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Biomedical subjects

M M Patterson

Publications and source records attributed to M M Patterson.

At least 19 recordsLinked to original sources
PubMed1996

Follow-up skeletal surveys in suspected child abuse.

OBJECTIVE: The purpose of this study was to assess the additional yield of a repeat skeletal survey in identifying and dating skeletal injury for cases in which child abuse was strongly suspected. MATERIALS AND METHODS: Twenty-three infants and toddlers strongly suspected of being physically abused on the basis of findings on the initial skeletal survey, other imaging studies, history, or physical examination underwent a follow-up examination approximately 2 weeks after the initial examination. The high-detail imaging system included a single-emulsion, single-screen combination with a low-absorption carbon-fiber cassette. The skeletal survey protocol entailed tightly collimated anteroposterior views of the appendicular skeleton and anteroposterior and lateral views of the axial skeleton. Between the two studies, all children were in Department of Social Services custody or living in a safe home. RESULTS: The follow-up skeletal survey yielded additional information regarding skeletal injury in 14 (61%) of 23 cases. Follow-up study increased the number of definite fractures detected from 70 to 89 (27%) (p = .005). Most of these additional injuries were classic metaphyseal lesions or rib fractures. In 13 of the 70 fractures previously detected, the follow-up skeletal survey also provided important information about the age of those injuries. CONCLUSION: When child abuse is strongly suspected on the basis of the findings on the initial skeletal survey, other imaging studies, history, or physical examination, a follow-up skeletal survey is recommended to provide a through and accurate assessment of osseous injuries.

Bone and Bones↗
PubMed1987

Hippocampal substrate of sensory associations.

The role of the hippocampus in the association of two conditional stimuli was evaluated using the conditioned rabbit NM preparation and a sensory preconditioning paradigm. Multiple-unit activity was recorded from field CA1 during preconditioning. Paired presentations of CS1 and CS2 resulted in increased excitability which was highly correlated with later performance during CS2 test sessions. Unpaired presentations evoked a response to stimulus onset often followed by an inhibitory period. Bilateral kainic acid lesions of CA1 had no deleterious effect on traditional CS-US conditioning but abolished the association of CS1 and CS2. These data suggest that the hippocampus may be vital to the association of sensory events. Further, the SPC paradigm could provide an excellent model for evaluating simple cognitive deficits.

Animals↗
PubMed1986

Failure of hippocampectomy to facilitate classical conditioning at an optimal interstimulus interval is not due to a "ceiling effect".

The effects of amphetamine injection, hippocampal lesions, and cortical lesions were examined during classical conditioning of the rabbit nictitating membrane response. An optimal interstimulus interval was employed. Whereas neocortical and hippocampal damage had no significant effect on the rate of acquisition, amphetamine treatment produced a marked facilitation. A control group of amphetamine-treated animals, which received explicitly unpaired presentations of the conditioned stimulus and unconditioned stimulus, failed to exceed spontaneous response rates throughout training. The failure of hippocampectomy to accelerate conditioning under an optimal interstimulus interval (ISI) does not appear to be due to a "ceiling effect." Rather, it was suggested that the response system is predisposed to conditioned responses of a given latency. Optimal ISIs may fall within this range. Thus, in short or long intervals, temporal aspects of the motor response must be adjusted to conform to the stimulus configuration. It appears that the hippocampus is a likely source of response modulation. Thus, loss of hippocampal input accelerates conditioning under nonoptimal intervals at the expense of proper timing. Conditioning under an optimal interval would occur at normal rates because no modulation is required.

Amphetamine↗
PubMed1986

Retention and acquisition of classical trace conditioned responses by rabbits with hippocampal lesions.

The effects of dorsal hippocampal lesions on retention of classical trace conditioned responses were examined using the rabbit nictitating membrane preparation. Animals were trained to criteria and then lesioned either in the cortex or in the hippocampus and the cortex. Hippocampal damage had no effect on the retention of responses but produced significantly longer onset latencies. A control group of hippocampal animals acquired conditioned responses (CRs) at least as quickly as the prelesion subjects, and they also exhibited longer response onset latency. A second experiment evaluated the performance of hippocampal lesioned animals in classical trace conditioning with either a low-intensity periorbital shock or corneal air puff as the unconditioned stimulus (UCS). Hippocampal animals successfully acquired CRs under both conditions but exhibited an alteration of response onset which was dependent on the form of the UCS. Hippocampal animals displayed shorter response onset in the air-puff condition and longer response onset in the shock condition. Cortical animals timed responses consistently regardless of the UCS. These findings strongly suggest that the hippocampus modulates temporal characteristics of learned behavior.

Animals↗
PubMed1986

Experimental obstruction to aqueous outflow by pigment particles in living monkeys.

Pigment particles (1 X 10(6)/microliters) isolated from the iris and ciliary body of enucleated cynomolgus monkey eyes were infused into the anterior chamber of seven living cynomolgus monkeys and aqueous humor outflow facility determined by the two-step constant-pressure perfusion technique. Outflow facility acutely decreased 64% in the experimental pigment perfused eyes compared to a 76% increase in the sham-manipulated fellow eyes (P less than 0.001). However, when next measured 1 wk later, facility in the pigment perfused eyes had returned to baseline levels. Repetitive pigment perfusions similarly failed to produce any long-term abnormality in outflow facility. Gonioscopically, a well-defined band of pigment was observed in the trabecular meshwork, which decreased in density with time. Scanning and transmission electron microscopy documented pigment particle phagocytosis by trabecular endothelial cells and macrophages. Forty-two and 105 days after pigment infusion the trabecular meshwork was normal morphologically, and, despite an observed decrease in trabecular pigmentation, morphometry failed to reveal a decrease in trabecular meshwork cellularity in experimental compared to control eyes. These results suggest that factors other than, or in addition to, pigment particle accumulation in the trabecular meshwork must be involved in the mechanism of human pigmentary glaucoma.

Animals↗
PubMed1985

Long-term retention of a peripherally induced flexor reflex alteration in rats.

The long-term nature of peripherally induced spinal fixation was examined in the present study. Sixty-three anesthetized rats received 45-90 min of hindlimb stimulation. After a 24-72 h waiting period, the animals were given a midthoracic spinal section and hindlimb asymmetry was assessed. Our results indicate that a compensatory mechanism was activated after stimulation to correct the postural imbalance. Long-lasting effects of stimulation were manifested, however, when the compensatory influence was eliminated by spinal section.

Animals↗
PubMed1985

Sensory preconditioning in the rabbit following ACTH injections.

The effects of ACTH elevation on sensory preconditioning were examined using the rabbit NM response. Sensory preconditioning is an associative form of learning which is presumed to rely on a "stimulus map" provided by the hippocampus. Elevation of levels of ACTH was found to have no significant effect on SPC. This finding was interpreted as evidence that not all deficits found in hippocampal lesioned animals may be attributed to hormonal mediation. It was suggested that ACTH elevation may selectively mimic those deficits ascribed to a "neural model" process involving the hippocampus.

Adrenocorticotropic Hormone↗