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Biomedical subjects

R O'Brien

Publications and source records attributed to R O'Brien.

At least 55 records · Page 3Linked to original sources
PubMed1984

The 'fixed' removable partial denture: report of case.

Careful monitoring of tissue that had been the site of three previous surgical procedures was necessary, but the patient needed a functional, esthetically acceptable prosthesis. The Andrews bridge was selected because it combines the stabilizing qualities of a fixed prosthesis with the accessibility to the tissues of a removable prosthesis. The recurring nature of the verrucous carcinoma along with extensive tissue loss were additional factors in selecting this appliance. The final results satisfied all the criteria. The patient has been seen at regular follow-up visits for 2 years since the last surgical procedure and there has been no clinical change in the previously involved tissue. The patient has tolerated the prosthesis well and is satisfied with her appearance.

Carcinoma, Papillary↗
PubMed1984

Pre-B cell acute lymphoblastic leukemia in the newborn.

Leukemia in the newborn is an infrequent disease that has not been well defined using modern laboratory techniques. We describe two infants, one at birth and one at four weeks, with acute lymphoblastic leukemia. The blasts from each patient were studied in great detail, using a battery of cytochemical and immunologic procedures in addition to ultrastructural studies. Immunologic cell marker studies, not previously reported in congenital leukemia, showed the lymphoblasts from each infant to be of the pre-B cell phenotype. Each infant relapsed, one after a 17-week clinical remission and the other after a 44-week remission. The former has died while the latter is in a second remission. The subtype of pre-B cell acute lymphoblastic leukemia (ALL) which in childhood appears to confer an unfavorable prognosis, may have the same significance in neonatal ALL.

Antineoplastic Agents↗
PubMed1981

The third component of complement: covalent attachment of a radioactive sugar to the labile binding site of C3 via the alternative pathway.

A complement- (C) fixing particle consisting of agarose beads to which 5-thioglucose was attached by a --S--S-- bond (agarose-thioglucose) was employed to investigate the mechanism of attachment of C3 to surfaces. When whole serum containing [125I] C3 was incubated with agarose-thioglucose, labeled C3b was taken up in a form that was not removed by 2 M NaCl but was released by 10 mM dithiothreitol. Deposition of DTT-releasable C3b was dependent upon the alternative pathway of C activation. Gel electrophoresis of DTT-releasable C3b from similar experiments performed with unlabeled serum and agarose-[3H]thioglucose showed that the liberated C3b contained a molecule of radioactive thioglucose attached to the alpha'-chain by a covalent bond that was stable to mercaptoethanol. We propose that the thioglucose-alpha' chain bond was formed during the course of C activation by a reaction between the "labile binding site" of newly released C3b and the (then) particle-bound sugar. This formulation implies that the reaction by which C3b attaches to 5-thioglucose in this system is the reaction responsible for opsonization by C3b, and that the C3b-linked sugar represents a marker for the labile binding site. Incubation of the particle-bound C3b in serum resulted in the cleavage of the covalently linked alpha'-chain to several smaller polypeptides, the major cleavage product having a m.w. of 70,000.

Binding Sites↗
PubMed1980

Controlled trial of behaviour therapy, pharmacotherapy, and their combination in the treatment of obesity.

Behaviour therapy, pharmacotherapy, and a combination of the two were compared in 120 obese women and 14 obese men during six months of treatment for obesity and at one-year follow-up. Patients who received the appetite suppressant fenfluramine lost 14.5 kg and those who received the combined treatment lost 15.3 kg, both significantly more than those who received only behaviour therapy (10.9 kg). One-year follow-up of all living patients who completed treatment showed a striking reversal of these effects: behaviour-therapy patients regained only 1.9 kg, significantly less than pharmacotherapy patients (8.2 kg) and combined-therapy patients (10.7 kg). Weight changes of the 14 men did not differ from those of the women. Although pharmacotherapy produced more rapid initial weight loss than behaviour therapy, it was followed by more rapid weight gain after treatment. Addition of pharmacotherapy apparently compromised the long-term effects of behaviour therapy. Better maintenance of weight loss and lower costs favour behaviour therapy over pharmacotherapy for the treatment of obesity.

Behavior Therapy↗
PubMed1979

Vitamin B12 absorption studied by vascular perfusion of rat intestine.

The study of vitamin B12 release from the ileal enterocyte has been hampered by the fact that B12 does not cross the serosa of traditional everted ileal sacs. We studied this release by perfusing the superior mesenteric arteries of starved, heparinized, etherized rats and collecting perfusate from the superior mesenteric vein. The rats were fed 57CoB12 well before study. The standard perfusion medium was Krebs-Henseleit-NaHCO3 buffer containing glucose, dextran, albumin, propranolol, and dexamethasone. The preparation utilized glucose and O2, produced lactate, and was relatively impermeable to [14C]inulin, to D-xylose, and to 57CoB12 bound to an inert human IF. Glucose placed in the gut lumen was transported much more rapidly than D-xylose. Vitamin B12 emerged in the perfusate bound to a protein with a molecular size similar to that of TC II. IF could not be identified in the perfusate. Rat serum, independently of its unsaturated TC II content, increased the rate of transfer of B12 into the perfusate.

Anemia, Megaloblastic↗
PubMed1979

Effect of colchicine on guinea pig intrinsic factor-vitamin B12 receptor.

Colchicine can induce the malabsorption of vitamin B12 and other nutrients. Previous investigations have suggested but not proved that this malabsorption was due to a lesion in the ileal mucosa. Employing the receptor assay of M. Katz and B. A. Cooper (J Clin Invest 54:733-739, 1974), the authors have observed a dose-related, reversible reduction in the quantity of intrinsic factor-vitamin B12 (IF-B12) receptor (from 5.78 ng to 1.3 ng of B12 binding) in the intestinal mucosa of guinea pigs fed 0.05-0.25 mg/100 g colchicine/day for 3 days. Malabsorption of vitamin B12 was also demonstrated in vivo in similarly treated animals. Increasing intestinal motility with cascara sagrada had no effect on the IF-B12 receptor. The quantity of IF-B12 receptor and the amount of vitamin B12 absorbed increased markedly to greater than normal levels during recovery from a 3-day course of colchicine. The total number of intestinal cells decreased after colchicine administration and increased during recovery; however, the fluctuations observed were not sufficient to explain the changes in the quantity of receptor. Histologic examination of the ileal mucosa showed a decrease in the population of villus cells after colchicine. The correlation between the changes in receptor quantity and in vivo B12-absorption prove that the IF-B12 receptor is a critical limiting factor in B12 absorption.

Animals↗
PubMed1977

Novel enzymic machinery for the metabolism of oxalacetate, phosphoenolpyruvate, and pyruvate in Pseudomonas citronellolis.

The metabolic pathways for the interconversion of oxalacetate, phosphoenolpyruvate, and pyruvate in Pseudomonas citronellolis form an interlocking system (Scheme 1) that would appear to require complex regulatory mechanisms to permit a proper flow of metabolites through the pathways and to prevent futile cycling. Oxalacetate decarboxylase (I in Scheme 1), P-enolpyruvate synthase (II), P-enolpyruvate carboxylase (III), and pyruvate kinase (V) are constitutive enzymes in this organism. Pyruvate carboxylase (VI) is inducible and has its highest activity in cells grown on glucose or lactate, moderate activity in cells grown on acetate, citrate, or glutamate, and virtually no activity in aspartate-grown cells. P-enolpyruvate carboxykinase (IV) was not detected. The presence of these five enzymes in a single cell has not been previously reported. In Scheme 1, three futile cycles are possible: the simultaneous operation of Reactions I and VI; of Reactions II and V; or of I, II, and III. An examination of the regulatory properties of the individual enzymes after partial purification offers support for the hypothesis of an intricate regulatory system. Oxalacetate decarboxylase (I) is inhibited by acetyl-CoA; phosphoenolpyruvate carboxylase (III) is activated by acetyl-CoA and ADP and inhibited by aspartate; phosphoenolpyruvate synthase (II) is inhibited by 5'-AMP and phosphoenolpyruvate; and pyruvate kinase (V) is activated by 5'-AMP and 2 keto, 3-deoxy,6-phosphogluconate and inhibited by ATP. The presence of metabolites with reciprocal but reinforcing functions is noteworthy. As an example, acetyl-CoA both inhibits the breakdown of oxalacetate and stimulates its formation. Only pyruvate carboxylase appears to be regulated by the carbon substrates of the growth medium.

Acetyl Coenzyme A↗
PubMed1977

Intracranial calcifications in childhood leukemia. An association with systemic chemotherapy.

Children with acute lymphocytic leukemia were examined for evidence of intracranial calcifications with roentgenograms of the skull and computerized tomography. Of 39 children in their initial complete remission, ten were found to have subcortical cerebral calcifications. Significant associations were found between the presence of cerebral calcifications and systemic treatment with large cumulative doses of methotrexate.

Adolescent↗
PubMed1975

Frequency and duration of interval training programs and changes in aerobic power.

This study was designed to ascertain whether 7- and 13-wk interval training programs with training frequencies of 2 days/wk would produce improvement in maximal aerobic power (VO2max) comparable to that obtained from 7- and 13-wk programs of the same intensity consisting of 4 training days/wk. Sixty-nine young healthy college males were used as subjects. After training, there was a significant increase in VO2max (bicycle ergometer, open-circuit spirometry) that was independent of both training frequency and duration. However, there was a trend for greater gains after 13 wk. Maximal heart rate (direct lead ECG) was significantly decreased following training, being independent of both training frequency and duration. Submaximal VO2 did not change with training but submaximal heart rate decreased significantly with greater decreases the more frequent and longer the training. Within the limitations of this study, these results indicate that: 1) maximal stroke volume and/or maximal avO2 difference, principle determinants of VO2max, are not dependent on training frequency nor training duration, and 2) one benefit of more frequent and longer duration interval training is less circulatory stress as evidenced by decreased heart rate, during submaximal exercise.

Adult↗