Light and scanning electron microscopic study of cerebellar cortex of teleost fishes

Summary The teleostean cerebellar cortex has been studied with respect to its cytoarchitectonic arrangement and intracortical neuronal circuits. Samples of fish cerebellum were fixed either by immersion or vascular perfusion in 5% glutaraldehyde solution and processed for light and scanning electron microscopy. The cerebellar cortex shows four distinct layers: granular; fibrous stratum; Purkinje cell; and molecular layers. In the granular layer, mossy and climbing fiber glomeruli were characterized. The mossy glomerular region appeared as polygonal, round or ovoid clews formed by the convergence of up to 17 dendritic profiles upon a thick mossy fiber branch. The en passant nature of mossy fiber-granule cell dendrite synaptic relationship was clearly appreciated. The climbing fibers showed tendril and glomerular collaterals. The latter form thin, elongated glomeruli. Remnants of a neuroglial envelope were observed in the mossy fiber glomeruli but are apparently absent from the climbing fiber glomeruli. The beaded-shape Golgi cell axonal ramifications were observed participating in the formation of both glomerular types. Velate protoplasmic astrocytes and oligodendrocytes were also identified. The fibrous stratum appeared to be formed by compact bundles of thick and thin myelinated axons, running horizontally beneath the Purkinje cell layer and apparently belonging to ascending climbing fibers and descending Purkinje cell axons. At the Purkinje cell layer a selective removal of Bergmann glial cells was observed allowing the visualization of the pericellular basket and the pinceaux. Climbing fiber stems and their tendril collaterals were seen on their way to the molecular layer ascending parallel to the Purkinje dendritic ramifications. Stellate neuron processes were found passing through the fan-like arborescence of Purkinje cell dendrites.     

Hydrogen exchange into soluble spinach chloroplast coupling factor during heat activation of its ATPase

Exchange of 500–600 atoms of ³H per mol of solubilized spinach chloroplast coupling factor (CF₁) occurs when the enzyme is incubated for 4 min in ³H₂O at 63°C. These ³H atoms are bound in parts of the protein where exchange is hindered by the three-dimensional structure at 25°C. Back-exchange at 25°C shows complex kinetics, with at least two kinetic components having half-times of 1.4 and 40 h, respectively. Back-exchange from the denatured enzyme is extremely rapid with an apparent half-time of the order of 20–30 s. The time courses for exchange and ATPase activation are very similar at 63°C, and reasonably close at 25°C. Both reactions have an optimum temperature of 60°C when measured after 4 min. Activation of ATPase requires a strong reducing agent to be present, but this is not needed for hydrogen exchange. It is suggested that an open conformation of CF₁ induced by heat may be a required intermediate for the rapid activation of ATPase, being a sporadic and rare occurrence at 25°C but also a required step in ATPase activation. This open conformation could be related to that induced in bound CF₁ by thylakoid membrane energization.     

Reproductive seasonality in a free-ranging troop of stumptail macaques (Macaca arctoides): A five-year report

Seasonality in births and fertile matings are reported for a stumptail macaque group living on an island for a period of five years: 1975–1979. During this period 26 births occurred of which 24 represent infants conceived on the island. While births and fertile matings occurred throughout the year 21% of the births were concentrated in March, 34% in June and July and 17% in November. Additionally 63% of the births occurred during the rainy season. Of the 24 infants, 4 died during the first year of life thus yielding a reproductive success of 83%. The sex ratio at birth for the five years was 1:1 corrected to 1:1.2 with the four deaths. The mean interval between fertile matings for females was 19 months and 2 days and the mean age for first conception was 4 years and 5 months. The pattern of birth and breeding seasonality was markedly similar to that of the parent troop while in Puerto Rico.     

Adrenocorticoid action in the spinal cord: Some unique molecular properties of glucocorticoid receptors

1. Glucocorticoid hormones affect several functions of the spinal cord, such as synaptic transmission, biogenic amine content, lipid metabolism, and the activity of some enzymes (ornithine decarboxylase, glycerolphosphate dehydrogenase), indicating that this tissue is a target of adrenal hormones. 2. Corticosterone, the main glucocorticoid of the rat, is detected at all regional levels of the spinal cord, and cold stress increases this steroid, predominantly in the cervical regions. 3. Intracellular glucocorticoid receptors have been found in the spinal cord, with higher concentrations in the cervical and lumbar enlargements. Prima facie, these receptors presented biochemical, stereospecifical, and physicochemical properties similar to those of receptors found in other regions of the nervous system. The prevalent form in the spinal cord is the type II receptor, although type I is also present in small amounts. 4. The type II glucocorticoid receptor of the spinal cord shows an affinity lower (Kd 3.5 nM) than that of the hippocampal type II site (Kd 0.7 nM) when incubated with [3H]dexamethasone. This condition may impair the nuclear translocation of the spinal cord receptor. 5. Another peculiar property of spinal cord type II site is a greater affinity for DNA-cellulose binding than the hippocampal receptor during heat-induced transformation. Also, the spinal cord receptor shows resistance to the action of RNAse A, an enzyme which increases DNA-cellulose binding of the hippocampal receptor, indicating that both receptors may be structurally different. 6. Therefore, it is possible that a different subclass of type II, or "classical glucocorticoid receptor," is present in the spinal cord. This possibility makes the cord a useful system for studying diversity of glucocorticoid receptors of the nervous system, especially the relationship between receptor structure and function.     

New sesquiterpenes from Pleocarphus revolutus

Six new sesquiterpenes of the guaiane and isopatchoulenone types have been isolated from the Chilean plant Pleocarphus revolutus. Of these, the compound hydroxy-isopatchoulenone and related esters showed cytotoxicity towards TLX5 mouse mammary lymphoma cells.     

L-type calcium channels and cytochrome b5 reductase are components of protein complexes tightly associated with lipid rafts microdomains of the neuronal plasma membrane

The presence of cytosolic calcium microcompartments in neurons is well established. L-type voltage calcium channels play a leading role in the rise of cytosolic calcium in the neuronal soma and are sensitive to redox modulation. In a recent work [Samhan-Arias, A.K., García-Bereguiaín, M.A., Martín-Romero, F.J. and Gutiérrez-Merino, C. (2009) Mol. and Cell. Neurosci. 40, 14–26], we have shown that cytochrome b₅ reductase, whose deregulation leads to an overshot of superoxide anion production at the neuronal plasma membrane that triggers apoptosis in primary cultures of cerebellar granule neurons in culture, forms a large mesh of redox centres associated with lipid rafts in these neurons. In this work, we have implemented the use of fluorescent antibodies as reagents for quantitative Förster resonance energy transfer measurements and analysis using fluorescence microscopy images of cerebellar granule neurons in culture. The results of this study show that L-type voltage-operated calcium channels are also enriched in lipid rafts associated protein microdomains at a distance between 10 and 100 nm from cytochrome b₅ reductase. The methodological improvements done in this work can be also valuable for the study of proteins compartmentalization within other subcellular microdomains in any cell type in culture.