Biomedical subjects

M Gonchar

Publications and source records attributed to M Gonchar.

4 recordsLinked to original sources

PubMed2006

Formaldehyde-sensitive sensor based on recombinant formaldehyde dehydrogenase using capacitance versus voltage measurements.

A new formaldehyde-selective biosensor was constructed using NAD(+)- and glutathione-dependent recombinant formaldehyde dehydrogenase as a bio-recognition element immobilised on the surface of Si/SiO(2)/Si(3)N(4) structure. Sensor's response to formaldehyde was evaluated by capacitance measurements. The calibration curves obtained for formaldehyde concentration range from 10 microM to 20mM showed a broad linear response with a sensitivity of 31 mV/decade and a detection limit about 10 microM. It has been shown that the output signal decreases with the increase of borate buffer concentration and the best sensitivity is observed in 2.5mM borate buffer, pH 8.40. The response of the created formaldehyde-sensitive biosensor has also been examined in 2.5mM Tris-HCl buffer, and the shift to the positive bias of the C(V) curves along with the potential axis has been observed, but the sensitivity of the biosensor in this buffer is decreased dramatically to the value of 2.4 mV/decade.

Aldehyde Oxidoreductases↗

PubMed2006

Formaldehyde assay by capacitance versus voltage and impedance measurements using bi-layer bio-recognition membrane.

A novel formaldehyde sensitive biosensor based on bacterial formaldehyde dehydrogenase (FDH) as a bio-recognition element has been developed. The bio-recognition membrane had bi-layer architecture and consisted of FDH, cross-linked with albumin, and of the cofactor NAD at a high concentration level (first layer). The second layer was a negatively charged Nafion membrane, which prevented a leakage of negatively charged NAD molecules from the bio-membrane. As transducers, gold electrodes SiO(2)/Si/SiO(2)/Ti/Au and electrolyte-insulator-semiconductor Si/SiO(2) (EIS) structures have been used. Changes in capacitance and impedance properties of the bio-recognition membrane have been used for monitoring formaldehyde concentration in a bulk solution. It has been shown that formaldehyde can be detected within a concentration range from 1 microM to 20mM depending on the type of transduction used, with a detection limit of 1 and 100 microM for gold-based and EIS-based transducers, respectively.

Aldehyde Oxidoreductases↗

PubMed1999

Kinetics of prostanoid synthesis by macrophages is regulated by arachidonic acid sources.

The dependence of prostanoid synthesis on the nature of free arachidonic acid (AA) appearance was investigated in mouse peritoneal macrophages. AA delivery from intracellular sources to the constitutive prostaglandin (PG)H synthase was provided by action of calcium-ionophore A23187; and from extracellular sources by AA addition to the culture medium. It was found that the kinetics of prostanoid synthesis dramatically depends on the sources of AA. Free AA concentration used for prostanoid synthesis is either a constant or a variable value depending upon the sources. The kinetics of cellular prostanoid synthesis can be regulated by the following processes: (a) the irreversible inactivation of PGH-synthase in the course of the reaction (kin), (b) prostanoid metabolism (kr), and (c) incorporation of exogenous AA into cellular membranes (ka). From our experiments and mathematical calculation these parameters were found to be kin = 0.20 +/- 0.02 min-1, kr = 0.17 +/- 0.03 min-1 in the case of stimulation with A23187, and kin = 0.0156 min-1, kr = 0. 0134 min-1, ka = 0.0025 min-1 in the case of exogenous AA addition. The studies of prostanoid biosynthesis by macrophage microsomes led to independent determination of kin = 0.20 +/- 0.02 min-1. This value perfectly fits the kinetics of the prostanoid cell synthesis under endogenous AA supply but shows a 10-fold decrease in the case of exogenous AA supply. Our study on the kinetics of prostanoid synthesis by mouse peritoneal macrophages clearly demonstrate that AA is able to regulate cellular prostanoid synthesis in the presence of constitutive PGH-synthase only. A regulation mechanism based on the co-operation of the constitutive PGH-synthase isoform and the availability of free AA is proposed and could be confirmed by mathematical modelling.

Animals↗

PubMedDate not supplied

Comparison of hydroxychloroquine with zidovudine in asymptomatic patients infected with human immunodeficiency virus type 1.

Hydroxychloroquine (HCQ), an antimalarial agent used to treat patients with autoimmune diseases, has been shown to suppress human immunodeficiency virus type 1 (HIV-1) replication in T cells and monocytes in vitro by inhibiting posttranscriptional modification of the virus. An initial randomized, placebo-controlled clinical trial conducted in 38 asymptomatic HIV-1-infected patients who had CD4+ counts between 200 and 500 cells/mm3 demonstrated that the amount of recoverable virus declined significantly in the HCQ group compared with the placebo group over the 8-week study period. These preliminary observations were expanded into a second 16-week clinical trial comparing the efficacy of HCQ with that of zidovudine (ZDV) in 72 asymptomatic HIV-1-infected patients with CD4+ counts between 200 and 500 cells/mm3. Patients were randomly assigned to receive either HCQ 800 mg/d (n = 35) or ZDV 500 mg/d (n = 37) for 16 weeks. No adverse reactions to the study medications were observed in either the HCQ or ZDV group. Patients in both groups had reduced levels of recoverable HIV-1 RNA in the plasma, reduced levels of cultured virus, and reduced levels of serum p24 antigen after the 16-week study period. However, no difference was noted in absolute CD4+ counts between the two groups. Interleukin-6 and serum immunoglobulin G levels were significantly reduced in the HCQ group but not in the ZDV group. These findings support the results of the previous clinical trial. Thus HCQ may be potentially useful in the treatment of patients with HIV-1 infection.

Adult↗