bluuebunny/crossref_metadata_2025 huggingface dataset:
Hypoxia activates BK and Kv channels in rat carotid body glomus cells
Authors: Kim Donghee , Wang Jiaju
Published: November 2023

Inhibition of BK and/or Kv has been proposed to be involved in hypoxia‐induced depolarization and subsequent elevation of intracellular [Ca2+] in carotid body glomus cells. However, depolarization and/or elevation of [Ca2+] are well known to activate BK and Kv, which would oppose glomus cell excitation. First we studied the effect of hypoxia on BK in cell‐attached patches, where the cell Em and intracellular [Ca2+] were allowed to change naturally in response to hypoxia. In cell‐attached patches (140 mM KCl in the pipette and 5 mM in the bath), hypoxia reversibly activated BK while causing inhibition of TASK. In cells partially depolarized by elevating extracellular [KCl] from 5 mM to 12–15 mM KCl, hypoxia also activated BK reversibly. In inside‐out patches showing different levels of BK activity, hypoxia produced no significant effect on BK. Kv could not be detected clearly in cell‐attached patches. Therefore, the role of Kv was tested indirectly by studying the effect of guangxitoxin (GxTX: Kv2 blocker) on hypoxia‐induced rise in intracellular [Ca2+]. GxTX inhibited the outward K+ current by ~50%, and enhanced the hypoxia‐induced elevation of intracellular [Ca2+] 2.3 fold, indicating that hypoxia activated Kv2. These results show that hypoxia activates BK and Kv in rat glomus cells, which helps to limit the hypoxia‐induced excitation of glomus cells.

Support or Funding Information

Supported by NIH
Macula Densa Cell Gene Profiling
Authors: Riquier‐Brison Anne , Desposito Dorinne , Moon Ju‐Young , Peti‐Peterdi Janos
Published: November 2023

Macula densa (MD) cells are chief but still mysterious cells localized at a strategically important anatomical location at the glomerular entrance, and play key regulatory roles in renal and glomerular hemodynamics, body fluid and electrolyte homeostasis, and blood pressure maintenance. The present study aimed to establish the true nature of MD cells by performing unbiased MD gene profiling using two separate and independent approaches. A new mouse model (MD‐GFP mice) was generated with inducible and conditional MD‐specific expression of the fluorescence reporter EGFP by crossing nNOS‐CreERT2 and mTmG‐floxed mice. MD cells were freshly isolated from digested kidneys of MD‐GFP mice using FACS sorting, followed by MD RNA isolation and sequencing. Alternatively, MD RNA isolation and sequencing was performed in another new mouse model by crossing floxed L10a‐EGFP and nNOS‐CreERT2 mice and using the Translating Ribosome Affinity Purification (TRAP) strategy. Compared to whole kidney and adjacent non‐MD tubular epithelial cells, MD‐specific enriched genes included members of secreted angiogenic (Ccn1, Pappa‐2, Gdf15), extracellular matrix remodeling (Mmp14, Ca12), growth factor (Fgf2), developmental and differentiation transcription factor (Bmp3/7, Wnt10a, Hoxa1, Fos), cell cycle and DNA damage regulating (Gmnn, Wee1, Gadd45b) gene families. Our results paint a new picture of MD cells and suggest their new non‐traditional roles in renal interstitial, vascular, and glomerular tissue remodeling.

Support or Funding Information

NIH R01 64324, AHA, ADA
Renal Response to Acidosis: RNA‐Seq and Role of NaDC1
Authors: Yadav Santosh , Huang Weitao , Coleman‐Barnett Joycelynn , Hamm Lee , Hering‐Smith Kathleen S
Published: November 2023

Metabolic acidosis is a common pathophysiologic condition that can occur either acutely or chronically in a variety of settings and diseases. Acidosis has a number of adverse effects including progression of chronic kidney disease, bone loss, and muscle wasting. The kidneys are the main organs which respond to acid loads to protect against systemic acidosis. To enhance our understanding of the renal response to acidosis, we performed RNA‐Seq on kidneys from acid loaded animals. Additionally, since NaDC1 (sodium dicarboxylate transporter 1 in the proximal tubule) is known to respond to acidosis, we addressed the role of NaDC1 in the response to acidosis. NaDC1 reabsorbs citrate and various dicarboxylate Krebs cycle intermediates, some of which have downstream G protein coupled receptors.

NaDC1 Knockout (KO) and wild type (WT) mice (C57BL/6 background) were studied on normal or acid diet (0.4M HCl added to chow, X 3 days). Kidney RNA was extracted & integrity validated. RNA‐seq was performed at the Tulane Center for Aging Genomics and Biostats Core using an Ion Proton platform with 20M reads/sample. Bioinformatics completed at Tulane Cancer Crusaders NGS Analysis Core. For qRT‐PCR, RNA was isolated from same kidneys & mRNA relative expression was calculated by ΔΔCt.

In WT with acidosis, 1173 transcripts were differentially expressed >1.5 fold (each statistically significant), 525 transcripts upregulated and 648 down regulated. Results were similar to prior microarray data (Nowik et al Physiol Genomics 2008). Among those upregulated many have been previously reported to be involved in the response to acidosis: e.g., PCK1, GLUD1, Car2, SNAT1, NaDC1. Also 36 genes from SLC family were identified and differentially expressed under acidosis. By qPCR, SLC genes 13a2, 13a3, 16a9, 26a6 & 38a3 were upregulated & consistent with RNA‐seq. But we also identified many additional genes that indicate a broader cellular metabolic response to acidosis. In contrast, in KO with acidosis many more transcripts (945) were upregulated >1.5 fold and downregulated (1270) >1.5 fold.

In sum, metabolic acidosis significantly alters the expression of hundreds of genes, some directly linked to homeostatic responses, but others involving a variety of metabolic and signaling pathways. The response to acidosis in NaDC1 KO mice is even more profound and may indicate that in the absence of NaDC1, additional response pathways are necessary. This implies that NaDC1 plays a more important role in the response to metabolic acidosis than previously recognized..

Support or Funding Information

NIH/NIDDK RO1 DK095879
Renal Role of Gprc5c in Regulating Systemic pH Homeostasis
Authors: Rajkumar Premraj , Cha Boyoung , Donowitz Mark , Hirabayashi Yoshio , Arend Lois J , Pluznick Jennifer L
Published: November 2023

Recent studies have identified orphan G‐protein coupled receptors (GPRs) as sensors of physiological metabolites. In this study, our goal is to elucidate the functional role of an understudied renal GPR, Gprc5c, which we previously found to be highly expressed in the kidney (Rajkumar et al., 2014). By immunofluorescence (IF), we find that Gprc5c localizes to the apical renal proximal tubules (PTs) in wild‐type (WT) mice, where it colocalizes with two PT markers ‐ LTA & megalin. Staining is absent in Gprc5c knockout (KO) mice kidneys. Gprc5c also localizes to the apical PTs by immunofluorescence in both rats and humans, suggesting an evolutionarily conserved role. In vivo, Gprc5c KO were not different from WT with respect to blood pressure, kidney/body weight, blood levels of Na+, Cl− & glucose, and urine levels of creatinine & glucose. However, Gprc5c KO have higher urine pH (WT: 5.48±0.01, n=6; KO: 5.81±0.06, n=6; p<0.05). In addition, the blood pH of Gprc5c KO mice trends acidic compared to WT in unanaesthetized mice (WT: 7.44±0.04, n=4; KO: 7.34±0.02, n=4; p=0.07), and in mice under isofluorane (WT: 7.22±0.03, n=5; KO: 7.03±0.04, n=5; p<0.05). In an in vitro GPCR internalization assay, alkaline pH (but not other chemicals tested) triggered Gprc5c internalization (an index of activation), with maximal internalization seen above pH 7.4 (pH 8.0>pH 7.4>pH 6.5). Other GPCRs tested as controls showed no changes in internalization over the pH range tested. On the apical membrane of the renal PT, sodium hydrogen exchanger 3 (NHE3) plays a key role in bicarbonate reabsorption, and therefore in maintaining pH homeostasis. Thus, we examined whether Gprc5c alters sodium proton exchanger activity. Using BCECF in a ratiometric fluorescence assay in Hek293T cells, we find that Gprc5c increases sodium proton exchange by 1.6 fold compared to empty vector controls in alkaline conditions (pH 8.0) (p<0.05), but not at pH 7.4. The increase seen at pH 8 is Tenapanor‐sensitive, implying that it is mediated via NHE3. In preliminary data, we also find that Gprc5c KO mice exhibit blunted changes in urinary pH when challenged with an alkali load for 7 days. Together, these data imply that Gprc5c localizes to the renal PTs apically where it contributes to systemic pH homeostasis via modulation of NHE3 function.
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 Information

Funding 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

Background

After 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.

Methods

In 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.

Results

In 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 <0.05

Conclusions

In 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 Information

VA 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 Information

The work was supported by the APS Undergraduate Summer Research Fellowship and NHLBI Intramural Research Program (project ZIA‐HL001285 and ZIA‐HL006129, M.A.K.).
Molecular basis of AVP‐regulated calcium signaling in the collecting duct
Authors: Mamenko Mykola , Dhande Isha , Tomilin Viktor , Zaika Oleg , Doris Peter A.
Published: November 2023

It is becoming increasingly appreciated that water reabsorption in the collecting duct (CD), regulated by arginine vasopressin (AVP), relies on sustained intracellular Ca2+ mobilization through store operated calcium entry (SOCE). AVP induces the release of Ca2+ from the endoplasmic reticulum (ER), depleting the stores. The decrease of ER Ca2+ is sensed by the stromal interaction molecules (STIM) 1 and/or 2. This promotes the association of STIM with the plasma membrane and activation of the Ca2+ permeable ORAI1 channel, triggering SOCE. Using an animal model with defective SOCE – spontaneously hypertensive stroke‐prone rats (SHR‐A3), we have recently demonstrated that disruption of SOCE results in a phenotype characteristic of nephrogenic diabetes insipidus. SHR‐A3 line was found to carry a truncating mutation in Stim1 gene, impairing the interaction between STIM1 and ORAI1. This mutation is absent in closely related spontaneously hypertensive stroke‐resistant rats (SHR‐B2) used as controls. Interestingly, shRNA‐mediated knockdown of STIM1, while markedly diminished, failed to completely abolish SOCE activity and AQP2 trafficking in cultured mpkCCDc14 cells. Thus, this study was developed around the hypothesis that molecular determinants other than STIM1 are involved in AVP‐dependent intracellular Ca2+ signal in the CD. We found that neither SOCE, nor the ability of the kidney to concentrate urine was affected in mice with CD‐specific deletion of Stim1. At the same time, we identified another Stim gene family member – Stim2, that is located in a region of genetic variation in SHR‐A3. This variation affects the promoter sequence of Stim2. Transfer of the chromosomal segment containing Stim2 from SHR‐B2 into SHR‐A3 background rejuvenates SOCE in CD cells. Moreover, congenic rats had urine osmolality similar to that in SHR‐B2 with intact SOCE, pointing to a restored urinary concentrating ability. Consistent with recent studies linking STIM2 to regulation of Ca2+ homeostasis in the cell, intracellular Ca2+ concentration was markedly increased in the CDs isolated from congenics, when compared to SHR‐A3, and resembled intracellular Ca2+ levels in CD cells with intact SOCE. Overall, our data suggest that, in addition to Stim1, Stim2‐containing genetic locus contributes to preservation of functional SOCE in CD cells and maintenance of AVP‐dependent water transport in the collecting duct.
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 Information

T.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 earlier

Support or Funding Information

University 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

Background

Obesity 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.

Methods

Male 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.

Results

The 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.

Conclusions

Our 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 Information

This 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

Background

Acute 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).

Methods

Nineteen 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).

Results

LPS 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).

Conclusion

Configurational 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 Information

The 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 Information

Research 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.
Predicting mountain ultra‐marathon performance using the critical velocity model
Authors: Rogers Michael , Ngo My Linh , Sandberg Olivia , Atashzay Parmida , Singh Prabhjot , Malcolm Corrine , Clarke David , Walsh Michael , White Matthew
Published: November 2023

PURPOSE

Critical Velocity (CV) and D′ were evaluated as predictors of mountain ultra marathon finishing times in cool conditions.

HYPOTHESIS

It was hypothesized that CV and D′ would both predict mountain ultra‐marathon performance.

METHODS

Nine healthy males volunteered to participate in the study. Their average age was 37.9 ± 10.0 y, height 1.79 ± 0.05 m, body mass 76.6 ± 11.2 kg, BMI 23.8 ± 3.0 kg•m−2. The SFU Office of Research Ethics approved the study and each volunteer gave a signed consent prior to participation. Each volunteer completed a 50‐km mountain ultra‐marathon and then each volunteer's CV and D′ was evaluated using a series of maximal‐effort timed 1200, 2400 and 3600 m running trials on the same day with 30 min rest before trials 2 and 3. A Latin square design was employed to determine the orders of the tests. Maximal aerobic capacity was also assessed using indirect calorimetry and a graded treadmill test.

RESULTS

The mean CV was 3.5 ± 0.5 m•s−1, D′ was 197.2 ± 83.2 m and mean absolute and relative aerobic powers were 4.8 ± 0.8 L min−1 and 63.5 ± 6.7 mL•kg−1•min−1, respectively. Stepwise multiple linear regression identified CV as the sole significant predictor of the mountain ultra‐marathon performance time (r=−0.88, p<0.05). Correlation analysis of the independent variables with finishing time indicated that aerobic power was significantly and positively correlated with finishing times (r=−0.72, p=0.002).

CONCLUSION

These preliminary results suggest that CV explains both a significant fraction of the variance in mountain marathon finishing time and that CV obtained via running track tests is an appropriate method for predicting these finishing times.

Support or Funding Information

Supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canadian Foundation for Innovation (CFI)
Effects of the Different Acute Exercise on Melatonin of Undergraduate
Authors: Sun Youping , He Jing , Qiu Linli
Published: November 2023

OBJECTIVE

To compare the effects of different acute exercise on Melatonin of undergraduate.

METHODS

Subjects (n=160)were randomized into endurance training(E, n=40), strength training (S, n=40), combined strength and endurance training(SE, n=40), or control group(C, n=40)for 45min, and take 4ml venous blood at before and after training.

RESULTS

1、 The Melatonin of female significantly increased in E (10.30±3.20 17.41±4.33; P < 0.05). Melatonin significantly increased in S (10.30±18.49; 16.96±5.00; P < 0.05). Melatonin significantly increased in SE (7.09±2.44; 15.53±6.96; P < 0.01). But it increased no significantly in C also (9.98±1.61; 14.56±2.5; P > 0.05). 2、 The Melatonin of male significantly increased in E (7.82±2.39; 23.22±2.69; P < 0.01). Melatonin significantly increased in S (9.30±6.17; 16.36±5.58; P < 0.05), Melatonin significantly increased in SE (8.19±4.69; 17.92±2.01; P < 0.01), but it increased no significantly in C (10.81±3.87; 13.87±6.34; P > 0.05). 3、 There were no significant difference on the change of the four groups (female: P > 0.05; male: P > 0.05).

CONCLUSION

Endurance training and Strength training and their combination all led to increase in Melatonin. The different acute exercises have no significant difference influence on Melatonin.

Support or Funding Information

The key lab of adolescent health intervention and exercise assessment, Ministry of China
Autonomic cardiovascular response during the isometric Cuban test of the sustained weight
Authors: Sanchez‐Hechavarria Miguel , Carrazana‐Escalona Ramon , Ricardo‐Ferro Beatriz , Cutino‐Clavel Ileana , Lopez‐Galan Erislandis
Published: November 2023

Introduction

The Test of the Sustained Weight (TSW) is an isometric exercise, similar to hand grip, often used in Cuba to induce hemodynamic responses in order to identify individuals with cardiovascular hyperreactivity. However the dynamic changes in the autonomic cardiovascular responses are not totally elucidated.

Objective

Determining the autonomic cardiovascular response during the isometric Cuban test of the sustained weight.

Methods

We used a quasi‐experimental (crossover) design of 20 healthy subjects. Following 10 min for acclimation, we evaluated 5 min before (basal), 2 min during TSW, and 3 min of recovery while performing ausculatory blood pressure measurement and analysis of the variability of the RR intervals (HRV) from DII derivation of ECG record (1kHz) using Powerlab® AD Instruments. R‐R intervals were analyzed using frequency (Fourier) and time‐frequency (Wavelet) methods of the bands of high frequency (HF: 0,15–0,4) and low frequency (LF: 0,04–0,15), as well as temporal and nonlinear (Sample Entropy) analysis.

Results

We did not observe significant differences in the indicators of the temporal (SDNN, RMSSD, pNN50) and frequency analyses (LF, HF, LF/HF). We did observe a significant change in arterial pressure in the TSW with respect to rest and this was associated with the increment of complexity (entropy) and with a peak in the LF and ratio LF/HF around the 2 min reflected by time‐frequency methods.

Conclusions

The dynamic changes in the sympathetic cardiovascular response during the Test of the Sustained Weight are not evident with traditional lineal methods of HRV due to the non‐stationary and to the increment of the complexity of this physiologic process with regard to basal state.

Support or Funding Information

Supported by University of Santiago de Cuba, Cuba.
Habitual Physical Activity Level Modifies Lung Function, But Not 8‐Isoprostane Generation, in Older Adults
Authors: Kurti Stephanie P. , Emerson Sam R. , Rosenkranz Sara K. , Smith Joshua R. , Harms Craig A.
Published: November 2023

INTRODUCTION

The development of asthma and chronic obstructive pulmonary disease is associated with elevated 8‐isoprostane (validated marker of oxidative stress) in the airways and systemically. Acutely, a single bout of exhaustive exercise elicits an increase in oxidative stress, which may lead to cardiorespiratory complications in older adults. Habitual physical activity (PA), however, is a natural anti‐oxidant and anti‐inflammatory. Therefore our purpose was to elucidate whether older adults who are active (OA) exhibit an attenuated airway and systemic 8‐isoprostane response to maximal exercise compared to older adults who are insufficiently active (IA). A secondary purpose was to determine whether chronic PA level in older adults modifies post‐exercise lung function.

METHODS

Seventeen older adults (≥60 years of age) completed the study (9 OA/ 8 IA: 65.1± 3.9 years). Subjects came into the laboratory for a single testing session after wearing an Actical accelerometer on their non‐dominant wrist to verify they were in the correct PA group. Upon arrival to the laboratory, baseline measurements were performed as follows: exhaled breath condensate (EBC) to assess airway 8‐isoprostane; an antecubital venipuncture for assessment of systemic 8‐isoprostane; followed by standard pulmonary function testing (PFTs) for assessment of forced expiratory volume in 1‐second (FEV1), forced vital capacity (FVC), FEV1/FVC, and forced expiratory flow at 25–75% of FVC (FEF25–75%). Subjects then completed an incremental cycle exercise test to reach peak oxygen consumption (VO2peak). Immediately following the VO2peak test, subjects performed post‐exercise PFTs, and a trained investigator took a post‐exercise blood draw directly prior to EBC.

RESULTS

There were no differences in airway (p=0.55) or systemic (p=0.94) 8‐isoprostane between OA and IA subjects. In the OA and IA combined, there was not a significant change in the generation of airway 8‐isoprostane (14.3±30.7%; p=0.10) or systemic 8‐isoprostane (13.9±69.3%; p=0.62) from pre‐ to post‐exercise. Habitual PA level did not impact 8‐isoprostane generation in the airways (p=0.62) or systemically (p=0.66) from pre‐ to post‐exercise. Post‐exercise FEV1 and FEF25–75% increased from pre‐ to post‐exercise in both groups (p<0.05), however the OA showed a greater post‐exercise bronchodilation as FEV1/FVC increased by 3.1±2.5% compared to 0.4±2.7% in the IA group (p=0.04). No other indices of lung‐function were different between OA and IA (p>0.05).

CONCLUSIONS

Our results suggest that habitual PA level does not impact the generation of airway and systemic 8‐isoprostane in response to exhaustive exercise in older adults. However, it appears that engaging in more PA per week elicits greater post‐exercise bronchodilation in older adults who are chronically physically active. These results suggest a potential bronchoprotective role for chronic PA in older adults.
SHORT TERM HIGH FAT FEEDING ALTERS EXPRESSION OF GLUCOREGULATORY PROTEINS IN SKELETAL MUSCLE OF MALE ADOLESCENT RATS
Authors: Crawford Melisa Shaunte , Liss Tyler , Sweazea Karen
Published: November 2023

Childhood obesity affects approximately 17% of children and adolescents in the United States. Prolonged consumption of energy‐dense foods, in addition to a sedentary lifestyle, continue to increase the prevalence of overweight and obese adolescents. Unfortunately, this trend is accompanied by serious metabolic conditions including, type II diabetes, cardiovascular disease, and skeletal muscle atrophy. Skeletal muscle, the most abundant tissue in the human body, is responsible for insulin‐mediated glucose uptake and many of the metabolic abnormalities associated with obesity. While it is known that a high‐fat diet (HFD) can impair insulin signaling, endothelium‐dependent vasodilation and increase the risk of oxidative stress, less is known about the effects of a short‐term HFD on skeletal muscle of adolescents. We hypothesized that short‐term high fat intake by adolescent rats would promote similar pathologies observed with chronic poor nutrition in adults. To examine this, six‐week‐old male Sprague Dawley rats were fed either a standard rodent chow diet (18.9% protein, 57.33% carbohydrates) or a HFD (20% protein, 20% carbohydrates [6.8% sucrose], 60% fat) for 6 weeks. Blood samples were collected then animals were euthanized (sodium pentobarbital; 200 mg/kg, i.p.) and pectoralis major muscles were extracted for analyses. Consistent with the development of obesity and type II diabetes, HFD rats had significantly lower plasma α‐amylase (24.7% decrease; p=0.007). However, Oil Red‐O and triglyceride assays showed no significant increase in muscle lipids (p>0.05). Data also suggests no significant increase in expression of proteins associated with insulin signaling (p‐PI3K; p=0.462) and inflammation (iNOS; p=0.406). In contrast, there was a tendency towards increased expression of the alpha subunit of the insulin receptor (180.9%, p=0.076) as well as the insulin‐responsive (GLUT‐4; 83.9%, p=0.093) and insulin‐independent (GLUT‐1; 89.9%, p=0.103) glucose transporters. The increased expression of these latter proteins likely reflect early compensation for the HFD. Further studies will confirm these findings and examine the effects of a short‐term HFD on the progression of inflammation, macrophage invasion and the impairment of insulin signaling intermediates in skeletal muscle of adolescent rats.

Support or Funding Information

This project was partially funded by the Barrett Honors College, Arizona State University
High Air‐Pressure Elevated Energy Expenditure in Mice
Authors: Xiang Dao , Fang Yiqun , Luo Beibei , Yan Shuo , Xu Ji , Chen Peijie
Published: November 2023

PURPOSE

When diving or working underwater, people would be exposed to the air‐pressure higher than standard atmospheric pressure. The higher pressure would be an extra load for divers to do exercises or even breathe. And the extra load would alter divers' energy expenditure (EE). Our study examined the effects of high‐pressure exposure on energy expenditure in mice.

METHOD

6 male C57 Mice, 8‐week old, were kept in pressure chamber separately with N2/O2 mixed gas at standard atmospheric pressure (101kPa). The temperature of the chamber was maintained at 22□ (±1.0 □). The energy expenditure was assessed by indirect calorimetric measurement. After acclimated to the chambers for 30 minutes, O2 consumption (ΔVO2 0m) and CO2 production (ΔVCO2 0m) of those mice within a sampling period (10 minutes) were recorded. Between periods was a 5‐minute venting. The exposure lasted for 6 hours. Then after 24 hours normal feed, mice exposed to N2/O2 mixed gas at 700kPa (to mimic 60 meters under water) for 6 hours in pressure chamber individually. The O2 consumption (ΔVO2 60m) and CO2 production (ΔVCO2 60m) were recorded as described before. The energy expenditure of mice under high pressure and under standard atmospheric pressure were compared.

RESULTS

Mice under high pressure consumed 5341.38±1666.02 ml oxygen and produced 4212.62±1116.23 ml CO2 per‐hour per‐kg bodyweight during the 6‐hour exposure. While under standard atmospheric pressure, the oxygen consumption was 2360.19±586.12 ml and CO2 production was 1930.55±503.85 ml per‐hour per‐kg bodyweight. The energy expenditure of mice under high pressure within 6 hours exposure (25.47±7.75 kcal/h.kg) were significantly higher than mice under standard atmospheric pressure (11.37±2.83 kcal/h.kg).

CONCLUSION

High‐pressure exposure markedly elevated oxygen consumption and CO2 production, as well as energy expenditure in mice. The main cause might be the extra load from breathing air with higher density.