Metabolism of 3H-1α,25-dihydroxyvitamin D3 in cultured human keratinocytes

In the present investigation we studied the metabolism of 1α,25-dihydroxy-[1β-³H] vitamin D₃ (³H-1,25(OH)₂D₃) in culture-grown human keratinocytes (CHK). Our results showed that the cellular uptake of ³H-1,25(OH)₂D₃, upon incubation with CHK, occurred very rapidly; and it paralleled a decrease in the concentration of ³H-1,25(OH)₂D₃ in the medium. The amount of ³H-calcitroic acid, on the other hand, increased slowly in the medium, while the concentration of ³H-calcitroic acid in the cell remained undetectable during the whole period of incubation. When the cells were preincubated with 1,25(OH)₂D₃ (10^?8M), conversion of ³H-1,25(OH)₂D₃ to ³H-calcitroic acid increased almost twofold, indicating that 1,25(OH)₂D₃ catalyzed its own catabolism. © 1995 Wiley-Liss, Inc.     

Aliphatic compounds from Costus speciosus roots

Two new compounds G and H isolated from the roots of Costus speciosus have been characterized as 8-hydroxytriacontan-25-one and Me tritriacontanoat     

Isopongaglabol and 6-methoxyisopongaglabol,two new hydroxyfuranoflavones from Pongamia glabra

Isopongaglabol and 6-methoxyisopongaglabol, two new hydroxyfuranoflavones, together with two furanoflavones 5-methoxyfurano(8,7-4″,5″)flavone and 5-methoxy-3′,4′-methylenedioxyfurano(8,7-4″,5″)flavone, two simple flavones, desmethoxykanugin and fisetin tetramethyl ether, a chromenoflavanone, ovalichromene B, two triterpenes, cycloart-23-ene-3β,25-diol and friedelin, and β-sitosterol-β-d-glucoside were isolated from the petrol and CHCl₃ extracts of the flowers of Pongamia glabra. The structures of isopongaglabol and 6-methoxyisopongaglabol have been established as 4′-hydroxyfurano(8,7-4″,5″)flavone and 4′-hydroxy-6-methoxyfurano(8,7-4″,5″)flavone, respectively, on the basis of the spectral evidence and they have been confirmed by synthesis.     

Conversion of a 24β-ethyl-25-methylene intermediate into poriferasterol by Trebouxia species

Clerosterol-[26-¹⁴C], a 24β-ethyl-25-methylene sterol [(24S)-24-ethylcholesta-5,25-dien-3β-ol], was incorporated into clionasterol and poriferasterol by cultures of the green algae Trebouxia sp. 213/3 and Trebouxia sp. 219/2. Degradation of the labelled poriferasterol showed that the ¹⁴C retained its identity and was not incorporated as a result of metabolism of the clerosterol-[26-¹⁴C] and randomisation of label. These results are consistent with the proposed production, and subsequent reduction, of a 24β-ethyl-25-methylene intermediate in 24β-ethyl sterol biosynthesis in algae of the order Chlorococcales.     

24β-Ethyl-31-norlanosta-8,25(27)-dien-3β-ol and 24β-ethyl-25(27)-dehydrolophenol in seeds of three cucurbitaceae species

The structures of two 4α-methylsterols is isolated from Cucumis sativus(Cucurbitaceae) seeds were determined based mainly on their ¹³CNMR spectra as 24β-ethyl-31-norlanosta-8,25(27)-dien-3β-ol and 24β-ethyl-25(27)- dehydrolophenol, respectively, of which the former is a new sterol from natural sources. These two 4α-methylsterols were identified in the seeds of two other Cucurbitaceae species, Lagenaria leucantha var. Gourda and Citrullus battich. The probable biogenetic significance of the two 4α-methylsterols is discussed. Other 4α-methylsterols identified in the seeds of the three Cucurbitaceae species were obtusifoliol, cycloeucalenol and gramisterol.     

Hormonal effects on diosgenin biosynthesis and growth in Dioscorea deltoidea tissue cultures

Analysis of Dioscorea deltoidea tissue cultures grown in the presence of 2,4-D, indole-3-butyric acid, isopentenyladenine, benzyladenine and GA singly and in combination showed that the medium with 2,4-D most consistently favored diosgenin production. GA and high benzyladenine concentrations were toxic.     

热胁迫对二化螟幼虫血淋巴细胞内活性氧、HSP90及细胞凋亡的影响

为探讨热激条件下二化螟Chilo suppressalis幼虫体内生理上的保护反应,本研究应用流式细胞术分析了热胁迫对二化螟幼虫血淋巴细胞内活性氧（ROS）、热休克蛋白90（HSP90）的产生和对细胞凋亡的影响。结果表明：暴露于33℃,36℃和39℃的二化螟5龄幼虫的ROS与对照（28℃）相比显著提高,分别增加了1.71,1.69和1.38倍;当温度达到33℃以后,ROS不再显著增加。实时定量PCR结果显示,二化螟HSP90基因在热胁迫诱导下表达。流式细胞术检测表明,HSP90的变化与在mRNA水平上的变化高度一致,热胁迫处理没有造成血淋巴细胞凋亡的显著变化。这些研究结果进一步证明热胁迫产生的ROS激活HSP90基因的表达,HSP90蛋白在保护机体免受ROS引起的伤害中起着重要作用,能够抑制血淋巴细胞凋亡的发生。     

PRIP (Phospholipase C-related but Catalytically Inactive Protein) Inhibits Exocytosis by Direct Interactions with Syntaxin 1 and SNAP-25 through Its C2 Domain

Membrane fusion for exocytosis is mediated by SNAREs, forming trans-ternary complexes to bridge vesicle and target membranes. There is an array of accessory proteins that directly interact with and regulate SNARE proteins. PRIP (phospholipase C-related but catalytically inactive protein) is likely one of these proteins; PRIP, consisting of multiple functional modules including pleckstrin homology and C2 domains, inhibited exocytosis, probably via the binding to membrane phosphoinositides through the pleckstrin homology domain. However, the roles of the C2 domain have not yet been investigated. In this study, we found that the C2 domain of PRIP directly interacts with syntaxin 1 and SNAP-25 but not with VAMP2. The C2 domain promoted PRIP to co-localize with syntaxin 1 and SNAP-25 in PC12 cells. The binding profile of the C2 domain to SNAP-25 was comparable with that of synaptotagmin I, and PRIP inhibited synaptotagmin I in binding to SNAP-25 and syntaxin 1. It was also shown that the C2 domain was required for PRIP to suppress SDS-resistant ternary SNARE complex formation and inhibit high K⁺-induced noradrenalin release from PC12 cells. These results suggest that PRIP inhibits regulated exocytosis through the interaction of its C2 domain with syntaxin 1 and SNAP-25, potentially competing with other SNARE-binding, C2 domain-containing accessory proteins such as synaptotagmin I and by directly inhibiting trans-SNARE complex formation.