The phylogeny of amphibian metamorphosis

Frogs have one of the most extreme metamorphoses among vertebrates. How did this metamorphosis evolve? By combining the methods previously proposed by Mabee and Humphries (1993) and Velhagen (1997), I develop a phylogenetic method suited for rigorous analysis of this question. In a preliminary analysis using 12 transformation sequence characters and 36 associated event sequence characters, all drawn from the osteology of the skull, the evolution of metamorphosis is traced on an assumed phylogeny. This phylogeny has lissamphibians (frogs, salamanders, and caecilians) monophyletic, with frogs the sister group of salamanders. Successive outgroups used are temnospondyls and discosauriscids, both of which are fossil groups for which ontogenetic data are available. In the reconstruction of character evolution, an unambiguous change (synapomorphy) along the branch leading to lissamphibians is a delay in the lengthening of the maxilla until metamorphosis, in accordance with my previous suggestion (Reiss, 1996). However, widening of the interpterygoid vacuity does not appear as a synapomophy of lissamphibians, due to variation in the character states in the outgroups. From a more theoretical perspective, the reconstructed evolution of amphibian metamorphosis involves examples of heterochrony, through the shift of ancestral premetamorphic events to the metamorphic period, caenogenesis, through the origin of new larval features, and terminal addition, through the origin of new adult features. Other changes don't readily fit these categories. This preliminary study provides evidence that metamorphic changes in frogs arose as further modifications of changes unique to lissamphibians, as well as a new method by which such questions can be examined.     

The relation between morphology and behaviour during ontogenetic and evolutionary changes

During development, form and function (behaviour) change while the match between them must be maintained. The quality of this match determines the importance of morphological parameters in constraining behaviour. If the match is close, the morphology of organisms will be more constraining to the behaviour than when there is a large reserve capacity that creates a certain flexibility. This leads to two questions: (1) How good is the match between form and function during development? The quality of the match necessarily changes during development because changes in structural capacity often cannot proceed at the same speed as changes in functional demand. The evidence for these changes is discussed. (2) What are the mechanisms that maintain the match between form and function during developmental and evolutionary changes? Two mechanisms for maintaining the match are discussed: (a) reserve capacity and (b) flexible muscle activity patterns. Special emphasis is given to fish examples throughout this review.     

Decreased intracellular Na+ concentration is an early event in murine erythroleukemic cell differentiation

A decrease in Na+/K+-pump activity is an early event of Friend murine erythroleukemic (MEL) cell differentiation along the erythroid pathway. This decreased Na+/K+-pump activity has been proposed to be an essential step in differentiation which would cause a rise in intracellular Na+ concentration and then, by means of Na+/Ca2+ exchange, an increase in intracellular Ca2+. An increase in intracellular Ca2+ has been proposed to be essential for induction of differentiation. A critical prediction of this Na+-Ca2+ hypothesis is the rise in intracellular Na+. To test this prediction we have measured intracellular Na+ using a novel triple isotope method involving 3H2O, [14C]sucrose, and 22Na to measure total water, extracellular fluid, and Na+, respectively. 22Na equilibration occurred in less than 10 min. In uninduced cells, intracellular Na+ was 15.2 +/- 2.2 mM (S.D., n = 22); after induction for 14-16 h with dimethyl sulfoxide, intracellular Na+ decreased significantly (p less than 0.0001) to 8.4 +/- 1.4 mM (n = 21). The time course of the decline in intracellular Na+ paralleled that of the decrease in the Na+/K+-pump activity. These results are in direct contradiction to the Na+-Ca2+ hypothesis and suggest that observed changes in Na+/K+-pump activity can be explained solely on the basis of changes in intracellular Na+. The drop in intracellular Na+ is due to a decrease in Na+ influx. We suggest, however, that the decrease in the Na+ influx is not itself an essential event of differentiation, but may be induced by a change in the flux of another ion coupled to Na+.     

Ca2+ and mitochondria as substrates for deficits in synaptic plasticity in normal brain ageing

Normal brain ageing is associated with a degree of functional impairment of neuronal activity that results in a reduction in memory and cognitive functions. One mechanism proposed to explain the age-dependent changes was the "Ca(2+) hypothesis of ageing" but data accumulated in the last decade revealed a number of inconsistencies. Two important questions were raised: (a) which are, if any, the most reliable age-associated change in neuronal Ca(2+) homeostasis and (b) are these changes primary, and thus determinant of the ageing phenotype, or are they secondary to other changes in the physiology of the aged neurones. After a brief review of the evidence accumulated for the age-induced changes in synaptic plasticity, we assess the proposal that these changes are, ultimately, determined by changes in the metabolic state of the aged neurones, that are manifest particularly after neuronal stimulation. In this context, it appears that the changes in mitochondrial status and function are of primary importance.     

Influence of glyphosate on flower morphogenesis and pigmentation in Petunia hybrida

Glyphosate showed a remarkable effect inducing the change of flower symmetry from the actinomorphic to the zygomorphic type in Petunia hybrida. Glyphosate [N-(phosphonomethyl)glycine] reduced the anthocyanin content and showed a weak inhibitory effect against phenylalanine ammonia-lyase (PAL) activity. L-2-Aminooxy-3-phenylpropionic acid (APA), an inhibitor of PAL activity, reduced the anthocyanin content but had no effect on flower shape. Additional phenylalanine or trans-cinnamic acid, the intermediates of glyphosate inhibition against PAL activity, could not recover the change of flower shape induced by glyphosate. These results suggested that the reduction of PAL activity alone could not account for the two characteristic changes of flower symmetry and pigmentation induced by glyphosate. On the other hand, the results of application of glyphosate-related compounds suggested that the structure of glyphosate contributed to induce the morphological change of Petunia flower. Glyphosate may thus be a very useful agent in the elucidation of unresolved questions of flower morphogenesis and the related metabolism.     

A method for parallel determination of choline acetyltransferase and muscarinic cholinergic receptors: Application in aged-rat brain

We have devised a method for the parallel determination of choline acetyltransferase (CAT) and muscarinic cholinergic receptor (mCh-R) in the same brain tissue. The method for CAT activity determination is more rapid, simplified, stable, and economical than the usual Fonnum's method. With our method, age-associated changes in CAT activity and mCh-R levels were examined. Although CAT activity hardly changed with age except in a few areas, mCh-R binding of aged-rats was markedly reduced in all areas. These results suggest that the change in mCh-R represents an age-associated biochemical change in the brain and that determination of CAT activity is not sufficient for the study of age-associated changes in the brain cholinergic system.     

Stadtamseln sind anders

City blackbirds are different Abiotic factors such as traffic noise and especially artificial light do not just influence species in cities but also change them. The example of the European blackbird (Turdus merula) illustrates how adaptions to city environments can initiate micro‐evolutionary changes. Artificial light clearly alters daily activity patterns and leads to changes in reproductive behaviour: blackbirds sing earlier in the morning, are awake for longer and start reproduction earlier in the year. Traffic noise also changes their song. In order to compensate for interfering traffic noise, city blackbirds sing louder and at higher frequencies. In addition, blackbirds in cities are less curious but also show less fear towards humans than their forest counterparts. Cities have the potential to become a home for some species, but they also change them. One of the big questions of the future will be if, in the globally expanding city environments, this process will lead to the evolution of adapated city species.     

Post‐fire vegetation and climate dynamics in low‐elevation forests over the last three millennia in Yellowstone National Park

Conifer forests of the western US are historically well adapted to wildfires, but current warming is creating novel disturbance regimes that may fundamentally change future forest dynamics. Stand‐replacing fires can catalyze forest reorganization by providing periodic opportunities for establishment of new tree cohorts that set the stage for stand development for centuries to come. Extensive research on modern and past fires in the Northern Rockies reveals how variations in climate and fire have led to large changes in forest distribution and composition. Unclear, however, is the importance of individual fire episodes in catalyzing change. We used high‐resolution paleoecologic and paleoclimatic data from Crevice Lake (Yellowstone National Park, Wyoming, USA), to explore the role of fire in driving low‐elevation forest dynamics over the last 2820 yr. We addressed two questions: 1) did low‐elevation forests at Crevice Lake experience abrupt community‐level vegetation changes in response to past fire events? 2) Did the interaction of short‐term disturbance events (fire) and long‐term climate change catalyze past shifts in forest composition? Over the last 2820 yr, we found no evidence for abrupt community‐level vegetation transitions at Crevice Lake, and no evidence that an interaction of climate and fire produced changes in the relative abundance of dominant plant taxa. In part, this result reflects limitations of the datasets to detect past event‐specific responses and their causes. Nonetheless, the relative stability of the vegetation to fires over the last 2820 yr provides a local baseline for assessing current and future ecological change. Observations of climate–fire–vegetation dynamics in recent decades suggest that this multi‐millennial‐scale baseline may soon be exceeded.     

3T3-L1 preadipocyte differentiation and poly(ADP-ribose) synthetase

Differentiation of 3T3-L1 preadipocytes, induced by methyl-isobutylxanthine (MIX), dexamethasone (DEX), and insulin, results in cells with the morphological and biochemical characteristics of adipocytes. Following incubation of 3T3-L1 cells with MIX, DEX, and insulin, poly(ADP-ribose) synthetase activity decreased abruptly, remained low for several hours and then increased; this rise was delayed by readdition of MIX, DEX, and insulin. The transient reduction in poly(ADP-ribose) synthetase activity in 3T3-L1 cells occurred prior to the appearance of the adipocyte phenotype induced by the above agents. It was not observed when preparations were assayed in the presence of DNase I, indicating that poly(ADP-ribose) synthetase activity was masked following treatment with MIX, DEX, and insulin. The change in synthetase activity represents the earliest alteration of a specific enzyme yet detected during the differentiation of 3T3-L1 cells. It appears to be differentiation specific since nondifferentiating 3T3-C2 control cells did not exhibit changes in poly(ADP-ribose) synthetase activity when treated with MIX, DEX, and insulin. The transient reduction in activity may be an early event in differentiation which reflects changes in chromatin structure.     

Quantitative conodont-based approaches for correlation of the Late Devonian Kellwasser anoxic events

We present the trends of absolute conodont abundance, relative genera abundance, and conodont morphometrics across the Late Devonian Kellwasser horizons at three northern Gondwanan epicontinental seaway locations.

At three contrasting depositional settings, the Kellwasser events are characterized by a decrease in conodont abundance, high percentage of the conodont genus Icriodus and morphological change of the conodont genus Palmatolepis. These changes can be identified in sections where the events are expressed as interbedded anoxic and oxic deposits as well as in settings characterized by continuous anoxic sediment accumulation. Hence, these changes are interpreted as global and synchronous and can be thus used for event correlation.

The paradox of these results is that despite quite similar isotopic signals, faunal change during the Lower Kellwasser event was less than during the Upper Kellwasser event. We interpret that this discrepancy is due to an unconformity (including topmost Frasnian to earliest Famennian) at several F/F sections which removed the record of peak paleoenvironmental change.     

Morphological and Functional Questions on the Growth and Plasticity of Mammalian and Avian Jaw Muscles

SYNOPSIS: Growth studies of mammalian jaw muscles and studiesdetermining the degree of plasticity of these muscles are few.There are questions concerning the degrees and types of morphologicaland physiological change occurring in these muscles during normalgrowth and the ability of external forces to modify this growthprocess. There are also questions on the effects of sensoryloss on muscle growth and on changes in the motor system asthese muscles change. In this report, questions are proposedand hypotheses presented that deal with these areas relativeto the jaw muscles. It is suggested that (1) changes in themorphology and function of jaw muscles during growth vary regionallyand are related to the action of the muscle and the loadingforces imposed; (2) the degree of muscle plasticity varies regionallyand varies depending on the type of loading forces and age ofthe animal; (3) loss of sensory input during the growth of thejaw muscles would produce marked changes in the histochemicalprofile, the distribution of motor neurons, and the activitypattern of these muscles; and (4) organization of the trigeminalmotor nucleus changes as the jaw muscles grow and may also changein response to sensory loss or application of different typesof loading forces. In addition, possible approaches to thesequestions are discussed.     

Allosteric interactions and QSAR: on the role of ligand hydrophobicity

A study of a very large database of QSAR (9100) has uncovered a few unusual examples where as one increases the hydrophobicity of the members of a set of congeners, activity decreases until at a certain point, activity begins to increase. Obviously a change in mechanism is involved. The only way we have found to rationalize this unusual event is by a change in the structure of the receptor. We have found this to occur with hemoglobin, a substance first used to define allosteric reactions.     

Time-series forecasting offers novel quantitative measure to assess loud sound event in an urban park with restored prairie

Soundscape ecology and ecoacoustics study the spatiotemporal dynamics of a soundscape and how the dynamics reflect and influence ecological processes in the environment. Soundscape analysis methods employ acoustic recording units (ARUs) that collect acoustic data in study areas over time. Analyzing these data includes computation of several acoustic diversity indices developed to quantify species abundance, richness, or habitat condition through digital audio processing and algorithm adaptations for within-group populations. However, the success of specific indices is often dependent on habitat type and biota richness present and analyzing these data can be challenging due to temporal pseudo-replication. Time-series analytical methods address the inherent problems of temporal autocorrelation for soundscape analyses challenges. Animal population dynamics fluctuate in a variety of ways due to changes in habitat or natural patterns of a landscape and chronic noise exposure, with soundscape phenology patterns evident in terrestrial and aquatic environments. Historical phenological soundscape patterns have been used to predict expected soundscape patterns in long-term studies but limited work has explored how forecasting can quantify changes in short-term studies. We evaluate how forecasting from an acoustic index can be used to quantify change in an acoustic community response to a loud, acute noise. We found that the acoustic community of a Midwestern restored prairie had decreased acoustic community activity after a loud sound event (LSE), a Civil War Reenactment, mainly driven by observed changes in the bird community and quantified using two methods: an automated acoustic index and species richness. Time-series forecasting maybe considered an underutilized tool in analyzing acoustic data whose experimental design can be flawed with temporal autocorrelation. Forecasting using auto ARIMA with acoustic indices could benefit decision makers who consider ecological questions at different time scales.     

Regulation of amino acid transport in chicken embryo fibroblasts by purified multiplication-stimulating activity (MSA)

Enhanced amino acid transport is observed when quiescent cultures of chicken embryo fibroblasts are stimulated to proliferate by the addition of purified multiplication-stimulating activity (MSA). This increase in amino acid transport is an early event occuring prior to the onset of DNA synthesis in stimulated cells. Results indicate that the changes in transport activity, as measured by α-aminoisobutyric acid (AIB) uptake, are due to stimulation of only the Na⁺-dependent A transport system. There is little or no change in the activities of transport systems ASC, L, or Ly⁺ upon exposure to MSA. A kinetic analysis shows this increased activity is due to a change in Vmax while K_m remains unaltered. Continuous exposure to the stimulus is required to maintain the increased level of transport activity and the presence of inhibitors of RNA and protein synthesis significantly inhibits the response. Results also indicate that a similar specific increase in the A transport system is initiated when RSV tsNY68 infected cells are shifted to the permissive temperature. It appears that the A system of mediation is emerging as a strategic regulatory site for cell function.     

Morphological transformation induced by activation of the mitogen-activated protein kinase pathway requires suppression of the T-type Ca2+ channel.

Transformation of fibroblasts by various oncogenes, including ras, mos, and src accompanies with characteristic morphological changes from flat to round (or spindle) shapes. Such morphological change is believed to play an important role in establishing malignant characteristics of cancer cells. Activation of the mitogen-activated protein kinase (MAPK) pathway is a converging downstream event of transforming activities of many oncogene products commonly found in human cancers. Intracellular calcium is known to regulate cellular morphology. In fibroblasts, Ca2+ influx is primarily controlled by two types of Ca2+ channels (T- and L-types). Here, we report that the T-type current was specifically inhibited in cells expressing oncogenically activated Ras as well as gain-of-function mutant MEK (MAPK/extracellular signal-regulated kinase (ERK) kinase, a direct activator of MAPK), whereas treatment of ras-transformed cells with a MEK-specific inhibitor restored T-type Ca2+ channel activity. Using a T-type Ca2+ channel antagonist, we further found that suppression of the T-type Ca2+ channel by the activated MAPK pathway is a prerequisite event for the induction and/or maintenance of transformation-associated morphological changes.     

Conformational selection in protein binding and function

Protein binding and function often involves conformational changes. Advanced nuclear magnetic resonance (NMR) experiments indicate that these conformational changes can occur in the absence of ligand molecules (or with bound ligands), and that the ligands may “select” protein conformations for binding (or unbinding). In this review, we argue that this conformational selection requires transition times for ligand binding and unbinding that are small compared to the dwell times of proteins in different conformations, which is plausible for small ligand molecules. Such a separation of timescales leads to a decoupling and temporal ordering of binding/unbinding events and conformational changes. We propose that conformational‐selection and induced‐change processes (such as induced fit) are two sides of the same coin, because the temporal ordering is reversed in binding and unbinding direction. Conformational‐selection processes can be characterized by a conformational excitation that occurs prior to a binding or unbinding event, while induced‐change processes exhibit a characteristic conformational relaxation that occurs after a binding or unbinding event. We discuss how the ordering of events can be determined from relaxation rates and effective on‐ and off‐rates determined in mixing experiments, and from the conformational exchange rates measured in advanced NMR or single‐molecule fluorescence resonance energy transfer experiments. For larger ligand molecules such as peptides, conformational changes and binding events can be intricately coupled and exhibit aspects of conformational‐selection and induced‐change processes in both binding and unbinding direction.     

Changes of testicular cholesteryl ester hydrolase activity in experimentally cryptorchid rats

A simple and reliable method was developed to determine the neutral cholesteryl ester hydrolase (CEH) activity in rat testes, using cholesteryl-[1-14C]-oleate as substrate. The activity was due to a soluble enzyme present in the cytoplasm of predominantly Sertoli cells, which could be shown after depleting the testes of Leydig cells with ethane dimethyl sulphonate. This treatment also revealed that the loss of CEH activity in abdominal testes of experimentally cryptorchid rats takes place in the Sertoli cells. In prepubertal rats made unilaterally cryptorchid at birth, the CEH activity was significantly higher in the abdominal than in the scrotal testes at 16 days of age. This is earlier than any previously described biochemical change and coincides with, or may even precede, the earliest morphological changes which are accumulation of lipid droplets in the Sertoli cells. The testicular CEH activity then decreased to 30 days of age in the abdominal testes, whereas the activity increased in the contralateral, scrotal testes. When adult rats were made unilaterally cryptorchid for 24 h, the CEH activity decreased rapidly in the abdominal testes. These results suggest that a derangement in cholesteryl ester metabolism is an early event in the pathogenesis of testicular degeneration in cryptorchidism.     

Pacific Ocean climate change: atmospheric forcing, ocean circulation and ecosystem response

A major climate change event that affected atmospheric forcing, ocean circulation and ecosystem structure of the Pacific Ocean began in the mid-1970s. Changes in biomass, and presumably productivity, of the lower trophic levels (phytoplankton and Zooplankton) were directly attributed to this event. It also appears that some individual species at higher trophic levels were influenced, but cause-and-effect relationships are more difficult to document at the species level. Recent work shows that at least five major pelagic ecosystems responded to this event, but in different ways, and both increases and decreases in biomass were seen. Changes of this magnitude are well documented in the paleo-oceanographic record. However, it remains to be determined to what extent the changes were caused by natural cycles versus anthropogenic change (global warming).     

Analysis of Homeostatic Mechanisms in Biochemical Networks

Cell metabolism is an extremely complicated dynamical system that maintains important cellular functions despite large changes in inputs. This “homeostasis” does not mean that the dynamical system is rigid and fixed. Typically, large changes in external variables cause large changes in some internal variables so that, through various regulatory mechanisms, certain other internal variables (concentrations or velocities) remain approximately constant over a finite range of inputs. Outside that range, the mechanisms cease to function and concentrations change rapidly with changes in inputs. In this paper we analyze four different common biochemical homeostatic mechanisms: feedforward excitation, feedback inhibition, kinetic homeostasis, and parallel inhibition. We show that all four mechanisms can occur in a single biological network, using folate and methionine metabolism as an example. Golubitsky and Stewart have proposed a method to find homeostatic nodes in networks. We show that their method works for two of these mechanisms but not the other two. We discuss the many interesting mathematical and biological questions that emerge from this analysis, and we explain why understanding homeostatic control is crucial for precision medicine.