Fertility and motility of sperm from Atlantic halibut (Hippoglossus hippoglossus) in relation to dose and timing of gonadotrophin-releasing hormone agonist implant     

Etiënne L. M. Vermeirssen  Carlos Mazorra de Quero  Robin J. Shields  Birgitta Norberg  David E. Kime  Alexander P. Scott 《Aquaculture (Amsterdam, Netherlands)》2004,230(1-4):547-567

In broodstocks of Atlantic halibut, Hippoglossus hippoglossus, male and female gamete production often becomes unsynchronised towards the end of the spawning season—milt becomes very viscous and difficult to express while the females are still producing batches of good quality eggs. Gonadotrophin-releasing hormone agonist (GnRHa) has been shown to stimulate spermiation in a number of fish species. Therefore, we conducted two experiments where male halibut were implanted intramuscularly with pellets containing GnRHa. The effect of the pellets was tested at three periods: before, at the height of and at the end of spermiation. In the middle period, GnRHa was tested at two doses (5 and 25 μg/kg bodyweight). Measurements were made of milt hydration, sperm motility and fertilisation rate. Implanted males began spermiation at least 4 weeks before control males. Both doses of GnRHa increased the fluidity of the milt. This effect lasted for at least 20 days in the low dose group and for 40 days in the high dose group. When applied at the end of the season, GnRHa reversed the normal trend for the milt to become more viscous. GnRHa treatments did not affect fertilisation rates obtained with the sperm. However, towards the end of the spawning season, sperm motility was enhanced in males treated with the high dose of GnRHa (25 μg/kg) compared to controls. As described previously, plasma concentrations of the gonadal steroids, 5β-pregnane-3β,17,20β-triol 20-sulphate and 17,20-dihydroxy-4-pregnen-3-one, were significantly enhanced by GnRHa treatment. Concentrations of testosterone on the other hand decreased when spermiating males were treated with GnRHa. Our data suggest that 17,20β-dihydroxy-4-pregnen-3-one or its metabolites are involved in milt hydration, possibly through affecting ion transport.  相似文献   

CD46 in meningococcal disease     

Johansson L  Rytkonen A  Bergman P  Albiger B  Källström H  Hökfelt T  Agerberth B  Cattaneo R  Jonsson AB 《Science (New York, N.Y.)》2003,301(5631):373-375

The human-specific bacterial pathogen Neisseria meningitidis is a major cause of sepsis and/or meningitis. The pili of N. meningitidis interact with CD46, a human cell-surface protein involved in regulation of complement activation. Transgenic mice expressing human CD46 were susceptible to meningococcal disease, because bacteria crossed the blood-brain barrier in these mice. Development of disease was more efficient with piliated bacteria after intranasal, but not intraperitoneal, challenge of CD46 transgenic mice, suggesting that human CD46 facilitates pilus-dependent interactions at the epithelial mucosa. Hence, the human CD46 transgenic mice model is a potentially useful tool for studying pathogenesis and for vaccine development against meningococcal disease.  相似文献   

Mercury in the Swedish environment — Recent research on causes,consequences and corrective methods   总被引：3，自引：0，他引：3  

Oliver Lindqvist  Kjell Johansson  Lage Bringmark  Birgitta Timm  Mats Aastrup  Arne Andersson  Gunnar Hovsenius  Lars Håkanson  Åke Iverfeldt  Markus Meili 《Water, air, and soil pollution》1991,55(1-2):xi-261

During the last decade a new pattern of Hg pollution has been discerned, mostly in Scandinavia and North America. Fish from low productive lakes, even in remote areas, have been found to have a high Hg content. This pollution problem cannot be connected to single Hg discharges but is due to more widespread air pollution and long-range transport of pollutants. A large number of waters are affected and the problem is of a regional character. The national limits for Hg in fish are exceeded in a large number of lakes. In Sweden alone, it has been estimated that the total number of lakes exceeding the blacklisting limit of 1 mg Hg kg-1 in 1-kg pike is about 10 000. The content of Hg in fish has markedly increased in a large part of Sweden, exceeding the estimate background level by about a factor of 2 to 6. Only in the northernmost part of the country is the content in fish close to natural values. There is, however, a large variation of Hg content in fish within the same region, which is basically due to natural conditions such as the geological and hydrological properties of the drainage area. Higher concentrations in fish are mostly found in smaller lakes and in waters with a higher content of humic matter. Since only a small percentage of the total flow of Hg through a lake basin is transferred into the biological system, the bioavailability and the accumulation pattern of Hg in the food web is of importance for the Hg concentrations in top predators like pike. Especially, the transfer of Hg to low trophic levels seems to be a very important factor in determining the concentration in the food web. The fluxes of biomass through the fish community appear to be dominated by fluxes in the pelagic food web. The Hg in the lake water is therefore probably more important as a secondary source of Hg in pike than is the sediment via the benthic food chain. Different remedy actions to reduce Hg in fish have been tested. Improvements have been obtained by measures designed to reduce the transport of Hg to the lakes from the catchment area, eg. wetland liming and drainage area liming, to reduce the Hg flow via the pelagic nutrient chains, eg. intensive fishing, and to reduce the biologically available proportion of the total lake dose of Hg, eg. lake liming with different types of lime and additions of selenium. The length of time necessary before the remedy gives result is a central question, due to the long half-time of Hg in pike. In general it has been possible to reduce the Hg content in perch by 20 to 30% two years after treatments like lake liming, wetland liming, drainage area liming and intensive fishing. Selenium treatment is also effective, but before this method can be recommended, dosing problems and questions concerning the effects of selenium on other species must be evaluated. Regardless how essential these kind of remedial measures may be in a short-term perspective, the only satisfactory long-term alternative is to minimize the Hg contamination in air, soil and water. Internationally, the major sources of Hg emissions to the atmosphere are chlor-alkali factories, waste incineration plants, coal and peat combustion units and metal smelter industries. In the combustion processes without flue gas cleaning systems, probably about 20 to 60% of the Hg is emitted in divalent forms. In Sweden, large amounts of Hg were emitted to the atmosphere during the 50s and 60s, mainly from chlor-alkali plants and from metal production. In those years, the discharges from point sources were about 20 to 30 t yr 1. Since the end of the 60s, the emission of Hg has been reduced dramatically due to better emission control legislation, improved technology, and reduction of polluting industrial production. At present, the annual emissions of Hg to air are about 3.5 t from point sources in Sweden. In air, more than 95% of Hg is present as the elemental Hg form, HgO⁰. The remaining non-elemental (oxidized) form is partly associated to particles with a high wash-out ratio, and therefore more easily deposited to soils and surface waters by precipitation. The total Hg concentration in air is normally in the range 1 to 4 ng m-3. In oceanic regions in the southern hemisphere, the concentration is generally about 1 ng m^?3, while the corresponding figure for the northern hemisphere is about 2 ng m-3. In remote continental regions, the concentrations are mainly about 2 to 4 ng m^?3. In precipitation, Hg concentrations are generally found in the range 1 to 100 ng L^?1. In the Nordic countries, yearly mean values in rural areas are about 20 to 40 ng L^?1 in the southern and central parts, and about 10 ng L^?1 in the northern part. Accordingly, wet deposition is about 20 (10 to 35) g km^?2 yr^?1 in southern Scandinavia and 5 (2 to 7) in the northern part. Calculations of Hg deposition based on forest moss mapping techniques give similar values. The general pattern of atmospheric deposition of Hg with decreasing values from the southwest part of the country towards the north, strongly suggests that the deposition over Sweden is dominated by sources in other European countries. This conclusion is supported by analyses of air parcel back trajectories and findings of significant covariations between Hg and other long range transported pollutants in the precipitation. Apart from the long range transport of anthropogenic Hg, the deposition over Sweden may also be affected by an oxidation of elemental Hg in the atmosphere. Atmospheric Hg deposited on podzolic soils, the most common type of forest soil in Sweden, is effectively bound in the humus-rich upper parts of the forest soil. In the Tiveden area in southern Sweden, about 75 to 80% of the yearly deposition is retained in the humus layer, chemically bound to S or Se atoms in the humic structure. The amount of Hg found in the B horizon of the soils is probably only slightly influenced by anthropogenic emissions. In the deeper layers of the soil, hardly any accumulation of Hg takes place. The dominating horizontal flow in the soils takes place in the uppermost soil layers (0 to 20 cm) during periods of high precipitation and high groun water level in the soils. The yearly transport of Hg within the soils has been calculated to be about 5 to 6 g km^?2. The specific transport of total Hg from the soil system to running waters and lakes in Sweden is about 1 to 6 g km^?2 yr¹. The transport of Hg is closely related to the transport of humic matter in the water. The main factors influencing the Hg content and the transport of Hg in run-off waters from soils are therefore the Hg content in soils, the transport of humic matter from the soils and the humus content of the water. Other factors, for example acidification of soils and waters, are of secondary importance. Large peatlands and major lake basins in the catchment area reduce the out-transport of Hg from such areas. About 25 to 75% of the total load of Hg of lakes in southern and central Sweden originates from run-off from the catchment area. In lakes where the total load is high, the transport from run-off is the dominating pathway. The total Hg concentrations in soil solution are usually in the range 1 to 50, in ground water 0.5 to 15 and in run-off and lake water 2 to 12 ng L^?1, respectively. The variation is largely due to differences in the humus content of the waters. In deep ground water with a low content of humic substances, the Hg concentration is usually below 1 ng L^?1. The present amount and concentrations of Hg in the mor layer of forest soils are affected by the total anthropogenic emissions of Hg to the atmosphere, mainly during this century. Especially in the southern part of Sweden and in the central part along the Bothnian coast, the concentrations in the mor layer are markedly high. In southern areas the anthropogenic part of the total Hg content is about 70 to 90%. Here, the increased content in these soils is mainly caused by long-range transport and emissions from other European countries, while high level areas in the central parts are markedly affected by local historical emissions, mainly from the chlor-alkali industry. When comparing the input/output fluxes to watersheds it is evident that the present atmospheric deposition is much higher than the output via run-off waters, on average about 3 to 10 times higher, with the highest ration in the southern parts of Sweden. Obviously, Hg is accumulating in forest soils in Sweden at the present atmospheric deposition rate and, accordingly, the concentrations in forest soils are still increasing despite the fact that the emissions of Hg have drastically been reduced in Sweden during the last decades. The increased content of Hg in forest soils may have an effect on the organisms and the biological processes in the soils. Hg is by far the most toxic metal to microorganisms. In some regions in Sweden, the content of Hg in soils is already today at a level that has been proposed as a critical concentration. To obtain a general decrease in the Hg content in fish and in forest soils, the atmospheric deposition of Hg has to be reduced. The critical atmospheric load of Hg can be defined as the load where the input to the forest soils is less than the output and, consequently, where the Hg content in the top soil layers and the transport of Hg to the surface waters start to decrease. A reduction by about 80% of the present atmospheric wet deposition has to be obtained to reach the critical load for Scandinavia.  相似文献   

Chemical reactions in chlorine dioxide stages of pulp bleaching     

J. J. Kolar  B. O. Lindgren  Birgitta Pettersson 《Wood Science and Technology》1983,17(2):117-128

  相似文献   

Germination of <Emphasis Type="Italic">Plasmodiophora brassicae</Emphasis> resting spores stimulated by a non-host plant     

Hanna?FribergEmail author  Jan?Lagerl?f  Birgitta?R?mert 《European journal of plant pathology / European Foundation for Plant Pathology》2005,113(3):275-281

Plant-induced germination of Plasmodiophora brassicae resting spores was studied in a laboratory experiment. Spore reaction was analysed in nutrient solution with exudates from growing roots of different plant species – one host plant (Brassica rapa var. pekinensis) and four non-host plants (Lolium perenne, Allium porrum, Secale cereale and Trifolium pratense) – and in controls with distilled water and nutrient solution. It was found that root exudates from L. perenne stimulated spore germination more than exudates from the other plants, including those from the host plant. The effect could not be explained by differences in the nutritional composition of the solutions due to differential uptake of the plant species, or by differences in root activity, measured as exudation of soluble sugars. This is the first time such a separation of factors has been done in analysing the influence of plants on P. brassicae germination. Although stimulation of P. brassicae resting spore germination is not restricted to the presence of host plants, it seems to vary depending on the plant species.  相似文献   

Sperm Distribution and Its Relation to Ovulation in Artificially Inseminated Heifers     

Birgitta Larsson 《Reproduction in domestic animals》1988,23(2):56-64

Contents: Blood samples were taken in ten heifers every two hours during prooestrus and oestrus for determination of the LH peak, which was used to calculote the time of expected ovulation. Artificial insemination with frozen/thawed semen was performed at different times from the beginning of oestrus and the animals were slaughtered two, twelve or 24 hours after insemination. The genital tract was flushed and the spermatozoa recovered from the flushing solution by microscopic investigation. Heifers slaughtered two hours after insemination and more than 19 hours before ovulation had more spermatozoa in the uterotubal junction (UTJ) than in the isthmus and ampulla. This sperm distribution differed from that in the other animals. In animals which were slaughtered closer to ovulation and in those who had already ovulated at slaughter, approximately the same number of spermatozoa were recovered from the UTJ and isthmus and only a few spermatozoa were recovered from the ampulla. Motile spermatozoa were found in both the isthmus, UTJ and uterus at two and twelve hours after insemination and approximately ten hours before ovulation. Their number decreased with time but some motile spermatozoa were also recovered 24 hours after insemination and after ovulation. The distribution of spermatozoa in the oviducts ipsi-and contralateral to the corpus haemorrhagicum-bearing ovary was compared in heifers that had ovulated. There were no differences in the number of oviductal segments containing spermatozoa, nor were there any differences within animal in the number of spermatozoa in the oviducts. It was concluded that ovulation does not seem to cause great changes in the distribution of spermatozoa in the oviducts. Inhalt: Spermienverteilung und deren Beziehung zur Ovulation bei kunstlich besamten Jungrindern Von 10 Färsen wurden wahrend des Diöstrus und Östrus Blutproben im Abstand von 2 Std. entnommen, um den LH-Gipfel festzustellen. Dieser wurde jür die Bestimmung des erwarteten Ovulationstermins herangezogen. Inseminationen mit Gefriersperma wurden von Brunstbeginn an in verschiedenen Intervallen vorgenommen. Die Tiere wurden 2, 12 oder 24 Std. nach der Besamung getötet, die Geschlechtsorgane gespült und die Spermien in den Spülflüssigkeiten mikroskopisch nachgewiesen. Färsen, die 2 Std. nach der Besamung und mehr als 19 Std. vor der Ovulation getötet wurden, hat-ten mehr Spermien im Ostium uterinum des Eileiters (OU) als im Isthmus und Ampulle. Diese Verteilung war von jener der anderen Tiere verschieden. Tiere, die kürzere Zeit vor der Ovulation getötet wurden, oder bei der Schlachtung schon ovuliert hatten, zeigten etwa dieselbe Anzahl von Spermien in OU und Isthmus, in der Ampulle wurden nur wenig Spermien gefunden. Bei Färsen, die ovuliert hatten, wurde die Sper-mienverteilung in den ipsi- und contralateralen Eileitern zum Corpus haemowhagicum des Ovars verglichen. Die Spermienxahlen in den Eileitersegmenten waren nicht verschieden und auch im rechten und linken Eileiter gleich. Es wurde gefolgert, daβ die Ovulation keinen groβen Einfluβ auf die Spermienverteilung in den Eileitern bewirkt.  相似文献   

Consumer reactions to boar meat - A reviewRéactions des consommateurs à la viande de porcs mâles entiers-une revueVerbraucherreaktionen auf Eberfleisch — ein Übersichtsreferat     

Birgitta Malmfors  Kerstin Lundström 《Livestock Production Science》1983,10(2):187-196

Over the last ten years, consumer reactions to boar meat have been studied in nine experiments performed in six European countries. In these different studies, conditions have differed with regard to experimental design, proportions of tainted boars and products tested. The proportions of consumers judging the odour of the tested boar meat to be less pleasant than that of normal pig meat has mainly varied from about 5 to 35%. This should be compared with 3–10% for meat tested from gilts and castrates. The results differ between countries and also between products. The most favourable results have been obtained for cured bacon, cooked ham and sausage. The conclusion must be drawn that most boar meat would be accepted by consumers. Further research should be directed to finding a reliable screening test for sorting out tainted boar carcasses.  相似文献   

Effect of repeated oral administration of glucose and leucine immediately after exercise on plasma insulin concentration and glycogen synthesis in horses     

Bröjer JT  Nostell KE  Essén-Gustavsson B  Hedenström UO 《American journal of veterinary research》2012,73(6):867-874

  相似文献   

Repeated post-exercise administration with a mixture of leucine and glucose alters the plasma amino acid profile in Standardbred trotters     

Katarina EA Nostell  Birgitta Essén-Gustavsson  Johan T Br?jer 《Acta veterinaria Scandinavica》2012,54(1):7

Background

The branched chain amino acid leucine is a potent stimulator of insulin secretion. Used in combination with glucose it can increase the insulin response and the post exercise re-synthesis of glycogen in man. Decreased plasma amino acid concentrations have been reported after intravenous or per oral administration of leucine in man as well as after a single per oral dose in horses. In man, a negative correlation between the insulin response and the concentrations of isoleucine, valine and methionine have been shown but results from horses are lacking. This study aims to determine the effect of repeated per oral administration with a mixture of glucose and leucine on the free amino acid profile and the insulin response in horses after glycogen-depleting exercise.

Methods

In a crossover design, after a glycogen depleting exercise, twelve Standardbred trotters received either repeated oral boluses of glucose, 1 g/kg body weight (BW) at 0, 2 and 4 h with addition of leucine 0.1 g/kg BW at 0 and 4 h (GLU+LEU), or repeated boluses of water at 0, 2 and 4 h (CON). Blood samples for analysis of glucose, insulin and amino acid concentrations were collected prior to exercise and over a 6 h post-exercise period. A mixed model approach was used for the statistical analyses.

Results

Plasma leucine, isoleucine, valine, tyrosine and phenylalanine concentrations increased after exercise. Post-exercise serum glucose and plasma insulin response were significantly higher in the GLU+LEU treatment compared to the CON treatment. Plasma leucine concentrations increased after supplementation. During the post-exercise period isoleucine, valine and methionine concentrations decreased in both treatments but were significantly lower in the GLU+LEU treatment. There was no correlation between the insulin response and the response in plasma leucine, isoleucine, valine and methionine.

Conclusions

Repeated post-exercise administration with a mixture of leucine and glucose caused a marked insulin response and altered the plasma amino acid profile in horses in a similar manner as described in man. However, the decreases seen in plasma amino acids in horses seem to be related more to an effect of leucine and not to the insulin response as seen in man.  相似文献   

Effect of earthworms and incorporation of grass on Plasmodiophora brassicae     

Hanna Friberg  Jan Lagerlöf  Birgitta Rämert 《Pedobiologia》2008,52(1):29-39

  相似文献