Bora phosphorylation substitutes in trans for T-loop phosphorylation in Aurora A to promote mitotic entry.

Polo-like kinase 1 (Plk1) is instrumental for mitotic entry and progression. Plk1 is activated by phosphorylation on a conserved residue Thr210 in its activation segment by the Aurora A kinase (AURKA), a reaction that critically requires the co-factor Bora phosphorylated by a CyclinA/B-Cdk1 kinase. Here we show that phospho-Bora is a direct activator of AURKA kinase activity. We localize the key determinants of phospho-Bora function to a 100 amino acid region encompassing two short Tpx2-like motifs and a phosphoSerine-Proline motif at Serine 112, through which Bora binds AURKA. The latter substitutes in trans for the Thr288 phospho-regulatory site of AURKA, which is essential for an active conformation of the kinase domain. We demonstrate the importance of these determinants for Bora function in mitotic entry both in Xenopus egg extracts and in human cells. Our findings unveil the activation mechanism of AURKA that is critical for mitotic entry.

[Irreversible bilateral amaurosis in a 36-year-old immigrant]. / Irreversible bilaterale Amaurose bei einem 36-jährigen Immigranten.

We report on a 36-year-old man with a history of mild head trauma. The initial clinical findings and the CT-scan of the brain revealed no pathological result, although the patient suffered from weakness of the right arm and bilateral blindness. Those findings were interpreted as psychogenic disorder. Nine days later he developed an instable gait, a child like attitude, amnesia and enuresis. The CT-scan revealed a subacute bilateral occipital stroke in the region of the arteriae cerebri posteriors. No cause for the stroke was found. In spite of the rareness of cortical blindness in young people as a cause of stroke, a detailed medical history and clinical examination should always be performed, and by unclearness additional investigations should be considered.

Technical advance: the DNA-binding activity of gal4 is inhibited by methylation of the gal4 binding site in plant chromatin.

Derivatives of the Saccharomyces cerevisiae transcription factor Gal4 which act as effective transcription activators in yeast, Drosophila, mammalian cells and plant protoplasts are shown to direct expression from a GUS reporter construct when expressed in transgenic tobacco. However, in comparison to 35S-GUS controls, Gal4-mediated expression of the reporter gene was relatively weak and extremely variable. GUS expression was lost as plants matured and it was almost undetectable in most of their progeny. Gal4-mediated gene expression could be restored by treating tissues with 5-aza-cytidine, implicating cytosine methylation in the loss of Gal4-mediated expression. Restoration of reporter expression was not accompanied by an increase in steady-state levels of the activator transcript. We propose that the DNA-binding activity of Gal4 is sensitive to methylation of its binding site in plant chromatin. The Gal4-DNA co-crystal predicts that 5-methylcytosine at either of the outer two positions of the binding site will effectively prevent Gal4 binding. We show that these positions become extensively methylated in transgenic plants and that methylation of Gal4-binding sites interferes with Gal4 binding in vitro. These observations suggest that the Gal4 DNA-binding domain is intrinsically sensitive to cytosine methylation and that, despite the success of Gal4-based expression systems in yeast and Drosophila, Gal4 is not ideal for use in plant gene expression technology.

Voltammetry on mercury and carbon electrodes as a tool for studies of metallothionein interactions with metal ions.

Rabbit liver Cd-metallothionein (CdMT) and Cd-complex of synthetically prepared pentapeptide (gamma-Glu-Cys)2-Gly were studied as examples of animal and plant metallothioneins. Using hanging mercury electrode, cathodic stripping voltammetry after adsorptive accumulation of the Cd(II)-SR complex at different potentials, is suitable for estimating changes occurring in metal coordination due to the presence of metal ions such as Zn2+, Cu2+, Hg2+ or excessive Cd2+. Conditions under which similar behaviour can be observed for both CdMT and Cd-pentapeptide complex are specified. On carbon electrodes, detailed study of reduction processes of Cd(II)-SR complexes is prevented by occurrence of a large catalytic current; oxidation processes are more suitable for study at these electrodes. Carbon composite paste electrode (10% SiO2) allows deposition of Cd(II)-SR complex during its reduction, as was demonstrated with Cd-cysteine, CdMT or Cd-pentapeptide complex. After deposition, oxidation peak of the uncomplexed Cd2+ ions and one or two oxidation peaks corresponding to a formation of the RS-Cd(II) complex are observed. Also, similarly as on Hg electrode, it was observed that excessive Cd2+ or Zn2+ ions influence oxidation peaks of the RS-Cd(II) complex formation. Combination of measurements on mercury electrode and composite paste electrode is recommended for studies of metallothionein interactions with metal ions or other metal complexes.

Environmental specimen banking in the Czech Republic: a pilot study.

In recognition of the importance of environmental specimen banking (ESB) as an important component of the described ongoing real-time environmental and health-related monitoring programmes, a proposal for a planned ESB pilot study in the Czech Republic is presented. Selection of biomonitors, analytes, sampling techniques and sites is discussed, especially with regard to the possible harmonization with ESB already operational abroad. Availability of validated analytical techniques for determination of up to 30 elements using nuclear and spectroscopic techniques, including speciation of several metals, and of the most important organic pollutants employing various chromatographic techniques in biological and environmental samples is demonstrated.

Combination of classical dry ashing with stripping voltammetry in trace element analysis of biological materials: review of literature published after 1978.

Critical statements have appeared recently in the literature concerning the need for classical dry ashing in trace element analysis of biological materials. In contrast, respected institutions (AOAC, Nordic Committee on Food Analysis, etc.) as well as numerous other laboratories have developed, verified, and/or successfully used classical dry ashing in practical analyses of a number of materials of biological origin. Hence, it is desirable to find out under which conditions the latter decomposition technique yields good and accurate results. Since electroanalytical techniques are among the most demanding with regard to the completeness of the biological matrix removal, we decided to critically review the literature published after 1978 in which classical dry ashing is combined with some version of electroanalytical measurement. It emerged from this review that in particular the charring step requires careful performing. When performed well, classical dry ashing leads to complete removal of the organic matrix and to accurate analytical results for a number of determined elements.

Interlaboratory analysis of IRM NSC-21 Compost Vitahum.

The preparation of internal reference material NSC-21 Compost Vitahum, including its stabilization, homogeneity testing, and evaluation of an interlaboratory comparison in which 19 laboratories took part using several analytical methods is described. From the results of the intercomparison, consensus values were derived for the contents of Cd, Cu, Ni, Pb, and Zn, whereas for As, Co, Cr, Fe, Hg and Mn, information values were derived. Bimodal distribution of the As and Cr results was obtained, presumably because of incomplete dissolution of the elements from the matrix if insufficiently aggressive decomposition procedures were employed. Some problems encountered were elucidated by application of neutron activation analysis (NAA) in its nondestructive and destructive (radiochemical) modes.

Cadmium, lead and mercury levels in feeding yeast produced in Czechoslovakia.

Ninety-six samples of the feeding yeast known as VITEX were analyzed for Cd, Pb and Hg content during 1987-1989. Cadmium content ranged from 0.30 to 5.12 mg/kg(-1), lead content from 0.21 to 3.01 mg/kg(-1) and mercury content from 0.008 to 0.187 mg/kg(-1). Our findings meet the current government standards (max. allowed Pb = 5.00, Cd = 0.50 and Hg = 0.100 mg/kg(-1)) only for lead, and with five exceptions, for mercury. With two exceptions, all cadmium levels found in the samples exceeded the limit. One raw material - the wood chips - was shown to be the main source of cadmium in the technological process. Relatively high Hg contents were measured in the wood chips (up to 0.155 mg/kg(-1)); the highest Hg level (1.105 mg/kg(-1)) however was found in a sample of KOH.

[Epikeratoplasty using lyophilized lenticles for the correction if aphakia in adults]. / L'épikératoplastie avec lenticules lyophilisés pour la correction de l'aphakie adulte.

Fifty adult aphakic patients were treated surgically by epikeratoplasty. Forty-one eyes had posttraumatic aphakia including 26 eyes with corneal scars. Results are presented with a mean follow-up of 31 months. 64% of eyes achieved an uncorrected visual acuity of 0.2 or better. Best visual acuity was 0.2 or better in 92% of eyes (this percentage is similar to the preoperative figure) and 0.5 or better in 62%. 78% of eyes had a refraction within 3 diopters of emmetropia. 10% of eyes lost 2 or more lines of best visual acuity. Mean keratometric results and spheric equivalent of the refraction show stability of the procedure during a 2 year follow up period. These results confirm, that in selected patients, epikeratoplasty is a valid surgical alternative for adult aphakia.

[Present problems of environmental contamination with so-called heavy metals]. / Soucasné problémy s kontaminací naseho zivotního prostredí tzv. tezkými kovy.

Till recently the true state and quality of the environment was kept secret. False pretension of a better state is one of the reasons not only for the poor state of our living environment but also for the poor health status of the population. The authors discuss the contemporary process of contamination and pollution of the environment as a result of economic activities and pays special attention to so-called heavy metals.

The surgical treatment of high myopia: comparison of epikeratoplasty, keratomileusis and minus power anterior chamber lenses.

Seventy high myopic eyes (-8.00 to -28.00 diopters) with epikeratoplasty (n = 29), myopic non-freeze keratomileusis (n = 26) or minus power anterior chamber intraocular lenses in phakic eyes (n = 15) were operated by two surgeons and were evaluated retrospectively. Results are reported at the 6-month postoperative interval. Eyes treated with epikeratoplasty had an average preoperative spherical equivalent of the cycloplegic refraction of -17.80 D (range -12.00 to -28.00 D). At 6 months, 66.6% of eyes were within 3 D of emmetropia and 7.4% of eyes had an uncorrected visual acuity of 20/40 or more. Average preoperative spectacle visual acuity was 20/50 (0.39); it was 20/50 (0.37) at both 6 and 24 months. Between 6 and 24 months, 32.2% of eyes had a change in refraction of 1.00 D or more. Two lenticules were removed. Eyes treated with non-freeze keratomileusis had an average preoperative refraction of -10.0 D (range -8 to -15 D). At 6 months, 61.5% of eyes were within 3.00 D of emmetropia and 30.7% of eyes had an uncorrected visual acuity of 20/40 or better. Average preoperative spectacle visual acuity was 20/30 (0.67), and 6 and 12 months afterward it was 20/30-20/40 (0.57) and 20/30 (0.66) respectively. Between 6 and 12 months, 8.3% of eyes, had a change in refraction of 1.00 D or more. Eyes treated with minus power anterior chamber lenses had an average preoperative refraction of -17.30 D (range -12.50 to -20.00 D).(ABSTRACT TRUNCATED AT 250 WORDS)

Natural levels of lead, cadmium and mercury in tissues and hair of newborn calves from different areas of Czechoslovakia.

Liver, kidney, muscle and hair samples from newborn, born-dead or found-dead calves were collected within 10 days after parturition, for the determination of Pb, Cd and Hg levels. Differential pulse anodic stripping voltammetry at the static mercury dropping electrode was used for Pb and Cd determination after dry ashing of the samples. Cold-vapour atomic absorption spectrometry was used for direct Hg determination. The aim of the study was to monitor background Pb, Cd and Hg levels in vital and important tissues of newborn calves in which nutritional influence was negligible. Three geographic areas in Czechoslovakia were monitored (A, B and C). The following ranges of mean values for all animals were obtained (mg kg-1, wet wt): Pb--muscle (0.04-0.25), liver (0.10-0.29), kidney (0.05-0.43), hair (0.11-0.55); Cd--muscle (0.007-0.038), liver (0.008-0.073), kidney (0.007-0.062), hair (0.009-0.074); Hg--muscle (0.002-0.071), liver (0.005-0.18), kidney (0.004-0.50), hair (0.07-0.77). The value obtained for heavy-metal levels (Pb, Cd, Hg) indicated that there is a significant difference between the groups of found-dead and slaughtered calves from the Nymburk region (muscle--Pb, Cd; liver--Pb; kidney--Pb, Cd). Unexplained high Hg levels in hair samples were measured in the Hradec Králové region.

[Histological study of 4 lenses from epikeratoplasty. Anatomo-clinical correlation]. / Etude histologique de 4 lenticules d'épikératoplastie. Corrélations anatomo-cliniques.

Four removed kerato-lens lenticles (1 for keratoconus, 1 for aphakia, and 2 for myopia) have been studied histologically. The reasons for removal of the lenticles were poor visual acuity in spite of a satisfactory anatomic result in three cases and epithelialization of the interface in one case. The epithelium presented modifications, particularly with exoserosis of basal cells and irregularities of thickness. The Bowman membrane was irregular and interrupted in some parts. The corneal stroma had few cells; the keratocytes were observed in the periphery of the lenticle and near the interface.

[A trial use of lenses of human placental collagen in epikeratoplasty procedures]. / Essai d'utilisation de lenticules en collagène placentaire humain dans la technique de l'épikératoplastie.

Epikeratoplasty is a refractive surgery procedure described by Werblin and Kaufman which is simple, effective and reversible. However its development is hampered by the need of human corneas. We evaluated this procedure in rabbits and monkeys using lenticules of human collagen. The collagen is obtained from frozen human placentas, washed and subjected to pepsin digestion; it is contained in the supernatant of centrifugation and can be isolated by a physico-chemical treatment. 15 days after surgery the lenses of 14 rabbits were completely covered with a layer of epithelial cells. 6 months after surgery, the eyes of 14 monkeys were quiet and the lenses were covered with an epithelium made up of 2 to 5 layers of cells. The lens exhibited no inflammatory infiltration and there was no inflammatory reaction around the lens. These studies are still preliminary and longer term tests are necessary. These initial results are very encouraging, prompting us to develop the use of this type of material in refractive surgery.

[Experimental modification of the resorption process and lead deposition in the body of the domestic duck]. / Studium der experimentellen Beeinflussung des Resorptionsprozesses und der Bleideposition im Organismus der Hausenten.

In an experiment with 40 domestic ducks (Peking White breed) being 40 days old, it was shown that the process of lead resorption and deposition was neither significantly modified by different kinds of therapy nor by changes of food composition. A single dose of 30 lead small shot given to the experimental animals resulted after 1 week in a significant increase of lead concentration in liver (4.32 mg/kg-1), kidney (11.36 mg/kg-1) and muscle tissue (1.15 mg/kg-1) as compared to the values of control animals (liver 0.07, kidney 0.11 and muscle 0.06 mg Pb/kg-1). After 3 weeks with different types of therapy and feeding of experimental diets, i.e. at the end of the experiment, no significant differences in liver, kidney and muscle lead concentrations between the control and experimental animals could be found.

[Experimental control of the process of lead absorption and deposition in domestic ducks]. / Experimentální ovlivnení procesu vstrebávání a depozice olova v organismu domácích kachen.

A trial was conducted with 40 domestic ducks of the White Pekin breed at the age of 40 days: thirty pieces of lead shot were introduced as a single dose in the gizzard. The process of lead resorption and deposition was found not to be significantly influenced by the therapeutic treatments nor changes in the composition of feed. A week after the administration of shot a significant increase was recorded in the content of lead to 4.32 mg in liver, to 11.36 mg in kidney and to 1.15 mg in muscle (the respective values for the control animals were 0.07, 0.11 and 0.06 mg per kg). At the end of the trial after three weeks of treatment and administration of experimental diets, no significant differences were recorded in lead content in liver, kidney and muscle between the untreated and treated ducks nor ducks fed experimental diets.