Effects of hypoxia on cardiac growth in neonatal rat

1976 ◽  
Vol 231 (5) ◽  
pp. 1445-1450 ◽  
Author(s):  
M Hollenberg ◽  
N Honbo ◽  
AJ Samorodin
Keyword(s):  
Body Weight ◽  
Left Ventricle ◽  
Cardiac Muscle ◽  
Neonatal Period ◽  
Vascular Endothelial Cells ◽  
Muscle Cells ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
Low Oxygen ◽  
Cardiac Muscle Cells

To determine whether low oxygen environments enhance cardiac cell division in the neonatal period, newborn rat pups were reared for 21 days in 12-15% oxygen. Left ventricle and right ventricle weights were 30 and 180% greater than controls matched for body weight (P less than 0.001) as were left ventricle/body weight ratios (3.68+/-0.26 vs. 2.99+/-0.05 mg LV/g body wt,P less than 0.001). Left ventricular total DNA and DNA concentration was 95 and 48% greater than controls (P less than 0.001). Autoradiography confirmed that this increase in ventricular DNA resulted from an increased rate of division of cardiac muscle cells, fibroblast, and vascular endothelial cells. When [3H]thymidine was injected on day ), autoradiographs prepared on day 21 reflected an increased dilution of label in hypoxic rats consistent with enhanced proliferation. The labeling index and grains per nucleus of ventricular muscle cells was 25% (P less than 0.01) and 20% (P less than 0.02) less than controls, Thus, hypoxic stress applied early in the neonatal period augments the rate of division and ultimate number of cardiac muscle cells. Whether this enhancement results from a primary effect of oxygen or from secondary hemodynamic factors remains unknown.

Cardiac cellular responses to altered nutrition in the neonatal rat

1977 ◽  
Vol 233 (3) ◽  
pp. H356-H360 ◽  
Author(s):  
M. Hollenberg ◽  
N. Honbo ◽  
A. J. Samorodin
Keyword(s):  
Vascular Endothelial Cells ◽  
Muscle Cells ◽  
Cellular Responses ◽  
Cell Number ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
Vascular Endothelial ◽  
Cardiac Muscle Cells ◽  
Total Dna ◽  
The Right

Rats reared in litters of 18, 12, and 6 to determine whether preweanling nutritional state would alter rates of cardiac cell division, weighed 31.7, 39.1, 48.2 g, respectively, at 21 days of age. Weights of left ventricles also increased (93.2, 123.5, and 167.2 mg) as did those of right ventricles (29.9, 43.2, and 54.3 mg). Total DNA content rose in both ventricles in the pups reared 6 per litter vs. those reared 18 per litter (6/litter vs. 18/litter), but more so in the left ventricle (79%) than in the right (24%). Autoradiography confirmed that this increase in ventricular DNA resulted from increased proliferation of cardiac muscle cells, fibroblasts, and vascular endothelial cells. When 3H-labeled thymidine was injected on day 1, autoradiographs prepared on day 21 reflected an increased dilution of label in the 6/litter rats, consistent with enhanced proliferation. The labeling index and grains per nucleus of left ventricular muscle cells of the 6/litter rats were 29% (P less than 0.005) and 20% (P less than 0.001) less than those of the 18/litter rats. Less vigorous but definite hyperplasia occurred in the right ventricle, which appeared to respond with an increase more in cell size than in cell number.

scholarly journals Structure of myofibrils at extra-junctional membrane attachment sites in cultured cardiac muscle cells

1988 ◽  
Vol 89 (1) ◽  
pp. 97-106
Author(s):  
B.T. Atherton ◽  
M.M. Behnke
Keyword(s):  
Cell Membrane ◽  
Cardiac Muscle ◽  
Muscle Cells ◽  
Neonatal Rat ◽  
Heart Cells ◽  
Cardiac Muscle Cells ◽  
Lateral Contact ◽  
Attachment Sites ◽  
Membrane Attachment ◽  
Actin Cables

The composition and organization of myofibrils at extra-junctional membrane attachment sites in cultured neonatal rat cardiac muscle cells were analysed by immunofluorescence and electron microscopy. When myofibril terminals attached to the cell membrane via focal contacts at regions of the sarcolemma that lacked intercalated discs, they appeared to be non-striated and resembled thick actin cables. Although the non-striated terminals contained actin, myosin and alpha-actinin, the proteins were not organized into recognizable sarcomeres at the light microscopic level. Analysis of the structure of the terminals in the electron microscope confirmed that the usual sarcomeric organization and attachments to the sarcolemma were markedly modified. The non-striated myofibril terminals differed in structure from both stress fibres in non-muscle cells and stress fibre-like structures present in embryonic heart cells in culture. Non-striated myofibril terminals attached to the cell membrane by lateral contact with extra-junctional electron-dense membrane plaques rather than by insertion by their ends into the fascia adherens. It is proposed that the structure and composition of membrane-attachment points for myofibrils may have an influence on the structure, organization or stability of contractile elements in cardiac muscle.

Lipid Droplet Accumulation in Cardiac Muscle Cells of the Bat: Induction by Reserpine and Antagonism by Atropine

1975 ◽  
Vol 33 ◽  
pp. 534-535
Author(s):  
Martin Hagopian ◽  
Eladio A. Nunez ◽  
Michael D. Gershon
Keyword(s):  
Cardiac Muscle ◽  
Lipid Droplets ◽  
Single Injection ◽  
Sympathetic Innervation ◽  
Muscle Cells ◽  
Left Ventricular ◽  
High Dose ◽  
Cardiac Muscle Cells ◽  
Cardiac Sympathetic Innervation ◽  
Point Count

Reserpine has been shown to induce the accumulation of large numbers of lipid inclusions in cardiac muscle cells of the bat. This effect of reserpine is seen 24 hours after a single injection of 5 mg/kg of the drug. Since the action of reserpine can be antagonized by chemical sympathectomy with 6-hydroxydopamine and mimicked by norepinephrine, we have postulated the involvement of the cardiac sympathetic innervation in mediating reserpine's effect. In the present investigation we have examined the ability of atropine to prevent the accumulation of lipid droplets in cardiac muscle after a single injection of reserpine. Two dose schedules of atropine were tried. A high dose consisted of 3 injections, 9 mg/kg each, given intraperitoneally at 8 hour intervals beginning one hour prior to challenge with reserpine. A low dose consisted of 2 mg/kg given the same way. Left ventricular muscle was examined by electron microscopy and the relative cardiocyte volume occupied by lipid droplets was quantitated from electron micrographs by point count planimetry.

Fine Structure of Cardiac Muscle Cells after Injection of Normal and Thiouracil-Treated Rats with Triiodothyronine.

1975 ◽  
Vol 33 ◽  
pp. 536-537
Author(s):  
Eladio A. Nunez ◽  
Martin Hagopian ◽  
Roger L. Greif ◽  
Michael D. Gershon
Keyword(s):  
Drinking Water ◽  
Fine Structure ◽  
Thyroid Hormones ◽  
Cardiac Muscle ◽  
Muscle Cells ◽  
Left Ventricular ◽  
Ventricular Muscle ◽  
Cardiac Muscle Cells ◽  
Mitochondrial Number ◽  
Morphologic Changes

It has been reported that morphologic changes occur in mitochondria of cardiac muscle cells following treatment with thyroid hormones (thyroxine, triiodothyronine). These observations have been used to support the view that under normal conditions, thyroid hormones control mitochondrial metabolism. We have examined the effect of triiodothyronine on the fine structure of cardiac muscle from normal and thiouracil-treated rats. Rats were given thiouracil (0.1 percent in drinking water) for 10 weeks. Normal and thiouracil-treated rats were injected with triiodothyronine (75 ug of triiodo-L-thyronine i.p. per day) for three days. The left ventricular muscle of normal rats, and rats given thiouracil, triiodothyronine or thiouracil followed by triiodothyronine was examined ultrastructurally. Morphometric analysis of electron micrographs showed that mitochondrial number was not significantly different in the four groups of animals. The fine structure of normal cardiac muscle is illustrated in figure 1. Thiouracil treatment did not alter the fine structure of cardiac muscle cells (Fig. 3).

Translation of heart preproenkephalin mRNA and secretion of enkephalin peptides from cultured cardiac myocytes

1992 ◽  
Vol 263 (5) ◽  
pp. H1560-H1566 ◽  
Author(s):  
J. P. Springhorn ◽  
W. C. Claycomb
Keyword(s):  
Cardiac Muscle ◽  
Muscle Cells ◽  
Neonatal Rat ◽  
Ribonuclease Protection Assay ◽  
Cardiac Muscle Cells ◽  
Adult Rat ◽  
Rabbit Reticulocyte Lysate System ◽  
Ribonuclease Protection ◽  
Carboxy Terminal

Rat ventricular cardiac muscle has previously been shown to contain exceptionally high levels of preproenkephalin mRNA (ppEnk mRNA). We have recently determined that the level of ppEnk mRNA is developmentally and hormonally regulated in rat ventricular cardiac muscle tissue and in cultured myocytes (J. P. Springhorn and W. C. Claycomb. Biochem. J. 258: 73-77, 1989). We demonstrate in the current study that heart ppEnk mRNA is structurally identical at the 5' end to brain ppEnk mRNA using a ribonuclease protection assay and that heart ppEnk mRNA can be translated in vitro using a rabbit reticulocyte lysate system. In vitro synthesized preproenkephalin peptides were immunoprecipitated with a polyclonal antibody directed to the carboxy-terminal seven amino acids of preproenkephalin. We have also established by radioimmunoassay that enkephalin-containing peptides are secreted from cultured neonatal and adult rat ventricular cardiac muscle cells. This secretion is linear with respect to time and can be stimulated by phorbol 12-myristate 13-acetate (PMA) and adenosine 3',5'-cyclic monophosphate (cAMP). It was determined by column chromatography that cAMP induced neonatal rat ventricular cardiac muscle cells to secrete Met5-enkephalin-Arg6-Phe7, whereas PMA plus 3-isobutyl-1-methylxanthine induced adult rat ventricular cardiac muscle cells to secrete Met5-enkephalin. These studies establish that ventricular heart muscle ppEnk mRNA can be translated and that enkephalin peptides are secreted from ventricular cardiac muscle cells.

scholarly journals Inhibition of p66ShcA redox activity in cardiac muscle cells attenuates hyperglycemia-induced oxidative stress and apoptosis

2009 ◽  
Vol 296 (2) ◽  
pp. H380-H388 ◽  
Author(s):  
Ashwani Malhotra ◽  
Himanshu Vashistha ◽  
Virendra S. Yadav ◽  
Michael G. Dube ◽  
Satya P. Kalra ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Cytochrome C ◽  
Cardiac Muscle ◽  
Ventricular Myocytes ◽  
Muscle Cells ◽  
Molecular Switch ◽  
Left Ventricular ◽  
Cardiac Muscle Cells ◽  
Rat Ventricular Myocytes ◽  
Adult Rat

Apoptotic myocyte cell death, diastolic dysfunction, and progressive deterioration in left ventricular pump function characterize the clinical course of diabetic cardiomyopathy. A key question concerns the mechanism(s) by which hyperglycemia (HG) transmits danger signals in cardiac muscle cells. The growth factor adapter protein p66ShcA is a genetic determinant of longevity, which controls mitochondrial metabolism and cellular responses to oxidative stress. Here we demonstrate that interventions which attenuate or prevent HG-induced phosphorylation at critical position 36 Ser residue (phospho-Ser36) inhibit the redox function of p66ShcA and promote the survival phenotype. Adult rat ventricular myocytes obtained by enzymatic dissociation were transduced with mutant-36 p66ShcA (mu-36) dominant-negative expression vector and plated in serum-free media containing 5 or 25 mM glucose. At HG, adult rat ventricular myocytes exhibit a marked increase in reactive oxygen species production, upregulation of phospho-Ser36, collapse of mitochondrial transmembrane potential, and increased formation of p66ShcA/cytochrome- c complexes. These indexes of oxidative stress were accompanied by a 40% increase in apoptosis and the upregulation of cleaved caspase-3 and the apoptosis-related proteins p53 and Bax. To test whether p66ShcA functions as a redox-sensitive molecular switch in vivo, we examined the hearts of male Akita diabetic nonobese (C57BL/6J) mice. Western blot analysis detected the upregulation of phospho-Ser36, the translocation of p66ShcA to mitochondria, and the formation of p66ShcA/cytochrome- c complexes. Conversely, the correction of HG by recombinant adeno-associated viral delivery of leptin reversed these alterations. We conclude that p66ShcA is a molecular switch whose redox function is turned on by phospho-Ser36 and turned off by interventions that prevent this modification.

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