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Biomedical subjects

M Strnad

Publications and source records attributed to M Strnad.

At least 37 records · Page 2Linked to original sources
PubMed1998

[Fluorescence methods for studying cell damage].

We have been studying some properties of the new generation photosensitizers--phthalocyanines. The influence of the certain phthalocyanine concentrations at combination with laser irradiation doses (semiconductor laser, lambda = 670 nm, P = 50 mW) have been studied by in vitro fluorescent methods. Cytotoxicity assay LIVE/DEAD for fluorescence microscopy and measurements of cells viability with multi-well plate scanner was used. The optimal phototoxic effect on MCF7--mamma carcinoma cells was observed 8 micrograms/ml ZnPcS2, 10 micrograms/ml ClAlPcS2 in combination with laser irradiation 50 J/cm2 and 100 J/cm2 respectively. This concentration and dose killed MCF7 carcinoma cells.

Breast Neoplasms↗
PubMed1997

Cytokinin-derived cyclin-dependent kinase inhibitors: synthesis and cdc2 inhibitory activity of olomoucine and related compounds.

Cyclin-dependent kinases (cdk) have recently raised considerable interest in view of their essential role in the regulation of the cell division cycle. The structure-activity relationships of cdk inhibition showed that the 1, 3; and 7 positions of the purine ring must remain free, probably for a direct interaction, in which it behaves as a hydrogen bond acceptor. Olomoucine (6-(benzylamino)-2-[(2-hydroxyethyl)amino]-9-methylpurine, OC), roscovitine (6-(benzylamino)-2(R)-[[1-(hydroxymethyl)propyl]amino]-9-isopropylpur ine), and other N6,2,9-trisubstituted adenines were found to exert a strong inhibitory effect on the p34cdc2/cyclin B kinase. Removal or change of the side chain at position 2 or the hydrophobic group at position 9 dramatically decreased the inhibitory activity of olomoucine or roscovitine. Inhibition of cdk with OC and related compounds clearly arrests cell proliferation of many tumor cell lines at G1/S and G2/M transitions and also triggers apoptosis in the target tumor cells in vitro and in vivo. Thus, from a pharmacological point of view, OC may represent a model compound for a new class of antimitotic and antitumor drugs.

Animals↗
PubMed1997

Inhibition of cyclin-dependent kinases by purine analogues: crystal structure of human cdk2 complexed with roscovitine.

Cyclin-dependent kinases (cdk) control the cell division cycle (cdc). These kinases and their regulators are frequently deregulated in human tumours. A potent inhibitor of cdks, roscovitine [2-(1-ethyl-2-hydroxyethylamino)-6-benzylamino-9-isopropylpurin e], was identified by screening a series of C2,N6,N9-substituted adenines on purified cdc2/cyclin B. Roscovitine displays high efficiency and high selectivity (Meijer, L., Borgne, A., Mulner, O., Chong, J. P. J., Blow, J. J., Inagaki, N., Inagaki, M., Delcros, J.-G. & Moulinoux, J.-P. (1997) Eur. J. Biochem. 243, 527-536). It behaves as a competitive inhibitor for ATP binding to cdc2. We determined the crystal structure of a complex between cdk2 and roscovitine at 0.24-nm (2.4 A) resolution and refined to an Rfactor of 0.18. The purine portion of the inhibitor binds to the adenine binding pocket of cdk2. The position of the benzyl ring group of the inhibitor enables the inhibitor to make contacts with the enzyme not observed in the ATP-complex structure. Analysis of the position of this benzyl ring explains the specificity of roscovitine in inhibiting cdk2. The structure also reveals that the (R)-stereoisomer of roscovitine is bound to cdk2. The (R)-isomer is about twice as potent in inhibiting cdc2/cyclin B than the (S)-isomer. Results from structure/activity studies and from analysis of the cdk2/roscovitine complex crystal structure should allow the design of even more potent cdk inhibitors.

Adenosine Triphosphate↗
PubMed1997

Conditional transgenic expression of the ipt gene indicates a function for cytokinins in paracrine signaling in whole tobacco plants.

This study investigated whether an increased production of the plant hormone cytokinin in roots, the main site of its synthesis and putative signaling organ, can influence developmental events, such as growth of axillary shoot meristems or leaf senescence, in the plant shoot. To this end, transgenic tobacco plants (Nicotiana tabacum L.) were generated that conditionally overproduce cytokinins. These plants harbour the ipt gene under the transcriptional control of a modified 35S promoter that is repressed in plants with high titers of tetracycline repressor protein. De-repression of transcription led to a rapid more than 50-fold increase of hormone concentration. The time course of changes in the steady-state levels of 16 different cytokinin metabolites, as a consequence of IPT enzyme activity, was monitored in different plant tissues. Zeatin riboside was the first and most dramatically increased product; zeatin, dihydrozeatin and glucosides accumulated later. The consequences of enhanced cytokinin synthesis remained mainly restricted to the site of hormone production. For example, de-repression of ipt gene transcription in lateral buds caused the growth of single buds only at the site of tetracycline application. In reciprocal grafts of transgenic plants with wild-type plants, no biological cytokinin effects, i.e. growth of lateral shoot meristems or sequential leaf senescence, were observed in the non-transgenic plant part. Also, the increase in steady-state levels of cytokinins remained restricted mainly to the transgenic part, despite a specific increase of the zeatin riboside concentration in the transpiration stream. These results question the role of cytokinins as a long-range root-to-shoot signal in correlative control of apical dominance and sequential leaf senescence of tobacco, and support the assumption that this hormone is relevant to paracrine signaling.

Aging↗
PubMed1997

Induction of apoptosis and regression of spontaneous dog melanoma following in vivo application of synthetic cyclin-dependent kinase inhibitor olomoucine.

This case report describes a dog with spontaneous melanoma of the orofacial region which was treated by a synthetic inhibitor of cyclin-dependent kinases, i.e. olomoucine (OC). The drug was applied i.v. in a single dose of 8 mg/kg/day for 7 days in succession. Repeated bioptic examinations of metastatic cervical lymph nodes showed rapid induction of apoptosis in tumor cells as early as on the third day of treatment. Standard clinical and laboratory examinations did not reveal side effects of the therapy. There were no detectable manifestations of myelosuppression, hepatotoxicity, nephrotoxicity or neurotoxicity. However, transient anemia developed following bleeding from a devitalized tumor mass. For this reason, the dog underwent surgery to minimize tumor load as well as to eliminate the source of bleeding. Two kilograms of primary tumor were extirpated in the course of surgery, including cervical node metastases. Unfortunately, the dog died soon after surgery due to respiratory depression. Histological examinations of the tumor tissue showed marked apoptosis of melanoma cells in both the primary tumor and metastases. The induction of programmed cell death of cancer cells by OC resulted in rapid eradication of at least 68% of the tumor cells. The remaining melanoma cells retained at least equally well in vitro sensitivity to OC as to drugs currently used in clinical practice.

Animals↗
PubMed1995

Croatian initial experience with the suitability of the ICIDH for classifying health status.

As consequences of disease and disorders cannot be expressed with the International Classification of Diseases (ICD), the International Classification of Impairments, Disabilities, and Handicaps (ICIDH) was tested on a data sample of 1800 persons from the Croatian Register of Psychophysical Development Disorders and Other Disabilities (CRPDOD). Persons with either a visceral impairment, skeletal impairment, disfiguring impairment or one from the group of generalized, sensory and other impairments, were selected. Despite favourable results some amendments are suggested. These involve several examples of coding practice, modified elaboration of consciousness and continence impairments, newly created categories and subcategories in classifications I and D, as well as common codes for cases having several disability categories simultaneously.

Croatia↗
PubMed1995

Differences between male and female breast cancer. I. Epidemiological features.

The authors' interest was focused on the direct determination of differences between the salient features of breast cancer in men and women in a large number of patients. Various epidemiological features were analyzed in a group of 386 male and 21,491 female breast cancer patients registered in the Cancer Registry of the Republic of Croatia from 1968 until 1988. This was a population-based study, and all male and female breast cancer cases recorded during the mentioned period were included in the study. During this 21-year period, the total incidence rate of breast cancer in men was about 0.83/100,000, and the mortality 0.2,/100.000. In the same interval, in women the rates doubled from 30 to 60/100,000, and 13 to 29/100,000, respectively. The highest incidence rates were recorded in the 80-84 age group in men, and 60-64 age group in women. The mean age at diagnosis was 63.4 years in men and 58.2 years in women. The distribution in terms of TNM-stages in men was: stage I-10.10%; II-40.67%; III-32.40%; IV-16.83%; in women; I-12.19%; II-49.36%; III-27-58%; IV-10.86%. The results showed that breast cancer in men had epidemiological characteristics of a sporadic disease, occurring continuously at a specific mean frequency in the general population and being little affected by environmental impacts. Conversely, in women affected by the disease there was a tendency of continuous rise in the morbidity and mortality, which might have been due to the trigger action of one or more environmental factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Inhibition of cyclin-dependent kinases by purine analogues.

While testing purines related to the non-specific protein kinase inhibitors N6-dimethylaminopurine and N6-(delta 2-isopentenyl)adenine as potential inhibitors of the p34cdc2/cyclin B kinase, we discovered a compound with high specificity, 2-(2-hydroxyethylamino)-6- benzylamino-9-methylpurine (olomoucine). Kinetic analysis of kinase inhibition reveals that olomoucine behaves as a competitive inhibitor for ATP and as a non-competitive inhibitor for histone H1 (linear inhibition for both substrates). The kinase specificity of this inhibition was investigated for 35 highly purified kinases (including p34cdk4/cyclin D1, p40cdk6/cyclin D3, cAMP-dependent and cGMP-dependent kinases, eight protein kinase C isoforms, calmodulin-dependent kinase II, myosin light-chain kinase, mitogen-activated S6 kinase, casein kinase 2, double-stranded RNA-activated protein kinase, AMP-stimulated kinase, eight tyrosine kinases). Most kinases are not significantly inhibited. Only the cell-cycle regulating p34cdc2/cyclin B, p33cdk2/cyclin A and p33cdk2/cyclin E kinases, the brain p33cdk5/p35 kinase and the ERK1/MAP-kinase (and its starfish homologue p44mpk) are substantially inhibited by olomoucine (IC50 values are 7, 7, 7, 3 and 25 microM, respectively). The cdk4/cyclin D1 and cdk6/cyclin D3 kinases are not significantly sensitive to olomoucine (IC50 values greater than 1 mM and 150 microM, respectively). N6-(delta 2-Isopentenyl)adenine is confirmed as a general kinase inhibitor with IC50 values of 50-100 microM for many kinases. The purine specificity of cyclin-dependent kinase inhibition was investigated: among 81 purine derivatives tested, only C2, N6 and N9-substituted purines exert a strong inhibitory effect on the p34cdc2/cyclin B kinase. An essentially similar sensitivity to this olomoucine family of compounds was observed for the brain-specific cdk5/p35 kinase. Structure/activity relationship studies allow speculation on the interactions of olomoucine and its analogues with the kinase catalytic subunit. Olomoucine inhibits in vitro M-phase-promoting factor activity in metaphase-arrested Xenopus egg extracts, inhibits in vitro DNA synthesis in Xenopus interphase egg extracts and inhibits the licensing factor, an essential replication factor ensuring that DNA is replicated only once in each cell cycle. Olomoucine inhibits the starfish oocyte G2/M transition in vivo. Through its unique selectivity olomoucine provides an anti-mitotic reagent that may preferentially inhibit certain steps of the cell cycle.

Animals↗
PubMed1994

Development and validation of an in-house radioimmunoassay for erythropoietin.

A sensitive radioimmunoassay (RIA) for the determination of erythropoietin (Epo) in blood serum and amniotic fluid has been developed and validated. The assay uses a polyclonal antibody obtained in rabbits immunized with recombinant human Epo by one of the authors. Tracer and second antibody are commercially available. With 100 microliters of sample, the assay can detect 3 U/l. The reproducibility of the assay compares well with commercial Epo RIAs. The normal values estimated in a group of blood donors are slightly higher than those reported for various RIA determinations. The clinical usefulness of the assay was demonstrated by observing the expected increases or decreases of Epo levels in various clinical states known to alter Epo production. The assay meets all requirements of a routine clinical assay at significantly reduced costs, which makes it particularly suitable for use in research applications.

Amniotic Fluid↗
PubMed1989

[Dynamics of occurrence and mortality in colorectal carcinoma in the community around Osijek].

The extent and dynamics of the occurrence of colorectal carcinoma were analysed in all the communes of the region of Osijek during the period from 1968 to 1982. The age and sex of patients, geographical distribution and other factors which might have influenced the colorectal carcinoma occurrence were taken into consideration. The dynamic of the occurrence of colorectal carcinoma was analysed by the method of regression. The incidence of the carcinoma of the large bowel in the region of Osijek in 1982 was between 10.3% and 33.7% per 100,000 inhabitants. In most communes the incidence was between 20.9% and 28.1%. During the period from 1968 to 1982 there was an increase in the occurrence of colorectal carcinoma in all communes, with the exception of the commune of Slavonska Orahovica which is one of the most undeveloped areas in the region. A significant increase of the new cases of colorectal carcinoma was recorded in the communes of Beli Manastir and highly significant increase in the communes of Djakovo, Podravska Slatina, Slavonska Pozega and Vukovar. During the same period there was an evident increase in the mortality rate from colorectal carcinoma in all the communes in the region of Osijek. The rate was 22.2% per 100,000 inhabitants which represents 1.9% of overall mortality or 11.6% of the mortality from all malignant diseases in the region. With regard to epidemiological data and the authors' own investigations it has become obvious that more care and attention should be paid to the prevention of colorectal carcinoma as an integral part of the chronic disease prevention programme.

Adult↗