The Grizzly, February 29, 2024

Dr. Harold Dean Trulear Talks Theology and Mass Incarceration • Newly Created Performing and Visual Arts Design and Technology Major • Ursinus Crossword Puzzle • Reimagine Ursinus-Collegeville: Planting a Seed of Change • Spring at Ursinus College Word Search • Meme Corner • Taco Tuesday! • UCWB Playoff Run Comes to an End in Baltimore • Pool Party at Gettysburg! Bears Accept Invitationhttps://digitalcommons.ursinus.edu/grizzlynews/2028/thumbnail.jp

Decomposing reflectance spectra to track gross primary production in a subalpine evergreen forest

Photosynthesis by terrestrial plants represents the majority of CO₂ uptake on Earth, yet it is difficult to measure directly from space. Estimation of gross primary production (GPP) from remote sensing indices represents a primary source of uncertainty, in particular for observing seasonal variations in evergreen forests. Recent vegetation remote sensing techniques have highlighted spectral regions sensitive to dynamic changes in leaf/needle carotenoid composition, showing promise for tracking seasonal changes in photosynthesis of evergreen forests. However, these have mostly been investigated with intermittent field campaigns or with narrow-band spectrometers in these ecosystems. To investigate this potential, we continuously measured vegetation reflectance (400–900 nm) using a canopy spectrometer system, PhotoSpec, mounted on top of an eddy-covariance flux tower in a subalpine evergreen forest at Niwot Ridge, Colorado, USA. We analyzed driving spectral components in the measured canopy reflectance using both statistical and process-based approaches. The decomposed spectral components co-varied with carotenoid content and GPP, supporting the interpretation of the photochemical reflectance index (PRI) and the chlorophyll/carotenoid index (CCI). Although the entire 400–900 nm range showed additional spectral changes near the red edge, it did not provide significant improvements in GPP predictions. We found little seasonal variation in both normalized difference vegetation index (NDVI) and the near-infrared vegetation index (NIRv) in this ecosystem. In addition, we quantitatively determined needle-scale chlorophyll-to-carotenoid ratios as well as anthocyanin contents using full-spectrum inversions, both of which were tightly correlated with seasonal GPP changes. Reconstructing GPP from vegetation reflectance using partial least-squares regression (PLSR) explained approximately 87 % of the variability in observed GPP. Our results linked the seasonal variation in reflectance to the pool size of photoprotective pigments, highlighting all spectral locations within 400–900 nm associated with GPP seasonality in evergreen forests

Enteric neural crest-derived cells promote their migration by modifying their microenvironment through tenascin-C production

The enteric nervous system (ENS) is derived from vagal and sacral neural crest cells that migrate, proliferate, and differentiate into enteric neurons and glia within the gut wall. The mechanisms regulating enteric neural crest-derived cell (ENCC) migration are poorly characterized despite the importance of this process in gut formation and function. Characterization of genes involved in ENCC migration is essential to understanding ENS development and could provide targets for treatment of human ENS disorders. We identified the extracellular matrix glycoprotein tenascin-C (TNC) as an important regulator of ENCC development. We find TNC dynamically expressed during avian gut development. It is absent from the cecal region just prior to ENCC arrival, but becomes strongly expressed around ENCCs as they enter the ceca and hindgut. In aganglionic hindguts, TNC expression is strong throughout the outer mesenchyme, but is absent from the submucosal region, supporting the presence of both ENCC-dependent and independent expression within the gut wall. Using rat-chick coelomic grafts, neural tube cultures, and gut explants, we show that ENCCs produce TNC and that this ECM protein promotes their migration. Interestingly, only vagal neural crest-derived ENCCs express TNC, whereas sacral neural crest-derived cells do not. These results demonstrate that vagal crest-derived ENCCs actively modify their microenvironment through TNC expression and thereby help to regulate their own migration

Prospective association of social circumstance, socioeconomic, lifestyle and mental health factors with subsequent hospitalisation over 6-7 year follow up in people living with HIV.

BACKGROUND: Predictors of hospitalisation in people with HIV (PLHIV) in the contemporary treatment era are not well understood. METHODS: This ASTRA sub-study used clinic data linkage and record review to determine occurrence of hospitalisations among 798 PLHIV from baseline questionnaire (February to December 2011) until 1 June 2018. Associations of baseline social circumstance, socioeconomic, lifestyle, mental health, demographic and clinical factors with repeated all-cause hospitalisation from longitudinal data were investigated using Prentice-Williams-Peterson models. Associations were also assessed in 461 individuals on antiretroviral therapy (ART) with viral load ≤50 copies/ml and CD4 count ≥500 cells/ µl. FINDINGS: Rate of hospitalisation was 5.8/100 person-years (95% CI: 5.1-6.5). Adjusted for age, demographic group and time with diagnosed HIV, the following social circumstance, socioeconomic, lifestyle and mental health factors predicted hospitalisation: no stable partner (adjusted hazard ratio (aHR)=1.59; 95% CI=1.16-2.20 vs living with partner); having children (aHR=1.50; 1.08-2.10); non-employment (aHR=1.56; 1.07-2.27 for unemployment; aHR=2.39; 1.70-3.37 for sick/disabled vs employed); rented housing (aHR=1.72; 1.26-2.37 vs homeowner); not enough money for basic needs (aHR=1.82; 1.19-2.78 vs enough); current smoking (aHR=1.39; 1.02-1.91 vs never); recent injection-drug use (aHR=2.11; 1.30-3.43); anxiety symptoms (aHRs=1.39; 1.01-1.91, 2.06; 1.43-2.95 for mild and moderate vs none/minimal); depressive symptoms (aHRs=1.67; 1.17-2.38, 1.91; 1.30-2.78 for moderate and severe vs none/minimal); treated/untreated depression (aHRs=1.65; 1.03-2.64 for treated depression only, 1.87; 1.39-2.52 for depressive symptoms only; 1.53; 1.05-2.24; for treated depression and depressive symptoms, versus neither). Associations were broadly similar in those with controlled HIV and high CD4. INTERPRETATION: Social circumstance, socioeconomic disadvantage, adverse lifestyle factors and poorer mental health are strong predictors of hospitalisation in PLHIV, highlighting the need for targeted interventions and care. FUNDING: British HIV Association (BHIVA) Research Award (2017); SMR funded by a PhD fellowship from the Royal Free Charity

Causes of hospitalisation among a cohort of people with HIV from a London centre followed from 2011 to 2018.

BACKGROUND: We describe the spectrum of ICD-10 classified causes for hospitalisations occurring between 2011 and 2018 in a cohort of people living with HIV (PLHIV). METHODS: This sub-study includes 798 PLHIV participating in the Antiretroviral, Sexual Transmission Risk and Attitudes (ASTRA) questionnaire study who were recruited from a large London centre. A medical record review identified the occurrence and causes of hospitalisation from the date of questionnaire completion (February-December 2011) until 1 June 2018. Up to five causes were classified by an HIV clinician using the ICD-10 system. RESULTS: There were 274 hospitalisations in 153 people (rate = 5.8/100 person-years; 95% CI: 5.1, 6.5). Causes were wide-ranging; the most common were circulatory (16.8%), digestive (13.1%), respiratory (11.7%), infectious diseases (11.0%), injury/poisoning (10.6%), genitourinary diseases (9.9%) and neoplasms (9.1%). A tenth (27/274) of hospitalisations were related to at least one AIDS-defining illness. Median duration of hospitalisation was 5 days (IQR 2-9). At the time of hospitalisation, median CD4 count was high (510 cells/μl; IQR: 315-739), while median CD4 nadir was relatively low (113 cells/μl; IQR: 40-239). At admission, half of individuals (51%) had a previous AIDS-defining illness and 21% had viral load > 50 copies/ml. Individuals admitted for infectious diseases were particularly likely to have unfavourable HIV-related clinical characteristics (low CD4, viral non-suppression, not on antiretroviral therapy (ART), previous AIDS). CONCLUSIONS: In the modern combination antiretroviral therapy era, the spectrum of causes of hospitalisation in PLHIV in the UK is wide-ranging, highlighting the importance of holistic care for PLHIV, including prevention, early detection and treatment of comorbidities

Mechanistic evidence for tracking the seasonality of photosynthesis with solar-induced fluorescence

Northern hemisphere evergreen forests assimilate a significant fraction of global atmospheric CO_2 but monitoring large-scale changes in gross primary production (GPP) in these systems is challenging. Recent advances in remote sensing allow the detection of solar-induced chlorophyll fluorescence (SIF) emission from vegetation, which has been empirically linked to GPP at large spatial scales. This is particularly important in evergreen forests, where traditional remote-sensing techniques and terrestrial biosphere models fail to reproduce the seasonality of GPP. Here, we examined the mechanistic relationship between SIF retrieved from a canopy spectrometer system and GPP at a winter-dormant conifer forest, which has little seasonal variation in canopy structure, needle chlorophyll content, and absorbed light. Both SIF and GPP track each other in a consistent, dynamic fashion in response to environmental conditions. SIF and GPP are well correlated (R^2 = 0.62–0.92) with an invariant slope over hourly to weekly timescales. Large seasonal variations in SIF yield capture changes in photoprotective pigments and photosystem II operating efficiency associated with winter acclimation, highlighting its unique ability to precisely track the seasonality of photosynthesis. Our results underscore the potential of new satellite-based SIF products (TROPOMI, OCO-2) as proxies for the timing and magnitude of GPP in evergreen forests at an unprecedented spatiotemporal resolution

Decomposing reflectance spectra to track gross primary production in a subalpine evergreen forest

Photosynthesis by terrestrial plants represents the majority of CO2 uptake on Earth, yet it is difficult to measure directly from space. Estimation of gross primary production (GPP) from remote sensing indices represents a primary source of uncertainty, in particular for observing seasonal variations in evergreen forests. Recent vegetation remote sensing techniques have highlighted spectral regions sensitive to dynamic changes in leaf/needle carotenoid composition, showing promise for tracking seasonal changes in photosynthesis of evergreen forests. However, these have mostly been investigated with intermittent field campaigns or with narrow-band spectrometers in these ecosystems. To investigate this potential, we continuously measured vegetation reflectance (400&ndash;900 nm) using a canopy spectrometer system, PhotoSpec, mounted on top of an eddy-covariance flux tower in a subalpine evergreen forest at Niwot Ridge, Colorado, USA. We analyzed driving spectral components in the measured canopy reflectance using both statistical and process-based approaches. The decomposed spectral components co-varied with carotenoid content and GPP, supporting the interpretation of the photochemical reflectance index (PRI) and the chlorophyll/carotenoid index (CCI). Although the entire 400&ndash;900 nm range showed additional spectral changes near the red edge, it did not provide significant improvements in GPP predictions. We found little seasonal variation in both normalized difference vegetation index (NDVI) and the near-infrared vegetation index (NIRv) in this ecosystem. In addition, we quantitatively determined needle-scale chlorophyll-to-carotenoid ratios as well as anthocyanin contents using full-spectrum inversions, both of which were tightly correlated with seasonal GPP changes. Reconstructing GPP from vegetation reflectance using partial least-squares regression (PLSR) explained approximately 87 % of the variability in observed GPP. Our results linked the seasonal variation in reflectance to the pool size of photoprotective pigments, highlighting all spectral locations within 400&ndash;900 nm associated with GPP seasonality in evergreen forests.</p

Mechanistic evidence for tracking the seasonality of photosynthesis with solar-induced fluorescence

Northern hemisphere evergreen forests assimilate a significant fraction of global atmospheric CO_2 but monitoring large-scale changes in gross primary production (GPP) in these systems is challenging. Recent advances in remote sensing allow the detection of solar-induced chlorophyll fluorescence (SIF) emission from vegetation, which has been empirically linked to GPP at large spatial scales. This is particularly important in evergreen forests, where traditional remote-sensing techniques and terrestrial biosphere models fail to reproduce the seasonality of GPP. Here, we examined the mechanistic relationship between SIF retrieved from a canopy spectrometer system and GPP at a winter-dormant conifer forest, which has little seasonal variation in canopy structure, needle chlorophyll content, and absorbed light. Both SIF and GPP track each other in a consistent, dynamic fashion in response to environmental conditions. SIF and GPP are well correlated (R^2 = 0.62–0.92) with an invariant slope over hourly to weekly timescales. Large seasonal variations in SIF yield capture changes in photoprotective pigments and photosystem II operating efficiency associated with winter acclimation, highlighting its unique ability to precisely track the seasonality of photosynthesis. Our results underscore the potential of new satellite-based SIF products (TROPOMI, OCO-2) as proxies for the timing and magnitude of GPP in evergreen forests at an unprecedented spatiotemporal resolution