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Biomedical subjects

E Pannese

Publications and source records attributed to E Pannese.

At least 55 records · Page 3Linked to original sources
PubMed1987

An electron microscope study of quantitative relationships between axon and Schwann cell sheath in myelinated fibres of peripheral nerves.

The quantitative relationships between the cross-sectional area of the Schwann cell sheath (myelin included) and that of its related axon were studied by electron microscopy in the nerve fibres of the spinal roots of lizard (Lacerta muralis). In both ventral and dorsal roots the cross-sectional area of the Schwann cell sheath (myelin included) was found to be directly proportional to that of its related axon (correlation coefficients between 0.88 and 0.92). The ratio between the cross-sectional area of the Schwann cell sheath (myelin included) and that of its related axon tends to diminish as the cross-sectional area of the latter increases. Thus, under normal conditions, in myelinated fibres of the spinal roots of the lizard a quantitative balance exists between the nerve tissue and its associated glial tissue. This result agrees with those previously obtained in the spinal ganglia of the lizard, gecko, cat and rabbit. Some of the mechanisms probably involved in the control of the quantitative balance between nerve tissue and its associated glial tissue in peripheral nerves are presented and discussed.

Animals↗
PubMed1987

Mitotic Schwann cells in normal mature spinal roots.

Some rare mitotic Schwann cells (one in about a thousand) were found in normal mature spinal roots of adult lizards. Mitotic cells retained their relationships with unmyelinated axons, a finding consistent with the hypothesis that the stimulation of Schwann cell proliferation requires direct contact between axons and Schwann cells. The observation presented in this paper shows that Schwann cells and the satellite cells of sensory and autonomic ganglia behave in the same way also with regard to their mitotic activity.

Animals↗
PubMed1986

Association between microtubules and mitochondria in myelinated axons of Lacerta muralis. A quantitative analysis.

The spatial relationship between microtubules and mitochondria was studied in myelinated axons of the ventral and dorsal spinal roots of the lizard Lacerta muralis by use of quantitative methods in single and serial sections. Microtubules mainly occurred in groups of 3 to 10. The mean density of microtubules was found to be significantly higher close to mitochondria than in the rest of the axoplasm. In single sections, 59-62% (according to the root region examined) of the microtubule groups were found to be 'associated' with mitochondria; this percentage rose to 74-76% in serial sections. The examination in serial sections of progressively longer segments of the same microtubule groups showed that the longer the segments of microtubule groups examined the higher was the percentage of microtubule groups 'associated' with mitochondria. The results obtained show that in the axons studied in the present research a non-accidental spatial association exists between microtubule groups and mitochondria. This evidence supports the suggestion that the microtubule groups play a role in the movement of mitochondria along the axon, even though it does not clarify the precise nature of this role.

Animals↗
PubMed1985

A quantitative electron microscope study of the perikaryal projections of sensory ganglion neurons. II. Gecko and lizard.

The perikaryal projections of the neurons in the thoracic spinal ganglia of gecko and lizard usually appear as finger-shaped evaginations running roughly parallel to the surface of the nerve cell body; they show a nearly circular cross section with a rather uniform transverse diameter having an average value of about 0.2 micron. In both gecko and lizard a very high correlation was found between the surface area of perikaryal projections and both the volume and smoothed surface area of the corresponding nerve cell body. The results of the present research agree with those obtained in a previous study on two mammal species (cat and rabbit) and lend further support to the hypothesis advanced in that study; i.e., that perikaryal projections in sensory ganglion neurons are normal formations which maintain the surface-to-volume ratio above the critical level for metabolic exchanges. Perikaryal projections increase the surface area of the nerve cell body by 32.5% in gecko and 30% in lizard, while they increase it by 43% in cat and 39.5% in rabbit. This difference may be related to the lower metabolic rate of the neurons in poikilotherms than in mammals.

Animals↗
PubMed1984

A comparison of the density of microtubules in the central and peripheral axonal branches of the pseudounipolar neurons of lizard spinal ganglia.

The number and density of microtubules were determined in cross sections of the two branches (central and peripheral) of the bifurcating axon of the pseudounipolar neurons of the lizard thoracic spinal ganglia. In both the central and peripheral branches the average number of microtubules rose, while the microtubular density decreased with an increase in the cross-sectional area of the axonal branch: More precisely, a linear relationship was observed between the logarithm of the microtubular density and the cross-sectional area of the axonal branch. Both the average number of microtubules per cross section of the axonal branch and the microtubular density were found to be significantly lower in the central than in the peripheral branch. Since the amount of material carried by fast transport was found by other authors to be greater in the peripheral than in the central branch, a positive correlation seems to exist between microtubular density and the quantity of material carried by fast transport along the two branches of the axon in pseudounipolar neurons. Such a correlation suggests that microtubules may be somehow involved in the fast transport of material along the axon. The average densities of microtubules were found to be the same comparing two sets of unmyelinated and myelinated central (or peripheral) branches of corresponding size. Therefore, different microtubular densities usually observed in unmyelinated and myelinated axons appear to be correlated with the different size ranges of the two types of axon rather than with the absence or presence of the myelin sheath.

Animals↗
PubMed1984

A quantitative study of microtubules in motor and sensory axons.

The number, density and distribution of microtubules were compared in the myelinated motor and sensory axons of the spinal roots of lizard (Lacerta muralis). In both motor and sensory axons the average number and density of microtubules were found to be related to the axonal size: the average number of microtubules rose, while the microtubular density decreased with an increase in the cross-sectional area of the axon. More precisely, a linear relationship was observed between the logarithm of the microtubular density and the cross-sectional area of the axon. No significant differences in the microtubular number and density were found between motor and sensory axons of corresponding size. Microtubules were unevenly distributed throughout the cross section of both motor and sensory axons. In particular, a nonaccidental association between microtubules and mitochondria was found in both axon types.

Animals↗
PubMed1983

A quantitative electron microscope study of the perikaryal projections of sensory ganglion neurons. I. Cat and rabbit.

With a quantitative method and serial sections a study was carried out under the electron microscope of the perikaryal projections of the neurons in the thoracic spinal ganglia of cat and rabbit. These projections usually appear as finger-shaped evaginations which run roughly parallel to the surface of the nerve cell body. Their length ranges between 0.3 and 3.25 microns, and they show a nearly circular cross section with a rather uniform transverse diameter having an average value of about 0.2 microns. Both in cat and rabbit a very high correlation was found between the surface area of perikaryal projections and both the volume and smoothed surface area of the corresponding nerve cell body. Perikaryal projections increase the surface area of the nerve cell body by 43% in cat and 39.5% in rabbit. These findings support the idea that perikaryal projections in sensory ganglion neurons are normal formations, which maintain the surface-to-volume ratio above the critical level for metabolic exchanges.

Animals↗
PubMed1978

The response of the satellite and other non-neuronal cells to the degeneration of neuroblasts in chick embryo spinal ganglia.

The responses of non-neuronal cells to the degeneration of neuroblasts were studied in the spinal ganglia of the chick embryo. Reactive changes of the non-neuronal cells were not apparent during the early stage of degeneration of the neuroblast, but during the later stages of degeneration evidence was found suggesting that non-neuronal cells subdivided and phagocytosed the affected neuroblasts. Three types of non-neuronal cells appeared to participate in the phagocytosis: satellite cells, cells resembling undifferentiated elements, and macrophages. The appearance of the latter coincided with the beginning of the vascularization of the ganglionic rudiment. The phagocytic capacity of satellite cells is discussed in the light of these and other studies by light and electron microscopy.

Animals↗
PubMed1976

Lysosomes in normal and degenerating neuroblasts of the chick embryo spinal ganglia. A cytochemical and quantitative study by electron microscopy.

Lysosomes were studied by both cytochemical and quantitative methods in normal and degenerating neuroblasts of the chick embryo spinal ganglia. In normal neuroblasts (primitive and intermediate neuroblasts) both primary lysosomes and autophagic vacuoles were found; these organelles were usually located in the region containing the Golgi complex. In degenerating neuroblasts lysosomes appeared sharply decreased in number with respect to normal neuroblasts. Moreover, lysosomes were always evident as intact organelles surrounded by a membrane and the acid phosphatase activity appeared localized exclusively within these bodies. A diffuse distribution of acid phosphatase activity was only found in a limited number of cases during the terminal stage of the process. Possibly in these cases the enzymatic activity depended on the cells which enveloped the degenerated neuroblast remnants. The present results indicate that lysosomes do not play a primary role in the degenerative process studied.

Acid Phosphatase↗
PubMed1975

Quantitative relationships between nerve and satellite cells in spinal ganglia: an electron microscopical study. II. Reptiles.

In the spinal ganglia of two species of reptiles (gecko and lizard) the volume of the perikaryal satellite cell sheath was found directly proportional both to the volume and surface area of the related neuronal body. This result agrees with that obtained in a previous research on two species of mammals (cat and rabbit). A quantitative balance between neuronal bodies and their associated glial tissue therefore exists also in the spinal ganglia of zoological species phylogenetically quite distant from mammals. The quantitative relationship between glial and nerve tissue was found to be lower in the gecko and lizard than in the cat and rabbit. This difference could have a phylogenetic significance, and/or it could be explained by the lower metabolic rate in the nervous system of the poikilotherms in respect to mammals.

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