Inhibition of hepatic deiodination of thyroxine is caused by selenium deficiency in rats.

Selenium (Se) deficiency produced up to a 14-fold decrease in hepatic tri-iodothyronine (T3) production from thyroxine (T4) in vitro. The T3 production rate could not be restored by the addition of a variety of cofactors, nor by the addition of control homogenate. The impairment in hepatic T3 production observed in Se deficiency was reflected in the concentrations of thyroid hormones circulating in plasma, T4 being increased approx. 40% and T3 being decreased by 30%. However, the fall in plasma T3 concentrations was smaller than might be expected in view of the marked decreased in T3 production. Se deficiency had no measurable effect on plasma reverse-tri-iodothyronine concentrations. The data suggest that Se deficiency produces an inhibition of both 5- and 5'-deiodination, consistent with the widely held view that these reactions are catalysed by the same enzyme complex. The mechanism of inhibition appears not be mediated by changes in thiol levels, but a direct role of Se in the activity of the deiodinase complex cannot be excluded.     

A simple and rapid method of quantitative analysis of phosphoamino acids by high-performance liquid chromatography

A high-performance liquid chromatographic system for the separation of nonradiolabeled phosphoamino acids and orthophosphate by ion-pair reverse-phase chromatography has been developed. By the use of low-ionic-strength phthalate buffers at pH 6.3, the phosphoamino acids can be visualized by virtue of this uv-active eluant. The technique is sensitive to 200 pmol of phosphoamino acid and has been shown to be directly applicable to the analysis of isolated phosphoproteins.     

Porphyran primary structure. An investigation using beta-agarase I from Pseudomonas atlantica and 13C-NMR spectroscopy

Porphyran, a highly substituted agarose from Porphyra umbilicalis was degraded by highly purified beta-agarase I from Pseudomonas atlantica. This enzyme cleaved at the reducing side of units of beta-neoagarobiose (3,6-anhydro-alpha-L-galactopyranosyl-(1 leads to 3)-beta-D-galactopyranose). The oligosaccharides were divided into fractions of low and high molecular weight by dialysis. The permeate (23% of total starting carbohydrate) was separated by ion-exchange into neutral and anionic fractions. Gel filtration of the neutral fraction (19%) resolved two major oligosaccharides. These were shown by 13C-NMR spectroscopy to be 6(3)-O-methyl-neoagarotetraose and 6(3),6(5)-di-O-methyl-neoagarohexaose. Gel filtration of the anionic oligosaccharides (3.3%) revealed two novel monosulphated tetrasaccharides, 6-O-sulphato-alpha-L-galacto-pyranosyl-(1 leads to 3)-beta-D-galactopyranosyl-(1 leads to 4)-3,6-anhydro-alpha-L-galactopyranosyl-(1 leads to 3)-D-galactopyranose and its 6(3)-O-methylated derivative. The 13C-NMR data from the sulphated tetrasaccharides provided a novel reference which was used to characterise higher, partially sulphated fragments in the dialysis permeate. The fraction retained on dialysis (77%) had an average degree of polymerisation of 40 and was homologous with the high-molecular-weight anionic permeate. From 13C-NMR spectroscopy porphyran was found to comprise 49% sulphated disaccharide units and these were calculated to occur in stretches averaging 2.0-2.5 contiguous units.     

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.      

Blood antioxidant status and erythrocyte lipid peroxidation following distance running

The relationship between prolonged exercise, oxidative stress, and the protective capacity of the antioxidant defense system has been determined. Venous blood samples were removed from seven trained athletes before and up to 120 h after completion of a half-marathon for measurements of blood antioxidants, antioxidant enzymes, and indices of lipid peroxidation. Plasma creatine kinase (CK) activity, an index of muscle damage, increased (P less than 0.05) to a maximum 24 h after the race but this was not accompanied by changes in conjugated dienes and thiobarbituric acid reactive substances (TBARS), which are indices of lipid peroxidation. An increase (P less than 0.05) in plasma cholesterol concentration (4%) immediately after the race was similar to the change in plasma volume (6%). However, transient increases (P less than 0.05) immediately postrace in the plasma concentrations of uric acid (24%), vitamin A (18%), and vitamin C (34%) were only partly accounted for by the fluid shifts. The immediate postrace increases in alpha- and gamma-tocopherol did not attain statistical significance. Erythrocyte antioxidant enzyme activities were unaffected by the exercise but the alpha- and gamma-tocopherol concentrations progressively increased (P less than 0.001 and P less than 0.05, respectively) up to 48 h postrace. Paradoxically, 24 h after the race erythrocyte susceptibility to in vitro peroxidation was markedly elevated (P less than 0.01). This enhanced susceptibility to peroxidation was maintained even at 120 h postrace and did not correspond to changes in the age of the red cell population. A decrease (P less than 0.001) in total erythrocyte glutathione immediately after the half-marathon was mainly due to a reduction in the reduced form (GSH). The results show that when trained athletes run a comparatively short distance sufficient to result in some degree of muscle damage but which is insufficient to cause elevations in plasma indices of lipid peroxidation, significant alterations in erythrocyte antioxidant status do occur.     

中国小菇属十个新记录种

报道了小菇科小菇属真菌10个中国新记录种,香菌组：橙盖小菇Mycena aurantiidisca、黄白小菇Mycena flavoalba、粉黄小菇Mycena floridula;棘刺组：异刺小菇Mycena heteracantha;纤柄组：碱味小菇Mycena amygdalina;脆足组：粉被小菇Mycena zephirus;冬生组：绣线菊小菇Mycena speirea、冬生小菇Mycena hiemalis;小菇组：绒柄小菇Mycena flos-nivium,分别来自吉林等11个省份、自治区。提供了每个物种的形态描述和线条图,以及与相近种的讨论。共计90条自测及下载ITS序列,在采用贝叶斯法和最大似然法构建的小菇属系统发育树中,新记录种均得到分子数据支持。凭证标本存放于吉林农业大学菌物标本馆（HMJAU）。