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Biomedical subjects

R M Nelson

Publications and source records attributed to R M Nelson.

At least 109 records · Page 6Linked to original sources
PubMed1986

Serum concentrations of prostacyclin and thromboxane in children before, during, and after cardiopulmonary bypass.

Twenty-six consecutive pediatric patients undergoing reparative procedures necessitating cardiopulmonary bypass were prospectively studied to determine changes in serum levels of 6-keto-prostaglandin F1 alpha and thromboxane B2. Cardiac lesions included acyanotic lesions (five patients), obstructive lesions (10 patients), and right-to-left shunts (11 patients). There was a significant (p less than 0.05) increase in 6-keto-prostaglandin F1 alpha from preoperative levels measured at the time of arterial and venous cannula insertion. This concentration was maintained throughout cardiopulmonary bypass and remained significantly elevated (p less than 0.001) in the recovery room, but returned to preoperative levels by the morning after the operation. Preoperative levels of thromboxane B2 varied widely and were not significantly different from intraoperative levels. The postoperative levels of thromboxane B2, however, were significantly different (p less than 0.05) from the intraoperative levels. In the pediatric age group undergoing cardiopulmonary bypass, 6-keto-prostaglandin F1 alpha and thromboxane B2 change during bypass but do not significantly differ when preoperative levels are compared to postoperative values.

6-Ketoprostaglandin F1 alpha↗
PubMed1985

The formation of chlorobenzene and benzene by the reductive metabolism of lindane in rat liver microsomes.

The major metabolite produced by incubating [14C]lindane with rat liver microsomes under anaerobic conditions was determined to be chlorobenzene, with lesser amounts of benzene also being formed. Using relatively high lindane concentrations (250 microM), four nonvolatile metabolites of lindane were also produced anaerobically, the predominant one being identified by mass spectrometry as tetrachlorocyclohexene (TCCH). TCCH, likewise, was reduced to chlorobenzene and benzene in microsomes under anaerobic conditions. Binding of [14C]lindane to microsomal protein occurred under aerobic as well as anaerobic incubation conditions; however, lindane protein binding was greatest in anaerobic incubations compared to those containing an atmosphere of air or 100% oxygen. Hemin reduced by dithionite also readily produced chlorobenzene and benzene from lindane. These results indicate that lindane interacts readily with heme and heme proteins, including cytochrome P-450, in the absence of oxygen to undergo multiple chloride eliminations forming chlorobenzene and benzene as end products.

Animals↗
PubMed1985

Postconceptional age and gentamicin elimination half-life.

We examined the correlation between the elimination half-life of gentamicin and postnatal or postconceptional age in 104 infants greater than 24 weeks to less than or equal to 48 weeks postconceptional age. A weak correlation was observed between half-life and postnatal age (R = -0.353). A better correlation existed between postconceptional age and half-life (R = -0.572). A plot of the log of the mean half-life against postconceptional age was virtually linear. We conclude that postconceptional age is a major determinant of an infant's ability to excrete gentamicin, and speculate that the relationship between half-life and decreasing postconceptional age is exponential.

Aging↗
PubMed1985

Cardiac tamponade due to an iatrogenic pericardial-diaphragmatic hernia.

Because of its ease, safety, and effectiveness, surgeons are increasingly using the subxiphoid approach to drain pericardial effusions and to insert epicardial pacemakers. Although we could find no previous reports of iatrogenic pericardial-diaphragmatic hernias in the literature, experience with a recent patient who developed this problem after a subxiphoid pericardial drainage suggests that it may become much more frequent. Physicians should strongly suspect this complication in patients with a triad of previous subxiphoid pericardial incision and signs of bowel obstruction and tamponade.

Aged↗
PubMed1985

Central nervous system involvement in congenital visceral fibromatosis.

Congenital visceral myofibromatosis is an uncommon disorder characterized by multiple tumors of myofibroblastic origin in the neonatal period. The natural history of the disorder has been well delineated. The myofibroblast is the cell of origin of the tumor. This is a report of a patient in whom multiple mesenchymal tumors occurred in the CNS as well as in other organs. Light and electron microscopic findings of the CNS lesions are similar to those of the somites and viscera.

Adult↗
PubMed1985

Clostridium perfringens bacteremia. Opportunist or killer?

Clostridia septicemia has traditionally been associated with severe histocytotoxic infections. Recently, due to better anaerobic culture techniques, clostridia bacteremia is seen with increasing frequency in patients without an obvious source of infection. The authors reviewed their experience with 29 patients with clostridia bacteremia. The overall mortality rate was 45 per cent. No obvious source for the clostridia bacteremia was identified in 21 patients (72%). Eighty-three per cent of the patients had polymicrobial infections. The patients were generally debilitated with significant associated systemic disease. Antibiotic therapy did not appear to have any effect on mortality. Patients with asymptomatic clostridial bacteremia are, in general, patients with advanced malignancies and chronic illnesses. Antibiotic therapy appears to have little effect on the patient's outcome.

Adult↗
PubMed1985

Antibiotic usage for methicillin-resistant Staphylococcus mycotic aneurysms.

Methicillin-resistant Staphylococcus aureus (MRSA) is increasing in incidence due to widespread use of cephalosporin antibiotics. These infections, generally, are characteristically hospital acquired and related to antibiotic pressure. The appearance of community acquired MRSA has recently been observed among IV drug abusers (IVDA). The duration and type of antibiotic therapy is controversial. Twenty patients with IVDA related mycotic aneurysms and associated soft tissue infections were evaluated. Particular attention was given to the bacteria cultured, the antibiotic therapy used and the response to therapy. Antibiotic use was inconsistent. Thirty per cent of the patients received no antibiotics. Although 62 per cent of the Staphylococcus aureus infections in this group were methicillin-resistant and quite extensive, the antibiotics used had no clinical importance. The need for vancomycin as therapy for extensive soft tissue infections with MRSA may be overrated and probably contributes to the development of increasing antibiotic resistance.

Adult↗
PubMed1985

Rhabdomyolysis and myoglobinemia in neonates.

Serial myoglobin determinations were made in 20 neonates during the first week of life to determine whether birth asphyxia results in ischemic damage to muscle with the subsequent pathologic release of myoglobin. Serum myoglobin values were significantly elevated in asphyxiated infants compared with control infants. High myoglobin values correlated with a longer duration of oliguria in the neonatal intensive care unit population. The value of urine dipstick testing for myoglobinuria screening was also evaluated. Infants with elevated myoglobin values were more likely to have a strongly positive urine dipstick for occult blood in the first 48 hours of life. These data suggest that ischemic damage to muscle with pathologic release of myoglobin occurs in the neonatal period and that urine dipstick testing provides a reasonable screening examination for myoglobinuria.

Asphyxia Neonatorum↗
PubMed1984

Characteristics, mortality, and outcome of higher-birth weight infants who require intensive care.

The improved outcome of small infants who have received intensive care is well documented; however, the mortality and morbidity of infants weighing greater than or equal to 2500 gm who require intensive care have not been emphasized. During a 2-year period these infants accounted for 41% of admissions and 34% of all deaths in our nursery. The most common diagnoses were pulmonary disease (32%), asphyxia (22%), congenital anomalies (18%), infant of diabetic mother (10%), hematologic disease (9%), and infection (4%). Mortality was 11% with 50% of the deaths from lethal malformations, 26% from asphyxia, 13% from infection, and 11% from miscellaneous causes. One half of the deaths were potentially preventable. According to developmental follow-up, over 90% of the survivors were developing normally. Thus, while outcome for survivors is usually good, mortality remains excessively high. This large and understudied group of infants requires increased investigative emphasis.

Birth Weight↗
PubMed1984

The development of capillaries in the telencephalon of beagle puppies.

The microvessels of the telencephalons of Beagle puppies between newborn and 72 hours of age were investigated ultrastructurally at 24-hour intervals. The morphometry of the microvasculature from the germinal matrix was compared with that of the microvasculature from the borderzone cerebral cortex. The endothelial cell walls of the microvessels from these two sites were similar during the study period, but the lumina of the matrical microvessels were significantly larger than the lumina of the control cortical microvessels. The proportion of matrical microvessels with large lumina undergoes progressive attrition with time. The values (areas) for the lumina of the matrical microvessels, and their distribution, come to resemble those of the cortex. The morphometry of the cortical microvasculature is comparatively static. The data suggest that there is an active modification in the microvasculature of the germinal matrix of the Beagle puppy in the immediate postnatal period.

Animals↗
PubMed1984

Murine monoclonal antibody to a single protein neutralizes the infectivity of human cytomegalovirus.

Murine monoclonal antibodies to human cytomegalovirus (CMV) strain AD169 were selected that neutralized virus infectivity. One monoclonal antibody-producing hybridoma, 1G6, was used to produce ascites fluid from which immunoglobulin was isolated. This antibody efficiently neutralized CMV AD169, other laboratory strains (Towne, Davis), and clinical isolates of CMV in early tissue culture passage (less than 10) in the absence of complement. The antibody immunoprecipitated a single 86,000-dalton protein from both laboratory and clinical strains. This viral protein was demonstrated by indirect immunofluorescence to be localized in the cytoplasm of CMV-infected cells.

Animals↗
PubMed1984

Alteration of motor-unit discharge characteristics in aged humans.

The purpose of this study was to determine and compare the discharge characteristics of single motor-unit action potentials (SMUAPs) in young and aged subjects during 5, 10, and 20 percent of maximum voluntary contraction (MVC) of the abductor digiti minimi manus muscle. Three decades of aged subjects ranging from 60 to 90 years of age were compared with a group of 20 to 35 year olds. Specially constructed fine-wire bifilar recording electrodes were used, and SMUAPs were identified by interactive computer processing. Although the results did not reach a statistically significant level, they showed the 70- to 79-year-old age group had the longest mean interspike intervals (ISI) in each of the three percentages of MVC. The prolonged ISI indicate a slow motor-unit discharge rate. In addition, the 70- to 79-year-old group had a statistically significant floating standard deviation, indicating increased variability of discharge, and a significantly different negative floating serial correlation coefficient. All three factors describing motor-unit discharge behavior in the 70- to 79-year-old age group suggest possible substitution of larger motor units for smaller motor units normally active at low tensions.

Action Potentials↗
PubMed1984

Iatrogenic hiatal and diaphragmatic hernias.

Seven patients with hernias occurring after Belsey hiatal hernia repair are described. These hernias were of two types. Four occurred through the hiatus, had the appearance of a parahiatal hernia, and were attributed to the failure to correct a shortened esophagus. In three patients the hernia occurred through a disrupted counterincision in the diaphragm. In the second group postoperative abdominal distension and possibly technical faults were incriminated. In the first group satisfactory repair was achieved by a Collis-Belsey gastroplasty and an antireflux procedure. In the second group reduction of the hernia and resuture of the diaphragm incision encompassing all layers corrected these life threatening hernias.

Female↗
PubMed1984

Comparison of porcine valve xenografts with mechanical prostheses. A 7 1/2 year experience.

A total of 479 valve replacements were performed in 469 patients for aortic, mitral, and tricuspid disease. A total of 529 valves were implanted (311 Carpentier-Edwards, 118 Hancock, 94 Björk-Shiley, and six other mechanical valves). Of the 479 operations, 51.1% (245) were carried out in male patients and 48.9% (234) were carried out in female patients. The mean age was 57.6 years; however, 28.6% (137) of the operations were performed in patients over 65 years of age. One hundred five patients (21.9%) had had previous cardiac operations of one type or another. Follow-up was 99.6% and the average length of follow-up was 36.2 months. The overall operative mortality was 5.6%. The operative mortality in the isolated aortic valve replacement group was 2.0% and that in the mitral valve replacement group, 4.4%. There was a 5.9% valve explant rate in the Hancock series; however, no valve explants were required because of valve dysfunction in either the Carpentier-Edwards or the Björk-Shiley groups. The thromboembolic rate in the aortic valve position was 2.4, 1.1, and 2.1 emboli per 100 patient-years in the Hancock, Carpentier-Edwards, and Björk-Shiley groups, respectively. The thromboembolic rate in the mitral valve position was 2.8, 2.2, and 1.0 emboli per 100 patient-years in the Hancock, Carpentier-Edwards, and Björk-Shiley groups, respectively.

Aged↗