In the cytoplasm of practically all living cells, potassium is the major cation while sodium dominates in the media (seawater, extracellular fluids). Both prokaryotes and eukaryotes have elaborate mechanisms and spend significant energy to maintain this asymmetric K+/Na+ distribution. This essay proposes an original line of evidence to explain how bacteria selected potassium at the very beginning of the evolutionary process and why it remains essential for eukaryotes.

Although Boyle has been regarded as a champion of the seventeenth century Cartesian mechanical philosophy, I defend the position that Boyle’s views conciliate between a strictly mechanistic conception of fundamental matter and a non-reductionist conception of chemical qualities. In particular, I argue that this conciliation is evident in Boyle’s ontological distinction between fundamental corpuscles endowed with mechanistic properties and higher-level corpuscular concretions endowed with chemical properties. Some of these points have already been acknowledged by contemporary scholars, and I actively engage (...) with their ideas in this paper. However I attempt to contribute to the debate over Boyle’s mechanical philosophy by arguing that Boyle’s writings suggest an emergentist, albeit still mechanistic, notion of chemical properties. I contrast Boyle’s views against those of strict reductionist mechanical philosophers, focusing on the famous debate with Spinoza over the redintegration of niter, and argue that Boyle’s complex chemical ontology provides a more satisfactory understanding of chemical phenomena than is provided by a strictly reductionist and Cartesian mechanical philosophy. (shrink)

The importance of electrical signalling in bacteria is an emerging paradigm. Bacillus subtilis biofilms exhibit electrical communication that regulates metabolic activity and biofilm growth. Starving cells initiate oscillatory extracellular potassium signals that help even the distribution of nutrients within the biofilm and thus help regulate biofilm development. Quorum sensing also regulates biofilm growth and crucially there is convergence between electrical and quorum sensing signalling axes. This makes B. subtilis an interesting model for cell signalling research. SpoOF is predicted to (...) act as a logic gate for signalling pathway convergence, raising interesting questions about the functional nature of this gate and the relative importance of these disparate signals on biofilm behaviour. How is an oscillating signal integrated with a quorum signal? The model presented offers rich opportunities for future experimental and theoretical modelling research. The importance of direct cell‐to‐cell electrical signalling in prokaryotes, so characteristic of multicellular eukaryotes, is also discussed. (shrink)

N‐type inactivation of potassium channels is controlled by cytosolic loops that are intrinsically disordered. Recent experiments have shown that the mechanism of N‐type inactivation through disordered regions can be stereospecific and vary depending on the channel type. Variations in mechanism occur despite shared coarse grain features such as the length and amino acid compositions of the cytosolic disordered regions. We have adapted a phenomenological model designed to explain how specificity in molecular recognition is achieved through disordered regions. We propose (...) that the channel‐specific observations for N‐type inactivation represent distinct mechanistic choices for achieving function through conformational selection versus induced fit. It follows that the dominant mechanism for binding and specificity can be modulated through subtle changes in the amino acid sequences of disordered regions, which is interesting given that specificity in function is realized in the absence of autonomous folding. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Philosophy, Psychiatry, & Psychology 9.3 (2002) 219-227 [Access article in PDF] The Practical Kinds Model as a Pragmatist Theory of Classification Peter Zachar Pragmatist theories of scientific classification are intended to be pluralistic models that recognize different ways of cutting up the world as valuable, but do not require us to adopt whatever-goes relativism or metaphysical antirealism. How ironic that my application of pragmatism to psychopathology has been charged (...) with not being sufficiently pluralistic because it tries to fit all psychiatric disorders into the Procrustean bed of practical kinds. The Practical Kinds Model in General As a point of clarification, the practical kinds model is not a description of a type of category combined with an argument that all psychiatric disorders should be seen as belonging to that type. If it were that kind of model, I would fully agree with Haslam that practical kinds, fuzzy kinds, and discrete kinds are all potential types of psychiatric disorders. Like Nick Haslam, I believe that there are many different things in the DSM-IV and the ICD-10, and they cannot neatly be classified as the same type of thing.Rather than identifying a type of category, the practical kinds model is a general theory of scientific classification. It is a nonessentialistic theory. Essentialism is the view that things have real essences. In the Aristotelian version of essentialism, an essence is an internal structure, and it is the internal structure that makes anything be the kind of thing it really is. In this classical category model, category members either have the essence or they do not, and everything that has the appropriate essence is a member of that category. The world is supposed to therefore have a well-defined structure, and the job of the scientist is to discover that structure. Ian Hacking (1999) has termed this view of categorization inherent structurism.The practical kinds model does not deny that things have internal structures; it only denies that internal structure by itself determines category membership. Internal structure is an important consideration in identifying categories, but external criteria can always play a role. External or relational criteria play more important roles in some cases than they do in others, but they cannot be eliminated once and for all. Essentialistic theories, which favor an almost exclusive focus on inherent structures, have the advantage of being more parsimonious, but they do so by ignoring real complexity.The best way to illustrate this point is to examine a category whose identification is heavily weighted in terms of internal criteria, or an inherent structure, such as a chemical element. [End Page 219] For example, hydrogen is defined as the element that has an atomic number of 1. This means that it has one proton in its nucleus and normally one electron orbiting its nucleus. The atomic number reflects an internal property, and anything that has an atomic number of 1 is hydrogen. The same is true for the other elements. Anything that has an atomic number of 79 is gold; anything that has an atomic number of 19 is potassium, and so on. Also part of the essentialistic view is the notion that all the important properties of an element are systematically (or lawfully) related to its internal structure.It would be foolish to deny the practical utility of the atomic theory of chemistry. But even in this strongest of cases, external criteria can potentially play a role in how we decide to carve up the world and what we identify as the relevant categories. The point can be clearly illustrated with a Gedanken experiment based on the ideas of Donnellan (1983). Assume that we were to make contact with extraterrestrial life, and the result of that contact was our initiation into a larger galactic community like those portrayed on Star Trek or Babylon 5. Fortunately for us, it turns out that all planets in the community use a gold-based currency, just like we do on Earth. What we call gold, however, is too common to be the galactic basis of a currency, but a particular isotope... (shrink)

In the year 2060, sophisticated investigative tools can help catch a killer. But there are some questions even the most advanced technologies cannot answer... Harlan Coben says, “J.D. Robb’s In Death novels are can’t-miss pleasures.” Her latest is no exception, as the priest at a Catholic funeral mass brings the chalice to his lips—and falls over dead... When Detective Lieutenant Eve Dallas confirms that the consecrated wine contained potassium cyanide, she’s determined to solve the murder of Father Miguel Flores, (...) despite her discomfort with her surroundings. It’s not the bodegas and pawn shops of East Harlem that bother her, though the neighborhood is a long way from the stone mansion she shares with her billionaire husband Roarke. It’s all that holiness flying around at St. Christobal’s that makes her uneasy. A search of the victim’s sparsely furnished room reveals little—except for a carefully hidden religious medal with a mysterious inscription, and a couple of underlined Bible passages. The autopsy reveals more: faint scars of knife wounds, a removed tattoo—and evidence of plastic surgery suggesting “Father Flores” may not be the man his parishioners thought. Now, as Eve pieces together clues that suggest identity theft, gang connections, and a deeply personal act of revenge, she hopes to track down whoever committed this unholy act. Until a second murder—in front of an even larger crowd of worshippers—knocks the whole investigation sideways. Raves for the In Death novels: “A taut, nerve-jangling, thriller.”—Ridley Pearson “A thrills-to-chills ratio that will raise the neck hairs of even the most jaded reader.”—Dennis Lehane “An authentic page-turner.”—Stephen King. (shrink)

By the early twentieth century there was a growing need within palaeoanthropology and prehistoric archaeology to find a way of dating fossils and artefacts in order to know the age of specific specimens, but more importantly to establish an absolute chronology for human prehistory. The radiocarbon and potassium–argon dating methods revolutionized palaeoanthropology during the last half of the twentieth century. However, prior to the invention of these methods there were attempts to devise chemical means of dating fossil bone. Collaborations (...) between Emile Rivière and Adolphe Carnot in the 1890s led to the development of the fluorine dating method, but it was not until the 1940s that this method was improved and widely implemented by Kenneth Oakley to resolve a number of problems in palaeoanthropology, including the Piltdown Man controversy. The invention of the fluorine dating method marked a significant advance in the quest for absolute dating in palaeoanthropology, but it also highlights interesting problems and issues relating to the ability of palaeoanthropologists and chemists to bring together different skills and bodies of knowledge in order successfully to develop and apply the fluorine dating method. (shrink)

This paper aims to defend the use of the notion of experimental individuation, which has recently been developed by Ruey-Lin Chen, as a criterion for the reality of theoretical entities. In short, when scientists experimentally individuate an entity, a realist conclusion about that entity is warranted. We embed this claim regarding experimental individuation within a framework that allows for other criteria of reality. And we understand so-called retail arguments regarding the reality of a particular theoretical entity as arguments that concern (...) choosing an appropriate criterion of reality for that entity and determining whether the relevant first-order scientific evidence satisfies that criterion. We argue that such retail arguments are philosophical because defending criteria of reality, and showing that they are or are not satisfied in particular cases, involves work that is distinctively philosophical. And we illustrate this philosophical work by applying our criterion of experimental individuation to three historical cases: Davy’s potassium, Lavoisier’s muriatic radical, and Thomson’s electrified particles. (shrink)

Mr. Paul Mills suffered from cancer of the esophagus. Three major surgeries were unsuccessful in correcting the problem, and other treatment methods likewise failed. His condition deteriorated to the point where there was no longer any hope of recovery. Dr. Morrison, who was Mr. Mills's intensive care physician at the Queen Elizabeth II Health Sciences Centre in Halifax, and Mr. Mills's family agreed that active life support should be discontinued. Dr. Morrison then removed Mr. Mills's ventilator. To everyone's surprise, and (...) dismay, Mr. Mills did not die. He continued to breathe spontaneously and started to show signs of distress. Dr. Morrison increased the dosage of morphine, to no effect. She increased it again to the point where death could reasonably be expected to occur; signs of distress continued. Dr. Morrison at this point administered a dose of potassium chloride and Mr. Mills died. (shrink)

The Classical Theory of function in the nervous system postulates that the nerve impulse is the result of a sequential reversal of the membrane potential due to an increased permeability of the membrane, first to sodium ions, then to potassium ions. The new theory presents a bio-physical model which depicts the nerve impulse as an event involving the motions of electrons and waves, and their interactions with sodium and potassium atoms and ions. The velocity of the nerve impulse (...) (the most important parameter of nerve function) is determined by the product of two constants: c = the speed of light, which is a constant for all nerves; k =a constant for each nerve and is believed to be a specific property of nerve matter related in some way to the atomic process. The theory proposes that the nerve impulse in the axon is dualistic in nature (particles and waves play equally significant roles). The dualistic nature accounts for the three most fundamental characteristics of conduction of the nerve impulse: periodicity (conduction of a nerve impulse over long distances with constant velocity and form); non-summing (two nerve impulses cannot be in the same place at the same time); quantum nature of each nerve impulse — i.e., the unit message of the nerve impulse is an indivisible unit. (shrink)

The occurrence of oscillatory behaviours in living cells can be viewed as a visible consequence of stable, regulatory homeostatic cycles. Therefore, they may be used as experimental windows on the underlying physiological mechanisms. Recent studies show that growing pollen tubes are an excellent biological model for these purposes. They unite experimental simplicity with clear oscillatory patterns of both structural and temporal features, most being measurable during real‐time in live cells. There is evidence that these cellular oscillators involve an integrated input (...) of plasma membrane ion fluxes, and a cytosolic choreography of protons, calcium and, most likely, potassium and chloride. In turn, these can create positive feedback regulation loops that are able to generate and self‐sustain a number of spatial and temporal patterns. Other features, including cell wall assembly and rheology, turgor, and the cytoskeleton, play important roles and are targets or modulators of ion dynamics. Many of these features have similarities with other cell types, notably with apical‐growing cells. Pollen tubes may thus serve as a powerful model for exploring the basis of cell growth and morphogenesis. BioEssays 23:86–94, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Bibliography of Resources by and about André E. Hellegers*Compiled by Doris Mueller Goldstein (bio)This bibliography is derived from the holdings of the National Reference Center for Bioethics Literature and the BIOETHICSLINE© database (both of which are at the Kennedy Institute of Ethics and supported by the National Library of Medicine); the archives of Lauinger Library, Georgetown University; the Medline databases of the National Library of Medicine; the WorldCat database (...) of OCLC, Dublin, Ohio, and selected Internet sites.Primarily comprised of writings by Dr. Hellegers, the list also includes interviews and media programs in which he participated, as well as writings about him that were written following his death. The arrangement within each section is by date. The 231 authored pieces reflect the transition from Dr. Hellegers’s early career as a researcher in fetal physiology at Johns Hopkins Medical School, where he published his first research report at the age of 29, to the early years of the Kennedy Institute, where he produced so many provocative columns on bioethical issues that influenced the growth of the field.Due to the diversity of sources and the 40-year time span covered, there are some variations in bibliographic style. Time and availability constraints precluded verifying all of the citations with the original documents. Any additions or corrections should be submitted to the compiler.Works Authored by André E. HellegersNo Date Ethical Issues in Sterilization of the Retarded. Unpublished paper.1956Vitamin B12 Serum Level and Pregnancy. American Journal of Clinical Nutrition 4: 440+, 1956. [With Bacon F. Chow and Kunio Okuda] [End Page 89]1957Vitamin B12 Absorption in Pregnancy and in the Newborn. American Journal of Clinical Nutrition 5: 327+, 1957. [With Bacon F. Chow, Robert E. L. Nesbitt, Kunio Okuda, and David W. Smith]1958The Effects of Acute Hypoxia on the Osmotic Pressure of the Plasma. Quarterly Journal of Experimental Physiology 43: 197+, 1958. [With Donald H. Barron, Frederick C. Battaglia, and Giacomo Meschia]Studies on the Absorption of Vitamin B12 in Human Pregnancy with Especial Reference to the Effect of D-Sorbitol. American Journal of Obstetrics and Gynecology 76: 91+, 1958. [With Bacon F. Chow, Harry Prystowsky, and Vernon Wong]1959The Alveolar PCO2 and PO2 in Pregnant and Nonpregnant Women at Altitude. Proceedings of the Society for Clinical Investigation 38: 1010+, 1959. [With Donald Barron, William Huckabee, Giacomo Meschia, James Metcalfe, and Harry Prystowsky]A Comparison of the Oxygen Dissociation Curves of the Bloods of Maternal and Fetal Goats at Various pHs. Quarterly Journal of Experimental Physiology 44: 215–21, July 1959. [With Donald Barron, Giacomo Meschia, Harry Prystowsky, and A. Stark Wolkoff]Fetal Blood Studies. XII. On the Relationship Between the Position of the Oxygen Dissociation Curve of Human Fetal Blood and Adult Fetal Hemoglobin. American Journal of Obstetrics and Gynecology 77: 585+, 1959. [With Paul D. Bruns, Julian Cotter, and Harry Prystowsky]Fetal Blood Studies. XIV. A Comparative Study of the Oxygen Dissociation Curve of Nonpregnant, Pregnant and Fetal Human Blood. American Journal of Obstetrics and Gynecology 78: 489–93, September 1959. [With Paul D. Bruns and Harry Prystowsky]Fetal Blood Studies. XVI. On the Changes in Total Osmotic Pressure and Sodium and Potassium Concentration of Amniotic Fluid During the Course of Human Gestation. Surgery, Gynecology and Obstetrics 109: 509–12, October 1959. [With Frederick Battaglia, Paul D. Bruns, Harry Prystowsky, and Clayton Smisson]Further Observations on the Metabolism of Vitamin B12 in Human Pregnancy. American Journal of Obstetrics and Gynecology 77: 1+, 1959. [With Bacon F. Chow, Harry Prystowsky, Bruno Ranke, and Elma Ranke]The Oxygen Dissociation Curves of the Bloods of Adult and Fetal Llamas. Federation Proceedings 18, 1959. [With Donald Barron, William Huckabee, Giacomo Meschia, James Metcalfe, and Harry Prystowsky] [End Page 90]Transfer of Oxygen Across the Sheep Placenta at High Altitude. Federation Proceedings 18, 1959. [With Donald Barron, William Huckabee, Giacomo Meschia, and Harry Prystowsky]Uterine Blood Flow and Metabolism in Pregnant Sheep at High Altitude. Federation Proceedings 18, 1959. [With Donald Barron, William Huckabee, Giacomo Meschia, James Metcalfe, and Harry Prystowsky]Uterine Blood Flow and Metabolism in Unanesthetized Pregnant Sheep. Federation Proceedings 18, 1959. [With Donald Barron, William Huckabee, Giacomo... (shrink)

In several experimental conditions, neuronal excitation at the perirhinal cortex (PC) does not propagate to the entorhinal cortex (EC) due to a “wall” of inhibition, which may help to create functional coupling and un‐coupling of the PC and EC in the medial temporal lobe. However, little is known regarding the coupling control process. Herein, we propose that the deep layer of area 35 in the PC plays a pivotal role in opening the gate for coupling, thus allowing the activity in (...) the PC to propagate to the EC. Using voltage‐sensitive dye imaging for the brain slices of rodents, we show that a slowly inactivating potassium conductance in this area is essential to induce excitation overtaking the inhibitory control. This coupling between the distinct neural circuits persists for at least 1 h. We elucidate further implications of this network‐level plastic behavior and its mechanism. (shrink)

This chapter examines the work in chemistry that led to the discovery of boron and explores the implications of this episode for the scientific realism debate. This episode begins with Lavoisier’s oxygen theory of acidity and his prediction that boracic acid contains oxygen and a hypothetical, combustible substance that he called the boracic radical. And it culminates in the work of Davy, Gay-Lussac, and Thénard, who used potassium to extract oxygen from boracic acid and thereby discovered boron. This episode (...) constitutes a novel predictive success of Lavoisier’s theory of acidity, which was not even approximately true. Selective realists attempt to accommodate such false-but-successful theories by showing that their success is due to the fact that they have approximately true parts. This episode poses a strong challenge to selective realism because the parts of Lavoisier’s theory that are responsible for its success are not even approximately true. (shrink)