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A C Collier

Publications and source records attributed to A C Collier.

115 records · Page 7Linked to original sources
PubMed1980

The ontogenesis of defensive reactions to shock in preweanling rats.

Behavioral observations were made on the reaction to tailshock and footshock in 5- to 20-day-old hooded rats. For detection thresholds, age differences were found for footshock but not for tailshock. During intershock intervals, more generalized activity and freezing were elicited by footshock, whereas more responding directed to the shock source was elicited by tailshock. The unconditional responding to shock indicated that the older animals had a larger behavioral repertoire of defensive reactions and responded differentially to different shock intensities. The younger animals appeared to have a more limited and stereotyped repertoire of defensive reactions and to be more sensitive to the same nominal shock level. These normative data should prove useful in evaluating motivational and response repertoire problems when assessing learning processes developmentally.

Aging↗
PubMed1976

Long-term retention of early Pavlovian fear conditioning in infant rats.

That organisms cannot remember events occurring during infancy may be the result of common forgetting processes exacerbated by the organism's increase in size during development or a unique process such as insufficient neurological development at the time of the early experience. To establish the uniqueness of infantile forgetting, size change was made irrelevant by exposing infant rats to "off-baseline" Pavlovian fear conditioning and assessing the effect of an apparatus-free conditioned stimulus upon independently established bar pressing. In Experiment 1, bar pressing by rats exposed to Pavlovian contingencies when 20-22 days old was substantially suppressed by the conditioned stimulus both 1 and 42 days after conditioning. In Experiment 2, pups conditioned when 17-19 and 20-22 days old again showed excellent retention, whereas pups conditioned when 11-13 and 14-16 days old showed total forgetting 42 days later. In Experiment 3, pups conditioned when 14-16 days old remembered well after 5 days, less well 10 days later, and not at all after 20 days. These findings suggest that size change may contribute to the forgetting of events occurring late in development, but that neurological immaturity may underly the forgetting of earlier events.

Acoustic Stimulation↗
PubMedDate not supplied

Relationship between antibody to LAV/HTLV-III and the natural course of subclinical cellular immune dysfunction in homosexual men.

To assess the epidemiology and natural history of persistent generalized lymphadenopathy (PGL) and subclinical immunodeficiency in relation to serologic evidence of lymphadenopathy-associated virus/human T-lymphotropic virus type III (LAV/HTLV-III) infection, 109 homosexual men with PGL, 47 homosexual men without lymphadenopathy who attended a sexually transmitted disease (STD) clinic, 25 homosexual male university students, and 26 heterosexual men who attended the STD clinic were studied. In 1982-1983 antibody to LAV/HTLV-III was present in 97%, 35%, 21%, and 4% of the four groups, respectively (P less than .001). Subclinical immunodeficiency was more closely associated with LAV/HTLV-III seropositivity than with lymphadenopathy. Cohorts of 78 homosexual subjects with PGL, 35 homosexual subjects from STD clinic, and 15 homosexual university students were followed for median periods of 13.5, 20, and 14.5 months, respectively. The seroconversion rate was 23% per year among seronegative subjects, and 4% of seropositive subjects developed overt acquired immunodeficiency syndrome (AIDS). Among seronegative subjects, there was significant improvement in T4:T8 ratios (P = .001), whereas most seropositive subjects continued to have subnormal total counts of T4 lymphocytes and low T4:T8 ratios. Some cases of subclinical cellular immunodeficiency apparently are unrelated to LAV/HTLV-III infection, and the presence of antibody to this virus is associated with an unfavorable immunologic prognosis.

AIDS-Related Complex↗
PubMedDate not supplied

Prospective cerebral MR study of HIV seropositive and seronegative men: correlation of MR findings with neurologic, neuropsychologic, and cerebrospinal fluid analysis.

PURPOSE: As part of a longitudinal study of human immunodeficiency virus type 1 (HIV) infection, we attempted to identify early cerebral MR findings that might correlate to clinical evidence of central nervous system involvement. METHODS: We studied 65 seropositive and 40 seronegative homosexual males using cranial MR, neurologic, immunologic, and neuropsychologic examinations. RESULTS: The incidence of mildly enlarged ventricles, sulci, and punctate areas of abnormal signal in both groups was similar in both groups. Diffuse, poorly defined areas of abnormal white matter signal were difficult to consistently identify in seropositives. Enlarged adenoidal lymphoid tissue was found in 30 (46%) of seropositives and 2 (5%) of seronegatives (P = .0001). The incidence of sinus inflammatory change was similar in the two groups. CONCLUSION: MR of intracranial contents is substantially normal in a non-AIDS HIV(+) population.

Adult↗