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Biomedical subjects

J K Nicholson

Publications and source records attributed to J K Nicholson.

At least 235 records · Page 13Linked to original sources
PubMed1988

Metabolic profiling of body fluids by proton NMR: self-poisoning episodes with paracetamol (acetaminophen).

1H NMR spectra of urine and plasma from subjects who had taken paracetamol (acetaminophen) at a therapeutic dose or in self-poisoning episodes (both fatal and nonfatal) are compared. They provide convenient metabolic profiles. For overdose cases, intense resonances corresponding to high levels of both drug and endogenous metabolites are observed. The ratios of glucuronide to sulfate conjugates are unusually high in urine from overdose cases. Elevated levels of the cysteinyl and N-acetyl cysteinyl conjugates reflect increased glutathione conjugation in the liver. The observed excretion of high levels of amino acids by overdose subjects is suggestive of drug-induced hepatic damage. No resonances for drug metabolites are detected in plasma samples. However, characteristic and abnormally intense resonances for the amino acids Phe, Tyr, His, Gln, Pro, Ala, Val, Lys, Met, Ser, and Thr are indicative of severe liver failure and disruption of normal deamination and transamination processes.

Acetaminophen↗
PubMed1988

Solid phase extraction chromatography and NMR spectroscopy (SPEC-NMR) for the rapid identification of drug metabolites in urine.

The use of solid phase extraction onto disposable columns containing a C18 bonded silica gel provides a rapid and simple procedure for the removal of interfering endogenous components from urine samples containing drug metabolites prior to detection and identification by (1)H NMR spectroscopy. In addition, these columns can be used to retain and concentrate the compounds of interest, thus improving the effective sensitivity of the NMR detection method. Using simple step gradients chromatographic separations can be performed, and metabolites may be rapidly fractionated. This approach (solid phase extraction chromatography with NMR or SPEC-NMR) utilises the multiparametric metabolite detection facility of a Fourier transform NMR spectrometer to monitor a chromatographic separation, as such it has some of the beneficial properties of a directly linked liquid chromatography-NMR system without any of the disadvantages. Applications of the SPEC-NMR method in the investigation of drug metabolism are illustrated here by reference to excretion studies on the drugs ibuprofen, paracetamol, aspirin, oxpentifylline and naproxen.

Journal Article↗
PubMed1988

Application of high resolution 1H-NMR spectroscopy to the detection of penicillamine and its metabolites in human urine.

Preliminary studies on the use of high resolution 1H-NMR spectroscopy for the detection of the thiol drug penicillamine and its metabolites in human urine are described. The technique is rapid, simple and requires minimal sample pretreatment. Application of NMR to the qualitative analysis of penicillamine in urine is illustrated by penicillamine disulphide formation from penicillamine following spiking into human urine and the detection of penicillamine, penicillamine disulphide and penicillamine-cysteine disulphide (following oral administration of the drug to patients).

Cysteine↗
PubMed1988

Hypergammaglobulinemia associated with human immunodeficiency virus infection.

The serum concentrations of 11 Ig isotypes (IgG, IgG1, IgG2, IgG3, IgG4, IgA, IgA1, IgA2, IgM, IgD, and IgE) were measured in four relatively small groups of homosexual (or bisexual) males. All these patients were seropositive for HIV. Two of the groups (nonprogressors) were clinically stable for approximately 2 years and were characterized either as asymptomatic or with PGL. The third group (progressors) developed AIDS 2-38 months after blood specimens were taken. The fourth group had AIDS. A fifth group of anti-HIV-seronegative heterosexual males completed the study. The geometric mean IgA serum concentration was more markedly elevated over normal control sera than any of the other study groups and was the only Ig isotype that was significantly higher in the progressor than in the nonprogressor group. The geometric IgG1 serum concentration was significantly higher in asymptomatic nonprogressors, PGL-nonprogressors, progressors, and AIDS patient groups than that in HIV-seronegative normals. In contrast, the geometric mean IgG2 serum concentration is depressed in all the anti-HIV-seropositive patients (but not significantly with the AIDS group). Multivariate analysis showed the Ig-isotype assays to have much less predictive power for progression to AIDS than the T-helper cell assays.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Interaction of Gc (vitamin-D binding protein) with membrane of activated natural cytolytic cells.

Gc (a vitamin D binding protein) has been speculated to play a role in the function of immune response, yet, it has not been examined for its biological response properties. Therefore, we tried to (a) characterize the appearance of membrane bound Gc (mGc) on non-activated and mitogen activated lymphocytes as well as on Interleukin-2 activated killer cells and (b) examine the role of serum isolated human Gc on human blastogenesis and cytotoxicity (natural killing and lymphokine-activated killing). Our data suggests that activated cells possess a greater number of cells with mGc than non-activated cells and that as a biological response modified we find modulation of blastogenesis and cytotoxicity to be consistently but not very significantly down-regulated. Anti-Gc antibody was observed to significantly inhibit NK activity.

Cell Membrane↗
PubMed1987

Assignment of resonances for 'acute-phase' glycoproteins in high resolution proton NMR spectra of human blood plasma.

Broad resonances at 2.04 and 2.08 ppm in 500 MHz Hahn spin-echo 1H NMR spectra of human blood plasma are assigned to the N-acetyl groups of mobile carbohydrate side-chains (largely N-acetylglucosamine and N-acetylneuraminic acid) of glycoproteins such as alpha 1-acid glycoprotein. Their intensities in spin-echo spectra correlate with clinical conditions in which an elevation of the level of 'acute-phase' glycoproteins is expected, and so may be of value in the study of certain diseases.

Acute-Phase Proteins↗
PubMed1987

Spin-echo proton NMR spectroscopy of urine samples. Water suppression via a urea-dependent T2 relaxation process.

Spin-echo methods have been used to effect solvent suppression during the collection of 400 and 500 MHz 1H NMR spectra of urine samples containing urea in the concentration range 0.7-1.2 M. There was a marked trough of water Tobs2 values in the pH range 2.6 to 4.1, due to acid-catalyzed proton exchange between urea and the solvent water. Minimum values of Tobs2 (9 ms at 500 MHz) of water were obtained at about pH 3.2 in urine samples containing 1.2 M urea. However, good solvent suppression factors were obtained with endogenous urea concentrations of only 0.7 M. There was a strong field dependence on the water, T2, over the pH range 2 to 4. Attenuation of the water signal was estimated to be at least an order of magnitude greater at 500 MHz rather than at 400 MHz. Using the Carr-Purcell-Meiboom-Gill spin-echo pulse sequence, water signals broader than 13 Hz were attenuated by factors of greater than 10(3), and factors of greater than 10(4) were possible with water linewidths greater than 20 Hz, thus allowing the signals from metabolites in the sample to be efficiently digitized. This approach allowed metabolite signals at or near the water resonance to be observed without serious distortion of their intensities. The utility of this approach to solvent suppression in real systems is illustrated by observation of paracetamol and benzyl penicillin metabolites in human urine samples.

Humans↗
PubMed1987

Probing the reactivity of the zinc and cadmium ions bound to rabbit liver metallothioneins with EDTA.

Reactions of native and reconstituted rabbit liver metallothioneins (MT's) with excess EDTA at pH 7 were studied by 1H NMR, electronic absorption and atomic absorption spectroscopy. There was a reasonable agreement between the amounts of Zn2+ and Cd2+ removed as determined by the various methods. Specific structural changes accompanying metal removal were observable by NMR. Most of the Zn2+ in Zn7-MT, reacted rapidly with EDTA. One to two g-ions of Zn2+ in native Cd,Zn-MT's were labile, but none of the Cd2+ was extracted rapidly by EDTA. The cadmium protein Cd7-MT1, reconstituted via the low pH-apothionein method, appeared to contain EDTA-reactive Cd2+ bound in a different manner to either Zn2+ or Cd2+ in the native protein.

Animals↗
PubMed1987

Phenotypic distribution of T cells of patients who have subsequently developed AIDS.

In a previous study of asymptomatic homosexual men, we found that CD8+ T-cell levels were higher in homosexual men infected with the human immunodeficiency virus (HIV) than in uninfected homosexual men because of higher numbers of CD8+ T cells that do not express the Leu15 marker, a phenotype associated with cytotoxic function. Among infected men, there was a positive correlation between the number of CD8+Leu15- T cells and the number of CD4+ T cells. If CD4+ T-cell levels are taken as a measure of severity of HIV infection and immunodeficiency, these results suggested that higher CD8+Leu15- cells may represent a phenotypic profile associated with less severe infection or better control of infection. In the present study, we extend the analysis to include a group of men who progressed to AIDS but were studied well before the onset of AIDS, and we compare results of CD8 subset analyses with results of infected men who have not progressed to AIDS. Phenotypic subsets associated with helper, suppressor, cytotoxic, and natural killer cell function were determined by two-color immunofluorescence. The only phenotypic subset that distinguished men who progressed to AIDS from those who have not was lower numbers of CD4+ T cells in the former group. If CD8+Leu15- cell numbers (or other phenotypic subsets examined) reflect effective control of HIV infection, the relationship is not strong enough to be of prognostic or predictive value with respect to outcome of infection.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Antibody response to human immunodeficiency virus in homosexual men. Relation of antibody specificity, titer, and isotype to clinical status, severity of immunodeficiency, and disease progression.

The titers and isotypes of antibodies to specific proteins of the human immunodeficiency virus were determined by Western blot analysis of sera from 107 homosexual men. Antibody titers were generally lower in sera from patients with the acquired immunodeficiency syndrome (AIDS) and in sera from men whose condition subsequently progressed to AIDS than in sera from men who had not progressed to AIDS. We found no evidence of isotypic prominence or restriction of the antibody response. In multivariate analysis, lower levels of CD4 helper cells were most highly associated with progression to AIDS. Lower antibody titers to the envelope protein gp110, the core protein p24, and the reverse transcriptase enzyme p51/65 were also predictive of progression to AIDS independent of their association with CD4 cell levels. These data suggest that differences in antibody levels are not simply a consequence of severe immunodeficiency but may be markers for control of infection.

Acquired Immunodeficiency Syndrome↗
PubMed1986

Binding of the human retrovirus HTLV-III/LAV/ARV/HIV to the CD4 (T4) molecule: conformation dependence, epitope mapping, antibody inhibition, and potential for idiotypic mimicry.

Human immunodeficiency virus (HIV), the retrovirus that causes the acquired immunodeficiency syndrome, is cytopathic for CD4+ T cells and binds to these cells via a complex of the 110,000 m.w. viral-envelope glycoprotein, gp110, and the CD4 molecule. We treated virus with several physical, chemical, and enzymic agents to determine their effect on the capacity of HIV to bind to the CD4+ T cell line, CEM. Reduction and alkylation (but not alkylation alone) and trypsin digestion (but not glycolytic enzyme digestions) of HIV destroyed its capacity to bind. If the tertiary protein structure conferred by disulfide bonding is not disrupted, the tertiary and secondary conformations dependent on noncovalent forces appear to be thermodynamically favored, because treatment with denaturants such as sodium dodecyl sulfate, 8 M urea, alcohol, or heat (56 degrees C or 65 degrees C for 30 min) followed by removal of the denaturants did not affect binding. Irreversible denaturation and loss of binding occurred after heating at 100 degrees C for 10 min. HIV binding to CD4+ T cells was inhibited either by murine monoclonal antibodies to the CD4 molecule or by human polyclonal or murine monoclonal antibodies to the gp110 molecule. On the basis of results of binding inhibition obtained with a panel of alpha-CD4 monoclonal antibodies, the receptor site for virus on the CD4 molecule was mapped to the amino-terminal portion of the molecule. Four candidate alpha-CD4 monoclonal antibodies that were potent inhibitors of virus binding (OKT4A, OKT4D, OKT4F, and Leu-3a) were examined for the possibility that their binding sites (idiotopes) might share structural and conformational similarity with the CD4-binding site on gp110. Polyclonal human or rabbit anti-HIV sera (that reacted with gp110 and inhibited virus binding) did not react with or inhibit the binding of these four alpha-CD4 monoclonal antibodies. Conversely, rabbit anti-idiotypic sera raised against each of the four candidate CD4 monoclonal antibodies did not react with virus or inhibit virus binding to CD4+ T cells. Further search or different approaches may yet yield an idiotype that is a structural and conformational "internal image" of the CD4-binding site of virus.

Antibodies, Monoclonal↗