Quantifying the effect of shade on cuticle morphology and carbon isotopes of sycamores: present and past

PREMISE

Reconstructing the light environment and architecture of the plant canopy from the fossil record requires the use of proxies, such as those derived from cell wall undulation, cell size, and carbon isotopes. All approaches assume that plant taxa will respond predictably to changes in light environments. However, most species-level studies looking at cell wall undulation only consider "sun" or "shade" leaves; therefore, we need a fully quantitative taxon-specific method.

METHODS

We quantified the response of cell wall undulation, cell size, and carbon isotopes of Platanus occidentalis using two experimental setups: (1) two growth chambers at low and high light and (2) a series of outdoor growth experiments using green and black shade cloth at different densities. We then developed and applied a proxy for daily light integral (DLI) to fossil Platanites leaves from two early Paleocene floras from the San Juan Basin in New Mexico.

RESULTS

All traits responded to light environment. Cell wall undulation was the most useful trait for reconstructing DLI in the geological record. Median reconstructed DLI from early Paleocene leaves was ~44 mol m^-2  d^-1 , with values from 28 to 54 mol m^-2  d^-1 .

CONCLUSIONS

Cell wall undulation of P. occidentalis is a robust, quantifiable measurement of light environment that can be used to reconstruct the paleo-light environment from fossil leaves. The distribution of high DLI values from fossil leaves may provide information on canopy architecture; indicating that either (1) most of the canopy mass is within the upper portion of the crown or (2) leaves exposed to more sunlight are preferentially preserved.

Clinical Characteristics of Active Tuberculosis Diagnosed After Starting Treatment for Latent Tuberculosis Infection

Although rare, subclinical tuberculosis disease can be missed during evaluations for latent tuberculosis infection, and can manifest with symptoms during latent tuberculosis treatment. Among over 8000 patients treated for latent tuberculosis we found no evidence of acquired drug resistance, underscoring the safety of rifampin monotherapy for latent tuberculosis.

Seizures in Human Immunodeficiency Virus-Associated Cryptococcal Meningitis: Predictors and Outcomes

Background

Seizures commonly occur in patients with cryptococcal meningitis, yet risk factors and outcomes related to seizures are not well described.

Methods

We performed post hoc analyses on participants prospectively enrolled in 3 separate human immunodeficiency virus (HIV)-associated cryptococcal meningitis clinical trials during 2010-2017. Documentation of seizures at presentation or during hospitalization and antiseizure medication receipt identified participants with seizures. We summarized participant characteristics by seizure status via Kruskal-Wallis and χ ² tests. Cox proportional hazards models analyzed the relationship between seizures and mortality. We compared mean quantitative neurocognitive performance Z (QNPZ-8) scores, and individual domain z-scores, at 3-months using independent t tests.

Results

Among 821 HIV-infected cryptococcal meningitis participants, 28% (231 of 821) experienced seizures: 15.5% (127 of 821) experienced seizures at presentation, and 12.7% (104 of 821) experienced incident seizures. Participants with seizures at presentation had a significantly lower Glasgow coma scale ([GCS] <15; P < .001), CD4 count (<50 cells/mcL; P = .02), and higher cerebrospinal fluid (CSF) opening pressure (>25 cm H₂O; P = .004) when compared with participants who never experienced seizures. Cerebrospinal fluid fungal burden was higher among those with seizures at presentation (125 000 Cryptococcus colony-forming units [CFU]/mL CSF) and with seizures during follow-up (92 000 CFU/mL) compared with those who never experienced seizures (36 000 CFU/mL, P < .001). Seizures were associated with increased 10-week mortality (adjusted hazard ratio = 1.45; 95% confidence interval, 1.11-1.89). Participants with seizures had lower neurocognitive function at 3 months (QNPZ-8 = -1.87) compared with those without seizures (QNPZ-8 = -1.36; P < .001).

Conclusions

Seizures were common in this HIV-associated cryptococcal meningitis cohort and were associated with decreased survival and neurocognitive function.

Socioeconomic position and ten-year survival and virologic outcomes in a Ugandan HIV cohort receiving antiretroviral therapy

Lifelong ART is essential to reducing HIV mortality and ending the epidemic, however the interplay between socioeconomic position and long-term outcomes of HIV-infected persons receiving antiretroviral therapy (ART) in sub-Saharan Africa is unknown. Furthering the understanding of factors related to long-term ART outcomes in this important region will aid the successful scale-up of ART programs. We enrolled 559 HIV-infected Ugandan adults starting ART in 2004-2005 at the Infectious Diseases Institute in Kampala, Uganda and followed them for 10 years. We documented baseline employment status, regular household income, education level, housing description, physical ability, and CD4 count. Viral load was measured every six months. Proportional hazard regression tested for associations between baseline characteristics and 1) mortality, 2) virologic failure, and 3) mortality or virologic failure as a composite outcome. Over ten years 23% (n = 127) of participants died, 6% (n = 31) were lost-to-follow-up and 23% (107/472) experienced virologic treatment failure. In Kaplan-Meier analysis we observed an association between employment and mortality, with the highest cumulative probability of death occurring in unemployed individuals. In univariate analysis unemployment and disease severity were associated with mortality, but in multivariable analysis the only association with mortality was disease severity. We observed an association between higher household income and an increased incidence of both virologic failure and the combined outcome, and an association between self-employment and lower incidence of virologic failure and the combined outcome when compared to unemployment. Formal education level and housing status were unrelated to outcomes. It is feasible to achieve good ten-year survival, retention-in-care, and viral suppression in a socioeconomically diverse population in a resource-limited setting. Unemployment appears to be related to adverse 10-year ART outcomes. A low level of formal education does not appear to be a barrier to successful long-term ART.

Evolving Failures in the Delivery of Human Immunodeficiency Virus Care: Lessons From a Ugandan Meningitis Cohort 2006-2016

Background

Because of investments in human immunodeficiency virus (HIV) care in sub-Saharan Africa, the number of people aware of their status and receiving antiretroviral therapy (ART) has increased; however, HIV/acquired immune deficiency syndrome (AIDS) mortality still remains high.

Methods

We performed retrospective analysis of 3 sequential prospective cohorts of HIV-infected Ugandan adults presenting with AIDS and meningitis from 2006 to 2009, 2010 to 2012, and 2013 to 2016. Participants were categorized as follows: (1) unknown HIV status; (2) known HIV⁺ without ART; (3) known HIV⁺ with previous ART. We further categorized 2006 and 2013 cohort participants by duration of HIV-status knowledge and of ART receipt.

Results

We screened 1353 persons with suspected meningitis. Cryptococcus was the most common pathogen (63%). Over the decade, we observed an absolute increase of 37% in HIV status knowledge and 59% in antecedent ART receipt at screening. The 2006 cohort participants were new/recent HIV diagnoses (65%) or known HIV⁺ but not receiving ART (35%). Many 2013 cohort participants were new/recent HIV diagnoses (34%) and known HIV⁺ with <1 month ART (20%), but a significant proportion were receiving ART 1–4 months (11%) and >4 months (30%). Four percent of participants discontinued ART. From 2010 to 2016, meningitis cases per month increased by 33%.

Conclusions

Although improved HIV screening and ART access remain much-needed interventions in resource-limited settings, greater investment in viral suppression and opportunistic infection care among the growing HIV-infected population receiving ART is essential to reducing ongoing AIDS mortality.

Consequences of elevated temperature and pCO2 on insect folivory at the ecosystem level: perspectives from the fossil record

Paleoecological studies document the net effects of atmospheric and climate change in a natural laboratory over timescales not accessible to laboratory or ecological studies. Insect feeding damage is visible on well‐preserved fossil leaves, and changes in leaf damage through time can be compared to environmental changes. We measured percent leaf area damaged on four fossil leaf assemblages from the Bighorn Basin, Wyoming, that range in age from 56.1 to 52.65 million years (Ma). We also include similar published data from three US sites 49.4 to ~45 Ma in our analyses. Regional climate was subtropical or warmer throughout this period, and the second oldest assemblage (56 Ma) was deposited during the Paleocene–Eocene Thermal Maximum (PETM), a geologically abrupt global warming event caused by massive release of carbon into the atmosphere. Total and leaf‐chewing damage are highest during the PETM, whether considering percent area damaged on the bulk flora, the average of individual host plants, or a single plant host that occurs at multiple sites. Another fossil assemblage in our study, the 52.65 Ma Fifteenmile Creek paleoflora, also lived during a period of globally high temperature and pCO₂, but does not have elevated herbivory. Comparison of these two sites, as well as regression analyses conducted on the entire dataset, demonstrates that, over long timescales, temperature and pCO₂ are uncorrelated with total insect consumption at the ecosystem level. Rather, the most important factor affecting herbivory is the relative abundance of plants with nitrogen‐fixing symbionts. Legumes dominate the PETM site; their prevalence would have decreased nitrogen limitation across the ecosystem, buffering generalist herbivore populations against decreased leaf nutritional quality that commonly occurs at high pCO₂. We hypothesize that nitrogen concentration regulates the opposing effects of elevated temperature and CO₂ on insect abundance and thereby total insect consumption, which has important implications for agricultural practices in today's world of steadily increasing pCO₂.