The Advantages of Obscurity: Charles Darwin's Negative Inference from the Histories of Domestic Breeds

In The Origin of Species, Charles Darwin famously accounted for the lack of fossil evidence in support of species evolution on the grounds that the fossil record is naturally incomplete. This essay examines a similar argument that Darwin applied to his analogy between natural and artificial selection: the scarcity of data about the historical backgrounds of domestic breeds was the natural by-product of an extremely gradual change process. The point was to enhance the ability of the artificial selection analogy to suggest that nature's species had undergone a similar transformation. Darwin did not depend on this negative inference alone, however, for in his writings he included whatever information he could find about the actual histories of particular breeds. A comparison with Darwin's treatment of the fossil record suggests the reasonableness of this combined use of opposite kinds of evidence to establish a single point. The comparison also suggests the unique qualities of negative inference as applied to the breeding analogy.     

Focusing on phosphomonohydrolases: a timely choice

Cellular and Molecular Life Sciences -     

Alfalfa seeds: Effects on cholesterol metabolism

Summary Plasma cholesterol concentrations were reduced in 3 human volunteers during ingestion of diets containing alfalfa seeds (AS) for 3 weeks. No signs of toxicity were detected through serum determinations of multiple parameters. The ingestion of AS in rats decreased the concentration of plasma cholesterol, reduced intestinal absorption of exogenous and endogenous cholesterol, and increased fecal biliary excretion.The work described in this article, Publication No. 1082 of the Oregon Regional Primate Research Center, was supported with grants RR-00163 and HL-16587 from the National Institutes of Health.     

Histone deacetylases: Focus on the nervous system

Neurodegenerative disease strikes millions worldwide and there is mounting evidence suggesting that underlying the onset and progression of these debilitating diseases is inappropriate neuronal apoptosis. Recent reports have implicated a family of proteins known as histone deacetylases (HDACs) in various neuronal processes including the neuronal death program. Initial headway in this field has been made largely through the use of broad-spectrum HDAC inhibitors. In fact, pharmacological inhibition of HDAC activity has been shown to protect neurons in several models of neurodegeneration. The observation that HDAC inhibitors can have opposing effects in different paradigms of neurodegeneration suggests that individual members of the HDAC protein family may play distinct roles that could depend on the specific cell type under study. The purpose of this review is to detail work involving the use of HDAC inhibitors within the context of neurodegeneration and examine the roles of individual HDAC members in the nervous system with specific focus on neuronal cell death. Received 25 January 2007; received after revision 3 April 2007; accepted 26 April 2007     

ACTH: Differential effects on avoidance and discrimination

Zusammenfassung Andauernde ACTH-Behandlung beeinflusst sowohl Vermeidungs- als auch Fehlerkomponenten im Zweiwahl-Y-Labyrinthtest. Die Einwirkungen waren von der Intensität des Elektroschocks wie auch von der Reaktionsfähigkeit der Tiere abhängig.

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This work was supported by Medical Research Council Grant No. MA 1746. Some of the work was done while the first author held a pre-doctoral terminal year grant from the USPHS and while the second author held a Research Career Award from the Canadian Association for Retarded Children. We are indebted toSusanna Kertesz for help in running the subjects in these studies. Requests for reprints should be sent to Dr.J. A. Corson, Allan Memorial Institute, 1033 Pine Avenue West, Montreal 112 (P.Q., Canada).     

Alpha-tocopherol: Its inhibition on human platelet aggregation

Summary Alpha-tocopherol inhibits human platelet aggregation induced by arachidonate sodium, collagen, epinephrine, adenosine diphosphate or thrombin — arachidonate sodium being the most susceptible. The second phase of the biphasic platelet aggregation induced by epinephrine or adenosine diphosphate is preferentially inhibited.This work was supported by the Medical Research Council of Canada, Quebec Medical Council, and a Fraser Scholarship, McGill University. I thank Drs.K. N. Drummond andS. O'Regan for their comments.     

Loperamide: novel effects on capacitative calcium influx

Loperamide is a widely used antidiarrheal that primarily acts at nanomolar concentrations through activation of opioid receptors in the gastrointestinal tract. At somewhat higher concentrations, loperamide blocks calmodulin activity, calcium channels, N-methyl-D-aspartate-receptor channels, and maitotoxin-elicited calcium influx. Loperamide at micromolar concentrations has now been shown to have a remarkable stimulatory effect on the capacitative calcium influx that is triggered in many cells by depletion of the inositol-trisphosphate-sensitive stores of calcium in the endoplasmic reticulum. The mechanism whereby loperamide enhances levels of intracellular calcium elevated by capacitative calcium influx is, as yet, undefined.     

Flagellar hairs on zoospores ofPhytophthora species: Tip hairs on the whiplash flagellum

Résumé Des mastigonèmes de 460–500 nm de longueur et 11–12 nm de largeur existent à l'extrémité du flagelle whiplash des zoospores desPhytophthora cinnamomi, P.megasperma var.sojae, P. palmivora etP. parasitica. Des mastigonèmes latéraux existent aussi sur le flagelle whiplash des 4 espèces. C'est la première mention de mastigonèmes latéraux sur le flagelle whiplash deP. cinnamomi et deP. megasperma var.sojae.     

The buzz on caffeine in invertebrates: effects on behavior and molecular mechanisms

A number of recent studies from as diverse fields as plant–pollinator interactions, analyses of caffeine as an environmental pollutant, and the ability of caffeine to provide protection against neurodegenerative diseases have generated interest in understanding the actions of caffeine in invertebrates. This review summarizes what is currently known about the effects of caffeine on behavior and its molecular mechanisms in invertebrates. Caffeine appears to have similar effects on locomotion and sleep in both invertebrates and mammals. Furthermore, as in mammals, caffeine appears to have complex effects on learning and memory. However, the underlying mechanisms for these effects may differ between invertebrates and vertebrates. While caffeine’s ability to cause release of intracellular calcium stores via ryanodine receptors and its actions as a phosphodiesterase inhibitor have been clearly established in invertebrates, its ability to interact with invertebrate adenosine receptors remains an important open question. Initial studies in insects and mollusks suggest an interaction between caffeine and the dopamine signaling pathway; more work needs to be done to understand the mechanisms by which caffeine influences signaling via biogenic amines. As of yet, little is known about whether other actions of caffeine in vertebrates, such as its effects on GABA_A and glycine receptors, are conserved. Furthermore, the pharmacokinetics of caffeine remains to be elucidated. Overall behavioral responses to caffeine appear to be conserved amongst organisms; however, we are just beginning to understand the mechanisms underlying its effects across animal phyla.