Biomedical subjects

N Sposito

Publications and source records attributed to N Sposito.

4 recordsLinked to original sources

PubMed1990

Cerebral capillary bed structure of normotensive and chronically hypertensive rats.

In this study cerebral capillary bed structure and the effects of chronic hypertension on these systems have been assessed in 6- to 7-month-old spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats. Capillary diameter (D), profile frequency (Na), volume fraction (Vv), and surface area (Sv) were quantitated by light microscopic morphometry of eight brain areas including the sensorimotor cortex and subfornical organ. Previously presented data from normotensive Sprague-Dawley rats (SpD) of similar age were also compared. Within each of the three rat strains, D, Na, Vv, and Sv varied among brain areas. For the sensorimotor cortex and subfornical organ, capillary profile frequency differed significantly among the three rat strains. In SHR and WKY, there was an inverse correlation between profile frequency and diameter, i.e., as Na increased among brain areas, D decreased. In six brain areas capillary volume fraction and surface area were identical in SHR and WKY, but were lower in SpD. Consistent differences between SHR and WKY were found only for the subfornical organ, which suggests some involvement of this structure in hypertension. Since there were few statistically significant differences between SHR and WKY and many statistically significant differences between the two normotensive strains, cerebral capillary bed structure seems to be independent of arterial blood pressure in most brain areas of these rats.

Animals↗

PubMed1988

Structural and functional variations in capillary systems within the brain.

The major hypothesis of this study is that there are differences among brain areas in capillary bed structure and function. Three general differences between circumventricular organ and non-CVO capillary beds were found. First, the PS products for AIB were about 300 times greater in CVO capillaries than in non-CVO (blood-brain barrier) capillaries. Second, the frequency of endothelial cell fenestrations was much greater in CVO capillaries than in non-CVO capillaries and the fenestrae may be structural modifications of endothelial cells that permit ready passage of solutes such as AIB. Third, the frequency of mitochondria was greater in BBB capillaries than in CVO capillaries; this high metabolic potential of BBB capillaries may be associated, in part, with "carrier-mediated" transport of various solutes between plasma and cerebral interstitial fluid. Capillary bed differences among all (i.e., both CVO and non-CVO) brain structures were also observed. Among these differences are: rate of blood flow, mean transit time of albumin, capillary volume and surface area, perfused microvessel blood volume, apparent percentage of perfused capillaries, PS products for AIB, and frequency within the endothelium of vesicular profiles.

Aminoisobutyric Acids↗

PubMed1984

Motoneuron axosomatic synapses are altered in axonopathy.

This study was designed to answer two questions: 1) are synapses on motoneuron cell bodies affected during toxic neuropathy and 2) what is the nature and extent of the changes? We describe synaptic alterations on motoneuron cell bodies during intoxication with 2,5-hexanedione, a prototype neurotoxin known to induce axonal degeneration. Ultrastructural study of lumbar motoneurons from experimental and control rats revealed an array of pathologic changes including: partial and, less frequently, complete detachment of synaptic boutons; synaptic degeneration in a minority of boutons; and involvement of both microglia and astrocytes. Quantitatively, there was a significant decrease in the percent of neuronal membrane contacted by both F and S boutons and a significant increase in F boutons displaying degeneration. These results suggest that some neurotoxin-induced diseases of axons are associated with alterations of synaptic complexes that may have important implications for neuronal functioning.

Animals↗

PubMedDate not supplied

2,5-Hexanedione and acrylamide produce reorganization of motoneuron perikarya.

During acrylamide and hexacarbon exposure few changes have been reported in motoneuron perikarya. In the present study, light microscopic examination of lumbar motoneurons from rats intoxicated with either 2,5-hexanedione (2,5-HD) or acrylamide showed relatively few nonspecific changes compared to controls. However, ultrastructural study of 2,5-HD-intoxicated perikarya revealed a range of cytological reorganization: nuclear eccentricity and capping, reduced numbers of large Nissl bodies, and mitochondrial hypertrophy and hyperplasia. In 2,5-HD-intoxicated perikarya, computer-assisted stereologic analysis demonstrated a significant increase in the volume density of mitochondria. Ultrastructurally, acrylamide-intoxicated perikarya showed a marked reduction in the size of Nissl bodies. Stereologic analysis showed reductions in Nissl bodies, granular endoplasmic reticulum and Golgi complexes, and an increase in mitochondria. Taken together, these qualitative and morphometric changes, which were not obvious on light microscopic examination, imply significant reorganization of perikaryal metabolism.

Acrylamide↗