in programs are designed to reduce out-of-pocket expenses of beneficiaries with modest income and assets. This article provides estimates of the size of the Medicare beneficiary population eligible for the Qualified Medicare Beneficiary (QMB) program, the Specified Low-Income Medicare Beneficiary (SLMB) program, and the Qualified Individual-1 (QI-1) program. The buy-in programs use the same resource limits (twice those used in the Supplemental Security Income (SSI) program) but different thresholds for determining income eligibility. The QMB program uses 100 percent of the poverty line as the cutoff, QI-1 covers persons above 120 percent but at or below 135 percent of the poverty line, and the SLMB program is in between. Making informed judgments about the rate of participation in the buy-in programs and the need for outreach requires an accurate estimate of the size of the eligible population. If that population is underestimated, policymakers might come to unduly optimistic conclusions about current buy-in participation. In contrast, an overestimate may make current participation seem too low. If policymakers react to an upwardly biased estimate of the eligible population by increasing outreach, they are bound to be disappointed by the results of that effort. Estimates of the eligible population from past studies of the QMB and SLMB programs range from 5.1 million to 9.1 million. In the absence of new information, it is difficult to judge the accuracy of those estimates because the methodologies had substantial shortcomings that might bias the results. The most common shortcomings include the lack of high-quality, monthly income data and the lack of information on assets from the same data file that was used to estimate participation and income eligibility for Medicare. The current study uses the most recently available (as of August 2000) Survey of Income and Program Participation (SIPP) file that is matched to the Social Security Administration's (SSA's) administrative records. The data file covers 1995 information. Estimates were also obtained using 1991 data to assess the sensitivity of eligibility estimates to the year chosen. The SIPP has several major advantages over other data sources because it contains relevant, high-quality information on both income and assets for establishing financial eligibility for the buy-in programs. First, the SIPP collects detailed and conceptually appropriate information on monthly, rather than annual, income and therefore has more complete information about income than do other surveys. As a result, SIPP-based estimates of poverty are substantially lower than estimates based on the Current Population Survey. Second, the SIPP also collects information on assets at the individual level. Thus, the survey provides enough detail to measure the major income and asset exclusions directly. Finally, the SIPP data are matched to SSA administrative records: Medicare eligibility can therefore be accurately measured, and self-reported data on Social Security and SSI benefits can be replaced with more accurate monthly information. Our 1995 simulation estimates that approximately 4.8 million persons in the U.S. noninstitutionalized population were eligible for the QMB program and an additional 1.6 million for the SLMB program. The total--roughly 6.5 million--is within the range of estimates from past studies but is closer to the lower end, suggesting that the eligible population is smaller than was previously believed. When the estimated QI-1 eligible population of 0.9 million is added, the total for the three buy-in programs is 7.4 million. Because the QI-1 program did not exist in 1995, only the estimated 6.5 million QMBs and SLMBs would actually have been eligible to receive benefits. The 7.4 million figure represents the 1995 Medicare beneficiaries who would be eligible for buy-in under program rules for 2000. Adjusting that number to account for increases in the Medicare population between 1995 and 1999 yields an estimated eligible population of 7.8 million in 1999. Compared with other elderly Medicare recipients, eligible elderly QMBs and SLMBs have poorer health, more functional limitations, and higher rates of health care use. Thus, not only are their income resources relatively limited, but their need for potentially expensive medical care is also greater. Similar differences were not found in health, functional limitations, and health care use among disabled participants in the QMB and SLMB programs. Our estimates imply that about 2.5 million noninstitutionalized individuals were eligible for but not enrolled in the QMB and SLMB programs in 1999. That finding suggests that fewer eligibles may be available for targeting by outreach efforts than was previously believed. Outreach may be more difficult than it would be with a larger eligible population. (ABSTRACT TRUNCATED)

Seimatoantlerium tepuiense gen. nov., a unique epiphytic fungus producing taxol from the Venezuelan Guyana

Seimatoantlerium gen. nov., type species, S. tepuiense sp. nov. is proposed for an acervular fungus producing 4-septate, holoblastic conidia with 6-8 unbranched, apical appendages that dehisce as an appendage apparatus and also commonly possessing one or two exogenous basal appendages as well as a pedicel. It is compared with Seimatosporium, Seimatosporiopsis, and other genera. It is epiphytic on Maguireothamnus speciosus, a rubiaceous plant endemic to the tepuis of southeastern Venezuela. It produces the anti-oomycetous anticancer compound, taxol, as shown by immunological and spectroscopic methods. Taxol production is discussed relative to the ability of this fungus to exist in an extremely moist ecosystem, as well as to its relationship to other plant associated fungi.

Surgical management of subfoveal neovascularization in children

OBJECTIVE

To report the authors' clinical experience with submacular surgery for subfoveal membranes in children and to evaluate the histopathologic findings of membranes in children with various etiologies of choroidal neovascularization.

DESIGN

Retrospective, noncomparative, interventional case series.

PARTICIPANTS

Twelve eyes of 12 consecutive children with subfoveal choroidal neovascularization treated by vitrectomy and excision of the choroidal neovascular complex.

INTERVENTION

Vitrectomy, excision of the choroidal neovascular complex, and air-fluid exchange.

MAIN OUTCOME MEASURES

Visual acuity and recurrence of choroidal neovascular membrane.

RESULTS

Preoperative visual acuities ranged from 20/60 to 20/800 (median, 20/300). Postoperative visual acuities ranged from 20/25 to 20/400 (median, 20/80) after an average follow-up of 20 months (range, 7-62 months). Ten of 12 eyes improved from immediate preoperative visual acuity, and four eyes developed recurrence of neovascular membranes over a mean follow-up of 18 months. Histopathologic examination of six excised membranes showed that the most common components of the membranes were retinal pigment epithelium, fibrocytes, vascular endothelium, and collagen.

CONCLUSION

Selected eyes of children with subfoveal neovascular membranes and no evidence of membrane regression may benefit from submacular surgery. The histopathologic findings were similar to adult choroidal neovascularization not associated with age-related macular degeneration.

Inherited retinal arteriolar tortuosity with retinal hemorrhages

BACKGROUND

Familial arteriolar tortuosity is an autosomal dominant disorder affecting the retinal arterioles.

OBJECTIVES

To report a pedigree with this disorder and describe a systemic workup to determine whether this vascular abnormality is limited to the eye.

RESULTS

A 58-year-old woman referred for retinal hemorrhages was found to have retinal arteriolar tortuosity of both eyes, especially in the macular area. Her 63-year-old brother had a history of retinal hemmorhages beginning at age 18 years and had similar fundoscopic examination findings. The proband had an extensive systemic workup, including magnetic resonance imaging, and cardiac and renal angiography, that failed to demonstrate any other sequelae of this inherited ocular syndrome. However, each member of the family expressing this phenotype did have hypertension.

CONCLUSION

Inherited retinal arteriolar tortuosity is an autosomal dominant disorder limited to the eye, at least in this pedigree, within the sensitivity of the systemic workup we used.

Ecomycins, unique antimycotics from Pseudomonas viridiflava

A novel family of peptide antimycotics, termed ecomycins, is described from Pseudomonas viridiflava, a plant-associated bacterium. Ecomycins B and C have molecular masses of 1153 and 1181. They contain equimolar amounts of a beta hydroxyaspartic acid, homoserine, threonine, serine, alanine, glycine and one unknown amino acid. Fatty acids were detectable after hydrolysis, methylation and gas chromatography and mass spectroscopy. The ecomycins have significant bioactivities against a wide range of human and plant pathogenic fungi. The minimum inhibitory concentration values for ecomycin B were 4.0 micrograms ml-1 against Cryptococcus neoformans and 31 micrograms ml-1 against Candida albicans. Pseudomonas viridiflava also produces what appears to be syringotoxin, an antifungal lipopeptide previously described from Ps. syringae.

Adrenergic-mediated connexin43 phosphorylation in the ocular ciliary epithelium

PURPOSE

Gap junctions provide metabolic cooperativity between the nonpigmented and pigmented cells of the ciliary epithelium. Connexin43 is the major protein of these junctions. To learn whether the phosphorylation state of this gap junction is sensitive to adrenergic mediators, we exposed isolated intact ciliary epithelia to agonists of the G-protein receptor-coupled system and analyzed the phosphorylation state of connexin43 by western blot.

METHODS

The double layer of intact ciliary epithelia was isolated and exposed to isoproterenol, forskolin, and the tumor promoter 12-o-tetradecanoylphorbol-13-acetate (TPA). The phosphorylation state of connexin43 was analyzed by western blot, using a monoclonal antibody that recognized both the phosphorylated and dephosphorylated connexin43. An upward shift in electrophoretic mobility confirmed the presence of a phosphate group.

RESULTS

Connexin43 phosphorylation was rapidly induced by each of these agonists. One microM isoproterenol and 5 microM forskolin induced phosphorylation of connexin43, as did 16 nanomolar TPA. The effect of isoproterenol was partially blocked by 1 microM timolol. Addition of a phosphatase after forskolin treatment reversed the effect of forskolin. Control explant tissue not treated with these agents exhibited a slower but definite phosphorylation of connexin43.

CONCLUSIONS

Phosphorylation of ciliary epithelial connexin43 is sensitive to modulators of the cAMP system as well as an agent that activates PKC. Isolated intact ciliary epithelia phosphorylate connexin43 by endogenous mechanisms, most likely as a protective response to stress.

Circadian aqueous flow mediated by beta-arrestin induced homologous desensitization

It was hypothesized that homologous desensitization regulates signal transduction from the beta-adrenergic receptor in the ocular ciliary epithelium to affect the circadian rhythm of aqueous humor secretion. beta-arrestin-1 was cloned from the rabbit ciliary epithelium, and the full length cDNA used as a probe for Northern blot analysis to examine the diurnal expression of beta-arrestin mRNA. Protein expression of beta-arrestin-1 at intervals during the circadian cycle of aqueous secretion showed a decrease in beta-arrestin expression when maximal activation of the beta-adrenergic receptor is known to increase secretion. Diurnal expression of beta-arrestin suggests that homologous desensitization can regulate the circadian rhythm of aqueous flow.

Transepithelial transport of ascorbic acid by the isolated intact ciliary epithelial bilayer of the rabbit eye

The purpose of these experiments was to test whether the isolated intact epithelial bilayer derived from rabbit ciliary processes transports ascorbic acid and to what degree the transport rate in vitro corresponds to the in vivo process. The intact ciliary epithelial bilayer of the rabbit eye isolated by perfusion was mounted in a particularly constructed Ussing type chamber. Fluxes were measured by additions of 14C ascorbate to the hemichamber on either the pigmented epithelium (PE) or the nonpigmented epithelium (NPE) side where equal concentrations of ascorbate from .02 to 2.0 mM were present. Samples were taken at intervals thereafter and counted in a liquid scintillation counter. The experiments were done under short circuit conditions to avoid the possible influence of fluctuating currents upon the movement of ascorbate. Like the earlier iris ciliary body preparations, separation of ascorbate fluxes is also done by the isolated intact ciliary epithelial bilayer, and the transport of ascorbic acid proceeds by saturation kinetics. The uptake process is accomplished entirely by the pigmented epithelium (PE). The Km of the process is 0.97 mM, and Vmax was valued at 130 nM/L/hr. Thus, assuming an aqueous flow rate of 2 microliters/min, the transfer of ascorbic acid across the bilayer occurs at a rate required to maintain the ordinary millimolar concentration of ascorbic acid in the aqueous humor found in vivo.

Lead concentrations in birds of prey in Britain

This paper reports on lead (Pb) concentrations in the livers of 424 individuals of 16 raptor species found dead and sent for analysis to the Institute of Terrestrial Ecology, Monkswood, from the early 1980s to the early 1990s. Elevated Pb concentrations in liver (>20 ppm dry wt), within the range associated with Pb poisoning mortality in raptors, were recorded in one peregrine (4% of species sample) and one buzzard (2% of species sample). These birds are likely to have ingested lead gunshot in the flesh of their prey. Another one each of these species had liver Pb concentrations of 15-20 ppm dry wt, reflecting unusually high absorption of Pb. No individuals of any other species had >15 ppm dry wt liver Pb, although some had 6-15 ppm. The source of Pb in these birds was unknown, but it could have resulted from high Pb concentrations in prey items, including some containing lead shot. Median liver Pb concentrations were generally very low (ranging from <0.07 to 1.61 ppm dry wt for species with sample sizes exceeding 10). In sparrowhawks, for which a large sample was available, liver Pb concentrations in all but one individual were low (<2.6 ppm dry wt). Pb concentrations in juveniles were significantly lower than in adults, and were lowest in recently fledged birds.

Identification of a new VP4 serotype of human rotaviruses

A new VP4 gene allele was identified by sequencing of two rotavirus recovered from infants with diarrhea. Strains HAL1166 (a VP7 serotype 8 human rotavirus from Finland) and PA169 (a VP7 serotype 6 human rotavirus from Italy) present 22-43% nucleotide sequence divergence and 14-45% amino acid divergence in the VP4 gene with rotaviruses belonging to various VP4 gene alleles previously reported. Cross-neutralization analysis between PA169 and rotaviruses belonging to the other recognized VP4 (P) serotypes had previously shown that none of them was similar to PA169. Hyperimmune serum prepared against a reassortant with the VP4 gene of strain PA169 and the VP7 gene of serotype 2 strain DS1 failed to neutralize previously recognized human rotavirus VP4 serotypes, indicating that PA169 represents a new VP4 serotype specificity. In addition, one of four neutralizing monoclonal antibodies directed to the VP4 of PA169 was specific for this virus, while three others had very limited cross-reactivity with rotaviruses possessing different VP4s.

A new serotype of the outer capsid protein VP4 shared by an unusual human rotavirus strain Ro1845 and canine rotaviruses

The VP4 protein of human rotavirus (HRV) strain Ro1845 and canine rotavirus strains K9 and CU-1 exhibited greater than 98% amino acid identity within their group, but showed less identity with VP4 proteins of other HRV and animal rotavirus strains, the simian rotavirus strain RRV VP4 being most similar to them (90% amino acid identity). To exclude the possibility that these three strains were members of the RRV VP4 serotype P3, neutralization studies were performed using antisera to reassortant viruses containing the VP4 gene from each of Ro1845, CU-1 and RRV. The result established close antigenic similarity among the VP4 proteins of Ro1845, K9 and CU-1 and revealed only a marginal degree of similarity between the VP4 proteins of these three strains and that of strain RRV. These sequence and serological data suggest that the VP4 proteins of Ro1845, K9 and CU-1 represent a new P serotype which we propose to assign P13.

Distribution of VP4 gene alleles in human rotaviruses by using probes to the hyperdivergent region of the VP4 gene

The rotavirus VP4 protein elicits the production of neutralizing antibodies and is known to play a role in inducing resistance to disease. At least five human rotavirus VP4 gene alleles have been described on the basis of antigenic polymorphism and/or nucleotide sequence differences. In the present study, we developed cDNA probes directed at the hyperdivergent region of the VP4 gene of the five described human rotavirus VP4 alleles (Wa, DS1, M37, AU228, and 69M) and used them in hybridization assays with human rotavirus strains from Latin America and Europe to determine the distribution of the VP4 gene alleles in nature. The Wa-like allele was detected most frequently, occurring in 57% of the 402 rotavirus strains tested, and the DS1-like allele was the next most common, occurring in 14% of the strains tested. The M37- and AU228-like alleles were detected in only 4 and 3% of the rotavirus strains tested, respectively, whereas the 69M-like VP4 gene allele was not detected. Several rotavirus strains from Europe did not react with any of the VP4 gene probes, although they did hybridize to a probe generated from a representative strain from the group. These data indicate the global distribution of various VP4 gene alleles and raise the possibility that other, unrecognized human VP4 alleles exist in nature because almost one-fourth of the strains could not be classified into any of the established VP4 groups.

Mechanism of irreversible inhibition of O2 evolution in photosystem II by Tris(hydroxymethyl)aminomethane

The dark reaction of tris(hydroxymethyl)aminomethane (Tris) with the O2-evolving center of photosystem II (PSII) in the S1 state causes irreversible inhibition of O2 evolution. Similar inhibition is observed for several other amines: NH3, CH3NH2, (CH3)2NH, ethanolamine, and 2-amino-2-ethyl-1,3-propanediol. In PSII membranes, both depleted of the 17- and 23-kDa polypeptides and undepleted, the rate of reaction of Tris depends inversely upon the Cl- concentration. However, the rate of reaction of Tris is about 2-fold greater with PSII membranes depleted of the 17- and 23-kDa polypeptides than with undepleted PSII membranes. We have used low-temperature electron paramagnetic resonance (EPR) spectroscopy to study the effect of Tris on the oxidation state of the Mn complex in the O2-evolving center, to monitor the electron-donation reactions in Tris-treated samples, and to observe any loss of the Mn complex (forming Mn2+ ions) after Tris treatment. We find that Tris treatment causes loss of electron-donation ability from the Mn complex at the same rate as inhibition of O2 evolution and that Mn2+ ions are released. We conclude that Tris reduces the Mn complex to labile Mn2+ ions, without generating any kinetically stable, partially reduced intermediates, and that the reaction occurs at the Cl(-)-sensitive site previously characterized in studies of the reversible inhibition of O2 evolution by amines.

Identification of human rotavirus serotype by hybridization to polymerase chain reaction-generated probes derived from a hyperdivergent region of the gene encoding outer capsid protein VP7

We have synthesized 32P-labeled hybridization probes from a hyperdivergent region (nucleotides 51 to 392) of the rotavirus gene encoding the VP7 glycoprotein by using the polymerase chain reaction method. Both RNA (after an initial reverse transcription step) and cloned cDNA from human rotavirus serotypes 1 through 4 could be used as templates to amplify this region. High-stringency hybridization of each of the four probes to rotavirus RNAs dotted on nylon membranes allowed the specific detection of corresponding sequences and thus permitted identification of the serotype of the strains dotted. The procedure was useful when applied to rotaviruses isolated from field studies.

A method for the treatment of lead poisoning in the mute swan (Cygnus olor) and its long-term success

A method for the treatment of lead poisoning in mute swans (Cygnus olor) is described. Chelation therapy, using sodium calcium edetate, was successful in resolving the clinical signs of lead poisoning in 49% of cases. Individually ringed swans were monitored after their release to the wild, in order to assess the long-term benefits of treatment. Re-sighting and recovery data suggested that at least 22% of swans treated for lead poisoning survived the first 2 years. The results indicate that despite treatment, once a swan becomes lead poisoned its chances of survival are reduced by 59% compared with untreated swans living in flocks.

A stepmother in the family

With the growing number of stepfamilies, more and more women find themselves in the role of stepmother. Nurses can help the stepmother develop realistic expectations and, through support, can help these women meet the daily challenges of family life.

Dot hybridization assay for distinction of rotavirus serotypes

We have developed a hybridization assay that permits distinction of rotavirus serotypes 1, 2, 3, and 4. The serotype of rotaviruses from stool samples or tissue culture was recognized by hybridization of specific probes to (i) blots of viral double-stranded RNAs electrophoresed in agarose gels (Northern blots) or (ii) heat-denatured double-stranded RNAs directly dotted on nylon membranes. The probes consisted of 32P-labeled cDNA synthesized by reverse transcription of in vitro derived rotavirus mRNA from rotavirus serotypes 1 to 4. To prepare these probes, mRNAs were primed with a 17-mer nucleotide common to all four serotypes whose sequence is complementary to bases 375 to 391 of the rotavirus gene encoding the VP7 glycoprotein (gene 8 or 9 depending on the rotavirus strain). The resulting downstream transcripts encompassed areas of major sequence divergence among the four serotypes. Hybridization at high stringency (50 degrees C, 50% formamide, 4 x SSC [1 x SSC is 0.15 M NaCl plus 0.015 M sodium citrate]) was performed for 16 to 48 h. Autoradiograms of the washed membranes allowed recognition of the rotavirus serotype present in the blotted or dotted specimens since each of them hybridized preferentially to one of the four probes. Twenty-four laboratory specimens and 103 clinical specimens from Washington, D.C., Venezuela, and Chile were "serotyped" with this assay. The results were similar to those obtained with a monoclonal antibody serotyping assay.

Genetic stability of rotaviruses recovered from asymptomatic neonatal infections

The sequence of the VP7 gene from 19 rotavirus strains recovered from asymptomatically infected newborn infants was determined by direct analysis of transcript RNAs synthesized from virus present in the stool. For five viruses the entire VP7 gene was sequenced, whereas in the remaining instances only a portion of the gene could be sequenced. In 19 specimens collected over a 4-year period, only five nucleotide substitutions were detected. None of them resulted in an amino acid substitution. Examination of a 306-nucleotide segment of gene 4 in 11 specimens yielded similar results. These results suggest that the mutation rate of rotaviruses in nature is lower than that of single-stranded RNA viruses such as poliovirus and influenza virus.

Relative frequencies of rotavirus serotypes 1, 2, 3, and 4 in Venezuelan infants with gastroenteritis

We have used a recently developed monoclonal antibody enzyme-linked immunosorbent assay (K. Taniguchi, T. Urasawa, Y. Morita, H. B. Greenberg, and S. Urasawa, J. Infect. Dis. 155:1159-1166, 1987) for serotyping rotaviruses recovered from 134 Venezuelan infants over a period of 15 months. One hundred and nine of the specimens were typed with the following distribution: serotype 1, 48%; serotype 2, 16%; serotype 3, 22%; and serotype 4, 14%. Three specimens reacted with two different monoclonal antibodies. In addition, 6 specimens (5%) containing enough outer capsid antigen could not be typed; partial RNA sequence analysis of the glycoprotein gene from three of these six strains failed to reveal sequence differences with prototype strains that could be serotyped with the monoclonal antibodies. Variations in the recovery rates of the different serotypes were observed. Serotypes 2, 3, and 4 predominated at the beginning of the study, and serotype 1 predominated at the end of the study. Diarrheal illness appeared to be more prolonged in infants shedding rotavirus serotypes 1 and 3 than in those shedding serotypes 2 and 4.

Replication of encephalomyocarditis virus in various mammalian cell types

Recently, the biological and biochemical characteristics of EMC virus have received considerable attention, but little is known concerning the relative susceptibility of various mammalian cells to EMC virus. In this study, a variety of mammalian cell types was evaluated for susceptibility to the M strain of EMC virus by comparing peak viral titers, time course of infection, plaquing efficiency, and formation of viral antigens. Infection of all murine and guinea pig cell types resulted in substantial virus replication and induction of viral antigens in greater than 95% of cells. Human cell lines supported replication with a slower time course, but significant increases in viral yield and plaquing efficiency occurred with viral adaptation following successive replication cycles in human cells. All rat cell lines were relatively resistant to EMC virus infection and replication, and less than 1% of rat cells expressed viral antigens. Attempts were unsuccessful to adapt virus by successive replication cycles in rat cells. The possible reasons for the relative resistance of rat cells are currently under investigation.

Effect of protective helmet mass on head/neck dynamics

The crash helmet which provides protection against injury due to direct head impact may actually contribute to injury in indirect head impact (e.g., hyperflexion or "whiplash") situations because of the added mass of the helmet on the head/neck system. It has been suggested that it may be possible to reduce this hyperflexion/hyperextension injury hazard while retaining the beneficial protection against direct impact through use of the helmet restraining collars, such as styrofoam or inflatable airbags. These claims are quantitatively and qualitatively examined and discussed in this paper. The UCIN HEAD/NECK computer stimulation model is used for the quantitative analysis. It is shown that the helmet can indeed contribute to the hyperflexion/hyperextension injury hazard and that the proposed restraining devices can potentially provide protection against this hazard.