Structural transformations of arabinogalactan from the Siberian larch during mechanochemical processing and the biological properties of the products

It has been found by gel-penetrating chromatography and quantitative ¹³C NMR spectroscopy that mechanochemical processing of arabinogalactan isolated from the wood of the Siberian larch changes the molecular mass distribution, monosaccharide composition, and the degree of branching of its macromolecules. This is due to the partial destruction of polysaccharide macromolecules and subsequent recombination of resulting fragments. The intensity of these processes depends on the conditions of mechanochemical processing. Based on the data of IR and ¹³C NMR spectra, the conclusion has been drawn that no functionalization of arabinogalactan macromolecules occurs under these conditions. The toxicopharmacological properties of mechanically processed arabinogalactan have been studied. Its acute toxicity is >5000 mg/kg.     

Neurogenic cholinergic dilation observed in isolated vessels of the skeletal muscles of cats (the caudal femoral artery)

Neuromediated behaviour of feline caudal femoral arteries was studied in vitro. Transmural stimulation of arteries, previously constricted by noradrenaline, caused an up to 58% relaxation of the induced tone. Atropine (10(-5) g/ml) blocked this response by 93%. The removal of endothelium did not affect the magnitude of the response. It is suggested that the caudal femoral artery is an example of a blood vessel which has muscarinic receptors located directly on its smooth muscles.     

Intracellular and extracellular alkaloids of Penicillium roqueforti

The alkaloid composition of mycelium and culture liquid filtrate of the fungus Penicillium roqueforti IBPM-F-141 was studied. The new metabolite--3,12-dihydroroquefortine, a derivative of roquefortine, the main component of the alkaloid fraction of this culture, has been isolated for the first time. The structure of 3,12-dihydroroquefortine was determined by chemical and physico-chemical methods. In addition to roquefortine and 3,12-dihydroroquefortine, representatives of a new alkaloid group, the clavine alkaloids, e. g. isofumigaclavine A, isofumigaclavine B and festuclavine, were also isolated and identified. The data on the content of these compounds in mycelium and culture medium are presented.     

Characteristics of ribosomal RNA synthesis in the blood lymphocytes of chronic lympholeukemia patients

A study was made of the number of silver grains over the nucleoli and of the content of ribosomes in the lymphocyte cytoplasm for six healthy persons and for 20 patients with chronic lymphatic leukemia. Besides ratios of compact, nucleolonemic and ring types of nucleoli were evaluated in addition to counts of the specific radioactivity of mature 28S rRNA in lymphocytes. In the majority of cases examined, cells with 1 or 2 nucleoli of compact and nucleolonemic types were seen dominating. The number of silver grains over the nucleoli in the control healthy persons did not differ from that in patients who did not receive any treatment, which contrasted with high value grain counts in the treated patients. The lymphocyte ribosome contents varied within the normal and decreased values in both the patient groups. The specific radioactivity in 28S rRNA leukemic lymphocytes was significantly lower in groups of patients with low ribosome contents than in those with the normal ones. The data suggest that in the leukemic cells with a high or unaltered activity of ribosome cistrons and low ribosome levels rRNA processing is broken.     

Identification of minor tightly bound H1 histone subfractions which fail to cleave their initiator methionine

Groups of CBA mice were administered [³⁵S] methionine (1 mCi/mouse). Non-histone proteins, H1 and H1⁰ histones and nucleosomal core histones were isolated from different issues by selective extractions. The measurements of radioactivity of individual bands and autoradiography of dry gels were used to identify methionine-containing and methionine-free histone variants. H1A and H1B histone variants extracted with 5% perchloric acid were methionine-free. However, minor sub-fractions of these histones which are more tightly bound to DNA (and which can be extracted only with 0.25 N HC1) contained [³⁵S] methionine and did show a higher specific activity than methionine-containing nucleosomal hitones. Cyanogen Bromide reaction which destroys non-histone proteins and methionine-containing nucleosomal histones removes radioactivity but does not alter the position of methionine-containing H1 minor bands. This indicates that the radioactive methionine occupies only the N-terminus of the H1 molecules. It is suggested that this methionine is an uncleaved initiator methionine. The presence of these methionine-containing minor H1 subfractions varies in different tissues.     

Production of DON-related trichothecenes byFusarium graminearum Schw from Krasnodarski krai of the USSR

34Fusarium graminearum Schw isolates produced 4-deoxynivalenol to form significant amounts of 4, 7 — dideoxynivalenol and lesser amounts of 4 — deoxynivalenol monoacetates on grain substratesin vitro. This is the first report on the capability a large group of naturally occurring isolates to produce 4,7-dideoxynivalenol. The average levels of 4,7-dideoxynivalenol on rice, corn, barley, and wheat as a substrate were respectively 26.8, 14.0, 12.8, and 10.5% of the level of 4-deoxynivalenol. 4, 7 — dideoxynivalenol was present in all examined naturally contaminated wheat kernel samples at levels of 1.7 to 7.9% of the level of 4-deoxynivalenol. These findings suggest that more attention should be given to the occurrence of 4,7-dideoxynivalenol in cereals.     

Variation in the ribosomal internal transcribed spacers (ITS1 and ITS2) among eight taxa of the Mimulus guttatus species complex

The internal transcribed spacer region (ITS1 and ITS2) of the 18S-25S nuclear ribosomal DNA sequence and the intervening 5.8S region were sequenced from three individuals in each of eight taxa of the Mimulus guttatus species complex. Three discrete variants, or "types," of ITS sequences were found, among which 30%-40% of sites differed, compared with 1%-2% within types. Dot plots indicate that these types were not related by conspicuous rearrangements or inversions. More than one ITS type was often found in the same taxon, and two of three ITS types span species boundaries, indicating their presence prior to speciation. These ITS sequences showed essentially no positional homology with the nearest sequenced relative, tomato. In contrast, the 5.8S region was relatively unvaried, with 8 of 162 sites varied in the sample among all eight taxa. The phylogeny inferred by the most common ITS sequence type, rooted by the two other ITS types, agreed with isozymes in showing the distinctness of M. nudatus, M. laciniatus, and M. tilingii from the other five taxa.