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Biomedical subjects

L M Adams

Publications and source records attributed to L M Adams.

64 records · Page 4Linked to original sources
PubMed1981

Effects of 6-hydroxydopamine lesions of locus coeruleus on startle in rats.

To examine the possible involvement of the norepinephrine (NE) containing neurons of the locus coeruleus in the modulation of behavioral reactivity to sensory stimulation, bilateral chemical lesions of the locus coeruleus were made by local injection of the catecholamine neurotoxin 6-hydroxydopamine. Both histochemical and biochemical analyses confirmed the effectiveness of the lesions in specifically eliminating the NE containing cell bodies of the locus coeruleus and reducing the NE content of the hippocampus and substantia nigra by 45% and 69% respectively. Rats were tested both 5 and 36 days after lesioning for their startle response to a repetitive series of tactile stimuli. On both days, locus coeruleus lesioned rats exhibited consistently reduced startle responses throughout the stimulus series. Additionally, lesioned rats showed a far more rapid rate of response habituation, particularly in the first test. The results are discussed in terms of a possible influence of the locus coeruleus on the process of sensitization to sensory stimuli.

Animals↗
PubMed1979

A characteristic effect of hallucinogens on investigatory responding in rats.

The disruption of the temporal distribution of investigatory responses by rats in a novel hole-board following lysergic acid diethylamide-25 (LSD), as described in a companion paper (Geyer and Light, 1979), was found to be a characteristic effect of a variety of hallucinogens. Similar effects were produced by indoleamine hallucinogens, such as LSD, N,N-dimethyltryptamine, and psilocin, and by phenylethylamine hallucinogens, such as mescaline or 2,5-dimethoxy-4-methylamphetamine (DOM). Congeners of DOM that are inactive in humans had no significant effects. Furthermore, of a variety of other psychoactive drugs tested, only apomorphine produced an effect similar to that of the hallucinogens. These results suggest that a simple behavioral measure of exploration in a hole-board may provide a useful animal model with which to examine the common effects of hallucinogens.

DOM 2,5-Dimethoxy-4-Methylamphetamine↗
PubMed1978

The effects of lysergic acid diethylamide and mescaline-derived hallucinogens on sensory-integrative function: tactile startle.

Tactile startle responding by male Sprague-Dawley rats given 60 presentations of air-puff stimuli (37.5 psi) was measured after the intraperitoneal administration of graded doses of hallucinogens and other psychoactive drugs. Among the drugs tested were the indoleamine-derived compounds, lysergic acid diethylamide (LSD), N,N-dimethyltryptamine and psilocin, and the phenylethylamine-derived compounds, mescaline, 2,5-dimethoxy-4-methylamphetamine and a series of active and inactive congeners of 2,5-dimethoxy-4-methylamphetamine. All of the active phenylethylamines increased startle response magnitudes throughout the test session. This pattern of augmented startle suggests that these drugs increase reactivity. However, none of the indoleamine hallucinogens increased startle responding. Of the nonhallucinogenic drugs tested, only apomorphine increased startle responding, while clonidine significantly decreased it, and amphetamine, chlorimipramine, scopolamine and methysergide had no effect. In additional studies with LSD, it was found that LSD increased the response to only the first stimulus when more intense air-puffs were used (50 psi). Furthermore, when the number of stimuli was increased from 60 to 240 (1 hr) so that appreciable habituation was evident in controls, LSD impaired this habituation. Whereas the response magnitudes of the control group decreased by 70% across the session, the responses of LSD-treated rats decreased by only 32%. These results suggest that LSD and phenylethylamine-derived hallucinogens may differ in their effects on tactile startle responding.

Animals↗
PubMed1975

Biomechanical appraisal of some skeletal features associated with head balance and posture in the Hominoidea.

The condylar position index, condylar angle and the area of insertion of the nuchal musculature corrected for condylar position, direction of muscle pull and skull size were determined in Homo sapiens, Gorilla, Pan and the casts of two Neanderthal and two australopithecine crania. In all three attributes, the values of H. sapiens exceeded, by statistically significant amounts, those for the ape genera. The greater value for the condylar position index indicates a better balance of the head, that for the condylar angle reflects the more vertical orientation of the vertebral column while that for the corrected nuchal area suggests a less effective nuchal musculature in H. sapiens as compared to the apes. In the casts of the Neanderthal crania, the values all came within, or close to, the ranges for H. sapiens. In the australopithecine casts, the condylar angle cane within the ranges for H. sapiens while the condylar position index and the corrected nuchal area were intermediate in value between H. sapiens and the extant apes. These findings are consistent with observations from other skeletal regions that while Australopithecus had an upright posture, this creature was, in the complex of posturally significant morphological features, distinct from extant hominoids.

Animals↗
PubMed1975

Development of skin interfacing cannula.

The skin interfacing potential of various velours, felts, foams and rough cast surfaces of some polymers was investigated by bonding these substances to solid core silastic rods using Dow-Corning Medical Adhesive Type A. These dummy cannulae were implanted as skin penetrating rods onto the dorsum of canines, goats, and swine. Vitreous carbon buttons were also investigated as to their potential. Over 200 individual implants were made and some retained in place for 2 yrs. Only the nylon and dacron velours held much promise as a long-term interfacing material. A "growth phenomenon" was observed using the velour material and this, we feel, is related to a permanent marriage between basal cells and adjacent monofilament fibers. Subsequent maturation of these cells carries the monofilament fibers to the surface causing the entire cannula to "grow". Since the maturation rate is apparently slower in humans, it does not detract from their potential application. The maturation rate is also much more rapid on the dorsum than on the ventral surfaces.

Animals↗
PubMedDate not supplied

Refractive versus corneal changes after photorefracive keratectomy for astigmatism.

PURPOSE: To define measures of assessing success and subsequent ways to improve excimer laser treatment of astigmatism. METHODS: We studied 97 eyes of 79 patients, followed for 12 months, that underwent photorefractive keratectomy (PRK) for myopia and astigmatism with a VISX 20/20 excimer laser. Preoperative spherical equivalent refraction at the corneal plane was between -1.00 and -15.00 D. Mean preoperative refractive astigmatism at the spectacle plan was -2.17 +/- 1.05 D (range, -1.25 to -6.00 D), which is -1.81 +/- 0.86 D (range -1.04 to -4.97 D) when calculated at the corneal plane. All patients were examined before and after surgery; examination included refraction, keratometry, and topography measurement. RESULTS: The success in treatment of astigmatism appeared measurably less than the treatment of sphere when analogous indices were used for assessment. Success in astigmatism surgery improved, as measured by all parameters, after an additional 20% was applied to astigmatism treatment magnitude indicated by the VISX computer algorithm. The sequential modes of treatment undercorrected astigmatism magnitude to a greater extent than elliptical, but equivalent success rates were present in view of the greater astigmatic changes attempted using the sequential mode. The elliptical mode tended to produce a greater undercorrection of associated sphere (p = 0.313). Results measured by refraction showed a larger change than those measured by topography and keratometry. CONCLUSION: During PRK with the VISX 20/20 laser, adjustment for undercorrection of astigmatism treatment achieves a fuller correction of astigmatism. When measuring astigmatic changes, results are different when comparing refractive astigmatism changes with corneal astigmatism changes measured by keratometry and topography.

Adult↗