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PubMed1984

Response of Earth's atmosphere to increases in solar flux and implications for loss of water from Venus.

A one-dimensional radiative-convective model is used to compute temperature and water vapor profiles as functions of solar flux for an Earth-like atmosphere. The troposphere is assumed to be fully saturated, with a moist adiabatic lapse rate, and changes in cloudiness are neglected. Predicted surface temperatures increase monotonically from -1 to 111 degrees C as the solar flux is increased from 0.81 to 1.45 times its present value. Surface temperatures corresponding to high solar fluxes may be underestimated, however, owing to neglect of H2O continuum absorption outside of the 8- to 12-micrometers window region. These results imply that the surface temperature of a primitive water-rich Venus should have been at least 80-100 degrees C and may have been much higher. The existence of liquid water at the surface depends on poorly known aspects of H2O continuum absorption and on uncertainties concerning relative humidity and cloudiness. In any case, water vapor should have been a major atmospheric constituent at all altitudes, leading to the rapid hydrodynamic escape of hydrogen. The oxygen left behind by this process was presumably consumed by reactions with reduced minerals in the crust. Both the loss of oxygen and the presently observed enrichment of the deuterium-to-hydrogen ratio are most easily explained if oceans of liquid water were initially present.

Atmosphere↗
PubMed2003

The Ancient Mariner and the transit of Venus.

The achievements of William Wales FRS - astronomer, classical scholar, demographer, editor, mathematician, meteorologist and humane teacher - have been overshadowed by the fame of Cook's extraordinary voyages, and overlooked as a significant influence on Samuel Taylor Coleridge's early development. The Royal Society sent Wales to Hudson Bay, Canada, and James Cook to Tahiti, both to observe the 1769 transit of Venus as part of an international project to calculate solar parallax, and hence the distance to the Sun. Wales later taught mathematics and navigation science at Christ's Hospital School to a precocious Coleridge, whose creative mind translated tales of polar adventures into memorable poetry.

Canada↗
PubMed2001

Production of nitrogen oxides by lightning and coronae discharges in simulated early Earth, Venus and Mars environments.

We present measurements for the production of nitrogen oxides (NO and N2O) in CO2-N2 mixtures that simulate different stages of the evolution of the atmospheres of the Earth, Venus and Mars. The nitrogen fixation rates by two different types of electrical discharges, namely lightning and coronae, were studied over a wide range in CO2 and N2 mixing ratios. Nitric oxide (NO) is formed with a maximum energy yield estimated to be ~1.3 x 10(16) molecule J-1 at 80% CO2 and ~1.3 x 10(14) molecule J-1 at 50% CO2 for lightning and coronae discharges, respectively. Nitrous oxide (N2O) is only formed by coronae discharge with a maximum energy yield estimated to be ~1.2 x 10(13) molecule J-1 at 50% CO2. The pronounced difference in NO production in lightning and coronae discharges and the lack of formation of N2O in lightning indicate that the physics and chemistry involved in nitrogen fixation differs substantially in these two forms of electric energy.

Atmosphere↗
PubMed1960

The responses of the Venus heart to catechol amines and high concentration of 5-hydroxytryptamine.

The catechol amines excite the isolated heart of Venus mercenaria in a characteristic manner. This response was not obtained with phenethylamine, tyramine, ephedrine, or mescaline, nor with histamine, nor with the basic n-alkylamines. 5-Hydroxytryptamine had a distinctive effect at high concentrations (above 3x10(-6) M) different from that at lower doses. The response to high concentrations was dominated by an increase in muscle tone. Hearts exposed to high concentrations of 5-hydroxytryptamine and other tryptamine analogues for long periods became tachyphylactic to low doses of these substances. However, high doses of 5-hydroxytryptamine (about 2x10(-5) M) still excited the tachyphylactic heart, but the response was then like that to the catechol amines. When high bath temperatures rendered the heart insensitive to 5-hydroxytryptamine, high concentrations of this compound again had the catechol amine effect. The possibility of a physiological role for the catechol amines or high 5-hydroxytryptamine concentrations is discussed.

Amines↗
PubMed1960

Structure-activity relationship of tryptamine analogues on the heart of Venus mercenaria.

A number of tryptamine analogues and other exciter agents have been tested on the heart of Venus mercenaria. The method of estimation of potency, especially for irreversibly acting compounds, is discussed. Specificity of action with respect to the site of action of 5-hydroxytryptamine is defined experimentally. The specific activity of tyramine and phenethylamine and the non-specific excitatory action of indole and skatole indicate that the indole ring is neither necessary nor sufficient for 5-hydroxytryptamine-like activity. Tryptamine analogues differ in mode of action as well as potency. Congeners without a 5-hydroxyl group tend to act more slowly and irreversibly as well as less strongly than 5-hydroxytryptamine. Methyl substitution also increases the time of action and difficulty of reversal. However, the potency of such compounds may be increased or decreased depending upon the position of substitution and the presence of the 5-hydroxyl group. The relations between structure and potency and mode of action are discussed. Suggestions are made concerning the effective conformation of the 5-hydroxytryptamine molecule and the nature of its receptor.

Animals↗
PubMed1962

Actions of derivatives of lysergic acid on the heart of Venus mercenaria.

5-Hydroxytryptamine and a number of (+)-lysergic acid derivatives have been tested on the heart of Venus mercenaria. One group of derivatives was found to increase the amplitude and frequency of heart beat in a manner much like 5-hydroxytryptamine. It included the monoethylamide, diethylamide, propanolamide (ergometrine), butanolamide (methylergometrine) and certain peptide derivatives of lysergic acid without substituents in positions 1 or 2. Of these, lysergic acid diethylamide was the most active. Given sufficient time (up to 4 hr), as little as 10 ml. of 10(-16) M lysergic acid diethylamide produced a maximum increase in amplitude and frequency in about one-half of the 80 hearts on which it was tested. Its action was very slowly reversed by washing, as was true of all lysergic acid derivatives. A second group of lysergic acid derivatives, substituted in positions 1 or 2, had weak excitor action, if any, and specific 5-hydroxytryptamine blocking action. This group consisted of 1-methyl-, 1-acetyl-, and 2-bromo-lysergic acid diethylamide and 1-methyllysergic acid butanolamide (methysergide). Of these, the last showed least signs of excitor action, usually none up to 10(-4) M, and it blocked 5-hydroxytryptamine in a molar ratio of about one to one.

Animals↗
PubMed1999

Overtone Transitions of 12CO2 beyond the Venus Bands.

Combination overtone transitions of 12CO2 much weaker than the Venus bands in the near infrared (11 700-14 200 cm-1) have been observed for the first time by using photoacoustic spectroscopy. A total of six bands from two Fermi polyad groups were recorded and both the band origins and relative intensities have been determined and compared with the calculated values. Through a comparison of the relative absorption cross sections within the same type of polyads, intensity shifts have been observed and will be discussed. Copyright 1999 Academic Press.

Journal Article↗
PubMed1991

The Venus of Milo and the dawn of facial asymmetry research.

The dawn of facial asymmetry research dates back to the second half of the last century and started with a discussion about the asymmetry of the face of the Venus of Milo. These early observations revealed some of the lateralized patterns of the two facial halves of which we are now aware. Since these studies have up until now been completely neglected, the present review tries to provide the forgotten beginning of this avenue of lateralization research.

Facial Asymmetry↗
PubMed2005

Elimination of environmental sensitivity in a cameleon FRET-based calcium sensor via replacement of the acceptor with Venus.

Genetically encoded sensors are becoming a powerful tool for investigating cellular signaling pathways and, potentially, signaling in vivo. Many sensors use changes in fluorescence resonance energy transfer (FRET) between donor and acceptor variants of GFP separated by a ligand binding domain sensitive to a particular signaling pathway. Accurate measurements require that sensors be insensitive to extraneous intracellular environmental factors. We have found that the responsiveness of the Ca(2+) sensor, cameleon YC6.1, varies linearly with the resting YFP/CFP emission ratio in the cell. However, cells expressing responsive or non-responsive sensor can easily be segregated by determining a resting YFP/CFP ratio cutoff for the sensor. This environmental sensitivity has been eliminated by replacing EYFP with Venus to produce a new cameleon we have designated VC6.1. Measurements show that VC6.1 has a greater dynamic range than YC6.1 and better environmental resistance. We also show that YC6.1 is inactivated by persistent activation of the IP(3) pathway following expression of constitutively active G(q), while VC6.1 is not. The stability of VC6.1 may make it well suited to studies utilizing mixed cell populations such as those encountered in vivo.

Animals↗
PubMed2006

Phylogeny of venus clams (Bivalvia: Venerinae) as inferred from nuclear and mitochondrial gene sequences.

Venerinae (Heterodonta: Veneridae) is a diverse, commercially important, and cosmopolitan marine bivalve subfamily. Recent workers synonymized it with the subfamily Chioninae, due to their overall morphological similarity. The use of traditional shell-based characters alone, however, is questionable for resolving phylogenetic relationships of this group. A phylogenetic study was carried out, based on nucleotide sequences of the mitochondrial large ribosomal subunit (16S), cytochrome oxidase subunit I (COI), and the nuclear protein-coding gene histone 3, to investigate the relationships and circumscription of Venerinae and the phylogenetic pattern of characters in this group. This study consists of a total of 55 taxa: 13 venerine genera, 24 chionine taxa, and 18 taxa of other venerid subfamilies. We analyzed the alignments using a Bayesian approach using Markov Chain Monte Carlo tree sampling and maximum parsimony methods. The resulting phylogenetic hypothesis suggests that Chioninae and Venerinae are actually discrete taxa, but that the circumscription suffered from misplacement of some genera. Our analysis showed that the former chionine genera Chamelea and Clausinella should be placed in Venerinae, as sister taxa to Venus. We re-analyzed morphological and anatomical features in light of the molecular data to describe monophyletic entities. Features of the hinge and internal shell as well as the degree of siphonal fusion are identified as characters to morphologically distinguish the two subfamilies. Of the three genes used in this study, only COI (commonly used as "barcoding" gene) posed substantial problems in obtaining sequence data from older museum material.

Animals↗
PubMed1986

Purification and kinetic studies of an alpha-L-fucosidase of Venus mercenaria.

An alpha-L-fucosidase activity has been isolated from the liver (hepatopancreas) of the common edible clam, Venus mercenaria, and has been purified approximately 300-fold (11% yield) by affinity chromatography on agarose-epsilon-amino-caproylfucosamine. Isoelectric focusing profiles were heterogeneous, revealing several isoenzymes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated the presence of a single subunit of Mr 50,000. The purified enzyme preparation contained only trace amounts of other alpha- and beta-D-glycosidases tested. In addition to p-nitrophenyl alpha-L-fucopyranoside, the enzyme hydrolyzed natural substrates such as fucose-containing milk pentasaccharides, thyroglobulin glycopeptides, human salivary glycoproteins, and blood-group-active glycosphingolipids. The enzyme preparation had a broad pH optimum range between 4.5 and 5.5. The apparent Km value with respect to p-nitrophenyl alpha-L-fucopyranoside was 0.26mM.

Animals↗
PubMed2003

Nitric oxide-mediated arachidonic acid release from perifused Venus verrucosa oocytes.

This study was undertaken in order to investigate the possible interactions between nitric oxide and arachidonic acid (AA) in Venus verrucosa oocytes. We perifused isolated oocytes to determine the effect of the following substances on [3H]arachidonic acid release ([3H]AA): (1) A 23187, a calcium ionophore; (2) nitric oxide (NO) donors; (3) 1,1,1-trifluoromethyl-6,9,12,15 heicosatetraen-2-one (AACOCF(3)), a specific phospholipase A(2) (PLA(2)) inhibitor; (4) [5'-hydroxymethyl-2'-furyl]-1-benzyl indazole (YC-1) and 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one (ODQ), specific soluble guanylyl cyclase activator and inhibitor, respectively; (5) L-arginine, the substrate of nitric oxide synthase; (6) L-nitroarginine methyl esther (L-NAME), an inhibitor of nitric oxide synthase. Our results demonstrated that: (a) the calcium ionophore dose-dependently increased [3H]arachidonic acid release; (b) the NO donors sodium nitroprusside (SNP) and linsidomine (SIN-1) highly increased [3H]arachidonic acid output, while S-nitroso-N-acetylpenicillamine (SNAP) was without effect; (c) AACOCF(3) completely blocked the [3H]arachidonic acid release induced by SNP and SIN-1; (d) YC-1 increased [3H]arachidonic acid release, while ODQ completely counteracted SNP response; (e) [3H]arachidonic acid output was also increased by L-arginine; (f) a similar effect was, paradoxically, obtained in the presence of L-NAME. Furthermore, using RT-PCR we demonstrated in the same cells the presence of a nitric oxide synthase (NOS) mRNA, whose expression was not modulated by interleukin 1beta (IL-1beta). These results demonstrate the presence of a both calcium-dependent and NO-sensitive PLA(2) and of nitric oxide synthase in V. verrucosa oocytes. Our data also suggest a co-action of the two pathways in the control of reproduction in this bivalve.

Animals↗
PubMed2003

An unusual receptor tyrosine kinase of Schistosoma mansoni contains a Venus Flytrap module.

Previous studies have suggested that successful development of the parasitic helminth Schistosoma mansoni must be dependent on an adaptative molecular dialogue with its hosts and on the existence of receptors for growth factors and hormones. Attempts to identify a homolog of the insulin receptor (IR) have led us to characterize a new receptor tyrosine kinase (RTK) molecule in S. mansoni. SmRTK-1 is an integral membrane protein with a single membrane-spanning sequence separating an extracellular ligand-binding domain and a cytoplasmic TK domain. Structural and phylogenetic analyses of the kinase domain of SmRTK-1 confirmed its similarity to IR catalytic domains. However, sequence analysis of the extracellular domain of SmRTK-1 revealed similarity with various proteins (such as drug receptors) that share a structure known as the Venus Flytrap (VFT) module. Alignment with other VFT modules for which the structure has been solved was used to generate a 3D model of the putative VFT module of SmRTK-1. Phylogenetic analysis indicated that the SmRTK-1 VFT module was closer to that of the GABA(B) receptor. Numerous RTK genes recently discovered in vertebrate and invertebrate species code for large families of modular proteins with diverse structures and ligand-binding specificities. SmRTK-1 probably represents a new class of RTK whose function remains to be determined. RTKs are present in all metazoans and associated with the control of metabolism, growth and development. The preferential localization of SmRTK-1 in sporocyst germinal cells and ovocytes could be in favor of its function in schistosome growth and differentiation.

Amino Acid Sequence↗
PubMed2001

Old iron, young copper: from Mars to Venus.

Iron and copper are metals which play an important role in the living world. From a brief consideration of their chemistry and biochemistry we conclude that the early chemistry of life used water soluble ferrous iron while copper was in the water-insoluble Cu(I) state as highly insoluble sulphides. The advent of oxygen was a catastrophic event for most living organisms, and can be considered to be the first general irreversible pollution of the earth. In contrast to the oxidation of iron and its loss of bioavailability as insoluble Fe(III), the oxidation of insoluble Cu(I) led to soluble Cu(II). A new iron biochemistry became possible after the advent of oxygen, with the development of chelators of Fe(III), which rendered iron once again accessible, and with the control of the potential toxicity of iron by its storage in a water soluble, non-toxic, bio-available storage protein (ferritin). Biology also discovered that whereas enzymes involved in anaerobic metabolism were designed to operate in the lower portion of the redox spectrum, the arrival of dioxygen created the need for a new redox active metal which could attain higher redox potentials. Copper, now bioavailable, was ideally suited to exploit the oxidizing power of dioxygen. The arrival of copper also coincided with the development of multicellular organisms which had extracellular cross-linked matrices capable of resisting attack by oxygen free radicals. After the initial 'iron age' subsequent evolution moved, not towards a 'copper age', but rather to an 'iron-copper' age. In the second part of the review, this symbiosis of iron and copper is examined in yeast. We then briefly consider iron and copper metabolism in mammals, before looking at iron-copper interactions in mammals, particularly man, and conclude with the reflection that, as in Greek and Roman mythology, a better understanding of the potentially positive interactions between Mars (iron) and Venus (copper) can only be to the advantage of our species.

Animals↗
PubMed2002

Closure of the Venus flytrap module of mGlu8 receptor and the activation process: Insights from mutations converting antagonists into agonists.

Ca2+, pheromones, sweet taste compounds, and the main neurotransmitters glutamate and gamma-aminobutyric acid activate G protein-coupled receptors (GPCRs) that constitute the GPCR family 3. These receptors are dimers, and each subunit has a large extracellular domain called a Venus flytrap module (VFTM), where agonists bind. This module is connected to a heptahelical domain that activates G proteins. Recently, the structure of the dimer of mGlu1 VFTMs revealed two important conformational changes resulting from glutamate binding. First, agonists can stabilize a closed state of at least one VFTM in the dimer. Second, the relative orientation of the two VFTMs in the dimer is different in the presence of glutamate, such that their C-terminal ends (which are connected to the G protein-activating heptahelical domain) become closer by more than 20 A. This latter change in orientation has been proposed to play a key role in receptor activation. To elucidate the respective role of VFTM closure and the change in orientation of the VFTMs in family 3 GPCR activation, we analyzed the mechanism of action of the mGlu8 receptor antagonists ACPT-II and MAP4. Molecular modeling studies suggest that these two compounds prevent the closure of the mGlu8 VFTM because of ionic and steric hindrance, respectively. We show here that the replacement of the residues responsible for these hindrances (Asp-309 and Tyr-227, respectively) by Ala allows ACPT-II or MAP4 to fully activate the receptors. These data are consistent with the requirement of the VFTM closure for family 3 GPCR activation.

Amino Acid Sequence↗
PubMed1980

Chemical composition of Earth, Venus, and Mercury.

Model compositions of Earth, Venus, and Mercury are calculated from the premise that planets and chondrites underwent four identical fractionation processes in the solar nebula. Because elements of similar properties stay together in these processes, five constraints suffice to define the composition of a planet: mass of the core, abundance of U, and the ratios K/U, Tl/U, and FeO/(FeO + MgO). Complete abundance tables, and normative mineralogies, are given for all three planets. Review of available data shows only a few gross trends for the inner planets: FeO decreases with heliocentric distance, whereas volatiles are depleted and refractories are enriched in the smaller planets.

Journal Article↗
PubMed1991

A transition metal complex (Venus flytrap cluster) for radioimmunodetection and radioimmunotherapy.

A novel transition metal complex, Venus flytrap cluster (VFC), is described for the preparation of radio-labeled antibodies. VFC contained 57Co, which was held tightly between the faces of two covalently bridged carborane ligands by cluster bonding of the metal with appropriate ligand orbitals. Anti-carcinoembryonic antigen monoclonal antibody T84.66 was conjugated to 57Co-VFC with full retention of immunological activity. Biodistribution studies in nude mice bearing carcinoembryonic antigen-producing tumors showed excellent tumor localization of 57Co-VFC-T84.66. The accumulation of radionuclide in normal liver was low and independent of dose, which may reflect the stability of the radionuclide complex. These results presage the use of VFC systems for binding transition metals that are clinically useful for radioimmunodiagnosis and radioimmunotherapy.

Animals↗