Biomedical subjects

D R Gross

Publications and source records attributed to D R Gross.

At least 73 records · Page 4Linked to original sources

PubMed1980

Physical characteristics of pulmonary artery stenosis murmurs in calves.

To better understnad the characteristics of cardiovascular murmurs and turbulent energy transmission, we made simultaneous measurements of pressure (sound) and velocity fluctuations in the vicinity of surgically produced stenoses in the pulmonary artery of calves. We did a spectral analysis of these data and found an identifiable break frequency at which the slopes of the pressure fluctuations changed. By use of these break frequencies and the corresponding blood jet velocity and vessel diameter measurements, Strouhal numbers were calculated. The jet velocity, Reynolds number, Strouhal number, and unsteadiness parameter values changed when the vessel was stenosed. When the power spectrum curves for the velocity fluctuations and the sound were compared, they tended to show a correlation between break frequencies. We speculate that this apparent correlation indicated a transfer from turbulent to acoustic energy.

Aging↗

PubMed1980

Pharmacokinetics, bioavailability, and dosage regimens of digoxin in dogs.

Digoxin, 30 micrograms/kg, was given by IV injection and orally, in the forms of pediatric elixir and tablet, on three separate occasions to six healthy dogs. Multiple serum samples were collected at timed intervals and assayed by radioimmunoassay. Data were analyzed, using nonlinear least squares regression analysis. The mean serum digoxin-time relationship was triexponential. Rapid and slow distributive phases with half lives of 9 minutes and 4.7 hours were followed by a biological disposition phase with a half life of 30.1 hours. Mean volume of distribution by extrapolation was 15.6 L/kg. When calculated by the area method, mean volume of distribution was 12.4 L/kg. Digoxin elixir was rapidly absorbed, with a mean bioavailability estimate of 71.4 +/- 8.2% SD. Digoxin tablets were less rapidly and less completely absorbed, with a mean bioavailability estimate of 58.0 +/- 11.6%. Data collected in this series of experiments and data from the literature were applied to standard pharmacokinetic equations to formulate loading and maintenance doses of digoxin for the IV injection, the elixir, and the tablet. Mean loading doses were, in micrograms/kg/24 hours: 27, 38, and 45 for the IV injection, elixir, and tablet, respectively. Corresponding mean maintenance doses were 13, 18, and 23.

Administration, Oral↗

PubMed1980

Application of individualized digoxin dosage regimens to canine therapeutic digitalization.

Congestive right heart failure was established in three dogs subjected to surgical tricuspid valvectomy and pulmonic stenosis. The eliminative dispositions of digoxin in serum and ascitic fluid were determined after administration of 30 micrograms of digoxin/kg of body weight by IV injection and radioimmunoassay of multiple serum and ascitic fluid samples. Individualized digoxin dosage regimens for the three dogs were calculated from data collected in the present experiment and data from the literature. The regimens were tested on the three dogs after their body weight had been corrected for the volume of ascitic fluid present. An IV maintenance therapy resulted in serum digoxin concentrations slightly lower than anticipated. The administration of digoxin tablets with no food restriction resulted in serum digoxin concentrations mostly in the expected range. The same doses of digoxin in tablet form were given to the three dogs after fasting. Fasting resulted in slight, but significant, increases in serum digoxin concentrations. Serum digoxin concentrations after administration of digoxin elixir were close to anticipated values. These experiments indicate that individualized digoxin dosage regimens may be useful to set serum digoxin concentrations within the therapeutic, nontoxic range.

Administration, Oral↗

PubMed1980

Digoxin pharmacokinetics, bioavailability, efficacy, and dosage regimens in the horse.

The pharmacokinetics of IV administered digoxin and the bioavailability of intragastrically administered powdered digoxin tables suspended in water were investigated in 6 clinically normal adult horses by 125I radioimmunoassay. The effect of 3 to 5 sequential IV doses of 5 micrograms of digoxin/kg of body weight at 2-hour intervals on a left ventricular index of contractility (Vmax) was assessed in 5 clinically normal horses. Standard pharmacokinetic equations and mean pharmacokinetic variables were used to derive parenteral and oral (loading and maintenance) doses for digoxin in horses. The calculated dosage regimens were administered and resulting plasma digoxin concentrations were monitored in 5 horses and 1 pony. Digoxin disposition after IV injection was triexponential. A rapid distributive phase with a half life (t 1/2 of 15 minutes was followed by a slow distributive phase with a t 1/2 of 4.1 hours. The biological disposition t 1/2 was 23.1 hours. The volume of distribution by extrapolation was 6.79 L/kg of body weight and 4.89 L/kg by the area method. The average bioavailability estimate for intragastrically administered digoxin was 19.2%. The Vmax increased significantly (P < 0.01) after IV digoxin administration. Greatest changes in Vmax were recorded after the first 2 injections (5 micrograms of digoxin/kg) corresponding to plasma digoxin concentrations of 0.83 and 1.68 ng/ml. Doses of digoxin were calculated as follows: IV loading 14, IV maintenance 7, oral loading 70, and oral maintenance 35 micrograms/kg/24 hours. When these doses were given to a group of horses, plasma digoxin concentrations measured 12 and 24 hours after administrated were mostly in the proposed therapeutic, nontoxic range of 0.5 to 2.0 ng/ml.

Administration, Oral↗

PubMed1979

Cardiovascular effects of intravenous administration of propylene glycol and of oxytetracycline in propylene glycol in calves.

Comparisons were made of the acute cardiovascular effects of oxytetracycline, oxytetracycline in propylene glycol, and propylene glycol alone given to conscious dairy calves. The calves were chronically instrumented with intravascular catheters and electromagnetic flowmeter transducers in and on the pulmonary and renal arteries. Injection (IV) of aqueous preparations of oxytetracycline produced no statistically significant (P greater than 0.05) cardiocirculatory changes in these calves. Oxytetracycline in propylene glycol and propylene glycol alone both produced transient (1 to 4 minute) periods of cardiovascular depression characterized by cardiac asystole, systemic hypotension, and decreased pulmonary and renal arterial blood flow. The two preparations, in equivalent doses and volumes, produced statistically similar hemodynamic changes in the calves. The data from this study support the conclusion that the monitored cardiovascular effects of the commercially available oxytetracycline in propylene glycol in the intact, awake calves were due to the solvent propylene glycol. This conclusion is consistent with reports of other injectable products containing the same solvent.

Animals↗

PubMed1978

Tricuspid atresia in a foal.

An Arabian crossbred foal was examined because of a suspected congenital cardiac anomaly. There was a grade V/V crescendo-decresendo holosystolic murmur and thrill in the left 4th intercostal space. The foal was slightly cyanotic and polycythemic. Electrocardiography suggested left ventricular hypertrophy. Angiography and cardiac and vascular pressure recordings led to a diagnosis of pulmonic stenosis. The foal died after cardiac bypass and corrective surgery. Postmortem examination revealed an enlarged right atrium, atresia of the tricuspid orifice, a large, fenestrated patent foramen ovale, eccentric left ventricular hypertrophy, and a large interventricular septal defect. The right ventricle had a small lumen and a relatively thick wall. There was valvular and supravalvular pulmonic stenosis, with poststenotic dilatation of the pulmonary artery. A single coronary artery originated from the anterior sinus of the aorta.

Animals↗

PubMed1976

Hot film coronary artery velocity measurements in horses.

Coronary velocity measurements have been carried out in anaesthetized, open-chest horses using a constant-temperature, hot-film anemometer system. L-shaped needle probes inserted by direct vessel puncture have been used to measure velocity profiles in the left common, left anterior descending (LAD), and left circumflex coronary arteries. The flow conditions were characterized by peak Reynolds numbers from approximately 200 to 1500 and values of the unsteadiness parameter from 3 to 10. These measurements indicate that in the left common coronary artery the profile is in general skewed towards the outer wall as would be expected for fully viscous flow in a curved tube. In the left anterior descending and left circumflex coronary arteries just distal to the bifurcation, the skewing was found in general to be away from the flow divider. However, in regions of the LAD and left circumflex 5-6 diameters downstream of the bifurcation, the peak systolic and diastolic profiles were indicative of a more fully developed, Poiseuille type flow with only slight skewing observed. The results of this study indicate that the flow in the coronary system, though in general laminar and disturbance free, is extremely varied in character and may exhibit large amplitude, low frequency flow oscillations. Furthermore, for these vessels which all lie on the surface of the myocardium, large systolic flows were observed to be present, even though the major portion of the volume flow was reserved for the diastolic period.

Animals↗

PubMed1976

Effects of angiotensin and prostaglandin A2 in perfused isolated kidneys of dogs.

Simultaneous recordings of pressure and flow were made from the renal artery in perfused isolate canine kidneys. The system was perturbated by the administration of angiotensin and prostaglandin A2. The data were recorded on frequency-modulated analog tape and converted to digital form, and a Fast Fourier Transform program was used to calculate input impedance. Changes in total renal volume and renal arterial pressure data were used to determine compliance values. in compliance were found, along with changes in both magnitude of impedance and phase angle, as a result of the perturbations introduced. Seemingly, renal vascular compliance has an important role in the autoregulatory mechanisms of the kidney.

Angiotensin II↗

PubMed1975