A Paramecium cell has a stereotypically patterned surface, with regularly arranged cilia, dense‐core secretory vesicles and subplasmalemmal calcium stores. Less strikingly, there is also a patterning of molecules; for instance, some ion channels are restricted to certain regions of the cell surface. This design may explain very effective and selective responses, such as that to Ca2+ upon stimulation. It enables the cell to respond to a Ca2+ signal precisely secretion (exocytosis) or by changing its ciliary activity. These responses depend (...) on the location and/or type of signal, even though these two target structures co‐exist side‐by‐side, and normally only limited overlap occurs between the different functions. Furthermore, the patterning of exocytotic sites and the possibility of synchronous exocytosis induction in the sub‐second time range have considerably facilitated analyses, and thus led to new concepts of exocytotic membrane fusion. It has been possible to dissect complicated events like overlapping Ca2+ fluxes produced from external sources and from internal stores. Since molecular genetic approaches have become available for Paramecium, many different gene products have been identified only some of which are known from “higher” eukaryotes. Although a variety of basic cellular functions are briefly addressed to demonstrate the uniqueness of this unicellular organism, this article focuses on exocytosis regulation. BioEssays 24:649–658, 2002. © 2002 Wiley Periodicals, Inc. (shrink)

The ciliated protozoan, Paramecium, broadcasts the activity of its individual ion channel classes through its swimming behaviour. This fact has made it possible to isolate mutants with defective ion currents, simply by selecting individuals with abnormal swimming patterns. At least four of Paramecium's ion currents are activated by rising intracellular calcium concentration, including two K+ currents and a Na+ current. A variety of cell lines with defects in these Ca2+‐dependent currents have been isolated: in several cases, the defects (...) have been traced to mutations in the structural gene for calmodulin. Sequence analysis of calmodulins from these and other Ca2+ ‐dependent ion‐current mutants may enable a detailed mapping of putative channel interaction domains on the surface of the calmodulin molecule. (shrink)

Ciliated protozoa have separate germline and somatic nuclei, yet unlike larger organisms, both nuclei reside in the same cytoplasm. The micronuclei contain the germline and the macronucleus is the somatic nucleus. Thousands of DNA elements are normally removed from the micronuclear genome as it forms a new macronucleus during each sexual cycle. A recent study directly links the excision of these internal eliminated sequences (IESs) to mating type determination by showing that a pleiotropic mutation affecting mating type also prevents the (...) excision of an IES from a surface protein gene(1). Remarkably, once the IES is present in the old macronucleus it prevents excision of that specific IES during formation of the next macronucleus. (shrink)

Relations occur on all levels of systems. Following a major assumption of generalized quantum theory, namely that the principles of quantum mechanics will occur on higher system levels as well, it was investigated in an a posteriori analysis of pre-existing data whether relational patterns found for two-photon experiments are similarly performed by two cell-populations. In particular, the typical pattern in outcomes of two-photon entanglement experiments was extrapolated to discover similar patterns of relationships in the cellular biological system of the Ciliate (...) Paramecium caudatum. In the former case we find one photon assuming a particular state when being measured and the other assuming a correlated state with regard to the first particle. From a perspective of degrees of freedom (df) the author interprets this outcome as follows: Each particle has only one df for assuming a particular state (e.g. its spin). When measured this is leading to a pattern: They use their two degrees of freedom for establishing a relation among them (particle-to-particle) and for a relation with the environment (particle-to-measurement). If this pattern is unique then we should find it also in cell-to-cell relationships. It was suggested to consider causations in cell-to-cell relations as the analogue to the relationship between the quantum particles (see above) and the dependence of repeating the experiments as the analogue to the measurement event in the quantum experiment. It was hypothesized that in a relational system of two cell populations only one should be sensitive to the repetition of the experiment. The other population, however, should establish a relation with the first one. Since the author had successfully performed experiments with pairs of cell populations that were separated with glass barriers from each other but having effects on each other (Fels in PLoS One 4:e5086, 2009), the system was perfectly well suited for testing the hypothesis. The assessed cell variable was cell division. An a posteriori analysis of three similar experiments confirmed that when populations were in a relation with each other, only one of them stood in relation with the repetition of the experiment. (shrink)

In the period 1875-1920, a debate about the generality and applicability of evolutionary theory to all organisms was motivated by work on unicellular ciliates like Paramecium because of their peculiar nuclear dualism and life cycles. The French cytologist Emile Maupas and the German zoologist August Weismann argued in the 1880s about the evolutionary origins and functions of sex (which in the ciliates is not linked to reproduction), and death (which appeared to be the inevitable fate of lineages denied sexual (...) conjugation), an argument rooted in the question of whether the ciliates and their processes where homologous to other cellular organisms. In the beginning of the twentieth century, this question of homology came to be less important as the ciliates were used by the British protozoologist Clifford Dobell and the American zoologist Herbert Spencer Jennings to study evolutionary processes in general rather than problems of development and cytology. For them, homology mattered less than analogy. This story illustrates two partially distinct problems in evolutionary biology: first, the question of whether all living things have common features and origins; and second, whether their history and current nature can be described by identical mechanisms. Where Maupas (contra Weismann) made the ciliates qualitatively the same as all other organisms in order to create a cohesive evolutionary theory for biology, Jennings and Dobell made them qualitatively different in order to achieve the same end. (shrink)

According to Bas van Fraassen, a postulated entity which can only be detected by means of some instrument should not be considered observable. In this paper I argue that (1) this is not correct; (2) someone can be a constructive empiricist, adhering to van Fraassen’s famous anti-realist position, even admitting that many entities only detectable with a microscope are observable. The case of the paramecium, a very well-known single-celled organism, is particularly instructive in this respect. I maintain that we (...) actually observe paramecia and not just detect them, contrary to what van Fraassen claims. As a matter of fact, even if we can only perceive these protozoans by using a microscope, we are in condition to know that the relevant counterfactual conditions (like the ones Bueno proposed in 2011) are met. Moreover, paramecia satisfy observability and existence criteria proposed by Buekens (1999) and Ghins (2005). But admitting paramecia and the like among the observables does not threaten Constructive Empiricism, for there will always be a line between observables and unobservables on which van Fraassen’s anti-realism can rest. (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Feminist Studies 45, no. 1. © 2019 by Elisabeth Blair 173 How it feels is a series of questions Are you home now, or in the body of a bird? Do you drown, or do you sit calm in the watery air? And the fire—did you light it yourself, or did someone you know, or someone you have yet to meet? Can you sit quiet by it or is (...) it bridging the wet and dry with its feet, consuming your shoes first, then your eyes, skipping the topography in between in fickle pecking like chicken for grain? Is the shower water or is it fire? What if you want to feel something? Are you tired of time, to be so locked into now in this way, in the shower, and later in the circle, where they’ll say, We saw your scars, we know you were abused— it’s OK—we were too— —? But you had only scratched your back in the shower (accidentally) that day. Elisabeth Blair 174 Elisabeth Blair What is the fire that is the fire of drowning and what is the urgency that is the command of fog, saying you’d better sit down? You’d better stand up. Wood. Upholstery. Snow. Mud. These are real, while you are sinister, not believed. There were welts on your back; now they’ve gone. You try to explain: You had a belly once. You had a body. This place stores you in the leg of a bird, and not an invested one but a chicken, pecking, running lines in the ground. Most of the time is gone. You’re a stream down which a foundling comes. You’re a paramecium—all the hints and holds of life are here in you, but you are just a little one. You’re a mouth. You use yourself to laugh, to clutch your chin with one hand, rest the other on your knee. You use yourself to say no, I do not have scars—to clarify. You use yourself like the chicken in the yard uses itself to get by. Elisabeth Blair 175 Listen. I haven’t hit you. I’ve only used your body to demonstrate the richness of your feeling and the piracy inherent in your unwillingness to brave the feeling. I’ve only pulled you up. I’ve only sheltered you with a slap. I’ve dipped into your orange blood with my finger and felt relief—I know how to help. You listen to me— your blood will redden, then your face. You’ll get better. 176 Elisabeth Blair The English boy dwells in any of many neurodivergent states, no doubt undiagnosed. You only speak when spoken to by the staff, but he will and does speak—and laugh. He pulls his pants down and shits in the mess tent. You look at the grain in the rough wooden bench. He kicks as they tackle him to the ground, and all the while—as they swear and shout and he fights—comes that laughter, making ripples on your eyes. They put him in a sleeping bag, wrap a tarp around it, tie it with rope, then leave him on the ground for days, on display, in March, in the mountains, in many feet of snow. They call it a burrito. Let him laugh, they say, let him wiggle and roll.  [we were not killed]  [I am not ungrateful  I am not ungrateful] Elisabeth Blair 177 Age 16 A few years before, your horns newly removed, there had come a drought. Once you felt it, and felt yourself not just alone but marked— once on the forehead and once on either side where you had been but now were not— you developed doubts. You had intended to be reasonable, to talk. But the melting ice: there was no container. The evaporating water: there was no shade. No room to meet in. No family to group. No wits to gather or weave, nothing to save. Your hands became a precipice attached to a belief. The belief was mismanaged, had a bad day. Stuff clattered onto you. You lay there in the stuff and knew you had broken hearts. People... (shrink)

This book explains the role of simple biological model systems in the growth of molecular biology. Essentially the whole history of molecular biology is presented here, tracing the work in bacteriophages in E. coli, the role of other prokaryotic systems, and also the protozoan and algal models—Paramecium and Chlamydomonas, primarily—and the move into eukaryotes with the fungal systems Neurospora, Aspergillus and yeast. Each model was selected for its appropriateness for asking a given class of questions, and each spawned its (...) own community of investigators. Some individuals made the transition to a new model over time, and remnant communities of investigators continue to pursue questions in all these models, as the cutting edge of molecular biological research flowed onward from model to model, and onward into higher organisms and, ultimately, mouse and man. (shrink)

Period homeostasis is the defining characteristic of a biological clock. Strict period homeostasis is found for the ultradian clocks of eukaryotic microbes. In addition to being temperature-compensated, the period of these rhythms is unaffected by differences in nutrient composition or changes in other environmental variables. The best-studied examples of ultradian clocks are those of the ciliates Paramecium tetraurelia and Tetrahymena sp. and of the fission yeast, Schizosaccharomyces pombe. In these single cell eukaryotes, up to seven different parameters display ultradian (...) rhythmicity with the same, species- and strain-specific period. In fission yeast, the molecular genetic analysis of ultradian clock mechanisms has begun with the systematic analysis of mutants in identified candidate genes. More than 40 “clock mutants” have already been identified, most of them affected in components of major regulatory and signalling pathways. These results indicate a high degree of complexity for a eukaryotic clock mechanism. BioEssays 22:16–22, 2000. ©2000 John Wiley & Sons, Inc. (shrink)

This article examines the critique of the biological species concept advanced by protozoan geneticist Tracy Sonneborn at the 1955 AAAS symposium on "the species problem," published subsequently in 1957. Although Sonneborn was a strong proponent of a population genetical conception of species, he became critical of the biological species concept for its failure to incorporate asexual and obligatory inbreeding organisms. It is argued that Sonneborn's intimate knowledge of the ciliate protozoan Paramecium aurelia species complex brought him into conflict with (...) a growing pressure in the biological sciences to emphasize universal principles of life. Faced with the need to defend the value of P. aurelia as an investigative tool, Sonneborn argued that the sharp break in nature between sexual and asexual organisms posited by proponents of the biological species concept was not an existential feature of the living world, but rather the misleading consequence of an operational definition of species based only upon sexual organisms. Drawing upon his knowledge of the immense variability of P. aurelia, he proposed instead a continuum of breeding systems from obligatory outbreeding to asexual organisms, and a more broadly unifying definition of species that incorporated asexual as well as sexual organisms. Paradoxically, the push for unification that then characterized the evolutionary synthesis served to debar critical consideration of Sonneborn's more unificatory alternative, and his underlying contention that biological anomaly could serve as an important source of conceptual unification. (shrink)