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love for the valley arises within us love to possess and thrive in this valley --Margaret Walker, 'Delta' (1942) (1) WILLIAM FAULKNER'S Absalom, Absalom! (1936) tells a history of the [...]

Extreme flood events can substantially affect riverine systems, modifying in-stream habitat and influencing fish assemblages and densities. Rare species are especially vulnerable to these disturbance events because of their small population size and often reduced phenotypic heterogeneity. In June 2016 the lower Elk River in West Virginia experienced severe flooding, resulting in a peak discharge that exceeded the 0.005 annual exceedance probability (>200 y flood) in the main stem. We obtained pre-flood and post-flood population count data and estimated abundances for one cohort of the federally endangered Diamond Darter (Crystallaria cincotla) at 15 sites. While both the total count data and total estimated abundance decreased following the flood, our analyses did not indicate the extreme flood event strongly impacted Diamond Darter abundance. This indicates individuals are able to withstand high velocities and resist displacement or mortality. In addition site-level abundances were estimated at three sentinel sites during 2015 and 2016 using a multinomial N-mixture model that accounted for variation in detectability resulting from water temperature. Mean estimated abundance varied among the three sites and between the 2 y. Our results suggest there is substantial variation in year-class strength between the two cohorts we sampled. It is suggested that survey efforts at established sentinel sites be continued on an annual basis in order to help determine factors influencing year-class strength., INTRODUCTION Disturbance events can drastically affect ecological systems, disrupting the physical environment and associated ecosystem, community, and population structure of organisms inhabiting these areas (Resh et al., 1988; Scheffer et [...]

Population monitoring is an essential component of endangered species recovery programs. The federally endangered Diamond Darter Crystallaria cincotta is in need of an effective monitoring design to improve our understanding of its distribution and track population trends. Because of their small size, cryptic coloration, and nocturnal behavior, along with limitations associated with current sampling methods, individuals are difficult to detect at known occupied sites. Therefore, research is needed to determine if survey efforts can be improved by increasing probability of individual detection. The primary objective of this study was to determine if there are seasonal and diel patterns in Diamond Darter detectability during population surveys. In addition to temporal factors, we also assessed five habitat variables that might influence individual detection. We used N-mixture models to estimate site abundances and relationships between covariates and individual detectability and ranked models using Akaike's information criteria. During 2013 three known occupied sites were sampled 15 times each between May and Oct. The best supported model included water temperature as a quadratic function influencing individual detectability, with temperatures around 22 C resulting in the highest detection probability. Detection probability when surveying at the optimal temperature was approximately 6% and 7.5% greater than when surveying at 16 C and 29 C, respectively. Time of Night and day of year were not strong predictors of Diamond Darter detectability. The results of this study will allow researchers and agencies to maximize detection probability when surveying populations, resulting in greater monitoring efficiency and likely more precise abundance estimates., Introduction Population monitoring is an essential component of endangered species recovery programs. One species for which monitoring is needed is the federally endangered Diamond Darter Crystallaria cincotta. It has been [...]

It has become a tradition to publish an image and some comments about photography from the PSA Board of Directors after they begin their two year term at the conclusion [...]

Anuran monitoring has increased in recent years in response to global population declines. Delineating abiotic factors that influence anuran activity patterns is important for maximizing monitoring and research efficiency. The Houston toad (Bufo (Anaxyrus) houstonensis) was the first amphibian to be listed as federally endangered in the United States, and populations have continued to decline since it was listed. In this study we investigated the influence of six abiotic factors and one biotic factor on Houston toad calling activity and terrestrial movement in the Lost Pines ecoregion of Texas. Using program PRESENCE, we treated the factors as survey-specific covariates to determine their influence on detection probabilities, and thus presumably activity levels. We found that average daily absolute humidity, average daily wind speed, and presence/absence of Houston toad calling activity the previous night were important factors influencing calling activity, and average daily absolute humidity and detection/non-detection of Houston toad movement activity the previous night were important factors influencing movement activity. We also found that multiple survey years were necessary to delineate influential factors for this species, a result with implications for activity patterns of other rare anurans. The results of this study contribute to our understanding of amphibian activity patterns, and will improve the efficiency of future Houston toad research and monitoring efforts., INTRODUCTION The worldwide decline in amphibians and reptiles is a major topic of current biodiversity research (Gibbons et al., 2000; Beebee and Griffiths, 2005; Reading et al., 2010). These declines [...]

The 2012 Lasker~Koshland Special Achievement Award in Medical Science recognizes Donald Brown (Carnegie Institute of Washington) and Thomas Maniatis (Columbia University) (Figure 1), two scientists whose career-long contributions were seminal [...]

Abstract.--Feral hogs (Sus scrofa) are considered a destructive exotic invasive species in the U.S., and their abundance appears to be increasing in the Lost Pines ecoregion of Texas. This is [...]

The news of Professor Allen Richmond Maxwell's death last week saddens his fellow anthropologists and Brunei researchers like us. Allen died on November 16, 2011, of a heart attack at [...]

On the fortieth anniversary of the Brunei Museum's publication of my monograph Brunei: The Structure and History of a Bornean Malay Sultanate, let me confess that in early 1966 I [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2009.10.041 Byline: Sandeep Mukhi, Liquan Cai, Donald D. Brown Keywords: Metamorphosis; Xenopus laevis; Gene expression; Remodelling; Thyroid hormone Abstract: During the climax of amphibian metamorphosis many tadpole organs remodel. The different remodeling strategies are controlled by thyroid hormone (TH). The liver, skin, and tail fibroblasts shut off tadpole genes and activate frog genes in the same cell without DNA replication. We refer to this as 'gene switching'. In contrast, the exocrine pancreas and the intestinal epithelium dedifferentiate to a progenitor state and then redifferentiate to the adult cell type. Tadpole and adult globin are not present in the same cell. Switching from red cells containing tadpole-specific globin to those with frog globin in the liver occurs at a progenitor cell stage of development and is preceded by DNA replication. Red cell switching is the only one of these remodeling strategies that resembles a stem cell mechanism. Author Affiliation: Carnegie Institution 3520 San Martin Dr., Baltimore, MD 21218, USA Article History: Received 18 August 2009; Revised 28 October 2009; Accepted 28 October 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2009.04.033 Byline: Alexander M. Schreiber, Sandeep Mukhi, Donald D. Brown Keywords: Metamorphosis; Remodeling; Intestine; Thyroid hormone; Transgenesis; Thyroid hormone receptors; Cell-cell interaction Abstract: Amphibian metamorphosis is accompanied by extensive intestinal remodeling. This process, mediated by thyroid hormone (TH) and its nuclear receptors, affects every cell type. Gut remodeling in Xenopus laevis involves epithelial and mesenchymal proliferation, smooth muscle thickening, neuronal aggregation, formation of intestinal folds, and shortening of its length by 75%. Transgenic tadpoles expressing a dominant negative TH receptor (TRDN) controlled by epithelial-, fibroblast-, and muscle-specific gene promoters were studied. TRDN expression in the epithelium caused abnormal development of virtually all cell types, with froglet guts displaying reduced intestinal folds, thin muscle and mesenchyme, absence of neurons, and reduced cell proliferation. TRDN expression in fibroblasts caused abnormal epithelia and mesenchyme development, and expression in muscle produced fewer enteric neurons and a reduced inter-muscular space. Gut shortening was inhibited only when TRDN was expressed in fibroblasts. Gut remodeling results from both cell-autonomous and cell-cell interactions. Author Affiliation: Carnegie Institution 3520 San Martin Dr., Baltimore, MD 21218, USA Article History: Received 5 February 2009; Revised 9 April 2009; Accepted 25 April 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2009.01.038 Byline: Sandeep Mukhi (a), Marko E. Horb (b)(c), Donald D. Brown (a) Keywords: Amphibian metamorphosis; Pancreas; [beta] cells; Thyroid hormone; Organ remodeling Abstract: Insulin-producing [beta]-cells are present as single cells or in small clusters distributed throughout the pancreas of the Xenopus laevis tadpole. During metamorphic climax when the exocrine pancreas dedifferentiates to progenitor cells, the [beta]-cells undergo two changes. Insulin mRNA is down regulated at the beginning of metamorphic climax (NF62) and reexpressed again near the end of climax. Secondly, the [beta]-cells aggregate to form islets. During climax the increase in insulin cluster size is not caused by cell proliferation or by acinar-to-[beta]-cell transdifferentiation, but rather is due to the aggregation of pre-existing [beta]-cells. The total number of [beta]-cells does not change during the 8 days of climax. Thyroid hormone (TH) induction of premetamorphic tadpoles causes an increase in islet size while prolonged treatment of tadpoles with the goitrogen methimazole inhibits this increase. Expression of a dominant negative form of the thyroid hormone receptor (TRDN) driven by the elastase promoter not only protects the exocrine pancreas of a transgenic tadpole from TH-induced dedifferentiation but also prevents aggregation of [beta]-cells at climax. These transgenic tadpoles do however undergo normal loss and resynthesis of insulin mRNA at the same stage as controls. In contrast transgenic tadpoles with the same TRDN transgene driven by an insulin promoter do not undergo down regulation of insulin mRNA, but do aggregate [beta]-cells to form islets like controls. These results demonstrate that TH controls the remodeling of [beta]-cells through cell-cell interaction with dedifferentiating acinar cells and a cell autonomous program that temporarily shuts off the insulin gene. Author Affiliation: (a) Department of Embryology, Carnegie Institution, 3520 San Martin Drive, Baltimore, MD 21218, USA (b) Laboratory of Molecular Organogenesis, Institut de Recherches Cliniques de Montreal, Montreal, Quebec, Canada (c) Departement de Medecine, Universite de Montreal, Canada Article History: Received 10 October 2008; Revised 13 January 2009; Accepted 28 January 2009

At metamorphosis the Xenopus laevis tadpole exocrine pancreas remodels in two stages. At the climax of metamorphosis thyroid hormone (TH) induces dedifferentiation of the entire exocrine pancreas to a progenitor state. The organ shrinks to 20% of its size, and [approximately equal to]40% of its cells die. The acinar cells lose their zymogen granules and [approximately equal to]75% of their RNA. The mRNAs that encode exocrine-specific proteins (including the transcription factor Ptf1a) undergo almost complete extinction at climax, whereas PDX-1, Notch-1, and Hes-1, genes implicated in differentiation of the progenitor cells, are activated. At the end of spontaneous metamorphosis when the endogenous TH has reached a low level, the pancreas begins to redifferentiate. Exogenous TH induces the dedifferentiation phase but not the redifferentation phase. The tadpole pancreas lacks the mature ductal system that is found in adult vertebrate pancreases, including the frog. Exocrine pancreases of transgenic tadpoles expressing a dominant negative form of the TH receptor controlled by the elastase promoter are resistant to TH. They do not shrink when subjected to TH. Their acinar cells do not dedifferentiate at climax, nor do they down-regulate exocrine-specific genes or activate Notch-1 and Hes-1. Even 2 months after metamorphosis these frogs have not developed a mature ductal system and the acinar cells are abnormally arranged. The TH-dependent dedifferentiation of the tadpole acinar cells at climax is a necessary step in the formation of a mature frog pancreas. dedifferentiation | thyroid hormone | Thyroid hormone receptor dominant negative | gene expression

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2007.03.021 Byline: Donald D. Brown, Liquan Cai Keywords: Amphibian metamorphosis; Thyroid hormone; Thyroid hormone receptor; Deiodinase; Gene expression; Xenopus leavis; Tadpole Author Affiliation: Department of Embryology, Carnegie Institution, 3520 San Martin Dr., Baltimore, MD 21218, USA Article History: Received 1 February 2007; Revised 9 March 2007; Accepted 18 March 2007

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2006.12.031 Byline: Liquan Cai, Biswajit Das, Donald D. Brown Keywords: Xenopus laevis; Metamorphosis; Thyroid hormone; Gene expression; Muscle development; Transgenesis Abstract: Transgenic Xenopus laevis tadpoles that express a dominant negative form of the thyroid hormone receptor (TRDN) controlled by the cardiac actin muscle promoter (pCar) develop with very little limb muscle. Under the control of the tetracycline system the transgene can be induced at will by adding doxycycline to the rearing water. Pre-existing limb muscle fibers begins to disintegrate within 2 days after up-regulation of the TRDN transgene. The muscle cells do not die even after weeks of transgene exposure when the myofibrils have degenerated completely and the tadpole is nearing death. A microarray analysis after 2 weeks of exposure to the transgene identified 24 muscle genes whose expression was altered in such a way that they might cause the muscle phenotype. These candidate genes are normally activated in growing limb muscle but they are repressed by the TRDN transgene. Several of these genes have been implicated in mammalian myopathies. However, the expression of only one of these genes, calsequestrin, is down-regulated in 1 day and therefore might initiate the degeneration. Calsequestrin is one of several affected genes that encode proteins involved in calcium sequestration, transport and utilization in muscle suggesting that uncontrolled calcium influx into the growing limb muscle fibers causes rhabdomyolysis. Many of the same genes that are down-regulated in the tail at the peak of metamorphic climax just before it is resorbed are suppressed in the transgenic limb muscle in effect turning the limb growth program into a tail resorption program. Author Affiliation: Carnegie Institution, 3520 San Martin Dr. Baltimore, MD 21218, USA Article History: Received 7 August 2006; Revised 14 November 2006; Accepted 13 December 2006

This paper presents a novel procedure for approximating the global optimum in structural design by combining multivariate adaptive regression splines (MARS) with a response surface methodology (RSM). MARS is a flexible regression technique that uses a modified recursive partitioning strategy to simplify high-dimensional problems into smaller yet highly accurate models. Combining MARS and RSM improves the conventional RSM by addressing highly nonlinear high-dimensional problems that can be simplified into lower dimensions, yet maintains a low computational cost and better interpretability when compared to neural networks and generalized additive models. MARS/RSM is also compared to simulated annealing and genetic algorithms in terms of computational efficiency and accuracy. The MARS/RSM procedure is applied to a set of low-dimensional test functions to demonstrate its convergence and limiting properties. Index Terms--Genetic algorithm (GA), neural network (NN), simulated annealing (SA), successive response surface methodology (SRSM).

In situ time-of-flight neutron diffraction is used to examine the martensitic phase transformation during quasistatic uniaxial compression testing of 304L stainless steel at 300 and 203 K. The findings have disclosed the orientation relationships between the austenite and the newly formed martensites.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2005.12.032 Byline: Biswajit Das (a), Liquan Cai (a), Mark G. Carter (b), Yu-Lan Piao (b), Alexei A. Sharov (b), Minoru S.H. Ko (b), Donald D. Brown (a) Keywords: Thyroid hormone; Metamorphosis; Tadpole; Xenopus laevis; Tail resorption; Limb growth; Brain ventricle proliferation; Mitochondrial electron transport chain; Cell cycle; Transcriptional regulation Abstract: Thyroid hormone (TH) controlled gene expression profiles have been studied in the tail, hind limb and brain tissues during TH-induced and spontaneous Xenopus laevis metamorphosis. Amplified cRNA probes mixed with a universal standard were hybridized to a set of 21,807-sense strand 60-mer oligonucleotides on each slide representing the entries in X. laevis UniGene Build 48. Most of the up-regulated genes in hind limb and brain are the same. This reflects in part the fact that the initial response to TH induction in both tissues is cell proliferation. A large number of up-regulated genes in the limb and brain programs encode common components of the cell cycle, DNA and RNA metabolism, transcription and translation. Notch is one of the few genes that is differentially expressed exclusively in the brain in the first 48 h of TH induction studied in these experiments. The TH-induced gene expression changes in the tail are different from the limb and brain programs. Distinct muscle and fibroblast programs were identified in the tail. Dying muscle fibers in tail (marked by active caspase-3) up-regulate a group of genes that include proteolytic enzymes. At the climax of metamorphosis, tail muscle down-regulates more than half of the genes that encode the glycolytic enzymes in the cytoplasm and the tricarboxylic acid pathway and all five complexes of the electron transport system in mitochondria. These changes in gene expression precede the activation of caspase-3. Some of these same energy metabolism-related genes are up-regulated in the limb and brain programs by TH. A prominent feature of the tail fibroblasts is the down-regulation of several collagen and other extra cellular matrix genes and the up-regulation of hydrolytic enzymes that are responsible for dissolving the notochord and resorbing the tail. Author Affiliation: (a) Department of Embryology, Carnegie Institution of Washington, 3520 San Martin Drive, Baltimore, MD 21218, USA (b) Developmental Genomics and Aging Section, Laboratory of Genetics, National Institute on Aging, NIH, Baltimore, MD 21224, USA Article History: Received 30 September 2005; Revised 8 December 2005; Accepted 14 December 2005

The role of thyroid hormones in causing gene expression changes during metamorphosis in tadpoles of Xenopus laevis is discussed.

Thyroid hormone (TH) is required for limb development in Xenopus laevis. Specific cell types in the growing limb were targeted for expression of a dominant negative form of the TH receptor by sperm-mediated transgenesis. Limb muscle development, the innervation of muscle from the spinal cord, and cartilage growth can be inhibited without affecting patterning of the limb or differentiation of other cell types. Remodeling of the skin occurs late in metamorphosis after the limb has formed. The coordination of these independent programs is affected in part by the control that TH exerts over DNA replication in all cell types of the limb. transgenesis | cell autonomy | thyroid hormone receptor | DNA replication

Thyroid hormone controls remodeling of the tadpole intestine during the climax of amphibian metamorphosis. In 8 days, the Xenopus laevis tadpole intestine shortens in length by 75%. Simultaneously, the longitudinal muscle fibers contract by about the same extent. The radial muscle fibers also shorten as the diameter narrows. Many radial fibers undergo programmed cell death. We conclude that muscle remodeling and contraction play key roles in the shortening process, Shortening is accompanied by a temporary 'heaping' of the epithelial cells into many layers at climax. Cells that face the lumen undergo apoptosis, By the end of metamorphosis, when the epithelium is folded into crypts and villi, the epithelium is a single-cell layer once again. Throughout this remodeling, DNA replication occurs uniformly throughout the epithelium, as do changes in gene expression. The larval epithelial cells as a whole, rather than a subpopulation of stem cells, are the progenitors of the adult epithelial cells. BrdUrd | caspase-3 | smooth muscle | epithelium | thyroid hormone

Epoch-based electromyogram (EMG) amplitude estimates have not incorporated signal whitening, even though whitening has demonstrated significant improvements for stream-based estimates. This paper presents new epoch-based algorithms, for both single- and multiple-channel EMG, which include a whitening stage. The best multiple-channel whitening processor provided a 21.4%-22.5% improvement over single-channel unwhitened estimation in an EMG-to-torque application. Index Terms--Biomedical signal processing, electromyography, EMG amplitude estimation, functional electrical stimulation, myoelectric signal processing, whitening.

With the rapid growth of the elderly population, there is a need to support the ability of elders to maintain an independent and healthy lifestyle in their homes rather than through more expensive and isolated care facilities. One approach to accomplish these objectives employs the concepts of ambient intelligence to remotely monitor an elder's activities and condition. The Smart-House project uses a system of basic sensors to monitor a person's in-home activity; a prototype of the system is being tested within a subject's home. We examined whether the system could be used to detect behavioral patterns and report the results in this paper. Mixture models were used to develop a probabilistic model of behavioral patterns. The results of the mixture-model analysis were then evaluated by using a log of events kept by the occupant. Index Terms--Ambient intelligence, human behavior models, mixture models.

Human universals--of which hundreds have been identified--consist of those features of culture, society, language, behavior, and mind that, so far as the record has been examined, are found among all [...]

Sperm-mediated transgenesis of Xenopus laevis is the first application of genetic methodology to an amphibian. However, some transgenes are lethal when they are expressed constitutively. To study the influence of these genes on amphibian metamorphosis and to generate [F.sub.1] progeny from mature transgenic adults, these transgenes must be placed under the control of an inducible system so that they can be activated at specific times in development. We show that two well known binary inducible gene expression systems supplement transgenesis for the study of X. laevis metamorphosis, one system controlled by the progesterone analogue RU-486 and the other controlled by the tetracycline derivative doxycycline. By inducing a dominant negative form of the thyroid hormone receptor under the control of doxycycline specifically in the nervous system we have delimited the developmental periods within which thyroid hormone controls innervation of the developing limb from the spinal cord.

The thyroid gland synthesizes thyroxine (T4), which passes through the larval tadpole's circulatory system. The enzyme type II iodothyronine deiodinase (D2) converts thyroxine (T4) to the active hormone 3,5,3'-triiodothyronine (T3) in peripheral tissues. An early response to thyroid hormone (TH) in the Xenopus laevis tadpole is the stimulation of cell division in cells that line the brain ventricles, the lumen of the spinal cord, and the limb buds. These cells express constitutively high levels of D2 mRNA. Exogenous T4 induces early DNA synthesis in brain, spinal cord, and limb buds as efficiently as T3. The deiodinase inhibitor iopanoic acid blocks T4- but not T3-induced cell division. At metamorphic climax, both TH-induced cell division and D2 expression decrease in the brain. Then D2 expression appears in late-responding tissues including the anterior pituitary, the intestine, and the tail where cell division is reduced or absent. Therefore, constitutive expression of D2 occurs in the earliest target tissues of TH that will grow and differentiate, while TH-induced expression of D2 takes place in late-responding tissues that will remodel or die. This pattern of constitutive and induced D2 expression contributes to the timing of metamorphic changes in these tissues. Keywords: Metamorphosis; Xenopus laevis; Thyroid hormone; Deiodinase; Gene expression; Cell division; Spinal cord; Intestine; Tail; Brain

During premetamorphic stages, Xenopus laevis tadpoles expressing either a dominant-negative thyroid hormone (TH) receptor or a type-III iodothyronine deiodinase transgene in the nervous system have reduced TH-induced proliferation in the spinal cord and produce fewer hindlimb-innervating motorneurons. During prometamorphic stages, innervation of the hindlimbs is reduced, and few functional neuromuscular connections are formed. By metamorphic climax, limb movement is impaired, ranging from uncoordinated leg swimming to complete quadriplegia. This phenotype is due to transgene action in the tadpole spinal cord. The requirement of TH for neurogenesis during premetamorphosis is the earliest TH-regulated process reported to date in the sequence of metamorphic changes in anurans. The muscle formed during limb growth was previously shown to be a direct target of TH control. Here, we show that the same is true of the development of spinal cord cells that innervate the limbs.

Transgenic tadpoles that express a dominant negative thyroid hormone (TH) receptor specifically in their skin undergo normal metamorphosis, with one exception: they retain a larval epidermis over the developing adult epithelium. TH-induced death of the tadpole epidermis is inhibited by the dominant negative TH receptor whereas the TH-induced response of the neighboring fibroblasts and the cells that form the adult skin occur normally. Therefore death of the tadpole skin is a direct and cell autonomous target of TH, and its protection has no detectable influence on TH-induced changes of other cell types.

Xenopus laevis tadpole tails contain fast muscle fibers oriented in chevrons and two pairs of slow muscle 'cords' along the length of the tail. When tail resorption is inhibited by a number of different treatments, fast muscle but not the slow cord muscle still is lost, demonstrating that the fast tail muscle is a direct target of the thyroid hormone-induced death program. Expression of a dominant negative form of the thyroid hormone receptor (TRDN[alpha]) was restricted to tadpole muscle by means of a muscle-specific promoter. Even though the transgene protects fast tail muscle from thyroid hormone (TH)-induced death, the tail shortens, and the distal muscle chevrons at the tail tip are degraded. This default pathway for muscle death is probably caused by the action of proteolytic enzymes secreted by neighboring fibroblasts. Non-muscle tissues that are sensitive to TH, such as the fibroblasts, are not protected by the transgene when it is expressed solely in muscle. If allowed to develop to metamorphosis, these transgenic animals die at the climax of metamorphosis before tail resorption has begun. Their limbs have very little muscle even though the rest of limb morphology is normal. Thus, fast tail muscle and limb muscle have their own cell autonomous death and growth programs, respectively, that are independent of the fate of the other neighboring cell types. In contrast, death of the slow muscle is controlled by the other cell types of the tail.