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Biomedical subjects

R O Weller

Publications and source records attributed to R O Weller.

152 records · Page 9Linked to original sources
PubMedDate not supplied

The blood-nerve barrier and reconstitution of the perineurium following nerve grafting.

Sural nerve autografts were performed on intact rat sural nerves and on sural nerves excised proximal to the site of grafting. The effect of the presence or absence of regenerating axons upon reconstitution of the perineurium at the graft junctions and upon re-establishment of the blood-nerve barrier to horseradish peroxidase (HRP) were studied over the succeeding 3--24 weeks. Compartmentation of the nerve fascicle occurred at the graft junctions where the perineurium was damaged. Each compartment contained Schwann cells with or without axons and was surrounded by elongated fibroblast-like cells which resembled perineurial cells in the longer surviving animals. It was concluded that, (a) compartments form in a nerve at the site of perineurial damage even in the absence of axons; (b) although compartmentation may be a mechanism for perineurial regeneration and reconstitution of the blood-nerve barrier, blood vessels and the cell layers forming compartments at graft junctions remain permeable to HRP for at least 6 months; and (c) the intact perineurium around the distal stump of a denervated nerve is permeable to HRP but the endoneurial blood vessels are not.

Animals↗
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Basement membrane surfaces and perivascular compartments in normal human brain and glial tumours. A scanning electron microscope study.

The relationship of perivascular tissues to arteries and veins in normal brain and glial tumors were investigated by light microscopy and by scanning and transmission electron microscopy. Vessels and perivascular tissues were separated through various planes by careful tearing of fixed tissue blocks of brain and tumour. Mirror surfaces of torn blocks were examined by scanning electron microscopy and the identity of the vessels and other structure confirmed by transmission electron microscopy. Perivascular glial basement membranes remained adherent to arterial adventitia in both normal brain and in tumour so that the torn surface around the vessel exposed perivascular glial processes attached to the vessel walls. A clear plane of separation of perivascular glial basement membrane from the adventitia of veins was achieved in glial tumours. Mirror surfaces showed the smooth undulating sheet of basement membrane separated from the fine fibrillary connective tissue of the vessel wall. Tears in the basement membrane revealed the perivascular glial processes. The structure of the perivascular basement membrane is discussed in relation to its role as an attachment site for perivascular glial and as an impedence to inflammatory cell migration into brain parenchyma.

Adolescent↗
PubMedDate not supplied

Pathology of Creutzfeldt-Jakob disease associated with pituitary-derived human growth hormone administration.

This report describes the pathological features in the brain of a 22 year old woman who died with Creutzfeldt-Jakob disease 8 1/2 years after completing a 4 year course of injections of human growth hormone derived from cadaver pituitaries. Spongiform change was seen in the frontal cortex. There was gliosis and neuronal loss throughout the frontal cortex, basal ganglia, thalamus, peri-aqueductal grey matter and tectum of the mid brain, pontine nuclei and dorsal medulla but no evidence of inflammation. Extensive atrophy and gliosis of the cerebellar cortex was present with widespread loss of neurons from the internal granular layer but relative sparing of Purkinje cells. Gliosis and atrophy of the mammillary bodies and gliosis of the hypothalamus may have been related to the previous surgical excision of a craniopharyngioma at the age of 2 1/2 years. The pattern of changes presented is comparable to that in other cases of Creutzfeldt-Jakob disease including those previously reported after human growth hormone administration.

Adult↗
PubMedDate not supplied

Calcification in the human choroid plexus, meningiomas and pineal gland.

Calcification in the stroma of adult telencephalic choroid plexus was studied of 20 postmortem brains and one biopsy by light microscopy, transmission and scanning electron microscopy and compared with calcification in psammoma bodies in normal arachnoid, five spinal meningiomas and in calcospherites of six pineal glands. Fifteen fetal and newborn choroid plexuses were also examined by light microscopy. Calcium deposition was observed in the subepithelial regions of the adult choroid plexus, in the walls of blood vessels but was mostly seen in spherical psammoma bodies. Collagen whorls 20-60 microns in diameter and surrounded by arachnoid cells, were observed in the stroma of the choroid plexus; calcium, phosphorous and iron were deposited in the collagen whorls to form psammoma bodies. Matrix vesicles and spicules resembling hydroxyapatite were associated with the arachnoid cells surrounding the collagen whorls and with the collagen fibres within the whorls. The dense amorphous calcified core of each psammoma body was surrounded by an outer coating of entwined collagen fibres readily visible by scanning electron microscopy. Similar psammoma bodies were occasionally observed in normal arachnoid. Psammoma bodies in meningiomas resembled those in the choroid plexus stroma. Calcospherites in the pineal differed from psammoma bodies; they were lobulated, more irregular in shape and did not have a collagen base. The results of this study suggest that psammoma bodies in the choroid plexus, as in meningiomas, form by a process of dystrophic calcification associated with arachnoid cells and collagen fibres. The presence of iron in the choroid plexus psammoma bodies may be a result of haemorrhage into the stroma. The mechanism of calcification in pineal remains unclear.

Adult↗
PubMedDate not supplied

Response of fetal and neonatal rat brain to injury.

Previous observations have suggested that a reactive astrocytic response to damage does not occur in fetal brain. In this study the time course of the astrocytic response to injury in fetal and neonatal rat brains has been assessed using the immunoperoxidase technique for glial fibrillary acidic protein (GFAP). Cold lesions were induced in utero to the forebrain and brain stem of rat fetuses at 16-18 days of gestation. The inflammatory response and the presence of GFAP in the processes of reactive astrocytes were studied in the brains of animals killed from 4 days (20-22 days of fetal life) to 12 days (9 days of post natal life) after the injury. Reactive astrocytes containing GFAP were present at the site of injury in all fetal and neonatal rat brains. Astrocyte processes were thin and short but stained strongly for GFAP. There was a greater amount of astrocytic scar tissue in animals killed 12 days after injury than in those killed after 4 days. In contrast to adults, little mesenchymal component was observed in newly formed scar tissue on the meningeal surfaces of the fetal and newborn rat brain.

Age Factors↗
PubMedDate not supplied

The cranial arachnoid and pia mater in man: anatomical and ultrastructural observations.

The objects of the present study were: (1) to define the relationships of the arachnoid mater to blood vessels in the subarachnoid space; (2) to establish the structure of leptomeningeal trabeculae and their relationships to the pia mater; and (3) to investigate the fine structure of the human pia mater. Intracranial portions of vertebral artery were taken at post mortem, and normal cerebral cortex and overlying leptomeninges were obtained from surgical lobectomies. Tissue from these specimens was examined by scanning and transmission electron microscopy, by light microscopy and by immunocytochemistry for the presence of basement membrane, desmosomal proteins and vimentin. Results of the study showed that as the vertebral artery pierced the posterior atlanto-occipital membrane and entered the subarachnoid space, it acquired a leptomeningeal coat as the arachnoid was reflected on to it. It has been demonstrated previously that as vessels enter the brain, the leptomeningeal coat is reflected on to the surface of the cortex as the pia mater. The arachnoid mater was seen to consist of a subdural mesothelial layer and a compact central layer as previously reported. From the inner layer of the arachnoid, collagen bundles coated by leptomeningeal cells extended as trabeculae across the subarachnoid space to fuse with the pia mater. The pia itself was composed of a delicate but apparently continuous layer of cells joined by desmosomes and gap junctions but no tight junctions were observed. It was possible to detect pia mater cells in the perivascular spaces of the brain by immunocytochemical techniques using light microscopy. The significance of the observed anatomical arrangement for cerebrospinal fluid physiology is discussed.

Adult↗