Bioactive jatrophane diterpenes from Euphorbia guyoniana

Chromatographic investigation of the methylenechloride/methanol extract of the aerial parts of Euphorbia guyoniana afforded two jatrophane diterpenes, designated guyonianins E and F, in addition to a known jatrophane diterpene. The structures of the compounds were determined by comprehensive NMR analyses, including DEPT, COSY, HMQC, HMBC, NOESY and HRMS. These compounds exhibited cytotoxicity against human embryonic kidney 293 (HEK293) cells with IC₅₀ values of 35–100 μM.     

Prolamellar body and saponins: Avenacosides are not constituents of Avena etioplasts

Etiolated Avena leaf cells were homogenized, then fractionated into four fractions in the presence of salts by differential centrifugation, and intact etioplasts were prepared by Percoll or sucrose density gradient centrifugation. Using thin layer chromatography steroidal saponins, avenacoside A and B were found in the leaf cells and heavy cell fractions which were rich in other cell structures besides intact etioplasts, but not detected in the purified etioplasts. We concluded that saponins are not constituents of the prolamellar bodies in etioplasts.     

Nuclear magnetic resonance evidence for the dimer formation of beta amyloid peptide 1–42 in 1,1,1,3,3,3-hexafluoro-2-propanol

Alzheimer's disease involves accumulation of senile plaques in which filamentous aggregates of amyloid beta (Aβ) peptides are deposited. Recent studies demonstrate that oligomerization pathways of Aβ peptides may be complicated. To understand the mechanisms of Aβ(1–42) oligomer formation in more detail, we have established a method to produce ¹⁵N-labeled Aβ(1–42) suited for nuclear magnetic resonance (NMR) studies. For physicochemical studies, the starting protein material should be solely monomeric and all Aβ aggregates must be removed. Here, we succeeded in fractionating a “precipitation-resistant” fraction of Aβ(1–42) from an “aggregation-prone” fraction by high-performance liquid chromatography (HPLC), even from bacterially overexpressed Aβ(1–42). However, both Aβ(1–42) fractions after 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) treatment formed amyloid fibrils. This indicates that the “aggregation seed” was not completely monomerized during HFIP treatment. In addition, Aβ(1–42) dissolved in HFIP was found to display a monomer–dimer equilibrium, as shown by two-dimensional ¹H–¹⁵N NMR. We demonstrated that the initial concentration of Aβ during the HFIP pretreatment altered the kinetic profiles of Aβ fibril formation in a thioflavin T fluorescence assay. The findings described here should ensure reproducible results when studying the Aβ(1–42) peptide.     

On the three-dimensional structure of quick-frozen hepatic Mallory bodies with special reference to the appearance of cytoplasmic vesicles.

Livers containing Mallory bodies (MBs, hyalin degenerative cytoplasmic inclusions) were examined using Heuser's and Van Harreveld's cryo-techniques. The tissues were collected from 1) a patient suffering from alcoholic hepatitis and 2) mice treated with griseofulvin (GF, an anti-mitotic drug). Normal mouse liver and isolated MBs from GF-treated mice were also analyzed by the same methods. Our results suggest that under the toxic influence of alcohol or GF on microtubular elements, MBs are generated by entanglement of elements of 10 nm filaments with microtubule elements. This in turn inhibits cellular transport processes. The reticular net of the ER-element which is usually observable in the normal tissue is changed into numerous small vesicles in the pathological and experimental tissues. The diameters of hepatocytes containing these vesicles were 1.5 to 2 times larger than control diameters. MBs have previously been described in thin sections as filamentous tangles. On replicas we found that they appear to be composed of pairs of filaments twisted in a roughly helical manner, each having a diameter less than 10 nm. The paired helical nature of the MB-filaments is reminiscent of other inclusion bodies, which are also composed of elements of 10 nm filaments, observable in various neurological diseases.