Biomedical subjects

D T Britt

Publications and source records attributed to D T Britt.

4 recordsLinked to original sources

PubMed2002

Observations of comet 19P/Borrelly by the miniature integrated camera and spectrometer aboard Deep Space 1.

The nucleus of the Jupiter-family comet 19P/Borrelly was closely observed by the Miniature Integrated Camera and Spectrometer aboard the Deep Space 1 spacecraft on 22 September 2001. The 8-kilometer-long body is highly variegated on a scale of 200 meters, exhibiting large albedo variations (0.01 to 0.03) and complex geologic relationships. Short-wavelength infrared spectra (1.3 to 2.6 micrometers) show a slope toward the red and a hot, dry surface (</=345 kelvin, with no trace of water ice or hydrated minerals), consistent with approximately 10% or less of the surface actively sublimating. Borrelly's coma exhibits two types of dust features: fans and highly collimated jets. At encounter, the near-nucleus coma was dominated by a prominent dust jet that resolved into at least three smaller jets emanating from a broad basin in the middle of the nucleus. Because the major dust jet remained fixed in orientation, it is evidently aligned near the rotation axis of the nucleus.

Carbon↗

PubMed1997

Results from the Mars Pathfinder camera.

Images of the martian surface returned by the Imager for Mars Pathfinder (IMP) show a complex surface of ridges and troughs covered by rocks that have been transported and modified by fluvial, aeolian, and impact processes. Analysis of the spectral signatures in the scene (at 440- to 1000-nanometer wavelength) reveal three types of rock and four classes of soil. Upward-looking IMP images of the predawn sky show thin, bluish clouds that probably represent water ice forming on local atmospheric haze (opacity approximately 0.5). Haze particles are about 1 micrometer in radius and the water vapor column abundance is about 10 precipitable micrometers.

Atmosphere↗

PubMed1993

Discriminative stimulus effects of delta 9-tetrahydrocannabinol and delta 9-11-tetrahydrocannabinol in rats and rhesus monkeys.

Previous reports have suggested that delta 9-11-tetrahydrocannabinol (delta 9-11-THC), an exocyclic analog of delta 9-tetrahydrocannabinol (delta 9-THC), may have weak agonist effects as well as antagonistic properties. The purpose of the present study was to examine the effects of delta 9-11-THC in substitution and antagonism tests in rats and in rhesus monkeys trained to discriminate delta 9-THC from vehicle in two-lever drug-discrimination procedures. The substitution studies showed that delta 9-11-THC generalizes from the training dose of delta 9-THC in rats and in monkeys, although it was less potent in both species. The magnitude of the potency difference was greater in monkeys than in rats. When administered immediately following injection with the training dose of delta 9-THC, delta 9-11-THC failed to block the delta 9-THC cue in rats and showed a lack of dose-responsive inhibition in monkeys. These results suggest that delta 9-11-THC is devoid of antagonistic properties in the drug discrimination paradigm.

Animals↗

PubMed1992

A comparison of the discriminative stimulus properties of delta 9-tetrahydrocannabinol and CP 55,940 in rats and rhesus monkeys.

CP 55,940 [(-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3- hydroxypropyl)cyclohexanol] is a potent bicyclic analog of delta 9-tetrahydrocannabinol (THC) which has been used as a probe for a cannabinoid recognition site in neural tissue. In the present study, CP 55,490 was evaluated for delta 9-THC-like effects in rats and rhesus monkeys trained to discriminate delta 9-THC from vehicle. Rats trained to discriminate delta 9-THC (3.0 mg/kg i.p.) from vehicle were tested with various doses of delta 9-THC and CP 55,940 at both 30 and 90 min postinjection. Catalepsy was measured immediately after these operant tests using an adaptation of the mouse ring-test. In rats, CP 55,940 substituted for delta 9-THC at both 30 and 90 min postinjection at a dose of 0.1 mg/kg that had minimal effects on rates of responding. Doses of delta 9-THC (greater than 3.0 mg/kg) and CP 55,940 (greater than 0.1 mg/kg) that reduced response rates by greater than 50% also produced substantial increases in catalepsy. CP 55,940 and delta 9-THC had a similar time course for discriminative stimulus effects, but CP 55,940 was about 30 times more potent. In monkeys, the training dose of delta 9-THC ranged from 0.04 to 0.16 mg/kg i.m., adjusted individually to minimize response-rate disruption. After training, monkeys were tested with various doses of delta 9-THC and CP 55,940 at 30 min postinjection.(ABSTRACT TRUNCATED AT 250 WORDS)

Analgesics↗