• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 23
  • 12
  • Tagged with
  • 35
  • 34
  • 24
  • 23
  • 22
  • 11
  • 7
  • 6
  • 6
  • 5
  • 5
  • 5
  • 4
  • 4
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Sperm Membrane Channels, Receptors and Kinematics : Using boar spermatozoa for drug toxicity screening

Vicente Carrillo, Alejandro January 2016 (has links)
Internal fertilization usually implies that a spermatozoon, with intact attributes for zygote formation, passes all hurdles during its transport through the female genitalia and reaches the oocyte. During this journey, millions to billions of other spermatozoa perish. Spermatozoa are highly differentiated motile cells without synthetic capabilities. They generate energy via glycolysis and oxidative phosphorylation to sustain motility and to maintain the stability and functionality of their plasma membrane. In vivo, they spend their short lifespan bathing in female genital tract fluids of different origins, or are in vitro exposed to defined media during diverse sperm handling i.e. extension, cryopreservation, in vitro fertilization, etc. Being excitable cells, spermatozoa respond in vivo to various stimuli during pre-fertilization (capacitation, hyperactivation, oocyte location) and fertilization (acrosome reaction, interaction with the oocyte) events, mediated via diverse membrane ion-conducting channels and ligand-gated receptors. The present Thesis has mapped the presence and reactivity (sperm intactness and kinematics) of selected receptors, water and ion channels in ejaculated boar spermatozoa. The final aim was to find a relevant alternative cell type for in vitro bioassays that could ease the early scrutiny of candidate drugs as well as decreasing our needs for experimental animals according to the 3R principles. Spermatozoa are often extended, cooled and thawed to warrant their availability as fertile gametes for breeding or in vitro testing. Such manipulations stress the cells via osmotic variations and hence spermatozoa need to maintain membrane intactness by controlling the exchange of water and the common cryoprotectant glycerol, via aquaporins (AQPs). Both AQPs-7 and -9 were studied for membrane domain changes in cauda- and ejaculated spermatozoa (un-processed, extended, chilled or frozen-thawed). While AQP-9 maintained location through source and handling, thawing of ejaculated spermatozoa clearly relocated the labelling of AQP-7, thus appearing as a relevant marker for non-empirical studies of sperm cryopreservation. Alongside water, spermatozoa interact with calcium (Ca2+) via the main Ca2+ sperm channel CatSper. Increments in intracellular Ca2+ initiate motility hyperactivation and the acrosome reaction. The four subunits of the CatSper channel were present in boar spermatozoa, mediating changes in sperm motility under in vitro capacitation-inducing conditions (increased extracellular Ca2+ availability and bicarbonate) or challenge by the CatSper antagonists mibefradil and NNC 55-0396. Uterine and oviduct fluids are richest in endogenous opioids as β-endorphins during mating and ovulation. Both μ- and δ- opioid receptors were present in boar spermatozoa modulating sperm motility, as in vitro challenge with known agonists (μ: morphine; δ: DPDPE and κ: U 50488) and antagonists (μ: naloxone; δ: naltrindole and κ: nor-binaltrorphimine) showed that the μ-opioid receptor maintained or increased motility while the δ-opioid receptor mediated decreased motility over time. Finally, boar spermatozoa depicted dose-response effects on sperm kinematics and mitochondrial potential following in vitro challenge with 130 pharmacological drugs and toxic compounds as well as with eight known mito-toxic compounds. In conclusion, boar spermatozoa expressing functional water (AQPs-7 and -9) and ion (CatSper 1-4) channels as well as μ- and δ-opioid receptors are able to adapt to stressful environmental variations, capacitation and pharmacological compounds and drug components. Ejaculated sperm suspensions are easily and painlessly obtained from breeding boars, and are suitable biosensors for in vitro drug-induced testing, complying with the 3R principles of reduction and replacement of experimental animals, during early toxicology screening.
32

Following the mevalonate pathway to bone heal alley

Skoglund, Björn January 2007 (has links)
The mevalonate pathway is an important biosynthetic pathway, found in all cells of virtually all known pro- as well as eukaryotic organisms. This thesis is an investigation into the use of two drugs, originally developed for different applications, but both affecting the mevalonate pathway, in to models of fracture repair. Using two different rodent models of fracture repair, a commonly used cholesterol lowering drug (statin) and two drugs used to treat osteoporosis (bisphosphonate) were applied both systemically as well as locally in order to enhance fracture repair. Papers I and II investigate the potential of simvastatin to improve the healing of femoral fractures in mice. Papers III and IV explore the use of two bisphosphonates to improve early fixation of stainless steel screws into rat bone. The statin simvastatin lead to an increased strength of the healing cellus. The application of bisphosphonates increased early screw fixation. It seems clear that both drugs have uses in orthopaedic applications. One interesting avenue of further research would be to combine the two classes of drugs and see if we can get the benefits while at the same time diminishing the drawbacks.
33

Hästavmaskningsmedels påverkan på miljö och välfärd

Landgren, Emilia, Wallman, Sabina January 2014 (has links)
Healthy, natural pastures is very valuable for biodiversity in the form of both plants and animals. An efficient use of pastures helps to preserve biodiversity, but grazing animals needs to be de-wormed to keep them healthy and to prevent harmful parasites spread on the pasture. The awareness about the environmental impact of the frequent use of deworming agents is low among the public. Some people are unaware that the absorption in horses of anthelmintics is incomplete, which make the circumstances about enviromental effect important to investigate further. The scientific evidence in this area is limited and more studies and trials are needed to deepen the knowledge about the effects of anthelmintics in the environment. Our report includes a compilation of studies conducted on anthelmintics and equine parasites, as well as an experiment which was conducted at the University of Halmstad biogaslaboratory April 2014. Anthelmintics have been shown to have negative impact on the manure ecosystem and especially against manure living fauna. Deworming routines has changed over the years as the equine industry has developed. Nevertheless, there’s still a lack of concrete approach to deworming.
34

Utvärdering av analys av pankreas-specifikt lipas hos hund och katt med Vcheck V200 : en prospektiv komparativ studie / Evaluation of analysis of pancreas-specific Lipase in dogs and cats with Vcheck V200 : a prospective comparative study

Carlsson, Felicia January 2021 (has links)
Pankreatit anses vara en vanligt förekommande sjukdom hos hundar och katter och kan diagnostiseras genom mätningar av koncentrationen Canine Pancreas-specific Lipase (cPL) respektive Feline Pancreas-specific Lipase (fPL) i serum. Utifrån dessa koncentrationer graderas patienten enligt normalvärde, gråzon eller indikation på pankreatit. Golden standardmetoden för att analysera cPL/fPL är Spec cPL respektive Spec fPL. Nya metoder har utvecklats för kvantitativ mätning av pankreas-specifik lipas såsom Vcheck V200, ett instrument, som analyserar cPL/fPL med en fluorescerande immunoassay. Syftet med studien var att utvärdera analys av cPL/fPL på Vcheck V200 samt jämföra resultatet från detta instrument med värdena från ett referenslaboratorium i Tyskland för att se om det fanns en signifikant skillnad mellan metoderna. Koncentrationen cPL i hundserum (n=37) och koncentrationen fPL i kattserum (n=29) analyserades på Vcheck V200. Dessa prover skickades även till referenslaboratoriet där analysen Spec cPL respektive Spec fPL utfördes. Spridningen var stor kring bias i Bland-Altman diagram för både cPL och fPL och jämförelsen mellan metoderna för de specifika koncentrationerna av cPL/fPL bedömdes vara statistiskt signifikant (p<0,05). 27% av hundproverna graderas olika enligt de båda metoderna och skillnaden var signifikant (p<0,05). 24% av kattproverna graderades olika men skillnaden var inte signifikant (p=0,257). Studien tyder på att jämförelsen mellan de båda metoderna var signifikant förutom vid graderingen av kattproverna. Beaktande detta och det faktum att kvalitetssäkringen brister vid analys av fPL på grund av avsaknad av kontroller kan i dagsläget inte cPL/fPL på Vcheck V200 ersätta den nuvarande golden standardmetoden, trots att ingen signifikant skillnad sågs vid gradering av kattprover. / Pancreatitis is a common disease in canine and felines and can be diagnosed by measuring the concentration of Canine Pancreas-specific Lipase (cPL) or Feline Pancreas-specific Lipase (fPL) in serum. Based on the concentration of cPL/fPL, the patient is then classified in different diagnostic categories (normal value, gray zone or indication of pancreatitis). Spec cPL and Spec fPL is currently the golden standard method for analysis of cPL and fPL. New methods have been developed for the quantitative measurement of pancreatic lipases. Vcheck V200, being one example, utilizing a fluorescent immunoassay for quantification of the lipase. The aim of this study was to evaluate the cPL and fPL analysis on the Vcheck V200 and to examine if there was a significant difference (p≤0,05) when comparing the result from Vcheck V200 with the results from a reference laboratory. The concentration of cPL (n=37) and fPL (n=29) in serum from canine or felines were analyzed using Vcheck V200. The samples were also sent to the reference laboratory where Spec cPL and Spec cPL were performed. A Bland-Altman plot comparison between the two methods showed a large spread for both analysis of cPL and fPL. Comparison of the specific values for analysis of cPL and fPL between the two methods revealed a significant difference (p<0,05). 27% of the dog samples were categorized differently according to the two methods and this difference was significant (p<0,05). 24% of the cat samples were categorized differently and no significant difference were observed (p=0,257). This study indicates that the difference between the two methods was significant, besides the classification of cat samples. Considering this and the lack of quality assurance regarding analysis of fPL due to lack of controls, the cPL/fPL analysis on Vcheck V200 cannot replace the Spec cPL or Spec fPL at present.
35

Quality Management and process development from scratch: Improving laboratory capabilities in Assam, India

Nilsson, Linda January 2019 (has links)
During the past ten years, the foreign direct investment in India has increased with 1828 percent which has led to more projects being initiated in India to improve the livestock industry. The World Bank is the foremost entity in such investments and an issue arises when translating western theories for project management in new cultures. Because of this, development projects tend to stagnate and become inefficient since project goals and templates cannot be applied. Previous studies conducted in Africa have created successful methods called SLMTA to make projects and processes more efficient. SLMTA is a framework to improve the capability and accreditation in laboratory environment. Total Quality Management is one of the methods used in this framework. This study examines how Total Quality Management and process mapping can improve the capability of a laboratory in Guwahati, Assam, India. The underlying theories of this study derives from project management and total quality management where role definition, project triangle, project process, process management and the pareto principle are used. The study is supported by methods from total quality management such as process mapping, affinity diagram, relationship diagram, and process decision program chart. The findings from the study indicate that the development project of the laboratory in central Guwahati is shaped as a project process where project management and process development are implemented in parallel which impairs the efficiency. The study also shows cultural knowledge is a key aspect to create efficient projects and processes in development countries. Finally, the study finds that culturally adapted quality management tools, process mapping and project management are vital for improved efficiency in laboratory environment. / De senaste tio åren har internationella direktinvesteringar i Indien ökat med 1 828 procent och detta har lett till att flera olika projekt initierats i Indien för att förbättra livsmedelsindustrin. Världsbanken är ledande i dessa investeringar och en problematik uppstår när deras västerländska teoretiska ramverk för projektplanering skall översättas i nya kulturer. På grund av detta tenderar utvecklingsprojekt att stagnera och bli ineffektiva eftersom projektmål och mallar inte kan appliceras i den kultur de verkar i. Framgångsrika metoder för att effektivisera projekt och processer har tagits fram i tidigare forskning utförda i Afrika vid namn SLMTA. SLMTA är ett ramverk för att effektivisera kapabilitetens och ansvarstagandet i utvecklandet av laboratorium. En del av de metoder som används är offensiv kvalitetsutveckling. Denna studie undersöker därför hur offensiv kvalitetsutveckling och processkartläggning kan effektivisera kapabiliteten i ett laboratorium i Guwahati, Assam, Indien. Teorin som understödjer studien är tagna från projektledning och offensiv kvalitetsutveckling där roll definitioner, projekttriangeln, process projekt, processledning och pareto principen används. Studien stödjs upp genom metoder från offensiv kvalitetsutveckling som processkartläggning, släktskaps-, relations- och processbesluts diagram. Studien finner att utvecklingsprojektet av laboratoriet i centrala Guwahati är utformat som ett projektprocess där projektledning och processutveckling sker parallellt vilket försvårar effektiviteten. Studien visar även att kulturellförståelse är en avgörande aspekt för att kunna skapa effektiva projekt och processer i ett utvecklingsland. Slutligen finner studien att offensiv kvalitetsutveckling och implementeringen av kulturellt anpassade kvalitetsverktyg, processkartläggning och projektledning är avgörande för att öka effektiviteten.

Page generated in 0.1533 seconds