Biomedical subjects

Joanna Kowalska

Publications and source records attributed to Joanna Kowalska.

11 recordsLinked to original sources

PubMed2006

Solid-liquid extraction and cation-exchange solid-phase extraction using a mixed-mode polymeric sorbent of Datura and related alkaloids.

Tropane alkaloids solid-liquid extraction methods were developed and comprised ambient pressure ones: extraction with hot solvent, extraction at room temperature, on ultrasonic bath as well as pressurised liquid extraction (PLE) techniques. The highest yields of l-hyoscyamine in methanol PLE method (3 x 5 min, 110 degrees C) and scopolamine extracted with 1% tartaric acid in methanol (15 min, 90 degrees C) were determined. A mixed-mode reversed-phase cation-exchange solid-phase extraction (SPE) procedure was optimised for simultaneous recoveries of L-hyoscyamine, scopolamine, scopolamine-N-oxide from plant extracts as well as quaternary alkaloid representative: scopolamine-N-methyl bromide. First three alkaloids were efficiently eluted (recoveries 80-100%) from an Oasis MCX cartridge with methanol-10% ammonia (3:1, v/v) solution, whereas for the quaternary salt tetrahydrofuran-methanol-25% ammonia (6:1:3, v/v) was used with recoveries 52-6%. HPTLC-densitometric assay on silica gel plates was elaborated at 205 nm without derivatization and included: single development (over a distance 9.5 cm) with acetone-methanol-water-25% ammonia (85:5:5:8, v/v) mobile phase for L-hyoscyamine and scopolamine separation, whereas for scopolamine-N-oxide and scopolamine-N-methyl bromide a second development (to a distance 5.5 cm) with acetonitrile-methanol-85% formic acid (120:5:5, v/v) was applied. Newly elaborated RP-HPLC-diode array detection method was performed on Waters XTerra RP-18 column with gradient of acetonitrile in 15 mM ammonia solution and alkaloids were baseline separated within 20 min. Both chromatographic methods were validated and their quantitative results were compared. Good correlation between HPLC and HPTLC quantitative results was measured (correlation coefficients of mean values were 0.92086 and 0.99995 for L-hyoscyamine and scopolamine, respectively). In the RP-HPLC method, which was from 1.5- up to 7-fold more sensitive than HPTLC, limits of detection (LOD) and limits of quantitation (LOQ, in bracket) were (in ng/microl) as follows: 0.25 (0.82) for L-hyoscyamine, 0.29 (0.97) for scopolamine, 0.13 (0.45) for scopolamine-N-oxide and 0.58 (1.91) for scopolamine-N-methyl bromide. By the use of the optimised chromatographic methods, 14 various samples from the leaves and fruits of Datura sp. were screened for L-hyoscyamine and scopolamine contents and the most promising samples were established.

Alkaloids↗

PubMed2006

The effect of congenital deafness on duration judgment.

OBJECTIVE: Congenital deafness provides the opportunity to study how atypical sensory and language experiences affect different aspects of information processing, e.g., time perception. METHODS: Using two methods of temporal estimation, reproduction (Exp. 1) and production (Exp. 2), the effect of deafness on duration judgment was investigated within a time domain of a few seconds. We examined 16 congenitally deaf adolescents, aged between 16 and 19 years, and 16 normally hearing subjects, matched for gender and age. In Exp. 1 subjects were asked to reproduce durations from 1 to 5.5 s, whereas in Exp. 2 they produced durations from 1 to 6 s. RESULTS: The results showed that in both experiments, the region of accurate estimation was significantly limited in deaf individuals, compared to normal hearing ones. Deaf adolescents judged accurately only intervals around 3 s, whereas they overestimated standards shorter than 2 s and underestimated those above 3 s. In contrast, controls correctly estimated the majority of standards applied in both experiments, with the exception of underreproduction of intervals longer than 3 s (Exp. 1). CONCLUSIONS: The effect of deafness on the accuracy of duration judgment can be linked to differences in the use of conventional time units, applied strategy as well as cognitive processes such as attention or working memory.

Adolescent↗

PubMed2006

Methylene analogues of adenosine 5'-tetraphosphate. Their chemical synthesis and recognition by human and plant mononucleoside tetraphosphatases and dinucleoside tetraphosphatases.

Adenosine 5'-polyphosphates have been identified in vitro, as products of certain enzymatic reactions, and in vivo. Although the biological role of these compounds is not known, there exist highly specific hydrolases that degrade nucleoside 5'-polyphosphates into the corresponding nucleoside 5'-triphosphates. One approach to understanding the mechanism and function of these enzymes is through the use of specifically designed phosphonate analogues. We synthesized novel nucleotides: alpha,beta-methylene-adenosine 5'-tetraphosphate (pppCH2pA), beta,gamma-methylene-adenosine 5'-tetraphosphate (ppCH2ppA), gamma,delta-methylene-adenosine 5'-tetraphosphate (pCH2pppA), alphabeta,gammadelta-bismethylene-adenosine 5'-tetraphosphate (pCH2ppCH2pA), alphabeta, betagamma-bismethylene-adenosine 5'-tetraphosphate (ppCH2pCH2pA) and betagamma, gammadelta-bis(dichloro)methylene-adenosine 5'-tetraphosphate (pCCl2pCCl2ppA), and tested them as potential substrates and/or inhibitors of three specific nucleoside tetraphosphatases. In addition, we employed these p4A analogues with two asymmetrically and one symmetrically acting dinucleoside tetraphosphatases. Of the six analogues, only pppCH2pA is a substrate of the two nucleoside tetraphosphatases (EC 3.6.1.14), from yellow lupin seeds and human placenta, and also of the yeast exopolyphosphatase (EC 3.6.1.11). Surprisingly, none of the six analogues inhibited these p4A-hydrolysing enzymes. By contrast, the analogues strongly inhibit the (asymmetrical) dinucleoside tetraphosphatases (EC 3.6.1.17) from human and the narrow-leafed lupin. ppCH2ppA and pCH2pppA, inhibited the human enzyme with Ki values of 1.6 and 2.3 nm, respectively, and the lupin enzyme with Ki values of 30 and 34 nm, respectively. They are thereby identified as being the strongest inhibitors ever reported for the (asymmetrical) dinucleoside tetraphosphatases. The three analogues having two halo/methylene bridges are much less potent inhibitors for these enzymes. These novel nucleotides should prove valuable tools for further studies on the cellular functions of mono- and dinucleoside polyphosphates and on the enzymes involved in their metabolism.

Acid Anhydride Hydrolases↗

PubMed2005

Synthesis and enzymatic characterization of methylene analogs of adenosine 5'-tetraphosphate (P4A).

A new methodology for synthesis of biologically important nucleoside tri- and tetraphosphates containing a bisphosphonate moiety instead of the terminal pyrophosphate bond is described. The series consists of tri- and tetraphosphate analogs of adenosine, guanosine and 7-methylguanosine (characteristic for mRNA cap). We have adopted a two-step procedure that allowed us to insert a methylene bridge into the phosphate chain. Nucleoside mono- or diphosphates were first activated (as imidazole derivatives) and then used in coupling reactions with organic salts of bisphosphonate. The resulting synthetic method enabled us to obtain the desired compounds with high yields and does not require any protective groups. This makes it very useful for the synthesis of labile compounds such as those containing the 7-methylguanosine ring. The structures of the synthesized compounds were confirmed by NMR spectroscopy. They were tested as potential substrates and inhibitors of several hydrolases.

Adenine Nucleotides↗

PubMed2005

Synthesis and properties of mRNA cap analogs containing phosphorothioate moiety in 5',5'-triphosphate chain.

Nucleosides and oligonucleotides with an oxygen replaced by sulfur atom are an interesting class of compounds because of their improved stability toward enzymatic cleavage by nucleases. We have synthesized several dinucleotide mRNA cap analogs containing a phosphorothioate moiety in the alpha, beta, or gamma position of 5',5'-triphosphate chain [m7Gp(s)ppG, m7Gpp(s)pG, and m7Gppp(s)G]. These are the first examples of the biologically important 5'mRNA cap analogs containing a phosphorothioate moiety, and these compounds may be useful in a variety of biochemical and biotechnological applications. Incorporation of a sulfur atom in the alpha or gamma position within the dinucleotide cap analog was achieved using PSCl3 in a nucleoside phosphorylation reaction followed by coupling the phosphorothioate of nucleoside with a second nucleotide. Synthesis of cap analogs with the phosphorothioate moiety in beta position was performed using an organic phosphorothioate salt in a coupling reaction with an activated nucleotide. The structures of newly synthesized compounds was confirmed using MS and 1H and 31P NMR spectroscopy. We present here the results of preliminary studies on their interaction with translation initiation factor eIF4E and enzymatic hydrolysis with human and nematode DcpS scavengers.

Animals↗

PubMed2005

[Exposure to hazardous chemical substances in furniture industry].

BACKGROUND: The aim of the study was to assess the exposure to organic solvents in plants of the furniture industry. MATERIALS AND METHODS: Studies were conducted in five furniture plants. Hazardous chemicals present in the air at workposts were determined by capillary gas chromatography with mass spectrometry and flame ionization detection. RESULTS: The analysis of air samples collected at the workposts allowed to identify the following chemicals occurring during varnishing and cleaning of furniture surface elements: acetone, butan-2-one, ethyl, isobutyl and methoxypropyl acetate, 4-methylpentan-2-on, toluene, ethylbenzene and xylenes. Indices characteristic of combined exposure ranged from 0.13 to 1.67 and exceeded the limit value at 21% of workposts. CONCLUSIONS: The results of the study indicate that chemicals present at representative workposts during the furniture production are harmful to health of workers, especially those involved in varnishing and cleaning of furniture elements.

Adult↗

PubMed2004

Temporal processing deficits in high-functioning children with autism.

It is well known that complex functions (e.g. perception, attention, memory, emotions, social interactions and language) are usually disturbed in autism. As these functions are characterized by specific temporal patterns, the present study examined whether children with autism show typical temporal processing in the time domain of a few seconds. Using a temporal-reproduction paradigm, we found that they were unable to link their responses to stimulus duration. Independently of stimulus duration, they reproduced auditory or visual stimuli with the same response duration of, on average, 3 s. These results demonstrate important deficits in duration judgment in individuals with autism. As other experiments provide evidence for a temporal processing platform of approximately 2-3 s in normal individuals, this platform may be preserved in a residual form in autism.

Adolescent↗

PubMed2004

Individual differences in temporal information processing in humans.

This article reviews some of our investigations concerning individual differences in temporal information processing. Two different levels of temporal information processing are discussed, namely the low-frequency (i.e., a few seconds time range) and the high-frequency processing level (i.e., some tens of milliseconds range) of temporal information with respect to various experimental paradigms. Evidence has been obtained indicating that the processing of temporal information on these two levels can be influenced by various subject-related factors, out of which age, gender, developmental disorders, auditory experience and localisation of damage in the brain seem to be the most significant.

Autistic Disorder↗

PubMed2003

Occupational exposure to polycyclic aromatic hydrocarbons during Diesel combustion.

Identification and determination of polycyclic aromatic hydrocarbons (PAHs) in Diesel exhaust in the working environment and assessment of workers' occupational exposure to these suspected human carcinogens were the aim of this experimental investigation. The range of exposure factors calculated on the basis of 9 individual PAH concentrations determined in personal air samples shows that time-averaged concentration of these compounds did not exceed the Polish Maximum Admissible Concentration (MAC) value for PAHs, that is, 2 microg.sup-3;. The highest concentrations of PAHs were determined in the breathing zone of forklift operators. The maximum exposure factor was 0.427 microg.msup-3; (about 1/4 of MAC).

Air Pollutants, Occupational↗

PubMed2002

Electroanalytical methods for determination of the metal content and acetic-acid-available metal fractions in soils.

The pseudo-total and available arsenic, cadmium, and lead content of soils have been determined by stripping voltammetry with a hanging-mercury-drop electrode and by atomic absorption spectrometry with electrothermal atomization. For determination of pseudo-total metals microwave digestion with a mixture of HNO3 and HClO4, with and without addition of HF, was investigated. The single-extraction procedure with 0.43 mol L-1 CH3COOH, proposed by BCR, was used to assess the availability of metals in soils. The results obtained were validated by analysis of a certified reference material.

Acetic Acid↗

PubMed2002

Duration processing in children as determined by time reproduction: implications for a few seconds temporal window.

From research carried out over recent years using different experimental paradigms, it has become apparent that central information processing is temporally segmented into sequential units of a few seconds. This segmentation presumably reflects a neuronal process of temporal integration (TI) which automatically binds successive events into temporal units. Support for such TI comes, for example, from studies on temporal reproduction where standards up to approximately 2-3 s are reproduced veridically. Using this paradigm of temporal reproduction, we investigated the effect of normal cognitive development of sensory modality and of the range of presented standards on TI. Sixty children aged 6-7, 9-10 and 13-14 years reproduced visual or auditory standard durations ranged from 1 to 5.5 s or from 1 to 3 s. The results showed that durations of approximately 2 s were reproduced correctly, whereas those longer than 2.5 s were under-reproduced in the three age groups. For standards shorter than 2 s substantial age-related differences were revealed: the youngest group displayed significant over-reproduction comparing to older subjects. These observations indicate that the upper limit for TI is a stable feature across the different age groups. Furthermore an age-related modulation within the temporal window of the operating TI seems to be linked to cognitive development.

Adolescent↗