Absence of a significant mixed lymphocyte reaction in a marsupial (Monodelphis domestica).

Previously we reported preliminary results suggesting that the marsupial Monodelphis domestica fails to exhibit a mixed lymphocyte reaction with allogeneic lymphocytes. To test whether this observation is simply a matter of a response too weak to detect, but capable of being augmented by immunization, we performed mixed lymphocyte culture tests on 23 of these animals that had been immunized with lymphocytes. Despite the fact that all recipients were sensitized to the lymphocytes of the donors, none of the animals had a substantial mixed lymphocyte response. Significant stimulation was noted with the mitogen concanavalin A; thus, the T cells were immunologically competent. It seems likely that the failure of this species to exhibit a significant mixed lymphocyte response is due to T cells whose ontogeny differs from that of the T cells of eutherian mammals.

Fate of allogeneic skin transplantations in a marsupial (Monodelphis domestica).

Previously we reported that the South American gray short-tailed opossum, Monodelphis domestica, had an MHC class-I locus similar to that of eutherian species. In addition to the detection of lymphocyte antigens by cytotoxic antisera, we concluded that this marsupial rejected allogeneic skin grafts, as would be expected of animals with MHC class-I polymorphism. However, this conclusion was based on a limited number of skin transplants that were assayed for only a short period. Here we report the results of 22 reciprocal skin grafts made between individuals of known genetic relationships. On the basis of gross inspection of the grafts and histologic examination, we found that the average time of the onset of graft rejection was about 19 days and that the average time for complete graft rejection was about 31 days. In general, it took longer for the onset of graft rejection among pairs of genetically related animals than among less related animals. These results indicate unequivocally that this marsupial species has a high degree of class-I polymorphism and rejects allogeneic skin transplants in a manner similar to but more slowly than eutherian mammals.

Effect of radiation and age on immunoglobulin levels in rhesus monkeys (Macaca mulatta).

We report the results of a study on the immunoglobulin levels of rhesus monkeys (Macaca mulatta) in a colony consisting of the survivors of monkeys that received a single whole-body exposure to protons, electrons or X rays between 1964 and 1969. This colony has been maintained to assess the long-term effects of ionizing radiation on astronauts and high-flying pilots. Of the original 358 monkeys that were retained for lifetime studies, 129 (97 irradiated and 32 controls) were available for our study. We found no significant difference between the irradiated and control monkeys in mean levels of IgA, IgG and IgM, irrespective of the radiation treatment. The availability of these aged monkeys provided a unique opportunity to compare their immunoglobulin levels to those of other monkeys of various ages, and thus assess the effect of age on immunoglobulin levels. We found that only the IgA levels increase with age.

The effect of age on the level of human ABO blood group antibodies.

It is generally assumed that cellular and humoral immunity decline in aging humans. Although there have been reports that the naturally-occurring ABO antibodies also decline with age, some of the data are incomplete and others contradictory. Our study involved only healthy women of various ages and included assays of anti-A and anti-B titers in A, B, and O subjects. Statistical analyses of the data showed that while the antibody titers decreased with age, the amount of change was very small relative to the amount of variability among individuals and the variability attributable to blood type and season of the year. Comparisons with a previous study (1) from our laboratory showed that the changes due to aging were also small relative to the variability in titer scores within an individual over the course of a year. Based on this study, we conclude that the decrease in antibody titers with age is of doubtful clinical significance.

Perceptual and academic patterns of learning-disabled/gifted students.

This research explored ways gifted children with learning disabilities perceive and recall auditory and visual input and apply this information to reading, mathematics, and spelling. 24 learning-disabled/gifted children and a matched control group of normally achieving gifted students were tested for oral reading, word recognition and analysis, listening comprehension, and spelling. In mathematics, they were tested for numeration, mental and written computation, word problems, and numerical reasoning. To explore perception and memory skills, students were administered formal tests of visual and auditory memory as well as auditory discrimination of sounds. Their responses to reading and to mathematical computations were further considered for evidence of problems in visual discrimination, visual sequencing, and visual spatial areas. Analyses indicated that these learning-disabled/gifted students were significantly weaker than controls in their decoding skills, in spelling, and in most areas of mathematics. They were also significantly weaker in auditory discrimination and memory, and in visual discrimination, sequencing, and spatial abilities. Conclusions are that these underlying perceptual and memory deficits may be related to students' academic problems.

Ontogeny of the thymus gland of a marsupial (Monodelphis domestica).

The gray short-tailed opossum (Monodelphis domestica) has recently been established as a laboratory animal; consequently, its utility as an animal model is enhanced as more of its basic biologic characteristics become defined. To this end, we studied the ontogeny of the thymus gland in M. domestica ranging in age from the day of birth to over three years. In contrast to most Australian marsupials, M. domestica possesses only a thoracic thymus. The thymus is large in neonates and remains large until young adulthood (six months of age). It has a well-defined cortex, medulla and Hassall's corpuscles. At about six months of age, the thymuses of most animals begin to atrophy, the cortex and medulla being replaced by fat. By 28 months of age, about 50% of animals have thymuses that are completely atrophied. Thus, the ontogeny of the thymus of M. domestica appears to be similar to that of eutherian mammals.

An analysis of WISC-R factors for gifted students with learning disabilities.

Intellectual patterns of gifted students with learning disabilities were studied to determine cognitive factors characterizing these children. Twenty-four gifted children with learning disabilities (LD) and a control group of nondisabled gifted children were administered the Wechsler Intelligence Scale for Children-Revised (WISC-R) (Wechsler, 1974). While differences between the two groups on individual subtests were examined, a comparison of broader factors was emphasized in discovering cognitive patterns that might suggest effective intervention. Experimental and control performances were compared on 14 factor scores, using cognitive classification systems of Bannatyne (1971), Kaufman (1975), Rapaport, Gill, and Schafer (1946), and Wechsler (1974). Gifted students with LD were more reliant on verbal conceptualization and reasoning than the control students. They also demonstrated deficiencies in short-term auditory memory and sound discrimination. The gifted group with LD exhibited the Organic Brain Syndrome factor (Wechsler, 1974) to a significantly greater extent than did the control group.

Changes in American A.I.D. practice during the past decade.

We conducted a survey of donor artificial insemination (AID) practices within the United States. The survey document was sent to 360 practitioners listed by national infertility organizations as performing AID. In addition, we queried 100 practices that had responded to a similar survey in 1978. AID was actually performed during the survey year by 167 of the 282 respondents. Relatively few practices (23%) inseminated more than 10 patients per month. Donor payments increased from a mean of $25 to $40 over that period. A significant increase in the use of frozen semen was found. A majority of practices (52%) used a combination of basal body temperature and urinary LH to time inseminations. The fraction of practitioners who inseminated unmarried women increased substantially since the previous survey. The maximum number of pregnancies resulting from a single donor has not changed over the decade. However, on the average, a single donor is fathering fewer children. The percentage (39%) of practices that inseminate women because of genetic disease in the husband's family has remained about the same. Records of donors and AID children were maintained by 40% of the respondents, representing no change from the previous survey. Our data suggest that as many as 23,400 infants may have resulted from AID conceptions during the survey year. Further changes in the practice of AID can be expected as a result of the 1988 federal recommendations that all donor inseminations be undertaken with cryopreserved, quarantined semen.