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Biomedical subjects

M J Rice

Publications and source records attributed to M J Rice.

At least 55 records · Page 3Linked to original sources
PubMed1991

Paradoxic embolism due to altered hemodynamic sequencing following transvenous pacing.

A young patient, who experienced a cerebral embolic event 30 days after transvenous pacemaker lead placement, is reported. This patient had previously been paced with an epicardial lead without evidence of right to left intracardiac shunt. However, hemodynamic evaluation post-embolism demonstrated a marked temporal disparity of the pulmonary and systemic ventricles. This phasic divergence resulted in a brief reversal of right and left ventricular pressure ratios, and a paradoxic intracardiac shunt at a small ventricular septal defect. The potential for similar events in the presence of any defect of the atrial or ventricular septum mandates caution in the use of transvenous pacemaker leads in such patients.

Blood Pressure↗
PubMed1991

Hypothermic preservation of hepatocytes. III. Effects of resuspension media on viability after up to 7 days of storage.

Hepatocyte suspensions provide a rapid method to determine how hypothermic storage affects liver cell metabolism and viability. Using these studies, improved methods of hypothermic liver preservation for transplantation may be developed. In this study, rat hepatocytes were cold-stored for up to 7 days in University of Wisconsin liver preservation solution. At the end of each day of storage hepatocytes were resuspended in Krebs-Henseleit buffer or tissue-culture medium (Liebovitz-15; Fischer's; modified Fischer's, which was similar to Fischer's but with glycine and cysteine added; or Waymouth's medium). Hepatocyte viability was assessed by rewarming and oxygenating the suspensions and measuring the percentage of leakage of lactate dehydrogenase from the cells, the cellular concentration of potassium and the stimulation of respiration by succinate, all measures of plasma membrane integrity. Additionally, concentrations of ATP and glutathione after rewarming and reoxygenation in the various resuspension media were measured. Hepatocyte permeability to lactate dehydrogenase did not increase during cold storage of 1 to 7 days (7.2% +/- 2% leakage), indicating that most of the hepatocytes remained viable during cold storage. However, when rewarmed, loss of viability (leakage of lactate dehydrogenase) was dependent on the composition of the resuspension media. In Krebs-Henseleit buffer, viability was reduced after 2 and 3 days of storage (lactate dehydrogenase leakage on rewarming = 70% to 90%). Leakage of lactate dehydrogenase was reduced significantly after resuspension in tissue-culture media. After 6 days of storage, lactate dehydrogenase leakage from hepatocytes stored in Liebovitz- 15 or modified Fischer's was only about 30%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1990

The timing of spontaneous closure of the ductus arteriosus in infants with respiratory distress syndrome.

Previous studies evaluating the incidence of patent ductus arteriosus have not made a distinction between physiologic ductal patency and abnormally persistent ductus arteriosus. However, it has recently been shown that healthy premature infants without respiratory distress syndrome (RDS) undergo spontaneous closure of the ductus arteriosus in the first 4 days of life at times comparable to full-term infants. Thus, ductal patency within this time frame would appear to be physiologic. Although sick premature infants are well recognized to be at risk for ductal shunting, the purpose of this investigation was to evaluate systematically the actual impact that RDS has on duration of ductal shunting by assessing the timing of spontaneous functional closure. The presence of ductal shunting was evaluated using echocardiographic color flow Doppler techniques. Thirty-six premature infants (30 to 37 weeks gestational age) were evaluated. By the fourth day of life, only 4 of 36 (11.1%) of the infants continued to have evidence of ductal patency. The remainder of the infants underwent spontaneous functional closure of the ductus arteriosus at times comparable to healthy infants without RDS. For most infants greater than or equal to 30 weeks gestation, uncomplicated RDS does not alter the usual timing of functional ductal closure.

Ductus Arteriosus, Patent↗
PubMed1990

New and versatile approaches to the synthesis of CPP-related competitive NMDA antagonists. Preliminary structure-activity relationships and pharmacological evaluation.

Fourteen new CPP analogues have been prepared with methyl 1-(phenylmethyl) (+/-)-1,2-piperazinedicarboxylate 3 as a versatile synthetic intermediate. Derivatives were evaluated as NMDA ligands by their ability to displace [3H]CPP from rat cortical membranes. The binding affinity of various chain lengths at the N4-position of the CPP analogues, 5a, 5b, and 9a mimics the binding affinity observed for the acyclic derivatives AP6, AP8, and AP5. Analogue 9a, with a single methylene group in its phosphonate side chain, exhibited diminished affinity for the NMDA receptor when compared to the structurally similar piperidine compound CGS 19755. Replacement of the phosphonic acid moiety with monoionizable acidic groups such as a carboxylate or a phosphinate resulted in a reduction of binding affinity. An aryl spacer between the N4-nitrogen and the distal acidic group was detrimental to binding as was alkylation at the N1-position. Steric bulk, however, was better tolerated when a phenyl group was positioned alpha to the phosphonate, as seen with analogues 21 and 22.

Animals↗
PubMed1989

The effect of halothane, isoflurane, and verapamil on ischemic-isolated rabbit renal tubules.

The effects of the volatile anesthetics halothane and isoflurane, and the calcium entry blocker verapamil, were studied in isolated rabbit renal tubules under nonischemic and simulated ischemic conditions. Isolated rabbit renal tubules were subjected to zero (control), 30 (I-30), or 60 (I-60) minutes of simulated ischemia following the method of Weinberg. Following the ischemic period, tubules were reoxygenated in a Gilson respirometer (simulated reperfusion) and treated with either halothane (1%) or isoflurane (1%) in the controls and at I-30, or halothane (1%, 2%, 4%) or verapamil (5 microM, 15 microM, 30 microM) at I-60. Tubules were analyzed for lactate dehydrogenase (LDH) release (measuring cell membrane integrity), intracellular potassium and adenosine triphosphate (ATP), and oxygen consumption (cellular respiratory rate). In nonischemic tubules, exposure to 1% isoflurane caused significantly reduced LDH release compared with that released by controls, indicating cell membrane protection, whereas 1% halothane had no effect on these cells. With 30 min of ischemia, 1% isoflurane was associated with significantly higher cellular LDH release and lower ATP concentration, suggesting increased cellular damage. Halothane (1%) was associated with only an increased ATP concentration in tubules exposed to 30 min of ischemia. Following 60 min of ischemia, halothane (4%) decreased LDH release by 45% (29.2 +/- 2.3% vs. 47.0 +/- 9.6% without halothane). Tubules exposed to halothane also had higher intracellular potassium and ATP concentrations, and increased respiratory rates. Halothane (2%) was less protective and only increased the ATP concentration. The release of LDH was not statistically different with or without 2% halothane.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1988

Synthesis and mass spectra of 4-O-acetyl-1,5-anhydro-2,3,6-tri-O-ethyl-D-glucitol and the positional isomers of 4-O-acetyl-1,5-anhydro-di-O-ethyl-O- methyl-D-glucitol and 4-O-acetyl-1,5-anhydro-O-ethyl-di-O-methyl-D-glucitol.

Reductive cleavage of fully methylated, partially O-ethylated cellulose or fully ethylated, partially O-methylated cellulose and subsequent acetylation had previously been shown to produce 4-O-acetyl-1,5-anhydro-2,3,6-tri-O-methyl-, -6- O-ethyl-2,3-di-O-methyl-, -3-O-ethyl-2,6-di-O-methyl-, -2-O-ethyl-3,6-di-O- methyl-, -2,3-di-O-ethyl-6-O-methyl-, -2,6-di-O-ethyl-3-O-methyl-, -3,6-di-O- ethyl-2-O-methyl-, and -2,3,6-tri-O-ethyl-D-glucitol. Described herein is the independent synthesis of these derivatives, except for the first (which had been reported); and their 1H-n.m.r. spectra, chemical-ionization (NH3) mass spectra, and electron-impact mass spectra are tabulated.

Chemical Phenomena↗
PubMed1988

Analysis of positions of substitution of O-methyl or O-ethyl groups in partially methylated or ethylated cellulose by the reductive-cleavage method.

A method is described for the analysis of positions of substitution of O-methyl and O-ethyl groups in commercial samples of O-methylcellulose and O-ethylcellulose, respectively. The method requires perethylation of O-methyl-cellulose and permethylation of O-ethylcellulose. Subsequent reductive cleavage of both polymers gives the same eight products, which are analyzed as their O-acetyl derivatives by gas-liquid chromatography.

Alkylation↗
PubMed1988

Fetal atrial septal aneurysm: a cause of fetal atrial arrhythmias.

Atrial arrhythmias are commonly found during fetal echocardiography performed during pregnancy to evaluate fetal arrhythmias. An association between atrial arrhythmias and an atrial septal aneurysm has been noted in children and adults. In this study, 105 fetuses were evaluated by fetal echocardiography, 39 (37%) referred to evaluate fetal arrhythmia and 66 (63%) to rule out congenital heart disease. An atrial septal aneurysm was found in 42 (40%) of the fetuses and an atrial arrhythmia in 37 (35%). An atrial septal aneurysm was found in 25 (64%) of the 39 fetuses referred to evaluate a fetal arrhythmia compared with only 17 (26%) of the 66 fetuses referred to rule out congenital heart disease. In this study, the association of an atrial septal aneurysm with an atrial arrhythmia was highly significant (p less than 0.001).

Arrhythmias, Cardiac↗
PubMed1988

Duration of ductal shunting in healthy preterm infants: an echocardiographic color flow Doppler study.

The purpose of this investigation was to assess the duration of ductal shunting after birth in healthy preterm infants (30 to 37 weeks gestational age) without evidence of respiratory distress. Thirty-six infants were evaluated in the first 12 hours of life by means of two-dimensional echocardiography and color flow Doppler techniques, and then once daily until no ductal flow was detected (defined as functional closure). Preterm infants were subdivided into two groups by gestational age: group 1 = 30 to 33 weeks (n = 12); group 2 = 34 to 37 weeks (n = 24). Sixteen full-term infants (38 to 41 weeks) were similarly evaluated as control subjects (Group 3). One infant from each group had a closed ductus at the time of the first study (performed at a mean of 7.7 +/- 3.2 hours). Subsequent studies for the entire group were performed at a mean of 31.3 +/- 5.4 hours (day 2), 55.0 +/- 4.5 hours (day 3), and 80.3 +/- 6.1 hours (day 4). For the three groups, the rates of ductal closure ranged from 50.0% to 58.3% on day 2 and 81.3% to 87.5% on day 3. For the entire group, all but one infant had demonstrated closure of the ductus arteriosus by day 4. Within the range of gestational ages studied, we conclude that prematurity, in the absence of respiratory distress syndrome, does not prolong the initial duration of physiologic ductal shunting.

Ductus Arteriosus↗
PubMed1987

Tricuspid regurgitation in newborn infants with respiratory distress: echo-Doppler study.

The purpose of this investigation was to use Doppler echocardiography to evaluate respiratory problems significant enough to warrant supplemental oxygenation in newborn infants. Of 17 infants (mean gestational age 37.5 weeks, mean birth weight 3070 g) 14 (82%) had detectable tricuspid regurgitation. By modified Bernoulli equation, all infants had right ventricular pressure greater than 60% of systemic pressure, and nine of 14 had estimated right ventricular pressure at or near systemic pressures. In eight infants for whom sequential evaluations could be obtained, right ventricular pressure as a percentage of systemic pressure gradually decreased, and corresponded to decreasing needs for supplemental oxygenation. Tricuspid regurgitation could no longer be detected between 3 and 16 days after the first study, and was associated with decreased right ventricular pressures (less than 50% systemic) and weaning from supplemental oxygenation. We conclude that in the near-term infant with early respiratory difficulties, tricuspid regurgitation is common and is associated with increased right ventricular pressure.

Blood Pressure↗
PubMed1987

Intermediate follow-up and predicted survival after the modified Fontan procedure for tricuspid atresia and double-inlet ventricle.

We reviewed the records of 135 patients with tricuspid atresia and 120 patients with double-inlet ventricle who underwent modified Fontan procedure from 1973 to June 1985. This represents 67% of the total number of patients undergoing the procedure during this period. There were 32 (12%) in-hospital deaths (14 tricuspid atresia, 18 double-inlet ventricle) and 23 late deaths (13 tricuspid atresia, 10 double-inlet ventricle). For patients surviving to hospital dismissal, the 5 year survival was 87%. Follow-up data (mean 3.9 years) were obtained for 157 patients who survived at least 1 year after operation. At last follow-up, of the 157 patients, 92% were in NYHA class I or II, 92% claimed to be improved clinically by the operation, and 98% could work or attend school. Fifty percent were not taking medication at last follow-up. Some degree of edema or ascites was found in 16%. The study showed that (1) the modified Fontan procedure can be performed with low in-hospital mortality (12%) in patients with tricuspid atresia and double-inlet ventricle, (2) hospital survivors have an estimated 5 year survival of 87%, (3) subjectively, functional status is good for hospital survivors at intermediate follow-up, and (4) fluid retention continues to be a problem in a minority (16%) of patients.

Blood Vessel Prosthesis↗
PubMed1986

Analysis of linkage positions in 2-acetamido-2-deoxy-D-glucopyranosyl residues by the reductive-cleavage method.

The fate of methylated 2-acetamido-2-deoxy-D-glucopyranosyl residues under reductive-cleavage conditions was investigated by using methyl 2-(acetylmethylamino)-2-deoxy-3,4,6-tri-O-methyl-beta-D-glucopyran oside (1), its alpha anomer (8), and fully methylated lacto-N-tetraitol as test compounds. Treatment of 1 with triethylsilane and trimethylsilyl trifluoromethanesulfonate in dichloromethane gave rise to (1,2-dideoxy-3,4,6-tri-O-methyl-alpha-D-glucopyrano)-2,3-dimethyl- [2,1-d]-2- oxazolinium trifluoromethanesulfonate. Quenching of the reaction by addition of aqueous sodium hydrogencarbonate resulted in hydrolysis of the oxazolinium salt. Compound 8 was fully stable to reductive-cleavage conditions. Thus, participation by the 2-acetamido group is necessary for glycosidic carbon-oxygen bond-cleavage to occur. Treatment of methyl 2-deoxy-2-(ethylmethylamino)-3,4,6-tri-O-methyl-alpha,beta-D-gluco pyranoside under reductive-cleavage conditions resulted in some anomerization, but neither hydrolysis nor reductive cleavage of the glycosidic carbon-oxygen bond was observed, as expected. Reductive cleavage of fully methylated lacto-N-tetraitol gave the products predicted on the basis of these and prior model studies, including 3-O-acetyl-2-(acetylmethylamino)-2-deoxy-4,6-di-O-methyl-D-glucopy ranose derived from the 3-linked 2-acetamido-2-deoxy-beta-D-glucopyranosyl residue.

Acetylglucosamine↗
PubMed1985

Straddling atrioventricular valve: two-dimensional echocardiographic diagnosis, classification and surgical implications.

The usefulness of subclassifying the anatomic variations of straddling and overriding atrioventricular (AV) valve by 2-dimensional echocardiographic observation were evaluated. Chordae straddling into a contralateral ventricle were subdivided into type A (chordae inserting into the contralateral ventricle near the crest of the ventricular septum), type B (chordae inserting along the contralateral ventricular septum) and type C (chordae inserting into the free wall or papillary muscles of the contralateral ventricle). Overriding AV valve anulus was described as minor (less than 50% of the anulus committed to the contralateral ventricle), major (about 50% of the anulus committed to each ventricle), and double-inlet ventricle (greater than 50% of both AV valves committed to a single ventricular chamber). In 52 patients straddling AV valve was diagnosed by echocardiography and confirmed by direct examination at surgery or autopsy. In 60 of 66 straddling AV valves (91%), the diagnosis and the degree of straddling (type A, B or C) were correctly identified by 2-D echocardiography. Major associated cardiac defects included double-outlet right ventricle (31%), complete transposition (23%), corrected transposition (19%), double-inlet ventricle (19%) and other complex defects (8%). Twenty-two patients (42%) had right-sided straddling, 21 (40%) had left-sided straddling and 9 (17%) had straddling of both AV valves. In 41% of the patients, straddling AV valve had a major impact on the type of surgery or the surgical outcome. Of these valves, 52% were type C (severe), 26% type B and 22% type A straddling.(ABSTRACT TRUNCATED AT 250 WORDS)

Chordae Tendineae↗
PubMed1985

Preservation of renal function by adenosine-stimulated ATP synthesis in hypothermically perfused dog kidneys.

Dog kidneys were hypothermically perfused for 1 to 5 days in the presence or absence of adenosine (5 mM). Following 1, 3, and 5 days, kidneys were reperfused at normothermia in an isolated perfusion system using a bovine serum albumin containing perfusate and renal function was determined. At the end of normothermic perfusion, kidney cortical slices were removed for biochemical analysis. Kidneys preserved in the presence of adenosine generated much higher concentrations of ATP during normothermic perfusion than kidneys preserved in the absence of adenosine at all time periods studied. In kidneys reperfused (37 degrees C) after 3 days of preservation, the ATP concentration averaged 9.15 mumol/g dry wt (+adenosine) vs. 4.75 mumol/g dry wt (-adenosine). After 5 days, the average was 12.65 mumol/g dry wt (+adenosine) vs. 4.00 mumol/g dry wt (-adenosine). The tissue concentration of K+ was higher in kidneys perfused in the presence of adenosine for all time periods studied. The presence of adenosine had little effect on the GFR (creatinine clearance) which was reduced by about 90% from control values at both 3 and 5 days of preservation. The primary effect of adenosine on renal function was a greater preservation of the capability of the isolated perfused kidney to reabsorb Na+ from the glomerular filtrate. In the absence of adenosine Na+ reabsorption was reduced from 97 to 50% whereas in the presence of adenosine was reduced to only 80% after 3 days of preservation. After 5 days of perfusion Na+ reabsorption was unaffected by the presence of adenosine and the amount resorbed was only 25-30% of the amount filtered.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1985

Effects of short-term hypothermic perfusion and cold storage on function of the isolated-perfused dog kidney.

The isolated-perfused dog kidney was used as a model to measure the effects of short-term hypothermic preservation on renal function and metabolism. Kidneys were cold-stored in Collins' solution, hypotonic citrate, or phosphate-buffered sucrose for 4 and 24 hr, or were continuously perfused for 4 and 24 hr with a synthetic perfusate. Following preservation kidneys were perfused with an albumin-containing perfusate at 37 degrees C for 60 min for determination of renal function. The results indicate that many of the effects of short-term preservation on renal function in dog kidneys are similar to results reported for rat and rabbit kidneys. Cold storage for 4 hr resulted in a large decrease in GFR (57%), but only a small decrease in Na reabsorption (from 97 to 87%). Cold storage for 24 hr caused a further decline in renal function (GFR = 95% decrease, Na reabsorption = 49-64%). Results were similar for all cold storage solutions tested. Perfusion for 4 hr was less damaging to renal function than cold storage. The GFR decreased only 14% and urine formation and Na reabsorption were practically normal. After 24 hr of hypothermic perfusion, the GFR was reduced by 79%, urine flow was normal, and Na reabsorption was 78%. There were no obvious biochemical correlates (adenine nucleotides, tissue edema, or electrolyte concentration) with the loss of renal function during short-term preservation. The results suggest that the isolated-perfused dog kidney can be used to test the effects of preservation on renal function, and yields results similar to those obtained using small animal models.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗