The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Leena Alhonen - One of the best experts on this subject based on the ideXlab platform.
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overexpression of spermidine spermine n1 acetyltransferase under the control of mouse metallothionein i promoter in Transgenic mice evidence for a striking post transcriptional regulation of transgene expression by a polyamine analogue
Biochemical Journal, 1999Co-Authors: Suvikki Suppola, Velipekka Korhonen, Maria Halmekyto, Leena Alhonen, Marko Pietila, Jyrki Parkkinen, Carl W Porter, Juhani JanneAbstract:We recently generated a Transgenic mouse line overexpressing spermidine/spermine N1-acetyltransferase (SSAT) gene under its own promoter. The tissue polyamine pools of these Animals were profoundly affected and the mice were hairless from early age. We have now generated another Transgenic-mouse line overexpressing the SSAT gene under the control of a heavy-metal-inducible mouse metallothionein I (MT) promoter. Even in the absence of heavy metals, changes in the tissue polyamine pools indicated that a marked activation of polyamine catabolism had occurred in the Transgenic Animals. As with the SSAT Transgenic mice generated previously, the mice of the new line (MT-SSAT) suffered permanent hair loss, but this occurred considerably later than in the previous SSAT Transgenic Animals. Liver was the most affected tissue in the MT-SSAT Transgenic Animals, revealed by putrescine overaccumulation, significant decrease in spermidine concentration and >90% reduction in the spermine pool. Even though hepatic SSAT mRNA accumulated to massive levels in non-induced Transgenic Animals, SSAT activity was only moderately elevated. Administration of ZnSO4 further elevated the level of hepatic SSAT message and induced enzyme activity, but not more than 2- to 3-fold. Treatment of the Transgenic Animals with the polyamine analogue N1,N11-diethylnorspermine (DENSPM) resulted in an immense induction, more than 40000-fold, of enzyme activity in the liver of Transgenic Animals, and minor changes in the SSAT mRNA level. Liver spermidine and spermine pools were virtually depleted within 1-2 days in response to the treatment with the analogue. The treatment also resulted in a marked mortality (up to 60%) among the Transgenic Animals which showed ultrastructural changes in the liver, most notably mitochondrial swelling, one of the earliest signs of cell injury. These results indicated that, even without its own promoter, SSAT is powerfully induced by the polyamine analogue through a mechanism that appears to involve a direct translational and/or heterogenous nuclear RNA processing control. It is likewise significant that overexpression of SSAT renders the Animals extremely sensitive to polyamine analogues.
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enhanced papilloma formation in response to skin tumor promotion in Transgenic mice overexpressing the human ornithine decarboxylase gene
Biochemical and Biophysical Research Communications, 1992Co-Authors: Maria Halmekyto, Karl Syrjanen, Juhani Janne, Leena AlhonenAbstract:We have studied the induction of papilloma formation in response to skin tumor promotion in Transgenic mice overexpressing the human ornithine decarboxylase gene and in their nonTransgenic littermates. The Transgenic Animals displayed a basal epidermal ornithine decarboxylase activity that was nearly 20 times higher than in their nonTransgenic littermates. A single topical application of 12-O-tetradecanoylphorbol-13-acetate induced a much more profound and longer-lasting increase in transgene-derived ornithine decarboxylase activity in comparison with the endogenous enzyme activity. Initiation of skin tumorigenesis with a single topical application of dimethylbenz[a]antracene followed by twice-weekly application of 12-O-tetradecanoylphorbol-13-acetate resulted in the appearance of first papillomas both in nonTransgenic and Transgenic Animals by week 7. However, after 11 weeks of 12-O-tetradecanoylphorbol-13-acetate application, the number of papillomas per animal was almost 100% higher in the Transgenic Animals than in their nonTransgenic littermates. These results indicate that an overexpression of epidermal ornithine decarboxylase confers a growth advantage on skin tumors in vivo.
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nuclear magnetic resonance spectroscopy study on energy metabolism intracellular ph and free mg2 concentration in the brain of Transgenic mice overexpressing human ornithine decarboxylase gene
Journal of Neurochemistry, 1992Co-Authors: Risto A Kauppinen, Maria Halmekyto, Leena Alhonen, Juhani JaimeAbstract:We have generated a Transgenic mouse line strikingly overexpressing the human ornithine decarboxylase (ODC) gene in their brain. Brain ODC activity was increased in the Transgenic Animals by a factor of 70 in comparison with their nonTransgenic littermates. The content of brain putrescine, the product of ODC, was greater than 60 mumol/g of tissue in the Transgenic mice, whereas in the normal Animals it was below the level that could be detected by an HPLC method. The concentrations of the higher polyamines (spermidine and spermine) were not significantly different from control values. 31P nuclear magnetic resonance (31P NMR) spectroscopy analyses revealed a significantly reduced (40%) free Mg2+ concentration as calculated from the chemical shift differences of the nucleoside triphosphate alpha and beta peaks in the brains of the Transgenic Animals. The lower free Mg2+ concentration in the brains of ODC Transgenic mice was not a consequence of altered intracellular pH or changes in cellular high-energy metabolites. 1H NMR showed no differences in brain choline/N-acetylaspartate and total creatine/N-acetylaspartate ratios between the two animal groups. These ODC Transgenic Animals may serve as models in vivo for studies on cerebral postischemic events and on epilepsy, as polyamines are supposed to be involved in these processes.
Maria Halmekyto - One of the best experts on this subject based on the ideXlab platform.
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overexpression of spermidine spermine n1 acetyltransferase under the control of mouse metallothionein i promoter in Transgenic mice evidence for a striking post transcriptional regulation of transgene expression by a polyamine analogue
Biochemical Journal, 1999Co-Authors: Suvikki Suppola, Velipekka Korhonen, Maria Halmekyto, Leena Alhonen, Marko Pietila, Jyrki Parkkinen, Carl W Porter, Juhani JanneAbstract:We recently generated a Transgenic mouse line overexpressing spermidine/spermine N1-acetyltransferase (SSAT) gene under its own promoter. The tissue polyamine pools of these Animals were profoundly affected and the mice were hairless from early age. We have now generated another Transgenic-mouse line overexpressing the SSAT gene under the control of a heavy-metal-inducible mouse metallothionein I (MT) promoter. Even in the absence of heavy metals, changes in the tissue polyamine pools indicated that a marked activation of polyamine catabolism had occurred in the Transgenic Animals. As with the SSAT Transgenic mice generated previously, the mice of the new line (MT-SSAT) suffered permanent hair loss, but this occurred considerably later than in the previous SSAT Transgenic Animals. Liver was the most affected tissue in the MT-SSAT Transgenic Animals, revealed by putrescine overaccumulation, significant decrease in spermidine concentration and >90% reduction in the spermine pool. Even though hepatic SSAT mRNA accumulated to massive levels in non-induced Transgenic Animals, SSAT activity was only moderately elevated. Administration of ZnSO4 further elevated the level of hepatic SSAT message and induced enzyme activity, but not more than 2- to 3-fold. Treatment of the Transgenic Animals with the polyamine analogue N1,N11-diethylnorspermine (DENSPM) resulted in an immense induction, more than 40000-fold, of enzyme activity in the liver of Transgenic Animals, and minor changes in the SSAT mRNA level. Liver spermidine and spermine pools were virtually depleted within 1-2 days in response to the treatment with the analogue. The treatment also resulted in a marked mortality (up to 60%) among the Transgenic Animals which showed ultrastructural changes in the liver, most notably mitochondrial swelling, one of the earliest signs of cell injury. These results indicated that, even without its own promoter, SSAT is powerfully induced by the polyamine analogue through a mechanism that appears to involve a direct translational and/or heterogenous nuclear RNA processing control. It is likewise significant that overexpression of SSAT renders the Animals extremely sensitive to polyamine analogues.
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enhanced papilloma formation in response to skin tumor promotion in Transgenic mice overexpressing the human ornithine decarboxylase gene
Biochemical and Biophysical Research Communications, 1992Co-Authors: Maria Halmekyto, Karl Syrjanen, Juhani Janne, Leena AlhonenAbstract:We have studied the induction of papilloma formation in response to skin tumor promotion in Transgenic mice overexpressing the human ornithine decarboxylase gene and in their nonTransgenic littermates. The Transgenic Animals displayed a basal epidermal ornithine decarboxylase activity that was nearly 20 times higher than in their nonTransgenic littermates. A single topical application of 12-O-tetradecanoylphorbol-13-acetate induced a much more profound and longer-lasting increase in transgene-derived ornithine decarboxylase activity in comparison with the endogenous enzyme activity. Initiation of skin tumorigenesis with a single topical application of dimethylbenz[a]antracene followed by twice-weekly application of 12-O-tetradecanoylphorbol-13-acetate resulted in the appearance of first papillomas both in nonTransgenic and Transgenic Animals by week 7. However, after 11 weeks of 12-O-tetradecanoylphorbol-13-acetate application, the number of papillomas per animal was almost 100% higher in the Transgenic Animals than in their nonTransgenic littermates. These results indicate that an overexpression of epidermal ornithine decarboxylase confers a growth advantage on skin tumors in vivo.
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nuclear magnetic resonance spectroscopy study on energy metabolism intracellular ph and free mg2 concentration in the brain of Transgenic mice overexpressing human ornithine decarboxylase gene
Journal of Neurochemistry, 1992Co-Authors: Risto A Kauppinen, Maria Halmekyto, Leena Alhonen, Juhani JaimeAbstract:We have generated a Transgenic mouse line strikingly overexpressing the human ornithine decarboxylase (ODC) gene in their brain. Brain ODC activity was increased in the Transgenic Animals by a factor of 70 in comparison with their nonTransgenic littermates. The content of brain putrescine, the product of ODC, was greater than 60 mumol/g of tissue in the Transgenic mice, whereas in the normal Animals it was below the level that could be detected by an HPLC method. The concentrations of the higher polyamines (spermidine and spermine) were not significantly different from control values. 31P nuclear magnetic resonance (31P NMR) spectroscopy analyses revealed a significantly reduced (40%) free Mg2+ concentration as calculated from the chemical shift differences of the nucleoside triphosphate alpha and beta peaks in the brains of the Transgenic Animals. The lower free Mg2+ concentration in the brains of ODC Transgenic mice was not a consequence of altered intracellular pH or changes in cellular high-energy metabolites. 1H NMR showed no differences in brain choline/N-acetylaspartate and total creatine/N-acetylaspartate ratios between the two animal groups. These ODC Transgenic Animals may serve as models in vivo for studies on cerebral postischemic events and on epilepsy, as polyamines are supposed to be involved in these processes.
Nils Lonberg - One of the best experts on this subject based on the ideXlab platform.
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Human antibodies from Transgenic Animals
Nature Biotechnology, 2005Co-Authors: Nils LonbergAbstract:Laboratory mice provide a ready source of diverse, high-affinity and high-specificity monoclonal antibodies (mAbs). However, development of rodent antibodies as therapeutic agents has been impaired by the inherent immunogenicity of these molecules. One technology that has been explored to generate low immunogenicity mAbs for in vivo therapy involves the use of Transgenic mice expressing repertoires of human antibody gene sequences. This technology has now been exploited by over a dozen different pharmaceutical and biotechnology companies toward developing new therapeutic mAbs, and currently at least 33 different drugs in clinical testing--including several in pivotal trials--contain variable regions encoded by human sequences from Transgenic mice. The emerging data from these trials provide an early glimpse of the safety and efficacy issues for these molecules. Nevertheless, actual product approval, the biggest challenge so far, is required to fully validate this technology as a drug discovery tool. In the future, it may be possible to extend this technology beyond rodents and use Transgenic farm Animals to directly generate and produce human sequence polyclonal sera.
Ignacio Anegon - One of the best experts on this subject based on the ideXlab platform.
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rapid and accurate determination of zygosity in Transgenic Animals by real time quantitative pcr
Transgenic Research, 2002Co-Authors: Laurent Tesson, Jeanmarie Heslan, Severine Menoret, Ignacio AnegonAbstract:Successful identification of homozygous and heterozygous Transgenic Animals with currently available techniques demands tedious and time-consuming procedures with a high proportion of ambiguous results. Real-time PCR is a quantitative and extremely precise method with high throughput that could be applied to the analysis of large numbers of Animals differing only by a factor of two in the amount of target sequences. We defined the technical conditions of real-time PCR to co-amplify a transgene and a reference gene using two fluorogenic probes and the comparative cycle threshold method. We applied these conditions to the analysis of zygosity in a line of Transgenic rats. Real-time PCR allowed clear-cut identification of all Transgenic Animals analysed (n = 45) as homozygous or heterozygous. Southern blot analysis of these Animals using an internal quantitative control and PhosphorImager quantification showed ambiguous results in six of them and was concordant with real-time PCR in the rest. Mating of homozygous and heterozygous Animals, as defined by real-time PCR, showed transgene transmission to the offspring following expected Mendelian laws. Real-time PCR allows rapid, precise, non-ambiguous and high throughput identification of zygosity in Transgenic Animals. This technique could be helpful in the establishment of breeding programs for Transgenic colonies and in experiments in which gene dosage effects could have a functional impact.
Juhani Janne - One of the best experts on this subject based on the ideXlab platform.
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overexpression of spermidine spermine n1 acetyltransferase under the control of mouse metallothionein i promoter in Transgenic mice evidence for a striking post transcriptional regulation of transgene expression by a polyamine analogue
Biochemical Journal, 1999Co-Authors: Suvikki Suppola, Velipekka Korhonen, Maria Halmekyto, Leena Alhonen, Marko Pietila, Jyrki Parkkinen, Carl W Porter, Juhani JanneAbstract:We recently generated a Transgenic mouse line overexpressing spermidine/spermine N1-acetyltransferase (SSAT) gene under its own promoter. The tissue polyamine pools of these Animals were profoundly affected and the mice were hairless from early age. We have now generated another Transgenic-mouse line overexpressing the SSAT gene under the control of a heavy-metal-inducible mouse metallothionein I (MT) promoter. Even in the absence of heavy metals, changes in the tissue polyamine pools indicated that a marked activation of polyamine catabolism had occurred in the Transgenic Animals. As with the SSAT Transgenic mice generated previously, the mice of the new line (MT-SSAT) suffered permanent hair loss, but this occurred considerably later than in the previous SSAT Transgenic Animals. Liver was the most affected tissue in the MT-SSAT Transgenic Animals, revealed by putrescine overaccumulation, significant decrease in spermidine concentration and >90% reduction in the spermine pool. Even though hepatic SSAT mRNA accumulated to massive levels in non-induced Transgenic Animals, SSAT activity was only moderately elevated. Administration of ZnSO4 further elevated the level of hepatic SSAT message and induced enzyme activity, but not more than 2- to 3-fold. Treatment of the Transgenic Animals with the polyamine analogue N1,N11-diethylnorspermine (DENSPM) resulted in an immense induction, more than 40000-fold, of enzyme activity in the liver of Transgenic Animals, and minor changes in the SSAT mRNA level. Liver spermidine and spermine pools were virtually depleted within 1-2 days in response to the treatment with the analogue. The treatment also resulted in a marked mortality (up to 60%) among the Transgenic Animals which showed ultrastructural changes in the liver, most notably mitochondrial swelling, one of the earliest signs of cell injury. These results indicated that, even without its own promoter, SSAT is powerfully induced by the polyamine analogue through a mechanism that appears to involve a direct translational and/or heterogenous nuclear RNA processing control. It is likewise significant that overexpression of SSAT renders the Animals extremely sensitive to polyamine analogues.
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enhanced papilloma formation in response to skin tumor promotion in Transgenic mice overexpressing the human ornithine decarboxylase gene
Biochemical and Biophysical Research Communications, 1992Co-Authors: Maria Halmekyto, Karl Syrjanen, Juhani Janne, Leena AlhonenAbstract:We have studied the induction of papilloma formation in response to skin tumor promotion in Transgenic mice overexpressing the human ornithine decarboxylase gene and in their nonTransgenic littermates. The Transgenic Animals displayed a basal epidermal ornithine decarboxylase activity that was nearly 20 times higher than in their nonTransgenic littermates. A single topical application of 12-O-tetradecanoylphorbol-13-acetate induced a much more profound and longer-lasting increase in transgene-derived ornithine decarboxylase activity in comparison with the endogenous enzyme activity. Initiation of skin tumorigenesis with a single topical application of dimethylbenz[a]antracene followed by twice-weekly application of 12-O-tetradecanoylphorbol-13-acetate resulted in the appearance of first papillomas both in nonTransgenic and Transgenic Animals by week 7. However, after 11 weeks of 12-O-tetradecanoylphorbol-13-acetate application, the number of papillomas per animal was almost 100% higher in the Transgenic Animals than in their nonTransgenic littermates. These results indicate that an overexpression of epidermal ornithine decarboxylase confers a growth advantage on skin tumors in vivo.
