Biomedical subjects

S Werner

Publications and source records attributed to S Werner.

At least 73 records · Page 4Linked to original sources

PubMed2000

Refined deletion mapping in sporadic breast cancer at chromosomal region 8p12-p21 and association with clinicopathological parameters.

We have further refined the loss of heterozygosity (LOH) pattern on the human chromosomal region 8p12-p21 using 15 well characterised microsatellite markers in a panel of 50 breast carcinomas. The allelic loss pattern of these tumours suggests the presence of five commonly deleted regions on 8p12-p21. The most commonly deleted region was located between markers D8S1734 and D81989, spanning a distance of approximately 3 cM and reaching 56% LOH at locus NEFL. LOH at 8p12-p21 was significantly correlated with large tumour size (T>5 cm). Patients with the age at diagnosis of breast cancer between 45 and 55 years showed significantly more LOH than patients older than 55 years or younger than 45 years. No correlation was observed between 8p12-p21 alterations and histological tumour type, grade and the presence of lymph node metastases.

Adult↗

PubMed2000

The role of fungal appressoria in plant infection.

Plant pathogenic fungi differentiate a highly specialized infection cell called an appressorium to infect their hosts. Appressorium formation is induced by specific physical or chemical cues provided by the host plant. Several components of signal transduction pathways have been identified that are involved in infection-related morphogenesis and virulence or pathogenicity. In this review we summarize current knowledge on appressorium differentiation and function, and discuss aspects of initial stages of fungal development in the plant.

Fungi↗

PubMed2000

Induction of activin A is essential for the neuroprotective action of basic fibroblast growth factor in vivo.

Exogenous application of neurotrophic growth factors has emerged as a new and particularly promising approach not only to promote functional recovery after acute brain injury but also to protect neurons against the immediate effect of the injury. Among the various growth factors and cytokines studied so far, the neuroprotective and neurotrophic profile of basic fibroblast growth factor (bFGF) is the best documented. Using an animal model of acute excitotoxic brain injury, we report here that the neuroprotective action of bFGF, which is now being tested in stroke patients, depends on the induction of activin A, a member of the transforming growth factor-beta superfamily. Our evidence for this previously unknown mechanism of action of bFGF is that bFGF strongly enhanced lesion-associated induction of activin A; in the presence of the activin-neutralizing protein follistatin, bFGF was no longer capable of rescuing neurons from excitotoxic death; and recombinant activin A exerted a neuroprotective effect by itself. Our data indicate that the development of substances influencing activin expression or receptor binding should offer new ways to fight neuronal loss in ischemic and traumatic brain injury.

Activins↗

PubMed2000

Expression and function of keratinocyte growth factor and activin in skin morphogenesis and cutaneous wound repair.

Reepithelialization and granulation tissue formation during cutaneous wound repair are mediated by a wide variety of growth and differentiation factors. Recent studies from our laboratory provided evidence for an important role of keratinocyte growth factor (KGF) in the repair of the injured epithelium and for a novel function of the transforming growth factor-beta superfamily member activin in granulation tissue formation. KGF is weakly expressed in human skin, but is strongly upregulated in dermal fibroblasts after skin injury. Its binding to a transmembrane receptor on keratinocytes induces proliferation and migration of these cells. Furthermore, KGF has been shown to protect epithelial cells from the toxic effects of reactive oxygen species. We have identified a series of KGF-regulated genes that are likely to play a role in these processes. In addition to KGF, activin seems to be a novel player in wound healing. Activin expression is hardly detectable in nonwounded skin, but this factor is highly expressed in redifferentiating keratinocytes of the hyperproliferative wound epithelium as well as in cells of the granulation tissue. To gain insight into the role of activin in wound repair, we generated transgenic mice that overexpress activin in basal keratinocytes of the epidermis. These mice were characterized by a hyperthickened epidermis and by dermal fibrosis. Most importantly, overexpression of activin strongly enhanced the process of granulation tissue formation, demonstrating a novel and important role of activin in cutaneous wound repair.

Activins↗

PubMed2000

Homodimeric reverse transcriptases from rous sarcoma virus mutated within the polymerase or RNase H active site of one subunit are active.

Heterodimeric reverse transcriptase (RT) alphabeta from Rous sarcoma virus (RSV) possesses an asymmetric subunit organization with the polymerase and RNase H active sites localized in the alpha subunit. To determine whether homodimeric RSV RTs alpha (63 kDa) or beta (95 kDa) assume alpha subunit organization similar to that of the heterodimer, an essential aspartic acid residue was mutated in the active site of either the polymerase (Asp181 > Asn) or the RNase H (Asp505 > Asn). Homodimeric alpha or beta RT consisting of one wild-type and one mutated subunit exhibit polymerase or RNase H activity, respectively, whereas the corresponding doubly mutated enzymes are inactive, indicating that the catalytic sites of the polymerase and RNase H domains are formed by only one subunit of the homodimer.

Animals↗

PubMed2000

Connective tissue growth factor: a novel player in tissue reorganization after brain injury?

Recent studies have suggested a role of connective tissue growth factor (CTGF) in repair processes of the skin as well as in various types of fibrotic disease. However, a function of this molecule in central nervous system (CNS) repair has not been demonstrated yet. In this study we analysed the temporal and spatial expression pattern of CTGF after unilateral kainic acid lesions of the hippocampal CA3 region in mice. We found a strong induction of CTGF mRNA and protein expression in neurons and glial cells of the lesioned hippocampus. Interestingly, increased expression of this mitogen was accompanied by elevated levels of the extracellular matrix molecule fibronectin, which is a known target of CTGF action. Therefore, our data indicate a novel function of CTGF in postlesional restructuring of the hippocampus, where it possibly participates in glial scar formation.

Animals↗

PubMed2000

Growth hormone and insulin-like growth factor-1 in acute myocardial infarction.

BACKGROUND: Growth hormone therapy after myocardial infarction improves cardiac function and survival in animals. Beneficial effects in humans are reported from studies where patients with idiopathic dilated cardiomyopathy were treated with growth hormone. We have studied the role of the endogenous growth hormone system in myocardial infarction. METHODS AND RESULTS: Fifty-two consecutive patients with acute myocardial infarction were studied during the first 5 days and at follow-up 6 and 12 weeks later. The time from chest pain onset was used in the analyses. The mean growth hormone level within the first 6 h was nearly three times higher (1.1 +/- 0.2 microg. l(-1)) than on the third day (0.4 +/- 0.05 microg. l(-1), P < 0.0002). It remained higher in patients with higher levels of cardiac enzymes, impaired left ventricular function and intense inflammatory response. Insulin-like growth factor-1 (IGF-1) declined slowly but remained within the normal range throughout the whole study period. Patients who died within 2 years had higher levels of growth hormone and lower levels of IGF-1, indicating growth hormone resistance. Endogenous levels of growth hormone or IGF-1 did not correlate with improvement in left ventricular function at 6 weeks. CONCLUSIONS: The growth hormone axis is stimulated early in acute myocardial infarction, particularly in patients with more severe cardiac damage. Whether treatment with growth hormone can be beneficial for patients with heart failure after myocardial infarction remains to be investigated.

Aged↗

PubMed2000

The angiogenesis inhibitor endostatin impairs blood vessel maturation during wound healing.

Endostatin is a cleavage product of collagen XVIII that strongly inhibits tumor angiogenesis. To determine if endostatin affects other angiogenic processes, we generated full-thickness excisional wounds on the back of mice that were systemically treated with recombinant murine endostatin. No macroscopic abnormalities of the wound healing process were observed. Histological analysis revealed normal wound contraction and re-epithelialization, but a slight reduction in granulation tissue formation and reduced matrix deposition at the wound edge. The blood vessel density in the wounds of endostatin-treated mice was not affected. However, ultrastructural analysis demonstrated severe abnormalities in blood vessel maturation. The wound vessels in the endostatin-treated mice were narrowed or closed with an irregular luminal surface, resulting in a severe reduction in the number of functional vessels and extravasation of erythrocytes. Endostatin treatment did not affect the expression level and localization of collagen XVIII mRNA and protein. Furthermore, the angiogenesis regulators vascular endothelial growth factor, angiopoietin-1, and angiopoietin-2 were normally expressed in the wounds of endostatin-treated mice. However, expression of the major wound matrix proteins fibronectin and collagens I and III was significantly reduced. This reduction is likely to explain the reduced density of the wound matrix. Our results demonstrate that endostatin treatment reduces the number of functional blood vessels and the matrix density in the granulation tissue, but does not significantly affect the overall wound healing process.

Angiogenesis Inhibitors↗

PubMed2000

Asymmetric subunit organization of heterodimeric Rous sarcoma virus reverse transcriptase alphabeta: localization of the polymerase and RNase H active sites in the alpha subunit.

The genes encoding the alpha (63-kDa) and beta (95-kDa) subunits of Rous sarcoma virus (RSV) reverse transcriptase (RT) or the entire Pol polypeptide (99 kDa) were mutated in the conserved aspartic acid residue Asp 181 of the polymerase active site (YMDD) or in the conserved Asp 505 residue of the RNase H active site. We have analyzed heterodimeric recombinant RSV alphabeta and alphaPol RTs within which one subunit was selectively mutated. When alphabeta heterodimers contained the Asp 181-->Asn mutation in their beta subunits, about 42% of the wild-type polymerase activity was detected, whereas when the heterodimers contained the same mutation in their alpha subunits, only 7.5% of the wild-type polymerase activity was detected. Similar results were obtained when the conserved Asp 505 residue of the RNase H active site was mutated to Asn. RNase H activity was clearly detectable in alphabeta heterodimers mutated in the beta subunit but was lost when the mutation was present in the alpha subunit. In summary, our data imply that the polymerase and RNase H active sites are located in the alpha subunit of the heterodimeric RSV RT alphabeta.

Avian Sarcoma Viruses↗

PubMed2000

Fibroblast growth factors-5 and -9 distinctly regulate expression and function of the gap junction protein connexin43 in cultured astroglial cells from different brain regions.

Astroglial cells contribute to neuronal maintenance and function in the normal and diseased brain. Gap junctions formed predominantly by connexin43 (cx43) provide important pathways to coordinate astroglial responses. We have previously shown that fibroblast growth factor (FGF)-2, which occurs ubiquitously in the CNS, downregulates gap junction communication in cortical and striatal, but not in mesencephalic astroglial cells in vitro (Reuss et al. Glia 22:19-30, 1998). Other members of the FGF family expressed in the CNS include FGF-5 and FGF-9. We show that both FGF-5 and FGF-9, like FGF-2, downregulate astroglial gap junctions and functional coupling. However, their effects are strikingly different from different brain regions, with regard to astroglial cells. FGF-5 specifically affects mesencephalic astroglial cells without changing coupling of cortical and striatal astroglia, while FGF-9 reduces gap junctional coupling in astroglia from all three brain regions. Both cx43 mRNA and protein levels as well as functional coupling assessed by dye spreading are affected. To clarify whether brain region-specific effects of FGFs on astroglial coupling are due to differential expression of FGF receptors (FGFR), we monitored expression of the four known FGFR mRNAs in astroglial cultures by RT-PCR. Irrespective of their regional origin, astroglial cells express mRNAs for FGFR-2 and FGFR-3. In summary, our results provide evidence for an important role of FGF-2, -5, and -9 in a distinct, CNS region-specific regulation mechanism of astroglial gap junction communication. The molecular basis underlying the regionally distinct responsiveness of astrocytes to different FGFs may be sought beyond distinct FGFR expression.

Animals↗

PubMed2000

[Flexibility of mental representations of spatial information as a function of perspective during learning].

View-based theories of the mental representation of spatial information claim that distinct views experienced during learning are represented separately in memory. Networks of such views are considered to be the basis for spatial navigation. Two experiments (N = 56) investigated the role of observer perspective on the resulting mental representation when learning a spatial configuration on the computer. Learning in route perspective, which induced the impression of passive navigation through the configuration, was compared with a survey perspective, which consisted of an overview of the whole configuration from one point of view. In accordance with view-based theories, previously seen views could be identified faster and with less error than new views for both perspectives during learning. Recoding the information into the alternative perspective was also possible. If participants were asked to integrate distinct route views into a survey view during learning, the flexibility of the resulting mental representation was greatly increased. This indicates that conscious processes such as imagery play an important role in the integration of spatial knowledge.

Adult↗

PubMed1999

Discoupling the Ca(2+)-activation from the pore-forming function of the bi-component Panton-Valentine leucocidin in human PMNs.

The consecutive cell activation, including Ca(2+)-channel opening, and pore formation leading to human neutrophil lysis were the two functions of the staphylococcal Panton-Valentine leucocidin attempted to be discoupled by site-directed mutagenesis. In a first approach consisting in deletions of the cytoplasmic extremity of the transmembranous domain, we produced a LukF-PV DeltaSer125-Leu128 with a slightly reduced Ca(2+) induction but with a significantly lowered lytic activity when combined with its synergistic protein LukS-PV. The second approach consisted in the modification of charges and/or introduction of a steric hindrance inside the pore, which also led to interesting mutated proteins: LukF-PV G131D, G131W and G130D. The latter had an intact Ca(2+) induction ability while the lytic one was 20-fold diminished. Binding properties and intrinsic pore diameters of these discoupled toxins remained comparable to the wild-type protein. The mutated proteins promoted interleukin-8 secretion, but they were rather inactive in an experimental model. New insights are brought concerning the role of the two functions in the virulence of this bi-component leucotoxin.

Amino Acid Substitution↗

PubMed1999

Growth factor-regulated expression of enzymes involved in nucleotide biosynthesis: a novel mechanism of growth factor action.

Keratinocyte growth factor (KGF) is a potent and specific mitogen for epithelial cells, including the keratinocytes of the skin. We investigated the mechanisms of action of KGF by searching for genes which are regulated by this growth factor in cultured human keratinocytes. Using the differential display RT-PCR technology we identified the gene encoding adenylosuccinate lyase [EC 4.3.2.2] as a novel KGF-regulated gene. Adenylosuccinate lyase plays an important role in purine de novo synthesis. To gain further insight into the potential role of nucleotide biosynthesis in the mitogenic effect of KGF, we cloned cDNA fragments of the key regulatory enzymes involved in purine and pyrimidine metabolism (adenylosuccinate synthetase [EC 6.3.4.4], phosphoribosyl pyrophosphate synthetase [EC 2.7.6.1], amidophosphoribosyl transferase [EC 2.4.2.14], hypoxanthine guanine phosphoribosyl transferase [EC 2.4.2.8] and the multifunctional protein CAD which includes the enzymatic activities of carbamoyl-phosphate synthetase II [EC 6.3.5.59], aspartate transcarbamylase [EC 2.1.3.2] and dihydroorotase [EC 3.5.2.3]). Expression of all of these enzymes was upregulated after treatment with KGF and also with epidermal growth factor (EGF), indicating that these mitogens stimulate nucleotide production by induction of these enzymes. To determine a possible in vivo correlation between the expression of KGF, EGF and the enzymes mentioned above, we analysed the expression of the enzymes during cutaneous wound repair, where high levels of these mitogens are present. Indeed, we found a strong mRNA expression of all of these enzymes in the EGF- and KGF-responsive keratinocytes of the hyperproliferative epithelium at the wound edge, indicating that their expression might also be regulated by growth factors during wound healing.

Animals↗

PubMed1999

Overexpression of activin A in the skin of transgenic mice reveals new activities of activin in epidermal morphogenesis, dermal fibrosis and wound repair.

Recently we demonstrated a strong induction of activin expression after skin injury, suggesting a function of this transforming growth factor-beta family member in wound repair. To test this possibility, we generated transgenic mice that overexpress the activin betaA chain in the epidermis under the control of a keratin 14 promoter. The transgenic mice were significantly smaller than control littermates, and they had smaller ears and shorter tails. In their skin, the fatty tissue was replaced by connective tissue and a severe thickening of the epidermis was found. The spinous cell layer was significantly increased, and the epidermal architecture was highly disorganized. These histological abnormalities seem to result from increased proliferation of the basal keratinocytes and abnormalities in the program of keratinocyte differentiation. After skin injury, a significant enhancement of granulation tissue formation was detected in the activin-overexpressing mice, possibly as a result of premature induction of fibronectin and tenascin-C expression. These data reveal novel activities of activin in the regulation of keratinocyte proliferation and differentiation as well as in dermal fibrosis and cutaneous wound repair.

Activins↗

PubMed1999

Soluble Rous sarcoma virus reverse transcriptases alpha, alphabeta, and beta purified from insect cells are processive DNA polymerases that lack an RNase H 3' --> 5' directed processing activity.

Reverse transcriptase (RT) isolated from Rous sarcoma virus (RSV) consists of heterodimeric RTalphabeta, RTalpha, and RTbeta. The alpha subunit (63 kDa) contains an N-terminal polymerase and a C-terminal RNase H domain. The N terminus of beta (95 kDa) corresponds to alpha with the integrase domain attached to the C terminus (32 kDa). We have constructed baculoviruses expressing the genes for alpha or beta or the entire pol (99 kDa). Infection of insect cells with recombinant virus yielded highly active and soluble RSV RT enzymes that could be purified to >90% homogeneity. HPLC gel filtration showed that alpha is a dimeric enzyme that can be partially monomerized upon the addition of 45% Me(2)SO. DNA synthesis on DNA-DNA and DNA-RNA primer-templates in the presence of competitor substrates revealed that alphabeta and beta as well as alpha are processive polymerases. However, the affinity of beta and alphabeta for primer-template substrates appears to be higher than that of alpha. All RSV enzymes investigated have the potential to displace RNA-RNA duplexes more efficiently than human immunodeficiency virus type 1 RT. Unlike human immunodeficiency virus type 1 RT, RSV RTs can catalyze an initial RNase H endonucleolytic cleavage of the RNA template but not a 3' --> 5' directed processing activity.

Animals↗

PubMed1999

Crystal lattice and phase transitions in Na4TiP2O9 (NTP) and Na4.5FeP2O8(O,F) (NFP) superionic conductors as a function of high pressures and temperatures.

The lattice dynamics of Na(4)TiP(2)O(9) (tetrasodium titanium diphosphorus nonaoxide, NTP) and Na(4.5)FeP(2)O(8)(O,F) (nonasodium diiron tetraphosphorus difluoride octadecaoxide, NFP) crystals, which are superionic conductors with Na(+)-ion conductivity, were studied under high pressures. Lattice constants as a function of hydrostatic pressure were measured on a four-circle diffractometer using a high-pressure cell with diamond anvils. At 1.78 +/- 0.15 GPa NTP undergoes a reversible phase transition from the modulated monoclinic (pseudo-orthorhombic) modification which is stable under atmospheric conditions. A similar phase transition in NTP is observed at 523 K. For NFP, it may be assumed that at least three phase transitions occur when the pressure increases from atmospheric to 12 GPa, at 1.39 +/- 0.08, 4.52 +/- 0.32, and 6.02 +/- 0.02 GPa, as concluded from the change in the unit-cell parameters and in the color of the crystals: the color changes from ginger (dark orange) to pink at ~1.5-2.0 GPa pressure and to violet at ~6.0 GPa.

Journal Article↗

PubMed1999

Cloning of novel injury-regulated genes. Implications for an important role of the muscle-specific protein skNAC in muscle repair.

To gain insight into the molecular mechanisms underlying the wound repair process, we searched for genes that are regulated by skin injury. Using the differential display reverse transcription-polymerase chain reaction technique, we identified a gene that was strongly induced as early as 12 h after wounding. Sequence analysis revealed the identity of the corresponding protein with skeletal muscle nascent polypeptide-associated complex (skNAC), a recently identified muscle-specific transcription factor. By in situ hybridization and immunohistochemistry, we demonstrated the specific expression of skNAC in skeletal muscle cells of the panniculus carnosus at the wound edge. Furthermore, in vitro studies with cultured myoblasts revealed expression of skNAC in differentiating and differentiated, but not in proliferating, nondifferentiated cells. Differentiation of cultured myoblasts was accompanied by simultaneous expression of skNAC and the muscle-specific transcription factor myogenin. Our results provide the first evidence for a role of skNAC in muscle repair processes. Furthermore, they demonstrate the usefulness of our approach in identifying new players in wound repair.

Animals↗

PubMed1999

[A Scandinavian multicenter study will investigate the question: surgery or not in mild primary hyperparathyroidism?].

Primary hyperparathyroidism is a common endocrine disease particularly prevalent among elderly women. A majority of these patients diagnosed today are mildly hypercalcaemic, and many seem to lack manifest symptoms or complications. In such cases, conservative follow-up rather than parathyroid surgery may be suggested. However, long-term follow-up may entail costly investigations and be difficult to accomplish. Moreover, conservative follow-up is associated with a risk of subsequent complications or even premature death due to cardiovascular disorders. A Scandinavian multicentre study has been initiated to assess survival, morbidity and quality of life in surgically vs. conservatively treated patients.

Aged↗