Preexposure prophylaxis with antiretroviral agents has been shown to reduce the transmission of human immunodeficiency virus (HIV) among men who have sex with men; however, the efficacy among ...heterosexuals is uncertain.
We randomly assigned HIV-seronegative men and women to receive either tenofovir disoproxil fumarate and emtricitabine (TDF-FTC) or matching placebo once daily. Monthly study visits were scheduled, and participants received a comprehensive package of prevention services, including HIV testing, counseling on adherence to medication, management of sexually transmitted infections, monitoring for adverse events, and individualized counseling on risk reduction; bone mineral density testing was performed semiannually in a subgroup of participants.
A total of 1219 men and women underwent randomization (45.7% women) and were followed for 1563 person-years (median, 1.1 years; maximum, 3.7 years). Because of low retention and logistic limitations, we concluded the study early and followed enrolled participants through an orderly study closure rather than expanding enrollment. The TDF-FTC group had higher rates of nausea (18.5% vs. 7.1%, P<0.001), vomiting (11.3% vs. 7.1%, P=0.008), and dizziness (15.1% vs. 11.0%, P=0.03) than the placebo group, but the rates of serious adverse events were similar (P=0.90). Participants who received TDF-FTC, as compared with those who received placebo, had a significant decline in bone mineral density. K65R, M184V, and A62V resistance mutations developed in 1 participant in the TDF-FTC group who had had an unrecognized acute HIV infection at enrollment. In a modified intention-to-treat analysis that included the 33 participants who became infected during the study (9 in the TDF-FTC group and 24 in the placebo group; 1.2 and 3.1 infections per 100 person-years, respectively), the efficacy of TDF-FTC was 62.2% (95% confidence interval, 21.5 to 83.4; P=0.03).
Daily TDF-FTC prophylaxis prevented HIV infection in sexually active heterosexual adults. The long-term safety of daily TDF-FTC prophylaxis, including the effect on bone mineral density, remains unknown. (Funded by the Centers for Disease Control and Prevention and the National Institutes of Health; TDF2 ClinicalTrials.gov number, NCT00448669.).
Australia has the highest historically recorded rate of mammalian extinction in the world, with 34 terrestrial species declared extinct since European colonization in 1788. Among Australian mammals, ...rodents have been the most severely affected by these recent extinctions; however, given a sparse historical record, the scale and timing of their decline remain unresolved. Using museum specimens up to 184 y old, we generate genomic-scale data from across the entire assemblage of Australian hydromyine rodents (i.e., eight extinct species and their 42 living relatives). We reconstruct a phylogenomic tree for these species spanning ∼5.2 million years, revealing a cumulative total of 10 million years (>10%) of unique evolutionary history lost to extinction within the past ∼150 y. We find no evidence for reduced genetic diversity in extinct species just prior to or during decline, indicating that their extinction was extremely rapid. This suggests that populations of extinct Australian rodents were large prior to European colonization, and that genetic diversity does not necessarily protect species from catastrophic extinction. In addition, comparative analyses suggest that body size and biome interact to predict extinction and decline, with larger species more likely to go extinct. Finally, we taxonomically resurrect a species from extinction, Gould's mouse (
Waterhouse, 1839), which survives as an island population in Shark Bay, Western Australia (currently classified as
Waite, 1896). With unprecedented sampling across a radiation of extinct and living species, we unlock a previously inaccessible historical perspective on extinction in Australia. Our results highlight the capacity of collections-based research to inform conservation and management of persisting species.
Maintaining high rates of photosynthesis in leaves requires efficient movement of CO2 from the atmosphere to the mesophyll cells inside the leaf where CO2 is converted into sugar. CO2 diffusion ...inside the leaf depends directly on the structure of the mesophyll cells and their surrounding airspace, which have been difficult to characterize because of their inherently three-dimensional organization. Yet faster CO2 diffusion inside the leaf was probably critical in elevating rates of photosynthesis that occurred among angiosperm lineages. Here we characterize the three-dimensional surface area of the leaf mesophyll across vascular plants. We show that genome size determines the sizes and packing densities of cells in all leaf tissues and that smaller cells enable more mesophyll surface area to be packed into the leaf volume, facilitating higher CO2 diffusion. Measurements and modelling revealed that the spongy mesophyll layer better facilitates gaseous phase diffusion while the palisade mesophyll layer better facilitates liquid-phase diffusion. Our results demonstrate that genome downsizing among the angiosperms was critical to restructuring the entire pathway of CO2 diffusion into and through the leaf, maintaining high rates of CO2 supply to the leaf mesophyll despite declining atmospheric CO2 levels during the Cretaceous.
Maintaining high rates of photosynthesis in leaves requires efficient movement of CO
from the atmosphere to the mesophyll cells inside the leaf where CO
is converted into sugar. CO
diffusion inside ...the leaf depends directly on the structure of the mesophyll cells and their surrounding airspace, which have been difficult to characterize because of their inherently three-dimensional organization. Yet faster CO
diffusion inside the leaf was probably critical in elevating rates of photosynthesis that occurred among angiosperm lineages. Here we characterize the three-dimensional surface area of the leaf mesophyll across vascular plants. We show that genome size determines the sizes and packing densities of cells in all leaf tissues and that smaller cells enable more mesophyll surface area to be packed into the leaf volume, facilitating higher CO
diffusion. Measurements and modelling revealed that the spongy mesophyll layer better facilitates gaseous phase diffusion while the palisade mesophyll layer better facilitates liquid-phase diffusion. Our results demonstrate that genome downsizing among the angiosperms was critical to restructuring the entire pathway of CO
diffusion into and through the leaf, maintaining high rates of CO
supply to the leaf mesophyll despite declining atmospheric CO
levels during the Cretaceous.
The bias of a two-dimensional view Théroux‐Rancourt, Guillaume; Earles, J. Mason; Gilbert, Matthew E. ...
New phytologist,
September 2017, Letnik:
215, Številka:
4
Journal Article
Recenzirano
Odprti dostop
The mesophyll surface area exposed to intercellular air space per leaf area (S
m) is closely associated with CO2 diffusion and photosynthetic rates. S
m is typically estimated from two-dimensional ...(2D) leaf sections and corrected for the three-dimensional (3D) geometry of mesophyll cells, leading to potential differences between the estimated and actual cell surface area.
Here, we examined how 2D methods used for estimating S
m compare with 3D values obtained from high-resolution X-ray microcomputed tomography (microCT) for 23 plant species, with broad phylogenetic and anatomical coverage.
Relative to 3D, uncorrected 2D S
m estimates were, on average, 15–30% lower. Two of the four 2D S
m methods typically fell within 10% of 3D values. For most species, only a few 2D slices were needed to accurately estimate S
m within 10% of the whole leaf sample median. However, leaves with reticulate vein networks required more sections because of a more heterogeneous vein coverage across slices.
These results provide the first comparison of the accuracy of 2D methods in estimating the complex 3D geometry of internal leaf surfaces. Because microCT is not readily available, we provide guidance for using standard light microscopy techniques, as well as recommending standardization of reporting S
m values.
Allopatric speciation has been difficult to examine among microorganisms, with prior reports of endemism restricted to sub-genus level taxa. Previous microbial community analysis via 16S rRNA gene ...sequencing of 925 geothermal springs from the Taupō Volcanic Zone (TVZ), Aotearoa-New Zealand, revealed widespread distribution and abundance of a single bacterial genus across 686 of these ecosystems (pH 1.2-9.6 and 17.4-99.8 °C). Here, we present evidence to suggest that this genus, Venenivibrio (phylum Aquificota), is endemic to Aotearoa-New Zealand. A specific environmental niche that increases habitat isolation was identified, with maximal read abundance of Venenivibrio occurring at pH 4-6, 50-70 °C, and low oxidation-reduction potentials. This was further highlighted by genomic and culture-based analyses of the only characterised species for the genus, Venenivibrio stagnispumantis CP.B2
, which confirmed a chemolithoautotrophic metabolism dependent on hydrogen oxidation. While similarity between Venenivibrio populations illustrated that dispersal is not limited across the TVZ, extensive amplicon, metagenomic, and phylogenomic analyses of global microbial communities from DNA sequence databases indicates Venenivibrio is geographically restricted to the Aotearoa-New Zealand archipelago. We conclude that geographic isolation, complemented by physicochemical constraints, has resulted in the establishment of an endemic bacterial genus.
Persons with human immunodeficiency virus (HIV) who get and keep a suppressed viral load are unlikely to transmit HIV. Simple, practical interventions to help achieve HIV viral suppression that are ...easy and inexpensive to administer in clinical settings are needed. We evaluated whether a brief video containing HIV-related health messages targeted to all patients in the waiting room improved treatment initiation, medication adherence, and retention in care.
In a quasi-experimental trial all patients (N = 2,023) attending two HIV clinics from June 2016 to March 2017 were exposed to a theory-based, 29-minute video depicting persons overcoming barriers to starting treatment, taking medication as prescribed, and keeping medical appointments. New prescriptions at index visit, HIV viral load test results, and dates of return visits were collected through review of medical records for all patients during the 10 months that the video was shown. Those data were compared with the same variables collected for all patients (N = 1,979) visiting the clinics during the prior 10 months (August 2015 to May 2016). Among patients exposed to the video, there was an overall 10.4 percentage point increase in patients prescribed treatment (60.3% to 70.7%, p< 0.01). Additionally, there was an overall 6.0 percentage point improvement in viral suppression (56.7% to 62.7%, p< 0.01), however mixed results between sites was observed. There was not a significant change in rates of return visits (77.5% to 78.8%). A study limitation is that, due to the lack of randomization, the findings may be subject to bias and secular trends.
Showing a brief treatment-focused video in HIV clinic waiting rooms can be effective at improving treatment initiation and may help patients achieve viral suppression. This feasible, low resource-reliant video intervention may be appropriate for adoption by other clinics treating persons with HIV.
http://www.ClinicalTrials.gov (NCT03508310).
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