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Biomedical subjects

D Franklin

Publications and source records attributed to D Franklin.

At least 73 records · Page 4Linked to original sources
PubMed1981

Functional evaluation of coronary collateral development in conscious dogs.

Gradual coronary constriction was elicited in conscious dogs by means of an implanted ameroid coronary constrictor. The functional state of the coronary collateral circulation was serially evaluated by means of regional contractile responses, using brief occlusions of the left circumflex coronary artery and strenuous running in the field. Although resting regional myocardial function was unchanged throughout the study, regional myocardial shortening during coronary occlusion decreased to 9% of control at 3-4 days after the operation; it then recovered progressively to 24% at 7-9 days, 45% at 15-18 days, and 94% at 20-24 days. Concomitantly, reactive hyperemia measured with a flowmeter declined from 300% at 3-4 days to 228, 88, and 0% at 7-9, 15-18, and 20-24 days, respectively. A bout of running held 21 days after the ameroid implant when resting regional function was well maintained induced severe regional and global dysfunction. These findings indicate the usefulness of regional myocardial contractile responses in assessing coronary collateral reserve.

Animals↗
PubMed1980

Responses of coronary collateral flow and dependent myocardial mechanical function to the calcium antagonist, diltiazem.

We sought to determine whether the calcium antagonist, diltiazem, increased regional myocardial collateral blood flow in a dog model in which the physiologic conditions thought to be associated with angina pectoris had been induced, and to determine if such changes would be reflected in alterations in function of the collateral-dependent myocardium. Regional myocardial function and blood flow were measured with instruments in dogs for weeks as the left circumflex artery was progressively stenosed to occlusion by an implanted ameroid constrictor. The extent of collateral development was determined in terms of the reduction in regional function induced by brief, total test occlusions. When collaterals had developed adequate for the metabolic requirements at rest, pacing tachycardia stress test produced ischemia-related hypofunction. Under these conditions, diltiazem, 20 mirogram/min/kg, increased blood flow via collateral channels from approximately 140 to 190 ml/min/100 g tissue (epicardium) and from 80 to 140 ml/min/100 g tissue (endocardium) in the colateral-dependent area without significant modification in hypofunction. Similar results were obtained in dogs with greater collateral flow reserve later in the collateral development process when the ameroid constrictor had completely occluded the vessel and stress testing did not produce hypofunction. Thus, diltiazem increased collateral flow to collateral-dependent myocardium under conditions simulating unstable angina pectoris.

Angina Pectoris↗
PubMed1978

Measurement of specific laryngeal muscle function by ultrasound.

Ultrasonic dimension gauges were implanted in the crico-arytenoideus dorsalis muscle in a mature horse. Resting and contracted muscle length and average contraction rate were measured serially in the conscious state over a period of 25 days. Results suggest that specific laryngeal muscle function in the horse may be defined with this approach. Since man and horse are both known to suffer from laryngeal hemiplegia, this experimental preparation may help provide information of benefit to both species.

Animals↗
PubMed1978

Rapid Production of Auxin-induced Ethylene.

The time course of auxin-induced ethylene production was determined in mesocotyl segments of etiolated sorghum (Sorghum bicolor L. Moench) seedlings. The latent period between addition of auxin and a detectable rise in ethylene release was 15 to 20 minutes in four different genotypes. This may indicate that the initial effect of auxin on ethylene production is too rapid to involve synthesis of an ethylene-producing enzyme. The technique devised for these experiments involves placing tissue segments end to end in a glass tube, and it allows simultaneous determination of growth and ethylene production.

Journal Article↗
PubMed1978

Myocardial infarction in the baboon: regional function and the collateral circulation.

Occlusion of the anterior descending coronary artery was produced in sedated baboons 7-15 days after implantation of a micromanometer and ultrasonic crystals for measurement of regional left ventricular dimensions in ischemic, marginal, and control segments. One minute after coronary occlusion (CO), ischemic segments exhibited a marked systolic bulge with wall thinning, and percent systolic shortening of marginal segments decreased. Over the ensuing weeks, there was a progressive increase of end-diastolic lengths in marginal and ischemic segments, whereas systolic shortening in these segments did not improve significantly. Control segments did not change. In control baboons, the coronary collateral index was 55 +/-25 (SE) compared to 560 +/- 74 in normal dogs. One month after CO, the collateral index was 543 +/- 144 in baboons compared to 6,685 +/- 716 in dogs, regions of normal tissue were seen in the infarct (14.2 +/- 2% of left ventricular mass). Minimal coronary collateral development in the baboon provides a likely explanation for differences from the dog in regional functional responses and in the character of the infarct.

Animals↗
PubMed1978

Measurement of multiple simultaneous small dimensions and study of arterial pressure-dimension relations in conscious animals.

This paper describes the development of several important modifications that were incorporated into the ultrasonic, transit-time dimension system in order to obtain multiple simultaneous, instantaneous, and continuous measurements of the external dimensions of the aorta and its major branches in conscious, unrestrained animals. At operation a pair of small piezoelectric crystals was sutured to arterial adventitia, and a miniature pressure gauge was implanted in the vessel at the same cross-sectional plane. After recovery from surgery, wall motion was not altered appreciably and scarring was minimal. This technique allows long-term monitoring of aortic pressure-dimension relations and is applicable for small (fetal and neonatal) as well as large (adult dogs and sheep) animals. When vessel wall thickness is measured, stress-radius analysis can be performed so as to compute vascular elastic stiffness as a function of stress. Moreover, the suitability for radiotelemetry of the pressure and dimension signals measured with this technique enables the study of these parameters in unrestrained animals, e.g., during spontaneous severe exercise.

Angiotensins↗
PubMed1978

Alteration of the left ventricular diastolic pressure-segment length relation produced by the pericardium. Effects of cardiac distension and afterload reduction in conscious dogs.

Left ventricular pressure and segment length were measured in seven conscious chronically instrumented dogs with the pericardium intact and 3-9 days after pericardiectomy. Diastolic pressure-length plots were obtained under control conditions and after acute volume loading followed by sodium nitroprusside infusion. In all dogs with intact pericardium, volume loading displaced the entire diastolic pressure-length curve upwards and sodium nitroprusside shifted it toward control. After pericardiectomy the pressure-segment length data during control, volume loading and sodium nitroprusside fell on a single curve (intercepts and slopes not statistically different); After dextran infusion, intrapericardial pressure rose from control 1.5 +/- 0.7 mm Hg to 8.2 +/- 0.5 mm Hg, and it fell to 4.8 +/- 0.1 mm Hg after nitroprusside. Therefore, in acute cardiac dilatation the pericardium contributed significantly to the increased left ventricular diastolic pressure and to the fall during sodium nitroprusside infusion and appeared responsible for shifts in the diastolic pressure-segment length relation.

Animals↗
PubMed1978

[Nitroglycerin in experimental myocardial infarction in the baboon. The effect of reducing the pre-charge and post-charge on regional myocardial function].

A left anterior descending coronary artery occlusion was produced in the sedated state in baboons previously instrumented with a left ventricular micromanometer and ultrasonic crystals measuring segmental myocardial lengths of control, marginal and ischemic regions. 3-8 days after the onset of the ischemia, nitroglycerin (0.4 mg IV) was injected. Following the injection (NG), heart rate increased significantly compared to the control ischemic state (CIS); end diastolic pressure and systolic pressure decreased significantly. In control segments, VCF increased from 0.99 +/- 0.11 circ/s to 1.26 +- 0.11 circ/s (p less than 0.01); in marginal segments VCF increased (CIS: 0.32 +/- 0.07 circ/s; NG: 0.42 +/- 0.09/s; p less than 0.01); in ischemic segments, the bulge observed before the injection persisted after nitroglycerin. Increased performances of control and marginal regions were attributed mainly to afterload reduction although preload reduction tended to decrease this response. The contribution of improved marginal function was small indicating that improvement of active hemodynamic function was largely due to changes in control segments function.

Animals↗
PubMed1977

Hyperfunction with normal inotropic state of the hypertrophied left ventricle.

Conscious dogs were instrumented with an inflatable cuff around the ascending aorta, a high-fidelity micromanometer in the left ventricle (LV), and pairs of ultrasonic crystals for measurements of LV wall thickness and internal LV diameter. Wall stress (WSt) and mean velocity of wall shortening (VCF) were calculated. Mean force-velocity relations and WSt-diameter loops in single contractions were then analyzed over a range of matched systolic pressures during acute aortic constrictions both before and after induction of chronic hypertrophy by sustained aortic constriction. At normal LV systolic pressures and at each matched level of systolic LV pressure, wall shortening velocity was increased in the hypertrophied ventricle. However, force-velocity relations obtained by relating mean VCF to mean WSt at various stress levels fell on the same relation as during control. The linear relation between LV diameter and pressure at the end of ventricular ejection was shifted to the left in the hypertrophied ventricle, indicating enhanced shortening. However, linear WSt-diameter relations at end-ejection were not different in control and hypertrophied hearts. These findings indicate that the ventricle hypertrophied by pressure overload exhibited hyperfunction as a pump but that its myocardium had a normal level of inotropic state.

Animals↗