Electron microscopic morphometry of isolated rat brain porosome complex.

Porosomes are the universal secretory portals at the cell plasma membrane where secretory vesicles dock and transiently fuse via the kiss-and-run mechanism of cellular secretion, to release intravesicular cargo to the outside of the cell. During last two decades discovery of porosome and a great volume of work from different laboratories provide molecular insights on the structure, function, and composition of the porosome complex, especially the neuronal porosome. In rat neurons 12-17 nm cup-shaped lipoprotein porosomes present at presynaptic membrane. They possess a central plug and sometimes are with docked synaptic vesicles. Although earlier studies have greatly progressed our understanding of the morphology and the proteome and limited lipidome of the neuronal porosome complex, the current study was carried out to determine the morphology of the bare protein backbone of the neuronal porosome complex. Results from our study demonstrate that although the eight-fold symmetry of the immunoisolated porosome is maintained, and the central plug is preserved in the isolated structures, there is a loss in the average size of the porosome complex, possibly due to a loss of lipids from the complex.

Ultrastructural changes to rat hippocampus in pentylenetetrazol- and kainic acid-induced status epilepticus: A study using electron microscopy.

A pentylenetetrazol (PTZ)-induced status epilepticus model in rats was used in the study. The brains were studied one month after treatment. Ultrastructural observations using electron microscopy performed on the neurons, glial cells, and synapses, in the hippocampal CA1 region of epileptic brains, demonstrated the following major changes over normal control brain tissue. (i) There is ultrastructural alterations in some neurons, glial cells and synapses in the hippocampal CA1 region. (ii) The destruction of cellular organelles and peripheral, partial or even total chromatolysis in some pyramidal cells and in interneurons are observed. Several astrocytes are proliferated or activated. Presynaptic terminals with granular vesicles and degenerated presynaptic profiles are rarely observed. (iii) The alterations observed are found to be dependent on the frequency of seizure activities following the PTZ treatment. It was observed that if seizure episodes are frequent and severe, the ultrastructure of hippocampal area is significantly changed. Interestingly, the ultrastructure of CA1 area is found to be only moderately altered if seizure episodes following the status epilepticus are rare and more superficial; (iv) alterations in mitochondria and dendrites are among the most common ultrastructural changes seen, suggesting cell stress and changes to cellular metabolism. These morphological changes, observed in brain neurons in status epilepticus, are a reflection of epileptic pathophysiology. Further studies at the chemical and molecular level of neurotransmitter release, such as at the level of porosomes (secretory portals) at the presynaptic membrane, will further reveal molecular details of these changes.

Hypokinetic stress and neuronal porosome complex in the rat brain: the electron microscopic study.

Porosomes are the universal secretory machinery in cells, where membrane-bound secretory vesicles transiently dock and fuse to release intravesicular contents to the outside of the cell during cell secretion. Studies using atomic force microscopy, electron microscopy, electron density and 3D contour mapping, provided rich nanoscale information on the structure and assembly of proteins within the neuronal porosome complex in normal brain. However it remains uncertain whether pathological conditions that alter process of neurotransmission, provoke alterations in the porosome structure also. To determine if porosomes are altered in disease states, the current study was undertaken for first time using high resolution electron microscope. One of pathologies that produce subtle alteration at the presynaptic terminals has been demonstrated to be hypokinetic stress. The central nucleus of amygdale is the brain region, where such alterations are mostly expressed. We have examined the width and depth of the neuronal porosome complex and their alterations provoked by chronic hypokinetic stress in above mentioned limbic region. Specifically, we have demonstrated that despite alterations in the presynaptic terminals and synaptic transmission provoked by this pathological condition in this region, the final step/structure in neurosecretion--the porosome--remains unaffected: the morphometric analysis of the depth and diameter of this cup-shaped structure at the presynaptic membrane point out to the heterogeneity of porosome dimensions, but with unchanged fluctuation in norm and pathology.

Immediate and persisting effect of toluene chronic exposure on hippocampal cell loss in adolescent and adult rats.

Abuse of toluene-containing volatile inhalants has become widespread among adolescents. Besides, because toluene is usually used as an industrial solvent in manufacturing of chemical pharmaceuticals and multiple commonly used household and commercial products, it has high potential for abuse for adults also. Long-term exposure to toluene vapor has a severe impact on the central nervous system, resulting in numerous neurological, neurobiological and behavioral impairments. Recently in the hippocampus some molecular and biochemical changes as a result of toluene chronic exposure were described. Such data point out the involvement of this area in the toluene addiction. However it remains uncertain whether toluene provokes structural alterations in the hippocampus. In this study we exposed male Wistar rats to 2000 ppm inhaled toluene for 40 days in rats at ages P 28-32 (adolescents) and P 70-75 (adults). The immediate and delayed effects of toluene chronic exposure (immediately after the end of toluene chronic inhalation and 90-day after the end of toluene chronic inhalation, correspondingly) on pyramidal cell loss in adolescent and adult rats was investigated. The results reveal that (i) chronic exposure to 2000 ppm of toluene chronic exposure alters the structure of hippocampus in adolescent and adult rats provoking both, immediate and delayed effects; (ii) the character of structural alterations depends upon the postnatal age of testing of the animals.