Biomedical subjects

Raymond C Boston

Publications and source records attributed to Raymond C Boston.

At least 19 recordsLinked to original sources

PubMed2007

High frame-rate simultaneous bilateral breast DCE-MRI.

A simultaneous bilateral back-projection method for 3D dynamic contrast-enhanced (DCE)-MRI of the breasts was developed and evaluated. Using a double-side band modulation of the RF slab excitation pulse, discontinuous volumes that included both breasts were simultaneously selected. The number of slice phase-encoding steps was undersampled by a factor of 2, and the resulting signal aliasing from one volume to the other was removed using SENSE processing. In-plane encoding was performed with an interleaved radial acquisition reconstructed using dynamic k-space-weighted image contrast (KWIC) temporal filtering. Image resolution was 0.5 x 0.5 x 3.0 mm(3) with an effective temporal resolution of 15 s for both breast volumes. Combined with the 2x acceleration from SENSE encoding, this is a 16x acceleration factor over a conventional MR bilateral breast scan. An initial evaluation of these methods was performed on a cohort of women who presented with palpable or mammographically visible breast abnormalities. A total of 73 abnormalities were found in 45 of the 54 bilateral examinations that were performed. In 11 of these cases there was a significant finding in the contralateral breast. DCE images of both breasts can be acquired simultaneously, resulting in high-resolution images as well as rapid sampling of the contrast kinetics.

Breast↗

PubMed2006

Effects of electrostimulated acupuncture on ground reaction forces and pain scores in dogs with chronic elbow joint arthritis.

OBJECTIVE: To determine whether use of electrostimuluated acupuncture (ESA) would result in significant improvements in ground reaction forces and lameness scores in dogs with chronic elbow joint osteoarthritis secondary to elbow joint dysplasia. DESIGN: Randomized, controlled, crossover clinical trial. ANIMALS: 9 dogs with chronic forelimb lameness and radiographic evidence of elbow joint osteoarthritis. PROCEDURES: All dogs had a 3-week control acclimation period during which gait analysis was performed weekly. Dogs then received ESA once weekly for 3 weeks followed by a sham treatment once weekly for 3 weeks or received the sham treatment followed by ESA. Gait analysis was repeated prior to each treatment, and owners were asked to provide pain scores by use of a visual analog scale method. RESULTS: Treatment (control, acupuncture, or sham) did not have a significant effect on ground reaction forces for any limb. Owners of 8 of the 9 dogs were able to correctly guess the time period when ESA was delivered. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that ESA did not have any significant effects on severity of lameness, as determined by measurement of ground reaction forces, or severity of pain, as determined by visual analog scale pain scores, in dogs with chronic elbow joint osteoarthritis secondary to elbow joint dysplasia.

Acupuncture Therapy↗

PubMed2005

Dynamic imaging of allogeneic mesenchymal stem cells trafficking to myocardial infarction.

BACKGROUND: Recent results from animal studies suggest that stem cells may be able to home to sites of myocardial injury to assist in tissue regeneration. However, the histological interpretation of postmortem tissue, on which many of these studies are based, has recently been widely debated. METHODS AND RESULTS: With the use of the high sensitivity of a combined single-photon emission CT (SPECT)/CT scanner, the in vivo trafficking of allogeneic mesenchymal stem cells (MSCs) colabeled with a radiotracer and MR contrast agent to acute myocardial infarction was dynamically determined. Redistribution of the labeled MSCs after intravenous injection from initial localization in the lungs to nontarget organs such as the liver, kidney, and spleen was observed within 24 to 48 hours after injection. Focal and diffuse uptake of MSCs in the infarcted myocardium was already visible in SPECT/CT images in the first 24 hours after injection and persisted until 7 days after injection and was validated by tissue counts of radioactivity. In contrast, MRI was unable to demonstrate targeted cardiac localization of MSCs in part because of the lower sensitivity of MRI. CONCLUSIONS: Noninvasive radionuclide imaging is well suited to dynamically track the biodistribution and trafficking of mesenchymal stem cells to both target and nontarget organs.

Animals↗

PubMed2005

Fasting triglyceride and the triglyceride-HDL cholesterol ratio are not markers of insulin resistance in African Americans.

BACKGROUND: The "lipid criteria" consist of a triglyceride (TG) level of 130 mg/dL (1.47 mmol/L) or greater and a ratio of TG to high-density lipoprotein cholesterol (HDL-C) of 3 or greater. In Caucasians, the lipid criteria predict insulin resistance in individuals with a body mass index (BMI) of 25 kg/m(2) or greater. Our goal was to determine whether TG levels or TG-HDL-C ratio predicted insulin resistance in African Americans with a BMI of 25 kg/m(2) or more. METHODS: Of 125 African Americans, the 98 with a BMI of 25 kg/m(2) or more participated. All subjects had frequently sampled intravenous glucose tolerance tests with insulin resistance determined by the insulin sensitivity index. Subjects were divided into the following tertiles by insulin sensitivity: 12.8 to 4.3, 4.2 to 2.3, and 2.2 to 0.2 mU/L per minute. Insulin resistance was defined as being in the third tertile. Across tertiles, the distribution of variables was compared by 1-way analysis of variance. Areas under the receiver operating characteristic curve were determined to identify variables that predicted insulin resistance. RESULTS: Fasting insulin level, BMI, and waist circumference increased across tertiles (all P<.01), but TG levels and TG-HDL-C ratio did not (all P>/=.3). The mean +/- SE areas under the curves for fasting insulin, BMI, and waist circumference were 0.85 +/- 0.04, 0.72 +/- 0.05, and 0.71 +/- 0.05, respectively. For TG level and TG-HDL-C ratio, the areas under the curves were 0.55 +/- 0.06 and 0.56 +/- 0.06, respectively, meaning that the true-positive rate was nearly equal to the false-positive rate. Therefore, they could not be used as markers of insulin resistance. Furthermore, 17 subjects met the lipid criteria but only 7 were in the insulin-resistant tertile, making the sensitivity of these criteria to identify insulin resistance only 17%. CONCLUSION: In African Americans, TG levels and TG-HDL-C ratio are not reliable markers of insulin resistance.

Adult↗

PubMed2005

Surgical and nonsurgical management of sagittal slab fractures of the third carpal bone in racehorses: 32 cases (1991-2001).

OBJECTIVE: To compare results (ie, return to racing and earnings per race start) of surgical versus nonsurgical management of sagittal slab fractures of the third carpal bone in racehorses. DESIGN: Retrospective study. ANIMALS: 32 racehorses (19 Thoroughbreds, 11 Standardbreds, and 2 Arabians). PROCEDURE: Medical records and radiographs were reviewed to obtain information regarding signalment and treatment. Follow-up information was obtained from race records. Robust regression analysis was performed to evaluate earnings per start in horses that raced at least once before and after injury. RESULTS: 22 (69%) horses raced at least once after treatment of the fracture. All 7 horses treated by means of interfragmentary compression raced after treatment, and horses that underwent interfragmentary compression had significantly higher earnings per start after the injury than did horses treated without surgery. Eight of 9 horses treated by means of arthroscopic debridement of the damaged cartilage and bone raced after treatment, but only 7 of 16 horses treated without surgery (ie, stall rest) were able to return to racing after treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that racehorses with sagittal slab fractures of the third carpal bone have a favorable prognosis for return to racing after treatment. Horses treated surgically were more likely to race after treatment than were horses treated without surgery.

Animals↗

PubMed2005

Complete deficiency of the low-density lipoprotein receptor is associated with increased apolipoprotein B-100 production.

OBJECTIVE: We addressed the role of the low-density lipoprotein (LDL) receptor in determining clearance rates and production rate (PR) of apolipoprotein B (apoB) in humans. METHODS AND RESULTS: Kinetic studies using endogenous labeling of apoB with deuterated leucine were performed in 7 genetically defined patients with homozygous familial hypercholesterolemia (FH) and compared with 4 controls. The fractional catabolic rates (FCR) and PRs for apoB were determined by multicompartmental modeling. The FCRs of very-low-density lipoprotein 1 (VLDL1), VLDL2, intermediate-density lipoprotein (IDL), and LDL apoB were lower in FH than in controls, with the LDL apoB FCR being significantly lower (0.148+/-0.049 versus 0.499+/-0.099 pools x d(-1); P=0.008). Whereas receptor-defective FH patients had a total apoB PR similar to controls, receptor-null FH patients had a significantly greater total apoB PR than controls (35.97+/-10.51 versus 21.32+/-4.21 mg x kg(-1) x d(-1), respectively; P=0.02). CONCLUSIONS: This first study of apoB metabolism in homozygous FH using endogenous labeling with stable isotopes demonstrates that the LDL receptor contributes significantly to the clearance of LDL from plasma but plays a lesser role in the clearance of larger apoB-containing lipoproteins. Furthermore, these data also indicate that absence of a LDL receptor in humans substantially influences the apoB PR in vivo.

Adolescent↗

PubMed2005

Normal triglyceride levels despite insulin resistance in African Americans: role of lipoprotein lipase.

Abstract Lipoprotein lipase (LPL), the enzyme responsible for hydrolyzing triglyceride (TG) in plasma lipoproteins, is a key regulator of plasma TG levels. In Caucasians, postheparin-LPL (PH-LPL) activity is impaired in the presence of insulin resistance and leads to elevated TG levels. However, African Americans are often both insulin-resistant and normotriglyceridemic. But in African Americans, the effect of insulin resistance on PH-LPL activity has not been studied. In African Americans, if insulin resistance is not associated with a decrease in PH-LPL activity, this could account for the simultaneous presence of insulin resistance and normotriglyceridemia. Therefore, our goal was to determine in African Americans the relationship between insulin resistance and PH-LPL activity. In a cross-sectional study of 107 nondiabetic African Americans (57 men and 50 women; age mean +/- SD, 35 +/- 8 years, range 22-50 years; body mass index 31.6 +/- 7.9 kg/m 2 , range 18.5-54.7 kg/m 2 ), fasting TG levels and PH-LPL activity were determined. Visceral adipose tissue was measured by abdominal computed tomographic scan. Insulin resistance was determined by the insulin sensitivity index ( S I ). Subjects were divided into tertiles by S I . The range of S I in each tertile was 12.75 to 3.99, 3.87 to 2.20, 2.06 to 0.17 mU . L -1 . min -1 . Insulin resistance was defined as being in the third tertile. TG levels in the men and women were 82.2 +/- 35.5 versus 56.4 +/- 30.1 mg/dL, P < .001. There were no sex difference in PH-LPL activity (8.9 +/- 2.5 vs 9.6 +/- 3.2 mmol/h per liter, P = .30) or S I (3.65 +/- 2.59 vs 3.23 +/- 1.89 L . mU -1 . min -1 , P = .49). Although 47% of the subjects were obese, only 4% of subjects had hypertriglyceridemia (TG > or =150 mg/dL). By 2 separate analyses, PH-LPL was a major determinant of TG levels. First, there was a significant inverse correlation between PH-LPL activity and TG levels (men: r = -0.46, P < .001; women: r = -0.28, P = .046). Second, in the multiple regression analysis with TG as the dependent variable and PH-LPL, age, sex, S I , and visceral adipose tissue as independent variables, adjusted R 2 was 54% and the effect of PH-LPL on TG levels was highly significant( P < .001). However, insulin resistance did not appear to influence PH-LPL activity. This is demonstrated in 3 ways: first, PH-LPL activity was not different in the S I tertiles (9.10 +/- 2.75, 9.52 +/- 2.91, 9.13 +/- 2.89 mmol/h per liter, P = .78); the correlation between PH-LPL and S I was not significant (men: r = 0.09, P = .51; women: r = -0.03, P = .78), and a multiple regression with PH-LPL as the dependent variable and age, S I , body mass index, and sex as independent variables, adjusted R 2 was <2% and the contribution of S I was not significant ( P = .53). Hence, in African Americans, increased PH-LPL activity is associated with a decrease in TG levels. The lack of an effect of insulin resistance on PH-LPL could allow LPL to clear TG even in the presence of insulin resistance and explain the coexistence of insulin resistance and normotriglyceridemia in African Americans.

Adipose Tissue↗

PubMed2005

Estimation of the content of fat and parenchyma in breast tissue using MRI T1 histograms and phantoms.

Mammographic breast density has been correlated with breast cancer risk. Estimation of the volumetric composition of breast tissue using three-dimensional MRI has been proposed, but accuracy depends upon the estimation methods employed. The use of segmentation based on T1 relaxation rates allows quantitative estimates of fat and parenchyma volume, but is limited by partial volume effects. An investigation employing phantom breast tissue composed of various combinations of chicken breast (to represent parenchyma) and cooking fats was carried out to elucidate the factors that influence MRI T1 histograms. Using the phantoms, T1 histograms and their known fat and parenchyma composition, a logistic distribution function was derived to describe the apportioning of the T1 histogram to fat and parenchyma. This function and T1 histograms were then used to predict the fat and parenchyma content of breasts from 14 women. Using this method, the composition of the breast tissue in the study population was as follows: fat 69.9+/-22.9% and parenchyma 30.1+/-22.9%.

Adipose Tissue↗

PubMed2005

AKA-Glucose: a program for kinetic and epidemiological analysis of frequently sampled intravenous glucose tolerance test data using database technology.

BACKGROUND: The Bergman Minimal Model enables estimation of two key indices of glucose/ insulin dynamics: glucose effectiveness and insulin sensitivity. METHODS AND RESULTS: In this paper we describe AKA-Glucose, a program that combines MINMOD Millennium (minimal model analysis software) with relational database technologies. AKA-Glucose enables the fitting of individual frequently sampled intravenous glucose tolerance test (FSIGT) data sets to the Minimal Model and the secure storage in a dedicated database (and retrieval from) of thousands of individual subjects' demographic data, their individual FSIGT data, and each subject's parameters and indices derived from minimal model analysis. AKA-Glucose also enables the population analysis of various strata or subpopulations within the database. AKA-Glucose has all of the capabilities of MINMOD Millennium, provides Minimal Model parameter estimates that are concordant with estimates from previous MINMOD software, and allows importation of data files from earlier versions of the MINMOD software. CONCLUSIONS: By combining FSIGT data fitting, population analysis, and relational database technologies, AKA-Glucose is the first minimal model software designed specifically for researchers confronted with minimal model and epidemiological analysis of large numbers of either human or animal FSIGT data sets.

Adult↗

PubMed2005

The pharmacokinetics of hemoglobin-based oxygen carrier hemoglobin glutamer-200 bovine in the horse.

Hemoglobin-glutamer-200 (HBOC-200) is a hemoglobin (Hb)-based oxygen carrier (HBOC) comprising glutaraldehyde-polymerized bovine Hb. In this study, we sought to determine the pharmacokinetics of this first generation HBOC after IV infusion of 32.5 g of HBOC-200 solution in horses. Quantification of HBOC-200 in equine plasma and urine was performed using a method recently developed by our laboratory. The elimination from plasma was based on size distribution of the bovine Hb polymer. The decline of plasma concentration-time curve of HBOC-200 was described by a noninterchanging 2-compartmental model. The median elimination half-lives of the small and large aggregates were 1.3 and 12.0 h, respectively. Of the HBOC-200 infused, 47.0% was eliminated as the smaller molecular weight and 53% as the larger molecular weight polymers. The area under the plasma concentration-time curve was 5143.1 microg.h(-1).mL(-1). The volumes of distribution of the small and large aggregates were 86.9 and 63.9 mL/kg and the clearances were 42.1 and 3.8 mL.kg(-1).h(-1), respectively. In conclusion, elimination of first generation HBOCs was shown to be more complex than previously assumed because of the heterogeneous nature of these solutions. Mammalian species dispose of Hb using similar mechanisms, and there is no unique metabolic process in the horse that would not allow a logical extension of the general interpretation of this study.

Algorithms↗

PubMed2005

Comparison of thermal dilution and electrical impedance dilution methods for measurement of cardiac output in standing and exercising horses.

OBJECTIVE: To compare cardiac output measured in the pulmonary artery and a carotid artery by use of thermal and electrical impedance dilution. Animals-7 fit, clinically normal Standardbreds between 2 and 5 years of age. PROCEDURE: Transient changes in electrical impedance and temperature of blood were induced by bolus injections of ice-cold saline hypertonic (6% and 9% NaCl) solutions. Cardiac output was calculated by applying Stewart-Hamilton principles to the indicator dilution transients. Measurements were made during sequential exercise episodes on a level treadmill over approximately an 8-fold range of cardiac output values. RESULTS: We detected agreement between cardiac output determined by use of electrical impedance dilution at the pulmonary artery and carotid artery. Cardiac output from thermal dilution measured at the carotid artery exceeded that measured at the pulmonary artery. Cardiac output from the thermal dilution technique exceeded cardiac output from the electrical impedance dilution technique at both locations. CONCLUSIONS AND CLINICAL RELEVANCE: The electrical impedance indicator is conserved on first transit; therefore cardiac output measured by electrical impedance dilution at the carotid artery is reliable over a large range of values. Thermal dilution provides a larger estimate of cardiac output, compared with the electrical impedance dilution technique, probably because of a loss of indicator. The transpulmonary electrical impedance dilution technique may have potential for clinical application, particularly in animals in which catheterization of the pulmonary artery is not appropriate or blood loss must be minimized.

Animals↗

PubMed2004

BMAL1 and CLOCK, two essential components of the circadian clock, are involved in glucose homeostasis.

Circadian timing is generated through a unique series of autoregulatory interactions termed the molecular clock. Behavioral rhythms subject to the molecular clock are well characterized. We demonstrate a role for Bmal1 and Clock in the regulation of glucose homeostasis. Inactivation of the known clock components Bmal1 (Mop3) and Clock suppress the diurnal variation in glucose and triglycerides. Gluconeogenesis is abolished by deletion of Bmal1 and is depressed in Clock mutants, but the counterregulatory response of corticosterone and glucagon to insulin-induced hypoglycaemia is retained. Furthermore, a high-fat diet modulates carbohydrate metabolism by amplifying circadian variation in glucose tolerance and insulin sensitivity, and mutation of Clock restores the chow-fed phenotype. Bmal1 and Clock, genes that function in the core molecular clock, exert profound control over recovery from insulin-induced hypoglycaemia. Furthermore, asynchronous dietary cues may modify glucose homeostasis via their interactions with peripheral molecular clocks.

ARNTL Transcription Factors↗

PubMed2004

Water exchange between the pregnant ewe, the foetus and its amniotic and allantoic fluids.

Water exchange between the ewe and its foetus was measured in two Merino ewes maintained with continuous feeding under thermoneutral conditions from about day 90 of gestation to term. Catheters were established in the maternal pulmonary artery (MPA), the foetal dorsal aorta (FDA) and the amniotic and allantoic sacs. Doses of tritiated water were given into either the MPA or the FDA on five occasions, three for one ewe and two for the other, at least 6 days apart and samples were taken from all catheters for 31 h following the dose. An open, eight-compartment restricted model was developed which simultaneously fitted the tracer data and the ewes' water balance, determined by measurement and calculation. The ewes delivered live lambs at term. Water was exchanged between ewe and foetus at 16-43 l h(-1) whereas net flow to the foetus averaged 82 ml day(-1). Turnover times were 20-39 min in the ewes' body water, 2-7 min in foetal body water, 10-58 min in amniotic water and 3-22 min in allantoic water; the whole-body half-times were 4.5-5.7 days. The data suggest that intramembranous exchange was the major contributor to water exchange in amniotic and allantoic fluids. The mean residence time of water in the rumen (39-52 min) was shorter than in non-pregnant sheep, suggesting that blood flow to the rumen increased during mid to late gestation.

Amniotic Fluid↗

PubMed2004

Reduction of "no-reflow" phenomenon by intra-aortic balloon counterpulsation in a randomized magnetic resonance imaging experimental study.

OBJECTIVES: Intra-aortic balloon counterpulsation (IABC) can improve post-myocardial infarction (MI) outcomes, but the mechanisms of such effect remain unclear. We hypothesized that IABC augmentation reduces the extent of microvascular obstruction after acute infarction. BACKGROUND: Microvascular obstruction or "no-reflow" (MO) has been shown to negatively influence left ventricular (LV) remodeling after myocardial infarction (MI). METHODS: Seventeen dogs underwent 90 min of coronary artery occlusion followed by reperfusion. Animals were then randomized to either IABC (n = 9) or control (n = 8); IABC augmentation was performed for 24 h after MI. Microvascular obstruction and infarct size by first-pass and delayed contrast-enhanced magnetic resonance imaging (MRI) were measured at 1 and 24 h after reperfusion and compared with postmortem infarct size and MO by microspheres. RESULTS: Microvascular obstruction by MRI, expressed as percent LV mass, decreased significantly in IABC (4.9 +/- 2.2% to 3.6 +/- 1.5%) and increased in controls (3.4 +/- 0.5% to 4.9 +/- 1.1% from 1 to 24 h, respectively; p < 0.001). Similar results were found for MO defined by microspheres. In the control group, MO increased significantly, during 24 h of study (from 8.8 +/- 1.7% to 43.2 +/- 11.1% of infarcted myocardium; p < 0.05), whereas not important change was observed in the IABC group (from 21.3 +/- 7.1% to 25.8 +/- 14.7%; p < 0.05 vs. control at 24 h). Infarct size, measured by MRI, increased in both groups (13.2 +/- 1.8 to 15.5 +/- 2.1 from 1 to 24 h, respectively; p < 0.05). CONCLUSIONS: Intra-aortic balloon counterpulsation augmentation performed after reperfusion improves myocardial perfusion at the tissue level, and reduces the extent of no-reflow caused by microvascular obstruction.

Animals↗

PubMed2004

A modified logistic model to describe gadolinium kinetics in breast tumors.

A five-parameter modified logistic equation is presented that describes the signal enhancement in magnetic resonance dynamic contrast enhanced imaging (MRI-DCE). In this heuristic model, P(1) approximates the baseline signal, P(2) is related to the magnitude of the peak signal enhancement, P(3) is the approximate time of the maximum rate of increase of signal, P(4) is related to the maximum rate of signal enhancement, and P(5) is the terminal slope of the signal enhancement curve. Six breast tumors were studied that exhibited diverse patterns of signal enhancement, and in each case, estimated model parameters were well identified. Three of the model parameters, P(2), P(4) and P(5) describe attributes of the signal enhancement curve that have previously been shown to have diagnostic value with respect to breast cancer. Procedures for using the primary model parameters to derive a number of secondary parameters that may also have diagnostic value are discussed. Sensitivity analysis shows that the signal enhancement curve is highly sensitive to P(3) in the region of the signal intensity curve associated with rapid uptake of the contrast reagent. Consequently, frequent signal sampling in this time domain is indicated to enable identification of P(3) and sensitive fitting of the signal intensity curve. The advantages of this heuristic model compared to commonly used compartmental modeling approaches are discussed.

Breast Neoplasms↗

PubMed2004

The rate of de novo galactose synthesis in patients with galactose-1-phosphate uridyltransferase deficiency.

Using both a continuous infusion of isotopically labeled [1-13C]galactose with a steady-state analysis and a single injection kinetic approach, we have calculated the apparent galactose appearance rate (GAR) in patients with galactose-1-phosphate uridyltransferase deficiency and control subjects. With the steady-state protocol, the GAR in 18 patients less than 18 years of age was 1.34+/-0.53 mg/kg/h (mean+/-SD) and was significantly greater than the mean of 0.56+/-0.01 mg/kg/h (p=0.004) in five patients above 18 years of age. Patients who were given a priming dose of [1-13C]galactose had a reduced GAR compared to those without a priming dose, 0.73+/-0.05 (n=9) vs 1.46+/-0.62 (n=14)mg/kg/h (p=0.005). The GAR in controls was lower than in patients ranging from 0.58 to 0.68 mg/kg/h in children and 0.07-0.09 mg/kg/h in adults. In the single bolus studies the plasma [13C]galactose enrichment decreased in a biexponential pattern suggesting at least a two-compartment system. The calculated GAR in three adult patients was similar to that found in them by the continuous infusion technique. The GAR in patients suggests the source of galactose for the continued elevation of galactose metabolites as well as the basis for the long-term complications in galactosemia despite restricted dietary galactose intake.

Adolescent↗

PubMed2004

Effects of insulin-like growth factor-II on the mitogenic and metabolic activities of equine articular cartilage with and without interleukin 1-beta.

OBJECTIVE: To investigate the effects of insulin-like growth factor-II (IGF-II) on DNA and glycosaminoglycan (GAG) synthesis and the expression of matrix-related genes in equine articular cartilage explants and chondrocytes, respectively, with and without interleukin 1-beta (IL1-beta). SAMPLE POPULATION: Articular cartilage from 12 adult horses. PROCEDURE: Articular cartilage was incubated in standard media with and without equine IL1-beta (10 ng/mL) containing various concentrations of IGF-II for 72 hours. Synthesis of DNA and GAG was determined by incorporation of thymidine labeled with radioactive hydrogen (3H) and sulfate labeled with radioactive sulfur (35S), respectively. Total GAG content of the explants and spent media was determined by use of the 1,9-dimethylmethylene blue assay. Northern blots of RNA from cultured equine articular cartilage chondrocytes were hybridized with cDNA of major matrix molecules. RESULTS: Insulin-like growth factor-II stimulated DNA and GAG synthesis at concentrations of 25 and 50 ng/mL, respectively. In cartilage explants conditioned with IL1-beta, IGF-II stimulated DNA and GAG synthesis at concentrations of 500 and 50 ng/mL, respectively. Insulin-like growth factor-II had no effect on total GAG content as determined by the 1,9-dimethylmethylene blue assay. No specific effects on steady-state levels of messenger RNAs were observed. CONCLUSIONS AND CLINICAL RELEVANCE: Insulin-like growth factor-II stimulated DNA and GAG synthesis in equine adult cartilage and may have potential application in vivo.

Analysis of Variance↗

PubMed2003

Quantitative ischemia detection during cardiac magnetic resonance stress testing by use of FastHARP.

BACKGROUND: Because ECG alterations caused by ischemia cannot be reliably detected in the high-field MRI environment, detection of wall motion abnormalities is often used to ensure patient safety during stress testing. However, an experienced observer is needed to detect these abnormalities. In this study, we investigate the use of fast harmonic phase (FastHARP) MRI for the quantitative, operator-independent detection of the onset of ischemia during acute coronary occlusion. METHODS AND RESULTS: Eight mongrel dogs underwent an acute 2-minute closed-chest coronary artery occlusion while continuous FastHARP images were acquired. Full regional wall strain was determined every other heartbeat in a single short-axis imaging slice. After 5 minutes of reperfusion, a second 2-minute ischemic episode was induced during the acquisition of conventional cine wall-motion images. The time at which ECG alterations were observed during the first ischemic period was recorded. The time from occlusion to the detection of ischemia, based on a consensus of 2 blinded observers, was determined for MRI. No significant ischemia was present in 2 animals. In the remaining animals, the onset of ischemia was detected significantly earlier by FastHARP than by cine MRI (9.5+/-5 versus 33+/-14 seconds, P<0.01). HARP ischemia detection preceded ECG changes, on average, by 54 seconds. CONCLUSIONS: The rapid acquisition and detection of induced ischemia with FastHARP MRI shows promise as a nonsubjective method to diagnose significant coronary lesions during MR stress testing.

Animals↗