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Biomedical subjects

J D Roberts

Publications and source records attributed to J D Roberts.

At least 145 records · Page 8Linked to original sources
PubMed1985

Low-dose cytosine arabinoside in the myelodysplastic syndromes and acute myelogenous leukemia.

Seven patients with a myelodysplastic syndrome or "smoldering" acute myelogenous leukemia were treated with cytosine arabinoside in low dosage. Four patients experienced transient, partial responses characterized by improved peripheral blood counts, cessation of transfusion requirements, and a decreased incidence of infection. Treatment was associated with significant, transient hematologic toxicity. The appropriate clinical role of low-dose cytosine arabinoside remains uncertain.

Adult↗
PubMed1985

Immunocytochemical evidence for neuroendocrine differentiation in human breast carcinomas.

Normal and neoplastic human breast tissues have been stained with antibodies recognizing neuroendrocrine differentiation. Fifteen out of 44 (34 per cent), breast carcinomas stained positively with monoclonal antibody LICRLON-E36, and 11 out of 44 (25 per cent) of these tumours stained with an antibody raised against neuron-specific enolase (NSE). Eight tumours stained positively with both antibodies. No correlation was observed between staining with these antibodies and the tumour histology, nor with the degree of cellular differentiation as indicated by staining with several cell surface directed monoclonal antibodies. Ultrastructural analysis of a series of breast tumours showed the presence of membrane-bound dense-core vesicles in almost all tumours, including E36 and NSE positive and negative tumours. The presence of these structures appears to be of little value in predicting neuroendocrine differentiation.

Antibodies, Monoclonal↗
PubMed1985

Extracellular fluid deficit following operation and its correction with Ringer's lactate. A reassessment.

The changes in extracellular fluid volume (ECV) in two groups of surgical patients, one receiving Ringer's lactate solution intraoperatively and the other receiving only dextrose and water, were assessed. A deficit in the ECV, as measured by radioactive sulfate, of 1.9 +/- 0.8 l (p less than 0.003) compared to the preoperative volume was found in the dextrose group. This was accompanied by a decrease in the mean creatinine clearance (-13% p less than 0.01), the mean urinary sodium excretion (-57% p less than 0.05), and the mean rate of clearance of the sulfate tracer (-18% p less than 0.01). The use of intraoperative Ringer's lactate (1660 cc +/- 96 cc) resulted in no change in the ECV, an increase in the mean creatinine clearance (+10% p less than 0.05), and no change in sodium excretion or tracer clearance. As a result of these findings, it appears that postoperative sodium retention is a physiologic response to a decreased ECV, which can be prevented by the administration of Ringer's lactate.

Adult↗
PubMed1984

Structure of the liver alcohol dehydrogenase-NAD+-pyrazole complex as determined by 15N NMR spectroscopy.

The structures of the liver alcohol dehydrogenase (LADH)-NAD+-pyrazole and LADH-NAD+-4-ethylpyrazole complexes were investigated by 15N nuclear magnetic resonance (NMR) spectroscopy. 15N chemical shifts were obtained for 15N-labeled inhibitors and 15N-labeled coenzyme bound in the ternary enzyme complexes. The structures of the two inhibitor complexes appear to be very similar. 15N NMR studies of model pyrazole-zinc chloride complexes were carried out to determine the effect of zinc complexation on pyrazole chemical shifts. The N1 nicotinamide chemical shift of the coenzyme of the LADH-NAD+-pyrazole complex demonstrates that the NAD+ is converted to a dihydronicotinamide derivative in the complex. The N1 chemical shift of the pyrazole in the ternary complex is consistent with covalent bond formation between pyrazole N1 and the nicotinamide ring of the coenzyme. The N2 chemical shift of the pyrazole in the ternary complex indicates that the nucleus of this nitrogen is about 40 ppm more shielded than those of the N2 nitrogens of typical pyrazoles. Such shielding is expected as the result of direct complexation of N2 to the active-site zinc. Shift comparisons with zinc-pyrazole complexes indicate a high degree of inner-sphere coordination of the pyrazole N2 to the active-site zinc in the ternary complex.

Alcohol Dehydrogenase↗
PubMed1984

Bovine alpha- and beta-thrombin. Reduced fibrinogen-clotting activity of beta-thrombin is not a consequence of reduced affinity for fibrinogen.

beta-Thrombin, a product of the limited proteolysis of alpha-thrombin, is characterized by greatly reduced fibrinogen-clotting activity as compared to alpha-thrombin but with unchanged activity toward ester substrates. The present study was designed to elucidate the basis for the changes in the catalytic activity resulting from the conversion of bovine alpha-thrombin to bovine beta-thrombin. Fibrinogen was utilized as a competitive inhibitor in the hydrolysis of a peptide nitroanilide substrate by bovine alpha- and beta-thrombin. The Ki values obtained for fibrinogen in these experiments were similar for alpha- and beta-thrombin (about 10 microM). Similar values for Ki were obtained when fibrinogen was used to inhibit the inactivation of bovine alpha- and beta-thrombin by diisopropylphosphorofluoridate. These experiments suggested that the conversion of bovine alpha- to beta-thrombin does not affect the fibrinogen-binding site on thrombin. Differences in the reactivity of functional groups at the active site were then explored. beta-Thrombin was observed to undergo modification at the active site histidine at a slower rate than that of alpha-thrombin when reacted with either tosyllysyl chloromethyl ketone or diethyl pyrocarbonate. It is suggested that the difference in the fibrinogen-clotting activity of these two forms of thrombin can result from changes in the reactivity of the active site histidine residue.

Affinity Labels↗
PubMed1984

Efficacy and toxicity of 4-(2-sulfonatoethylthio)-cyclophosphamide cyclohexylamine salt (ASTA Z 7557, INN mafosfamide) after intraperitoneal administration to mice.

4-(2-sulfonatoethylthio)-cyclophosphamide cyclohexylamine salt (AZ; ASTA Z 7557) is a cyclophosphamide (CP) analog designed to be without acute bladder toxicity and to undergo spontaneous activation yielding phosphoramide mustard (PM). Studies in murine systems with intraperitoneal (i.p.) administration suggest that AZ may have a therapeutic index favorable to CP without an associated risk of bladder toxicity. Pericapsular hepatic fibrosis after i.p. administration suggests that regional AZ therapy may cause local toxicity. Further study of this compound, especially with intravenous (i.v.) administration, will be of interest.

Animals↗
PubMed1984

Monoclonal antibody LICR-LON-E36 recognizes gonadotrophs in female rat pituitaries.

The distribution of the antigen localized by monoclonal antibody LICR-LON-E36 has been studied by means of light and electron microscopical immunocytochemical procedures on resin-embedded pituitaries from male and female rats. Using both immunoperoxidase and immunogold labeling techniques, the localization of LICR-LON-E36 has been compared with that obtained with antibodies against the beta subunit of rat luteinizing hormone (beta LH) and human follicle stimulating hormone (beta FSH), porcine adrenocroticotropic hormone (ACTH) and rat S-100. LICR-LON-E36 is localized in a portion of beta LH-containing cells in female rat pituitaries and where present both antigens are localized within the same storage granules. LICR-LON-E36 is rarely detectable within beta LH-containing cells of male rat pituitaries that also stain positively with anti-beta FSH antibodies. ACTH and S-100 were localized within different cell populations.

Adrenocorticotropic Hormone↗
PubMed1984

Immobilization hypercalcemia in acute spinal cord injury treated with etidronate.

Hypercalcemia developed in a 30-year-old C5 quadriplegic six months after he received a gunshot wound in the cervical spine. Short-term treatment consisted of fluids and diuretics, but conventional drug therapy for long-term maintenance of normocalcemia was not effective. A regimen of etidronate disodium was then instituted, which resulted in normocalcemia. When use of this drug was discontinued at intervals during the therapy, the hypercalcemia recurred. The patient's condition was maintained on the etidronate regimen until full mobilization occurred, at which time the drug therapy was discontinued and normocalcemia persisted. This case represents, to our knowledge, the first reported success with the use of etidronate in the treatment of hypercalcemia in the immobilized patient with acute spinal injury.

Acute Disease↗
PubMed1983

The floating heart or the heart too fat to sink: analysis of 55 necropsy patients.

Certain clinical and morphologic findings are described in 55 patients whose hearts at necropsy contained so much fat that they floated in water. The patients were 47 to 89 years old (mean 67). Symptomatic coronary heart disease was present in 28 (51%) and valvular heart disease (mitral stenosis) in 3 (5%). The heart at necropsy was enlarged (greater than 350 g for women and greater than 400 g for men) in 45 patients (82%). The mean heart weight for the 31 women was 470 g and for the 24 men, 515 g. In addition to the severe increase in fat in the atrioventricular sulci and over both ventricles, the amount of fat in the atrial septum was increased in all patients. In 14 patients (25%), the thickness of the atrial septum cephaled to the fossa ovale was greater than or equal to 2 cm. Excessive fat in this location is called "lipomatous hypertrophy of the atrial septum." Of the 16 patients (29%) with fatal acute myocardial infarction, 7 (44%) had rupture of either the left ventricular free wall or ventricular septum. The high frequency of cardiac rupture in these patients supports the contention that rupture during acute myocardial infarction is more common in the fatty than in the non-fatty heart.

Adipose Tissue↗
PubMed1983

The bacteriophage lambda O replication protein: isolation and characterization of the amplified initiator.

The bacteriophage lambda O protein participates in the initiation of lambda DNA replication. The lambda O gene was cloned into plasmid pKC30 such that its expression was controlled by the lambda PL promoter. A lambda prophage-coded thermosensitive cI repressor was used to regulate transcription of the cloned O gene. Thermal inactivation of the lambda cI repressor resulted in overproduction of the O protein until it constituted approximately 20% of the total cellular protein of Escherichia coli. A simple three-step purification protocol was developed that yields several milligrams of homogeneous O protein per gram of cell paste. The precise position of the O gene in the known lambda DNA sequence was identified from the amino-terminal sequence of the isolated O protein. Purified O protein stimulated the replication of plasmid lambda dv DNA in vitro and specifically bound to duplex DNA fragments carrying the lambda replication origin.

Amino Acid Sequence↗
PubMed1983

Measurements of cytoplasmic and vacuolar pH in Neurospora using nitrogen-15 nuclear magnetic resonance spectroscopy.

The nitrogen-15 chemical shift of the N1 (tau)-nitrogen of 15N-labeled histidine and the half-height line widths of proton-coupled resonances of the delta- and omega,omega'-nitrogens of 15N-labeled arginine and of the alpha-nitrogens of 15N-labeled alanine and proline were measured in intact mycelia of Neurospora crassa to obtain to estimates of intracellular pH. For intracellular 15N-labeled histidine, the N1 (tau)-nitrogen chemical shift was 200.2 ppm. In vitro measurements showed that the chemical shift was slightly affected by the presence of phosphate, with which the basic amino acids may be associated in vivo. These considerations indicate a pH of 5.7-6.0 for the environment of intracellular histidine. The half-height line widths of the delta- and omega,omega'-nitrogens of [15N]arginine were 15 and 26 Hz, respectively. In vitro studies showed that these line widths also are influenced by the presence of phosphate, and, after suitable allowance for this, the line widths indicate pH 6.1-6.5 for intracellular arginine. The half-height line widths for intracellular alanine and proline were 17 and 12 Hz, respectively, which are consistent with an intracellular pH of 7.1-7.2. Pools of histidine and arginine are found principally in the vacuole of Neurospora, most likely in association with polyphosphates. Proline and alanine are cytoplasmic. The results reported here are consistent with these localizations and indicate that the vacuolar pH is 6.1 +/- 0.4 while the cytoplasmic pH is 7.15 +/- 0.10. Comparisons of these estimates with those obtained by other techniques and their implications for vacuolar function are discussed.

Arginine↗
PubMed1983

Studies of N-hydroxy-N'-aminoguanidine derivatives by nitrogen-15 nuclear magnetic resonance spectroscopy and as ribonucleotide reductase inhibitors.

Hydroxyguanidine, with the imino group of guanidine and the hydroxyamino group of hydroxyurea, has functional groups believed to be important for both anticancer and antiviral activities (Adamson, R.H. Nature (London) 1972, 236, 400-401). Three new N-hydroxy-N'-aminoguanidine derivatives have been synthesized and found to be 20-30 times more active than the hydroxyguanidine itself as inhibitors of ribonucleotide reductase from rat Novikoff tumors (Tai, W.A.; Lai, M.M.; Lien, E.J. "Novel N-Hydroxyguanidine Derivatives as Antiviral Agents", North American Medicinal Chemistry Symposium, University of Toronto, Toronto, Canada, June 20-24, 1982; Abstr, p 144). The character of the tautomeric equilibria, the pKa values, and the protonation sites of these hydroxyguanidine derivatives have been determined by 15N NMR spectroscopy.

Guanidines↗
PubMed1982

Effect of the nitrogen source on glutamine and alanine biosynthesis in Neurospora crassa. An in vivo 15N nuclear magnetic resonance study.

The influences of different nitrogen sources on the relative rates of biosynthesis of glutamine and alanine have been studied by 15N nuclear magnetic resonance spectroscopy of intact Neurospora crassa mycelia suspensions. The rate of glutamine synthesis was fastest after growth in media deficient in free ammonium ion, whereas it was slowest following growth in media containing both glutamic acid and glutamine. The reverse trend was observed for the biosynthesis of alanine. A competition between the two biosynthetic pathways for the same substrate, glutamic acid, was found to limit the rate of alanine synthesis when glutamine synthesis was rapid. The observed in vivo rates of these reactions are compared to the reported specific activities of the enzymes catalyzing the reactions, and implications of these results for nitrogen regulation of these pathways under various physiological conditions are discussed.

Alanine↗
PubMed1982

Nitrogen-15 spin-lattice relaxation times of amino acids in Neurospora crassa as a probe of intracellular environment.

The nitrogen-15 spin-lattice relaxation time, T1, and the nuclear Overhauser enhancement (NOE) have been measured for intracellular glutamine, alanine, and arginine in intact Neurospora crassa mycelia to probe their various intracellular environments. The relaxations of 15N gamma of glutamine, 15N alpha of alanine, and 15N omega, omega ' of arginine in N. crassa were found, on the basis of their NOE values, to be predominantly the result of 15N-H dipolar relaxation. These relaxations are therefore related to the microviscosities of the various environments and associations of the respective molecules with other cellular components that act to increase the effective molecular sizes. For 15N gamma of glutamine in the cytoplasm, the intracellular T1 (4.1 s) was only slightly shorter than that in the culture medium (4.9 s). This indicates that the microviscosity of the cytoplasm surrounding the glutamine molecules is not much greater than 1.3 cP. By contrast, for 15N omega, omega ' of arginine, which is sequestered in vacuoles containing polyphosphates, the intracellular T1 (1.1 s) was only one-fourth of that in the medium (4.6 s). In model systems, the T1 of 15N omega, omega ' in a 1 M aqueous solution of arginine containing 0.2 M pentaphosphate was 0.95 s, whereas in an isoviscous (2.8 cP) solution without pentaphosphate, the T1 was 1.8 s. These results suggest either that the vacuolar viscosity is substantially above 2.8 cP or that the omega, omega '-nitrogens of vacuolar arginine are associated with a polyanion, possibly polyphosphate. The implications of these results for the properties of the vacuolar interior are discussed in relation to the mechanism of amino acid compartmentation.

Alanine↗