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  • 1
    Electronic Resource
    Electronic Resource
    Resistance exercise training and the orthostatic response (1997)
    Springer
    European journal of applied physiology 76 (1997), S. 32-40 
    Details
    ISSN: 1439-6327
    Keywords: Key words Blood volume ; Carotid baroreflexes Leg compliance ; Blood pressure ; Muscle mass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Resistance exercise has been suggested to increase blood volume, increase the sensitivity of the carotid baroreceptor cardiac reflex response (BARO), and decrease leg compliance, all factors that are expected to improve orthostatic tolerance. To further test these hypotheses, cardiovascular responses to standing and to pre-syncopal limited lower body negative pressure (LBNP) were measured in two groups of sedentary men before and after a 12-week period of either exercise (n = 10) or no exercise (control, n = 9). Resistance exercise training consisted of nine isotonic exercises, four sets of each, 3 days per week, stressing all major muscle groups. After exercise training, leg muscle volumes increased (P 〈 0.05) by 4–14%, lean body mass increased (P = 0.00) by 2.0 (0.5) kg, leg compliance and BARO were not significantly altered, and the maximal LBNP tolerated without pre-syncope was not significantly different. Supine resting heart rate was reduced (P = 0.03) without attenuating the heart rate or blood pressure responses during the stand test or LBNP. Also, blood volume (125I and 51Cr) and red cell mass were increased (P 〈 0.02) by 2.8% and 3.9%, respectively. These findings indicate that intense resistance exercise increases blood volume but does not consistently improve orthostatic tolerance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050209
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  • 2
    Electronic Resource
    Electronic Resource
    Cardiovascular adjustments to rhythmic handgrip exercise: relationship to electromyographic activity and post-exercise hyperemia (1988)
    Springer
    European journal of applied physiology 58 (1988), S. 32-38 
    Details
    ISSN: 1439-6327
    Keywords: Exercise ; Blood pressure ; Vasodilation ; Autonomic nervous system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The purpose of this study was to examine the association among electromyographic (EMG) activity, recovery blood flow, and the magnitude of the autonomic adjustments to rhythmic exercise in humans. To accomplish this, 10 healthy subjects (aged 23–37 y) performed rhythmic handgrip exercise for 2 min at 5, 15, 25, 40, and 60% of maximal voluntary force. Heart rate and arterial blood pressure were measured at rest (control), during each level of exercise, and for 2 min following exercise (recovery). The rectified, filtered EMG activity of the exercising forearm was measured continuously during each level of exercise and was used as an index of the level of central command. Post-exercise hyperemia was calculated as the difference between the control and the average recovery (2 min) forearm blood flows (venous occlusion plethysmography) and was examined as a possible index of the stimulus for muscle chemoreflex activation. Heart rate, arterial pressure, forearm EMG activity, and post-exercise hyperemia all increased progressively with increasing exercise intensity. The magnitudes of the increases in heart rate and arterial pressure from control to exercise were directly related to both the level of EMG activity and the degree of post-exercise hyperemia across the five exercise intensities (Δheart rate vs EMG activity:r=0.99; Δarterial pressure vs EMG activity:r=0.99; Δheart rate vs hyperemia:r=0.99; and Δarterial pressure vs hyperemia:r=0.98; allp〈0.01). Furthermore, the level of EMG activity was directly related (r=0.99) to the corresponding degree of hyperemia. These results are consistent with the hypothesis that central command is a primary mechanism by which tachycardia is mediated during submaximal, rhythmic exercise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00636600
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  • 3
    Electronic Resource
    Electronic Resource
    The helix-coil transitions of poly (dA). Poly (dT) and poly (dA-dT). Poly (dA-dT) (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 745-759 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Helix-coil transition curves are calculated for poly (dA) poly(dT) and poly (dA-dT) poly (dA-dT) using the integral equation approach of Goel and Montroll.5 The transitions are described by the loop entropy model with the exponent of the loop entropy factor, k, remaining an arbitrary constant. The theoretical calculations are compared with experimental transition curves of the two polymers. Results indicate that the stacking energies for these two polymers differ by about 1 kcal/mole of base pairs. Also, a fit between theory and experiment was not possible for k 〉 1.70.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1972.360110403
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  • 4
    Electronic Resource
    Electronic Resource
    The A and B conformations of DNA and RNA subunits. Potential energy calculations for dGpdC (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 2625-2637 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to obtain a molecular picture of the A and B forms of a DNA subunit, potential energy calculations have been made for dGpdC with C(3′)-endo and C(2′)-endo [or C(3′)-exo] sugar puckerings. These are compared with results for GpC. The global minima for dGpdC and GpC are almost identical. They are like A-form duplex DNA and RNA, respectively, with bases anti, the ω′, ω angle pair near 300°, 280°, and sugar pucker C(3′)-endo. For dGpdC, a B-form helical conformer, with sugar pucker C(2′)-endo and ω′ = 257°, ω = 298°, is found only 0.4 kcal/mol above the global minimum. A second low-energy conformation (2.3 kcal/mol) has ω′ = 263°, ω = 158° and ψ near 180°. This has dihedral angles like the original Watson-Crick model of the double helix. In contrast, for GpC, the C(2′)-endo B form is 6.9 kcal/mol above the global minimum. These theoretical results are consistent with experimental studies on DNA and RNA fibers. DNA fibers exist in both A and B forms, while RNA fibers generally assume only the A form. A low-energy conformation unlike the A or B forms was found for both dGpdC and GpC when the sugars were C(3′)-endo. This conformation - ω′,ω near 20°,80° - was not observed for C(2′)-endo dGpdC. Energy surface maps in the ω′,ω plane showed that C(2′)-endo dGpdC has one low-energy valley. It is in the B-form helical region (ω′ ∼ 260°, ω ∼ 300). When the sugar pucker is C(3′)-endo, dGpdC has two low-energy regions: the A-form helical region and the region with the minimum at ω′ = 16°, ω = 85°.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360141217
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  • 5
    Electronic Resource
    Electronic Resource
    Evidence for long-range interactions in DNA. Analysis of melting curves of block polymers d(C15A15)·d(T15G15), d(C20A15)·d(T15G20), and d(C20A10)·d(T10G20) (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1461-1479 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of one DNA region on the stability of an adjoining region (telestability) was examined. Melting curves of three block DNA's, d(C15A15)·d(T15G15), d(C20A15)·d(T15G20), and d(C20A10)·d(T10G20) were analyzed in terms of the nearest neighbor Ising model. Comparisons of predicted and experimental curves were made in 0.01 M and 0.1 M sodium ion solutions. The nearest neighbor formalism was also employed to analyze block DNA transition in the presence of actinomycin, a G·C specific molecule. The results show that nearest neighbor base-pair interaction cannot predict the melting curves of the block DNA's. Adjustments in theoretical parameters to account for phosphate repulsion assuming a B conformation throughout the DNA's do not alter this conclusion. Changes in the theoretical parameters, which provide good overall agreement, are consistent with a substantial stabilization of the A·T region nearest the G·C block. The melting temperature T A·T for the average A·T pari in d(C20A10)·d(T10G20), with 10 A·T pairs, appears to be 4°C greater than TA·T for d(C15A15)·d(T15G15) and d(C20A15)·d(T15G20), both with 15 A·T pairs. Actinomycin bound to the G·C end effectively stabilizes the A·T end by 9°C. These results indicate a long-range contribution to the interactions governing DNA stability. A possible mechanism for these interactions will be discussed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360150803
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  • 6
    Electronic Resource
    Electronic Resource
    Influence of ribose 2′-O-methylation on GpC conformation by classical potential energy calculations (1976)
    New York : Wiley-Blackwell
    Biopolymers 15 (1976), S. 1951-1964 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Potential energy calculations were employed to examine the effect of ribose 2′-O-methylation on the conformation of GpC. Minimum energy conformations and allowed conformational regions were calculated for 2′MeGpC and Gp2′MeC. The two lowest energy conformations of 2′MeGpC and Gp2′MeC are similar to those of GpC itself. The helical RNA conformation (sugar pucker-C(3′)-endo, ω′ and ω,g-g-, bases-anti) is the global minimum, and a helix-reversing conformation with ω′, ω in the vicinity of 20°, 80° is next in energy. However, subtle differences between the three molecules are noted. When the substitution is on the 5′ ribose (Gp2′MeC), the energy of the helical conformation is less than that of GpC, due to favorable interactions of the added methyl group. When the substitution is at the 3′ ribose (2′MeGpC) these stabilizing interactions are outweighed by steric restrictions, and the helical conformation is of higher energy than for GpC. Furthermore, the statistical weight of the 2′MeGpC g- g- helical region is substantially less than the corresponding weight for Gp2′MeC. In addition, 2′MeGpC′s methoxy group is conformationally restricted to a narrow range centered at 76°. This group has a broadly allowed region between 50 and 175° in Gp2′MeC. These differences occur because the appended methyl group in 2′MeGpC is located in the interior of the helix cylinder, as it would be in polynucleotide, while it hangs unimpeded in Gp2′MeC. These findings suggest that 2′-O-methylation has both stabilizing and destabilizing influences on the helical conformation of RNA. For 2′MeGpC the destabilizing steric hindrance imposed by the nature of the guanine base dominates.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1976.360151007
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  • 7
    Electronic Resource
    Electronic Resource
    Classical potential energy calculations for ApA, CpC, GpG, and UpU. The influence of the bases on RNA subunit conformations (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1597-1613 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Classical potential energy calculations have been made for the ribodinucleoside monophosphates ApA, CpC, GpG, and UpU. Van der Waal's, electrostatic, and torsional contributions to the energy were calculated, and the energy was minimized with the seven backbone conformational angles as simultaneously variable parameters. At the global minimum, ApA and CpC have conformations like double helical RNA: the angles ω′ and ω are g-g-, the sugar pucker is C3′-endo, and the bases are anti. GpG and UpU, on the other hand, have the ω′,ω angle pair g-t at the global minimum, and for GpG the bases are syn. Energy contour maps for ω′ and ω show two broad, low energy regions for ApA, CpC, and UpU: one is g-g-, and the second encompasses g-t and g+g+ within a single lowenergy contour. The two regions are connected by a path at 10-13 kcal./mole. For GpG, with bases syn, however, only a small low-energy region at g-t is found. The helical ‘A’ RNA conformation is 8.5 kcal/mole higher for this molecule. Thus, the base composition is shown to influence the conformations adopted by dinucleoside phosphates. Comparison of calculations with experimetal data, where available, show good agreement.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140805
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  • 8
    Electronic Resource
    Electronic Resource
    Helix coil transitions of d (A)n·d(T)n, d(A-T)n·d(A-T)n, and d(A-A-T)n·d(A-T-T)n; evaluation of parameters governing DNA stability (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1115-1137 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermally induced helix-coil transitions of three A-T DNAs, d(A)n·d(T)n, d(A-T)n·d(A-T)n, and d(A-A-T)n·d(A-T-T)n, were studied. Experimental transition curves of the DNAs were analyzed using the loop entropy model of DNA melting. The calculation of the melting curve of d(A-A-T)n·d(A-T-T)n is presented using the integral equation formalism of Goel and Montroll. The aim of this work was to evaluate thermodynamic parameters which govern DNA stability and to test the theoretical model employed in the analysis. Our results show (1) an excellent over-all agreement between theory and experiment, (2) a loop entropy exponent k = 1.55 ± 0.05 provided the best fit to all the polymer transition curves, (3) the evaluated stacking free energies reflect the relative stability of the DNAs, and (4) the stacking energies of the ApA·TpT dimer evaluated from d(A)n·d(T)n and d(A-A-T)n·d(A-T-T)n differ. The last result is consistent with different conformations for the dimer in these two polymers.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160512
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  • 9
    Electronic Resource
    Electronic Resource
    Fluctuational base-pair opening in DNA at temperatures below the helix-coil transition region (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 1137-1139 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360230614
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  • 10
    Electronic Resource
    Electronic Resource
    Inverted repeat sequences can influence the melting transitions of linear DNAs (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1745-1758 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of inverted repeat sequences on the melting transitions of linear of DNAs has been examined. Derivative melting curves (DMC) of a 514 base pair (bp) DNA, seven subfragments of this DNA, and four other DNAs have been compared to predictions of DNA melting theory. The 514-bp DNA contains three inverted repeat sequences that can form cruciform structures in supercoiled DNA. We refer to these sequences as c-inverted repeats. Previous work showed that the DMC of this DNA, unlike a number of other DNAs, is not accurately predicted by DNA melting theory. Since the theoretical model does not include hairpin-like structures, it was suggested that hairpin or cruciform formation in these inverted repeats may be responsible for this discrepancy. Our results support this hypothesis. Predicted DMCs are in good agreement with DNAs with no inverted repeats, or inverted repeats not evident in supercoiled DNA. Differences between the theoretical and experimental Tm's are ≤ 0.3°C. DNA molecules that contain one or more of the three c-inverted repeats are not as accurately predicted. Experimental Tm values are lower than predicted values by 0.7-3.8°C. It is concluded that some inverted repeat sequences can form hairpin-like structures during the melting of linear DNAs. These structures appear to lower overall DNA stability.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281008
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