Calcitonin, an enigmatic hormone: does it have a function?

This editorial presents our view of the status of thyroidal calcitonin (TCT) in mammalian physiology. The discovery of calcitonin (CT) enabled the development of a valuable therapeutic agent but the early experiments most likely misled us with regard to its physiological significance. These early purported roles for TCT, first as an agent important in blood calcium regulation and later as an agent to prevent hypercalcemia, are no longer considered as physiological functions. While large supraphysiological doses of CT have an effect on the morphology and function of osteoclasts, it is unlikely that these effects of CT are important in the normal physiology of osteoclasts or bone remodeling. It is surprising that 38 years after the discovery of TCT there is no consensus as to its role in normal mammalian physiology. This editorial concerns three possibilities with respect to TCT: 1) the hormone is vestigial; 2) the hormone plays a role in water metabolism, ionic concentrations, and/or acid-base balance, actions that may not involve calcium metabolism at all; and 3) TCT acts to store phosphate postprandially on bone surfaces as a labile calcium-phosphate colloid, an action that may provide calcium needed for use in non-feeding periods or to reduce postprandial loss of phosphate when dietary phosphate is limited. Also discussed are recent publications indicating that CT synthesized in non-thyroidal tissues (NTCT) may have paracrine actions.     

If a bird flies in the forest,does an insect hear it?

Birds are major predators of many eared insects including moths, butterflies, crickets and cicadas. We provide evidence supporting the hypothesis that insect ears can function as ‘bird detectors’. First, we show that birds produce flight sounds while foraging. Eastern phoebes (Sayornis phoebe) and chickadees (Poecile atricapillus) generate broadband sounds composed of distinct repetitive elements (approx. 18 and 20 Hz, respectively) that correspond to cyclic wing beating. We estimate that insects can detect an approaching bird from distances of at least 2.5 m, based on insect hearing thresholds and sound level measurements of bird flight. Second, we show that insects with both high and low frequency hearing can hear bird flight sounds. Auditory nerve cells of noctuid moths (Trichoplusia ni) and nymphalid butterflies (Morpho peleides) responded in a bursting pattern to playbacks of an attacking bird. This is the first study to demonstrate that foraging birds generate flight sound cues that are detectable by eared insects. Whether insects exploit these sound cues, and alternatively, if birds have evolved sound-reducing foraging tactics to render them acoustically ‘cryptic’ to their prey, are tantalizing questions worthy of further investigation.     

Stereum sanguinolentum: Is it an amphithallic basidiomycete?

Monobasidiospore isolates were prepared from basidiocarps of Stereum sanguinolentum. Five isolates per basidiome were paired with each other and with isolates from the trama. Interbasidiome pairings of the trama isolates and of a selection of single-spore isolates also were performed. Thin sections of the hymenium were stained with DAPI and examined by fluorescence microscopy to study the nuclei in the basidia. Spore prints were stained with DAPI to count the number of nuclei per spore. SEM was used to determine the number of basidiospores per basidium. All intrabasidiome pairings were compatible. In contrast, interbasidiome pairings, except one, were incompatible, independent of whether single-spore or trama isolates were paired. Fertile basidiomes were formed in single-basidiospore cultures. Basidia were regularly four-spored. On average, 5% of the basidiospores possessed one nucleus, 82% two, 2% three and 1% four nuclei. Ten percent of the spores appeared to be empty. Karyogamy, meiosis and postmeiotic mitosis were observed in the basidia. Nuclei resulting directly from meiosis, i.e., without having undergone postmeiotic mitosis, sometimes were observed in the sterigmata or spore primordia. The high number of vegetative compatibility groups (VCG) of S. sanguinolentum observed in this study and earlier studies is difficult to explain without sexual or parasexual recombination. We suppose that the majority of spores with ≥2 nuclei are amphithallic, possessing at least one nucleus of each mating type. Recombination could occur by exchange of nuclei among VCGs via anastomoses between homothallic compartments. Transfer of nuclei from heterothallic to homothallic mycelia or matings between homothallic mycelia, which originate from monokaryotic spores, might be other paths for gene exchange.     

Acanthamoeba: could it be an environmental host of Shigella?

Shigellosis is a serious public health problem in Korea, because large outbreaks of Shigella sonnei infections were recorded in many parts of the country during the period 1998-2000. However, the epidemiological features of shigellosis are not well known. In this study, we devised conditions suitable for the growth and replication of Shigella in an amoebic intracellular environment, and investigate whether medium conditions affect the survival and replication of Shigella within Acanthamoeba. We evaluated the uptake rates of invasive and non invasive S. sonnei strains by three Acanthamoeba species, namely, A. castellanii Neff, A. astronyxis Ray & Hayes, and A. healyi OC-3A. When A. castellanii Neff was infected with S. sonnei 99OBS1 or 80DH248, shigellae was maintained for a longer time in cytoplasms than in other Acanthamoeba species. S. sonnei 99OBS1 strain (a virulent strain) was recovered in higher numbers than the non-virulent S. sonnei 80DH248 strain in all experiments. Moreover, S. sonnei was more easily engulfed by Acanthamoeba at 18 degrees C. The shigellae uptake rates of Neff strain, which was cultured in free-media (less nutrition), were higher (>10-fold) than those observed in original amoeba culture media (PYG medium) in all time points. S. sonnei 99OBS1 was localized, with an intact membrane, to the vacuoles of Acanthamoeba. We conclude that free-living amoebae more likely act as environmental hosts for shigellae, and thus, may have contributed to outbreaks of shigellosis in Korea.     

Malocclusion in an African rodent. Is it necessarily fatal?

The greater cane rat, Thryonomys swinderianus , is the second largest rodent in the southern African subregion; only the porcupine is larger. The incisors are very large and curved and their gnawing action against each other gives them chisel edges. The common belief that a broken incisor may lead to severe stress or even death because growth of the corresponding incisor, in the opposing jaw, cannot be controlled by wearing away, is not necessarily true for all rodents. At least in the greater cane rat malocclusion does not necessarily lead to the incisors entering the skull or any obvious signs of stress or suffering.     

Microvascular anastomosis in an optical cavity: is it possible?

Microsurgery is one of the highly interesting surgical procedures that can be performed using different applications and in different specialties, including plastic surgery. The endoscope is a popular instrument used in many fields, including plastic surgery. Although the operating microscope is still a must for microsurgical performance, microsurgery could be performed, depending on the experiences and facilities, by using other visual-assisting equipment. From this point of view, the authors tried to find less costly and more widespread equipment suitable for performing microsurgery that can, furthermore, be applied in special situations and indications, such as operating in an optical cavity. The authors investigated this issue with the endoscope. In this experimental project, the authors performed vascular microsurgical anastomoses of the rats' femoral vessels to create an optical cavity in a prefabricated skin retraction model in the groin area of 10 Sprague-Dawley male rats. The microsurgical anastomoses of the femoral vessels and nerves were performed easily in a reasonable time, without recorded difficulties, and with maximum physical and visual comfort for the surgeon. The authors spent a mean time of 28.1, 27.3, and 19.2 minutes for the arterial, venous, and neural anastomoses, respectively. In this group of animals, 90 percent vascular patency and 100 percent accurate neural anastomoses were recorded. The advantage the authors noted was that this new technique of operating in the field of microsurgery, with its feasibility and difficulties, would be a point of research and application for the young generations of microsurgeons.     

Metastatic melanoma, or is it?

A case of pigmented axillary nodes in the presence of malignant melanoma of the upper extremity points out the caution necessary in making intraoperative decisions based on gross appearance at the time of surgery. Had our preoperative plans been abandoned in consideration of the "obvious pathology," the patient might not have done as well. Histologic confirmation should always precede any altering of preoperative plans despite gross findings.     

Additivity in protein-DNA interactions: how good an approximation is it?

Man and Stormo and Bulyk et al. recently presented their results on the study of the DNA binding affinity of proteins. In both of these studies the main conclusion is that the additivity assumption, usually applied in methods to search for binding sites, is not true. In the first study, the analysis of binding affinity data from the Mnt repressor protein bound to all possible DNA (sub)targets at positions 16 and 17 of the binding site, showed that those positions are not independent. In the second study, the authors analysed DNA binding affinity data of the wild-type mouse EGR1 protein and four variants differing on the middle finger. The binding affinity of these proteins was measured to all 64 possible trinucleotide (sub)targets of the middle finger using microarray technology. The analysis of the measurements also showed interdependence among the positions in the DNA target. In the present report, we review the data of both studies and we re- analyse them using various statistical methods, including a comparison with a multiple regression approach. We conclude that despite the fact that the additivity assumption does not fit the data perfectly, in most cases it provides a very good approximation of the true nature of the specific protein–DNA interactions. Therefore, additive models can be very useful for the discovery and prediction of binding sites in genomic DNA.     

Curvilinear, geometric and phylogenetic modeling of basicranial flexion: is it adaptive, is it constrained?

Prior work has shown that the degree of basicranial flexion among primates is determined by relative brain size, with anatomically modern humans possibly having a less flexed basicranium than expected for their relative brain size. Basicranial flexion has also been suggested to be adaptive in that it maintains a spheroid brain shape, thereby minimizing connections between different parts of the brain. In addition, it has been argued that the degree of flexion might be constrained such that increases in relative brain size beyond that seen in Australopithecus africanus were accommodated by mechanisms other than basicranial flexion. These hypotheses were evaluated by collating an extensive data set on basicranial flexion and relative brain size in primates and other mammals. The data were analyzed using standard least squares regression, geometric and curvilinear modeling, and phylogenetically independent contrasts (PICs). Geometric modeling does not support the hypothesis that flexion is an adaptation that facilitates enlargement of a spheroid brain. Whether humans have a less flexed basicranium than expected for their relative brain size depends on the phylogenetic vantage point from which it is evaluated. They are as flexed as expected for a descendant of the last common ancestor of the Paranthropus-Homo clade, but their degree of flexion cannot be predicted from the basal hominoid node, even if their relative brain size is specified. Humans undoubtedly occupy an unusual part of morphospace in terms of basicranial flexion and relative brain size, but this does not mean that their degree of flexion is or is not constrained. Curvilinear regression models and standard linear regression models describe the relationship between flexion and relative brain size equally well. Hypotheses that the degree of flexion is or is not constrained cannot be discriminated at present. Consideration of recently published ontogenetic data in the context of the interspecific data for adults suggests that much of the variance in basicranial flexion can still be explained as a mechanical consequence of brain enlargement relative to basicranial length.     

Is it better to give information, receive it, or be ignorant in a two-player game?

The standard approach in a biological two-player game is toassume both players choose their actions independently of oneanother, having no information about their opponent's action(simultaneous game). However, this approach is not realisticin some circumstances. In many cases, one player chooses hisaction first and then the second player chooses her action withinformation about his action (Stackelberg game). We comparethese two games, which can be mathematically analyzed into twotypes, depending on the direction of the best response function(BRF) at the evolutionarily stable strategy in the simultaneousgame (ESS_sim). We subcategorize each type of game into two cases,depending on the change in payoff to one player, when both playersare at the ESS_sim, and the other player increases his action.Our results show that in cases where the BRF is decreasing atthe ESS_sim, the first player in the Stackelberg game receivesthe highest payoff, followed by both players in the simultaneousgame, followed by the second player in the Stackelberg game.In these cases, it is best to be the first Stackelberg player.In cases where the BRF is increasing at the ESS_sim, both Stackelbergplayers receive a higher payoff than players in a simultaneousgame. In these cases, it is better for both players to playa Stackelberg game rather than a simultaneous game. However,in some cases the first Stackelberg player receives a higherpayoff than the second Stackelberg player, and in some casesthe opposite is true.     

Nucleosome positioning: How is it established, and why does it matter?

Packaging of eukaryotic genomes into chromatin affects every process that occurs on DNA. The positioning of nucleosomes on underlying DNA plays a key role in the regulation of these processes, as the nucleosome occludes underlying DNA sequences. Here, we review the literature on mapping nucleosome positions in various organisms, and discuss how nucleosome positions are established, what effect nucleosome positioning has on control of gene expression, and touch on the correlations between chromatin packaging, sequence evolution, and the evolution of gene expression programs.     

Negative anticipatory contrast: does it involve anticipation of an impending reward?

Negative anticipatory contrast (NAC) corresponds to the suppression in consumption of a first rewarding substance (e.g., saccharin 0.15%) when it is followed daily by a second preferred substance (e.g., sucrose 32%). The NAC has been interpreted as resulting from anticipation of the impending preferred reward and its comparison with the currently available first reward [Flaherty, C.F., Rowan, G.A., 1985. Anticipatory contrast: within-subjects analysis. Anim. Learn. Behav. 13, 2-5]. In this context, one should expect that devaluation of the preferred substance after the establishment of the NAC would either reduce or abolish the contrast effect. However, contrary to this prediction, the results of the present study show that the NAC is insensitive to devaluation of the second, preferred, substance. This allows one to question that interpretation. The results reported in this study support the view that the NAC effect is controlled by memory of the relative value of the first solution, which is updated daily by means of both a gustatory and/or post-ingestive comparison of the first and second solutions, and memory of past pairings.     

Assessing the control/eradication of an invasive species,the American mink,based on field data; how much would it cost?

Biological invasions are an important cause of biodiversity loss, American mink being one of the worst invasive species in Europe. We performed a 13-week control program of the species in the Butron river system (Northern Spain), where a natural population of the European mink is found. Three population estimates were considered: an absolute minimum, an intermediate scenario and a pessimistic one (n = 35, 49 and 70 animals, respectively). After 2,242 cage trap-nights, trapping success varied from 44 to 89% of these estimates. In addition, we evaluated the costs of eradicating the estimated populations; costs ranged between 652.5 and 2,970 € per mink, and would rise up to 83,462 € for the intermediate estimate under an exponential function linking captures and costs, or ca. 172.500 € to capture the highest estimate under a log-function. The implications of these numbers for the design and implementation of future control projects are discussed.