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Biomedical subjects

R Ladenstein

Publications and source records attributed to R Ladenstein.

At least 73 records · Page 4Linked to original sources
PubMed1997

1070 myeloablative megatherapy procedures followed by stem cell rescue for neuroblastoma: 17 years of European experience and conclusions. European Group for Blood and Marrow Transplant Registry Solid Tumour Working Party.

1070 myeloablative procedures followed by stem cell rescue for neuroblastoma are reviewed. These 1070 procedures are part of the European Group for Blood and Marrow Transplant (EBMTG) registry from the last 17 years (in 4536 patients). In 1070 neuroblastoma patients, survival at 2 years was 49%, at 5 years, 33% and relapses were observed as late as 7 years post-BMT (bone marrow transplant). However, 5-year survivors after megatherapy with BMT for stage 4 disease do have an 80% chance of becoming a long-term survivor. When BMT had been used in first complete response (CR1) no salvage was possible, whereas 15% survivors may be seen if BMT is used for the first time at relapse. Infants with stage 4 neuroblastoma had a 17% toxic death rate and indication in this group is exceptional and not recommended. In a matched cohort (17 allogeneic and 34 autologous), autologous stem cell rescue (SCR) was shown to be at least equal to allogeneic SCR. Multivariate analysis of clinical prognostic factors in children with stage 4 disease over 1 year showed that event-free survival was mainly influenced by two adverse factors before the megatherapy procedure: persisting skeleton lesions (99Tc and/or mIBG scan positive) as well as persisting bone marrow (BM) involvement.

Adolescent↗
PubMed1997

Autologous stem cell transplantation for solid tumors in children.

The dose-effect relationship in pediatric oncology conventional chemotherapy is emphasized. Rationales for the use of megatherapy protocols with stem cell support and associated procedures are given. It has been more than 15 years since this approach was used in neuroblastoma, and it has subsequently been applied to most of advanced, common childhood solid tumors. The ongoing use of new strategies for dose intensification with peripheral blood stem cell or autologous purged bone marrow rescue has raised expectations for cure. To date, results of megatherapy followed by autologous stem cell reinfusion are encouraging in metastatic neuroblastoma and Ewing's sarcoma, with an increase in event-free survival rates of about 30% as compared with that of conventional treatments. However, with the exception of metastatic neuroblastoma, there is still no proven role for this treatment strategy. Thus, there is still an urgent need for international collaboration to design randomized studies that could rapidly address the issue of these expensive and high-morbidity procedures in childhood cancer.

Bone Marrow Purging↗
PubMed1996

Thermal unfolding of the DNA-binding protein Sso7d from the hyperthermophile Sulfolobus solfataricus.

Thermal unfolding of the small hyperthermophilic DNA-binding protein Sso7d was studied by circular dichroism spectroscopy and differential scanning calorimetry. The unfolding transition can be described by a reversible two state process. Maximum stability was observed in the region between pH 4.5 and 7.0 where Sso7d unfolds with a melting temperature between 370.8 to 371.9 K and an unfolding enthalpy between 62.9 and 65.4 kcal/mol. The heat capacity differences between the native and the heat denatured states obtained by differential scanning calorimetry (620 cal/(molK)) and circular dichroism spectroscopy (580 cal/(mol K)) resulted in comparable values. The thermodynamic reason for the high melting temperature of Sso7d is the shallow stability curve with a broad free energy maximum, corresponding to the relatively small heat capacity change which was obtained. The calculated stability curve shows that Sso7d has, despite of its high melting temperature, an only moderate intrinsic stability, which reaches its maximum (approximately 7 kcal/mol) at 282 K. Sso7d is particularly poorly stabilized (approximately 1 kcal/mol) at the maximum physiological growth temperature of Sulfolobus solfataricus. Sso7d has furthermore untypically low specific enthalpy (0.99 kcal/(mol residue)) and entropy (2.99 cal/(mol K)) values at convergence temperatures. No significant differences in thermal stability of the partially methylated Sso7d from Sulfolobus solfataricus and the cloned non-methylated form of the protein expressed in Escherichia coli were observed.

Amino Acid Sequence↗
PubMed1996

Role of ploidy, chromosome 1p, and Schwann cells in the maturation of neuroblastoma.

BACKGROUND: Neuroblastoma is a heterogeneous disease, with manifestations ranging from spontaneous regression to lethal spread. Sometimes the tumor spontaneously differentiates toward a benign ganglioneuroma (maturing neuroblastoma). The prognosis is frequently related to ploidy, deletions in the short arm of chromosome 1, and amplifications of the N-myc oncogene. Maturing neuroblastomas consist of both neuronal cells and Schwann cells. We investigated the genetic composition of both cell types in maturing neuroblastomas, to determine the relation between genetic abnormalities and maturation. METHODS: We studied 20 maturing and mature neuroblastomas by in situ hybridization to count the chromosomes and evaluate possible deletions in the short arm of chromosome 1 in neuronal and Schwann cells. The DNA content of the cells was measured by flow cytometry. RESULTS: Neuroblastic and ganglionic cells showed aberrations in the number of chromosomes. In situ hybridization and flow cytometry demonstrated near-trip-loidy in 18 of 19 tumors and pentaploidy in the remaining tumor. The Schwann cells in all 20 neuroblastomas contained normal numbers of chromosomes. In 18 tumors studied, there were no chromosome 1 deletions in either type of cell. CONCLUSIONS: The Schwann cells in maturing neuroblastomas differ genetically from the neuronal cells. The normal number of chromosomes in Schwann cells and the abnormal number in neuroblastic ganglionic cells suggests that Schwann cells are a reactive population of normal cells that invade the neuroblastoma. Near-trip-loidy of neuroblastoma cells and intact chromosome 1 are presumably genetic prerequisites for spontaneous organoid maturation, because we found no diploidy or chromosome 1 depletions in the neuronal cells of spontaneously maturing neuroblastomas.

Child↗
PubMed1996

Locating a local symmetry axis from patterson map cross vectors: application to crystal data from GroEl, GTP cyclohydrolase I and the proteosome.

The cross vectors of the native Patterson map are shown to exhibit non-crystallographic symmetry in the case of local axes parallel to one another. This information can be used to determine the translation component of such axes. A program is described to search for this cross vector, and is tested on low-resolution data from crystals of the tetradecameric GroEL molecule, the decameric GTP cyclohydrolase I and the tetradecameric proteosome. For GroEL, the function produces a packing arrangement optimal for sevenfold symmetry, and is in agreement with the dimensions of the molecule as given by electron microscopy data and the recently determined crystal structure. Positioning of local axes is confirmed by two high-resolution crystal structure analyses: the fivefold axis in cyclohydrolase I and the sevenfold axis in the proteosome. Implications for the location of heavy-atom positions are discussed for these two cases.

Journal Article↗
PubMed1996

Crystallization and crystal packing of recombinant 3 (or 17) beta-hydroxysteroid dehydrogenase from Comamonas testosteroni ATTC 11996.

The enzyme 3 (or 17) beta-hydroxysteroid dehydrogenase from Comamonas testosteroni was crystallized. Crystals, of up to 0.6 mm in their longest dimension and suitable for a crystallographic analysis have been obtained by the vapour diffusion method. They belong to the orthorhombic lattice type and diffract to a maximum resolution of 0.23 nm. A final data set obtained by merging data from three crystals resulted in a completeness of 90% with an Rmerge of 6%. A molecular replacement search carried out by using 3 alpha (or 20 beta)-hydroxysteroid dehydrogenase from Streptomyces hydrogenans as a search model allowed us to assign I222 as the correct space group and to propose a model for the crystal packing, with one monomer per asymmetric unit. Thus, the whole unit cell contains two tetramers. The R-factor after rigid body refinement is 48.1%.

17-Hydroxysteroid Dehydrogenases↗
PubMed1996

Screening for neuroblastoma in late infancy by use of EIA (enzyme-linked immunoassay) method: 115000 screened infants in Austria.

The aim of this study was to investigate the feasibility of a neuroblastoma screening programme for children in late infancy, based on collaboration of general paediatricians and practitioners in Austria, using the technique of enzyme-linked immunoassay (EIA) for biochemical analyses. Analysis of catecholamine metabolites in spot urine samples by EIA with high performance liquid chromatography as a backup was undertaken. Austrian infants (median age 8.7 months) were screened. Overall compliance was 30%. The EIA method had a high rate (6.7%) of false-positive results. 28 infants were admitted to hospital. In 15 cases, neuroblastoma was found (four stage 1, five stage 2B, six stage 3). The EIA method can be used for neuroblastoma screening, but requires a backup analytical technique in order to avoid unnecessary hospital admissions. The stage distribution and biological features of neuroblastomas diagnosed by screening at a later age are different from those detected by earlier screening. Screening in late infancy might be of more benefit than early screening.

Austria↗
PubMed1996

[5 years neuroblastoma screening in Austria: rate of participation, results and a comparison with other screening areas].

In late 1990 a screening program for the early detection of neuroblastoma in infants was introduced in Austria. The program is performed on a voluntary basis in collaboration with general pediatricians and practitioners. Filter strips for urine collection are distributed to parents of infants aged seven to nine months on the occasion of a routine check up. The samples are sent to the laboratory by parents and analysed for vanillylmandelic acid (VMA) and homovanillic acid (HVA). Between January 1991 and December 1995 125,201 infants were screened. The compliance rate was 26.8% for Austria, but great differences were seen for different regions (65% in Carinthia, 10% in Vorarlberg). 30 children were admitted to hospital for investigation of repeatedly elevated urine catecholamines. A neuroblastoma was identified in 16 cases. In 12 of these cases at least one unfavorable prognostic factor was present (stage > or = 3, elevated LDH, unfavorable histology, N-myc amplification, di- or tetraploidy). Neuroblastoma screening of infants aged more than six months seems to detect predominantly those tumors which are unlikely to regress spontaneously. The observation of one false negative case, however, demonstrates that neuroblastomas which become clinically manifest at a later date may remain undetected by early screening. Possible advantages of shifting screening to a later age and repeated screening are discussed.

Austria↗
PubMed1995

Studies on the lumazine synthase/riboflavin synthase complex of Bacillus subtilis: crystal structure analysis of reconstituted, icosahedral beta-subunit capsids with bound substrate analogue inhibitor at 2.4 A resolution.

The lumazine synthase/riboflavin synthase of Bacillus subtilis is a bifunctional enzyme complex catalysing the formation of riboflavin from 5-amino-6-(D-ribitylamino)-2,4(1H,3H)-pyrimidinedione and L-3,4-dihydroxy-2-butanone-4-phosphate via 6,7-dimethyl-8-ribityllumazine. The complex is composed of 3 alpha (riboflavin synthase) subunits and 60 beta (lumazine synthase) subunits and has a relative mass of 1 MDa. The 60 beta subunits are arranged in an icosahedral capsid enclosing the alpha trimer in the central core. The protein was crystallised, and an X-ray structure of the icosahedral capsid was obtained at 3.3 A resolution with a crystallographic R-factor of 0.33. Hollow, icosahedral capsids consisting of 60 beta subunits can be obtained by inhibitor-driven renaturation of isolated beta subunits. They catalyse the formation of 6,7-dimethyl-8-ribityllumazine at the same rate as the native alpha 3 beta 60 complex and can be crystallised in two different hexagonal and one monoclinic form. Crystallographic intensity data of the monoclinic crystals to a resolution of 2.4 A were obtained using synchrotron radiation and an image plate detector system. The orientation of the icosahedral molecules in the monoclinic cell was deduced by real space vector search procedures from a 3.5 A Patterson map. Phases were calculated from the model of the alpha 3 beta 60 protein and were extended by cyclic averaging exploring the 30-fold redundancy of the electron density. The 2.4 A map allowed us to refine the existing atomic model of lumazine synthase. The refined model includes 154 amino acid residues, one inhibitor molecule, 58 water molecules and one phosphate ion. Applying non-crystallographic-symmetry restraints the crystallographic R-factor is 16.7% for 100,092 reflections between 10 and 2.4 A. The chain folding of the beta subunits is closely similar to the native alpha 3 beta 60 enzyme. The lumazine synthase bears resemblance to the sugar binding proteins. The significantly higher resolution compared to the alpha 3 beta 60 structure determination allows a detailed description of the substrate analogue binding site. The environment of the 5-nitro-6-(D-ribitylamino)-2,4(1H,3H)-pyrimidinedione inhibitor is particularly rigid, and the chain segments involved in forming the active site are highly conserved for lumazine synthases of different species. A residual density feature in the final map is interpreted as a bound phosphate which mimics the binding of the second substrate. We discuss the reaction mechanism on this structural basis.

Amino Acid Sequence↗
PubMed1995

Preliminary crystallographic analysis of an extremely thermostable glutamate dehydrogenase from the archaeon Pyrococcus woesei.

The extremely heat-stable glutamate dehydrogenase (GluDH) from Pyrococcus woesei was crystallized by the hanging-drop vapour-diffusion method. Crystals suitable for X-ray crystallographic investigations were obtained using polyethylene glycol (PEG) 4000 and ammonium acetate as precipitating agents. The crystals obtained diffract to a resolution of 2.8 A, have a prismatic shape and grow up to 0.5 mm in their maximal dimension. They belong to the triclinic system (space group P1; a = 90.9, b = 92.8, c = 107.1 A, alpha = 69.1, beta = 80.7, Vgamma = 65.0 degrees ) with a unit-cell volume of 765052 A(3) which accommodates one GluDH hexamer of 276 kDa. The averaged density of the crystal determined by Ficoll-gradient centrifugation is 1.15 g cm(-3), which corresponds to a molecular mass of 255 kDa in the unit cell. A native data set has been collected on an MAR image-plate system using Cu Kalpha radiation. The completeness of the data set in the range 316-3 A is 74%, and contains 64% of the data in the outer shell (3.4-2.8 A), with an average R(merge) value of 9%. Calculation of self-rotation functions revealed the 32 symmetry of the hexamer; 3 non-crystallographic twofold axes were found at a distance of 120 degrees in a plane perpendicular to the non-crystallographic threefold axis.

Journal Article↗
PubMed1995

DNA-binding surface of the Sso7d protein from Sulfolobus solfataricus.

We have used nuclear magnetic resonance (n.m.r.) spectroscopy to identify the DNA-binding surface of the abundant, small and basic protein Sso7d from the hyperthermophilic archaebacterium Sulfolobus solfataricus. The Sso7d protein was previously found to bind strongly to double-stranded DNA sequences and to protect DNA from thermal denaturation, indicating that it might assume a similar function in vivo. Several amide resonances in two-dimensional n.m.r. 1H, 15N correlation spectra of 15N-enriched Sso7d are shifted and broadened upon addition of small amounts of ten base-pair or 19 base-pair duplex DNA oligomers under conditions where Sso7d-DNA complexes exchange rapidly on the n.m.r. time scale. The locations of the corresponding amides in the Sso7d structure define the surface that interacts with DNA. This surface coincides with a continuous region of strong positive electrostatic potential, which was calculated by means of numerical solution of the Poisson-Boltzmann equation. A model of the non-specific Sso7d-DNA complex is suggested based on the present data and previously obtained evidence that Sso7d interacts with the DNA major groove. The protein-DNA interface consists of a triple-stranded beta-sheet, which interacts with the DNA major groove and a reverse turn connecting the two strands of a double-stranded beta-sheet, which interacts with the minor groove. We note that the five (of 14) lysine side-chains that are specifically subjected to N zeta-monomethylation in the cell are located on surfaces of Sso7d that are exposed to the solvent in the proposed Sso7d-DNA complex.

Archaeal Proteins↗
PubMed1995

Well ordered crystals of a short-chain alcohol dehydrogenase from Drosophila lebanonensis: re-evaluation of the crystallographic data and rotation-function analysis.

Alcohol dehydrogenase prepared from Drosophila lebanonensis yields well ordered plate-like crystals which diffract to better than 2.3 A resolution. The crystals belong to space group P2(1) of the monoclinic system; the unit-cell dimensions are a = 65.25, b = 55.77, c = 70.02 A, alpha = 90, beta = 107.08, gamma = 90 degrees. The asymmetric unit of the crystal cell is most probably occupied by a dimer, corresponding to a packing density of 2.15 A(3) Da-L. The orientation of the non-crystallographic twofold symmetry axes is determined by analysis of a self-rotation function calculated with native intensity data.

Journal Article↗
PubMed1995

The optimization of protein-solvent interactions: thermostability and the role of hydrophobic and electrostatic interactions.

Protein-solvent interactions were analyzed using an optimization parameter based on the ratio of the solvent-accessible area in the native and the unfolded protein structure. The calculations were performed for a set of 183 nonhomologous proteins with known three-dimensional structure available in the Protein Data Bank. The dependence of the total solvent-accessible surface area on the protein molecular mass was analyzed. It was shown that there is no difference between the monomeric and oligomeric proteins with respect to the solvent-accessible area. The results also suggested that for proteins with molecular mass above some critical mass, which is about 28 kDa, a formation of domain structure or subunit aggregation into oligomers is preferred rather than a further enlargement of a single domain structure. An analysis of the optimization of both protein-solvent and charge-charge interactions was performed for 14 proteins from thermophilic organisms. The comparison of the optimization parameters calculated for proteins from thermophiles and mesophiles showed that the former are generally characterized by a high degree of optimization of the hydrophobic interactions or, in cases where the optimization of the hydrophobic interactions is not sufficiently high, by highly optimized charge-charge interactions.

Bacterial Proteins↗
PubMed1995

Crystallization and preliminary crystallographic analysis of an amylopullulanase from the hyperthermophilic archaeon Pyrococcus woesei.

The thermostable amylopullulanase from Pyrococcus woesei was crystallized. Crystals, suitable for a crystallographic analysis up to a size of 0.6 mm in their longest dimension, have been obtained by the vapor diffusion method in a solution containing polyethyleneglycol 4000 (PEG 4000), isopropanol, and Tris/Cl- buffer pH 7.5. Crystals grown under these conditions form hexagonal rods and diffract to a maximum resolution of 3 A. The crystals belong to the trigonal lattice type with the spacegroup P3(1)21 or P3(2)21, respectively, have the cell dimensions a = b = 96.8 A, c = 196.2 A, alpha = beta = 90 degrees, gamma = 120 degrees. The crystals have a theoretical packing density of 2.7 A3/Da, assuming one molecule with a molecule weight of 88.8 kDa in the asymmetric unit. Furthermore the self-rotation analysis of the dataset revealed only crystallographic symmetries. The merged native data of two crystals resulted in a 88% complete dataset.

Archaea↗