Localization of deletion breakpoints in radiation-induced mutants of the hprt gene in hamster cells

DNA was analysed from a large set of hamster hprt gene mutants, some induced by ionising radiations and others occurring naturally, to identify those with large alterations in part of the gene. DNA from these mutants was restricted further with different endonucleases and probed to establish the patterns of restriction fragments remaining. Of 15 mutants characterized, one showed a duplication of part of the 5' end of the gene, and the remainder showed deletions of various sizes. It was possible to approximately locate the breakpoints of the deletions by comparison of fragment patterns to a recently-established map of the hamster gene. The relatively small number of mutants examined precludes rigorous analysis of the distribution of breakpoints in the hprt gene, but taken with other recent studies of deletion mutagenesis it is suggested that non-random induction or selection of this type of mutation may occur.     

Inhibitors of the cleavage of aclacinomycins

Summary The reductive cleavage of the aclacinomycins A (I), Y (II), and B (III) by intact mycelia or subcellular fractions of the producer strain S. spec. AM 33352/F43 is suppressed in the presence of uncouplers, complex-forming agents, detergents, and some metal anions such as chromate. Increased concentration of the latter in complete cultures caused rearrangement of I to III.     

Herbicide effects on planktonic systems of different complexity

Bioassays of different complexity were compared with respect to their capability to predict the environmental impact of the herbicide atrazine in aquatic systems. Acute toxicity tests with Daphnia did not yield meaningful results. Sublethal tests with Daphnia (feeding inhibition, reduction of growth and reproduction) were more sensitive, but effective concentrations of atrazine were still rather high (2 mg/L). A relatively complicated artificial food chain system that incorporated direct and indirect effects on Daphnia yielded significant reduction of daphnid population growth at 0.1 mg/L. Enclosure experiments with natural communities were by far the most sensitive tools. Community responses could be measured at concentrations as low as 1 µg/L and 0.1 µg atrazine/L. At the lowest concentration, however, communities recovered after three weeks. We conclude that in complex systems indirect effects can be more important than direct effects, so that, contrary to the conditions in simple tests, non-target organisms may be the better indicators of herbicide stress to natural communities.     

The swi4+ gene of Schizosaccharomyces pombe encodes a homologue of mismatch repair enzymes.

The swi4+ gene of Schizosaccharomyces pombe is involved in termination of copy-synthesis during mating-type switching. The gene was cloned by functional complementation of a swi4 mutant transformed with a genomic library. Determination of the nucleotide sequence revealed an open reading frame of 2979 nucleotides which is interrupted by a 68 bp long intron. The putative Swi4 protein shows homology to Duc-1 (human), Rep-3 (mouse), HexA (Streptococcus pneumoniae) and MutS (Salmonella typhimurium). The prokaryotic proteins are known as essential components involved in mismatch repair. A strain with a disrupted swi4+ gene was constructed and analysed with respect to the switching process. As in swi4 mutants duplications occur in the mating-type region of the swi4 (null) strain, reducing the efficiency of switching.     

Amino acid sequence of Manduca sexta adipokinetic hormone elucidated by combined fast atom bombardment (FAB)/tandem mass spectrometry

Combination of Fast Atom Bombardment Tandem Mass Spectrometry with Amino Acid Analysis assigns the amino acid sequence of the Manduca sexta adipokinetic hormone as pGlu-Leu-Thr-Phe-Thr-Ser-Ser-Trp-GlyNH2. Similarities and differences with other invertebrate hormones and with mammalian glucagon are discussed.     

Screening for antimalarial maculopathy in rheumatology clinics.

Ophthalmoscopy and three tests of visual function were undertaken in 39 patients with rheumatoid arthritis receiving treatment with antimalarial drugs and in a control group of 16 patients with rheumatoid arthritis who were not receiving such treatment. Visual contrast sensitivity, macular threshold to red light, and central visual fields to red targets were not significantly different in treated patients and controls. There were no abnormalities in visual acuity, but 11 of 76 eyes of treated patients showed minor macular abnormalities on ophthalmoscopy that were not seen in control patients, suggesting that ophthalmoscopy may be the most sensitive measure of early drug toxicity. Five rheumatologists were able to identify 52 of 65 minor changes detected by an ophthalmologist. These studies, and a critical review of published reports, suggest that in clinical practice antimalarial drugs can be administered safely to patients with rheumatoid arthritis without the need for repetitive routine examination by an ophthalmologist or the use of complicated physiological tests. Recording of visual acuity in each eye and ophthalmoscopy by the prescribing doctor may be all that are required to detect early antimalarial maculopathy.     

Pleiotropic effects of a butyrolactone-type autoregulator on mutants of Streptomyces griseus blocked in cytodifferentiation

Mutants of Streptomyces griseus blocked in cytodifferentiation regained their capacity to form differentiated mycelia and/or anthracycline pigments in the presence of butyrolactone-type autoregulatory effectors such as trans-2-(6'-methylheptanol-1'-yl)-3-hydroxymethyl-4-butanolide+ ++. In the pertinent indicator strains, the effect has been correlated with the increase of lipid synthesis, with changes in the composition of lipid fraction and with the restoration of the production of neutral proteinases. The results suggest that autoregulatory butyrolactones from streptomycetes stimulate cytodifferentiation of their producers at an early stage of development.