bluuebunny/crossref_metadata_2025_split huggingface dataset:
Importance of adenylyl cyclase 6 in developing lithium‐induced nephrogenic diabetes insipidus
Authors: Poulsen Søren Brandt , Kristensen Tina Bøgelund , Brooks Heddwen L. , Rieg Timo , Fenton Robert A 
Published: November 2023

Nephrogenic diabetes insipidus (NDI) develops in approximately 50% of psychiatric patients being treated with lithium (Li+). The mechanism behind Li+‐induced NDI (Li‐NDI) is only poorly understood, but it occurs at least partly due to reduced aquaporin‐2 (AQP2) expression, leading to lower water reabsorption in collecting ducts (CD) of the kidney. A suggested mechanism inducing these effects is that Li+ inhibits adenylyl cyclase (AC) activity and thereby decreases cAMP levels and subsequently reduces AQP2 abundance and membrane targeting. In the present study, we tested the hypothesis that Li‐NDI would not develop in mice lacking AC6, the AC isoform responsible for the majority of vasopressin‐induced inner medullary (IM) cAMP formation. Total‐body AC6 knockout (AC6−/−) mice and newly developed connecting tubule/principal cell‐specific AC6 knockout mice (AC6loxloxCre) were studied. Similar to AC6−/− mice, the novel AC6loxloxCre mice had lower urine osmolality [mean ± SE (n): control 2363 ± 114 mmol/kg (17), AC6loxloxCre 1219 ± 49 mmol/kg (9); P < 0.05] and higher water intake [control 0.19 ± 0.01 g/g BW/24h (7), AC6loxloxCre 0.28 ± 0.02 g/g BW/24h (6); P < 0.05]. In both controls, AC6−/−, and in AC6loxloxCre mice, dietary Li+ administration increased the water intake (P < 0.05) and reduced the urine osmolality (P < 0.05). Similar to AC6−/− mice, the AC6loxloxCre mice showed under standard conditions lower medullary levels of AQP2 (42% reduction, P < 0.05) and pS256‐AQP2 and (51% reduction, P < 0.05) and the levels were further reduced by respectively 54% and 57% after Li+ administration (P < 0.05). Furthermore, Li+ induced an increase in the numbers of proliferating cell nuclear antigen‐positive cells in the IMCD in both AC6loxloxCre (~2200% increase, P < 0.05) and control mice (~2600% increase, P < 0.05). However, compared to control mice, a greater % of H+‐ATPase B1 subunit‐positive cells were found in the AC6loxloxCre mice under both standard condition (32%, P < 0.05) and after Li+‐administration (33%, P < 0.05). Collectively, AC6 plays a minor role in the development of Li‐NDI, but could have an important function in determining the intercalated‐to‐principal cell ratio, which is altered during Li‐NDI.Support or Funding InformationFunding to R.A.F. is provided by the Novo Nordisk Foundation, the Lundbeck Foundation and Danish Medical Research Council. T.R. is supported by NIDDK 1R01DK110621‐01, the O'Brien Center for Acute Kidney Injury Research Grant P30DK079337, the Diabetes Endocrinology Research Center P30DK063491, the AHA 15BGIA22410018 and Satellite Healthcare (a not‐for‐profit renal care provider).
Ischemia leads to increases in tight junction mobility following FRAP in vivo
Authors: Kolb Alexander , Amsler Kurt , Bacallao Robert 
Published: November 2023

BackgroundAfter an injury to a cells tight junction it is hypothesized that these junctions become immobile and have a slow turnover rate contributing to leak and polarity changes leading to cell death. However, our in vivo data indicates ischemia increases the rate of tight junction turnover compared to pre ischemic tight junctions.MethodsIn vivo‐Adenoviral GFP occludin was hydrodynamically delivered through the renal vein. Four days later the kidney was exposed and labeled tight junctions were selected for FRAP. FRAP was conducted on both pre and post ischemic tight junctions and on non‐tight junction regions. In vitro‐GFP occludin transduced MDCK cells were serum starved overnight. Cells were treated with 0 μM H2O2, 55 μM H2O2 or 110 μM H2O2 for 2 hours at 37°C before FRAP. The tight junction region or a non‐tight junction region of the apical membrane was selected for FRAP.ResultsIn vivo‐The immobility of pre ischemic tight junctions is 93% (SD 9%). The immobility of ischemic tight junctions is 34% (SD 24%). The average half‐life for recovery of ischemic tight junctions is 23.13 seconds (SD 1.07). The pre ischemic tight junctions show minimal recovery at 180 seconds post FRAP. In vitro: Control cells treated with 0 μM H2O2 have an immobility of 43% (SD 14%;) with a half‐life of 68.2 seconds (SD 17.3 seconds). Cells treated with 55 μM H2O2 have an immobility of 32% (SD 16%) with a half‐life of 88.5 seconds (SD 23.7 seconds). Cells treated with 110 μM H2O2 have an immobility of 37% (SD 15%) with a half‐life of 82.3 seconds (SD 21.03 seconds). Results are statistically significant, p value <0.05ConclusionsIn vitro tight junction turnover following FRAP occurs much faster in wild type cells then it does in injured cells. This data indicates that injury actually slows down tight junction turnover compared to control cells. However, these results are contradictory to the in vivo data that indicates ischemic injury increases tight junction turnover.Support or Funding InformationVA Merit
Identification of β‐Catenin Interacting Proteins in the Nuclei of Native Rat Renal Inner Medullary Collecting Duct Cells
Authors: Hwang Jacqueline , Jung Hyun Jun , Chou Chung‐Lin , Knepper Mark 
Published: November 2023

The gene encoding the aquaporin‐2 water channel (AQP2) is regulated transcriptionally in response to vasopressin. Vasopressin increases phosphorylation of many proteins in collecting duct cells including AQP2 and β‐catenin (at Serine‐552), a multifunctional protein that can function as a transcriptional co‐regulator in the nucleus. β‐catenin phosphorylation is associated with translocation of β‐catenin from the cytoplasm to the nucleus of collecting duct cells where it may bind to transcription factors and other regulatory proteins. The purpose of this study was to identify β‐catenin interacting proteins in the nuclei of inner medullary collecting duct (IMCD) cells isolated from rat kidneys using chromatin immunoprecipitation coupled to mass spectrometry (ChIP‐MS). Samples were analyzed from rat IMCD suspensions treated either with the vasopressin analog dDAVP or its vehicle for 30 minutes in vitro. After crosslinking and nuclear isolation, chromatin immunoprecipitation was performed using a well characterized β‐catenin antibody (or with pre‐immune IgG). The co‐immunoprecipitated proteins were identified by protein mass spectrometry (n=4 for both dDAVP and control). We reproducibly identified 43 β‐catenin binding proteins present with β‐catenin antibody but not pre‐immune IgG, which included a number of known β‐catenin binding partners as well as many novel interacting proteins. There were no sequence‐specific transcription factors, but there were multiple proteins known to be involved in transcriptional regulation (Jup, Tdrd3, Lgr4, Cdh1, Cenpj, Taf1, and several histones). Binding of some proteins to β‐catenin changed in response to dDAVP (Minimum Bayes' Factor < 0.01) (Plec [down], Cdh1 [up], Krt4 [up], Lrba [up], Sptbn2 [up], and Tenm3 [up]). These findings provide key information necessary for modeling the transcriptional response to vasopressin. [JH supported by APS Undergraduate Summer Research Fellowship Program.]Support or Funding InformationThe work was supported by the APS Undergraduate Summer Research Fellowship and NHLBI Intramural Research Program (project ZIA‐HL001285 and ZIA‐HL006129, M.A.K.).
Intestinal adenylyl cyclase 6 mediates cholera toxin‐induced diarrhea
Authors: Rieg Timo , Kaji Izumi , Akiba Yasutada , Kaunitz Jonathan , Poulsen Søren B. , Dominguez Rieg Jessica A. , Fenton Robert A. 
Published: November 2023

It is commonly considered that the action of cholera toxin (CT) depends on cAMP‐mediated active Cl− secretion via cystic fibrosis transmembrane conductance regulator (CFTR). The constitutive activation of adenylyl cyclase (AC) in response to CT is caused by ADP‐ribosylation of Gsα causing CFTR activation and consequently rice water diarrhea. However, the AC isoform(s) involved remains unknown. Here we report that AC6 mRNA levels are the highest of all 9 membrane‐bound AC isoforms in epithelial cells isolated from mouse small intestine and colon. To define its in vivo role, we compared AC6loxlox (Con) and newly generated intestinal specific (VillinCre) AC6 knockout (AC6loxloxCre) mice. AC6loxloxCre mice have undetectable AC6 protein and mRNA in enterocytes and colonocytes. With free access to food and water, AC6loxloxCre mice show no significant differences in fluid or food intake or plasma electrolytes (Na+, K+ and Ca+) compared to Con mice. Intestinal/colon length and villus length/crypt depth were comparable between genotypes. Both genotypes had comparable fecal water content (66±3 vs 66±2%, not significant; NS). Six hours after oral gavage of 10 μg CT, Con mice had a significant increase in intestinal fluid accumulation ratio (FAR, weight of intestine before vs after fluid removal) compared to vehicle (1.58±0.05 vs 1.18±0.05, P<0.05). In contrast, FAR in response to CT was not different from vehicle in AC6loxloxCre mice (1.20±0.05 vs 1.16±0.04, NS). Ussing chamber experiments using whole thickness ileum showed no significant differences in baseline short‐circuit current (Isc) between AC6loxlox and AC6loxloxCre mice (36±8 vs 38±8 μA/cm2, NS). In response to forskolin (unselective AC activator, 1 μM) or CT (120 nM) Isc increased significantly in Con mice (ΔIsc: 36±4 and 40±7 μA/cm2, P<0.05, respectively); however, responses in AC6loxloxCre mice were absent (1.6±0.8 and 3.9±2.2 μA/cm2, NS, respectively). These results demonstrate that AC6 is mediating forskolin and CT‐induced changes in Isc, consequently AC6loxloxCre mice are resistant to CT‐induced diarrhea.Support or Funding InformationT.R.: NIDDK 1R01DK110621‐01, O'Brien Center for Acute Kidney Injury P30DK079337, Diabetes Endocrinology Research Center P30DK063491, AHA 15BGIA22410018.J.D.R.: Bastyr University Faculty Research Seed Grant.R.A.F.: Lundbeck Foundation, the Danish Medical Research Council, Novo Nordisk Foundation
AVP dynamically increases paracellular Na+ permeability and transcellular NaCl transport in the medullary thick ascending limb of Henle's loop
Authors: Leipziger Jens , Himmerkus Nina , Plain Allein , Marques Rita D , Sonntag Svenja , Paliege Alexander , Bleich Markus 
Published: November 2023

The medullary thick ascending limb of Henle's loop (mTAL) is crucial for urine concentrating ability of the kidney. It is water tight and able to dilute the luminal fluid by active transcellular NaCl transport, fueling the counter current mechanism by increasing interstitial osmolality. While chloride is exclusively transported transcellularly, approx. 50% of sodium transport occurs via the paracellular route, driven by the lumen positive transepithelial potential. Antidiuretic hormone (AVP) is known to increase active NaCl transport to support collecting duct water reabsorption. Here we investigated the concomitant effects of AVP on the paracellular properties of mTAL. Freshly isolated mouse mTALs were perfused and electrophysiological trans‐ and paracelluar properties were assessed in a paired fashion before and after AVP stimulation. In addition the same parameters were measured in mice on a water restricted (WR) or water loaded (WL) diet for 5 days. Acute ex vivo stimulation as well as long term in vivo water restriction increased equivalent short circuit current as a measure of active transcellular NaCl transport. Intriguingly, in both experimental approaches this was accompanied by markedly increased paracellular Na+ selectivity.Thus, AVP is able to acutely regulate paracellular cation selectivity in parallel to transcellular NaCl transport, allowing balanced paracellular Na+ absorption under an increased transepithelial driving force.
Death by a thousand cuts: Moringa oleifera lysis Escherichia coli by altering multiple biological processes
Authors: Smith Brandon , Orders Tanner , Emrani Jahangir , Idassi Joshua , Frank Martin , Mowa Chishimba Nathan 
Published: November 2023

We know that bacterial infections are associated with and are the primary cause of preterm labor. We also know that current antibiotic‐based therapies are either unsafe or are increasingly less effective due to bacterial resistance. Previously, we reported that Moringa oleifera (MO), a medicinal plant, exhibits anti‐bacterial properties against Escherichia coli (E. coli), a key bacteria associated with preterm labor infections. In the current study, we attempt to delineate the underlying mechanisms for MO's anti‐bacterial activity against E.coli using proteomics. Our data shows that MO alters the expression of over 64 proteins in E. coli, 13 of which undergo significant alterations associated with stress response (4), metabolism (2), translation (1), ribosomal synthesis (1), membrane synthesis (1), ATP synthesis (3), and periplasmic‐binding (1). Specifically, MO inhibits ribosomal synthesis and translation while enhancing oxidative stress, membrane instability, DNA packaging, DNA fragmentation and breakdown, ultimately leading to E. coli lysis. The present study supports the use of MO as a natural antibacterial agent to manage and prevent the infection‐induced preterm labor. MO has the potential to address the shortfalls of the current therapies for infection‐induced preterm labor, cited earlierSupport or Funding InformationUniversity Research Council, Appalachian State University.
Early Post‐Ischemic Blood‐Brain Barrier (BBB) Disruption in Long‐Standing Obesity
Authors: Li Chun , Xu Guodong , McCarter Kimberly D , Sun Hong 
Published: November 2023

BackgroundObesity is an independent risk factor for ischemic stroke. Early BBB disruption is an antecedent event to infarction and hemorrhagic transformation. We determined the influence of long‐standing obesity on early BBB disruption following transient focal cerebral ischemia.MethodsMale C57BL/6J mice were fed with a high‐fat diet (HFD) or standard chow for 12 months. A cranial window was prepared over the left frontal, parietal and temporal cortex. Transient focal cerebral Ischemia was induced by directly ligating the middle cerebral artery (MCA) for two hours. Early BBB disruption was assessed by measuring Evans Blue extravasation at 3 hours of reperfusion.ResultsThe body weight was significantly increased in HFD‐fed mice (60.6 ± 1.0g) compared to standard chow‐fed mice (32.75 ± 1.0g). There was no significant difference in conscious blood pressure and fasting blood glucose between HFD‐fed mice and standard chow‐fed mice. Although long‐term HFD feeding significantly decreased MnSOD and Claudin‐5 in the cerebral cortex, there is no significant difference in early post‐ischemic EB extravasation between HFD‐fed and standard chow‐fed groups. Topical treatment with Mito‐Tempo (a mitochondrially targeted antioxidant) similarly prevented the BBB disruption in both groups. Interestingly, obesity produced an increase in cerebral vasodilation during ischemia and reperfusion.ConclusionsOur findings suggest that increased cerebral vasoreactivity during ischemia and reperfusion may be a beneficial factor to prevent early post‐ischemic BBB disruption in long‐standing obesity.Support or Funding InformationThis work was funded by a fellowship from Center for Cardiovascular Diseases and Sciences, Louisiana State University Health Sciences Center‐Shreveport.
Changes in the Oxyhemoglobin Dissociation Curve and Cerebral Oxygenation During Acute Systemic Inflammation in Healthy Volunteers
Authors: Dahl Rasmus , Plovsing Ronni , Berg Ronan 
Published: November 2023

BackgroundAcute systemic inflammation, as encountered in patients with sepsis in the clinical setting, has previously been found to be associated with a progressive decrease in brain tissue oxygen tension (Taccone et al. 2014). In the present study, we used an established human‐experimental model of acute systemic inflammation to investigate whether this involves a reduction in the oxygen availability to the brain tissue by means of configurational changes in the oxyhemoglobin dissociation curve (ODC).MethodsNineteen healthy male volunteers received a four‐hour intravenous lipopolysaccharide (LPS) infusion (total dose 2 ng kg−1). Nine of the volunteers (group 1) were poikilocapnic, while CO2 was added to the inspired air in ten of the volunteers (group 2). Paired arterial‐jugular venous blood samples were obtained. From these the P50 and Hill's coefficient of hemoglobin were calculated on the basis of a mathematical model of the ODC (Dash et al. 2016), and adjusted to the cerebral capillary level for the calculation of the oxygen tension PcapO2 (Gjedde 2005).ResultsLPS induced configurational changes in the ODC which became more hyperbolic with a consequent left‐shift at the cerebral capillary level, changes that were notably pronounced in group 1 (Figure 1). Even though the cerebral oxygen delivery and extraction fraction, arterial‐to‐jugular venous oxygen differences, as well as arterial oxygenation were unaffected after LPS, PcapO2 was reduced in both groups (Figure 2), and more so in group 1 than in group 2 (p < 0.05).ConclusionConfigurational changes in the ODC which are facilitated by hyperventilation are likely to contribute to a reduction in cerebral oxygenation during acute systemic inflammation.Support or Funding InformationThe study was supported by The Foundation of Merchant Jakob Ehrenreich and Grete Ehrenreich, The Foundation of 1870, Christian Larsen and Judge Ella Larsen's grant, The Classen Trust Jubilee Foundation, The P. Carl Petersen Foundation, University Hospital Rigshospitalet, and the Faculty of Health Sciences, University of Copenhagen.
Impaired Dynamic Cerebral Autoregulation to Postural Stress Following Concussive Injuries in Adolescents
Authors: Moir M. Erin , Abbott Kolten C. , Balestrini Christopher S. , Fischer Lisa K. , Fraser Douglas D. , Shoemaker J. Kevin 
Published: November 2023

Concussions disproportionately affect adolescents and ongoing maturation places this population at increased risk for prolonged recovery and long‐term impairments in neurologic functioning. Although cerebrovascular impairments are believed to contribute to concussion symptoms and recovery, little information exists regarding brain vasomotor control in adolescent concussion, particularly during rapid changes in blood pressure that demand a dynamic cerebral autoregulatory response. The current investigation tested the hypothesis that adolescent concussion is marked by impaired dynamic cerebral autoregulation (CA). Twenty‐two adolescents diagnosed with a concussion (CONC; 13 females; 15 ± 1 years; 26 ± 20 days post‐injury, SCAT3 symptom score = 12 ± 6) and twenty‐seven healthy controls (CTRL; 15 females; 14 ± 2 years; SCAT3 symptom score = 6 ± 4) completed two repeated sit‐to‐stand trials. CONC were followed through their rehabilitation for up to 12‐weeks. Arterial blood pressure (ABP), cerebral blood flow velocity (CBFV), end‐tidal carbon dioxide partial pressure (PetCO2), and heart rate (HR) were measured continuously with finger photoplethysmography (Finapres Medical Systems BV), transcranial Doppler ultrasound (Multigon Industries), a gas analyzer (AD Instruments), and a standard 3‐lead electrocardiogram (ECG), respectively. Furthermore, cardiac output (CO) was provided via the Model flow algorithm and cerebrovascular resistance (CVR) was calculated. The rate of the drop in CVR relative to the change in ABP provided the rate of regulation (RoR). The drop in ABP with standing was similar between CONC and CTRL (25 ± 8 vs. 24 ± 7 mmHg; p = 0.62) although the time to ABP nadir was longer in CONC compared with CTRL (7.2 ± 1.1 vs. 6.1 ± 1.3 sec; p = 0.002). Similarly, time to CBFV nadir was longer in CONC compared with CTRL (5.9 ± 1.4 vs. 4.4 ± 2.0 sec; p = 0.003). Compared to CTRL, RoR was reduced in CONC at study entry (0.21 ± 0.06 vs. 0.16 ± 0.04 sec−1; p = 0.005). However, at the time of CONC final visit (SCAT3 symptom score = 4 ± 5), RoR improved to levels similar to CTRL (0.20 ± 0.08 vs. 0.21 ± 0.06 sec−1; p = 0.55). During sitting and standing, CONC and CTRL had similar PetCO2. The change in heart rate with standing was similar between CONC and CTRL (30 ± 6 vs. 26 ± 9 bpm; p = 0.09) although the time to peak HR was longer in CONC compared with CTRL (10.8 ± 2.5 vs. 9.4 ± 2.0 sec; p = 0.004). Furthermore, a similar increase in CO was witnessed with standing in CONC and CTRL (1.4 ± 1.6 vs. 1.7 ± 0.7 L/min; p = 0.28). Impairments in dynamic CA are evident in adolescents following a concussive injury which recover in accordance with clinical symptoms. Therefore, RoR may aid decisions regarding diagnosis, rehabilitation, and recovery of adolescent concussion.Support or Funding InformationResearch supported by the Children's Health Research Institute (London, Canada).
Dynamics of locomotor fatigue during supra‐critical power exercise in humans
Authors: Swisher Austin , Koehn Blake , Yong Stanley , Cunha Jonathan , Ferguson Carrie , Cannon Daniel T 
Published: November 2023

At the limit of tolerance to ramp‐incremental exercise, maximal voluntary isokinetic power is not different to the power required by the task in endurance‐trained athletes (Ferguson et al., J Appl Physiol 120(1):70–7, 2016). This is consistent with the physiologic limits for power production having been attained at the limit of ramp‐incremental exercise. The dynamics of the decline in locomotor power, and whether the physiologic limits are similarly attained during constant‐power cycling are unknown. We aimed to measure 1) the dynamics of locomotor fatigue during constant supra‐critical power cycling, and 2) the magnitude of any reserve in locomotor power immediately at the tolerable limit of both constant and ramp‐incremental cycling in recreationally active volunteers.Fifteen participants (7 females, 8 males, 22 ± 3 yr, 65.9 ± 12.4 kg, VO2peak 3.34 ± 0.67 L.min−1) completed ramp‐incremental (25 W.min−1) and constant power (205 ± 46 W) exercise to the limit of tolerance. Immediately following intolerance, participants completed a short (<5 s) maximal isokinetic effort at 70 rpm. The time course of locomotor fatigue during constant supra‐critical power exercise was characterized using short maximal isokinetic sprints interleaved at 30 s, 60 s, 120 s, 180 s, and at the limit of tolerance.Constant power exercise duration was 312 ± 37 s. Isokinetic power production at 30, 60, 120, 180 s and the limit of tolerance was 609 ± 165, 503 ± 195, 443 ± 157, 449 ± 133, and 337 ± 94 W, respectively. Of the total decline in isokinetic power, ~50% occurred within the first minute of exercise and significant (p<0.05) reductions in isokinetic power occurred at all time‐points vs the baseline maximal isokinetic power (666 ± 158 W). Additionally, a significant power reserve of 132 ± 74 (64 % of the task requirement) and 119 ± 80 W (47 %) was present at the limit of constant power and ramp‐incremental exercise.Locomotor fatigue occurred rapidly during supra‐critical power exercise with pseudo‐exponential kinetics. The dynamics of locomotor fatigue were similar to the dynamics reported for primary fatigue‐related intramuscular metabolites, suggesting a close mechanistic link between the intramuscular milieu and voluntary muscle power. Instantaneous isokinetic power production at the limit of tolerance exceeded that of the task requirement, regardless of the work rate profile. Thus, the perceptual and physiologic limits were dissociated at the limit of tolerance in recreationally active volunteers.