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M Istin

Publications and source records attributed to M Istin.

At least 19 recordsLinked to original sources
PubMed1993

Enzyme immunoassay using a rat prolactin-alkaline phosphatase recombinant tracer.

This paper describes a competitive enzyme immunoassay of rat prolactin (rPrl) using a recombinant conjugate as a colorimetric tracer. rPrl was inserted into the N-terminal end of Escherichia coli alkaline phosphatase (AP), using an expression vector which allows insertion of foreign DNA sequences between codons +6 and +7 of the phoA gene. The assay was performed in 96-well microtiter plates coated with a mouse monoclonal antibody raised against rabbit immunoglobulin G. Each component (recombinant tracer, rabbit antiserum against rPrl, and rPrl standard) was added in a volume of 50 microL. The sensitivity of the assay was sufficiently high to allow titration of rPrl in plasma. The detection threshold was 15 pg (0.3 ng/mL) and the B/B0 50% value was 150 pg (3 ng/mL). The intraassay coefficient of variation was less than 10% over a wide range of rPrl concentrations (2.9-50 ng/mL). The interassay coefficient of variation was less than 15% for rat plasma samples in the concentration range of 4-40 ng/mL. The good parallelism observed between the standard curve and sample dilution curves showed that the immunoreactivity in rat plasma behaves like standard rPrl. Together with recovery experiments, these results indicated that assay without extraction is possible. A single immunoreactive peak that comigrates with standard rPrl is observed after molecular sieve fractionation of plasma samples. The reliability of the assay was confirmed by good correlation with conventional radioimmunoassay (r = 0.996, slope 0.978).

Alkaline Phosphatase↗
PubMed1993

Production and characterization of antibodies directed against organophosphorus nerve agent VX.

A strategy is described to raise high-affinity antibodies directed against the organophosphorus nerve agent VX [O-ethyl S-(2-diisopropylamino)ethyl)methyl phosponothionate]. Ten chemical derivatives of VX (haptens) have been synthesized. Their structures differ principally from VX structure by substitution of S-atom by an O-atom or CH2-group and by introduction of a reactive group (carboxylic acid, arylamine or primary amine) on the O-ethyl side chain. None of these haptens, except one, exhibit potential toxicity as tested by their inhability to inhibit acetylcholinesterase (E.C. 3.1.1.7.). After coupling with a protein carrier, they were injected intradermally to rabbits. Nine of these immunogenic conjugates led to the appearance of antibodies able to bind VX in a competitive solid phase immunoassay. The apparent titer and affinity of the antisera differed greatly depending on the hapten used. The highest affinity (9 nM) was observed with the VX derivative bearing O-S substitution and O-ethyl-carboxylic side chains. The antibodies appear specific for VX, since cross-reactivity with other nerve agents (Soman, Sarin or Tabun) was low. However, two haptens elicited antibodies with affinity to Soman or Sarin in the micromolar range. Antibodies were able to neutralize VX inhibition of acetylcholinesterase in vitro but not in vivo.

Animals↗
PubMed1992

[The pharmacokinetics of dihydroergocristine after intravenous and oral administration in rats].

The pharmacokinetic properties of dihydroergocristine (DHEC, CAS 17479-19-5) were investigated in rats using a specific radioimmunoassay technique specific for non-metabolized drugs. DHEC, administered intravenously at the dose of 6 mg/kg, showed a plasma profile conforming to an open two-compartment pharmacokinetic model with a long terminal half-life (t1/2 = 13.6 h). DHEC kinetics after oral administration (6 mg/kg) showed two peaks. The first peak (C = 37 micrograms/l) occurred at the first collection point (0.5 h) indicating a quick absorption of the drug. The second peak (C = 34 micrograms/l) occurred at 2 h and may be considered an indication of an enterohepatic cycle. A long terminal half-life (t1/2 = 18.1 h) was observed. An extensive biotransformation of DHEC was indicated by an almost complete absence of unchanged drug in the urine and a high systemic clearance (2.65 l.h-1 x kg-1). A large volume of distribution (52 l.kg-1) was calculated.

Administration, Oral↗
PubMed1991

Pharmacokinetics of alpha-dihydroergokryptine in monkeys after oral administration.

The pharmacokinetic profile of a single dose (6 mg/kg) of alpha-dihydroergokryptine (alpha-DHEK) was established after oral administration in monkeys using a radio-immunoassay technique for non-metabolized drug. alpha-DHEK showed a plasma profile according to an open three-compartment pharmacokinetic model with a long half-life (mean = 5.787 h). The disposition of alpha-DHEK involves a fast absorption, a slow distribution phase and a slow elimination phase. alpha-DHEK showed an high total clearance and distribution volume; the drug is largely metabolized, as concluded from the very low urinary excretion.

Administration, Oral↗
PubMed1991

Pharmacokinetics of alpha-dihydroergocryptine in rats after intravenous and oral administration.

The pharmacokinetic properties of alpha-dihydroergocryptine methanesulphonate (alpha-DHEK, CAS 19467-62-0) were investigated in rat using a radioimmunoassay technique for nonmetabolized drug. alpha-DHEK, intravenously administered at the dose of 6 mg/kg, showed a plasma profile according to an open 3-compartment pharmacokinetic model with a long half-life (about 7.56 h). The kinetics of alpha-DHEK after oral administration (6 mg/kg) showed two peaks; the second peak at 8 h was probably due to an enterohepatic cycle. The disposition of alpha-DHEK consisted in a fast absorption and a slow elimination (t1/2el about 6.78 h). The alpha-DHEK was largely metabolized as results from the complex metabolite profile in body fluids and from very low urinary elimination of unchanged drug.

Administration, Oral↗
PubMed1991

Comparison of HPLC and RIA methods applied to the quantification of amisulpride in human plasma.

Quantification of amisulpride occurred up-till now using radioimmunoassay (RIA). A high performance liquid chromatographic (HPLC) assay with fluorimetric detection has been developed, which can be reproduced easily by any other laboratory. The aim of this paper is to compare amisulpride plasma levels (determined by RIA and HPLC) in 51 patients who received daily up to 800 mg of amisulpride in fractioned doses by IM or oral route, eventually together with other medications. Assay conditions and characteristics are briefly described and discussed. Results obtained with RIA and HPLC are compared and relative errors between both methods are calculated and examined as a function of the concentrations quantified. Correlation analysis using the concentrations (linear correlation) or their logarithm (logarithmic correlation) were realized for different concentration ranges. In fact, in the present case, logarithmic correlation was a more appropriate data processing method, which showed intercepts close to 0 and slopes close to 1. In conclusion, both methods are specific and sensitive enough to ensure the follow up of clinical studies. RIA may therefore be replaced whenever necessary by PHLC, without subsequent influence on the results.

Amisulpride↗
PubMed1982

[In vitro study of tubulin polymerisation. Effects of ATP, vinblastine and isaxonine (author's transl)].

The dual action of vinblastine on tubulin, namely disruption and aggregation, is analyzed by turbidimetry. The existence of two different binding sites for the alkaloid is confirmed. The high affinity site binds vinblastine at low concentrations, at which no effect is observed on depolymerized tubulin, but where pre-formed microtubules are disrupted. The low affinity site is associated with tubulin aggregation. The binding constants of these two sites have been evaluated. Isaxonine (N-isopropyl-amino-2 pyrimidine) partially inhibits the effects of vinblastine, both on microtubule disruption and tubulin aggregation.

Adenosine Triphosphate↗
PubMed1977

[Acceleration of the speed of neuronal growth by a new neurotropic substance: N-isopropyl-amino-2-pyrimidine].

16 hrs. after per os administration of 14C N-isopropyl-amino-2-pyrimidine (IAP) in the Rat, radioactivity of the sciatic nerve is significantly higher than in plasma and other organs. In vitro IAP (base, orthophosphate or dichloracetate) accelerates neurite outgrowth of explained spinal ganglion after 48 hrs. of incubation in nutritive medium. Results suggest that IAP incorporated in nerve cell acts on cellular mechanisms controlling nerve growth.

Animals↗
PubMed1975

[Isoenzymes of carbonic anhydrase of an euryhaline fish. Variations related to the osmoregulation].

A chemical study of carbonic anhydrase (EC 4.2.1.1) from the red blood cells and the gills of an euryhaline fish (Anguilla anguilla) is presented. Animals adapted to fresh water were compared to those adapted to sea water. The physiochemical constants of the various molecular formsisolated by chromatography and isoelectric focusing were determined; isoelectric pH, molecular weight, and the Km and V/E of the enzyme dehydration activity were compared. In both red cells and gills of fish adapted in either media various forms were isolated, characterized by different enzymatic kinetics (high- and low- activity forms) but having the same molecular weight (27 250). Some isoenzymes isolated from the gills differed significantly from those isolated from the red cells. Adaptation to fresh water or sea water is accompanied by modifications in the distribution of the isoenzymes in both red cells and gills: adaptation to sea water is characterized by a shift of the molecular forms towards an isoelectric pH higher than pH equals 6. The role of these enzymes is discussed under both a physiological and biochemical point of view in relation to the electrolyte exchange across fish gill. The origin of the different molecular forms of the carbonic anhydrase is discussed in relation to the prevailing theories on this subject.

Adaptation, Physiological↗
PubMed1971

Does DDT inhibit carbonic anhydrase?

At a concentration of 50 to 100 micrograms per milliliter, p,p'-DDT (and p,p'-DDE) did not inhibit the rate of hydration or dehydration of carbon dioxide by carbonic anhydrase. At concentrations greater than 500 micrograms per milliliter, partial inhibition of the rate of dehydration of carbonic acid was observed, but this involved precipitation of drug in the reaction vessel. This degree of inhibition suggests that DDT may not inhibit carbonic anhydrase effectively at the usual concentrations found in tissue after exposure of organisms to DDT in the environment.

Carbonic Anhydrase Inhibitors↗
PubMed1968

On the origin of the bioelectrical potential gverated by the freshwater clam mantle.

Mantles from freshwater clams develop potential differences (PD's) between the two surfaces when they are bathed in vitro with artificial saline solutions. The magnitude and polarity of the PD is dependent on [Ca(2+)] in the solution bathing the mantle's shell surface. When the solutions are gassed with 5% CO(2) in oxygen, the PD is in the range 25 to 50 mv, shell side positive. It decreases if [Ca(2+)] in the shell solution is elevated. The concentration dependence is logarithmic with a slope of about -27 mv per 10-fold change in [Ca(2+)], slightly less than predicted by the Nernst equation for a membrane acting as a calcium electrode. Analysis of the electrical behavior both in intact mantles and in isolated epithelia indicates that most of the PD develops across the external membranes of epithelial cells on the shell side. There is no evidence that an active calcium transport system is involved in electrogenesis, and a model based on calcium diffusion across a selectively permeable membrane can explain existent data. If CO(2) is absent, the mantle PD is very small (2-10 mv), but still sensitive to change in external [Ca(2+)]. It is proposed that CO(2) alters intracellular pH, thereby changing the equilibrium between a large store of nonionized calcium and [Ca(2+)] in the cells. A role for carbonic anhydrase in the CO(2) effect is suggested by the action of a specific inhibitor of this enzyme. The diffusion model predicts that increasing ionized calcium should increase the PD as is actually observed. Some implications of this system for the physiology of calcium movement in vivo are discussed.

Acetazolamide↗
PubMedDate not supplied

Development and in vivo assessment of a transdermal system for physostigmine.

A copolymer was developed as a transdermal (TD) system for physostigmine. The loading was carried out with a solution of physostigmine (PHY) base (20 mg/ml) in water/ethanol: 80/20 (v/v) at 40 degrees C for 3 h. The PHY load was 5.3 mg/cm2 (n = 3). Desorption carried out in vitro showed that 70% was desorbed during the first 6 h. More than 50% of the PHY was degraded within 45 min in skin homogenate. The TD was tested in vivo in rabbits during a 24 h experiment. PHY was quantified using a validated HPLC method. AUC0-24 h was 245.2 +/- 337.2 h.ng/ml. The mean pad flux reached 4.6 +/- 6.3 micrograms/cm2 from 0 to 24 h and, 24 h after the application of the pad, 110 micrograms/cm2 of PHY had been passed through the skin. After removed of the patch, plasma concentrations first increased from 15.8 +/- 28.6 ng/ml (at 24 h) to 21.4 +/- 36.7 ng/ml, then decreased with an elimination half-life of 0.7 +/- 0.2 h. AChE inhibition percentages increased from 6.5 +/- 2.3% to 16.0 +/- 27.7%. In vitro and in vivo studies in rabbit have shown that this system is suitable for further investigations in order to obtain a possible carrier for PHY therapy.

Administration, Topical↗