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Biomedical subjects

M Nemec

Publications and source records attributed to M Nemec.

At least 19 recordsLinked to original sources
PubMed2005

Antimutagenic properties of green tea.

In this work biological effects of two common kinds of green tea (Chinese Gunpowder and Japanese Sencha) were analyzed using three independent tests of antimutagenicity: 1) the Ames test with Salmonella typhimurium TA98, 2) cytogenetic analysis of peripheral blood lymphocytes (CAPL), and 3) test with Saccharomyces cerevisiae D7. Tea extracts were allowed to be antimutagenic based on their ability to inhibit the mutagenic effect of standard mutagens. Amounts of (-)catechin and (-)catechin gallate in tea extracts were determined by high performance liquid chromatography on reversed phase (RP-HPLC). Antioxidant capacity was found using total radical-trapping antioxidant parameter (TRAP) method. Extracts from Gunpowder and Sencha exhibited high antimutagenic activity in the Ames test (24.7+/-3.7% and 34.1+/-2, 1% of inhibition without metabolic activation; 74.9+/-1.7% and 62.7+/-4.3% of inhibition with metabolic activation, respectively) as well as in S. cerevisiae D7 test (Gunpowder: 62.7+/-5.7% of Trp convertants inhibition and 52.6+/-5.3% of Ilv revertants inhibition; Sencha: 45.6+/-4.2% of Trp convertants inhibition, 50.0+/-4.8% of Ilv revertants inhibition). In the CAPL method reduced number of abberant cells as well as decreased number of chromosome breaks was observed using both green tea extracts. Antioxidant capacity and antimutagenicity of green tea extracts was higher than activity of tea catechins and flavonoids.

Antimutagenic Agents↗
PubMed2005

Tolerance of therapeutic doses of abamectin and doramectin in Istrian Pramenka sheep.

Avermectin endectocides are very effective and safe veterinary drugs, when used at recommended doses. Adverse reactions are described in some species and breeds of animals. In this study, the effects of therapeutic doses of abamectin and doramectin on some haematological and biochemical parameters in Istrian Pramenka sheep are discussed. In the pilot trial, we compared selected haematological and blood biochemical parameters of an experimental sheep flock (40 sheep) with the reference values. Then, two groups of 12 sheep (and their suckling lambs) were chosen from the experimental sheep flock. Each group was subdivided into a control (six animals) and treated (six sheep and their six suckling lambs) groups. We compared haematological and biochemical parameters between control and treated group before subcutaneous administration of abamectin or doramectin (0.2 mg/kg b.w.) and on days 15 and 42 after treatment. In addition, animals were observed for neurological signs. We detected some significant differences (P < 0.05) in some haematological and biochemical parameters between control and treated animals, but none of them appeared to be of clinical importance. No neurological symptoms were observed. Therefore, abamectin and doramectin might be well tolerated in Istrian Pramenka sheep.

Animals↗
PubMed2004

Degradation of 5-nitroguaiacol by soil bacteria of the genus Rhodococcus.

Two bacterial strains were isolated from forest soil by selective enrichment of the mineral medium containing 4-nitropyrocatechol as the sole carbon and energy source. Both strains could utilize 4-nitropyrocatechol and 5-nitroguaiacol. Degradation of 5-nitroguaiacol and stoichiometric release of nitrites was measured during its degradation both in growing culture and for resting cells. Both strains were unable to degrade other nitroaromatic compounds such as 4-nitroguaiacol, 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, 2,4-dinitrobenzoic acid, 4,5-dimethoxy-2-nitrobenzoic acid and 2,3-difluoro-6-nitrophenol. One strain was identified as Rhodococcus opacus and the second one as Rhodococcus sp.

Biodegradation, Environmental↗
PubMed2003

An EPR study of the secretion of G-CSF heterologous protein from Pichia pastoris.

The biologically active protein known as human granulocyte colony stimulating factor (G-CSF) can be efficiently secreted from the transformed GS115 Pichia pastoris (GS115/pPIC9/G-CSF), which contains an alpha-mating-factor prepro signal sequence and an alcohol oxidase I promoter, both introduced using the pPIC9 plasmid. To study the P. pastoris G-CSF protein-secretion process, changes to the plasma membrane's lateral domain structure were monitored using electron paramagnetic resonance (EPR). The GS115 and its transformed analogue show that the plasma membrane can be described by fluid-disordered and fluid-ordered lateral domains. The relative proportion of these domains is a sensitive parameter that is able to describe the membrane's involvement in the protein-excretion process. Here, P. pastoris GS115 served as a control for us to compare with the GS115/pPIC9/G-CSF heterologous protein-secreting cells. Electron paramagnetic resonance studies using the spin-probe 5-doxyl methyl ester of palmitic acid [MeFASL (10,3)] showed that during cultivation in a glycerol medium all types of cells had a relatively high proportion of cell-membrane fluid-disordered domains, while during the production phase the G-CSF protein-secreting cells showed a decrease in the proportion of fluid-disordered domains. We ascribe this effect to the vesicular lipid exchange caused by the fusion of secretary vesicles with the plasma membrane during exocytosis. Using electron microscopy and immunocytochemistry intracellular vesicles containing the G-CSF protein were detected. Our studies support the exocytotic mechanism of the heterologous protein secretion.

Cell Membrane Permeability↗
PubMed2001

The action of mercury on cell membranes.

The action of mercuric chloride and methyl mercuric chloride on the membrane lateral domain organization of bovine, equine, and canine erythrocytes was studied. Electron paramagnetic resonance (EPR) spectra of spin-labeled erythrocytes were analyzed with respect to their lateral domain structure. Continuous alteration of the membrane domain populations revealed that mercuric compounds affect the membrane via the evolution of toxic events in the cells.

Animals↗
PubMed2000

Conservative treatment versus surgery in spondylotic cervical myelopathy: a prospective randomised study.

A prospective randomised 2-year study was performed to compare the conservative and operative treatment of mild and moderate forms of spondylotic cervical myelopathy (SCM). Forty-eight patients presenting with the clinical syndrome of SCM, with a modified Japanese Orthopaedic Association (mJOA) score of 12 points or more, were randomised into two groups. Group A, treated conservatively, consisted of 27 patients, mean age 55.6 +/- 8.6 years, while group B was treated surgically (21 patients, mean age 52.7 +/- 8.1 years). The clinical outcome was measured by the mJOA score, recovery rate (RR), timed 10 m walk, score of daily activities (recorded by video and evaluated by two observers blinded to the therapy), and by the subjective assessment of the patients at 6, 12, and 24 months of the follow-up. There was, on average, no significant deterioration in mJOA score, recovery ratio, or timed 10 m walk within either group during the 2 years of follow-up. In the surgery group there was a slight decline in the scores for daily activities and subjective evaluation. A comparison of the two groups showed no significant differences in changes over time in mJOA score or quantified gait, but there were significant differences in the score of daily activities recorded by video at 24 months, which was a little lower in the surgical group, and also in RR and subjective evaluation, which were both worse in the surgical group at months 12 and 24. However, at month 6, this last parameter was significantly better in the surgical than in conservative group. Surgical treatment of mild and moderate forms of SCM in the present study design, comprising the patients with no or very slow, insidious progression and a relatively long duration of symptoms, did not show better results than conservative treatment over the 2-year follow-up.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1999

Conserved domains and lack of evidence for polyglutamine length polymorphism in the chicken homolog of the Machado-Joseph disease gene product ataxin-3.

Ataxin-3 is a protein of unknown function which is mutated in Machado-Joseph disease by expansion of a genetically unstable CAG repeat encoding polyglutamine. By analysis of chicken ataxin-3 we were able to identify four conserved domains of the protein and detected widespread expression in chicken tissues. In the first such analysis in a non-primate species we found that in contrast to primates, the chicken CAG repeat is short and genetically stable.

Amino Acid Sequence↗
PubMed1999

Er:YAG and alexandrite laser radiation propagation in root canal and its effect on bacteria.

OBJECTIVE: The objective of this study was to compare the bactericidal effect of the Er:YAG (wavelength 2.94 microm) and the Alexandrite (wavelength 0.75 microm) laser radiation. The spreading laser energy in the surrounding hard dental tissues round the root canal was evaluated and the bactericidal effect of both these different laser wavelengths was analyzed. SUMMARY BACKGROUND DATA: The use of a laser to clean and shape the root canal space is the latest method used for cleaning of root canals. The interest in laser endodontics was concentrated on the possibility to extirpate the contents of the root canal, to sterilize and to "melt" the walls of the root canals. The previous reports were performed with CO2, excimer, argon, Nd:YAG, Ho:YAG, and Er:YAG lasers. METHODS: Er:YAG laser system (2.94 microm, energy 100 mJ or 300 mJ, repetition rate 1 Hz, 30 pulses) and alexandrite laser system (0.75 microm, energy 250 mJ, repetition rate 1 Hz, 30 pulses) were prepared and three experimental arrangements were used during the measurements. First the energy transport through the tooth tissue was observed (frontal and side experimental setups) and then, the bactericidal effect was evaluated. RESULTS: It was demonstrated that due to the absorption in the hydroxyapatite and water content in the dentin, the Er:YAG laser radiation is fully absorbed in the root canal wall. This direct influence of the radiation could be expected only close to the sapphire tip. It was found that the tissue, which was not directly affected by the laser radiation, cannot be disinfected by the subablative effect of Er:YAG laser radiation. In the second part of the experiment the real bactericidal effect of Er:YAG ablative energy (300 mJ) could be observed. It was also shown that the alexandrite laser radiation with a wavelength of 0.75 microm spreads through the canal system space and leaks into the surrounding tooth tissues. Both lasers have bactericidal effect. CONCLUSIONS: The pulsed Er:YAG and alexandrite lasers can be efficiently used for killing dental bacteria but the spreading of their radiation in the tooth tissues are different.

Dental Pulp Cavity↗
PubMed1995

Transport and dynamics of molecules dissolved in maize root cortex membranes.

Translational diffusion of a fluorescent sterol probe was measured in the plasma membranes of protoplasts isolated from cortical cells of the primary root of maize seedlings. The apparent lateral diffusion coefficient was typically observed to be nearly insensitive to temperature, while the mobile fraction increased with increasing temperature. These fluorescence photobleaching recovery (FPR) measurements were compared with the electron paramagnetic resonance (EPR) spectra of the methyl ester of 13-doxyl palmitic acid in membranes of corn root tissue in situ. The complex spectra observed with this probe were analyzed as weighted sums of simpler spectra of various order parameters and rotational correlation times. The reconstituted spectra calculated from the model show that EPR also detects a mobile (less ordered, fluid) fraction, distinguished by the order parameter S = 0.1 to 0.2, which becomes more abundant as temperature increases and is qualitatively comparable to the mobile fraction determined by the FPR method. The observed results on the mobile fractions and the diffusion rates for translational (FPR) as well as rotational (EPR) motions are interpreted in terms of membrane organization, thus providing information on the population and structural patterns of the coexisting domains with a special emphasis on the response of the membrane to temperature changes.

Biological Transport↗
PubMed1995

Inhibition of protein kinase C results in a switch from a non-motile to a motile phenotype in diverse human lymphocyte populations.

Circulating lymphocytes are rounded, non-motile cells which on contact with cytokines, specialized or activated endothelium, acquire a constantly shape-changing, polarized morphology which enables migration into appropriate sites. The biochemical mechanisms which regulate this switch are not understood but the various stimuli may have a common final pathway. In this study we show that protein kinase C (PKC) inhibitors of the bisindolylmaleimide type (GF 109203X, Ro 31-8220, CGP 41,251) induce resting, spherical lymphocytes to change rapidly (< 30 min) into polarized, locomotory cells. This phenomenon was seen with diverse populations of blood T lymphocytes, tonsillar B cells and Jurkat and Molt4 T-cell lines. Consistent with this, down-regulation of PKC by chronic treatment (44 hr) with bryostatin also induced the polarized phenotype in blood lymphocytes and non-motile Molt4 cells. Conversely, treatment of a spontaneously motile subline of Molt4 cells with various PKC activators caused a reversion to the non-motile phenotype within minutes. PKC activation must be sufficient to overcome the effects of a constitutively active phosphatase because bisindolylmaleimide induction of motility could be prevented by pretreatment of the cells with a phosphatase inhibitor, calyculin A. It is concluded that, in resting lymphocytes, chronic activation of a PKC offsets the action of a constitutively active phosphatase and the net result is maintenance of the non-motile state. Agents which alter the kinase/phosphatase balance in favour of dephosphorylation result in induction of the locomotory phenotype.

Alkaloids↗
PubMed1994

Effect of supplementing gilts' diets with different levels of vitamin E and different fats on the humoral and cellular immunity of gilts and their progeny.

The effects of supplementing gestation and lactation diets of gilts with different combinations of vitamin E at or above NRC recommended levels (22, 44, or 88 IU/kg during gestation and 55, 110, and 220 IU/kg during lactation) and types of fat (5% added tallow or fish oil or no added fat) on humoral and cellular immunity of gilts and their pigs were evaluated. With only two exceptions, total IgG, IgM, and IgA in colostrum, milk, and plasma of gilts and in plasma of their pigs did not show significant (P > .05) effects, and no interactions between vitamin E and fat supplementation were observed. Cellular immunity was measured as lymphocyte proliferation response to phytohemagglutinin (PHA), concanavalin A (Con A), purified protein derivative of Mycobacterium avium, keyhole limpet hemocyanin, Escherichia coli lipopolysaccharide (LPS), and Salmonella typhimurium LPS. Only the nonspecific mitogens, PHA and Con A, induced proliferation of gilt and pig lymphocytes. Fish oil supplementation in the gilts' diets resulted in lower (P < .01) postpartum PHA response in gilts and slower (P < .05) acquisition of PHA response in newborn pigs compared with groups with added tallow or no added fat. The vitamin E supplementation did not have a significant positive effect on either PHA or Con A response of the gilts. However, the rate of acquisition of PHA response and Con A response in newborn pigs was greater (P < .05) for groups supplemented with 110 and 220 IU/kg of vitamin E than for the group supplemented with 55 IU/kg vitamin E.

Animals↗
PubMed1992

Spin-labeled phorbol esters and their interactions with cellular membranes--IV. Lipophilic binding and molecular orientation of spin-labeled phorbol-12,13-diesters in human erythrocyte membrane.

In human erythrocyte membranes, membrane binding of spin-labeled TPA-analogous phorbol (doxyl)esters [(n,m)PA] was investigated during measurement of the kinetics of the decay of their electron paramagnetic resonance signal by ascorbate reduction. In membrane-bound (n,m)PA the reduction rate was dependent of the position of doxyl in the aliphatic chain of their 12-O-acyl moiety. To describe quantitatively the reaction kinetics observed, two hypotheses (models) were developed and used. Model 1 is based on the assumption that ascorbate reduction takes place in the extracellular space. In this case the experimental data could be fitted by the partition and permeability coefficients of (n,m)PA determining model 1 only, if non-realistic values of these parameters were used. The more refined model 2, corresponding to a bilayer membrane structure, assumes the reduction to take place in the hydrophilic region of the membrane. Assuming a finite probability of finding the doxyl group within the hydrophilic membrane region, model 2 describes quantitatively the dependence of the reduction rate on the position of the doxyl in the aliphatic chain of the (n,m)PA used. From the validity of this model it may be postulated that the molecular orientation of TPA-analogous (n,m)PA in the bilayer membrane is determined by an anchoring of their lipophilic ester moiety in the lipophilic region of the membrane bilayer, thus locating the hydrophilic phorbol moiety within the hydrophilic region of the membrane. With regard to the well-known categories of non-specific versus specific binding of bioactive phorbol esters to protein kinase C/membrane complexes it is deduced that anchoring of (n,m)PA (and hence TPA) in the hydrophobic interior of the membrane structure may be the molecular equivalent of their non-specific binding.

Ascorbic Acid↗