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PubMed1982

Actions of Ptychodiscus brevis red tide toxin on metabolic and transmitter-releasing properties of synaptosomes.

A pure toxin isolated from Ptychodiscus brevis stimulated differential release of amino acid neurotransmitters from mammalian cortical synaptosomes together with loss of K+ content and respiratory stimulation at 40 ng/ml. The effect was blocked by tetrodotoxin and by verapamil, implicating Na+ channel activation and possibly Ca2+ influx as necessary for the response, although the response did not change upon omission of Ca2+. Verapamil was therefore likely to be acting as a Na+ channel blocker in this instance. The toxin at 40 ng/ml caused acetylcholine release from guinea pig ileum, which is consistent with the proposed depolarising action for the toxin.

Acetylcholine↗
PubMedDate not supplied

Ecology of the red-tide dinoflagellate Ceratium furca: distribution, mixotrophy, and grazing impact on ciliate populations of Chesapeake Bay.

Ceratium furca is a primarily photosynthetic dinoflagellate also capable of ingesting other protists. During 1995 and 1996, we documented the abundance of C. furca in Chesapeake Bay and determined grazing rates on prey labeled with fluorescent microspheres. Abundance usually remained below 20 cells ml(-1), although the species was capable of localized late-summer blooms (< or = 478 cells ml(-1)) in the more saline lower to mid-Bay region. Feeding rates ranged from 0 to 0.11 prey dinoflagellate(-1) h(-1) or from 0 to 37 pg C dinoflagellate(-1) h(-1) and were highest at lower salinities. Clearance rates averaged 2.5 +/- 0.35 microl dinoflagellate(-1) h(-1). Impact of C. furca feeding on prey populations was higher in the lower Bay, averaging 67% of Strobilidium spp. removed d(-1). Ingestion rates were positively correlated with prey abundance and dissolved inorganic nitrogen, but negatively with salinity, depth, dissolved inorganic phosphorus, and inorganic P:N ratio. Daily consumption of prey biomass by C. furca averaged 4.6% of body carbon, 6.5% of body nitrogen, and 4.0% of body phosphorus. with maximal values of 36, 51, and 32%, respectively. Thus, the ability to exploit an organic nutrient source when inorganic nutrients are limiting may give C. furca a competitive advantage over purely photosynthetic species.

Animals↗
PubMed2003

Fluid core size of Mars from detection of the solar tide.

The solar tidal deformation of Mars, measured by its k2 potential Love number, has been obtained from an analysis of Mars Global Surveyor radio tracking. The observed k2 of 0.153 +/- 0.017 is large enough to rule out a solid iron core and so indicates that at least the outer part of the core is liquid. The inferred core radius is between 1520 and 1840 kilometers and is independent of many interior properties, although partial melt of the mantle is one factor that could reduce core size. Ice-cap mass changes can be deduced from the seasonal variations in air pressure and the odd gravity harmonic J3, given knowledge of cap mass distribution with latitude. The south cap seasonal mass change is about 30 to 40% larger than that of the north cap.

Atmosphere↗
PubMed1996

Late Proterozoic and Paleozoic Tides, Retreat of the Moon, and Rotation of the Earth

The tidal rhythmites in the Proterozoic Big Cottonwood Formation (Utah, United States), the Neoproterozoic Elatina Formation of the Flinders Range (southern Australia), and the Lower Pennsylvanian Pottsville Formation (Alabama, United States) and Mansfield Formation (Indiana, United States) indicate that the rate of retreat of the lunar orbit is dxi/dt approximately k2 sin(2delta) (where xi is the Earth-moon radius vector, k2 is the tidal Love number, and delta is the tidal lag angle) and that this rate has been approximately constant since the late Precambrian. When the contribution to tidal friction from the sun is taken into account, these data imply that the length of the terrestrial day 900 million years ago was approximately18 hours.

Journal Article↗
PubMed2000

Global AIDS epidemic: time to turn the tide.

HIV/AIDS is catastrophic both from a public health perspective and in terms of its impact on economic and social stability in many of the most severely affected nations, including virtually all of southern Africa. A public health response alone is insufficient to address this devastating epidemic. Political leadership at the highest levels is needed to mobilize a multisectoral response to the impact of HIV/AIDS on educational systems, industry, agriculture, the military, and other sectors. With a few notable exceptions, political response was slow to mobilize in the early years of the epidemic, but response has dramatically improved in the past 18 months. The Joint United Nations Programme on HIV/AIDS (UNAIDS) is involved in ongoing efforts to encourage political leaders to make a multisectoral response to the epidemic a major focus of their national plans.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Has America's tide of violence receded for good?

Experts in the young field of violence epidemiology blame guns and crack cocaine for America's deadly crime surge in the early 1990s. Explaining the subsequent decline in violent crime rates has been more difficult, however. Some of the factors that seem to have helped squelch crime could be temporary, such as low unemployment rates. But others, including a growing intolerance for violence as a means of settling interpersonal disputes, seem to have become cultural norms.

Abortion, Legal↗