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Biomedical subjects

P O'Brien

Publications and source records attributed to P O'Brien.

At least 55 records · Page 3Linked to original sources
PubMed1990

Micro-organisms as fertilizers and pest control agents in agricultural crops.

Micro-organisms can potentially supplement or replace the use of chemical fertilizers and pesticides in many agricultural cropping systems. Their increased use may reduce the need for nitrogen and phosphorus fertilizers, particularly in legume and cereal crops, and provide a more ecologically sound method of controlling pests and phytopathogens. Recombinant DNA technology offers the potential to extend and improve these applications. However, genetically modified micro-organisms may occasionally themselves pose environmental risks. Model ecosystems such as intact soil-core microcosms may be useful for both testing efficacy and evaluating environmental risk prior to proceeding with field trials.

Bacteria↗
PubMed1990

Metastatic malignant melanoma in pregnancy.

A 29 year old expectant mother was critically ill at 27 weeks gestation with disseminated metastatic malignant melanoma and was treated with dacarbazine. A dramatic remission was induced and at 38 weeks gestation she went into labour spontaneously and delivered a healthy infant. She relapsed and died eight weeks post partum. This is the first reported use of dacarbazine in pregnancy.

Dacarbazine↗
PubMed1990

Orthotopic heart transplantation for complex congenital heart disease.

Orthotopic heart transplantation has become standard therapy for end-stage cardiomyopathy in children and adults, but there has been much less experience with transplantation for complex congenital heart disease. In this report experience with orthotopic transplantation in seven children with various forms of complex congenital heart disease is reviewed. Diagnoses included hypoplastic left heart syndrome in two (after stage I palliation), left ventricular diverticulum in one, single ventricle in two (dextrocardia, atrial situs inversus, and total anomalous pulmonary venous return in one patient and post-Fontan repair in the second), D-transposition of the great arteries and ventricular septal defect (post-Senning repair and ventricular septal defect closure) in one, and Ebstein's anomaly with biventricular dysplasia in one. Six of the seven were hospital survivors and there has been one late death at 2 1/3 years. Modifications of the standard operative technique to fit the anatomic variations in these defects are reviewed.

Adolescent↗
PubMed1989

The interaction of beta-N-methylamino-L-alanine with bicarbonate: an 1H-NMR study.

The mode of action of the neurotoxic, non-protein amino acid beta-N-methylamino-L-alanine (L-BMAA) is unknown. We have shown, using 1H-NMR spectroscopy, that L-BMAA forms a stable adduct with bicarbonate (probably a carbamate). The properties of this adduct may explain the observation that L-BMAA and N-methyl-D-aspartic acid appear to act at the same central nervous system receptors.

Amino Acids, Diamino↗
PubMed1989

Otitis media and hearing loss in the children of the Ruatoki valley: a continuing public health problem.

A longitudinal survey of ear disease using repeated otomicroscopy has demonstrated cases of persistent middle ear effusion, cholesteatoma and perforation in a group of 275 Maori children. The hearing of 194 of the children was assessed, and 25% of them were found to have a hearing loss. It is concluded a public health problem exists with these children. Improved detection and treatment of ear disease and hearing loss in this population is recommended.

Acoustic Impedance Tests↗
PubMed1989

Single-dose antibiotic prophylaxis in contaminated abdominal surgery.

Although perioperative antibiotic cover reduces the incidence of septic complications associated with abdominal surgery, the optimum duration of antibiotic exposure is open to question. This clinical trial compared the efficacy of a single dose of moxalactam (1 g intravenously) with an extended course of moxalactam (1 g intravenously for eight doses) in 1027 patients undergoing contaminated abdominal surgery. The wound infection rate was 5.4% (28/519) for the single-dose schedule and 6.1% (31/508) for the extended-cover regimen (the respective 95% confidence intervals being 3.6% to 7.7% and 4.2% to 8.6%). Over 80% of all patients undergoing abdominal surgery during the period of study were entered into the trial. There was no significant difference in the incidence of other complications between the two groups under study. It is concluded that a single dose of moxalactam is as effective as a 48-hour course when attempting to prevent infection after contaminated abdominal surgery.

Biliary Tract Surgical Procedures↗
PubMed1989

Complexes of zinc, copper, and nickel with the nonprotein amino acid L-alpha-amino-beta-methylaminopropionic acid: a naturally occurring neurotoxin.

The non-protein amino acid L-alpha-amino-beta-methylaminopropionic acid (L-MeDAP) causes motor neuron dysfunction in macaques. The amino acid is a potent chelator of divalent metal ions such as copper and zinc. Binding constants nickel(II) for copper(II) and zinc(II) with L-MeDAP have been measured. Some copper(II) complexes of L-MeDAP have been synthesized and characterized by their electronic, infrared, and epr spectra. These results are used to comment on the possibility that metal ion complexation in the central nervous system is involved in the expression of the meurotoxicity of L-MeDAP.

Amino Acids, Diamino↗
PubMed1989

Generation of PM2 DNA breaks in the course of reduction of chromium(VI) by glutathione.

The carcinogen chromate is efficiently taken up and reduced to chromium(III) compounds by various biological systems. To test the possible DNA damage induced in the course of chromium(VI) reduction, we used a combination of chromate with the reductant glutathione (GSH) as well as a green complex of chromium(V), which is formed in the reaction of chromate with GSH. The combination of chromate and glutathione was found to cause single-strand breaks in supercoiled circular DNA of the bacteriophage PM2. The green chromium(V) complex Na4(GSH)4Cr(V).8H2O, prepared from chromate and glutathione, also cleaved supercoiled PM2 DNA. No DNA-degrading effects were observed with either chromate or the final product of the reaction with GSH, a purple anionic chromium(III) GSH complex. The nature of the buffering agents revealed a strong influence on the extent of DNA strand breaks produced by chromate and GSH. A variation of the GSH concentration in the reaction with chromate and PM2 DNA, performed in sodium phosphate-buffered solutions showed an initial increase in the number of strand breaks at GSH concentrations up to 1 mM followed by a decline at higher GSH concentrations. Since neither chromate, when administered individually, nor the final product of chromium(VI) reduction, the purple chromium(III) GSH complex, produced any detectable DNA cleavage, the critical steps leading to DNA strand breaks occur in the course of the conversion of chromium(VI) to chromium(III) by GSH, the most abundant intracellular low molecular thiol. Moreover, the demonstration that DNA cleavage is induced in the presence of the chromium(V) complex identifies chromium(V) as the oxidation state of the metal, which is involved in the steps leading to DNA-damaging effects of chromate.

Bacteriophages↗
PubMed1989

Streptokinase use in children undergoing cardiac catheterization.

The development of cardiac catheterization procedures in the pediatric population has evolved from diagnostic in nature to present day advanced technology and interventions. A complication of vessel occlusion secondary to large catheters, length of procedures, and patient size requires immediate intervention. The advent of thrombolytic agents has provided a highly effective mode of treatment in restoring circulation. The use of streptokinase, its efficacy, side effects, and nursing management are discussed.

Cardiac Catheterization↗
PubMed1989

Discharge planning for children with heart disease.

Almost all children with heart disease are successfully cared for at home by their parents. Pediatric cardiovascular nurses play a major role in preparing parents to meet their child's medical needs, in aiding families to cope with a chronic condition, and in encouraging normal growth and development for their young patients. Through assessment, collaboration with other members of the health care team, planning with the family, teaching, counseling and supportive interventions, and evaluating care, nurses assist in a smooth transition to home and appropriate use of community resources.

Child↗
PubMed1988

Topological studies of monomeric and dimeric cytochrome c oxidase and identification of the copper A site using a fluorescence probe.

Beef heart cytochrome c oxidase was labeled at a single sulfhydryl group by treatment with 5 mM N-iodoacetylamidoethyl-1-aminonaphthalene-5-sulfonate (1,5-I-AEDANS) at pH 8.0 for 4 h. Sodium dodecyl sulfate gel electrophoresis revealed that the enzyme was exclusively labeled at subunit III, presumably at Cys-115. The high affinity phase of the electron transfer reaction with horse cytochrome c was not affected by acetylamidoethyl-1-aminonaphthalene-5-sulfonate (AEDANS) labeling. Addition of horse cytochrome c to dimeric AEDANS-cytochrome c oxidase resulted in a 55% decrease in the AEDANS fluorescence due to the formation of a 1:1 complex between the two proteins. Forster energy transfer calculations indicated that the distance from the AEDANS label on subunit III to the heme group of cytochrome c was in the range 26-40 A. In contrast to the results with the dimeric enzyme, the fluorescence of monomeric AEDANS-cytochrome c oxidase was not quenched at all by binding horse heart cytochrome c, indicating that the AEDANS label on subunit III was at least 54 A from the heme group of cytochrome c. These results support a model in which the lysines surrounding the heme crevice of cytochrome c interact with carboxylates on subunit II of one monomer of the cytochrome c oxidase dimer and the back of the molecule is close to subunit III on the other monomer. In order to identify the cysteine residues that ligand copper A, a new procedure was developed to specifically remove copper A from cytochrome c oxidase by incubation with 2-mercaptoethanol followed by gel chromatography. Treatment of the copper A-depleted cytochrome c oxidase preparation with 1,5-I-AEDANS resulted in labeling sulfhydryl groups on subunit II as well as on subunit III. No additional subunits were labeled. This result indicates that the copper A binding site is located at cysteines 196 and/or 200 of subunit II and that removal of copper A exposes these residues for labeling by 1,5-I-AEDANS. Alternative copper A depletion methods involving incubation with bathocuproine sulfonate (Weintraub, S.T., and Wharton, D.C. (1981) J. Biol. Chem. 256, 1669-1676) or p-(hydroxymercuri)benzoate (Li, P.M., Gelles, J., Chan, S.I., Sullivan, R.J., and Scott, R.A. (1987) Biochemistry 26, 2091-2095) were also investigated. Treatment of these preparations with 1,5-I-AEDANS resulted in labeling cysteine residues on subunits II and III. However, additional sulfhydryl residues on other subunits were also labeled, preventing a definitive assignment of the location of copper A using these depletion procedures.

Algorithms↗
PubMed1988

Toxicity following protein A treatment of metastatic breast adenocarcinoma.

The toxic effects of protein A (Prosorba, IMRE Corporation, Seattle, WA) treatments given as part of an on-line plasmapheresis or off-line procedure were determined in a Phase I Study. Patients were randomized and treated 12 times either once per week or three times per week with a Prosorba column containing 50 or 200 mg protein A. Treated plasma volumes varied from 150 ml off-line to 2000 ml on-line. Seven patients having advanced metastatic breast adenocarcinoma patients were evaluated. All had advanced progressive disease that was resistant to chemotherapy and/or radiation therapy. Greater than 50% regression of measurable tumor volume occurred in four of seven patients; an additional patient responded with 33.5% regression. Two patients with only bony metastases demonstrated stable disease for a 60-day period. Side effects resulting from protein A treatments included transient fever, chills, rigors, and infrequently nausea, vomiting, diarrhea, episodic hyper and/or hypotension, bronchospasm, venospasm, headache, joint and tumor pain. Mild to moderate reactions were seen in all patients regardless of clinical response, but abated spontaneously or were controlled with pretreatment and/or post treatment with antipyretics and/or antihistaminics. The side effects decreased notably during the course of the week with the more intense reaction occurring during the first treatment of the week. Side effects occurred regardless of column size or volume of plasma treated. In the course of 12 treatments, anemia requiring transfusion developed in two of seven patients. Significant tumor regression was obtained in this group of patients with advanced disease. In light of the mild to moderate side effects and tumor regression in five of seven of the patients treated, protein A treatment merits further evaluation to determine the effectiveness of this treatment in breast adenocarcinoma.

Adenocarcinoma↗
PubMed1988

Thermal studies on the interaction of water and microcrystalline cellulose.

The interaction between water and microcrystalline cellulose in the absence and presence of lactose has been studied by thermogravimetric analysis, differential thermal analysis and immersional calorimetry. The results indicate that most of the water held within a system used for the preparation of spherical granules by extrusion/spheronization is present as free water which may be readily lost by evaporation. There is approximately 0.856 mol of water per 100 g of microcrystalline cellulose which appears to be absorbed as structured water. Microcrystalline cellulose may therefore be described as a 'molecular sponge'. The enthalpy of fusion of the 'free' water offers a simple method of estimating the effective surface area of the microcrystalline cellulose.

Calorimetry↗
PubMed1987

The reaction of cytochromes c and c2 with the Rhodospirillum rubrum reaction center involves the heme crevice domain.

In order to define the interaction domain on Rhodospirillum rubrum cytochrome c2 for the photosynthetic reaction center, positively charged lysine amino groups on cytochrome c2 were modified to form negatively charged carboxydinitrophenyl lysines. The reaction mixture was separated into six different fractions by ion exchange chromatography on carboxymethylcellulose and sulfopropyl-Sepharose. Peptide mapping studies indicated that fraction A consisted of a mixture of singly labeled derivatives modified at lysines 58, 81, and 109 on the back of cytochrome c2. Fractions C1, C2, C3, and C4 were found to be mixtures of singly labeled derivatives modified at lysines 9, 13, 75, 86, and 88 on the front of cytochrome c2 surrounding the heme crevice. The photooxidation of the carboxydinitrophenyl-cytochrome c2 derivatives by reaction centers purified from R. rubrum was measured following excitation with a laser pulse. The second-order rate constant of fraction A modified at backside lysines was found to be 2.3 X 10(7) M-1 s-1, nearly the same as that of native cytochrome c2, 2.6 X 10(7) M-1 s-1. However, the rate constants of fractions C1-C4 were found to be 6 to 12-fold smaller than that of native cytochrome c2. These results indicate that lysines surrounding the heme crevice of cytochrome c2 are involved in electrostatic interactions with carboxylate groups at the binding site of the reaction center. The reaction rates of horse heart cytochrome c derivatives modified at single lysine amino groups with trifluoroacetyl or trifluoromethylphenylcarbamoyl were also measured. Modification of lysines 8, 13, 25, 27, 72, 79, or 87 surrounding the heme crevice was found to significantly lower the rate of reaction, while modification of lysines in other regions had no effect. This indicates that the reaction of horse heart cytochrome c with the reaction center also involves the heme crevice domain.

Binding Sites↗
PubMed1987

Reaction of cytochromes c and c2 with the Rhodobacter sphaeroides reaction center involves the heme crevice domain.

In order to define the interaction domain on Rhodobacter sphaeroides cytochrome c2 for the photosynthetic reaction center, positively charged lysine amino groups on cytochrome c2 were modified to form negatively charged (carboxydinitrophenyl)- (CDNP-) lysines. The reaction mixture was separated into several different fractions by ion-exchange chromatography on (carboxymethyl)cellulose. Tryptic digests of these fractions were analyzed by reverse-phase peptide mapping to determine the lysines that had been modified. Fraction A was found to consist of a mixture of singly labeled derivatives modified at lysine-35, -88, -95, -97, and -105 and several other unidentified lysines comprising 32% of the total. Although it was not possible to resolve these derivatives, all of the identified lysines are located on the front surface of cytochrome c2 near the heme crevice. The second-order rate constant for the reaction of native cytochrome c2 with reaction centers was 2.0 X 10(8) M-1 s-1, while that for fraction A was 20-fold less, 1.0 X 10(7) M-1 s-1. This suggests that lysines surrounding the heme crevice of cytochrome c2 are involved in electrostatic interactions with carboxylate groups at the binding site of the reaction center. The reaction rates of horse heart cytochrome c derivatives modified at single lysine amino groups with trifluoroacetyl or trifluoromethylphenylcarbamoyl were also measured. Modification of lysine-8, -13, -27, -72, -79, and -87 surrounding the heme crevice significantly lowered the rate of reaction, while modification of lysines in other regions had no effect. This indicates that the reaction of horse heart cytochrome c with the reaction center also involves the heme crevice domain.

Amino Acid Sequence↗
PubMed1987

Genetic analysis of UV mutagenesis of the Escherichia coli glyU gene.

By genetic analysis we examined UV mutagenesis of the Escherichia coli glyU gene. When carried by M13 phage mp9, glyU is subject to induced UV mutagenesis which is dependent on the umuC+ and recF+ genes. When carried by M13 phage mp8, glyU is not subject to induced UV mutagenesis. This difference is correlated with the nature of the target nucleotides: CTC in the mp9 derivative and GAG in the mp8 derivative. Thus, we conclude that the induced (umuC and recF dependent) mutagenesis is locally targeted on pyrimidine cyclobutane or 6-4 dimers. glyU carried by M13 is equally subject to uninduced UV mutagenesis whether carried by mp8 or mp9. This uninduced mutagenesis is independent of the umuC+, recF+ and recA+ genes and we hypothesize that it is regionally targeted on pyrimidine cyclobutane or 6-4 dimers in the vicinity of the target CTC and GAG nucleotides. The role of recF in UV mutagenesis was tested in two ways. First, mutagenesis of glyU carried by M13 mp9 in a recA730 genetic background was found to be recF dependent. Because recA730 renders induced UV mutagenesis partially constitutive, we conclude that the RecF product plays a direct role in UV mutagenesis rather than, or in addition to, any indirect regulatory role it may play. Second, UV mutagenesis of E. coli chromosomal glyU was found to be recF independent while UV mutagenesis of M13-bourne glyU was recF dependent. We conclude that the mechanism of induced UV mutagenesis of the E. coli chromosome is at least partly different from that of M13 phage and we discuss the biochemical basis for such a difference.

Bacterial Proteins↗