Decreased UDP-GlcNAc:Glycopeptideβ-2-N-Acetylglucosaminyltransferase II activity in a ricin-resistant mutant of baby hamster kidney (BHK) cells

The ricin-resistant mutant baby hamster kidney (BHK) cell line RIC^R21 is unable to make the sialylated bi- or triantennary complexN-glycans found in wild type cells and accumulates instead non-bisected hybrid structures containing three Man residues and one or two sialylated antennae (Hugheset al 1983, Carbohydr Res 120215-34). Specific assays forN-acetylglucosaminyltransferases I, II, III and IV were applied to Triton X-100 extracts of wild type BHK, RIC^R14 and RIC^R21 cells. It was shown that RIC^R21 cell extracts had a decreasedN-acetylglucosaminyltransferase II specific activity (17 to 27% of wild type values). It is suggested that in wild type cellsN-acetylglucosaminyltransferase II action proceeds quickly, leading to complexN-glycan synthesis, while in RIC^R21 cells potential substrates forN-acetylglucosaminyltransferase II move into the trans-Golgi compartment before the transferase can act, thereby leading to hybrid structures.     

Beta-adrenergic induced potassium current in Xenopus oocyte: involvement of cyclic AMP

The effect of a beta-adrenergic agonist, on full-grown Xenopus oocytes, still surrounded by their ovarian envelopes, has been studied by electrophysiological methods. The oocytes were hyperpolarized by isoproterenol. Under voltage clamp, the elicited outward current reversed at a membrane potential of - 95 mV, a value close to the K+ equilibrium potential. The isoproterenol induced current varied linearly with the membrane potential in the range studied (- 120 mV, - 30 mV). Half-maximum current was obtained at 3.10(-8) M isoproterenol. Propranolol (10(-7) M) completely suppressed the response to isoproterenol (10(-9) to 10(-5) M). 8-Br-cAMP induced a current which also reversed at - 95 mV. Methyl-isobutyl-xanthine (MIX), a potent inhibitor of phosphodiesterases, potentiated the current induced by isoproterenol. These experiments strongly suggest that the increase in K+ permeability due to catecholamines is mediated by cAMP.     

Chemical activity and biological effect of sludge-borne heavy metals and inorganic metal salts added to soils

Summary A greenhouse experiment was conducted in order to evaluate the chemical activity and the uptake by Italian ryegrass (Lolium perenne cv. S24) of Zn, Cu, Cd and Ni added to a sandy and a heavy clay soil in two different forms: as inorganic salts and sludge-borne.The chemical activity of heavy metals as evaluated with different extractants was higher for the inorganic salt treatment and for the sandy soil, indicating that the chemical form of the metal and soil characteristics largely affect their extractability.The different chemical activity was also reflected in plant uptake. For all metals the degree of plant accumulation decreased in the following order: sandy soil-salt sandy soil-sludge> clay soil-salt>clay soil-sludge.These findings indicate that caution must be used when using results of inorganic salt treatments and different soil types to evaluate plant uptake of heavy metals from sludge amended soils.     

Human genes for glutathione S-transferases

The tissue distribution of different glutathione S-transferases (GST) is analysed by electrophoresis. The existence of GST"e" (erythrocyte), GST3, GST1, and GST2 is confirmed. GST"e" the fastest and most thermolabile of different GST analysed is observed only in erythrocyte cells. GST3 which migrates more slowly than GST"e" is present in all tissues and cells analysed, excepted for erythrocyte cells in which only GST"e" is observed. GST1 presents a polymorphism with four phenotypes, 1, 1/2, 2, and 0 controlled by three alleles 1, 2, and 0 (null). With the sample of 56 livers analysed the different frequencies obtained are 9%, 5%, 43%, 43% for the phenotypes 1, 1/2, 2, and 0 respectively and 0.074 (p), 0.279 (q), 0.647 (r) for the alleles, 1, 2, and 0 (null). GST2 presents variant patterns due probably, in the majority of cases, to post-synthetic modifications rather than allelic variation. Two new GST are described, GST4 and GST5. GST4 abundant in muscle tissue is a dimeric protein. GST4 forms with GST1 a heterodimeric band. GST5 is observed in brain homogenates. For the chromosome localization the results obtained by man (leucocytes)-mouse somatic cell hybrid analysis indicate that the gene for leucocytes GST is on chromosome 11. This gene is the structural GST3 gene.     

Inactivation pattern of the fragile X in heterozygous carriers

Summary Chromosome analysis with conventional staining, G-banding, and R-banding with 5-bromodeoxyuridine (BrdU) incorporation were performed on the lymphocytes of ten females, who were heterozygous for the fragile X-chromosome. Mental development of these females varied greatly: moderate to severe mental retardation was found in one and moderate mental retardation in four females. Normal to borderline intelligence was found in three and normal intelligence was noted in two further females. The discrepancy in percentage of active fragile X-chromosomes in the five females with moderate mental retardation was found to be 60–100% (mean value: 80%). The three women with normal to borderline intelligence showed a corresponding discrepancy from 57 to 86% (mean value: 77%) of active fragile X-chromosomes. Finally, two female heterozygotes for fragile X with normal intelligence showed 70 and 76% (mean value 73%) of active fragile X-chromosomes. The phenotypic features also did not seem to correspond with the X-chromosome inactivation pattern. Based on the data obtained, we suggest that there is no evident correlation between the frequency of the active fragile X chromosomes and the mental status of these females.     

The sequence of the gene for cytochrome c oxidase subunit I, a frameshift containing gene for cytochrome c oxidase subunit II and seven unassigned reading frames in Trypanosoma brucei mitochrondrial maxi-circle DNA.

A 9.2 kb segment of the maxi-circle of Trypanosoma brucei mitochondrial DNA contains the genes for cytochrome c oxidase subunits I and II (coxI and coxII) and seven Unassigned Reading Frames ("URFs"). The genes for coxI and coxII display considerable homology at the aminoacid level (38 and 25%, respectively) to the corresponding genes in fungal and mammalian mtDNA, the only striking point of divergence being an unusually high cysteine content (about 4.5%). The reading frame coding for cytochrome c oxidase subunit II is discontinuous: the C-terminal portion of about 40 aminoacids, is present in the DNA-sequence in a -1 reading frame with respect to the N-terminal moiety. URF5, 8 and 10, show a low but distinct homology (about 20%) to mammalian mitochondrial URF-1, 4 and 5, respectively. In URF5, the first AUG is found at codon 145, whereas extensive homology to mammalian URF-1 sequences occurs upstream of this position. The possibility exists that UUG can serve as an initiator codon. URF7 and URF9 have a highly unusual aminoacid composition and do not possess AUG or UUG initiator codons. These URFs probably do not have a protein-coding function. The segment does not contain conventional tRNA genes.     

The beta chorionic gonadotropin-beta luteinizing gene cluster maps to human chromosome 19

Summary We used a cloned human cDNA probe homologous to the placenta chorionic gonadotropin subunit (CGB) and to the pituitary luteinizing hormone subunit (LHB) and Southern blotting techniques to analyse DNA from a series of rodent x human somatic cell hybrids for the presence of specific gonadotropin subunit related sequences. Our results provide evidence for the assignment and linkage of the eight genes (or pseudogenes) coding for the subunit of these glycoprotein hormones to chromosome 19. Moreover, we observed a strict concordance between the permissivity of mouse x man hybrid cells to enteroviruses (which is linked to the presence of specific cell receptors encoded by human chromosome 19) and the presence of CGB and LHB related sequences, thus confirming the localization of the structural genes for the subunits on chromosome 19.This work was supported in part by INSERM grants CRL 81 1041 and by MRC grant MT 4860     

Assignment of the gene for uroporphyrinogen decarboxylase to human chromosome 1 by somatic cell hybridization and specific enzyme immunoassay

Summary A specific enzyme immunoassay of uroporphyrinogen decarboxylase was developed and applied to the detection of the human enzyme in man-rodent somatic cell hybrids. This method allowed to assign the gene for uroporphyrinogen decarboxylase to human chromosome 1.