Lateral distribution of intramembrane particles in Purkinje and granule cells of the rat cerebellar cortex

The cellular effects of estrogens on neuroendocrine tissues

Estrogen action on sensitive neurons in the rat diencephalon has been studied by morphologic techniques; evidence of estrogen action at every level is presented, including tracts, cells, circuitry and subcellular organelles. The demonstration in the arcuate nucleus of estrogen-induced synaptic remodelling, estrogen-induced postsynaptic membrane phenotypes, changes in intracellular membranes and rapid estrogen actions on neuronal endo-exocytosis indicates that cellular estrogen actions may underlie the neuronal control of reproduction.

Harmaline-induced changes in plasma membrane of Purkinje cells: a trans-synaptic effect mediated by climbing fibers

Fixed cerebellar cortex slices of adult male albino rats injected with saline, were exposed to the cholesterol probe filipin and freeze-fractured. Under these conditions, the plasma membrane of Purkinje cell dendrites was labeled with only a limited number of typical, 25-30 nm diameter filipin-sterol complexes. In contrast, in rats injected with harmaline, a drug that induces a rhythmic activation of climbing fibers, dendritic membranes showed an increased number of filipin-sterol complexes. This increased filipin labeling of Purkinje cell dendrites was not observed, however, when harmaline was injected into rats after destruction of climbing fibers. These results suggest that climbing fiber activation may induce a reorganization of the lipid matrix in the plasma membrane of Purkinje cells.

Differential distribution of intermembranous particles in the plasmalemma of the migrating cerebellar granule cells

The size and distribution of intramembraneous particles in 5 different plasmalemma domains of migrating cerebellar granule cells was studied by the freeze-fracture method. The quantitative analysis in 5-20-day-old rats reveals that the membrane of the leading tip of the descending process, the soma and vertical process that are associated with Bergmann glial fibers, have a significantly higher density of small (less than 11 nm diameter) intramembraneous protein particles than the horizontal processes and their growth cones which grow along previously generated parallel fibers. This regional difference in density of membrane associated particles may be related to the selective outgrowth of the two classes of granule cell neurites along glial and neuronal surfaces.

Sex differences and maturational changes in arcuate nucleus neuronal plasma membrane organization

Intramembrane particles (IMP) are believed to represent protein-containing structures in the membrane. Hypothalamic arcuate nucleus neuronal plasma membranes from male and female rats studied from birth to adulthood were quantitatively assessed for IMP number and size using freeze-fracture techniques. We found that newborn female rats have a significantly greater number of IMP than newborn males. There is also a progressive increase in the number of IMP during the first 20 days of postnatal life in both sexes. The rate of protein particle insertion favors females, maintaining the unequal protein particle content into adulthood with female rats having more IMP than males of the same age. The differences in IMP concentration are mainly due to greater numbers of small (less than 10 nm) particles in neuronal membranes from female rats. These data extend previous reports of sexual dimorphism in the arcuate nucleus to the level of plasma membrane organization.