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Biomedical subjects

R L Friede

Publications and source records attributed to R L Friede.

At least 73 records · Page 4Linked to original sources
PubMed1984

Internodal length in ventral roots of bovine spinal nerves varies independently of fibre calibre.

The length of internodes in bovine ventral spinal nerve root fibres varies in an irregular pattern along the spinal cord with short internodes for the cervicothoracic and lumbosacral segments, and long internodes for the high cervical, thoracic and sacral segments. This pattern of variation is independent of axon calibre, which is fairly constant between roots. The data show that internode length and fibre calibre vary independently of each other, resulting in internodes of different proportions (length/diameter quotient) for different roots. Maximum internode length was determined at approximately 2400 microns; the longest internode found measured 2847 microns. The segmental variance in ventral root internode length in the cow differs from that in man or rat, which show a craniocaudal increase in internode length. These species-dependent differences relate to differences in the degree of the 'developmental ascensus' of the spinal cord.

Animals↗
PubMed1983

Neurologic complications induced by gold treatment.

Two patients developed a Guillain-Barre-like syndrome and a third suffered neuropathy and myokymia during therapy with sodium aurothiomalate. The cumulative dose at the time of development of neuropathy was different in all 3 cases. Evidence for gold toxicity was suggested by clinical, electromyographic, and histologic findings, as well as the disappearance of symptoms and signs on cessation of gold injections.

Aged↗
PubMed1983

Ventricular diverticula with localized dysgenesis of the temporal lobe in cloverleaf skull anomaly.

An early fetal case of cloverleaf skull anomaly associated with thanatophoric chondrodystrophy is described. Localized ventricular diverticula are a peculiar finding. In addition there are previously described malformations limited to the temporal lobes and comprising plump gyri with abnormal deep sulci, thick periventricular heterotopias, dysgenesis of the parahippocampal gyrus, agenesis of the Ammon's horn, and small micropolygyria. The skull deformity is not dependent on hydrocephalus, demonstrating inconsistencies in previous pathogenetic concepts.

Abortion, Legal↗
PubMed1983

Variance in relative internode length (l/d) in the rat and its presumed significance for the safety factor and neuropathy.

(1) Previous work has shown that the quotient l/d (internode length/fiber diameter) is the product of independent variations in internode length (increasing with fiber elongation) and in axon caliber (whose growth is not as yet well understood). Using these guiding principles, the distribution of l/d in 19 nerves and 7 roots of the rat was determined. (2) Each nerve or root showed a linear decrease of the l/d with fiber caliber, the thin fibers always having relatively longer internodes than the thick ones. Comparing nerves, the highest l/d was found for extremity nerves, particularly those in the hindlimbs. Nerves of the trunk (phrenic, intercostal) had lower l/d with further decreases for the extracranical branches of cranical nerves, the intercranial roots and a minimum for the acoustic nerve. In the facial nerve, the l/d of the intraosseous portions was distinctly lower than that of its branches in the face. Ventral roots showed a cranio-caudal increase in their l/d. For some fiber systems, e.g. cranial nerves, the l/d reflected variance in axon caliber, their internode length being relatively uniform. For others, e.g. roots, the l/d was dominated by their large variation in internode length. (3) Variation of the l/d in fiber populations may correlate with such parameters as internodal conduction time, different sensitivities of thick and thin fibers and, particularly, the safety factor. It is also proposed that the regional variation in the l/d is a critical parameter affecting the regional vulnerability of fiber populations to polyneuropathies or to radiculopathies.

Animals↗
PubMed1983

The role of endothelial gap junctions in the enlargement of chronic subdural hematomas.

The structure of macrocapillaries (also called 'sinusoids") in the outer membrane of chronic subdural hematomas was investigated by electron microscopy, with particular attention paid to vascular permeability. One characteristic of macrocapillaries is the frequent formation of gap junctions between adjacent endothelial cells. In endothelial gap junctions 0.6 to 8 microns in diameter, numerous blood components, including red blood cells and plasma, can be seen squeezing or spilling into the interstitial space of the outer membrane. Irregularly deformed erythrocytes are located around the macrocapillaries, and amorphous material is seen among scattered thin collagen fibers. It is suggested that endothelial gap junctions of macrocapillaries play an important role in the leakage of blood, causing enlargement of chronic subdural hematomas.

Capillaries↗
PubMed1983

Lhermitte-Duclos disease--its minimal lesions in electron microscope data and CT findings.

Clinical, necropsy, and electron microscope findings are described for a patient with Lhermitte-Duclos disease. Evidence that the disease originated from granule cell precursors was obtained from electron microscopy and from reconstruction in step serial sections of microscopic lesions found in the contralateral cerebellar hemisphere. The latter indicate a process of proliferation and hypertrophy of granule cells at their site of origin in the superficial granular layer, along their normal path of migration, or else at their destination in the cerebellar granular layer.

Adult↗
PubMed1982

How are sheath dimensions affected by axon caliber and internode length?

The significance of internode length for sheath thickness was analyzed by electron microscopic morphometry in isolated internodes from the human roots C3 and S1. These populations differ in length but have similar caliber. The amount of myelin per internode was in linear relation with the product of axon circumference and the length of the ensheathed axon segment. Neither one of these two vectors was in a statistically significant relationship with sheath thickness. The ratio between the axolemmal area covered by the Schwann cell and the area of the myelin leaflet averaged 1:163 for human root fibers. It was 1:177 for previous data from canine sciatic nerve. The proportions of an internode were defined by an 1/d-quotient, expressing its length as multiples of axon diameter. Relative sheath thickness (g-ratio: diameter axon/diameter fiber) relates inversely with the 1/d-quotient. For a given axon caliber, the g-ratio (sheath thickness) decreases by 0.006 for every 10.0 increase in 1/d-quotient (relative internode length). Thus, internodes relatively long for axon caliber possess slightly thicker sheaths than internodes short for axon caliber. Axon caliber and relative internode length emerge as the two key factors determining the amount of myelin in a sheath.

Humans↗
PubMed1982

Infantile small cell gliomas.

Fourteen juvenile patients with small cell gliomas were studied at two institutes. These tumors are believed to form a distinct entity. They arise mostly in the diencephalon or the brain stem and are composed of a poorly differentiated small cell component having a pronounced tendency to differentiate into a glioma. Signs of neuroblastic differentiation were also found with the electron microscope. Small cell gliomas disseminate early and profusely throughout the ventricular walls and the subarachnoid spaces including the spinal meninges. Prognosis is grave, most patients dying within 1 year of diagnosis or surgical intervention. The designation "infantile small cell glioma" overlaps with both the "metastasising gliomas in young subjects" of Eade and Urich (1971) and with the primitive neuroectodermal tumor of infancy of Hart and Earle (1973).

Adolescent↗
PubMed1981

Direct drainage of extracranial arteries into the superior sagittal sinus associated with dementia.

A 62 year-old-man suffered from progressive dementia for the last 5 years of his life. Angiography disclosed draining of multiple extracranial, galeal arteries directly into the superior sagittal sinus with retrograde filling of cerebral veins. At necropsy there was arterialization of the walls of the sinus and a multichannelled lumen in its middle third. The sinus was not distended, the dura normal, and no angioma was found. The leptomeninges and the cerebral white matter contained excessively distended veins, some with thickened fibrotic walls. Many arteries in the arterial white matter were mineralized. There were widespread patches of incomplete demyelination about these abnormal vessels. The lesion was classified as a developmental anomaly with direct shunting of extracranial arteries into the superior sagittal sinus.

Brain↗
PubMed1981

Do Rosenthal fibers contain glial fibrillary acid protein?

Sixteen cases of pilocytic astrocytomas with excessive Rosenthal fiber (RF) formation were examined by the indirect immunoperoxidase method for the localization of glial fibrillary acid protein (GFAP). RF never contained GFAP but they were often enclosed in plump and thickened GFAP-positive astrocytic processes. The border between the negative RF and the surrounding positive rim of cytoplasm was always sharp and without gradual transitions. The antigenic difference between RFs and glial filaments imply that glial filaments undergo a profound change in their chemical composition during their transformation into RFs. The possibility that RFs are not degradation products of glial filaments but consist of some chemically unknown substance produced by metabolically activated astrocytes cannot be excluded.

Astrocytes↗
PubMed1981

How is the exact length of an internode determined.

(1) The length of the human ventral spinal roots in the newborn and in the adult were compared with the length of the internodes in these roots. Internodes of fibers of a given caliber were more than twice as long in the adult sacral roots than in the cervical roots. The factors of root elongation corresponded closely to the factors of internode elongation. (2) Internode length was in a statistically significant linear relation with fiber caliber in individual roots. The slope of the regression lines differed among roots, and were steeper caudally. If data from roots having different elongation factors were pooled there was no longer a linear relationship between fiber caliber and internode length. Internode length, therefore, correlated directly and quantitatively with root elongation; it was not directly linked to fiber caliber. (3) The total Schwann cell population per fiber was nearly stable from the newborn to the adult, but the sacral roots had 5 times as many Schwann cells as the cervical roots. Calculations based on the number of internodes and on the length of fetal roots at the onset of myelination showed that the mean "initial length" of the Schwann cell at the onset of myelination was 187 micrometer, the same for all roots. (4) The Schwann cell population per fiber is determined by 2 reciprocal growth phases: elongation of the fetal fiber up to the onset of myelination corresponds to a multiplication of Schwann cells each having a given initial length. Schwann cell populations stabilize after the onset of myelination; from then on the geometry of each internode is determined by its passive elongation. The timing of myelination is critical for determining the ultimate length of the Schwann cell. If myelination does not begin before a fiber system has attained approximately one eighth of its definitive size, the longest internodes of that system will average 1.5 mm and most will remain below 2 mm, regardless of body size.

Adult↗
PubMed1981

The morphological changes in unmyelinated peripheral nerve fibers exposed to low sodium and high potassium concentrations.

Frog sciatic nerves were incubated in vitro in isotonic solutions in which the relative concentrations of sodium and potassium were varied. The cross-sectional areas of the unmyelinated axons, the Schwann cells ensheathing the axons, and the periaxonal spaces were measured, and the densities of the axoplasmic organelles were determined. It was found that the nerve fibers were relatively resistant to solutions with low sodium and high potassium concentrations. At very low sodium and high potassium concentrations, there was swelling of the Schwann cells with compression of the axons. A slight degeneration of the axoplasmic organelles was also noted. In an extremely low sodium and high potassium solution, the mesaxons of a few nerve fibers opened up; this was associated with swelling of the axons and slippage of the opposing surfaces of the axolemma and schwann cell membrane. The width of the periaxonal space remained unchanged even with extreme shrinkage or swelling of the axons. These findings indicate that the Schwann cell and axon react differently to low sodium and high potassium concentrations and that the Schwann cell appears to act as a buffer zone, protecting the axon by maintaining optimal ionic concentrations in the periaxonal space.

Animals↗
PubMed1981

The role of endoneurial fibroblasts in myelin degradation.

Counts of nuclei in electron micrographs of rat sciatic nerve show that approximately one third of the nuclear population is fibroblasts. Comparison of these figures with counts in teased fibers indicates that the majority of fibroblasts adheres tightly to myelinated nerve fibers. The early reactions and cellular transformations of the endoneurial fibroblast population upon intraneurial injections of india ink or of a purified preparation of rat sciatic myelin were studied for intervals of from 6 hours to 3 days after injection. There was phagocytosis of carbon or myelin by endoneurial fibroblasts as early as 6 hours after injection. A subsequent massive increase in phagocytic endoneurial cells appeared to develop from, and at the expense of, the normal endoneurial fibroblast population. The extent to which hematogenous monocytes also contributed to the macrophage population could not be assessed accurately by morphological criteria. Schwann cells never ingested carbon or myelin preparation during the period of investigation. Early invasion of the Schwann tube by macrophages from the endoneurial spaces could be demonstrated however. These macrophages were labeled by either carbon or myelin preparation which they had taken up from the endoneurial spaces before they entered the fibers through small gaps of the basal lamina, preferentially at the nodes of Ranvier. Carbon- or myelin-labeled hematogenous granulocytes entered nerve fibers in the same way, but the invasion of fibers by granulocytes was a transient early response limited to the first two days after injection. The data demonstrate the phagocytic capacities of endoneurial fibroblasts, their capacity for myelin degradation, and an invasion of Schwann tubes by elements of the endoneurial macrophage population during very early phases of fiber injury.

Animals↗