穿鞘花（鸭跖草科）的核形态

本文对鸭跖草科的穿鞘花Ａｍｉｓｃｈｏｔｏｌｙｐｅｈｉｓｐｉｄａ（ＬｅｓｓｅｔＡ．Ｒｉｃｈ．）Ｈｏｎｇ进行了核形态研究。其静止核和有丝分裂前期染色体分别属于复杂中央染色微粒型和中间型;染色体数目为２ｎ＝３６,核型公式为２ｎ＝４ｍ＋２８ｓｍ＋４ｓｔ。本种的核型为首次报道。     

荸荠营养器官的发育与解剖学研究

荸荠同化茎起源于肉质主茎倒２或倒３叶的叶腋内。同化茎基部着生二鞘状叶,鞘状叶对早期同化茎穿出土面具保护作用。匍匐茎大多起源于同化茎基部鞘状叶的叶腋内。当植株开始抽生花茎时,地下匍匐茎顶端开始膨大。球茎的膨大是匍匐茎顶端５－６节的基本组织经细胞有丝分裂,增加细胞数目,然后由细胞体积的扩大来实现的。球茎具足够的营养物质供来年顶芽萌发的需要,故属水生植物冬芽的性质。     

美口菌属二新种

本文报道了美口菌属 Calostoma Desv.的两个新种:云南美口菌 Calostoma yunnanensisL.J.Li et Liu sp.nov.和彭氏美口菌 Calostoma pengii Liu et Y.H.Liu sp.nov.     

Assessment of a model for intron RNA secondary structure relevant to RNA self-splicing--a review

A widespread class of introns is characterized by a particular RNA secondary structure, based upon four conserved nucleotide sequences. Among such "class I" introns are found the majority of introns in fungal mitochondrial genes and the self-splicing intron of the large ribosomal RNA of several species of Tetrahymena. A model of the RNA secondary structure, which must underlie the self-splicing activity, is here evaluated in the light of data on 16 further introns. The main body or "core structure" of the intron always consists of the base-paired regions P3 to P9 with the associated single-stranded loops, with P2 present also in most cases. Two minority sub-classes of core structure occur, one of which is typical of introns in fungal ribosomal RNA. Introns in which the core structure is close to the 5' splice site all have an internal guide sequence (IGS) which can pair with exon sequences adjacent to the 5' and 3' splice sites to align them precisely, as proposed by Davies et al. [Nature 300 (1982) 719-724]. In these cases, the internal guide model allows us to predict correctly the exact location of splice sites. All other introns probably use other mechanisms of alignment. This analysis provides strong support for the RNA splicing model which we have developed.     

Distributional patterns and an additional species of thePassiflora vitifolia complex: Amazonian species diversity due to edaphically differentiated communities

Field studies in Amazonian Peru show that thePassiflora vitifolia complex, a microcosm of many larger taxa, is concentrated in Amazonia with 4 ecologically separated species. One species is restricted to seasonally inundated forests, a second to non-inundated white sand soils, a third to non-inundated lateritic soils, and the fourth mostly to non-inundated alluvial soils. A new combination is formally proposed to recognize the white sand taxon, previously regarded as a variety, as a distinct species:P. involucrata. The importance of -diversity in maintaining high Amazonian species diversity is emphasized.     

Two Possibly Distinct Prostaglandin E1 Receptors in N1E-115 Clone: One Mediating Inositol Trisphosphate Formation, Cyclic GMP Formation, and Intracellular Calcium Mobilization and the Other Mediating Cyclic AMP Formation

Prostaglandin E1 (PGE1)-mediated transmembrane signal control systems were investigated in intact murine neuroblastoma cells (clone N1E-115). PGE1 increased intracellular levels of total inositol phosphates (IP), cyclic GMP, cyclic AMP, and calcium ([Ca2+]i). PGE1 transiently increased inositol 1,4,5-trisphosphate formation, peaking at 20 s. There was more than a 10-fold difference between the ED50 for PGE1 at cyclic AMP formation (70 nM) and its ED50 values at IP accumulation (1 microM), cyclic GMP formation (2 microM), and [Ca2+]i increase (5 microM). PGE1-mediated IP accumulation, cyclic GMP formation, and [Ca2+]i increase depended on both the concentration of PGE1 and extracellular calcium ions. PGE1 had more potent intrinsic activity in cyclic AMP formation, IP accumulation, and cyclic GMP formation than did PGE2, PGF2 alpha, or PGD2. A protein kinase C activator, 4 beta-phorbol 12 beta-myristate 13 alpha-acetate, had opposite effects on PGE1-mediated IP release and cyclic GMP formation (inhibitory) and cyclic AMP formation (stimulatory). These data suggest that there may be subtypes of the PGE1 receptor in this clone: a high-affinity receptor mediating cyclic AMP formation, and a low-affinity receptor mediating IP accumulation, cyclic GMP formation, and intracellular calcium mobilization.     

Classical Conditioning-Induced Changes in Low-Molecular-Weight GTP-Binding Proteins in Rabbit Hippocampus

Classical conditioning of Hermissenda, involving paired light-rotation events, results in a 30-35% decrease in the levels of a 20-kDa G protein (cp20). To test whether a similar protein exists in vertebrates, rabbits were trained to associate a tone with periorbital electrical stimulation and G proteins were analyzed by photoaffinity labeling with [alpha-32P]GTP-azidoanilide. A 20-kDa G protein similar to cp20 decreased by 36% in the hippocampus of rabbits subjected to paired tone and electrical stimulation, but not in unpaired controls. Learning-specific decreases were also found in the amount of ras protein.     

Synergistic Regulation of Cytosolic Ca2+ Concentration in Mouse Astrocytes by NK1 Tachykinin and Adenosine Agonists

The effects on cytosolic Ca2+ concentration of 2-chloroadenosine and [L-Pro9]-substance P, a selective agonist of NK1 receptors, were investigated on astrocytes from embryonic mice in primary culture. Cells responded to [L-Pro9]-substance P with a transitory increase in cytosolic Ca2+ which was of shorter duration when external Ca2+ was removed. A transient response to 2-chloroadenosine alone occurred. When simultaneously applied, [L-Pro9]-substance P and 2-chloroadenosine evoked a prolonged elevation of cytosolic Ca2+ (up to 30 min). This phenomenon was dependent on the presence of extracellular Ca2+, but insensitive to dihydropyridines, La3+, and Co2+, excluding the implication of voltage-operated Ca2+ channels. Arachidonic acid also induced a sustained elevation of cytosolic Ca2+, but did not increase further the response evoked by [L-Pro9]-substance P and 2-chloroadenosine. The activation of protein kinase C by a diacylglycerol analogue mimicked the effect of [L-Pro9]-substance P in potentiating the 2-chloroadenosine-evoked response. Like 2-chloroadenosine, pinacidil, which hyperpolarizes the cells by opening K+ channels, prolonged the elevation of cytosolic Ca2+ concentration induced by [L-Pro9]-substance P. Conversely, depolarization with 50 mM KCl canceled the effects of either pinacidil or 2-chloroadenosine applied with [L-Pro9]-substance P. Pertussis toxin pretreatment suppressed all the effects induced by 2-chloroadenosine.