Publications by authors named "Joseph D White"

15 Publications

  • Page 1 of 1

Novel perspectives on stomatal impressions: Rapid and non-invasive surface characterization of plant leaves by scanning electron microscopy.

PLoS One 2020 3;15(9):e0238589. Epub 2020 Sep 3.

Center for Microscopy and Imaging, Baylor University, Waco, Texas, United States of America.

Scanning electron microscopy (SEM) is widely used to investigate the surface morphology, and physiological state of plant leaves. Conventionally used methods for sample preparation are invasive, irreversible, require skill and expensive equipment, and are time and labor consuming. This study demonstrates a method to obtain in vivo surface information of plant leaves by imaging replicas with SEM that is rapid and non-invasive. Dental putty was applied to the leaves for 5 minutes and then removed. Replicas were then imaged with SEM and compared to fresh leaves, and leaves that were processed conventionally by chemical fixation, dehydration and critical point drying. The surface structure of leaves was well preserved on the replicas. The outline of epidermal as well as guard cells could be clearly distinguished enabling determination of stomatal density. Comparison of the dimensions of guard cells revealed that replicas did not differ from fresh leaves, while conventional sample preparation induced strong shrinkage (-40% in length and -38% in width) of the cells when compared to guard cells on fresh leaves. Tilting the replicas enabled clear measurement of stomatal aperture dimensions. Summing up, the major advantages of this method are that it is inexpensive, non-toxic, simple to apply, can be performed in the field, and that results on stomatal density and in vivo stomatal dimensions in 3D can be obtained in a few minutes.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0238589PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7470294PMC
October 2020

Carboniferous plant physiology breaks the mold.

New Phytol 2020 08 8;227(3):667-679. Epub 2020 Apr 8.

Center for Integrative Geosciences, University of Connecticut, Storrs, CT, 06269, USA.

How plants have shaped Earth surface feedbacks over geologic time is a key question in botanical and geological inquiry. Recent work has suggested that biomes during the Carboniferous Period contained plants with extraordinary physiological capacity to shape their environment, contradicting the previously dominant view that plants only began to actively moderate the Earth's surface with the rise of angiosperms during the Mesozoic Era. A recently published Viewpoint disputes this recent work, thus here, we document in detail, the mechanistic underpinnings of our modeling and illustrate the extraordinary ecophysiological nature of Carboniferous plants.
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http://dx.doi.org/10.1111/nph.16460DOI Listing
August 2020

The beneficial effects of brown adipose tissue transplantation.

Mol Aspects Med 2019 08 21;68:74-81. Epub 2019 Jun 21.

Dorothy M. Davis Heart and Lung Research Institute, Department of Physiology and Cell Biology, The Ohio State University Wexner Medical Center, Columbus, OH, 43210, USA. Electronic address:

Obesity is a disease that results from an imbalance between energy intake and energy expenditure. Brown adipose tissue (BAT) is a potential therapeutic target to improve the comorbidities associated with obesity due to its inherent thermogenic capacity and its ability to improve glucose metabolism. Multiple studies have shown that activation of BAT using either pharmacological treatments or cold exposure had an acute effect to increase metabolic function and reduce adiposity. Recent preclinical investigations have explored whether increasing BAT mass or activation through transplantation models could improve glucose metabolism and metabolic health. Successful BAT transplantation models have shown improvements in glucose metabolism and insulin sensitivity, as well as reductions in body mass and decreased adiposity in recipients. BAT transplantation may confer its beneficial effects through several different mechanisms, including endocrine effects via the release of 'batokines'. More recent studies have demonstrated that beige and brown adipocytes isolated from human progenitor cells and transplanted into mouse models result in metabolic improvements similar to transplantation of whole BAT; this could represent a clinically translatable model. In this review we will discuss the impetus for both early and recent investigations utilizing BAT transplantation models, the outcomes of these studies, and review the mechanisms associated with the beneficial effects of BAT transplant to confer improvements in metabolic health.
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http://dx.doi.org/10.1016/j.mam.2019.06.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6708446PMC
August 2019

Cold and Exercise: Therapeutic Tools to Activate Brown Adipose Tissue and Combat Obesity.

Biology (Basel) 2019 Feb 12;8(1). Epub 2019 Feb 12.

Dorothy M. Davis Heart and Lung Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA.

The rise in obesity over the last several decades has reached pandemic proportions. Brown adipose tissue (BAT) is a thermogenic organ that is involved in energy expenditure and represents an attractive target to combat both obesity and type 2 diabetes. Cold exposure and exercise training are two stimuli that have been investigated with respect to BAT activation, metabolism, and the contribution of BAT to metabolic health. These two stimuli are of great interest because they have both disparate and converging effects on BAT activation and metabolism. Cold exposure is an effective mechanism to stimulate BAT activity and increase glucose and lipid uptake through mitochondrial uncoupling, resulting in metabolic benefits including elevated energy expenditure and increased insulin sensitivity. Exercise is a therapeutic tool that has marked benefits on systemic metabolism and affects several tissues, including BAT. Compared to cold exposure, studies focused on BAT metabolism and exercise display conflicting results; the majority of studies in rodents and humans demonstrate a reduction in BAT activity and reduced glucose and lipid uptake and storage. In addition to investigations of energy uptake and utilization, recent studies have focused on the effects of cold exposure and exercise on the structural lipids in BAT and secreted factors released from BAT, termed batokines. Cold exposure and exercise induce opposite responses in terms of structural lipids, but an important overlap exists between the effects of cold and exercise on batokines. In this review, we will discuss the similarities and differences of cold exposure and exercise in relation to their effects on BAT activity and metabolism and its relevance for the prevention of obesity and the development of type 2 diabetes.
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http://dx.doi.org/10.3390/biology8010009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6466122PMC
February 2019

Paternal Exercise Improves Glucose Metabolism in Adult Offspring.

Diabetes 2018 12 21;67(12):2530-2540. Epub 2018 Oct 21.

Section on Integrative Physiology and Metabolism, Joslin Diabetes Center, Boston, MA

Poor paternal diet has emerged as a risk factor for metabolic disease in offspring, and alterations in sperm may be a major mechanism mediating these detrimental effects of diet. Although exercise in the general population is known to improve health, the effects of paternal exercise on sperm and offspring metabolic health are largely unknown. Here, we studied 7-week-old C57BL/6 male mice fed a chow or high-fat diet and housed either in static cages (sedentary) or cages with attached running wheels (exercise trained). After 3 weeks, one cohort of males was sacrificed and cauda sperm obtained, while the other cohort was bred with chow-fed sedentary C57BL/6 females. Offspring were chow fed, sedentary, and studied during the first year of life. We found that high-fat feeding of sires impairs glucose tolerance and increases the percentage of fat mass in both male and female offspring at 52 weeks of age. Strikingly, paternal exercise suppresses the effects of paternal high-fat diet on offspring, reversing the observed impairment in glucose tolerance, percentage of fat mass, and glucose uptake in skeletal muscles of the offspring. These changes in offspring phenotype are accompanied by changes in sperm physiology, as, for example, high-fat feeding results in decreased sperm motility, an effect normalized in males subject to exercise training. Deep sequencing of sperm reveals pronounced effects of exercise training on multiple classes of small RNAs, as multiple changes to the sperm RNA payload observed in animals consuming a high-fat diet are suppressed by exercise training. Thus, voluntary exercise training of male mice results in pronounced improvements in the metabolic health of adult male and female offspring. We provide the first in-depth analysis of small RNAs in sperm from exercise-trained males, revealing a marked change in the levels of multiple small RNAs with the potential to alter phenotypes in the next generation.
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http://dx.doi.org/10.2337/db18-0667DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6245224PMC
December 2018

Seed value influences cache pilfering rates by desert rodents.

Integr Zool 2019 Jan;14(1):75-86

Department of Biological Sciences, University of Cape Town, Cape Town, Republic of South Africa.

Some rodents gather and store seeds. How many seeds they gather and how they treat those seeds is largely determined by seed traits such as mass, nutrient content, hardness of the seed coat, presence of secondary compounds, and germination schedule. Through their consumption and dispersal of seeds, rodents act as agents of natural selection on seed traits, and those traits influence how rodents forage. Many seeds that are scatter-hoarded by rodents are pilfered, or stolen, by other rodents, and seed traits also likely influence pilfering rates and seed fates of pilfered seeds. To clarify coevolutionary relationships between rodents and the plants that they disperse, one needs to understand the role of seed traits in rodent foraging decisions. We compared how the seeds of 4 species of plants that are dispersed by scatter-hoarding animals and that differ in value (singleleaf piñon pine, Pinus monophylla; desert peach, Prunus andersonii; antelope bitterbrush, Purshia tridentata; Utah juniper, Juniperus osteosperma) were pilfered and recached by rodents. One hundred artificial caches of the 4 seed species (25 per species) were prepared, and removal by rodents was monitored. Rodents pilfered high-value seeds more rapidly than the other seeds. Desert peach seeds, which contain toxic secondary compounds, were more frequently recached. Relatively low value seeds like Utah juniper and antelope bitterbrush were pilfered more slowly and were sometimes left at cache sites, and seeds of the latter species were transported shorter distances to new cache sites. The background density of seeds also appeared to influence the relative value of seeds.
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http://dx.doi.org/10.1111/1749-4877.12358DOI Listing
January 2019

Conserv Biol 2018 02 6;32(1):258-259. Epub 2017 Dec 6.

U.S. Geological Survey, Wetland and Aquatic Research Center, 700 Cajundome Boulevard, Lafayette, Louisiana 70506, U.S.A.

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http://dx.doi.org/10.1111/cobi.13055DOI Listing
February 2018

Dynamic Carboniferous tropical forests: new views of plant function and potential for physiological forcing of climate.

New Phytol 2017 Sep 25;215(4):1333-1353. Epub 2017 Jul 25.

Center for Integrative Geosciences, University of Connecticut, Storrs, CT, 06269, USA.

Contents 1333 I. 1334 II. 1335 III. 1339 IV. 1344 V. 1347 VI. 1347 1348 1348 References 1348 SUMMARY: The Carboniferous, the time of Earth's penultimate icehouse and widespread coal formation, was dominated by extinct lineages of early-diverging vascular plants. Studies of nearest living relatives of key Carboniferous plants suggest that their physiologies and growth forms differed substantially from most types of modern vegetation, particularly forests. It remains a matter of debate precisely how differently and to what degree these long-extinct plants influenced the environment. Integrating biophysical analysis of stomatal and vascular conductivity with geochemical analysis of fossilized tissues and process-based ecosystem-scale modeling yields a dynamic and unique perspective on these paleoforests. This integrated approach indicates that key Carboniferous plants were capable of growth and transpiration rates that approach values found in extant crown-group angiosperms, differing greatly from comparatively modest rates found in their closest living relatives. Ecosystem modeling suggests that divergent stomatal conductance, leaf sizes and stem life span between dominant clades would have shifted the balance of soil-atmosphere water fluxes, and thus surface runoff flux, during repeated, climate-driven, vegetation turnovers. This synthesis highlights the importance of 'whole plant' physiological reconstruction of extinct plants and the potential of vascular plants to have influenced the Earth system hundreds of millions of years ago through vegetation-climate feedbacks.
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http://dx.doi.org/10.1111/nph.14700DOI Listing
September 2017

Microvascular Endothelial Dysfunction in Sedentary, Obese Humans Is Mediated by NADPH Oxidase: Influence of Exercise Training.

Arterioscler Thromb Vasc Biol 2016 12 20;36(12):2412-2420. Epub 2016 Oct 20.

From the Human Performance Laboratory, Departments of Kinesiology (J.D.L.F., G.S.D., H.Y., J.D.W., R.C.H.), Pharmacology and Toxicology (M.A.M.N., E.J.A.), Physiology (R.C.H.), East Carolina Diabetes and Obesity Institute (J.D.L.F., M.A.M.N., E.J.A., R.C.H.), Center for Health Disparities (R.C.H.), East Carolina University, Greenville, NC; Department of Urology, The James Buchannan Brady Urological Institute, The Johns Hopkins School of Medicine, Baltimore, MD (J.D.L.F.); Department of Pharmaceutical Sciences and Experimental Therapeutics, College of Pharmacy, University of Iowa, Iowa City (E.J.A.); and Department of Biokinetics, Exercise and Leisure Science, University of KwaZulu-Natal, Durban, South Africa (R.C.H.).

Objective: The objectives of this study were to determine the impact of in vivo reactive oxygen species (ROS) on microvascular endothelial function in obese human subjects and the efficacy of an aerobic exercise intervention on alleviating obesity-associated dysfunctionality.

Approach And Results: Young, sedentary men and women were divided into lean (body mass index 18-25; n=14), intermediate (body mass index 28-32.5; n=13), and obese (body mass index 33-40; n=15) groups. A novel microdialysis technique was utilized to detect elevated interstitial hydrogen peroxide (HO) and superoxide levels in the vastus lateralis of obese compared with both lean and intermediate subjects. Nutritive blood flow was monitored in the vastus lateralis via the microdialysis-ethanol technique. A decrement in acetylcholine-stimulated blood flow revealed impaired microvascular endothelial function in the obese subjects. Perfusion of apocynin, an NADPH oxidase inhibitor, lowered (normalized) HO and superoxide levels, and reversed microvascular endothelial dysfunction in obese subjects. After 8 weeks of exercise, HO levels were decreased in the obese subjects and microvascular endothelial function in these subjects was restored to levels similar to lean subjects. Skeletal muscle protein expression of the NADPH oxidase subunits p22, p47, and p67 was increased in obese relative to lean subjects, where p22 and p67 expression was attenuated by exercise training in obese subjects.

Conclusions: This study implicates NADPH oxidase as a source of excessive ROS production in skeletal muscle of obese individuals and links excessive NADPH oxidase-derived ROS to microvascular endothelial dysfunction in obesity. Furthermore, aerobic exercise training proved to be an effective strategy for alleviating these maladies.
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http://dx.doi.org/10.1161/ATVBAHA.116.308339DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5123754PMC
December 2016

CLIMATE CHANGE. Long-term climate forcing by atmospheric oxygen concentrations.

Science 2015 Jun 11;348(6240):1238-41. Epub 2015 Jun 11.

Department of Biology, Baylor University, Waco, TX 76798, USA.

The percentage of oxygen in Earth's atmosphere varied between 10% and 35% throughout the Phanerozoic. These changes have been linked to the evolution, radiation, and size of animals but have not been considered to affect climate. We conducted simulations showing that modulation of the partial pressure of oxygen (pO2), as a result of its contribution to atmospheric mass and density, influences the optical depth of the atmosphere. Under low pO2 and a reduced-density atmosphere, shortwave scattering by air molecules and clouds is less frequent, leading to a substantial increase in surface shortwave forcing. Through feedbacks involving latent heat fluxes to the atmosphere and marine stratus clouds, surface shortwave forcing drives increases in atmospheric water vapor and global precipitation, enhances greenhouse forcing, and raises global surface temperature. Our results implicate pO2 as an important factor in climate forcing throughout geologic time.
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http://dx.doi.org/10.1126/science.1260670DOI Listing
June 2015

Faecal mimicry by seeds ensures dispersal by dung beetles.

Nat Plants 2015 Oct 5;1:15141. Epub 2015 Oct 5.

Department of Biological Sciences, University of Cape Town, P bag, Rondebosch 7701, South Africa.

The large brown, round, strongly scented seeds of Ceratocaryum argenteum (Restionaceae) emit many volatiles found to be present in herbivore dung. These seeds attract dung beetles that roll and bury them. As the seeds are hard and offer no reward to the dung beetles, this is a remarkable example of deception in plant seed dispersal.
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http://dx.doi.org/10.1038/nplants.2015.141DOI Listing
October 2015

Plant water use characteristics of five dominant shrub species of the Lower Rio Grande Valley, Texas, USA: implications for shrubland restoration and conservation.

Conserv Physiol 2014 18;2(1):cou005. Epub 2014 Feb 18.

The Department of Biology, Baylor University, One Bear Place #97388, Waco, TX 76798, USA; The Institute of Ecological, Earth, and Environmental Sciences, Baylor University, One Bear Place #97205, Waco, TX 76798, USA.

The biogeographic distribution of plant species is inherently associated with the plasticity of physiological adaptations to environmental variation. For semi-arid shrublands with a legacy of saline soils, characterization of soil water-tolerant shrub species is necessary for habitat restoration given future projection of increased drought magnitude and persistence in these ecosystems. Five dominant native shrub species commonly found in the Lower Rio Grande Valley, TX, USA, were studied, namely Acacia farnesiana, Celtis ehrenbergiana, Forestiera angustifolia, Parkinsonia aculeata and Prosopis glandulosa. To simulate drought conditions, we suspended watering of healthy, greenhouse-grown plants for 4 weeks. Effects of soil salinity were also studied by dosing plants with 10% NaCl solution with suspended watering. For soil water deficit treatment, the soil water potential of P. glandulosa was the highest (-1.20 MPa), followed by A. farnesiana (-4.69 MPa), P. aculeata (-5.39 MPa), F. angustifolia (-6.20 MPa) and C. ehrenbergiana (-10.02 MPa). For the soil salinity treatment, P. glandulosa also had the highest soil water potential value (-1.60 MPa), followed by C. ehrenbergiana (-1.70 MPa), A. farnesiana (-1.84 MPa), P. aculeata (-2.04 MPa) and F. angustifolia (-6.99 MPa). Within the species, only C. ehrenbergiana and F. angustifolia for soil water deficit treatment and A. farnesiana for the salinity treatment had significantly lower soil water potential after 4 weeks of treatment (P < 0.05). We found that soil water potential, stomatal conductance and net photosynthesis of the species significantly reduced over time for both treatments (P < 0.05). We conclude that while all species exhibited capacities to withstand current water availability, some species demonstrated limited tolerance for extreme water stress that may be important for management of future shrub diversity in Lower Rio Grande Valley.
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http://dx.doi.org/10.1093/conphys/cou005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4806726PMC
June 2016

Understanding interaction effects of climate change and fire management on bird distributions through combined process and habitat models.

Conserv Biol 2011 Jun 28;25(3):536-46. Epub 2011 Apr 28.

Department of Biology, Baylor University, Waco, TX 76798, USA.

Avian conservation efforts must account for changes in vegetation composition and structure associated with climate change. We modeled vegetation change and the probability of occurrence of birds to project changes in winter bird distributions associated with climate change and fire management in the northern Chihuahuan Desert (southwestern U.S.A.). We simulated vegetation change in a process-based model (Landscape and Fire Simulator) in which anticipated climate change was associated with doubling of current atmospheric carbon dioxide over the next 50 years. We estimated the relative probability of bird occurrence on the basis of statistical models derived from field observations of birds and data on vegetation type, topography, and roads. We selected 3 focal species, Scaled Quail (Callipepla squamata), Loggerhead Shrike (Lanius ludovicianus), and Rock Wren (Salpinctes obsoletus), that had a range of probabilities of occurrence for our study area. Our simulations projected increases in relative probability of bird occurrence in shrubland and decreases in grassland and Yucca spp. and ocotillo (Fouquieria splendens) vegetation. Generally, the relative probability of occurrence of all 3 species was highest in shrubland because leaf-area index values were lower in shrubland. This high probability of occurrence likely is related to the species' use of open vegetation for foraging. Fire suppression had little effect on projected vegetation composition because as climate changed there was less fuel and burned area. Our results show that if future water limits on plant type are considered, models that incorporate spatial data may suggest how and where different species of birds may respond to vegetation changes.
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http://dx.doi.org/10.1111/j.1523-1739.2011.01684.xDOI Listing
June 2011

Are watershed and lacustrine controls on planktonic N2 fixation hierarchically structured?

Ecol Appl 2008 Apr;18(3):805-19

Center for Reservoir and Aquatic Systems Research, Baylor University, Waco, Texas, USA.

N2 fixation can be an important source of N to limnetic ecosystems and can influence the structure of phytoplankton communities. However, watershed-scale conditions that favor N2 fixation in lakes and reservoirs have not been well studied. We measured N2 fixation and lacustrine variables monthly over a 19-month period in Waco Reservoir, Texas, USA, and linked these data with nutrient-loading estimates from a physically based watershed model. Readily available topographic, soil, land cover, effluent discharge, and climate data were used in the Soil and Water Assessment Tool (SWAT) to derive watershed nutrient-loading estimates. Categorical and regression tree (CART) analysis revealed that lacustrine and watershed correlates of N2 fixation were hierarchically structured. Lacustrine conditions showed greater predictive capability temporally. For instance, low NO3(-) concentration (<25 microg N/L) and high water temperatures (>27 degrees C) in the reservoir were correlated with the initiation of N2 fixation seasonally. When lacustrine conditions were favorable for N2 fixation, watershed conditions appeared to influence spatial patterns of N2 fixation within the reservoir. For example, spatially explicit patterns of N2 fixation were correlated with the ratio of N:P in nutrient loadings and the N loading rate, which were driven by anthropogenic activity in the watershed and periods of low stream flow, respectively. Although N2 fixation contributed <5% of the annual N load to the reservoir, 37% of the N load was derived from atmospheric N2 fixation during summertime when stream flow in the watershed was low. This study provides evidence that watershed anthropogenic activity can exert control on planktonic N2 fixation, but that temporality is controlled by lacustrine conditions. Furthermore, this study also supports suggestions that reduced inflows may increase the propensity of N2-fixing cyanobacterial blooms in receiving waters of anthropogenically modified landscapes.
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http://dx.doi.org/10.1890/07-0105.1DOI Listing
April 2008

Healing the body and the soul of the CKD/ESRD patient.

Authors:
Joseph D White

Nephrol News Issues 2004 Feb;18(2):51-3

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February 2004