USGS Science⌕ Search

SEARCH · USGS Science

Results for “Cells”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources
USGS2000

Test functions for three-dimensional control-volume mixed finite-element methods on irregular grids

Numerical methods based on unstructured grids, with irregular cells, usually require discrete shape functions to approximate the distribution of quantities across cells. For control-volume mixed finite-element methods, vector shape functions are used to approximate the distribution of velocities across cells and vector test functions are used to minimize the error associated with the numerical approximation scheme. For a logically cubic mesh, the lowest-order shape functions are chosen in a natural way to conserve intercell fluxes that vary linearly in logical space. Vector test functions, while somewhat restricted by the mapping into the logical reference cube, admit a wider class of possibilities. Ideally, an error minimization procedure to select the test function from an acceptable class of candidates would be the best procedure. Lacking such a procedure, we first investigate the effect of possible test functions on the pressure distribution over the control volume; specifically, we look for test functions that allow for the elimination of intermediate pressures on cell faces. From these results, we select three forms for the test function for use in a control-volume mixed method code and subject them to an error analysis for different forms of grid irregularity; errors are reported in terms of the discrete L2 norm of the velocity error. Of these three forms, one appears to produce optimal results for most forms of grid irregularity.

Conference Paper↗
USGS2006

Non-invasive method to obtain DNA from freshwater mussels (Bivalvia: Unionidae)

To determine whether DNA could be isolated from tissues obtained by brush-swabbing the mantle, viscera and foot, mantle-clips and swabbed cells were obtained from eight Quadrula pustulosa (Lea, 1831). DNA yields from clips and swabbings were 447.0 and 975.3 ??g/??L, respectively. Furthermore, comparisons of sequences from the ND-1 mitochondrial gene region showed a 100% sequence agreement of DNA from cells obtained by clips and swabs. To determine the number of swabs needed to obtain adequate yields of DNA for analyses, the visceras and feet of 5 Q. pustulosa each were successively swabbed 2, 4 and 6 times. DNA yields from the 2, 4 and 6 swabbed mussel groups were 399.4, 833.8 and 852.6 ng/??L, respectively. ND-1 sequences from the lowest yield still provided 846-901 bp for the ND-1 region. Nevertheless, to ensure adequate DNA yield from cell samples obtained by swabbing, we recommend that 4 swab-strokes of the viscera and foot be obtained. The use of integumental swabbing for collection of cells for determination of genetic relationships among freshwater mussels is noninvasive, when compared with tissue collection by mantle-clipping. Therefore, its use is recommended for freshwater mussels, especially state-protected or federally listed mussel species.

Journal of Shellfish Research↗
USGS2013

Urban runoff (URO) process for MODFLOW 2005: simulation of sub-grid scale urban hydrologic processes in Broward County, FL

Climate change and sea-level rise could cause substantial changes in urban runoff and flooding in low-lying coast landscapes. A major challenge for local government officials and decision makers is to translate the potential global effects of climate change into actionable and cost-effective adaptation and mitigation strategies at county and municipal scales. A MODFLOW process is used to represent sub-grid scale hydrology in urban settings to help address these issues. Coupled interception, surface water, depression, and unsaturated zone storage are represented. A two-dimensional diffusive wave approximation is used to represent overland flow. Three different options for representing infiltration and recharge are presented. Additional features include structure, barrier, and culvert flow between adjacent cells, specified stage boundaries, critical flow boundaries, source/sink surface-water terms, and the bi-directional runoff to MODFLOW Surface-Water Routing process. Some abilities of the U rban R un O ff (URO) process are demonstrated with a synthetic problem using four land uses and varying cell coverages. Precipitation from a hypothetical storm was applied and cell by cell surface-water depth, groundwater level, infiltration rate, and groundwater recharge rate are shown. Results indicate the URO process has the ability to produce time-varying, water-content dependent infiltration and leakage, and successfully interacts with MODFLOW.

Florida↗
USGS2014

Viral erythrocytic necrosis

Viral erythrocytic necrosis (VEN), originally termed piscine erythrocytic necrosis, is a condition that has been reported to affect the red blood cells (RBCs) of many species of marine and anadromous fishes in both the Atlantic and Pacific Oceans (Nicholson and Reno 1981; Smail 1982; Wolf 1988; Dannevig and Thorud 1999). Fish with VEN may develop a severe anemia that can reduce their stamina, predispose them to other infections or increase the impact of other stressors (MacMillan et al. 1980; Nicholson and Reno 1981; Meyers et al. 1986; Haney et al. 1992) resulting in population-scale impacts in susceptible species (Hershberger et al. 2009). In spite of extensive efforts, the etiological agent of VEN has not been propagated in fish cell lines making its characterization difficult. However, transmission electron microscopy (TEM) of red blood cells from diseased fish convincingly demonstrates the presence of iridovirus-like particles that have been given the name erythrocytic necrosis virus (ENV). While the ENV virions in red blood cells of various species of fish from differing geographic locations may appear morphologically distinct (Smail 1982; Wolf 1988), at least one strain of ENV has now been partially sequenced, confirming it to be a member of the family Iridoviridae (Emmenegger et al. in press). However, the genetic relatedness of ENV from various fish hosts has not yet been investigated.

Book chapter↗
USGS2015

Mixing effects on nitrogen and oxygen concentrations and the relationship to mean residence time in a hyporheic zone of a riffle-pool sequence

Flow paths and residence times in the hyporheic zone are known to influence biogeochemical processes such as nitrification and denitrification. The exchange across the sediment-water interface may involve mixing of surface water and groundwater through complex hyporheic flow paths that contribute to highly variable biogeochemically active zones. Despite the recognition of these patterns in the literature, conceptualization and analysis of flow paths and nitrogen transformations beneath riffle-pool sequences often neglect to consider bed form driven exchange along the entire reach. In this study, the spatial and temporal distribution of dissolved oxygen (DO), nitrate (NO 3 - ) and ammonium (NH 4 + ) were monitored in the hyporheic zone beneath a riffle-pool sequence on a losing section of the Truckee River, NV. Spatially-varying hyporheic exchange and the occurrence of multi-scale hyporheic mixing cells are shown to influence concentrations of DO and NO 3 - and the mean residence time (MRT) of riffle and pool areas. Distinct patterns observed in piezometers are shown to be influenced by the first large flow event following a steady 8 month period of low flow conditions. Increases in surface water discharge resulted in reversed hydraulic gradients and production of nitrate through nitrification at small vertical spatial scales (0.10 to 0.25 m) beneath the sediment-water interface. In areas with high downward flow rates and low MRT, denitrification may be limited. The use of a longitudinal two-dimensional flow model helped identify important mechanisms such as multi-scale hyporheic mixing cells and spatially varying MRT, an important driver for nitrogen transformation in the riverbed. Our observations of DO and NO 3 - concentrations and model simulations highlight the role of multi-scale hyporheic mixing cells on MRT and nitrogen transformations in the hyporheic zone of riffle-pool sequences. This article is protected by copyright. All rights reserved.

Water Resources Research↗
USGS2023

Susceptibility of Pallid Sturgeon to viral hemorrhagic septicemia virus genotype IVb

Objective Viral hemorrhagic septicemia virus (VHSV) is an aquatic rhabdovirus causing severe disease in freshwater and saltwater fish species. The susceptibility of endangered Pallid Sturgeon Scaphirhynchus albus to VHSV genotype IVb (VHSV-IVb) infection was investigated. Methods An in vitro assessment using two Pallid Sturgeon cell lines derived from skin and spleen tissue and in vivo evaluation of juvenile Pallid Sturgeon after exposure to VHSV-IVb were performed. Result Plaque assay and RT-PCR results confirmed VHSV-IVb replication in Pallid Sturgeon cell lines. Sturgeon were also susceptible to VHSV-IVb infection after immersion and injection exposures during laboratory experiments. However, after widespread mortality occurred in all treatment groups, including negative control fish, it was determined that the Pallid Sturgeon stock fish were infected with Missouri River sturgeon iridovirus (MRSIV) prior to experimental challenge. Nevertheless, mortalities were equal or higher among VHSV-exposed fish than among negative controls (MRSIV infected), and histopathological assessments indicated reduced hematopoietic cells in spleen and kidney tissues and hemorrhage in the gastrointestinal organs only in fish from the VHSV treatment. Conclusion These results indicate that Pallid Sturgeon is a susceptible host for VHSV-IVb, but the degree of pathogenicity was confounded by the underlying MRSIV infection. Research comparing susceptibility of specific pathogen-free and MRSIV-infected fish to VHSV-IVb is needed to accurately assess the vulnerability of Pallid Sturgeon to VHSV-IVb.

Journal of Aquatic Animal Health↗
USGS2005

Cortisol receptor blockade and seawater adaptation in the euryhaline teleost Fundulus heteroclitus

To examine the role of cortisol in seawater osmoregulation in a euryhaline teleost, adult killifish were acclimated to brackish water (10???) and RU486 or vehicle was administered orally in peanut oil daily for five days at low (40 mg.kg-1) or high dose (200 mg.kg-1). Fish were transferred to 1.5 x seawater (45???) or to brackish water (control) and sampled at 24 h and 48 h after transfer, when Cl- secretion is upregulated. At 24 h, opercular membrane Cl- secretion rate, as Isc, was increased only in the high dose RU486 group. Stimulation of membranes by 3-isobutyl-1-methylxanthine and cAMP increased Isc in vehicle treated controls but those from RU486-treated animals were unchanged and membranes from brackish water animals showed a decrease in Isc. At 48 h, Isc increased and transepithelial resistance decreased in vehicle and RU486 groups, compared to brackish water controls. Plasma cortisol increased in all groups transferred to high salinity, compared to brackish water controls. RU486 treated animals had higher cortisol levels compared to vehicle controls. Vehicle treated controls had lower cortisol levels than untreated or RU486 treated animals, higher stimulation of Isc, and lower hematocrit at 24 h, beneficial effects attributed to increased caloric intake from the peanut oil vehicle. Chloride cell density was significantly increased in the high dose RU486 group at 48 hours, yet Isc was unchanged, suggesting a decrease in Cl- secretion per cell. Thus cortisol enhances NaCl secretion capacity in chloride cells, likely via glucocorticoid type receptors. ?? 2005 Wiley-Liss, Inc.

Journal of Experimental Zoology Part A: Comparativ↗
USGS2007

Differential expression and localization of four connexins in the ovary of the ayu (Plecoglossus Altivelis)

The post-vitellogenic oocytes of teleost fish are generally unresponsive to maturation-inducing hormone (MIH) until a luteinizing hormone (LH) surge stimulates sensitivity via the acquisition of oocyte-maturational competence (OMC). Heterologous gap junctions (GJs) between granulosa cells and the oocyte have been previously implicated in the regulation of oocyte maturation in various vertebrate species. Although heterologous GJ are present in ovarian follicles of ayu (Plecoglossus altivelis), their role in maturation remains unclear. In the present study, we cloned and characterized complementary DNAs for GJ protein connexin (Cx), and examined the expression pattern of Cx messenger RNAs in the ayu ovary. Four Cx cDNAs with predicted molecular masses of 32.1 (Cx32.1), 34.9 (Cx34.9), 44.1 (Cx44.1), and 44.2 (Cx44.2) kDa, respectively, were cloned. Northern blot analysis revealed that the levels of Cx44.1 and Cx44.2 transcripts were similar during the vitellogenic and ovulatory stages. Cx32.1 transcripts were more abundant during the vitellogenic stage, but their levels declined thereafter. Cx34.9 transcript levels increased during the vitellogenic stage and remained high during the acquisition of OMC. In situ hybridization revealed that Cx44.1 and Cx44.2 signals were restricted to the oocyte, whereas the Cx32.1 and Cx34.9 signals were detected in both cellular fractions. Furthermore, a dye-transfer assay revealed the presence of functional GJs between the oocytes and follicle cells. These results suggest that Cx34.9 contributes to the formation of heterologous GJs between oocytes and granulosa cells. Moreover, GJs formed by Cx34.9 may function during the LH-dependent acquisition of OMC and the MIH-dependent resumption of meiosis in ayu. ?? 2007 Wiley-Liss, Inc.

Molecular Reproduction and Development↗
USGS2006

Application and testing of a procedure to evaluate transferability of habitat suitability criteria

A procedure designed to test the transferability of habitat suitability criteria was evaluated in the Cache la Poudre River, Colorado. Habitat suitability criteria were developed for active adult and juvenile rainbow trout in the South Platte River, Colorado. These criteria were tested by comparing microhabitat use predicted from the criteria with observed microhabitat use by adult rainbow trout in the Cache la Poudre River. A one-sided X 2 test, using counts of occupied and unoccupied cells in each suitability classification, was used to test for non-random selection for optimum habitat use over usable habitat and for suitable over unsuitable habitat. Criteria for adult rainbow trout were judged to be transferable to the Cache la Poudre River, but juvenile criteria (applied to adults) were not transferable. Random subsampling of occupied and unoccupied cells was conducted to determine the effect of sample size on the reliability of the test procedure. The incidence of type I and type II errors increased rapidly as the sample size was reduced below 55 occupied and 200 unoccupied cells. Recommended modifications to the procedure included the adoption of a systematic or randomized sampling design and direct measurement of microhabitat variables. With these modifications, the procedure is economical, simple and reliable. Use of the procedure as a quality assurance device in routine applications of the instream flow incremental methodology was encouraged.

Colorado↗
USGS2005

Cryogenic preservation of semen from the Aleutian Canada goose (Branta canadensis leucopareia)

Aleutian Canada geese ( Branta canadensis leucopareia ) were inseminated with frozen-thawed semen containing 6% or 7% dimethylsulfoxide (DMSO) resulting in 32 fertile eggs and 17 goslings; with 7% DMSO, 19 of 31 eggs were fertile. Beltsville Poultry Semen Extender (BPSE), adjusted to 270 ± 30 mOs and 7.5 ± 0.4 pH, was used to dilute semen samples and the DMSO before cryopreservation. About half of the live spermatozoa in the fresh semen (92.9 ± 2.5% live cells, laboratory studies; 87.3 ± 7.3%, insemination trials) survived the freeze-thaw process (46.7 ± 7.8%, laboratory; 33.3 ± 17.8%, insemination trials). Samples of frozen-thawed semen contained a greater percentage of bent spermatozoa (27.1 ± 8.4% of live cells) than fresh semen (14.4 ± 3.0% of live cells). Fecal- and urate-contaminated semen (a common problem when collecting goose semen) reduced the sperm motility score from 3.2 ± 0.6 to 2.7 ± 0.7 and number of live spermatozoa in frozen-thawed semen from 49 ± 9% to 24 ± 18%. Other variables examined that had less of an effect on semen quality included semen extenders, semen holding temperature, dilution and equilibration, relationship between hour of semen collection and level of semen contamination, and the relationship between season and sperm concentration.

Zoo Biology↗
USGS1998

Fish thymocyte viability, apoptosis and necrosis: In-vitro effects of organochlorine contaminants

The thymus is believed to be a central component of haematopoiesis and immune function in teleosts. Hence, chemically-elicited adverse effects to the thymus may result in immunomodulation and organ dysfunction. The objective of this research was to assess the levels of active (apoptotic) and passive (necrotic) cell death in untreated and organochlorine treated fish thymocytes. Lake trout ( Salvelinus namaycush ) thymocytes were challenged with Aroclor 1254 (concentration range 1·5–10·5 μg ml −1 ) and alpha, beta, gamma, delta isomers of hexachlorocyclohexane (concentration range 10–100 μ M ). The resulting maintenance or loss of viability was assessed by cytofluorometry (expression of phosphatidylserine and exclusion of propidium iodide) and confirmed with fluorescence microscopy. The results indicate that 20–60% of thymocytes in healthy fish undergo apoptosis, whereas thymocytes treated for 6–24 h with organochlorines exhibit increased levels of apoptotic cell death. This study demonstrates that given sufficient concentration, contact time and cellular receptors, organochlorines such as Aroclor 1254 and hexachloro-cyclohexanes may induce direct or indirect toxicity, altered functionality, or cell death to an organ important for fish immunocompetence.

Fish and Shellfish Immunology↗
USGS2003

Measurement of in vitro leucocyte mitogenesis in fish: ELISA based detection of the thymidine analogue 5'-bromo-2'-deoxyuridine

In this study we present a method for the measurement of in vitro mitogenesis in fish leucocytes that is based on the incorporation of the thymidine analogue 5′-bromo-2′-deoxyuridine (BrdU) into the DNA of replicating cells, followed by ELISA-based detection. This technique, adapted from methods developed for mammalian cells, operates on a similar biological principle to 3 H-thymidine incorporation, but circumvents the logistical and safety issues inherent with the radioactive label. Because it directly measures DNA proliferation, the assay has advantages over other colorimetric methods that may be strongly influenced by leucocyte metabolic status. Using BrdU incorporation followed by ELISA, we evaluate the responsiveness of rainbow trout ( Oncorhynchus mykiss [Walbaum]) leucocytes to the mammalian T-cell mitogen Concanavalin A (Con A) as well as the differential response of white perch ( Morone americana [Gmelin]) leucocytes to Con A and pokeweed mitogen. Specific considerations intrinsic to the assay system are discussed, including the implications of utilising enzyme-based detection.

Fish and Shellfish Immunology↗
USGS2001

Effects of growth hormone and cortisol on Na+-K+-2C1-cotransporter localization and abundance the gills of Atlantic salmon

The hormones responsible for the regulation of the teleostean gill Na + –K + –2Cl − cotransporter have not been elucidated. With Western blotting and immunocytochemistry, Na + –K + –2Cl − cotransporter abundance and localization were examined in the gills of Atlantic salmon ( Salmo salar ) following 2-week treatment with growth hormone (GH; 5.0 μg · g −1 ), cortisol (50 μg · g −1 ), and both hormones in combination (GH+cortisol). GH and cortisol treatments increased gill Na + –K + –2Cl − cotransporter abundance over levels seen in controls, and both hormones together (GH+cortisol) produced a greater effect than either hormone alone. Gill Na + ,K + –ATPase activity was also elevated by all three hormone treatments. Compared to controls, Na + –K + –2Cl − cotransporter immunoreactive chloride cells on the primary filament were greater in number and size following all three treatments. Although the number of immunoreactive chloride cells on the secondary lamellae did not differ among the treatment groups, GH+cortisol increased their size. These data indicate that GH and cortisol increase gill Na + –K + –2Cl − cotransporter abundance through chloride cell proliferation and differentiation in the gills of Atlantic salmon and are likely the hormones responsible for Na + –K + –2Cl − cotransporter regulation during smolting and seawater acclimation.

Massachusetts↗
USGS1989

Comparison of whole body and tissue blood volumes in rainbow trout (Salmo gairdneri) with 125 I bovine serum albumin and 51 Cr-erythrocyte tracers

Total, packed cell and, plasma volume estimates were made for the whole body and selected tissues of rainbow trout by the simultaneous injection of radiolabelled trout erythrocyte ( 51 Cr-RBC) and radioiodinated bovine serum albumin ( 125 I-BSA) tracers. Blood volumes were estimated with both markers separately by the tracer-hematocrit method and as the combination of the 51 Cr-RBC packed cell and 125 I-BSA plasma volumes. Mean whole body blood volume was significantly less when calculated from the 51 Cr-RBC tracer data (3.52±0.78 ml/100 g; ±SD) than when calculated with the 125 I-BSA tracer (5.06±0.86 ml/100 g) or as the sum of the two volumes combined (4.49±0.60 ml/100 g). The whole body hematocrit (28±5%), estimated as the quotient of the 51 Cr-RBC volume divided by the sum of the 125 I-BSA and the 51 Cr-RBC volumes, also was significantly less than the dorsal aortic microhematocrit (36±4%). Estimates of total blood volumes in most tissues were significantly smaller when calculated from the 51 Cr-RBC data than when calculated by the other two methods. Tissue blood volumes were greatest in highly vascularized and well perfused tissues and least in poorly vascularized tissues. The relative degree of vascularization among tissues generally remained the same regardless of whether the red cell or the plasma tracer was used to calculated blood volume. It is not clear whether the expanded plasma volume is the result of the distribution of erythrocyte-poor blood into the secondary circulation or the result of extravascular exchange of plasma proteins.

Fish Physiology and Biochemistry↗
USGS1994

An integrated data-directed numerical method for estimating the undiscovered mineral endowment in a region

An integrated data-directed numerical method has been developed to estimate the undiscovered mineral endowment within a given area. The method has been used to estimate the undiscovered uranium endowment in the San Juan Basin, New Mexico, U.S.A. The favorability of uranium concentration was evaluated in each of 2,068 cells defined within the Basin. Favorability was based on the correlated similarity of the geologic characteristics of each cell to the geologic characteristics of five area-related deposit models. Estimates of the undiscovered endowment for each cell were categorized according to deposit type, depth, and cutoff grade. The method can be applied to any mineral or energy commodity provided that the data collected reflect discovered endowment. ?? 1994 Oxford University Press.

Nonrenewable Resources↗
USGS2007

A GIS-based groundwater travel time model to evaluate stream nitrate concentration reductions from land use change

Excessive nitrate-nitrogen (nitrate) loss from agricultural watersheds is an environmental concern. A common conservation practice to improve stream water quality is to retire vulnerable row croplands to grass. In this paper, a groundwater travel time model based on a geographic information system (GIS) analysis of readily available soil and topographic variables was used to evaluate the time needed to observe stream nitrate concentration reductions from conversion of row crop land to native prairie in Walnut Creek watershed, Iowa. Average linear groundwater velocity in 5-m cells was estimated by overlaying GIS layers of soil permeability, land slope (surrogates for hydraulic conductivity and gradient, respectively) and porosity. Cells were summed backwards from the stream network to watershed divide to develop a travel time distribution map. Results suggested that groundwater from half of the land planted in prairie has reached the stream network during the 10 years of ongoing water quality monitoring. The mean travel time for the watershed was estimated to be 10.1 years, consistent with results from a simple analytical model. The proportion of land in the watershed and subbasins with prairie groundwater reaching the stream (10-22%) was similar to the measured reduction of stream nitrate (11-36%). Results provide encouragement that additional nitrate reductions in Walnut Creek are probable in the future as reduced nitrate groundwater from distal locations discharges to the stream network in the coming years. The high spatial resolution of the model (5-m cells) and its simplicity may make it potentially applicable for land managers interested in communicating lag time issues to the public, particularly related to nitrate concentration reductions over time. ?? 2007 Springer-Verlag.

Environmental Geology↗
USGS2018

Monitoring responses to variation in food supply for a migratory waterfowl: American Black Duck (Anas rubripes) in winter

Wintering Black Ducks ( Anas rubripes ) concentrate in wetlands along the Atlantic coast where natural and anthropogenic disturbances have increased over the last 50 years, a period in which the population of Black Ducks has declined. We studied the sensitivity of Black Ducks to perturbations in food supply that often result from disturbances by storms, predators, and people. In the paper, we characterize the responses of captive Black Ducks to shifts in food quality and availability during winter and apply those measures to a comparison of wild birds. Captive ducks that were fed intermittently (3 consecutive days/week) compensated for fasted days to achieve similar body mass and body fat to control birds that were fed every day on both animal- and plant-based diets. However, birds that were fed intermittently expended 15% more energy each day than controls when both groups were fed (536 vs. 464 kJ/kg 0.75 ), which indicates that variable food supply increases the costs of maintenance and thus reduces the number of birds that can be supported on the same resource of food without interruptions to foraging. Egg production was not affected by diet quality provided in spring or by the frequency of feeding during the preceding winter months. Black Ducks lost body fat through winter in captivity and in the wild. Fat stores of birds in New Jersey were greater than those of birds in Maine (13.3 vs. 8.3% of body mass) in January, which reflected the high energy demands of cold temperatures in Maine. Values for ∂ 15 N were greater in Maine than in New Jersey for both red blood cells and plasma, which indicated a consistent diet of marine invertebrates in Maine. Greater isotopic variation in red blood cells indicated that diets were more diverse in New Jersey than in Maine for both ∂ 15 N (9.7 ± 1.1 vs. 11.2 ± 0.4‰) and for ∂ 13 C (− 15.1 ± 2.2 vs. − 13.8 ± 1.4‰). Plasma ∂ 13 C was enriched over red blood cells in wild birds especially those with low fat stores, which suggested birds with low energy stores were shifting diets. Black Ducks can compensate for disturbances in feeding by increasing intakes if they have access to high quality wetlands where they are able to find abundant food. High energy demands at cold temperatures may constrain fat stores and thus the tolerance of feeding disturbances especially at the northern limits of the winter range. We hypothesize that decreasing variation in diet may indicate an increase in vulnerability to disturbance in winter when body fat is low. Recent efforts to assess and improve habitat quality of Black Ducks could be enhanced by monitoring the body composition and diet of birds to assess their vulnerability to disturbances in food supply and energy demands.

Journal of Comparative Physiology B: Biochemical, ↗
USGS1999

Cutaneous mastocytomas in the neotenic caudate amphibians Ambystoma mexicanum (axolotl) and Ambystoma tigrinum (tiger salamander)

Spontaneous mastocytomas studied in 18 axolotls ( Ambystoma mexicanum ) and six tiger salamanders ( Ambystoma tigrinum ) were gray-white, uni- to multilobular cutaneous protrusions from 2 mm to 2 cm in diameter. Tumors were moderately cellular unencapsulated masses that usually infiltrated the dermis and hypodermis with the destruction of intervening tissues. Some tumors were invading superficial bundles of the underlying skeletal muscle. Tumors consisted of mitotically active cells derived from a single lineage but showing a range of differentiation. Immature cells had nearly smooth to lightly cleft or folded basophilic nuclei bordered by a band of cytoplasm with few cytoplasmic processes and containing a few small uniform eccentric granules. Mature cells had basophilic nuclei with deep clefts or folds and abundant eosinophilic cytoplasm with multiple long intertwining cytoplasmic extensions packed with metachromatic granules. The axolotls were old individuals from an inbred laboratory colony. The tiger salamanders were wild animals from a single polluted pond. They could have been old and inbred. Both groups were neotenic. These are the first mastocytomas discovered in cold-blooded animals.

Texas↗