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J L Bock

Publications and source records attributed to J L Bock.

At least 37 records · Page 2Linked to original sources
PubMed1989

Nuclear magnetic resonance in the clinical laboratory.

Nuclear magnetic resonance (NMR) which now has widespread clinical use as an imaging technique, may also have significant application to diagnostic pathology. High-field proton NMR spectroscopy can perform rapid multicomponent analysis of serum, urine, cerebrospinal fluid, and even intact cells. This technique allows unusually detailed studies of certain metabolic derangements and toxic ingestions. Phosphorus NMR spectroscopy in vivo can measure ATP and other phosphometabolites, intracellular pH, and free Mg2+. It has been applied to diagnosing inborn errors of metabolism such as glycogen storage disease, monitoring growth and regression of tumors, and assessing tissue viability. The basics of NMR spectroscopy are reviewed in this article, along with a survey of applications in human pathology.

Body Fluids↗
PubMed1988

Further studies on alterations in magnesium binding during cold storage of erythrocytes.

Free intracellular Mg2+ concentration ([Mg2+]i) was measured in cold-stored human erythrocytes by the method of null-point titration with ionophore A23187. [Mg2+]i was 311 +/- 41 microM (mean +/- S.D.) for cells stored 0-10 days, increasing to 458 +/- 64 microM for cells stored 22-48 days. The values for stored cells were higher than those previously determined by a 31P-NMR method (Bock et al. (1985) Blood 65, 1526-1530); however, the null-point method requires extensive washing of the cells, which we have found to increase NMR-measured [Mg2+]i. The null-point values still represent a small fraction of total cell Mg2+, and confirm that binding of Mg2+ to ligands other than ATP and 2,3-bisphosphoglycerate must increase during storage. As an initial test of whether this may imply suboptimal availability of Mg2+ for cell preservation, we used A23187 to prepare erythrocytes with altered Mg2+ content, then removed ionophore and stored the cells in plasma-free medium for up to 2 weeks. Higher Mg2+ content had a very significant positive correlation (P less than 0.0001) with higher cell ATP concentrations. Storage did not significantly affect basal or Na+-stimulated efflux of Mg2+ from Mg2+-loaded red cells.

2,3-Diphosphoglycerate↗
PubMed1987

Studies on the mechanism of decreased NMR-measured free magnesium in stored erythrocytes.

31P-NMR spectra have been recorded on erythrocytes stored at 4 degrees C in various preservation media. Storage was always associated with an upfield shift of the inorganic phosphate (Pi) resonance and a pronounced upfield shift of the ATP beta resonance, indicating decreased intracellular pH (pHi) and decreased intracellular free magnesium ([Mg2+]i). The decreased [Mg2+]i occurred in preservation media not containing citrate and even in media supplemented with Mg2+. It could not be attributed to the changes in pHi, Na+, K+, lactate, Pi or 2,3-diphosphoglycerate, that occur with storage. The decrease in [Mg2+]i was largely reversed when stored cells were incubated for 1 h at 37 degrees C in fresh plasma. Stored cells were found to contain significant amounts of inorganic pyrophosphate, up to about 200 mumol per liter cell water. Being a tight binder of Mg2+, pyrophosphate could account for some of the observed decrease in [Mg2+]i. Additional mechanisms may involve precipitation of some other Mg2+ complex during cold storage or enhancement of Mg2+ binding to membrane components.

Blood Preservation↗
PubMed1985

False positive immunometric assays caused by anti-immunoglobulin antibodies: a case report.

A serological phenomenon causing aberrant results with monoclonal immunoenzymetric assays (IEMA's) is reported. Two different commercial IEMA kits detected low levels of choriogonadotropin (hCG) in the serum of a non-pregnant woman. These assays detected between 32 and 55 IU/l of serum hCG over a 3-wk period; however, an RIA for beta-subunit and two monoclonal immunoradiometric assays (IRMA's) detected no hCG (less than 5 IU/l). An IEMA measurement of creatine kinase MB isozyme was also elevated. Antisera to either human immunoglobulin or specifically to human IgM, added to the serum prior to assay, substantially decreased these IEMA reactions. Addition of either mouse serum or purified mouse IgG totally abolished them. It is concluded that these spurious reactions were most likely caused by an IgM antibody which binds to native and enzyme-labelled mouse IgG, but not to iodinated IgG.

Adult↗
PubMed1985

Rapid measurement of free anticonvulsant drugs by direct liquid chromatography of serum ultrafiltrates.

In this simultaneous assay of unbound phenobarbital, phenytoin, primidone, and carbamazepine, serum ultrafiltrate is prepared by centrifugation in disposable filter units (Centrifree Micropartition System, Amicon Corp.) and injected directly onto a reversed-phase liquid-chromatography column. Drugs in the effluent are detected by absorbance at 210 nm. The measured concentrations were not critically dependent on the exact conditions of ultrafiltration (rotor angle, speed or time of centrifugation, amount of sample filtered). Pooled serum containing all four drugs gave reproducible results in repeated analyses during several days. For comparison we assayed 113 clinical specimens for one or more of these drugs by this method, and for the total (bound plus unbound) concentration of each drug by immunoassay. For each drug there was a nearly linear relationship between the two types of measurements, except for six specimens that had unusually high fractions of unbound drug. This assay appears highly suitable for routine determination of the free, biologically active fraction of anticonvulsant drugs, possibly as an alternative to measurements of total drug concentrations.

Anticonvulsants↗
PubMed1985

Choriogonadotropin measured with the Tandem-E immunoenzymetric assay system.

We evaluated the Hybritech Tandem-E procedure for quantifying choriogonadotropin (hCG) in human serum. In this "sandwich"-type assay, two monoclonal antibodies directed against different regions of the hCG molecule are used, one coated on a plastic bead, the second conjugated to alkaline phosphatase. The assay can detect as little as 1.0 int. unit of the hormone per liter, shows a linear response up to at least 200 int. units/L, and has good precision. By prolonging the incubations for formation of the sandwich and for substrate hydrolysis, one can achieve higher sensitivity at the expense of a narrower linear range. Correlation with a conventional radioimmunoassay for the beta subunit of hCG was generally excellent, but in one instance the Tandem-E gave an apparently false positive result.

Adult↗
PubMed1985

Changes in intracellular Mg adenosine triphosphate and ionized Mg2+ during blood storage: detection by 31P nuclear magnetic resonance spectroscopy.

31P nuclear magnetic resonance (NMR) spectroscopy was used to measure changes in intra-erythrocyte Mg adenosine triphosphate (MgATP) and free Mg2+ during blood storage at 4 degrees C in standard citrate preservation media. The extent of Mg2+ complexation of ATP and the concentration of free Mg2+ were measured from the Mg2+-dependent chemical shift differences, at 22 degrees C, between the P beta and P alpha resonances of intracellular ATP. This difference changed from 721.0 +/- 1.4 Hz (mean +/- SE) on the day of collection to 741.0 +/- 3.4 Hz after three to seven days and 774.0 +/- 2.8 Hz after 11 to 40 days storage in either acid-citrate-dextrose (ACD) or citrate-phosphate-dextrose-adenine (CPDA-1). Changes in intracellular pH, detected from shifts in the intracellular Pi resonance, averaged 0.27 units after 11 to 40 days of storage. These data indicate a sizable decrease in the extent of Mg2+ complexation of ATP, and a decrease by a factor of 2.6 in free Mg2+, during the shelf-life of blood stored in ACD or CPDA-1.

Adenosine Triphosphate↗
PubMed1983

Clinical implications of 2-hydroxydesipramine plasma concentrations.

The clinical utility of 2-hydroxydesipramine (2-OH-DMI) measurements was evaluated by examining the relationship of 2-OH-DMI concentrations in plasma to clinical outcome and side effects in depressed inpatients treated with desipramine (DMI). Studies were performed in responders and nonresponders to treatment and in patients experiencing subjective side effects or major adverse reactions necessitating interruption of treatment. Unlike DMI concentrations, 2-OH-DMI concentrations did not correlate with response. Summing the concentrations of parent drug and metabolite (DMI + 2-OH-DMI) did not improve the correlation over that achieved with DMI alone. Neither DMI, 2-OH-DMI, nor their sum correlated with subjective side effect totals or major adverse reactions. While our data do not permit any conclusions regarding the clinical activity of 2-OH-DMI, they suggest that its routine measurement in plasma is not likely to be useful in the management of depression.

Depressive Disorder↗
PubMed1983

Desipramine hydroxylation: variability and effect of antipsychotic drugs.

Steady-state plasma concentrations of desipramine (DMI), unconjugated 2-OH DMI, and total 2-OH DMI were measured in 82 depressed inpatients, 35 of whom were concurrently receiving a phenothiazine or butyrophenone antipsychotic drug. In the patients not on an antipsychotic, the ratio of unconjugated metabolite to parent varied from 0.01 to 1.5, with a median of 0.48, and was inversely related to the parent drug level. Antipsychotic drug was associated with higher DMI levels and a lower proportion of OH-metabolite (median, 0.23). In both groups the unconjugated form accounted for only about 10% of the total metabolite. No relationship of age, sex, drinking history, or smoking to DMI or 2-OH DMI levels was found.

Adult↗
PubMed1983

D-Lactic acidosis after jejunoileal bypass: identification of organic anions by nuclear magnetic resonance spectroscopy.

A 40-year-old man with jejunoileal bypass developed a syndrome of bizarre behavior, slurred speech, ataxic gait, and inappropriate affect, associated with a metabolic acidosis characterized by an increase in the anion gap. Serum L-lactate level was normal, but high-resolution proton nuclear magnetic resonance spectrums of the patient's serum showed a high concentration of lactate. A diagnosis of D-lactic acidosis was confirmed by a specific enzymatic assay for D-lactate. The D-lactic acidosis was cleared using antibiotic therapy, suggesting that D-lactate is produced from fermentation of ingested carbohydrate by colonic bacteria. Nuclear magnetic resonance spectroscopy is a rapid screening test for identifying organic acids in patients with unexplained acidosis. Neuropsychiatric symptoms in patients with short bowel syndrome may be associated with D-lactic acidosis.

Acid-Base Equilibrium↗
PubMed1982

Steady-state plasma concentrations of cis- and trans-10-OH amitriptyline metabolites.

Plasma concentrations of the geometric isomers of 10-OH amitriptyline (10-OH AT) and 10-OH nortriptyline (10-OH-NT) were determined by reversed-phase high-pressure liquid chromatography. Steady-state concentrations of At, NT, and the four 10-OH metabolites were measured in 27 patients taking AT for depression. All of the unconjugated hydroxylated metabolites were usually detectable and trans-10-OH NT always predominated. Mean concentrations, expressed as percentage of the sum of all six compounds, were: AT 30%, NT 27%, cis-10-OH AT 1.1%, trans-10-OH AT 4.0%, cis-10-OH NT 4.0%, and trans-10-OH NT 33%. Repeated measurements on 10 patients over several weeks indicated that interindividual variations in absolute and relative 10-OH metabolite concentrations are much greater than day-to-day variations. Five patients who also received a phenothiazine had a lower proportion of 10-OH metabolites.

Adult↗
PubMed1982

Analysis of serum by high-field proton nuclear magnetic resonance.

Improvements in nuclear magnetic resonance (NMR) technology are generating an expanding variety of medical applications. In this investigation I have used high-field proton NMR to identify and quantity endogenous and ingested substances in human serum. After addition of a small amount of 2H2O and a reference compound to a 0.4-mL specimen, spectra were recorded for 3 min in Fourier-transform mode, with use of presaturation to suppress the extremely intense H2O peak. Compounds detected at clinically significant concentrations include glucose, alcohols, acetone, organic acids, and salicylate. Less than 1 mmol/L of some of these substances could be detected. For serum containing 20--500 mg of added methanol per liter, peak area was a linear function of concentration (r = 0.998). High-field proton NMR, despite the drawback of expensive, sophisticated instrumentation, offers some unique advantages for clinical chemistry: it permits rapid, specific, nondestructive measurement of several compounds simultaneously, including some that may be inconvenient to measure by conventional means.

Acidosis↗
PubMed1980

Stacking interactions in fluorescent nucleotide analogs containing 1-aminonaphthalene-5-sulfonate at the phosphoryl terminus.

The conformational properties of nucleotides containing the fluorophore 1-aminonaphthalene-5-sulfonate attached via a gamma-phosphoamidate bond have been examined. Measurements of fluorescence excitation spectra show that energy absorbed by adenine in the ATP analog is transferred to the naphthalene moiety with an efficiency of approximately 43%. In nonpolar solvents transfer is almost eliminated. The fluorescence intensity of the UTP analog is quenched. Measurements of quantum yield and excited state lifetime show that this occurs by both dynamic and static mechanisms. Thus, fluorescence studies show that both the purine and pyrimidine analogs exist in an equilibrium mixture of stacked and unstacked forms. NMR studies show that the base and ribose protons of the ATP and UTP analogs are shifted upfield by about 0.2 to 0.3 ppm, presumably due to ring current effects produced by stacking interactions. Phosphorus NMR spectra of the ATP analog are generally similar to spectra of unmodified ATP. The strong dependence on conformation of the fluorescence of the pyrimidine analogs may prove useful in studies of protein-nucleotide interactions.

Adenosine Triphosphate↗
PubMed1980

The binding of metal ions to ATP: a proton and phosphorus nmr investigation of diamagnetic metal--ATP complexes.

Phosphorus and proton nmr spectra were recorded for complexes of ATp with Mg(II), Ca(II), Sr(II), Zn(II), Cd(II), Pb(II), Hg(II), Ag(I), and Tl(I) ions. Each of these ions except Hg(II) affected the 31P nmr of ATP, usually by shifting all three resonances downfield and decreasing the 31P-31P coupling constants. Pb(II) exerted the greatest shifts, while Mg(II) caused the greatest change in coupling constants. Effects on the adenine proton resonances were generally small and attributable to base stacking, but a direct metal-adenine binding is likely for Zn(II), Cd(II), and Ag(I). Effects on the ribose proton resonance were small in all of the ATP complexes, but were much larger in Zn(II)ADP and Cd(II)ADP. Formation of metal-bis(nucleotide) complexes occurred with Sn(II), Zn(II), and Cd(II).

Adenosine Diphosphate↗