Biomedical subjects

H Niemann

Publications and source records attributed to H Niemann.

At least 19 recordsLinked to original sources

PubMed1999

SNAP-25a and -25b isoforms are both expressed in insulin-secreting cells and can function in insulin secretion.

The tSNARE (the target-membrane soluble NSF-attachment protein receptor, where NSF is N-ethylmaleimide-sensitive fusion protein) synaptosomal-associated protein of 25 kDa (SNAP-25) is expressed in pancreatic B-cells and its cleavage by botulinum neurotoxin E (BoNT/E) abolishes stimulated secretion of insulin. In the nervous system, two SNAP-25 isoforms (a and b) have been described that are produced by alternative splicing. Here it is shown, using reverse transcriptase PCR, that messages for both SNAP-25 isoforms are expressed in primary pancreatic B and non-B cells as well as in insulin-secreting cell lines. After transfection, both isoforms can be detected at the plasma membrane as well as in an intracellular perinuclear region in the insulin-secreting cell line, HIT. To test for the functional role of the two isoforms in insulin secretion, mutant forms of SNAP-25a and b resistant against cleavage by BoNT/E were generated. Such mutant SNAP-25, when expressed in HIT cells, is not inactivated by BoNT/E and its ability to restore insulin secretion can thus be investigated. To obtain the toxin-resistant mutant isoforms, the sequence around the BoNT/E cleavage site (R176QIDRIM182) was changed to P176QIKRIT182. This is the sequence of the equivalent region of human SNAP-23 (P187-T194), which has been shown to be resistant to BoNT/E. The mutant SNAP-25 was resistant to BoNT/E in vitro and in vivo and both mutant isoforms were able to reconstitute insulin secretion from toxin-treated HIT cells.

Animals↗

PubMed1999

Alterations in the relative abundance of gene transcripts in preimplantation bovine embryos cultured in medium supplemented with either serum or PVA.

In preimplantation bovine embryos, the relative abundance of various developmentally important gene transcripts was determined by a semi-quantitative RT-PCR assay to analyze the effects of two medium supplements, serum or polyvinyl alcohol (PVA). Development to morula, blastocyst, and hatched blastocyst stages was higher (P < or = 0.05) in medium supplemented with serum than in medium supplemented with PVA. Connexin43 mRNA expression virtually disappeared from the 8-16 cell stage onward, but reappeared in the hatched blastocyst in serum-supplemented medium, whereas it was detected in PVA-derived embryos throughout development. No differences were found for plakophilin mRNA between both culture groups. Desmocollin II mRNA showed a sharp increase at the blastocyst stage in both groups with a higher transcription level in PVA-generated embryos. A significant difference in desmocollin III transcripts was detectable at the 8-16-cell stage between serum- and PVA-derived embryos. Transcripts for desmoglein 1 and desmocollin I were not detected at any preimplantation stage, irrespective of medium supplementation. The relative abundance of glucose-transporter-1 mRNA was significantly increased at the 8-16-cell stage in embryos produced in medium supplemented with PVA, but not serum. Heat shock protein and poly(A)polymerase mRNA were continuously expressed during preimplantation development in both culture groups. Although poly(A)polymerase mRNA was significantly elevated in PVA- over serum-derived embryos, heat shock protein mRNA expression was significantly enhanced in serum-generated embryos over PVA-derived embryos. Interferon tau mRNA showed a significant increase at the hatched blastocyst stage only in PVA-supplemented medium. These data suggest that alterations in mRNA expression are associated with culture environment. Timing and magnitude of the alterations varied among the different transcripts and were significantly affected by the presence of exogenous protein in a stage-specific manner, predominantly at critical developmental time points.

Animals↗

PubMed1999

Cryopreservation of bovine in vitro produced embryos using ethylene glycol in controlled freezing or vitrification.

In this study, the cryoprotectant ethylene glycol (EG) was tested for its ability to improve and facilitate the cryopreservation of in vitro produced (IVP) bovine embryos. Embryos were cryopreserved in EG solutions supplemented with either newborn calf serum (NBCS) or polyvinyl alcohol (PVA). To assess EG toxicity, the embryos were equilibrated in EG concentrations from 1.8 to 8.9 M at room temperature for 10 min and then cultured for 72 h on a cumulus cell monolayer. The hatching rate was highest for day 7 blastocysts frozen in 3.6 M EG (98%) and was not different from the control group (85%). The controlled freezing (0.3 degrees C/min to -35 degrees C) of expanded day 7 blastocysts resulted in a hatching rate of 81%, which was similar to that of the nonfrozen controls (76%). Differential staining revealed only very few degenerate blastomeres attributed to freezing and thawing. Upon direct nonsurgical transfer of day 7 expanded blastocysts frozen in 3.6 M EG, a pregnancy rate of 43% was achieved, while the pregnancy rate after transfer of other developmental stages was significantly lower (22% with expanded day 8 blastocysts). When bovine IVP embryos were incubated at room temperature in 7.2 M EG preceded by preequilibration in 3.6 M EG, the hatching rate of day 7 expanded blastocysts reached 93%. Upon vitrification of IVP day 7 and day 8 blastocysts and expanded blastocysts in 7.2 M EG, the latter showed a higher hatching rate (42%) than blastocysts (12%). Overall, PVA as supplement to the basic freezing solution instead of NBCS had deleterious effects on survival after controlled freezing or vitrification. The simple cryopreservation protocol employed in this study and the low toxicity of ethylene glycol highlight the usefulness of this approach for controlled freezing of IVP embryos. However, further experiments are needed to improve the pregnancy rate following embryo transfer and to enhance survival after vitrification.

Animals↗

PubMed1999

The nuclear distribution of Polycomb during Drosophila melanogaster development shown with a GFP fusion protein.

The chromatin protein Polycomb (PC) is necessary for keeping homeotic genes repressed in a permanent and heritable manner. PC is part of a large multimeric complex (PcG proteins) involved in generating silenced chromatin domains at target genes, thus preventing their inappropriate expression. In order to assess the intranuclear distribution of PC during mitosis in different developmental stages as well as in the germ line we generated transgenic fly lines expressing a PC-GFP (Green Fluorescent Protein) fusion protein. Rapidly dividing nuclei were found to display a rather homogeneous PC-GFP distribution. However, with increasing differentiation a pronounced subnuclear pattern was observed. In all investigated diploid somatic tissues the bulk of PC-GFP fusion protein is depleted from the chromosomes during mitosis: however, a detectable fraction remains associated. In the male germ line in early spermatogenesis, PC-GFP was closely associated with the chromosomal bivalents and gradually lost at later stages. Interestingly, we found that PC is associated with the nucleolus in spermatocytes, unlike somatic nuclei. In contrast to mature sperm showing no PC-GFP signal the female germ line retains PC in the germinal vesicle.

Animals↗

PubMed1999

Proteolysis of SNAP-25 isoforms by botulinum neurotoxin types A, C, and E: domains and amino acid residues controlling the formation of enzyme-substrate complexes and cleavage.

Tetanus toxin and the seven serologically distinct botulinal neurotoxins (BoNT/A to BoNT/G) abrogate synaptic transmission at nerve endings through the action of their light chains (L chains), which proteolytically cleave VAMP (vesicle-associated membrane protein)/synaptobrevin, SNAP-25 (synaptosome-associated protein of 25 kDa), or syntaxin. BoNT/C was reported to proteolyze both syntaxin and SNAP-25. Here, we demonstrate that cleavage of SNAP-25 occurs between Arg198 and Ala199, depends on the presence of regions Asn93 to Glu145 and Ile156 to Met202, and requires about 1,000-fold higher L chain concentrations in comparison with BoNT/A and BoNT/E. Analyses of the BoNT/A and BoNT/E cleavage sites revealed that changes in the carboxyl-terminal residues, in contrast with changes in the amino-terminal residues, drastically impair proteolysis. A proteolytically inactive BoNT/A L chain mutant failed to bind to VAMP/synaptobrevin and syntaxin, but formed a stable complex (KD = 1.9 x 10(-7) M) with SNAP-25. The minimal essential domain of SNAP-25 required for cleavage by BoNT/A involves the segment Met146-Gln197, and binding was optimal only with full-length SNAP-25. Proteolysis by BoNT/E required the presence of the domain Ile156-Asp186. Murine SNAP-23 was cleaved by BoNT/E and, to a reduced extent, by BoNT/A, whereas human SNAP-23 was resistant to all clostridial L chains. Lys185Asp or Pro182Arg mutations of human SNAP-23 induced susceptibility toward BoNT/E or toward both BoNT/A and BoNT/E, respectively.

Amino Acid Sequence↗

PubMed1999

Interpolated markov chains for eukaryotic promoter recognition.

MOTIVATION: We describe a new content-based approach for the detection of promoter regions of eukaryotic protein encoding genes. Our system is based on three interpolated Markov chains (IMCs) of different order which are trained on coding, non-coding and promoter sequences. It was recently shown that the interpolation of Markov chains leads to stable parameters and improves on the results in microbial gene finding (Salzberg et al., Nucleic Acids Res., 26, 544-548, 1998). Here, we present new methods for an automated estimation of optimal interpolation parameters and show how the IMCs can be applied to detect promoters in contiguous DNA sequences. Our interpolation approach can also be employed to obtain a reliable scoring function for human coding DNA regions, and the trained models can easily be incorporated in the general framework for gene recognition systems. RESULTS: A 5-fold cross-validation evaluation of our IMC approach on a representative sequence set yielded a mean correlation coefficient of 0.84 (promoter versus coding sequences) and 0.53 (promoter versus non-coding sequences). Applied to the task of eukaryotic promoter region identification in genomic DNA sequences, our classifier identifies 50% of the promoter regions in the sequences used in the most recent review and comparison by Fickett and Hatzigeorgiou ( Genome Res., 7, 861-878, 1997), while having a false-positive rate of 1/849 bp.

Algorithms↗

PubMed1999

[Transgenic pigs for xenotransplantation for humans].

Transgenic livestock have been generated via microinjection of DNA-constructs into pronuclei of zygotes. However, efficiency is low and only 1-3% transgenic offspring are to be obtained. Integration of the transgene occurs at random and expression is independent from the number of integrated copies but can be affected by the integration site. To overcome the shortage of human organs, transgenic pigs have been generated that express human complement regulatory genes. This approach enables to overcome the hyperacute rejection response as shown by an average survival rate (40-90 days) of the immunosuppressed primate recipients receiving a heart from a transgenic pig. It is expected that transgenic pigs would be available as organ donors in the next 5-10 years. A major prerequisite, however, is the prevention of the potential transfer of pathogenic microorganisms, in particular porcine endogenous retroviruses (PERV). Improvements of the efficiency in the generation of transgenic pigs will be achieved by the use of genetically modified donor cells in nuclear transfer technology (cloning).

Animals↗

PubMed1998

A detailed analysis of pronucleus development in bovine zygotes in vitro: cell-cycle chronology and ultrastructure.

The aim of the present experiment was to analyze the chronology of pronucleus development and DNA synthesis, as well as the ultrastructure of intranuclear bodies, in bovine zygotes produced in vitro. Bovine oocytes were matured and fertilized in vitro, and sperm penetration and pronucleus development were examined. DNA synthesis was investigated by sequential incubation with [3H]- and [14C]thymidine followed by autoradiography on semithin sections. Ultrathin sections for transmission electron microscopy were prepared from the same zygotes. Sperm penetration was noted for the first time at 4 hr after in vitro insemination and reached a maximum at 6 hr. Pronucleus formation was initiated at 4 hr, and up to at least 11 hr the maternal pronucleus was more developed than its paternal counterpart. DNA synthesis was initiated at 14-15 hr, and the S-phase lasted for 8-10 hr. The most prominent ultrastructural entities of the pronuclei were the nucleolus precursor bodies (NPBs). During the S- and G2-phases, the NPBs spatially associated with clusters of interchromatin-like granules. The two components were firmly attached to each other by an electron-dense reticulum. During the late G2-phase, the NPBs were apparently detached from the interchromatin-like granules and the electron-dense reticulum again. The interaction between the intranuclear bodies and granules appears to be comparable with the situation previously described for in vivo-produced bovine zygotes (J Laurincík et al., Mol Reprod Dev 43:62-69, 1996), except for the lack of vacuolization of the NPBs during the S-phase in vitro.

Animals↗

PubMed1998

Multiple kinetic components of exocytosis distinguished by neurotoxin sensitivity.

The secretion of synaptic and other vesicles is a complex process involving multiple steps. Many molecular components of the secretory apparatus have been identified, but how they relate to the different stages of vesicle release is not clear. We examined this issue in adrenal chromaffin cells, where capacitance measurements and amperometry allow us to measure vesicle fusion and hormone release simultaneously. Using flash photolysis of caged intracellular calcium to induce exocytosis, we observed three distinct kinetic components to vesicle fusion, of which only two are related to catecholamine release. Intracellular dialysis with botulinum neurotoxin E, D or C1 or tetanus-toxin light chains abolishes the catecholamine-related components, but leaves the third component untouched. Botulinum neurotoxin A, which removes nine amino acids from the carboxy(C)-terminal end of SNAP-25, does not eliminate catecholamine release completely, but slows down both catecholamine-related components. Thus we assign a dual role to SNAP-25 and suggest that its nine C-terminal amino acids are directly involved in coupling the calcium sensor to the final step in exocytosis.

Adenosine Triphosphate↗

PubMed1998

Exogenous protein affects developmental competence and metabolic activity of bovine pre-implantation embryos in vitro.

The role of exogenous protein during bovine pre-implantation embryo development in two in vitro production systems was investigated. Morphological development, survival after vitrification and metabolic activity before and after vitrification were recorded in blastocysts generated in vitro in synthetic oviduct fluid (SOF) medium in the presence of either bovine serum albumin (BSA) or polyvinyl-alcohol (PVA). Metabolic activity was determined by measuring oxygen consumption, glucose and pyruvate uptake as well as lactate production. Development to blastocysts and survival after vitrification were reduced significantly in medium lacking protein. Of the metabolic parameters measured, only pyruvate uptake was increased significantly in embryos cultured in medium supplemented with PVA. Whereas in BSA-supplemented medium pyruvate uptake was correlated with lactate production, in PVA-supplemented medium glucose uptake was correlated with lactate production. Lactate production increased significantly after vitrification as compared with fresh embryos. Thus, exogenously added protein significantly alters oxidative metabolism. In medium lacking protein, the additional pyruvate may be used for the maintenance of intracellular amino acid pools. Vitrification appears to alter glycolytic metabolic profiles indicating a stress-response. In conclusion, the perturbed metabolism corresponding to reduced developmental capacity of embryos produced under protein-free conditions emphasizes the ambiguity between maximum development, technical and hygienic requirements and physiological demands of the early bovine embryo in vitro. The use of well-defined recombinant proteins might assist in closing this gap.

Animals↗

PubMed1998

A novel tetanus neurotoxin-insensitive vesicle-associated membrane protein in SNARE complexes of the apical plasma membrane of epithelial cells.

The importance of soluble N-ethyl maleimide (NEM)-sensitive fusion protein (NSF) attachment protein (SNAP) receptors (SNAREs) in synaptic vesicle exocytosis is well established because it has been demonstrated that clostridial neurotoxins (NTs) proteolyze the vesicle SNAREs (v-SNAREs) vesicle-associated membrane protein (VAMP)/brevins and their partners, the target SNAREs (t-SNAREs) syntaxin 1 and SNAP25. Yet, several exocytotic events, including apical exocytosis in epithelial cells, are insensitive to numerous clostridial NTs, suggesting the presence of SNARE-independent mechanisms of exocytosis. In this study we found that syntaxin 3, SNAP23, and a newly identified VAMP/brevin, tetanus neurotoxin (TeNT)-insensitive VAMP (TI-VAMP), are insensitive to clostridial NTs. In epithelial cells, TI-VAMP-containing vesicles were concentrated in the apical domain, and the protein was detected at the apical plasma membrane by immunogold labeling on ultrathin cryosections. Syntaxin 3 and SNAP23 were codistributed at the apical plasma membrane where they formed NEM-dependent SNARE complexes with TI-VAMP and cellubrevin. We suggest that TI-VAMP, SNAP23, and syntaxin 3 can participate in exocytotic processes at the apical plasma membrane of epithelial cells and, more generally, domain-specific exocytosis in clostridial NT-resistant pathways.

Amino Acid Sequence↗

PubMed1998

mRNA expression of leukaemia inhibitory factor (LIF) and its receptor subunits glycoprotein 130 and LIF-receptor-beta in bovine embryos derived in vitro or in vivo.

Leukaemia inhibitory factor (LIF) plays an essential role during cell differentiation and implantation in the mouse exerting its effects via the two dimerizing receptor subunits glycoprotein 130 (gp130) and LIF-receptor beta (LR-beta). This study investigated the mRNA expression of bovine LIF (bLIF), gp130 and LR-beta in pooled or individual bovine oocytes and embryos generated in vitro or in vivo after superovulation. Transcripts of gp130 and LR-beta were detectable in as little material as 1/3 oocyte equivalent and bLIF transcripts in two embryo equivalents employing a simple, rapid and robust one-step reverse transcription-polymerase chain reaction (RT-PCR) protocol using random hexamer priming during reverse transcription and 60 amplification cycles in the PCR. All mRNA fragments were also found in cumulus cells and various bovine tissues. While gp130 and LR-beta mRNA were present in pooled material throughout embryo development in vitro from the immature oocyte to the hatched blastocyst, bLIF-transcripts were absent in immature oocytes, inconsistently expressed from the matured oocyte up to the 16-cell stage as well as in blastocysts dependent on embryo batch. It was not found in morulae, but again present in hatched blastocysts. In contrast, in in-vivo derived embryos no bLIF was found, LR-beta was not detected at the morula to blastocyst transition while gp130 transcripts were observed from the morula to the hatched blastocyst. In individual embryos the mRNA expression pattern was similar for both in-vitro and in-vivo derived embryos as found in pooled material. These results indicate perturbation of the mRNA expression pattern of the specific LIF-LIF-receptor system in embryos generated in vitro that could lead to abnormal differentiation of the cell compartments forming the blastocyst. Cumulus cells, frequently used as supportive factor in co-culture in bovine in-vitro embryo production, are a rich source of the LIF-LIF-receptor system acting in a paracrine and/or autocrine manner. The biological function of the LIF-LIF-receptor system during bovine preimplantation development warrants further investigation.

Animals↗

PubMed1998

Only a truncated epidermal growth factor receptor protein is present in porcine endometrium.

The epidermal growth factor receptor (EGF-R) is a 170-kDa transmembrane protein, of which a truncated 100-kDa form (trEGF-R) lacking the cytoplasmic and the transmembrane domains, and an oncogenic 68-kDa form (v-erb) lacking the extracellular domain have been described. The trEGF-R is secreted and not able to transmit signals into the cell. Growth factors of the EGF family have been shown in porcine uterine fluids and blastocyst. Employing differential immunohistochemistry, we found the extracellular domain, but not the cytoplasmic domain, of the EGF-R in porcine endometrium on Days 9-11 of pregnancy. Blastocysts from Days 9 to 11 post coitum (p.c.) were positive for both antibodies, indicating the presence of the full-size receptor. Western Blotting of endometrial protein resulted in a 100-kDa band, but no 170-kDa band. No evidence for a coexpression of the 170- or 68-kDa forms of the receptor was found. ELISA analysis demonstrated trEGF-R in porcine uterine flushings. We conclude that 1) the trEGF-R is the only EGF-R form present in porcine endometrium, and 2) growth factors of the EGF family in porcine uterine fluids can exert their function via the EGF-R only on blastocysts, not on the endometrium.

Animals↗

PubMed1998

TetR is a positive regulator of the tetanus toxin gene in Clostridium tetani and is homologous to botR.

The TetR gene immediately upstream from the tetanus toxin (TeTx) gene was characterized. It encodes a 21,562-Da protein which is related (50 to 65% identity) to the equivalent genes (botR) in Clostridium botulinum. TetR has the feature of a DNA binding protein with a basic pI (9.53). It contains a helix-turn-helix motif and shows 29% identity with other putative regulatory genes in Clostridium, i.e., uviA from C. perfringens and txeR from C. difficile. We report for the first time the transformation of C. tetani by electroporation, which permitted us to investigate the function of tetR. Overexpression of tetR in C. tetani induced an increase in TeTx production and in the level of the corresponding mRNA. This indicates that TetR is a transcriptional activator of the TeTx gene. Overexpression of botR/A (60% identity with TetR at the amino acid level) in C. tetani induced an increase in TeTx production comparable to that for overexpression of tetR. However, botR/C (50% identity with TetR at the amino acid level) was less efficient. This supports that TetR positively regulates the TeTx gene in C. tetani and that a conserved mechanism of regulation of the neurotoxin genes is involved in C. tetani and C. botulinum.

Amino Acid Sequence↗

PubMed1998

Expression of RNA from developmentally important genes in preimplantation bovine embryos produced in TCM supplemented with BSA.

This study investigated the effects of a semi-defined culture system on the temporal pattern of expression of RNA from genes involved in compaction and cavitation: gap junction protein connexin43 (Cx43), desmosomal glycoproteins desmoglein 1 (Dg 1), desmocollins I, II and III (Dc I, Dc II, Dc III), desmosomal protein plakophilin (Plako); metabolism glucosetransporter-1 (Glut-1); RNA processing poly(A)polymerase (PolyA); heat shock protein 70.1 (HSP); and trophoblastic function trophoblast protein (TP) in bovine oocytes and embryos generated in vitro using TCM199 supplemented with BSA as the culture medium. Morulae and blastocysts derived in vivo were collected from superovulated heifers and also used for this study. Poly(A)+ RNA was extracted from pools of 20-50 oocytes or embryos, analysed by reverse transcription-polymerase chain reaction and the amplified fragments were verified by sequencing. Assays were repeated at least three times for each developmental stage and provided consistent results in all replicates. In bovine embryos produced in vitro, mRNA encoding Cx43 was detectable up to the morula stage, whereas blastocysts and hatched blastocysts did not express this gene. No transcripts were found for Dg 1 and Dc I throughout the tested preimplantation stages. Dc II and Dc III transcripts were found from 2-4-cell embryos up to the hatched blastocyst stage. mRNA encoding Plako was detected in immature and mature oocytes and zygotes, while no transcripts were seen in 2-4-cell and 8-16-cell embryos. The gene was expressed again from the morulae to the hatched blastocyst stage. Oocytes and bovine embryos produced in vitro showed transcripts for Glut-1, PolyA and HSP throughout preimplantation development up to the hatched blastocyst stage. The gene encoding TP was transcribed only in blastocysts and hatched blastocysts. Morulae and blastocysts produced in vivo showed the same expression as their in vitro counterparts, with one exception: the in vivo embryos transcribed Cx43. The results of this study reveal for the first time the transcriptional pattern of a set of 'marker' genes involved in various processes in early bovine embryonic development. Transferable morulae and blastocysts produced in vitro expressed most genes similar to their in vivo counterparts. These data contribute to the molecular characterization of this widely used in vitro culture system for bovine embryos and provide a major advance towards production of 'physiologically normal' embryos.

Animals↗

PubMed1998

Automated recording of RNA differential display patterns from pig granulosa cells.

We have developed a protocol for fast, nonradioactive, mRNA differential display reverse transcription PCR (DDRT-PCR) based on a commercial automated sequencer with RNA isolated from pig granulosa cells. We sought to discover conditions that would minimize the problem of using relatively small primers labeled with large infrared dye molecule, IR41, required for the sequencer. Extended IR41-labeled primers IR41-AAGC-T11-A, IE41-AAGC-T11-C and IR41-AAGC-T11-G gave more consistent differential display patterns than shorter anchored primers (IR41-T11A, IR41-T11C and IR41-T11G) without the additional (AAGC) cloning site. The optimal concentration of the extended labeled (downstream) primers was 20 pmol when 13-mer arbitrary (upstream) primers were used at a concentration of 4 pmol. Background smear and the intensity of amplified bands was significantly improved by changing from conventional Taq DNA polymerase to AmpliTaq Gold polymerase, which permits an improved "hot start" for the reaction. Running time (during which a digitized gel image is recorded) for a 26-cm polyacrylamide gel was 4 h, enabling us to analyze 90 reactions in an 8-h day. This protocol offers a rapid and reliable nonradioactive method for comparing gene expression patterns for various research or diagnostic purposes.

Animals↗

PubMed1998

[Transgenic pigs for xenotransplants for humans].

Microinjection of foreign DNA is currently the only successful procedure to achieve gene transfer in farm animals, though at low efficiency (1-3% transgenic offspring). Integration of the transgene occurs random, expression is normally independent from the number of integrated copies, but can be affected by the site of integration. In most cases, the transgene is inherited according to the Mendelian rules. To achieve xenotransplantation complement regulating gene constructs have been integrated and expressed in transgenic pigs. Upon transfer of hearts from such transgenic pigs to primates the hyperacute rejection response was overcome and an average survival of approximately 40 days was obtained. It is expected that organs from transgenic pigs will be clinically available within the next 5 to 10 years after open questions in particular on the potential transmission of pathogens have been clarified.

Animals↗

PubMed1998

[Thyroid hormones in Old German Black Pied- and Holstein-Friesian suckling calves. Effects of parturition and postpartum adaptation].

The present trial deals with the effects of birth stress on the thyreoidea respectively on the thyroxine- and triiodthyronine-concentration as well as on their unbound fraction (FT4 and FT3) of suckler calves and the evolution of those parameters in the first three months of life. T4- and T3 concentrations in blood serum of calves were beyond maternal levels increasing significantly in the first 24 hours with strong individual specificity and reaching levels of adult animals at the end of the three-month-period. The different increasing rates of the four parameters show a stimulation of the thyreoideal activity and of the monodejodinase-system as well and they show also a greater decomposition rate of the binding proteins. An influence of the course of parturition on the T3 level p.n. and the T4/T3 ratio in the first 24 hours could be disclosed. The hormone concentrations p.n. showed correlations to the pH and pCO2 of the neonatal calves. For T4 and T3 a strong influence of maternal levels on the hormone levels of the calves p.n. could be ascertained. Effects of breed, surrounding temperatures and type of husbandry on the investigated parameters could be established.

Acclimatization↗