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R Weber

Publications and source records attributed to R Weber.

At least 361 records · Page 20Linked to original sources
PubMed1985

Comparative nucleotide sequence analysis of two types of larval beta-globin mRNAs of Xenopus laevis.

The complete nucleotide sequence of the cDNA insert of the clone pXGL25 derived from the larval beta II-globin mRNA of Xenopus laevis has been determined. The sequence of 593 nucleotides represents part of the 5'nontranslated region, the coding region for 146 amino acids and the entire 3'nontranslated region. It diverges from the related larval beta I-sequence by 24.9% in the coding region. Alignment of the 5' and 3'nontranslated regions of the two related larval beta-sequences to maximum matching resulted in 31.2% and 46.7% divergence, respectively. Divergence between the corresponding adult and larval sequences considerably exceeds that of related larval sequences, suggesting that larval genes may have arisen by gene duplication prior to genome duplication. In contrast to mammalian beta-globin mRNAs, replacement and silent base substitutions are equally abundant, thus indicating less functional constraint on the larval Xenopus laevis beta-globin chains. The larval beta I- and beta II-globins diverge by 30.8% and show most variation in the alpha 1/beta 2-chain interaction sites.

Amino Acid Sequence↗
PubMed1985

[Acute myelomonocytic and monoblastic leukemia with polyradicular symptoms].

Meningeal leukaemia, developed in 4 female patients with M4 or M5 leukaemia during a period of haematological remission. Polyradicular symptoms and signs dominated neurologically, but 3 patients also exhibited cranial nerve palsies. The neurological findings showed no reversal following intrathecal chemotherapy with normalization of liquor cytology. Patchy demyelinization in the region of the anterior spinal roots and of the proximal segments of the affected cranial nerves were responsible for the neurological features. Peripherally located streaky demyelinization of the olfactory bulb and of the optic chiasm were not found to cause any neurological manifestations.

Abducens Nerve↗
PubMed1985

The ilvB locus of Escherichia coli K-12 is an operon encoding both subunits of acetohydroxyacid synthase I.

The ilvB locus of Escherichia coli K-12 encloses two open reading frames defining polypeptides of 60,000 and 11,200 molecular weight. The entire locus, about 2.3 kb, is co-transcribed as an operon. The molecular weights and amino acid compositions of the presumptive operon polypeptides agree with those of the large and small subunit polypeptides of acetohydroxyacid synthase (AHAS) I, for which ilvB is the structural locus. We reserve the designation ilvB for the promoter proximal (longer) cistron and designate the promoter distal cistron ilvN. The molecular weight and amino acid sequence of the ilvB polypeptide are strikingly similar to those of the I1vI (larger subunit of AHAS III) and I1vG (larger subunit of AHAS II) polypeptides. There is less size uniformity among the I1vN, I1vH (smaller subunit of AHAS III), and I1vM (smaller subunit of AHAS II) polypeptides. Nevertheless, there is significant amino acid sequence homology among the three small subunit polypeptides. Thus, all three AHAS isozymes of E. coli K-12 probably have a common evolutionary origin.

Acetolactate Synthase↗
PubMed1985

[Determination of 5-methoxypsoralen in suntan cosmetics].

A method for the determination of 5-methoxypsoralene in suntan-cosmetics is described. After liquid chromatographic clean-up, the final extract is screened by twodimensional thin layer chromatography. For positive extracts 5-methoxypsoralene is analysed quantitatively by capillary gas chromatography, using 5-alpha-cholestane as an internal standard and flame ionization detection (FID). The results were confirmed by gas chromatography-mass spectrometry (GC-MS). The recoveries for suntan-cosmetics of emulsion type were 70% and for tanning oils 90%. Detection limits of the method were 0,1 to 0,5 mg/kg, depending on the sample type. By application of this method 5-methoxypsoralene was detected in 6 of the 21 cosmetic products at levels up to 28 mg/kg.

5-Methoxypsoralen↗
PubMed1985

[Gas chromatographic study of deoxynivalenol and nivalenol in cereals following derivatization with heptafluorobutyrates].

A method for the analysis of deoxynivalenol (DON) und nivalenol (NV) in cereals is described. This method is suitable for routine use for control purposes. The extract is purified on a florisil column. Derivatization with heptafluorobutyrylimidazole is followed by quantitative determination by means of capillary gas chromatography and electron capture detection (ECD). For verification purposes two-dimensional thin layer chromatography is applied to gc-positive extracts. 67 cereal samples and cereal products from the Berlin market place have been assayed. Depending on the type of sample the limit of detection was 20 to 30 micrograms/kg for DON, and 100 to 300 micrograms/kg for NV.

Chemical Phenomena↗
PubMed1984

The primary structure of the larval beta 1-globin gene of Xenopus laevis and its flanking regions.

We present the complete nucleotide sequence of the larval beta I-globin gene of Xenopus laevis including 240 nucleotides of the 5' flanking region and 594 nucleotides beyond the polyadenylation site. The site of transcription initiation was mapped by S1 nuclease, and the site of polyadenylation was determined by comparison with corresponding cDNA clones. The larval Xenopus beta I-gene shows the same internal structure as the beta-globin genes of higher vertebrates, viz. 3 exons interrupted by 2 intervening sequences. The first intervening sequence, which is of exceptional length, spans over 564 nucleotides and interrupts the coding sequence at amino acid 30, whereas the second one comprises 968 nucleotides and is located between the amino acids 104 and 105. The second intervening sequence contains a long inverted repeat of almost perfect homology. The 5' flanking region contains a TATA- and a CAAT-box at positions -33 and -58, respectively. An additional TATA-box is located at -197 and two more CAAT-boxes occur at positions -105 and -237.

Amino Acid Sequence↗
PubMed1984

Comparative analysis of the cDNA sequences derived from the larval and the adult alpha 1-globin mRNAs of Xenopus laevis.

The complete nucleotide sequences of cloned cDNA segments derived from the larval and the adult alpha 1-globin mRNA of Xenopus laevis have been determined. These sequences comprise part of the 5' noncoding region, the entire coding region and the 3' noncoding region, including the polyadenylation site. The larval sequence differs from the adult one by a much longer 3' noncoding region. The sequences diverge by 47%, but codon usage is similar. Comparison of the amino acid sequences of vertebrates shows that the sites of heme contact are highly conserved, whereas the alpha 1/beta 1- and the alpha 1/beta 11-interfaces diverge to different degrees. In these regions the larval alpha 1-globin diverges less from embryonic than from adult alpha-like globins of vertebrates. This suggests that these sites are mainly responsible for the functional peculiarities of the larval amphibian hemoglobins.

Animals↗
PubMed1984

[Determination of deoxynivalenol and nivalenol in cereals at the microgram/kilogram range].

A method is described for the determination of Deoxynivalenol (DON) and Nivalenol (NV). A liquid chromatographic clean-up step is followed by silylation of the extract and the trimethylsilylether are determined by gas-chromatography-mass-spectrometry (GC-MS), monitoring the characteristic ions in the negative chemical ionisation mode. 71% of 42 food-samples were contaminated with DON and 38% with NV. The highest contamination detected was 2000 micrograms/kg DON and 120 micrograms/kg NV in a wheat bran sample. Deoxynivalenol and Nivalenol in concentrations of 10 micrograms/kg can be detected easily by this method.

Chromatography, Thin Layer↗
PubMed1983

Structure and evolution of the Xenopus laevis albumin genes.

The 68K and 74K albumin genes of Xenopus laevis arose by duplication approximately 30 million years ago. Electron microscopic analysis showed that both genes contain 15 coding sequences. The lengths of corresponding coding sequences are almost identical and are extremely similar to those of mammalian albumin genes. A block of four coding sequences, which in mammals codes for one protein domain, is repeated three times. The corresponding introns are usually different in length and have therefore diverged as a result of insertion/deletion events. The extensive homology between these gene sequences is neither confined to nor most extensive in the coding sequences and similar amounts of homologous sequences are found in the flanking DNAs as in the gene regions. Various structures were formed in the 5'-flanking DNA by mutually exclusive pairing of different homology regions. Analysis of the two 74K albumin gene sequences isolated suggests that the X. laevis genome may contain one 68K albumin gene and two very closely related 74K albumin genes.

Animals↗