Key adaptations enabling mammals to cope with oxygen deficiency at high elevations relate to oxygen transfer into the blood. Among others, the efficiency of this mechanism depends on haematocrit (Hct, the volumetric fraction of red blood cells in blood). Although blood of high-elevation mammals is usually characterised by normal or slightly increased Hct, there are contradictory findings from studies along different elevational gradients. The aim of this study was to explore variability of Hct at both inter- and intraspecific levels in six rodent species from lower and higher elevations of Choke Mountain in Ethiopia. We found that Stenocephalemys sp. A from higher elevation had higher Hct than its congener Stenocephalemys albipes from lower elevation and a similar but weaker tendency was observed intraspecifically in Lophuromys simensis. Furthermore, Hct among four species occupying the high-elevation Afroalpine zone was comparable, and higher than in animals from lower elevations. Higher Hct in the three Afroalpine specialists probably contributes to local adaptations for life in high elevation environments under hypobaric hypoxia.
In the field, the blister beetle Mylabris phalerata Pallas (Coleoptera: Meloidae) undergoes larval diapause in the ground, which lasts for nearly six months. The effect of the soil environment on this diapause was examined. Final instar larvae kept at temperatures of >= 26°C do not enter diapause and continued to develop regardless of the soil water content and photoperiod. Below 25°C the final instar larvae entered diapause regardless of soil water content and photoperiod. The early stages, particularly L2, appeared to be more important for diapause induction than the later stages. However, the other instars were also sensitive. Temperature, rather then photoperiod was the main factor influencing pupal duration.
AIMS: Authors studied potential side effects of fetal calf serum (FCS) in cultivation media on human dental pulp stem cells (DPSC) during long-term cultivation. METHODS: Two lines of DPSC obtained healthy donors (male 22 years, female 23 years) were used. Both lines were cultivated under standard cultivation conditions in four different media containing 10% or 2% FCS and substituted with growth factors. During long-term cultivation proliferation ability, karyotype and phenotype of DPSC were measured. RESULTS: Both lines of DPSC cultivated in a media containing 2% FCS and ITS supplement showed the highest number of population doublings. On the other hand the proliferation rate of DPSC cultivated in a media with 2% FCS without ITS supplement was slowest. Proliferation rate of DPSC cultivated in 10% FCS media with or without FGF-2 was comparable. DPSC cultivated in a media with 10% FCS showed a significantly higher amount of chromosomal aberrations. These chromosomal aberrations do not seem to be clonal but surprisingly we found large amounts of tetraploid cells in the 9th passage in both media containing 10% FCS. CONCLUSIONS: Our study proved that cultivation of DPSC in media containing higher concentration of FCS has critical side effects on cell chromosomal stability. and J. Suchánek, TS. Kleplová, M. Kapitán, T. Soukup
Increased and prolonged postprandial lipemia has been identified as a risk factor of cardiovascular disease. However, there is no consensus on how to test postprandial lipemia, especia lly with respect to the composition of an experimental meal. To address this question of how glucose, when added to a fat load, affects the selected parameters of postprandial lipemia, we carried out a study in 30 healthy male volunteers. Men consumed an experimental meal containing either 75 g of fat + 25 g of glucose (F+G meal) or 75 g of fat (F meal) in a control experiment. Blood was taken before the meal and at selected time points within the following 8 h. Glucose, when added to a fat load, induced an increase of glycemia and insulinemia and, surprisingly, a 20 % reduction in the response of both total and active glucagon -like peptide -1 (GLP -1) concentration. The addition of glucose did not affect the magnitude of postprandial triglyceridemia and TRL -C and TRL -TG concentrations but stimulated a faster response of chylomicrons to the test meal, evaluated by changes in apolipoprotein B -48 concentrations. The addition of glucose induced the physiological response of insulin and the lower response of GLP -1 to the test meal during the early postprandial phase, but had no effect on changes of TRL -cholesterol and TRL -TG within 8 h after the meal., K. Zemánková, J. Mrázková, J. Piťha, J. Kovář., and Obsahuje bibliografii
A study on the effect of heat stress on the activity of the medial A1 and A2 neurosecretory neurons (NSN), and the activity of midgut a-amylase and protease was performed on the fifth larval instar of Morimus funereus. Exposure of the larvae to 35°C led to a decrease in the activity of both A1 and A2 NSN, the former being more marked than the latter. These neurons responded differently to heat stress in terms of neurosecretory material synthesis and release. The changes in the size of both A1 NSN and their nuclei and protease activity in the larvae exposed to elevated temperature were significantly correlated, which suggests that A1 NSN play a role in the regulation of the activity of this enzyme during heat stress. The significant correlations between the size of A2 NSN and protease activity in the controls, and the size of both A2 NSN and their nuclei and amylase activity in larvae exposed to heat stress, similarly may mean that A2 NSN regulate both digestive enzyme activities depending on environmental temperature.
The rose grain aphid, Metopolophium dirhodum (Walker) (Hemiptera: Aphididae) is one of the three most important cereal aphid species in Europe. High temperature is detrimental for the survival of this species. Detailed experiments were conducted on the effect of high temperature (27, 28, 29, 30, 31, 31.5, 32.5, 33 and 34°C), period of exposure (2, 3, 4, 6 and 8 h per day for 1, 2, 4, 6 days) and developmental stage (2nd, 3rd, 4th instar nymph and adult) on the survival of the aphid. The results show that all three factors significantly affect survival. Temperatures over 29°C for 8 h significantly reduced survival, which decreased generally as the temperature increased. The survival was inversely related to the period of exposure. Exposing aphids to 32.5°C for 4 h or longer significantly reduced survival. Mature aphids had a lower tolerance of high temperatures than nymphs. Periods of high temperature experienced by 4th instar and adult aphids can greatly affect their survival. The value of these results for forecasting and determining control thresholds, the effect of global warming on cereal aphid abundance and the dropping off behaviour of the aphids are discussed.
Genetic differentiation is a consequence of the combination of drift and restriction in gene flow between populations due to barriers to dispersal, or selection against individuals resulting from inter-population matings. In phytophagous insects, local adaptation to different kinds of host plants can sometimes lead to reproductive isolation and thus to genetic structuring, or even to speciation. Acanthoscelides obtectus Say is a bean bruchid specialized on beans of the Phaseolus vulgaris group, attacking both wild and domesticated forms of P. vulgaris and P. coccineus. This study reveals that the genetic structure of populations of this bruchid is explained mainly by their geographical location and is not related to a particular kind (wild or domesticated) of bean. In contrast, the species of bean might have led, to some extent, to genetic structuring in these bruchids, although our sampling is too limited to address such process unambiguously. If confirmed, it would corroborate preliminary results found for the parasitoid species that attack Acanthoscelides species, which might show a genetic structure depending on the species of host plant.
T-2 toxin and its metabolite HT-2 toxin are one of the most toxic mycotoxins of type A-trichothecenes, which are produced mainly by Fusarium species. Therefore, study of Fusarium toxins T-2 toxin and HT-2 toxin is an essential issue because they could also play role in failures of reproductive functions as well as endocrine system of domestic animals. Assessment of the effect of A-trichothecene mycotoxin HT-2 toxin alone or combined with insulin-like growth factor (IGF-I), leptin and ghrelin on estradiol secretion by rabbit ovarian fragments in vitro was done. Rabbit ovarian fragments were incubated without (control group) or with HT-2 toxin, or its combinations with IGF-I, leptin and ghrelin at various concentrations for 24 h. Secretion of 17β-estradiol was determined by ELISA. Firstly, HT-2 toxin at the doses 10 and 100 ng.ml-1, but not at 1 ng.ml-1 decreased 17β-estradiol secretion by ovarian fragments. Secondly, 17β-estradiol secretion was not affected by HT-2 toxin exposure combined with growth factor IGF-I, metabolic hormones leptin and ghrelin. In conclusion, HT-2 toxin has potent direct dose-dependent effects on ovarian steroidogenesis in rabbits. These direct effects of HT-2 mycotoxin on ovarian steroidogenesis could impact negatively on the reproductive performance of rabbits., A. Kolesarova, N. Maruniakova, A. Kadasi, M. Halenar, M. Marak, A. V. Sirotkin., and Obsahuje bibliografii