bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluctuations in surface pH of maturing rat incisor enamel are a result of cycles of H+‐secretion by ameloblasts and variations in enamel buffer characteristics (1098.1)
Authors: Frische Sebastian , Damkier Helle , Josephsen Kaj , Takano Yoshiro , Zahn Dirk , Fejerskov Ole 
Published: June 2021

The large hydroxyapatite (HA) crystals in dental enamel results from a long lasting process called enamel maturation, which follows a stage of enamel matrix secretion. Thus, after the full thickness of enamel is reached, the enamel still requires about 60‐70 % mineral to be deposited by HA‐crystals growing in width and thickness. This is facilitated by the ameloblasts, which during maturation change morphology every 6‐8th hour. This study aims to test the role of the ameloblasts in maintaining enamel pH in the maturation zone in order to elucidate the role of the cyclic changes in ameloblast morphology for HA‐crystal growth.Colorimetric pH‐indicators and ratiometric fluorometry were used to measure surface pH in maturation zone enamel of rat incisors. Alternating acidic (down to pH 6.24±0.06) and alkaline zones (up to pH 7.34±0.08) corresponding to ruffled‐ended and smooth‐ended ameloblasts, respectively, were found along the tooth thus coinciding with ameloblast morphological cycles. Underlying the cyclic pattern, a gradual decrease in pH towards the incisal edge was seen. Vinblastine or FR167356 (H+‐ATPase‐inhibitor) disturbed ameloblast acid‐secretion, especially in the early parts of acidic zones.At the pH‐values observed, PO43‐ would be protonated (pKa >12) and HA dissolved. However, by molecular dynamics simulations we estimate the pKa of HPO42‐ at an ideal HA surface to be 4.3. The acidic pH measured at the enamel surface may thus only dissolve non‐perfect domains of HA crystals in which HPO42‐ is less electrostatically shielded. As a result of the repeated alkaline/acidic cycles induced by ameloblasts, near‐perfect domains will therefore gradually replace less perfect domains and large near‐perfect HA crystals will be produced.In conclusion, fluctuations in surface pH of maturing rat incisor enamel are a result of cycles of H+‐secretion by ameloblasts and variations in enamel buffer characteristics.
Regulation of ENaC, AE1 and H+ ATPase in renal intercalated cell specific NBCe2 knockout mice (1098.5)
Authors: Pedersen Fredrik , Praetorius Jeppe , Damkier Helle 
Published: June 2021

Regulation of ENaC, AE1 and H+ ATPase in renal intercalated cell specific NBCe2 knockout mice Fredrik D Pedersen, Jeppe Praetorius and Helle H Damkier, Department of Biomedicine, Health, Aarhus University, Denmark NBCe2 is an electrogenic Na+ HCO3‐ cotransporter expressed in the brain and kidney. In mouse, NBCe2 mRNA is localized in the collecting duct principal cells; however, attempts to locate the protein in mice have been unsuccessful. In humans, immunohistochemical studies localized NBCe2 to the apical membrane of apparent intercalated cells. Mice lacking NBCe2 are hypertensive and have lower urinary pH, but the mechanism behind and cellular origin of this phenotype is unknown.The aim of the study is to define the cell type responsible for development of hypertension in NBCe2 knockout mice.Intercalated cell specific NBCe2 knockout mice (IC‐KO) were generated using the loxP/cre system. Mice expressing cre recombinase driven by the promotor for the intercalated cell H+ ATPase, B1 were crossed with floxed NBCe2 mice.Tail cuff measurements and urine electrolyte analyses revealed no differences in blood pressure or urine composition between the IC‐KO mice and wildtype littermates. However, immunoblot analysis revealed decreased abundance of the membrane transporters AE1, αENaC and H+ ATPase in the IC‐KO mice. Furthermore, immunohistochemical analysis showed increased γENaC abundance in the apical plasma membrane of the IC‐KO mice.In conclusion, the IC‐KO mouse model does not display the hypertensive phenotype of the full NBCe2 knockout mouse. Nevertheless, the changes in abundance and subcellular localization of key renal membrane transporters indicate a significance of NBCe2 in intercalated cells in mice. However, the changes could also reflect the activity of cre recombinase in a subset of cortical principal cells that has been described for the cre mouse.
Aquaglyceroporin HC‐3 mediates hypotonicity‐induced cell volume and shape changes in cultured erythrocytes from Cope’s gray treefrog, Hyla chrysoscelis (1099.4)
Authors: Hawk Mark , Nickell Philip , Frisbie James , Goldstein David , Krane Carissa 
Published: June 2021

Freeze tolerant Cope’s gray treefrog, Hyla chrysoscelis, accumulates glycerol during a process of cold‐acclimation in anticipation of freezing. Glycerol acts as a cryoprotectant to control osmotic gradients formed by extracellular ice crystals during freezing. The aquaglyceroporin, HC‐3, is abundantly expressed in the membrane of erythrocytes from H. chrysoscelis, where it facilitates osmotically driven transmembrane water flux and glycerol diffusion, both important in freeze tolerance. We hypothesize that HC‐3 functions to moderate the dynamic cell shape changes that occur during the freeze/thaw process as a result of hypotonicity induced cell volume expansion. Cultured erythrocytes subjected to moderate hypotonic stress (70 mOsM) in the absence of 0.3 mM HgCl2, underwent a series of shape changes: they swelled, initially elongated, then became swollen and round, before returning to an elongated state. Erythrocytes treated with an HC‐3 morpholino to knockdown HC‐3 expression become spherical and remained spherical in response to hypotonic challenge. Within 600 seconds of the initiation of the hypotonic challenge, 80% of control cells succumbed to hypotonicity‐induced cell lysis, whereas 70% of the morpholino‐treated cells remained intact. These data indicate that HC‐3 functions in regulating erythrocyte cell volume in response to hypotonic challenge, implicating a role for HC‐3 in cellular freeze tolerance.Grant Funding Source: This research was supported by NSF Research Grant IOS‐1121457.
Impact of hypercapnic incubation on hatchling common snapping turtle (Chelydra serpentina) growth and metabolism (1101.3)
Authors: Wearing Oliver , Eme John , Kemp Adam , Crossley Dane 
Published: June 2021

Some reptilian embryos are naturally exposed to low levels of O2 and high levels of CO2. This phenomenon has provoked much research on the physiological effects of developmental hypoxia in reptiles and associated implications on survival. However, notably less attention has been given to the effects of hypercapnia. In this study, we investigated the growth trajectories and metabolic rates (resting and postprandial) of common snapping turtle (Chelydra serpentina) hatchlings that were chronically incubated as embryos in one of three environmental conditions: Atmospheric CO2 (control); 3.5% CO2 (3.5%); and 7% CO2 (7%). Control and 7% hatchlings had similar growth trajectories and mean masses. However, the 3.5% animals had both a higher mean mass and a steeper trajectory compared to the other conditions. VO2 experiments revealed that resting metabolic rate was significantly elevated in the hypercapnic conditions compared to the control condition. Moreover, the postprandial metabolic rate was 1.6‐ to 1.7‐fold higher than resting in the hypercapnic, compared to a 2‐fold increase in the normal incubated turtles. This study not only demonstrates that snapping turtles can survive considerable hypercapnia during embryonic development, but also that incubation condition has lasting effects on physiology post‐hatching.Grant Funding Source: Supported by NSF CAREER IBN IOS‐0845741 to DAC
Role of synemin, an intermediate filament protein, in adult skeletal muscle (1102.25)
Authors: Garcia‐Pelagio Karla , Muriel Joaquin , Lund Linda , Bond Meredith , Bloch Robert 
Published: June 2021

Intermediate filament (IF) related diseases are linked to defects in proteins that are associated with the contractile apparatus of skeletal and cardiac muscle, and with costameres. Synemin is a large IF protein that associates with dystrobrevin, vinculin, and talin at costameres at the sarcolemma of striated muscle, as well as with α‐actinin and desmin at Z disks. Synemin can be expressed in either 210 kDa α‐ or 180 kDa β‐ alternatively spliced forms. We generated mice null for synemin by homologous recombination to study synemin’s function in skeletal muscle. Skeletal muscle in the knock out (syn KO) mouse does not make synemin mRNA or protein. Preliminary characterization of the syn KO mouse suggests that it has a mild skeletal muscle phenotype. The organization of costameres appears to be normal, but the fibers appear smaller than controls. Treadmill running uphill test results was not significantly affected when compared to controls. More notably, we have observed differences in the biomechanical properties of the sarcolemma. Stabilization time of blebs generated by applying fixed suction pressure through a pipette to the surface membrane of single Extensor digitorum longus fibers, were slower in the syn KO than in controls but faster than in desmin KO and mdx fibers, which lack dystrophin. Furthermore, the pressure at which the blebs separated from underlying contractile structures were lower than in controls. These results suggest that the viscoelastic properties of the sarcolemma‐costamere‐myofibril complex are significantly influenced by synemin, but less than by desmin and dystrophin.Grant Funding Source: Supported by APS Postdoctoral Fellowship Physiological Genomics and CONACyT to KGP. By NIH to RJB
Regional differences in the cutaneous thermal sensitivity to wetness across the torso (1104.10)
Authors: Filingeri Davide , Redortier Bernard , Hodder Simon , Havenith George 
Published: June 2021

Humans are not provided with humidity receptors and the ability to perceive skin wetness seems to rely on the sensory inputs arising from thermal cold afferents. Given the regional variability in thermal sensitivity across the torso, we examined whether regional differences in the sensitivity to wetness exist. Sixteen male participants were tested at rest. Twelve regions of the torso were stimulated with a dry or wet thermal probe (25cm²) set at a temperature of 15°C below the local skin temperature, which was measured pre and post stimulation. Thermal and wetness sensations were recorded using likert scales. As a result of the same relative cold stimuli, the skin cooling response varied by location and regional differences were found in thermal and wetness sensations. The lateral chest showed the greater drop in local skin temperature. Colder sensations were reported on the lateral abdomen and lower back. Greater wetness was reported on the lower back. No differences were perceived between wet and dry stimuli, the dry ones perceived as wet as the wet ones. The regional variability in wetness sensitivity showed a pattern similar to the thermal sensitivity to cold. We conclude that, as thermal cold afferents seem to have a critical role in driving the perception of wetness, based on the regional variability in thermal sensitivity, humans present regional differences in the cutaneous sensitivity to wetness across the torso.Grant Funding Source: Supported by Loughborough University and Oxylane Research
Efficacy of a novel green coffee bean extract (GCB‐70) in weight management (1107.2)
Authors: Swaroop Anand , Bagchi Manashi , Kumar Pawan , Bagchi Debasis 
Published: June 2021

Green coffee beans (GCB) are the unroasted beans or raw seeds from the Coffee fruits, which are novel, natural source of a powerful antioxidant, chlorogenic acids, as well as caffeine, caffeic acid, vanillic acid, quinides, lignans and trigonelline. Chlorogenic acids enhance the taste and caffeine solubility. Chlorogenic acid has been demonstrated to reduce the absorption of fat from food intake and improves glucose metabolism, and promotes anti‐aging pathophysiology. Our laboratories have developed a novel, patented GCB extract GCB‐70 enriched with 70% total chlorogenic acids (tCGA) which includes 35% of 5‐caffeoylquinic acid (5‐CQA). The presently available GCB extracts contain only 45% tCGA including 15% 5‐CQA. Studies demonstrated that GCB‐70 is safe, potent, which potentiates antioxidant efficacy against oxidative stress, regulates blood pressure and improve cognitive functions. Furthermore, GCB‐70 accelerates glucose and fat metabolism, and may be an effective and inexpensive means for weight management. These results are very encouraging. Further research studies are in progress.Grant Funding Source: Company
Compound 21 ameliorates type 2 diabetes in Zucker diabetic fatty rats by islet preservation (1108.13)
Authors: Shao Chunhong , Yu Li , Gao Lie 
Published: June 2021

This study aimed to evaluate the therapeutic potential of Compound 21 (C21), a nonpeptide AT2R agonist, on type 2 diabetes in Zucker Diabetic Fatty (ZDF) rats. Rats received C21 infusion (0.3 mg/rat/day; saline as the control) from the age of 4 weeks to 16 weeks. The blood glucose, water intake, and urine excretion were monitored weekly. At the end of C21 treatment, the islet function, morphology, endoplasmic reticulum (ER) stress markers, beta‐cell proliferation markers, and apoptosis were examined by oral glucose tolerance test, immunofluorescence, western blotting, and TUNEL staining. The serum insulin concentration was measured by ELISA. We found that, compared with control ZDF rats, C21‐treated ZDF rats displayed significantly lower blood glucose, water intake, and urine excretion from the day 7 post C21 treatment. These rats also exhibited significantly less islet destruction, elevated serum insulin level (2.45 ± 0.21 vs 1.24 ± 0.04 ng/ml; P < 0.05), and improved glucose tolerance (peak glucose level: 131.5 ± 1.7 vs 219.0 ± 17.0 mg/dl; P < 0.05). In the islets of these rats, we found lower Bip (17.1 ± 1.24 vs 54.2 ± 3.6 %; P < 0.05) and Chop signals, less apoptosis (21.3 ± 1.07 vs 61.0 ± 5.34 %; P < 0.05), and up‐regulated Ki67 expressions. Our data suggested that C21 treatment ameliorated type 2 diabetes by preserving islets through suppressing ER stress, attenuating apoptosis, and promoting proliferation of beta‐cells.Grant Funding Source: Supported by NIH
AMPK regulates the vacuolar proton‐ATPase via 14‐3‐3 proteins (1109.11)
Authors: Al‐bataineh Mohammad , Gong Fan , Li Hui , Marciszyn Allison , Bhalla Vivek , Hallows Kenneth , Pastor‐Soler Núria 
Published: June 2021

The vacuolar proton‐ATPase (V‐ATPase) mediates proton transport across membranes. The V‐ATPase is expressed at the apical membrane of kidney type A collecting duct intercalated cells (ICs). Defects in the V‐ATPase may cause renal tubular acidosis with kidney and systemic complications. In a cell line of IC origin, Clone C cells, we showed that the V‐ATPase A subunit is phosphorylated directly by AMPK at Ser‐384. In addition, AMPK activators induced an acute cytoplasmic redistribution of the V‐ATPase in ICs. AMPK regulates transport proteins by promoting their ubiquitination and degradation, mechanisms that are likely important for inhibition of membrane transport during cellular metabolic stress. We have shown that Ser‐384 is necessary for the AMPK‐mediated cytoplasmic redistribution of the pump. It has been previously shown that the V‐ATPase A subunit binds to 14‐3‐3 proteins (14‐3‐3s), and we noticed that Ser‐384 exists within a ‘mode 1’ 14‐3‐3 binding motif. Dimeric 14‐3‐3s bind to phosphorylated sites on target proteins and thereby modulate protein‐protein interactions. We thus hypothesized that AMPK may promote V‐ATPase A subunit ubiquitination as well as increased binding to 14‐3‐3s. We detected increased co­immunoprecipitation of 14‐3‐3s to FLAG‐tagged A subunit expressed in Clone C ICs treated with the AMPK activator AICAR as compared with untreated cells. Furthermore, AICAR‐treated Clone C ICs had greater A subunit ubiquitination than untreated cells. We propose that A subunit 14‐3‐3 binding and ubiquitination are mediated by AMPK‐dependent Ser‐384 phosphorylation, thus linking regulation of the V­ATPase to AMPK during metabolic depletion in ICs.Grant Funding Source: Supported by NIH/NIDDK
Loss of carbonic anhydrase IX expression impairs gastric mucosal defence against luminal acid (1109.13)
Authors: Li Taolang , Liu Xuemei , Singh Anurag , Riederer Brigitte , Gros Gerolf , Bartels Helmut , Tuo Biguang , Seidler Ursula 
Published: June 2021

Background: The exoenzyme carbonic anhydrase IX is strongly expressed in tumours. In normal tissues, CA IX is expressed during embryogenesis but downregulated postnatally, except in the stomach. Aim and Methods: We studied the cellular differentiation pattern and acid secretory capacity in gastric mucosa from CAIX KO and WT mice at age 8 days to 1,3,6,9,12 months. Surface pH and mucus layer thickness, as well as the ability of the surface epithelial cells to withstand a luminal acid load was assessed in young adult CAIX KO and WT mice by in vivo two photon microscopy. Results: CAIX KO gastric mucosa developed a unique phenotype with a gradual expansion of the surface cell zone, and regression of the parietal cell zone to the lower gland area. Concomitantly, the acid secretory capacity, which was normal at young age, declined. HCO3‐ output into the lumen and mucus layer thickness were not significantly different between CAIX KO and WT. However, the ability of the surface cells to withstand a luminal acid load, as well as to maintain a more alkaline surface pH than the luminal pH, was significantly impaired in CAIX KO compared to WT stomach. Conclusion: We speculate that the CAIX at the basolateral membrane of the gastric surface cells rapidly converts extruded protons with blood‐borne HCO3‐ to CO2 and thus augments interstitial buffer capacity, surface cell pHi regulation, and maintenance of the pH microclimate in the mucus layer.Grant Funding Source: Supported by DFG Se 13‐4 and 9‐6 to Ursula Seidler
Actin depolymerizing factor but not cofilin‐1 is necessary to have a normal intestinal brush border (1109.16)
Authors: Gao Lucy , Sarker Rafiquel , Donowitz Mark 
Published: June 2021

Two highly conserved isoforms of the cofilin gene family (actin severing proteins expressed in intestinal epithelial cells) are cofilin‐1 (COF) and actin depolymerizing factor (ADF). COF and ADF take part in Arp2/3 remodeling and seem to play overlapping roles since both rescue the knockdown (KD) phenotypes of the other. Their precise role in the intestine is unknown. We hypothesized that COF and/or ADF change local actin polymerization at the base of epithelial cell microvilli by terminal web remodeling. COF and ADF were KD using lentivirus/puromycin in Caco‐2 cells, a polarized intestinal Na‐absorptive cell line. Both were normally subapical, as well as diffusely cytosolic in the cells. Structural studies were performed using confocal and electron microscopy with brush border (BB) characterization by phalloidin and wheat germ agglutinin binding. ADF KD, but not COF, significantly changed epithelial cell structure with a) shorter cell heights; b) greater cell diameter; c) shorter/sparser BB. In addition, Western blot showed increased B‐actin and villin amount in ADF KD cells, normalized to GAPDH. In contrast, COF KD had less dramatic changes in intestinal cell structure: a) slight increase in cell height; b) taller/denser microvilli; c) minimally increased B‐actin and villin. We conclude that in spite of similar sub‐apical localization, ADF but not COF is necessary to have a normal intestinal BB, including the microvilli.Grant Funding Source: Supported by APS UGSRF, NIH NIDDK R01DK26523, R01DK61765, P01DK72084, P30DK89502
Impaired serotonin transporter function in the small intestine of mice on a high fat diet (1110.6)
Authors: France Marion , Galligan James , Swain Greg 
Published: June 2021

Background: Obesity can alter 5‐HT (serotonin) availability in the gut mucosa disrupting motility. 5‐HT availability depends on 5‐HT released from enterochromaffin (EC) cells and by 5‐HT uptake by the serotonin transporter (SERT). We determined if 5‐HT availability was altered in the jejunum of control and high fat fed (HF) obese mice.Methods: 5‐HT mucosal levels were measured using high‐performance liquid chromatography. Amperometry measured 5‐HT availability in real time near the mucosal surface (i.e. near sites of release and uptake). We generated current approach curves in which the electrode distance in relation to the mucosa decreased in a step‐wise fashion. We obtained the slope derived from a linear fit of the ln(current) vs. electrode distance plot. A decrease in 5‐HT uptake caused by the SERT inhibitor fluoxetine (1 μmol L‐1) or cocaine (10 μmol L‐1) was indicated by a decrease in the slope.Results: 5‐HT mucosal levels were not different in HF mice compared to controls. In HF mice, 5‐HT clearance was insensitive to fluoxetine and cocaine compared to controls suggesting SERT function was impaired and other monoamine transporters did not compensate for loss of SERT function.Conclusions: Our data suggests SERT function is impaired in HF mice whereas mucosal 5‐HT levels are unchanged. Impaired SERT function can change GI motility by elevating extracellular 5‐HT and increasing 5‐HT signaling.Grant Funding Source: Supported by R01DK094932
Modeling ZO‐1‐C‐terminal domain exchange at the membrane as a diffusion problem (1111.4)
Authors: Nepomuceno Helene , Nguyen Crystal , Ogawa Katherine , Hasfura‐Buenaga J. Roberto , Balreira E. Cabral , King Jonathan 
Published: June 2021

Zonula occludens‐1 (ZO‐1) is a membrane‐associated tight junction protein that has been observed to participate in ATP‐dependent exchange via an intracellular pool. We hypothesized that a diffusion model can explain the ZO‐1‐C‐terminal domain exchange dynamics at the tight junction. We developed stable cell lines with GFP‐ZO‐1 carboxy‐terminus fusion constructs in Madin‐Darby canine kidney cells. Fluorescence recovery after photobleaching (FRAP) experiments were conducted using a Nikon A1R laser scanning confocal microscope to photobleach the localized construct and acquire intensity data over time. Recovery was analyzed by partitioning the bleach region of interest into one‐square micron sections or the entire bleach ROI. The local fluorescence recovery in the photobleached area yields curves that are modeled to be solutions of the diffusion process. Fitting experimental data to a one‐ or two‐dimensional diffusion model will quantitatively reveal if the exchange occurs within the membrane or via an intracellular pool, respectively. Future research will compare the behavior of different ZO‐1 constructs and relate the quantity of ZO‐1 expression to its recovery behavior.Grant Funding Source: Supported in part by NSF‐MRI #1229702 and NSF Award #0926702.