A new autosomal recessive mouse mutation, Purkinje cell degeneration (ped), is described. Mutants exhibit a moderate ataxia beginning at 3 to 4 weeks of age. The ataxia results from postnatal degeneration of virtually all cerebellar Purkinje cells beginning around 15 to 18 days of age and progressing rapidly over the next 2 weeks. In addition to the cerebellar disease there is slow progressive degeneration in the retina (photoreceptor cells) and olfactory bulb. Also, adult males have abnormal sperm.Because of the uniform, stereotyped, and relatively simple organization of the cerebellar cortex many neuroscientists have chosen to study its functional organization (1), cytology and synaptic architecture (2), or development (3). Since the most obvious functions of the cerebellum involve posture and motor coordination, most mutations will affect behavior and are readily detected. In mice, a number of cerebellar mutants have been described (4) MATERIALS AND METHODSThe pcd mutation occurred in the C57BR/cdJ strain at The Jackson Laboratory. Because of the poor breeding performance of this strain, pcd/pcd females were mated to C3H/ HeJ males and the Fj-animals were intercrossed to produce pcd/pcd F2 females. These females were then crossed back to C57BR/cdJ males and the pcd mutation was maintained thereafter by brother-sister matings. The mutant gene is also being transferred to the C57BL/6J strain. The animals used in this study came from both lines.For histological studies, the mice were fixed by perfusion through the heart with 1% formaldehyde and 1.25% glutaraldehyde in 0.1 M sodium phosphate buffer, pH 7.2. The brains were removed, dehydrated, and embedded in either paraffin or celloidin. Sections were cut at 7 or 20 gm and stained with cresyl violet. In addition, pieces of cerebellum and eyes were postfixed in OS04, dehydrated, embedded in an Epon-Araldite mixture, and sectioned at 1 Am, and the sections were stained with toluidine blue.The various brain regions are designated according to the atlas of Sidman et al. (14). Day of birth is considered day 0.To determine if there was any difference in body weights between mutants and controls, all young in 8 litters were earmarked on day 15

Chimeric rats were produced by the aggregation of embryos of the pinkeyed, retinal dystrophic RCS strain with those of pigmented, normal rats. In the mosaic eyes, patches of neural retina with abnormal and degenerated photoreceptors were present only opposite patches of nonpigmented, mutant pigment epithelium. This indicates that the retinal dystrophy gene acts in the pigment epithelial cell rather than in the photoreceptor cell.

A recent study by Masters (1992) investigated the effect of stress upon the performance of a well-learned motor skill, golf putting, acquired under implicit and explicit learning conditions. Masters found that stress had a detrimental effect on performance for the explicit learning group but not for the implicit learning group. However, the implicit learning group was required to perform articulatory suppression during the learning trials but not during the stress trials. As such, it is possible that the subjects in the implicit learning group continued to improve during the stress session simply because they were performing an easier task. This paper reports an experiment which re-examines Masters' (1992) conclusions by replicating and extending his method. An additional implicit learning group was included which was required to carry out articulatory suppression during both the learning trials and the stress trials. It was hypothesized that this 'new' implicit learning group would suffer the same disruption to performance as the explicit learning group, providing evidence which would contradict Masters' explanation. Thirty-two subjects were allocated to one of four groups. Performance measures were analysed using two-factor analysis of variance (4 x 5: groups x sessions) with repeated measures on the sessions factor. The main dependent variable was the number of putts successfully completed. The analysis revealed that both the implicit learning groups continued to improve their performance under stress whilst the explicit learning group did not. Despite limitations to both Masters' (1992) and the present study, these results add support to Masters' explicit knowledge hypothesis.

A battery of monoclonal antibodies (mAbs) against brain cell nuclei has been generated by repeated immunizations. One of these, mAb A60, recognizes a vertebrate nervous system- and neuron-specific nuclear protein that we have named NeuN (Neuronal Nuclei). The expression of NeuN is observed in most neuronal cell types throughout the nervous system of adult mice. However, some major cell types appear devoid of immunoreactivity including cerebellar Purkinje cells, olfactory bulb mitral cells, and retinal photoreceptor cells. NeuN can also be detected in neurons in primary cerebellar cultures and in retinoic acid-stimulated P19 embryonal carcinoma cells. Immunohistochemically detectable NeuN protein first appears at developmental timepoints which correspond with the withdrawal of the neuron from the cell cycle and/or with the initiation of terminal differentiation of the neuron. NeuN is a soluble nuclear protein, appears as 3 bands (46-48 × 10(3) M(r)) on immunoblots, and binds to DNA in vitro. The mAb crossreacts immunohistochemically with nervous tissue from rats, chicks, humans, and salamanders. This mAb and the protein recognized by it serve as an excellent marker for neurons in the central and peripheral nervous systems in both the embryo and adult, and the protein may be important in the determination of neuronal phenotype.