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Aims: To investigate routes of dispersal of enzyme, its regional uptake and the effect of posture when replacement enzyme is administered directly into the cerebrospinal fluid (CSF)., Methods: Dispersal pathways of particles and solutes were investigated using intracisternal injections of india ink with visual assessment, and a contrast medium (Iohexol) with computer tomography (CT). Replacement enzyme was measured at 46 loci within the central nervous system (CNS) in four groups of dogs subjected to different post-injection postural changes., Results: India ink and CT studies showed dispersal pathways for CSF to be mainly via cisterns and sulci. Replacement enzyme reached all areas of the CNS tested, although mean concentrations varied 49-fold over different areas of the brain. Posttreatment posture had only modest effects on enzyme uptake in limited anatomical sites., Conclusions: Dispersal of solutes after injection is rapid and initially enhanced by the injection process. Preferential pathways for CSF flow in the subarachnoid spaces of the brain involve cisterns and sulci. The splenial and suprasplenial sulci in particular appear important conduits for dispersal to more dorsal and rostral areas of the brain. Expansion and contraction of these sulci during brain pulsation is considered important to the forward flow of solutes in CSF through these compartments. Following intracisternal enzyme replacement therapy, enzyme reached all areas of the brain, but there was considerable disparity of enzyme uptake with some areas recording much higher levels than others. Posttreatment posture made only modest differences to enzyme uptake., (© 2012 Massey University. Neuropathology and Applied Neurobiology © 2012 British Neuropathological Society.)

Aims: The research concerns enzyme replacement therapy in lysosomal storage diseases with central nervous system involvement. The principle aim was to understand the routes of entry of enzyme into the brain when delivered directly into the cerebrospinal fluid (CSF) via the cerebellomedullary cistern., Methods: Pathways for absorption of replacement enzyme were investigated in dogs with mucopolysaccharidosis IIIA (MPSIIIA) following intracisternal injections of human recombinant N-sulphoglucosamine sulphohydrolase (rhSGSH, EC3.10.1.1) by light and confocal microscopy using chromogenic and fluorescent immune probes., Results: Enzyme entered the brain superficially by penetration of the pia/glia limitans interface, but the main route was perivascular along large veins, arteries and arterioles extending onto capillaries. It further dispersed into surrounding neuropil to be taken up by neurones, macrophages, astrocytes and oligodendroglia. Enzyme also entered the lateral ventricles adjacent to the choroid plexus, probably also by the tela choroidea and medullary velum, with further spread throughout the ventricular system and spinal canal. There was secondary spread back across the ependyma into nervous tissue of brain and spinal cord., Conclusions: Enzyme mainly enters the brain by a perivascular route involving both arteries and veins with subsequent spread within the neuropil from where it is taken up by a proportion of neurones and other cells. Penetration of enzyme through the pia/glia limitans is minor and superficial., (© 2011 The Authors. Neuropathology and Applied Neurobiology © 2011 British Neuropathological Society.)

The ceroid-lipofuscinoses are a group of inherited neurodegenerative diseases of human beings characterized by the accumulation of a fluorescent lipopigment in neurons and other cells within the body. There is usually atrophy of both brain and retina with preferential loss of particular neurons. Biochemically, the diseases divide into at least two groups, i.e. those that accumulate subunit c of mitochondrial ATP synthase and those that do not. Dolichol pyrophosphate linked oligosaccharides are also present in storage material. As the underlying biochemical anomalies are not known, the various clinicopathological entities are classified on clinical grounds, by age of onset and, to a lesser extent, by the course of the disease. The best recognized diseases are infantile, late infantile, early juvenile, juvenile and adult onset forms but other variants occur indicating considerable heterogeneity within the group. The infantile, late infantile and juvenile diseases are not allelic. Analogous diseases occur in a variety of animal species. That in the sheep has been extensively studied as a model of the human disease and is the prototype subunit c storage disease.

Blindness is a feature of the group of storage diseases of children known as the ceroid-lipofuscinoses. Sequential studies in the ovine model, which most resembles the juvenile form of human disease, showed clearly that blindness had two components, a central and a peripheral. Whereas the central component, attributable to neuronal death and atrophy of the cerebral cortex, was responsible for early loss of vision, retinal atrophy was also extremely advanced in terminal stages of the disease. The primary retinal change was one of dystrophy of photoreceptor outer segments which preceded degeneration and necrosis of the photoreceptors cells themselves. Electroretinography showed that there was a progressive loss of a- and b-waves during the course of the disease, but this was preceded by a diminished c-wave which was eventually replaced by a negative potential. However, the pigment epithelium remained functionally (azide responsive) and ultrastructurally intact throughout the study. Loss of brain weight with selective cerebral atrophy also correlated with abnormal behaviour and facial manoeuvres that were interpreted as partial seizures that did not become generalized.

The majority of lysosomal storage diseases affect the central nervous system. Those that reflect a primary lysosomal disorder are associated with genetically determined deficiencies of specific lysosomal enzymes and storage of the relevant substrate. Autofluorescent lipopigments accumulate in the ceroid-lipofuscinoses, a heterogeneous group of diseases in which lysosomal storage is thought to be a secondary event. In animals, there occurs a group of toxic storage diseases whose pathology mimics that of some of the genetic diseases. In humans some element of control may be achieved by heterozygote detection programmes and/or prenatal diagnosis of pregnancies at risk with elective abortion of an affected foetus. The outlook for specific therapy is not encouraging at this stage.

An inherited neurological disease of sheep was characterized by the intracellular accumulation of autofluorescent lipopigments in neurones and a wide variety of other cells within the body. The staining, fluorescent, ultrastructural and physical characteristics of the storage material were similar to those found in a heterogeneous group of storage diseases of children known as Batten's disease or the ceroid-lipofuscinoses. The ovine disease did not exactly fit any of the main human entities, but had features in common with both the late infantile and juvenile forms. It was concluded that this was a useful model for studying the pathogenesis of this type of storage disease and for therapeutic trials. A flock of sheep is maintained for this purpose.

A detailed investigation of the neuropathology of a horse affected with stringhalt was performed. Qualitative and quantitative light and electron microscopy, and single teased fibre preparations of peripheral nerve demonstrated predominantly axonal degeneration, the stage of which was appropriate for the duration of clinical signs. There was selective involvement of large myelinated nerve fibres. A proximal to distal increase in the severity of pathological changes was present in the peripheral nerves. The long left recurrent laryngeal nerve was the most severely affected, followed in order by its right counterpart, the hindlimb and forelimb nerves. Neurogenic atrophy of muscles innervated by affected peripheral nerves also showed a distally graded increase in severity. No lesions were observed in the central nervous system. It was concluded that this disease should be classified as a distal axonopathy.

A sequential morphological study of ovine ceroid-lipofuscinosis showed that brains of affected lambs were normal at birth, grew until four months of age but then atrophied. Laminar necrosis of cerebral cortex was noted at 10 weeks, occurring first in the parietal area, then spreading to involve frontal and occipital areas while the temporal lobe was least and last affected. With progression of the disease, the laminar pattern was lost. Neuronal necrosis was accompanied by a severe astrocytosis. The granular and multilamellar storage cytosomes increased in size with age. Their structure was interpreted as paracrystalline in which repeating molecules of the dominantly stored lipid binding subunit of mitochondrial ATP synthase interact with neutral lipids and phospholipids. Abnormal cytosomes in neurons of lamb fetuses and a neonate were interpreted as early lesions which contained whorls or stacks of bilayered membrane as well as the more complex multilamellar material. The underlying anomaly leading to the storage of the lipid binding subunit of mitochondrial ATPsynthase remains to be defined. However, it is noted that this disease should be regarded as a lipid binding protein proteinosis or alternatively as a proteolipid proteinosis.