bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cellular aging of skeletal muscle: evidence that physical inactivity is responsible and not age (1102.14)
Authors: Venturelli Massimo , Morgan Garrett , Donato Anthony , Reese Van , Tarperi Cantor , Milanese Chiara , Schena Federico , Bottura Renato , Reggiani Carlo , Naro Fabio , Cawthon Richard , Richardson Russell 
Published: June 2021

Telomeres, not only provide a marker of cellular aging, but also play an essential role in maintaining chromosomal integrity in the face of physiological stressors, such as free radicals, that result in DNA damage. Although, the age‐related shortening of telomere length (TL) in highly proliferative tissue, is thought to be predominantly due to the replication process, the mechanism for telomere shortening in skeletal muscle, which is minimally proliferative, is unclear. By studying TL in both the upper and lower limbs of the young (Y), old mobile (OM), and old immobile (OI) and by virtue of the bipedal nature of human locomotion, which declines with age, it may be possible to elucidate the mechanism responsible for cellular aging of skeletal muscle. With this approach, we revealed that TL (~15 kb) in arm skeletal muscle is unaffected by age and mobility. In contrast TL fell progressively in the legs across the young (~15 kb), the old mobile (~13 kb), and old immobile (~11 kb). Interestingly, there was a reciprocal rise in leg muscle free radical concentration across these groups that was significantly correlated with TL (r=0.7), with no such relationship in the arm (r=0.09). Our results document that chronologic age, per se, does not affect cellular aging of skeletal muscle, but reveals that physical inactivity, likely mediated by free radicals, has a profound effect upon this process.Grant Funding Source: NIH (PO1 HL, 09830), and VA (Merit Grant E6910R)
Cigarette smoke impairs the in situ fatigue resistance of locomotor skeletal muscle in mice (1102.18)
Authors: Trisko Breanna , Nogueira Leonardo , Wagner Peter , Breen Ellen 
Published: June 2021

Muscle dysfunction is thought to contribute to exercise intolerance in smokers with COPD. In this study, cigarette smoke (CS) was hypothesized to impair skeletal muscle fatigue resistance. To test this hypothesis, adult C57Bl6 mice were exposed via a nose‐only system to daily periods of CS (5 cigarettes/period for 2 periods, 5 days/week) for 8 weeks and compared to mice delivered CS‐extract (weekly, i.p) and control, unexposed mice. Body weights were recorded each week. Gastrocnemius complex fatigue resistance was evaluated by measuring the time to reach 50% of maximal force when electrically stimulated to contract in situ. Compared to control mice, body weights were decreased in CS‐exposed mice, but not CS‐extract mice, at 3‐weeks (7.4%, p<0.05), 7‐weeks (7.9%, p<0.05), and 8‐weeks (12.4%, p<0.001). However, gastrocnemius, soleus, and plantaris mass / body weight ratios were not different between groups. A trend to earlier fatigue was seen in CS‐extract mice (Con. 342 ± 72 sec., CS‐exposed 310 ± 111 sec., CS‐extract 177 ± 16 sec., p=0.06). These data suggest the route or amount of CS that circulates in the blood may influence the extent of peripheral skeletal muscle dysfunction.Grant Funding Source: Supported by NIH 1 PO1 HL091830‐01A1
SPRED1 in quadriceps of patients with mild chronic obstructive pulmonary disease (1102.21)
Authors: Porlier Alexandra , Dubé Annie , Debigaré Richard , Maltais François 
Published: June 2021

Limb muscle dysfunction contributes to exercise intolerance in chronic obstructive pulmonary disease (COPD). In turn, quadriceps capillarization is a determinant of muscle function. In our previous study, the number of capillaries and mRNA level of VEGFA were both reduced in mild COPD. MicroRNAs (miRs) regulate biological processes such as angiogenesis. Based on the literature, angiogenesis can be regulated by miR‐126 which blocked the expression of an inhibitor of angiogenesis, SPRED1. In this study, we assessed the expression of miR‐126 in the context of capillarization characterization in muscle tissue obtained from a needle biopsy in 5 patients with mild COPD and 5 healthy age‐matched controls. We hypothesized that miR‐126 will be downregulated and SPRED1 will be enhanced in COPD. Vastus lateralis muscle samples were analyzed for miRs and mRNA content by qPCR and the number of capillaries was obtained by immunochemistry. Levels of miR‐126 were similar between mild COPD and healthy controls. SPRED1 level was enhanced by 2.1 fold (p=0.01) and the number of capillaries tended to be reduced in mild COPD compared to healthy controls. SPRED1 may have a role in limb muscle capillarization in mild COPD. Investigations targeting specifically endothelial cells will better dissect the biochemical process involved in muscle angiogenesis in the context of COPD.Grant Funding Source: CHIR/IRSC
Effects of CaMKII activity on cardiac and skeletal muscle pathology in a mouse model of Duchenne muscular dystrophy (1102.3)
Authors: Johnson Nicolette , Levy Jennifer , Grumbach Isabella , Anderson Mark , Campbell Kevin 
Published: June 2021

Patients with Duchenne Muscular Dystrophy (DMD) lack functional dystrophin, an essential member of the dystrophin‐glycoprotein complex. Without dystrophin, the actin cytoskeleton is not anchored to the extracellular matrix, which leads to membrane damage. Patients with DMD have dystrophic and weakened skeletal muscle and often develop dilated cardiomyopathy. The aim of this project is to study the effects of Ca2+ and Calmodulin‐dependent protein kinase II (CaMKII) activity on the development of the dystrophic phenotype. CaMKII is an intracellular signaling protein involved in many pathways, including excitation‐contraction coupling and Ca2+ homeostasis. Hyperactivity of CaMKII is linked with cardiac hypertrophy, arrhythmias, and heart failure. We hypothesized that increased CaMKII activity would cause an increase in skeletal muscle and cardiac pathology in mdx mice, which lack dystrophin and serve as a model of DMD. A mouse model of inhibited CaMKII activity expresses a transgenic peptide inhibitor of CaMKII. A mouse model of CaMKII hyperactivity lacks the CaMKII regulatory protein, Methionine Sulfoxide Reductase A. We crossed the mouse models of inhibited and hyperactive CaMKII activity onto a dystrophic mdx background. Several pathological parameters were used to quantitatively measure disease progression in the different models.Grant Funding Source: Supported by a Wellstone Muscular Dystrophy Cooperative Research Center grant (KPC), HHMI, APS (NMJ)
Collective effects of low cell pH and inorganic phosphate on force, velocity, stiffness, and power in rat slow and fast muscle fibers (1102.7)
Authors: Nelson Cassandra , Fitts Robert 
Published: June 2021

Muscle fatigue is a loss of power resulting from a decline in both force and velocity. Intense exercise induces high rates of ATP hydrolysis and glycolysis, increasing inorganic phosphate (Pi) and H+. These factors are thought to induce fatigue by interfering with key steps in the cross bridge cycle, including ATP hydrolysis, ADP release, and rate and extent of cross‐bridge transition from the low‐ to high‐force state. Skinned fibers from rat soleus (slow) and gastrocnemius (fast) were isolated, and the combined effects of elevated H+ (pH 6.2) and Pi (30 mM) on force, velocity, stiffness, and power at low (15°C) and high (30°C) temperatures studied. At 30°C, pH 6.2 plus 30 mM Pi depressed force by 39% (158 to 97 kN/m2) in slow fibers and 42% (189 to 111 kN/m2) in fast fibers. Velocity was depressed by 17% (Vmax 4.23 to 3.56 Fl/s) in slow fibers and 44% (6.91 to 3.88 Fl/s) in fast fibers. The a/Po ratio was depressed in slow fibers but increased in fast fibers in pH 6.2, 30 mM Pi conditions, resulting in a greater power loss in slow (67%) versus fast (58%) fibers. Force‐stiffness plots normalized to rigor tension and stiffness show a higher number of low‐force cross bridges in fast versus slow fibers in pH 6.2, 30 mM Pi conditions. Our results show that the effects of elevated H+ and Pi are fiber‐type specific, and the larger decrease in force and velocity in type II fibers may in part be explained by a higher population of low‐force cross bridges.Grant Funding Source: Supported by a Marquette University Way Klinger Fellowship to RH Fitts
Time course of heat acclimation in burn survivors with well‐healed grafted skin (1104.11)
Authors: Rivas Eric , Schlader Zachary , Ganio Matthew , Pearson James , Lucas Rebekah , Gagnon Daniel , Crandall Craig 
Published: June 2021

Repeated bouts of exercise in a hot environment improves the physiological capacity for heat loss, i.e., heat acclimation. This study tested the hypothesis that the time course of this adaptive response is reduced in burn survivors with well healed skin grafts. Twenty‐nine burn survivors were stratified into two groups: <40% body surface area (BSA) of grafted skin (N=13) and >40% BSA grafted (N=16). Nine similarly aged, non‐injured subjects served as controls. Subjects underwent a 7 day heat acclimation regimen wherein they exercised daily for 90 min in 40°C, 30% relative humidity. On each day, after 90 min of exercise, heart rate (HR) and the change in core (intestinal) temperature (∆TC) were measured. Despite an increased HR and ∆TC (both P<0.05) in the >40% BSA group compared to the control group, HR and ∆TC decreased (P<0.01) across the 7‐day heat acclimation regimen similarly between groups (day x group interaction: HR: P=0.76, ∆TC: P=0.11). Independent of group, in comparison to day 1, HR was reduced by day 2 (‐8 ± 14 bpm, P=0.01) through day 7 (‐17 ± 14 bpm, P<0.01) and ∆TC was attenuated by day 6 (‐0.3°C ± 0.5, P=0.02) and day 7 (‐0.3°C ± 0.4, P<0.01). These data indicate that the time course of heat acclimation in well‐healed burned survivors with grafted skin is similar to non‐burned individuals.Grant Funding Source: Supported by National Institute of General Medical Sciences GM068865
Large differences in body fat do not independently alter changes in core temperature during exercise (1104.2)
Authors: Dervis Sheila , Smoljanic Jovana , Jay Ollie 
Published: June 2021

No previous study has isolated the independent influence of body fat (BF) on thermoregulatory responses from the biophysical factors of body mass and metabolic heat production (Hprod). Therefore, six lean (L, BF:11.1±4.2%) and six non‐lean (NL, BF:32.1±7.1%) males matched for total body mass (TBM, L: 89.6 ±7.9 kg, NL: 91.0±7.0 kg; P= 0.74), cycled for 60 min in a 28.2 ±0.2°C and 30 ±9% RH room at i) a Hprod of 490 W; and ii) a Hprod of 7.5 W/kg lean body mass (LBM). Rectal (Tre) and esophageal (Tes) temperatures, and local sweat rate (LSR) were measured continuously; while whole body sweat loss (WBSL) was measured from 0‐60 mins. At 490 W, changes in Tre (L: 0.75 ±0.16°C, NL: 0.78 ±0.15°C), Tes (L: 0.49 ±0.15°C, NL: 0.51 ±0.14°C), MLSR (L: 0.61±0.18, NL: 0.51±0.12 mgcm‐2min‐1) and WBSL (L: 568±85 mL, NL: 565±80 mL) were similar (P>0.80). At 7.5 W/kg LBM, the L group had greater changes in Tre (L: 0.92 ±0.18°C, NL: 0.53 ±0.12°C), Tes (L: 0.62 ±0.17°C, NL: 0.41 ±0.12°C), MLSR (L: 0.72±0.31, NL: 0.40±0.12 mgcm‐2min‐1) and WBSL (L: 556±104 mL, NL: 409±94 mL) (P<0.05). In conclusion, i) body fat does not independently alter thermoregulatory responses during exercise; ii) core temperature comparisons between groups differing in BF should be performed using a Hprod normalized for TBM, not LBM.Grant Funding Source: Supported by, NSERC Discovery Grant, Grant holder: Ollie Jay
Steady‐state local sweat rate is determined by the evaporation required for heat balance relative to body surface area (1104.9)
Authors: Cramer Matthew , Jay Ollie 
Published: June 2021

Recent evidence suggests whole‐body sweat rate (WBSR, g·min–1) is determined by the absolute evaporation required for heat balance (Ereq, W). However, since differences in body surface area (BSA) should theoretically modify local sweat rate (LSR, mg·cm–2·min–1) for a given absolute Ereq, we hypothesized that LSR is determined by Ereq relative to BSA (W·m–2) rather than absolute Ereq (W). Sixteen males of large (L: 2.12±0.09 m2, n=8) and small (S: 1.80±0.09 m2, n=8) BSA cycled in 25°C at workloads eliciting Ereq of 340 and 400 W, and 165 and 190 W·m–2. Heat production was estimated via indirect calorimetry. WBSR was estimated from changes in body mass between 45 and 60 min, and LSR was taken as the mean of back and forearm ventilated capsule measurements from 45‐60 min. WBSR was similar between groups at 340 and 400 W (p蠅0.54), but LSR was greater at 400 W (p=0.03), and 340 W (p=0.07), in S. At 165 and 190 W·m–2, no differences in LSR were evident (p蠅0.86), while WBSR was greater in L at 165 W·m–2 (p=0.01) but not at 190 W·m–2 (p=0.13). Differences in BSA modify LSR for a given absolute Ereq, while the prescription of Ereq in W·m–2 results in similar LSR irrespective of BSA.Grant Funding Source: Supported by a NSERC Discovery Grant (O. Jay)
High‐fat diet alters neuromuscular transmission and smooth muscle excitability in the mouse distal colon (1110.10)
Authors: Bhattarai Yogesh , Fried David , Galligan James 
Published: June 2021

We tested the hypothesis that a high‐fat diet disrupts neuromuscular transmission and smooth muscle electrical activity in the distal colon of mice. Methods: Distal colon segments from mice placed on a control (10 Kcal%) or high‐fat (HF) diet (60 Kcal%) were used in vitro. Circular muscle reactivity to electrical field stimulation (EFS) and bethanechol were measured in organ baths. Circular smooth muscle action potentials were recorded using intracellular microelectrodes in vitro. Colonic migrating motor complexes (CMMCs) were measured in vitro. Results: Bethanechol caused larger contractions in colon rings from control vs. HF mice. Colon rings from HF had reduced neurogenic contractions compared to rings from control mice. Colon segments from HF mice exhibited continuous action potential firing while control segments had bursting action potential firing. The membrane potential of the smooth muscle cells from HF mice was depolarized compared to control mice. Retrogradely propagated CMMCs occurred more often in the distal colon of HF mice compared to control mice. HF mice had reduced CMMC propagation speed compared to control mice. Conclusion: We conclude that HF diet impairs neuromuscular transmission and smooth muscle electrical activity in the colon. This would cause altered colon motility and propulsion.Grant Funding Source: NIH (DK094932)
Ostrich oil failed to improve intestinal barrier function following 5‐fluorouracil‐induced mucositis in rats (1111.5)
Authors: Cheah Ker , Mashtoub Suzanne , Howarth Gordon 
Published: June 2021

INTRODUCTION. Mucositis is characterized by intestinal barrier disruption following chemotherapy. Emu Oil promoted small intestinal repair in a rat model of mucositis (Mashtoub, 2013). However, the effects of Ostrich Oil (OO) remain unexplored. We investigated the effects of OO on mucin‐secreting goblet cells (GC) during the recovery phase of mucositis. METHODS. Female Dark Agouti rats were allocated to groups (n=8/group): Saline+Water; Saline+OO; 5‐Fluorouracil (5‐FU)+Water; 5‐FU+OO. Mucositis was induced on day 5 by 5‐FU injection and rats were euthanized on day 10. Intestinal villus height (VH), crypt depth (CD) and GC were quantified. p<0.05 was considered significant. RESULTS. Compared to water controls, VH was increased 15% by OO (p<0.05), however, VH was unaffected by 5‐FU. 5‐FU tended to decrease GC count in the villi, relative to water controls (p=0.069). GC count was unaffected by OO in 5‐FU‐treated rats compared to 5‐FU controls. CD was increased 24% by 5‐FU (p<0.01); an effect that was not altered by OO. 5‐FU reduced GC count in crypts (33%; p<0.01) compared to water controls. However, OO did not attenuate the decrease in GC count in 5‐FU‐treated rats. CONCLUSIONS. Ostrich Oil treatment failed to improve intestinal barrier function indicated by mucin‐secreting goblet cells. As this is the first report of Ostrich Oil in bowel disease, further studies are required to explore dosage and timing regimens.Grant Funding Source: Supported by The Rural Industries Research and Development Corporation Australia
miR‐93 downregulation of PTK6 attenuates TNFα/IFNγ mediated of colonic epithelial barrier dysfunction (1113.2)
Authors: Haines Ricci , Beard Richard , Yuan Sarah , Wu Mack 
Published: June 2021

The role of protein tyrosine kinase 6 (PTK6, also known as breast tumor kinase BRK) has been mainly studied in mechanisms underlying metastasis and cancer. However, it has also been shown that PTK6 null mice demonstrate particularly strong (greater than 10 fold increase in basal TER resistance measurement relative to PTK6+/+) colonic epithelial monolayers. To this end, we investigated the role of PTK6 in TNFα/IFNγ mediated disruption of colonic epithelial barrier function. Consistent with previous findings, PTK6 knockdown increased basal resistance in YAMC monolayers. In addition, we showed that PTK6 knockdown significantly attenuated TNFα/IFNγ mediated decrease in resistance of young adult mouse colonic epithelial cell (YAMC) monolayers. In order to determine mechanisms of endogenous regulation of PTK6, we performed microRNA prediction analysis on the 3’UTR of PTK6 and identified miR‐93 as being highly likely to target PTK6 in epithelial cells. We investigated the role of miR‐93 in regulating PTK6 in YAMCs and determined that transfection of miR‐93 similarly attenuated TNFα/IFNγ mediated decrease in TER. We also show by Western blot that miR‐93 significantly decreased PTK6 expression following stimulant challenge. Using immunocytochemistry and confocal microscopy, we further characterized the process by which PTK6 modulates epithelial barrier function in YAMCs. Our results indicate that miR‐93 targeting of PTK6 may serve as a novel therapeutic strategy in treating diseases involving inflammation driven hyperpermeability of the colonic epithelium.Grant Funding Source: Supported by VA Merit Review 5101BX000799, the NIH grants HL96640, HL61507 and HL70752
Low copper and dietary sucrose drive fibrosis pathways in a rat model of non‐alcoholic fatty‐liver disease (1116.11)
Authors: Tallino Savannah , Burkhead Jason 
Published: June 2021

Nonalcoholic fatty‐liver disease (NAFLD) is increasing in prevalence worldwide with the affected US population estimated near 30%. However, the molecular changes that drive NAFLD and its progression to non‐alcoholic steatohepatitis (NASH) and fibrosis are not well understood. Recently, a negative correlation has been observed between copper (Cu) status and NAFLD/NASH severity in patients, while rodent models fed low‐Cu diets also develop NAFLD pathology. The relationship between Cu status and liver disease is further complicated by consumption of simple sugars such as sucrose. We investigated effects of marginal Cu deficiency independently and in combination with 30% w/v sucrose in a mature rat model of NAFLD. Significant reductions of hepatic and serum Cu (p < 0.05) associated with significantly increased oxidative stress (p < 0.05) and up‐regulated expression of transcripts involved in inflammation and hepatic stellate cell activation (FC >= 2, p < 0.02), while rats fed low‐Cu/high sucrose also developed insulin resistance. The severity of fibrosis in particular has been implicated as a critical diagnostic tool for chronic liver disease and is likely prognostic for long‐term outcomes of liver complications and mortality. This study reveals low dietary Cu and sucrose consumption as potential drivers for NAFLD and NASH progression and transcriptional activation of fibrosis.Grant Funding Source: Supported by UAA Innovate Award and Alaska INBRE
Reversible transgene expression in mice: now you see it, now you don’t (1121.1)
Authors: Matthaei Klaus , Morton Susan , Chaston Daniel , Baillie Brett , Hill Caryl 
Published: June 2021

Transgenic mice can suffer from the “Position effect” whereby the transgene integration site, per se, influences the observed phenotype. Multiple ‘Founder’ animals must therefore be studied to determine the actual phenotype of each transgene. We describe a method whereby a transgene can be switched off and on, allowing reliable validation of phenotype.We modified the endothelial specific Tie2 promoter with LacO sequences derived from the E. coli LacO/LacI system and generated transgenic mice expressing defective Connexin(Cx)40 molecules, with EGFP as reporter. Transgene expression was down‐regulated by breeding with mice expressing the inhibitor protein LacI and up‐regulated by Isopropyl β‐D‐1‐thiogalacto‐pyranoside (IPTG) in the drinking water. EGFP was quantified using immunohistochemistry and Western blotting. Blood pressure was measured by tail cuff plethysmography and telemetry.EGFP expression was exclusively endothelial and correlated with transgene copy number. Defective Cx40 expression increased blood pressure. Breeding with LacI mice significantly reduced EGFP expression and blood pressure by 70‐100%. EGFP expression could be reinstated by IPTG in some, but not all, founder lines in a time dependent manner.We conclude that the LacO/LacI system allows temporal transgene regulation and can reliably control for artifactual phenotypes arising from the “Position effect”.
In vivo microelectrode assessment of NBCe2 activity in the distal nephron during an acid load (1122.2)
Authors: Yuan yang , Li huaqing , Wen Donghai , Boettger Thomas , Sansom Steven 
Published: June 2021

The electrogenic Na bicarbonate co‐transporter (NBCe2) reabsorbs one Na and two or three bicarbonates in the distal nephron but its electrogenic function has not been demonstrated in‐vivo. Micropuncture was used to determine the transepithelial potential (Vte) in the distal convoluted tubule 2 (DCT2) of wild type mice (WT) and mice with a knock‐out of NBCe2 (NBCe2‐/‐). The DCT2 is the segment where expression of ENaC‐mediated Na reabsorption and ROMK‐mediated K secretion begins. Fine tip microelectrodes were placed in the lumen of the DCT2. A ground reference electrode was placed in the surface saline solution near the luminal microelectrode. Each group: n 蠅 3. We validated the microelectrode measurements by determining the effects on Vte of proximal tubule in control (‐5.6 ± 0.3 mV) and after giving 2% IP phloridzin (Vte = ‐0.2 ± 0.2 mV), an inhibitor of Na‐glucose cotransport. The Vte of the DCT2 was ‐11.0 ± 0.6 mV in WT control diet mice. When treated with acidic (280 mM NH4Cl) drinking water, the Vte of WT decreased to 0.4 ± 1.1 mV, a value significantly greater than WT, consistent with H+ secretion and/or bicarbonate reabsorption in this segment. When treated with acid water, the Vte of NBCe2‐/‐ was ‐3.4 ± 0.3 mV, a value significantly less than that of WT on acid water. We conclude that the NBCe2 is located in the DCT2 where it contributes to a more positive luminal potential when mice consume an acid load.Grant Funding Source: NIDDK