Biomedical subjects

L Novotný

Publications and source records attributed to L Novotný.

At least 55 records · Page 3Linked to original sources

PubMed1993

Potentiation of cis-DDP and pyridoxal effect on isolated DNA during simultaneous application.

Pyridoxal and cis-diamminedichloroplatinum (II) (cis-DDP) have a different mode of interaction with DNA. Cis-DDP caused extensive transforming inactivation of pBR322 DNA but did not form strand breaks in DNA molecules. On the other hand, pyridoxal formed frank strand breaks in the DNA chains and decreased DNA transforming activity. A higher level of DNA transforming inactivation was obtained during simultaneous application of both compounds than would be an additive effect of these compounds applied to DNA independently. This synergistic effect can be ascribed to the introduction of thermolabile sites by the combined action of cis-DDP and pyridoxal. These lesions were converted by heat-treatment to DNA strand breaks and detected electrophoretically. Using two different methods, cis-DDP and pyridoxal, during simultaneous application, interacted with DNA with higher efficiency.

Cisplatin↗

PubMed1993

Polarographic study of cytosine nucleosides.

The conditions for polarographic reduction of several nucleic acid components were determined. These components were the pyrimidine base cytosine and nucleoside cytidine, and its synthetic analogs arabinosylcytosine and cyclocytidine hydrochloride which are cytotoxic and antileukemic agents. Polarographic reduction, its character and mechanism were studied in aqueous conditions of Britton Robinson buffer at different pH and in nonaqueous conditions of dry dimethylformamide. It was found that the polarographic wave of all compounds had a diffuse character and that the whole process was a two-electron event which in dependence on pH may consist of two one-electron steps. It was demonstrated on the hydrolysis reaction of cyclocytidine hydrochloride to arabinosylcytosine at alkaline pH that the polarographic method may be used for the documentation of structural changes of pyrimidine nucleoside going on in the polarographic chamber.

Cytosine Nucleotides↗

PubMed1991

Treatment of leukemia L1210 and P388 by arabinosylcytosine-polysaccharide conjugates.

Conjugates of 1-beta-D-arabinofuranosylcytosine (araC) with two polysaccharides such as polygalacturonic acid (PGA) and carboxymethylated yeast beta-D-glucan (CMG) were tested for their antileukemic activity in vitro on a L1210 cell line in suspension culture, in soft agar assay and in vivo on L1210, L1210/araC- and P388-leukemia-bearing mice. Both conjugates showed high activity in vitro in soft agar assay, compared with araC. Single administration of PGA-araC or CMG-araC increased the survival time 1.5 x or 1.7 x, respectively, compared with araC in vivo in L1210-leukemia-bearing mice. The conjugates were not active against araC-resistant leukemia line L1210/araC. The marked effect of both PGA-araC and CMG-araC against leukemia L1210 and P388 is probably due to the prolonged release of free araC from conjugates caused by hydrolysis.

Animals↗

PubMed1991

Evaluation of synergism of drugs cis-diamminedichloroplatinum (II) and arabinosylcytosine on the level of chemical interaction with DNA and on the growth of mouse leukemia.

1. Cytotoxic synergism of drugs cis-diamminedichloroplatinum(II) (cis-DDP) and arabinosylcytosine (araC) was studied both on the level of interaction with DNA in chemically determined conditions and on leukemia L1210 bearing mice. 2. AraC and its structural natural precursor cytidine were tested for the modulation of kinetics of bifunctional adducts production induced by cis-DDP in DNA. 3. This process plays the basic role in cytotoxic mechanism and antitumor activity of cis-DDP. 4. No interaction was seen between cis-DDP and araC. Further, presence of araC in reaction mixture had no effect on cis-DDP-DNA interaction. 5. Therefore, cytotoxic synergism does not arise in the araC-cis-DDP-DNA interaction and its origin is different. 6. Finding that cytidine has no synergistic effect on life span of leukemia L1210 bearing mice when administered together with cis-DDP it shows the difference between cytidine and araC. 7. The small structural difference between cytidine and araC is very important for synergism of cytotoxicity.

Animals↗

PubMed1991

Biotransformation and in vitro activity of an arabinosylcytosine 5'-chloro-5'-deoxy analog.

5'-Chloro-5'-deoxyarabinosylcytosine (5'-chloro-araC), a lipophilic and cytidine-deaminase resistant analog of the cytotoxic agent arabinosylcytosine (araC) was evaluated in terms of bioactivation, transformation and its cytotoxic activity in vitro. 5'-Chloro-araC interferes with DNA synthesis (IC50 = 2.8 mumol/l) and inhibits the growth of L1210 cells in suspension culture (IC50 = 1.05 mumol/l) and in the soft agar assay (IC50 = 0.65 mumol/l). Being phosphorylated to the triphosphate of araC-araCTP (5'-triphosphate of araC), 5'-chloro-araC has the same mechanism of action as arabinosylcytosine. In alkaline solutions 5'-chloro-araC is transformed to another (cytostatically inactive) araC analog--2',5'-anhydroarabinosylcytosine--but at physiological pH and temperature conditions, it has sufficient stability to be phosphorylated and thus activated. A lower rate of araCTP formation from 5'-chloro-araC explains the somewhat lower cytotoxic effect of this compound against various established cell lines in vitro compared to araC. Lipophilicity that would allow an oral drug formulation and certain other superior physico-chemical and biochemical characteristics of 5'-chloro-araC make this compound an interesting candidate for further investigations.

Animals↗

PubMed1991

Some electrochemical characteristics of synthetic analogs of nucleic acid components. IV. 5-Cyano-, 5-carboxy- and 5-azaderivatives, and the effect of this substitution on potential carcinogenicity.

The relation between polarographic reduction, values of half-wave potentials, and the parameter of potential carcinogenicity (tg alpha) was studied in a series of synthetic analogs of natural nucleic acid components modified by different substituents at position 5 of the base. The series included pyrimidine nucleobases (5-cyanouracil, 5-carboxycytosine, 5-azacytosine), ribofuranosyl nucleosides (5-cyanouridine, 5-carboxycytidine, 5-azacytidine) as well as 2'-deoxy-5-azacytidine and 5-carboxy-1-beta-D-arabinosylcytosine. No direct correlation was found between the reducibility of the studied compounds and the parameter of potential carcinogenicity tg alpha since event a slight alteration in the structure of these molecules markedly affected the properties of these compounds.

Aza Compounds↗

PubMed1991

[The role of bronchoalveolar lavage in the diagnosis and therapy of recurrent respiratory tract diseases in children].

In 32 patients with relapsing bronchopneumonia, bronchiectasis, relapsing obstructive bronchitis and asthma bronchiale during aimed bronchoscopy bronchoalveolar lavage was made (BAL). The authors found typical cytological findings and deviations in the phosphatidyl choline level which is the main constituent of the pulmonary surfactant. The authors evaluated the importance of the surfactant for the proper function of the lungs and outlined possible therapeutic measures which by the action of some drugs will influence its formation.

Asthma↗

PubMed1991

Some electrochemical characteristics of synthetic analogs of nucleic acid components. III. Derivatives of 5-fluorouridine. An attempt to find correlation between some of their characteristics.

The polarographic reduction and parameter tg alpha of a series of synthetic 5-fluorouracil derivatives (various 5'-modified nucleosides) were studied. The studied compounds were compared with analogous nucleosides of the uridine series. It was confirmed that the value of tg alpha which may suggest a potential carcinogenic activity of the compound studied, is dependent upon the reducibility of the compound and is associated with the cleavability of the nucleoside bond, i.e. with the ability to liberate fluorouracil. It was found that Ftorafur, an antitumor agent widely used in clinical practice, displayed a very high value of tg alpha. In the group of polyaromates such high tg alpha values had been found in compounds which are known to have carcinogenic activity.

Animals↗

PubMed1990

Preparation, properties and antileukemic activity of arabinosylcytosine polysaccharide conjugates.

1. Conjugates of 1-beta-D-arabinofuranosylcytosine (araC) with polysaccharides containing carboxyl groups, such as polygalacturonic acid (PGA) and carboxymethylated yeast beta-D-glucan (CMG) were prepared. 2. Activation of the polysaccharidic carboxyl group by isobutylchloroformiate and formation of a peptide bond via 4-NH2 group of araC was used for a coupling reaction. 3. Elementary analysis, u.v. and i.r. spectra confirmed the structures of the conjugates. 4. The conjugates were most stable against the hydrolysis under the mild acid conditions. 5. It was also shown that under the physiological conditions trypsin catalyze the conjugate hydrolysis and the catalytic effect is higher than that of chymotrypsine. 6. It is suggested that trypsin or trypsin-like proteases could participate in the hydrolysis of the conjugates in vivo. PGA-araC and CMG-araC showed 1.5- or 2.5-times higher antileukemic activity than both free araC or polysaccharides.

Animals↗

PubMed1990

Comparison of some biochemical parameters of arabinosylcytosine and cyclocytidine in L1210 murine leukemia cells.

The basic biochemical characteristics of cyclocytidine hydrochloride (cC.HCl) and arabinosylcytosine (araC) were compared. It was demonstrated that despite different lipophilicity and different pK (4.15 for araC and 6.60 for cC.HCl), the mechanism of inhibition of DNA synthesis by both compounds is the same (ID50 for araC was 0.048 mumol/l and for cC. HCl 0.23 mumol/l). The compounds had a different mechanism of inhibition of RNA synthesis (ID50 for araC was 2.69 mmol/l and for cC.HCl 1.08 mmol/l) and showed a marginal effect on protein synthesis. Hydrolysis of the 0(2),2'-anhydro bond in cC.HCl and formation of araC in vivo was characterized by a Km = 280 mumol/l using HPLC. Deamination of araC in vivo was studied in healthy mice (Km = 247 mumol/l), 8.6% of arabinosyluracil 15 minutes after araC administration) and in mice with sensitive and araC resistant leukemia L1210 (15.5% and 8.5% of arabinosyluracil 15 minutes after araC administration, respectively). On the basis of different physico-chemical properties of cC.HCl and different mechanisms of inhibition of RNA synthesis it can be assumed that cC.HCl, when therapeutically used, may have its own mechanism of biological effect(s) and that its application may be therapeutically advantageous in some aspects as compared to araC.

Ancitabine↗

PubMed1990

Antiviral activities of pyrimidine nucleoside analogues: some structure--activity relationships.

Seventeen nucleoside derivatives (derived from arabinosylcytosine, resp. cytidine, 5-fluorouracil and uracil) were tested by agar-diffusion plaque-inhibition test for their antiviral activity with herpes simplex, vaccinia, fowl plague, Newcastle disease and western equine encephalomyelitis viruses. The highest antiviral activity against DNA viruses exhibited arabinosylcytosine, N4-acylarabinosylcytosines, arabinosylthiouracil, cyclocytidine and its 5'-chloroderivative. RNA viruses were inhibited by 5-fluorouridine only, whereas other tested compounds were ineffective or showing marginal activity only. By search for relationship between chemical structure and antiviral activity a tendency was found of higher antiviral activity at lower lipophilicity. This is probably due to better transport of the studied compounds into cell. The chemical structure, however, is the main reason of antiviral activity.

Animals↗

PubMed1990

Some electrochemical characteristics of synthetic analogs of nucleic acid components. I. Derivatives of cytidine and arabinosylcytosine. An attempt to find correlation among some of their properties.

The polarographic reduction and parameter tg alpha of a series of natural and synthetic pyrimidine nucleosides, cytidine derivatives, and the cancerostatic agent arabinosylcytosine were studied. Correlations were found between these newly determined characteristics and capacity factor kappa from HPLC analysis, growth inhibition of E. coli B bacteria, deamination of nucleosides by cytidine deaminase, DNA synthesis, and rate of biotransformation and lipophilicity expressed as log P. It was confirmed that the molecule of nucleosides is complex to such an extent that no linear correlation could be revealed among the respective parameters. Linear correlation was found only in smaller, structurally similar groups of derivatives.

Cytarabine↗

PubMed1990

Some electrochemical characteristics of synthetic analogs of nucleic acid components. II. Derivatives of uridine and arabinosyluracil. An attempt to find correlation between some of their properties.

The relation between half-wave potentials E1/2, parameter tg alpha, and chemical structure of a series of natural and synthetic compounds of nucleic acids were studied. This series included the pyrimidine nucleobase uracil, the natural pyrimidine nucleoside uridine and its deoxy-derivatives, the synthetic analog arabinosyluracil, its deoxy- and thio-analogs, and some cyclonucleosides. It was confirmed that the value of tg alpha, which may suggest a potential carcinogenic activity of the compounds studied, is dependent upon lipophilicity and rate of biotransformation of these compounds. Generally, it was shown that the complexity of nucleoside molecules makes it impossible to find parameters showing correlation. Linear correlation was found only in small, structurally similar groups of derivatives.

Arabinofuranosyluracil↗

PubMed1989

The effect of structural modifications of 5-fluorouracil derivatives on their transport and biodegradation by isolated rat jejunum.

The continuous-perfusion technique was used in an isolated segment of everted rat jejunum to study transport and biotransformation processes in a series of cancerostatic derivatives of 5-fluorouracil. Metabolic alterations during penetration of the intestinal wall were assessed by high-performance liquid chromatography (HPLC). Octanol-buffer partition coefficients were measured, and the lipophilicity of the study compounds and fragmental constants for their sugar moieties were assessed. In the present series of 5-fluorouracil derivatives, there was no correlation between lipophilicity and metabolic cleavage to 5-fluorouracil, but a correlation was found between lipophilicity and the transport rate. Remarkable stability of the nucleoside bond and high biotransport were observed with 5'-chloro-5-fluorouridine, suggesting a different mode of activation for this derivative.

Animals↗

PubMed1988

Comparative study of cyclocytidine and arabinosylcytosine disposition in rats.

The stability of cyclocytidine (II) in aqueous solutions decreased with increasing pH and temperature. After intravenous injection to rats the biphasic decline of cyclocytidine in the serum was accompanied by simultaneous formation of arabinosylcytosine. Since under physiological conditions (37 degrees C, pH 7.2) the half-lifetime of cyclocytidine dissolved in water was 5 hours, the very early appearance of arabinosylcytosine in the serum of rats suggests that various hydrolytic enzymes may also be responsible for the conversion of cyclocytidine in to arabinosylcytosine in vivo. An equimolar dose of arabinosylcytosine (I) injected to rats produced serum levels which were several times higher than those of cyclocytidine under the same conditions. Since the rate constant of overall elimination was similar for both compounds, this difference in serum levels may most probably be explained by a much higher distribution volume of cyclocytidine resulting also in a higher plasmatic clearance of this compound.

Ancitabine↗

PubMed1987

5'-Fluorosulfonylbenzoyl derivatives of therapeutic nucleoside analogs.

Several fluorosulfonylbenzoyl /FSB/ purine and pyrimidine nucleoside analogs of the clinically useful antimetabolites which belong to endo affinity labeling compounds were synthetized. Structures were confirmed by both 1H NMR and UV spectroscopy and by elemental analysis. Procedure for preparation of microamount of [3H] FSB-araC was developed. Bonding of radioactive FSB-araC to nucleotide utilizing enzymes in K562 myeloblasts soluble protein extract was compared with araCTP-degradating activities in this extract after DEAE-cellulose column chromatography. There was found that five major peaks of the radioactivity bound to the protein coincident with peaks of araCTP degradation. Bonding of [3H] FSB-araC in CCRF-CEM lymphoblasts exhibits only 3 major peaks of the bound radioactivity. This result correlates with the higher sensitivity of the CEM cells to araC.

Antimetabolites, Antineoplastic↗

PubMed1984

Kinetics of transport and metabolism of 1-beta-D-arabinofuranosylcytosine and structural analogs by everted perfused rat jejunum.

Few reports have dealt with the kinetics and metabolism of AraC and analogs by rat intestine. Using everted rat jejunum with continuous perfusion, it was possible to demonstrate that AraC and Cyd cross the intestinal barrier(s) by a carrier mediated process which was saturable and exhibited fairly good fitting of the flux rate by Michaelis-Menten equation. The transport rate of different analogs was not consistent with the pH-partition theory of membrane transport of drugs being rather dependent on the chemical structure of the nucleoside. A free amino group of cytosine increased the rate of transport within the present series of AraC analogs. There was a detectable deaminase as well as esterase activity towards AraC and its analogs in rat jejunum.

Animals↗

PubMed1984

Structure-intestinal transport and structure-metabolism correlations of some potential cancerostatic pyrimidine nucleosides in isolated rat jejunum.

Both transport and biotransformation processes for a series of pyrimidine nucleobases, ribonucleosides, 2'-deoxyribonucleosides, and acetyl and 5'-substituted derivatives of the cancerostatic agent araC were studied in the isolated everted rat jejunum with a continuous perfusion technique. Metabolic alterations during penetration were assessed by HPLC. 5'-Halogeno and 5'-deoxy derivatives of cytosine nucleosides exhibited higher transport rates and higher stability towards the deamination reaction than did unsubstituted derivatives. Octanol-buffer partition coefficients were estimated for the study compounds, and fragmental constants for the sugar moieties of nucleosides were assessed. With the present study compounds there was no correlation between lipophilicity and transport rate, as previously reported, but there was a correlation between lipophilicity and metabolic alteration of araC derivatives (r = 0.99, n = 5).

Animals↗