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L Roth

Publications and source records attributed to L Roth.

At least 19 recordsLinked to original sources
PubMed2007

The lakes of Titan.

The surface of Saturn's haze-shrouded moon Titan has long been proposed to have oceans or lakes, on the basis of the stability of liquid methane at the surface. Initial visible and radar imaging failed to find any evidence of an ocean, although abundant evidence was found that flowing liquids have existed on the surface. Here we provide definitive evidence for the presence of lakes on the surface of Titan, obtained during the Cassini Radar flyby of Titan on 22 July 2006 (T16). The radar imaging polewards of 70 degrees north shows more than 75 circular to irregular radar-dark patches, in a region where liquid methane and ethane are expected to be abundant and stable on the surface. The radar-dark patches are interpreted as lakes on the basis of their very low radar reflectivity and morphological similarities to lakes, including associated channels and location in topographic depressions. Some of the lakes do not completely fill the depressions in which they lie, and apparently dry depressions are present. We interpret this to indicate that lakes are present in a number of states, including partly dry and liquid-filled. These northern-hemisphere lakes constitute the strongest evidence yet that a condensable-liquid hydrological cycle is active in Titan's surface and atmosphere, in which the lakes are filled through rainfall and/or intersection with the subsurface 'liquid methane' table.

Journal Article↗
PubMed2006

Functional interaction between matrix metalloproteinase-3 and semaphorin-3C during cortical axonal growth and guidance.

In the developing cortex, axons and dendrites extend progressively in response to environmental cues attracting or repelling growing processes. Recent evidence suggests the existence of a functional link between guidance molecules and metalloproteinases. Here, we analyzed the putative functional interaction of matrix metalloproteinases (MMPs) with guidance cues of the semaphorin family during growth and guidance of cortical axons. Our results demonstrate that the expression pattern and the proteolytic activity of MMP-3 are consistent with a role of this particular MMP during cortical axon outgrowth. We found that MMP-3 is required for an optimal axon extension and is involved in the Sema3C-dependent chemoattraction of cortical axons by modulating both the growth capacity and the orientation of growth. Interestingly, the inhibitory Sema3A decreased both the expression and activity of MMP-3. Taken together, our results reveal a molecular interaction between MMPs and semaphorins providing new insight into the molecular mechanism allowing axonal growth cone to respond to environmental guidance cues in the context of cortical development.

Animals↗
PubMed2006

Titan Radar Mapper observations from Cassini's T3 fly-by.

Cassini's Titan Radar Mapper imaged the surface of Saturn's moon Titan on its February 2005 fly-by (denoted T3), collecting high-resolution synthetic-aperture radar and larger-scale radiometry and scatterometry data. These data provide the first definitive identification of impact craters on the surface of Titan, networks of fluvial channels and surficial dark streaks that may be longitudinal dunes. Here we describe this great diversity of landforms. We conclude that much of the surface thus far imaged by radar of the haze-shrouded Titan is very young, with persistent geologic activity.

Journal Article↗
PubMed2006

The sand seas of Titan: Cassini RADAR observations of longitudinal dunes.

The most recent Cassini RADAR images of Titan show widespread regions (up to 1500 kilometers by 200 kilometers) of near-parallel radar-dark linear features that appear to be seas of longitudinal dunes similar to those seen in the Namib desert on Earth. The Ku-band (2.17-centimeter wavelength) images show approximately 100-meter ridges consistent with duneforms and reveal flow interactions with underlying hills. The distribution and orientation of the dunes support a model of fluctuating surface winds of approximately 0.5 meter per second resulting from the combination of an eastward flow with a variable tidal wind. The existence of dunes also requires geological processes that create sand-sized (100- to 300-micrometer) particulates and a lack of persistent equatorial surface liquids to act as sand traps.

Extraterrestrial Environment↗
PubMed2005

Cassini radar views the surface of Titan.

The Cassini Titan Radar Mapper imaged about 1% of Titan's surface at a resolution of approximately 0.5 kilometer, and larger areas of the globe in lower resolution modes. The images reveal a complex surface, with areas of low relief and a variety of geologic features suggestive of dome-like volcanic constructs, flows, and sinuous channels. The surface appears to be young, with few impact craters. Scattering and dielectric properties are consistent with porous ice or organics. Dark patches in the radar images show high brightness temperatures and high emissivity and are consistent with frozen hydrocarbons.

Atmosphere↗
PubMed2003

Lithium augmentation in venlafaxine non-responders: an open study.

Thirteen major depressive patients not responding to a 4-week venlafaxine 300 mg treatment were eligible for a 4-week open trial of lithium addition. Two patients had to stop lithium for a possible moderate serotonin syndrome and five patients became responders, including one dramatic response and two semi-rapid responses.

Adult↗
PubMed2003

Lithium dose prediction based on 24 hours single dose levels: a prospective evaluation.

The authors present the results of the utilization of a pharmacokinetic prediction test for lithium posology. Based on a single point (plasma lithium determination 24 h after a single dose) such a test aims to adapt the posology as soon as the second day of treatment rather than after one week as clinicians must wait for a steady state to be achieved. Built on the previous work of Perry, the test targeted the plasma lithium level at 0.8 +/- 0.1 mmol l(-1). Thirty-one patients took part in the study. There were two drop-out cases and the results were available for 29 patients: among them, 51% had their plasma level in the targeted zone. Although there was no control group, the prediction test often allowed us to use a higher dose than the usual fixed dose whose amount is limited by the risk of overdosing for the slower metabolizers.

Adult↗
PubMed2002

Ultra-relativistic electrons in Jupiter's radiation belts.

Ground-based observations have shown that Jupiter is a two-component source of microwave radio emission: thermal atmospheric emission and synchrotron emission from energetic electrons spiralling in Jupiter's magnetic field. Later in situ measurements confirmed the existence of Jupiter's high-energy electron-radiation belts, with evidence for electrons at energies up to 20[?]MeV. Although most radiation belt models predict electrons at higher energies, adiabatic diffusion theory can account only for energies up to around 20[?]MeV. Unambiguous evidence for more energetic electrons is lacking. Here we report observations of 13.8[?]GHz synchrotron emission that confirm the presence of electrons with energies up to 50[?]MeV; the data were collected during the Cassini fly-by of Jupiter. These energetic electrons may be repeatedly accelerated through an interaction with plasma waves, which can transfer energy into the electrons. Preliminary comparison of our data with model results suggests that electrons with energies of less than 20[?]MeV are more numerous than previously believed.

Journal Article↗
PubMed2001

Eph signalling functions downstream of Val to regulate cell sorting and boundary formation in the caudal hindbrain.

Rhombomeres are segmental units of the developing vertebrate hindbrain that underlie the reiterated organisation of cranial neural crest migration and neuronal differentiation. valentino (val), a zebrafish homologue of the mouse bzip transcription factor-encoding gene, kreisler, is required for segment boundary formation caudal to rhombomere 4 (r4). val is normally expressed in r5/6 and is required for cells to contribute to this region. In val(-) mutants, rX, a region one rhombomere in length and of mixed identity, lies between r4 and r7. While a number of genes involved in establishing rhombomeric identity are known, it is still largely unclear how segmental integrity is established and boundaries are formed. Members of the Eph family of receptor tyrosine kinases and their ligands, the ephrins, are candidates for functioning in rhombomere boundary formation. Indeed, expression of the receptor ephB4a coincides with val in r5/6, whilst ephrin-B2a, which encodes a ligand for EphB4a, is expressed in r4 and r7, complementary to the domain of val expression. Here we show that in val(-) embryos, ephB4a expression is downregulated and ephrin-B2a expression is upregulated between r4 and r7, indicating that Val is normally required to establish the mutually exclusive expression domains of these two genes. We show that juxtaposition of ephB4a-expressing cells and ephrin-B2a-expressing cells in the hindbrain leads to boundary formation. Loss of the normal spatial regulation of eph/ephrin expression in val mutants correlates not only with absence of boundaries but also with the inability of mutant cells to contribute to wild-type r5/6. Using a genetic mosaic approach, we show that spatially inappropriate Eph signalling underlies the repulsion of val(-) cells from r5/6. We propose that Val controls eph expression and that interactions between EphB4a and Ephrin-B2a mediate cell sorting and boundary formation in the segmenting caudal hindbrain.

Animals↗
PubMed2000

A theoretical reappraisal of mixed states: dysphoria as a third dimension.

Mixed states are heterogeneous clinical entities difficult to define precisely. The stringent actual DSM IV criteria are unsatisfactory for current clinical use. Many frequently encountered mixed patients benefit without an accurate diagnosis from biological therapeutic interventions such as the introduction of mood stabilizers. We propose a brief review of the definition and characteristics of mixed states and propose a new approach to the typology of mixed states. Based on recent literature data, we add to the depressive and manic syndrome the concept of dysphoria as a third dimension. Integrating this three dimensional approach with recent factor analysis, we describe in addition to the DSM IV mixed state (type I) two new subtypes of mixed states (type IIM and IID). This new typology can give the clinician a more accurate understanding of the complex and polymorphous reality of mixed states and help him make more specific therapeutic interventions. These subtypes of mixed states will need validation through prospective clinical studies. Biological differences, differential outcome over time, and differential response to treatment will be important validation criteria.

Affect↗
PubMed1999

Evaluation of low sodium:potassium ratios in dogs.

The results of general chemistry profiles of canine patients from Angell Memorial Animal Hospital, Boston, Massachusetts, during 1993 were reviewed for low (<24) serum sodium:potassium (Na:K) ratios. Thirty-seven dogs had low Na:K ratios. The medical records for 34 these patients were available and sufficiently complete to identify conditions that were associated with low Na:K ratios. Of these 34 dogs, 8 (24%) had hypoadrenocorticism, and 14 had renal disease. Twenty-two of the 34 (65%) had Na:K ratios between 24 and 20. Of these 22 dogs, 9 (41%) had renal or urinary tract disease, and 2 (9%) had hypoadrenocorticism. Other diagnoses in this group included pancreatic disease (3), disseminated neoplasia (3), circulatory disturbance (2), pyometra (1), mushroom poisoning (1), and behavior problem (1). Eight of 34 dogs had Na:K ratios between 19.9 and 15. Of these 8 dogs, 4 (50%) had urinary tract disease, 2 had hypoadrenocorticism, 1 had pancreatic disease, and 1 had severe anemia and hypoproteinemia due to severe parasitism. All of the 4 dogs with Na:K ratios <15 had hypoadrenocorticism, and 1 of these 4 had concurrent renal failure. In all dogs, serum potassium concentration was above the laboratory's reference range, but sodium was below the laboratory's reference range in only 18 dogs (53%). Two of the 8 (25%) dogs with hypoadrenocorticism had serum sodium concentrations within the laboratory's reference range. In this population, low Na:K ratios were invariably associated with hyperkalemia but not always with hyponatremia. Although numerous conditions were associated with a low Na:K ratio, renal disease was the most common. Hypoadrenocorticism was present in only 13% of dogs with Na:K ratios between 24 and 15 but was present in all dogs with Na:K ratios <15.

Adrenal Insufficiency↗
PubMed1997

Relationship between the Millon Clinical Multiaxial Inventory-II and Coolidge Axis II Inventory in chronically mentally ill older adults: a pilot study.

The purpose of this study was to investigate the relationship between two self-report measures of personality disorders in older chronically mentally ill inpatients. A random sample of 30 chronically mentally ill (DSM-III-R schizophrenia, schizoaffective disorder, recurrent major depression) inpatients aged 55 and older completed the Millon Clinical Multiaxial Inventory-II (MCMI-II) and the Coolidge Axis II Inventory (CATI). The personality inventories were concurrently administered in counterbalanced fashion to assess concurrent validity of the CATI and MCMI in this older adult group. Data were submitted for correlational analysis. Median concurrent validity (raw score sums) between the CATI and MCMI-II for the 13 personality disorder scales was moderate (r = .55). Individual scale correlations ranged from -.13 for schizoid disorder to .88 for borderline disorder. Individual scale correlations were somewhat lower than previously reported values, but were above .54 for 7 of 13 disorders. Findings provide preliminary support for use of the CATI and MCMI with chronically mentally ill elders. Suggestions for future research are offered.

Aged↗
PubMed1997

Interinterpreter variability in determining the SP/AP ratio in clinical electrocochleography.

Calculating the SP/AP ratio in electrocochleography requires the interpreting audiologist to unequivocally identify the peak of the SP wave form. If different points are selected, different SP/AP ratios will result. To investigate this effect, 50 electrocochleographic tracings were sent to 10 different audiologists (500 tracings). Twenty of the wave forms sent to each audiologist were identified as "easy," 10 as "somewhat difficult," 10 as "very difficult," and 10 as "no response." The ranges and standard deviations of the resulting SP/AP ratios were quite high. Analysis of variance showed statistically significant differences in the very difficult and no response group. There is significant interinterpreter difference among SP/AP ratios calculated from the same tracing. This variability affects clinical patient management and investigational projects.

Analysis of Variance↗
PubMed1996

The effect of maternal blood contamination on amniotic fluid glucose and white blood cell count from preterm gestations.

OBJECTIVE: To determine the influence of maternal blood contamination on amniotic fluid (AF) glucose and white blood cell count (WBC). METHODS: Amniotic fluid from 23 preterm, nondiabetic pregnant women was studied. Maternal blood was added to the AF at increasing concentrations, and glucose and WBCs were assessed. RESULTS: The median AF glucose in the uncontaminated specimen was 43 mg/dL (range 11-86). Median glucose levels were unchanged by the addition of maternal blood until a mean +/- standard deviation AF red blood cell count of 63,000 +/- 22,000/mm3 was exceeded, at which time the median glucose level significantly increased to a median of 45 mg/dL (range 19-90). The ratio of observed to expected values of WBCs ranged from 0.12-1.8, regardless of the level of maternal blood contamination. CONCLUSION: Glucose levels in preterm AF-containing maternal blood are accurate in all except the most heavily contaminated specimens. Accurate determination of the WBC in contaminated AF is difficult.

Adult↗