Expression of class I histocompatibility antigens in neuroectodermal tumors is independent of the expression of a transfected neuroblastoma myc gene

We have evaluated the relationship between the neuronal myc gene (NMYC) and class I major histocompatibility complex (MHC) expression in human neuroblastoma (NB) tumor cell lines. Class I MHC surface Ag expression in NB cell lines varied from nearly undetectable to levels nearly as high as in a lymphoblastoid cell line. Class I MHC mRNA levels in NMYC-amplified NB cell lines were lower than levels observed in single copy NMYC NB cell lines. However, considerable variation in class I MHC surface Ag and mRNA expression was evident in NMYC-amplified cell lines. To determine directly whether NMYC might modulate class I MHC expression in NB, we transfected a plasmid containing a recombinant NMYC gene into two tumor cell lines derived from a NB and a related neuroepithelioma tumor. Constitutive overexpression of the recombinant NMYC gene produced no consistent change in class I MHC surface Ag or mRNA levels. To determine whether class I MHC expression might be developmentally regulated in adrenal medullary cells, the precursor cells of adrenal NB tumors, beta 2-microglobulin expression was measured in fetal and adult adrenal glands. beta 2-Microglobulin expression was not evident in the neuroblasts of a 24-wk-old fetal adrenal gland, whereas beta 2-microglobulin expression was present in the adult adrenal medulla. These data suggest that variation in class I MHC expression among NB cells may reflect the developmental stage at which neuroblasts were arrested during tumorigenesis.     

In vitro DNA methylation inhibits gene expression in transgenic tobacco.

A hemimethylated chimeric gene, containing the cauliflower mosaic virus 35S promoter, the beta-glucuronidase coding region and the polyadenylation signal of nopaline synthase, was introduced into tobacco protoplasts by polyethylene glycol mediated transfection. Hemimethylation led to complete inhibition of transient gene expression. In regenerated transgenic plants the integrated gene was constitutively hypermethylated at the sequences CpG and CpNpG and this was correlated with an inactivation of beta-glucuronidase in 12 out of 18 analyzed plant lines whereas two showed slight and four strong activity. From 10 control lines transformed with nonmethylated DNA, only two were inactive; three showed slight and five strong activity. 5-aza-cytidine treatment of plant tissue from 'hypermethylated' lines led to induction of beta-glucuronidase in most cases. Shoots regenerated from azaC treated calli revealed stable enzyme restoration and demethylation of the integrated transgene.     

Stereospecific Preparation of an Excitatory Amino Acid Antagonist with d-Hydantoinase from Agrobacterium tumefaciens as a Biocatalyst

Extracts of Agrobacterium tumefaciens were used to mediate the stereospecific conversion of a racemic hydantoin to a carbamyl d-amino acid derivative, which is a precursor to (2R,4R,5S)-2-amino-4,5-(1,2-cyclohexyl)-7-phosphonoheptanoic acid (ACPA). ACPA has therapeutic value as an excitatory amino acid antagonist.     

Homozygotes for the autosomal dominant neoplasia syndrome (MEN1).

Families in which both parents are heterozygotes for the same autosomal dominant neoplasia syndrome are extremely unusual. Recently, we had the unique opportunity to evaluate three symptomatic siblings from the union between two unrelated individuals affected by multiple endocrine neoplasia type 1 (MEN1). When the three siblings and their parents and relatives were genotyped for 12 markers tightly linked to the MEN1 locus, at 11q13, two of the siblings were found to be homozygotes, and one a heterozygote, for MEN1. With regard to the MEN1 syndrome, no phenotypic differences were observed between the two homozygotes and the heterozygotes. However, the two homozygotes showed unexplained infertility, which was not the case for any of the heterozygotes. Thus, MEN1 appears to be a disease with complete dominance, and the presence of two MEN1 alleles with mutations of the type that occur constitutionally may be insufficient for tumor development.     

FrühblühendeAesculus-Bäume

Zusammenfassung EinAesculus-Baum, der sich im Frühling alljährlich vorzeitig belaubt, entlaubt sich im Herbst auffallend spät. Die Knospen dieses Baumes haben eine sehr kurze freiwillige Winterruhe, bei günstigen Temperaturen treiben sie bereits Mitte Dezember aus, ein Warmbad verzögert das Austreiben. Die frühtreibenden Kastanien sind durch Spätfröste, ja selbst durch Winterfröste gefährdet, denn ihre vorzeitig in Saft stehenden Knospen und Triebe fallen dem Frost leichter zum Opfer als diejenigen der länger ruhenden Bäume.Herrn Prof. Dr. H. v.Guttenberg zum 80. Geburtstag gewidmet.     

Prebiotic polymerization: Oxidative polymerization of 2,3-dimercapto-l-propanol on the surface of iron(III) hydroxide oxide

The oxidation of 2,3-dimercapto-l-propanol by ferric ions on the surface of iron(III) hydroxide oxide (Fe(OH)O) yielded polydisulfide oligomers. This polymerization occurred readily at low dithiol concentration under mild aqueous conditions. Polydisulfide polymers up to the 15-mer were synthesized from 1 mM dithiol in 5 ml water reacted with iron(III) hydroxide oxide (20 mg, 160 µ mole Fe) for 3 days under anaerobic conditions at 40 °C and pH 4. About 91% of the dithiol was converted to short soluble oligomers and 9% to insoluble larger oligomers that were isolated with the Fe (OH)O phase. Reactions carried out at the same ratio of dithiol to Fe(OH)O but at higher dithiol concentrations gave higher yields of the larger insoluble oligomers. The relationship of these results to prebiotic polymer synthesis is discussed.