Postrest contraction in the ventricular papillary muscle of spontaneously diabetic WBN/Kob rat.

In the present study, we investigated the characteristics of the postrest contraction (PRC) in chronic diabetic ventricular muscle. We used WBN/Kob rats of 7-8 weeks as the spontaneously diabetic animal and Wistar rats of 7-8 weeks as the control. We found: (1) No significant differences were seen in the amplitude, the contracting speed, and the relaxing speed of electrically stimulated twitch tension between control and WBN/Kob rats. In addition, the relationship between amplitude of twitch tension and stimulus cycle lengths (0.2-5 sec) was very similar in both animals. (2) The ratios of the first twitch tension (T1) of PRC with various rest intervals (5-600 sec) to the steady-state tension (Tss) were significantly smaller in the diabetic rats than in the controls. (3) When the preparation was stimulated at shorter cycle lengths, the recovery process of PRC was separated into at least two components (fast and slow components). In the diabetic rats, the time constant (tau) of both components was significantly longer than in controls. (4) After caffeine (10(-3) M) treatment, tau of the fast component in the control rats became longer, whereas it remained unchanged in diabetic rats. These findings suggest a dysfunction of the intracellular calcium handling system in spontaneously diabetic heart that is likely to include impaired calcium sequestration and/or extrusion.     

What is critical for plant thermogenesis? Differences in mitochondrial activity and protein expression between thermogenic and non-thermogenic skunk cabbages

Thermogenesis during the blooming of inflorescence is found in several but not all aroids. To understand what is critical for thermogenesis, we investigated the difference between thermogenic and non-thermogenic skunk cabbages (Symplocarpus renifolius and Lysichiton camtschatcensis), which are closely related in morphology and phylogeny. Critical parameters of mitochondrial biogenesis, including density, respiratory activity, and protein expression were compared between these two species. Mitochondrial density, respiratory activity, and the amount of alternative oxidase (AOX) in L. camtschatcensis spadix mitochondria were lower than in S. renifolius spadix mitochondria, while the level of uncoupling protein (UCP) was higher. AOX and UCP mRNAs in L. camtschatcensis were constitutively expressed in various tissues, such as the spadix, the spathe, the stalk, and the leaves. cDNA encoding two putative thermogenic proteins, AOX and UCP were isolated from L. camtschatcensis, and their primary structure was analyzed by multiple alignment and phylogenetic tree reconstruction. AOX and UCP protein of two the skunk cabbage species are closely related in structure, compared with other isoforms in thermogenic plants. Our results suggest that mitochondrial density, respiratory activity, and protein expression, rather than the primary structure of AOX or UCP proteins, may play critical roles in thermogenesis in plants.     

Monoclonal Antibodies to Spirosin of Yersinia enterocolitica and Analysis of the Localization of Spirosome by Use of Them

Two hybridomas producing monoclonal antibodies (MAbs) were prepared by fusing myeloma cells (Sp2/0-Ag14) with mouse spleen cells immunized with purified spirosin from Yersinia enterocolitica SYT-11–72 (YE72). The antibodies produced by them were designated MAbs-S5 and S27. They were IgG_2a and IgG₁, respectively, both with χ light chains. MAbs-S5 and S27 reacted specifically with spirosin from YE72. On Western blotting after limited proteolysis with Staphylococcus aureus V8 protease, YE72 spirosin revealed peptide fragments of 35 and 37 kDa reacting markedly with MAb-S5, which suggested the presence of an antigenic determinant on these fragments. By cellular fractionation of YE72 and subsequent EIA and Western blot analysis, spirosome was shown to be present in the cytoplasm of YE72.