PubMed Health⌕ Search

Biomedical subjects

A R Twardock

Publications and source records attributed to A R Twardock.

At least 37 records · Page 2Linked to original sources
PubMed1989

Comparison of left ventricular ejection fractions determined in healthy anesthetized dogs by echocardiography and gated equilibrium radionuclide ventriculography.

Left ventricular ejection fractions (LVEF) of 8 pentobarbital-anesthetized dogs were calculated by gated equilibrium radionuclide ventriculography (RVG) and by M-mode and two-dimensional echocardiography (2-DE) prior to and during constant IV infusion of isoproterenol. Mean LVEF (+/- SD), determined with RVG by use of an automatic edge detection algorithm (RVG-auto) to define the left ventricular region of interest, increased from a resting value of 53.5% (+/- 4.9%) to 71.9% (+/- 6.8%) during isoproterenol infusion. Mean LVEF, determined with RVG by use of visual inspection (RVG-manual) to define the left ventricular region of interest increased from a resting value of 51.6% +/- 3.8% to 67.0% +/- 5.6% during isoproterenol infusion. Using 2-DE and the bullet formula to calculate left ventricular volume (LVV = 5/6 x cross-sectional area x length), mean LVEF increased from 52.3% (+/- 3.50) to 74.7% (+/- 5.0%). Using 2-DE area measurements and Teicholz formula, mean LVEF increased from 48.9% (+/- 5.1%) to 69.5% (+/- 6.0%). Using M-mode echocardiographic left ventricular diameter measurements and Teicholz formula, mean LVEF increased from 52.3 (+/- 9.0%) to 78.3% (+/- 8.1%). Before and during isoproterenol infusion, the mean LVEF values calculated by RVG agreed closely with mean LVEF values calculated from M-mode and 2-DE. Correlation coefficients determined from linear regression analysis of LVEF by echocardiography vs LVEF by radionuclide ventriculography ranged from 0.79 to 0.88. Correlation coefficients were higher and SEM were lower when LVEF was determined by RVG-manual, rather than by RVG-auto methods and when LVEF was calculated from 2-DE measurements, rather than from M-mode measurements.

Animals↗
PubMed1989

Nuclear scintigraphic assessment of liver size in clinically normal dogs.

Measurement of liver size was made on nuclear scintigraphic images obtained from 16 clinically normal, anesthetized dogs in ventral, dorsal, right and left lateral, and left dorsal oblique positions after administration of technetium 99m-sulfur colloid. Linear measurements of liver length and width were made from each scintiscan, and liver surface area was determined by setting a region of interest manually and by use of a computer count of pixels above a minimal intensity (threshold method). All linear measurements had a statistically significant (P less than 0.05) correlation with liver and body weight, with the exception of the measurements of liver width made on dogs in dorsal and left lateral dorsal oblique positions. The highest correlation (r = 0.89) between the scintigraphic measurements and liver weight was the multiplication of measurements of liver width and length from the right lateral view. Although all area determinations were significantly (P less than 0.05) correlated with liver and body weight, for most views, the manual method of determining the region of interest had a slightly better correlation with the liver weight than did the threshold method.

Animals↗
PubMed1988

Use of 99mTc diethylenetriaminepentaacetic acid for assessment of renal function in dogs with suspected renal disease.

The effectiveness of technetium 99m-labeled diethylenetriaminepentaacetic acid (99mTc DTPA) to assess renal function in 13 dogs with suspected renal disease was evaluated. Glomerular filtration rates (actual GFR) were determined on the basis of endogenous creatinine clearance. Predicted GFR were determined by using 99mTc DTPA within 72 hours after the determination of creatinine clearance. The percentage of an IV administered dose of 99mTc DTPA in the kidneys (percentage dose) was determined. Two equations were used to calculate predicted GFR, which were derived from previously reported linear regression analysis of inulin (In) and creatinine (Cr) GFR vs percentage dose 99mTc DTPA in dog kidneys. The correlations of actual GFR vs predicted GFR (In) and actual GFR vs predicted GFR (Cr) were both r = 0.92. The dogs' mean actual GFR was 1.73 +/- 1.35 ml/min/kg. Their mean predicted GFR (In) and predicted GFR (Cr) were 1.92 +/- 1.42 ml/min/kg and 1.85 +/- 1.27 ml/min/kg, respectively. Therefore, 99mTc DTPA can be used with high accuracy as an agent to predict GFR in dogs with suspected renal disease. The procedure for determining GFR by use of nuclear medicine was rapid and noninvasive and appeared to induce little stress in the animals evaluated.

Animals↗
PubMed1988

Clinical, radiographic, and scintigraphic findings associated with enthesitis of the lateral collateral ligaments of the tarsocrural joint in standardbred racehorses.

Injury of the lateral collateral ligaments of the tarsocrural joints was diagnosed in nine Standardbred pacers. The average age was 4.9 years. The severity of the lameness varied from severe to subtle and joint effusion was seen in eight of 10 tarsocrural joints. A positive hindlimb flexion test was seen in four of six cases in which results were recorded. The identification of the site of involvement was based on a focal intense 'hot spot' seen on scintigraphy, and new bone formation seen radiographically at the anatomical sites of insertion of the long lateral collateral ligament of the tarsocrural joint in nine limbs and the short lateral collateral ligament of one limb. The authors believe this injury to be enthesitis caused by the cyclic trauma of training and racing speed. The primary therapy was rest. Of six cases which returned to training, three raced as well or better than before injury.

Animals↗
PubMed1988

Evaluation of a short-term saline diuresis protocol for the administration of cisplatin.

A study was undertaken to determine the toxic effects of cisplatin, an antineoplastic agent, on canine kidneys and bone marrow when administered during a 6-hour saline diuresis. Cisplatin (70 mg/m2 of body surface) was administered IV to 6 healthy dogs over a 20-minute period after 0.9% NaCl solution (saline) was administered IV for 4 hours at a rate of 18.3 ml/kg/hr. After cisplatin injection, saline diuresis was continued at the same rate for 2 hours. Each dog vomited within 8 hours after the drug was administered. Clinical status, weight gain, and food consumption were normal throughout the 27-day study. All measures of renal function remained unchanged and were within normal limits for 27 days after the drug was administered. Nadirs in the daily neutrophil count were observed on days 6 (3,240 +/- 404/microliters) and 15 (1,196 +/- 275/microliters). There were no important gross or histologic abnormalities referable to cisplatin administration when the dogs were necropsied at the conclusion of the study (day 27). We concluded that cisplatin can be administered safely at a dosage of 70 mg/m2 of body surface, using a short-term diuresis protocol, and that the drug induces a nadir in the neutrophil count on days 6 and 15.

Animals↗
PubMed1986

Nuclear angiography in a dog with congestive cardiomyopathy.

Nuclear angiography was used as a diagnostic aid and in monitoring the clinical course of a case of congestive cardiomyopathy in a dog. Serial examinations revealed progressively deteriorating values for left ventricular ejection fraction before the dog's death. This noninvasive technique can be an alternative to echocardiography for the evaluation of cardiac performance.

Animals↗
PubMed1986

Evaluation of 99mTc-diethylenetriaminepentaacetic acid nuclear imaging for quantitative determination of the glomerular filtration rate of dogs.

The suitability of 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA) as an agent to assess glomerular filtration rate (GFR) in dogs was evaluated. Glomerular filtration rates of 12 healthy dogs were determined on the basis of creatinine and/or inulin clearance. Glomerular filtration rates also were determined in 7 dogs after induction of acute renal failure by administration of amphotericin B. The healthy dogs and the amphotericin B-treated dogs were given 99mTc-DTPA (1 to 2 mCi) IV. The percentage of the 99mTc-DTPA dose in the kidneys (percentage dose) was determined, with background activity subtracted from total activity at 15-s intervals 0 to 6 minutes after 99mTc-DTPA infusion. Linear regression analyses (LRA) were performed to determine whether the percentage dose at various time intervals after injection correlated with GFR calculated on the basis of creatinine and inulin clearance data. One to 3 minutes after 99mTc-DTPA administration appeared to be the best period for analysis of the data. The percentage dose of 99mTc-DTPA (corrected for kidney depth differences) was determined and LRA against GFR were performed. The percentage dose correlated better with inulin clearance (r = 0.94) than with endogenous creatinine clearance (r = 0.83). Only inulin clearance correlations improved with kidney depth correction. The LRA was used to derive an equation that could be used to calculate GFR on the basis of the percentage dose. The equation derived from inulin regression was: GFR (milliliter/minute/kilogram of body weight) = 0.194 (depth-corrected percentage dose)--0.37; the equation derived from the creatinine regression was: GFR (milliliter/minute/kilogram) = 0.171 (depth-corrected percentage dose)-0.15.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Kidney Injury↗
PubMed1985

Direct current stimulation of bone production in the horse: preliminary study with a "gap healing" model.

The effect of a 20-microA direct-current implantable bone growth stimulator (BGS) on bone production with a "gap healing" model in the horse was evaluated. The right and left 4th metatarsal bones (Mt-4) were used in 7 adult horses to create the "gap healing" model. A 4-mm section of the Mt-4 bone was resected bilaterally in each horse. The BGS was surgically placed into the 7 left Mt-4 defects. The 7 right Mt-4 defects served as controls. Six horses survived the 16-week experimental period. Signs of pain, decreased range of limb motion, or lameness was not observed in any animal during the 16 weeks. None of the animals showed complete healing radiographically. Four stimulated sites showed less periosteal reaction and 2 showed greater reaction than the 6 controls. The greatest amount of periosteal reaction or bone resorption was seen around the screws and plates in both groups. Uptakes of 99mTc-MDP in counts/pixel for control sites and stimulated sites were 7.90 and 8.25 in the "gap defect" and 5.19 and 5.06 in the areas adjacent to the gap defect. The ratio of uptake between the gap defect and adjacent area was 1.5 and 1.58 respectively. Biocompatability of the BGS was excellent; however, 1 horse had a broken cathode wire 5 cm from the generator capsule at 6 weeks. All polyethylene cathode sheaths were fluid filled at 16 weeks. The average mineralization rates were 1.57 +/- 0.34, 1.71 +/- 0.28 mm/day and bone formation activity was 0.0182 +/- 0.171, and 0.0168 +/- 0.0149 mm2/day for control limbs and stimulated limbs, respectively. There was no significant difference between groups in any of the histomorphometric values measured. Direct current (20 microA) did not increase bone production in this experiment. Methods to objectively evaluate electrically induced osteogenesis and a "gap defect" model for BGS research on the horse are discussed. The results provide a basis for additional research on electrical stimulation of fractures in the horse and for dose-response studies.

Animals↗
PubMed1978

The effect of litter size on placental blood flow and placental calcium transfer in the multifoetate guinea-pig.

1. Placental blood flow rate and calcium transfer rate were measured at 61 d of pregnancy in guinea-pigs carrying between one and eight foetuses. 2. Placental blood flow rate was significantly correlated with foetal weight. Ca transfer rate was related to placental size. Irrespective of litter size the mean amount of Ca transferred across a placenta was between 0.22 and 0.34 mg/h per g placental tissue. 3. It was concluded that there was a limit to the rate of transfer which was produced by a combination of limitations in placental blood flow rate, maternal plasma Ca concentration and placental tissue transfer capacity.

Animals↗
PubMed1978

Blood metabolic profiles: their use and relation to nutritional status of dairy cows.

Profiles of blood metabolites have been used widely to identify problem herds and to indicate dietary causes of disease or low production. Related herd survey studies and designed experiments are reviewed. An initial study of profiles and estimated nutrient intake of five "normal" and four "problem" herds was conducted between 1972 and 1974 to establish baseline values for blood metabolites. Profiles of blood metabolites for additional problem herds were obtained during 1974 through 1977. Variation due to herd of origin, production, stage of lactation, and season of year are important causes of variation in concentrations of metabolites in jugular blood of dairy cows. They need to be considered carefully in interpreting profiles of blood metabolites. Several relationships between dietary intake of nutrients and concentrations of associated components in jugular blood are significant. Concentrations of metabolites are of almost no practical use for individual cows because of extreme variations in diet required to generate abnormal concentrations of blood metabolites. Averages of glucose of blood and nitrogen in urea on seven to ten cows, adjusted for the factors mentioned above, have limited practical value in detecting inadequate energy and protein intake, respectively.

Animal Nutritional Physiological Phenomena↗