Effects of gonadectomy on prolactin and LH secretion and the pituitary-thyroid axis in male dogs

The effects of gonadectomy on the secretion of prolactin, LH, TSH, and thyroxine were investigated. Blood serum hormone concentrations were analysed before and at 20, 120, and 180 min after a single iv TRH injection in each of eight healthy intact and castrated male beagle dogs before (control) and after 4-week treatment with the dopamine-2 receptor agonist cabergoline. Under control conditions the mean prolactin, TSH, and thyroxine concentrations were similar in intact and gonadectomised dogs, and administration of TRH provoked a significant (p < 0.01) increase in concentrations of the three hormones. The overall inhibitory effect of cabergoline treatment on prolactin secretion was more pronounced in the castrated dogs compared with the intact group. Cabergoline significantly suppressed the TRH-induced prolactin increase in each group (p < 0.01). Corresponding TRH-stimulated TSH concentrations were not affected by cabergoline. In the gonadectomised dogs, thyroxine concentrations before and at 120 and 180 min after TRH injection were significantly lower than under control conditions. LH concentrations were always higher (p < 0.01) in gonadectomised dogs compared with the intact dogs, but appeared to be affected neither by TRH nor by cabergoline administration. It can thus be concluded from the results, that gonadectomy does not result in hyperprolactinaemia in male dogs, while LH concentrations are significantly increased due to missing androgen feedback. Thyroid function remains unaffected by gonadectomy. Testicular steroids appear to interact with central dopaminergic and probably other neuroendocrine mechanisms regulating the secretion of prolactin, TSH, and thyroxine. Thus, long-term dopamine-2 receptor agonistic treatment may lead to a hypothyroid condition in castrated male dogs.     

Does sperm quality and DNA integrity differ in cryopreserved semen samples from young,adult, and aged Nellore bulls?

Background

In humans, it is now well documented that rising paternal age is correlated with decreased sperm DNA integrity and embryonic developmental failures. On the other side of the coin, it is also reported that very young fathers such as teenagers carry an increased risk of adverse birth outcomes. These observations suggest that, at least in humans, there is an age window for optimal sperm DNA integrity. In bovine, little is known about sperm DNA quality in young bulls and how it evolves with age. This study aimed to fill in this gap as it may be of importance for the bovine industry to know when exactly a bull is an optimal performer for reproductive programs.

Methods

Forty Nellore bulls were divided into three age groups: 1.8 to 2 years – young bulls; 3.5 to 7 years – adult bulls; and 8 to 14.3 years – aged bulls. Three ejaculates were collected from each bull, cryopreserved and evaluated for various parameters including: computer-assisted sperm analysis (CASA), plasma membrane and acrosome integrity, mitochondrial potential, sperm nuclear protamination, DNA oxidative damage, and Sperm Chromatin Structure Assay (SCSA).

Results

We report here that young bulls presented superior values for motility, plasma and acrosomal membrane integrity, and high mitochondrial potential. However, they also presented higher values for sperm morphological abnormalities compared to adult and aged animal groups (p?<?0.05). In addition, young bulls exhibited more defective protamination than older animals did. The oldest bulls showed more nuclear oxidative damage than the younger groups of bulls while both the young and aged groups were found more susceptible to DNA denaturation as revealed with the SCSA test (p?<?0.05).

Conclusion

These results indicate that young bulls spermatozoa best survived the freezing procedure, followed by adult and aged bulls. However, young and aged bulls were found to be more susceptible to DNA damage, respectively caused by protamine deficiency and oxidation. Therefore, although young bulls have correct semen parameters according to classical evaluation, our results indicate that they may show some structural nuclear immaturity.

     

Hydrology is reflected in the functioning and community composition of methanotrophs in the littoral wetland of a boreal lake

In lake ecosystems a major proportion of methane (CH(4) ) emissions originate from the littoral zone, which can have a great spatial variability in hydrology, soil quality and vegetation. Hitherto, spatial heterogeneity and the effects it has on functioning and diversity of methanotrophs in littoral wetlands have been poorly understood. A diagnostic microarray based on the particulate methane monooxygenase gene coupled with geostatistics was used to analyse spatial patterns of methanotrophs in the littoral wetland of a eutrophic boreal lake (Lake Kev?t?n, Eastern Finland). The wetland had a hydrology gradient with a mean water table varying from -8 to -25 cm. The wettest area, comprising the highest CH(4) oxidation, had the highest abundance and species richness of methanotrophs. A high water table favoured the occurrence of type Ib methanotrophs, whereas types Ia and II were found under all moisture conditions. Thus the spatial heterogeneity in functioning and diversity of methanotrophs in littoral wetlands is highly dependent on the water table, which in turn varies spatially in relation to the geomorphology of the wetland. We suggest that changes in water levels resulting from regulation of lakes and/or global change will affect the abundance, activity and diversity of methanotrophs, and consequently CH(4) emissions from such systems.     

Spatial patterns of microbial diversity and activity in an aged creosote-contaminated site

Restoration of polluted sites via in situ bioremediation relies heavily on the indigenous microbes and their activities. Spatial heterogeneity of microbial populations, contaminants and soil chemical parameters on such sites is a major hurdle in optimizing and implementing an appropriate bioremediation regime. We performed a grid-based sampling of an aged creosote-contaminated site followed by geostatistical modelling to illustrate the spatial patterns of microbial diversity and activity and to relate these patterns to the distribution of pollutants. Spatial distribution of bacterial groups unveiled patterns of niche differentiation regulated by patchy distribution of pollutants and an east-to-west pH gradient at the studied site. Proteobacteria clearly dominated in the hot spots of creosote pollution, whereas the abundance of Actinobacteria, TM7 and Planctomycetes was considerably reduced from the hot spots. The pH preferences of proteobacterial groups dominating in pollution could be recognized by examining the order and family-level responses. Acidobacterial classes came across as generalists in hydrocarbon pollution whose spatial distribution seemed to be regulated solely by the pH gradient. Although the community evenness decreased in the heavily polluted zones, basal respiration and fluorescein diacetate hydrolysis rates were higher, indicating the adaptation of specific indigenous microbial populations to hydrocarbon pollution. Combining the information from the kriged maps of microbial and soil chemistry data provided a comprehensive understanding of the long-term impacts of creosote pollution on the subsurface microbial communities. This study also highlighted the prospect of interpreting taxa-specific spatial patterns and applying them as indicators or proxies for monitoring polluted sites.     

Nocturnal drift of mayfly nymphs as a post-contact antipredator mechanism

1. The predominantly nocturnal constrained drift of stream invertebrates is commonly regarded as a behaviour that avoids encounters with visually foraging fish in the water column. The alternative explanation, that drift peaks are caused by bottom-feeding, nocturnal predators, has rarely been tested.
2. We examined these hypotheses by collecting invertebrate drift in five streams in northern Finland: one with brown trout ( Salmo trutta , a drift-feeding fish), one with alpine bullhead ( Cottus poecilopus , a benthic fish), one with both species, and two fishless streams.
3. Drift by Baetis mayflies was aperiodic or slightly diurnal in both fishless streams on all sampling occasions. In contrast, drift was nocturnal in streams with trout and, to a lesser extent, in the stream with bullhead. Non-dipteran prey drifted mainly nocturnally in all streams with fish, whereas Diptera larvae were less responsive to the presence of fish.
4. In laboratory experiments, bullheads were night-active, causing a much higher frequency of drift by touching Baetis at night than during the day. Thus, increased nocturnal drift may serve to avoid both visual predators (a pre-contact response) and benthic fish (a post-contact response). In streams with bottom-feeding fish, nocturnal drift should be caused by increased drift by night rather than by reduced drift by day.     

DNA adducts in human placenta as biomarkers for environmental pollution, analysed by the 32P-HPLC method

During pregnancy, mothers are exposed to complex chemical mixtures, such as air pollution and smoke from incomplete combustion. In this study DNA adducts were measured in human placentas from 29 mothers. Environmental exposure and several possible biomarkers in relation to levels of DNA adducts were measured. Placental aromatic and bulky DNA adducts were measured with the ³²     

Seasonal variation in CH4 emissions and production and oxidation potentials at microsites on an oligotrophic pine fen

 Temporal and spatial variation in CH₄ emissions was studied at hummock, Eriophorum lawn, flark and Carex lawn microsites in an oligotrophic pine fen over the growing season using a static chamber method, and CH₄ production and oxidation potentials in peat profiles from hummock and flark were determined in laboratory incubation experiments. Emissions were lowest in the hummocks, and decreased with increasing hummock height, while in the lawns and flarks they increased with increasing sedge cover. Statistical response functions with water table and peat temperature as independent variables were calculated in order to reconstruct seasonal CH₄ emissions by reference to the time series for peat temperature and water table specific to each microsite type. Mean CH₄ emissions in the whole area in the snow-free period of 1993, weighted in terms of the proportions of the microsites, were 1.7 mol CH₄ m^–2. Potential CH₄ production and oxidation rates were very low in the hummocks rising above the groundwater table, but were relatively similar when expressed per dry weight of peat both in the hummocks and flarks below the water table. The CH₄ production potential increased in autumn at both microsites and CH₄ oxidation potential seemed to decrease. The decrease in temperature in autumn certainly reduced in situ decomposition processes, possibly leaving unused substrates in the peat, which would explain the increase in CH₄ production potential. Received: 16 August 1996 / Accepted: 30 November 1996     

Afforestation does not necessarily reduce nitrous oxide emissions from managed boreal peat soils

Pristine peatlands have generally low nitrous oxide (N₂O) emissions but drainage and management practices enhance the microbial processes and associated N₂O emissions. It is assumed that leaving peat soils from intensive management, such as agriculture, will decrease their N₂O emissions. In this paper we report how the annual N₂O emission rates will change when agricultural peat soil is either left abandoned or afforested and also N₂O emissions from afforested peat extraction sites. In addition, we evaluated a biogeochemical model (DNDC) with a view to explaining GHG emissions from peat soils under different land uses. The abandoned agricultural peat soils had lower mean annual N₂O emissions (5.5?±?5.4?kg?N?ha^?1) than the peat soils in active agricultural use in Finland. Surprisingly, N₂O emissions from afforested organic agricultural soils (12.8?±?9.4?kg?N?ha^?1) were similar to those from organic agricultural soils in active use. These emissions were much higher than those from the forests on nutrient rich peat soils. Abandoned and afforested peat extraction sites emitted more N₂O, (2.4?±?2.1?kg?N?ha^?1), than the areas under active peat extraction (0.7?±?0.5?kg?N?ha^?1). Emissions outside the growing season contributed significantly, 40% on an average, to the annual emissions. The DNDC model overestimated N₂O emission rates during the growing season and indicated no emissions during winter. The differences in the N₂O emission rates were not associated with the age of the land use change, vegetation characteristics, peat depth or peat bulk density. The highest N₂O emissions occurred when the soil C:N ratio was below 20 with a significant variability within the measured C:N range (13–27). Low soil pH, high nitrate availability and water table depth (50–70?cm) were also associated with high N₂O emissions. Mineral soil has been added to most of the soils studied here to improve the fertility and this may have an impact on the N₂O emissions. We infer from the multi-site dataset presented in this paper that afforestation is not necessarily an efficient way to reduce N₂O emissions from drained boreal organic fields.     

Mineralization of carbon and nitrogen in soil samples taken from three fertilized pine stands: Long-term effects

Seven years after fertilization the rate of CO₂ production in the soil samples taken from the organic horizons of a poor pine forest site (Calluna vulgaris site type), treated with urea or ammonium nitrate with lime, was lower than that in the unfertilized soil. The same trend was also observed in samples of theEmpetrum-Calluna site type 14 years after fertilization. In the more fertileVaccinium myrtillus site type these rapidly-soluble N fertilizers had a long-term enhancing effect on the production of CO₂. Apatite and biotite eliminated the decreasing effect of urea on the production of CO₂. One reason for this might be the long-term increase in soil pH caused by apatite and biotite, or their constituents (Ca, Mg, K, P). Nitroform (a slow-releasing N fertilizer) had no statistically significant effect on the production of CO₂ in soil samples from any of the forest types. Despite the high N mineralization in the samples from nitroform fertilized soils there was no nitrification, and the high content of total N indicated that after nitroform fertilization the losses of N were low.The correlation between the net mineralization values for C (CO₂ production) and N was poor. However, multiple linear regression analysis, which also took into account the effect of nutrients and pH, indicated that there was a link between the mineralization of C and N.