Teaching "Species"

A clear understanding of the term "species" is fundamental to the subject of evolution. However, introductory textbooks often fail to address this topic until one of the later chapters, after having used the term species in all preceding chapters. Furthermore, definitions of terms critical to a clear understanding of this subject are often vague or absent in chapters on species concepts. We feel the popular notion of a "species problem" has been unnecessarily inflated by this less-than-effective educational approach. Clearly addressing this essential subject at the beginning of a course on evolution will prepare students to learn the details and complexities of evolution. Here we provide the background for an alternative approach to this foundational topic, followed by an outlined lesson plan. We emphasize early introduction of this subject in texts and courses using unambiguous terminology and including the historical development of species concepts.     

Supramolecular photochemical self-assemblies for fluorescence "turn on" and "turn off" assays for chem-bio-helices.

We describe the development of an optical sensing system for the high-throughput screening (HTS) of a broad range of biological molecules, whole cells, organisms and pathogens, and illustrate the technology applications by a hyaluronidase enzyme activity assay as a specific example. At the core of the technology described in this paper, is the exciton concept that is relevant to molecular aggregation. J-aggregates of cyanine dyes have a narrower, red-shifted absorption band compared to monomer. We demonstrate that self-assembly may be driven by the helicogenic nature of the cyanine dye, converting the linear polymers of hyaluronic acid or carboxymethyl cellulose into supramolecular helical assemblies. This self-assembly is accompanied by an intense, sharp, red-shifted J-aggregate fluorescence. We utilized this property to develop an assay for the enzyme hyaluronidase, based upon the concept of "scaffold destruction," whereby the disruption/destruction of the hyaluronic acid polymer by hyaluronidase is accompanied by an attenuation of light emission from the J-aggregate. The extent of light attenuation provides an index of hyaluronidase activity. Other polymers of carbohydrates, proteins, nucleic acids and chemical polymers (such as the carbon nanotube) might provide a similar scaffold for helicogenic dyes upon which molecular aggregation can occur. A key feature of these assays is that they are label-free.     

Maladaptive "gambling" by pigeons

When humans buy a lottery ticket or gamble at a casino they are engaging in an activity that on average leads to a loss of money. Although animals are purported to engage in optimal foraging behavior, similar sub-optimal behavior can be found in pigeons. They show a preference for an alternative that is associated with a low probability of reinforcement (e.g., one that is followed by a red hue on 20% of the trials and then reinforcement or by a green hue on 80% of the trials and then the absence of reinforcement) over an alternative that is associated with a higher probability of reinforcement (e.g., blue or yellow each of which is followed by reinforcement 50% of the time). This effect appears to result from the strong conditioned reinforcement associated with the stimulus that is always followed by reinforcement. Surprisingly, although it is experienced four times as much, the stimulus that is never followed by reinforcement does not appear to result in significant conditioned inhibition (perhaps due to the absence of observing behavior). Similarly, human gamblers tend to overvalue wins and undervalue losses. Thus, this animal model may provide a useful analog to human gambling behavior, one that is free from the influence of human culture, language, social reinforcement, and other experiential biases that may influence human gambling behavior.     

Coding "what" and "when" in the Archer fish retina

Traditionally, the information content of the neural response is quantified using statistics of the responses relative to stimulus onset time with the assumption that the brain uses onset time to infer stimulus identity. However, stimulus onset time must also be estimated by the brain, making the utility of such an approach questionable. How can stimulus onset be estimated from the neural responses with sufficient accuracy to ensure reliable stimulus identification? We address this question using the framework of colour coding by the archer fish retinal ganglion cell. We found that stimulus identity, “what”, can be estimated from the responses of best single cells with an accuracy comparable to that of the animal''s psychophysical estimation. However, to extract this information, an accurate estimation of stimulus onset is essential. We show that stimulus onset time, “when”, can be estimated using a linear-nonlinear readout mechanism that requires the response of a population of 100 cells. Thus, stimulus onset time can be estimated using a relatively simple readout. However, large nerve cell populations are required to achieve sufficient accuracy.

Authors Summary

In our interaction with the environment we are flooded with a stream of numerous objects and events. Our brain needs to understand the nature of these complex and rich stimuli in order to react. Research has shown ways in which a ‘what’ stimulus was presented can be encoded by the neural responses. However, to understand ‘what was the nature of the stimulus’ the brain needs to know ‘when’ the stimulus was presented. Here, we investigated how the onset of visual stimulus can be signalled by the retina to higher brain regions. We used archer fish as a framework to test the notion that the answer to the question of ‘when’ something has been presented lies within the larger cell population, whereas the answer to the question of ‘what’ has been presented may be found at the single-neuron level. The utility of the archer fish as model animal stems from its remarkable ability to shoot down insects settling on the foliage above the water level, and its ability to distinguish between artificial targets. Thus, the archer fish can provide the fish equivalent of a monkey or a human that can report psychophysical decisions.     

"I" becomes "L": modification of vertical mammaplasty

The problems of the vertical mammaplasty by Lejour (i.e., gathering the skin envelope in one vertical suture, frequent secondary healing problems, and later sagging of the inferior glandular part in the case of large and very large breasts) are well known. A simple modification of the Lejour technique, that is, adding a lateral inframammary scar to shorten the vertical scar length, is presented. The modified L technique was used in 45 patients (90 breasts) between October of 1999 and August of 2001. With an average follow-up of 13 months, the jugular notch-to-nipple distance was 21 cm, the vertical scar length was 8.4 cm, the lateral inframammary scar length was 11 cm, and the average resection weight was 625 g per breast (range, 200 g to 2080 g). Even among patients who had very large glandular bases and resection weights it was possible to achieve a breast base reduction, modeling the glandular corpus to a harmonic, well-projecting, and youthful shape. Slight wound-healing problems with spontaneous cicatrization within 2 weeks occurred in six patients. In two patients who exhibited gigantomastia up to 2080 g per breast, partial mamilla necrosis occurred on one side. Ninety-one percent of the patients reported being "very satisfied" with the outcome, and 9 percent reporting being "satisfied." The authors' modification of the vertical mammaplasty to an L-shaped scar technique enables the surgeon to apply the principles of the Lejour technique for higher resection weights and diminishes wound-healing problems, and it is still a scar-minimizing technique that results in a scar-free cleavage. It is easy to learn and an ideal standard technique for a teaching hospital.     

Short electric-field pulses convert DNA from "condensed" to "free" conformation

Electric-field pulses of e.g. 20 kV/cm and 100 μs induce a strong decrease in the scattered light intensity of DNA condensed by spermine. Analysis of this effect demonstrates that the decrease of the scattered light intensity results from decondensation of DNA. The decondensation reaction requires an electric-field strength exceeding a threshold value. Complete decondensation can be achieved at field strength that are only slightly higher than the threshold value. The decondensation process is strongly accelerated at high electric-field strengths. At 30 kV/cm, the decondensation time constant is ～8 μs, corresponding to an acceleation factor of 10⁵ relative to the field-free decondensation reaction. The dependence of the time constants on the electric-field strength suggests that the field-induced decondensation is due to a dissociation field effect. The condensation process observed after electric-field pulses at low concentrations of DNA and spermine shows a characteristic induction period, which strongly depends on the spermine concentration. This induction period reflects the time required for the binding of spermine to DNA, until the degree of binding is sufficiently high for the condensation reaction. The fast dissociation of condensed DNA by electric-field pulses together with a relatively long lifetime of the free DNA results in a reaction cycle resembling a hysteresis loop.     

Rethinking Ancient Maya Social Organization: Replacing "Lineage" with "House"

Long-standing disagreements concerning prehispanic Maya kinship and social organization have focused on the nature of their corporate groups, generally presumed to have been lineages. Specific debates center on whether the lineages were patrilineal or incorporated some kind of double-descent reckoning, how descent was combined with locality to define a group, and the status of lineage-outsiders within a group. It is argued here that Maya social organization is better approached within the contemporary critique of kinship, replacing "lineage" with Lévi-Strauss's model of the "house"—a corporate group maintaining an estate perpetuated by the recruitment of members whose relationships are expressed "in the language" of kinship and affinity and affirmed by purposeful actions. In this perspective, the operation of corporate groups is the primary concern, and relationships construed in terms of consanguinity and affinity are seen as strategies pursued to enhance and perpetuate the group, [ancestor veneration, house society, kinship, Maya, social organization]     

"DRUMMING" BY SWIFTS

On 27 April 1958, while my wife and I were watching a party of 20–30 Mottled Swifts Apus aequatorialis over a dam ten miles west of Nairobi, Kenya, we repeatedly heard quite a loud "prrrpt-prrrpt-prrrpt". We discovered that the swifts were making this noise by spreading and slightly depressing their tails and moving them sideways so that the outer feather was almost parallel with the wing. The 'leading' feather thus projected into the slipstream was quite clearly seen to vibrate at the same time as the noise was heard. We watched this performance for about half an hour and noted that the tails were invariably turned to the right; we were both using binoculars. We saw that several birds were performing in this manner but it did not appear to be in connection with any display towards any other particular member of the party. The sexes of the Mottled Swift are indistinguishable in the field. The 'drumming' took place in the early part of the dive towards the surface of the dam from which the birds were drinking on the wing; it did not appear to cause any deflection of the flight path.     

Visualizing "greengold" clusters in the STEM.

"Greengold" is a large metallic cluster thought to contain 75 gold atoms in a compact 1.4-nm-diameter core surrounded by an organic shell. Scanning transmission electron microscope imaging shows uniform mass and size distributions with an apparent mass of 24 kDa, unaffected by radiation damage. The signal-to-noise ratio is adequate for visualization at low dose and in the presence of a relatively thick biological matrix. Under some conditions these clusters have a slight tendency to form linear chains and 2-D hexagonal arrays with a spacing of 2.6 nm. The parameters presented permit estimation of the feasibility of proposed labeling experiments.     

Low-resolution density maps from atomic models: how stepping "back" can be a step "forward"

Atomic-resolution structures have had a tremendous impact on modern biological science. Much useful information also has been gleaned by merging and correlating atomic-resolution structural details with lower-resolution (15-40 A), three-dimensional (3D) reconstructions computed from images recorded with cryo-transmission electron microscopy (cryoTEM) procedures. One way to merge these structures involves reducing the resolution of an atomic model to a level comparable to a cryoTEM reconstruction. A low-resolution density map can be derived from an atomic-resolution structure by retrieving a set of atomic coordinates editing the coordinate file, computing structure factors from the model coordinates, and computing the inverse Fourier transform of the structure factors. This method is a useful tool for structural studies primarily in combination with 3D cryoTEM reconstructions. It has been used to assess the quality of 3D reconstructions, to determine corrections for the phase-contrast transfer function of the transmission electron microscope, to calibrate the dimensions and handedness of 3D reconstructions, to produce difference maps, to model features in macromolecules or macromolecular complexes, and to generate models to initiate model-based determination of particle orientation and origin parameters for 3D reconstruction.     

Reproductive biotechnology and "big" biological questions

In recent decades, scientists have learned to manipulate that cardinal characteristic of life, reproduction, with powerful techniques like artificial insemination, contraception, embryo transfer, cryopreservation, and cloning by nuclear transfer. While these technologies often are used for practical applications and basic research, they have another profound intrinsic quality, which is to engender deep-seated thinking about important biological questions. Examples that stimulate such thinking include a goat's giving birth to her identical twin sister via splitting embryos, cryopreservation, and embryo transfer; that a parthenogenetic embryo can never become an animal but can become a genetic mother via an aggregation chimera; or that a somatic cell can become the sole genetic parent of a calf via cloning. In this paper, I illustrate this thought-stimulating quality by considering contributions of reproductive technologies to understanding, if not completely answering, several important biological questions.     

The "Moi-peau"

To construct a coherent identity, humans must distinguish what belongs to the external, perceived world from what belongs to their own inner world and the inner world of other individuals. Based on the theory developed by S. Freud and on work by ethologists, a number of psychoanalysts (J. Bowlby, R.A. Spitz, D.W. Winnicott, etc.) have underlined the importance of early tactile exchanges with the mother if a child is to become an autonomous individual who feels secure within what he or she perceives to be sound and reliable mental and physical boundaries. More recently, other psychoanalysts (E. Bick, W.R. Bion, etc.) have studied the fantasized mental structures that form the limits between an individual's inner mental space and the external world (including other individuals). As part of this theoretical psychoanalytical movement, Didier Anzieu, a French psychoanalyst, started to develop the concept of the "Moi-peau" in 1974. The "Moi-peau" designates a fantasized reality that a child uses during its early development to represent itself as "me", based on its experience of the body surface. The child, enveloped in its mother's care, fantasizes of a skin shared with its mother: on one side the mother (the outer layer of the "Moi-peau"), and on the other side the child (the inner layer of the "Moi-peau"). These two layers must separate gradually if the child is to acquire its own me-skin. D. Anzieu's work allowed dermatologists and other specialists, such as pediatricians, to focus on the quality of early tactile exchanges between a mother and her child, including the child with a chronic skin disorder. It also helped dermatologists to recognize patients with "borderline" states, which are particularly frequent in dermatology (ereutophobia, dysmorphophobia, tattooing, self-mutilation, artefacta dermatitis). These borderline patients are adults who, as a result of their mental conflicts, adopt defense mechanisms derived from both neurotic and psychotic functioning. Their complaints reflect difficulties with the solidity of their mental and physical limits: their real skin is metaphorically linked to the fantasized mental structure that delimits the individual mental space. Among other clinical characteristics, they have a "pathology of action" and frequently attack their own skin, paradoxically, in order to test the solidity and reliability of their own limits. Finally, D. Anzieu's work encouraged dermatologists to use psychotherapeutic approaches in parallel to classical dermatologic approaches, when necessary, and helped them better understand how psychoanalysts work with patients who have not yet acquired their own "Moi-peau". As a result, D. Anzieu was among the first to reconcile dermatologists and psychoanalysts.     

Properties of "creep currents" in single frog atrial cells

Changes in membrane current in response to an elevation of [Na]i were studied in enzymatically dispersed frog atrial cells. Na loading by either intracellular dialysis or exposure to the Na ionophore monensin produces changes in membrane current that resemble the "creep currents" originally observed in cardiac Purkinje fibers during exposure to low-K solutions. Na loading induces a transient outward current during depolarizing voltage-clamp pulses, followed by an inward current in response to repolarization back to the holding potential. In contrast to cardiac Purkinje fibers, Na loading of frog atrial cells induces creep currents without accompanying transient inward currents. Creep currents induced by Na loading are insensitive to K channel antagonists like Cs and 4-aminopyridine; they are not influenced by doses of Ca channel antagonists that abolish iCa, but are sensitive to changes in [Ca]o or [Na]o. A comparison of the time course of development of inward creep currents are not tail currents associated with iCa. Inward creep currents can also be induced by experimental interventions that increase the iCa amplitude. Exposure to isoproterenol enhances the iCa amplitude and induces inward creep currents; both can be attenuated by Ca channel antagonists. Both inward and outward creep currents are blocked by low doses of La, independently of La's ability to block iCa. It is concluded that (a) creep currents are not mediated by voltage-gated Na, Ca, or K channels or by an electrogenic Na,K pump; (b) inward creep currents induced either by Na loading or in response to an increase in the amplitude of iCa are triggered by an elevation of [Ca]i; and (c) creep currents may be generated by either an electrogenic Na/Ca exchange mechanism or by a nonselective cation channel activated by [Ca]i.     

Correction of thin lips: "lip lift"

Thin, atrophied lips are a stigma of old age. This paper discusses the so-called lip lift, an operation that consists of lifting, everting, and increasing the bulk of the upper and lower lips by means of a simple but meticulous procedure along the vermilion border. An introductory study on lip aesthetics is presented. Preoperative planning is greatly emphasized. This technique has been used by the author in 32 cases as an adjunct to facial lifts or as a separate procedure. The patients were followed for up to 3 years. The results were quite satisfactory.     

50th anniversary of the word "allosteric"

A brief historical account on the origin and meaning of the word "allosteric" is presented. The word was coined in an attempt to qualify the chemical mechanism of the feedback inhibition of bacterial enzymes by regulatory ligands. The data lead to the proposal that, at variance with the classical mechanism of mutual exclusion by steric hindrance, the inhibition takes place through an "allosteric" interaction between "no overlapping", stereospecifically distinct, sites for substrate and feedback inhibitor, mediated by a discrete reversible alteration of the molecular structure of the protein.     

Plasmodium berghei: a mouse model for the "sudden death" and "malarial lung" syndromes

A mouse model for the "sudden death" and "malarial lung" syndromes is described. Mice of the C3H/z strain succumb suddenly approximately 7 days after an infection with Plasmodium berghei becomes patent, at a time when parasitemia is still moderate (6 to 8%). Death could be shown to be due to anaphylactoid shock, probably induced by soluble immune complexes. Increased vascular permeability caused transudation and leakage of serum proteins into the interstitium and the alveoli. The lungs were found to be edematous, with a fine granular precipitate in the alveoli and adherent to the vascular walls. The precipitates reacted with antiglobulins G and M, and could be shown to also contain malaria antigens and C3/4. A dramatic drop in hematocrit was recorded several hours before death, indicating the sudden release of malaria antigens. The myocardium of animals that had died very suddenly showed a patchy loss of phosphorylase activity. This loss of activity was much more extensive, and sometimes almost total, when there had been an agonal period of several (1 to 3) hours before death. In these cases the irreversibility of the myocardial damage was also indicated by the loss of activity of the dehydrogenases, as well as by typical inflammatory reactions of granulocytic and histiocytic infiltrations. The hearts thus presented a typical picture of the acute and peracute shock syndromes. In acute shock cardiac insufficiency develops so suddenly that death ensues before irreversible damage has occurred, and cardiac insufficiency can only be demonstrated by the most sensitive of enzyme histochemical means. In the present case shock was induced by the anaphylactoid activity of immune complexes with the lung as target organ. The described syndrome appears analogous to human "malarial lung."     

Once again about "Gregg paradox" and its solution

"Gregg paradox" means that monotypical groups containing the same species (or groups of species) will be equal each other although systematics considers them as different taxa. Thus if the order of placental mammalia Tubilidentata includes one species aardvark Orycteropus after, the order itself, its single family Orycteropodiaceae, single genus of the family Orycteropus and the single species Orycteropus after can be considered as equal to each other. To solve this disagreement the author asserts that taxa of any level can be regarded as an individual according to the taxa of higher rank. Possibility of such interpretation was already suggested by Georg Cantor (1985). He supposed that a set (class) can be regarded as unity by itself. In this case connections between taxa of different levels can be realized by Peano ratio of intrasitive conformities. In this model a genus will consist of species but not individuals, a type--of classes, etc. Thus, if a taxon x as an individual is an element of taxon y, and taxon y as an individual is an element of taxon z, then z according to x will be not only logical class, but class of classes and, hence we could not consider x as an element of z, because the latter consists of indecomposable individual-class y or some similar classes. In this situation "Gregg paradox" does not arise.     

"Halo nevi" and UV radiation

Halo nevi, also termed Sutton nevi, are defined as benign melanocytic nevi that are surrounded by an area of depigmentation resembling a halo. Halo nevi are common in children and young adults, with a mean age at onset of 15 years. The incidence in the population is estimated to be approximately 1%. Affected individuals frequently have multiple lesions which are usually localized on the back. A familial tendency for halo nevi has been reported. The etiology of halo nevi is unknown. It is an autoimmune response and T lymphocytes are considered to play a key role in the progressive destruction of nevus cells. Halo nevi may be associated with autoimmune disorders such as vitiligo, Hashimoto thyroiditis, alopecia areata, celiac disease, atopic dermatitis and others. It has been proved that halo nevi are detected after an intense sun exposure especially after sunburns. The etiology of halo nevi, association with malignant melanoma and the role of sun exposure in the development of halo nevi are discussed.     

"Nature" and "environment" in German and Portuguese sustainable development strategies for Johannesburg 2002

The recent Johannesburg Summit on Sustainable Development was an important symbolic moment, in spite of the poor results some people claim to have emerged from it. The very fact that official written texts were produced for a wide discussion in many participating countries is a positive side-effect, as it enables the almost unique possibility of using parallel corpora for the analysis of the respective language and underlying assumptions. This could lead to the identification of some potential causes for conflicts and misunderstandings. Both texts were produced according to a (supposedly, at least) common intention, so they may be seen as functionally equivalent. In spite of that, there are obviously huge differences, not only in extension, but also in the type of lexical combinations and stylistic features used. Words like ambiente, in the Portuguese language, and Umwelt, in German, as well as natureza/Natur, appear in very different lexical environments, so that one can, by means of a distributive methodology, obtain a picture of what might be intended with their use in the two countries. Another issue brought about by this analysis was a reflection on the concept of "foreign" language. This raises the question not only of knowing whether, or to what extent, written texts like these are really intended to have an effect on (local) people's minds, but also about pragmatic/cultural constraints that have influenced their very shaping.     

"Wet dog shakes" during olfactory bulb kindling

Kindling phenomenon provides an experimental model of limbic secondarily generalized epilepsy. It can be easily obtained by stimulation of the olfactory bulb (OB) which is strongly connected to limbic structures. The after-discharge induced by subconvulsant electrical stimulations, is followed by a behavioral phenomenon, named Wet Dog Shakes (WDS). In the course of the Rat OB kindling, the development of WDS is biphasic: 1) an ascendant phase during the first three stages, and 2) a descendant phase in the stages 4 and 5, that may give evidence of the installation and the intensification of the kindling process. The significance of this behavior in seizure generalization is discussed.