Human medulloblastoma gangliosides

To establish a model system for the study of ganglioside metabolismof the human brain tumor, medulloblastoma, we have chemicallycharacterized the gangliosides of the Daoy cell line. Thesecells contain a high concentration of gangliosides (143 ±13 nmol LBSA/10⁸ cells). The major species have been structurallyconfirmed to be G_M2 (65.9%), G_M3 (13.0%), and G_Dla (10.3%).Isolation of individual gangliosides homogeneous in both carbohydrateand ceramide moieties by reversed-phase HPLC and analysis bynegative-ion fast atom bombardment collisionally activated dissociationtandem mass spectrometry have allowed us to unequivocally characterizeceramide structures. In the case of G_M2, 10 major ceramide subspecieswere identified: d18:1-hC16:0, d18:1-C16:0, d18:0-C16:0, d18:1-C18:0,d18:1-C20:0, d18:1-C22:0, d18:2-C24:1, d18: 1-C23:1, d18:1-C24:1,and d18:1-C24:0. Taken together with previous studies, thesefindings in human medullo-blastoma cells support the view thathigh expression and marked heterogeneity of ceramide structureare general characteristics of tumor gangliosides, moleculeswhich are shed by the tumor cells and which are biologicallyactive in vivo. medulloblastoma gangliosides ceramide structure HPLC mass spectrometry     

Interactions of Drosophila Ultrabithorax Regulatory Regions with Native and Foreign Promoters

The Ultrabithorax (Ubx) gene of the Drosophila bithorax complex is required to specify parasegments 5 and 6. Two P-element ``enhancer traps' have been recovered within the locus that contain the bacterial lacZ gene under the control of the P-element promoter. The P insertion that is closer to the Ubx promoter expresses lacZ in a pattern similar to that of the normal Ubx gene, but also in parasegment 4 during embryonic development. Two deletions have been recovered that remove the normal Ubx promoter plus several kilobases on either side, but retain the lacZ reporter gene. The lacZ patterns from the deletion derivatives closely match the normal pattern of Ubx expression in late embryos and imaginal discs. The lacZ genes in the deletion derivatives are also negatively regulated by Ubx and activated in trans by Contrabithorax mutations, again like the normal Ubx gene. Thus, the deleted regions, including several kilobases around the Ubx promoter, are not required for long range interactions with Ubx regulatory regions. The deletion derivatives also stimulate transvection, a pairing-dependent interaction with the Ubx promoter on the homologous chromosome.     

Skeletal troponin I as a marker of exercise-induced muscle damage

Sorichter, Stephan, Johannes Mair, Arnold Koller, WalterGebert, Daniel Rama, Charles Calzolari, Erika Artner-Dworzak, and BerndPuschendorf. Skeletal troponin I as a marker of exercise-inducedmuscle damage. J. Appl. Physiol.83(4): 1076-1082, 1997.The utility of skeletal troponin I (sTnI)as a plasma marker of skeletal muscle damage after exercise wascompared against creatine kinase (CK), myoglobin (Mb), and myosin heavychain (MHC) fragments. These markers were serially measured in normalphysical education teacher trainees after four different exerciseregimens: 20 min of level or downhill (16% decline) running(intensity: 70% maximal O₂uptake), high-force eccentric contractions (70 repetitions), orhigh-force isokinetic concentric contractions of the quadriceps group(40 repetitions). Eccentrically biased exercise (downhill running andeccentric contractions) promoted greater increases in all parameters.The highest plasma concentration were found after downhill running{median peaks: 309 U/l CK concentration ([CK])}, 466 µg/l Mb concentration([Mb]), 1,021 µU/l MHC concentration ([MHC]),and 27.3 µg/l sTnI concentration ([sTnI]). Level running produced a moderate response (median peaks: 178 U/l [CK],98 µg/l [Mb], 501 µU/l [MHC], and 6.6 µg/l [sTnI]), whereas the concentric contraction protocoldid not elicit significant changes in any of the markers assayed. sTnIincreased and peaked in parallel to CK and stayed elevated (>2.2µg/l) for at least 1-2 days after exercise. In contrast to MHC,sTnI is an initial, specific marker of exercise-induced muscle injury,which may be partly explained by their different intracellularcompartmentation with essentially no (MHC <0.1%) or a small solublepool (sTnI: median 3.4%).

     

Perturbation analysis of a two-locus model with directional selection and recombination

A population genetic two-locus model with additive, directional selection and recombination is considered. It is assumed that recombination is weaker than selection; i.e., the recombination parameter r is smaller than the selection coefficients. This assumption is appropriate for describing the effects of two-locus selection at the molecular level. The model is formulated in terms of ordinary differential equations (ODES) for the gamete frequencies x = (x ₁, x ₂, x ₃, x ₄), defined on the simplex S ₄. The ODEs are analyzed using first a regular pertubation technique. However, this approach yields satisfactory results only if r is very small relative to the selection coefficients and if the initial values x(0) are in the interior part of S ₄. To cope with this problem, a novel two-scale perturbation method is proposed which rests on the theory of averaging of vectorfields. It is demonstrated that the zeroth-order solution of this two-scale approach approximates the numerical solution of the model well, even if recombination rate is on the order of the selection coefficients.     

Tissue specific loss of proliferative capacity of parthenogenetic cells in fetal mouse chimeras

Parthenogenetic cells are lost from fetal chimeras. This may be due to decreased proliferative potential. To address this question, we have made use of combined cell lineage and cell proliferation analysis. Thus, the incorporation of bromodeoxyuridine in S-phase was determined for both parthenogenetic and normal cells in several tissues of fetal day 13 and 17 chimeras. A pronounced reduction of bromodesoxyuridine incorporation by parthenogenetic cells at both developmental stages was only observed in cartilage. In brain, skeletal muscle, heart and intestinal epithelium, this reduction was either less pronounced or observed only at one of the developmental stages analysed. No difference between parthenogenetic and normal cells was observed in epidermis and ganglia. Our results show that a loss of proliferative potential of parthenogenetic cells during fetal development contributes to their rapid elimination in some tissues. The analysis of the fate of parthenogenetic cells in skeletal muscle and cartilage development demonstrated different selection mechanisms in these tissues. In skeletal muscle, parthenogenetic cells were largely excluded from the myogenic lineage proper by early post-midgestation. In primary hyaline cartilage, parthenogenetic cells persisted into adulthood but were lost from cartilages that undergo ossification during late fetal development.     

Book Review

Book reviewed in this article:
Archeology: Archaeology as Human Ecology . Karl W. Butzer
Archeology: Environmental Archaeology . Myra Shackley     

Human C4 polymorphism: Pedigree analysis of qualitative,quantiative, and functional parameters as a basis for phenotype interpretations

Summary Ten families with 82 members were investigated for C4A- and B polymorphism in a blind trial. Phenotyping was done on neuraminidase treated sera by immunofixation and simulataneously by hemolytic overlay electrophoresis. In addition Rg, Ch, BF, C2, HLA-A, B, C, DR, and GLO were determined. After decoding the samples the reliability of blind typing was found to be 84.4% according to segregation patters. Inconsistencies occurred mostly when A 4, A 2, or A 92 were present. The detection of silent A*Q0 and B*Q0 alleles was more critical than that of difficult allotypes. The quantitation of the C4A/B ratio by densitometry of stained gels or by conventional immunochemical measurements of serum C4 level could not substantially improve the identification of A*Q0 or B*Q0. C4 dependent activity in radial diffusion hemolysis showed satisfactory correspondence with the number of expressed C4B alleles. At least three haplotypes with two C4A genes (duplicated A genes) were observed as ascertained from offspring analysis in accordance with the MHC segregation pattern. Individuals with the duplicated C4A gene (C4A*3. A*2. in the absence of any other expressed A allele or together with C4A*92) showed only partial inhibition of Rodgers antisera. Partial inhibition of Chido antisera was seen in individuals with C4B 2 (in the absence of other B allotypes). The findings support the hypothesis of at least two structural C4 loci. The also demonstrate the inconsistency of quantitative data in the recognition of silent alleles.     

Molecular species of epidermal growth factor carrying immunosuppressive activity

The suppression of antibody formation to sheep red cells in mice by partially purified fractions of mouse submaxillary gland was shown to be caused by epidermal growth factor (EGF). Purification of EGF by the method of Savage and Cohen resolved three components referred to as EGF a, EGF b, and EGF c. All three induced premature eye opening in neonatal mice, but only EGF a (identified as EGF 1-53) had full immunosuppressive activity. EGF c was shown by micropeptide mapping of chymotryptic and thermolytic digests and amino-terminal analysis to differ from EGF a only by the presence of beta-aspartyl instead of an asparaginyl residue. EGF b differed from EGF a in that it lacked the N-terminal asparagine. EGF shortened enzymatically at its carboxy terminal by two or five amino acids did not have any immunosuppressive activity. These findings suggest that, in contrast to some other biological effects of EGF, intact amino and carboxy terminals are required for the expression of immunosuppressive activity.