Reduced cardiac response to the adrenergic system is a key limiting factor for physical capacity in old age

2021 ◽  
pp. 111339
Author(s):  
Luke A. Howlett ◽  
Matthew K. Lancaster
Keyword(s):  
Old Age ◽  
Physical Capacity ◽  
Cardiac Response ◽  
Adrenergic System ◽  
Limiting Factor

Regression of myocardial hypertrophy and influence of adrenergic system

1983 ◽  
Vol 244 (1) ◽  
pp. H97-H101 ◽  
Author(s):  
S. Sen ◽  
R. C. Tarazi
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Regression Analysis ◽  
Arterial Pressure ◽  
Spontaneously Hypertensive Rats ◽  
Myocardial Hypertrophy ◽  
Cardiac Response ◽  
Adrenergic System ◽  
Hypertensive Rats ◽  
Spontaneously Hypertensive

Studies of regression of myocardial hypertrophy in spontaneously hypertensive rats (SHR) suggest that the adrenergic system may play an important role in the reversal of hypertrophy. The effect of propranolol on reversal of hypertrophy, however, is still controversial. This study describes the effect of propranolol, given alone or in combination with hydralazine in different ratios for 4 wk, on blood pressure (BP), ventricular weight, and myocardial catecholamine (MC) concentrations. The data show that a certain ratio of propranolol to hydralazine (750:30) leads to moderate BP control (196-156 mmHg) without increased MC (634 vs. 552 ng/g) and moderately reduced hypertrophy. Reduction of BP alone with increased MC (hydralazine alone) or reduction of MC without BP control (propranolol alone) failed to reduce hypertrophy. A significant correlation between both ventricular weight and heart rate with MC (r = 0.6) was obtained by multiple regression analysis. This study suggests that adrenergic factors seem to play an important role in modulating structural cardiac response to variations in arterial pressure.

scholarly journals Old Age and Physical Capacity: Use It or Lose It

1984 ◽  
Vol 30 (4) ◽  
pp. 115-120 ◽  
Author(s):  
LANCE T. TWOMEY ◽  
JAMES R. TAYLOR
Keyword(s):  
Old Age ◽  
Physical Capacity

Altered coronary and cardiac adrenergic response in the failing hamster heart: role of cyclooxygenase derivatives

2002 ◽  
Vol 80 (3) ◽  
pp. 218-225 ◽  
Author(s):  
Danica Brousseau ◽  
Jean-François Desjardins ◽  
Gaëtan Jasmin ◽  
Louis Dumont
Keyword(s):  
Heart Failure ◽  
Coronary Flow ◽  
Cardiac Response ◽  
Adrenergic System ◽  
Inotropic Response ◽  
Adrenergic Stimulation ◽  
Isolated Hearts ◽  
Cardiac Dynamics ◽  
Before And After ◽  
Hamster Heart

Although the influence of the adrenergic system has been studied in the presence of heart failure, controversies still exist. Since cyclooxygenase derivatives appear to modulate coronary and cardiac adaptation in the failing heart, we hypothesized that cyclooxygenase derivatives may participate in the altered adrenergic responses in this situation. Isolated hearts from cardiomyopathic (UM-X7.1 subline) and normal hamsters, aged >240 days, were utilized. Coronary and cardiac response to α1-, β1-, and β2-adrenergic stimulations was observed before and after pretreatment with indomethacin, a cyclooxygenase inhibitor. Reduction of coronary flow elicited by α1-adrenergic stimulation was unchanged in the presence of heart failure, while β1- and β2-induced vasodilatations were reduced. Inotropic response to α1 and β1 stimulations were also reduced in failing hearts, while β2-adrenergic action was unchanged. Pretreatment with indomethacin exacerbated coronary flow reduction observed with α1 stimulation in failing hearts only. β2-induced coronary vasodilatation and inotropic response to α1 and β2 stimulations were impaired similarly in the presence of indomethacin in normal and failing hearts. The results suggest a complex interaction between adrenergic and cyclooxygenase activation.Key words: adrenergic, cyclooxygenase, heart failure, coronary flow, cardiac dynamics.

scholarly journals Effect of micromolar concentrations of free calcium ions on the reduction of heart mitochondrial NAD(P) by 2-oxoglutarate

1981 ◽  
Vol 198 (3) ◽  
pp. 525-533 ◽  
Author(s):  
R G Hansford ◽  
F Castro
Keyword(s):  
Steady State ◽  
Dehydrogenase Activity ◽  
Old Age ◽  
Atomic Absorption Spectrophotometry ◽  
Free Calcium ◽  
Limiting Factor ◽  
State Reduction ◽  
Oxoglutarate Dehydrogenase ◽  
Marked Dependence ◽  
Tricarboxylate Cycle

1. The reduction of mitochondrial NAD(P) by 2-oxoglutarate was monitored as a measure of 2-oxoglutarate dehydrogenase activity in its intramitochondrial locale. In the absence of ADP, steady-state reduction of NAD(P) by 0.5 mM-2-oxoglutarate in the presence of 0.5 mM-L-malate was markedly increased by extramitochondrial Ca2+, with 50% activation at pCa 6.58, when the Na+ concentration was 10 mM, the Pi concentration ws 5 mM and the added Mg2+ concentration was 1 mM. Omission of Pi resulted in 50% activation at pCa 6.77; omission of Mg2+ resulted in 50% activation at pCA greater than or equal to 7.3. 2. The activation of 2-oxoglutarate dehydrogenase could be reversed on addition of an excess of EGTA. The rate of inactivation was dependent on the concentration of Na+, with K0.5 2.5 mM, which is consistent with the rate of withdrawal of Ca2+ from the mitochondria being the limiting factor. 3. The steady-state reduction of cytochrome c by 2-oxoglutarate (0.5 mM) also showed a marked dependence on pCa in the absence of ADP; in the presence of an excess of ADP, no such effect of Ca2+ was detectable. 4. Mitochondria from the hearts of senescent rats showed an undiminished rate of dehydrogenase activation by Ca2+ but a rate of inactivation by excess EGTA that was diminished by 40%. Direct studies of Ca2+ egress with Arsenazo III confirmed a decrement in rate with old age. 5. Studies of 2-oxoglutarate dehydrogenase activity as a function of the mitochondrial context of Ca2+, as measured by atomic-absorption spectrophotometry, showed half-maximal activation at a mitochondrial content of 1.0 nmol of Ca2+/mg of protein, and saturation at 3 nmol/mg. 6. These findings support the model advanced by Denton, Richards & Chin [(1978) Biochem. J. 176, 899-906], of a control of the tricarboxylate cycle by intramitochondrial Ca2+, and demonstrate the range of mitochondrial Ca2+ content over which this may occur. In addition, they raise the possibility of a disturbance of this control mechanism in old age.

scholarly journals Bronchodilator test in extreme old age: Adverse effects of short-acting beta-2 adrenergic agonists with clinical repercussion and bronchodilator response

2019 ◽  
Vol 65 (11) ◽  
pp. 1343-1348
Author(s):  
Saulo Maia d'Avila Melo ◽  
Larissa Alves de Oliveira ◽  
Rodrigo dos Anjos Rocha ◽  
José Lucas Farias Wanderley
Keyword(s):  
Adverse Effects ◽  
Old Age ◽  
Test Methods ◽  
Chronological Age ◽  
Limiting Factor ◽  
Cross Sectional ◽  
Short Acting ◽  
Bronchodilator Response ◽  
Minimum Age ◽  
Beta 2

SUMMARY OBJECTIVE: To evaluate chronological age as a limiting factor to perform the bronchodilator test, determine significant adverse effects of short-acting beta 2 agonists with clinical repercussions, and assess bronchodilator response in extreme-old-age patients who undergo the spirometry test. METHODS: This is a cross-sectional and retrospective study. The sample was extracted from the database (spirometer and respiratory questionnaire) of a pulmonary function service. Patients over 90 years old were included in the research, and we evaluated their bronchodilator response and its significant adverse effects that may have clinical repercussions related to the bronchodilator. RESULTS: A sample of 25 patients aged 92.12 ± 2.22 years (95% CI, 91.20 - 93.04), with a minimum age of 90 years and a maximum of 97 years and a predominance of females with 72% (18/25). The bronchodilator test was performed in 84% (21/25) of the patients. The bronchodilator response was evaluated in 19 of the 21 patients (90.47%) who underwent the bronchodilator test. Two tests did not meet the criteria of acceptability and reproducibility. No clinical adverse effects were observed with the bronchodilator medication (salbutamol) during or after the exam. CONCLUSIONS: Chronological age is not a limiting factor for the bronchodilator test, short-acting beta-2 agonists did not present adverse effects with significant clinical repercussion and were useful in the diagnosis and therapeutic guidance of extreme-old-age patients.

Utilizing Dark Field Electron Microscopy to Produce Lantern Slides

1974 ◽  
Vol 32 ◽  
pp. 116-117
Author(s):  
J. N. Meador ◽  
C. N. Sun ◽  
H. J. White
Keyword(s):  
Electron Microscope ◽  
Electron Micrographs ◽  
Dark Field ◽  
Limiting Factor ◽  
Clinical Laboratories ◽  
Field Electron ◽  
Time Element ◽  
Field Electron Microscopy ◽  
Dark Field Electron ◽  
Dark Field Micrographs

The electron microscope is being utilized more and more in clinical laboratories for pathologic diagnosis. One of the major problems in the utilization of the electron microscope for diagnostic purposes is the time element involved. Recent experimentation with rapid embedding has shown that this long phase of the process can be greatly shortened. In rush cases the making of projection slides can be eliminated by taking dark field electron micrographs which show up as a positive ready for use. The major limiting factor for use of dark field micrographs is resolution. However, for conference purposes electron micrographs are usually taken at 2.500X to 8.000X. At these low magnifications the resolution obtained is quite acceptable.

Toward High-Resolution Low-Voltage SEM

1988 ◽  
Vol 46 ◽  
pp. 218-219
Author(s):  
Zhifeng Shao
Keyword(s):  
Low Voltage ◽  
Spherical Aberration ◽  
Chromatic Aberration ◽  
Limiting Factor ◽  
Operating Voltage ◽  
Probe Radius ◽  
Non Local ◽  
Electron Microscopes ◽  
Image Position ◽  
Scanning Electron Microscopes

Recently, low voltage (≤5kV) scanning electron microscopes have become popular because of their unprecedented advantages, such as minimized charging effects and smaller specimen damage, etc. Perhaps the most important advantage of LVSEM is that they may be able to provide ultrahigh resolution since the interaction volume decreases when electron energy is reduced. It is obvious that no matter how low the operating voltage is, the resolution is always poorer than the probe radius. To achieve 10Å resolution at 5kV (including non-local effects), we would require a probe radius of 5∽6 Å. At low voltages, we can no longer ignore the effects of chromatic aberration because of the increased ratio δV/V. The 3rd order spherical aberration is another major limiting factor. The optimized aperture should be calculated as

Computer averaging of lattice images of poly-4-methyl-pentene-1 (P4mp1): Noise created artifacts

1987 ◽  
Vol 45 ◽  
pp. 388-389
Author(s):  
P. Pradère ◽  
J.F. Revol ◽  
R. St. John Manley
Keyword(s):  
Low Dose ◽  
Polymer Concentration ◽  
Processing System ◽  
Limiting Factor ◽  
Dilute Solution ◽  
New Techniques ◽  
Dose Unit ◽  
Lattice Images ◽  
Dose Imaging ◽  
Imaging Conditions

Although radiation damage is the limiting factor in HREM of polymers, new techniques based on low dose imaging at low magnification have permitted lattice images to be obtained from very radiation sensitive polymers such as polyethylene (PE). This paper describes the computer averaging of P4MP1 lattice images. P4MP1 is even more sensitive than PE (total end point dose of 27 C m-2 as compared to 100 C m-2 for PE at 120 kV). It does, however, have the advantage of forming flat crystals from dilute solution and no change in d-spacings is observed during irradiation.Crystals of P4MP1 were grown at 60°C in xylene (polymer concentration 0.05%). Electron microscopy was performed with a Philips EM 400 T microscope equipped with a Low Dose Unit and operated at 120 kV. Imaging conditions were the same as already described elsewhere. Enlarged micrographs were digitized and processed with the Spider image processing system.

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