A Combination of Amino Acid Mutations Leads to Resistance to Multiple Nucleoside Analogs in Reverse Transcriptases from HIV-1 Subtypes B and C.

Resistance to anti-HIV drugs has been a problem from the beginning of antiviral drug treatments. The recent expansion of combination antiretroviral therapy worldwide has led to an increase in resistance to antiretrovirals; understanding the mechanisms of resistance is increasingly important. In this study, we analyzed reverse transcriptase (RT) variants based on sequences derived from an individual who had low-level rebound viremia while undergoing therapy with abacavir, azidothymidine (AZT) (zidovudine), and (-)-l-2',3'-dideoxy-3'-thiacytidine (3TC) (lamivudine). The RT had mutations at positions 64, 67, 70, 184, and 219 and a threonine insertion after amino acid 69 in RT. The virus remained partially susceptible to the nucleoside RT inhibitor (NRTI) regimen. We show how these mutations affect the ability of NRTIs to inhibit DNA synthesis by RT. The presence of the inserted threonine reduced the susceptibility of the RT mutant to inhibition by tenofovir.

Dimerization of the SP1 Region of HIV-1 Gag Induces a Helical Conformation and Association into Helical Bundles: Implications for Particle Assembly.

UNLABELLED: HIV-1 immature particle (virus-like particle [VLP]) assembly is mediated largely by interactions between the capsid (CA) domains of Gag molecules but is facilitated by binding of the nucleocapsid (NC) domain to nucleic acid. We previously investigated the role of SP1, a "spacer" between CA and NC, in VLP assembly. We found that small changes in SP1 drastically disrupt assembly and that a peptide representing the sequence around the CA-SP1 junction is helical at high but not low concentrations. We suggested that by virtue of such a concentration-dependent change, this region could act as a molecular switch to activate HIV-1 Gag for VLP assembly. A leucine zipper domain can replace NC in Gag and still lead to the efficient assembly of VLPs. We find that SP1 mutants also disrupt assembly by these Gag-Zip proteins and have now studied a small fragment of this Gag-Zip protein, i.e., the CA-SP1 junction region fused to a leucine zipper. Dimerization of the zipper places SP1 at a high local concentration, even at low total concentrations. In this context, the CA-SP1 junction region spontaneously adopts a helical conformation, and the proteins associate into tetramers. Tetramerization requires residues from both CA and SP1. The data suggest that once this region becomes helical, its propensity to self-associate could contribute to Gag-Gag interactions and thus to particle assembly. There is complete congruence between CA/SP1 sequences that promote tetramerization when fused to zippers and those that permit the proper assembly of full-length Gag; thus, equivalent interactions apparently participate in VLP assembly and in SP1-Zip tetramerization. IMPORTANCE: Assembly of HIV-1 Gag into virus-like particles (VLPs) appears to require an interaction with nucleic acid, but replacement of its principal nucleic acid-binding domain with a dimerizing leucine zipper domain leads to the assembly of RNA-free VLPs. It has not been clear how dimerization triggers assembly. Results here show that the SP1 region spontaneously switches to a helical state when fused to a leucine zipper and that these helical molecules further associate into tetramers, mediated by interactions between hydrophobic faces of the helices. Thus, the correct juxtaposition of the SP1 region makes it "association competent." Residues from both capsid and SP1 contribute to tetramerization, while mutations disrupting proper assembly in Gag also prevent tetramerization. Thus, this region is part of an associating interface within Gag, and its intermolecular interactions evidently help stabilize the immature Gag lattice. These interactions are disrupted by proteolysis of the CA-SP1 junction during virus maturation.

How does the close surgical margin impact recurrence and survival when treating oral squamous cell carcinoma?

PURPOSE: The surgical margin is the main prognostic factor over which the surgeon has control during resection of oral squamous cell carcinoma (OSCC). This study examined the association between surgical excision margins of patients with OSCC and outcomes of disease-free and overall survival. MATERIALS AND METHODS: The authors implemented a retrospective cohort study. The sample was composed of patients with OSCC having resection as their initial treatment. The predictor variable was the pathologic surgical margin, defined as clear (>5 mm), close (1 to 5 mm), or involved (<1 mm). The outcome variables were disease-free (absence of locoregional recurrence) and overall survival. Data were analyzed using Kaplan-Meier survival curves and Cox regression hazard model. RESULTS: The sample was composed of 54 patients with a mean age of 60.5 years (range, 19 to 85 yr) and 26% were women. The 2- and 5-year overall survival rates were 59 and 50%, respectively. The clear surgical margin group showed higher disease-free survival rates than patients with close and involved margins (5-yr probability, 0.78 vs 0.43 and 0.29; P = .014) and a trend toward increased overall survival at 2 and 5 years (P = .093). CONCLUSION: The results suggest that the presence of a close surgical margin (1 to 5 mm) is an adverse risk feature comparable to an involved margin and therefore is associated with decreased disease-free and overall survival. Future studies are needed to replicate these findings before they can be used as a basis for clinical recommendations.

Walking the Labyrinth: Considering Mental Health Consumer Experience, Meaning Making, and the Illumination of the Sacred in a Forensic Mental Health Setting.

The purpose of this study is to explore the unique meaning and experience associated with walking a unicursal seven circuit outdoor Chartress Labyrinth and 11 circuit indoor Chartress Labyrinth for persons residing at a forensic mental health care facility. Over the past several decades labyrinths have enjoyed something of a renaissance and are often utilized by spiritual care practitioners and health care clinicians in order to support reflection, stress reduction, and the exploration of personal wellness in a sacred setting. Labyrinths are used in many settings including places of worship, hospitals, long-term care facilities, and parks. While labyrinths are becoming more prevalent, an understanding of their impact, particularly in the mental health context, is limited. This qualitative study supports a novel investigation of the meaning associated with participation in walking a labyrinth for persons residing at a forensic mental health care facility. The study design is a qualitative methodology involving transcribed interviews with 12 individuals resident at the Southwest Centre for Forensic Mental Health Care who participated in the 'Walking the Labyrinth' program as facilitated by spiritual care staff. A standardized interview protocol was utilized and the collected data was coded for themes. Several methods were employed to establish trustworthiness including triangulation by analyst and by theory/perspective. Member checking was also utilized in order to further validate the themes. Recommendations related to potential health care applications for labyrinths are identified. These include a focus upon the linkage between mental health care planning and labyrinth participation.

The LTAR Grazing Land Common Experiment at the Great Basin.

The Long-Term Agroecosystem Research Network (LTAR), through its Common Experiment (CE) framework, contrasts prevailing and alternative agricultural practices for efficacy and sustainability within the indicator domains of environment, productivity, economics, and society. Invasive species, wildfire, and climate change are principal threats to Great Basin agroecosystems. Prescribed grazing may be an effective tool for restoring lands degraded by these disturbances. At the Great Basin (GB) LTAR site headquartered in Boise, ID, our contribution to the CE contrasts a prevailing (PRV), cattle grazing practice of fixed moderate stocking and duration with an alternative (ALT), prescribed grazing practice called high-intensity low-frequency (HILF) grazing where stocking and duration are tailored to suppress invasive annual grass competition with native or desirable plant species and thus promote recovery of rangelands degraded by annual grass invasion and recurrent wildfire. Preliminary results indicate cheatgrass density and fuel height have been reduced in ALT-treated paddocks compared to PRV paddocks. Since its inception in 2014, our GB CE has been a research co-production effort among ranchers, public land managers, and researchers. Future directions for this research will center on expanding the experiment to multiple study areas to better address the scope of the annual grass/wildfire problem. We expect this research will lead to effective and sustainable grazing practices for restoring >41 million hectares of degraded rangelands in the Great Basin and other areas of the western United States.

Resource selection by Sarda cattle in a Mediterranean silvopastoral system.

Knowledge of how grazing cattle utilize heterogeneous landscapes in Mediterranean silvopastoral areas is scarce. Global positioning systems (GPS) to track animals, together with geographic information systems (GIS), can relate animal distribution to landscape features. With the aim to develop a general spatial model that provides accurate prediction of cattle resource selection patterns within a Mediterranean mountainous silvopastoral area, free-roaming Sarda cows were fitted with GPS collars to track their spatial behaviors. Resource selection function models (RSF) were developed to estimate the probability of resource use as a function of environmental variables. A set of over 500 candidate RSF models, composed of up to five environmental predictor variables, were fitted to data. To identify a final model providing a robust prediction of cattle resource selection pattern across the different seasons, the 10 best models (ranked on the basis of the AIC score) were fitted to seasonal data. Prediction performance of the models was evaluated with a Spearman correlation analysis using the GPS position data sets previously reserved for model validation. The final model emphasized that watering point, elevation, and distance to fences were important factors affecting cattle resource-selection patterns. The prediction performances (as Spearman rank correlation scores) of the final model, when fitted to each season, ranged between 0.7 and 0.94. The cows were more likely to select areas lower in elevation and farther from the watering point in winter than in summer (693 ± 1 m and 847 ± 13 m vs. 707 ± 1 m and 635 ± 21 m, respectively), and in spring opted for the areas furthest from the water (963 ± 12). Although caution should be exercised in generalizing to other silvopastoral areas, the satisfactory Spearman correlations scores from the final RSF model applied to different seasons indicate resource selection function is a powerful predictive model. The relative importance of the individual predictors within the model varied among the different seasons, demonstrating the RSF model's ability to interpret changes in animal behavior at different times of the year. The RSF model has proven to be a useful tool to interpret the spatial behaviors of cows grazing in Mediterranean silvopastoral areas and could therefore be helpful in managing and preserving ecosystem services of these areas.

HIV-1 and HIV-2 reverse transcriptases: different mechanisms of resistance to nucleoside reverse transcriptase inhibitors.

As anti-HIV therapy becomes more widely available in developing nations, it is clear that drug resistance will continue to be a major problem. The related viruses HIV-1 and HIV-2 share many of the same resistance pathways to nucleoside reverse transcriptase inhibitors (NRTIs). However, clinical data suggest that while HIV-1 reverse transcriptase (RT) usually uses an ATP-dependent excision pathway to develop resistance to the nucleoside analog zidovudine (AZT), HIV-2 RT does not appear to use this pathway. We previously described data that suggested that wild-type (WT) HIV-2 RT has a much lower ability to excise AZT monophosphate (AZTMP) than does WT HIV-1 RT and suggested that this is the reason that HIV-2 RT more readily adopts an exclusion pathway against AZT triphosphate (AZTTP), while HIV-1 RT is better able to exploit the ATP-dependent pyrophosphorolysis mechanism. However, we have now done additional experiments, which show that while HIV-1 RT can adopt either an exclusion- or excision-based resistance mechanism against AZT, HIV-2 RT can use only the exclusion mechanism. All of our attempts to make HIV-2 RT excision competent did not produce an AZT-resistant RT but instead yielded RTs that were less able to polymerize than the WT. This suggests that the exclusion pathway is the only pathway available to HIV-2.

Indicators of water use efficiency across diverse agroecosystems and spatiotemporal scales.

Understanding the relationship between water and production within and across agroecosystems is essential for addressing several agricultural challenges of the 21st century: providing food, fuel, and fiber to a growing human population, reducing the environmental impacts of agricultural production, and adapting food systems to climate change. Of all human activities, agriculture has the highest demand for water globally. Therefore, increasing water use efficiency (WUE), or producing 'more crop per drop', has been a long-term goal of agricultural management, engineering, and crop breeding. WUE is a widely used term applied across a diverse array of spatial scales, spanning from the leaf to the globe, and over temporal scales ranging from seconds to months to years. The measurement, interpretation, and complexity of WUE varies enormously across these spatial and temporal scales, challenging comparisons within and across diverse agroecosystems. The goals of this review are to evaluate common indicators of WUE in agricultural production and assess tradeoffs when applying these indicators within and across agroecosystems amidst a changing climate. We examine three questions: (1) what are the uses and limitations of common WUE indicators, (2) how can WUE indicators be applied within and across agroecosystems, and (3) how can WUE indicators help adapt agriculture to climate change? Addressing these agricultural challenges will require land managers, producers, policy makers, researchers, and consumers to evaluate costs and benefits of practices and innovations of water use in agricultural production. Clearly defining and interpreting WUE in the most scale-appropriate way is crucial for advancing agroecosystem sustainability.

Foamy retrovirus integrase contains a Pol dimerization domain required for protease activation.

Unlike orthoretroviruses, foamy retroviruses (FV) synthesize Pol independently of Gag. The FV Pol precursor is cleaved only once between reverse transcriptase (RT) and integrase (IN) by the protease (PR), resulting in a PR-RT and an IN protein. Only the Pol precursor, not the cleaved subunits, is packaged into virions. Like orthoretroviral PRs, FV PR needs to dimerize to be active. Previously, we showed that a Pol mutant lacking IN has defects in PR activity and Pol packaging into virions. We now show that introduction of a leucine zipper (zip) dimerization motif in an IN truncation mutant can restore PR activity, leading to Pol processing in cells. However, these zip mutants neither cleave Gag nor incorporate Pol into virions. We propose that IN is required for Pol dimerization, which is necessary for the creation of a functional PR active site.

Solution properties of murine leukemia virus gag protein: differences from HIV-1 gag.

Immature retrovirus particles are assembled from the multidomain Gag protein. In these particles, the Gag proteins are arranged radially as elongated rods. We have previously characterized the properties of HIV-1 Gag in solution. In the absence of nucleic acid, HIV-1 Gag displays moderately weak interprotein interactions, existing in monomer-dimer equilibrium. Neutron scattering and hydrodynamic studies suggest that the protein is compact, and biochemical studies indicate that the two ends can approach close in three-dimensional space, implying the need for a significant conformational change during assembly. We now describe the properties of the Gag protein of Moloney murine leukemia virus (MLV), a gammaretrovirus. We found that this protein is very different from HIV-1 Gag: it has much weaker protein-protein interaction and is predominantly monomeric in solution. This has allowed us to study the protein by small-angle X-ray scattering and to build a low-resolution molecular envelope for the protein. We found that MLV Gag is extended in solution, with an axial ratio of ∼7, comparable to its dimensions in immature particles. Mutational analysis suggests that runs of prolines in its matrix and p12 domains and the highly charged stretch at the C terminus of its capsid domain all contribute to this extended conformation. These differences between MLV Gag and HIV-1 Gag and their implications for retroviral assembly are discussed.

Water quality effects of herded stream crossings by domestic sheep bands.

Livestock impacts on total suspended solids (TSS) and pathogen (e.g., ) levels in rangeland streams are a serious concern worldwide. Herded stream crossings by domestic sheep () are periodic, necessary managerial events on high-elevation rangelands, but their impacts on stream water quality are largely unknown. We evaluated the effects of herded, one-way crossings by sheep bands (about 2000 individuals) on TSS and concentration and load responses in downstream waters. Crossing trials were conducted during the summers of 2005 and 2006 on two reaches within each of three perennial streams in the Centennial Mountains of eastern Idaho and southwestern Montana. Water samples were collected at 2-min intervals at an upstream background station and at stations 25, 100, 500, and 1500 m downstream just before and during each crossing trial. Crossings produced substantial increases in TSS and concentrations and loads downstream, but these concentration increases were localized and short lived. Maximum TSS concentration was highest 25 m downstream, declined as a function of downstream distance, and at 500 m downstream was similar to background. Post-peak TSS concentrations at all downstream stations decreased to <25 mg L within 24 to 48 min after reaching their maxima. Findings for concentration and load responses were similar to that of TSS but less clear cut. Stream-crossing sheep do affect water quality; therefore, producers and resource managers should continue to evaluate the efficacy of herdsmanship techniques for reducing water quality impact.

Evaluation of a sustainable remediation option: beneficial reuse of petroleum-contaminated sediment as an energy source.

The characteristics of petroleum-contaminated sediment (PCS) have been evaluated to assess whether the practice of its beneficial reuse as a sole or supplemental energy source is sustainable relative to other sediment remediation options such as monitored natural recovery (MNR), capping, or off-site disposal. Some of these remediation options for PCS are energy-intensive and/or require land utilization. The energy and compositional analysis results indicate a low carbon content (15-17%(wt)) and corresponding low energy values of 5,200 kJ/kg (2,200 Btu/lb) to 5,600 kJ/kg (2,400 Btu/lb). However, given other decision-making criteria, the sediment may contain enough value to be added as a supplemental fuel given that it is normally considered a waste product and is readily available. The thermogravimetric profiles obtained under both combustion and pyrolytic conditions showed that the sulfur contents were comparable to typical low sulfur bituminous or lignite coals found in the United States, and most of the volatiles could be vaporized below 750 degrees C. The heavy metal concentrations determined before and after combustion of the PCS indicated that further engineering controls may be required for mercury, arsenic, and lead. Due to the potential for reduction of public health and environmental threats, potential economic savings, and conservation of natural resources (petroleum and land), removal of PCS by dredging and beneficial reuse as a supplemental fuel clearly has merit to be considered as a sustainable remediation option.

Development and acceptability of a mobile health application integrated with the electronic heath record for treatment of chronic insomnia disorder.

STUDY OBJECTIVES: To describe the development and feasibility of a cognitive behavioral therapy for insomnia (CBT-I) program delivered via personal digital devices and fully integrated with the electronic health record (EHR). METHODS: A multidisciplinary team of clinicians and members of our Center for Digital Health collaborated to develop a Chronic Insomnia Interactive Care Plan (ChI-ICP), an application that provides personalized and just in time education and promotes self-management using CBT-I concepts, and is activated from and fully integrated into the EHR. Following development, we evaluated patient engagement and workflows, assessed changes to provider workload, and examined outcomes on measures of insomnia during a pilot deployment of the application. RESULTS: A total of 222 patients were enrolled and 179 engaged with the plan during the 3-month pilot program. Enrolled patients generated an average of 3.9 ± 2.3 In Basket messages, most being automated notifications related to noncompletion of assigned tasks, while only a few were related to patients requesting additional training or help with insomnia. Sleep efficiency improved from baseline until the completion of the program from 74.5% ± 16.7% to 87.6% ± 10.8% (P = .001), and the Insomnia Severity Index improved from 14.9 ± 5.22 to 11.6 ± 4.80 (P = .006). CONCLUSIONS: In this pilot implementation of an integrated ChI-ICP, patient engagement was favorable, workflows and workload were not significantly burdensome for the care teams, and initial evaluation of efficacy was favorable. This provides evidence for an application that is a scalable method to assist patients with chronic insomnia and future work should assess its efficacy in controlled trials. CITATION: Morgenthaler TI, Kolla BP, Anderson SE, et al. Development and acceptability of a mobile health application integrated with the electronic heath record for treatment of chronic insomnia disorder. J Clin Sleep Med. 2022;18(12):2785-2792.

Magnetic resonance spectroscopy outperforms perfusion in distinguishing between pseudoprogression and disease progression in patients with glioblastoma.

Background: There is a need to establish biomarkers that distinguish between pseudoprogression (PsP) and true tumor progression in patients with glioblastoma (GBM) treated with chemoradiation. Methods: We analyzed magnetic resonance spectroscopic imaging (MRSI) and dynamic susceptibility contrast (DSC) MR perfusion data in patients with GBM with PsP or disease progression after chemoradiation. MRSI metabolites of interest included intratumoral choline (Cho), myo-inositol (mI), glutamate + glutamine (Glx), lactate (Lac), and creatine on the contralateral hemisphere (c-Cr). Student T-tests and area under the ROC curve analyses were used to detect group differences in metabolic ratios and their ability to predict clinical status, respectively. Results: 28 subjects (63 ± 9 years, 19 men) were evaluated. Subjects with true progression (n = 20) had decreased enhancing region mI/c-Cr (P = .011), a marker for more aggressive tumors, compared to those with PsP, which predicted tumor progression (AUC: 0.84 [0.76, 0.92]). Those with true progression had elevated Lac/Glx (P = .0009), a proxy of the Warburg effect, compared to those with PsP which predicted tumor progression (AUC: 0.84 [0.75, 0.92]). Cho/c-Cr did not distinguish between PsP and true tumor progression. Despite rCBV (AUC: 0.70 [0.60, 0.80]) and rCBF (AUC: 0.75 [0.65, 0.84]) being individually predictive of tumor response, they added no additional predictive value when combined with MRSI metabolic markers. Conclusions: Incorporating enhancing lesion MRSI measures of mI/c-Cr and Lac/Glx into brain tumor imaging protocols can distinguish between PsP and true progression and inform patient management decisions.

Global application of an unoccupied aerial vehicle photogrammetry protocol for predicting aboveground biomass in non-forest ecosystems.

Non-forest ecosystems, dominated by shrubs, grasses and herbaceous plants, provide ecosystem services including carbon sequestration and forage for grazing, and are highly sensitive to climatic changes. Yet these ecosystems are poorly represented in remotely sensed biomass products and are undersampled by in situ monitoring. Current global change threats emphasize the need for new tools to capture biomass change in non-forest ecosystems at appropriate scales. Here we developed and deployed a new protocol for photogrammetric height using unoccupied aerial vehicle (UAV) images to test its capability for delivering standardized measurements of biomass across a globally distributed field experiment. We assessed whether canopy height inferred from UAV photogrammetry allows the prediction of aboveground biomass (AGB) across low-stature plant species by conducting 38 photogrammetric surveys over 741 harvested plots to sample 50 species. We found mean canopy height was strongly predictive of AGB across species, with a median adjusted R 2 of 0.87 (ranging from 0.46 to 0.99) and median prediction error from leave-one-out cross-validation of 3.9%. Biomass per-unit-of-height was similar within but different among, plant functional types. We found that photogrammetric reconstructions of canopy height were sensitive to wind speed but not sun elevation during surveys. We demonstrated that our photogrammetric approach produced generalizable measurements across growth forms and environmental settings and yielded accuracies as good as those obtained from in situ approaches. We demonstrate that using a standardized approach for UAV photogrammetry can deliver accurate AGB estimates across a wide range of dynamic and heterogeneous ecosystems. Many academic and land management institutions have the technical capacity to deploy these approaches over extents of 1-10 ha-1. Photogrammetric approaches could provide much-needed information required to calibrate and validate the vegetation models and satellite-derived biomass products that are essential to understand vulnerable and understudied non-forested ecosystems around the globe.

Optical filter effects on night vision goggle acuity and preservation of dark adaptation.

INTRODUCTION: The high output of night vision goggles (NVGs) can cause a loss of dark adaptation, resulting in suboptimal unaided vision. Optical filters have been designed to mitigate this problem by changing the overall output characteristics of the NVGs. METHODS: Several aspects of visual performance related to NVG use were studied in a repeated measures design, filters versus no filters. NVG acuity was assessed using a 25% contrast chart, while preservation of dark adaptation after NVG use was measured with a scotopic sensitivity tester (SST) and a low luminance acuity chart. Testing was accomplished at two light levels, roughly corresponding to starlight and quarter moon conditions. RESULTS: Use of the filters resulted in a statistically significant loss of acuity of about a 1/2 line (approximately 2.5 letters) at both light levels. The second part of the study identified a 47% improvement in preservation of dark adaptation under simulated starlight conditions and a 31% improvement under simulated quarter moon conditions with filter use; however, only the starlight finding was statistically significant. No significant differences in performance were seen with the low luminance chart. DISCUSSION: Despite a small loss of visual acuity with filter use, the improvement in retention of dark adaptation may be beneficial in certain operational environments. Aviators, airmen, and commanders should evaluate how the potential for slightly poorer visual acuity and improved recovery of dark adapted vision relates to their mission specific requirements prior to implementing use of NVG filters.

Corrective lens use and refractive error among United States Air Force aircrew.

Corrective lens use by military aviators is an important consideration in the design of head-mounted equipment. The United States Air Force (USAF) has periodically monitored lens use by aviators; however, it has been over a decade since the last study. We provide an update on the prevalence of corrective lenses and refractive error among USAF aircrew based on eyeglass orders processed through the Spectacle Request Transmission System (SRTS). Currently, 41% of active duty USAF pilots and 54% of other aircrew require corrective lenses to perform flight duties. Refractive errors are characterized by low to moderate levels of myopia with a mean spherical equivalent power of -1.01 diopters (D) for pilots and -1.68 D for others. Contact lenses, and more recently refractive surgery, reduce the number of aircrew that must rely on spectacles when flying; however, spectacle compatibility remains an important consideration in the cockpit.

Grazing behavior and production characteristics among cows differing in residual feed intake while grazing late season Idaho rangeland.

The objectives were to determine whether cows previously classified during a postweaning test as either low or high residual feed intake (LRFI or HRFI) differed in BW, BCS, and winter grazing activity while consuming poor-quality forage. Thirty Hereford × Angus (LRFI = 16; HRFI = 14) 2-yr-old mid- to late-gestation cows (pregnant with second calf) grazed sagebrush steppe for 78 d beginning 29 September 2015. BW and BCS were collected before and after grazing. Five cows of each RFI classification were fitted with global positioning system (GPS) collars on 16 November 2015 with data collection commencing 3 d later and continuing for 25 d in a 323-ha pasture. The GPS units collected location coordinates every 2 min from which total daily travel distance (DTD) was calculated. Visual counts for bite rate were obtained from collared cows over 8 d. Coordinate data, daily bite rate, BW, and BCS were analyzed as repeated measures using a mixed model, which included RFI group, day, and RFI group × day as fixed effects and cow within RFI group as the random effect. Change in BW and BCS was analyzed by ANOVA with RFI group as the main effect. Cow BCS and BW differed for both day (P < 0.0001) and day × RFI (P < 0.05). Body condition was less (P < 0.05) in LRFI cows at the beginning (5.8 ±â€…0.13 vs. 6.2 ±â€…0.14 BCS), but similar (P = 0.67) to HRFI at the end of the study (4.6 ±â€…0.13 vs. 4.6 ±â€…0.14). BW among the RFI groups did not differ (P = 0.20) prior to going to range. However, BW-change and BCS-change differed (P < 0.05) between RFI groups. Not only did the LRFI cows lose less BW (-50.0 ±â€…5.41 kg vs. -66.6 ±â€…5.78 kg) over the trial, they also were less variable with respect to BW loss. Cows did not differ (P > 0.21) by RFI for DTD or bite rate, but day was significant (P < 0.0001) with cows increasing bite rate as the season of year progressed (55.2 ±â€…5.63 bites/min for day 4 vs. 84.8 ±â€…5.32 bites/min for day 21) and increasing DTD as snow storms occurred. Although LRFI cows were leaner than HRFI cows at the commencement of the project, they lost less BW in a late season rangeland environment.

Structures of HIV-1 RT-DNA complexes before and after incorporation of the anti-AIDS drug tenofovir.

Tenofovir, also known as PMPA, R-9-(2-(phosphonomethoxypropyl)adenine, is a nucleotide reverse transcriptase (RT) inhibitor. We have determined the crystal structures of two related complexes of HIV-1 RT with template primer and tenofovir: (i) a ternary complex at a resolution of 3.0 A of RT crosslinked to a dideoxy-terminated DNA with tenofovir-diphosphate bound as the incoming substrate; and (ii) a RT-DNA complex at a resolution of 3.1 A with tenofovir at the 3' primer terminus. The tenofovir nucleotide in the tenofovir-terminated structure seems to adopt multiple conformations. Some nucleoside reverse transcriptase inhibitors, including 3TC and AZT, have elements ('handles') that project beyond the corresponding elements on normal dNTPs (the 'substrate envelope'). HIV-1 RT resistance mechanisms to AZT and 3TC take advantage of these handles; tenofovir's structure lacks handles that could protrude through the substrate envelope to cause resistance.