bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ligand Induced Changes in Flexibility & Allosteric Interactions in Glutamate Dehydrogenase
Authors: Scheel Carolyn , Bell Ellis 
Published: June 2021

Higher eukaryotic glutamate dehydrogenases exhibit complex homo and hetero tropic regulation involving subunit interactions and ligand induced conformational changes. Ligands either have little effect or significantly increase or decrease global stability of the protein. Correlation of guanidine hydrochloride induced unfolding and dynamic light scattering allow the dissociation of the subunits to be followed and indicates that Norvaline which does not support subunit interactions or efficient catalysis significantly stabilizes the protein also affects subunit dissociation. Limited proteolysis studies using immobilized trypsin is allowing differential effects of some ligands to be localized to specific regions of the polypeptide chain. GDH is digested with immobilized protease and the time dependence of fragmentation followed using MALDI tof mass spectrometry and Protein Prospector to identify cleavage sites from the masses of the resultant fragments. Other studies using H/D exchange coupled with a complete proteolysis using pepsin as the protease will allow a more precise view of the conformational changes. Overall these studies indicate that both activity and allosteric regulation of this complex enzyme are linked to changes in conformational flexibility rather than discrete ligand induced changes in conformation.Funded by NSF Grant MCB 0448905 to EB
Studies on the Role of Subunit d for V‐ATPase Reversible Disassembly
Authors: Ediger Benjamin , Parra Karlett 
Published: June 2021

V1V0‐ATPase proton pumps are multisubunit proteins consisting of integral and peripheral subunits regulated by reversible disassembly in response to the extracellular concentration of glucose; it is hypothesized that disassembly is an energy conserving strategy to preserve ATP due to limited glucose. In the absence of glucose, the peropheral sub‐complex (V1) is released into the cytoplasm and the membrane sub‐complex (Vo) remains integral. The disassembled enzyme is catalytically inactive but addition of glucose to glucose‐deprived cells yields reassembly of a functional holoenzyme. This project studies subunit d, a key subunit coupling ATP hydrolysis to proton transport. Subunit d remains bound to the membrane upon disassembly and interacts with different V1 and Vo subunits depending on the V‐ATPase's state of assembly. We used computational models of subunit d to introduce cysteine residues that will be photo‐chemically cross‐linked to neighboring V‐ATPase subunits using the sulfhydryl reagent MBP. This study will map subunit interactions involving subunit d in the assembled and disassembled states. It will generate new information regarding the roles of subunit d for V‐ATPase function and the mechanism of glucose‐dependent dissociation.Supported by NSF
Major parameters of zinc (Zn) homeostasis in adult women with a wide range of habitual zinc intake
Authors: Sheng Xiao‐Yang , Hambidge K Michael , Miller Leland V , Bailey Karl B , Gibson Rosalind S , Westcott Jamie E , Lei Sian , Grunwald Gary , Krebs Nancy F 
Published: June 2021

A clear understanding of optimal public health strategies to prevent human Zn deficiency depends on improved understanding of human Zn homeostasis. Adequate Zn nutrition is of special importance in all women of child‐bearing age. The objective of this study was to measure major parameters of Zn homeostasis in healthy young free‐living adult women with a wide range of total dietary Zn (TDZ, mg Zn/d) and phytate (TDP) based on habitual intake. Methodology included administration of two Zn stable isotopes (67Zn & 68Zn) intravenously at different times to measure fractional absorption of Zn (FAZ) and endogenous fecal Zn (EFZ, mg Zn/d). A third tracer, 70Zn, and dysprosium were administered orally with all meals for 6 consecutive days to 24 healthy women. Zn and phytate were measured in duplicate meals, and Zn & Zn isotope ratios in feces and urine. Mean ± SD results included: TDZ 11.7 ± 7.2 mg Zn/d (5.5 – 29 mg Zn/d); FAZ 0.30 ± 0.10; total absorbed Zn (TAZ) 3.0 ± 1.1 mg Zn/d; EFZ 2.7 ± 0.8 mg Zn/d. The slope of linear regression of endogenous zinc in feces + urine vs TAZ = 0.31, r2 = 0.15, p = 0.081. Fitting TAZ data with a saturation response model gave an Amax = 5.5 mg Zn/d, r2 = 0.60. Calculations from these factorial data were consistent with current EAR for Zn for adult women.Supported by USDA 2003‐00900; GCRC M01RR00051; MO1 RR00069‐41; Science & Technology Commission, Shanghai Municipality 03JC14042.
Tubuloglomerular feedback signal transduction in a model of a compliant thick ascending limb
Authors: Layton Harold E , Moore Leon C , Layton Anita T 
Published: June 2021

We used a mathematical model to predict the impact of tubular compliance on tubuloglomerular feedback (TGF) signal transduction in the thick acending limb (TAL). In several previous studies, we used a mathematical model that represented the TAL as a rigid tube. That model predicts that TGF signal transduction by the TAL is a generator of nonlinearities: if a sinusoidal oscillation is added to constant intratubular fluid flow, the NaCl concentration alongside the macula densa will be nonsinusoidal owing to an accumulation of harmonics. We have hypothesized that complexity found in power spectra based on in vivo time series of key TGF variables arises in part from those harmonics and that nonlinearities in TGF‐mediated oscillations may result in increased NaCl delivery to the distal nephron. To address the concern that a more realistic TAL would damp harmonics, we have conducted simulations in a model TAL that has compliant walls and thus a tubular radius that depends on transmural pressure. These simulations predict that compliant TAL walls do not damp, but instead, intensify the harmonics.This research supported in part by NSF grant DMS‐0715021 and NIH grant DK‐42091.
The Mechanism of Zinc Inhibition of Glutamate Dehydrogenase Involves Subunit Communication
Authors: Sinanan Leander , Bell Ellis 
Published: June 2021

Zinc is a potent inhibitor of higher eukaryotic glutamate dehydrogenases. The mechanism of inhibition has previously been investigated using initial rate kinetic studies with either the dicarboxylic amino acid glutamate or the mono carboxylic alternative substrate norvaline. With glutamate zinc potently inhibits with the apparent affinity for zinc decreasing as the glutamate concentration decreases. With norvaline, no inhibition is seen. The goals of the current study were to quantitate the zinc binding, identify potential binding sites and determine whether or not zinc binding may be a] close to one of the three tryptophans in the protein, and b] induce conformational effects in the protein. Using the zinc sensitive chromophore 4‐par it is shown that zinc binds to glutamate dehydrogenase with a 1:1 stoichiometry with respect to polypeptide chains. Using tryptophan fluorescence spectroscopy it appears that zinc affects the most hydrophobic of the three tryptophans in the protein. Examination of the three dimensional structure of the enzyme raises the possibility that zinc binds at the subunit interface in the “twisty tie” region of the molecule. This is consistent with both the location of the most hydrophobic tryptophan and the fact that zinc appears to inhibit by disrupting subunit interactions necessary for full activity with glutamate as substrate.Supported by NSF grant MCB 0448905 to EB
Investigating the role of the eukaryotic elongation factors 1B‐α (1, 2) and eEF1B‐β (1, 2) from Arabidopsis thaliana in plant thermotolerance
Authors: Paul Megan Rose , Basha Eman , Vierling Elizabeth 
Published: June 2021

All organisms respond to heat stress by producing heat shock proteins (HSPs). The small HSPs (sHSPs) are a class of chaperones thought to prevent irreversible heat denaturation of other proteins and to facilitate refolding during recovery. In higher plants, sHSPs represent a major component of the response to heat stress. To understand the mechanism of protection by sHSPs, we have sought to identify substrates of cytosolic class I sHSPs in the model plant Arabidopsis thaliana. Putative substrates were identified as associated with sHSPs in vivo during heat stress. Among the proteins identified were several of the eukaryotic translation elongation factors (eEFs). Four of these, eEF1B‐α (1, 2) and eEF1B‐β (1, 2), have been selected to be investigated further. They are required for GDP exchange from eEF1A, a GTPase which delivers the tRNA to the ribosome. To study the interaction of these factors with, and their protection by sHSPs, we are purifying these eEFs. Recombinant proteins will be used to make antibodies to study interactions of sHSPs and these factors in vivo. The proteins will be used to investigate the mechanism by which the sHSPs protect these eEFs in vitro. We have also obtained T‐DNA insertion lines of these genes to examine their importance in plant thermotolerance.Project funding was provided by USDA‐NRICGP Grant 351001485 and NSF Grant IBN‐0213128 to EV and HHMI Grant 52005889 to the University of Arizona.
Control materials for validating measurement of vitamin D in key foods for the USDA National Food and Nutrient Analysis Program (NFNAP)
Authors: Holden Joanne M , Byrdwell William Craig , Exler Jacob , Harnly James , Hollick Michael , Hollis Bruce , Horst Ronald L , Patterson Kristine , Phillips Katherine , Wolf Wayne 
Published: June 2021

Data for vitamin D in the National Nutrient Database for Standard Reference are being updated. High priority foods including fish and vitamin D fortified orange juice, breakfast cereals, milk, American cheese, and yogurt were sampled (n=446) according to a nationwide plan, to be analyzed by qualified laboratories. A lack of certified reference materials required development of control materials to ensure accurate measurements. Matrix‐specific food homogenates (e.g. salmon, orange juice) were prepared and analyzed by six laboratories experienced in determining Vitamin D. Initial results showed wide disparity among the laboratories (CV = 26–46%). Subsequent recovery studies, mass spectrometric analysis, verification of standards, optimization of extraction solvents resulted in reliable values. The three labs chosen for future analyses obtained statistically similar results. These data were used to assign mean values and tolerance limits for four of the control materials. Due to inconsistent data for salmon, further work is required to validate those results.This research was supported by USDA, NIH, and the Beverage Institute for Health & Wellness (Coca‐Cola).
Do Americans eat more on weekends?
Authors: Rhodes Donna G. , Goldman Joseph D. , Moshfegh Alanna J. 
Published: June 2021

Nationally representative one‐day dietary data from What We Eat In America, NHANES 2001–2004 were analyzed for differences in estimated nutrient intakes and eating patterns on weekends and weekdays. The USDA Automated Multiple Pass Method was used to collect the 24‐hour recall from adult, aged 20 years and older, men (n=4385) and non‐pregnant/lactating women (n=4240). Overall, energy intake increased on weekend days (Fri‐Sun) compared to weekdays (Mon‐Thurs) for males (p<0.001) and females (p<0.01). Mean energy intake (±SEM) for males was 2464 ± 38 kcal/d on weekdays and 2747 ± 29 kcal/d on weekend days. Energy intake for females was 1773 ± 22 kcal/d and 1856 ± 17 kcal/d for weekdays and weekend days, respectively. Although total fat intake increased on weekend days, the proportion of energy from fat was similar on weekdays and weekend days. The proportion of energy from alcohol increased, whereas the proportion of energy from carbohydrate decreased on weekend days. These changes were significant (p<0.01) for both genders. Differences were also observed for nutrient intakes by eating occasion. In general, American adults are eating more kilocalories on weekend days compared to weekdays; these observations highlight the need for obesity prevention strategies to include a focus on weekend eating behaviors. The results of this study also illustrate the importance of considering weekend/weekday effects in dietary assessment.Funding source for this study is USDA.
Chromatographic profiles of Ginkgo biloba leaves and selected products
Authors: Lin Longze , Chen Pei , Ozcan Mustafa , Harnly James 
Published: June 2021

Ginkgo biloba leaves and their extracts are one of the most widely used herbal products in the world. Their flavonoids and terpene lactones are considered to be the main beneficial components. Previous studies have focused on specific components, or families of components, but a comprehensive study to identify all phenolic components is lacking. A method based on liquid chromatography separation and detection by diode array and electrospray ionization/mass spectrometry (LC‐DAD‐ESI/MS) was developed to obtain chromatographic profiles for the flavonoids and terpene lactones of Ginkgo biloba leaves. The method was used to identify 46 glycosylated flavonols and flavones, 3 free aglycones, catechin, 10 biflavones, 3,4‐dihydroxybenzoic acid, and 4 terpene lactones in aqueous methanol extracts of the leaf materials. The phenolics content of the Ginkgo biloba products were the same as the raw leaves, with the exception of the biflavones, which were only found in the raw leaves. This is the first report for more than 20 of the flavonoids found in Ginkgo biloba leaves.This research was funded by USDA and the Office of Dietary Supplements at the National Institutes of Health.
How geometric, electrical and contractile alterations effect cardiac function in the failing heart
Authors: Kerckhoffs Roy , Mulligan Larry , Omens Jeffrey , McCulloch Andrew 
Published: June 2021

In heart failure patients with left bundle branch block (LBBB) global and regional cardiac function is reduced.The goal of this study was to investigate how geometric, electrical and contractile alterations as they occur in heart failure with LBBB contribute to changes in global and regional function, using a numerical cardiovascular model.A 3D ventricular model was coupled to a closed circulation (with no mitral regurgitation). Cardiac cycles were simulated for all combinations of 4 altered input parameters (dilation, slower conduction, reduced peak fiber stress, longer fiber force twitch). Contributions of alterations and their interactions to cardiac global (stroke volume, SV) and regional function (CURE index of mechanical synchrony: 0<CURE<1) were calculated.Dilation increased SV, reduced peak stress, decreased SV, and their interaction was important for a decrease in SV (figure) in heart failure. Slower conduction was less important for SV. CURE depended on interactions between slower conduction and dilation, but reduced peak stress played a minor role.This study has been supported by Medtronic, UC Discovery Grant ITL06‐10159, NIH grants P41 RR08605 and HL32583, and NSF grant BES‐0506252.
Validation of Sun Exposure and Vitamin D Intake Recall Questionnaires for Estimating Vitamin D Status
Authors: Hall Laura Marie , Stephensen Charles B , Aronov Pavel A , Hammock Bruce D , Kimlin Michael G , Slusser James R 
Published: June 2021

Individual sun exposure and dietary intake both contribute to vitamin D status but simple, validated recall methods to assess these exposures are lacking. The objectives of our study were to validate both a sun exposure recall questionnaire, relative to a validated daily exposure log, and a vitamin D‐specific food frequency questionnaire (FFQ), relative to food records. We then assessed the ability of these methods, in conjunction with skin reflectance, to predict serum 25‐hydroxy vitamin D (25OHD) measured by LC‐MS. The study involved 72 healthy young adults each followed for 7‐8 wks during each season in Davis, CA. Spearman's correlation coefficients and validity coefficients were used to validate the methods. Multiple linear regression was used to predict serum 25OHD using sun exposure, skin reflectance and diet. The recall methods were highly correlated to the reference methods (sun: r = 0.83‐0.95, diet: r = 0.69‐0.77, p < 0.0001) and moderately correlated to serum 25OHD (sun: r = 0.40‐0.51, diet: r = 0.36‐0.37, p < 0.005). The recall measurements were all significant predictors of serum 25OHD (p < 0.05) and were not significantly different than the reference measurements in the regression model. These results show that the contribution of sun and diet to vitamin D status can be assessed using simple recall methods which may be used by nutritionists to predict individual needs for vitamin D intake.Grant Funding SourceNIH Grant P60 MD00222 and USDA Project 5306‐51530‐006‐00D
Alterations in splenic HSP70 and IL‐6 associated protein expression following heat stroke in mice
Authors: Helwig Bryan Glen , Leon Lisa R 
Published: June 2021

Plasma protein expression of HSP70 and IL‐6 are elevated following heat stroke (HS) in mice. The spleen is the largest secondary lymphoid organ in the body and we have shown this organ to be damaged following HS. Despite this, splenic expression of HSP70, IL‐6, and the IL‐6 receptor (IL‐6R) are not well understood. This study tested the hypothesis that HS would be accompanied by increased protein expression of IL‐6, IL‐6R, and HSP70 at HS collapse (Tc,Max=42.7°C), hypothermia depth (HD), and fever (24h) in splenic tissue. Spleens were harvested from control (n=4 per group) and HS mice at HS collapse (n=4), HD (n=4), and fever (n=4), protein isolated, and immunoblotting performed. Splenic HSP70 protein expression was only modestly increased at HS collapse but significantly elevated at HD through 24h of recovery. Splenic IL‐6 protein was not detected at any time point whereas IL‐6R was expressed, but not altered, at any point during or after HS. These data demonstrate that IL‐6 and IL‐6R protein expression are not significantly affected by HS or contribute to the development of splenic tissue damage. In contrast, splenic HSP70 protein expression is dynamic. Although HSP70 expression is significantly enhanced by HD and 24h the molecular chaperone is unable to protect the spleen against HS‐related tissue damage. Research supported by USAMRMC.Author views not official US Army or DoD policy
Role of Maternal/Fetal Iron Status on Placental Transferrin Receptor Expression
Authors: Young Melissa Fox , Foehr Marisa , McNanley Thomas , Cooper Elizabeth , Pressman Eva , Guillet Ronnie , Orlando Mark , McIntyre Allison , Lafond Julie , O'Brien Kimberly O 
Published: June 2021

The placenta plays an important role in mediating iron transfer to the fetus. However, the responsiveness of the placenta to maternal and fetal demands remains unclear. Placental transferrin receptor (TfR) is a key placental iron transport protein on the apical membrane. Placentas were collected from twelve pregnant adolescents (38‐40 wks gestation) and protein expression of TfR was examined. Iron status indicators were assessed from maternal blood obtained during the second trimester and at delivery. Cord blood samples were also collected at birth. There was a significant inverse relationship between cord serum ferritin (SF) and placental TfR expression (P=0.042). A non‐significant inverse trend was detected between maternal SF in the second trimester and placental TfR expression (P=0.075). Relationships between maternal SF in the second trimester and cord SF approached significance (P=0.055). However, maternal SF at birth was not significantly related to placental TfR expression or cord SF. Hemoglobin and TfR in both the infant and mother were not significantly related to placental TfR expression. In conclusion both maternal and fetal iron status appear to impact placental expression of TfR. Studies are on‐going to assess the impact of maternal iron status on neonatal iron stores at birth in the planned cohort of 300 pregnant teens.Grant Funding SourceSupported by USDA Grant no. 2008‐0857.
A diet high in meat protein and potential renal acid load increases absorption and urinary excretion of calcium, as well as serum IGF‐I in postmenopausal women
Authors: Cao Jay J , Johnson LuAnn K , Hunt Janet R 
Published: June 2021

The objective was to determine the effect of increasing protein and potential renal acid load (PRAL) on Ca retention and markers of bone metabolism.In a randomized crossover design, twenty postmenopausal women consumed two diets: one low protein, low PRAL (LPLP) and one high protein (mostly meat), high PRAL (HPHP) for 7 wk each, separated by a one‐week break. After 3 wk, the entire 2‐d menu of each diet was radio‐labeled with 47Ca and retention was measured by whole body scintillation counting for 4 weeks. Biomarkers of bone metabolism in blood and urine were measured.ResultsCompared with the LPLP diet, the HPHP diet increased urinary acidity (pH: 7.1 vs. 5.9, ±0.25*, p < 0.01), urinary Ca excretion (156 vs. 203, ±63 mg/d, p < 0.01), and blood IGF‐I levels** [137 (103 ‐ 184) vs. 174 (130 ‐ 232) ng/ml, p < 0.01) consistently from week 1 through 7. The fractional Ca absorption was lower in subjects with LPLP than with HPHP diet (25.0 vs. 30.4, ±5.4%, respectively, p < 0.02). The HPHP diet tended to increase the absolute amount of Ca absorbed compared with LPLP diet (227 vs. 258, ±47 mg/d, p < 0.08).ConclusionsIn postmenopausal women, a diet high in both meat protein and PRAL increased serum IGF‐I and Ca absorption, which compensated the increase in urinary excretion. A high meat diet does not appear detrimental for bone health.*Pooled SD; **Geometric means (range).Supported by USDA‐ARS and the National Cattlemen's Beef Association.
Green tea EGCG suppresses T cell proliferation by impairing IL‐2/IL‐2R signaling leading to inhibition of cell cycle
Authors: Pae Munkyong , Meydani Simin Nikbin , Meydani Mohsen , Shang Fu , Wu Dayong 
Published: June 2021

Epigallocatechin‐3‐gallate (EGCG), an active ingredient of green tea, has been indicated to have various health benefits. However, little is known about the effect of EGCG on immune function. In this study, we investigated the effect of in vitro EGCG supplementation at physiologically relevant levels on T cell proliferation and its underlying mechanism. Purified T cells were isolated from the spleens of male C57BL/6 mice and stimulated with anti‐CD3/CD28 in the presence of EGCG (2.5‐15 μM). EGCG dose‐dependently inhibited T cell proliferation and cell division, which was more pronounced in CD4+ than in CD8+ T cells. The EGCG‐induced inhibition of T cell division was due to cell cycle arrest as fewer cells entered S‐G2‐M phase. Since IL‐2 is a key factor for T cell proliferation, we determined the effect of EGCG on IL‐2 and IL‐2 receptor (IL‐2R, CD25) levels. Surprisingly, EGCG increased IL‐2 secretion in total T cells. Intracellular staining for IL‐2 indicates that EGCG increased percentage of IL‐2+ cells in CD8+ but not CD4+ population. Furthermore, EGCG reduced the mean intensity of IL‐2 in both CD8+ and CD4+ cells. EGCG did not significantly affect the percentage of CD25+ (IL‐2R) cells but reduced the IL‐2R expression per cell. This suggests that EGCG may inhibit T cell proliferation by inducing cell cycle arrest, which is in turn due to impaired IL‐2/IL‐2R signaling. Increased extracellular IL‐2 might result from decreased internalization and utilization due to less expression of IL‐2R. T cell‐suppressive effect of EGCG might be utilized to ameliorate T cell‐mediated autoimmune diseases.Grant Funding SourceUSDA #58‐1950‐7‐707