Geographical patterns of species turnover in aquatic plant communities

1. A classic theory in biogeography predicts that high latitude communities are unstable. This may be because of decreased species richness or decreased environmental predictability and productivity towards the poles.
2. We studied latitudinal patterns in long-term community persistence of aquatic vascular plants in 112 Finnish lakes, situated within a 1000-km range from the northernmost to the southernmost lake.
3. Contrary to theoretical predictions, we found that the turnover rate of plant species in 45 years was inversely related to latitude. That is, plant communities in northern lakes were more persistent than communities in southern lakes. When we used multiple regression to find the best predictors of species turnover rate (TR), latitude was the only variable that was highly significantly related to species turnover rate. Area, species number, water transparency, pH and change in transparency did not notably explain the gradient observed.
4. The latitudinal trend was mainly because of lower species immigration rates at higher latitudes, whereas extinction rate did not so strongly decrease with increasing latitude. Immigrations and extinctions in the lakes were not in balance: the species numbers between the 1930s and 1980s increased more strongly in the southern than northern lakes.
5. We suggest that the inverse relationship between latitude and plant species TR in Finland is most probably caused by human influence on lakes, especially eutrophication and immigration of new species in southern latitudes. In addition, although species richness per lake did not decrease towards the north, the total species pool probably does, which means that in the north there are fewer species that can actually immigrate.     

Effect of nutrition of oocyte donor on the outcomes of somatic cell nuclear transfer in the sheep

The purpose of this study was to determine if the nutrition of the oocyte donor ewe influenced the success of somatic cell cloning. Merino ewes were fed at either a high- or a low-nutrition level for 3-5 mo before superovulation treatments. Freshly ovulated oocytes were enucleated and fused with serum-starved adult granulosa cells, and resulting reconstructed embryos were cultured for 6 days in modified synthetic oviduct fluid. Embryo cleavage and development to blastocysts were recorded, and good-quality embryos were transferred to synchronized recipient ewes either fresh or, on a few occasions, after vitrification. Pregnancies were monitored by ultrasonography from Day 40 of pregnancy, and offspring were delivered by either cesarean section or vaginal delivery. No differences occurred in the numbers of follicles aspirated, of oocytes recovered, or of oocytes utilizable for cloning between the high and low groups. Neither were there treatment differences in development to the blastocyst stage. However, transfer of embryos from the high group led to significantly more pregnancies and implanted fetuses. Also, more of the established pregnancies from the high group were carried to term, although this difference was not statistically significant. Lamb mortality was high, with half the live-born perishing soon after birth and more succumbing to various infections within days or weeks of birth, but no clear association between the offspring fate and the treatment group could be established. These results suggest that more research into the effect of nutrition on oocyte quality and its subsequent effect on cloning is warranted.     

Circannual leptin and ghrelin levels of the blue fox (Alopex lagopus) in reference to seasonal rhythms of body mass, adiposity, and food intake

The aim of the study was to investigate the circannual rhythms of leptin and ghrelin in the blue fox, a variant of the endangered arctic fox, in relation to its seasonal cycles of body mass, adiposity and food intake. The effects of long-term fasting and exogenous melatonin treatment on these weight-regulatory hormones were also investigated. The leptin concentrations of the blue fox increased during the autumnal accumulation of fat and decreased during the wintertime and vernal weight loss periods. The leptin levels peaked 2-6 weeks before the maximum values were observed for the body mass indices, voluntary food intake, and body masses. The ghrelin concentrations fluctuated widely during the autumn but decreased in the winter in association with suppression of food intake. Exogenous melatonin advanced the seasonal changes in the food intake of the blue fox but did not affect the seasonal rhythms of leptin and ghrelin concentrations. The leptin concentrations did not respond to the 3-week fasting periods in a consistent way, but the ghrelin levels increased due to food deprivation. In addition to the amount of fat in the body the leptin secretion of the blue fox may be regulated also by other factors. The blue fox may also express seasonal changes in its leptin sensitivity. Our results reinforce the hypothesis that leptin does not function as an acute indicator of body adiposity in seasonal carnivores but rather as a long-term signal of nutritional status.     

Endocrine response to fasting in the overwintering captive raccoon dog (Nyctereutes procyonoides)

The raccoon dog (Nyctereutes procyonoides) is an omnivorous canid utilizing the passive wintering strategy in the boreal climate. Farmed raccoon dogs (n=12) were randomly assigned into two study groups on 26 November 2003. Between 3 December 2003 and 27 January 2004, half of the animals were fasted for 8 weeks and plasma weight-regulatory hormone concentrations determined on 26 November and 30 December 2003 and on 27 January 2004. The plasma peptide YY, ghrelin, and growth hormone (GH) concentrations increased due to food deprivation, while the T4 and Acrp30 concentrations decreased. Furthermore, the plasma GH concentrations were higher in the fasted raccoon dogs than in the fed animals, which had higher plasma insulin, glucagon, and T4 concentrations. However, fasting had no effect on the plasma leptin concentrations. The results confirm previous findings with unchanged leptin levels in fasting carnivores. Increased GH levels probably contribute to increased lipolysis and mobilization of fat stores. Ghrelin can also enhance lipolysis by increasing the GH levels. The decreased levels of T4 may reduce the metabolic rate. The plasma dopamine concentrations decreased due to fasting unlike observed previously in rats. Together with the unaffected adrenaline, noradrenaline, and cortisol concentrations, this suggests that food deprivation in winter does not cause stress to the raccoon dog but is an integral part of its natural life history.     

Land-use history of Riekkalansaari Island in the northern archipelago of Lake Ladoga,Karelian Republic,Russia

Agricultural history was investigated by means of pollen and charcoal analyses from the sediment of Lake Kirjavalampi in the Riekkalansaari Island, in the northern archipelago of Lake Ladoga, NW Russia (61°44N, 30°46E). Pollen and charcoal stratigraphies, and loss-on-ignition were analysed from a 0–294-cm profile cored from the deepest part of the small lake. The pollen profile was divided into six local pollen assemblage zones Kir 1–6 and dated by three radiocarbon samples. Lake Kirjavalampi was isolated from Lake Ladoga between 1460–1300 b.c., when the River Neva was formed as a new outlet for Lake Ladoga and the water level rapidly fell. The isolation is seen as a phase of rapid sedimentation in Kir 2 (237–173 cm). Spruce (Picea) starts to decline at 113 cm ca. a.d. 70, and the earliest cereal (Secale cereale) pollen was encountered at the 97-cm level, empirically dating the onset of cultivation to ca. a.d. 600. A marked intensification in agricultural activities occurs around a.d. 1200, and the indication of an open cultivated landscape is at its strongest during the time period 1700 to 1850.     

No effects of mobile phone use on cortical auditory change‐detection in children: An ERP study

We investigated the effect of mobile phone use on the auditory sensory memory in children. Auditory event‐related potentials (ERPs), P1, N2, mismatch negativity (MMN), and P3a, were recorded from 17 children, aged 11–12 years, in the recently developed multi‐feature paradigm. This paradigm allows one to determine the neural change‐detection profile consisting of several different types of acoustic changes. During the recording, an ordinary GSM (Global System for Mobile Communications) mobile phone emitting 902 MHz (pulsed at 217 Hz) electromagnetic field (EMF) was placed on the ear, over the left or right temporal area (SAR_1g = 1.14 W/kg, SAR_10g = 0.82 W/kg, peak value = 1.21 W/kg). The EMF was either on or off in a single‐blind manner. We found that a short exposure (two 6 min blocks for each side) to mobile phone EMF has no statistically significant effects on the neural change‐detection profile measured with the MMN. Furthermore, the multi‐feature paradigm was shown to be well suited for studies of perception accuracy and sensory memory in children. However, it should be noted that the present study only had sufficient statistical power to detect a large effect size. Bioelectromagnetics 31:191–199, 2010. © 2009 Wiley‐Liss, Inc.     

Gonadotropins and cyclic adenosine 3',5'-monophosphate (cAMP) alter the morphology of cultured human granulosa cells

Morphological changes in human granulosa cells in culture were observed by phase, fluorescent, scanning electron and transmission electron microscopy following the addition of human chorionic gonadotropin (hCG), luteinizing hormone (LH), 8-bromocyclic adenosine 3',5'-monophosphate (cAMP) and cytochalasins B and D. In response to these agents, polygon-shaped granulosa cells with granular cytoplasm became rounded, leaving fingerlike processes attached to the substratum and adjacent cells. The changes in cell shape were accompanied by a centripetal movement of mitochondria and lysosomes to a perinuclear location. The morphological alterations appeared to be mediated by cyclic AMP and to be the result of a dismantling and reorganization of microfilament-containing stress fibers. Follicle-stimulating hormone (FSH), prolactin (PRL), growth hormone (GH), and human placental lactogen (hPL) did not provoke cell shape changes. We conclude that tropic hormones capable of stimulating progestin secretion by luteinized granulosa cells cause a change in cell structure in vitro which leads to a redistribution of organelles involved in steroid synthesis. The possible relationship of the cytoskeleton to steroidogenesis is considered.