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Biomedical subjects

R Singleton

Publications and source records attributed to R Singleton.

At least 37 records · Page 2Linked to original sources
PubMed1990

Neuropathy in Navajo children: clinical and epidemiologic features.

We describe a rare and apparently unique neuropathic syndrome among Navajo children living on the Navajo Reservation. Clinical features include sensorimotor neuropathy, corneal ulcerations, acral mutilation, poor weight gain, short stature, sexual infantilism, serious systemic infections, and liver derangement including Reye's syndrome-like episodes. Progressive CNS white matter lesions were diagnosed through magnetic resonance imaging. We identified 20 definite and 4 probable cases occurring between 1959 and 1986. Mean age at the time of 1st recognized symptom was 13 months (range, 1 month to 4 years 6 months). Ten individuals have died; 6 of the deaths occurred before 5 years of age. The incidence of this syndrome on the western Navajo reservation is 5 times higher than that on the eastern reservation (38 compared with 7 cases per 100,000 births). Although the etiology is unknown, this syndrome is consistent with an inborn error of metabolism, inherited in an autosomal recessive manner.

Adolescent↗
PubMed1986

Preliminary observation of impaired water excretion in treated status asthmaticus.

Patients in status asthmaticus often have elevated plasma antidiuretic hormone levels. To determine if children in status asthmaticus have impaired water excretion and an increased risk of developing significant hyponatremia when given a fluid challenge, five consecutive patients who showed moderate asthmatic symptoms after taking two doses of epinephrine hydrochloride were given a fluid challenge (20 mL/kg of 5% dextrose in 0.2% normal saline solution given intravenously over 30 minutes followed by maintenance fluids [1,500 mL/sq m/24 hr] for 50 minutes). Urine was collected at 20-minute intervals for measurement of free-water clearance and percent water-load excretion in 80 minutes. This protocol was repeated 24 to 48 hours later, after clinical improvement. None of the patients was hyponatremic during status asthmaticus before water loading. However, four of five patients were mildly hyponatremic (serum sodium level between 130 and 132 mEq/L) between status asthmaticus and after clinical improvement. These same four patients also became mildly hyponatremic after fluid challenge during status asthmaticus. Maximal free-water clearance and percent water load excretion in 80 minutes were significantly lower during status asthmaticus after fluid challenge compared with results obtained after water loading when the patients' conditions were clinically improved. We conclude that patients in status asthmaticus have impaired water excretion after water loading but with a small risk of significant hyponatremia; a patient remaining in status asthmaticus and given large volumes of hypotonic fluid over a prolonged period of time may be at higher risk for significant hyponatremia.

Adolescent↗
PubMed1986

Long-term complications in a premature infant with tracheoesophageal fistula.

This is a report of the short- and long-term complications in a premature infant with tracheoesophageal fistula, including those related to central venous alimentation, seizures, chylothorax, bronchopulmonary dysplasia, dental erosions, gastroesophageal reflux, pulmonary problems, and gall stones. It offers analyses of possible alternate methods and treatments, which may have provided a better course.

Abnormalities, Multiple↗
PubMed1986

Multiple organ donation: its impact on the recovery of cadaver kidneys.

Cyclosporin A not only has improved renal allograft survival but it also has caused a renewed interest in cardiac and hepatic transplantation. The South Texas Organ Bank was sensitive to the need for multiple organ donors and also concerned that the recovery of multiple organs could have a negative impact on the quantity or quality of kidneys recovered. From July 1983 through March 1985 cadaveric kidneys were obtained from 43 renal donors and multiple vital organs were obtained from 11 additional donors. There was no statistical difference between the renal and multiple organ donors in the incidence of renal contamination, post-transplant acute renal failure or renal discard rate (p greater than 0.3 in each comparison). No donor family rescinded permission for renal donation because other vital organs were requested. Urologists involved in cadaveric renal recovery are encouraged to view every cadaver donor as a potential multiple organ donor.

Adolescent↗
PubMed1982

Cytochrome c3 from the sulfate-reducing anaerobe Desulfovibrio africanus Benghazi: antigenic properties.

Antisera were prepared against cytochromes c3 from Desulfovibrio africanus, D. vulgaris, and D. salexigens. Cross-reactions were observed between antisera to D. vulgaris and D. africanus cytochromes and heterologous cytochromes c3. A weak cross-reaction with antisera against both D. vulgaris and D. africanus cytochromes and the acid form of the D. salexigens cytochrome was seen; the basic form did not react.

Cross Reactions↗
PubMed1980

Cardiac myxoma.

Ten patients with cardiac myxoma were reviewed. The ranged from 23 months to 60 years old. Echocardiography was the most helpful noninvasive diagnostic technique. The tumor was demonstrated by angiocardiography, left atrial myxomas frequently migrating to the left ventricle in diastole. Hemodynamically, left atrial myxomas were associated with moderately severe pulmonary hypertension and simulated mitral stenosis or insufficiency and right atrial myxomas, with right atrial hypertension. There were 7 myxomas in the left atrium, 2 in the right atrium, and 1 in the right ventricle. Eight patients underwent open-heart operation with removal of the myxoma, 1 had concomitant tricuspid valve replacement, and 1 had biopsy of the right ventricle only. The other patient was a Jehovah's Witness and refused operation. One patient died of cardiac arrest intraoperatively, and another died of a bilateral cerebral infarct. One patient had recurrence requiring reoperation. Postoperative hemodynamic and clinical improvement was more striking in patients with a left atrial myxoma presumably due to a normal mitral valve in contradistinction to the tricuspid valve.

Adult↗
PubMed1979

Cytochrome c3 from the sulfate-reducing anaerobe Desulfovibrio africanus Benghazi: purification and properties.

Cytochrome c3 was purified from Desulfovibrio africanus Benghazi by extraction with alkaline deoxyribonuclease, fractionation with ammonium sulfate, batch elution from carboxymethyl Sephadex followed by chromatography on the same resin, and gel filtration on Sephadex G-75. The preparation was judge homogeneous by a variety of criteria. The molecular weight was determined in an analytical ultracentrifuge, and values between 14,400 and 15,490 were obtained, depending upon the presumed value of partial specific volume. Gel filtration on a calibrated column of Sephadex G-75 gave a value of 14,900 daltons. The amino acid composition was very similar to that observed for the cytochrome from other species of Desulfovibrio, with the exception of increased levels of ThR and PhE. S-Carboxymethylation of the protein before and after heme removal by HgCl2 demonstrated eight Cys molecules involved in heme binding or four heme sites per molecule. Titration with sodium dithionite under N2 gave an electrochemical potential (E' 0) of -276 mV relative to the normal hydrogen electrode. Electrochemical titration of the cytochrome gave a Nernst plot with two linear regions with E' 0 values of -0.376 and -0.534 V. The spectra produced at various potentials exhibited shifts in isosbestic points upon reduction, suggesting changes in conformation during the reaction.

Amino Acids↗
PubMed1977

Comparison of proteins from thermophilic and nonthermophilic sources in terms of structural parameters inferred from amino acid composition.

The amino acid composition of 14 different proteins from thermophilic bacteria were compiled along with the amino acid compositions of 56 corresponding proteins from nonthermophilic sources. A comparison was made between proteins serving the same catalytic function, and significant differences in composition were noted for those proteins from thermophilic bacteria. However, no consistent pattern was evident and the differences were often small. The two data pools were treated as two distinct classes and a thermophilic versus non-thermophilic comparison of amino acid composition was made using the Student's t-test. Significant differences in composition were found for Asx (sum of Asp and Asn, if known), Ser, and Arg. Both classes of data have similar standard deviations for the mean of any single amino acid, suggesting a similar tolerance of variation in the two classes of proteins. This would argue against the hypothesis that thermophiles exhibit a greater frequency of errors in protein synthesis. The amino acid compositions were used to calculate structural parameters (% helix, % beta, % turn, hydrophobicity, and melting temperatures) for the two classes of proteins. Of these, only the predicted % beta content was significantly lower for proteins of thermophilic origin. No differences in hydrophobicity or predicted melting temperature were observed for the two classes of proteins. This study supports the hypothesis that while small differences may occur in the amino acid composition of thermophilic proteins, they are quite varied and often are very subtle.

Amino Acids↗
PubMed1977

Analysis of left ventricular function from multiple gated acquisition cardiac blood pool imaging. Comparison to contrast angiography.

Global ventricular function was evaluated by both multiple gated cardiac blood pool scans (MUGA) and contrast ventriculograms in a group of 17 patients with suspected coronary artery disease. The contrast ventriculograms were analyzed frame by frame to generate a volume versus time curve for each patient, while the tracer data were analyzed by two methods: 1) the standard method, in which the left ventricle is identified on the end-diastolic frame and the background corrected activity under the region of interest obtained from the entire cardiac cycle, and displayed as a time versus activity curve; and 2) by a semi-automatic method in which the computer applies a threshold detection program to define the ventricular borders, and activity in the chamber at each point in the cardiac cycle is defined after background correction. The tracer data in each patient were analyzed independently by four observers. The tracer data correlated with the contrast data on a point by point basis r = 0.87 for the standard method, and 0.93 for the semi-automatic technique. An F test of variance revealed the semi-automatic method superior to the standard approach (P less than 0.05).

Computers↗