Hypothermia and minimal gradient requirements for excitation of cardiac muscle

1961 ◽  
Vol 200 (4) ◽  
pp. 718-722 ◽  
Author(s):  
J. Ushiyama ◽  
C. McC. Brooks
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Muscle ◽  
Rectangular Pulse ◽  
Nerve Fibers ◽  
Spinal Neurons ◽  
Long Duration ◽  
Minimal Gradient

A method is described for testing the stimulating-effectiveness of linearly rising current. It was found that cardiac muscle, like nerve fibers, spinal neurons and skeletal muscle has a minimal gradient requirement. Dog trabecular muscles showed great differences in their minimal gradients even at the same temperature but the requirements of individual muscles were rather constant. During hypothermia (24°–27°C) there was a reduction in threshold to stimulation by a rectangular pulse and a great prolongation of the minimal gradient requirement for stimulation as though a type of accommodative reaction present at normal temperatures had been suppressed. Determination of minimal gradient requirements by exponentially rising current gave the same results as obtained with linearly rising currents. Excitation occurred when the rheobasic strengths, as determined by rectangular pulses of long duration, were attained if stimuli satisfied the minimal gradient requirement. The likelihood that a number of accommodative processes occur in tissues subject to stimulatory forces is discussed.

Skeletal and cardiac muscle protein turnover during cold acclimation in young rats

2000 ◽  
Vol 278 (3) ◽  
pp. R705-R711 ◽  
Author(s):  
T. A. McAllister ◽  
J. R. Thompson ◽  
S. E. Samuels
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Cardiac Muscle ◽  
Cold Acclimation ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Muscle Protein Turnover ◽  
Protein Mass ◽  
The Absolute

The effect of long-term cold exposure on skeletal and cardiac muscle protein turnover was investigated in young growing animals. Two groups of 36 male 28-day-old rats were maintained at either 5°C (cold) or 25°C (control). Rates of protein synthesis and degradation were measured in vivo on days 5, 10, 15, and 20. Protein mass by day 20 was ∼28% lower in skeletal muscle (gastrocnemius and soleus) and ∼24% higher in heart in cold compared with control rats ( P < 0.05). In skeletal muscle, the fractional rates of protein synthesis ( k syn) and degradation ( k deg) were not significantly different between cold and control rats, although k syn was lower (approximately −26%) in cold rats on day 5; consequent to the lower protein mass, the absolute rates of protein synthesis (approximately −21%; P < 0.05) and degradation (approximately −13%; P < 0.1) were lower in cold compared with control rats. In heart, overall, k syn(approximately +12%; P < 0.1) and k deg(approximately +22%; P < 0.05) were higher in cold compared with control rats; consequently, the absolute rates of synthesis (approximately +44%) and degradation (approximately +54%) were higher in cold compared with control rats ( P < 0.05). Plasma triiodothyronine concentration was higher ( P < 0.05) in cold compared with control rats. These data indicate that long-term cold acclimation in skeletal muscle is associated with the establishment of a new homeostasis in protein turnover with decreased protein mass and normal fractional rates of protein turnover. In heart, unlike skeletal muscle, rates of protein turnover did not appear to immediately return to normal as increased rates of protein turnover were observed beyond day 5. These data also indicate that increased rates of protein turnover in skeletal muscle are unlikely to contribute to increased metabolic heat production during cold acclimation.

scholarly journals Prion Infection of Skeletal Muscle Cells and Papillae in the Tongue

2004 ◽  
Vol 78 (13) ◽  
pp. 6792-6798 ◽  
Author(s):  
Ellyn R. Mulcahy ◽  
Jason C. Bartz ◽  
Anthony E. Kincaid ◽  
Richard A. Bessen
Keyword(s):  
Skeletal Muscle ◽  
Sensory Nerve ◽  
Meat Products ◽  
Muscle Cells ◽  
Nerve Fibers ◽  
Skeletal Muscle Cells ◽  
Lingual Papillae ◽  
Intracerebral Inoculation ◽  
Axon Terminals ◽  
Prion Infection

ABSTRACT The presence of the prion agent in skeletal muscle is thought to be due to the infection of nerve fibers located within the muscle. We report here that the pathological isoform of the prion protein, PrPSc, accumulates within skeletal muscle cells, in addition to axons, in the tongue of hamsters following intralingual and intracerebral inoculation of the HY strain of the transmissible mink encephalopathy agent. Localization of PrPSc to the neuromuscular junction suggests that this synapse is a site for prion agent spread between motor axon terminals and muscle cells. Following intracerebral inoculation, the majority of PrPSc in the tongue was found in the lamina propria, where it was associated with sensory nerve fibers in the core of the lingual papillae. PrPSc staining was also identified in the stratified squamous epithelium of the lingual mucosa. These findings indicate that prion infection of skeletal muscle cells and the epithelial layer in the tongue can be established following the spread of the prion agent from nerve terminals and/or axons that innervate the tongue. Our data suggest that ingestion of meat products containing prion-infected tongue could result in human exposure to the prion agent, while sloughing of prion-infected epithelial cells at the mucosal surface of the tongue could be a mechanism for prion agent shedding and subsequent prion transmission in animals.

scholarly journals Glycogenin is Dispensable for Glycogen Synthesis in Human Muscle, and Glycogenin Deficiency Causes Polyglucosan Storage

2019 ◽  
Vol 105 (2) ◽  
pp. 557-566 ◽  
Author(s):  
Kittichate Visuttijai ◽  
Carola Hedberg-Oldfors ◽  
Christer Thomsen ◽  
Emma Glamuzina ◽  
Cornelia Kornblum ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Skeletal Muscle ◽  
Western Blot ◽  
Cardiac Muscle ◽  
Glycogen Synthesis ◽  
Muscle Fibers ◽  
Human Muscle ◽  
Missense Mutations ◽  
Skeletal Muscle Fibers ◽  
Glycogen Biosynthesis

Abstract Context Glycogenin is considered to be an essential primer for glycogen biosynthesis. Nevertheless, patients with glycogenin-1 deficiency due to biallelic GYG1 (NM_004130.3) mutations can store glycogen in muscle. Glycogenin-2 has been suggested as an alternative primer for glycogen synthesis in patients with glycogenin-1 deficiency. Objective The objective of this article is to investigate the importance of glycogenin-1 and glycogenin-2 for glycogen synthesis in skeletal and cardiac muscle. Design, Setting, and Patients Glycogenin-1 and glycogenin-2 expression was analyzed by Western blot, mass spectrometry, and immunohistochemistry in liver, heart, and skeletal muscle from controls and in skeletal and cardiac muscle from patients with glycogenin-1 deficiency. Results Glycogenin-1 and glycogenin-2 both were found to be expressed in the liver, but only glycogenin-1 was identified in heart and skeletal muscle from controls. In patients with truncating GYG1 mutations, neither glycogenin-1 nor glycogenin-2 was expressed in skeletal muscle. However, nonfunctional glycogenin-1 but not glycogenin-2 was identified in cardiac muscle from patients with cardiomyopathy due to GYG1 missense mutations. By immunohistochemistry, the mutated glycogenin-1 colocalized with the storage of glycogen and polyglucosan in cardiomyocytes. Conclusions Glycogen can be synthesized in the absence of glycogenin, and glycogenin-1 deficiency is not compensated for by upregulation of functional glycogenin-2. Absence of glycogenin-1 leads to the focal accumulation of glycogen and polyglucosan in skeletal muscle fibers. Expression of mutated glycogenin-1 in the heart is deleterious, and it leads to storage of abnormal glycogen and cardiomyopathy.

scholarly journals The phosphorylation of troponin I from cardiac muscle

1975 ◽  
Vol 149 (3) ◽  
pp. 525-533 ◽  
Author(s):  
H A Cole ◽  
S V Perry
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase ◽  
Cyclic Amp ◽  
Cardiac Muscle ◽  
Cardiac Troponin ◽  
Troponin I ◽  
Cardiac Troponin I ◽  
Phosphorylase Kinase ◽  
Dependent Protein Kinase ◽  
Dependent Protein

1. Troponin I isolated from fresh cardiac muscle by affinity chromatography contains about 1.9 mol of covalently bound phosphate/mol. Similar preparations of white-skeletal-muscle troponin I contain about 0.5 mol of phosphate/mol. 2. A 3':5'-cyclic AMP-dependent protein kinase and a protein phosphatase are associated with troponin isolated from cardiac muscle. 3. Bovine cardiac 3':5'-cyclic AMP-dependent protein kinase catalyses the phosphorylation of cardiac troponin I 30 times faster than white-skeletal-muscle troponin I. 4. Troponin I is the only component of cardiac troponin phosphorylated at a significant rate by the endogenous or a bovine cardiac 3':5'-cyclic AMP-dependent protein kinase. 5. Phosphorylase kinase catalyses the phosphorylation of cardiac troponin I at similar or slightly faster rates than white-skeletal-muscle troponin I. 6. Troponin C inhibits the phosphorylation of cardiac and skeletal troponin I catalysed by phosphorylase kinase and the phosphorylation of white skeletal troponin I catalysed by 3':5'-cyclic AMP-dependent protein kinase; the phosphorylation of cardiac troponin I catalysed by the latter enzyme is not inhibited.

scholarly journals Adhesive multiplicity in the interaction of embryonic fibroblasts and myoblasts with extracellular matrices.

1984 ◽  
Vol 99 (4) ◽  
pp. 1398-1404 ◽  
Author(s):  
C Decker ◽  
R Greggs ◽  
K Duggan ◽  
J Stubbs ◽  
A Horwitz
Keyword(s):  
Skeletal Muscle ◽  
Cardiac Muscle ◽  
Cardiac Fibroblasts ◽  
Cell Types ◽  
Extracellular Matrices ◽  
Common Denominator ◽  
Cell Matrix ◽  
Skeletal Myoblasts ◽  
A Cell ◽  
Cell Matrix Adhesion

Neff et al. (1982, J. Cell Biol., 95:654-666) have described a monoclonal antibody, CSAT, directed against a cell surface antigen that participates in the adhesion of skeletal muscle to extracellular matrices. We used the same antibody to compare and parse the determinants of adhesion and morphology on myogenic and fibrogenic cells. We report here that the antigen is present on skeletal and cardiac muscle and on tendon, skeletal, dermal, and cardiac fibroblasts; however, its contribution to their morphology and adhesion is different. The antibody produces large alterations in the morphology and adhesion of skeletal myoblasts and tendon fibroblasts; in contrast, its effects on the cardiac fibroblasts are not readily detected. The effects of CSAT on the other cell types, i.e., dermal and skeletal fibroblasts, cardiac muscle, 5-bromodeoxyuridine-treated skeletal muscle, lie between these extremes. The effects of CSAT on the skeletal myoblasts depends on the calcium concentration in the growth medium and on the culture age. We interpret these differential responses to CSAT as revealing differences in the adhesion of the various cells to extracellular matrices. This interpretation is supported by parallel studies using quantitative assays of cell-matrix adhesion. The likely origin of these adhesive differences is the progressive display of different kinds of adhesion-related molecules and their organizational complexes on increasingly adhesive cells. The antigen to which CSAT is directed is present on all of the above cells and thus appears to be a lowest common denominator of their adhesion to extracellular matrices.

Antecubital Vein Cannula Position Impacts Assessment of Forearm Glucose Uptake During an Oral Glucose Challenge in Healthy Volunteers

2020 ◽  
Author(s):  
Cécile Bétry ◽  
Aline V. Nixon ◽  
Paul L. Greenhaff ◽  
Elizabeth J. Simpson
Keyword(s):  
Skeletal Muscle ◽  
Blood Glucose ◽  
Glucose Uptake ◽  
Venous Blood ◽  
Whole Body ◽  
Oral Glucose ◽  
Antecubital Vein ◽  
Glucose Challenge ◽  
The Impact

Abstract Introduction Skeletal muscle is a major site for whole-body glucose disposal, and determination of skeletal muscle glucose uptake is an important metabolic measurement, particularly in research focussed on interventions that impact muscle insulin sensitivity. Calculating arterial-venous difference in blood glucose can be used as an indirect measure for assessing glucose uptake. However, the possibility of multiple tissues contributing to the composition of venous blood, and the differential in glucose uptake kinetics between tissue types, suggests that sampling from different vein sites could influence the estimation of glucose uptake. This study aimed to determine the impact of venous cannula position on calculated forearm glucose uptake following an oral glucose challenge in resting and post-exercise states. Materials and Methods In 9 young, lean, males, the impact of sampling blood from two antecubital vein positions; the perforating vein (‘perforating’ visit) and, at the bifurcation of superficial and perforating veins (‘bifurcation’ visit), was assessed. Brachial artery blood flow and arterialised-venous and venous blood glucose concentrations were measured in 3 physiological states; resting-fasted, resting-fed, and fed following intermittent forearm muscle contraction (fed-exercise). Results Following glucose ingestion, forearm glucose uptake area under the curve was greater for the ‘perforating’ than for the ‘bifurcation’ visit in the resting-fed (5.92±1.56 vs. 3.69±1.35 mmol/60 min, P<0.01) and fed-exercise (17.38±7.73 vs. 11.40±7.31 mmol/75 min, P<0.05) states. Discussion Antecubital vein cannula position impacts calculated postprandial forearm glucose uptake. These findings have implications for longitudinal intervention studies where serial determination of forearm glucose uptake is required.

Contraction duration affects metabolic energy cost and fatigue in skeletal muscle

1998 ◽  
Vol 274 (3) ◽  
pp. E397-E402 ◽  
Author(s):  
Michael C. Hogan ◽  
Erica Ingham ◽  
S. Sadi Kurdak
Keyword(s):  
Skeletal Muscle ◽  
Short Duration ◽  
Energy Cost ◽  
Lactate Concentration ◽  
Metabolic Energy ◽  
Muscle Lactate ◽  
Contracting Muscle ◽  
Contraction Duration ◽  
Long Duration ◽  
The Difference

It has been suggested that during a skeletal muscle contraction the metabolic energy cost at the onset may be greater than the energy cost related to holding steady-state force. The purpose of the present study was to investigate the effect of contraction duration on the metabolic energy cost and fatigue process in fully perfused contracting muscle in situ. Canine gastrocnemius muscle ( n = 6) was isolated, and two contractile periods (3 min of isometric, tetanic contractions with 45-min rest between) were conducted by each muscle in a balanced order design. The two contractile periods had stimulation patterns that resulted in a 1:3 contraction-to-rest ratio, with the difference in the two contractile periods being in the duration of each contraction: short duration 0.25-s stimulation/0.75-s rest vs. long duration 1-s stimulation/3-s rest. These stimulation patterns resulted in the same total time of stimulation, number of stimulation pulses, and total time in contraction for each 3-min period. Muscle O2 uptake, the fall in developed force (fatigue), the O2 cost of developed force, and the estimated total energy cost (ATP utilization) of developed force were significantly greater ( P < 0.05) with contractions of short duration. Lactate efflux from the working muscle and muscle lactate concentration were significantly greater with contractions of short duration, such that the calculated energy derived from glycolysis was three times greater in this condition. These results demonstrate that contraction duration can significantly affect both the aerobic and anaerobic metabolic energy cost and fatigue in contracting muscle. In addition, it is likely that the greater rate of fatigue with more rapid contractions was a result of elevated glycolytic production of lactic acid.

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