Inducibility of gene conversion in Saccharomyces cerevisiae treated with MMS

At high survival levels (85%), point mutation and gene conversion frequencies were determined in strain D7 of Saccharomyces cerevisiae after treatment with methyl methanesulfonate (MMS) either after cells were incubated in complete medium before plating or following a split-dose protocol. It is shown that induction of gene conversion by MMS post-incubation leads to an additional enhancement in frequency. This increase is not observed for point mutation. By fractionation of the MMS dose (1 mM + 1 mM) with incubation in complete medium between the 2 doses the frequency of gene conversion is twice as high as with a single equal total dose (2 mM). This treatment does not modify the frequencies of point mutation. These data support the notion that an inducible recombinogenic function exists in wild-type yeast.     

Differential effects of various vasoactive drugs on basal and stimulated levels of TXB2 and 6-keto-PGF1α in rat brain

Thromboxane B₂ and 6-keto-PGF_1α (6KPGF_1α), the major stable metabolites of thromboxane and prostacyclin, are present in the CNS, where they appear to be mainly produced within and/or acting upon the vascular district. Their concentrations are of few pg/mg protein in rat brain cortex of animals sacrificed by microwave (MW) radiation, procedure which inactivates tissue enzymes and allows the determination of endogenous “basal” levels of eicosanoids. Levels of 6KPGF_1α and especially those of TxB₂ increase several fold over the basal values in brain cortex of animals sacrificed by decapitation followed by a few minute interval before analysis (post-decapitation ischemia, PDI). Pretreatment of animals with the vasoactive drug papaverine, resulted in elevation of brain basal levels of 6KPGF_1α and with the carbochromene derivartive AD₆ in reduction of basal levels of TxB₂, whereas the calcium antagonist nifedipine and dipyridamole did not modify basal levels of the two eicosanoids. Treatments with papaverine and AD₆ reduced the accumulation of TxB₂ and enhanced that of 6KPGF_1α occurring after PDI, to different extents, both resulting, however, in reduction of the TxB₂/6KPGF_1α ratio. Nifedipine instead, decreased the release of both eicosanoids and resulted in elevation of the TxB₂/6KPGF_1α ratio, whereas dipyridamole had no effect. In conclusion, the evaluation of the overall effects of drug treatments on the TxB₂/6KPGF_1α ratio in cerebral tissue, provided useful informations on the pharmacological modulation of vascular eicosanoids in this district.     

BRAIN RECOVERY FROM ESSENTIAL FATTY ACID DEFICIENCY IN DEVELOPING RATS 1

Abstract— Rats were supplied from before birth with an essential fatty acid (EFA) deficient, a control, or an EFA deficient-control combination diet for various periods up to 6 months. It was found that EFA deficiency resulted in brain weights decreased in comparison with control values throughout development. The brain weight/body weight relationship, however, expressed by Donaldson's equation was generally maintained in animals fed either totally deficient or control diets. Animals deficient even during the brain's most actively growing period were able to recover completely on restoration of the control diet for a sufficiently long period. Fatty acid alterations in brain ethanolamine phosphoglyceride (EPG) during EFA deficiency were extensive. Acids of the ω6 family (18:2, 20:2, 20:3, 20:4, 22:3, 22:4 but not 22:5) were reduced from control figures. In the w9 family 20:3 and 22:3 were especially elevated whereas 22:6 ω3 levels were similar to those of the controls, finally decreasing only after a lengthy period of EFA deprivation. Mean unsaturation contents, as expressed by the proposed unsaturation index notation (Ul_mol) agreed closely in EPG fatty acids of deficient and control rats at a particular age. On substitution of the control for the deficient diet the ω6 family rebounded in a manner such that values for 20:4, 22:4, and 22:5 exceeded comparable figures in control animals. Concomitantly the ω9 family receded below control levels, and ω3 acids remained or returned to normal. This overadjustment in ω6 and ω9 families continued even after a prolonged period on the control diet.     

LIPID COMPOSITION OF THE CENTRAL NERVOUS SYSTEM OF MARINE VERTEBRATES

—The lipid composition of the central nervous system of some marine vertebrates and two mammalian species (rat and man) was analysed by one- and two-dimensional quantitative thin-layer chromatography, and the cerebroside fatty acids were analysed by gas chromatography. The concentrations of sphingomyelin and cerebrosides are higher in mammals than in fishes, while no significant differences are observed for other lipid classes. Furthermore, in mammals the ratio between hydroxy and normal fatty acids in the cerebrosides is much higher than in fishes. The cerebrosides of mammals contain more very long chain fatty acids than those of marine vertebrates.     

A new member of a secretory protein gene family in the dipteranChironomus tentans has a variant repeat structure

Summary We describe the structure of a gene expressed in the salivary gland cells of the dipteranChironomus tentans and show that it encodes 1 of the approximately 15 secretory proteins exported by the gland cells. This sp115,140 gene consists of approximately 65 copies of a 42-bp sequence in a central uninterrupted core block, surrounded by short nonrepetitive regions. The repeats within the gene are highly similar to each other, but divergent repeats are present in a pattern which suggests that the repeat structure has been remodeled during evolution. The 42-bp repeat in the gene is a simple variant of the more complex repeat unit present in the Balbiani ring genes, encoding four of the other secretory proteins. The structure of the sp115,140 gene suggests that related repeat structures have evolved from a common origin and resulted in the set of genes whose secretory proteins interact in the assembly of the secreted protein fibers.     

Accumulation of Arachidonic Acid Cyclo- and Lipoxygenase Products in Rat Brain During Ischemia and Reperfusion: Effects of Treatment with GM1-Lactone

The aim of our study was to investigate the changes of various biochemical parameters (concentrations of lactate, free arachidonate, cyclo- and lipoxygenase products) in rat brain after ischemia and reperfusion and the effects of pretreatment with the ganglioside derivative GM1-lactone on the same parameters. Ischemia was induced by reversible occlusion of common carotid arteries for 20 min, which included a final 5 min of respiration of 5% oxygen in nitrogen. Reperfusion was obtained by removing the occlusion. Pre-ischemic conditions were obtained on sham-operated animals. Animals were killed by microwave irradiation of their heads. Brain levels of lactate and of free arachidonate were markedly increased after ischemia and returned to normal values at 5 min of reperfusion. Levels of the cyclooxygenase metabolites prostaglandin F2 alpha, 6-keto-prostaglandin F1 alpha, and thromboxane B2 were increased after ischemia, whereas levels of the lipoxygenase metabolite leukotriene C4 (LTC4) did not change. After reperfusion, a very marked increase of the cyclooxygenase products occurred but not of LTC4. Treatment with GM1-lactone prevented the elevation of cyclo- and lipoxygenase metabolites especially during reperfusion, with limited effects on lactate and free arachidonate levels.     

X-linked Alport syndrome: an SSCP-based mutation survey over all 51 exons of the COL4A5 gene.

The COL4A5 gene encodes the alpha5 (type IV) collagen chain and is defective in X-linked Alport syndrome (AS). Here, we report the first systematic analysis of all 51 exons of COL4A5 gene in a series of 201 Italian AS patients. We have previously reported nine major rearrangements, as well as 18 small mutations identified in the same patient series by SSCP analysis of several exons. After systematic analysis of all 51 exons of COL4A5, we have now identified 30 different mutations: 10 glycine substitutions in the triple helical domain of the protein, 9 frameshift mutations, 4 in-frame deletions, 1 start codon, 1 nonsense, and 5 splice-site mutations. These mutations were either unique or found in two unrelated families, thus excluding the presence of a common mutation in the coding part of the gene. Overall, mutations were detected in only 45% of individuals with a certain or likely diagnosis of X-linked AS. This finding suggests that mutations in noncoding segments of COL4A5 account for a high number of X-linked AS cases. An alternative hypothesis is the presence of locus heterogeneity, even within the X-linked form of the disease. A genotype/phenotype comparison enabled us to better substantiate a significant correlation between the degree of predicted disruption of the alpha5 chain and the severity of phenotype in affected male individuals. Our study has significant implications in the diagnosis and follow-up of AS patients.     

Characterization of two virulent Lactobacillus fermentum bacteriophages isolated from sour dough

Two different bacteriophages, FE5-B1 and Z63-B1, active against strains of Lactobacillus fermentum were isolated from a sample of sour dough of a regional wheat bread. They showed different host specificities when tested against 58 strains of obligately heterofermentative lactic acid bacteria, as well as differences in adsorption and one-step growth kinetics. The burst size of FE5-B1 was about 100 pfu cell⁻¹. This phage belonged to the A₁ morphotype of Myoviridae family, having an icosahedral head (83 nm diam.) and a sheathed contractile tail (170 nm in length). The phage consisted of five major structural proteins and had a genome of 86 kbp. Z63-B1 showed a burst size of 10 pfu cell⁻¹ and belonged to the B₁ morphotype or Siphoviridae family. Z63-B1 had an isometric head (60 nm diam.) and a non-contractile tail (160 nm in length), with eight major different structural proteins and a genome of 32 kbp.