Role ofDrosophila TRP in inositide-mediated Ca2+ entry

Inositol lipid signaling relies on an InsP₃-induced Ca²⁺ release from intracellular stores and on extracellular Ca²⁺ entry, which takes place when the Ca²⁺ stores become depleted of Ca²⁺. This interplay between Ca²⁺ release and Ca²⁺ entry has been termed capacitative Ca²⁺ entry and the inward current calcium release activated current (CRAC) to indicate gating of Ca²⁺ entry by Ca²⁺-store depletion. The signaling pathway and the gating mechanism of capacitative Ca²⁺ entry, however, are largely unknown and the molecular participants in this process have not been identified. In this article we review genetic, molecular, and functional studies of wild-type and mutantDrosophila photoreceptors, suggesting that thetransient receptor potential mutant (trp) is the first putative capacitative Ca²⁺ entry mutant. Furthermore, several lines of evidence suggest that thetrp gene product TRP is a candidate subunit of the plasma membrane channel that is activated by Ca²⁺ store depletion.     

A general assay for restriction endonucleases and other DNA-modifying enzymes with plasmid substrates

A procedure for measuring the activities of enzymes that alter the covalent structure of DNA is described. The assay utilizes covalently closed circles of DNA as the substrate and yields quantitative data on the fraction of this DNA converted to both open-circle and linear forms.     

Epidermal growth factor,phorbol esters,and aurintricarboxylic acid are survival factors for MDA-231 cells exposed to adriamycin

Summary The ability of epidermal growth factor (EGF), insulinlike growth factor-1 (IGF-1), insulin, 12-O-tetradecanoylphorbol-13-acetate (TPA), and aurintricarboxylic acid (ATA) to protect the human breast cancer cell line MDA-231 from death induced by the anticancer drug adriamycin was investigated. Cell death was induced in the MDA-231 cells either by a short-time exposure to a high dose of adriamycin (2 μg · ml⁻¹ · 1 h⁻¹) and further culturing in the absence of the drug, or by continuous exposure to a low dose of adriamycin (0.3μg/ml). Cell death was evaluated after 48 h of incubation by several techniques (trypan blue dye exclusion, lactic dehydrogenase activity, cellular ATP content, transmission electron microscopy, and DNA fragmentation). EGF, TPA, and ATA, each at an optimal concentration of 20 ng/ml, 5 ng/ml, and 100μg/ml respectively, substantially enhanced survival of cells exposed either to a high or low dose of adriamycin. Neither IGF-1 nor insulin, each at concentrations of 20 ng/ml, had an effect on cell survival. The three survival factors enhanced protein synthesis in the untreated cells and attenuated the continuous decrease in protein synthesis in the adriamycin-treated cells. Moreover, the three survival factors protected the MDA-231 cells from death in the absence of protein synthesis (cycloheximide 30μg/ml). These results suggest that EGF, TPA, and ATA promote survival of adriamycin pretreated cells by at least two mechanisms: enhancement of protein synthesis and by a protein synthesis independent process, probably a posttranslational modification effect.     

Extracellular Neuroactive Amino Acids in the Rat Striatum During Ischaemia: Comparison Between Penumbral Conditions and Ischaemia with Sustained Anoxic Depolarisation

Abstract: Changes in the extracellular levels of excitatory and inhibitory amino acid transmitters were studied in the rat striatum during penumbral ischaemia using intracerebral microdialysis. Effects of penumbral forebrain ischaemia were compared with those of ischaemia with sustained anoxic depolarisation and K⁺ (100 m M ). Comparisons were also made between different groups of animals at 2 and 24 h after dialysis probe implantation. The K⁺ stimulus did not provoke any release of excitatory amino acids in the 24-h group, probably reflecting a decrease of functional synapses adjacent to the probe. During 30 min of penumbral ischaemia, excitatory amino acids did not reach critical concentrations in the extracellular fluid, and increases in levels of inhibitory/modulatory amino acids were similar. On the other hand, severe transient ischaemia resulted in massive synchronous release of many neuroactive excitatory and inhibitory compounds, in both the 2- and 24-h groups. These and other data suggest that changes during severe ischaemia may arise from both neurotransmitter and metabolic pools. It is concluded that is- chaemic damage in the penumbra may not be related to extracellular neuroactive amino acid changes generated within this region.     

FUNCTIONAL DIOECY AND ANDROMONOECY IN SOLANUM

Field and laboratory studies of 19 diclinous species endemic to Australia help to clarify the nature and evolution of andromonoecy, androdioecy, and dioecy in the genus Solanum. Ten species are andromonoecious; typically these species bear inflorescences with a single, large basal hermaphroditic flower and 12–60 distal, smaller staminate flowers. We suggest that the andromonoecious condition was derived from hermaphroditic-flowered ancestors in part by hemisterilization of flowers but largely by addition of staminate flowers. The resultant larger inflorescences are hypothesized to serve both to attract and to entrain pollinators, yielding more or higher-quality seed set in hermaphroditic flowers and/or greater dispersion of pollen from staminate flowers. We suggest that andromonoecy may also serve to reduce selling. Nine other species are morphologically androdioecious but functionally dioecious. In these species, staminate flowers, like those of the andromonoecious species, bear anthers with copious tricolporate pollen and a highly reduced gynoecium. The morphologically hermaphroditic flowers are functionally pistillate and borne singly in inflorescences, and they bear anthers with inaperturate pollen. The inaperturate pollen, although viable, never germinates and is hypothesized to be retained in pistillate flowers as a reward to pollinators in the nectarless Solanum flowers. All other species of Solanum studied with pollen dimorphism in which one pollen morph is inaperturate are also best treated as functionally dioecious. We conclude that there is no evidence for androdioecy in Solanum. A review of other families suggests that there is little support for this unusual breeding system in any other angiosperm group either. Preliminary analyses suggest that andromonoecy and dioecy are polyphyletic in Solanum. Furthermore, dioecy is as likely to have arisen from hermaphroditic as from andromonoecious ancestors.     

Backbone Cyclization of the C-terminal Part of Substance P. Part 1: The Important Role of the Sulphur in Position 11

Novel backbone-to-side chain and backbone-to-backbone cyclic analogues of substance P (SP) were prepared by solid-phase synthesis and screened for biological activity. An analogue containing a thioether- lactam ring between positions 9 and 11 showed an EC₅₀ value of 20nM toward the neurokinin 1 (NK-1) and was inactive toward the NK-2 and NK-3 receptors. On the other hand, in a multiple backbone cyclic peptide library of similar analogues, in which the sulphur was excluded from the ring, very low activity was detected. The activity was re-evaluated and was found to be even lower (EC₅₀=0.11 mM ) than the previously published data. These results indicate that the thioether moiety has a crucial role in receptor activation. The results also show tolerance of the NK-1 receptor, but not NK-2 or NK-3, to cyclization of the C-terminal portion of the SP_6–11 hexapeptide.     

Parietochloris incisa comb. nov. (Trebouxiophyceae, Chlorophyta)

A coccoid green alga, Myrmecia incisa Reisigl, was isolated from the soil of Mt Tateyama, Japan. Electronmicroscopy revealed that the organism has pyrenoids sparsely covered with starch segments and traversed by many parallel thylakoid membranes, and zoo-spores with counterclockwise basal body orientation. Due to the presence of these features, we have proposed a reclassification of M. incisa into the genus Parietochloris, Trebouxiophyceae.     

SINGLE-CELL PIGMENTATION OF PORPHYRA LINEARIS ANALYZED BY FOURIER TRANSFORM MULTI-PIXEL SPECTROSCOPY AND IMAGE ANALYSIS1

The novel method of Fourier transform multi-pixel spectroscopy was used for the nondestructive analysis of and comparison of pigmentation in different regions of live thalli of the red alga Porphyra linearis. Because the thallus in this alga consists of a monolayer of nonoverlapping cells, we were able to analyze the pigmentation of single cells by combining light absorbance with natural fluorescence data. From the image of each cell in the vegetative male and female reproductive and holdfast regions, more than 4 ± 10⁴ fluorescence and absorbance spectra were obtained. Specific pigments in the different regions were localized by the use of a software program of similarity mapping followed by image construction. The reconstructed images revealed subcellular localization of each pigment according to specific spectroscopic fingerprints. The results showed that the vegetative and female reproductive cell types had a significantly higher content of phycoerythrin than of phycocyanin, and quite similar chlorophyll a levels. Most of the holdfast cells were poorly pigmented, but had more chlorophyll a than phycoerythrin or phycocyanin. The male reproductive cells contained only traces of pigments. Thus, by using Fourier transform multipixel spectroscopy, we were able to characterize the pigmentation of different regions of the thallus and follow the distribution patterns of the different pigments on the subcellular level along the differentiation gradient of the alga.     

A defective conditioned behavior and a defective adenylate cyclase in theDrosophila mutantrutabaga

Summary TheDrosophila X-linked mutantrutabaga (Duerr and Quinn 1982) fails to perform normally in olfactory conditioning paradigms, in spite of being able to sense odorants and shock (Figs. 1–3).rut is capable of forming an association between shock and odorant, but memory decays rapidly; the memory of the mutant following intensive training resembles that of normal flies following very brief training (Fig. 4).rut flies also display in vitro a defective adenylate cyclase activity (Fig. 6). The enzyme in the mutant is responsive to stimulation by a putative neurotransmitter and by a guanyl nucleotide (Fig. 8) but the activity is lower than normal even in the presence of forskolin (Fig. 8) and MnATP (Fig. 9), suggesting that the lesion is closely associated with the function of the catalytic subunit.rut/ + heterozygotes are semi-recessive with regard to both the behavioral defect and the biochemical defect (Figs. 5, 7). The behavioral and the biochemical lesions detected inrut flies are discussed in light of current molecular models of learning.     

Smoking and subarachnoid haemorrhage.

A retrospective study of 208 patients with ruptured cerebral aneurysms showed a highly significant excess of cigarette smokers among both men and women compared with the expected incidence. Results suggested that continued smoking increases the risk of suffering a subarachnoid haemorrhage (SAH) by a factor of 3.9 for men and 3.7 for women. Other factors besides smoking must affect the genesis of aneurysmal SAH since it is found in non-smokers, but continued cigarette smoking appears to increase substantially the risk of aneurysmal SAH occurring.