<p>Syftet med detta projekt var att undersöka om det är möjligt att använda en fungicid vid odling av celler från Oncidium crispum, för att slippa kontaminering av mykorrhizasvamp. Kontaminering från denna sorts svamp har i tidigare försök varit ett stort promlem. I undersökningen användes fungiciden Nystain. Ett första försök gjordes för att testa om Nystatin hade effekt på den aktuella svampen. På näringsmedium fick hyfer från mykorrhizasvampen växa mot ett filterpapper indränkt i Nystatinlösning med olika koncentrationer. Som kontroll användes filterpapper indränkta i vatten och 20 % etanol. Efter 72 h mättes hur nära svampen växt pappret eller om den växt över pappret. Det kunde konstateras att Nystatin vid den starkaste koncentrationen hindrade svampens framväxt. Där stannade svampen innan pappret i större utsträckning än hos de lägre koncentrationerna. Av första försöket drogs därför slutsatsen att Nystatin hämmar mykorrhizasvampen. I ett andra försök doppades explantat från Oncidium crispum i en lösning av Nystatin i olika koncentrationer, som kontroll användes vatten och 20 % etanol. Explantaten lades på MS-medium med hormonerna auxin och cytokinin. Vid den starkaste koncentrationen av Nystatin hämmades tillväxten av svamphyfer fullständigt. Däremot kunde ingen kallustillväxt urskiljas hos något av explantaten. Som kontroll för att försäkra sig om att Nystainet inte påverkade växtmaterialet negativt gjordes andra delen av försöket även med Stapelia grandiflora, ett växtmaterial som är känt för att lätt kunna bilda kallus. Kallustillväxten var fullständig hos kontrollen med vatten, hos de övriga lösningarna var kallustillväxten tyvärr mycket begränsad.</p> / <p>The purpose of this project was to examine if it’s possible to use a fungicide when growing cells from Oncidium crispum, to avoid the contamination of mycorrhizafungus. The contamination from this kind of fungus has been a big problem in earlier experiments. The fungicide used in the experiment was Nystatin. In a first experiment the effect of Nystatin against the mycorrhizafungus was tested. On a nutrient medium hyphae from the mycorrhizafungus were growing towards a paper disc soaked with a solution of Nystatin in different concentration. Paper discs soaked with water and 20 % ethanol were used as a reference. After 72 h it was measured how close the hyphae has got to the paper disc or if it had grown over the paper. It was established that the strongest concentration of Nystatin inhibited the growth of hyphae, in this concentration it stopped growing before it came to the paper disc in a greater extent then by the other concentrations. Therefore the conclusion was drawn, that Nystatin inhibits growth of the mycorrhizafungus. In a second experiment explants from Oncidium crispum were dipped in a solution of Nystatin in different concentrations, water and 20 % ethanol was used as a reference. The explants were placed on a MS-medium with the hormones auxin and cytokinin. By the strongest concentration of Nystatin there was no growth of hyphae. Callus formation couldn’t be distinguished by any of the explants. To make sure that Nystatin did not have a bad influence on the plant material the second part of the experiment was also performed on Stapelia grandiflora, a plant material that is known for its ability to form callus. In the reference with water the callus formation was complete, but in the other solutions the callus formation was very limited.</p>

Syftet med detta projekt var att undersöka om det är möjligt att använda en fungicid vid odling av celler från Oncidium crispum, för att slippa kontaminering av mykorrhizasvamp. Kontaminering från denna sorts svamp har i tidigare försök varit ett stort promlem. I undersökningen användes fungiciden Nystain. Ett första försök gjordes för att testa om Nystatin hade effekt på den aktuella svampen. På näringsmedium fick hyfer från mykorrhizasvampen växa mot ett filterpapper indränkt i Nystatinlösning med olika koncentrationer. Som kontroll användes filterpapper indränkta i vatten och 20 % etanol. Efter 72 h mättes hur nära svampen växt pappret eller om den växt över pappret. Det kunde konstateras att Nystatin vid den starkaste koncentrationen hindrade svampens framväxt. Där stannade svampen innan pappret i större utsträckning än hos de lägre koncentrationerna. Av första försöket drogs därför slutsatsen att Nystatin hämmar mykorrhizasvampen. I ett andra försök doppades explantat från Oncidium crispum i en lösning av Nystatin i olika koncentrationer, som kontroll användes vatten och 20 % etanol. Explantaten lades på MS-medium med hormonerna auxin och cytokinin. Vid den starkaste koncentrationen av Nystatin hämmades tillväxten av svamphyfer fullständigt. Däremot kunde ingen kallustillväxt urskiljas hos något av explantaten. Som kontroll för att försäkra sig om att Nystainet inte påverkade växtmaterialet negativt gjordes andra delen av försöket även med Stapelia grandiflora, ett växtmaterial som är känt för att lätt kunna bilda kallus. Kallustillväxten var fullständig hos kontrollen med vatten, hos de övriga lösningarna var kallustillväxten tyvärr mycket begränsad. / The purpose of this project was to examine if it’s possible to use a fungicide when growing cells from Oncidium crispum, to avoid the contamination of mycorrhizafungus. The contamination from this kind of fungus has been a big problem in earlier experiments. The fungicide used in the experiment was Nystatin. In a first experiment the effect of Nystatin against the mycorrhizafungus was tested. On a nutrient medium hyphae from the mycorrhizafungus were growing towards a paper disc soaked with a solution of Nystatin in different concentration. Paper discs soaked with water and 20 % ethanol were used as a reference. After 72 h it was measured how close the hyphae has got to the paper disc or if it had grown over the paper. It was established that the strongest concentration of Nystatin inhibited the growth of hyphae, in this concentration it stopped growing before it came to the paper disc in a greater extent then by the other concentrations. Therefore the conclusion was drawn, that Nystatin inhibits growth of the mycorrhizafungus. In a second experiment explants from Oncidium crispum were dipped in a solution of Nystatin in different concentrations, water and 20 % ethanol was used as a reference. The explants were placed on a MS-medium with the hormones auxin and cytokinin. By the strongest concentration of Nystatin there was no growth of hyphae. Callus formation couldn’t be distinguished by any of the explants. To make sure that Nystatin did not have a bad influence on the plant material the second part of the experiment was also performed on Stapelia grandiflora, a plant material that is known for its ability to form callus. In the reference with water the callus formation was complete, but in the other solutions the callus formation was very limited.

Die Pflanzenbiotechnologie ermöglicht die nachhaltige Gewinnung pflanzlicher Wertstoffe mittels innovativer biotechnologischer Methoden. Bisher mangelt es auf diesem Gebiet jedoch an Grundlagenwissen und aussagekräftigen Studien, z. B. zur Anwendung biotechnologischer Standardverfahren beim Respirationsmonitoring. Im Rahmen der vorliegenden Arbeit werden grundlegende Untersuchungen zur Erzeugung (Induktion) pflanzlicher in-vitro-Kulturen und zu geeigneten Kultivierungssystemen sowie Prozessüberwachungsstrategien vorgestellt und diskutiert. Als Modellsystem dient die Einjährige Sonnenblume Helianthus annuus. Die Induktion pflanzlicher Zellkulturen (Kallus und Suspensionen) mit photomixotrophem Stoffwechsel wurde unter unterschiedlichen Bedingungen untersucht und geeignete Induktionsparameter ermittelt. Sowohl pflanzliche Gewebekulturen (Hairy roots) als auch die erzeugten photomixotrophen und heterotrophe Suspensionen konnten in verschiedenen Reaktorsystemen erfolgreich kultiviert und die Produktbildung nachgewiesen werden. Protokolle zu Induktion sowie Erhaltung von Zell- und Gewebekulturen von H. annuus wurden etabliert. Ein modernes Prozessüberwachungssystem für Schüttelkolben, das RAMOS® (Respiration Activity Monitoring System®) wurde erstmals umfassend für Untersuchungen des Wachstumsverhaltens und zum Screening pflanzlicher Zell- und Gewebekulturen eingesetzt. Dabei wurde die Problematik der Verdunstung (Evaporation) aus den Kulturgefäßen als signifikant bei den langen Kultivierungen von pflanzlichen in-vitro-Kulturen diagnostiziert und ein Modell zur Korrektur der Atmungstransferraten entwickelt. Erstmalig in der Pflanzenbiotechnologie kam das RAMOS® für Studien mit Zell- und Gewebekulturen von H. annuus im Speziellen sowie für Untersuchungen von Hairy roots im Allgemeinen zum Einsatz. Mit Hilfe der vorliegenden Arbeit werden relevante Kriterien zur Anwendung des innovativen Messsystems RAMOS® im Rahmen pflanzenbiotechnologischer Untersuchungen vorgestellt. Es wird ein Überblick über geeignete Kultivierungssysteme und zu publizierten Modellierungsstrategien für Applikationen in der Pflanzenbiotechnologie gegeben. Ein Literaturüberblick zu publizierten Modellierungsstrategien mit pflanzenbiotechnologischem Bezug vervollständigt die Arbeit. / Plant biotechnology enables a sustainable production of valuable plant resources using innovative biotechnological methods. However, a comprehensive knowledge base as well as significant studies, e. g. concerning the application of biotechnological standard procedures of respiration monitoring, are missing so far. In this work, basic investigations regarding the induction of plant in vitro cultures and appropriate cultivation systems as well as process monitoring strategies will be introduced and discussed. The annual sunflower Helianthus annuus serves as biological model system. The induction of plant cell cultures (callus and suspension) with photomixotroph metabolism was investigated at different conditions and appropriate induction parameter were determined. Both, plant tissues (Hairy roots) and induced photomixotroph as well as heterotrophic suspensions were cultivated successfully in various reactor systems. The production of desired metabolites was proven. Protocols concerning induction respectively maintenance of cell and tissue cultures of H. annuus have been established. For extensive investigations of growth behavior and for screening of plant cell and tissue cultures, a modern process monitoring tool for shake flasks, the RAMOS® (Respiration Activity Monitoring System®), was used for the first time. Thereby, the problem of evaporation off the culture vessels was identified as significant for time-intensive cultivations of plant in vitro cultures. A model for the correction of respiration transfer rates has been developed. For the first time in plant biotechnology, the RAMOS® has been applied for studies with H. annuus in special, and for studying the growth and respiration behavior of Hairy roots in general. With the help of the present work, relevant criteria concerning the application of the innovative measuring system RAMOS® for plant biotechnological investigations will be given. Furthermore, a survey over appropriate cultivation systems and published modelling strategies in plant biotechnology are introduced. A literature survey concerning model strategies regarding plant biotechnology completes this work.

No description available.

Oleanolic and ursolic acid (OA and UA) are triterpenic acids with diverse biological activities that are of interest to the pharmaceutical industry. To investigate the scope for producing these compound using cell suspension cultures of Salvia species, calli from S. officinalis, S. virgata and S. fruticosa were induced using several plant growth regulator (PGR) combinations. Eleven lines were selected for suspension induction from a pool of calli. Six suspension cultures were established successfully and cultivated in the Respiration Activity MOnitoring System® (RAMOS®) to obtain online data on their growth kinetics and to establish appropriate sampling schedules for the determination of their OA and UA production. Based on their observed growth behaviour, OA and UA contents, and aggregation properties, one suspension culture from each studied Salvia species was selected for further optimisation. The μmax values for these suspension cultures ranged from 0.20 to 0.37°d-1, their OA and UA contents were greater than 1.3 and 1.2 mg g-1, respectively, and they afforded maximum volumetric yields of 21.0 mg l-1 for OA and 32.8 mg l-1 for UA. These results will be useful in the development of a refined Salvia suspension-based process for OA and UA production.

The embryogenic calli were grown on MS medium containing NaCl with concentrations from 50 to 300 mM. After 2 weeks of culture, salinity tolerance threshold was identified at 150 mM NaCl. Higher concentrations of NaCl stimulated a significant reduction in the calli survival rate and the highest rate was 78.67% at 50 mM. After subculturing callus to the embryo culture medium containing NaCl, the growth and embryogenesis were not affected at the concentrations of 50 – 100 mM. Especially, at 50 mM NaCl the embryogenesis rate reached 83.33%. In contrast, 150 mM NaCl inhibited the somatic embryogenesis. After 4 weeks, culturing somatic embryos on medium MS with addition of 0.07 mg/l spermidin at 50 – 100 mM NaCl, the embryogenesis was considered good and embryos developed through several stages: globular, heart, torpedo and cotyledonary. However, at 150 mM NaCl the globular stage appeared in the culture process. The process of morphohistology and using dye carmine – iod and acridine orange observed the structure of generative callus and embryos at several stages. / Mô sẹo có khả năng phát sinh phôi được nuôi cấy trong môi trường có chứa muối NaCl với nồng độ thay đổi từ 50 – 300 mM. Sau 2 tuần nuôi cấy, chúng tôi xác định được ngưỡng chịu mặn của mô sẹo có khả năng sinh phôi cây Cọc rào là 150 mM. Nồng độ muối NaCl càng cao thì tỷ lệ sống của mô sẹo giảm dần và đạt giá trị cao nhất là 78,67% tại nồng độ 50 mM NaCl. Khi chuyển mô sẹo sang môi trường phát sinh phôi có chứa muối NaCl với nồng độ thay đổi, chúng tôi thấy ở nồng độ muối NaCl 50 – 100 mM không ảnh hưởng đến khả năng sinh trưởng và phát sinh phôi, đặc biệt là tại nồng độ 50 mM NaCl giúp kích thích sự hình thành phôi từ mô sẹo với tỷ lệ hình thành phôi đạt 83,33%. Ngược lại, nồng độ từ 150 mM NaCl gây ức chế quá trình hình thành phôi soma từ mô sẹo. Tiếp tục khảo sát ảnh hưởng của muối đến khả năng phát triển và nảy mầm của phôi soma. Ghi nhận kết quả sau 4 tuần nuôi cấy phôi soma trong môi trường MS có bổ sung 0.07 mg/l spermidin, tại nồng độ 50 – 100 mM NaCl khả năng hình thành phôi tốt và phôi phát triển qua các giai đoạn phôi hình cầu, hình tim, hình thủy lôi và hình lá mầm. Đặc biệt ở nồng độ 50 mM số lượng phôi lá mầm đạt giá trị cao với 13,33 phôi. Nồng độ muối NaCl 150 mM chỉ xuất hiện phôi hình cầu trong suốt thời gian nuôi cấy. Quá trình giải phẫu hình thái phôi và sử dụng thuốc nhuộm 2 màu carmin – iod và acridine orange đã cho thấy rõ hơn về cấu trúc mô sẹo có khả năng sinh phôi và phôi hình thái.

Die Pflanzenbiotechnologie ermöglicht die nachhaltige Gewinnung pflanzlicher Wertstoffe mittels innovativer biotechnologischer Methoden. Bisher mangelt es auf diesem Gebiet jedoch an Grundlagenwissen und aussagekräftigen Studien, z. B. zur Anwendung biotechnologischer Standardverfahren beim Respirationsmonitoring. Im Rahmen der vorliegenden Arbeit werden grundlegende Untersuchungen zur Erzeugung (Induktion) pflanzlicher in-vitro-Kulturen und zu geeigneten Kultivierungssystemen sowie Prozessüberwachungsstrategien vorgestellt und diskutiert. Als Modellsystem dient die Einjährige Sonnenblume Helianthus annuus. Die Induktion pflanzlicher Zellkulturen (Kallus und Suspensionen) mit photomixotrophem Stoffwechsel wurde unter unterschiedlichen Bedingungen untersucht und geeignete Induktionsparameter ermittelt. Sowohl pflanzliche Gewebekulturen (Hairy roots) als auch die erzeugten photomixotrophen und heterotrophe Suspensionen konnten in verschiedenen Reaktorsystemen erfolgreich kultiviert und die Produktbildung nachgewiesen werden. Protokolle zu Induktion sowie Erhaltung von Zell- und Gewebekulturen von H. annuus wurden etabliert. Ein modernes Prozessüberwachungssystem für Schüttelkolben, das RAMOS® (Respiration Activity Monitoring System®) wurde erstmals umfassend für Untersuchungen des Wachstumsverhaltens und zum Screening pflanzlicher Zell- und Gewebekulturen eingesetzt. Dabei wurde die Problematik der Verdunstung (Evaporation) aus den Kulturgefäßen als signifikant bei den langen Kultivierungen von pflanzlichen in-vitro-Kulturen diagnostiziert und ein Modell zur Korrektur der Atmungstransferraten entwickelt. Erstmalig in der Pflanzenbiotechnologie kam das RAMOS® für Studien mit Zell- und Gewebekulturen von H. annuus im Speziellen sowie für Untersuchungen von Hairy roots im Allgemeinen zum Einsatz. Mit Hilfe der vorliegenden Arbeit werden relevante Kriterien zur Anwendung des innovativen Messsystems RAMOS® im Rahmen pflanzenbiotechnologischer Untersuchungen vorgestellt. Es wird ein Überblick über geeignete Kultivierungssysteme und zu publizierten Modellierungsstrategien für Applikationen in der Pflanzenbiotechnologie gegeben. Ein Literaturüberblick zu publizierten Modellierungsstrategien mit pflanzenbiotechnologischem Bezug vervollständigt die Arbeit. / Plant biotechnology enables a sustainable production of valuable plant resources using innovative biotechnological methods. However, a comprehensive knowledge base as well as significant studies, e. g. concerning the application of biotechnological standard procedures of respiration monitoring, are missing so far. In this work, basic investigations regarding the induction of plant in vitro cultures and appropriate cultivation systems as well as process monitoring strategies will be introduced and discussed. The annual sunflower Helianthus annuus serves as biological model system. The induction of plant cell cultures (callus and suspension) with photomixotroph metabolism was investigated at different conditions and appropriate induction parameter were determined. Both, plant tissues (Hairy roots) and induced photomixotroph as well as heterotrophic suspensions were cultivated successfully in various reactor systems. The production of desired metabolites was proven. Protocols concerning induction respectively maintenance of cell and tissue cultures of H. annuus have been established. For extensive investigations of growth behavior and for screening of plant cell and tissue cultures, a modern process monitoring tool for shake flasks, the RAMOS® (Respiration Activity Monitoring System®), was used for the first time. Thereby, the problem of evaporation off the culture vessels was identified as significant for time-intensive cultivations of plant in vitro cultures. A model for the correction of respiration transfer rates has been developed. For the first time in plant biotechnology, the RAMOS® has been applied for studies with H. annuus in special, and for studying the growth and respiration behavior of Hairy roots in general. With the help of the present work, relevant criteria concerning the application of the innovative measuring system RAMOS® for plant biotechnological investigations will be given. Furthermore, a survey over appropriate cultivation systems and published modelling strategies in plant biotechnology are introduced. A literature survey concerning model strategies regarding plant biotechnology completes this work.

The embryogenic calli were grown on MS medium containing NaCl with concentrations from 50 to 300 mM. After 2 weeks of culture, salinity tolerance threshold was identified at 150 mM NaCl. Higher concentrations of NaCl stimulated a significant reduction in the calli survival rate and the highest rate was 78.67% at 50 mM. After subculturing callus to the embryo culture medium containing NaCl, the growth and embryogenesis were not affected at the concentrations of 50 – 100 mM. Especially, at 50 mM NaCl the embryogenesis rate reached 83.33%. In contrast, 150 mM NaCl inhibited the somatic embryogenesis. After 4 weeks, culturing somatic embryos on medium MS with addition of 0.07 mg/l spermidin at 50 – 100 mM NaCl, the embryogenesis was considered good and embryos developed through several stages: globular, heart, torpedo and cotyledonary. However, at 150 mM NaCl the globular stage appeared in the culture process. The process of morphohistology and using dye carmine – iod and acridine orange observed the structure of generative callus and embryos at several stages. / Mô sẹo có khả năng phát sinh phôi được nuôi cấy trong môi trường có chứa muối NaCl với nồng độ thay đổi từ 50 – 300 mM. Sau 2 tuần nuôi cấy, chúng tôi xác định được ngưỡng chịu mặn của mô sẹo có khả năng sinh phôi cây Cọc rào là 150 mM. Nồng độ muối NaCl càng cao thì tỷ lệ sống của mô sẹo giảm dần và đạt giá trị cao nhất là 78,67% tại nồng độ 50 mM NaCl. Khi chuyển mô sẹo sang môi trường phát sinh phôi có chứa muối NaCl với nồng độ thay đổi, chúng tôi thấy ở nồng độ muối NaCl 50 – 100 mM không ảnh hưởng đến khả năng sinh trưởng và phát sinh phôi, đặc biệt là tại nồng độ 50 mM NaCl giúp kích thích sự hình thành phôi từ mô sẹo với tỷ lệ hình thành phôi đạt 83,33%. Ngược lại, nồng độ từ 150 mM NaCl gây ức chế quá trình hình thành phôi soma từ mô sẹo. Tiếp tục khảo sát ảnh hưởng của muối đến khả năng phát triển và nảy mầm của phôi soma. Ghi nhận kết quả sau 4 tuần nuôi cấy phôi soma trong môi trường MS có bổ sung 0.07 mg/l spermidin, tại nồng độ 50 – 100 mM NaCl khả năng hình thành phôi tốt và phôi phát triển qua các giai đoạn phôi hình cầu, hình tim, hình thủy lôi và hình lá mầm. Đặc biệt ở nồng độ 50 mM số lượng phôi lá mầm đạt giá trị cao với 13,33 phôi. Nồng độ muối NaCl 150 mM chỉ xuất hiện phôi hình cầu trong suốt thời gian nuôi cấy. Quá trình giải phẫu hình thái phôi và sử dụng thuốc nhuộm 2 màu carmin – iod và acridine orange đã cho thấy rõ hơn về cấu trúc mô sẹo có khả năng sinh phôi và phôi hình thái.

Oleanolic and ursolic acid (OA and UA) are triterpenic acids with diverse biological activities that are of interest to the pharmaceutical industry. To investigate the scope for producing these compound using cell suspension cultures of Salvia species, calli from S. officinalis, S. virgata and S. fruticosa were induced using several plant growth regulator (PGR) combinations. Eleven lines were selected for suspension induction from a pool of calli. Six suspension cultures were established successfully and cultivated in the Respiration Activity MOnitoring System® (RAMOS®) to obtain online data on their growth kinetics and to establish appropriate sampling schedules for the determination of their OA and UA production. Based on their observed growth behaviour, OA and UA contents, and aggregation properties, one suspension culture from each studied Salvia species was selected for further optimisation. The μmax values for these suspension cultures ranged from 0.20 to 0.37°d-1, their OA and UA contents were greater than 1.3 and 1.2 mg g-1, respectively, and they afforded maximum volumetric yields of 21.0 mg l-1 for OA and 32.8 mg l-1 for UA. These results will be useful in the development of a refined Salvia suspension-based process for OA and UA production.

Externe Fixateure werden häufig für die Stabilisierung und Behandlung schwerer Frakturen genutzt. Schraubenkanalinfektionen können dabei zu Komplikationen, wie Osteomyelitis und Stabilitätsverlusten führen. Es ist unklar, ob Schraubenkanalinfektionen zu Schraubenlockerungen führen, oder aber ob der Stabilitätsverlust von Schrauben in Schraubenkanalinfektionen resultiert. Das Ziel dieser Studie ist es, einen Zusammenhang zwischen der mechanischen Stabilität, dem Auftreten von Infektionen und der osseären Verankerung darzustellen. An 27 Schafen wurde eine standardisierte Osteotomie (3mm weiter Frakturspalt) der rechten Tibia durchgeführt und mit einem monolateralem Fixateur externe stabilisiert. Während der täglichen Pinpflege wurde die Haut um die Schraubeneintrittsstellen begutachtet. Radiologische Verlaufskontrollen erfolgten in wöchentlichen Abständen. Nach 3, 6 und 9 Wochen wurden die Tiere getötet, die Ausdrehmomente der Schrauben gemessen und mikrobiologische Abstriche genommen. Knochenschnitte durch die Schraubenkanäle wurden für histologische, histochemische und histomorphometrische Analysen genommen. In dieser Studie scheint es zu einer Zunahme der Stabilisierung der osseären Verankerung während des Heilungsverlaufes zu kommen. Da die kortikale Knochendichte über die Zeit abnimmt, kann die zunehmend stabilere Verankerung der Schrauben einzig über eine gleichzeitige periostale Kallusdichtezunahme erklärt werden. Die größten Ausdrehmomente des neugebildeten periostalen Kallus wurden zum Sechswochenzeitpunkt gemessen. Danach nimmt die periostale Kallusfläche ab, wohingegen die Kallusdichte zunimmt. Die mikrobiologische Besiedelungsrate (15%) war dreifach höher als die klinisch bestätigten Infektionen. Hingegen war die Osteolyserate (28%) doppelt so hoch wie die mikrobiologisch bestätigte Infektionsrate. Eine Korrelation zwischen Infektion, Osteolyse und Pinlockerung konnte nicht gefunden werden. / External fixators are frequently used for the stabilization and the treatment of problematic fractures. Pin track infections have been shown to cause complications such as osteomyelitis and loss of stability of osteosynthesis. It remains unclear, whether pin track infection provokes pin loosening, or loss of the pin stability results in pin track infections. The aim of this study was to investigate the correlation between the mechanical stability of pins, the incidence of pin track infections and the osseus anchorage of pins. 27 sheep underwent a standardized osteotomy (3 mm gap) of the right tibia. The tibiae were stabilized by a monolateral external fixator. Within the daily pin care routine, the skin around the pin entries was scored. Radiographs were taken at weekly intervals. After 3, 6 and 9 weeks, the animals were sacrificed, the extraction torque of all pins was determined and microbiological analyses were taken. Bone sections through the pintracks were taken for histological, histochemical and histomorphometrical analysis. This study reveals an increasing stability of osseous pinanchorage over the course of healing. As the cortical bone density decreased over time, the increased anchorage-stability of the pins can only be explained by the simultaneous increase of the periosteal callus bone density. The magnitude of the extraction force is determined by the newbuilt periosteal callus, which is at its biggest value at six weeks. Afterwards, the periosteal callus area abates, while the callus bone density accumulates. The microbiologically affirmed infection rate (15%) was three times higher than the one clinical ascertained. In contrast the evidence of osteolysis (28%) was twice as high as the microbiologically diagnosed infection-rate. Despite the low infection rate, evidence of cortical lysis coud not be prevented. No correlation could be found between infection, osteolysis and pin loosening.