Force variability depends on core and muscle temperature

The aim of this study was to investigate if voluntary activation and force variability during maximal voluntary contraction (MVC) depends more on muscle (local) or body (core) temperature. Ten volunteers performed a 2-min MVC of the knee extensors under the control (CON) conditions (ambient temperature (21 °C), relative humidity (30%), and air velocity (∼0.1 m/s)) as well as after heating (HT) and cooling (CL) of the lower body. During water manipulation procedure lower body was immersed up to the waist in a water bath at ∼44 °C for 45 min for HT experiment, and ∼15 °C for 30 min for CL experiment. Peak torque, torque variability, muscle voluntary activation and half-relaxation time were assessed during the exercise. HT increased muscle (2.8±0.2 °C) and rectal (1.9±0.1 °C) temperatures while CL lowered muscle (2.2±0.2 °C) temperature, but did not affect rectal temperature. During 2-min MVC, peak torque decreased (P<0.05; SP>90%) and to a lower level in HT compared to CON and CL experiments (52.6±2.3% versus 69.0±2.3% and 65.6±1.9% MVC, respectively, P<0.05; SP>90%). Torque variability increased significantly during exercise and was significantly larger in HT and lower in CL compared to CON experiment. Voluntary activation of exercising muscle was more depressed in HT (i.e. greater central fatigue) and the smallest effect was found in CL compared to CON. In conclusion increased core and muscle temperature impairs voluntary activation and increases force variability of the exercising muscles while a local muscle cooling decrease force variability but has a small effect on central fatigue.     

Field resistance of spring barley cultivars to powdery mildew in Lithuania

During vegetative period 2004–2005 powdery mildew (Erysiphe graminis DC. f. sp. hordei Em. Marchal) field resistance of spring barley cultivars was investigated at the Lithuanian Institute of Agriculture. The spring barley genotypes tested were Lithuania-registered cultivars, cultivars from genetic resources collection, and the new cultivars used for initial breeding. In total, 23 resistance genes were present in the 84 cultivars studied. Among mono-genes only mlo and 1-B-53 showed very high resistance. Slight powdery mildew necroses (up to 3 scores) formed on cultivars possessing these genes. The maximal powdery mildew (PM) severity reached a score of 8.5 and the area under disease progress curve (AUDPC) a value of 1216.8. The cultivars ‘Primus’, ‘Astoria’, ‘Power’, ‘Harrington’ and ‘Scarlett’ were the most resistant among the non mlo cultivars. Severity of PM on ‘Primus’ reached a score of 3.5 (3.0 of PM necrosis) in average, the other cultivars were diseased from 4.5 (3.0) to 5.0 (2.0). The AUDPC values for these cultivars except ‘Scarlett’ were the lowest (85.0–145.3) among the other cultivars. The highest contrast in development of the other leaf diseases was between highly resistant and susceptible to PM cultivar groups. The fast development of PM depressed development of the other diseases 4.7 times.     

New information on the invasive to Europe aphid species <Emphasis Type="Italic">Brachycaudus divaricatae</Emphasis> Shaposhnikov, 1956 (Hemiptera: Aphididae)

Brachycaudus divaricatae (Hemiptera: Aphididae), a recent invader to Europe, has already reached Czech Republic. Partial sequences of mitochondrial COI and nuclear EF-1α genes have been analysed across the sixteen Czech samples of B. divaricatae, together with morphometric analysis of the same samples based on eighteen morphological characters of the apterous viviparous females. For comparative studies, thirteen samples from the Eastern Baltic region of Europe (Latvia, Lithuania and Poland) were used. All sampled populations appeared similar in their genetic and morphological characters studied. One haplotype of mitochondrial COI gene was predominant; it was characteristic for all samples from Czech Republic and 8 out of 13 samples from Eastern Baltic region. Two other haplotypes were found in the Eastern Baltic region only. Four different haplotypes of EF-1α gene were detected. Most of the samples (except one sample from the Eastern Baltic region and two samples from Czech Republic) had the same haplotype. Out of remaining three haplotypes, one was unique for the Eastern Baltic region, whilst two were found in Czech Republic only. For the present, Moravia is the southernmost region in Europe, where B. divaricatae has been already reported. Presumably, this invasive aphid species has entered the Czech Republic from the north via the Moravian Gate, a natural pass formed by the depression between the Western Carpathians and Eastern Sudetes.     

A chromosome study ofSchistocephalus solidus (Müller, 1776) (Cestoda: Pseudophyllidea)

Analysis of Giemsa-stained metaphase plates of plerocercoids ofSchistocephalus solidus revealed the mode diploid number of chromosomes for this species as 2n=18. Chromosome pairs 1, 5, 6, 8 and 9 are metacentric, pairs 2, 4 and 7 are subtelocentric, and pair 3 is subtelocentric to acrocentric. The karyotype is characterised by mean absolute chromosome length between 1.9 and 5.9 m and a total chromosome length of the haploid complement of 32 m. A comparison with other known karyotypes of related species of pseudophyllidean cestodes was made.     

Morphological,reproductive and karyological variability in <Emphasis Type="Italic">Allium oleraceum</Emphasis> in Lithuania

Morphological, reproductive and karyological variability were investigated in fifteen populations of Allium oleraceum transferred from natural populations in Lithuania to the field collection of medicinal and aromatic plants of the Institute of Botany of the Nature Research Centre in Vilnius. Nine populations were tetraploid (2n = 4x = 32), four pentaploid (2n = 5x = 40) and two consisted of both cytotypes. The greatest differences among the populations and between the ploidy levels were observed in stem height and mass of aerial bulbils per plant. The seed production was very low and did not differ significantly between the ploidy levels, while neither tetraploids nor pentaploids did produce any seed if insects were prevented from visiting their flowers. The means of the morphological characters were higher in pentaploids than in tetraploids. However, none of them provided the possibility of determining ploidy level without chromosome counting.     

β3-Adrenergic Regulation of L-Type Ca2+ Current and Force of Contraction in Human Ventricle

β₃-Adrenergic receptor (β₃-AR) is expressed in human atrial and ventricular tissues. Recently, we have demonstrated that it was involved in the activation of L-type Ca²⁺ current (I _Ca,L) in human atrial myocytes and the force of contraction of human atrial trabeculae. In the present study, we examined the effect of β₃-AR agonist CGP12177 which also is a β₁-AR/β₂-AR antagonist on I _Ca,L in human ventricular myocytes (HVMs) and the force of contraction of human ventricular trabeculae. CGP12177 stimulated I _Ca,L in HVMs with high potency but much lower efficacy than isoprenaline. The β₃-AR antagonist L-748,337 inhibited the effect of CGP12177. CGP12177 and L748,337 competed selectively on β₃-ARs because L748,337 had no effect on isoprenaline-induced stimulation of I _Ca,L, while CGP12177 completely blocked the effect of isoprenaline. The activation of β₃-ARs by CGP12177 does not involve the activation of G_i proteins because CGP12177 had no effect on forskolin-induced stimulation of I _Ca,L. CGP12177 had no effect on the force of contraction of human ventricular trabeculae. L-NMMA, an inhibitor of NO synthase, and IBMX, a nonselective inhibitor of phosphodiesterases, did not potentiate the effect of CGP12177 either on contraction of human ventricular trabeculae or on I _Ca,L in HVMs. We conclude that in human ventricles β₃-AR activation has no inotropic effect, while it slightly increases I _Ca,L. In contrast to human atrium, the activation of β₃-ARs in human ventricle is not accompanied by increased activity of phosphodiesterases.