A number of effects which can affect the low-mass IMF derived from the local luminosity function is studied. We consider an influence of unresolved binairies, variations in fine structure of mass-luminosity relation, BC-scale, chemical composition, and evolution of brown dwarfs. The mass-luminosity relation is found to be the main factor defining the IMF. As analysis shows, different theoretical relations calculated for Pop I composition result in different IMFs /from a power law, to a lognormal one/. The presence at faintest magnitudes /Mν > 20^m/ of a large number of brown dwarfs, slowly evolving with decreasing luminosity, leads to the depletion of the luminosity function for both lognormal and power IMFs.
Optical mapping is a fluorescence-based physiological method to image spreading of action potential in excitable tissues, such as the heart and central nervous system. Because of the requirements for high speed imaging in low light conditions, highly sensitive high-speed cameras together with an optical system with maximum photon efficiency are required. While the optimization of these two components is relatively straightforward, the choice of the perfect light source is less simple; depending on the other (usually fixed) components, various parameters may acquire different weight in decisionmaking process. Here we describe the rationale for building an optical mapping setup and consider the relative advantages and disadvantages of three different commonly available light sources: mercury vapor lamp (HBO), xenon lamp (XBO), and light emitting diode (LED). Using the same optical system (fluorescence macroscope) and high-speed camera (Ultima L), we have tested each of the sources for its ability to provide bright and even illumination of the field of view and measured its temporal fluctuations in intensity. Then we used each in the actual optical mapping experiment using isolated, perfused adult mouse heart or chick embryonic heart to determine the actual signal to noise ratio at various acquisition rates. While the LED sources have undergone significant improvements in the recent past, the other alternatives may still surpass them in some parameters, so LEDs may not be the automatic number one choice for every application., Veronika Olejnickova, David Sedmera., and Obsahuje bibliografii
Epileptic afterdischarges (ADs) elicited by electrical stimulation of sensorimotor cortical area were used as a model to study the role of neurotransmitter systems in cortical seizures in three age groups of developing rats. Drugs augmenting inhibition mediated by GABAA receptors were found to suppress ADs in all age groups, their activity was usually more marked in younger than in 25-day-old rat pups. Drugs potentiating GABAB receptors exhibit lower efficacy and more complicated developmental profile than GABAA-ergic drugs. Effects of an antagonist of GABAB receptor – marked prolongation of ADs in all three age groups – suggest an important role of GABAB receptors in arrest of cortical seizures. Drugs affecting glutamate receptors exhibit variable effects, usually better expressed in older animals than in 12-day-old ones. No specific role for ionotropic as well as metabotropic glutamate receptors could be predicted. Activation of adenosinergic inhibitory modulatory system also exhibited anticonvulsant action in the present model. All three neurotransmitter systems probably participate in mechanisms of generation, maintenance and arrest of cortical seizures., P. Mareš, H. Kubová., and Obsahuje bibliografii a bibliografické odkazy
Psychostimulants, as well as cannabinoids, have been shown to
significantly affect a great variety of behaviors in both humans
and laboratory animals. Our previous studies have repeatedly
demonstrated that the application of the vehicle for
psychostimulants, i.e. saline, to control groups, generated
different behavioral test results compared to absolute naïve
controls (i.e. without any injection). Therefore, our present study
has set three goals: (1) to evaluate the effect of three different
psychostimulant drugs, (2) to evaluate the effect of three doses
of delta 9-tetrahydrocannabinol (THC), and (3) to evaluate the
effect of saline and ethanol injections vs sham injections and no
injection on spontaneous behavior of adult male rats. The
LABORAS test (Metris B.V., Netherlands) was used to examine
spontaneous locomotor activity and exploratory behavior in an
unknown environment over 1 h. In Experiment 1,
psychostimulant drugs were tested: single subcutaneous (s.c.)
injections of amphetamine (5 mg/kg), cocaine (5 mg/kg), and
3,4-methylenedioxymethamphetamine (MDMA) (5 mg/kg) were
applied prior to testing. Control animals received the same
volume (1 ml/kg) of s.c. saline. In Experiment 2, the effect of
three doses of THC (1, 2, and 5 mg/kg, s.c.) were examined.
An s.c. injection of vehicle (ethanol) was used as a control. In
Experiment 3, injections of saline and ethanol were compared to
the group receiving a sham s.c. injection and to a group of
absolute “naïve” controls. Our results demonstrated that (1) all
psychostimulants increased locomotion time, distance traveled,
and speed while decreasing immobility time of adult male rats
relative to saline controls. The most prominent effect was
associated with MDMA; (2) The effect of THC was dosedependent and was most apparent within the first 10 min of the
LABORAS test. (3) With regard to the effect of injection: absolute
controls (without injection) compared to animals injected with
ethanol, saline, or sham-injected displayed reduced immobility
time, traveled longer distances, and had increased speed. In
conclusion, our data showed drug dependent behavioral changes
in adult male rats after application of psychostimulants and
cannabinoids. Our findings also suggest that not only drugs but
the actual single injection per se also affects the behavior of
laboratory animals in an unknown environment. This effect
seems to be associated with the acute stress associated
with the injection.
The quality of stored blood can be deteriorated by hemolysis caused by free radicals. The purpose of this study was to elucidate whether neutrophile leukocytes are the source of free radicals in stored blood as in hemodialyzed patients. Resuspensions with low (LL) or high (HL) leukocyte concentrations were prepared from samples of twenty healthy volunteers. The samples were incubated for 10 days at 4 °C and then for one day at 37 °C. Markers of hemolysis and free radical metabolism were examined before and after incubation in LL and HL samples. In spite of the difference of leukocytes counts in LL and HL resuspensions (p<0.0001), the pre-incubation values of all laboratory parameters were practically identical. In post-storage samples, superoxide dismutase and glutathione peroxidase activities did not differ in either group. Reduced glutathione in erythrocytes and extracellular antioxidant capacity were insignificantly lower in HL resuspensions, but the increase of malondialdehyde was much more pronounced in the HL samples (p<0.0001). The degree of hemolysis, expressed as the extracellular increase of potassium (p<0.001), hemoglobin (p<0.05) and lactate dehydrogenase (p<0.05), was higher in the HL samples. Our results support the hypothesis that leukocytes participate in free radical production in stored blood., J. Racek, R. Herynková, V. Holeček, J. Faltysová, I. Krejčová., and Obsahuje bibliografii
The carbon dioxide concentrating system in C4 photosynthesis allows high net photosynthetic rates (PN) at low internal carbon dioxide concentrations (Ci), permitting higher PN relative to stomatal conductance (gs) than in C3 plants. This relation would be reflected in the ratio of Ci to external ambient (Ca) carbon dioxide concentration, which is often given as 0.3 or 0.4 for C4 plants. For a Ca of 360 µmol mol-1 that would mean a Ci about 110-140 µmol mol-1. Our field observations made near midday on three weedy C4 species, Amaranthus retroflexus, Echinochloa crus-galli, and Setaria faberi, and the C4 crop Sorghum bicolor indicated mean values of Ci of 183-212 µ mol mol-1 at Ca = 360 µmol mol-1. Measurements in two other C4 crop species grown with three levels of N fertilizer indicated that while midday values of Ci at high photon flux were higher at limiting N, even at high nitrogen Ci averaged 212 and 196 µmol mol-1 for Amaranthus hypochondriacus and Zea mays, respectively. In these two crops midday Ci decreased with increasing leaf to air water vapor pressure difference. Averaged over all measurement days, the mean Ci across all C4 species was 198 µmol mol-1, for a Ci/Ca ratio of 0.55. Prior measurements on four herbaceous C3 species using the same instrument indicated an average Ci/Ca ratio of 0.69. Hence midday Ci values in C4 species under field conditions may often be considerably higher and more similar to those of C3 species than expected from measurements made on plants in controlled environments. Reducing gs in C4 crops at low water vapor pressure differences could potentially improve their water use efficiency without decreasing PN.
Polycystic ovary syndrome (PCOS), the most common endocrinopathy in women (with a prevalence of 5-10 %), is characterized by hormonal and metabolic imbalance. Complexity of symptoms of close relatives of women with PCOS and genetic autosomal trait initiated a hypothesis about the existence of a male equivalent of PCOS. Premature alopecia was suggested as one of the signs of a male phenotype of this syndrome. The present study investigated a group of 30 men, in which premature hair loss started before 30 years of age. In all patients, their hormonal profile was determined. It was possible to form two subgroups. The first one showed similar hormonal changes as women with PCOS, the other had either no anomalies in steroid spectrum or just only lower level of sexual hormones binding globulin (SHBG). Both subgroups did not differ in either BMI or age. In all men with premature alopecia insulin tolerance test was also carried out and the occurrence of allele 3 INS VNTR was investigated, which is one of the candidate genes for PCOS. The subgroup with hormonal changes resembling those of women with PCOS showed a significantly higher insulin resistance than the group without these changes. About one third of the premature balding men showed the combination of hormonal shifts and higher insulin resistance. This frequency corresponds to the prevalence of PCOS in women. There was no significant difference between the two subgroups in the occurrence of allele 3 INS VNTR.
The article considers the nature of descriptive statements and the ontological status of descriptive constructs in linguistics, taking the example of a phoneme of English. It is argued that descriptive statements should be seen as expressions of the content of descriptive models or as hypotheses. Furthermore, it is argued that descriptive models and constructs in linguistics have a purely explanatory function in relation to speech events and without ontological commitment to corresponding entities in the real world., Článek pojednává o povaze popisných výroků a ontologickém stavu deskriptivních konstrukcí v lingvistice, přičemž vychází z příkladu fonému angličtiny. Argumentuje se tím, že popisná prohlášení by měla být chápána jako vyjádření obsahu popisných modelů nebo jako hypotézy. Dále, to je argumentoval, že popisné modely a konstrukce v lingvistice mají čistě vysvětlující funkci ve vztahu k událostem řeči a bez ontologického závazku k odpovídajícím entitám v reálném světě., and Paul Rastall
The paper sketches and defends two instances of the strategy Let N’s be whatever they have to be to explain our knowledge of them—one in which N’s are natural numbers and one in which N’s are propositions. The former, which makes heavy use of Hume’s principle and plural quantification, grounds our initial knowledge of number in (a) our identification of objects as falling under various types, (b) our ability to count (i.e. to pair memorized numerals with individuated objects of one’s attention), (c) our (initially perceptual) recognition of plural properties (e.g. being three in number), and (d) our predication of those properties of pluralities that possess them (even though no individuals in the pluralities do). Given this foundation, one can use Fregean techniques to non-paradoxically generate more extensive arithmetical knowledge. The second instance of my metaphysics-in-the-service-of-epistemology identifies propositions (i.e. semantic contents of some sentences, objects of the attitudes, and bearers of truth, falsity, necessity, contingency, and apriority) with certain kinds of purely representational cognitive acts, operations, or states. In addition to providing natural solutions to traditionally un-addressed epistemic problems involving linguistic cognition and language use, I argue that this metaphysical conception of propositions expands the solution spaces of many of the most recalcitrant and long-standing problems in natural-language semantics and the philosophy of language.