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Biomedical subjects

R J Boucek

Publications and source records attributed to R J Boucek.

121 records · Page 7Linked to original sources
PubMed1965

Incorporation of sulphate by chick-embryo corium. Nature and products of the process in vitro.

1. The incorporation of sulphate into the trichloroacetic acid-precipitable fraction of 9-day chick-embryo corium, incubated in Krebs-Ringer phosphate buffer, pH7, is dependent on the sulphate concentration of the medium. Uptake of sulphate is linear with time for 3.5-4hr. and is maximal at 37.5 degrees in the presence of air or oxygen. d-Glucose stimulates the incorporation of sulphate but l-glutamine has no effect. 2. Incorporation of sulphate by the chick corium is enzymic and apparently involves the synthesis of active sulphate (adenosine 3'-phosphate 5'-sulphatophosphate) and the transfer of sulphate from adenosine 3'-phosphate 5'-sulphatophosphate to acceptor glycosaminoglycuronoglycan. This proposal on the nature of the process is suggested by the similarity between the energy of activation calculated for sulphate-incorporation in the chick-corium preparation and the energy requirement reported for sulphate-activation with purified yeast enzymes. 3. The 9-day chick-embryo corium is composed principally of fibroblasts; there are no histologically demonstrable mast cells. The young fibroblast is apparently responsible for the incorporation of sulphate into glycosaminoglycuronoglycans tentatively identified as chondroitin sulphate(s), heparan sulphate and heparin-like material.

Journal Article↗
PubMedDate not supplied

Relationship between the in-situ activity of ornithine decarboxylase and contractile function of the rabbit papillary muscle.

The relationship between isometric contraction and myocardial ornithine decarboxylase (ODC; EC.4.1.1.17) activity was studied in right ventricular papillary muscles isolated from rabbits. ODC specific activity and polyamine content were significantly increased in papillary muscles contracting isometrically 90 times per minute at the apex of the length-tension relationship for 4 to 5 hours when compared with paired non-contracting muscles or isometrically contracting muscles stimulated at 30 times per min. The increase in ODC activity appeared to be due to new protein synthesis since cycloheximide blocked the increase in ODC activity without affecting isometric function. Thus, the present results suggest that increased contractile demands of the heart may stimulate the synthesis of myocardial ODC, increase ODC activity and polyamine content.

Animals↗
PubMedDate not supplied

Myocellular calcium regulation by the sarcolemmal membrane in the adult and immature rabbit heart.

Previous studies have suggested ontogenic differences in Ca-mediated excitation-contraction coupling in mammalian heart. Sarcolemmal (SL) Ca regulation may predominate prior to the development of the specialized Ca-regulatory properties of the sarcoplasmic reticulum (SR). The effect of development on selected Ca-regulatory properties of cardiac SL was evaluated utilizing membrane vesicles obtained from immature (14 to 21-day-old) and adult rabbit heart. Methods were adapted to comparably enrich SL membrane vesicles from immature and adult rabbit heart. The global fluidity characteristics were determined by the polarized fluorescence of diphenylhexatriene passively incorporated into enriched SL membrane vesicles. No age-related differences in either the membrane microviscosity of the lipid-order parameter between 10 degrees C and 37 degrees C were observed. The membrane characteristics of the voltage-gated Ca channel were determined by the membrane binding characteristics of 3[H]-nitrendipine. Scatchard analysis of high affinity specific nitrendipine binding demonstrated comparable binding affinity (KD; 511 +/- 40 vs 484 +/- 40 pM) and theoretical maximal binding site density (Bmax; 218 +/- 19 vs 240 +/- 40 fmoles/mg prot.) in immature and adult respectively. ATP-independent Ca binding to SL membrane vesicles was determined between 1.5 and 10 mM [Ca]. Ca binding was greater in the immature at 10 mM [Ca] as compared to the adult (840 +/- 120 vs 350 +/- 30 nmoles/mg). Ca bound to SL over this Ca concentration range is indicative of a "pool" of Ca for cellular influx across the SL by the Na-Ca exchange mechanism and the voltage-gated Ca channel. In view of electrophysiologic evidence also suggesting that Ca-channel-mediated Ca conductance is greater in the immature than the adult, it is proposed that the number of voltage-activatable Ca channels localized to the SL is greater in the immature than the adult. The larger transsarcolemmal Ca fluxes plays a larger role in the beat-to-beat- regulation of cardiac contraction in the developing mammalian heart prior to full expression of the specialized Ca regulatory properties of the SR.

Aging↗
PubMedDate not supplied

Effects of postnatal maturation on myocardial contractile responses to calcium antagonists and changes in contraction frequency.

The inotropic responses to verapamil and nitrendipine (5.0 X 10(-8)-1.0 X 10(-5) M) were compared in right ventricular papillary muscles isolated from immature (14-21 days of age) and adult rabbits. In addition, the effects of changing the contraction frequency (force-frequency response) were studied in both age groups in the presence and absence of the calcium antagonists. Immature myocardium exhibited a greater sensitivity to the negative inotropic effect of both calcium antagonists. The concentrations of verapamil which reduced basal developed tension by 50% were 0.70 X 10(-6) M in the immature rabbit and 4.51 X 10(-6) M in the adult (p less than 0.05). For nitrendipine, these values were 0.48 X 10(-6) M in the immature rabbit and 1.21 X 10(-6) M in the adult (p less than 0.05). Raising the contraction frequency increased the contractile force (positive staircase) in both age groups, and verapamil abolished the positive staircase in both groups. Nitrendipine preserved but attenuated the positive staircase in the adult, but, in contrast, augmented the positive-staircase response in the immature myocardium. These age-related differences suggest that the mechanisms regulating calcium influx across the sarcolemma undergo postnatal maturation.

Aging↗
PubMedDate not supplied

Treatment of postischemic reperfusion cardiac injury with a perfluorochemical solution.

We assessed the effects of a perfluorochemical solution on reperfusion injury in a globally ischemic heart model. An isolated rabbit heart, retrogradely perfused at a constant flow rate, served as our experimental model. After initial perfusion with whole blood, hearts were exposed to 30 min of normothermic global ischemia. Reperfusion was then begun with either whole blood or a 20% perfluorochemical solution (FC-43). After 120 min of reperfusion, a markedly greater recovery of contractile function was observed in the perfluorochemical-reperfused hearts (85 +/- 5% of baseline developed pressure) compared with blood-reperfused hearts (57 +/- 3% of baseline developed pressure). This recovery of function was accomplished with only 1 h of perfluorochemical reperfusion and was not lost on returning to blood perfusion. The improved recovery of function could not be attributed to the chemical composition, oxygen-carrying capacity, pH, or temperature of the perfluorochemical perfusate. Neither could the beneficial effects of perfluorochemical be related to differences in left ventricular resting pressure. We speculate that, because of marked differences in coronary resistance during reperfusion with perfluorochemical solution and blood, improved recovery of cardiac function is related to the superior rheological properties of perfluorochemicals.

Animals↗
PubMedDate not supplied

Prospective evaluation of echocardiography for primary rejection surveillance after infant heart transplantation: comparison with endomyocardial biopsy.

Rejection surveillance is critical to successful heart transplantation, and infant recipients have necessitated the use of noninvasive measures. The survival, incidence of rejection, and accuracy of echocardiography in predicting treatable rejection, as detected on right ventricular endomyocardial biopsy, were prospectively studied in infants. The survival rate (82%) and rejection rate (1.4 rejection episodes per 100 patient days) of infants who underwent transplantation during the study were comparable to other studies that used heart biopsy only. Echocardiography was 98% accurate at predicting biopsy results. The sensitivity of echocardiography was 92%, and the specificity was 98%. We conclude that echocardiography can be used successfully for primary rejection surveillance in infants and that right ventricular biopsy is infrequently required.

Biopsy↗
PubMedDate not supplied

Serial echocardiographic evaluation of cardiac graft rejection after infant heart transplantation.

The effects of cardiac graft rejection on infant myocardial function as assessed by echocardiography are largely unknown. To quantitate the myocardial response to rejection, serial echocardiographic studies were prospectively performed on 20 infants (less than 1 year of age at transplantation). Two-dimensional guided-M-mode tracings were digitized and quantified with a computer-assisted format. Rejection was diagnosed by clinical criteria, and 85% were graded as mild, that is without cardiac signs or symptoms. Echocardiographic analysis was blinded to rejection status, with studies available 4.2 +/- 2.9 days before rejection, on the day of rejection diagnosis, and 2.9 +/- 1.5 days after rejection treatment. Left ventricular mass increased acutely from 109% of predicted normal to 129% with rejection and decreased to 110% with therapy (p < 0.01). Left ventricular volume also tended to fall with rejection and increase with therapy. The left ventricular volume/mass ratio fell from 0.29 +/- 0.10 to 0.25 +/- 0.13 and increased to 0.37 +/- 0.15 (p < 0.05) with treatment. Systolic function was depressed by rejection as reflected in the posterior wall thickening fraction and velocity of wall thickening. Diastolic dysfunction was reflected in a decreased velocity of posterior wall thinning (-9.7 +/- 3.9 to -7.7 +/- 2.7 and recovery to -10.8 +/- 3.8 (1/second, p < 0.05) and depressed average velocity of cavity enlargement (41.2 +/- 9.6 to 36.4 +/- 8.9 and recovery to 40.7 +/- 8.6 mm/sec, p < 0.05). The utility of these echocardiographic measurements to predict rejection has not been prospectively compared with the endomyocardial biopsy.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Volume↗
PubMedDate not supplied

Pattern of echocardiographic abnormalities with acute cardiac allograft rejection in adults: correlation with endomyocardial biopsy.

In patients who have undergone successful orthotopic heart transplantation, a noninvasive method for rejection surveillance would reduce the frequency of endomyocardial biopsy, guide the timing of biopsies, and allow for more frequent monitoring. This study identified the pattern of change in echocardiographically determined indexes of left ventricular mass, volume, and function that characterized biopsy-positive acute rejection in adult heart transplant patients receiving triple-drug immunosuppressive therapy and describes a simple computer-driven algorithm capable of identifying rejection with high sensitivity and specificity. Two-dimensional and M-mode echocardiography and Doppler color flow analyses were performed within 24 hours of endomyocardial biopsy. M-mode echocardiograms of the left ventricle were digitized and analyzed blinded to the biopsy interpretation, using a computer-assisted measurement format, for size, mass, and wall motion in systole and diastole. Twenty-nine studies were retrospectively analyzed to define the echocardiographic pattern characteristic for rejection. Left ventricular chamber size decreased, and indexes of diastolic function were significantly depressed in patients with biopsy evidence of moderate or severe rejection. However, no single parameter was sufficiently sensitive to detect all episodes of rejection partly because of differences between patients in the echocardiographic manifestations of acute rejection. To accommodate this patient variability, multiple echocardiographic parameters were clustered into a unique scoring algorithm (ECHO score). When applied prospectively to 49 studies, the likelihood that a patient would have an ECHO score not indicative of rejection but with moderate/severe rejection on biopsy was low (less than 3%) or a negative predictive value of 97.4%.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMedDate not supplied

Echocardiographic abnormalities with acute cardiac allograft rejection in children: correlation with endomyocardial biopsy.

In patients who have undergone successful orthotopic heart transplantation, echocardiography has the potential to be a noninvasive method for rejection surveillance that would reduce the frequency and guide the timing of endomyocardial biopsies, as well as allow for more frequent monitoring, with less cost and risk to the patient. To determine the applicability of echocardiography to detect moderate to severe rejection in children, 26 two-dimensional-guided M-mode echocardiograms with Doppler/color flow mapping were performed within 24 hours of endomyocardial biopsy. M-mode echocardiograms of the left ventricle were digitized and analyzed with a computer-assisted measurement format for left ventricular size, mass, and wall motion in systole and diastole. These echocardiographic parameters were clustered and analyzed by a unique echocardiographic scoring algorithm blinded to the biopsy interpretation. In eight cases in which findings of biopsies were consistent with moderate to severe rejection, left ventricular mass was increased and indexes of systolic and diastolic function were depressed compared with the remainder of the cases (n = 18), in which findings of biopsies included either no evidence or mild evidence of rejection. The echocardiographic score of the group with moderate to severe rejection was significantly greater than the score of the group that was normal or had mild rejection (5.4 +/- 0.7 vs 2.2 +/- 0.3; p < 0.001). With rejection prospectively defined as an echocardiographic score of greater than or equal to score 4, echocardiography achieved 88% sensitivity and 83% specificity in detecting moderate to severe rejection.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗