Biomedical subjects

J Beránek

Publications and source records attributed to J Beránek.

At least 19 recordsLinked to original sources

PubMed2000

[Rehabilitation of the upper respiratory muscles (orofacial stimulation--OFS) in the sleep apnea syndrome].

Orofacial stimulation seems to be one of further possibilities of curing SAS. It is especially suitable in the case of mixed or central type of SAS [3, 4]. It may favourably influence some subjective complaints of the patients, but also the sleep profile and apnea index. The advantage of this method is that it does not stress the patient and may be used individually or in combination with CPAP [7] or surgical treatment [5]. In our country we have applied this method as the first in the treatment of snoring and SAS. We have not find this treatment of SAS in world literature.

Facial Muscles↗

PubMed2000

[Erroneous and complicating diagnoses in patients with the sleep apnea syndrome].

A great number of patients suffering from SAS (19.5% according to our study) exhibit other complicating illnesses. This requires a complex diagnostic and therapeutic approach. Of these complicating illnesses the most frequent are neuropathy, thyreopathy and similar metabolic diseases. A polygraphic investigation alone may not suffice. It is necessary for a neurological specialist, acquainted with sleep disorders. This neurologist co-operates with the other specialists. A correctly indicated therapeutic procedure (conservative or surgical) will prevent a future relapse of the illness.

Diagnosis, Differential↗

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↗

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↗

PubMed1986

A study on structure-activity relationships of nucleoside analogues.

A selected series of nucleoside analogues were tested for inhibitory activity vs DNA and/or RNA synthesis at L1210 cells. The structure-activity relationship was studied among derivatives of 5-fluorouracil and arabinosylcytosine (araC), compounds clinically used in cancer chemotherapy. 5-Fluorouridine was found to be a selective, most potent inhibitor of RNA synthesis. Arabinosylcytosine was the most potent selective inhibitor of DNA synthesis. Only cyclocytidine stands very close to the carcinostatic antibiotics in its strong simultaneous inhibition of both DNA and RNA synthesis. A biologically interesting new group of 5'-deoxy derivatives of arabinosylcytosine was investigated. The inhibitory activity vs DNA and/or RNA synthesis is compared with the activity against growth of E. coli and against herpes simplex virus type I (HSV). The system for inhibition of NA synthesis is proposed as a preliminary first step: an in vitro screening method promising for the discovery of new types of potential carcinostatic agents. Both transport and biotransformation processes of nucleoside analogues were studied in the isolated everted rat jejunum with a continuous perfusion technique. The 5'-substituted derivatives of araC and 5'-chloro-5-fluorouridine exhibited higher transport rates and higher metabolic stability during intestinal penetration than the parent nucleosides. There was found to be no correlation between lipophilicity and transport rate, but there is a correlation between lipophilicity and metabolic alterations among the nucleoside derivatives studied.

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↗

PubMed1983