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21.
Spermatozoa are unique cells because of their morphological and physiological characteristics. They are produced during the process called spermatogenesis. Spermatogenesis consists of three phases: spermatocytogenesis, spermiogenesis and spermiation, during which spermatozoa undergo several changes. Spermatogenesis takes place within the seminiferous tubules containing two types of cells—the germ cells and the Sertoli cells—that alongside the Leydig cells, which play an important role when it comes to normal fertility. Everything is regulated by the hypothalamic–pituitary–gonadal axis and specific hormones due to multi-hormonal feedback systems. Spermatozoa possess morphological and physiological features, which are sometimes completely different from what is observed in various somatic cells. What is more, canine spermatozoa have specific characteristics making them special compared to the spermatozoa of other mammalian species. The metabolic energy production, which is crucial for the appropriate functioning of spermatozoa, can be fuelled by different metabolic pathways utilizing different chemical substrates. Inseparable from the oxidative phosphorylation process is the production of reactive oxygen species, which are both essential and toxic to spermatozoa. Furthermore, epididymis is a very important structure, responsible for the transport and maturation of spermatozoa, which are then stored in the last segment of epididymis—the epididymal cauda. Moreover, the retrieval of spermatozoa from the epididymides is crucial for the development of assisted reproduction techniques and sperm cryopreservation methods. The information gained from the research on domestic dogs might be transferred to their wild relatives, especially those species categorized as endangered. 相似文献
22.
Anna German 《Phytoparasitica》1985,13(3-4):209-213
A 5-minute contact of nursing mothers of the Levant vole,Microtus guentheri, with paper impregnated with a DES suspension in soybean oil (125 μg/cm2 ) caused sterilization of 60% of the newborn female offspring. A 1-hour contact was sufficient to sterilize more than 90% of them. When the DES concentration was decreased to 1 μg/cm2 only 44% of the newborn female offspring were sterile although their nursing mothers had been exposed to contact with the treated paper for a period of 2 hours. The concentration of 0.1 μg/cm2 was totally ineffective in causing sterilization. Treatment of nesting material with DES offers a promising means of reproductive suppression in Levant voles. 相似文献
23.
Nostell K Bröjer J Höglund K Edner A Häggström J 《Veterinary journal (London, England : 1997)》2012,191(2):171-175
Branding is the traditional and well-established method used to mark horses, but recently microchip transponders for implantation have become available. In this study, behaviour, physiological stress variables and skin temperature in foals were determined in response to hot-iron branding (n=7) and microchip implantation (n=7). Salivary cortisol concentrations increased in response to branding (1.8 ± 0.2 ng/mL) and microchip implantation (1.4 ± 0.1ng/mL), but cortisol release over time did not differ. In response to both manipulations there was a transient increase in heart rate (P<0.001) and heart rate variability (P<0.01). Branding and microchip implantation induced a comparable aversive behaviour (branding, score 3.86 ± 0.85; microchip, score 4.00 ± 0.82). Both techniques thus caused similar physiological and behavioural changes indicative of stress. Acutely, implantation of a microchip was as stressful as branding in foals. Branding caused a necrotising skin burn lasting at least 7 days. Moreover branding, but not microchip implantation (P<0.001), was accompanied by a generalized increase in skin temperature which was comparable to low degree post-burn hypermetabolism in humans. 相似文献
24.
Zaks KL Tan EO Thrall MA 《Journal of the American Veterinary Medical Association》2005,226(9):1516-8, 1500
A 5-year-old pit bull-type dog was examined because of lethargy and black feces, and a presumptive diagnosis of methemoglobinemia was made on the basis of grossly visible brown discoloration of the mucous membranes and urine. Heinz body formation was seen on examination of blood smears, and severe anemia developed 3 days later. The dog did not have any history of exposure to toxins or drugs that have been associated with Heinz body formation. The only remarkable historical finding was that the dog had been wandering loose the day prior to initial examination and returned home smelling strongly of skunk spray. Skunk spray contains thiols and other compounds that are strong oxidizing agents. It was speculated that the methemoglobinemia and Heinz body anemia were a result of exposure to these compounds. Skunk interactions with dogs usually have malodorous but otherwise harmless results. However, findings in this dog suggest that more serious consequences may develop in isolated cases. 相似文献
25.
The average amount of precipitation in spring and summer 2010 and 2011 coupled with relatively high temperatures caused massive Fusarium spp. infection of maize and yield losses in southern Poland. In order to examine the cause of this disease outbreak, Fusarium spp. were isolated and fungal strains were identified based on morphological characters and species-specific PCR assays. A total of 200 maize samples were processed, resulting in the obtention of 71 strains, which belonged to five Fusarium species, F. poae being the predominant one (74.56%). Other isolates were identified as F. graminearum, F. oxysporum, F. verticillioides and F. proliferatum. PCR-based detection of mycotoxin-synthesis-pathway genes was also used to determine the potential of the analyzed strains to produce trichothecenes (DON and NIV) and fumonisins (FUM). Only 14 isolates revealed the potential to produce DON (11 strains) and FUM (3 strains). HPLC analyses of grain samples revealed the presence of DON only – other mycotoxins were not detected. Moreover, 57.1% of potentially mycotoxin-producing isolates indicated the toxicity in a biological test. 相似文献
26.
27.
木霉对植物的促生及诱导抗性研究进展 总被引:4,自引:0,他引:4
木霉不仅能够直接抑制植物病原菌的生长,还可通过定殖于植物的根部引起植物新陈代谢的改变。本文综述了木霉在植物根部定殖后,通过产生植物生长调节剂、抑制或降解根际有害物质、增加养分利用率以促进植物生长以及通过产生激发子诱导植物形成胞壁沉积物、合成抗菌物质以诱导植物局部或系统抗性的研究进展,以期为进一步扩大木霉在农业生产中的应用提供参考。 相似文献
28.
29.
Claire Bouvard Isabelle Galy-Fauroux Fran?oise Grelac Wassila Carpentier Anna Lokajczyk Sophie Gandrille Sylvia Colliec-Jouault Anne-Marie Fischer Dominique Helley 《Marine drugs》2015,13(12):7446-7462
Low-molecular-weight fucoidan (LMWF) is a sulfated polysaccharide extracted from brown seaweed that presents antithrombotic and pro-angiogenic properties. However, its mechanism of action is not well-characterized. Here, we studied the effects of LMWF on cell signaling and whole genome expression in human umbilical vein endothelial cells and endothelial colony forming cells. We observed that LMWF and vascular endothelial growth factor had synergistic effects on cell signaling, and more interestingly that LMWF by itself, in the absence of other growth factors, was able to trigger the activation of the PI3K/AKT pathway, which plays a crucial role in angiogenesis and vasculogenesis. We also observed that the effects of LMWF on cell migration were PI3K/AKT-dependent and that LMWF modulated the expression of genes involved at different levels of the neovessel formation process, such as cell migration and cytoskeleton organization, cell mobilization and homing. This provides a better understanding of LMWF’s mechanism of action and confirms that it could be an interesting therapeutic approach for vascular repair. 相似文献
30.
Organic geochemical parameters for estimation of petrogenic inputs in the coastal area of Kavala City,Greece 总被引:1,自引:0,他引:1
Anna Grigoriadou Jan Schwarzbauer Andreas Georgakopoulos 《Journal of Soils and Sediments》2008,8(4):253-262
Background, aims, and scope Sediments and soils in coastal areas are frequently polluted by anthropogenic contaminants as the result of both riverine
or terrestrial discharge and autochthonic marine emissions. In order to determine petrogenic contamination in the coastal
industrial area of Kavala City in northern Greece, a combination of polycyclic aromatic hydrocarbon (PAH) and organic geochemical
petroleum biomarker analyses has been performed on marine and freshwater sediments as well as soils.
Materials and methods Soils, freshwater, and marine sediments have been treated by standard extraction methods. The dried and desulphurized sample
extracts have been fractionated by column chromatography, followed by addition of surrogate standards. Qualitative and quantitative
data were obtained by gas chromatograph connected with a flame ionization and electron capture detector (GC-FID/ECD) and by
GC linked to a mass spectrometer (GC/MS), whereas identification of compounds was based on EI+-mass spectra and gas chromatographic retention times. Quantitative data were obtained by integration of specific ion chromatograms.
Results The total PAH concentrations measured in the area varied highly, showing different levels from 18 up to 318,000 ng g−1 dry weight (dw). Several PAH ratios, as well as the ratio of pristane (Pr) to phytane (Phyt), have been considered. Out of
39 samples, 22 revealed a specific distribution of hopane fingerprints indicating petrogenic input. Finally, in numerous samples,
the ratio of 17α(H)-22,29,30-trisnorhopane (Tm) and 18α(H)-22,29,30-trisnorhopane (Ts) was calculated, as well as the ratio
of 22S-17α(H),21β(H)-30 homohopane (αβC31-hopane 22S) and 22R-17α(H),21β(H)-30 homohopane (αβC31-hopane 22R).
Discussion Based on the specific PAH ratios, a group of samples was clearly characterized to be contaminated dominantly by combustion-derived
emissions, whereas a second group of samples exhibited mixed influence from petrogenic and pyrogenic PAHs. On the other hand,
the exhibition of specific hopane fingerprints in many samples indicates a direct petrogenic input. Finally, the values of
the ratio of Tm/(Ts + Tm) and of αβC31-hopanes 22S/(22S+22R)-isomer demonstrated an input of highly mature organic matter that has to be clearly attributed to petroleum-derived
contamination, while the ratio of Pr/Phyt showed that most samples exhibited an input of organic matter.
Conclusions The coastal area of Kavala is strongly affected by anthropogenic contaminants. Petrogenic emissions were pointed out firstly
by PAH analyses that separated dominantly pyrogenic contaminated sites from areas affected by both pyrogenic and petrogenic
emissions. However, analyses of organic geochemical biomarkers revealed a much higher sensitivity in identifying petroleum-derived
contaminations and were successfully used to differentiate several petrogenic contaminations in the marine and terrestrial
samples.
Recommendations and perspectives Based on this study, it was recommended to use a complementary approach of source-specific substances to successfully characterize
petrogenic emissions. Generally, a PAH-based source identification of petrogenic versus pyrogenic contaminations should be
combined with petroleum biomarker analysis. PAH and biomarker ratios as well as individual biomarker fingerprints revealed
a more comprehensive view on the quality and quantity of petrogenic emissions in sediments and soils. 相似文献