Midbrains from 43 fresh human embryos and fetuses at 8–22 weeks of gestation were processed for routine histology, Golgi staining, tyrosine hydroxylase (TH) immunolabelling and retrograde tracing with the fluorescent dye DiI. Cells were immature and densely packed between 8 and 10 weeks. By 13 weeks cells could be identified as neurons and glia. Neurons matured gradually and achieved adult characteristics by 20–22 weeks. Neurons in the paramedian regions of the tegmentum, raphae region and substantia nigra were positive for TH from 13 weeks onwards, the earliest age group used for this technique. The presence of TH-positive neurons in the paramedian part of the tegmentum until 18 weeks and radial glial fibers extending from the aqueductal lining to the ventral part until 20 weeks were suggestive of migration of neurons to the ventral mesencephalon region. DiI labelling of the neurons and fibers of ipsilateral nigra from the caudate as early as 10 weeks demonstrated early nigrostriatal connections. The mature nature of the neurons appeared only by 13 weeks by this method. The present study shows that the nigral neurons in the human migrate and mature until mid-gestation. The nigrostriatal connection at 10 weeks suggests a trophic influence of nigra on the proliferating and maturing neurons of the striatum.

Electron microscopy of the maturing neurons and developing and maturing synapses in the substantia nigra of 14 human embryos/foetuses of 8-24 weeks of gestation are reported. At 8 weeks, cells were immature with very little cytoplasm and cellular organelles. Contact sites of processes appeared more electron dense than the other areas. At 12 weeks, many of the cells had acquired more cytoplasm and cellular organelles and could be identified as neurons. Asymmetric synapses with clear, round synaptic vesicles also were identifiable at this age. Such synapses, first to appear in the developing substantia nigra, are reported to be formed by recurrent collateral nigro-striatal fibres. Substance P fibres from the striatum also are contributing to this type of synapse. At 15-16 weeks, not only was the number of such synapses increased, but many appeared morphologically mature. Symmetric synapses having clear round vesicles along with a few dense core vesicles also appeared at this stage, suggesting striatal input. By 24 weeks of gestation, most of the neurons had cytological features comparable to that of the mature neurons. There was an increase in the total number of synapses and the individual variety from 15 to 24 weeks of gestation. The present study indicates that synaptogenesis starts at 8 weeks and continues beyond 24 weeks of gestation.

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Fetal ventral mesencephalon from the 15th gestational day was grafted into the striatum of neonatal and adult rats. In one group of adult rats, fetal nigra was transplanted into normal striatum. In a second group, the tissue was transplanted at sites where dopaminergic fibers were denervated with 6-hydroxydopamine. The behavior of the dopaminergic neurons and glial reactions were studied by staining with cresyl violet to localize the transplants and by immunolabeling tyrosine hydroxylase (TH) and glial fibrillary acidic protein. In normal adults, the transplants were small. At the edge of the transplants, TH-positive neurons were packed into clusters, and an interface without any significant crossover of TH-positive fibers was present. Glial reaction was minimal in and around the transplant. In the denervated striatum, transplants were generally larger than those in normal striatum and surrounded by a glial scar. TH-positive neurons were both closely packed and loosely arranged at the periphery of the transplants. Processes could be clearly defined and could be traced to the adjacent host striatum through the TH-free denervated area. In neonates, the transplants were large and at times extended beyond the striatum. Most TH-positive neurons were arranged linearly along the periphery of the transplant. Cell bodies were widely separated and a well-developed neuropil was present. Fibers from the transplant mingled freely with the host striatum without any interface. In all three transplant groups, tracing the TH-positive neurites was easy because they were thicker and coarser than other elements. No apparent glial reaction occurred in the neonates. Thus, the growth and maturation of dopaminergic neurons seemed to vary in different environments. The most conducive environment appears to be neonatal brain in which growth factors are readily available.

Objective: The purpose of this pilot study was to determine if occupational therapy informed yoga could decrease barriers to occupational engagement in African American breast cancer survivors. Methods: A single-arm pretest-posttest design was used to study African American breast cancer survivors who participated in six weekly group yoga sessions that were delivered by occupational therapists. Variables were selected to operationalize barriers to occupational engagement and included mental health, bodily pain, role-physical and emotional, fatigue, self-efficacy, acute pain, balance, and upper extremity disability. Descriptive statistics and repeated measures analysis via linear mixed effects modeling were conducted to describe the participants and determine the efficacy of occupational therapy informed yoga. Results: Barriers to occupational engagement (health related quality of life, self-efficacy and balance, pain, upper-extremity disability) were evident in participants at baseline. Occupational therapy informed yoga reduced some of these barriers through significant changes in pain, mental health, and balance. Conclusion: These findings provide initial support for the development of group programming to deliver occupational therapy informed yoga to African American breast cancer survivors.