Response of Growth Dynamics of Two Spring Geophytes to Light Regime in a Lime-Beech Forest

Blomaee accumulation, leaf longevity and growth rate of two spring forest geophytes, Scllla blfolla L. and Arum maculatum L. were estimated separately for three size groups within each population of these species. Despite the differences in leaf longevity, both species showed a similar pattern of blomass accumulation In relation to their phenologles and reproductive demands. Eco-physlological acclimation to changing light environment was assumed through photosynthetic parameters and dynamics of leaf area Index In the predominant size group of each species. A light response curve was measured under natural light for each species through the continuum of Its phenology to quantify the photosynthetic photon flux density at light saturation, light-saturated photosynthetic rate, light compensation point, and dark respiration. Light-saturated assimilation per leaf area basis, dark respiration rate and light compensation points were significantly higher in S. blfolla relative to A. maculatum. However, the acclimation of photosynthesis that would respond to light changes in environment was not found in S. bifolla. In contrast, In A. maculatum a marked shift In the light dependence of photosynthesis through the season was noticed, which resulted In a strong photosynthetic acclimation to the low-light conditions. Accompanied by significant leaf area Index, this efficient low-light photosynthesis enabled greater leaf longevity, and consequently longer accumulative period to A. maculatum. From the different parameters that we determined （both photosynthetic acclimation and growth strategy） it would appear that these species belong to two distinct subgroups： S. blfolla to the early and A. maculatum to the late vernals.     

The incidence of stroke in Baranya county (east Croatia)

The aim of this retrospective study was to provide a survey of the incidence of stroke in Baranya, Croatia, on patients examined at Beli Manastir Health Center Department of Emergency from November 1, 1997 (the time of Baranya reintegration into the legal system of the Republic of Croatia after the war) till December 31, 2001. A total of 513 patients with symptoms of cerebrovascular diseases, or one patient every third day on an average, were examined. Total incidence of stroke was 16.09 per 10,000 population. The majority of patients were in the 61-80 age group with an incidence of 46.94/10,000 after the age of 60, 15-fold that was recorded in younger age groups. The most common risk factors recorded in examined group included hypertension, heart diseases, hyperlipidemia and diabetes mellitus. Total stroke mortality was 38.38%, whereas mortality in patients with hemorrhagic and ischemic stroke was 62.85% and 33.52%, respectively. The ratio of ischemic and hemorrhagic stroke in study subjects was 5:1, and in the causes of death 2.5:1. Out of 81 deceased stroke patients, 96.3% died within first 28 of admission. All of the patients with hemorrhagic stroke died within first 28 days, most within first 7 days (81.8%), whereas 94.9% of patients with ischemic stroke died within first 28 days.     

Swelling pressure induced phase-volume transition in hybrid biopolymer gels caused by unfolding of folded crosslinks: a model

A thermodynamic model is proposed describing swelling changes and swelling transitions of hybrid gels in which domains of folded chains are chemically built in as cross-links. These folded domains can be unfolded to random coils by osmotic forces produced by the synthetic gel matrix. Uncoiling takes place if the osmotic force acting on the cross-links exceeds the critical value. By unfolding, a new interacting surface is exposed to interactions and affects the swelling pressure. The chains of the folded domains may have ionized groups. The model is based on mean-field statistical-thermodynamic treatment of swelling of polyelectrolyte gels with finite extensibility of network chains. This study is related to hybrid hydrogels with built in protein motifs. A continuous change in external variables increasing the degree of swelling of the hydrogel brings about an abrupt increase in volume (transition) of the gel. The position and magnitude of the transition depend on structural parameters of the hybrid gel, such as fraction of the folded domains in the gel, degree of ionization of chains in the domain, presence of additional chemical cross-links, or degree of dilution at gel formation. Two options for reversibility of the changes are considered: (a) unfolding is irreversible and deswelling proceeds along other curve than swelling and (b) swelling is reversible when the osmotic force decrease below the critical value. In the latter case, swelling changes are described by a closed loop with two transitions. Under certain conditions (high dilution at network formation and sufficiently high degree of ionization of chains of the folded domains), a transition appears known as the collapse transition induced by balance of hydrophobic and hydrophillic interactions. This collapse transition induces the folding transition by which the folded domains are reformed.     

Cattle pathogen tritrichomonas foetus (Riedmüller, 1928) and pig commensal Tritrichomonas suis (Gruby & Delafond, 1843) belong to the same species

A number of reports suggest that the sexually transmitted pathogen of cattle, Tritrichomonasfoetus, and a gastrointestinal commensal of pigs, Tritrichomonas suis, are very similar and may be co-specific. A conclusive review of the taxonomic and nomenclatural status of these species has not been presented so far. Toward this end, we reexamined and compared porcine and bovine trichomonads with regard to their morphology, pathogenic potential, and DNA polymorphism. Using light and electron microscopy, no distinguishing features between T. foetus and T. suis strains were found in size, general morphology, and karyomastigont structure. Both bovine and porcine trichomonads showed pathogenic potential in the subcutaneous mouse assays and did not separate into distinct groups according to strain virulence. Three DNA fingerprinting methods (i.e. RFLP, RAPD, and PCR-based analysis of variable-length DNA repeats) that produce species-specific DNA fragment patterns did not distinguish between the bovine and porcine strains. Sequencing of a variable 502-bp DNA fragment as well as comparison of 16S rRNA gene sequences did not reveal species-specific differences between the cattle and porcine strains. Therefore, we conclude that T. foetus and T. suis belong to the same species. To prevent confusion that may arise from T. foetus-T. suis synonymy, we propose to suppress the older name suis and maintain its accustomed junior synonym foetus as a nomen protectum for both cattle and porcine trichomonads. The case has been submitted to the International Commission on Zoological Nomenclature for ruling under its plenary power.     

Identification of human placental wheat germ agglutinin-immunoreactive protein by mass spectrometry

A preparation of polyclonal antibodies to human placental calcium-dependent, carbohydrate-binding glycoprotein, previously identified as wheat germ agglutinin-immunoreactive protein, was applied as the ligand in an immunoaffinity procedure. Following electrophoretic separation of purified material, the specific 66-kDa antigen band was excised and subjected to in-gel protein cleavage. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis of the tryptic digest yielded 42 isotopically resolved peptide fragments from mass 860 to 2,690. Empirical data from MALDI-MS were analyzed by computer assistance using ProteoMetrics PROFOUND software. Protein candidates reported in the specified identification database search are discussed in relation to the biochemical characteristics of the protein analyzed and its possible antigenic relatedness to wheat germ agglutinin. We speculate that a fibulin-like member of the epidermal growth factor-repeat protein family might be selected as a positive match.     

Acidification of lakes in Šumava (Bohemia) and in the High Tatra Mountains (Slovakia)

Acidification of lakes takes place when pH of rainwater is less than 4.5 and the catchments lie on sensitive geology. Both conditions are met for most lakes in Bohemia and Slovakia. Since 1978 we have studied mountain lakes in the Sumava and in the High Tatra Mountains. In Šumava the three lakes under study are of glacial origin. The catchments are small, with steep sides covered by spruce. The bedrocks are biotite-rich paragneiss, together with gneiss, quartzite and granite. In summer 1936 surface pH was 5.7–6.9 in the Lake Čertovo and 6.9–7.0 in the Lake Černé. Now the pH values are 4.3–4.8 in the two lakes and in the Lake Prášilské as well. Old reports on zooplankton are from the years 1871, 1892–96, 1935–37, 1947 and 1960. Since 1979 we have not found any planktonic Crustacea in the lakes Černé and Čertovo. Lake Prášilské is inhabited by Daphnia longispina and Cyclops abyssorum. In July 1989 the pH values were 4.4, 4.7 and 4.7, concentrations of labile monomeric Al were 0.83, 0.68 and 0.24 mg l^-1 in the lakes Čertovo, Černé and Prašilské, respectively. High levels of toxic Al compounds might be responsible for the extinction of planktonic Crustacea in the lakes Čertovo and Černé. All the three lakes are void of fish at present. In the High Tatra Mts. we examined more than 40 lakes above timberline in altitudes 1612–2145 m. They are all clearwater, naturally fishless lakes. The bedrock is granite. Owing to different levels of calcium the lakes are now in different stages of acidification. According to recent changes in the zooplankton they can be divided into three groups: (1) Species composition of planktonic Crustacea has not changed. (2) Planktonic Crustacea were present until 1973 but are absent now. (3) From the original species of Crustacea only Chydorus sphaericus is present. The three groups are well separated along the gradients of calcium, ANC and pH. They can be identified with the Henriksen's bicarbonate (our group 1), intermediate (our group 2) and acid (our group 3) lakes. We suppose that in the process of acidification the lakes of the group (2) have been shifted from oligotrophy to ultraoligotrophy.     

On the unidirectionality of arginine uptake in the yeast Saccharomyces cerevisiae

The reversibility of arginine accumulation was followed in exponentially growing cells of Saccharomyces cerevisiae and in the same cells transferred to non-growing energized conditions. Under non-growing conditions the accumulated arginine is retained in the cells while in exponentially growing cells the accumulated radioactivity is released after the addition of high external concentrations of arginine. There are indications that the process is saturable. The accumulated arginine is not exchanged for other related amino acids (l-citrulline, l-histidine). Only l-lysine (a low-affinity substrate of the specific arginine permease) provokes partial radioactivity efflux from the cells. The switch of the arginine-related radioactive label efflux to its complete retention in the cells after changing the growth conditions occurs within a few minutes and is tentatively attributed to two concomitantly occurring events: (1) the actual presence of radioactive arginine (not its metabolite(s)) in the cell and (2) a modification of the specific arginine permease. The specific exchange of arginine described in the present study contrasts with the currently widely accepted opinion of unidirectionality of amino acid fluxes in yeast. The reasons why this phenomenon has not been observed before are discussed.     

Aspirin induces platelet receptor shedding via ADAM17 (TACE)

Aspirin is effective in the therapy of cardiovascular diseases, because it causes acetylation of cyclooxygenase 1 (COX-1) leading to irreversible inhibition of platelets. Additional mechanisms can be suspected, because patients treated with other platelet COX inhibitors such as indomethacin do not display an increased bleeding tendency as observed for aspirin-treated patients. Recently, aspirin and other anti-inflammatory drugs were shown to induce shedding of L-selectin in neutrophils in a metalloproteinase-dependent manner. Therefore, we investigated the effects of aspirin on the von Willebrand Factor receptor complex glycoprotein (GP) Ib-V-IX, whose lack or dysfunction causes bleeding in patients. As quantified by fluorescence-activated cell sorting analysis in whole blood, aspirin, but not its metabolite salicylic acid, induced dose-dependent shedding of human and murine GPIbalpha and GPV from the platelet surface, whereas other glycoproteins remained unaffected by this treatment. Biotinylated fragments of GPV were detected by immunoprecipitation in the supernatant of washed mouse platelets, and the expression level of GPIbalpha was decreased in these platelets as measured by Western blot analysis. Although shedding occurred normally in COX-1-deficient murine platelets, shedding was completely blocked by a broad-range metalloproteinase inhibitor and, more importantly, in mouse platelets expressing an inactive form of ADAM17. Shed fragments of GPIbalpha and GPV were elevated in the plasma of aspirin-injected mice compared with animals injected with control buffer. These data demonstrate that aspirin at high concentrations induces shedding of GPIbalpha and GPV by an ADAM17-dependent mechanism and that this process can occur in vivo.     

Patterns in size and shedding of Fasciola hepatica eggs by naturally and experimentally infected murid rodents

Using samples collected on the island of Corsica, a comparative study was done of the morphometry of Fasciola hepatica eggs shed by cattle and by naturally and experimentally infected murid rodents (wild Mus musculus and Rattus rattus and Rattus norvegicus Wistar laboratory strain). Eggs shed by murids are smaller in size than those shed by naturally infected cattle. A second study analyzed the number of F. hepatica eggs shed in murid feces at different time intervals, i.e., months, days, and 6-hr periods, by the Kato-Katz technique. Both experimentally and naturally infected black rats (R. rattus) were used, and Wistar rats were experimentally infected and included for comparison. The present studies prove that black rats R. rattus are able to shed eggs independently from the liver fluke isolate and that egg shedding occurs throughout the life of this host species, uninterrupted during all the months analyzed in a 2-yr period. Moreover, the results suggest that this shedding is continuous, with eggs appearing in the feces daily. The results on egg shedding by wild black rats R. rattus reach their maximum shedding in spring and autumn and a maximum during twilight hr. These chronobiological patterns appear to favor parasite transmission, both seasonally and daily.     

Long-term preservation of active luminous bacteria by lyophilization

A simple method for long-term preservation of luminous bacteria is described. Cells of Vibrio fischeri, Photobacterium leiognathi and four strains of P. phosphoreum were suspended in a protective medium of low ionic strength (1% NaCI) supplemented with 15% lactose and 2% soluble starch, and lyophilized. The freeze-dried preparations were sealed under vacuum and stored at 4°C. Luminous bacteria were resuscitated affer six months by adding 2% NaCl up to the original volume. The rehydrated cells exhibited 16-28% of initial bioluminescence so that they could be used for a microbial test of toxicity (the Microtox test). This method is also useful for maintaining luminous bacteria in strain collections.