Biomedical subjects

R R Sturrock

Publications and source records attributed to R R Sturrock.

At least 55 records · Page 3Linked to original sources

PubMed1988

A quantitative histological study of neuroglial number in the retrofacial, facial and trigeminal motor nuclei in the ageing mouse brain.

The number of neuroglia was estimated in the retrofacial, facial and trigeminal motor nuclei of the mouse brain at 6, 25, 28 and 31 months of age. There was no statistically significant variation in neuroglial number in either the facial or trigeminal motor nuclei despite changes in neuron number. There was a decrease in the number of neuroglia in the retrofacial nucleus between 25 and 28 months which was slightly greater than the decrease in neuronal number, followed by a small increase in neuroglial number between 28 and 31 months of age. The glia-to-neuron ratio in the facial and trigeminal motor nuclei was identical (between 5 and 6) and did not vary with age. The ratio in the retrofacial nucleus was lower (between 1.6 and 0.9) and this reflects the differences in structure between the retrofacial nucleus and the other two nuclei.

Aging↗

PubMed1988

An ultrastructural study of intraventricular macrophages in the brains of aged mice.

Intraventricular macrophages in brains of mice aged 25 to 31 months were examined in the transmission electron microscope. A wide spectrum of phagocytic activity was found ranging from resting, inactive macrophages to extremely large active macrophages. Most of the phagocytosed debris appeared to be of lipid origin and a possible sequence of lipid breakdown was postulated. There was evidence of phagocytosis of degenerating choroid plexus epithelial cells and also of mitosis of intraventricular macrophages. The most striking feature of intraventricular macrophages in the ageing brain was the presence of some extremely large cells in which most of the cytoplasm was filled with phagocytosed debris.

Aging↗

PubMed1988

An ultrastructural study of the development of leptomeningeal macrophages in the mouse and rabbit.

Macrophages can be identified in the leptomeninges of the mouse and rabbit spinal cord at E11 and E12 respectively. Initially macrophages contained few cytoplasmic organelles and had long, narrow convoluted processes. By E14 in the mouse and E16 in the rabbit the macrophages were well differentiated with short processes; the cytoplasm contained vacuoles of varying sizes, dense bodies, mitochondria, free ribosomes and rough endoplasmic reticulum. In the young postnatal mouse leptomeningeal macrophages contained numerous small cytoplasmic vacuoles. Leptomeningeal fibroblasts containing varying amounts of cell debris were also found in both pial and arachnoid layers in both species examined but there was no evidence of transformation of leptomeningeal fibroblasts into macrophages.

Animals↗

PubMed1988

An ultrastructural study of the choroid plexus of aged mice.

The choroid plexus of mice aged 25, 28 and 31 months was examined in the transmission electron microscope. The main changes noted with age were the presence of lipid droplets, dense bodies and, much more rarely, vacuoles surrounded by a fine lamellar membrane. The cytoplasm of light choroid epithelial cells seemed more electron-dense than in young adults and the microvilli were long and slender in contrast with the short, spatulate microvilli seen in young mice. Glycogen was rarely present in choroid plexus cells in old age. The morphological changes suggest a decrease in efficiency of choroid plexus epithelial cells in old age.

Aging↗

PubMed1987

Development of granular pial cells and granular perithelial cells in the spinal cords of mouse and rabbit.

Free cells containing large dense granules first appear in the leptomeninges of spinal cord at E14 in the mouse and at E16 in the rabbit. These ages represent a similar stage of development of the spinal cord and meninges. Despite the early appearance of granular pial cells, granular perithelial cells are not found around blood vessels in the spinal cord until 5 days postnatum in the mouse and E28 in the rabbit. The first appearance of granular perithelial cells coincides with the development of large vessels in the spinal cord. Although there is some correlation between the onset of myelination and the age of appearance of granular perithelial cells in the spinal cord, this appears to be spurious. The early stages of the development of sense granules into honeycomb bodies can be seen as early as 15 days postnatum in the mouse spinal cord.

Animals↗

PubMed1987

Development of the meninges of the human embryonic optic nerve.

From 8 to 14 weeks post-conception the human embryonic optic nerve is surrounded by loosely packed layers of connective tissue. From 8 weeks onwards the innermost layers of this sheath consist of fibroblast-like cells whereas the cells of the middle and outer layers, although similar in appearance, contain increasing amounts of glycogen, until by 14 weeks very large amounts of glycogen are present in these cells. A collagen-rich dural layer first appears at 15 weeks post-conception. This layer contains few cells. The outer-most cells have the appearance of fibroblasts and are joined to each other by long sheet-like processes. Cell in the middle of the dura are glycogen-containing cells, apparently actively engaged in collagen production. These cells are similar to those found in the adjacent arachnoid. By 18 weeks of age the meninges are well-differentiated. The endothelial cells of all capillaries found in the meninges from 8 weeks post-conception, including dural capillaries, are sealed by zonulae occludentes. At 15 and 18 weeks a few fenestrated capillaries were observed at the junction of the dura and the surrounding loose connective tissue. Peripheral nerves are closely related to the meninges from 8 weeks post-conception and peripheral nerve bundles are present in the dura from 15 weeks. At 18 weeks the first signs of myelination were observed in these bundles.

Arachnoid↗

PubMed1987

Vascularization of the human embryonic optic nerve.

Vascularization was examined in perfusion-fixed optic nerves from human embryos aged from 8 to 18 weeks post-conception. The volume density of blood vessels increased from 0.7% at 8 weeks to 24% at 18 weeks; the surface area of blood vessels increased from 2.1 mm2/mm3 at 8 weeks to 49.9 mm2/mm3 at 18 weeks. At all ages endothelial cells were joined by zonulae occludentes. Capillary basement membranes were present at all ages and blood vessels not lying in developing fibrous septa were invested with a complete glial sheath from 8 weeks of age. Only extremely rarely were parts of small capillary walls not covered by glial processes. Arterioles were absent from the optic nerves until 18 weeks post-conception. At first vascularization was most obvious in the central part of the nerve but there was no evidence for the presence of a central artery of the optic nerve. There did not appear to be a direct correlation between the degree of vascularization and increase in glial or axonal number.

Arterioles↗

PubMed1987

Changes in the number of axons in the human embryonic optic nerve from 8 to 18 weeks gestation.

The number of axons was estimated in optic nerves from human embryos aged 8, 10, 12, 14, 15 and 18 weeks post-conception. At 8 weeks there were 2.67 million axons. The number fell to 1.94 million at 10 weeks then increased to reach a peak of 5.86 million at 14 weeks before falling to 3.58 million at 18 weeks. Mean axon-diameter increased slowly from 0.17 micron at 8 weeks to 0.24 micron at 18 weeks. Growth cones declined in number from 34,400 at 8 weeks to 9,400 at 14 weeks and were not found thereafter. Degenerating axons were most numerous at 12 and 15 weeks.

Axons↗

PubMed1987

A quantitative histological study of cell division and changes in cell number in the meningeal sheath of the embryonic human optic nerve.

Mitotic cells are present in all layers of the meninges of the human optic nerve between 8 and 18 weeks post-conception. The number of meningeal cells per section remains constant between 8 and 12 weeks before rising rapidly from 234 at 12 weeks to 747 at 18 weeks. The mitotic index is only 0.17% at 8 weeks but rises to 1.02% at 10 weeks before falling gradually to 0.29% at 18 weeks. A comparison of the results of this study with a previous one on gliogenesis in the same nerves (Sturrock, 1975) leads to the tentative conclusion that mitotic activity in the layers of the meninges is probably sufficient to account for the increase in meningeal cell number between 8 and 18 weeks. The substantial increase in thickness of the meninges found between 14 and 15 weeks is due to a large increase in the amount of collagen in the developing dural layer rather than the modest increase in cell number. During mitosis meningeal cells do not retract their processes and cell division usually occurs tangentially.

Cell Count↗

PubMed1987

Ultrastructural evidence for the mitotic division of neurons in the anterior horn of the fetal rabbit in the later stages of gestation.

Two mitotic cells found in the ventral horn of the fetal rabbit spinal cord at 26 and 28 days post-conception are described. Both are large cells with a much more extensive cytoplasm than is usual during mitosis. The cytoplasm of both cells contained an extensive dilated vesicular structure which was identified as the endoplasmic reticulum. Ribosomes were not present on its surface. The 26 days post-conception cell had an axosomatic synapse on its perikaryon and serial ultrathin sections of the 28 days post-conception cell showed a number of dendrite-like processes arising from its perikaryon and a myelinated axon approaching the pole of the cell opposite the plane of cleavage. These two cells were structurally different from mitotic cells previously described in the central nervous system and appear to be neurons that are at least partially differentiated.

Animals↗

PubMed1987

Age-related changes in the number of myelinated axons and glial cells in the anterior and posterior limbs of the mouse anterior commissure.

The total number of axons and the number of myelinated axons was estimated in both limbs of the anterior commissure of mouse brains from 5 to 31 months of age. The total number of glial cells and the percentage of each type of glial cell was estimated in both limbs of the anterior commissure at 25, 28 and 31 months since similar estimations had already been carried out in mice aged between 5 and 22 months. The total number of axons and the number of myelinated axons both appeared to fall between 9 and 12 months and to increase again between 22 and 25 months in the anterior limb whereas in the posterior limb the total number of axons remained constant but the number of myelinated axons increased between 22 and 28 months. Two types of abnormality were seen in myelinated fibres at all ages after 12 months. These consisted of degenerating axons enclosed in normal myelin sheaths and apparently normal axons surrounded by vacuolated sheaths. The total number of glial cells in both limbs decreased between 9 and 12 months and increased substantially between 22 and 25 months. There was a statistically significant correlation between the number of oligodendrocytes and the percentage of myelinated axons in both limbs at different ages. There was no change in the very small number of mitotic figures in the anterior commissure to account for the fluctuation in glial number. It is postulated that there is a continuous loss and replacement of myelinated axons in both limbs of the commissure from 12 to 31 months of age and that this is possible since the amount of axon loss is so small that there is no significant phagocytic or astrocytic response. An increased requirement for myelination appears capable of bringing about an increase in the number of oligodendrocytes even in aged animals.

Aging↗

PubMed1987

Changes in the number of neurons in the mesencephalic and motor nuclei of the trigeminal nerve in the ageing mouse brain.

The number of neurons and neuronal nuclear diameter was estimated in the mesencephalic and motor nuclei of the mouse trigeminal nerve at 6, 9, 12, 15, 22, 25, 28 and 31 months of age. Analyses of variance showed that neuronal number decreased significantly (P less than 0.01) in the mesencephalic nucleus between 25 and 31 months, but, although lowest at 31 months of age in the motor nucleus, the decrease in neuronal number in the motor nucleus was not statistically significant. Neuronal nuclear diameter increased significantly in both nuclei between 25 and 31 months, being obvious first in the mesencephalic nucleus. The main histological features of ageing were a marked accumulation of lipofuscin granules in neurons of the mesencephalic nucleus and a loss of Nissl substance from the motor neurons of the trigeminal motor nucleus.

Aging↗

PubMed1987

Fluorescent granular perithelial cells and granular pial cells in the brains of aged mice.

The majority of fluorescent granular perithelial cells (FGPs) in the brains of aged mice contain large honeycomb bodies which probably represent a specialised type of phagosome. The other characteristic feature of FGPs is the presence of large numbers of small coated vesicles in the cytoplasm. Granular pial cells are structurally identical to FGPs and in particular they contain large honeycomb bodies. The evidence indicates that FGPs and granular pial cells represent one cell type whose major function in the aged brain is to act as a scavenger of substances such as lipid but which does not phagocytose degenerating cells or large masses of cellular debris. FGPs and granular pial cells are different from intraventricular macrophages both structurally and in their response to ageing. The similarity between FGPs and granular pial cells in the ageing brain supports the view that FGPs are derived from pial cells.

Aging↗

PubMed1987

A morphological study of the neostriatum of aged mice with particular reference to neuroglia.

The most prominent feature of the aged mouse neostriatum is the presence of large vacuoles. Careful inspection showed that these are vacuolated myelin sheaths and are invariably found in, or at the periphery of, the nerve fibre bundles which traverse the neostriatum. Oligodendrocytes showed little evidence of ageing but satellite oligodendrocytes contain more lipofuscin than oligodendrocytes associated with myelin sheaths. Most astrocytes contain pigment-prominent lipofuscin granules but a small minority contain numerous large pigment lipofuscin granules, and are packed with microfilaments and glycogen granules. A few astrocytes have circular nuclear inclusions filled with a fine granular material. Microglial cells contain the largest amount and variety of lipofuscin; in most cases, however, the lipofuscin is of the lipid-pigment type.

Aging↗

PubMed1986

A quantitative histological study of the indusium griseum and neostriatum in elderly mice.

A quantitative histological examination of brains from mice aged 25, 28 and 31 months of age showed that there was no loss of neurons from the indusium griseum and the number of glia per 100 neurons also remained constant. In contrast the number of glia per 100 neurons in the neostriatum fell between 25 and 28 months. The percentage of oligodendrocytes was significantly higher than in younger mice but the percentage of microglia fell in both regions from 25 to 31 months. Unlike the indusium griseum, in which there was a significant variation in the mitotic and pyknotic indices with age, the neostriatum showed no variation in the mitotic and pyknotic indices between 6 and 31 months. The mitotic index was always lower in the neostriatum.

Aging↗

PubMed1985

Age related changes in cellularity, mitotic activity and pyknotic cell number in the mouse subependymal layer.

The mouse subependymal layer shows a decrease in cellularity between 22 and 31 months of age after having remained fairly constant between 6 and 22 months. The mitotic index falls from 2.32% at 6 months to 1.19% at 18 months before rising to 2.37% at 28 months. The variation in the mitotic index prevents the number of mitotic cells decreasing between 22 and 28 months along with decreasing cellularity. There is no statistical correlation between the number of mitotic cells and the number of pyknotic cells in the subependymal layer although, at all ages, mitotic cells out-number pyknotic cells.

Aging↗

PubMed1984

A scanning electron microscopic study of Reissner's fibre in elderly mice.

Reissner's fibre was investigated in brains and cervical spinal cords of mice aged 28 and 31 months using scanning electron microscopy. At both 28 and 31 months Reissner's fibre was present. It arose from a fusing together of numerous smaller fibres in the subcommissural organ and was observed in the aqueduct, fourth ventricle and central canal of the medulla and spinal cord. For most of its length it was a ridged structure similar to a stick of celery but in places small processes could be seen arising from its surface. Cilia, supraependymal cells and other debris appeared to be adherent to the fibre and this may support the view that Reissner's fibre has a detoxifying function which is still present in old age.

Aging↗

PubMed1984

Microglia in the human embryonic optic nerve.

Microglial cells were identified electron microscopically in optic nerves from 8, 10, 12, 14, 15 and 18 weeks post-conception human embryos. In 8 and 10 weeks embryos, most microglia were relatively undifferentiated and the cytoplasm contained numerous large vacuoles. These were similar to the tuberous and amoeboid microglia described by earlier authors. In older embryos well differentiated microglia were present. At all ages microglia contained cellular debris and evidence of lipid droplets. Although there was a statistically significant correlation between vascularity and the number of microglia it is postulated that this is coincidental rather than biologically significant. Most microglia were found within bundles of axons and there was no preferential distribution in relation to blood vessels or to the pial surface at any stage of development. The percentage of microglia present increased from 1.3% at 8 weeks to 2.7% at 18 weeks.

Cell Count↗