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Subglacial lakes have been mapped across Antarctica with two methods, radio‐echo sounding (RES) and ice‐surface deformation. At sites where both are coincident, these methods typically provide conflicting interpretations about the ice‐bed interface. With a single exception, active subglacial lakes identified by surface deformation do not display the expected flat, bright, and specular bed reflection in RES data, characteristic of non‐active lakes. This observational conundrum suggests that our understanding of Antarctic subglacial hydrology, especially beneath important fast‐moving ice streams, remains incomplete. Here, we use an airborne RES campaign that surveyed a well‐characterized group of active subglacial lakes on lower Mercer and Whillans ice streams, West Antarctica, to explore inconsistency between the two observational techniques. We test hypotheses of increased scattering and attenuation due to the presence of an active subglacial lake system that could suppress reflected bed‐echo power for RES observations in these locations, finding that entrained water is most plausible. Plain Language Summary: The bottom of an ice sheet is insulated from cold air temperatures, often warm enough to melt and pond liquid water into lakes. These lakes beneath the ice sheet have been identified by two independent measurements, first with radar methods and second with changes in height of the ice surface (altimetry). Interestingly, the two methods rarely identify the same lakes: radar generally detects lakes in the ice‐sheet interior, whereas altimetry detects active lakes near the ice‐sheet margins that fill and drain within the time series of repeated measurements (∼years). In this study, we investigate a group of active subglacial lakes at which both radar and altimetry data sets are available. We demonstrate that the radar returns from active lake reflections are much dimmer than expected based on non‐active lake signatures and investigate the physical processes controlling those dim reflections. We argue that water moves into the ice when the lake fills or drains and that is the most plausible explanation for the observational discrepancy. Key Points: Active subglacial lakes, identified by surface deformation, do not create the expected bright and specular radar reflectionEntrained water in basal ice suppresses radar power by scattering and attenuation, and it also likely alters the basal ice mechanicsUnderstanding the radar expression of subglacial water on Earth provides context for investigations of subsurface water on planetary bodies [ABSTRACT FROM AUTHOR]

The majority of ice mass loss from Antarctica flows through narrow, fast sliding regions of ice. The lateral boundaries of these regions, termed shear margins, are characterized by lateral shear strains in excess of ∼10−3 yr−1. Shear heating within these margins could warm ice significantly–even to the melting point–but other processes such as lateral advection of cold ice and fabric development compete with this effect. Radar observations can help constrain where temperate ice exists because englacial temperature increases electric conductivity which increases radar attenuation. We utilize the temperature‐dependent attenuation of ice to develop a novel method for constraining englacial temperature in shear margins by combining existing thermal models with very high frequency radar depth‐sounding data. We find evidence supporting temperate shear margins in 18 locations and find evidence for non‐temperate margins in 37 locations, notably in the Amundsen Sea Embayment. Plain Language Summary: Most of the ice lost from Antarctica to the ocean goes through narrow areas of fast sliding ice. At the sides of these fast sliding areas the fast ice abuts slow ice and heavily deforms. Deformation warms the ice–potentially to its melting temperature. This warming should be noticeable in radar data because ice at or near the melting point reduces the power of radar waves. We develop a method for using airborne radar measurements to look for the presence of this warm ice, and apply our method across the Antarctic continent. We find evidence supportive of warm ice in many locations, but we notably find little evidence of warm ice in the Amundsen Sea Embayment where the inflow of cold ice may offset warming. Key Points: We develop a novel method for identifying evidence for temperate ice in Antarctic shear margins using existing airborne radar data setsWe find evidence for temperate ice in 18, and evidence contrary in 37, of 106 radar lines over shear margins we consider across AntarcticaNeglecting heats sinks like advective cooling overpredicts the size of temperate zones, particularly in the Amundsen Sea Embayment [ABSTRACT FROM AUTHOR]

With radar sounders, coherent backscattering simulations from global planetary digital elevation models (DEMs) typically display a deficit in diffuse clutter, which is mainly due to the implicit assumption that roughness at scales below the resolution of the DEM is absent. Indeed, while polynomial approximations of the phase evolution across the facet allow for fast and mathematically rigorous simulators, the coarse resolution of these planetary DEMs leads to a potentially significant portion of the backscattering response being neglected. In this paper, we derive the analytical phase response of a rough rectangular facet characterized by Gaussian roughness and a Gaussian isotropic correlation function under the linear phase approximation. Formulae for the coherent and incoherent power scattered by such an object are obtained for arbitrary bistatic scattering angles. Validation is done both in isolation and after inclusion in different Stratton‐Chu simulators. In order to illustrate the different uses of such a formulation, we reproduce two lunar radargrams acquired by the Lunar Radar Sounder instrument with a Stratton‐Chu simulator incorporating the proposed rough facet phase integral, and we show that the original radargrams are significantly better‐reproduced than with state‐of‐the‐art methods, at a similar computational cost. We also show how the rough facet integral formulation can be used in isolation to better characterize subglacial water bodies on Earth. Key Points: Planetary digital elevation models are often of coarse resolution and depict a surface that is smooth at scales below that resolutionPolynomial phase approximations can be used to simulate radar scattering rigorously but they overestimate the coherence of reflected signalsWe analytically derive the linear phase approximation formula on a rough rectangular facet, leading to much better clutter simulations [ABSTRACT FROM AUTHOR]

Surface and basal boundary conditions at the Southern McMurdo and Ross Ice Shelves, Antarctica - CORRIGENDUM. [Extracted from the article]

Over the past 50 years, the discovery and initial investigation of subglacial lakes in Antarctica have highlighted the paleoglaciological information that may be recorded in sediments at their beds. In December 2018, we accessed Mercer Subglacial Lake, West Antarctica, and recovered the first in situ subglacial lake-sediment record--120 mm of finely laminated mud. We combined geophysical observations, image analysis, and quantitative stratigraphy techniques to estimate long-term mean lake sedimentation rates (SRs) between 0.49 ± 0.12 mm a-1 and 2.3 ± 0.2 mm a-1, with a most likely SR of 0.68 ± 0.08 mm a-1. These estimates suggest that this lake formed between 53 and 260 a before core recovery (BCR), with a most likely age of 180 ± 20 a BCR--coincident with the stagnation of the nearby Kamb Ice Stream. Our work demonstrates that interconnected subglacial lake systems are fundamentally linked to larger-scale ice dynamics and highlights that subglacial sediment archives contain powerful, century-scale records of ice history and provide a modern process-based analogue for interpreting paleo--subglacial lake facies. [ABSTRACT FROM AUTHOR]

The alpha subtype of the estrogen receptor (ERalpha) is present in nociceptive and parasympathetic regions of the adult rat spinal cord. The pattern of ERalpha expression in the rat spinal cord during development, however, is unknown. We used a polyclonal antibody (ER-21) to examine the expression of ERalpha in male rat lumbosacral spinal cords at embryonic day (E) 17, E21 (the day before birth), postnatal day (P) 1 (the day of birth), P8, P17, P21, and P36. At E17, ERalpha immunoreactivity (ERalpha-ir) was observed predominantly in ependymal cells. Perinatally, ERalpha-ir was also present in neurons in dorsal root ganglia and in fibers capping and within laminae I and II. By P8, ERalpha-ir was absent in ependymal cells, but ERalpha-ir fibers were dense in laminae I and II and in sympathetic and parasympathetic areas. ERalpha-ir was also present in neurons in the dorsal horns. To determine whether ERalpha-ir fibers in laminae I and II were processes of spinal neurons or primary afferents, dorsal rhizotomies were performed on P17 and P21 animals. Unilateral transection of the lumbosacral dorsal roots virtually eliminated ERalpha-ir fibers in the ipsilateral superficial laminae, demonstrating that the majority of ERalpha-ir fibers in these laminae were primary afferents. We show for the first time that ERalpha-ir is present in neurons and fibers of male prenatal and postnatal spinal cord. The presence of ERalpha in neuronal nuclei and processes may reflect diverse roles and novel mechanisms of action for 17 beta-estradiol in development of spinal sensory and autonomic circuitry., (Copyright 2000 Wiley-Liss, Inc.)

Breast cancer concerns were measured among 353 women, ages 40-75, from North Dakota. One year later, participants were recontacted and asked about their screening behavior during the previous year. Greater concern about breast cancer, even the highest level of concern, was related to a higher likelihood that women performed breast self-examination, had a mammography screening, and had a clinical breast examination. These data do not support the idea that worry inhibits action; instead, they suggest that nonpathological worry motivates self-protective behavior.

This meta-analytic review addresses the issue of how a woman's risk of breast cancer relates to the likelihood that she will obtain mammography screenings. Studies that compared women with or without a family history of breast cancer (n = 19) showed that women with a family history were more likely to have been screened. Studies that measured perceived risk (n = 19) showed that feeling vulnerable to breast cancer was positively related to having obtained a screening. Studies that compared women who did or did not have a history of breast problems (n = 10) showed that those with a positive history were more likely to have been screened. Finally, studies that measured worry (n = 6) showed that greater worry was related to higher screening levels. Taken together, these data suggest that increasing perceptions of personal vulnerability may increase screening behavior for breast cancer.

A methodology was developed to combine extracellular electrophysiological recording techniques in awake, behaving rats with immunohistochemical protocols to determine the placement of recording sites in the patch (striosome) or matrix (extrastriosome) regions of the striatum. The recording system includes a 3-barrel glass micropipette, which can be used to deposit Pontamine Sky Blue to mark a small number of neurons at the recording site. Subsequent immunostaining for calbindin allows the site to be localized within the patch-matrix organization. Other dyes or neuroanatomical probes can be ejected from other barrels of the recording pipette to label afferent and efferent structures. The methodology can be applied to many brain regions, providing for integrative studies of behavior and nervous system structure and function.

We examined the anatomy of the nasal cavity and forebrain in the axolotl (Ambystoma mexicanum) to determine whether the olfactory and vomeronasal systems are present in this neotenic aquatic salamander. The current study was motivated by two considerations: (a) little is known of the anatomy of the vomeronasal system in aquatic vertebrates, and (b) the presence of both olfactory and vomeronasal systems in larval amphibians has broad implications for the evaluation of these systems in vertebrates. From cresyl-violet-stained sections of snouts we determined that the nasal cavity of axolotls is much like that of terrestrial salamanders. The main chamber of the nasal cavity contains an olfactory epithelium, which is confined to grooves between longitudinal ridges of connective tissue covered in a nonsensory epithelium which lacks goblet cells. Using transmission electron microscopy, we found morphologically distinct olfactory receptor cells: many receptor cells terminate in microvillar dendrites, and fewer terminate in motile cilia with the 9 + 2 microtubule array typical of vertebrate olfactory receptor cells. The ciliated and microvillar cells occur in clusters with little intermingling. Horseradish peroxidase labeling revealed that axons of the olfactory receptor cells terminate in large glomeruli in the main olfactory bulb at the rostral end of the telencephalon. Lateral to the main chamber of the nasal cavity is a diverticulum that is entirely lined with a vomeronasal epithelium containing basal cells, microvillar receptor cells, sustentacular cells that lack specialized processes on the apical surface, and large ciliated cells that may function to move fluid across the vomeronasal epithelium. Unlike the olfactory epithelium, the vomeronasal epithelium lacks Bowman's glands. Using horseradish peroxidase, we determined that the axons of the vomeronasal receptor cells project to the accessory olfactory bulb, a distinct structure dorsal and caudal to the main olfactory bulb. The presence of both olfactory and vomeronasal systems in axolotls and other neotenic salamanders implies that both systems are pleiomorphic in larval amphibians; we therefore suggest that the vomeronasal system may not have originated as an adaptation to terrestrial life.

Previously reported anatomical and electrophysiological studies have shown that there are neurons in the lamprey's spinal cord that respond to stretching of the spinal cord. Neurons in similar locations are especially prominent in reptiles, where they form the marginal nuclei. These nuclei have been examined in snakes, and it has become apparent that the denticulate ligament is both structurally and functionally closely related to the marginal nuclei. The ligament loses collagen in a short segment of every intervertebral area, and the marginal nuclei are located only in this area. The marginal nuclei consist of a group of medium-sized neurons along the edge of the spinal cord, with a strip of neuropil separating them from the ligament; the neurons extend dendritic processes into this lateral neuropil area and give rise to long finger-like processes. In the present study, these processes were found to be longer than the ones that have been described for peripheral mechanoreceptors; they are thought to be important in sensory transduction. Closely associated with these processes were axon-like structures. They did not make any type of contact with the finger-like processes; however, an occasional synaptic-like contact, consisting of membrane specialization and a congregation of vesicles, was made with dendritic processes. The conclusion is that these finger-like processes are similar to those of peripheral mechanoreceptors, but that there is no equivalent process to the axon-like structure.

The Holocentrus has large eyes and a well-developed optic tectum. Nissl and fibers stains and various Golgi techniques show that the optic tectum of Holocentrus has six strata which can be subdivided into 14 alternating cell and fiber layers, some of which have additional organization. The stratum marginale (SM) is especially impressive in this fish and contains dendrites of pyramidal neurons, marginal fibers from torus longitudinalis, and axon-like processes (the SM ascending axons) from cells located in the stratum griseum centrale (SGC). Stratum opticum (SO) and stratum fibrosum et griseum superficiale (SFGS) have many small neurons with limited dendritic fields. The large, so-called pyramidal cell of SFGS has an extensive dendritic tree in SM and descending dendrites and axon to SGC. The latter has a variety of neurons with large dendritic fields in various layers of the tectum; the most distinctive, however, is the large fusiform neuron with its shepherd's crook axon. This stratum also has a dense layer of neuropil, the internal plexiform layer. Stratum album centrale (SAC) is primarily a fibrous layer, and stratum periventriculare (SPV) is a dense cellular area with the upper portion containing neuronal types also found in SGC and different from the typical neurons found in SPV. The latter have a major ascending branch with various dendritic patterns, and often do not have an identifiable axon; however, some of these cells have extensive branches throughout SFGS with an axon-like appearance. Some general conclusions were made about the functional significance of the various tectal layers and cell types.

Crotaline snakes have detectors for infrared radiation and this information is projected to the optic tectum in a spatiotopic manner. The tectal projections were examined in Crotalus viridis with the use of silver methods for degenerating fibers and the autoradiographic and horseradish peroxidase tracing methods. Large lesions included all of the tectal layers but not the underlying structures. Projections to the thalamus include a sparse input to the ipsilateral ventral and dorsal lateral geniculate nuclei, the ventromedial nucleus, and nucleus lentiformis thalami. Nucleus rotundus was not detected. The projections to the pretectal nuclei are primarily ipsilateral to the nucleus lentiformis mesencephali and pretectal nucleus. At the level of the mesencephalon, tectal efferents are bilateral to nucleus profundus mesencephali and the tegmentum. There is minimal input to the contralateral deep tectal layers. There are ipsilateral terminations in a nucleus identified as the posterolateral tegmental nucleus. Descending fibers include the two major tracts--the ventral tectobulbar tract that terminates in the ipsilateral lateral reticular formation and the predorsal bundle that distributes throughout the contralateral medial reticular formation. Two small descending tracts were noted--the intermediate and dorsal tectobulbar tracts. All of these descending tracts appear to terminate by the time they reach the caudal medulla. After superficial lesions terminals could be found in the ventral lateral geniculate nucleus, the nucleus profundus mesencephali, and the posterolateral tegmental nucleus; the two major descending tracts contained degenerated fibers as well. The areas receiving tectal input in Crotalus were compared to those of other reptiles and discussed.

The retinal afferents and efferents were examined in Crotalus viridis. Retinofugal fibers were traced by injecting horseradish peroxidase (HRP) or tritiated leucine into the eye, or by removing the eye and staining degenerating axons with silver methods. Terminations were seen contralaterally in the suprachiasmatic nucleus, the dorsal and ventral lateral geniculate nuclei (extensive), the pretectal nuclei, including the nucleus posterodorsalis (a very heavy input), the nucleus lentiformis mesencephali, nucleus geniculatus pretectalis, and nucleus pretectalis, the superficial layers of the optic tectum, including the stratum zonale, the stratum opticum, the stratum griseum et fibrosum centrale and the upper portion of stratum griseum centrale, and the basal optic nucleus. Ipsilateral input reaches the intermediate portion of the dorsal lateral geniculate nucleus, a small portion of the pretectal nucleus and nucleus posterodorsalis, and the basal optic nucleus (very minimally). Retinopedal fibers were traced with the HRP method. The cell bodies lie in the ventral thalamus within the nucleus of the ventral supraoptic decussation. These neurons project primarily to the contralateral retina, but some more rostrally located neurons project to the ipsilateral retina.

The cytoarchitecture of the tectum mesencephali in the siluroid teleosts Bagrus and Ictalurus was studied by means of the Golgi method. These animals are known to have a restricted visual system and it seemed important to study whether this fact would affect the existence or the shape of the main neuron types which have been described for highly visual teleosts. It had been shown for a variety of teleosts that the retinotectal axons and terminals occupy almost exclusively the stratum opticum and the stratum fibrosum et griseum superficiale. The thickness of these strata in Bagrus and Ictalurus was found to be reduced. However, the main types of especially the vertically oriented neurons, such as the pyramidal, fusiform, large pyriform and periventricular neurons which have been described for highly visual species of teleosts, were also found in Bagrus and Ictalurus. Although their shape was somewhat distorted, these neurons, nevertheless, showed processes distributed to the same tectal layers as in highly visual teleosts and are accessible to horizontally distributed fiber systems such as marginal, telencephalotectal and commissural tectal fibers, as well as the retinotectal fibers. Nonvisual inputs appear to be considerably involved in the maintenance of the main neuron types in the siluroid tectum. For example, the pyramidal neuron's apical dendritic tree, which receives the excitatory input from the marginal fibers, is as well developed in siluroids as in highly visual teleosts.

To study the somatosensory input to the inferior colliculus, lesions were made in the dorsal column nuclei of the hedgehog, tree shrew, slow loris, marmoset and African green monkey, and spinal cord of the hedgehog, tree shrew and slow loris. The degenerating fibers stained with silver impregnation methods. The dorsal column system projects primarily to an area lateral to the central nucleus of the inferior colliculus, whereas the spinotectal projection is primarily to the medial region in the hedgehog and medial and dorsal regions in the tree shrew and slow loris. Both fiber systems are quantitatively quite constant in the various species. It is apparent from published data on a variety of mammals that the central nucleus is primarily part of the auditory system in which the intercollicular area is involved only indirectly via projections from the central nucleus and auditory cortex. In nonmammalian vertebrates, the data available suggest that there is a comparable area in the mesencephalon that is involved with somatosensory as well as auditory sensation. Since low frequency stimulation, generally characterized as vibration, stimulates both modalities, the intercollicular area may be the input side of a mechanism for alterting the animal to vibratory stimuli.

Large neurons at the ventrolateral edge of the snake's spinal cord are intimately associated with ligaments that closely adhere to the whole length of the spinal cord. Ultrastructural studies show close similarities of these cells and their processes with those of other mechanoreceptors. Furthermore, the ligaments undergo changes within the intervertebral areas that would enhance focusing the stimulus to the receptor area.